ARCHIVED REPORTS_XR0007147 - Laserfiche WebLink

Home Browse Search

d PHONE 285 7400 CABLE ADDRESS T6,011- SEATTLE IwIOILSEATTLE TE (FAX) 206 283 8036 TACOM PORTLA D STOCKTON T &ENOOS EDLES u '� o 0 TIME ® L o ?; l — r S TS 2737 WEST COMMODORE WAY SEATTLE WA 98199 1233 PRODUCTS , PO BOX 24447 SEATTLE WA 98124 0447 TIME TESTED E July 22, 2002 Mr Harlin Knoll cn San Joaquin County Public Health Services �� o w U Environmental Health Division rscc P O Box 2009 u,c/ Stockton, California 95201 T?' ui o RE Submittal of"Quarterly MonitoringApri � Jackpot Food Mart, 14000 E Highwrt,8, Lock d rd, Califoaa�Property No 04-049) Dear Mr Knoll, 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, April - June 2002 dated July 19, 2002 This document presents analytical results and field observations collected during Second Quarter 2002 groundwater sampling, and discusses the efficiency of the remediation system currently in operation Second Quarter 2002 Groundwater Sampling Results On May 16, 2002, groundwater samples were collected from MW-1 through MW-4 and MW-6 through MW- 10 at the subject site by a representative of SECOR MW-5 was not sampled as it did not recharge following purging 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 03 ft/ft was encountered in the wells at depths of 70 74 feet to 78 66 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 March 2002 sampling event, groundwater elevation increased in each of the wells by 1 78 feet to 8 22 feet, resulting in an overall average increase in groundwater elevation of 2 75 feet across the site Changes in groundwater elevation are most likely a result of seasonal variation, operation of the remediation system, and recent re-surveying of the wells 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 MW-1 (1,700 ppb TPH- g, 5 2 ppb toluene, 28 ppb ethylbenzene, and 250 ppb xylenes) Residual concentrations of hydrocarbons were identified in the samples collected from MW-2 (0 5 ppb toluene), MW-3 (0 6 ppb toluene), and MW-8 (0 8 ppb toluene and 1 0 ppb xylenes) TPH-g and BTEX were not identified in the groundwater samples submitted from MW-4, MW-6, MW-7, MW-9 and MW-10 Analyses identified low concentrations of MTBE in the samples collected from MW-2 (0 7 ppb), MW-4 (1 6 ppb), MW-7 (0 6 ppb), and MW-9 (0 6 ppb), however none of the other samples contained detectable concentrations of MTBE Table 2, Table 3, and Figure 3 in the attached report summarize groundwater analytical data and laboratory reports are included as Attachment 2