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(III. NITRATE LOADING STUDY FINDINGS A. WASTEWATER FLOW VOLUME PROJECTIONS AND CHARACTERISTICS Wastewater Flow Volume Projections To determine nitrate-nitrogen loading from any project, wastewater flow volumes must be determined as accurately as possible. Flow volume projections will be approximated from the potential number of on-site truck drivers/employees/customers, as illustrated below. It is my understanding that the proposed modular restroom will be the only domestic wastewater fixture units for this project. The following chart illustrates the anticipated wastewater flow volumes. Typically, cement truck drivers come to the facility, load their trucks and leave for job sites where restroom facilities are normally available. TABLE 3 Number of Employees Customers per Shift Vehicles per Shift 70 0 15 Taking a reasonable usage factor of four gallons per day (2.0 gals AM, 2.0 gals PM @ 1.5 gals flush + 0.5 gals hand washing) = for truck drivers (vehicles), we find the following: 15 drivers x 4 gpd/person = 60 gpd Wastewater flow volumes for the remaining 5 on-site employees (20 on-site -15 drivers = 5) from the facility will be based on an assumed maximum fixture usage of 4x/hr during an 8 hr day: 2 gals/use (1.5 gals flush + 0.5 gals hand washing) =2 gals/use x 2 uses/hr = 4 gals/hr x 8 hr/workday = 32 gpd. Total wastewater flow volume = 60 gpd + 32 gpd =92 gpd 92 gpd x 5 dpw = 460 gpw x 50 wks/yr = 23,000 gpy = 0.071 ac ft. This yearly wastewater generation will be used for the nitrate loading calculations below. Wastewater Characteristics The domestic wastewater generated from the facility will be composed of blackwater from toilets and greywater from hand washing. There will be no high organic loading from kitchen use, etc. Additional wastewater constituents may consist of other liquids to the system, such as coffee, juices, low strength cleaning liquids, etc. No industrial or commercial chemicals, solvents, etc. should ever be introduced into the wastewater treatment system. It is imperative that low strength and low volumes of cleaners are used in the restroom since they can disrupt septic tank biology. The scientific literature cites nitrogen concentrations in domestic septic effluent typically ranging from 17 mg N/L for basins, sinks, etc. to 140 mg N/L for toilet wastes. A value of 62 mg N/L is typically used for domestic calculations, as indicated in the scientific literature (See Kaplan - Septic Systems Handbook, Pg. 147), based upon a mixture of the concentrations referenced above. Page -6- Chesney Consulting