|
LE 1 -CHECKLIST OF REQUIRED DATA
<br /> FOR NO FURTHER ACTION REQUESTS AT UNDERGROUND TANK SiTES,
<br /> Site Name and Location: Chevron 119-8264,3775 N. Tracy Blvd., Tracy, San Joaquin County(RB 11390795)
<br /> y 1. Distance to production wells for municipal,domestic, A 1.998 sensitive receptor survey map shows fourteen
<br /> supply wells are located within 2,000'of the Site. The
<br /> agriculture, industry and other uses within 2000 feet of the site. nearest well was onsite;however,a 2002 site
<br /> investi anon could not find the well.
<br /> Y 2. Site maps, to scale, of area impacted showing locations of I In November 1995, two 10,000-gatlon and one 6,000-
<br /> any former and existing tank systems, excavation contours and gallon gasoline,and one 1,500-gallon waste oil USTs
<br /> sample locations, boring and monitoring well elevation were removed.
<br /> contours, gradients, and nearby surface waters, buildings,
<br /> streets, and subsurface utilities;
<br /> Site!lthology consists of clay,silt,and sand to 35'P the
<br /> Y F3. Figures depicting lithology(cross.section), treatment system total depth investigated.
<br /> diagrams;
<br /> Y] 4. Stockpiled soil remaining on-site or off-site disposal(quantity); Approximately 590 cubic yards excavated sot!was
<br /> transported to Redwood Landfilll in Novato and to
<br /> Browing-Ferris,OX Landfill in Mountain.
<br /> Four monitoring wells(MW-? through MW-4)will be properly abandoned.
<br /> 5. Monito►in wells remainingon-site, fate; 1
<br /> 6. Tabulated results of all groundwater. Depth to groundwater varied from 81 to 12'bgs. Groundwater flow
<br /> elevations and depths to water, direction was primarily towards the northeast.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 /> Detection limits for confirmation
<br /> 4
<br /> sampling
<br /> 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 osite: contamination is shown in applicable
<br /> off
<br /> reports.
<br /> 0 Lateral and �Vertical extent of soil contamination
<br /> EJ Lateral and My Vertical extent of groundwater contamination
<br /> 9. Zone of influence calculated and assumptions used for subsurface remediation Over-excavation of soil and oxygen.
<br /> system and the zone of capture attained for the soil and groundwater remediation injection into groundwater were the
<br /> system; approved remediation.
<br /> 1 o.Reports/information MY Unauthorized Release Form QMRs 57 from M6 to 10/09 .
<br /> Welland boring logs PAR FRP Other'Closure Report,2/10 Revised Closure Report, 5/10
<br /> Y ?1.8est Available Technology(SAT)used or an explanation for not UST removal,over-excavation, oxygen injection into
<br /> aero BAT,' monitoring wells,and natural attenuation.
<br /> Y 12. Reasons why background waslrs Minor residual soil and groundwater contamination remain on-site.
<br /> ttainable using BAT;
<br /> y 13.Mass balance calculation estimates 109.6 lbs of TPH were present in soil prior to
<br /> alculation of substance treated The consulta
<br /> versus that remaining; remediation. Approximately 20 lbs.of TPH was removed from
<br /> groundwater, while 98.6 lbs. of TPH remain in soil and 5.4 lbs.of TPH
<br /> remain in groundwater.
<br /> Y 14. Assumptions, parameters, calculations and The soil exceeded the San Francisco Bay Regional Board ESLs for
<br /> model used in risk assessments, and fate and TPHg(830 mg/kg)for direct exposure and gross contamination.Due to
<br /> transport modeling; the depth(12.5'), distance from building(y50'),and low residual soil
<br /> concentrations(no benzene in TPHg sample),a vapor intrusion
<br /> investigation was not uired b the re ulato a enc .
<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(service station)is not expected to change in the foreseeable
<br /> other beneficial uses;and future. WQGs will be reached in 5 years.
<br /> By: JLB Comments:In November 1995, two 10,000-gallon and one 6,000-gallon gasoline,and one 1,500-gallon waste
<br /> oil USTs were removed from the subject site. Based upon 57 quarters of groundwater monitoring showing a
<br /> Date: stable plume with declining concentrations, the limited extent of contamination remaining in soil and
<br /> 7/1312010 groundwater,no foreseeable changes in land use,and minimal threats from soil vapor intrusion, direct
<br /> contact and aross contamination R_eqional Board staff concur with San Joa uln County's Closure
<br />
|