Laserfiche WebLink
Ah AM, <br /> MW NW 11� <br /> modifications to existing septic systems were for additional drainage (leachlines) and seepage pits. <br /> This can be considered a high number of permits in comparison to the low density housing and <br /> indicates the shallow soils in the area are not conducive to acceptable management of sewage effluent. <br /> [3] SOIL PROFILE AND PERCOLATION TESTING <br /> A percolation test on the Parcel 1 was conducted according to San Joaquin County Department of <br /> Environmental Health regulations. The test location is illustrated on the attached Parcel Map. <br /> Percolation test results can be found on the Field Test Data Sheet in the Appendix. The percolation <br /> test boring was drilled to a depth of 42 inches below existing grade in an area west of the residence <br /> on Parcel 1. This is the depth where effluent percolation will normally take place in leachlines. Soil <br /> structure consists of a fine sandy clay (SC) throughout the shallow soil profile with a hardpan layer <br /> located at approximately 36 inches which extends to 42 inches. Smeared soil surfaces were opened <br /> with a flat-edge probe. The borings were not pre-saturated 24 hrs prior to starting the perc tests <br /> because the soil was already wet from recent rains. <br /> Perc rates for the shallow test boring indicate slight percolation initially of 120 min/in falling to non- <br /> existent percolation after one and a half hours. <br /> [4] LOCAL GROUNDWATER AND SURFACE WATER INFORMATION <br /> The static water table depth, or the zone of saturation is located at approximately 130 feet below <br /> grade according to the 1996 "Lines of Equal Depth" published by the San Joaquin County Flood <br /> Control District. It is possible there may be perched water table conditions under the subject property <br /> at a higher elevation that the static water level. There is no potential for septic impact to any surface <br /> waters, providing applicable requirements are followed. The property is not in the flood plain. <br /> Analysis of water drawn from the domestic well at the residence indicates a nitrate concentration of <br /> 13 ppm NO3. The Maximum Contaminant Level (MCL) for NO3 in drinking water is 45 ppm. The <br /> pesticides DBCP and EDB were not detected(ND). A nitrate concentration of 13 ppm indicates the <br /> underlying aquifers have not been significantly impacted from nitrogen contributors. Additionally, <br /> there are significant clay layers which may attenuate the downward migration of nitrate from nitrogen <br /> sources. <br /> [5] CONCLUSIONS <br /> The non-existent shallow percolation rate for the subject parcel suggests there would be no <br /> effluent percolation at the leachline depths of approximately 42 inches below grade. This is due <br /> of course, to the heavy clay content soil and hardpan layer. Percolative capacity does exist at <br /> deeper depths as evidenced by the attached perc rates which were obtained from projects directly <br /> across Henry Road. As referenced earlier, there are no plans to build on the two parcels and they <br /> will remain as a homesite and in agricultural production. <br /> E) (�­Ilty Control Inspection <br />