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2.5 Additional Soil and Groundwater Investigation Seven monitoring wells had previously been installed on or near the site. The Se n groundwater m g p y wells were installed to depths of 55 feet At the time of installation, groundwater depth was approximately 42 feet Subsequently,groundwater depth fell below 55 feet and all wells were dry IOn June 13 and 14, 1994, four soil borings were dnlled at the site. Borings MW-8 and MW- 9 were advanced to depths of 75 feet and completed as groundwater monitoring wells Borings CB-1 and CB-2 were advanced to a depth of 65 feet and backfilled with Portland cement. Hydrocarbon odors were noted in samples from boring CB-1 at depths from 20 feet to 45 feet and in boring CB-2 at depths from 35 feet to 45 feet Organic vapors were detected by the PID at concentrations up to 564 ppm (CB2-35) No hydrocarbon odors or organic vapors were detected in borings MW-8 or MW-9, no petroleum hydrocarbons were detected in the samples analyzed from MW-8 or MW-9 Petroleum hydrocarbons were detected in boring CB-1 at depths of 20 feet and 35 feet and in boring CB-2 at depths from 30 feet to 40 feet No benzene was detected in any of the samples analyzed Two soil samples were also analyzed for total lead Lead was detected in Isamples CBI-15 and CB1-20 at concentrations of 12 ppm and 9 ppm, respectively On June 16, 1994, quarterly groundwater monitoring was resumed at the site The depth-to- water was measured in MW-8, MW-9 and EW-1 and the wells were purged and sampled Groundwater gradient was calculated to be 0 0024 ft/ft directed N 80° E Toluene and xylenes were detected in the sample from MW-9 at concentrations of 0 52 ppb and 2 9 ppb respectively No other petroleum hydrocarbons were detected in any of the samples 3.0 PROCEDURES 3.1 Monitoring Well Purge Procedures On September 16, 1994, groundwater depths in monitoring wells MW-8, MW-9 and EW-1 were measured relative to the top of the casing using a Solmst water level meter The relative piezometnc level in each well and hydraulic gradient were determined by subtracting the depth to groundwater from the relative casing elevation (Table 1) After water levels were measured, a clean PVC bailer was used to purge approximately 5 to 6 gallons of water from monitoring wells MW-8, MW-9 and EW-1 Temperature, pH and conductivity were measured at one-gallon intervals using an ICM water analyzer The purge water was stored in 55-gallon DOT-approved drums and stored on-site Field data sheets are included in Appendix A a�pwi At&Semis,1� 0a.h.',awv-pn 1 5