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• Sian i The site's station building and garage were demolished in December 1994, in part to facilitate the removal of hydrocarbon contaminated soil which is suspected beneath the station building The demolition of the station building was requested in PHS/EHD correspondence dated July 7, 1994 A required demolition asbestos survey conducted previously on the station building, determined the presence of asbestos containing materials E T Abatement, of Modesto California, properly removed and disposed of the site's suspected asbestos containing materials on November 11, 1994 GROUNDWATER MONITORING AND SAMPLING Smith Environmental performed quarterly groundwater monitoring and sampling on March 30, 1995 Field work included measuring the depth-to-water in wells MW1 through MW6, purging and sampling the water from wells MW2 through MW6, and analyzing the samples for the presence of dissolved petroleum hydrocarbons The water table elevation has risen an average of approximately 5 37 feet since the last monitoring event in December 1995 Groundwater monitoring data are summarized in Table 1 Groundwater beneath the site generally flows southwest with an overall gradient of 0 0007 ft/ft, or approximately 3 7 feet/mile This is consistent with the previous monitoring data A groundwater gradient map for the March 30, 1995 monitoring episode is shown on Figure 2 depicting an apparent mounding of goundwater in the vicinity of the former excavation Groundwater samples were collected from wells MW2, MW3, MW4, MWS, and MW6 after purging 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 LABORATORY ANALYSIS Collected groundwater samples were placed on ice and transported under chain-of-custody protocol 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 Petroleum hydrocarbon constituents were not detected above the laboratory detection limits in samples collected from wells MW2, MW5, and MW6 The laboratory method detection levels of BTEX and TPHg were 0 50 and 50 ppb, respectively Results are generally consistent with historical levels with the exception of well MW2 which previously contained reportable concentrations benzene, toluene, xylenes, and TPHg Analytical results are summarized in Table 2 Laboratory reports and chain-of-custody documentation are presented in Attachment 2