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TABtt 1 - CHECKLIST OF REQUIRED bl(TA
<br /> FOR NO FURTHER ACTION REQUESTS AT UNDERGROUND TANK SITES
<br /> Site Name and Location: N and S Irrigation, 215 Main Street, Ripon, San Joaquin County
<br /> 1. Distance to production wells for municipal, domestic, agriculture, A well survey in 2004 shows two public water supply
<br /> industry and other uses within 2000 feet of the site; wells, one municipal located approximately 150 feet
<br /> north(down gradient)is not used due to impacts from
<br /> the Nestle's VOCs plum; the other municipal well is
<br /> 1800 feet south(upgradient)of the site.
<br /> 2. Site maps, to scale, of area impacted showing locations of former and existing tank One 1,500-gallon gallon and one
<br /> systems, excavation contours and sample locations, boring and monitoring well 2,500-gallon gasoline USTs were
<br /> elevation contours, gradients, and nearby surface waters, buildings, streets, and removed in 3/90.
<br /> asubsurface utilities;
<br /> Y
<br /> 3. Figures depicting lithology(cross section), treatment system diagrams; Site lithology consists of sand, silt and clay to
<br /> 45 feet, the total depth investigated.
<br /> Pil 4. Stockpiled soil disposed off-site (quantity); The fate and amount of the excavated soil is unknown.
<br /> 5. Monitoring wells remaining on-site, fate Three monitoring wells(MW-1 through MW-3)) installed for this investigation
<br /> will be properly destroyed.
<br /> �Y 6. Tabulated results of all groundwater elevations and depths to water, The depth to water varied from 21 to 29 feet, and
<br /> the groundwater flow direction varied from
<br /> northeast to northwest.
<br /> 7.Tabulated results of all sampling and analyses: In 7/98,maximum soil results were: TPHg, 300 mg/kg;ethylbenzene,
<br /> EY 0.44 mg/kg, and xylenes,0.69 mg/kg. Maximum groundwater
<br /> Y] limits for confirmation sampling monitoring results in 2/99 were TPHg,4,700 pg/L;benzene, 13 Ng/L;
<br /> Y Lead analyses ethylbenzene, 99 Ng/L;and xylenes,49 pg/L. In 6/05, maximum
<br /> groundwater monitoring results were: TPHg, 2,100 Ng/L;benzene,
<br /> 4.6 Ng/L;toluene,3.2 Ng/L;ethylbenzene, 24 Ng/L;xylenes, 100 Ng/L,
<br /> TBA, 17 Ng/L;and 1,2-DCA, 0.9 Ng/L.
<br /> Y� 8. Concentration contours of contaminants found and those remaining in soil
<br /> nad groundwater, both on and off-site: The extent of contamination is defined by
<br /> Rateral
<br /> ateral and Vertical extent of soil contamination on-site soil borings, grab groundwater
<br /> and Vertical extent of groundwater contamination samples and monitoring wells.
<br /> 0 9. Zone of influence calculated and assumptions used for subsurface A pump test and batch groundwater
<br /> remediation system and the zone of capture attained for the soil and removal events were required at this site.
<br /> groundwater remedia tion em;
<br /> Y� 10.Reports/information LJ Unauthorized Release Form Y❑ QMRs 2/99 to 6/05.
<br /> Boring logs PAR a FRP Y❑ Other Feasibility Study, Interim RAP, Closure Report
<br /> Y� 11.Best Available Technology(BAT) used or an explanation for not using BAT, Remove USTs, batch groundwater
<br /> extraction,and natural attenuation.
<br /> 0 12.Reasons why background wasris Decreasing concentrations have been attained at all monitoring wells. Minor
<br /> unattainable using BAT; soil contamination remains on-site.
<br /> 13.Mass balance calculation of substance The consultant estimates 589 gallons of TPHg and that 0.5 gallons of benzene
<br /> treated versus that remaining; remain in soil.
<br /> 14.Assumptions, parameters, calculations and model used in risk A risk assessment was not required. Remaining
<br /> assessments, and fate and transport modeling;and concentrations exceed Region 2 ESLs for TPHg.
<br /> Y� 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. twenty six sampling events, contamination is not
<br /> continuing to leach to groundwater. Groundwater
<br /> monitoring shows a decreasing trend in concentrations.
<br /> By: Comments: One 1,500-gallon gallon and one 2,500-gallon gasoline USTs were removed in 3/90. In 7/98, maximum soil
<br /> JLB results were: TPHg, 300 mg/kg;ethylbenzene, 0.44 mg/kg, and xylenes, 0.69 mg/kg. Maximum groundwater monitoring
<br /> results in 2/99 were TPHg, 4,700 Ng/L;benzene, 13 Ng/L;ethylbenzene, 99 Ng/L;and xylenes, 49 pg/L. In 6/05, maximum
<br /> Date: groundwater monitoring results were: TPHg, 2,100 pg/L;benzene, 4.6 Ng/L;toluene, 3.2 pg/L;ethylbenzene, 24 pg/L;
<br /> xylenes, 100 pg/L, TBA, 17 pg/L;and 1,2-DCA, 0.9 pg/L. MtBE has not been detected. Based on declining
<br /> 10/26/05 concentrations in groundwater, Regional Board staff concur with San Joaquin County's Closure Recommendation.
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