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e ,) Working 7o Restore Nature Based on the conducted investigations n u limited to the g cted to date t appears that soil contamination is vicinity of the former USTs Groundwater contamination was noted only in wells MW 1 and MW2. THIRD QUARTER 1994 ACTIVITIES On July 18 and 19, 1994, a RESNA field geologist observed Western Strata Exploration (Westex) drill and install four groundwater monitoring wells (MW4, MWS, MW6, MW7) to depths ranging from 23 to 24 feet below grade to further define the extent of groundwater contamination beneath the site The newly installed wells were developed on August 1 and 2, 1994 A detailed discussion of the installation and development of these wells can be found in the September 2, 1994 Summary Letter Report, Supplemental Soil and Groundwater Investigation, prepared by RESNA. Fluid level measurements were collected on August 1 and August 22, 1994 Field procedures are outlined in Attachment 1. No measurable floating product was noted in any site wells. However, product sheen was noted in wells MW 1 and MW2. Groundwater monitoring data are summarized in Table 1. Monitoring logs are included in Attachment 2. Monitoring wells MW 1 through MW7 were surveyed by Enke and Associates, Inc. on August 22, 1994 The respective wellheads were tied into USGS Benchmark M1128 1961, located approximately 250 feet north of the intersection of Durham 4 erry and .Bird Roads. The surveyed elevations and the depth to groundwater measurements, summarized in Table 1, were used to evaluate the potentiometric surface beneath the site. The groundwater flow direction on August 1, 1994 was generally to the southwest with the hydraulic gradient of approximately TUR (Plate 3). The groundwater gradient on August 22, 1994 was generally northwesterly at approximately 0.0009 (Plate 4). This shift in groundwater flow direction is apparently due to a heterogeneous drop in water levels across the site. Water levels declined an average of 1.57 feet between August 1 and August 22, with the greatest drop in water levels generally occurring in the northern portion of the site. The groundwater flow direction beneath the site has historically vaned from the northeast to the southwest. Groundwater samples were collected from wells MW2 through MW7 on August 22, 1994. Well MW 1 was not sampled because product sheen was observed in the well. Groundwater sampling procedures are included in Attachment 1. Well purge logs are included in Attachment 2. Groundwater samples were analyzed for total petroleum hydrocarbons as gasoline (TPHg) using modified Environmental Protection Agency (EPA) Method 8015 and benzene, toluene, ethylbenzene, and total xylene isomers (BTEX) using EPA Method 8020. The samples were analyzed at Sparger Technology, Inc. in Sacramento, California (Hazardous Waste Testing 1230201QMR3Q44 FNL 2