ARCHIVED REPORTS_XR0007156 - Laserfiche WebLink

Home Browse Search

�f WASHINGTON TE PHONE(206)285-2400 OREGON x CALIFORNIA 12 Tp FAX(206)283-8036 DAHONEVADA g 123 N TAME OIL C � o B 4 1 66 5 TS 2737 WEST COMMODORE WAY SEATTLE,WA 98199-1233 PRODUCTS TQM PO BOX 24447 SEATTLE,WA 98124-0447 TIME TESTED E November 14, 2001 Mr Harlin Knoll San Joaquin County Public Health Services Environmental Health Division P O Box 2009 Stockton, California 95201 RE Submittal of"Quarterly Monitoring Report, July- September 2001"for Jackpot Food Mart, 14000 E Highway 88, Lockeford, California (Property No 04-049) Dear Mr Knoll, At the request of the San Joaquin County Public Health Services Environmental Health Division (PHSIEHD), an environmental Investigation was implemented at the subject site in December 1994 to evaluate the extent of hydrocarbon-impacted soils and to determine whether or not groundwater had been impacted A total of four monitoring wells were installed during this Investigation In July 1996, six additional monitoring wells were installed on and off of the subject site to assist in defining the extent of groundwater Impacts and quarterly monitoring was implemented In August and September 1999, SECOR installed a vapor extraction/air sparging system at the subject site to remediate hydrocarbon-impacted soils and groundwater System operation began December 13, 1999 Please find enclosed SECOR's "Quarterly Monitoring Report, July - September 2001" dated November 12, 2001 This document presents analytical results and field observations collected during Third Quarter 2001 groundwater sampling, and discusses the efficiency of the remediation system currently in operation Third Quarter 2001 Groundwater Sampling Results On August 20, 2001, groundwater samples were collected from MW-2 through MW-10 at the subject site by a representative of SECOR Prior to purging, the depth to water In all wells (MW-1 through MW-10) was measured to evaluate elevation, flow direction, and gradient As noted in the attached report, groundwater with a southwesterly flow direction and a gradient of 0 02 ft/ft was encountered in the wells at depths of 68 90 feet to 76 94 feet below ground surface Approximately 0 52 feet of free product was encountered in MWA The locations of the wells are identified on Figure 2 of the attached report Since the April 2001 sampling event, groundwater elevation increased in MWA by 0 91 feet and in MW-3 by 0 67 feet while it decreased in the remaining wells by 0 94 feet to 3 96 feet These changes resulted in an overall average decrease in groundwater elevation of 145 feet across the site Changes in groundwater elevation are most likely a result of seasonal variation and operation of the remediation system Groundwater gradient and flow direction remained consistent with previously collected data Table 1 in the attached report summarizes historical groundwater elevation data TPH-g and BTEX were not identified in the groundwater samples submitted from MW-2 thorough MW-10 Analyses identified 1 1 ppb MTBE in the sample collected from MW-4, however none of the other samples contained detectable concentrations of MTBE No sample was collected from MWA, as It contained free product Table 2, Table 3, and Figure 3 in the attached report summarize groundwater analytical data and . laboratory reports are included as Attachment 2 The highest concentrations of hydrocarbons appear to remain onsite in the vicinity of the pump islands (MW- 1) When compared to the April 2001 sampling event, hydrocarbon concentrations decreased in MWA (as shown by a decrease in free product thickness)while they remained relatively unchanged In the remainder of the wells Changes In hydrocarbon concentrations are most likely a result of groundwater elevation