ARCHIVED REPORTS_XR0007138 - Laserfiche WebLink

Home Browse Search

PHo%F ae5 a .:.a CABLE A30i31 SS T, O,l SEATTLE a (FAX) 206 283 8036 TACOMA N PORTLAND r ,JMWTOCKTON IF12 I EO CN MOND LOS ANGELES y i i Za "E TIME O I L CO . 7 n 5 5 2737 WEST COMMODORE WAY SEATTLE WA 98199 1233 PRDoucrs M P O BOX 24447 SEATTLE WA 98124-0447 TIME TESTED e July 28, 2003 Mr Harlin Knoll San Joaquin County Public Health Services Environmental Health Division JU L �� P O Box 2009 Stockton, California 95201 E��VIROniI''lEly t EfU�' RE Submittal of"Quarterly Monitoring Report, April -Ydr4l�p EA ICES Jackpot Food Mart, 14000 E Highway 88, Lockeford, California (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 Four monitoring wells were installed during this investigation (MW-1 through MW-4) 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 (MW-5 through MW-10), 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 2003" dated July 23, 2003 This document presents analytical results and field observations collected during Second Quarter 2003 groundwater sampling, and discusses the efficiency of the remediation system currently in operation Second Quarter 2003 Groundwater Sampling Results On May 15, 2003, 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 was dry Prior to purging, the depth to water in each well (MW-1 through MW-10) was measured to evaluate elevation, flow direction, and gradient As noted in the attached report, groundwater with a south-southwesterly flow direction and a gradient of 0 05 ft/ft was encountered in the wells at depths of 71 2 feet to 90 11 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 January 2003 sampling event, groundwater elevation increased in MW-5 by 3 92 feet and in MW-8 by 1 93 feet, while it decreased by 0 00 feet to 5 46 feet in the remaining wells These changes resulted in an overall average decrease in groundwater elevation of 0 12 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 Hydrocarbons were identified in the samples collected from MW-1 (4,300 ugll TPH-g, 1 2 ugll benzene, 4 3 ugll ethylbenzene, and 128 ugll xylenes) and MW-10 (120 ugll TPH-g and 3 7 ugll xylenes) TPH-g and BTEX were not identified in the groundwater samples submitted from MW-2 through MW-4 and MW-6 through MW-9 Analyses identified low concentrations of MTBE in the samples collected from MW-3 (0 5 ug/1)and MW-9(2 9 ug/1), however, none of the other samples contained detectable concentrations of MTBE Other fuel oxygenates (TBA, DIPE, ETBE, and TAME)were not present at detectable concentrations in any of the samples 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 January 2003 sampling data, hydrocarbon concentrations increased in MW-1