SITE INFORMATION AND CORRESPONDENCE_FILE 2

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1 Complaint No. 11917 - 2 - P 8 November 2013 Valero/Jamar Service Station Stockton, San Joaquin County A review of the Jamar case file and the available reports, including thirteen (13) years of monitoring reports, does not indicate a connection between the oil and grease detected in your toilet tank and sewer cleanout and the groundwater pollution emanating from the Jamar Site. Our response to each of the concerns expressed in the Complaint follow: 1. Oil in the holding tank of the household toilet and oil in sewage clean out drains. In our inspection on 20 August 2013 we observed the sewer cleanout in your backyard that you indicated was the "trap" cleaned out to collect the dark sediment sample (Photo 1) you showed us . After we entered the residence to view the toilet tank and bowl mentioned in the complaint, you took a clean Q-tip and scrapped the toilet tank "ring" (Photo 2), which was black and greasy. Neither the dark sediment sample nor the grease from the toilet tank had any odor. Samples were collected the following Monday (26 August 2013) from the outside water tap and the toilet tank to evaluate for petroleum hydrocarbons. Results indicated the elevated levels of oil and grease were present in the toilet tank and the water sample collected from the spigot in the backyard. The laboratory did not detect diesel or gasoline constituents in the samples. Water samples collected from your toilet tank and outside spigot on 26 August 2013 found the following constituents. Sam le Acetone BromodichloromethaneE727.7 oroform Oil & Grease TT 3.2 1.1 26.6 4,100 SP <0.6 1.1 25.6 4,600 S-1 NA 2.2 NA MCLs 20,000 25,000 90 80 None TT=toilet tank SP=outside spigot S-1 =CWS service sample NA=not analyzed MCLs—California Maximum Contaminant Levels for drinking water 1 =taste and odor 2=USEPA Health Advisory 3=Primary MCL 4=no MCL for human health 25,000 ug/L for protection of aquatic life(30-day average) The groundwater plume from Jamar Service is approximately 50' below the ground surface. The Site Conceptual Model (SCM) for the Jamar case shows the gasoline release occurred at the USTs pit on the east side of the property, with pollution travelling down through soil and reaching groundwater at 55' to 70' bgs. The data show the groundwater plume has migrated vertically to 110 feet below the ground surface and horizontally to the southeast and east. Monitoring has shown groundwater in the area flows in an easterly direction (northeast to southeast). The data show the plume has not migrated to the north- northwest in the direction of your property. The monitoring conducted as part of the investigation and cleanup of the Jamar Site show methyl t-butyl ether (MTBE) at 112 micrograms per Liter (ug/L) in monitoring well MW-12A, the closest well to your residence (Figure 1). The latest semi-annual groundwater monitoring results show groundwater impacts at MW-12A in micrograms per Liter(ug/L) in the following table: TPHg Benzene Toluene Ethylbenzene Xylenes MTBE 1,2-DCA MCLS NA 1 150 300 1750 13 0.5 12/13/2012 170 11 <2 8.7 <4 170 4.9 TPHg=total petroleum hydrocarbons as gasoline MTBE=methyl tertbutyl ether 1,2-DCA=1,2-dichloroethane 1 =California Drinking Water Standards,Primary Maximum Contaminant Level NA=no MCL drinking water standard for gasoline MW-12A was constructed in February 2011 and the highest concentration of MTBE reported was