Clean Harbors (CLH) 10-Q 1 Aug 18 2018 Q2 Quarterly report Financial data

DOCUMENT AND ENTITY INFORMATION

DOCUMENT AND ENTITY INFORMATION - shares	6 Months Ended
	Jun. 30, 2018	Jul. 30, 2018
Document and Entity Information [Abstract]
Entity Registrant Name	CLEAN HARBORS INC
Entity Central Index Key	822,818
Current Fiscal Year End Date	--12-31
Entity Filer Category	Large Accelerated Filer
Document Type	10-Q
Document Period End Date	Jun. 30, 2018
Document Fiscal Year Focus	2,018
Document Fiscal Period Focus	Q2
Amendment Flag	false
Entity Common Stock, Shares Outstanding		56,088,908

CONSOLIDATED BALANCE SHEETS

CONSOLIDATED BALANCE SHEETS - USD ($) $ in Thousands	Jun. 30, 2018	Dec. 31, 2017
Current assets:
Cash and cash equivalents	$ 197,068	$ 319,399
Short-term marketable securities	36,862	38,179
Accounts receivable, net of allowances aggregating $34,033 and $27,799, respectively	590,580	528,924
Unbilled accounts receivable	62,762	35,922
Deferred costs	20,832	20,445
Inventories and supplies	193,544	176,012
Prepaid expenses and other current assets	34,834	35,175
Total current assets	1,136,482	1,154,056
Property, plant and equipment, net	1,609,382	1,587,365
Other assets:
Goodwill	497,251	478,523
Permits and other intangibles, net	455,920	469,128
Other	16,426	17,498
Total other assets	969,597	965,149
Total assets	3,715,461	3,706,570
Current liabilities:
Current portion of long-term obligations	4,000	4,000
Accounts payable	247,821	224,231
Deferred revenue	68,705	67,822
Accrued expenses	200,135	187,982
Current portion of closure, post-closure and remedial liabilities	23,007	19,782
Total current liabilities	543,668	503,817
Other liabilities:
Closure and post-closure liabilities, less current portion of $6,514 and $6,444, respectively	58,990	54,593
Remedial liabilities, less current portion of $16,493 and $13,338, respectively	104,782	111,130
Long-term obligations, less current portion	1,624,727	1,625,537
Deferred taxes, unrecognized tax benefits and other long-term liabilities	222,246	223,291
Total other liabilities	2,010,745	2,014,551
Commitments and contingent liabilities (See Note 16)
Stockholders’ equity:
Authorized 80,000,000; shares issued and outstanding 56,087,256 and 56,501,190 shares, respectively	561	565
Additional paid-in capital	664,948	686,962
Accumulated other comprehensive loss	(194,095)	(172,407)
Accumulated earnings	689,634	673,082
Total stockholders’ equity	1,161,048	1,188,202
Total liabilities and stockholders’ equity	$ 3,715,461	$ 3,706,570

CONSOLIDATED BALANCE SHEETS (Pa

CONSOLIDATED BALANCE SHEETS (Parenthetical) - USD ($) $ in Thousands	Jun. 30, 2018	Dec. 31, 2017
Statement of Financial Position [Abstract]
Account receivable, allowances aggregating	$ 34,033	$ 27,799
Closure and post-closure liabilities, current portion	6,514	6,444
Remedial liabilities, current portion	$ 16,493	$ 13,338
Common stock, par value (in USD per share)	$ 0.01	$ 0.01
Common stock, authorized shares (in shares)	80,000,000	80,000,000
Common stock, issued shares (in shares)	56,087,256	56,501,190
Common stock, outstanding shares (in shares)	56,087,256	56,501,190

UNAUDITED CONSOLIDATED STATEMEN

UNAUDITED CONSOLIDATED STATEMENTS OF OPERATIONS - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Revenues:
Total revenues	$ 849,140	$ 752,788	$ 1,598,918	$ 1,441,729
Cost of revenues: (exclusive of items shown separately below)
Total cost of revenues	583,584	519,803	1,130,009	1,016,388
Selling, general and administrative expenses	125,995	112,294	241,083	224,515
Accretion of environmental liabilities	2,448	2,416	4,878	4,706
Depreciation and amortization	72,760	71,531	147,604	143,943
Income from operations	64,353	46,744	75,344	52,177
Other income (expense), net	846	(833)	547	(2,382)
Loss on early extinguishment of debt	0	(6,045)	0	(6,045)
Gain on sale of business	0	31,722	0	31,722
Interest expense, net of interest income of $587, $311, $1,350 and $520, respectively	(20,769)	(22,492)	(41,039)	(45,068)
Income before (benefit) provision for income taxes	44,430	49,096	34,852	30,404
Provision for income taxes	13,683	23,216	16,736	25,917
Net income	$ 30,747	$ 25,880	$ 18,116	$ 4,487
Earnings per share:
Basic (in USD per share)	$ 0.55	$ 0.45	$ 0.32	$ 0.08
Diluted (in USD per share)	$ 0.54	$ 0.45	$ 0.32	$ 0.08
Shares used to compute loss per share - Basic (in shares)	56,410	57,190	56,304	57,226
Shares used to compute loss per share - Diluted (in shares)	56,505	57,336	56,399	57,349
Service
Revenues:
Total revenues	$ 696,779	$ 610,940	$ 1,316,498	$ 1,171,154
Cost of revenues: (exclusive of items shown separately below)
Total cost of revenues	473,423	412,356	921,072	803,443
Product
Revenues:
Total revenues	152,361	141,848	282,420	270,575
Cost of revenues: (exclusive of items shown separately below)
Total cost of revenues	$ 110,161	$ 107,447	$ 208,937	$ 212,945

UNAUDITED CONSOLIDATED STATEME5

UNAUDITED CONSOLIDATED STATEMENTS OF OPERATIONS (Parenthetical) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Income Statement [Abstract]
Interest expense	$ 587	$ 311	$ 1,350	$ 520

UNAUDITED CONSOLIDATED STATEME6

UNAUDITED CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (LOSS) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Statement of Comprehensive Income [Abstract]
Net income	$ 30,747	$ 25,880	$ 18,116	$ 4,487
Other comprehensive (loss) income:
Unrealized (losses) gains on available-for-sale securities (net of tax of $8, $20, $88 and $122, respectively)	(11)	27	(206)	159
Reclassification adjustment for losses on available-for-sale securities included in net income (net of taxes of $0, $29, $0 and $79, respectively)	0	47	0	143
Foreign currency translation adjustments (including a tax benefit of $5.6 million in 2018)	(4,931)	15,024	(21,482)	20,847
Other comprehensive (loss) income	(4,942)	15,098	(21,688)	21,149
Comprehensive income (loss)	$ 25,805	$ 40,978	$ (3,572)	$ 25,636

UNAUDITED CONSOLIDATED STATEME7

UNAUDITED CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (LOSS) (Parenthetical) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Statement of Comprehensive Income [Abstract]
Unrealized gains (losses) on available-for-sale securities, taxes	$ 8	$ 20	$ 88	$ 122
Reclassification adjustment for gains on available-for-sale securities included in net (loss) income taxes			0	$ 0
Foreign currency translation adjustments, tax benefit			$ (5,600)

UNAUDITED CONSOLIDATED STATEME8

UNAUDITED CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017
Cash flows from operating activities:
Net income	$ 18,116	$ 4,487
Adjustments to reconcile net income to net cash from operating activities:
Depreciation and amortization	147,604	143,943
Allowance for doubtful accounts	7,389	3,580
Amortization of deferred financing costs and debt discount	1,881	1,660
Accretion of environmental liabilities	4,878	4,706
Changes in environmental liability estimates	(673)	(129)
Deferred income taxes	(10)	190
Stock-based compensation	6,639	5,172
Other (income) expense, net	(547)	2,382
Gain on sale of business	0	(31,722)
Loss on early extinguishment of debt	0	6,045
Environmental expenditures	(4,585)	(6,102)
Changes in assets and liabilities, net of acquisitions
Accounts receivable and unbilled accounts receivable	(62,764)	(31,154)
Inventories and supplies	(18,625)	(6,307)
Other current assets	180	13,918
Accounts payable	23,605	(2,686)
Other current and long-term liabilities	6,582	8,948
Net cash from operating activities	129,670	116,931
Cash flows used in investing activities:
Additions to property, plant and equipment	(94,139)	(88,742)
Proceeds from sale and disposal of fixed assets	2,641	2,121
Acquisitions, net of cash acquired	(123,750)	(9,277)
Proceeds from sale of businesses, net of transactional costs	0	46,391
Additions to intangible assets, including costs to obtain or renew permits	(2,106)	(1,239)
Proceeds from sale of available-for-sale securities	11,214	376
Purchases of available-for-sale securities	(10,001)	0
Net cash used in investing activities	(216,141)	(50,370)
Cash flows (used in) from financing activities:
Change in uncashed checks	(2,803)	(8,361)
Proceeds from exercise of stock options	0	46
Tax payments related to withholdings on vested restricted stock	(2,175)	(2,132)
Repurchases of common stock	(26,482)	(12,257)
Deferred financing costs paid	(468)	(4,727)
Premiums paid on early extinguishment of debt	0	(4,665)
Principal payment on debt	(2,000)	(296,202)
Issuance of senior secured notes, net of discount	0	399,000
Net cash (used in) from financing activities	(33,928)	70,702
Effect of exchange rate change on cash	(1,932)	2,106
(Decrease) increase in cash and cash equivalents	(122,331)	139,369
Cash and cash equivalents, beginning of period	319,399	306,997
Cash and cash equivalents, end of period	197,068	446,366
Cash payments for interest and income taxes:
Interest paid	40,745	50,432
Income taxes paid	14,118	13,407
Non-cash investing activities:
Property, plant and equipment accrued	13,041	16,213
Transfer of inventory to property, plant and equipment	$ 0	$ 12,641

UNAUDITED CONSOLIDATED STATEME9

UNAUDITED CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY - 6 months ended Jun. 30, 2018 - USD ($) shares in Thousands, $ in Thousands	Total	Common Stock	Additional Paid-in Capital	Accumulated Other Comprehensive Loss	Accumulated Earnings
Balance at beginning of period at Dec. 31, 2017	$ 1,188,202	$ 565	$ 686,962	$ (172,407)	$ 673,082
Balance beginning of period (in shares) at Dec. 31, 2017		56,501
Increase (Decrease) in Stockholders' Equity
Net income	18,116				18,116
Other comprehensive loss	(21,688)			(21,688)
Stock-based compensation	6,639		6,639
Issuance of restricted shares, net of shares remitted and tax withholdings	(2,175)	$ 1	(2,176)
Issuance of restricted shares, net of shares remitted and tax withholdings (in shares)		118
Repurchases of common stock	$ (26,482)	$ (5)	(26,477)
Repurchases of common stock (in shares)	(500)	(532)
Balance at end of period at Jun. 30, 2018	$ 1,161,048	$ 561	$ 664,948	$ (194,095)	689,634
Balance ending of period (in shares) at Jun. 30, 2018		56,087
Increase (Decrease) in Stockholders' Equity
Cumulative effect of change in accounting principle	$ (1,564)
Cumulative effect of change in accounting principle | Accounting Standards Update 2016-16					$ (1,564)

UNAUDITED CONSOLIDATED STATEM10

UNAUDITED CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY (Parenthetical) - $ / shares	Jun. 30, 2018	Dec. 31, 2017
Statement of Stockholders' Equity [Abstract]
Common stock, par value (in USD per share)	$ 0.01	$ 0.01

BASIS OF PRESENTATION

BASIS OF PRESENTATION	6 Months Ended
	Jun. 30, 2018
Organization, Consolidation and Presentation of Financial Statements [Abstract]
BASIS OF PRESENTATION	BASIS OF PRESENTATION The accompanying consolidated interim financial statements are unaudited and include the accounts of Clean Harbors, Inc. and its subsidiaries (collectively, “Clean Harbors,” the “Company” or "we") and have been prepared pursuant to the rules and regulations of the Securities and Exchange Commission (the “SEC”) and, in the opinion of management, include all adjustments which are of a normal recurring nature, necessary for a fair presentation of the financial position, results of operations, and cash flows for the periods presented. Management has made estimates and assumptions affecting the amounts reported in the Company's consolidated interim financial statements and accompanying footnotes, actual results could differ from those estimates and judgments. The results for interim periods are not necessarily indicative of results for the entire year or any other interim periods. The financial statements presented herein should be read in connection with the financial statements included in the Company’s Annual Report on Form 10-K for the year ended December 31, 2017 .

SIGNIFICANT ACCOUNTING POLICIES

SIGNIFICANT ACCOUNTING POLICIES	6 Months Ended
	Jun. 30, 2018
Accounting Policies [Abstract]
SIGNIFICANT ACCOUNTING POLICIES	SIGNIFICANT ACCOUNTING POLICIES The Company's significant accounting policies are described in Note 2, "Significant Accounting Policies," in the Company's Annual Report on Form 10-K for the year ended December 31, 2017 . There have been no material changes in these policies or their application except for the changes described below. Reclassifications During the first quarter of fiscal year 2018, certain of the Company's businesses undertook a reorganization which included changes to the underlying business and management structures. The reorganization resulted in combining the Environmental Services businesses from an operational and management perspective and is expected to deepen customer relationships and allow for efficiencies across the Company's operations through the sharing of resources, namely labor and equipment which will reduce third party spend and promote the cross selling of such business offerings. In connection with this reorganization, the Company’s chief operating decision maker also requested changes in the information that he regularly reviews for purposes of allocating resources and assessing performance. These changes required a reconsideration of the Company’s operating segments in the first quarter of 2018 and resulted in a change in the Company’s assessment of its operating segments. Upon reconsideration of the identification of the Company’s operating segments, the Company concluded that there are now two operating segments for disclosure in accordance with ASC 280 Segment reporting; (i) the Environmental Services segment which consists of the Company’s historical Technical Services, Industrial Services, Field Services and Oil, Gas and Lodging businesses and (ii) the Safety-Kleen segment. See Note 18, " Segment Reporting ," for more information. The amounts presented for the three and six months ended June 30, 2017 have been recast to reflect the impact of such changes. These reclassifications and adjustments had no effect on the consolidated statements of operations, consolidated statements of comprehensive loss, consolidated statements of cash flows or consolidated statements of stockholders' equity for any of the periods presented. Recent Accounting Pronouncements Standards implemented In May 2014, the Financial Accounting Standards Board ("FASB") issued ASU 2014-09, Revenue from Contracts with Customers (Topic 606) , which replaces numerous requirements in U.S. GAAP, including industry-specific requirements, and provides companies with a single revenue recognition model for recognizing revenue from contracts with customers. The guidance permits two methods of adoption: retrospectively to each prior reporting period presented (full retrospective method), or retrospectively with the cumulative effect of initially applying the guidance recognized at the date of initial application (the modified retrospective method). On January 1, 2018, the Company adopted Topic 606 using the modified retrospective method for all contracts. Results for reporting periods beginning on the date of adoption are presented under ASC 606, while prior period amounts have not been adjusted and continue to be reported in accordance with the Company's historical accounting methodology pursuant to ASC 605, Revenue Recognition (“ASC 605”). Upon adoption, a cumulative effect adjustment was not required as the majority of the Company’s contracts are recognized based on time and materials incurred and were not impacted by the new guidance. The Company has concluded that the most significant impact of the standard relates to the incremental disclosures required. In October 2016, the FASB issued ASU 2016-16, Income Tax - Intra-Entity Transfers of Assets Other than Inventory . The amendment improves the accounting for the income tax consequences of intra-entity transfers of assets other than inventory. The Company adopted the amendment on a modified retrospective basis effective January 1, 2018. As a result of adoption, the Company recorded a cumulative effect adjustment that reduced retained earnings by $1.6 million . In March 2017, the FASB issued ASU 2017-07, Compensation-Retirement Benefits (Topic 715): Improving the Presentation of Net Periodic Pension Cost and Net Periodic Postretirement Benefit Cost . The amendment requires an employer to report the service cost component of net benefit cost in the same line item as other compensation costs arising from services rendered by the pertinent employees during the period. The other components of net benefit cost are required to be presented in the income statement separately from the service cost component and outside a subtotal of income from operations. In addition, the amendment allows only the service cost component to be eligible for capitalization when applicable. The Company adopted the amendment in the first quarter of 2018. Adoption did not have a material impact on the Company's consolidated financial statements. Standards to be implemented The Company is evaluating the impact that the below standards to be implemented will have on the Company's consolidated financial statements. In February 2016, FASB issued ASU 2016-02, Leases (Topic 842) . The amendment increases transparency and comparability among organizations by recognizing lease assets and lease liabilities on the balance sheet and disclosing key information about leasing arrangements. In February 2018, FASB issued ASU 2018-01, Leases (Topic 842): Land Easement Practical Expedient for Transition to Topic 842 . The amendment clarifies that land easements are within the scope of the new leases standard (ASC 842) and introduces a new transition practical expedient allowing a company to not assess whether existing and expired land easements that were not previously accounted for as leases under current US GAAP (ASC 840) are or contain leases under ASC 842. In July 2018, FASB issued ASU 2018-10, Codification Improvements to Topic 842, Leases . The amendment provides improvements that clarify specific aspects of the guidance in ASU 2016-02. The Company will adopt the new standard beginning on January 1, 2019. A modified retrospective transition approach is required for leases existing at, or entered into after, the beginning of the earliest comparative period presented in the financial statements, with certain practical expedients available. While the Company is still continuing to assess the effect of adoption, it expects that the new standard will have a material effect on its consolidated balance sheet related to the recognition of new assets and lease liabilities. In preparation for the adoption of the guidance, the Company is in the process of implementing new software and assessing changes to controls and processes to enable the preparation of financial information. In June 2016, FASB issued ASU 2016-13, Financial Instruments—Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments . The amendment changes the way entities recognize impairment of many financial assets, including accounts receivable and investments in debt securities, by requiring immediate recognition of estimated credit losses expected to occur over their remaining lives. The amendment should be applied using a modified-retrospective approach and is effective for the Company for annual and interim reporting periods beginning after January 1, 2020, with early adoption permitted. The Company is currently evaluating the impact ASU 2016-13 will have on its consolidated financial statements. In August 2017, the FASB issued ASU 2017-12, Derivatives and Hedging (Topic 815): Targeted Improvements to Accounting for Hedging Activities. The amendment better aligns an entity’s risk management activities and financial reporting for hedging relationships through changes to both the designation and measurement guidance for qualifying hedging relationships and the presentation of hedge results. The amendment is effective for the Company for annual and interim reporting periods beginning after December 15, 2018, with early adoption permitted. The Company is currently evaluating the impact ASU 2017-12 will have on its consolidated financial statements.

REVENUES

REVENUES	6 Months Ended
	Jun. 30, 2018
Revenue from Contract with Customer [Abstract]
REVENUES	REVENUES Revenue Recognition Revenues are recognized when control of the promised goods or services is transferred to the Company’s customers, in an amount that reflects the consideration the Company expects to be entitled to in exchange for those goods or services. Nature of Goods and Services The Company generates services and product revenues through its Environmental Services and Safety-Kleen operating segments. The majority of the Company’s contracts are for services, which are recognized based on time and materials incurred at contractually agreed-upon rates. Product revenues are recognized when the products are delivered and control transfers to the customer. The Company’s payment terms vary by the type and location of its customers and the products or services offered. The term between invoicing and when payment is due is not significant. The Company excludes sales taxes that it collects from customers from its revenues. Disaggregation of Revenue The following table presents the Company’s revenues disaggregated by revenue source (in thousands): For the Three Months Ended June 30, 2018 Environmental Services Safety-Kleen Corporate Total Primary Geographical Markets United States $ 408,127 $ 306,059 $ 363 $ 714,549 Canada 111,789 22,656 146 134,591 519,916 328,715 509 849,140 Sources of Revenue (1) Technical Services 257,006 — — $ 257,006 Field and Emergency Response Services 76,092 — — 76,092 Industrial Services 161,046 — — 161,046 Oil, Gas and Lodging Services and Other 25,772 — 509 26,281 Safety-Kleen Environmental Services — 200,034 — 200,034 Kleen Performance Products — 128,681 — 128,681 Total third party revenues $ 519,916 $ 328,715 $ 509 $ 849,140 For the Three Months Ended June 30, 2017 Environmental Services Safety-Kleen Corporate Total Primary Geographical Markets United States $ 343,323 $ 280,617 $ 155 $ 624,095 Canada 106,308 22,339 46 128,693 449,631 302,956 201 752,788 Sources of Revenue (1) Technical Services 254,487 — — 254,487 Field and Emergency Response Services 70,707 — — 70,707 Industrial Services 99,733 — — 99,733 Oil, Gas and Lodging Services and Other 24,704 — 201 24,905 Safety-Kleen Environmental Services — 192,817 — 192,817 Kleen Performance Products — 110,139 — 110,139 Total third party revenues $ 449,631 $ 302,956 $ 201 $ 752,788 For the Six Months Ended June 30, 2018 Environmental Services Safety-Kleen Corporate Total Primary Geographical Markets United States $ 752,099 $ 593,701 $ 508 $ 1,346,308 Canada 207,505 44,932 173 252,610 959,604 638,633 681 1,598,918 Sources of Revenue (1) Technical Services 493,312 — — 493,312 Field and Emergency Response Services 146,027 — — 146,027 Industrial Services 264,809 — — 264,809 Oil, Gas and Lodging Services and Other 55,456 — 681 56,137 Safety-Kleen Environmental Services — 394,195 — 394,195 Kleen Performance Products — 244,438 — 244,438 Total third party revenues $ 959,604 $ 638,633 $ 681 $ 1,598,918 For the Six Months Ended June 30, 2017 Environmental Services Safety-Kleen Corporate Total Primary Geographical Markets United States $ 657,106 $ 552,688 $ 288 $ 1,210,082 Canada 188,432 43,169 46 231,647 845,538 595,857 334 1,441,729 Sources of Revenue (1) Technical Services 484,705 — — 484,705 Field and Emergency Response Services 131,726 — — 131,726 Industrial Services 174,801 — — 174,801 Oil, Gas and Lodging Services and Other 54,306 — 334 54,640 Safety-Kleen Environmental Services — 384,544 — 384,544 Kleen Performance Products — 211,313 — 211,313 Total third party revenues $ 845,538 $ 595,857 $ 334 $ 1,441,729 ______________________ 1. All revenue except Kleen Performance Products and product sales within Safety-Kleen Environmental Services, including allied products and direct blended oil sales, are recognized over time. Kleen Performance Products and Safety-Kleen Environmental Services product revenues are recognized at a point in time. Technical Services. Technical Services revenues are generated from fees charged for waste material management and disposal services including onsite environmental management services, collection and transportation, packaging, recycling, treatment and disposal of waste. Revenue is primarily generated by short-term projects, most of which are governed by master service agreements that are long-term in nature. These master service agreements are typically entered into with the Company's larger customers and outline the pricing and legal frameworks for such arrangements. Services are provided based on purchase orders or agreements with the customer and include prices based upon units of volume of waste, and transportation and other fees. Collection and transportation revenues are recognized over time, as the customer receives and consumes the benefits of the service as they are being performed and the Company has a right to payment for performance completed to date. The Company uses the input method to recognize revenue over time, based on time and materials incurred. Revenues for treatment and disposal of waste are recognized upon completion of treatment, final disposition in a landfill or incineration, or when the waste is shipped to a third party for processing and disposal. The Company periodically enters into bundled arrangements for the collection and transportation and disposal of waste. For such arrangements, transportation and disposal are considered distinct performance obligations and the Company allocates revenue to each based on their relative standalone selling price (i.e. the estimated price that a customer would pay for the services on a standalone basis). Revenues from waste that is not yet completely processed and disposed and the related costs are deferred. The revenue is recognized and the deferred costs are expensed when the related services are completed. The period between collection and transportation and the final processing and disposal ranges depending on location of the customer, but generally is measured in days. Field and Emergency Response Services. Field Services revenues are generated from cleanup services at customer sites, including municipalities and utilities, or other locations on a scheduled or emergency response basis. Services include confined space entry for tank cleaning, site decontamination, large remediation projects, demolition, spill cleanup on land and water, railcar cleaning, product recovery and transfer and vacuum services. Additional services include filtration and water treatment services. Response services for environmental emergencies include any scale from man-made disasters such as oil spills, to natural disasters such as hurricanes. These services are provided based on purchase orders or agreements with customers and include prices generally based upon daily, hourly or job rates for equipment, materials and personnel. The Company recognizes revenue for these services over time, as the customer receives and consumes the benefits of the service as they are being performed and the Company has a right to payment for performance completed to date. The Company uses the input method to recognize revenue over time, based on time and materials incurred. The duration of such services can be over a number of hours, several days or even months for larger scale projects. Industrial Services. Industrial Services revenues are generated from industrial and specialty services provided to refineries, mines, upgraders, chemical plants, pulp and paper mills, manufacturing facilities, power generation facilities and other industrial customers throughout North America. Services include in-plant cleaning and maintenance services, plant outage and turnaround services, decoking and pigging, chemical cleaning, high and ultra-high pressure water cleaning, pipeline inspection and coating services, large tank and surface impoundment cleaning, oilfield transport, daylighting, production services and directional boring services (previously included in Oil, Gas and Lodging service offerings) supporting drilling, completions and production programs. These services are provided based on purchase orders or agreements with the customer and include prices based upon daily, hourly or job rates for equipment, materials and personnel. The Company recognizes revenue for these services over time, as the customer receives and consumes the benefits of the service as they are being performed and the Company has a right to payment for performance completed to date. The Company uses the input method to recognize revenue over time, based on time and materials incurred. Safety-Kleen Environmental Services. Safety-Kleen Environmental Services revenues are generated from providing parts washer services, containerized waste handling and disposal services, oil collection services, direct sales of blended oil products, and other complementary services and product sales. Containerized waste services consist of profiling, collecting, transporting and recycling or disposing of a wide variety of waste. Other complementary products and services include vacuum services, sale of allied supply products and other environmental services. Revenues from parts washer services include fees charged to customers for their use of parts washer equipment, to clean and maintain parts washer equipment and to remove and replace used cleaning fluids. Parts washer services are considered a single performance obligation due to the highly integrated and interdependent nature of the arrangement. Revenue from parts washer services is recognized over the service interval as the customer receives the benefit of the service. Collection and transportation revenues are recognized over time, as the customer receives and consumes the benefits of the service as they are being performed and the Company has a right to payment for performance completed to date. The Company uses the input method to recognize revenue over time, based on time and materials incurred. Product revenue is recognized upon the transfer of control. Control transfers when the products are delivered to the customer. Kleen Performance Products. Kleen Performance Products revenues are generated from sales of high quality base and blended lubricating oils to third-party distributors, government agencies, fleets, railroads and industrial customers. The business also sells recycled fuel oil to asphalt plants, industrial plants, blenders, pulp and paper companies, vacuum gas oil producers and marine diesel oil producers. Revenue for oil products is recognized at a point in time, upon the transfer of control. Control transfers when the products are delivered to the customer. Oil, Gas and Lodging Services and Other. Oil, Gas and Lodging Services and Other is primarily comprised of revenues generated from providing Oil and Gas Field Services that support upstream activities such as exploration and drilling for oil and gas companies and Lodging Services to customers in Western Canada. The Company recognizes Oil and Gas Field Services revenue over time, as the customer receives and consumes the benefits of the service as they are being performed and the Company has a right to payment for performance completed to date. The Company uses the input method to recognize revenue over time, based on time and materials incurred. Revenue for lodging accommodation services is recognized over time based on passage of time. Revenue for manufacturing services is recognized over time using a cost-to-cost measure of progress or completed units to depict the transfer of assets to the customer. Contract Balances June 30, 2018 December 31, 2017 June 30, 2017 December 31, 2016 Receivables $ 590,580 $ 528,924 $ 512,375 $ 496,226 Contract Assets (Unbilled Receivables) 62,762 35,922 46,576 36,190 Contract Liabilities (Deferred Revenue) 68,705 67,822 72,089 64,397 The timing of revenue recognition, billings and cash collections results in billed accounts receivable, unbilled receivables (contract assets), and customer advances and deposits or deferred revenue (contract liabilities) on the Consolidated Balance Sheet. Generally, billing occurs subsequent to revenue recognition, as a right to payment is not just subject to passage of time, resulting in contract assets. Contract assets are generally classified as current. The Company sometimes receives advances or deposits from its customers before revenue is recognized, resulting in contract liabilities. These assets and liabilities are reported on the Consolidated Balance Sheet on a contract-by-contract basis at the end of each reporting period. As part of the acquisition of the Veolia Business on February 23, 2018, the Company acquired receivables and contract assets of $20.5 million and $17.6 million , respectively. Changes in the contract asset and liability balances during the six-month period ended June 30, 2018 and June 30, 2017 were not materially impacted by any other factors. The contract liability balances at the beginning of each period presented were fully recognized in the subsequent three-month period. Remaining Performance Obligations Remaining performance obligations represent the transaction price of orders for which work has not been performed. As of June 30, 2018 , all remaining performance obligations were for contracts with an original expected length of one year or less. Variable Consideration The nature of the Company's contracts gives rise to certain types of variable consideration, including in limited cases volume and payment discounts. The Company estimates the amount of variable consideration to include in the estimated transaction price based on historical experience, anticipated performance and its best judgment at the time and to the extent it is probable that a significant reversal of cumulative revenue recognized will not occur when the uncertainty associated with the variable consideration is resolved. Variable consideration was not material in any of the periods presented. Contract Costs Contract costs include direct and incremental costs to obtain or fulfill a contract. The Company’s contract costs that are subject to capitalization are comprised of costs associated with parts washer services and costs associated with the treatment and disposal of waste. Parts washer costs include costs of solvent, commissions paid relating to revenue generated from parts washer services, and transportation costs associated with transferring the product picked up from the services as it is returned to the Company’s facilities or a third party site. Costs related to the treatment of waste include costs for waste receiving, drum movement and storage, waste consolidation and transportation between facilities. Deferred costs associated with parts washer services are amortized ratably over the average service interval, which ranges between seven and 14 weeks. Deferred costs related to treatment and disposal of waste are recognized when the corresponding waste is disposed of and are included in Deferred Costs within total current assets in the Company’s consolidated balance sheets. The deferred contract cost balances at the beginning of each period presented were fully recognized in cost of revenue in the subsequent three-month period.

BUSINESS COMBINATIONS

BUSINESS COMBINATIONS	6 Months Ended
	Jun. 30, 2018
Business Combinations [Abstract]
BUSINESS COMBINATIONS	BUSINESS COMBINATIONS 2018 Acquisition On February 23, 2018, the Company completed the acquisition of the U.S. Industrial Cleaning Business of Veolia Environmental Services North America LLC (the "Veolia Business"). The acquisition will provide significant scale and industrial services capabilities while increasing the size of the Company's existing U.S. Industrial Services business. The Company acquired the Veolia Business for a purchase price of $120.0 million subject to certain post-closing adjustments. The acquisition was financed with cash on hand. The amount of revenue from the Veolia Business included in the Company's results of operations for the three and six months ended June 30, 2018 was $46.3 million and $63.9 million , respectively. The amount of pre-tax income for the three and six months ended June 30, 2018 was $2.1 million and $3.3 million , respectively. During the three and six months ended June 30, 2018 , the Company incurred acquisition-related costs of approximately $0.4 million and $0.9 million , respectively, in connection with the transaction which are included in selling, general and administrative expenses in the consolidated statements of operations. The allocation of the purchase price was based on preliminary estimates of the fair value of assets acquired and liabilities assumed as of February 23, 2018, as the Company is continuing to obtain information to complete its valuation of these accounts and the associated tax accounting. The components and preliminary allocation of the purchase price consist of the following amounts (in thousands): At Acquisition Date Measurement Period Adjustments At Acquisition Date As Reported June 30, 2018 Accounts receivable, including unbilled receivables $ 40,773 $ (2,691 ) $ 38,082 Inventories and supplies 1,442 (316 ) 1,126 Prepaid expenses and other current assets 1,005 (80 ) 925 Property, plant and equipment 72,244 — 72,244 Permits and other intangibles 5,140 — 5,140 Current liabilities (15,908 ) (2,631 ) (18,539 ) Closure and post-closure liabilities (604 ) — (604 ) Total identifiable net assets 104,092 (5,718 ) 98,374 Goodwill 15,908 5,718 21,626 Total purchase price $ 120,000 $ — $ 120,000 The weighted average amortization period for the intangibles acquired is 8.2 years . The excess of the total purchase price, which includes the aggregate cash consideration paid in excess of the fair value of the tangible net assets and intangible assets acquired, was recorded as goodwill. The goodwill recognized is attributable to the expected operating synergies and growth potential that the Company expects to realize from this acquisition. Goodwill generated from the acquisition is deductible for tax purposes. Pro forma revenue and earnings amounts on a combined basis as if this acquisition had been completed on January 1, 2017 are immaterial to the consolidated financial statements of the Company since that date. 2017 Acquisitions On July 14, 2017, the Company acquired Lonestar West Inc. ("Lonestar"), a public company headquartered in Alberta, Canada, for approximately CAD $41.8 million , ( $33.1 million USD), net of cash acquired, which included an equity payout of CAD $0.72 per share to Lonestar shareholders and the assumption of approximately CAD $21.3 million ( $16.8 million USD) in outstanding debt, which Clean Harbors subsequently repaid. The acquisition supports the Company's growth in the daylighting and hydro excavation services markets. In addition to increasing the size of the Company's hydro vac fleet, Lonestar's network of locations provides the Company with direct access to key geographic markets in both the United States and Canada. The acquired company is included in the Environmental Services segment. In connection with this acquisition, a goodwill amount of $ 2.8 million was recognized. On January 31, 2017, the Company acquired a privately held company for a purchase price of approximately $ 11.9 million in cash, net of cash acquired. The acquired business produces and distributes oil products and therefore complements the Company's closed loop model as it relates to the sale of its oil products. The acquired company is included in the Safety-Kleen segment. In connection with this acquisition, a goodwill amount of $ 5.0 million was recognized. Pro forma revenue and earnings amounts on a combined basis as if these acquisitions had been completed on January 1, 2017 are immaterial to the consolidated financial statements of the Company since that date.

DISPOSITION OF BUSINESS

DISPOSITION OF BUSINESS	6 Months Ended
	Jun. 30, 2018
Discontinued Operations and Disposal Groups [Abstract]
DISPOSITION OF BUSINESS	DISPOSITION OF BUSINESS On June 30, 2017, the Company completed the sale of its Transformer Services business, as part of its continuous focus on improving or divesting certain non-core operations. The sale price was $45.5 million . The Transformer Services business was a non-core business previously included within the legacy Technical Services operating segment. The following table presents income attributable to the Transformer Services business included in the Company's consolidated results of operations for the three and six months ended June 30, 2017 (in thousands): Three Months Ended Six Months Ended June 30, 2017 June 30, 2017 Income before provision for income taxes $ 1,873 $ 2,771

INVENTORIES AND SUPPLIES

INVENTORIES AND SUPPLIES	6 Months Ended
	Jun. 30, 2018
Inventory Disclosure [Abstract]
INVENTORIES AND SUPPLIES	INVENTORIES AND SUPPLIES Inventories and supplies consisted of the following (in thousands): June 30, 2018 December 31, 2017 Oil and oil products $ 68,125 $ 58,142 Supplies and drums 100,118 94,242 Solvent and solutions 9,230 9,167 Modular camp accommodations 2,494 1,826 Other 13,577 12,635 Total inventories and supplies $ 193,544 $ 176,012 As of June 30, 2018 and December 31, 2017 , other inventories consisted primarily of parts washer components, cleaning fluids, absorbents and automotive fluids, such as windshield washer fluid and antifreeze. Supplies and drums consisted primarily of drums and containers as well as critical spare parts to support the Company's incinerator and re-refinery operations.

PROPERTY, PLANT AND EQUIPMENT

PROPERTY, PLANT AND EQUIPMENT	6 Months Ended
	Jun. 30, 2018
Property, Plant and Equipment [Abstract]
PROPERTY, PLANT AND EQUIPMENT	PROPERTY, PLANT AND EQUIPMENT Property, plant and equipment consisted of the following (in thousands): June 30, 2018 December 31, 2017 Land $ 123,984 $ 121,658 Asset retirement costs (non-landfill) 14,780 14,593 Landfill assets 145,068 144,539 Buildings and improvements 429,880 414,384 Camp equipment 161,899 170,012 Vehicles 689,846 617,959 Equipment 1,675,920 1,644,102 Furniture and fixtures 5,623 5,708 Construction in progress 39,569 57,618 3,286,569 3,190,573 Less - accumulated depreciation and amortization 1,677,187 1,603,208 Total property, plant and equipment, net $ 1,609,382 $ 1,587,365 Interest in the amount of $0.1 million and $0.4 million was capitalized to property, plant and equipment during the three and six months ended June 30, 2018 , respectively. Interest in the amount of $0.1 million and $0.2 million was capitalized to property, plant and equipment during the three and six months ended June 30, 2017 , respectively. Depreciation expense, inclusive of landfill amortization, was $64.2 million and $129.8 million for the three and six months ended June 30, 2018 , respectively. Depreciation expense, inclusive of landfill amortization, was $61.8 million and $125.2 million for the three and six months ended June 30, 2017 , respectively.

GOODWILL AND OTHER INTANGIBLE A

GOODWILL AND OTHER INTANGIBLE ASSETS	6 Months Ended
	Jun. 30, 2018
Goodwill and Intangible Assets Disclosure [Abstract]
GOODWILL AND OTHER INTANGIBLE ASSETS	GOODWILL AND OTHER INTANGIBLE ASSETS The changes in goodwill by segment for the six months ended June 30, 2018 were as follows (in thousands): Environmental Services Safety-Kleen Totals Balance at January 1, 2018 $ 172,386 $ 306,137 $ 478,523 Increase from current period acquisition 21,626 — 21,626 Measurement period adjustments from prior period acquisitions (78 ) — (78 ) Foreign currency translation (1,305 ) (1,515 ) (2,820 ) Balance at June 30, 2018 $ 192,629 $ 304,622 $ 497,251 The Company assesses goodwill for impairment on an annual basis as of December 31, or at an interim date when events or changes in the business environment would more likely than not reduce the fair value of a reporting unit below its carrying value. As discussed in Note 18, “Segment Reporting,” during the first quarter of fiscal year 2018 and as a result of operational and managerial changes in several of the Company’s businesses, the identification of operating segments in accordance with ASC 280, Segment Information , was changed. As a result of the Company's conclusions around the identification of operating segments, the Company also concluded that, for purposes of reviewing for potential goodwill impairment, it now has four reporting units, consisting of Environmental Sales and Service, Environmental Facilities, Kleen Performance Products and Safety-Kleen Environmental Services. The Company allocated goodwill to the newly identified reporting units using a relative fair value approach. In addition, the Company completed an assessment of any potential goodwill impairment for all reporting units immediately prior and subsequent to the reallocation and determined that no impairment existed. As of June 30, 2018 and December 31, 2017 , the Company's total finite-lived and indefinite-lived intangible assets consisted of the following (in thousands): June 30, 2018 December 31, 2017 Cost Accumulated Net Cost Accumulated Net Permits $ 175,317 $ 76,707 $ 98,610 $ 174,721 $ 74,347 $ 100,374 Customer and supplier relationships 399,012 170,866 228,146 399,224 158,972 240,252 Other intangible assets 37,431 31,107 6,324 36,766 31,592 5,174 Total amortizable permits and other intangible assets 611,760 278,680 333,080 610,711 264,911 345,800 Indefinite lived trademarks and trade names 122,840 — 122,840 123,328 — 123,328 Total permits and other intangible assets $ 734,600 $ 278,680 $ 455,920 $ 734,039 $ 264,911 $ 469,128 Amortization expense of permits and other intangible assets was $8.6 million and $17.8 million in the three and six months ended June 30, 2018 , respectively. Amortization expense of permits and other intangible assets was $9.7 million and $18.8 million in the three and six months ended June 30, 2017 , respectively. The expected amortization of the net carrying amount of finite-lived intangible assets at June 30, 2018 was as follows (in thousands): Years Ending December 31, Expected Amortization 2018 (six months) $ 16,927 2019 32,143 2020 29,850 2021 27,381 2022 27,222 Thereafter 199,557 $ 333,080

ACCRUED EXPENSES

ACCRUED EXPENSES	6 Months Ended
	Jun. 30, 2018
Payables and Accruals [Abstract]
ACCRUED EXPENSES	ACCRUED EXPENSES Accrued expenses consisted of the following at June 30, 2018 and December 31, 2017 (in thousands): June 30, 2018 December 31, 2017 Insurance $ 68,701 $ 57,889 Interest 12,693 12,660 Accrued compensation and benefits 56,073 55,861 Income, real estate, sales and other taxes 27,116 27,330 Other 35,552 34,242 $ 200,135 $ 187,982

CLOSURE AND POST-CLOSURE LIABIL

CLOSURE AND POST-CLOSURE LIABILITIES	6 Months Ended
	Jun. 30, 2018
Asset Retirement Obligation Disclosure [Abstract]
CLOSURE AND POST-CLOSURE LIABILITIES	CLOSURE AND POST-CLOSURE LIABILITIES The changes to closure and post-closure liabilities (also referred to as “asset retirement obligations”) from January 1, 2018 through June 30, 2018 were as follows (in thousands): Landfill Non-Landfill Total Balance at January 1, 2018 $ 32,382 $ 28,655 $ 61,037 Liabilities assumed in acquisition — 604 604 New asset retirement obligations 1,478 — 1,478 Accretion 1,284 1,245 2,529 Changes in estimates recorded to statement of operations — 85 85 Changes in estimates recorded to balance sheet 430 — 430 Expenditures (359 ) (88 ) (447 ) Currency translation and other (127 ) (85 ) (212 ) Balance at June 30, 2018 $ 35,088 $ 30,416 $ 65,504 All of the landfill facilities included in the above were active as of June 30, 2018 . There were no significant charges (benefits) in 2018 resulting from changes in estimates for closure and post-closure liabilities. New asset retirement obligations incurred during the first six months of 2018 were discounted at the credit-adjusted risk-free rate of 5.66% .

REMEDIAL LIABILITIES

REMEDIAL LIABILITIES	6 Months Ended
	Jun. 30, 2018
Environmental Remediation Obligations [Abstract]
REMEDIAL LIABILITIES	REMEDIAL LIABILITIES The changes to remedial liabilities for the six months ended June 30, 2018 were as follows (in thousands): Remedial Liabilities for Landfill Sites Remedial Liabilities for Inactive Sites Remedial Liabilities (Including Superfund) for Non-Landfill Operations Total Balance at January 1, 2018 $ 1,800 $ 65,342 $ 57,326 $ 124,468 Accretion 43 1,375 931 2,349 Changes in estimates recorded to statement of operations — 83 (841 ) (758 ) Expenditures (23 ) (1,939 ) (2,176 ) (4,138 ) Currency translation and other — 882 (1,528 ) (646 ) Balance at June 30, 2018 $ 1,820 $ 65,743 $ 53,712 $ 121,275 In the six months ended June 30, 2018 , there were no significant charges (benefits) resulting from changes in estimates for remedial liabilities.

FINANCING ARRANGEMENTS

FINANCING ARRANGEMENTS	6 Months Ended
	Jun. 30, 2018
Debt Disclosure [Abstract]
FINANCING ARRANGEMENTS	FINANCING ARRANGEMENTS The following table is a summary of the Company’s financing arrangements (in thousands): June 30, 2018 December 31, 2017 Senior secured Term Loan Agreement ("Term Loan Agreement") $ 4,000 $ 4,000 Current portion of long-term obligations, at carrying value $ 4,000 $ 4,000 Senior secured Term Loan Agreement due June 30, 2024 $ 392,000 $ 394,000 Senior unsecured notes, at 5.25%, due August 1, 2020 ("2020 Notes") 400,000 400,000 Senior unsecured notes, at 5.125%, due June 1, 2021 ("2021 Notes") 845,000 845,000 Long-term obligations, at par $ 1,637,000 $ 1,639,000 Unamortized debt issuance costs and premium, net (12,273 ) (13,463 ) Long-term obligations, at carrying value $ 1,624,727 $ 1,625,537 Total current and long-term obligations, at carrying value $ 1,628,727 $ 1,629,537 On April 17, 2018, the Company, and substantially all of the Company's domestic subsidiaries as guarantors, entered into the first amendment (“First Amendment”) of the Term Loan Agreement. The First Amendment reduced the applicable interest rate margin for the Company’s initial term loans outstanding (the "Term Loans") under the Term Loan Agreement by 25 basis points for both Eurocurrency borrowings and base rate borrowings. After giving effect to the repricing, the applicable interest rate margin for the Term Loans are 1.75% for Eurocurrency borrowings and 0.75% for base rate borrowings. On July 19, 2018, the Company, and substantially all of the Company’s domestic subsidiaries as guarantors, entered into an Incremental Facility Amendment (the “Incremental Facility Amendment”) to the Company’s existing Term Loan Agreement. The Incremental Facility Amendment increases the principal amount of the initial term loans (the “Initial Term Loans”) outstanding under the Term Loan Agreement by $350.0 million and, as a result of such increase, an aggregate of $746.0 million of principal was outstanding at July 19, 2018. Initial Term Loans under the Term Loan Agreement will mature on June 30, 2024 and may be prepaid at any time without premium or penalty other than customary breakage costs with respect to Eurodollar based loans or if the Company engages in certain repricing transactions before January 19, 2019, in which event a 1.0% prepayment premium would be due. The Company’s obligations under the Term Loan Agreement are guaranteed by all of the Company’s domestic restricted subsidiaries and secured by liens on substantially all of the assets of the Company and the guarantors. Concurrently with the closing on July 19, 2018 of the Incremental Facility Amendment, the Company purchased $322.0 million aggregate principal of 2020 Notes. Total amount paid in purchasing the 2020 Notes was $330.9 including $7.9 million of accrued interest. On August 1, 2018, the Company redeemed the remaining $78.0 million outstanding 2020 Notes. In connection with the redemption of the $78.0 million of 2020 Notes, the Company borrowed $50.0 million under the Company's revolving credit facility. At June 30, 2018 and December 31, 2017 , the fair value of the Term Loans was $394.5 million and $400.5 million , respectively, based on quoted market prices or other available market data. At June 30, 2018 and December 31, 2017 , the fair value of the Company's 2020 Notes was $400.9 million and $404.6 million , respectively, based on quoted market prices for the instrument. At June 30, 2018 and December 31, 2017 , the fair value of the Company's 2021 Notes was $848.6 million and $855.7 million , respectively, based on quoted market prices for the instrument. The fair values of the Term Loans, 2020 Notes and 2021 Notes are considered Level 2 measures according to the fair value hierarchy. The Company also maintains a $400.0 million revolving credit facility under which the Company had no outstanding loan balances as of June 30, 2018 and December 31, 2017 . At June 30, 2018 , approximately $244.3 million was available to borrow and outstanding letters of credit were $132.4 million . At December 31, 2017 , $217.8 million was available to borrow and outstanding letters of credit were $134.1 million .

EARNINGS PER SHARE

EARNINGS PER SHARE	6 Months Ended
	Jun. 30, 2018
Earnings Per Share [Abstract]
EARNINGS PER SHARE	EARNINGS PER SHARE The following are computations of basic and diluted earnings per share (in thousands except for per share amounts): Three Months Ended Six Months Ended June 30, June 30, 2018 2017 2018 2017 Numerator for basic and diluted earnings per share: Net income $ 30,747 $ 25,880 $ 18,116 $ 4,487 Denominator: Basic shares outstanding 56,410 57,190 56,304 57,226 Dilutive effect of equity-based compensation awards 95 146 95 123 Dilutive shares outstanding 56,505 57,336 56,399 57,349 Basic income per share: $ 0.55 $ 0.45 $ 0.32 $ 0.08 Diluted income per share: $ 0.54 $ 0.45 $ 0.32 $ 0.08 For the three months ended June 30, 2018 and June 30, 2017 , the dilutive effect of all then outstanding restricted stock and performance awards is included in the EPS calculation above except for 146,159 and 142,503 of performance stock awards for which the performance criteria were not attained at that time and 136,155 and 14,699 , respectively, of restricted stock awards which were antidilutive at that time. For the six months ended June 30, 2018 and June 30, 2017 , the dilutive effect of all then outstanding restricted stock and performance awards is included in the EPS calculation above except for 146,159 and 142,503 of performance stock awards for which the performance criteria were not attained at that time and 130,932 and 21,013 , respectively, of restricted stock awards which were antidilutive at that time.

ACCUMULATED OTHER COMPREHENSIVE

ACCUMULATED OTHER COMPREHENSIVE LOSS	6 Months Ended
	Jun. 30, 2018
Equity [Abstract]
ACCUMULATED OTHER COMPREHENSIVE LOSS	ACCUMULATED OTHER COMPREHENSIVE LOSS The changes in accumulated other comprehensive loss by component and related tax effects for the six months ended June 30, 2018 were as follows (in thousands): Foreign Currency Translation Unrealized Losses on Available-For-Sale Securities Unfunded Pension Liability Total Balance at January 1, 2018 $ (170,575 ) $ (146 ) $ (1,686 ) $ (172,407 ) Other comprehensive loss before tax effects (27,091 ) (118 ) — (27,209 ) Tax effects 5,609 (88 ) — 5,521 Other comprehensive loss $ (21,482 ) $ (206 ) $ — $ (21,688 ) Balance at June 30, 2018 $ (192,057 ) $ (352 ) $ (1,686 ) $ (194,095 )

STOCK-BASED COMPENSATION

STOCK-BASED COMPENSATION	6 Months Ended
	Jun. 30, 2018
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
STOCK-BASED COMPENSATION	STOCK-BASED COMPENSATION Total stock-based compensation cost charged to selling, general and administrative expenses for the three and six months ended June 30, 2018 was $3.5 million and $6.6 million , respectively. Total stock-based compensation cost charged to selling, general and administrative expenses for the three and six months ended June 30, 2017 was $2.9 million and $5.2 million , respectively. The total income tax benefit recognized in the consolidated statements of operations from stock-based compensation was $0.7 million and $1.3 million for the three and six months ended June 30, 2018 , respectively. The total income tax benefit recognized in the consolidated statements of operations from stock-based compensation was $0.8 million and $1.5 million for the three and six months ended June 30, 2017 , respectively. Restricted Stock Awards The following information relates to restricted stock awards that have been granted to employees and directors under the Company's equity incentive plans (the "Plans"). The restricted stock awards are not transferable until vested and the restrictions generally lapse upon the achievement of continued employment over a three -to- five -year period or service as a director until the following annual meeting of shareholders. The fair value of each restricted stock grant is based on the closing price of the Company's common stock on the date of grant and is amortized to expense over its vesting period. The following table summarizes information about restricted stock awards for the six months ended June 30, 2018 : Restricted Stock Number of Shares Weighted Average Grant-Date Fair Value Balance at January 1, 2018 604,933 $ 54.23 Granted 200,688 $ 52.92 Vested (152,283 ) $ 54.65 Forfeited (17,136 ) $ 53.63 Balance at June 30, 2018 636,202 $ 53.73 As of June 30, 2018 , there was $27.1 million of total unrecognized compensation cost arising from restricted stock awards under the Company's Plans. This cost is expected to be recognized over a weighted average period of 2.7 years. The total fair value of restricted stock vested during the three and six months ended June 30, 2018 was $7.0 million and $8.3 million , respectively. The total fair value of restricted stock vested during the three and six months ended June 30, 2017 was $4.5 million and $6.0 million , respectively. Performance Stock Awards The following information relates to performance stock awards that have been granted to employees under the Company's Plans. Performance stock awards are subject to performance criteria established by the compensation committee of the Company's board of directors prior to or at the date of grant. The vesting of the performance stock awards is based on achieving such targets typically based on revenue, Adjusted EBITDA margin, Adjusted Free Cash Flow and Total Recordable Incident Rate. In addition, performance stock awards include continued service conditions. The fair value of each performance stock award is based on the closing price of the Company's common stock on the date of grant and is amortized to expense over the service period if achievement of performance measures is considered probable. The following table summarizes information about performance stock awards for the six months ended June 30, 2018 : Performance Stock Number of Shares Weighted Average Grant-Date Fair Value Balance at January 1, 2018 190,129 $ 55.63 Vested (8,696 ) $ 54.26 Forfeited (12,889 ) $ 55.09 Balance at June 30, 2018 168,544 $ 55.75 As of June 30, 2018 , there was $1.3 million of total unrecognized compensation cost arising from unvested performance stock awards deemed probable of vesting under the Company's Plans. No performance awards vested during the three months ended June 30, 2018 . The total fair value of performance awards vested during six months ended June 30, 2018 was $0.5 million . No performance awards vested during the three months ended June 30, 2017 . The total fair value of performance awards vested during the six months ended June 30, 2017 was $1.4 million . Common Stock Repurchases On October 31, 2017, the Company's board of directors increased the size of the Company’s current share repurchase program from $300 million to $600 million . During the three and six months ended June 30, 2018 , the Company repurchased and retired a total of 0.2 million shares and 0.5 million shares, respectively, of the Company's common stock for a total cost of $12.2 million and $26.5 million , respectively. During the three and six months ended June 30, 2017 , the Company repurchased and retired a total of 0.1 million and 0.2 million , respectively, of the Company's common stock for a total cost of $5.5 million and $12.3 million , respectively. Through June 30, 2018 , the Company has repurchased and retired a total of 5.3 million shares of the Company's common stock for a total cost of $275.3 million under this program. As of June 30, 2018 , an additional $324.7 million remained available for repurchase of shares under the current authorized program.

COMMITMENTS AND CONTINGENCIES

COMMITMENTS AND CONTINGENCIES	6 Months Ended
	Jun. 30, 2018
Commitments and Contingencies Disclosure [Abstract]
COMMITMENTS AND CONTINGENCIES	COMMITMENTS AND CONTINGENCIES Legal and Administrative Proceedings The Company and its subsidiaries are subject to legal proceedings and claims arising in the ordinary course of business. Actions filed against the Company arise from commercial and employment-related claims including alleged class actions related to sales practices and wage and hour claims. The plaintiffs in these actions may be seeking damages or injunctive relief or both. These actions are in various jurisdictions and stages of proceedings, and some are covered in part by insurance. In addition, the Company’s waste management services operations are regulated by federal, state, provincial and local laws enacted to regulate discharge of materials into the environment, remediation of contaminated soil and groundwater or otherwise protect the environment. This ongoing regulation results in the Company frequently becoming a party to legal or administrative proceedings involving all levels of governmental authorities and other interested parties. The issues involved in such proceedings generally relate to alleged violations of existing permits and licenses or alleged responsibility under federal or state Superfund laws to remediate contamination at properties owned either by the Company or by other parties (“third party sites”) to which either the Company or the prior owners of certain of the Company’s facilities shipped wastes. At June 30, 2018 and December 31, 2017 , the Company had recorded reserves of $21.6 million and $19.3 million , respectively, in the Company's financial statements for actual or probable liabilities related to the legal and administrative proceedings in which the Company was then involved, the principal of which are described below. At June 30, 2018 and December 31, 2017 , the Company also believed that it was reasonably possible that the amount of these potential liabilities could be as much as $1.7 million and $1.8 million more, respectively. The Company periodically adjusts the aggregate amount of these reserves when actual or probable liabilities are paid or otherwise discharged, new claims arise, or additional relevant information about existing or probable claims becomes available. As of June 30, 2018 and December 31, 2017 , the $21.6 million and $19.3 million , respectively, of reserves consisted of (i) $17.0 million and $17.9 million , respectively, related to pending legal or administrative proceedings, including Superfund liabilities, which were included in remedial liabilities on the consolidated balance sheets, and (ii) $4.6 million and $1.4 million , respectively, primarily related to federal, state and provincial enforcement actions, which were included in accrued expenses on the consolidated balance sheets. As of June 30, 2018 , the principal legal and administrative proceedings in which the Company was involved, or which had been terminated during 2018 , were as follows: Ville Mercier. In September 2002, the Company acquired the stock of a subsidiary (the "Mercier Subsidiary") which owns a hazardous waste incinerator in Ville Mercier, Quebec (the "Mercier Facility"). The property adjacent to the Mercier Facility, which is also owned by the Mercier Subsidiary, is now contaminated as a result of actions dating back to 1968, when the Government of Quebec issued to a company unrelated to the Mercier Subsidiary two permits to dump organic liquids into lagoons on the property. In 1999, Ville Mercier and three neighboring municipalities filed separate legal proceedings against the Mercier Subsidiary and the Government of Quebec. In 2012, the municipalities amended their existing statement of claim to seek $2.9 million (CAD) in general damages and $10.0 million (CAD) in punitive damages, plus interest and costs, as well as injunctive relief. Both the Government of Quebec and the Company have filed summary judgment motions against the municipalities. The parties are currently attempting to negotiate a resolution and hearings on the motions have been delayed. In September 2007, the Quebec Minister of Sustainable Development, Environment and Parks issued a Notice pursuant to Section 115.1 of the Environment Quality Act, superseding Notices issued in 1992, which are the subject of the pending litigation. The more recent Notice notifies the Mercier Subsidiary that, if the Mercier Subsidiary does not take certain remedial measures at the site, the Minister intends to undertake those measures at the site and claim direct and indirect costs related to such measures. The Company has accrued for costs expected to be incurred relative to the resolution of this matter and believes this matter will not have future material effect on its financial position or results of operations. Safety-Kleen Legal Proceedings. On December 28, 2012, the Company acquired Safety-Kleen, Inc. ("Safety-Kleen") and thereby became subject to the legal proceedings in which Safety-Kleen was a party on that date. In addition to certain Superfund proceedings in which Safety-Kleen has been named as a potentially responsible party as described below under “Superfund Proceedings,” the principal such legal proceedings involving Safety-Kleen which were outstanding as of June 30, 2018 were as follows: Product Liability Cases. Safety-Kleen has been named as a defendant in various lawsuits that are currently pending in various courts and jurisdictions throughout the United States, including approximately 60 proceedings (excluding cases which have been settled but not formally dismissed) as of June 30, 2018 , wherein persons claim personal injury resulting from the use of Safety-Kleen's parts cleaning equipment or cleaning products. These proceedings typically involve allegations that the solvent used in Safety-Kleen's parts cleaning equipment contains contaminants and/or that Safety-Kleen's recycling process does not effectively remove the contaminants that become entrained in the solvent during their use. In addition, certain claimants assert that Safety-Kleen failed to warn adequately the product user of potential risks, including a historic failure to warn that solvent contains trace amounts of toxic or hazardous substances such as benzene. Safety-Kleen maintains insurance that it believes will provide coverage for these product liability claims (over amounts accrued for self-insured retentions and deductibles in certain limited cases), except for punitive damages to the extent not insurable under state law or excluded from insurance coverage. Safety-Kleen also believes that these claims lack merit and has historically vigorously defended, and intends to continue to vigorously defend, itself and the safety of its products against all of these claims. Such matters are subject to many uncertainties and outcomes are not predictable with assurance. Consequently, Safety-Kleen is unable to ascertain the ultimate aggregate amount of monetary liability or financial impact with respect to these matters as of June 30, 2018 . From January 1, 2018 to June 30, 2018 , three product liability claims were settled or dismissed. Due to the nature of these claims and the related insurance, the Company did not incur any expense as Safety-Kleen's insurance provided coverage in full for all such claims. Safety-Kleen may be named in similar, additional lawsuits in the future, including claims for which insurance coverage may not be available. Superfund Proceedings The Company has been notified that either the Company (which, since December 28, 2012, includes Safety-Kleen) or the prior owners of certain of the Company's facilities for which the Company may have indemnification obligations have been identified as potentially responsible parties ("PRPs") or potential PRPs in connection with 127 sites which are subject to or are proposed to become subject to proceedings under federal or state Superfund laws. Of the 127 sites, three (including the BR Facility described below) involve facilities that are now owned or leased by the Company and 124 involve third party sites to which either the Company or the prior owners of certain of the Company’s facilities shipped wastes. Of the 124 third party sites, 34 are now settled, 17 are currently requiring expenditures on remediation and 73 are not currently requiring expenditures on remediation. In connection with each site, the Company has estimated the extent, if any, to which it may be subject, either directly or as a result of any indemnification obligations, for cleanup and remediation costs, related legal and consulting costs associated with PRP investigations, settlements, and related legal and administrative proceedings. The amount of such actual and potential liability is inherently difficult to estimate because of, among other relevant factors, uncertainties as to the legal liability (if any) of the Company or the prior owners of certain of the Company's facilities to contribute a portion of the cleanup costs, the assumptions that must be made in calculating the estimated cost and timing of remediation, the identification of other PRPs and their respective capability and obligation to contribute to remediation efforts, and the existence and legal standing of indemnification agreements (if any) with prior owners, which may either benefit the Company or subject the Company to potential indemnification obligations. The Company believes its potential liability could exceed $100,000 at 10 of the 124 third party sites. BR Facility. The Company acquired in 2002 a former hazardous waste incinerator and landfill in Baton Rouge (the "BR Facility"), for which operations had been previously discontinued by the prior owner. In September 2007, the Environmental Protection Agency (the "EPA") issued a special notice letter to the Company related to the Devil's Swamp Lake Site ("Devil's Swamp") in East Baton Rouge Parish, Louisiana. Devil's Swamp includes a lake located downstream of an outfall ditch where wastewater and storm water have been discharged, and Devil's Swamp is proposed to be included on the National Priorities List due to the presence of Contaminants of Concern ("COC") cited by the EPA. These COCs include substances of the kind found in wastewater and storm water discharged from the BR Facility in past operations. The EPA originally requested COC generators to submit a good faith offer to conduct a remedial investigation feasibility study directed towards the eventual remediation of the site. The Company is currently performing corrective actions at the BR Facility under an order issued by the Louisiana Department of Environmental Quality, and has begun conducting the remedial investigation and feasibility study under an order issued by the EPA. The Company cannot presently estimate the potential additional liability for the Devil's Swamp cleanup until a final remedy is selected by the EPA. Third Party Sites. Of the 124 third party sites at which the Company has been notified it is a PRP or potential PRP or may have indemnification obligations, Clean Harbors has an indemnification agreement at 11 of these sites with ChemWaste, a former subsidiary of Waste Management, Inc., and at six additional of these third party sites, Safety-Kleen has a similar indemnification agreement with McKesson Corporation. These agreements indemnify the Company (which now includes Safety-Kleen) with respect to any liability at the 17 sites for waste disposed prior to the Company's (or Safety-Kleen's) acquisition of the former subsidiaries of Waste Management and McKesson which had shipped wastes to those sites. Accordingly, Waste Management or McKesson are paying all costs of defending those subsidiaries in those 17 cases, including legal fees and settlement costs. However, there can be no guarantee that the Company's ultimate liabilities for those sites will not exceed the amount recorded or that indemnities applicable to any of these sites will be available to pay all or a portion of related costs. Except for the indemnification agreements which the Company holds from ChemWaste, McKesson and one other entity, the Company does not have an indemnity agreement with respect to any of the 124 third party sites discussed above. Federal, State and Provincial Enforcement Actions From time to time, the Company pays fines or penalties in regulatory proceedings relating primarily to waste treatment, storage or disposal facilities. As of June 30, 2018 and December 31, 2017 , there were six and five , respectively, proceedings for which the Company reasonably believes that the sanctions could equal or exceed $100,000 . The Company believes that the fines or other penalties in these or any of the other regulatory proceedings will, individually or in the aggregate, not have a material effect on its financial condition, results of operations or cash flows.

INCOME TAXES

INCOME TAXES	6 Months Ended
	Jun. 30, 2018
Income Tax Disclosure [Abstract]
INCOME TAXES	INCOME TAXES The Company records a tax provision or benefit on an interim basis using an estimated annual effective tax rate. This rate is applied to the current period ordinary income or loss to determine the income tax provision or benefit allocated to the interim period. Losses from jurisdictions for which no benefit can be recognized and the income tax effects of unusual or infrequent items are excluded from the estimated annual effective tax rate and are recognized in the impacted interim period. The estimated annual effective tax rate may be significantly impacted by projected earnings mix by tax jurisdiction. Adjustments to the estimated annual effective income tax rate are recognized in the period when such estimates are revised. The Company’s effective tax rate for the three and six months ended June 30, 2018 was 30.8% and 48.0% compared to 47.3% and 85.2% for the same periods in 2017 . The variations in the effective income tax rates for the six months ended June 30, 2018 and the three and six months ended June 30, 2017 as compared to more customary relationships between pre-tax income and the provision for income taxes were primarily due to not recognizing income tax benefits from current operating losses related to certain Canadian entities during these periods. On December 22, 2017, the “Tax Cuts and Jobs Act” (the “Tax Act”) was signed into law, making significant changes to the federal tax law. Changes include, but are not limited to, a corporate tax rate decrease from 35% to 21% effective for tax years beginning after December 31, 2017, the transition of U.S. international taxation from a worldwide tax system to a territorial tax system, and a one-time transition tax on the mandatory deemed repatriation of cumulative foreign earnings as of December 31, 2017. The Company recognized its best estimate of the income tax effects of the 2017 Tax Act in the financial statements included in its 2017 Annual Report on Form 10-K in accordance with Staff Accounting Bulletin No. 118, which provides SEC staff guidance for the application of ASC Topic 740, Income Taxes, in the reporting period in which the 2017 Tax Act was signed into law. During the three and six months ended June 30, 2018, the Company did not recognize any changes to the provisional amounts recorded in its 2017 Annual Report on Form 10-K in connection with the 2017 Tax Act. The Company is continuing to evaluate the impact of the Tax Act on its business and the consolidated financial statements and will make any adjustments to its provisional amounts in subsequent reporting periods upon obtaining, preparing or analyzing additional information affecting the income tax effects initially reported as a provisional amount. Any subsequent adjustment to these amounts will be recorded to tax expense in the quarter of 2018 when the analysis is completed. As of June 30, 2018 and December 31, 2017 , the Company had recorded $5.0 million and $5.1 million , respectively, of liabilities for unrecognized tax benefits and $1.0 million and $0.9 million of interest, respectively. Due to expiring statute of limitation periods, the Company believes that total unrecognized tax benefits will decrease by $1.4 million within the next 12 months.

SEGMENT REPORTING

SEGMENT REPORTING	6 Months Ended
	Jun. 30, 2018
Segment Reporting [Abstract]
SEGMENT REPORTING	SEGMENT REPORTING Segment reporting is prepared on the same basis that the Company's chief executive officer, who is the Company's chief operating decision maker, manages the business, makes operating decisions and assesses performance. During the first quarter of fiscal year 2018, certain of the Company's businesses undertook a reorganization which included changes to the underlying business and management structures. The reorganization resulted in combining the Environmental Services businesses from an operational and management perspective and is expected to deepen customer relationships and allow for efficiencies across the Company's operations through the sharing of resources, namely labor and equipment which will reduce third party spend and promote the cross selling of such business offerings. In connection with this reorganization, the Company’s chief operating decision maker also requested changes in the information that he regularly reviews for purposes of allocating resources and assessing performance. These changes required a reconsideration of the Company’s operating segments in the first quarter of 2018 and resulted in a change in the Company’s assessment of its operating segments. Upon reconsideration of the identification of the Company’s operating segments, the Company concluded that there are now two operating segments for disclosure in accordance with ASC 280 Segment reporting; (i) the Environmental Services segment which consists of the Company’s historical Technical Services, Industrial Services, Field Services and Oil, Gas and Lodging businesses and (ii) the Safety-Kleen segment. Third-party revenue is revenue billed to outside customers by a particular segment. Direct revenue is revenue allocated to the segment providing the product or service. Intersegment revenues represent the sharing of third-party revenues among the segments based on products and services provided by each segment as if the products and services were sold directly to the third-party. The intersegment revenues are shown net. The negative intersegment revenues are due to more transfers out of customer revenues to other segments than transfers in of customer revenues from other segments. The operations not managed through the Company’s operating segments described above are recorded as “Corporate Items.” Corporate Items revenues consist of two different operations for which the revenues are insignificant. Corporate Items cost of revenues represents certain central services that are not allocated to the Company's operating segments for internal reporting purposes. Corporate Items selling, general and administrative expenses include typical corporate items such as legal, accounting and other items of a general corporate nature that are not allocated to the Company’s operating segments. The following table reconciles third party revenues to direct revenues for the three and six months ended June 30, 2018 and 2017 (in thousands): For the Three Months Ended June 30, 2018 For the Three Months Ended June 30, 2017 Third party revenues Intersegment revenues, net Corporate Items, net Direct revenues Third party revenues Intersegment revenues, net Corporate Items, net Direct revenues Environmental Services $ 519,916 $ 34,291 $ 607 $ 554,814 $ 449,631 $ 31,639 $ 320 $ 481,590 Safety-Kleen 328,715 (34,291 ) 11 294,435 302,956 (31,639 ) (2 ) 271,315 Corporate Items 509 — (618 ) (109 ) 201 — (318 ) (117 ) Total $ 849,140 $ — $ — $ 849,140 $ 752,788 $ — $ — $ 752,788 For the Six Months Ended June 30, 2018 For the Six Months Ended June 30, 2017 Third party revenues Intersegment revenues, net Corporate Items, net Direct revenues Third party revenues Intersegment revenues, net Corporate Items, net Direct revenues Environmental Services $ 959,604 $ 66,256 $ 1,401 $ 1,027,261 $ 845,538 $ 63,708 $ 1,240 $ 910,486 Safety-Kleen 638,633 (66,256 ) 22 572,399 595,857 (63,708 ) 1 532,150 Corporate Items 681 — (1,423 ) (742 ) 334 — (1,241 ) (907 ) Total $ 1,598,918 $ — $ — $ 1,598,918 $ 1,441,729 $ — $ — $ 1,441,729 The primary financial measure by which the Company evaluates the performance of its segments is "Adjusted EBITDA" which consists of net income plus accretion of environmental liabilities, depreciation and amortization, interest expense, net, loss on early extinguishment of debt, provision for income taxes and excludes gain on sale of business and other income (expense), net. Transactions between the segments are accounted for at the Company’s best estimate based on similar transactions with outside customers. The following table presents Adjusted EBITDA information used by management by reported segment (in thousands): For the Three Months Ended For the Six Months Ended June 30, June 30, 2018 2017 2018 2017 Adjusted EBITDA: Environmental Services $ 109,199 $ 94,832 $ 170,616 $ 155,022 Safety-Kleen 73,069 60,281 134,953 112,649 Corporate Items (42,707 ) (34,422 ) (77,743 ) (66,845 ) Total $ 139,561 $ 120,691 $ 227,826 $ 200,826 Reconciliation to Consolidated Statements of Operations: Accretion of environmental liabilities 2,448 2,416 4,878 4,706 Depreciation and amortization 72,760 71,531 147,604 143,943 Income from operations 64,353 46,744 75,344 52,177 Other (income) expense, net (846 ) 833 (547 ) 2,382 Loss on early extinguishment of debt — 6,045 — 6,045 Gain on sale of business — (31,722 ) — (31,722 ) Interest expense, net of interest income 20,769 22,492 41,039 45,068 Income before provision for income taxes $ 44,430 $ 49,096 $ 34,852 $ 30,404 The following table presents certain assets by reportable segment and in the aggregate (in thousands): June 30, 2018 Environmental Safety-Kleen Corporate Totals Property, plant and equipment, net $ 988,957 $ 555,124 $ 65,301 $ 1,609,382 Goodwill 192,629 304,622 — 497,251 Permits and other intangibles, net 96,165 359,755 — 455,920 Total assets $ 1,681,627 $ 1,436,014 $ 597,820 $ 3,715,461 December 31, 2017 Environmental Safety-Kleen Corporate Totals Property, plant and equipment, net $ 927,139 $ 582,162 $ 78,064 $ 1,587,365 Goodwill 172,386 306,137 — 478,523 Permits and other intangibles, net 97,519 371,609 — 469,128 Total assets $ 1,541,241 $ 1,471,291 $ 694,038 $ 3,706,570 The following table presents total assets by geographical area (in thousands): June 30, 2018 December 31, 2017 United States $ 3,041,509 $ 2,985,394 Canada 673,836 721,176 Other foreign 116 — Total $ 3,715,461 $ 3,706,570

GUARANTOR AND NON-GUARANTOR SUB

GUARANTOR AND NON-GUARANTOR SUBSIDIARIES FINANCIAL INFORMATION	6 Months Ended
	Jun. 30, 2018
Guarantor and Non-Guarantor Subsidiaries Financial Information [Abstract]
GUARANTOR AND NON-GUARANTOR SUBSIDIARIES FINANCIAL INFORMATION	GUARANTOR AND NON-GUARANTOR SUBSIDIARIES FINANCIAL INFORMATION The 2020 Notes and the 2021 Notes (collectively, the "Senior Unsecured Notes") and the Company's obligations under its Term Loan Agreement are guaranteed by substantially all of the Company’s subsidiaries organized in the United States. Each guarantor is a 100% owned subsidiary of Clean Harbors, Inc. and its guarantee is both full and unconditional and joint and several. The guarantees are, however, subject to customary release provisions under which, in particular, the guarantee of any domestic restricted subsidiary will be released if the Company sells such subsidiary to an unrelated third party in accordance with the terms of the indentures which govern the Senior Unsecured Notes and of the Term Loan Agreement. The Senior Unsecured Notes and the Company's obligations under its Term Loan Agreement are not guaranteed by the Company’s subsidiaries organized outside the United States. The following supplemental condensed consolidating financial information for the parent company, the guarantor subsidiaries and the non-guarantor subsidiaries, respectively, is presented in conformity with the requirements of Rule 3-10 of SEC Regulation S-X (“Rule 3-10”). Following is the condensed consolidating balance sheet at June 30, 2018 (in thousands): Clean Harbors, Inc. Guarantor Subsidiaries Non-Guarantor Subsidiaries Consolidating Adjustments Total Assets: Cash and cash equivalents $ 51,960 $ 92,833 $ 52,275 $ — $ 197,068 Short-term marketable securities — — 36,862 — 36,862 Intercompany receivables 250,206 651,218 61,125 (962,549 ) — Accounts receivable, net — 497,775 92,805 — 590,580 Other current assets — 260,489 60,225 (8,742 ) 311,972 Property, plant and equipment, net — 1,243,171 366,211 — 1,609,382 Investments in subsidiaries 3,135,271 599,091 — (3,734,362 ) — Intercompany debt receivable — 15,224 21,000 (36,224 ) — Goodwill — 437,229 60,022 — 497,251 Permits and other intangibles, net — 402,096 53,824 — 455,920 Other long-term assets 2,283 12,337 1,811 (5 ) 16,426 Total assets $ 3,439,720 $ 4,211,463 $ 806,160 $ (4,741,882 ) $ 3,715,461 Liabilities and Stockholders’ Equity: Current liabilities $ 16,627 $ 406,111 $ 129,672 $ (8,742 ) $ 543,668 Intercompany payables 637,318 309,423 15,808 (962,549 ) — Closure, post-closure and remedial liabilities, net — 146,922 16,850 — 163,772 Long-term obligations, net 1,624,727 — — — 1,624,727 Intercompany debt payable — 21,000 15,224 (36,224 ) — Other long-term liabilities — 200,999 21,252 (5 ) 222,246 Total liabilities 2,278,672 1,084,455 198,806 (1,007,520 ) 2,554,413 Stockholders’ equity 1,161,048 3,127,008 607,354 (3,734,362 ) 1,161,048 Total liabilities and stockholders’ equity $ 3,439,720 $ 4,211,463 $ 806,160 $ (4,741,882 ) $ 3,715,461 Following is the condensed consolidating balance sheet at December 31, 2017 (in thousands): Clean Harbors, Inc. Guarantor Subsidiaries Non-Guarantor Subsidiaries Consolidating Adjustments Total Assets: Cash and cash equivalents $ 51,638 $ 207,777 $ 59,984 $ — $ 319,399 Short-term marketable securities — — 38,179 — 38,179 Intercompany receivables 238,339 590,100 52,909 (881,348 ) — Accounts receivable, net — 433,042 95,882 — 528,924 Other current assets 897 233,602 52,947 (19,892 ) 267,554 Property, plant and equipment, net — 1,174,975 412,390 — 1,587,365 Investments in subsidiaries 3,112,547 569,568 — (3,682,115 ) — Intercompany debt receivable — 92,530 21,000 (113,530 ) — Goodwill — 415,641 62,882 — 478,523 Permits and other intangibles, net — 408,655 60,473 — 469,128 Other long-term assets 2,084 12,064 3,350 — 17,498 Total assets $ 3,405,505 $ 4,137,954 $ 859,996 $ (4,696,885 ) $ 3,706,570 Liabilities and Stockholders’ Equity: Current liabilities $ 16,954 $ 371,135 $ 135,620 $ (19,892 ) $ 503,817 Intercompany payables 574,812 289,531 17,005 (881,348 ) — Closure, post-closure and remedial liabilities, net — 148,872 16,851 — 165,723 Long-term obligations, net 1,625,537 — — — 1,625,537 Intercompany debt payable — 21,000 92,530 (113,530 ) — Other long-term liabilities — 201,086 22,205 — 223,291 Total liabilities 2,217,303 1,031,624 284,211 (1,014,770 ) 2,518,368 Stockholders’ equity 1,188,202 3,106,330 575,785 (3,682,115 ) 1,188,202 Total liabilities and stockholders’ equity $ 3,405,505 $ 4,137,954 $ 859,996 $ (4,696,885 ) $ 3,706,570 Following is the consolidating statement of operations for the three months ended June 30, 2018 (in thousands): Clean Harbors, Inc. Guarantor Subsidiaries Non-Guarantor Subsidiaries Consolidating Adjustments Total Revenues Service revenues $ — $ 544,521 $ 165,435 $ (13,177 ) $ 696,779 Product revenues — 137,891 17,363 (2,893 ) 152,361 Total revenues — 682,412 182,798 (16,070 ) 849,140 Cost of revenues (exclusive of items shown separately below) Service cost of revenues — 361,644 124,956 (13,177 ) 473,423 Product cost of revenues — 102,442 10,612 (2,893 ) 110,161 Total cost of revenues — 464,086 135,568 (16,070 ) 583,584 Selling, general and administrative expenses 133 105,022 20,840 — 125,995 Accretion of environmental liabilities — 2,194 254 — 2,448 Depreciation and amortization — 52,864 19,896 — 72,760 (Loss) income from operations (133 ) 58,246 6,240 — 64,353 Other income, net — 269 577 — 846 Interest (expense) income, net (21,216 ) 238 209 — (20,769 ) Equity in earnings of subsidiaries, net of taxes 46,118 2,230 — (48,348 ) — Intercompany interest income (expense) — 1,084 (1,084 ) — — Income before (benefit) provision for income taxes 24,769 62,067 5,942 (48,348 ) 44,430 (Benefit) provision for income taxes (5,978 ) 18,228 1,433 — 13,683 Net income 30,747 43,839 4,509 (48,348 ) 30,747 Other comprehensive loss (4,942 ) (4,942 ) (10,435 ) 15,377 (4,942 ) Comprehensive income (loss) $ 25,805 $ 38,897 $ (5,926 ) $ (32,971 ) $ 25,805 Following is the consolidating statement of operations for the three months ended June 30, 2017 (in thousands): Clean Harbors, Inc. Guarantor Subsidiaries Non-Guarantor Subsidiaries Consolidating Adjustments Total Revenues Service revenues $ — $ 474,801 $ 147,924 $ (11,785 ) $ 610,940 Product revenues — 125,859 18,730 (2,741 ) 141,848 Total revenues — 600,660 166,654 (14,526 ) 752,788 Cost of revenues (exclusive of items shown separately below) Service cost of revenues — 306,960 117,181 (11,785 ) 412,356 Product cost of revenues — 98,645 11,543 (2,741 ) 107,447 Total cost of revenues — 405,605 128,724 (14,526 ) 519,803 Selling, general and administrative expenses 27 92,504 19,763 — 112,294 Accretion of environmental liabilities — 2,181 235 — 2,416 Depreciation and amortization — 51,937 19,594 — 71,531 (Loss) income from operations (27 ) 48,433 (1,662 ) — 46,744 Other expense, net (76 ) (406 ) (351 ) — (833 ) Loss on early extinguishment of debt (6,045 ) — — — (6,045 ) Gain on sale of business — 31,722 — — 31,722 Interest (expense) income, net (22,614 ) 240 (118 ) — (22,492 ) Equity in earnings of subsidiaries, net of taxes 43,167 (5,332 ) — (37,835 ) — Intercompany interest income (expense) — 1,268 (1,268 ) — — Income (loss) before (benefit) provision for income taxes 14,405 75,925 (3,399 ) (37,835 ) 49,096 (Benefit) provision for income taxes (11,475 ) 31,981 2,710 — 23,216 Net income (loss) 25,880 43,944 (6,109 ) (37,835 ) 25,880 Other comprehensive income 15,098 15,098 12,837 (27,935 ) 15,098 Comprehensive income $ 40,978 $ 59,042 $ 6,728 $ (65,770 ) $ 40,978 Following is the consolidating statement of operations for the six months ended June 30, 2018 (in thousands): Clean Harbors, Inc. Guarantor Subsidiaries Non-Guarantor Subsidiaries Consolidating Adjustments Total Revenues Service revenues $ — $ 1,026,004 $ 317,836 $ (27,342 ) $ 1,316,498 Product revenues — 259,473 28,813 (5,866 ) 282,420 Total revenues — 1,285,477 346,649 (33,208 ) 1,598,918 Cost of revenues (exclusive of items shown separately below) Service cost of revenues — 689,824 258,590 (27,342 ) 921,072 Product cost of revenues — 197,480 17,323 (5,866 ) 208,937 Total cost of revenues — 887,304 275,913 (33,208 ) 1,130,009 Selling, general and administrative expenses 168 198,865 42,050 — 241,083 Accretion of environmental liabilities — 4,370 508 — 4,878 Depreciation and amortization — 106,568 41,036 — 147,604 (Loss) income from operations (168 ) 88,370 (12,858 ) — 75,344 Other income, net — 184 363 — 547 Interest (expense) income, net (42,215 ) 743 433 — (41,039 ) Equity in earnings of subsidiaries, net of taxes 48,632 (17,832 ) — (30,800 ) — Intercompany interest income (expense) — 2,445 (2,445 ) — — Income (loss) before (benefit) provision for income taxes 6,249 73,910 (14,507 ) (30,800 ) 34,852 (Benefit) provision for income taxes (11,867 ) 27,329 1,274 — 16,736 Net income (loss) 18,116 46,581 (15,781 ) (30,800 ) 18,116 Other comprehensive loss (21,688 ) (21,688 ) (24,442 ) 46,130 (21,688 ) Comprehensive (loss) income $ (3,572 ) $ 24,893 $ (40,223 ) $ 15,330 $ (3,572 ) Following is the consolidating statement of operations for the six months ended June 30, 2017 (in thousands): Clean Harbors, Inc. Guarantor Subsidiaries Non-Guarantor Subsidiaries Consolidating Adjustments Total Revenues Service revenues $ — $ 918,106 $ 278,995 $ (25,947 ) $ 1,171,154 Product revenues — 242,509 34,061 (5,995 ) 270,575 Total revenues — 1,160,615 313,056 (31,942 ) 1,441,729 Cost of revenues (exclusive of items shown separately below) Service cost of revenues — 601,105 228,285 (25,947 ) 803,443 Product cost of revenues — 195,150 23,790 (5,995 ) 212,945 Total cost of revenues — 796,255 252,075 (31,942 ) 1,016,388 Selling, general and administrative expenses 51 184,675 39,789 — 224,515 Accretion of environmental liabilities — 4,236 470 — 4,706 Depreciation and amortization — 103,837 40,106 — 143,943 (Loss) income from operations (51 ) 71,612 (19,384 ) — 52,177 Other expense, net (222 ) (1,795 ) (365 ) — (2,382 ) Loss on early extinguishment of debt (6,045 ) — — — (6,045 ) Gain on sale of business — 31,722 — — 31,722 Interest (expense) income, net (45,273 ) 359 (154 ) — (45,068 ) Equity in earnings of subsidiaries, net of taxes 35,530 (27,156 ) — (8,374 ) — Intercompany interest income (expense) — 2,565 (2,565 ) — — (Loss) income before (benefit) provision for income taxes (16,061 ) 77,307 (22,468 ) (8,374 ) 30,404 (Benefit) provision for income taxes (20,548 ) 41,618 4,847 — 25,917 Net income (loss) 4,487 35,689 (27,315 ) (8,374 ) 4,487 Other comprehensive income 21,149 21,149 17,869 (39,018 ) 21,149 Comprehensive income (loss) $ 25,636 $ 56,838 $ (9,446 ) $ (47,392 ) $ 25,636 Following is the condensed consolidating statement of cash flows for the six months ended June 30, 2018 (in thousands): Clean Harbors, Inc. Guarantor Subsidiaries Non-Guarantor Subsidiaries Consolidating Adjustments Total Net cash from operating activities $ 790 $ 121,021 $ 7,859 $ — $ 129,670 Cash flows used in investing activities: Additions to property, plant and equipment — (77,773 ) (16,366 ) — (94,139 ) Proceeds from sale and disposal of fixed assets — 1,035 1,606 — 2,641 Acquisitions, net of cash acquired — (123,750 ) — — (123,750 ) Additions to intangible assets, including costs to obtain or renew permits — (1,991 ) (115 ) — (2,106 ) Proceeds from sale of available-for-sale securities — — 11,214 — 11,214 Purchases of available-for-sale securities — — (10,001 ) — (10,001 ) Intercompany — (30,657 ) — 30,657 — Net cash used in investing activities — (233,136 ) (13,662 ) 30,657 (216,141 ) Cash flows (used in) from financing activities: Change in uncashed checks — (2,829 ) 26 — (2,803 ) Tax payments related to withholdings on vested restricted stock (2,175 ) — — — (2,175 ) Repurchases of common stock (26,482 ) — — — (26,482 ) Deferred financing costs paid (468 ) — — — (468 ) Principal payment on debt (2,000 ) — — — (2,000 ) Intercompany 30,657 — — (30,657 ) — Net cash (used) from in financing activities (468 ) (2,829 ) 26 (30,657 ) (33,928 ) Effect of exchange rate change on cash — — (1,932 ) — (1,932 ) Increase (decrease) in cash and cash equivalents 322 (114,944 ) (7,709 ) — (122,331 ) Cash and cash equivalents, beginning of period 51,638 207,777 59,984 — 319,399 Cash and cash equivalents, end of period $ 51,960 $ 92,833 $ 52,275 $ — $ 197,068 Following is the condensed consolidating statement of cash flows for the six months ended June 30, 2017 (in thousands): Clean Harbors, Inc. Guarantor Subsidiaries Non-Guarantor Subsidiaries Consolidating Adjustments Total Net cash (used in) from operating activities $ (93,808 ) $ 206,496 $ 4,243 $ — $ 116,931 Cash flows from (used in) investing activities: Additions to property, plant and equipment — (75,152 ) (13,590 ) — (88,742 ) Proceeds from sale and disposal of fixed assets — 984 1,137 — 2,121 Acquisitions, net of cash acquired — (9,277 ) — — (9,277 ) Proceeds from sale of businesses, net of transactional costs — 46,210 181 — 46,391 Additions to intangible assets, including costs to obtain or renew permits — (888 ) (351 ) — (1,239 ) Proceeds from sale of available-for-sale securities 376 — — — 376 Intercompany — (14,343 ) — 14,343 — Net cash from (used in) investing activities 376 (52,466 ) (12,623 ) 14,343 (50,370 ) Cash flows from (used in) financing activities: Change in uncashed checks — (5,977 ) (2,384 ) — (8,361 ) Proceeds from exercise of stock options 46 — — — 46 Tax payments related to withholdings on vested restricted stock (2,132 ) — — — (2,132 ) Repurchases of common stock (12,257 ) — — — (12,257 ) Deferred financing costs paid (4,727 ) — — — (4,727 ) Premium paid on early extinguishment of debt (4,665 ) — — — (4,665 ) Principal payment on debt (296,202 ) — — — (296,202 ) Issuance of senior secured notes, net of discount 399,000 — — — 399,000 Intercompany 14,343 — — (14,343 ) — Net cash from (used) in financing activities 93,406 (5,977 ) (2,384 ) (14,343 ) 70,702 Effect of exchange rate change on cash — — 2,106 — 2,106 (Decrease) increase in cash and cash equivalents (26 ) 148,053 (8,658 ) — 139,369 Cash and cash equivalents, beginning of period 51,417 155,943 99,637 — 306,997 Cash and cash equivalents, end of period $ 51,391 $ 303,996 $ 90,979 $ — $ 446,366

SIGNIFICANT ACCOUNTING POLICI30

SIGNIFICANT ACCOUNTING POLICIES (Policies)	6 Months Ended
	Jun. 30, 2018
Accounting Policies [Abstract]
Reclassifications	Reclassifications During the first quarter of fiscal year 2018, certain of the Company's businesses undertook a reorganization which included changes to the underlying business and management structures. The reorganization resulted in combining the Environmental Services businesses from an operational and management perspective and is expected to deepen customer relationships and allow for efficiencies across the Company's operations through the sharing of resources, namely labor and equipment which will reduce third party spend and promote the cross selling of such business offerings. In connection with this reorganization, the Company’s chief operating decision maker also requested changes in the information that he regularly reviews for purposes of allocating resources and assessing performance. These changes required a reconsideration of the Company’s operating segments in the first quarter of 2018 and resulted in a change in the Company’s assessment of its operating segments. Upon reconsideration of the identification of the Company’s operating segments, the Company concluded that there are now two operating segments for disclosure in accordance with ASC 280 Segment reporting; (i) the Environmental Services segment which consists of the Company’s historical Technical Services, Industrial Services, Field Services and Oil, Gas and Lodging businesses and (ii) the Safety-Kleen segment. See Note 18, " Segment Reporting ," for more information. The amounts presented for the three and six months ended June 30, 2017 have been recast to reflect the impact of such changes. These reclassifications and adjustments had no effect on the consolidated statements of operations, consolidated statements of comprehensive loss, consolidated statements of cash flows or consolidated statements of stockholders' equity for any of the periods presented.
Recent Accounting Pronouncements	Recent Accounting Pronouncements Standards implemented In May 2014, the Financial Accounting Standards Board ("FASB") issued ASU 2014-09, Revenue from Contracts with Customers (Topic 606) , which replaces numerous requirements in U.S. GAAP, including industry-specific requirements, and provides companies with a single revenue recognition model for recognizing revenue from contracts with customers. The guidance permits two methods of adoption: retrospectively to each prior reporting period presented (full retrospective method), or retrospectively with the cumulative effect of initially applying the guidance recognized at the date of initial application (the modified retrospective method). On January 1, 2018, the Company adopted Topic 606 using the modified retrospective method for all contracts. Results for reporting periods beginning on the date of adoption are presented under ASC 606, while prior period amounts have not been adjusted and continue to be reported in accordance with the Company's historical accounting methodology pursuant to ASC 605, Revenue Recognition (“ASC 605”). Upon adoption, a cumulative effect adjustment was not required as the majority of the Company’s contracts are recognized based on time and materials incurred and were not impacted by the new guidance. The Company has concluded that the most significant impact of the standard relates to the incremental disclosures required. In October 2016, the FASB issued ASU 2016-16, Income Tax - Intra-Entity Transfers of Assets Other than Inventory . The amendment improves the accounting for the income tax consequences of intra-entity transfers of assets other than inventory. The Company adopted the amendment on a modified retrospective basis effective January 1, 2018. As a result of adoption, the Company recorded a cumulative effect adjustment that reduced retained earnings by $1.6 million . In March 2017, the FASB issued ASU 2017-07, Compensation-Retirement Benefits (Topic 715): Improving the Presentation of Net Periodic Pension Cost and Net Periodic Postretirement Benefit Cost . The amendment requires an employer to report the service cost component of net benefit cost in the same line item as other compensation costs arising from services rendered by the pertinent employees during the period. The other components of net benefit cost are required to be presented in the income statement separately from the service cost component and outside a subtotal of income from operations. In addition, the amendment allows only the service cost component to be eligible for capitalization when applicable. The Company adopted the amendment in the first quarter of 2018. Adoption did not have a material impact on the Company's consolidated financial statements. Standards to be implemented The Company is evaluating the impact that the below standards to be implemented will have on the Company's consolidated financial statements. In February 2016, FASB issued ASU 2016-02, Leases (Topic 842) . The amendment increases transparency and comparability among organizations by recognizing lease assets and lease liabilities on the balance sheet and disclosing key information about leasing arrangements. In February 2018, FASB issued ASU 2018-01, Leases (Topic 842): Land Easement Practical Expedient for Transition to Topic 842 . The amendment clarifies that land easements are within the scope of the new leases standard (ASC 842) and introduces a new transition practical expedient allowing a company to not assess whether existing and expired land easements that were not previously accounted for as leases under current US GAAP (ASC 840) are or contain leases under ASC 842. In July 2018, FASB issued ASU 2018-10, Codification Improvements to Topic 842, Leases . The amendment provides improvements that clarify specific aspects of the guidance in ASU 2016-02. The Company will adopt the new standard beginning on January 1, 2019. A modified retrospective transition approach is required for leases existing at, or entered into after, the beginning of the earliest comparative period presented in the financial statements, with certain practical expedients available. While the Company is still continuing to assess the effect of adoption, it expects that the new standard will have a material effect on its consolidated balance sheet related to the recognition of new assets and lease liabilities. In preparation for the adoption of the guidance, the Company is in the process of implementing new software and assessing changes to controls and processes to enable the preparation of financial information. In June 2016, FASB issued ASU 2016-13, Financial Instruments—Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments . The amendment changes the way entities recognize impairment of many financial assets, including accounts receivable and investments in debt securities, by requiring immediate recognition of estimated credit losses expected to occur over their remaining lives. The amendment should be applied using a modified-retrospective approach and is effective for the Company for annual and interim reporting periods beginning after January 1, 2020, with early adoption permitted. The Company is currently evaluating the impact ASU 2016-13 will have on its consolidated financial statements. In August 2017, the FASB issued ASU 2017-12, Derivatives and Hedging (Topic 815): Targeted Improvements to Accounting for Hedging Activities. The amendment better aligns an entity’s risk management activities and financial reporting for hedging relationships through changes to both the designation and measurement guidance for qualifying hedging relationships and the presentation of hedge results. The amendment is effective for the Company for annual and interim reporting periods beginning after December 15, 2018, with early adoption permitted. The Company is currently evaluating the impact ASU 2017-12 will have on its consolidated financial statements.

REVENUES (Tables)

REVENUES (Tables)	6 Months Ended
	Jun. 30, 2018
Revenue from Contract with Customer [Abstract]
Disaggregation of Revenue	The following table presents the Company’s revenues disaggregated by revenue source (in thousands): For the Three Months Ended June 30, 2018 Environmental Services Safety-Kleen Corporate Total Primary Geographical Markets United States $ 408,127 $ 306,059 $ 363 $ 714,549 Canada 111,789 22,656 146 134,591 519,916 328,715 509 849,140 Sources of Revenue (1) Technical Services 257,006 — — $ 257,006 Field and Emergency Response Services 76,092 — — 76,092 Industrial Services 161,046 — — 161,046 Oil, Gas and Lodging Services and Other 25,772 — 509 26,281 Safety-Kleen Environmental Services — 200,034 — 200,034 Kleen Performance Products — 128,681 — 128,681 Total third party revenues $ 519,916 $ 328,715 $ 509 $ 849,140 For the Three Months Ended June 30, 2017 Environmental Services Safety-Kleen Corporate Total Primary Geographical Markets United States $ 343,323 $ 280,617 $ 155 $ 624,095 Canada 106,308 22,339 46 128,693 449,631 302,956 201 752,788 Sources of Revenue (1) Technical Services 254,487 — — 254,487 Field and Emergency Response Services 70,707 — — 70,707 Industrial Services 99,733 — — 99,733 Oil, Gas and Lodging Services and Other 24,704 — 201 24,905 Safety-Kleen Environmental Services — 192,817 — 192,817 Kleen Performance Products — 110,139 — 110,139 Total third party revenues $ 449,631 $ 302,956 $ 201 $ 752,788 For the Six Months Ended June 30, 2018 Environmental Services Safety-Kleen Corporate Total Primary Geographical Markets United States $ 752,099 $ 593,701 $ 508 $ 1,346,308 Canada 207,505 44,932 173 252,610 959,604 638,633 681 1,598,918 Sources of Revenue (1) Technical Services 493,312 — — 493,312 Field and Emergency Response Services 146,027 — — 146,027 Industrial Services 264,809 — — 264,809 Oil, Gas and Lodging Services and Other 55,456 — 681 56,137 Safety-Kleen Environmental Services — 394,195 — 394,195 Kleen Performance Products — 244,438 — 244,438 Total third party revenues $ 959,604 $ 638,633 $ 681 $ 1,598,918 For the Six Months Ended June 30, 2017 Environmental Services Safety-Kleen Corporate Total Primary Geographical Markets United States $ 657,106 $ 552,688 $ 288 $ 1,210,082 Canada 188,432 43,169 46 231,647 845,538 595,857 334 1,441,729 Sources of Revenue (1) Technical Services 484,705 — — 484,705 Field and Emergency Response Services 131,726 — — 131,726 Industrial Services 174,801 — — 174,801 Oil, Gas and Lodging Services and Other 54,306 — 334 54,640 Safety-Kleen Environmental Services — 384,544 — 384,544 Kleen Performance Products — 211,313 — 211,313 Total third party revenues $ 845,538 $ 595,857 $ 334 $ 1,441,729 ______________________ 1. All revenue except Kleen Performance Products and product sales within Safety-Kleen Environmental Services, including allied products and direct blended oil sales, are recognized over time. Kleen Performance Products and Safety-Kleen Environmental Services product revenues are recognized at a point in time.
Contract Balances	Contract Balances June 30, 2018 December 31, 2017 June 30, 2017 December 31, 2016 Receivables $ 590,580 $ 528,924 $ 512,375 $ 496,226 Contract Assets (Unbilled Receivables) 62,762 35,922 46,576 36,190 Contract Liabilities (Deferred Revenue) 68,705 67,822 72,089 64,397

BUSINESS COMBINATIONS (Tables)

BUSINESS COMBINATIONS (Tables)	6 Months Ended
	Jun. 30, 2018
Business Combinations [Abstract]
Schedule of Business Acquisitions, by Acquisition	The components and preliminary allocation of the purchase price consist of the following amounts (in thousands): At Acquisition Date Measurement Period Adjustments At Acquisition Date As Reported June 30, 2018 Accounts receivable, including unbilled receivables $ 40,773 $ (2,691 ) $ 38,082 Inventories and supplies 1,442 (316 ) 1,126 Prepaid expenses and other current assets 1,005 (80 ) 925 Property, plant and equipment 72,244 — 72,244 Permits and other intangibles 5,140 — 5,140 Current liabilities (15,908 ) (2,631 ) (18,539 ) Closure and post-closure liabilities (604 ) — (604 ) Total identifiable net assets 104,092 (5,718 ) 98,374 Goodwill 15,908 5,718 21,626 Total purchase price $ 120,000 $ — $ 120,000

DISPOSITION OF BUSINESS (Tables

DISPOSITION OF BUSINESS (Tables)	6 Months Ended
	Jun. 30, 2018
Discontinued Operations and Disposal Groups [Abstract]
Disposition of Business	The following table presents income attributable to the Transformer Services business included in the Company's consolidated results of operations for the three and six months ended June 30, 2017 (in thousands): Three Months Ended Six Months Ended June 30, 2017 June 30, 2017 Income before provision for income taxes $ 1,873 $ 2,771

INVENTORIES AND SUPPLIES (Table

INVENTORIES AND SUPPLIES (Tables)	6 Months Ended
	Jun. 30, 2018
Inventory Disclosure [Abstract]
Schedule of Inventory	Inventories and supplies consisted of the following (in thousands): June 30, 2018 December 31, 2017 Oil and oil products $ 68,125 $ 58,142 Supplies and drums 100,118 94,242 Solvent and solutions 9,230 9,167 Modular camp accommodations 2,494 1,826 Other 13,577 12,635 Total inventories and supplies $ 193,544 $ 176,012

PROPERTY, PLANT AND EQUIPMENT (

PROPERTY, PLANT AND EQUIPMENT (Tables)	6 Months Ended
	Jun. 30, 2018
Property, Plant and Equipment [Abstract]
Property, Plant and Equipment	Property, plant and equipment consisted of the following (in thousands): June 30, 2018 December 31, 2017 Land $ 123,984 $ 121,658 Asset retirement costs (non-landfill) 14,780 14,593 Landfill assets 145,068 144,539 Buildings and improvements 429,880 414,384 Camp equipment 161,899 170,012 Vehicles 689,846 617,959 Equipment 1,675,920 1,644,102 Furniture and fixtures 5,623 5,708 Construction in progress 39,569 57,618 3,286,569 3,190,573 Less - accumulated depreciation and amortization 1,677,187 1,603,208 Total property, plant and equipment, net $ 1,609,382 $ 1,587,365

GOODWILL AND OTHER INTANGIBLE36

GOODWILL AND OTHER INTANGIBLE ASSETS (Tables)	6 Months Ended
	Jun. 30, 2018
Goodwill and Intangible Assets Disclosure [Abstract]
Schedule of changes to goodwill	The changes in goodwill by segment for the six months ended June 30, 2018 were as follows (in thousands): Environmental Services Safety-Kleen Totals Balance at January 1, 2018 $ 172,386 $ 306,137 $ 478,523 Increase from current period acquisition 21,626 — 21,626 Measurement period adjustments from prior period acquisitions (78 ) — (78 ) Foreign currency translation (1,305 ) (1,515 ) (2,820 ) Balance at June 30, 2018 $ 192,629 $ 304,622 $ 497,251
Summary of indefinite-lived intangible assets	As of June 30, 2018 and December 31, 2017 , the Company's total finite-lived and indefinite-lived intangible assets consisted of the following (in thousands): June 30, 2018 December 31, 2017 Cost Accumulated Net Cost Accumulated Net Permits $ 175,317 $ 76,707 $ 98,610 $ 174,721 $ 74,347 $ 100,374 Customer and supplier relationships 399,012 170,866 228,146 399,224 158,972 240,252 Other intangible assets 37,431 31,107 6,324 36,766 31,592 5,174 Total amortizable permits and other intangible assets 611,760 278,680 333,080 610,711 264,911 345,800 Indefinite lived trademarks and trade names 122,840 — 122,840 123,328 — 123,328 Total permits and other intangible assets $ 734,600 $ 278,680 $ 455,920 $ 734,039 $ 264,911 $ 469,128
Schedule of finite-lived intangible assets	As of June 30, 2018 and December 31, 2017 , the Company's total finite-lived and indefinite-lived intangible assets consisted of the following (in thousands): June 30, 2018 December 31, 2017 Cost Accumulated Net Cost Accumulated Net Permits $ 175,317 $ 76,707 $ 98,610 $ 174,721 $ 74,347 $ 100,374 Customer and supplier relationships 399,012 170,866 228,146 399,224 158,972 240,252 Other intangible assets 37,431 31,107 6,324 36,766 31,592 5,174 Total amortizable permits and other intangible assets 611,760 278,680 333,080 610,711 264,911 345,800 Indefinite lived trademarks and trade names 122,840 — 122,840 123,328 — 123,328 Total permits and other intangible assets $ 734,600 $ 278,680 $ 455,920 $ 734,039 $ 264,911 $ 469,128
Schedule of expected amortization for the net carrying amount of finite lived intangible assets	The expected amortization of the net carrying amount of finite-lived intangible assets at June 30, 2018 was as follows (in thousands): Years Ending December 31, Expected Amortization 2018 (six months) $ 16,927 2019 32,143 2020 29,850 2021 27,381 2022 27,222 Thereafter 199,557 $ 333,080

ACCRUED EXPENSES (Tables)

ACCRUED EXPENSES (Tables)	6 Months Ended
	Jun. 30, 2018
Payables and Accruals [Abstract]
Accrued expenses	Accrued expenses consisted of the following at June 30, 2018 and December 31, 2017 (in thousands): June 30, 2018 December 31, 2017 Insurance $ 68,701 $ 57,889 Interest 12,693 12,660 Accrued compensation and benefits 56,073 55,861 Income, real estate, sales and other taxes 27,116 27,330 Other 35,552 34,242 $ 200,135 $ 187,982

CLOSURE AND POST-CLOSURE LIAB38

CLOSURE AND POST-CLOSURE LIABILITIES (Tables)	6 Months Ended
	Jun. 30, 2018
Asset Retirement Obligation Disclosure [Abstract]
Schedule of closure and post-closure liabilities	The changes to closure and post-closure liabilities (also referred to as “asset retirement obligations”) from January 1, 2018 through June 30, 2018 were as follows (in thousands): Landfill Non-Landfill Total Balance at January 1, 2018 $ 32,382 $ 28,655 $ 61,037 Liabilities assumed in acquisition — 604 604 New asset retirement obligations 1,478 — 1,478 Accretion 1,284 1,245 2,529 Changes in estimates recorded to statement of operations — 85 85 Changes in estimates recorded to balance sheet 430 — 430 Expenditures (359 ) (88 ) (447 ) Currency translation and other (127 ) (85 ) (212 ) Balance at June 30, 2018 $ 35,088 $ 30,416 $ 65,504

REMEDIAL LIABILITIES (Tables)

REMEDIAL LIABILITIES (Tables)	6 Months Ended
	Jun. 30, 2018
Environmental Remediation Obligations [Abstract]
Changes to remedial liabilities	The changes to remedial liabilities for the six months ended June 30, 2018 were as follows (in thousands): Remedial Liabilities for Landfill Sites Remedial Liabilities for Inactive Sites Remedial Liabilities (Including Superfund) for Non-Landfill Operations Total Balance at January 1, 2018 $ 1,800 $ 65,342 $ 57,326 $ 124,468 Accretion 43 1,375 931 2,349 Changes in estimates recorded to statement of operations — 83 (841 ) (758 ) Expenditures (23 ) (1,939 ) (2,176 ) (4,138 ) Currency translation and other — 882 (1,528 ) (646 ) Balance at June 30, 2018 $ 1,820 $ 65,743 $ 53,712 $ 121,275

FINANCING ARRANGEMENTS (Tables)

FINANCING ARRANGEMENTS (Tables)	6 Months Ended
	Jun. 30, 2018
Debt Disclosure [Abstract]
Summary of the entity's financial arrangements	The following table is a summary of the Company’s financing arrangements (in thousands): June 30, 2018 December 31, 2017 Senior secured Term Loan Agreement ("Term Loan Agreement") $ 4,000 $ 4,000 Current portion of long-term obligations, at carrying value $ 4,000 $ 4,000 Senior secured Term Loan Agreement due June 30, 2024 $ 392,000 $ 394,000 Senior unsecured notes, at 5.25%, due August 1, 2020 ("2020 Notes") 400,000 400,000 Senior unsecured notes, at 5.125%, due June 1, 2021 ("2021 Notes") 845,000 845,000 Long-term obligations, at par $ 1,637,000 $ 1,639,000 Unamortized debt issuance costs and premium, net (12,273 ) (13,463 ) Long-term obligations, at carrying value $ 1,624,727 $ 1,625,537 Total current and long-term obligations, at carrying value $ 1,628,727 $ 1,629,537

EARNINGS PER SHARE (Tables)

EARNINGS PER SHARE (Tables)	6 Months Ended
	Jun. 30, 2018
Earnings Per Share [Abstract]
Reconciliation of basic and diluted earnings per share computations	The following are computations of basic and diluted earnings per share (in thousands except for per share amounts): Three Months Ended Six Months Ended June 30, June 30, 2018 2017 2018 2017 Numerator for basic and diluted earnings per share: Net income $ 30,747 $ 25,880 $ 18,116 $ 4,487 Denominator: Basic shares outstanding 56,410 57,190 56,304 57,226 Dilutive effect of equity-based compensation awards 95 146 95 123 Dilutive shares outstanding 56,505 57,336 56,399 57,349 Basic income per share: $ 0.55 $ 0.45 $ 0.32 $ 0.08 Diluted income per share: $ 0.54 $ 0.45 $ 0.32 $ 0.08

ACCUMULATED OTHER COMPREHENSI42

ACCUMULATED OTHER COMPREHENSIVE LOSS (Tables)	6 Months Ended
	Jun. 30, 2018
Equity [Abstract]
Schedule of accumulated other comprehensive loss	The changes in accumulated other comprehensive loss by component and related tax effects for the six months ended June 30, 2018 were as follows (in thousands): Foreign Currency Translation Unrealized Losses on Available-For-Sale Securities Unfunded Pension Liability Total Balance at January 1, 2018 $ (170,575 ) $ (146 ) $ (1,686 ) $ (172,407 ) Other comprehensive loss before tax effects (27,091 ) (118 ) — (27,209 ) Tax effects 5,609 (88 ) — 5,521 Other comprehensive loss $ (21,482 ) $ (206 ) $ — $ (21,688 ) Balance at June 30, 2018 $ (192,057 ) $ (352 ) $ (1,686 ) $ (194,095 )

STOCK-BASED COMPENSATION (Table

STOCK-BASED COMPENSATION (Tables)	6 Months Ended
	Jun. 30, 2018
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Summary of restricted stock awards	The following table summarizes information about restricted stock awards for the six months ended June 30, 2018 : Restricted Stock Number of Shares Weighted Average Grant-Date Fair Value Balance at January 1, 2018 604,933 $ 54.23 Granted 200,688 $ 52.92 Vested (152,283 ) $ 54.65 Forfeited (17,136 ) $ 53.63 Balance at June 30, 2018 636,202 $ 53.73
Summary of performance stock awards	The following table summarizes information about performance stock awards for the six months ended June 30, 2018 : Performance Stock Number of Shares Weighted Average Grant-Date Fair Value Balance at January 1, 2018 190,129 $ 55.63 Vested (8,696 ) $ 54.26 Forfeited (12,889 ) $ 55.09 Balance at June 30, 2018 168,544 $ 55.75

SEGMENT REPORTING (Tables)

SEGMENT REPORTING (Tables)	6 Months Ended
	Jun. 30, 2018
Segment Reporting [Abstract]
Reconciliation of third party revenues to direct revenues	The following table reconciles third party revenues to direct revenues for the three and six months ended June 30, 2018 and 2017 (in thousands): For the Three Months Ended June 30, 2018 For the Three Months Ended June 30, 2017 Third party revenues Intersegment revenues, net Corporate Items, net Direct revenues Third party revenues Intersegment revenues, net Corporate Items, net Direct revenues Environmental Services $ 519,916 $ 34,291 $ 607 $ 554,814 $ 449,631 $ 31,639 $ 320 $ 481,590 Safety-Kleen 328,715 (34,291 ) 11 294,435 302,956 (31,639 ) (2 ) 271,315 Corporate Items 509 — (618 ) (109 ) 201 — (318 ) (117 ) Total $ 849,140 $ — $ — $ 849,140 $ 752,788 $ — $ — $ 752,788 For the Six Months Ended June 30, 2018 For the Six Months Ended June 30, 2017 Third party revenues Intersegment revenues, net Corporate Items, net Direct revenues Third party revenues Intersegment revenues, net Corporate Items, net Direct revenues Environmental Services $ 959,604 $ 66,256 $ 1,401 $ 1,027,261 $ 845,538 $ 63,708 $ 1,240 $ 910,486 Safety-Kleen 638,633 (66,256 ) 22 572,399 595,857 (63,708 ) 1 532,150 Corporate Items 681 — (1,423 ) (742 ) 334 — (1,241 ) (907 ) Total $ 1,598,918 $ — $ — $ 1,598,918 $ 1,441,729 $ — $ — $ 1,441,729
Reconciliation to consolidated statements of income from adjusted EBITDA	The following table presents Adjusted EBITDA information used by management by reported segment (in thousands): For the Three Months Ended For the Six Months Ended June 30, June 30, 2018 2017 2018 2017 Adjusted EBITDA: Environmental Services $ 109,199 $ 94,832 $ 170,616 $ 155,022 Safety-Kleen 73,069 60,281 134,953 112,649 Corporate Items (42,707 ) (34,422 ) (77,743 ) (66,845 ) Total $ 139,561 $ 120,691 $ 227,826 $ 200,826 Reconciliation to Consolidated Statements of Operations: Accretion of environmental liabilities 2,448 2,416 4,878 4,706 Depreciation and amortization 72,760 71,531 147,604 143,943 Income from operations 64,353 46,744 75,344 52,177 Other (income) expense, net (846 ) 833 (547 ) 2,382 Loss on early extinguishment of debt — 6,045 — 6,045 Gain on sale of business — (31,722 ) — (31,722 ) Interest expense, net of interest income 20,769 22,492 41,039 45,068 Income before provision for income taxes $ 44,430 $ 49,096 $ 34,852 $ 30,404
PP&E, intangible assets and total assets by segment	The following table presents certain assets by reportable segment and in the aggregate (in thousands): June 30, 2018 Environmental Safety-Kleen Corporate Totals Property, plant and equipment, net $ 988,957 $ 555,124 $ 65,301 $ 1,609,382 Goodwill 192,629 304,622 — 497,251 Permits and other intangibles, net 96,165 359,755 — 455,920 Total assets $ 1,681,627 $ 1,436,014 $ 597,820 $ 3,715,461 December 31, 2017 Environmental Safety-Kleen Corporate Totals Property, plant and equipment, net $ 927,139 $ 582,162 $ 78,064 $ 1,587,365 Goodwill 172,386 306,137 — 478,523 Permits and other intangibles, net 97,519 371,609 — 469,128 Total assets $ 1,541,241 $ 1,471,291 $ 694,038 $ 3,706,570
Total assets by geographical area	The following table presents total assets by geographical area (in thousands): June 30, 2018 December 31, 2017 United States $ 3,041,509 $ 2,985,394 Canada 673,836 721,176 Other foreign 116 — Total $ 3,715,461 $ 3,706,570

GUARANTOR AND NON-GUARANTOR S45

GUARANTOR AND NON-GUARANTOR SUBSIDIARIES FINANCIAL INFORMATION (Tables)	6 Months Ended
	Jun. 30, 2018
Guarantor and Non-Guarantor Subsidiaries Financial Information [Abstract]
Schedule of condensed consolidating balance sheet	Following is the condensed consolidating balance sheet at June 30, 2018 (in thousands): Clean Harbors, Inc. Guarantor Subsidiaries Non-Guarantor Subsidiaries Consolidating Adjustments Total Assets: Cash and cash equivalents $ 51,960 $ 92,833 $ 52,275 $ — $ 197,068 Short-term marketable securities — — 36,862 — 36,862 Intercompany receivables 250,206 651,218 61,125 (962,549 ) — Accounts receivable, net — 497,775 92,805 — 590,580 Other current assets — 260,489 60,225 (8,742 ) 311,972 Property, plant and equipment, net — 1,243,171 366,211 — 1,609,382 Investments in subsidiaries 3,135,271 599,091 — (3,734,362 ) — Intercompany debt receivable — 15,224 21,000 (36,224 ) — Goodwill — 437,229 60,022 — 497,251 Permits and other intangibles, net — 402,096 53,824 — 455,920 Other long-term assets 2,283 12,337 1,811 (5 ) 16,426 Total assets $ 3,439,720 $ 4,211,463 $ 806,160 $ (4,741,882 ) $ 3,715,461 Liabilities and Stockholders’ Equity: Current liabilities $ 16,627 $ 406,111 $ 129,672 $ (8,742 ) $ 543,668 Intercompany payables 637,318 309,423 15,808 (962,549 ) — Closure, post-closure and remedial liabilities, net — 146,922 16,850 — 163,772 Long-term obligations, net 1,624,727 — — — 1,624,727 Intercompany debt payable — 21,000 15,224 (36,224 ) — Other long-term liabilities — 200,999 21,252 (5 ) 222,246 Total liabilities 2,278,672 1,084,455 198,806 (1,007,520 ) 2,554,413 Stockholders’ equity 1,161,048 3,127,008 607,354 (3,734,362 ) 1,161,048 Total liabilities and stockholders’ equity $ 3,439,720 $ 4,211,463 $ 806,160 $ (4,741,882 ) $ 3,715,461 Following is the condensed consolidating balance sheet at December 31, 2017 (in thousands): Clean Harbors, Inc. Guarantor Subsidiaries Non-Guarantor Subsidiaries Consolidating Adjustments Total Assets: Cash and cash equivalents $ 51,638 $ 207,777 $ 59,984 $ — $ 319,399 Short-term marketable securities — — 38,179 — 38,179 Intercompany receivables 238,339 590,100 52,909 (881,348 ) — Accounts receivable, net — 433,042 95,882 — 528,924 Other current assets 897 233,602 52,947 (19,892 ) 267,554 Property, plant and equipment, net — 1,174,975 412,390 — 1,587,365 Investments in subsidiaries 3,112,547 569,568 — (3,682,115 ) — Intercompany debt receivable — 92,530 21,000 (113,530 ) — Goodwill — 415,641 62,882 — 478,523 Permits and other intangibles, net — 408,655 60,473 — 469,128 Other long-term assets 2,084 12,064 3,350 — 17,498 Total assets $ 3,405,505 $ 4,137,954 $ 859,996 $ (4,696,885 ) $ 3,706,570 Liabilities and Stockholders’ Equity: Current liabilities $ 16,954 $ 371,135 $ 135,620 $ (19,892 ) $ 503,817 Intercompany payables 574,812 289,531 17,005 (881,348 ) — Closure, post-closure and remedial liabilities, net — 148,872 16,851 — 165,723 Long-term obligations, net 1,625,537 — — — 1,625,537 Intercompany debt payable — 21,000 92,530 (113,530 ) — Other long-term liabilities — 201,086 22,205 — 223,291 Total liabilities 2,217,303 1,031,624 284,211 (1,014,770 ) 2,518,368 Stockholders’ equity 1,188,202 3,106,330 575,785 (3,682,115 ) 1,188,202 Total liabilities and stockholders’ equity $ 3,405,505 $ 4,137,954 $ 859,996 $ (4,696,885 ) $ 3,706,570
Schedule of condensed consolidating statement of income	Following is the consolidating statement of operations for the three months ended June 30, 2018 (in thousands): Clean Harbors, Inc. Guarantor Subsidiaries Non-Guarantor Subsidiaries Consolidating Adjustments Total Revenues Service revenues $ — $ 544,521 $ 165,435 $ (13,177 ) $ 696,779 Product revenues — 137,891 17,363 (2,893 ) 152,361 Total revenues — 682,412 182,798 (16,070 ) 849,140 Cost of revenues (exclusive of items shown separately below) Service cost of revenues — 361,644 124,956 (13,177 ) 473,423 Product cost of revenues — 102,442 10,612 (2,893 ) 110,161 Total cost of revenues — 464,086 135,568 (16,070 ) 583,584 Selling, general and administrative expenses 133 105,022 20,840 — 125,995 Accretion of environmental liabilities — 2,194 254 — 2,448 Depreciation and amortization — 52,864 19,896 — 72,760 (Loss) income from operations (133 ) 58,246 6,240 — 64,353 Other income, net — 269 577 — 846 Interest (expense) income, net (21,216 ) 238 209 — (20,769 ) Equity in earnings of subsidiaries, net of taxes 46,118 2,230 — (48,348 ) — Intercompany interest income (expense) — 1,084 (1,084 ) — — Income before (benefit) provision for income taxes 24,769 62,067 5,942 (48,348 ) 44,430 (Benefit) provision for income taxes (5,978 ) 18,228 1,433 — 13,683 Net income 30,747 43,839 4,509 (48,348 ) 30,747 Other comprehensive loss (4,942 ) (4,942 ) (10,435 ) 15,377 (4,942 ) Comprehensive income (loss) $ 25,805 $ 38,897 $ (5,926 ) $ (32,971 ) $ 25,805 Following is the consolidating statement of operations for the three months ended June 30, 2017 (in thousands): Clean Harbors, Inc. Guarantor Subsidiaries Non-Guarantor Subsidiaries Consolidating Adjustments Total Revenues Service revenues $ — $ 474,801 $ 147,924 $ (11,785 ) $ 610,940 Product revenues — 125,859 18,730 (2,741 ) 141,848 Total revenues — 600,660 166,654 (14,526 ) 752,788 Cost of revenues (exclusive of items shown separately below) Service cost of revenues — 306,960 117,181 (11,785 ) 412,356 Product cost of revenues — 98,645 11,543 (2,741 ) 107,447 Total cost of revenues — 405,605 128,724 (14,526 ) 519,803 Selling, general and administrative expenses 27 92,504 19,763 — 112,294 Accretion of environmental liabilities — 2,181 235 — 2,416 Depreciation and amortization — 51,937 19,594 — 71,531 (Loss) income from operations (27 ) 48,433 (1,662 ) — 46,744 Other expense, net (76 ) (406 ) (351 ) — (833 ) Loss on early extinguishment of debt (6,045 ) — — — (6,045 ) Gain on sale of business — 31,722 — — 31,722 Interest (expense) income, net (22,614 ) 240 (118 ) — (22,492 ) Equity in earnings of subsidiaries, net of taxes 43,167 (5,332 ) — (37,835 ) — Intercompany interest income (expense) — 1,268 (1,268 ) — — Income (loss) before (benefit) provision for income taxes 14,405 75,925 (3,399 ) (37,835 ) 49,096 (Benefit) provision for income taxes (11,475 ) 31,981 2,710 — 23,216 Net income (loss) 25,880 43,944 (6,109 ) (37,835 ) 25,880 Other comprehensive income 15,098 15,098 12,837 (27,935 ) 15,098 Comprehensive income $ 40,978 $ 59,042 $ 6,728 $ (65,770 ) $ 40,978
Schedule of condensed consolidating statement of cash flows	Following is the condensed consolidating statement of cash flows for the six months ended June 30, 2018 (in thousands): Clean Harbors, Inc. Guarantor Subsidiaries Non-Guarantor Subsidiaries Consolidating Adjustments Total Net cash from operating activities $ 790 $ 121,021 $ 7,859 $ — $ 129,670 Cash flows used in investing activities: Additions to property, plant and equipment — (77,773 ) (16,366 ) — (94,139 ) Proceeds from sale and disposal of fixed assets — 1,035 1,606 — 2,641 Acquisitions, net of cash acquired — (123,750 ) — — (123,750 ) Additions to intangible assets, including costs to obtain or renew permits — (1,991 ) (115 ) — (2,106 ) Proceeds from sale of available-for-sale securities — — 11,214 — 11,214 Purchases of available-for-sale securities — — (10,001 ) — (10,001 ) Intercompany — (30,657 ) — 30,657 — Net cash used in investing activities — (233,136 ) (13,662 ) 30,657 (216,141 ) Cash flows (used in) from financing activities: Change in uncashed checks — (2,829 ) 26 — (2,803 ) Tax payments related to withholdings on vested restricted stock (2,175 ) — — — (2,175 ) Repurchases of common stock (26,482 ) — — — (26,482 ) Deferred financing costs paid (468 ) — — — (468 ) Principal payment on debt (2,000 ) — — — (2,000 ) Intercompany 30,657 — — (30,657 ) — Net cash (used) from in financing activities (468 ) (2,829 ) 26 (30,657 ) (33,928 ) Effect of exchange rate change on cash — — (1,932 ) — (1,932 ) Increase (decrease) in cash and cash equivalents 322 (114,944 ) (7,709 ) — (122,331 ) Cash and cash equivalents, beginning of period 51,638 207,777 59,984 — 319,399 Cash and cash equivalents, end of period $ 51,960 $ 92,833 $ 52,275 $ — $ 197,068 Following is the condensed consolidating statement of cash flows for the six months ended June 30, 2017 (in thousands): Clean Harbors, Inc. Guarantor Subsidiaries Non-Guarantor Subsidiaries Consolidating Adjustments Total Net cash (used in) from operating activities $ (93,808 ) $ 206,496 $ 4,243 $ — $ 116,931 Cash flows from (used in) investing activities: Additions to property, plant and equipment — (75,152 ) (13,590 ) — (88,742 ) Proceeds from sale and disposal of fixed assets — 984 1,137 — 2,121 Acquisitions, net of cash acquired — (9,277 ) — — (9,277 ) Proceeds from sale of businesses, net of transactional costs — 46,210 181 — 46,391 Additions to intangible assets, including costs to obtain or renew permits — (888 ) (351 ) — (1,239 ) Proceeds from sale of available-for-sale securities 376 — — — 376 Intercompany — (14,343 ) — 14,343 — Net cash from (used in) investing activities 376 (52,466 ) (12,623 ) 14,343 (50,370 ) Cash flows from (used in) financing activities: Change in uncashed checks — (5,977 ) (2,384 ) — (8,361 ) Proceeds from exercise of stock options 46 — — — 46 Tax payments related to withholdings on vested restricted stock (2,132 ) — — — (2,132 ) Repurchases of common stock (12,257 ) — — — (12,257 ) Deferred financing costs paid (4,727 ) — — — (4,727 ) Premium paid on early extinguishment of debt (4,665 ) — — — (4,665 ) Principal payment on debt (296,202 ) — — — (296,202 ) Issuance of senior secured notes, net of discount 399,000 — — — 399,000 Intercompany 14,343 — — (14,343 ) — Net cash from (used) in financing activities 93,406 (5,977 ) (2,384 ) (14,343 ) 70,702 Effect of exchange rate change on cash — — 2,106 — 2,106 (Decrease) increase in cash and cash equivalents (26 ) 148,053 (8,658 ) — 139,369 Cash and cash equivalents, beginning of period 51,417 155,943 99,637 — 306,997 Cash and cash equivalents, end of period $ 51,391 $ 303,996 $ 90,979 $ — $ 446,366

SIGNIFICANT ACCOUNTING POLICI46

SIGNIFICANT ACCOUNTING POLICIES (Narrative) (Details) $ in Thousands	6 Months Ended
	Jun. 30, 2018USD ($)segment
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Number of operating segments | segment	2
Cumulative effect of change in accounting principle	$ (1,564)
Accumulated Earnings | Accounting Standards Update 2016-16
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cumulative effect of change in accounting principle	$ (1,564)

REVENUES (Disaggregation of Rev

REVENUES (Disaggregation of Revenue) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Disaggregation of Revenue [Line Items]
Revenues	$ 849,140	$ 752,788	$ 1,598,918	$ 1,441,729
United States
Disaggregation of Revenue [Line Items]
Revenues	714,549	624,095	1,346,308	1,210,082
Canada
Disaggregation of Revenue [Line Items]
Revenues	134,591	128,693	252,610	231,647
Technical Services
Disaggregation of Revenue [Line Items]
Revenues	257,006	254,487	493,312	484,705
Field and Emergency Response Services
Disaggregation of Revenue [Line Items]
Revenues	76,092	70,707	146,027	131,726
Industrial Services
Disaggregation of Revenue [Line Items]
Revenues	161,046	99,733	264,809	174,801
Oil, Gas and Lodging Services and Other
Disaggregation of Revenue [Line Items]
Revenues	26,281	24,905	56,137	54,640
Safety-Kleen Environmental Services
Disaggregation of Revenue [Line Items]
Revenues	200,034	192,817	394,195	384,544
Kleen Performance Products
Disaggregation of Revenue [Line Items]
Revenues	128,681	110,139	244,438	211,313
Environmental Services
Disaggregation of Revenue [Line Items]
Revenues	519,916	449,631	959,604	845,538
Environmental Services | United States
Disaggregation of Revenue [Line Items]
Revenues	408,127	343,323	752,099	657,106
Environmental Services | Canada
Disaggregation of Revenue [Line Items]
Revenues	111,789	106,308	207,505	188,432
Environmental Services | Technical Services
Disaggregation of Revenue [Line Items]
Revenues	257,006	254,487	493,312	484,705
Environmental Services | Field and Emergency Response Services
Disaggregation of Revenue [Line Items]
Revenues	76,092	70,707	146,027	131,726
Environmental Services | Industrial Services
Disaggregation of Revenue [Line Items]
Revenues	161,046	99,733	264,809	174,801
Environmental Services | Oil, Gas and Lodging Services and Other
Disaggregation of Revenue [Line Items]
Revenues	25,772	24,704	55,456	54,306
Environmental Services | Safety-Kleen Environmental Services
Disaggregation of Revenue [Line Items]
Revenues	0	0	0	0
Environmental Services | Kleen Performance Products
Disaggregation of Revenue [Line Items]
Revenues	0	0	0	0
Safety-Kleen
Disaggregation of Revenue [Line Items]
Revenues	328,715	302,956	638,633	595,857
Safety-Kleen | United States
Disaggregation of Revenue [Line Items]
Revenues	306,059	280,617	593,701	552,688
Safety-Kleen | Canada
Disaggregation of Revenue [Line Items]
Revenues	22,656	22,339	44,932	43,169
Safety-Kleen | Technical Services
Disaggregation of Revenue [Line Items]
Revenues	0	0	0	0
Safety-Kleen | Field and Emergency Response Services
Disaggregation of Revenue [Line Items]
Revenues	0	0	0	0
Safety-Kleen | Industrial Services
Disaggregation of Revenue [Line Items]
Revenues	0	0	0	0
Safety-Kleen | Oil, Gas and Lodging Services and Other
Disaggregation of Revenue [Line Items]
Revenues	0	0	0	0
Safety-Kleen | Safety-Kleen Environmental Services
Disaggregation of Revenue [Line Items]
Revenues	200,034	192,817	394,195	384,544
Safety-Kleen | Kleen Performance Products
Disaggregation of Revenue [Line Items]
Revenues	128,681	110,139	244,438	211,313
Corporate
Disaggregation of Revenue [Line Items]
Revenues	509	201	681	334
Corporate | United States
Disaggregation of Revenue [Line Items]
Revenues	363	155	508	288
Corporate | Canada
Disaggregation of Revenue [Line Items]
Revenues	146	46	173	46
Corporate | Technical Services
Disaggregation of Revenue [Line Items]
Revenues	0	0	0	0
Corporate | Field and Emergency Response Services
Disaggregation of Revenue [Line Items]
Revenues	0	0	0	0
Corporate | Industrial Services
Disaggregation of Revenue [Line Items]
Revenues	0	0	0	0
Corporate | Oil, Gas and Lodging Services and Other
Disaggregation of Revenue [Line Items]
Revenues	509	201	681	334
Corporate | Safety-Kleen Environmental Services
Disaggregation of Revenue [Line Items]
Revenues	0	0	0	0
Corporate | Kleen Performance Products
Disaggregation of Revenue [Line Items]
Revenues	$ 0	$ 0	$ 0	$ 0

REVENUES (Contract Balances) (D

REVENUES (Contract Balances) (Details) - USD ($) $ in Thousands	Jun. 30, 2018	Dec. 31, 2017	Jun. 30, 2017	Dec. 31, 2016
Revenue from Contract with Customer [Abstract]
Receivables	$ 590,580	$ 528,924	$ 512,375	$ 496,226
Contract Assets	62,762	35,922	46,576	36,190
Contract Liabilities	$ 68,705	$ 67,822	$ 72,089	$ 64,397

REVENUES (Narrative) (Details)

REVENUES (Narrative) (Details) - Veolia Division $ in Millions	Feb. 23, 2018USD ($)
Business Acquisition [Line Items]
Acquired receivables	$ 20.5
Customer contracts
Business Acquisition [Line Items]
Acquired contract assets	$ 17.6

BUSINESS COMBINATIONS (2018 Acq

BUSINESS COMBINATIONS (2018 Acquisition) (Details) - Veolia Division - USD ($) $ in Millions	Feb. 23, 2018	Jun. 30, 2018	Jun. 30, 2018
Business Acquisition [Line Items]
Purchase price	$ 120
Revenue from acquisition included in results of operations		$ 46.3	$ 63.9
Pre-tax income		2.1	3.3
Acquisition-related costs		$ 0.4	$ 0.9
Weighted average amortization period (in years)	8 years 2 months

BUSINESS COMBINATIONS (Assets A

BUSINESS COMBINATIONS (Assets Acquired and Liabilities Assumed) (Details) - USD ($) $ in Thousands	4 Months Ended
	Jun. 30, 2018	Feb. 23, 2018	Dec. 31, 2017
Business Acquisition [Line Items]
Goodwill	$ 497,251		$ 478,523
Veolia Division
Business Acquisition [Line Items]
Accounts receivable	38,082	$ 40,773
Measurement Period Adjustments, Accounts receivable, including unbilled receivables	(2,691)
Inventories and supplies	1,126	1,442
Measurement Period Adjustments, Inventories and supplies	(316)
Prepaid and other current assets	925	1,005
Measurement Period Adjustments, Prepaid expenses and other current assets	(80)
Property, plant and equipment	72,244	72,244
Measurement Period Adjustments, Property, plant and equipment	0
Permits and other intangibles	5,140	5,140
Measurement Period Adjustments, Permits and other intangibles	0
Current liabilities	(18,539)	(15,908)
Measurement Period Adjustments, Current liabilities	(2,631)
Closure and post-closure liabilities	(604)	(604)
Measurement Period Adjustments, Closure and post-closure liabilities	0
Total identifiable net assets	98,374	104,092
Measurement Period Adjustments, Total identifiable net assets	(5,718)
Goodwill	21,626	15,908
Measurement Period Adjustments, Goodwill	5,718
Total purchase price, net of cash acquired	120,000	$ 120,000
Measurement Period Adjustments, Total purchase price, net of cash acquired	$ 0

BUSINESS COMBINATIONS (2017 Acq

BUSINESS COMBINATIONS (2017 Acquisitions) (Details) $ / shares in Units, $ in Thousands, $ in Millions	Jul. 14, 2017CAD ($)$ / shares	Jul. 14, 2017USD ($)	Jan. 31, 2017USD ($)	Jun. 30, 2018USD ($)	Jul. 14, 2017USD ($)
Business Acquisition [Line Items]
Goodwill recognized				$ 21,626
Lonestar
Business Acquisition [Line Items]
Cash paid to acquire Lonestar	$ 41.8	$ 33,100
Equity payout (in CAD per share) | $ / shares	$ 0.72
Debt outstanding assumed	$ 21.3				$ 16,800
Goodwill recognized		$ 2,800
2017 Acquisitions
Business Acquisition [Line Items]
Goodwill recognized			$ 5,000
Purchase price			$ 11,900

DISPOSITION OF BUSINESS (Narrat

DISPOSITION OF BUSINESS (Narrative) (Details) $ in Millions	Jun. 30, 2017USD ($)
Disposal Group, Disposed of by Sale, Not Discontinued Operations
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Final sale proceeds	$ 45.5

DISPOSITION OF BUSINESS (Income

DISPOSITION OF BUSINESS (Income (Loss) Attributable to Transformer Services) (Details) - USD ($) $ in Thousands	3 Months Ended	6 Months Ended
	Jun. 30, 2017	Jun. 30, 2017
Disposal Group, Disposed of by Sale, Not Discontinued Operations
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Income before provision for income taxes	$ 1,873	$ 2,771

INVENTORIES AND SUPPLIES (Detai

INVENTORIES AND SUPPLIES (Details) - USD ($) $ in Thousands	Jun. 30, 2018	Dec. 31, 2017
Inventory Disclosure [Abstract]
Oil and oil products	$ 68,125	$ 58,142
Supplies and drums	100,118	94,242
Solvent and solutions	9,230	9,167
Modular camp accommodations	2,494	1,826
Other	13,577	12,635
Total inventories and supplies	$ 193,544	$ 176,012

PROPERTY, PLANT AND EQUIPMENT56

PROPERTY, PLANT AND EQUIPMENT (Schedule of Property, Plant and Equipment) (Details) - USD ($) $ in Thousands	Jun. 30, 2018	Dec. 31, 2017
Property, Plant and Equipment [Line Items]
Total property, plant and equipment, gross	$ 3,286,569	$ 3,190,573
Less - accumulated depreciation and amortization	1,677,187	1,603,208
Total property, plant and equipment, net	1,609,382	1,587,365
Land
Property, Plant and Equipment [Line Items]
Total property, plant and equipment, gross	123,984	121,658
Asset retirement costs (non-landfill)
Property, Plant and Equipment [Line Items]
Total property, plant and equipment, gross	14,780	14,593
Landfill assets
Property, Plant and Equipment [Line Items]
Total property, plant and equipment, gross	145,068	144,539
Buildings and improvements
Property, Plant and Equipment [Line Items]
Total property, plant and equipment, gross	429,880	414,384
Camp equipment
Property, Plant and Equipment [Line Items]
Total property, plant and equipment, gross	161,899	170,012
Vehicles
Property, Plant and Equipment [Line Items]
Total property, plant and equipment, gross	689,846	617,959
Equipment
Property, Plant and Equipment [Line Items]
Total property, plant and equipment, gross	1,675,920	1,644,102
Furniture and fixtures
Property, Plant and Equipment [Line Items]
Total property, plant and equipment, gross	5,623	5,708
Construction in progress
Property, Plant and Equipment [Line Items]
Total property, plant and equipment, gross	$ 39,569	$ 57,618

PROPERTY, PLANT AND EQUIPMENT57

PROPERTY, PLANT AND EQUIPMENT (Narrative) (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Property, Plant and Equipment [Abstract]
Interest costs capitalized adjustment	$ 0.1	$ 0.1	$ 0.4	$ 0.2
Depreciation inclusive of amortization	$ 64.2	$ 61.8	$ 129.8	$ 125.2

GOODWILL AND OTHER INTANGIBLE58

GOODWILL AND OTHER INTANGIBLE ASSETS (Rollforward of Goodwill) (Details) $ in Thousands	6 Months Ended
	Jun. 30, 2018USD ($)
Goodwill [Roll Forward]
Balance at beginning of year	$ 478,523
Increase from current period acquisition	21,626
Measurement period adjustments from prior period acquisitions	(78)
Foreign currency translation	(2,820)
Balance at end of year	497,251
Environmental Services
Goodwill [Roll Forward]
Balance at beginning of year	172,386
Increase from current period acquisition	21,626
Measurement period adjustments from prior period acquisitions	(78)
Foreign currency translation	(1,305)
Balance at end of year	192,629
Safety-Kleen
Goodwill [Roll Forward]
Balance at beginning of year	306,137
Increase from current period acquisition	0
Measurement period adjustments from prior period acquisitions	0
Foreign currency translation	(1,515)
Balance at end of year	$ 304,622

GOODWILL AND OTHER INTANGIBLE59

GOODWILL AND OTHER INTANGIBLE ASSETS (Narrative) (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Goodwill and Intangible Assets Disclosure [Abstract]
Amortization of permits and other intangible assets	$ 8.6	$ 9.7	$ 17.8	$ 18.8

GOODWILL AND OTHER INTANGIBLE60

GOODWILL AND OTHER INTANGIBLE ASSETS (Amortizable Other Intangible Assets) (Details) - USD ($) $ in Thousands	Jun. 30, 2018	Dec. 31, 2017
Schedule of Finite-lived and Indefinite-lived Intangible Assets [Line Items]
Cost	$ 611,760	$ 610,711
Accumulated Amortization	278,680	264,911
Net	333,080	345,800
Total permits and other intangible assets, Cost	734,600	734,039
Total permits and other intangible assets, Net	455,920	469,128
Indefinite lived trademarks and trade names
Schedule of Finite-lived and Indefinite-lived Intangible Assets [Line Items]
Indefinite lived trademarks and trade names	122,840	123,328
Permits
Schedule of Finite-lived and Indefinite-lived Intangible Assets [Line Items]
Cost	175,317	174,721
Accumulated Amortization	76,707	74,347
Net	98,610	100,374
Customer and supplier relationships
Schedule of Finite-lived and Indefinite-lived Intangible Assets [Line Items]
Cost	399,012	399,224
Accumulated Amortization	170,866	158,972
Net	228,146	240,252
Other intangible assets
Schedule of Finite-lived and Indefinite-lived Intangible Assets [Line Items]
Cost	37,431	36,766
Accumulated Amortization	31,107	31,592
Net	$ 6,324	$ 5,174

GOODWILL AND OTHER INTANGIBLE61

GOODWILL AND OTHER INTANGIBLE ASSETS (Expected Future Amortization) (Details) - USD ($) $ in Thousands	Jun. 30, 2018	Dec. 31, 2017
Goodwill and Intangible Assets Disclosure [Abstract]
2018 (six months)	$ 16,927
2,019	32,143
2,020	29,850
2,021	27,381
2,022	27,222
Thereafter	199,557
Net	$ 333,080	$ 345,800

ACCRUED EXPENSES (Details)

ACCRUED EXPENSES (Details) - USD ($) $ in Thousands	Jun. 30, 2018	Dec. 31, 2017
Payables and Accruals [Abstract]
Insurance	$ 68,701	$ 57,889
Interest	12,693	12,660
Accrued compensation and benefits	56,073	55,861
Income, real estate, sales and other taxes	27,116	27,330
Other	35,552	34,242
Total accrued expenses	$ 200,135	$ 187,982

CLOSURE AND POST-CLOSURE LIAB63

CLOSURE AND POST-CLOSURE LIABILITIES (Details) $ in Thousands	6 Months Ended
	Jun. 30, 2018USD ($)
Changes to post-closure liabilities
Beginning balance	$ 61,037
Liabilities assumed in acquisition	604
New asset retirement obligations	1,478
Accretion	2,529
Changes in estimates recorded to statement of operations	85
Changes in estimates recorded to balance sheet	430
Expenditures	(447)
Currency translation and other	(212)
Ending balance	$ 65,504
Credit-adjusted risk-free rate	5.66%
Landfill Retirement Liability
Changes to post-closure liabilities
Beginning balance	$ 32,382
Liabilities assumed in acquisition	0
New asset retirement obligations	1,478
Accretion	1,284
Changes in estimates recorded to statement of operations	0
Changes in estimates recorded to balance sheet	430
Expenditures	(359)
Currency translation and other	(127)
Ending balance	35,088
Non-Landfill Retirement Liability
Changes to post-closure liabilities
Beginning balance	28,655
Liabilities assumed in acquisition	604
New asset retirement obligations	0
Accretion	1,245
Changes in estimates recorded to statement of operations	85
Changes in estimates recorded to balance sheet	0
Expenditures	(88)
Currency translation and other	(85)
Ending balance	$ 30,416

REMEDIAL LIABILITIES (Details)

REMEDIAL LIABILITIES (Details) $ in Thousands	6 Months Ended
	Jun. 30, 2018USD ($)
Accrual for Environmental Loss Contingencies [Roll Forward]
Balance at beginning of year	$ 124,468
Accretion	2,349
Changes in estimates recorded to statement of operations	(758)
Expenditures	(4,138)
Currency translation and other	(646)
Balance at end of year	121,275
Remedial Liabilities for Landfill Sites
Accrual for Environmental Loss Contingencies [Roll Forward]
Balance at beginning of year	1,800
Accretion	43
Changes in estimates recorded to statement of operations	0
Expenditures	(23)
Currency translation and other	0
Balance at end of year	1,820
Remedial Liabilities for Inactive Sites
Accrual for Environmental Loss Contingencies [Roll Forward]
Balance at beginning of year	65,342
Accretion	1,375
Changes in estimates recorded to statement of operations	83
Expenditures	(1,939)
Currency translation and other	882
Balance at end of year	65,743
Remedial Liabilities (Including Superfund) for Non-Landfill Operations
Accrual for Environmental Loss Contingencies [Roll Forward]
Balance at beginning of year	57,326
Accretion	931
Changes in estimates recorded to statement of operations	(841)
Expenditures	(2,176)
Currency translation and other	(1,528)
Balance at end of year	$ 53,712

FINANCING ARRANGEMENTS (Summary

FINANCING ARRANGEMENTS (Summary of Financing Arrangements) (Details) - USD ($) $ in Thousands	Jun. 30, 2018	Dec. 31, 2017
Debt Instrument [Line Items]
Current portion of long-term obligations	$ 4,000	$ 4,000
Long-term obligations, at par	1,637,000	1,639,000
Unamortized debt issuance costs and premium, net	(12,273)	(13,463)
Long-term obligations, at carrying value	1,624,727	1,625,537
Total current and long-term obligations, at carrying value	1,628,727	1,629,537
Secured debt | Term Loan Agreement
Debt Instrument [Line Items]
Current portion of long-term obligations	4,000	4,000
Long-term obligations, at par	392,000	394,000
Unsecured debt | Senior unsecured notes, at 5.25%, due August 1, 2020 (2020 Notes)
Debt Instrument [Line Items]
Long-term obligations, at par	$ 400,000	400,000
Interest rate	5.25%
Unsecured debt | Senior unsecured notes, at 5.125%, due June 1, 2021 (2021 Notes)
Debt Instrument [Line Items]
Long-term obligations, at par	$ 845,000	$ 845,000
Interest rate	5.125%

FINANCING ARRANGEMENTS (Narrati

FINANCING ARRANGEMENTS (Narrative) (Details)	Aug. 01, 2018USD ($)	Jul. 19, 2018USD ($)	Jun. 30, 2018USD ($)	Apr. 17, 2018	Dec. 31, 2017USD ($)
Debt Instrument [Line Items]
Debt outstanding			$ 1,628,727,000		$ 1,629,537,000
Long-term obligations, at par			1,637,000,000		1,639,000,000
Outstanding loan balances			0		0
Available to borrow and outstanding letters of credit			244,300,000		217,800,000
Outstanding letters of credit			132,400,000		134,100,000
Secured debt | Term Loan Agreement
Debt Instrument [Line Items]
Long-term obligations, at par			392,000,000		394,000,000
Debt fair value			$ 394,500,000		400,500,000
Unsecured debt | Senior unsecured notes, at 5.25%, due August 1, 2020 (2020 Notes)
Debt Instrument [Line Items]
Interest rate			5.25%
Long-term obligations, at par			$ 400,000,000		400,000,000
Debt fair value			$ 400,900,000		404,600,000
Unsecured debt | Senior unsecured notes, at 5.125%, due June 1, 2021 (2021 Notes)
Debt Instrument [Line Items]
Interest rate			5.125%
Long-term obligations, at par			$ 845,000,000		845,000,000
Debt fair value			848,600,000		855,700,000
Revolving Credit Facility | Line of Credit
Debt Instrument [Line Items]
Revolving credit facility maximum borrowing capacity			$ 400,000,000		$ 400,000,000
Eurodollar | Secured debt | First Amendment
Debt Instrument [Line Items]
Interest rate				1.75%
Decrease in interest rate				0.0025
Base Rate | Secured debt | First Amendment
Debt Instrument [Line Items]
Interest rate				0.75%
Decrease in interest rate				0.0025
Subsequent Event [Member] | Term Loan Agreement
Debt Instrument [Line Items]
Increase in principal amount of initial term loans		$ 350,000,000
Debt outstanding		$ 746,000,000
Debt Instrument, Prepayment Premium, Percentage		1.00%
Subsequent Event [Member] | Senior unsecured notes, at 5.25%, due August 1, 2020 (2020 Notes)
Debt Instrument [Line Items]
Debt outstanding	$ 78,000,000	$ 322,000,000
Proceeds from Lines of Credit	$ 50,000,000
Purchase price per $1,000		330,900,000
Long-term Debt, Purchase Price, Accrued Interest		$ 7,900,000

EARNINGS PER SHARE (Computation

EARNINGS PER SHARE (Computation of Basic and Diluted Earnings Per Share) (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Numerator for basic and diluted earnings per share:
Net income	$ 30,747	$ 25,880	$ 18,116	$ 4,487
Denominator:
Basic shares outstanding (in shares)	56,410	57,190	56,304	57,226
Dilutive effect of equity-based compensation awards (in shares)	95	146	95	123
Dilutive shares outstanding (in shares)	56,505	57,336	56,399	57,349
Basic income per share (in USD per share)	$ 0.55	$ 0.45	$ 0.32	$ 0.08
Diluted income per share (in USD per share)	$ 0.54	$ 0.45	$ 0.32	$ 0.08

EARNINGS PER SHARE (Narrative)

EARNINGS PER SHARE (Narrative) (Details) - shares	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Performance stock awards
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Shares excluded from computation of earning per share (in shares)	146,159	142,503	146,159	142,503
Restricted stock awards
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Shares excluded from computation of earning per share (in shares)	136,155	14,699	130,932	21,013

ACCUMULATED OTHER COMPREHENSI69

ACCUMULATED OTHER COMPREHENSIVE LOSS (Changes in Accumulated Other Comprehensive Loss by Component) (Details) $ in Thousands	6 Months Ended
	Jun. 30, 2018USD ($)
Components of Other Accumulated Income, Net of Tax [Roll Forward]
Balance at beginning of period	$ 1,188,202
Other comprehensive loss before tax effects	(27,209)
Tax effects	5,521
Other comprehensive income	(21,688)
Balance at end of period	1,161,048
Foreign Currency Translation
Components of Other Accumulated Income, Net of Tax [Roll Forward]
Balance at beginning of period	(170,575)
Other comprehensive loss before tax effects	(27,091)
Tax effects	5,609
Other comprehensive income	(21,482)
Balance at end of period	(192,057)
Unrealized Losses on Available-For-Sale Securities
Components of Other Accumulated Income, Net of Tax [Roll Forward]
Balance at beginning of period	(146)
Other comprehensive loss before tax effects	(118)
Tax effects	(88)
Other comprehensive income	(206)
Balance at end of period	(352)
Unfunded Pension Liability
Components of Other Accumulated Income, Net of Tax [Roll Forward]
Balance at beginning of period	(1,686)
Other comprehensive loss before tax effects	0
Tax effects	0
Other comprehensive income	0
Balance at end of period	(1,686)
Total
Components of Other Accumulated Income, Net of Tax [Roll Forward]
Balance at beginning of period	(172,407)
Balance at end of period	$ (194,095)

STOCK-BASED COMPENSATION (Narra

STOCK-BASED COMPENSATION (Narrative) (Details) - USD ($) shares in Millions	3 Months Ended		6 Months Ended		52 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Oct. 31, 2017	Oct. 30, 2017
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation	$ 3,500,000	$ 2,900,000	$ 6,600,000	$ 5,200,000
Income tax benefit	$ 700,000	$ 800,000	$ 1,300,000	$ 1,500,000
Shares authorized for repurchase						$ 600,000,000	$ 300,000,000
Repurchases of common stock (in shares)	0.2	0.1	0.5	0.2	5.3
Repurchases of common stock	$ 12,200,000	$ 5,500,000	$ 26,482,000	$ 12,300,000	$ 275,300,000
Stock repurchase program, remaining authorized repurchase amount	324,700,000		324,700,000		324,700,000
Restricted stock awards
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unrecognized compensation cost	27,100,000		$ 27,100,000		27,100,000
Period for recognition (in years)			2 years 8 months
Fair value restricted stock	7,000,000	$ 4,500,000	$ 8,300,000	6,000,000
Performance stock awards
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unrecognized compensation cost	$ 1,300,000		1,300,000		$ 1,300,000
Fair value restricted stock			$ 500,000	$ 1,400,000
Minimum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period (in years)			3 years
Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period (in years)			5 years

STOCK-BASED COMPENSATION (Restr

STOCK-BASED COMPENSATION (Restricted Stock) (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Restricted stock awards
Number of Shares
Beginning balance (in shares)			604,933
Granted (in shares)			200,688
Vested (in shares)			(152,283)
Forfeited (in shares)			(17,136)
Ending balance (in shares)	636,202		636,202
Weighted Average Grant-Date Fair Value
Beginning of period (in USD per share)			$ 54.23
Granted (in USD per share)			52.92
Vested (in USD per share)			54.65
Forfeited (in USD per share)			53.63
End of period (in USD per share)	$ 53.73		$ 53.73
Unrecognized compensation cost	$ 27.1		$ 27.1
Period for recognition (in years)			2 years 8 months
Fair value restricted stock	$ 7	$ 4.5	$ 8.3	$ 6
Minimum
Weighted Average Grant-Date Fair Value
Vesting period (in years)			3 years
Maximum
Weighted Average Grant-Date Fair Value
Vesting period (in years)			5 years

STOCK-BASED COMPENSATION (Perfo

STOCK-BASED COMPENSATION (Performance Stock Awards (Details) - Performance stock awards $ / shares in Units, $ in Millions	6 Months Ended
	Jun. 30, 2018USD ($)$ / sharesshares	Jun. 30, 2017USD ($)
Number of Shares
Beginning balance (in shares) | shares	190,129
Vested (in shares) | shares	(8,696)
Forfeited (in shares) | shares	(12,889)
Ending balance (in shares) | shares	168,544
Weighted Average Grant-Date Fair Value
Beginning of period (in USD per share) | $ / shares	$ 55.63
Vested (in USD per share) | $ / shares	54.26
Forfeited (in USD per share) | $ / shares	55.09
End of period (in USD per share) | $ / shares	$ 55.75
Unrecognized compensation cost | $	$ 1.3
Fair value restricted stock | $	$ 0.5	$ 1.4

COMMITMENTS AND CONTINGENCIES (

COMMITMENTS AND CONTINGENCIES (Details) $ in Millions	6 Months Ended	12 Months Ended
	Jun. 30, 2018USD ($)proceedingsiteclaim	Dec. 31, 2012CAD ($)	Dec. 31, 1999municipality	Dec. 31, 1968permit	Dec. 31, 2017USD ($)proceeding
Contingencies [Line Items]
Recorded reserves for actual or probable liabilities | $	$ 21,600,000				$ 19,300,000
Number of proceedings as defendant | proceeding	60
Number of product liability claims settled or dismissed | claim	3
Legal and Administrative Proceedings
Contingencies [Line Items]
Recorded reserves for actual or probable liabilities | $	$ 17,000,000				17,900,000
Possible increase in legal and administrative proceedings | $	$ 1,700,000				1,800,000
Ville Mercier
Contingencies [Line Items]
Number of permits issued by government, for dumping organic liquid | permit				2
Number of neighboring municipalities filing separate legal proceedings against the Mercier Subsidiary and the Government of Quebec | municipality			3
General damages sought | $		$ 2.9
Punitive damages sought | $		$ 10
Superfund Proceedings
Contingencies [Line Items]
Number of sites owned by third party excluded from cleanup or related liabilities	127
Number of sites owned by the entity subject to proceedings under federal or state superfund laws	3
Notices received from owners of third party sites seeking indemnification from the company	124
Number of sites for which environmental remediation expense is settled	34
Third party sites requiring expenditure on remediation	17
Number of sites not currently requiring expenditures on remediation	73
Number of sites which potential liability could exceed $100,000	10
Notices received from owners of third party sites seeking indemnification from the company	17
Superfund Proceedings | Minimum
Contingencies [Line Items]
Minimum potential liability | $	$ 100,000
ChemWaste
Contingencies [Line Items]
Indemnification agreement with third party sites	11
Kleen Performance Products
Contingencies [Line Items]
Notices received from owners of third party sites seeking indemnification from the company	6
Federal and State Enforcement Actions
Contingencies [Line Items]
Recorded reserves for actual or probable liabilities | $	$ 4,600,000				$ 1,400,000
Number of proceedings as defendant | proceeding	6				5
Federal and State Enforcement Actions | Minimum
Contingencies [Line Items]
Minimum potential liability | $	$ 100,000				$ 100,000

INCOME TAXES (Details)

INCOME TAXES (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017	Dec. 31, 2017
Income Tax Disclosure [Abstract]
Effective income tax rate	30.80%	47.30%	48.00%	85.20%
Unrecognized tax benefits	$ 5		$ 5		$ 5.1
Interest on unrecognized tax benefits	$ 1		1		$ 0.9
Reduction in unrecognized tax benefits from expiring statue of limitations			$ 1.4

SEGMENT REPORTING (Narrative) (

SEGMENT REPORTING (Narrative) (Details)	6 Months Ended
	Jun. 30, 2018segment
Segment Reporting [Abstract]
Number of operating segments	2

SEGMENT REPORTING (Third Party

SEGMENT REPORTING (Third Party Revenues to Direct Revenues) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Segment Reporting Information [Line Items]
Total revenues	$ 849,140	$ 752,788	$ 1,598,918	$ 1,441,729
Intersegment revenues, net
Segment Reporting Information [Line Items]
Total revenues	0	0	0	0
Corporate Items, net
Segment Reporting Information [Line Items]
Total revenues	0	0	0	0
Direct revenues
Segment Reporting Information [Line Items]
Total revenues	849,140	752,788	1,598,918	1,441,729
Environmental Services
Segment Reporting Information [Line Items]
Total revenues	519,916	449,631	959,604	845,538
Environmental Services | Intersegment revenues, net
Segment Reporting Information [Line Items]
Total revenues	34,291	31,639	66,256	63,708
Environmental Services | Corporate Items, net
Segment Reporting Information [Line Items]
Total revenues	607	320	1,401	1,240
Environmental Services | Direct revenues
Segment Reporting Information [Line Items]
Total revenues	554,814	481,590	1,027,261	910,486
Safety-Kleen
Segment Reporting Information [Line Items]
Total revenues	328,715	302,956	638,633	595,857
Safety-Kleen | Intersegment revenues, net
Segment Reporting Information [Line Items]
Total revenues	(34,291)	(31,639)	(66,256)	(63,708)
Safety-Kleen | Corporate Items, net
Segment Reporting Information [Line Items]
Total revenues	11	(2)	22	1
Safety-Kleen | Direct revenues
Segment Reporting Information [Line Items]
Total revenues	294,435	271,315	572,399	532,150
Corporate Items
Segment Reporting Information [Line Items]
Total revenues	509	201	681	334
Corporate Items | Intersegment revenues, net
Segment Reporting Information [Line Items]
Total revenues	0	0	0	0
Corporate Items | Corporate Items, net
Segment Reporting Information [Line Items]
Total revenues	(618)	(318)	(1,423)	(1,241)
Corporate Items | Direct revenues
Segment Reporting Information [Line Items]
Total revenues	$ (109)	$ (117)	$ (742)	$ (907)

SEGMENT REPORTING (Adjusted EBI

SEGMENT REPORTING (Adjusted EBITDA Information) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Segment Reporting Information [Line Items]
Adjusted EBITDA	$ 139,561	$ 120,691	$ 227,826	$ 200,826
Reconciliation to Consolidated Statements of Operations:
Accretion of environmental liabilities	2,448	2,416	4,878	4,706
Depreciation and amortization	72,760	71,531	147,604	143,943
Income from operations	64,353	46,744	75,344	52,177
Other (income) expense, net	(846)	833	(547)	2,382
Loss on early extinguishment of debt	0	6,045	0	6,045
Gain on sale of business	0	(31,722)	0	(31,722)
Interest expense, net of interest income	20,769	22,492	41,039	45,068
Income before (benefit) provision for income taxes	44,430	49,096	34,852	30,404
Environmental Services
Segment Reporting Information [Line Items]
Adjusted EBITDA	109,199	94,832	170,616	155,022
Safety-Kleen
Segment Reporting Information [Line Items]
Adjusted EBITDA	73,069	60,281	134,953	112,649
Corporate Items
Segment Reporting Information [Line Items]
Adjusted EBITDA	$ (42,707)	$ (34,422)	$ (77,743)	$ (66,845)

SEGMENT REPORTING (Assets by Re

SEGMENT REPORTING (Assets by Reportable Segment) (Details) - USD ($) $ in Thousands	Jun. 30, 2018	Dec. 31, 2017
Segment Reporting Information [Line Items]
Property, plant and equipment, net	$ 1,609,382	$ 1,587,365
Goodwill	497,251	478,523
Permits and other intangibles, net	455,920	469,128
Total assets	3,715,461	3,706,570
Environmental Services
Segment Reporting Information [Line Items]
Property, plant and equipment, net	988,957	927,139
Goodwill	192,629	172,386
Permits and other intangibles, net	96,165	97,519
Total assets	1,681,627	1,541,241
Safety-Kleen
Segment Reporting Information [Line Items]
Property, plant and equipment, net	555,124	582,162
Goodwill	304,622	306,137
Permits and other intangibles, net	359,755	371,609
Total assets	1,436,014	1,471,291
Corporate Items
Segment Reporting Information [Line Items]
Property, plant and equipment, net	65,301	78,064
Goodwill	0	0
Permits and other intangibles, net	0	0
Total assets	$ 597,820	$ 694,038

SEGMENT REPORTING (Total Assets

SEGMENT REPORTING (Total Assets by Geographical Area) (Details) - USD ($) $ in Thousands	Jun. 30, 2018	Dec. 31, 2017
Revenues from External Customers and Long-Lived Assets [Line Items]
Total assets	$ 3,715,461	$ 3,706,570
United States
Revenues from External Customers and Long-Lived Assets [Line Items]
Total assets	3,041,509	2,985,394
Canada
Revenues from External Customers and Long-Lived Assets [Line Items]
Total assets	673,836	721,176
Other foreign
Revenues from External Customers and Long-Lived Assets [Line Items]
Total assets	$ 116	$ 0

GUARANTOR AND NON-GUARANTOR S80

GUARANTOR AND NON-GUARANTOR SUBSIDIARIES FINANCIAL INFORMATION (Narrative) (Details)	6 Months Ended
	Jun. 30, 2018
Guarantor and Non-Guarantor Subsidiaries Financial Information [Abstract]
Ownership percentage of U.S. guarantor subsidiaries	100.00%

GUARANTOR AND NON-GUARANTOR S81

GUARANTOR AND NON-GUARANTOR SUBSIDIARIES FINANCIAL INFORMATION (Condensed Consolidating Balance Sheets) (Details) - USD ($) $ in Thousands	Jun. 30, 2018	Dec. 31, 2017	Jun. 30, 2017	Dec. 31, 2016
ASSETS
Cash and cash equivalents	$ 197,068	$ 319,399	$ 446,366	$ 306,997
Short-term marketable securities	36,862	38,179
Intercompany receivables	0	0
Accounts receivable, net	590,580	528,924
Other current assets	311,972	267,554
Property, plant and equipment, net	1,609,382	1,587,365
Investments in subsidiaries	0	0
Intercompany debt receivable	0	0
Goodwill	497,251	478,523
Permits and other intangibles, net	455,920	469,128
Other long-term assets	16,426	17,498
Total assets	3,715,461	3,706,570
LIABILITIES AND STOCKHOLDERS' EQUITY
Current liabilities	543,668	503,817
Intercompany payables	0	0
Closure, post-closure and remedial liabilities, net	163,772	165,723
Long-term obligations, less current portion	1,624,727	1,625,537
Intercompany debt payable	0	0
Other long-term liabilities	222,246	223,291
Total liabilities	2,554,413	2,518,368
Stockholders’ equity	1,161,048	1,188,202
Total liabilities and stockholders’ equity	3,715,461	3,706,570
Reportable Legal Entities | Clean Harbors, Inc.
ASSETS
Cash and cash equivalents	51,960	51,638	51,391	51,417
Short-term marketable securities	0	0
Intercompany receivables	250,206	238,339
Accounts receivable, net	0	0
Other current assets	0	897
Property, plant and equipment, net	0	0
Investments in subsidiaries	3,135,271	3,112,547
Intercompany debt receivable	0	0
Goodwill	0	0
Permits and other intangibles, net	0	0
Other long-term assets	2,283	2,084
Total assets	3,439,720	3,405,505
LIABILITIES AND STOCKHOLDERS' EQUITY
Current liabilities	16,627	16,954
Intercompany payables	637,318	574,812
Closure, post-closure and remedial liabilities, net	0	0
Long-term obligations, less current portion	1,624,727	1,625,537
Intercompany debt payable	0	0
Other long-term liabilities	0	0
Total liabilities	2,278,672	2,217,303
Stockholders’ equity	1,161,048	1,188,202
Total liabilities and stockholders’ equity	3,439,720	3,405,505
Reportable Legal Entities | Guarantor Subsidiaries
ASSETS
Cash and cash equivalents	92,833	207,777	303,996	155,943
Short-term marketable securities	0	0
Intercompany receivables	651,218	590,100
Accounts receivable, net	497,775	433,042
Other current assets	260,489	233,602
Property, plant and equipment, net	1,243,171	1,174,975
Investments in subsidiaries	599,091	569,568
Intercompany debt receivable	15,224	92,530
Goodwill	437,229	415,641
Permits and other intangibles, net	402,096	408,655
Other long-term assets	12,337	12,064
Total assets	4,211,463	4,137,954
LIABILITIES AND STOCKHOLDERS' EQUITY
Current liabilities	406,111	371,135
Intercompany payables	309,423	289,531
Closure, post-closure and remedial liabilities, net	146,922	148,872
Long-term obligations, less current portion	0	0
Intercompany debt payable	21,000	21,000
Other long-term liabilities	200,999	201,086
Total liabilities	1,084,455	1,031,624
Stockholders’ equity	3,127,008	3,106,330
Total liabilities and stockholders’ equity	4,211,463	4,137,954
Reportable Legal Entities | Non-Guarantor Subsidiaries
ASSETS
Cash and cash equivalents	52,275	59,984	90,979	99,637
Short-term marketable securities	36,862	38,179
Intercompany receivables	61,125	52,909
Accounts receivable, net	92,805	95,882
Other current assets	60,225	52,947
Property, plant and equipment, net	366,211	412,390
Investments in subsidiaries	0	0
Intercompany debt receivable	21,000	21,000
Goodwill	60,022	62,882
Permits and other intangibles, net	53,824	60,473
Other long-term assets	1,811	3,350
Total assets	806,160	859,996
LIABILITIES AND STOCKHOLDERS' EQUITY
Current liabilities	129,672	135,620
Intercompany payables	15,808	17,005
Closure, post-closure and remedial liabilities, net	16,850	16,851
Long-term obligations, less current portion	0	0
Intercompany debt payable	15,224	92,530
Other long-term liabilities	21,252	22,205
Total liabilities	198,806	284,211
Stockholders’ equity	607,354	575,785
Total liabilities and stockholders’ equity	806,160	859,996
Consolidating Adjustments
ASSETS
Cash and cash equivalents	0	0	$ 0	$ 0
Short-term marketable securities	0	0
Intercompany receivables	(962,549)	(881,348)
Accounts receivable, net	0	0
Other current assets	(8,742)	(19,892)
Property, plant and equipment, net	0	0
Investments in subsidiaries	(3,734,362)	(3,682,115)
Intercompany debt receivable	(36,224)	(113,530)
Goodwill	0	0
Permits and other intangibles, net	0	0
Other long-term assets	(5)	0
Total assets	(4,741,882)	(4,696,885)
LIABILITIES AND STOCKHOLDERS' EQUITY
Current liabilities	(8,742)	(19,892)
Intercompany payables	(962,549)	(881,348)
Closure, post-closure and remedial liabilities, net	0	0
Long-term obligations, less current portion	0	0
Intercompany debt payable	(36,224)	(113,530)
Other long-term liabilities	(5)	0
Total liabilities	(1,007,520)	(1,014,770)
Stockholders’ equity	(3,734,362)	(3,682,115)
Total liabilities and stockholders’ equity	$ (4,741,882)	$ (4,696,885)

GUARANTOR AND NON-GUARANTOR S82

GUARANTOR AND NON-GUARANTOR SUBSIDIARIES FINANCIAL INFORMATION (Consolidating Statement of Operations) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Revenues:
Total revenues	$ 849,140	$ 752,788	$ 1,598,918	$ 1,441,729
Cost of revenues: (exclusive of items shown separately below)
Total cost of revenues	583,584	519,803	1,130,009	1,016,388
Selling, general and administrative expenses	125,995	112,294	241,083	224,515
Accretion of environmental liabilities	2,448	2,416	4,878	4,706
Depreciation and amortization	72,760	71,531	147,604	143,943
Income from operations	64,353	46,744	75,344	52,177
Other income (expense), net	846	(833)	547	(2,382)
Loss on early extinguishment of debt	0	(6,045)	0	(6,045)
Gain on sale of business	0	31,722	0	31,722
Interest (expense) income, net	(20,769)	(22,492)	(41,039)	(45,068)
Equity in earnings of subsidiaries, net of taxes	0	0	0	0
Intercompany interest income (expense)	0	0	0	0
Income before (benefit) provision for income taxes	44,430	49,096	34,852	30,404
(Benefit) provision for income taxes	13,683	23,216	16,736	25,917
Net income	30,747	25,880	18,116	4,487
Other comprehensive loss	(4,942)	15,098	(21,688)	21,149
Comprehensive income (loss)	25,805	40,978	(3,572)	25,636
Reportable Legal Entities | Clean Harbors, Inc.
Revenues:
Total revenues	0	0	0	0
Cost of revenues: (exclusive of items shown separately below)
Total cost of revenues	0	0	0	0
Selling, general and administrative expenses	133	27	168	51
Accretion of environmental liabilities	0	0	0	0
Depreciation and amortization	0	0	0	0
Income from operations	(133)	(27)	(168)	(51)
Other income (expense), net	0	(76)	0	(222)
Loss on early extinguishment of debt		(6,045)		(6,045)
Gain on sale of business		0		0
Interest (expense) income, net	(21,216)	(22,614)	(42,215)	(45,273)
Equity in earnings of subsidiaries, net of taxes	46,118	43,167	48,632	35,530
Intercompany interest income (expense)	0	0	0	0
Income before (benefit) provision for income taxes	24,769	14,405	6,249	(16,061)
(Benefit) provision for income taxes	(5,978)	(11,475)	(11,867)	(20,548)
Net income	30,747	25,880	18,116	4,487
Other comprehensive loss	(4,942)	15,098	(21,688)	21,149
Comprehensive income (loss)	25,805	40,978	(3,572)	25,636
Reportable Legal Entities | Guarantor Subsidiaries
Revenues:
Total revenues	682,412	600,660	1,285,477	1,160,615
Cost of revenues: (exclusive of items shown separately below)
Total cost of revenues	464,086	405,605	887,304	796,255
Selling, general and administrative expenses	105,022	92,504	198,865	184,675
Accretion of environmental liabilities	2,194	2,181	4,370	4,236
Depreciation and amortization	52,864	51,937	106,568	103,837
Income from operations	58,246	48,433	88,370	71,612
Other income (expense), net	269	(406)	184	(1,795)
Loss on early extinguishment of debt		0		0
Gain on sale of business		31,722		31,722
Interest (expense) income, net	238	240	743	359
Equity in earnings of subsidiaries, net of taxes	2,230	(5,332)	(17,832)	(27,156)
Intercompany interest income (expense)	1,084	1,268	2,445	2,565
Income before (benefit) provision for income taxes	62,067	75,925	73,910	77,307
(Benefit) provision for income taxes	18,228	31,981	27,329	41,618
Net income	43,839	43,944	46,581	35,689
Other comprehensive loss	(4,942)	15,098	(21,688)	21,149
Comprehensive income (loss)	38,897	59,042	24,893	56,838
Reportable Legal Entities | Non-Guarantor Subsidiaries
Revenues:
Total revenues	182,798	166,654	346,649	313,056
Cost of revenues: (exclusive of items shown separately below)
Total cost of revenues	135,568	128,724	275,913	252,075
Selling, general and administrative expenses	20,840	19,763	42,050	39,789
Accretion of environmental liabilities	254	235	508	470
Depreciation and amortization	19,896	19,594	41,036	40,106
Income from operations	6,240	(1,662)	(12,858)	(19,384)
Other income (expense), net	577	(351)	363	(365)
Loss on early extinguishment of debt		0		0
Gain on sale of business		0		0
Interest (expense) income, net	209	(118)	433	(154)
Equity in earnings of subsidiaries, net of taxes	0	0	0	0
Intercompany interest income (expense)	(1,084)	(1,268)	(2,445)	(2,565)
Income before (benefit) provision for income taxes	5,942	(3,399)	(14,507)	(22,468)
(Benefit) provision for income taxes	1,433	2,710	1,274	4,847
Net income	4,509	(6,109)	(15,781)	(27,315)
Other comprehensive loss	(10,435)	12,837	(24,442)	17,869
Comprehensive income (loss)	(5,926)	6,728	(40,223)	(9,446)
Consolidating Adjustments
Revenues:
Total revenues	(16,070)	(14,526)	(33,208)	(31,942)
Cost of revenues: (exclusive of items shown separately below)
Total cost of revenues	(16,070)	(14,526)	(33,208)	(31,942)
Selling, general and administrative expenses	0	0	0	0
Accretion of environmental liabilities	0	0	0	0
Depreciation and amortization	0	0	0	0
Income from operations	0	0	0	0
Other income (expense), net	0	0	0	0
Loss on early extinguishment of debt		0		0
Gain on sale of business		0		0
Interest (expense) income, net	0	0	0	0
Equity in earnings of subsidiaries, net of taxes	(48,348)	(37,835)	(30,800)	(8,374)
Intercompany interest income (expense)	0	0	0	0
Income before (benefit) provision for income taxes	(48,348)	(37,835)	(30,800)	(8,374)
(Benefit) provision for income taxes	0	0	0	0
Net income	(48,348)	(37,835)	(30,800)	(8,374)
Other comprehensive loss	15,377	(27,935)	46,130	(39,018)
Comprehensive income (loss)	(32,971)	(65,770)	15,330	(47,392)
Service
Revenues:
Total revenues	696,779	610,940	1,316,498	1,171,154
Cost of revenues: (exclusive of items shown separately below)
Total cost of revenues	473,423	412,356	921,072	803,443
Service | Reportable Legal Entities | Clean Harbors, Inc.
Revenues:
Total revenues	0	0	0	0
Cost of revenues: (exclusive of items shown separately below)
Total cost of revenues	0	0	0	0
Service | Reportable Legal Entities | Guarantor Subsidiaries
Revenues:
Total revenues	544,521	474,801	1,026,004	918,106
Cost of revenues: (exclusive of items shown separately below)
Total cost of revenues	361,644	306,960	689,824	601,105
Service | Reportable Legal Entities | Non-Guarantor Subsidiaries
Revenues:
Total revenues	165,435	147,924	317,836	278,995
Cost of revenues: (exclusive of items shown separately below)
Total cost of revenues	124,956	117,181	258,590	228,285
Service | Consolidating Adjustments
Revenues:
Total revenues	(13,177)	(11,785)	(27,342)	(25,947)
Cost of revenues: (exclusive of items shown separately below)
Total cost of revenues	(13,177)	(11,785)	(27,342)	(25,947)
Product
Revenues:
Total revenues	152,361	141,848	282,420	270,575
Cost of revenues: (exclusive of items shown separately below)
Total cost of revenues	110,161	107,447	208,937	212,945
Product | Reportable Legal Entities | Clean Harbors, Inc.
Revenues:
Total revenues	0	0	0	0
Cost of revenues: (exclusive of items shown separately below)
Total cost of revenues	0	0	0	0
Product | Reportable Legal Entities | Guarantor Subsidiaries
Revenues:
Total revenues	137,891	125,859	259,473	242,509
Cost of revenues: (exclusive of items shown separately below)
Total cost of revenues	102,442	98,645	197,480	195,150
Product | Reportable Legal Entities | Non-Guarantor Subsidiaries
Revenues:
Total revenues	17,363	18,730	28,813	34,061
Cost of revenues: (exclusive of items shown separately below)
Total cost of revenues	10,612	11,543	17,323	23,790
Product | Consolidating Adjustments
Revenues:
Total revenues	(2,893)	(2,741)	(5,866)	(5,995)
Cost of revenues: (exclusive of items shown separately below)
Total cost of revenues	$ (2,893)	$ (2,741)	$ (5,866)	$ (5,995)

GUARANTOR AND NON-GUARANTOR S83

GUARANTOR AND NON-GUARANTOR SUBSIDIARIES FINANCIAL INFORMATION (Condensed Consolidating Statements of Cash Flows) (Details) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017
Condensed consolidating statement of cash flows
Net cash from operating activities	$ 129,670	$ 116,931
Cash flows used in investing activities:
Additions to property, plant and equipment	(94,139)	(88,742)
Proceeds from sale and disposal of fixed assets	2,641	2,121
Acquisitions, net of cash acquired	(123,750)	(9,277)
Proceeds from sale of businesses, net of transactional costs	0	46,391
Additions to intangible assets, including costs to obtain or renew permits	(2,106)	(1,239)
Proceeds from sale of available-for-sale securities	11,214
Purchases of available-for-sale securities	(10,001)	0
Proceeds from sale of available-for-sale securities		376
Intercompany	0	0
Net cash used in investing activities	(216,141)	(50,370)
Cash flows (used in) from financing activities:
Change in uncashed checks	(2,803)	(8,361)
Proceeds from exercise of stock options	0	46
Tax payments related to withholdings on vested restricted stock	(2,175)	(2,132)
Repurchases of common stock	(26,482)	(12,257)
Deferred financing costs paid	(468)	(4,727)
Premiums paid on early extinguishment of debt	0	(4,665)
Principal payment on debt	(2,000)	(296,202)
Issuance of senior secured notes, net of discount		399,000
Intercompany	0	0
Net cash (used in) from financing activities	(33,928)	70,702
Effect of exchange rate change on cash	(1,932)	2,106
Increase (decrease) in cash and cash equivalents	(122,331)	139,369
Cash and cash equivalents, beginning of period	319,399	306,997
Cash and cash equivalents, end of period	197,068	446,366
Consolidating Adjustments
Condensed consolidating statement of cash flows
Net cash from operating activities	0	0
Cash flows used in investing activities:
Additions to property, plant and equipment	0	0
Proceeds from sale and disposal of fixed assets	0	0
Acquisitions, net of cash acquired	0	0
Proceeds from sale of businesses, net of transactional costs		0
Additions to intangible assets, including costs to obtain or renew permits	0	0
Proceeds from sale of available-for-sale securities	0
Purchases of available-for-sale securities	0
Proceeds from sale of available-for-sale securities		0
Intercompany	30,657	14,343
Net cash used in investing activities	30,657	14,343
Cash flows (used in) from financing activities:
Change in uncashed checks	0	0
Proceeds from exercise of stock options		0
Tax payments related to withholdings on vested restricted stock	0	0
Repurchases of common stock	0	0
Deferred financing costs paid	0	0
Premiums paid on early extinguishment of debt		0
Principal payment on debt	0	0
Issuance of senior secured notes, net of discount		0
Intercompany	(30,657)	(14,343)
Net cash (used in) from financing activities	(30,657)	(14,343)
Effect of exchange rate change on cash	0	0
Increase (decrease) in cash and cash equivalents	0	0
Cash and cash equivalents, beginning of period	0	0
Cash and cash equivalents, end of period	0	0
Clean Harbors, Inc. | Reportable Legal Entities
Condensed consolidating statement of cash flows
Net cash from operating activities	790	(93,808)
Cash flows used in investing activities:
Additions to property, plant and equipment	0	0
Proceeds from sale and disposal of fixed assets	0	0
Acquisitions, net of cash acquired	0	0
Proceeds from sale of businesses, net of transactional costs		0
Additions to intangible assets, including costs to obtain or renew permits	0	0
Proceeds from sale of available-for-sale securities	0
Purchases of available-for-sale securities	0
Proceeds from sale of available-for-sale securities		376
Intercompany	0	0
Net cash used in investing activities	0	376
Cash flows (used in) from financing activities:
Change in uncashed checks	0	0
Proceeds from exercise of stock options		46
Tax payments related to withholdings on vested restricted stock	(2,175)	(2,132)
Repurchases of common stock	(26,482)	(12,257)
Deferred financing costs paid	(468)	(4,727)
Premiums paid on early extinguishment of debt		(4,665)
Principal payment on debt	(2,000)	(296,202)
Issuance of senior secured notes, net of discount		399,000
Intercompany	30,657	14,343
Net cash (used in) from financing activities	(468)	93,406
Effect of exchange rate change on cash	0	0
Increase (decrease) in cash and cash equivalents	322	(26)
Cash and cash equivalents, beginning of period	51,638	51,417
Cash and cash equivalents, end of period	51,960	51,391
Guarantor Subsidiaries | Reportable Legal Entities
Condensed consolidating statement of cash flows
Net cash from operating activities	121,021	206,496
Cash flows used in investing activities:
Additions to property, plant and equipment	(77,773)	(75,152)
Proceeds from sale and disposal of fixed assets	1,035	984
Acquisitions, net of cash acquired	(123,750)	(9,277)
Proceeds from sale of businesses, net of transactional costs		46,210
Additions to intangible assets, including costs to obtain or renew permits	(1,991)	(888)
Proceeds from sale of available-for-sale securities	0
Purchases of available-for-sale securities	0
Proceeds from sale of available-for-sale securities		0
Intercompany	(30,657)	(14,343)
Net cash used in investing activities	(233,136)	(52,466)
Cash flows (used in) from financing activities:
Change in uncashed checks	(2,829)	(5,977)
Proceeds from exercise of stock options		0
Tax payments related to withholdings on vested restricted stock	0	0
Repurchases of common stock	0	0
Deferred financing costs paid	0	0
Premiums paid on early extinguishment of debt		0
Principal payment on debt	0	0
Issuance of senior secured notes, net of discount		0
Intercompany	0	0
Net cash (used in) from financing activities	(2,829)	(5,977)
Effect of exchange rate change on cash	0	0
Increase (decrease) in cash and cash equivalents	(114,944)	148,053
Cash and cash equivalents, beginning of period	207,777	155,943
Cash and cash equivalents, end of period	92,833	303,996
Non-Guarantor Subsidiaries | Reportable Legal Entities
Condensed consolidating statement of cash flows
Net cash from operating activities	7,859	4,243
Cash flows used in investing activities:
Additions to property, plant and equipment	(16,366)	(13,590)
Proceeds from sale and disposal of fixed assets	1,606	1,137
Acquisitions, net of cash acquired	0	0
Proceeds from sale of businesses, net of transactional costs		181
Additions to intangible assets, including costs to obtain or renew permits	(115)	(351)
Proceeds from sale of available-for-sale securities	11,214
Purchases of available-for-sale securities	(10,001)
Proceeds from sale of available-for-sale securities		0
Intercompany	0	0
Net cash used in investing activities	(13,662)	(12,623)
Cash flows (used in) from financing activities:
Change in uncashed checks	26	(2,384)
Proceeds from exercise of stock options		0
Tax payments related to withholdings on vested restricted stock	0	0
Repurchases of common stock	0	0
Deferred financing costs paid	0	0
Premiums paid on early extinguishment of debt		0
Principal payment on debt	0	0
Issuance of senior secured notes, net of discount		0
Intercompany	0	0
Net cash (used in) from financing activities	26	(2,384)
Effect of exchange rate change on cash	(1,932)	2,106
Increase (decrease) in cash and cash equivalents	(7,709)	(8,658)
Cash and cash equivalents, beginning of period	59,984	99,637
Cash and cash equivalents, end of period	$ 52,275	$ 90,979