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Two sources of information which attempt to document and define on-site and surrounding past land use were also utilized. The first is the use of aerial photographs. Aerial photographs of the subject area from 1970 through 1977 found on USDA Soil Maps show the residential structure and metal building and no other building on the property. The USDA Soil Map shows the soil to consist of a Shinkee muck(#247). Typically, these soil types are poorly drained with slow permeability. Sufficient soil "fines" exist to impede rapid percolation so treatment of effluent can occur before reaching the water table, unlike what would be encountered with a sandy soil. The second source of information can be found on USGS maps. The property is located within the Terminous Quadrangle map, found in Appendix "A," and shows only the referenced buildings. It is a possibility that agrichemicals sprayed on surrounding agricultural production land may drift onto the subject property. Additionally, past and present business practices at the Alpine Helicopters property are unknown. San Joaquin County Mosquito Abatement District sprays for mosquitos in the surrounding open irrigation conveyances that may contain stagnant water. Noted on the Environmental Questionnaire, is the response to pesticide applications to the property and the previous crops grown on the property. The following list of pesticides have been applied to the property during the last three years. As noted, no chemical mixing occurs on-site: Lambda Cyhalothrin; Common Name: Warrior Trifluralin; Common Name: Treflan Diuron; Common Name: Direx Hexazinone; Common Name: Velpar Gramoxone; Common Name: Paraquat 3 Environmental fate data for these specifically applied agrichemicals as a nonpoint source of potential contamination was done, and are found in Appendix "C." In reviewing the environmental fate data of the applied agrichemicals used, we find most of them have moderate persistence in the soil and water environments. However,their use in terms of volume is minimal, and measured in ounces per acre. 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 environment are beyond the scope of this investigation. The agrichemicals used on the property are widely used throughout California, with only Diuron found to be impacting groundwater in certain areas. These areas are typically in sandy soils and are called Pest Management Zones (PMZ), where the use of Diuron is highly restricted. Pesticides with long half-lives that may have been used or drifted onto the property decades ago, primarily DDT,may be of a very 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 L(if extremely low probability of adverse health effects from soil DDT/DDD and DDE concentrations the concentrations even exist). Page -4- Chesney Cmisulting