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r? NA Working To Restore Nature Field activities performed at the site are summarized in separate Problem Assessment Reports submitted by RESNA on May 30, 1991 and May 20, 1992 QUARTERLY MONITORING AND SAMPLING Groundwater monitoring and sampling of site wells was conducted on November 9, 1993, by RESNA personnel Water level measurements were collected from each site monitoring well (Table 1) prior to purging and sampling activities Groundwater elevations across the site have dropped an average of 1 5 feet since the last monitoring event in August 1993 The groundwater gradient was calculated using the November 9, 1993 groundwater elevation data and is illustrated on Figure 2 The figure depicts a variant gradient between 0 6 to 2 1 per cent, or 32 to 111 feet per mile in a southeasterly direction In accordance with San Joaquin County Public Health Services, Environmental Health Division (PHSIEHD)correspondence dated May 5, 1993, monitoring wells MW2, MW3, and MW6 were sampled Prior to groundwater sample collection, a minimum of 3 casing volumes of water was purged from each monitoring well All purged water was contained on-site in DOT approved 55-gallon drums pending analytical results Purge water determined through laboratory analysis to be free of petroleum hydrocarbons will be disposed of through surface discharge Groundwater samples were collected from each well after stabilization of groundwater parameters (pH, electrical conductivity, temperature) Water samples were collected using dedicated disposable bailers Field purge logs are contained in Attachment 1 Groundwater samples were placed on ice and transported under chain-of-custody protocol to state-certified Sequoia Analytical in Redwood City, California All samples were analyzed for benzene, toluene, ethylbenzene, xylenes (BTEX) using EPA method 8020, and total petroleum hydrocarbons as gasoline (TPHg) using modified EPA method 8015 Dissolved petroleum hydrocarbons and BTEX constituents were not detected in monitoring wells MW3 and MW6 The sample collected from MW2 contained benzene, toluene, ethylbenzene, and xylenes at 0 66, 0 80, 5 0 and 0.79 parts per billion (ppb), respectively No TPHg was detected in well MW2 BTEX levels in well MW2 were below the respective Maximum Contaminant Levels (MCLS) established by the Department of Health Services Laboratory results are summanzed in Table 2 Laboratory reports and chain-of-custody documentation are presented in Attachment 2 STOCKPILED SOIL Excavated stockpiled soils previously documented to be impacted by petroleum hydrocarbon constituents have remained on site since March 1991 excavation The stockpiled soil has been aerating in accordance with the exemptions specified in San Joaquin Valley Unified Air Pollution Control District (APCD) Rule 463 5 Volatile Organic Compound Emissions from Decontamination of Soil 15000214QR-1993 FAIL 2