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ABLE I -CHECKLIST 0 TA
<br /> F REQUIRED DA
<br /> FOR NO FURTHER ACTION REQUESTS AT UNDERGROUND TANK SITES
<br /> Site Name and LoLenz Property; 1648 Shaw Road,- Stockton, San Joaquin County(RB#390128)
<br /> =Y 1. Distance to production wells for municipal, domestic, A sensitive receptor survey In 2000 identified no
<br /> agriculture,industry and other uses within 2000 feet of the site, municipal supply and eleven domesticlagricultural wells
<br /> within 2,000' the nearest wells are 900'S and 1250' K9.
<br /> Y1 2. Site maps, to scale, of area impacted showing locations of Two 550-gallon USTs reportedly containing diesel were
<br /> any former and existing tank systems, excavation contours and removed 10186 from the former Disco Warehouse.
<br /> sample locations, boring and monitoring well elevation - Gasoline and lead scavengers 1,2-DCA and EDB were
<br /> contours, gradients, and nearby surface waters, buildings, also reported in soil andlor groundwater samples
<br /> streets, and subsurface utilities;
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<br /> 7_
<br /> V 1f 3. Figures depicting lithology(cross section); treatment system Site lithology consists of clay, silt,and sand to 134'$ the
<br /> diagrams, total depth investigated.
<br /> :ND I 4. Stockpiled soil remaining on-site or off-site disposal(quantity); The available reports do not describe the fate of the soil excavated during the USTs removal.
<br /> Twelve monitoring wells(MW-1 through MW-12)and three SVE wells(VW-1
<br /> it
<br /> M
<br /> . Monitoring Wells remaining on-site, fate;
<br /> Y 5through VW-3) will be properly abandoned.
<br /> YJ 6. Tabulated results of all groundwater Depth to groundwater varied from 32'to 62'bgs. Groundwater flow
<br /> directionvaried-in-all-compass directions-,^.S,,E,-and M;groundwater
<br /> ele�atioris'inV d6plh�'t—owdt&, wadient varied from 0.001 to 0.011 ft/ft.
<br /> 7. Tabulated results of a//sampling, Maximum soil boring concentrations on 12105 were TPHd,52,000 mg/kg;and on
<br /> al
<br /> and analyses: 9197 were TPHg, 14,000 mg/kg;toluene, 340 mg/kg;ethylbenzene,270 mg/kg;and
<br /> xylenes, 1,600 mg/kg. In 4109,confirmation soil boring results were tPI40,
<br /> byd Detection limits for confirmation'- 25 mg/kg;and TPHg,46 mg/kg- In 3105,typical groundwater monitoring
<br /> sampling concentrations(MW-2)were TPHd,25,000 ug/L; TPHg,46,000 ug/L;benzene,
<br /> 40 ugIL;toluene, 2,500 ug/L;ethylbenzene, 2,900 ug/L;and xylenes, 18,000 ugIL.
<br /> FY� Lead analyses Maximum groundwater monitoring concentration for 1,2-DCA was 200 ug/L; while
<br /> EDS was 21 uglL. In 8/08,all groundwater monitoring results were ND.
<br /> y 8. Concentration contours of contaminants found and those remaining in soil and The extentof the iderifified
<br /> groundwater, and both on-site and off-site: contamination is described in the
<br /> reports.
<br /> Lateral and
<br /> Vertical extent of soil contamination
<br /> F
<br /> MY Lateral and ry-1 Vertical extent of groundwater contamination
<br /> 9. Zone of influence calculated and assumptions used for subsurface remediation Soil Vapor Extraction was required by
<br /> system and the zone of capture attained.for the soil and groundwater remediation the lead agency.
<br /> system;
<br /> 10.Reports linformation nY Unauthorized Release Form FYI QMRs 21 from-3/00 to 8/08
<br /> L_:_J
<br /> fy-lWell and boring logs F7 PAR FYJFRP 0 Other CPT Rpt(1/02);SVE Pilot Test Rpt. (11102),
<br /> Confirmation Soil Boring Rpt. (5109)
<br /> 11.Best Available Technology(BA 7)used or an explanation for not using USTs removal, S VE soil treatment,and
<br /> BATnatural attenuation.
<br /> ,
<br /> -ft*lg BAT,
<br /> Y 13.Mass balance calculation of substance treated In 5109, the calculated mass removed from soil was TPHg, 2219
<br /> versus that remaining; pounds. Estimated remaining soil mass was,TPHg, 169 pounds.
<br /> 714. Assumptions,parameters, calculations and The April 2009 confirmation soil sample results(TPHd,25' bgs)reveal
<br /> Y model used in risk assessments, and fate and that Region 2 ESLS(commercial,deep soil)were exceeded for direct-
<br /> transport modeling; exposure and gross contamination. The consultant stated vapor
<br /> intrusion is not a riskat the depth of contamination(25'bgs). The site
<br /> is located in a commercially zoned area of Stockton.
<br /> Y
<br /> 15. Rationale why conditions remaining at site will Soil contamination reportedly is limited in extent. Land use is not
<br /> I not adversely impact water quality, health,
<br /> or other expected to change in the.foreseeable future.
<br /> beneficial uses, and
<br /> BY: JL8 Comments: Two 550-gallon USTs containing diesel were removed 10186 from the subject site, the former
<br /> Disco Warehouse. Gasoline and lead scavengers 1,2-DCA and EDS were also reported in soil andlor
<br /> Date: groundwater samples. Remediation by SVE resulted in a 93%reduction in estimated TPHg mass in soil.
<br /> 6/4/2009 Based upon 21 quarters of groundwater monitoring showing a stable plume with declining concentrations to.
<br /> NO, the limited extent of contamination remaining in soil,no foreseeable changes in land use(commercial),
<br /> and the only TPHd ESLS exceedance for gross contamination and direct contact at a depth(25'bgs)where
<br /> worker exposure and vapor intrusion are unlikely,Regional Board staff concur with San Joaquin County's
<br /> Closure Recommendation.
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