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IV. SEPTIC SYSTEM DESIGN, OPERATIONAL CRITERIA, AND NITRATE-NITROGEN IMPACT MITIGATION A. Septic System Operation The new septic system for the proposed restroom facility has been designed f r 150 gpd This Average Daily Flow (ADF) is based on an unlikely,but possible, maximum o ployees (owner, secretary, salesman and two mechanic), and five customers per day. Typically, EHD uses a number of criteria to project wastewater flow volumes based upon 1.) Published data(e.g., 15 gals/employee-customer/day), 2.) The number of bathroom fixtures or bedrooms, and/or 3.) The number of parking stalls. It is our understandine that there will be one bathroom in the office ante 5ink. Considering that if the toilet (1.5 gallon/flush) was flushed every one-quarter hours over the an eight hour work day,we have: 4 flushes/hr x 8 hrs x 1.5 gals/flush x I toilet =48 gallons, which leaves approximately 100 gallons for additional use. Therefore, this is a plausible ADF water usage. The primary filter bed, and ultimately the 100% replacement area filter bed will consist of Standard Infiltrator Chambers® SC (Shallow Cover), Six inch spacers between chambers with the effluent trickling into the"front'of the chambers fro a seven port distribution box. /`— Cl"<t Backfill soil over the chambers must consist of sante loam material with four toiX iCbQ Qf cover soil material over the chambers. A grass-type plant should be planted over the disposal area so that the plant roots can evapotranspire effluent during able times of the year. ��__Al_ Ritz" B. Wastewater Disposal System Design Specifications Septic Tanks Influent from the office will gravity flow into a 1,200 gallon, septic tank that does not need to be traffic rated since it will be inside a gated area, and therefore cannot be driven over. A filter, (e.g., Zabel or Orenco) must be installed in the second compartment. Effluent from this tank will level gravity to a seven-outlet distri�io 2Q (7ah_Pl_.Part.Nn:-GL1s..1313,47-L). 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 every three years, depending on sludge/scum accumulation. Peaking factors for users on septic tanks vary with usage during the hour of the day, and day of the week. Peak hourly rates are associated with normal working hours. The ratio of the peak day to the average day can vary from 1.5 to>5, depending upon the usage. However, peaking factors are not as relevant since the effluent pump will dose on demand. A peaking factor of 2.5 (average between 0 and 5) will be used in the calculation below: Pa e-6- Chesney Consulting