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III. NITRATE LOADING STUDY FINDINGS A. WASTEWATER FLOW VOLUME PROJECTIONS AND CHARACTERISTICS Wastewater Flow Volume Projections Typically, loading projections for commercial facilities are based on the maximum anticipated wastewater flows generated by people that occur daily, weekly,monthly, or for singular events. The number of people on-site for this facility at any given time is quite variable and basically unknown. Therefore, determination of nitrate loading from the existing restroom is based upon the maximum conceivable daily usage. It is my understanding that the general public (customers) of the facility will not have access to the restroom. However, it has been the policy of the EHD that on-site restrooms that may not necessarily be made available to customers,must be made available upon request by customers. Consequently, since there presently is only one unisex restroom and no proposal to install another restroom,the plumbing fixtures within this restroom will be used to calculate an average daily flow (ADFs). The ADF from the entire 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 hmd washing)=2 gals/use x 4 uses/hr= 8 gals/hr x 8 hr/workday=64 gals/day. This ADF figure will be used in the disposal design parameters. For the nitrate loading calculations below,the yearly wastewater generation is: 64 gals/day x 6 days/wk=384 gals/wk x 52 weeks/yr= 19,968 gals/yr. Wastewater Characteristics The domestic wastewater generated from the facility will be composed of blackwater from toilets and greywater from hand washing. There should 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 the 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 literature (See Kaplan-septic Systems Handbook,Pg. 147),based upon a mixture of the concentrations referenced above. B. CALCULATED NITRATE-NITROGEN LOADING i NLS§3 4,3'.'5,3.6. The calculated nitrate-nitrogen impact to the soil and ultimately to the groundwater is difficult to determine due to the large number of variables involved and variables unknown at this time. These include: 1.) Impact from upgradient nitrate sources, 2.) Variability in wastewater flows, effluent nitrogen concentrations and dilution effects from stormwater recharge, Page -6-