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(VIABLE 1 -CHECKLIST OF REQUIRED DATA '
<br /> FOR NO FURTHER ACTION REQUESTS AT UNDERGROUND TANK SiTES
<br /> Site Name and Location: Stockton Plating Inc., 632 S.El Dorado Street,Stockton, San Joaquin°County(RB#390106)
<br /> y 1. Distance to production wells for municipal, domestic, The NFAR sensitive receptor survey found no active
<br /> water supply wells within 2,000'of the Site.
<br /> agriculture, industry and other uses within 2400 feet of the site.
<br /> Y 2. site maps, to scale, of area impacted showing locations of In August 1986, one 1,000-gallon gasoline UST was
<br /> any former and existing Tank systems, excavation contours and removed. In December 1990, one 2,000-gallon gasoline
<br /> sample locations, boring and monitoring well elevation UST was removed.
<br /> contours, gradients, and nearby surface waters, buildings,
<br /> streets, and subsurface utilities;
<br /> Site lithology consists of clay, silt, and sand to 80', the
<br /> =Y3. Figures depicting lithology(cross section), treatment system total,depth investigated.
<br /> diagrams;
<br /> The fate of over-excavated soil was not discussed in
<br /> N 4. Stockpiled soil remaining on-site or off-site disposal(quantity); the available reports
<br /> e orts.
<br /> A
<br /> 1
<br /> Y1 5. Monitoring wells remaining on-site, fate; Eight monitoring wells(MW-1 through MW--8), four soil vapor extraction wells
<br /> (VW-1 through VW-4), and two groundwater extraction wells(EW-1 and
<br /> EW-2)will be proper!y proper! abandoned.
<br /> 6. Tabulated results of all groundwater Depth to groundwater varied from 23'to 47'bgs. Groundwater flow w
<br /> _direction yd_frQm southeast to_northwest. Groundwater gradient
<br /> -- — elevafio std depth-s water varied from 0.002 to 0.022 ft/ft.
<br /> Y 7. Tabulated results of all sampling All data adequately tabularized in various reports,including closure report.
<br /> and analyses:
<br /> FYIi;
<br /> Detection limits for confirmation
<br /> sampling
<br /> nY Lead analyses
<br /> 8. Concentration contours of contaminants found and those remaining in soil and The extent.,of the identified
<br /> groundwater, and both on-site and off-site: contamination shown in applicable
<br /> reports.
<br /> QLateral and FXI Vertical extent of soil contamination
<br /> Lateral and Vertical extent of groundwater contamination
<br /> 9. Zone of influence calculated and assumptions used for subsurface remediation Soil vaporlextraction and groundwater
<br /> system and the zone of capture attained for the soil and groundwater remediation pump and,,treatment were the approved
<br /> system; remediation.
<br /> 10.Reports/information RY Unauthorized Release Form EY QMRs 35 from 12/95 to 1/109
<br /> FY] Well and boring logs PAR 0 FRP ❑y Other Soil Rem Conf Rpt(6/7);NFAR(5/10)
<br /> Y 11.Best Available Technology(BAT) used or an explanation for not USTs removai, soil vapor extraction,groundwater
<br /> singBAT; pump and treatment, and natural attenuation.
<br /> UY 12. Reasons why background wasps Minor residual soil and groundwater contamination remains on-site.
<br /> ttainable using BAT,
<br /> �3:lUlass ba7anc— cola rt an of su�sfanc�teafe l--SVEremoved-approximately-856-1bs_of_TP_H_from_soil.-P_ump_and -
<br /> treatment removed approximately 740 lbs of TPH from groundwater.
<br /> versus that remaining,
<br /> Y 14. Assumptions,parameters, calculations and The regulatory agency did not require a soil vapor survey, due to the
<br /> model used in risk assessments, and fate and depth of residual soil contaminants(>30',bgs), distance to buildings
<br /> transport modeling, 30',and industrial site use former plating shop).
<br /> 15. Rationale why conditions remaining at site Soil and groundwater contamination reportedly is limited in extent.
<br /> 4Y
<br /> will not adversely impact water quality, health, or 'Land use(commercial)is not expected to change in the foreseeable
<br /> other beneficial uses;and future. Vapor intrusion risk has been addressed. The majority of the
<br /> residual soil contamination remains below 30'b s.
<br /> By: JLB Comments:In August 1986, one 1,000-gallon gasoline UST was removed;and'in December 1990, one
<br /> r 2,000-gallon gasoline UST was removed. Based upon 35 quarters of groundwater monitoring showing a
<br /> Date: stable plume with declining concentrations, the limited extent of contamination remaining in soil and
<br /> 7/29/2009 groundwater, no foreseeable changes in land use,and limited threats from soil and soil vapor intrusion,
<br /> Regional Board staff concur with San Joaquin County's Closure Recommendation.
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