ARCHIVED REPORTS_XR0007150 - Laserfiche WebLink

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l JHONL 985 1 �C CABs F A3DHESS T1 0, SEATTLE TE �FAXl7 20G 283 8033 TACOMA N PORTLAND STOCKTON1,_ T iI I RENO RICHMOND LOS ANGELES 9 `a NE TIME OIL CO . 7-TF 2737 WEST COMMODORE WAY SEATTLE WA 98199 1233 PP O BOX 24447 SEATTLE WA 98124-0447 TME TESTED EM E May 28, 2002 Mr Harlin Knoll ll tt (r"E %S E 0 ro San Joaquin County Public Health Services Environmental Health Division JUK P O Box 2009 Stockton, California 95201 ENVIRONMENT HEALTH RE Submittal of"Quarterly Monitoring Report, January—March 2002"for PERMIT/SERVICES 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 sods and groundwater System operation began December 13, 1999 Please find enclosed SECOR's "Quarterly Monitoring Report, January— March 2002" dated May 21, 2002 This document presents analytical results and field observations collected during First Quarter 2002 groundwater sampling, and discusses the efficiency of the remediation system currently in operation First Quarter 2002 Groundwater Sampling Results On November 28, 2001, groundwater samples were collected from MW-1 through MWA 0 at the subject site by a representative of SECOR Prior to purging, the depth to water in all wells 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 to the wells at depths of 70 23 feet to 84 67 feet below ground surface Free product was not encountered in any of the wells The locations of the wells are identified on Figure 2 of the attached report Since the November 2001 sampling event, groundwater elevation increased in MWA by 0 25 feet, in MW-3 by 1 31 feet, and in MW-9 by 0 08 feet while it decreased in the remainder of the wells by 0 01 feet to 0 42 feet These changes resulted in an overall average increase in groundwater elevation of 0 03 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 Elevated concentrations of hydrocarbons were identified in the sample collected from MWA (220,000 ppb TPH-g, 570 ppb toluene, 1,300 ppb ethylbenzene, and 13,000 ppb xylenes) TPH-g and BTEX were not identified in the groundwater samples submitted from MW-2 thorough MW-10 Analyses identified 0 7 ppb MTBE in the sample collected from MW-4 and 0 5 ppb MTBE in the sample collected from MW-5, however none of the other samples contained detectable concentrations of MTBE Table 2, Table 3, and Figure 3 to 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 November 2001 sampling event, hydrocarbon concentrations decreased in MW-1 (as shown by a decrease in free product thickness)while they remained"non-detect" in the remainder of the