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y. II i r DDD. Common name: DDD, TDE (tetrachlorodiphenylethane), product of DDT deg. Half-lives in the environment: Air: 17.7-177 h Surface water: 2-15.6 yr. k Groundwater: 1680-270,000 h based on anaerobic soil study data If Sediment: NIA Soil: Field half life of 2-15.6 yrs based on observed rates of biodeg. of DDT Biota: 119 hr in mussels. Environmental Fate Rate Constants or Half-Lives: Volatilization: Aquatic approx. 1 mo. Oxidation: Aquatic half-life approx. 22 yr Hydrolysis: half-life of 570 d @ pH 9 and 190 yr @ pH 5 Biodegradation: Aqueous aerobic half-life of 2-15.6 yr CONCLUSIONS AND RECOMMENDATIONS From visual observations, there is no surface contamination on the subject property, other than used motor oil spillage onto the asphaltic concrete driveway. This should pose no environmental concern and is prevalent everywhere. Therefore, at this point in time, no corrective action is required within the boundaries of the subject property. The probability of subsurface contamination from pesticides can be considered extremely low-to- nonexistent, considering the environmental fate data for DDT and related compounds presented above. Additionally, the surface and subsurface soil types are predominately a clay soil with the biological activity expected to be higher than in a sandier soil. During earthwork procedures, there should be a relatively high aerobic capacity in the soil environment which may promote a higher level of degradation and decomposition of any adverse organic molecules that may exist. The depth of groundwater to 62 feet would also make impact from adverse constituents unlikely. It has been documented that impact to the upper, intermediate and lower groundwater bearing strata originating from the Marley Cooling Tower is in the process of being remediated and has s not affected the upper aquifers under the subject property. There may be impact from the Marley facility to the intermediate groundwater zones. However,since the property and the entire locale are on City of Stockton domestic water supply, this should not pose a concern for future development of the property. No domestic, or water well of any type may be drilled on the subject property: The probability for nitrate contamination of the underlying aquifers from previous septic systems is also low due to the favorable surface and subsurface soils consisting of clays and silts, intervening clay layers, and a medium-to-deep depth to groundwater. Page -5- Chesney Consulting