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(ABLE 1 -CHECKLIST OF REQUIRED DATA
<br /> FOR NO FURTHER ACTION REQUESTS AT UNDERGROUND TANK SITES
<br /> Site Name and Location: Former 76 Unocal Station#5886, 2701 March Ln., Stockton, San Joaquin County(RB#390892)
<br /> y 1. Distance to production wells for municipal,domestic, One municipal supply well is located 1,300 feet west
<br /> agriculture, industry and other uses within 2000 feetof the site.
<br /> (downgrodient)of the Site.
<br /> I 2. Site maps, to scale, of area impacted showing locations of In October 1995, three 12,000-gallon gasoline USTs and
<br /> any former and existing tank systems, excavation contours and associated piping were removed.
<br /> sample locations, boring and monitoring well elevation
<br /> contours, gradients, and nearby surface waters,.buildings,
<br /> streets, and subsurface utilities;
<br /> Site lithology consists of clay,slit, and sand to 36', the
<br /> Y 3. Figures depicting lithology(cross section), treatment system total depth investigated.
<br /> dia rams;
<br /> Approximately 1,200 y excavated soil was over-
<br /> t 4. Stockpiled soil remaining on-site or off-site disposal(quantity); excavated and transported to Forward Landfill in
<br /> Manteca.
<br /> y 5. Monitoring wells remaining on-site, fate; Twenty monitoring wells(MW-1, MW-2,MW-3, MW-4S, MW-4D, MW-5S,MW-
<br /> 5D, MW-6S, MW-6D, MW-7S, MW-70, MW-8S, MW-81, MW-8D, MW 9S, MW-91,
<br /> MW-9D, MW-10S, MW-101, and MW-10D)and thirteen remedlation wells
<br /> (UST-1,AS-1 through AS-5,AS-6S,AS-6D,AS-7,AS-8,AS-9S,AS-9D, and
<br /> _..,_.. ,AS 1D_wilLbe_ ro erl. _abandoned..,, �_ � - _ ._ _- -y.-..
<br /> 6. Tabulated results of groundwater Depth to groundwater varied from 5'to 8'bgs. Groundwater flow
<br /> elevations and depths to water,' direction varied from southeast to northwest and groundwater gradient
<br /> varied from 0.002 to 0.006 ft/ft.
<br /> 7. Tabulated results of all sampling All data adequately tabularized in various reports, including closure report.
<br /> and analyses:
<br /> Y❑ Detection limits for confirmation
<br /> sampling
<br /> QY 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 /> 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 remediation Over-excavation,periodic batch
<br /> system and the zone of capture attained for the soil and groundwater remediation groundwater extraction, and ozone
<br /> system; infection were the approved remediation.
<br /> 10.Reports/information QY Unauthorized Release Form nY QMRs 57 from 9/96 to 7/10
<br /> FY] Well and boring logs [A PAR Ey FRP ❑y Other Sensitive Receptor Survey(12(09)NFARs(5/10,
<br /> 10/10
<br /> Y 11.Best Available Technology(BAT) used or an explanation for not USTs removal, over-excavation,periodic batch
<br /> -_=usrg_ffA�--�- :-_�-.r;.- .�gcoundwatecrxtraction,_ozone,injection,_andsatural_..__
<br /> '^---'�---F attenuation. - -
<br /> attainable Reasons why background was/is Minimal residual soil and groundwater contamination remains on-site.
<br /> ttainab/e usingBAT,
<br /> y 13.Mass balance calculation of substance treated The consultant estimates 32 lbs of MTBE remain in soil and 0.2 lbs
<br /> versus that remaining; MTBE remain in groundwater.
<br /> Y 14. Assumptions,parameters, calculations and The shallow soil passed the SAM Level 1 Vapor Risk Assessment r
<br /> model used in risk assessments, and fate and Model(calc. concentration less than the sof/gas ESL)and Region 2 soil
<br /> transport modeling; ESLs.
<br /> y 15. Rationale why conditions remaining at site Soil and groundwater contamination reportedly are limited in extent.
<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. Water quality goals
<br /> will be reached in 2 years.
<br /> By: J Comments:In October 1995; three 12,000-gallon gasoline USTs and associated piping were removed from
<br /> the subject Site. Based upon 57 quarters of groundwater monitoring showing a stable plume with declining
<br /> Date: concentrations, the limited extent of contamination remaining in soil and groundwater, no foreseeable
<br /> 2/7/2010 changes in land use, and limited threats from groundwater, soil and soft vapor intrusion, Regional Board
<br /> staff concur with San Joaquin County's Closure Recommendation.
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