EXHIBIT 10.6
DOCUMENTATION SUPPORTING
RESPONSE ACTION OUTCOME
Fuel Oil and Trichloroethene in Groundwater
580 Winter Street, Waltham, Massachusetts
DEP Site No. 3-2117
Prepared For:
WASA Management
30 Federal Street, 6th Floor
Boston, Massachusetts
Submitted To:
Massachusetts Department of Environmental Protection
Northeast Region
10 Commerce Way
Woburn, Massachusetts
Prepared By:
Environmental Science Services
49 Walnut Park, Building 3
Wellesley Hills, Massachusetts
ESS Project No. W028
October 2, 1995
Environmental Science Services An Equal Opportunity Employer 49 Walnut
Park, Building No. 3, Wellesley Hills, Massachusetts 02181 (617) 43 1-0500 Fax
(617) 431-7434
DOCUMENTATION SUPPORTING
RESPONSE ACTION OUTCOME
Fuel Oil and Trichloroethene in Groundwater
580 Winter Street, Waltham, Massachusetts
DEP Site No. 3-2117
1.0 INTRODUCTION
This document presents information, an evaluation, and conclusions in
support of a Response Action Outcome (RAO) Statement for the property located
at
580 Winter Street, Waltham, Massachusetts (the Site). This document and the
included RAO forms address the presence of fuel oil and trichloroethene
detected
in groundwater on a portion of the Site.
A LSP Evaluation Opinion by Environmental Science Services (ESS) dated
June 17, 1994 concluded that the site presents no significant risk to its
occupants, the surrounding properties, or the City of Cambridge water supply
based on the existing levels of groundwater contamination at the Site and a
reporting category for groundwater at the site of RCGW-2. Subsequent review
of
this document by DEP in a memorandum dated May 16, 1995 stated that the
reporting category for groundwater at the Site should be RCGW-1 based on its
proximity to the Cambridge Reservoir. This review noted that the residual
concentrations of fuel oil and trichloroethene exceed the RCGW-1 Standards.
Therefore, the LSP Evaluation Opinion was not an appropriate end point for the
evaluation of this Site, and a risk characterization is required.
This document presents an opinion that, despite the RCGW-1 designation
affirmed in DEP's communication, the groundwater should not be classified as
GW-1 for the purposes of risk characterization. This opinion is supported by
our interpretation of the particular hydrogeologic conditions at the Site.
This document describes:
- - the location and nature of the releases;
- - the assessment of residual-conditions; and
- - a risk characterization based upon the results of the assessment work.
A Class B-2 RAO has been designated for the Site based on the following
conclusions:
1) A level of "no significant risk" exists.
2) No remediation was undertaken at the Site.
3) Residual concentrations of fuel oil and several solvents exceed
background levels.
Also included with this documentation is a completed copy of the Response
Action Outcome Statement and Downgradient Property Status Transmittal Form
(BWSC-104).
2.0 DESCRIPTION OF THE SITE
The Site is located in the industrial park near the 'intersection of
Winter Street and Route 128 in Waltham, Massachusetts. The building is on the
southwest comer of the intersection of Winter Street and First Avenue. The
larger parking lot abuts West Street and is southwest of the building lot.
The
building is surrounded on the east, west, and south by other commercial and
industrial proper-ties. Across Winter Street to the north is the Cambridge
Reservoir, a primary storage reservoir serving the public water supply of the
City of Cambridge. A locus map and site plan map are attached as Figures I
and 2, respectively.
3.0 HISTORY OF RELEASE
The initial site investigation was conducted by Goldberg-Zoino &
Associates, Inc. (GZA) with their report dated January 1989. A follow up
effort
was conducted by Certified Engineering and Testing (CET) with their report
dated
May 1989. The sampling by these firms in December 1988 and March 1989
detected
low levels of chlorinated solvents, such as trichloroethene, as well as total
petroleum hydrocarbons (TPH). The Site was subsequently reported to the
Massachusetts Department of Environmental Protection (DEP). No specific
source
was identified for the solvents, whereas the TPH contamination was attributed
to
small overfills of a former underground fuel oil tank, found to be intact on
removal.
A Preliminary Environmental Assessment and Limited Subsurface
Investigation was completed by ESS in April 1993. This included analysis of
groundwater samples collected in December 1992 from the four existing
accessible
monitoring wells on the property. ESS concluded that there was no visual
evidence of a release or a significant threat of a release of oil or hazardous
material to the property. However, analysis of the groundwater samples
detected
low levels of volatile organic compounds (VOCs). A summary of all available
analytical results for groundwater is attached as Table 1.
4.0 GROUNDWATER CLASSIFICATION
The subject Site was located on the 7.5- by 7.5-minute Concord quadrangle
of the Massachusetts Geographical Information System (MASSGIS) maps at the DEP
Northeast Region office in Woburn, Massachusetts. According to that map,
there
are no wells or pumping stations for public water supply within a radius of at
least 1 mile from the subject Site. The building on the property is
approximately 325 feet from the southern edge of the Cambridge Reservoir, and
1,500 feet from the ghettoize which regulates the reservoir's outlet into Hobs
Brook, but there is no protected zone designation associated with the
Cambridge
Reservoir noted on the
MASSGIS maps in this area. According to the maps entitled "Hydrology and
Water Resources of the Charles River Basin, Massachusetts," published by the
USGS, the subject property is not underlain by any aquifer that is favorable
for
development of water supply wells.
In accordance with 3 1 0 CMR 40.0932, and based on the proximity of the
Site to the Cambridge Reservoir, the Site is in the Zone A of a Class A
Surface
Water Body. As stated in DEP's memorandum of May 16, 1995, this condition
requires classification of Site groundwater as RCGW-1 for reporting purposes.
However, for the purposes of Risk Characterization, ESS believes that the
appropriate classification of the groundwater at the Site is GW-2 and GW-3,
based on its particular hydrogeologic setting. The following discussion on
this
topic is based on three sources of information: the USGS Topographic Map for
the
Maynard Quadrangle, the GZA environmental site assessment of the Site dated
January 5, 1989, and the CET environmental site assessment for the Site dated
May 9, 1989.
Although this Site is within 400 feet of a Class A Surface Water Body, the
water body in question is a dammed reservoir, and, based on the topography as
depicted in the USGS Maynard Quadrangle, the Site is located on the regionally
downgradient side of the dam. Surface water bodies typically gain part of
their
recharge from inflowing groundwater. However, along a certain portion (along
the regionally downgradient side) of the perimeter of water bodies,
groundwater
is often recharged from surface water, flowing away from the water body. This
is more consistently and predictably the case for dammed water bodies, where
surface water is artificially maintained above its natural elevation.
In this case, two observations support the conclusion that the Site is
located in such a zone, and that groundwater beneath the Site flows to the
more
distant Hobbs Brook 'rather than the Cambridge Reservoir. The first
observation
is that relative groundwater elevations at the Site, as measured on two
occasions (December 1989 and May 1989), show groundwater flow in a southerly
direction, away from the reservoir. The second observation is that estimated
absolute groundwater elevations at the Site are below the elevation of the
water
surface of the reservoir, as depicted on the USGS Topographic map. ESS
estimated the absolute groundwater elevations (above MSL) at the Site based on
the topographic contours provided on the USGS Quadrangle map. The average
elevation of the four monitoring wells GZA-1, GZA-2, GZA-3 and MW-103 was
assumed to be 177.1 feet. The elevation of each individual well was then
estimated based on the difference from average as determined from the relative
elevation survey provided by CET. Groundwater elevations were then computed
for
the four wells based on measured depth to water on two separate occasions.
These elevations can be directly compared with the elevation of the water
surface of the reservoir. These data are summarized in Table 2.
Whereas the elevation of the reservoir surface is 172.2 feet above MSL,
the groundwater elevations at the Site are between 161.78 and 163.51 ft, with
the exception of one measurement in well MW-103 of 169.6. Groundwater
elevations
at the Site are therefore generally about 10
feet below the elevation of the reservoir surface as reported on the USGS
Quadrangle map. In the case of MW-103, in which groundwater is 2.6 feet below
the elevation of the reservoir, two points need to be considered. First, this
well is the closest to the reservoir of all the wells at the Site, and second,
this well is installed directly above the shallow refusal depth of 10 feet.
It
is possible that the groundwater elevation in this well reflects a local
condition. In any case, the data indicates a hydraulic gradient away from the
reservoir.
For groundwater elevations across the Site to rise above the level of the
reservoir, the reservoir level would have to drop as much as 10 feet. The
drought conditions that would cause this condition would of course also cause
groundwater levels at the Site to drop as well, making it unlikely that the
flow
in this region would reverse for any significant length of time. Even so,
based
on reasonable and conservative estimates of hydraulic conductivity and
porosity,
the hypothetical travel times for transport of pollutants from the Site to the
reservoir can be computed. Assuming a hydraulic conductivity of 100 feet per
day and a porosity of 0.3, the reservoir would have to drop 15 feet without
the
groundwater dropping at all and stay this way for 60 days for groundwater at
the
Site to reach the reservoir. This scenario is not within the realm of
possibility. It is more likely that groundwater levels at the Site would drop
along with the reservoir level, increasing the travel time to the reservoir to
the order of years, long enough that seasonal increases in reservoir level
would
return the gradient to its average direction long before any contaminant
migrating in groundwater could reach the reservoir.
Table 2. Estimated Groundwater Elevations
Well Estimated GZA (12/88) Groundwater CET (5/89) Groundwater
Elevation depth-to-water elevation depth-to-water elevation
GZA-1 177.11 14.02 163.09 13.208 163.9
GZA-2 176.64 14.2 162.44 13.125 163.51
GZA-3 178.68 16.9 161.78 15.438 163.24
MW-103 175.52 well not installed 5.917 169.6
These observations indicate that either: 1) a groundwater divide exists
between the reservoir and the Site, or 2) that the southern shore of the
reservoir is located in the zone where surface water recharges groundwater,
and
groundwater flow between the reservoir and the Site is generally towards the
Site. In either case, groundwater quality at the Site should have no
significant impact on water quality in the reservoir, and therefore should not
be classified as GW-1. This opinion is based on logic parallel to that
appearing in 310 CMR 40.0932(5), which allows for exceptions to the GW-1
classification to be made based on local hydrogeologic conditions in the case
of groundwater resources. Specifically, the exceptions are made relative to
groundwater resources when a lack of hydrogeologic connection between the site
and the resource area is shown or the regulated boundaries of a resource area
are shown to be inaccurate based on site-specific data. Although these
provisions are not explicitly granted in the case of surface water resources,
ESS believes that both of these conditions apply to this Site, and concludes
that the applicable groundwater standard for this Site should be GW-2 and GW-3.
5.0 RISK CHARACTERIZATION
A Method 1 risk characterization has been performed in accordance with 310
CMR 40.0970 and 40.0980 of the Massachusetts Contingency Plan (MCP). This
characterization is made based on the residual concentration of several
solvents and TPH existing in areas classified as GW-2 and GW-3, as described
above.
5.1 Exposure Point Concentrations
Exposure point concentrations (EPCs) have been calculated for the
various solvents detected at the Site as the maximum concentration detected in
any well over the period of investigation. These concentrations, along with
the relevant GW-2 and GW-3 standards, are provided in Table 3.
Table 3.
Maximum Concentrations of TPH and Solvents Detected in Groundwater at the Site
and Relevant GW-2/GW-3 Standards
Compound Maximum Consultant Well Method 1, Method 1,
Concentration Date GW-2 Limit GW-3 Limit
(ppb)
Total Petroleum 6000 Certified 3/89 MW-103 NA 50,000
Hydrocarbons (TPH)
Chlorobenzene 48 ESS 11/92 GZA-1 1,000 500
1,1,1-Trichloroethane14 ESS 11192 GZA-3A 4,000 50,000
Trichlorethene 55 Certified 3/89 MW-101 300 20,000
Ethyl Benzene 16 Certified 3/89 GZA-1 30,000 4,000
Total Xylenes 6.9 Certified 3/89 GZA-1 6,000 50,000
1,3-Dichlorobenzene 9.9 Certified 3/89 GZA-1 10,000 8,000
Trichlorofluoro 58 Certified 3/89 GZA-3A NSA NSA
Methane
1,1-Dichloroethane Trace (5) Certified3/89 GZA-2,3 9,000 50,000
cis- 1,2- Trace (5) Certified 3/89 GZA-3A NA 50,000
Dichloroethylene
Tetrachloroethylene Trace (5) Certified 3/89 MW-101 3,000 5,000
Total 1,2- 8.9 GZA 12/88 GZA-2 NA 50,000
Dichloroethenes
Notes:
> GZA's screening analysis was not per-formed by an EPA test method.
> NT = Not tested for or well not sampleable (e.g., well not yet
installed [MW-103] or covered over with budding [MW-1011).
> NSA No standard available
> Trace probable presence below detection limit (detection limit)
Potential Receptors and Migratory Pathways
As part of this risk characterization, ESS has considered what potential
receptors and migratory pathways exist at the Site. The dissolved solvent and
TPH concentrations are not large enough to pose a threat to air quality. The
Site is not functionally located in a GW-l area, and the nearest known water
supply wells are located over I mile from the Site. The Cambridge Reservoir,
located 325 feet north of the Site, is upgradient. A wetland south of the
Site,
the likely discharge point for groundwater flowing under the Site, is located
approximately 2,000 feet downgradient. Hobbs Brook, which probably receives
recharge from water flowing through the wetland, is the eventual receptor of
groundwater flowing through the Site. However, during the considerable travel
time between the site and the brook, the low levels of organic compounds
present
will be most likely be greatly diminished due to sorption, biodegradation, and
volatilization.
5.3 Risk Characterization
Based on a comparison of the maximum concentrations of all compounds
detected at the Site to below the applicable Method 1 GW-2/3 standards, ESS
concludes that no significant risk is posed by the presence of residual
contamination at this Site.
6.0 RAO OPINION
After reviewing laboratory data from assessments conducted at the Site,
ESS has reached the following conclusions:
dissolved concentrations of various solvents and TPH are below GW-
2/3 standards;
the contaminants detected in groundwater at the Site will not pose a
significant risk of harm to health, public welfare or the environment;
and the Site meets the requirements for a Class B-1 RAO.
MAP SHOWING LOCATION OF PREMISES IN CLOSE PROXIMITY TO RESERVOIR.
SITE SKETCH OF PREMISES DEPICTING THE LOCATION OF THE VARIOUS MONITORING WELL
SITES.
TABLE 1 RESULTS OF GROUNDWATER ANALYSIS
Table of results of Groundwater Analysis Samples of Various Well Test Sites
taken by various enviornmental engineers from 1988 through 1993. Tests were
done in 1988, 1989, 1992 and 1993. Not all wells were tested each year. The
test well showing the level of total petroleum hydrocarbon level and the test
well showing the trichloroethene level which levels the Massachusetts
Department of Environmental Protection indicated exceeded the public drinking
water standard (GW-1) have not been tested since 1989. The summary of all of
these test results at their highest levels of detection appears in Section 5.1
(of this Exhibit 10.6) as "Table 3 Maximum Concentrations of TPH and Solvents
Detected in Groundwater at the Site and Relevant GW-2/GW-3 Standards."