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TAE 9 - CHECKLIST OF REQUIRED L' 0.17A
<br /> FOR NO FURTHER ACTION REQUESTS AT UNDERGROUND TANK SITES
<br /> Site Name and Location: Ripon Unified School District,304 North Acacia Avenue, Ripon,San Joaquin County
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<br /> Y 1. Distance to production wells for municipal, domestic, agriculture, A sensitive receptor survey identified 16 wells within
<br /> industry and other uses within 2000 feet of the site; 2,000 feet. The two closest wells were sampled and
<br /> found to be non-detect for all constituents analyzed.
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<br /> Y 2. Site maps, to scale, of area impacted showing locations of former and existing tank systems,
<br /> Three USTs were removed in
<br /> ❑ excavation contours and sample locations, boring and monitoring well elevation contours, 1997, and one 10,000 gallon
<br /> gradients, and nearby surface waters, buildings, streets, and subsurface utilities; UST was removed in 1998.
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<br /> 3. Figures depicting lithology(cross section), treatment system diagrams; Site lithology consists of sand and silty sand to
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<br /> 45 feet, the total depth investigated.
<br /> 0 4. Stockpiled soil disposed off-site(quantity); Excavated soils were ae;a ted on-site and placed back into the
<br /> excavations. �}
<br /> ❑ 5. Monitoring wells remaining on-site, fate; Five monitoring wells remain on-site. The wells will be properly destroyed
<br /> Y pending site closure.
<br /> ❑ 6. Tabulated results of all groundwater elevations and depths to water; The depth to water varies from 19 to 24 feet, and
<br /> the groundwater flow is to the southwest.
<br /> 7.Tabulated results of all sampling and analyses:
<br /> The maximum groundwater monitoring results for July 2002(in Ng/1),
<br /> Defection limits far confirmation sampling which were all identified in MW-2, are TPHg at 1,400, ethyl benzene at
<br /> 29, and xylenes at 92. All other constituents including MtBE were non-
<br /> Lead analyses detect at acceptable detection limits. Lead was identified in soil at a
<br /> maximum of 15 mg/kg,and in groundwater at 5.9 pg/l.
<br /> ❑Y 8. Concentration contours of contaminants found and those remaining in soil The extent of soil and groundwater
<br /> and groundwater, both on-site and off-site: I,p contamination has been defined.
<br /> Y❑ Lateral and Y❑ Vertical extent of soil contamination I�
<br /> Lateral and Vertical extent of groundwater contamination
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<br /> i 9. Zone of influence calculated and assumptions used for subsurfaceBased on the decreasing concentrations
<br /> Qremediation system and the zone of capture attained for the soil and ! identified in monitoring wells,site
<br /> f groundwater remediation system; !� remediation beyond UST and impacted soil
<br /> removal was not required. }
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<br /> y❑ 10.Reports/information y❑ Unauthorized Release Form y❑ QMRs(Febuary 1999 to July 2002) i
<br /> Boring logs PAR El FRP Closure Report, June 2002
<br /> Y❑ 11.Best Available Technology(BAT)used or an explanation for not using BAT h The USTs and visually impacted soils were
<br /> removed.
<br /> 12.Reasons why background wasrs d Soil Soangroundwater contamin
<br /> unattainable using_BAT_ 9 l etion remains in the area of the former USTs.
<br /> ED13.Mass balance calculation of substance The consultant estimates that 960 pounds(157 gallons)of petroleum
<br /> treated versus that remaining; hydrocarbons remain in site soils, and 0.7 pounds(0.1 gallons)remain in
<br /> groundwater at the site. i
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<br /> 14.Assumptions,parameters, calculations and model used in risk Base �
<br /> assessments, and fate and transport modeling; assessment
<br /> limited soil contamination, a risk
<br /> was not required.
<br /> 15. Rcontaminationaironale why conditions remaining at site will not adversely Contamination�s limited in extent,and
<br /> impact water quality, health, or other beneficial uses;and will continue to degrade. r
<br /> By: Comments: The site is a Ripon School District maintenance and refueling yard. Four US Ts(one 10,000-gallon diesel,
<br /> MH one 550 gallon and one 7,500 gallon gasoline, and one 550-gallon unknown contents) were removed from the site
<br /> between February 1991 and July 1998. Soil contamination was identified during the tank removal activities, and multiple r
<br /> soil borings were completed to define the extent of soil and groundwater contamination. Five groundwater monitoring
<br /> Date: wells were installed, and groundwater has been monitored from February 1999 to July 2002. Currently, only MW-2 shows
<br /> residual TPHg contamination, and TPHg in MW-2 has degraded from aimaximum of 27,900 ug/1 in February 1999 to
<br /> 9123102 1,400 ug/i in July 2002. Benzene is non-detect of all monitoring well locations, and fuel oxygenates have not been
<br /> detected at this site. Based on the limited extent of groundwater contamination, and the degradation of site constituents,
<br /> Board staff concur with San Joaquin County's Closure Recommendatlon.
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