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!� 1 • beneath the site generally flows in a westerly direction with average gradient of 0 0009 ft/ft, or approximately 4 7 feet/mile Groundwater monitoring data are summarized in Table 1 A groundwater gradient map for the March 25, 1997 monitoring episode is shown on Figure 2 Groundwater samples were collected from wells MW2 p through MW6 after urging and stabilization of physical parameters (pH, electrical conductivity, and temperature) The monitoring wells were purged and sampled according to RESNA Industries Quality Assurance/Quality Control Plan, on file with PHS/EHD Well purge logs are included in Attachment 1 The community well was sampled through an existing sampling port Collected groundwater samples were placed on ice and transported under chain-of-custody to State-certified Argon Laboratories Samples were analyzed for benzene, toluene, ethylbenzene, and xylenes (BTEX) and TPHg by EPA methods 8020 and modified 8015, respectively Laboratory analyses detected elevated concentrations of petroleum hydrocarbons in the samples collected from wells MW3 and MW4 Groundwater samples collected from wells MW2, MW5, MW6, and the municipal well contained no detectable concentrations of BTEX or TPHg The laboratory method detection levels for BTEX and TPHg were 0 50 and 50 ppb, respectively The analytical results are generally consistent with historical levels Analytical results are summarized in Table 1 Laboratory reports and chain-of-custody documentation are presented in Attachment 2 • In accordance with PHS/EHD correspondence dated December 27, 1993, the sampling schedule of MW 1 has been reduced to annually and wells MW5 and MW6 to semi-annually Wells MW2, MW3 and MW4 will continue to be sampled quarterly Additionally, the nearby community well will be sampled quarterly This schedule is based upon lustoncal groundwater analytical data SOIL CELL SAMPLING On March 24, 1997, soil samples were collected from the on-site soil aeration cell to monitor the progress of soil remediation Four soil samples were collected for every 100 cubic yards of soil and were composited in the laboratory at a 4 1 ratio Soil samples were placed on ice and transported under chain-of-custody to Argon Laboratories, in Ceres, California Samples were analyzed for TPHg and BTEX No soil samples contained TPHg or BTEX at concentrations above laboratory detection limits Soil sampling locations are shown on Figure 3 Analytical data sheets are contained in Attachment 3 Based on laboratory results, the soil in the aeration cell appears to be remediated Smith Technology is currently evaluating soil disposal alternatives which may include transferring the soil to a nearby farm where it would be utilized for agricultural purposes Pending PHS/EHD approval, Smith Technology will begin making arrangements for the deposition of the soil cell w 1943261quart1y\1gr-1997 doc 3 • SMTH