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TABLE 1 - CHECKLIST OF REQUIRED DATA
<br /> FOR NO FURTHER ACTION REQUESTS AT UNDERGROUND TANK SiTES
<br /> Site Name and Location: Central Valley Construction, 146 Klo Road (AKA 12565 Manthey Road), Lathrop,
<br /> San Joaquin County
<br /> Awell survey in 2002 shows no municipal supply wells
<br /> Y 1. Distance to production wells for municipal, domestic, agriculture, located within 2000 feet of the site. Twenty-three
<br /> industry and other uses within 2000 feet of the site; domestic wells are located within 2000 feet of the site.
<br /> Two 10,000-gallon gasoline,
<br /> 2. Site maps, to scale, of area impacted showing locations of former and existing tank one 1,000-gallon gasoline, and
<br /> systems, excavation contours and sample locations, boring and monitoring well elevation one 1,000-gallon diesel USTs
<br /> contours, gradients, and nearby surface wafers, buildings, streets, and subsurface utilities; were removed in August 1989.
<br /> Site lithology consists of silt, silty sand,sand
<br /> Y� 3. Figures depicting lithology(cross section), treatment system diagrams; and clay to 31 feet, the total depth investigated.
<br /> 0 4. Stockpiled soil disposed off-site(quantity); Approximately 200 cubic yards of soil was excavated, and aerated
<br /> onsite.
<br /> 5. Monitoring wells remaining on-site, fate; Three monitoring wells(MW-1, MW-2, and MW-3) were properly destroyed on
<br /> 24 February 2003.
<br /> FE6. Tabulated results of all groundwater elevations and depths to water; The depth to water is approximately 18 feet, and the
<br /> groundwater flow direction varies from northeast to
<br /> northwest at a gradient of 0.0007 ft/ff.
<br /> 7. Tabulated results of all sampling and analyses: On 4101, TPHg (170 mg/kg) and TPHd (120 mg/kg)were detected in soil,
<br /> F 7YPY
<br /> and a grab groundwater sample detected TPHd (21,000 pg/L),TPHg
<br /> Defection limits for confirmation sampling (30,000 pg/L), benzene (27 pg/L), toluene (35 pgiL), ethylbenzene(14
<br /> Lead analyses pg/L), and xylenes (4.8 pg/L. On 9102 after 4 quarters, all groundwater
<br /> monitoring well results were non-detect. Six quarters of groundwater
<br /> sampling of the onsite domestic well did not detect contamination.
<br /> Fuel oxygenates, including MtBE,were not detected in soil or
<br /> groundwater. Lead was not detected in groundwater.
<br /> 8. Concentration contours of contaminants found and those remaining in soil The extent of contamination is defined by
<br /> and groundwater, both on-site and off-site:
<br /> on-site soil borings and monitoring wells.
<br /> Y� Lateral and Vertical extent of soil contamination
<br /> Lateral and Vertical extent of groundwater contamination
<br /> FE 9. Zone of influence calculated and assumptions used for subsurface Based on the limited extent of soil
<br /> remediation system and the zone of capture attained for the soil and contamination, an engineered remediation
<br /> groundwater remediation system; system was not required at this site.
<br /> 10.Reports/information Y❑ Unauthorized Release Form 0 QMRs(11/01 to 9/02)
<br /> F] Boring logs SiR F FRP 19 (File Closure Report, 11/02)
<br /> 0 11.Best Available Technology(BAT) used or an explanation for not using BAT Remove USTs, over-excavation and natural
<br /> attenuation.
<br /> 12.Reasons why background waslis
<br /> unattainable using BAT,' Decreasing concentrations have been attained at all monitoring wells. Minor
<br /> soil contamination remains on-site.
<br /> 0 13.Mass balance calculation of substance
<br /> The consultant estimates that 2.6 gallons of TPHd remains in soil.
<br /> treated versus that remaining;
<br /> 14.Assumptions,parameters, calculations and model used in risk
<br /> assessments, and fate and transport modeling;and A risk assessment was not required.
<br /> ya15. Rationale why conditions remaining at site will not adversely Soil contamination is limited in extent after excavation.
<br /> impact water quality, health, or other beneficial uses. Based on four sampling events, contamination is not
<br /> continuing to leach to groundwater.
<br /> By: Comments: Two 10,000-gallon gasoline, one 1,000-gallon gasoline, and one 1,000-gallon diesel USTs were removed
<br /> JLB from the subject site in August 1989. Soil contamination (TPHd) was identified at the USTs area. Multiple borings and
<br /> three monitoring wells were completed to delineate and monitor contamination at this site. In 8/01, approximately 200
<br /> Date: cubic yards of excavated soil from the USTs and AGT areas was aerated onsite. Monitoring wells MW-1, MW-2, and MW-
<br /> D were sampled from 11/01 to 9/02. In 9/02, groundwater contaminant concentrations declined to <50 ug/L for TPHg and
<br /> 4,'8/03 TPHd, and<0.5 Ng/L for benzene. MtBE was not detected in soil or groundwater. Lead was not detected in groundwater.
<br /> From 12/01 to 9/02, an onsite domestic well located 40 feet from the USTs area was sampled, and no contaminants were
<br /> detected. Additionally, results from the nearest offsite domestic well(600'downgradient) were non-detect for
<br /> contaminants. The site does not pose a threat to water quality, human health, and safety.
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