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TA&9 1 - CHECKLIST OF REQUIRED BATA
<br /> FOR NO FURTHER ACTION REQUESTS AT UNDERGROUND TANK SITES
<br /> Site Name and Location: Elkhorn Country Club, 1050 Elkhorn Drive, Stockton, San Joaquin County
<br /> Ell 1. Distance to production wells for municipal, domestic, agriculture, Three water supply wells are located within 2,000 feet f
<br /> industry and other.uses within 2000 feet of the site; of the site,and a small man-made pond is 50 feet
<br /> upgradient of the former UST area.
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<br /> 1, -gaon gasoline
<br /> Y 2. Site maps, to scale, of area impacted showing locations of former and existing tank systems, One !
<br /> excavation contours and sample locations, boring and monitoring well elevation contours, UST was removed in 5191. f
<br /> gradients, and nearby surface waters, buildings, streets, and subsurface utilities; Site maps are provided.
<br /> Y� 3. Figures depicting lithology(cross section), treatment system diagrams; Boring logs and cross-sections show sand with
<br /> sandy silt to silty clay to 35 feet k
<br /> 4. Stockpiled soil disposed off-site(quantity); (Excavated soils were returned to the tank pit excavation.
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<br />-- — 5=Monitoring-wells-remaining-on-site;-fate;- Six monttoring_wells and eight combination SVE/AS wells_currently,exist—_,
<br /> ' on-site: The wells will be properly destroyed following site closure.
<br /> 0 6. Tabulated results of all groundwater elevations and depths to water, Groundwater levels varied from 6 to 37 feet below
<br /> ground surface,and flow is to the northeast.
<br /> ED7.Tabulated results of all sampling and analyses: Maximum groundwater monitoring results for April 2001 in pgll show
<br /> TPHg at 570, toluene at 0.66,and xylenes at 15. Benzene, ethyl
<br /> Detection limits for confirmation sampling benzene,MtBE,and other oxygenates were non-detect at appropriate
<br /> Lead analyses detection limits. Lead was non-detect in soil at<5 mg/kg during UST {
<br /> removal activities in May 1991.
<br /> 8. Concentration contours of contaminants found and those remaining in soil The lateral and vertical extent of soil and
<br /> and groundwater, and both on-site and off-site: groundwater contamination has been
<br /> © Lateral and Y� Vertical extent of soil contamination defined.
<br /> Lateral and Vertical extent of groundwater contamination -
<br /> y 9. Zone of influence calculated and assumptions used for subsurface A combination SVE/AS remediation system
<br /> remediation system and the zone of capture attained for the soil and operated from 8199 to 9/00. Consultant
<br /> groundwater remediation system;- estimates that 134 gallons of gasoline was
<br /> removed from site soils.
<br /> FTI 10.Reports/information y❑ Unauthorized Release Form y❑ QMRs(3rd Qtr 1995 to 2nd Qtr 200 1)
<br /> 71 Boring logs Q PAR FRPY❑ Other(Closure Summary Report, 2/01)
<br /> Y� 11.Best Available Technology(BAT)used or an explanation for not using BAT, Removed USTs. SVE/AS.utilized to remove
<br /> 95% of contaminants
<br /> Y� 12.Reasons why background waslis Minor contamination remains in shallow soil and groundwaier near the former
<br /> unattainable using BAT; UST and dispenser. The groundwater contamination is limited in extent, and
<br /> remaining concentrations do not present a significant threat to water quality.
<br /> Further remediation is not cost effective.
<br /> Y� 13.Mass balance calculation of substance The consultant estimates the initial mass was approximately 238 pounds of M
<br /> treated versus that remaining; TPHg, and the remaining mass determined from confirmation borings is
<br /> approximately 11 pounds,a 95 percent reduction. -
<br /> N� 14.Assumptions,parameters, calculations and model used in risk Based on the limited extent of groundwater
<br /> assessments, and fate and transport modeling; contamination, a risk assessment was not required.
<br /> 70 15. Rationale why conditions remaining at site will not adversely Remaining contamination is limited in extent.
<br /> impact water quality, health, or other beneficial uses;and Contamination will naturally degrade.
<br /> By, Comments: One 1,000-gallon gasoline UST was removed from the site in May 1991. Contamination was identified during
<br /> assessment activities, and multiple soil borings and monitoring wells were installed. A SVE/AS system was operated on
<br /> the site from August 1999 to September 2000;and quarterly monitoring reports document the reduction in groundwater
<br /> contamination. MtBE was identified in a water sample from one monitoring well at a maximum of 98 pg/I in February 1998, f
<br /> - Date: but has been non-detect at<5.0 pgA in all wells since April 1999. All other fuel oxygenates and fuel additives are non-
<br /> detect at appropriate detection limits. Two municipal wells are 1,000 and 1,250 feet northwest of the site, and an on-site k
<br /> 30/e1 irrigation well is 1,000 feet east of the site. All three wells are cross gradient to the former UST site. Based on the
<br /> investigation and remediation completed to date, Board staff concur with San Joaquin County's closure recommendation. !
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