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V. SEPTIC SYSTEM DESIGN, OPERATIONAL CRITERIA. AND NITRATE-NITROGEN IMPACT .MITIGATION ( A. Septic System Oper�ttiun The new septic system for the proposed restroom facility has been designed for 150 gpd. 'I hitt Average Daily Flow(ADF) is based on an unlikely,but possible, maximum of five employees l (owner, secretary, salesman and two mechanic), and five customers per day. Typically, EHD uses a number of criteria to project wastewater now volumes based upon I.) Published data (e.g., 15 galstemployee-customer/day), 2.)The number of bathroom fixtures or bedruoms, and/or 3.)The number of parking stalls. It is our understandillg that,there_will be cine / bathroom in the office and one sink. Considering that if the toilet 0.5 gallon/flush) was flushed t every one-quarter hours over the an eight hour work day, we have: 4 flushes/hr x 8 lirs x 1.5 gawflush x 1 toilet =48 gallons, which leaves approximately 100 gallons for additional use. Therefore, this is a plausible ADF Nvater usage. The primary filter bed, and ultimately the 100%replacement area filter bed will consist of Standard 1 Infiltrator Chambers(As SC (Shallow Cover). Six inch spacers between chambers with the effluent trickling into the"front"of the chambers from a seven port distribution box. j Backfill soil over the chambers must cp�rsisr of a sand} loctin material. with 14Iti.Jasiac incllcs of coyer soil material over the chambers. A grass-type plant should be planted over the disposal area SO that the plant roots can evapotranspirc effluent during favorable times of the year. B. Wastewater Disposal Svstem Design Specifications Septic 'ranks influent from the office will gravity now into a 1,200 gallon, septic tank that docs not aced to h� traffic rated since it a ill be inside a gated area, and therefore cannot be drivq! ov r. A filter, (c.�, . Zabel or Orenco) must be installed in the second compartment. Effluent from this tank N ill level i gavity to a seven-outlet distribution.hox.(Zabel Part No:GDS DB 7L). Effluent from this distribution box will flow equally into six Infiltrator Chambers. This primary tank will provide preliminary treatment and trap paper, etc. The tank must be pumped on a prescribed interval basis depending on direct observations of paper and scum accumulation; e.g.. every six months to even i three years, depending on sludge/scum accumulation. L",Pea , aors for users on septic tanks vary with usage during the hour of the day, and day of the hourly rates are associated with normal working hours. The ratio of the peak day to ay can vary from 1.5 to >5. depending upon the usage. However, peaking factors are nt since the effluent pump will dose on demand. A peaking factor of 2.5 (average d 5) will be used in the calculation below: _ Page -G- ----- — Chesney Consufthl