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As noted firom the percolation test results, Lots 1, 5, 6, and 7 possess perc test results at depths,., representative of sumps and not seepage pits. It has been the policy of EHD to require the installation of seepage pits to a depth of 25 feet in areas of the county designated for seepage pits, even though test results demonstrate that sumps may be suitable. A new law that is to be implemented may restrict the installation of seepage pits (Assembly Bill 885). Before this law is implemented, EHD may require the installation of seepage pits on the subject Lots because: 1.) They are the typical and principle effluent management structure installed in this area, 2.)There is a distance of approximately 45 feet between the bottom of a seepage pit at 25 feet b.g.s. and the current groundwater depth of 70 feet and will probably never rise closer than 10 feet to the bottom of a seepage pit (groundwater 35 It deep), 3.) Seepage pits allow head pressure buildup to force effluent into the underlying anaerobic clay soils (although this has recently been apparently refuted in the Black Oaks subdivision of the Morada area), and 4.) If effluent levels within the seepage pit rise 10 to 18 feet above the bottom of the pit, the effluent could then be managed by the more permeable silty sand strata encountered at the medium test depths. The soil analytical test results show low-to-very low concentrations of subsurface soil nitrate-nitrogen, even though the subject property has been under agricultural production for the last several decades. It is unknown if the crops grown on the property were fertilized. However, decomposing organic matter from residual crop decomposition could certainly supply subsurface nitrate-nitrogen higher than those concentrations observed, indicating substantial denitrification potential. Soil chemistry directly under the on-site leachline that served the residential structure on the property demonstrated a very high nitrate-nitrogen concentration of 97 ppm. Unfortunately due to a lack of the proper excavating equipment, soil could not be sampled at five-foot interval depths directly under the leachline to test and quantify denitrification potential. It is assumed the denitrification potential would be comparatively high due to the high clay content of the indigenous soils, the higher soil pH, high soil moisture content and the organic matter fraction content. Soil particle size analysis for the two subsurface soil profiles under Lots 3 and 10 illustrate varying percentages of sand, silt and clay at the sampled depths. Clay content percentages are somewhat consistent under Lot 3 within the 20%- 28%range with the 15-foot depth decreasing to 12%clay. The soil under Lot 10 shows a generally decreasing clay content percentage; however, the clay content percentage is sufficient for biological action. It is noted that in the deep exploratory borings down to 25 feet, the soil became increasingly moist with increasing depth. High soil moisture content is beneficial in promoting denitrification. Jenssen and Siegrist(1990) found the factors that favor denitrification are fine-grained soils such as clays and silts layered with soils consisting of alternating fine-grained and coarser grained soils with distinct boundaries between the texturally different strata, as observed under Lot 3 and other Lots. This stratification may also contribute to the aforementioned increase in soil moisture content. Percolating water encountering coarser soil strata will accumulate on top of this coarser stratum until sufficient soil moisture builds up for the water to travel into this stratum. The nitrate loading calculations that demonstrate loading from two separate methods, illustrate that the impact from the on-site systems fall below the Maximum Contaminant Level (MCL) standard for drinking water. Page -12- Chesney Consulting