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TA&4 1 - CHECKLIST OF REQUIREDYTA
<br /> FOR NO FURTHER ACTION REQUESTS AT UNDERGROUND TANK SITES
<br /> Site Name and Location: Former BridgestonelFirestone,400 North EI Dorado Street;Stockton,San Joaquin County
<br /> 0 1. Distance to production wells for municipal, domestic, agriculture, industry No water supply wells were identified
<br /> and other uses within 2000 feet of the site; within 2,000 feet of the site.
<br /> 2. Site maps, to scale, of area impacted showing locations of former and existing tank systems, Three gasoline USTs were
<br /> excavation contours and sample locations, boring and monitoring well elevation contours, closed in place in 1967. Site
<br /> gradients, and nearby surface waters, buildings,streets, and subsurface utilities; maps are provided.
<br /> ET] g depicting gy(cross section), treatment system diagrams; Lithology figures show predominant) clay
<br /> 3. Figures de icfln 1ltholo and silt to 25 feet and silty sand to 35 feet.
<br /> EN1{ USTs were closed in lace. No oils were generated.
<br /> 4. Stockpiled sot!disposed off-site (quantify}; p p
<br /> 5. Monitoring wells remaining on-site, fate; Four monitoring-wells remain on-site. The wells will be destroyed pending
<br /> site closure.
<br /> �Y 6. Tabulated results of all groundwater elevations and depths to water,• Depth to groundwater varied from 17 to 19 feet bgs,
<br /> and groundwater flow is to the east/northeast.
<br /> r 0 7. Tabulated results of all sampling and analyses: June 2001 maximum groundwater monitoring results in pg/1 show
<br /> TPHg at 170, benzene at<0.3, toluene at 3.1, ethyl benzene at 0.67,
<br /> k Defection limits for confirmation sampling xylenes at 2.7, and MtBE at 5. Lead was identified at a maximum of
<br /> r Lead analyses 12.9 mg/kg in soil samples collected during a 1991 investigation.
<br /> Y 8. Concentration contours of contaminants found and those remaining in soil The extent of soil contamination has'been
<br /> and groundwater, and both on-site and off-site: defined_ The lateral and vertical extent of
<br /> Lateral andVertical extent of soil contamination TPHg and BTEX is defined in groundwater.
<br /> r Lateral and F1Verticalextent of groundwater contamination MtBE has been defined in groundwater at
<br /> Iq lig
<br /> ED 9. Zone of influence calculated and assumptions used for subsurface Based on the limited extent of
<br /> remediation system and the zone of capture attained for the soil and contamination,site remediation was not
<br /> groundwater remediation system; required.
<br /> 10.Reports/information Y❑ Unauthorized Release Form 19 QMRs(1/00 to 6/01)
<br /> Welland boring logs EIPAR N❑ FRP El Other(Request for Closure, 6/01)
<br /> • -�r11.Best Available Technology(BAT) usedor an explanation for not using BAT; Close USTs in place. The remaining �
<br /> , m .:contamination Will_natura By degrade.
<br /> Y� 12.Reasons why background was/is
<br /> Soil and groundwater contamination remains in the tank pit area. The
<br /> unattainable using BAT, remaining contamination is limited in extent,and does not present a
<br /> significant threat to water quality.
<br /> y� 13.Mass balance calculation of substance The consultant estimates that approximately 259 pounds or 38 gallons of
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<br /> treated versus that remaining; degraded TPHg remains in soil at the site.
<br /> N❑ 14.Assumptions,parameters, calculations and model used in Based on the limited extent of contamination,a risk
<br /> risk assessments, and fate and transport modeling; assessment was not required.
<br /> 15.Rationale why conditions remaining at site will not adversely Remaining groundwater contamination is stable.
<br /> impact water quality, health, or other beneficial uses. Contamination will naturally degrade.
<br /> Comments: The site is currently an automotive repair shop. Three USTs located in the sidewalk were closed in place in
<br /> By: 1967. During a Phase//site assessment in 1991, soil contamination was identified near the three closed USTs, and
<br /> MH borings and monitoring wells were completed. TPHg, toluene, ethyl benzene, xylenes, and MtBE contamination was i
<br /> identified in groundwater, and groundwater monitoring has been conducted quarterly from 1/00 to 4/01: The four
<br /> monitoring wells show stable trends for these constituents. MtBE was identified in monitoring well MW-1 at a maximum
<br /> Date: concentration of 42 jug/l;however, gasoline with MtBE was never dispensed at this site. MtBE in MW-1 is currently at
<br /> 10/10/01 5.0 pg/l. The site is covered with concrete and asphalt, which should limit leaching of residual contaminants. Based on the I
<br /> investigation completed to date, Board staff concur with San Joaquin County's closure recommendation. ,
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