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F44.1 EVALUATION OF PAST AND CURRENT SOURCES OF CONTAMINATION IDENTIFIED AT OR NEAR THE SITE AND RECOMMENDATIONS FOR FURTHER ACTION luation of each not and/or known source of contamination identified in the previous and following Sections have been discussed in these respective Sections to facilitate the transfer of information to the reader. Recommendations are proposed in Section 5.0. Based upon the State Water Resources Control Board-GeoTracker System, the nearest Leaking Underground Fuel Tanks(LUFTs)are located approximately 7,500 feet to the south of the property. These sites are illustrated on the attached GeoTracker Site Map. Although these two tanks are upgradient to the property,potential environmental impact from these tanks is impossible due to the distances involved. The nearest underground storage tank(UST)to the subject property is approximately 6,500 feet to the southeast of the property. This tank location can be considered crossgradient and highly unlikely to impact the site, again due to the distance involved. Potential environmental impacts from past,present or future facilities within a one mile radius of the property are unknown at this time. The science of pesticide residues in soil, air, surface water and groundwater is extremely complex and variable. Environmental models that attempt to predict pesticide behavior and transport in the environmem are beyond the scope of this investigation. Pesticides with long half-lives that may have been used or drifted onto the property decades ago,primarily DDT, may be of an extremely slight concern. DDT was used extensively throughout the agricultural fields of the San Joaquin Valley and degradates of DDT can be found in nearly all 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,based upon the following environmental fate data: 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 in, 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 fast-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>300 d in lakes. Groundwater:N/A Sediment:N/A 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:N/A.Hydrolysis:>120 yr. Page -6- Chesney Consulting