|
TABLE 1 -CHECKLIST OF REQUIRED DATA
<br /> FOR NO FURTHER ACTION REQUESTS AT UNDERGROUND TANK SITES
<br /> Sale Name and Locabon 7-Eleven Store 92243-17647,1048 Yosemite Avenue East, Manteca, San Joaquin County
<br /> 1 Distance to production wells for municipal, domestic, agriculture, One public supplywell is located 1000 feet north of the
<br /> industry and other uses within 2000 feet of the site, site. No other wells are located within 500 feet of the
<br /> site.
<br /> 0 2 Site maps,to scale,of area impacted showing locations of former and existing tank Two 10,000-gallon and one
<br /> systems,excavation contours and sample locations,bonng and monitoring well elevation 6,000-gallon gasoline USTs
<br /> contours,gradients, and nearby surface waters, buildings, streets, and subsurface utilities, were removed In 12/98
<br /> 3 Figures depicting lithology(cross section), treatment system diagrams, Site llthology consists of silty sand grading to a
<br /> medium sand The total depth investigated was
<br /> 20 feet
<br /> 0 4 Stockpiled soil disposed off-site(quantity), Approximately 450 cubic yards of soil was excavated and transported
<br /> otfslte to a licensed disposal facility
<br /> EY-1 5 Monitoring wells remaining on-site, fate, Three monitoring wells(MW-1 to MW-3) were installed for this investigation
<br /> The three wells will be properly abandoned
<br /> 6 Tabulated results of all groundwater elevations and depths to water, The depth to water varied from 12 to 17 feet The
<br /> groundwater flow direction varied from northwest
<br /> to east
<br /> 7 Tabulated results of all sampling and analyses In 12198,soil analyses reported TPHg(14 mg/kg),and MtBE
<br /> QDetection limits for confirmation sampling (2 3 mg/kg) After overexcavatlon in 12/98 and resampling in 3/02, only
<br /> MtBE(0 0026 mglkg) was detected in soil Grab groundwater sample
<br /> ©Lead analyses results in 6/99 were 19,400 yglL for TPHg,and 126 pg/L for MtBE In
<br /> 7/03,groundwater results from monitoring wells were 0 56 pg/L(MTBE)
<br /> ETJ 8 Concentration contours of contaminants found and those remaining in soil The extent of contamination is defined by
<br /> d groundwater,both on-mW and off-site on-slie soil borings and monitoring wells
<br /> Y Lateral and Y Vertical extent of soil contamination
<br /> Lateral and Vertical extent of groundwater contamination
<br /> 9 Zone of influence calculated and assumptions used for subsurface Based on the limited extent of soil
<br /> remediation system and the zone of capture attained for the soil and contamination,an engineered remediation
<br /> groundwaterremedâșation system, system was not required at this site
<br /> 7: 10 Reports/information [9 Unauthorized Release Form fourteen QM4s(1/00 to 7/03)
<br /> q Boring logs El PAR E] FRP Other
<br /> 11 Best Available Technology(BAT) used or an explanation for nal using BAT, Remove USTs,overexcavatlon with offsite
<br /> soil disposal,and natural attenuation
<br /> 0 12 Reasons why background warms
<br /> unattainable using BAT, Decreasing concentrations have been attained at all monitoring wells Minor
<br /> soil contamination remains on-site
<br /> 0 13 Mass balance calculation of substance
<br /> treated versus that remaining, The consultant did not estimate remaining soil contamination Minimal
<br /> contamination was detected in groundwater In 2003
<br /> 0 14 Assumptions,parameters,calculations and model used in risk A risk assessment was not required
<br /> assessments,and fate and transport modeling,and q
<br /> 15 Rationale why conditions remaining at site will not adversely Soil contamination is limited in extent,and based on
<br /> impact water quality, health, or other beneficial uses fourteen sampling events, contamination is not
<br /> continuing to leach to groundwater Groundwater
<br /> monitoring shows a decreasing trend in concentrations
<br /> By Comments Two 10,000-gallon and one 6,000-gallon gasoline USTs were removed from the subject site in 12/98
<br /> JLB Multiple bonngs and three monitoring wells(MW-1 to MW-3)were completed in 2000 to delineate and monitor
<br /> contamination at this site Additional borings and grab sampling were completed in 1999 and 2003 In 1998, maximum
<br /> Date soil concentrations reported were TPHg(14 mg/kg), and UBE(2 3 mg/kg) in 3102 additional soil analyses detected only
<br /> MtBE(0 0026 mg/kg) Grab groundwater monitoring results in 6199 were 19,400 pg/L for TPHg and 126 irg/L for MISE
<br /> 10/29/03 In 7103 after 14 quarters of monitoring groundwater,monitonng well results were 0 56 NglL for MfBE Groundwater flow
<br /> direction vaned from northwest to east Based on the limited extent of sod contamination and decreasing contaminant
<br /> concentrations in groundwater, Board staff concur with San Joaquin County's Closure Recommendation
<br />
|