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Case Closure Summary Page 2 <br /> ' making Underground Fuel Storage Tank Pro ram <br /> III Release and Site Characterization Information (continued) <br /> Maximum Documented Contaminant Concentrations - - Before and After Cleanup <br /> Contaminant Soil (ppm) Water (ppm2 Contaminant Soil (ppm) Water (ppm) <br /> Before After Befores After Before After Before After <br /> TPH (Gas) 6,100' 1,1003 1.8 NA Ethylbenzene 500' 1203 .005 <.0005 <br /> TPH (Diesel) 92 144 <.5 <,5 Xylene 1,400' 193 .240 <.0005 <br /> Benzene 50' 243 .140 <.0005 Oil &Grease <br /> Toluene 440' 1203 .097 <.0005 Heavy Metals <br /> Lead <2.5' <2.5' <br /> Comments: Groundwater contamination was detected on 7/12/93 at the time of over excavation. Soil sample notations <br /> made for identification: 1. T2-13 on 6/15/93. 2. T3-B@14.5' on 6/15/93. 3. F-5-16' on 7/9/93. 4. MW-3-12' on 7/12/93. 5. <br /> Excavation pit on 7/12/93. 6. Monitoring well samples on 3/22/96. 1,600 cubic yards of contaminated soil and 7,500 <br /> gallons of water were removed. The extent of residual soil contamination was defined by five soil borings, three of which <br /> were converted into monitoring wells. Additional contaminants were detected at the time of tank removal 6/15/93 including: <br /> bromomethane, bromodichloromethane, chloromethane, 4-methyl-2-pentanone, 1,1,2,2-tetrachloroethane, 1,1,2- <br /> trichloroethane, and styrene. Subsequent over-excavation confirmation soil samples were non-detect for these <br /> contaminants. The excavation was backfilled with pea gravel. <br /> IV. Closure <br /> Does completed corrective action protect existing beneficial uses per the Regional Board <br /> Basin Plan? Yes. <br /> Does completed corrective action protect potential beneficial uses per the Regional Board <br /> Basin Plan? Yes. <br /> Does corrective action protect public health for current land use? Yes. <br /> Site management requirements: None. <br /> Should corrective action be reviewed if land use changes? No. <br /> Monitoring wells decommissioned: (Yes) Number Decommissioned: (3) Number retained: (0) <br /> List enforcement actions taken: NOR sent 6/30/93. <br /> List enforcement actions rescinded: None. <br /> V. Local Agency Representative Data <br /> Name: DoTs4e Heran Title: Director of Environmental Health <br /> Signature: Date: <br /> VI. Central Valley Regional Water Quality Control Board (RB) Notification <br /> Date Submitted to RB: Response Date: None. <br /> RB Staff: J. Brathovde Response: None necessary - Soil <br /> Title: Assoc Eng Geologist contamination only. <br /> VII. Additional Comments, Data, etc. <br /> Jeanne Homsey, Registered PE #47410, with Smith Environmental stated that the estimated 220 <br /> cubic yards of contaminated soil that remains, with concentrations up to 1,100 ppm TPH-gas <br /> and 24 ppm benzene, does not pose a threat to groundwater and will be reduced by natural <br /> biodegradation over time. The residual soil contamination is confined mainly on the northern <br /> end of the excavation between 15 to 18 feet below grade. The residual mass of contamination <br /> was estimated by Jeanne Homsey to comprise 131.77 lbs of TPH-gas, 3.31 lbs of benzene, 24.95 <br /> lbs toluene, 14.60 lbs of ethylbenzene, and 4.88 lbs of xylene for a total mass of <br /> contaminants in soil of 179.51 lbs. Monitoring well, MW1 was within 10 feet of the edge of <br /> the excavation and contamination was not detected. <br /> This document and t e related L LETTER, ha be retainid by the lead agency as part of the o ficial <br /> site file. (08124193) Exhibit N Page 2 of 2 <br />