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LE 1 -CHECKLIST OF REQUIRED DATA
<br /> FOR NO FURTHER ACTION REQUESTS AT UNDERGROUND TANK SITES
<br /> Site Name and Location: ARCO#5450, 1617 W. Fremont St., Stockton,San Joaquin County(Lustis Case 2#L911 8)
<br /> Y 1. Distance to production wells for municipal, domestic, agriculture, A well survey in 2004 showed no wells within
<br /> industry and other uses within 2000 feet of the site; 2000 feet of the site.
<br /> Y Site maps, to scale, of area impacted showing locations of any former Approximately 700 feet of gasoline USTs piping
<br /> and existing tank systems, excavation contours and sample locations, was removed in 10/95, and another 480 feet was
<br /> boring and monitoring well elevation contours, gradients, and nearby removed 11/99.
<br /> surface waters, buildin s, streets, and subsurface utilities;
<br /> Site lithology consists of sand and clay to
<br /> Y 3. Figures depicting lithology(cross section), treatment system diagrams; 25 feet, the total depth investigated.
<br /> Y 4. Stockpiled soil remaining on-site or off-site disposal(quantity); Approximately 35 yards of over-excavated soil wasremoved in 10/95 and transported to an unnamed
<br /> landfill.
<br /> Three monitoring wells(MW-2 through MW-4)remaining on-site will be
<br /> Y 5. Monitoring wells remaining on-site, fate; roper!roperly abandoned. MW.1 was abandoned after the first closure in 10/97.
<br /> 6. Tabulated results of all groundwater Depth to groundwater varied from 8 to 12 feet below ground surface
<br /> {6ras} he,grounrfavatar-_nr^^1;^�,,,�.-,�,•��:�d ire 4:006-to-0Ul-ft/ft;and=the.---
<br /> -elevations-arrd-ddowngradient direction varied from Northwest to Southeast.
<br /> 7. Tabulated results of all sampling and In 11/99, maximum soil concentration from piping samples from 4.5 to 5.5 feet
<br /> analyses: depth were:toluene, 0.436 mg/kg;ethylbenxene,0.0925 mg/kg;.xylenes 0.0925
<br /> Y mg/kg,and MtSE 0.201 mg/kg. In 2/01 maximum soil boring.concentration at 20
<br /> Detection limits for confirmation feet was:MtBE, 0.01 mg/kg. Maximum groundwater concentrations in 9/02 were:
<br /> sampling TPHg 98 pg/L;and MtBE, 62,ug/L. In 11105, maximum groundwater
<br /> concentration was:MtBE, 9.3 pg/L.
<br /> ❑N Lead analyses
<br /> 8. Concentration contours of contaminants found and those remaining in soil and The extent of contamination is
<br /> roundwater, and both on-site and off-site: adequately defined by soil borings
<br /> Y Lateral and e Vertical extent of soil contamination and monitoring.wells. The
<br /> Latera!and Vertical extent of groundwater contamination proximity of Interstate 5 to the site
<br /> precludes investigation to the
<br /> north.
<br /> -71 9. Zone of influence calculated and assumptions used for subsurface remediation An engineered remediation was
<br /> system and the zone of capture attained for the soil and groundwater remediation not required by the lead agency.
<br /> s stem;
<br /> 10.Reports/information FY] Unauthorized Release Form FYI QMRs(14 from 2002-.2005)
<br /> n Well and boring logs QY PAR FRP El Other'Site Investigation and Site Closure Reports
<br /> YJ 11.Best Available Technology(BAT) used or an explanation for not using BAT,' I Removal of piping, minor over-excavation
<br /> and natural attenuation.
<br /> i _,.,..�. .. .. .. �, Limited soil contamination and groundwater pollution
<br /> "Y X92.Rea_sons why backgrogtid-wasrs unattairiable using BAT-,----- remains on=site:
<br /> !i
<br /> Y1 13.Mass balance calculation of substance treated versus that An engineered remediation was not required. In 12/05,
<br /> the residual contamination was estimated at X0.001 lbs.
<br /> remaining; of TP14-q and MtBE in groundwater.
<br /> Y 14. Assumptions, parameters, calculations and model used in Soil ESLs are not exceeded. Secondary MCL Water
<br /> risk assessments, and fate and transport modeling; Quality Goals(WQGs)are exceeded for MtBE.
<br /> Y 15. Rationale why conditions remaining at site will not adversely Soil contamination is limited in extent. Results of
<br /> T
<br /> impact water quality, health, or other beneficial uses;'and 14 quarters of groundwater monitoring show a
<br /> decreasing trend in concentrations. WQGs will be
<br /> reached in less than two years.
<br /> By., JLB Comments:Approximately 700 feet of gasoline USTs piping was removed in 10/95, and another 480 feet was
<br /> removed 11/99 from subject site. Site is an active service station adjacent to Interstate 5,-so threats from vapor
<br /> i ation
<br /> compliance with public participation
<br /> Date: intrusion are minimal. San Joaquin County staff has stated they are in comp p p p
<br /> 5/23/2006 requirements. Based upon 14 quarters of declining groundwater concentrations, and the limited extent of
<br /> contamination nresent in soil. Reaional Board staff concur with San Joaquin Countv's Closure Recommendation. .
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