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<br /> Ms. Lori Duncan Page 3
<br /> San Joaquin County Environmental Health Department
<br /> January 28, 2005
<br /> Soil Sampling and Analysis
<br /> Soil samples were collected at 5-foot intervals with a 2-inch-diameter sampler using 6-inch brass liners.
<br /> The samples were capped with Teflon® tape and plastic end caps, labeled, sealed in clean resealable
<br /> �y bags, and placed in a cooler on ice for delivery to Sequoia Analytical Laboratories in Morgan Hill,
<br /> California, under chain of custody. A photoionization detector (PID) was used to field screen soil
<br /> samples for the presence of volatile organic compounds (VOCs). Due to heavy fog and high humidity,
<br /> the PID malfunctioned during drilling activities and qualitative screening was conducted. Hydrocarbon
<br /> odor and staining were observed in soil samples from 35 feet to 89 feet bgs in MW-8. Soil samples
<br /> 1 collected at approximately 30 feet bgs in MW-7, and 25, 30, 45, 55, 68,78, 89, and 98 feet bgs in MW-8
<br /> were selected for laboratory analysis. Soil sampling and laboratory procedures are described in the
<br /> Workplan for Additional Assessment prepared by URS dated August 27, 2004.
<br /> Soil samples were analyzed for gasoline-range organics (GRO) by EPA Method 8015B (preparation by
<br /> EPA Method 5030), and for benzene, ethylbenzene, toluene, and xylenes, (BTEX), methyl-tert butyl
<br /> ehter (MtBE), tert butyl alcohol (TBA), di-isopropyl ether (DIPE), ethyl tert-butyl ether (EtBE), tert-
<br /> amyl methyl ether (TAME), 1,2-dichloroethane (1,2-DCA), and 1,2-dibromomethane (EDB), by EPA
<br /> Method 8260B (preparation by EPA Method 5030).
<br /> Soil Analytical Results
<br /> GRO, ethylbenzene, and xylenes were reported in soil samples from MW-8 at 45, 55, 68, 78, 89, and 98
<br /> feet bgs. The maximum concentrations of GRO, toluene, ethylbenzene, and xylenes reported were 17
<br /> milligrams per kilogram(mg/kg), 0.06 mg/kg, 0.17 mg/kg, and 091 mg/kg, respectively at 89 feet bgs in
<br /> MW-8. Benzene was reported at 0.0066 mg/kg in one sample from MW-8 at 78 feet bgs. All other fuel
<br /> oxygenates analyzed were reported as below laboratory detection limits. The soil sample collected from
<br /> �j MW-7 was reported below laboratory detection limits for all analytes. Soil analytical data are
<br /> �1 summarized in Tables 1 and 2. Laboratory analytical reports and chain-of-custody documentation are
<br /> included in Attachment C.
<br /> Monitoring Well Installation, Development, and Surveying
<br /> Monitoring wells MW-7 and MW-8 were constructed using 2-inch-diameter, Schedule 40, flush-
<br /> threaded polyvinyl chloride (PVC) well casing. Total depths of wells MW-7 and MW-8 are 40 feet and
<br /> i100 feet, respectively. Fifteen feet of 0.020-inch machine-slotted well screen was set from 40 feet to 25
<br /> feet bgs in MW-7. Five feet of 0.020-inch machine-slotted well screen was set from 100 feet to 95 feet
<br /> bgs in MW-8. A Monterey No. 3 silica sand filter pack was installed from the bottom of each boring to 2
<br /> feet above the top of each well screen. A 3-foot bentonite seal was placed above each sand pack, and
<br /> neat cement was used to fill the annular space to within 1 foot of the surface. Each well was completed
<br /> j with a traffic-rated, flush-mounted well box, and a locking well cap was placed on the top of the casing.
<br /> Well construction details for these wells are presented in Attachment B.
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