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July 2, 2007 NOA Project Number: E06122A Page 2 capital cost and low maintenance over the life of the system when complaried to a package treatment system. Please refer to the article for details. The approach that Marselille and Anderson (2001)have taken has several advantages including simpler design,readily available carbon source in the sand to enhance denitrification, lower capital cost, and low maintenance in the long-term. The sand bed is contained within the trenches and acts like a intermediate sand filter design. Denitrification is promoted in an anaerobic environment in the bottom of the trenches. An initial target goal was set for nitrogen reduction of 50 to 60 percent within soils below the leach line trenches. Since our office will monitor the system for the first year including taking water meter readings, measuring actual denitrification, and influent concentrations, it will be possible to re- assess the nitrate loading of the site and if a buildup of nitrates in the ground water above 10- mgfL is occurring. The successful operation of the septic system will not only depend on the design factors discussed, but will also depend on the quality of the influent entering the system from the three buildings. The septic system is not designed to handle any other waste stream other than residential strength waste. Strong chemicals and solvents could seriously damage the septic system. Water softener brines are not acceptable, for disposal in the septic system. please call our office or ERD for more information regarding suitable waste streams. Calculating Flow Rates and Measuring Available Surge Volume Based on the results of the SS/NLS, the maximum peak use for the site is estimated to be approximately 2,108 gallons per day. This number was derived from 130 parking spaces (NOA, 2007). The average daily flow is estimated to be approximately 1,186 gallons per day(NOA, 2007). The septic system drain field was designed to handle 1,186 gallons per day with sufficient volume and disposal area in the pits to contain occasional peak flows at a rate of 2,108 gallons per day, The leach field adsorption area was determined by the following: Percolation rate (PR): 83 minutes per inch (mpi) (using slowest percolalion rate in shallow soil) Average daily_flow 1,186 gallons per day (gpd) Peakflow: 2,108 gallons per day (gpd) Loading Rate: Q (gpolsO = 5/(PR mpi)^0.5 (equation from Manual o . e tic Tank Practice Q == 5183^0.5 Q = 0.55 gpd/sf f C) 51Z_G