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IV. CONCLUSIONS AND RECOMMENDATIONS SSS§ 6.7, 6.8. The percolation test results for this project reveal slow permeability in the surface soils at typical leachline depth, and medium depth soils at typical sump depth. The deep perc tests demonstrate highly permeable soils, representative of seepage pits. Of significant importance is the large number of OWTS failures in this locale. Therefore, it is recommended to install at a minimum, an additional leachline trench and seepage pit to the number of leachline and seepage pits promulgated in Table 9.7.1 - Standard OWTS Design Requirements. It is favorable to force the leachline trenches to manage effluent flows as much as possible, and by adding an additional trench(s) will be environmentally beneficial and add lifespan to the systems installed. In accordance with EHD rules, the septic system disposal area for each proposed Parcel must be installed within 100 feet of the percolation test location. The criteria for perc test locations are described on Page 3. If OWTS installation is proposed outside this 100 ft radius, a registered civil engineer must approve this proposal. There is currently a distance of approximately 55 feet between the bottom of a 25 ft deep seepage pit and the current groundwater depth of 80 feet. It is extremely unlikely that groundwater will ever rise closer than 10 feet from the bottom of a seepage pit due to over -pumping and drought conditions. The soil analytical test results show low concentrations of soil nitrate -nitrogen, even though the subject property has been under agricultural production for the last several decades. Crops grown on the property were in all likelihood fertilized with nitrogen. Additionally, decomposing organic matter from residual crop decomposition supplies nitrate -nitrogen, also indicating substantial denitrification potential. Soil particle size analysis of the two sampled Parcels illustrate varying percentages of sand, silt and clay from the sampled depths. Clay content percentages are relatively consistent in decreasing percentages with increasing depths. 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, which has been observed in the soil test results. This stratification may also contribute to an increase in soil moisture content. Percolating water encountering coarser soil stratum will accumulate on top of this coarser stratum until sufficient soil moisture increases before percolating water enters the underlying stratum, thus creating anaerobic conditions and promoting denitrification. The nitrate loading calculations demonstrate potential loading from the total number of bedrooms each Parcel can support. SSS§ 6.7. For this project, it is important that: 1.) The architect/engineer/designer of the residential structures, 2.) The plumber, 3.) The septic system contractor, and 4.) The landscaper or landscape architect, should coordinate their services simultaneously for each individual Parcel. The architect/engineer/designer must orientate the house on each Parcel, taking into consideration the size of the house, perc test location, location of the OWTS primary disposal area, and the 100% replacement area. -11- Chesney Consn[ting