ARCHIVED REPORTS_XR0010804 - Laserfiche WebLink

Home Browse Search

1i c Working To Restore Nature GROUNDWATER MONITORING AND SAMPLING RESNA personnel performed quarterly groundwater monitoring and sampling on September 16, 1994 Field work consisted of measuring the depth-to-water in wells MW1 through MW6, purging and sampling the water from wells MW1 through MW6 and analyzing the samples for the presence of dissolved petroleum hydrocarbons The water table elevation has dropped an average of approximately 2 3 feet since the last monitoring event in June 1994 Groundwater monitoring data are summarized in Table 1 Groundwater beneath the site flows southwest with an overall gradient of 0 001 ft/ft, or approximately 5 3 feet/mile This is consistent with the previous monitoring data A groundwater gradient map for the September 16, 1994 monitoring episode is shown on Figure 2 Groundwater samples were collected from wells MW 1 through MW6 after purging and stabilization of physical parameters (pH, electrical conductivity, and temperature) The monitoring wells were purged and sampled according to RESNA's Quality Assurance/Quality Control Plan, on file with PHS/EHD Well purge logs are included in Attachment 1 LABORATORY ANALYSIS j Collected groundwater samples were placed on ice and transported under chain-of-custody protocol to state certified Sequoia Analytical Laboratory 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 MW2, MW3, and MW4 Results are generally consistent with historical levels Analytical results are summarized in Table 2 Laboratory reports and chain-of- custody hain-ofcustody documentation are presented in Attachment 2 OTHER SITE ACTIVITIES The site's station building and garage have been scheduled for demolition in December 1994 These buildings, in part, are being demolished 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 The lateral extent of the dissolved contaminant plume associated with the former underground fuel storage tank has been essentially defined, except in the vicinity of well MW4, north of the former tank It is unclear whether contamination at MW4 can be attributed to the former tank or from a potential off-site contributing source The next sampling round is scheduled for the fourth quarter of 1994 and the subsequent monitoring report will be submitted by January 31, 1995