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FDDD. Environmental Fate Rate Constants or Half-Lives: Volatilization: N/A Oxidation:N/A Hydrolysis: >120 yr Biodegradation:N/A 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. Groundwater: 1680-270,000 h based on anaerobic soil study data Sediment: N/A 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 ONCLUSIONS AND RECOMMENDATIONS From visual observations, there is no surface contamination of the soil on the subject property. `. Therefore, at this point in time,no corrective action is required within the boundaries of the subject property, as of the date of this report. The origin of the observed soil depressions as discussed in this report are unknown. As discussed, if any subsurface artifact of a hazardous materials nature is uncovered unng underground work, the San Joaquin County Environmental / Health Department must be contacted immediately. / 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 j' above. The depth of groundwater of 50 feet would also make impact from adverse constituents unlikely and it has been documented that impact originating from any known(public)release of hazardous material has not been located on the subject property. 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. This has been documented with a photograph illustrating the soil surface cracking indicative of clay soils. 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 be present. The probability for nitrate contamination of the underlying aquifers is also low due to the favorable surface soils consisting of clays and silts, intervening clay layers, deep depth to f groundwater and a very low, original septic system density. Page -5- Chesney Consulting