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<br /> Ms. Angela Lee
<br /> Huntbrook Holdings, LLC
<br /> February 12, 2014
<br /> Page 8
<br /> Utilizing the December 3, 2013 depth to groundwater measurements and the surveyed elevations of
<br /> monitoring well casings, RDM prepared a groundwater elevation contour map (Figure 3). On
<br /> December 3, 2013, groundwater flow was generally toward the northeast with gradient of
<br /> approximately 0.0009 ft/ft. Groundwater monitoring and sampling field notes recorded during the
<br /> monitoring event are included in Enclosure J.
<br /> The groundwater samples were submitted to Kiff laboratory in Davis,California,for analysis of:
<br /> • BTEX, TPHg, fuel oxygenates (MTBE, TAME, DIPE, TBA, and ETBE), lead scavengers
<br /> (1,2 DCA and EDB), naphthalene, and chlorinated VOCs (full list) by EPA Method 8260 B;
<br /> and,
<br /> • TPHd by EPA Method 8015 Modified with and without silica gel cleanup (if TPHd was
<br /> reported in initial sample); silica gel cleanup was performed using EPA Method 3630C
<br /> Modified;
<br /> The groundwater analytical results, including the previous consultant's analytical results dating to the
<br /> third quarter 2011, are summarized in Table 2. Copies of the laboratory analytical reports with chain-
<br /> of-custody documentation are presented in Enclosure K.
<br /> On December 3, 2013, in the four newly-installed monitoring wells, BTEX, fuel oxygenates, EDB,
<br /> and naphthalene concentrations were non-detect (less than 0.50 micrograms per liter (µg/L)); TPHg
<br /> • was reported in MW-6 and MW-7 at concentrations of 77 (noted by lab as primarily compounds not
<br /> found in typical gasoline) and 220 pg/L, respectively; 1,2 DCA was reported in MW-4 and MW-7 at
<br /> concentrations of 42 and 2.1 µg/L, respectively. TPHd was reported in MW-4, MW-7 and MW-8 at
<br /> concentrations of 140, 86, and 81 pg/L, respectively. However, following silica gel cleanup, TPHd
<br /> was only reported in MW-4 at 84 µg/L, and was noted by the laboratory to be discrete peaks, higher
<br /> i boiling hydrocarbons present,atypical of diesel fuel.
<br /> In addition to the petroleum hydrocarbon constituents detected in groundwater beneath the site,
<br /> chlorinated solvents were detected in monitoring wells MW-6,MW-7 and MW-8.
<br /> Trichloroethene (TCE) was reported in monitoring well MW-6 at 4.6 pg/L. Tetrachloroethene (PCE)
<br /> ti♦ was reported in monitoring wells MW-6,MW-7 and MW-8 at concentrations of 36,0.69 and 0.90 µg/L,
<br /> respectively.
<br /> Groundwater concentration maps illustrating dissolved benzene, TPHg, TPHd, MTBE, PCE and TCE
<br /> in shallow groundwater on December 3, 2013, are presented in Figures 4, 5, 6, 7, 8 and 9
<br /> respectively.
<br /> •
<br /> Additional Soil Assessment-Soil Borine RDM-1
<br /> On October 8, 2013, RDM attempted to hand auger one soil boring (RDM-1) inside the former station
<br /> building, immediately adjacent to the suspected former fuel dispenser island. The location of the boring
<br /> is illustrated on Figure 2. Due to physical limitations, RDM was only able to hand auger to a depth of
<br /> 15 tbgs. Soil samples were collected at depths of 2.5, 5, 10 and 15 fogs from RDM-1 and submitted for
<br /> laboratory analysis (refer to analyses described below). The borehole was left open pending laboratory
<br /> analytical results and further discussions with the CVRWQCB to determine if a limited access
<br /> Geoprobe drilling rig was needed to complete the boring.
<br />•
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