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1 <br /> GEOMATRIX <br /> 6.7 Closure of Underground Storage Tank <br /> The underground storage tank is a buried steel tank encased in concrete. The tank will be <br /> removed during closure activities and transported to an plastic lined area within the rail car loading <br /> area. Prior to removal, any sludge or tank residuals will be removed. <br /> Once the tank has been moved to the lined area, the top of the tank will be exposed and the <br /> ' interior will be hydroblasted. Rinseate from the hydroblasting will be stored in a Baker Tank, <br /> tested for hazardous waste characteristics, and disposed of as hazardous waste, if necessary. If <br /> non-hazardous, the rinseate will be disposed of at a permitted hazardous waste disposal facility: <br /> ' It is assumed that approximately 100 gallons of rinseate will be generated. Closure of the tank <br /> will be demonstrated by collecting a final rinseate samples. The sample will be analyzed for DBCP <br /> ' and EDB using EPA Method 8011, organochlorine pesticides using EPA Method 8080, and <br /> organophosphorus pesticides using EPA Method 8140. Clean closure will be achieved if the <br /> results of the analyses are all non-detect. Upon demonstration of clean closure, the tank will be <br /> disposed of as non-hazardous. If clean closure is not achieved, the tank will be disposed of as a <br /> hazardous waste. <br /> A total of two soil samples will be collected within the bottom of the tank excavation. If <br /> groundwater is encountered in the bottom of the excavation, the samples will be obtained from <br /> the excavation sidewalls. The approximate location of the samples are indicated on Figure 2. The <br /> actual locations will be determined by the licensed engineer during closure. <br /> Soil samples will be collected using a drive sampler fitted with pre-cleaned brass sample tubes. <br /> ' The samples will be collected approximately 6 to$ inches below the excavation surface. The drive <br /> sampler will be cleaned between sample locations. The tubes will be sealed with plastic end caps <br /> and tape. The samples will be sealed, labeled, and placed in an iced cooler for transport to the <br /> ' laboratory under chain-of-custody procedures. The soil samples will be analyzed for DBCP and <br /> EDB using EPA Method 8011, organochlorine pesticides using EPA Method 8080, and organo- <br /> phosphorus pesticides using EPA Method 8140. <br /> If the soil samples contain hazardous waste concentrations of pesticide residues, depending or. the <br /> ' quantities involved, Simplot may arrange to remove, treat (if necessary), and dispose of the soil <br /> at a permitted hazardous waste landfill. Groundwater below the site is being collected and treated <br /> ' to remove pesticide residues, as described above in Section 2.5. The soil surface over most of the <br /> Ag Chem area is paved. These conditions provide effective controls for exposure routes and <br /> cleanup beyond hazardous waste concentrations does not appear warranted. <br /> 12 <br />