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D. 100% RESERVE AREA DOCUMENTATION Since the existing and operable filter beds were sized for the maximum Average Daily Flow maximum of the EnviroServer's 1,200 gallons, this same disposal area must be designated for "reserve"or"replacement" in the event of a failure, or another unforeseen condition. The existing filter bed areas are illustrated on the Site Plan found in Appendix F. As can be noted, the existing filter beds consist of a 300 s.£ bed, a 1,000 s.f bed and a 600 s.f. bed, for a total of 1,900 s.f primary filter beds. In calculating the filter bed area requirements, we have the following information: ADF based upon existing gpd flow plus the gpd from complete build-out of the project using a highly conservative estimate of assigning 15 gallons per parking area for the new development= 1,162 gpd ADF (Pg. 2). 1200 BTC + 1,162 gpd = 2,362 x 0.250 LLSF (Clay Leachline Soil Factor)= 591 LFLL(Lineal Feet of Leachline). 591 x 4 =2,362 s.f of filter bed. Theoretically, the filter bed area is deficient by: 2,362 - 1,900 =462 s.f., or 19%. However, the calculated ADF after complete build-out is based upon the following: Given that the people who will occupy every new parking space must use an on-site restroom IOx (1.5 gals per low flow flush x 10 flushes = 15 gallons); this provides a significant safety factor which compensates for the calculated filter bed area deficiency. The 100% reserve or replacement area of 1,900 s.f. is also denoted on the Site Plan found in Appendix F, and consists of a 780 s.f. bed, another 780 s.f bed, a 246 s.f. bed and a 136 s.f. bed, for a total of 1,942 s.£ of replacement/reserve area. Note that the smaller replacement/reserve areas (246 s.f. and 136 s.f)have been shown with the proper set-backs from driveways and parking areas. III. SOIL CHEMISTRY INFORMATION After receiving the test results from the EnviroServer effluent chemistry indicating a nitrate concentration of 177 ppm nitrate (as nitrate; MCL=45 ppm), analyses of the soil underlying the filter bed became more critical for two reasons. First, it became necessary to quantify the nitrate- nitrogen concentration within the soil since it is unknown as to the length of time and variability in the nitrate concentration. Data found in the EHD files for this project indicate an average nitrate- nitrogen(nitrate as N) of all effluent tests of approximately 14 ppm, which is 62.3 ppm as nitrate. Secondly, it is well-documented in the scientific literature that clay soils have a profound effect on nitrification and denitrification processes. From the soil test results, it appears the indigenous clay soils have significant denitrification potential. Technically, the most accurate method of measuring nitrate within the vadose zone soil is to capture vadose zone water for analysis. Irrometer Corporation of Riverside, California makes a Soil Solution Access Tube, which is similar to a suction lysimeter. Unfortunately in a clay soil, such as the soils under the filter beds, it is virtually impossible under low flow conditions to extract a vadose water sample. Page -4- Chesney Consulting