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I ., 1960s before it was banned in 1972. DDT was used extensively throughout the agricultural fields of the San Joaquin Valley and degradates of DDT are found in virtually all of these soils. Previous Exposure Assessments made on typical San Joaquin Valley soils suggest an extremely low probability of adverse health effects from soil DDT/DDD and DDE concentrations (if the concentrations even exist). It is important to note that the surface soils currently in-place will undergo significant and considerable physical and chemical changes during project development. These alterations include increases in ultraviolet light exposure, moisture content and aeration. Regarding worker r protection standards during construction: best available technology for dust control during construction procedures is the wetting of soils. Final concentrations of DDT and its degradates k in the play areas or garden areas of the new SFR cannot be predicted. It can be reasonably concluded that the DDT, DDE and DDD concentrations will continue to degrade as reported in the published environmental fate data. The environmental fate data for DDT and its degradates DDD and DDE are illustrated below: DDT. Common name: Agritan, Anofex, Azotox, et al. Half-lives in the environment: Air: 17.7 -177 h. Surface water: 73.9 h for a pond 1 in deep. Degradation half-life of about 10 yr- average from loss rates determined in Lake Michigan. Groundwater: 16 d to 31.3 yr. Sediment: 3 to 5 yr Soil: 2-15.6 yrs based on observed rates of biodegradation in aerobic soils under field conditions. Avg. half life of--12 yrs in 3 different soils for -50 ppm in soil. (conversion of p,p'-DDT to p,p'-DDE). Environmental Fate Rate Constants or Half-Lives: Volatilization: Half-life of 3.7 d for water depth of 1 m, from soil w/h-1 of 578 h Oxidation: Photooxidation half-life of 168-8400 h in water, 17.7-177 h in air Hydrolysis: Estimated first-order half life of 22 yr Biodegradation. Aqueous aerobic half-life of 2-15.6 yrs DDE. Common name: DDE (p,p'-DDE; o,p'-DDE), product of DDT degradation. Half-lives in the environment: Air: Atmos. transformation lifetime est. to be < 1 d. Surface water: Hydrolytic half-life of >120 yr, est. half-life X300 d in lakes. Groundwater: NIA Sediment: NIA Soil: Field half life of 1000 d Biota: Elimination half-life of 340 d (rainbow trout), 300 d for birds. Environmental Fate Rate Constants or Half-Lives: Volatilization: NIA Oxidation: NIA Hydrolysis: >120 yr Biodegradation: NIA 4 Page -4- Clcr-mery Consulting '�