ARCHIVED REPORTS_XR0002475 - Laserfiche WebLink

Home Browse Search

CLEAW- mATER C R O U P Environmental Services t In January 1999, Clearwater supervised the installation of three additional groundwater monitoring wells (MW-4 through MW-6) to delineate the extent of dissolved-phase contamination Concurrently, Clearwater also performed a sensitive receptor survey The results of the investigation indicated that the extent of sorbed-phase contamination was delineated and existed from approximately 10 to 25 feet bgs near the former USTs Analysis of the groundwater samples indicated that the extent of dissolved-phase contamination remained undelineated downgradient from the former UST system However, high contaminant concentrations in cross-gradient positioned wells suggested that off-site sources could be contributing to contamination detected beneath the site Inquines suggested and later confirmed the existence of a fuel transport Iine in the area of the site The line was found to be currently filled with nitrogen gas Based on this information, Clearwater recommended additional investigation along South Fresno Avenue to better understand the distribution of contamination and possible contribution from potential off-site sources The results of this phase of ainvestigation were presented in Clearwater's Well Installation and Groundwater Monitoring Report - First Quarter 1999 In March 2000, Clearwater supervised the completion of one hydropunch, six soil borings, the destruction of MW-5, and the installation of three monitoring wells (M W-5B, MW-7, and MW- 8) in three of the soil borings All three wells were placed on the downgradient portion of the plume to help determine the downgradient extent of contaminants The hydropunch was performed in the former UST location to assess the vertical extent of groundwater contamination at 36 feet bgs Three soil borings were taken to define the lateral extent of soil and groundwater contamination on the northeastern portion of the site and assess possible off-site sources Three soil samples and one groundwater sample were analyzed from each boring Soil concentrations of TPHg and BTEX were detected only in boring MW-5B The highest soil concentration of TPHg (1,000 mg/kg) was detected at 25 feet bgs in MW-5B This sample was also analyzed for TPH as Jet Fuel (TPHjf) and found to contain 55 mg/kg TPHjf is unlikely to be present, but is an indicator of a hydrocarbon range on a chromatographic pattern, not a specific product Detectable concentrations of BTEX were present in soil samples collected from boring MW-513 ZB178C/4Q03 Monitoring Rpt 3 January 29,2004