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Stantec
<br /> Site History and Previous Investigations
<br /> Former ARCO Service Station No. 595
<br /> May 18, 2009
<br /> Also in 2001, SECOR performed a 500-foot radius, door-to-door WSW survey. WSW survey
<br /> forms were submitted to four adjacent businesses (EI Rancho Motel, Wienerschnitzel, Auto
<br /> Factory, and Denny Boy Restaurant) and one residential property (8100 North Highway 99).
<br /> The returned survey form from Wienerschnitzel indicated the presence of a domestic well (well
<br /> 6/DW-1), which supplies the restaurant. The well was constructed of six inch steel casing;
<br /> however, the total depth of the well could not be verified, though the manager of
<br /> Wienerschnitzel estimated its depth to be approximately 170 feet. Subsequent sampling of this
<br /> well for petroleum hydrocarbon constituents indicated that the well had been impacted by
<br /> 1,2-DCA.
<br /> In addition to dispersing survey forms, SECOR conducted a physical search of the area. During
<br /> the site visit, a domestic well (7/DW-2) was identified on the northern portion of the Auto Factory
<br /> property, and a well (8/DW-3) was found in a fenced compound west of the Auto Factory
<br /> property. Conversations with a Denny Boy Restaurant employee revealed that the well on the
<br /> Auto Factory property (7/DW-2) served both the Auto Factory and the Denny Boy Restaurant.
<br /> Well 8/DW-3 was located in an unmarked fenced compound. Details of its well construction are
<br /> known; however, the well is most likely an irrigation well. As indicated in San Joaquin County
<br /> Environmental Health Department (SJC/EHD) letter dated October 26, 2000, no public water is
<br /> distributed along the Highway 99 East Frontage Road (SECOR's Site Assessment Report dated
<br /> December 11, 2001).
<br /> In March 2002, four 1,000-pound granular activated carbon (GAC) vessels were installed near
<br /> the wellhead of DW-1 to treat the groundwater supply to the nearby Wienerschnitzel business.
<br /> A groundwater extraction (GWE) system was activated on April 8, 2002. Extracted groundwater
<br /> from DW-1 was routed through two cartridge filters, two GAC vessels plumbed in series, and a
<br /> particulate filter. The treated groundwater is routed to the Wienerschnitzel main water supply
<br /> line at a maximum capacity of 30 gallons per minute. The GWE system was checked on a
<br /> weekly basis and water samples were collected monthly at the influent, midpoint, and effluent
<br /> sampling ports within the GWE system.
<br /> In June 2005, two deep on-site groundwater monitoring wells (DMW-1 and DMW-2), one deep
<br /> off-site groundwater monitoring well (DMW-3), and three shallow off-site groundwater
<br /> monitoring wells (MW-8 through MW-10) were installed by Cascade Drilling, Inc. (Cascade) of
<br /> Rancho Cordova, California under SECOR supervision between June 24 and 27, 2002. Deep
<br /> wells DMW-1, DMW-2, and DMW-3 were installed at depths of 101.5 feet, 102 feet, and 102.5
<br /> feet below ground surface (bgs), respectively. Shallow wells MW-8 through MW-10 were
<br /> installed at depths of 74 feet, 70.5 feet and 70.5 feet bgs, respectively. TPHg, BTEX, total
<br /> petroleum hydrocarbons as diesel, methyl tert-butyl ether, and other fuel oxygenates were not
<br /> detected in soil samples.
<br /> Ten monitoring wells were destroyed on February 28 through March 4, and April 28 and 29,
<br /> 2005 in accordance with SJC/EHD requirements. Wells MW-2, MW-4 through MW-8, MW-10
<br /> and DMW-1 through DMW-3 were over-drilled to the total depth of the well, and then grouted to
<br /> ground surface using a tremie pipe with neat cement. Two underground utilities were
<br /> encountered during hand auguring activities around MW-3, therefore MW-3 was abandoned
<br /> On December 29, 2005 and January 3, 2006, URS Corporation of Sacramento, California
<br /> oversaw the removal of the three USTs, four dispensers, and associated piping by Paradiso
<br /> 595 Site History and Previous Investigations.doc 2
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