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w1I - TA6W 1 - CHECKLIST OF REQUIREDWTA FOR NO FURTHER ACTION REQUESTS AT UNDERGROUND TANK SITES Site Name and Location: BBB Equipment,3132 Farmington Road,Stockton,San Joaquin County 0 I.Distance to production wells for municipal, domestic, agriculture, As shown in GeoTracker, the closest municipal well is i industry and other uses within 2000 feet of the site; about 804 feet southeast of the site. An on-site well is approximately 100 feet northwest of the former UST. 2. Site maps, to scale, of area impacted showing locations of former and existing tank systems, One wasgallon waste oil UST was removed in 4/89. A excavation contours and sample locations, boring and monitoring well elevation contours, site map is provided in the gradients, and nearby surface wafers, buildings, streets, and subsurface utilities; it Investigation Report ❑y 3. Figures depicting ir'thology(cross section), treatment system diagrams; The backfill material consists of gravelly clay to 5 feet,and the native material consists of silty clay to 12 feet the total depth investigated. ❑N 4. Stockpiled soil disposed off-site(quantify); The disposition of excavated soil was not presented. The Bolls were likely returned to the tank pit excavation. 5. Monitoringwells remainingon-site, fate; Groundwater was not encountered during assessment activities, and . monitoring.wells=were not installed. FN 1 6. Tabulated results of all groundwater elevations and.depths'to water,• Groundwater was not encountered at 12 feet The depth to water is estimated at 50 to 90 feet 7.Tabulated results of all sampling and analyses: The maximum concentrations in soil show TPHd at 240 mg/kg in one sample,and lead at 140 mg/kg in a second sample. All other Detection limits for confirmation sampling constituents including MtBE were non-detect at acceptable detection f Lead analyses limits. Maximum lead using the distilled water WET procedure show soluble concentrations at 0.2 mg/1 at 12 feet y� 8. Concentration contours of contaminants found and those remaining in soil !i A backhoe was used to excavate a trench and groundwater, both on-site and off-site: across the former UST area. Four discrete soli samples identified TPHd and lead in Y❑ Lateral and Vertical extent of soil contamination 1 soil to 12 feet Groundwater was not ❑ Lateral and ❑ Vertical extent of groundwater contamination encountered. 9. Zone of influence calculated and assumptions used for subsurface N soil contamination for he soil and Based on the limited remediation system and the zone of capture attained o f groundwater remediation system; site remediation was not required. E .i 0 10.Reports/information Y❑ Unauthorized Release Form [9 QMRs El Baring logs 0 PAR 0 FRP E] Soil Sampling Report, !November 2001 ❑ 11.Best Available Technology(BAT)used or an explanation for not using BAT;' The UST was removed. " " _'* " r """"""" Soil contamination remains ince formerr tankpit-area.—Th e contamination sj ❑ 12.Reasons why background warms unattainable using BAT, limited in extent,relatively immobile,and does not present a significant threat • to water quality. ❑ 13.Mass balance calculation of substance M treated versus that remaining, Based on the limited sail contamination,a mass balance was not required. j it ❑ 14.Assumptions,parameters, calculations and model used in risk Based on the limited soil contamination,a risk assessments, and fate and transport modeling; assessment was not required. 15. Rationale why conditions remaining at site will not adversely Contaminants In soil are relatively immobile and limited impact water quality, health, or other beneficial uses;and in extent.' The contamination will naturally attenuate and degrade.'i. By: Comments: One 110-gallon waste oil UST was removed from the B&B Equipment maintenance garage area in MH April 1989. Soil contamination was identified during the tank removal activities, and additional soil samples were collected from a 17'x 2'x 12'deep trench in September 2001. These samples were analyzed for TPHg, TPHd, BTEX, II Date: and fuel oxygenates, and only TPHd and lead were identified. The soil samples were also analyzed for lead using the j 215102 distilled water WET procedure, and concentrations are reported at 0.2 jmg17. The native soil to 12 feet consists of silty clay, and the depth to groundwater is estimated at 50 to 90 feet. Due to the fine-grained nature of subsurface lithology, �. and the low mobility and solubility of lead, Board staff believe that sufficient attenuation will occur and the lead will likely j not impact groundwater. Based on the investigation completed to date, Board staff concur with San Joaquin County's closure recommendation. !° 1