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[3] SOIL PROFILE AND PERCOLATION TESTING Our percolation tests on Parcels A and B were conducted according to San Joaquin County Department of Environmental Health regulations. The perc tests were performed in the areas most likely to be developed in the future and are denoted on the Tentative Map. The Field Test Data Sheet with the percolation test results can be found in the Appendix. The percolation test borings were composed of silt (ML) in the upper horizons and a silty, fine-to-medium sand (SM) at the bottom of the perc test borings (- 42 in). There was no pre-saturation due to recent irrigations in the perc test areas. No hardpan or other type of restrictive layer was encountered in the test borings. The attached Well Driller's Log for an adjacent well show varied soil strata of sand, clay and gravel down to 308 feet in depth. The 42 inch perc test depth represents percolation which will take place in a leachfield. Since the groundwater is comparatively deep in the location of proposed future development, sumps are allowed. As indicated on the attached Application for Permit and Plot Plan for the subject property, the existing residence has two, 100 foot leachlines with eight foot sumps at the ends. The subject area soils possess percolative capacity even though there was high moisture content throughout the soil profile. As can be noted from the perc tests, once the soils become saturated, percolation capacity diminishes rapidly. 141 LOCAL GROUNDWATER AND SURFACE WATER INFORMATION The static water table depth, or the zone of saturation is located at approximately 55 feet below grade at the elevation equal with Burwood Road. This is according to the attached 1996 "Lines of Equal Depth" published by the San Joaquin County Flood Control District. However, the water table is approximately eight feet below grade near the Stanislaus River elevation. There is no potential for septic impact to any surface waters, providing applicable requirements are followed. Since the domestic well is downslope and to the west of the existing residence, this well location should be taken into consideration if there is to be future development on Parcel B. Septic effluent should not be allowed to migrate or percolate downslope in line with the existing well. Analysis of water drawn from the domestic well which services the house, indicates a nitrate concentration of 53 ppm NO3. The Maximum Contaminant Level (MCL) for NO3 in drinking water is 45 ppm. The pesticides DBCP and EDB were not detected (ND). OQ ontrol Inspection