Summary of Significant Accounting Policies | Summary of Significant Accounting Policies Use of Estimates The preparation of financial statements in accordance with GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent liabilities at the date of the financial statements, and the reported amounts of revenues and expenses during the reporting period. Significant estimates used in the preparation of these financial statements include, but are not limited to, the sand reserves and its impact on calculating the depletion expense under the units-of-production method, the depreciation associated with property and equipment, purchase price allocation for businesses acquired, impairment considerations of assets (including impairment of identified intangible assets, goodwill and other long-lived assets), estimated cost of future asset retirement obligations, stock-based compensation, recoverability of deferred tax assets, inventory reserve, contingent consideration and collectability of receivables and certain liabilities. Actual results could differ from management’s best estimates as additional information or actual results become available in the future, and those differences could be material. Revenue Recognition On January 1, 2018, the Company adopted new accounting standard Accounting Standards Codification (“ASC”) 606, “Revenue from Contracts with Customers” and all the related amendments (“ASC 606”) in relation to all contracts that were not completed or expired as of January 1, 2018, using the modified retrospective method. There was no adjustment made to the opening balance of retained earnings as a result of applying the new revenue standard. Results for reporting periods beginning after January 1, 2018 are presented under ASC 606, while the comparative information is not restated and will continue to be reported under the accounting standards in effect for those periods. With the adoption of the standard, the consolidated financial statements are supplemented by new disclosure requirements. Areas of focus and updated presentation requirements include disclosures regarding contracts with customers, disaggregation of revenue, contract balances, performance obligations, significant judgments used in the application of the guidance and transaction price allocation to remaining performance obligations. Revenue Recognition Revenues are recognized when control of the promised goods or services is transferred to our customers, the amount of which reflects the consideration the Company expects to be entitled to in exchange for those goods or services. Sand Sales Revenue The Company derives its sand sales revenue by mining and processing sand. Its revenues are primarily a function of the price per ton realized and the volumes sold. The Company’s sales are generally free carrier (“FCA”) at the origination point at the Company’s facility, with title passing as the product is loaded into railcars hired by the customer or provided by the Company and revenue being recognized when title transfers at the Company’s facility. For sand delivered in-basin to certain contract and spot-rate customers, the Company recognizes the revenue when title passes at the destination, delivery at terminal, (“DAT”). The amount invoiced reflects product, transportation and any other additional handling services, such as storage or transloading the product from railcar to truck. Prices under the Company’s long-term agreements with customers are generally indexed to the Average Cushing Oklahoma WTI Spot Prices and contain provisions allowing for adjustments including: (i) annual percentage price increases; and/or (ii) market factor adjustments, including a natural gas surcharge/reduction and a propane surcharge/reduction which are applied if the Average Natural Gas Price or the Average Quarterly Mont Belvieu TX Propane Spot Price, respectively, as listed by the U.S. Energy Information Administration, are above or below the applicable benchmark set forth in the contract for the preceding calendar quarter. Shortfall Payments The Company’s shortfall revenues are based on negotiated contract terms and are recognized when rights of use are expired. The Company recognizes revenue to the extent of the unfulfilled minimum contracted quantity at the shortfall price per ton as stated in the contract once payment is received or probable. For the three months ended September 30, 2018 and 2017 , the Company recognized $1,426 and $1,169 , respectively, of revenue for shortfall payments relating to minimum commitments under take-or-pay contracts. For the nine months ended September 30, 2018 and 2017 , the Company recognized $2,094 and $1,244 , respectively, of revenue for shortfall payments relating to minimum commitments under take-or-pay contracts. Railcar Usage Revenue Railcar usage revenue consists of revenue derived from the usage of the Company’s railcars by customers under long-term contracts or on an as-used basis. Based on the customer contract, the Company either recognizes revenue on the usage of railcars based on when the terms of the agreement state that the railcar is available to the customer for use, or based on a specified price per ton shipped. For the three months ended September 30, 2018 and 2017 , the Company recognized $2,234 and $2,021 , respectively, of railcar revenue. For the nine months ended September 30, 2018 and 2017 , the Company recognized $6,126 and $5,605 , respectively, of railcar revenue. Transportation Revenue Transportation revenue consists primarily of railway transportation and transload services to deliver products to customers. The Company’s transportation revenue fluctuates based on many factors, including the volume of product it transports and the distance between its plant and customers. Revenue generated from transportation was $14,796 and $13,925 , respectively, for the three months ended September 30, 2018 and 2017 . Revenue generated from transportation was $37,929 and $31,547 , respectively, for the nine months ended September 30, 2018 and 2017 . Contract Balances The timing of revenue recognition, billings and cash collections results in billed accounts receivable, unbilled receivables and deferred revenue on the consolidated balance sheet. For the Company’s sand sales, amounts are billed as sand is loaded on the railcars to fill customer orders for FCA origination point sales or when sand is received at the destination for FCA or DAT destination point sales and recorded as accounts receivable. For the Company’s freight revenue, amounts billed depend on the shipping terms and are recorded as receivables accordingly. Generally, billing occurs subsequent to revenue recognition, though certain billing occurs in advance, resulting in contract assets and liabilities, respectively. In addition, the Company sometimes receives shortfall payments from its customers and recognizes the revenue once the rights of use are expired. Changes in the contract asset and liability balances during the three and nine months ended September 30, 2018 were not materially impacted by any other factors. Deferred Revenues The Company receives advance payments from certain customers in order to secure and procure a reliable provision and delivery of product. The Company classifies such advances as current or noncurrent liabilities depending upon the anticipated timing of delivery of the supplied product. Revenue is recognized upon the delivery of the product. The Company may receive an advance payment from a customer, based on the terms of the customer’s long-term contract, for a certain volume of product to be delivered. Revenue is recognized as product is delivered and the deferred revenue is reduced. Revenue recognized for the nine months ended September 30, 2018 that was included in the deferred revenue balance at the beginning of the year was $0 . The deferred revenue balance at September 30, 2018 and December 31, 2017 was $4,030 and $0 , respectively, and classified as a current liability in the accompanying condensed consolidated balance sheets. Performance Obligations A performance obligation is a promise in a contract to transfer a distinct good or service to the customer, and is the unit of account in accordance with ASC 606. A contract’s transaction price is allocated to each distinct performance obligation and recognized as revenue when, or as, the performance obligation is satisfied. Generally, the Company’s contracts include a single performance obligation that is separately identifiable, and therefore, distinct. Under ASC 606, the allocation of transaction price is not necessary if only one performance obligation is identified. The Company expects to recognize approximately 14% of this remaining performance obligation as revenue throughout the remainder of 2018 and expects to recognize the remaining 86% as revenue by 2022. Revenue from sand sales are recognized at a point in time, either upon shipment or upon delivery, and accounted for 70% and 56% of the Company’s revenue for the three months ended September 30, 2018 and 2017 , respectively, and for 71% and 59% of the Company’s revenue for the nine months ended September 30, 2018 and 2017 , respectively. Revenue from railcar usage and transportation is recognized at a point in time, upon shipment, and accounted for 27% and 41% of revenue for the three months ended September 30, 2018 and 2017 , respectively, and for 27% and 39% of revenue for the nine months ended September 30, 2018 and 2017 , respectively. Significant Judgments Accounting for long-term contracts involves the use of various techniques to estimate total contract revenue, costs and satisfaction of performance obligation. The Company satisfies its performance obligation and subsequently recognizes revenue, at a point in time, upon shipment of the products as the customer obtains control over the goods once the sand is loaded into the railcars or sand is delivered to the customer’s destination. In the case of sand being delivered to customers, the transaction price is variable in nature and is directly tied to the Average Cushing Oklahoma WTI Spot Prices per barrel. There were no changes to the significant judgments used by the Company to determine the timing of satisfaction of the performance obligation under ASC 606. Costs to Obtain or Fulfill Contracts The Company’s costs to fulfill or obtain contracts with customers primarily consist of commissions and legal costs. Under take-or-pay contracts, the Company provides sales team members with commissions at set per ton prices. These commissions are paid on a monthly basis, when and if the sand is taken by the customer. Although sales commissions are incremental in nature and are only incurred when a contract is obtained, there is no up-front commission paid on the satisfactory obtainment of a contract, resulting in no sales commissions being capitalized at September 30, 2018 . The Company also incurs legal costs relating to the drafting and negotiating of contracts with select customers. Because legal costs are not incremental in nature and are incurred regardless of whether a contract is ultimately obtained, there were no legal costs capitalized as of September 30, 2018 . As a result, the Company did not record amortization of costs incurred to obtain the contract or any impairment losses for the three and nine months ended September 30, 2018 . Accounts Receivable and Unbilled Receivables Accounts receivable represents customer transactions that have been invoiced as of the balance sheet date; unbilled receivables represent customer transactions that have not yet been invoiced as of the balance sheet date. Accounts receivable are due within 30 days from the date of invoice, or in accordance with terms agreed upon with customers, and are stated at amounts due from customers net of any allowance for doubtful accounts. The Company considers accounts outstanding longer than the payment terms are past due. The Company determines the allowance by considering a number of factors, including the length of time trade accounts receivable are past due, previous loss history, the customer’s current ability to pay its obligation, and the condition of the general economy and the industry as a whole. Accounts receivable are written off when they are deemed uncollectible, and payments subsequently received on such receivables are credited to bad debt expense. As of September 30, 2018 and December 31, 2017 , the Company determined no allowance for doubtful accounts was necessary. As of September 30, 2018 and December 31, 2017 , no portion of unbilled revenue represents transactions included in deferred revenue. Transportation Transportation costs are classified as cost of goods sold. Transportation costs consist of railway transportation and transload costs to deliver products to customers. Cost of sales generated from transportation was $23,128 and $15,390 for the three months ended September 30, 2018 and 2017 , respectively. Cost of sales generated from transportation was $53,611 and $33,544 for the nine months ended September 30, 2018 and 2017 , respectively. Inventories The Company’s sand inventory consists of raw material (sand that has been excavated but not processed), work-in-progress (sand that has undergone some but not all processing) and finished goods (sand that has been completely processed and is ready for sale). Costs applied to sand inventory include direct excavation costs, processing costs, overhead allocation, depreciation and depletion, transportation and additional service costs, as applicable. Stockpile tonnages are calculated by measuring the number of tons added and removed from the stockpile. Costs are calculated on a per ton basis and are applied to the stockpiles based on the number of tons in the stockpile. The Company performs monthly physical inventory measurements to verify the quantity of sand inventory on hand. Due to variation in sand density and moisture content and production processes utilized to manufacture the Company’s products, physical inventories will not necessarily detect all variances. To mitigate this risk, the Company recognizes a yield adjustment on its inventories. Sand inventory is stated at the lower of cost or net realizable value using the average cost method. For the three and nine months ended September 30, 2018 and 2017 , the Company had no write-down of sand inventory as a result of any lower of cost or net realizable value assessment. The spare parts inventory consists of critical spare parts. Spare parts inventory is accounted for on a first-in, first-out basis at the lower of cost or net realizable value. Deferred Financing Charges Direct costs incurred in connection with the Credit Facility (as defined in Note 11) have been capitalized and are being amortized using the straight-line method, which approximates the effective interest method, over the term of the debt. Fees attributable to the lender and third parties of $1,372 were presented as components of deferred financing charges since there was no outstanding balance on the Credit Facility as of December 31, 2017 . As of September 30, 2018 , fees attributable to the lender of $728 are presented as a discount to the carrying value of the debt and the unamortized amount is presented as a reduction of long-term debt on the consolidated balance sheets. Amortization expense of the deferred financing charges of $85 and $116 is included in interest expense for the three months ended September 30, 2018 and 2017 , respectively. Amortization expense of the deferred financing charges of $223 and $339 is included in interest expense for the nine months ended September 30, 2018 and 2017 , respectively. Accretion of debt discount of $65 and $0 is included in interest expense for the three months ended September 30, 2018 and 2017 , respectively. Accretion of debt discount of $181 and $0 is included in interest expense for the nine months ended September 30, 2018 and 2017 , respectively. Financial Instruments The carrying value of the Company’s financial instruments, consisting of cash and cash equivalents, accounts receivable, accounts payable and accrued expenses, approximates their fair value due to the short maturity of such instruments. Financial instruments also consist of debt for which fair value approximates carrying values as the debt bears interest at a variable rate which is reflective of current rates otherwise available to the Company. Unless otherwise noted, it is management’s opinion that the Company is not exposed to significant interest, currency or credit risks arising from these financial instruments. Property, Plant and Equipment Property, plant and equipment are recorded at cost. Costs related to researching, surveying, drilling, and related activities are recorded at cost and capitalized once a determination has been made that the Company’s property has proven and probable reserves. Capitalized mining costs are depleted using the units-of-production method. Construction in progress is primarily comprised of machinery and equipment which has not been placed in service and is not depreciated until the related assets or improvements are ready to be placed in service. Depreciation is calculated using the straight-line method over the estimated useful lives of the property, plant and equipment, which are: Years Land improvements 10 Plant and buildings 5-15 Real estate properties 10-40 Railroad and sidings 30 Vehicles 3-5 Machinery, equipment and tooling 3-15 Wellsite storage solutions 5-15 Furniture and fixtures 3-10 Deferred stripping costs 3 Expenditures for maintenance and repairs are charged against income as incurred; betterments that increase the value or materially extend the life of the related assets are capitalized. Upon sale or disposition of property and equipment, the cost and related accumulated depreciation and amortization are removed from the accounts and any resulting gain or loss is recognized in the consolidated income statements. Acquisitions The Company determines whether a transaction or other event is a business combination, which requires that the assets acquired and liabilities assumed constitute a business. Each business combination is then accounted for by applying the acquisition method. If the assets acquired are not a business, the Company accounts for the transaction or other event as an asset acquisition. Under both methods, the Company recognizes the identifiable assets acquired, the liabilities assumed, contingent considerations and any non-controlling interest in the acquired entity. In addition, for transactions that are business combinations, the Company evaluates the existence of goodwill or a gain from a bargain purchase. The Company capitalizes acquisition-related costs and fees associated with asset acquisitions and expenses acquisition-related costs and fees associated with business combinations in the period in which they are incurred. Long-Lived Assets, Including Definite-Lived Intangible Assets Long-lived assets, other than goodwill and other indefinite-lived intangibles, are evaluated for impairment whenever events or changes in circumstances indicate that the carrying amount of the assets may not be recoverable through the estimated undiscounted future cash flows derived from such assets. Definite-lived intangible assets primarily consist of developed technology and customer relationships. For long-lived assets used in operations, impairment losses are only recorded if the asset’s carrying amount is not recoverable through its undiscounted, probability-weighted future cash flows. The Company measures the impairment loss based on the difference between the carrying amount and the estimated fair value. When an impairment exists, the related assets are written down to fair value. Goodwill and Other Indefinite-Lived Intangible Assets The Company conducts its evaluation of goodwill and other indefinite-lived intangible assets at the reporting unit level on an annual basis as of December 31 and more frequently if events or circumstances indicate that the carrying value of a reporting unit exceeds its fair value. Prior to performing an impairment test, the Company assesses qualitative factors to determine whether the existence of events or circumstances leads to a determination that it is more likely than not that the fair value of a reporting unit is less than its carrying amount. If the qualitative assessment determines that an impairment is more likely than not, the Company performs a quantitative comparison of the fair value with the carrying amount, including goodwill. If this comparison reflects impairment, then the loss would be measured as the excess of recorded goodwill, or other intangible assets with indefinite lives, over its implied fair value. Fair Value Measurements The Company has categorized its assets and liabilities that are measured at fair value on a recurring and non-recurring basis into a three-level fair value hierarchy, of which the first two are considered observable and the last unobservable, which are as follows: • Level 1—Inputs are unadjusted quoted prices in active markets for identical assets or liabilities that the Company has the ability to access at the measurement date; • Level 2—Inputs other than Level 1 that are observable, either directly or indirectly, such as quoted prices for similar assets or liabilities in active markets, quoted prices for identical or similar assets or liabilities in markets that are not active or other inputs corroborated by observable market data for substantially the full term of the assets or liabilities; and • Level 3—Unobservable inputs that reflect the Company’s assumptions that market participants would use in pricing assets or liabilities based on the best information available. Contingent Consideration The Company’s contingent consideration is measured at fair value on a recurring basis and is comprised of payments for production of silos and related equipment during the three -year period after the Quickthree acquisition (Note 4). Contingent liabilities are valued using significant inputs that are not observable in the market, which are defined as Level 3 inputs according to fair value measurement accounting. The Company used a probability-weighted average between 9 and 63 manufactured fleets over the earnout period, as the basis of its fair value determination. The actual contingent consideration could vary from the determined amount based on the actual number of silos and related equipment produced and the timing thereof. The Company estimates the fair value of contingent liabilities using a Monte Carlo simulation-based, real option pricing methodology implementation of the Income Approach. This approach utilizes inputs including market comparable information and management assessments regarding potential future scenarios, then discounts the liabilities to present value. The Company believes its estimates and assumptions are reasonable, however, there is significant judgment involved. The fair value of the Company’s financial instruments carried at fair value were as follows: September 30, 2018 Level 1 Level 2 Level 3 Contingent consideration $ 7,100 $ — $ — $ 7,100 Total liabilities $ 7,100 $ — $ — $ 7,100 The following table provides a summary of changes in the fair value of the Company’s Level 3 financial instruments for the nine months ended September 30, 2018 : Balance as of January 1, 2018 $ — Contingent consideration pursuant to acquisition 9,200 Payment of contingent consideration — Unrealized gain (2,100 ) Balance as of September 30, 2018 $ 7,100 Stock-Based Compensation The Company issues restricted stock to certain employees and members of the board of directors of the Company (the “Board”) for their services on the Board. The Company estimates the grant date fair value of each share of restricted stock at issuance. For awards subject to service-based vesting conditions, the Company recognizes, in the consolidated income statements, stock-based compensation expense, net of estimated forfeitures, equal to the grant date fair value of the award on a straight-line basis over the requisite service period, which is generally the vesting term. For awards subject to both performance and service-based vesting conditions, the Company recognizes stock-based compensation expense using the straight-line recognition method when it is probable that the performance condition will be achieved. Forfeitures are accounted for when they occur. Share-based payments issued to non-employees are recorded at their fair values, and are periodically revalued as the equity instruments vest and are recognized as expense, in the consolidated income statements, over the related service period. Once the Company’s shares became publicly traded on November 4, 2016, the Company began to use the actual market price of its shares as the grant date fair value for restricted stock awards. Income Taxes On December 22, 2017, the U.S. Tax Cuts and Jobs Act (the “Tax Reform Act”) was signed into law. As a result of the Tax Reform Act, the Company recorded a tax benefit of approximately $8,500 due to a re-measurement of deferred tax assets and liabilities in the fourth quarter of 2017. The Company has finalized the accounting for the income tax effects of the Tax Reform Act. The Company applies the provisions of ASC 740, “Income Taxes” (“ASC 740”), which principally utilizes a balance sheet approach to provide for income taxes. Under this method, deferred tax assets and liabilities are recognized for the expected future tax consequences of net operating loss carryforwards and temporary differences between the carrying amounts and the tax bases of assets and liabilities. ASC 740 clarifies the accounting for uncertainty in income taxes recognized in an enterprise’s financial statements. The impact of an uncertain income tax position on the income tax returns must be recognized at the largest amount that is more-likely-than-not to be required to be recognized upon audit by the relevant taxing authority. This standard also provides guidance on de-recognition, measurement, classification, interest and penalties, accounting for interim periods, disclosure and transition issues with respect to tax positions. The Company includes interest and penalties as a component of income tax expense in the consolidated income statements. For the periods presented, no interest and penalties were recorded. Environmental Matters The Company is subject to various federal, state and local laws and regulations relating to the protection of the environment. Management has established procedures for the ongoing evaluation of the Company’s operations, to identify potential environmental exposures and to comply with regulatory policies and procedures. Environmental expenditures that relate to current operations are expensed or capitalized as appropriate. Expenditures that relate to an existing condition caused by past operations and do not contribute to current or future revenue generation are expensed as incurred. Liabilities are recorded when environmental costs are probable, and the costs can be reasonably estimated. The Company maintains insurance which may cover in whole or in part certain environmental expenditures. As of September 30, 2018 and December 31, 2017 , there were no probable environmental matters. Other Comprehensive Income Other comprehensive income represents foreign currency translation adjustments. The following table presents the changes in accumulated other comprehensive income during the three and nine months ended September 30, 2018 . Three Months Ended Nine Months Ended Foreign currency translation adjustments Foreign currency translation adjustments Beginning balance $ 76 $ — Other comprehensive income before reclassifications (130 ) (54 ) Amounts reclassed from accumulated other comprehensive income — — Ending balance $ (54 ) $ (54 ) Segment Information Operating segments are identified as components of an enterprise about which separate discrete financial information is available for evaluation by the chief operating decision maker, or decision-making group, in making decisions on how to allocate resources and assess performance. The Company’s chief operating decision maker is the Chief Executive Officer. The Company and the Chief Executive Officer view the Company’s operations and manage its business, including the recently acquired logistics assets and wellsite storage solutions business, as one operating segment. Substantially all long-lived assets of the Company reside in the United States. Basic and Diluted Net Income Per Share of Common Stock Basic net income per share of common stock is computed by dividing net income attributable to common stockholders by the weighted-average number of shares of common stock outstanding during the period, excluding the dilutive effects of restricted stock. Diluted net income per share of common stock is computed by dividing the net income attributable to common stockholders by the sum of the weighted-average number of shares of common stock outstanding during the period plus the potential dilutive effects of restricted stock outstanding during the period calculated in accordance with the treasury stock method, although restricted stock is excluded if their effect is anti-dilutive. The number of shares underlying equity-based awards that were excluded from the calculation of diluted earnings per share as their effect would be anti-dilutive was 1,022 and 451 for each of the three months ended September 30, 2018 and 2017 , respectively. The number of shares underlying equity-based awards that were excluded from the calculation of diluted earnings per share as their effect would be anti-dilutive was 646 and 252 for each of the nine months ended September 30, 2018 and 2017 , respectively. The following table reconciles the weighted-average common shares outstanding used in the calculation of basic net income per share to the weighted average common shares outstanding used in the calculation of diluted net income per share: Three Months Ended September 30, Nine Months Ended September 30, 2018 2017 2018 2017 Weighted average common shares outstanding 40,541 40,384 40,483 40,145 Assumed conversion of restricted stock 10 32 65 112 Diluted weighted average common stock outstanding 40,551 40,416 40,548 40,257 Reclassification Certain 2017 balance sheet items have been reclassified to conform to the current financial statement presentation. These reclassifications have no effect on previous reported net income. Recent Accounting Pronouncements Adopted In January 2017, the Financial Accounting Standards Board (“FASB”) issued ASU 2017-01, “Business Combinations (Topic 805) Clarifying the Definition of a Business” (“ASU 2017-01”), which clarifies the definition of a business with the objective of adding guidance to assist entities with evaluating whether transactions should be accounted for as acquisitions (or disposals) of assets or businesses. The definition of a business affects many areas of accounting including acquisitions, disposals, goodwill, and consolidation. ASU 2017-01 is effective for annual periods beginning after December 15, 2017, including interim periods within those periods. The Company adopted this standard on January 1, 2018. The adoption of this guidance did not have a material effect on the Company’s financial position, results of operation or cash flows. In August 2016, the FASB issued ASU 2016-15, “Statement of Cash Flows (Topic 230) Classification of Certain Cash Receipts and Cash Payments” (“ASU 2016-15”), which eliminates the diversity in practice related to the classification of certain cash receipts and payments for debt prepayment or extinguishment costs, the maturing of a zero-coupon bond, the settlement of contingent liabilities arising from a business combination, proceeds from insurance settlements, distributions from certain equity method investees and beneficial interests obtained in a financial asset securitization. ASU 2016-15 designates the appropriate cash flow classification, including requirements to allocate certain components of these cash receipts and payments among operating, investing and financing activities. The guidance is effective for the Company beginning after December 15, 2017. The Company adopted this guidance effective January 1, 2018. The adoption of this guidance did not have a material effect on the Company’s financial position, results of operation or cash flows. In May 2014, the FASB issued ASU 2014-09, “Revenue from Contracts with Customers” (“ASU 2014-09”). The |