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FILTER BED DESIGN The primary and 100% replacement areas will be denoted on the Site Plans that will be drawn for submittal to EHD and other County Departments. These Plans were not complete at the time of the submittal of this report. It is my understanding the new 1,200 gallon septic tank and filter bed is to be installed west of the pre-manufactured home. After the effluent gravity flows from the septic tank, it will travel to a D-box to be equally distributed over the filter bed. The 100% replacement area will be to the east of the new home, near the barn. It appears the effluent will have to be pumped to this location in the event of failure. CONCLUSIONS AND RECOMMENDATIONS NLS§ 4.2. The shallow subsurface soils underlying the subject property where the new filter bed is to be installed, reveals a very high clay content soil material with a high degree of denitrification potential. NLS§ 4.1. The nitrate loading calculations show the resultant effluent from the entire subject property will theoretically possess a concentration of approximately 18.1 ppm as nitrate-nitrogen, which is 1.8x over the Maximum Contaminant Level (MCL). Given that the ADF of 840 gpd has two extreme components promulgated by EHD of two people per bedroom, and that this flow volume will occur every single day of any given year, has created a very large nitrate loading safety factor. This factor is conservatively estimated at greater than 4. Consequently, the nitrate loading mitigation procedure of placing four inches of a highly organic peat or a wood chip type material on the floor of the filter bed shall be implemented. This will greatly increase the carbon to nitrogen(C:N)ratio of the soil at the soil-effluent interface. These materials can exceed a C:N ratio of greater than 100. Nitrification will only occur if the C:N ratio is below 20. Therefore, nitrification cannot occur from ammonium molecules entering the highly organic soil-effluent interface. Additionally, ammonium that has nitrified, will theoretically denitrify within the anaerobic environment and high carbon material within the interface due to saturated conditions promoted by the organic material. NLS§ 4.2. All decentralized wastewater management systems (septic systems) will eventually fail. A reasonable long lifespan of the primary and reserve area system can be expected based on the proposed components of the septic system. A nearby project that was conducted ten years ago, found the underlying groundwater table to have a nitrate concentration greater than 100 mg/L. Given the large amount of surrounding agricultural production and subsequent nitrogen fertilizer use, this nitrate concentration would be expected. Page 6 of 13