ARCHIVED REPORTS_XR0010809 - Laserfiche WebLink

Home Browse Search

� AM • Working To Restore Nature on Figure 2 Field methodology and analytical results are discussed in detail in RESNA's Interim Problem Assessment Report, dated January 13, 1992. GROUNDWATER MONITORING AND SAMPLING RESNA personnel performed quarterly groundwater monitoring and sampling on December 27, 1993 Field work consisted of measuring the depth-to-water in wells MW 1 through MW6, purging and sampling the water from wells MW2, MW3 and MW4, and analyzing the samples for the presence of dissolved petroleum hydrocarbons The water table elevation has dropped an average of approximately 0 83 feet since the last monitoring event in July 1993 Groundwater monitoring data are summarized in Table 1 Groundwater beneath the site flows southwest with an overall gradient of 0 0009 ft/ft, or approximately 4 8 feet/mile A groundwater gradient map for the December 27, 1993 monitoring episode is shown on Figure 2 Groundwater samples were collected from wells MW2, MW3 and MW4 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 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 the historical levels Analytical results are summarized in Table 2 Laboratory reports and chain-of-custody documentation are presented in Attachment 2 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 first quarter of 1994 and the subsequent monitoring report submitted by April 30, 1994 As granted in PHS/EHD correspondence dated December 27, 1993, the sampling frequency of MW1 will be reduced to annually and wells MW5 and MW6 to semi-annually Wells MW2, MW3 and MW4 will continue to sampled quarterly This schedule is based upon historical groundwater analytical data. OW0309/ 2 Quart1y14QR-1993 FNL