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Soil Suitability / Nitrate Loading Study Ernst Property Tracy, CA Irerracon February 21, 2019 Terracon Project No. NA197000 Water Use 2010 Data, average daily domestic use per capita was estimated at 69-gallons per day. The EHD recommends a residential use rate of 70-gallons per person/day with an average potential occupancy of two persons per bedroom. The following table presents the proposed potential septic wastewater use for the site based on EHD use rate and occupancy. The rates presented from the references provide general guidance but do not always reflect a match in usage. Should any of the above information provided to our office change or is inconsistent with what is stated, our office shall be contacted to make any necessary modifications to our calculations. Examination and professional judgement, and experience shall be used when selecting a reasonable flowrate. Table 5. Potential Quantity of Effluent. Average Number of Effluent days Number of days of Average Daily Flow Category People per Quantity per Bedrooms Bedroom Person use per (gpd*) (gpd`) year Existing (5 bedrooms x 2 people per bedroom Residence 5 2 70 365 x 70 gal. per day x 365 days per year)/365 days per year=700 gpd 3 bedrooms x 2 people per bedroom Proposed 3 2 70 365 x 70 gal. per day x 365 days per Mobile Home year)/365 days per year=420 gpd Potential Average Daily Flow 1,120 gallons per day *gpd - gallons per day Based on a review of Table 5, the estimated potential sewage flow rate for the existing five bedroom residence is 700 gallons per day. The proposed three bedroom mobile is estimated to add an additional 420 gallons per day for a combined total of 1,120 gallons per day. The average total nitrogen concentration of domestic wastewater is normally considered to be 20 to 85 mg/L-N with 35 to 45 mg/L-N being typical (Crites and Tchobanoglous, 1998). It is estimated that commercial use will have higher concentrations of total nitrogen when compared to residential use. For the purposes of the nitrate loading estimate, it is estimated that the average concentration for total nitrogen in wastewater for the project is�pproximately 35 mg/L-N over the long term. ' �6 2.3.4.2 Denitrification Estimate I Denitrification is an important process which occurs within the leach field whereby certain bacteria utilize the oxygen in the nitrate (NO3) and release nitrogen gas (N2) to the atmosphere. Denitrification is expressed as a percentage, and the normally accepted range is 10 percent to 35 Responsive ■ Resourceful ■ Reliable 14