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33503 S Koster Road Project No. 2021-00073 P a g e | 7 <br />Existing <br />Main House – 3 <br />Bedroom <br />1 100 365 <br />(100 gallons per 1st bedroom per <br />day x 1 bedroom x 365 days) / <br />365 days = 100 gal <br />2 50 365 <br />(50 gallons per bedroom per day <br />x 3 bedrooms x 365 days) / 365 <br />days = 100 gal <br />Proposed <br />2nd Unit Dwelling – 2 <br />Bedroom <br />1 100 365 <br />(100 gallons per 1st bedroom per <br />day x 1 bedroom x 365 days) / <br />365 days = 100 gal <br />1 50 365 <br />(50 gallons per bedroom per day <br />x 2 bedrooms x 365 days) / 365 <br />days = 50 gal <br />* Based on EHD request with previous studies <br />For the site, the total daily toilet use contributing wastewater quantity, considering the <br />existing and planned residential dwellings is 350 gallons per day. The average total nitrogen <br />concentration of domestic wastewater is normally considered to be 20-85 mg/L-N with 35 <br />to 45 mg/L-N being typical (Crites and Tchobanoglous, 1998). Based on EHD request with <br />previous studies, it is estimated that residential domestic wastewater concentration will be <br />approximately 35 mg/L-N. <br />5.4.2 Denitrification Estimate <br />Denitrification is an important process which occurs within the leach field whereby certain <br />bacteria utilize the oxygen in the nitrate (NO3) and release nitrogen gas (N2) to the <br />atmosphere. Denitrification is expressed as a percentage, and the normally accepted range <br />is 10 percent to 35 percent. Soils with higher clay content, moist soil conditions, high pH, <br />and organic material denitrify by about 35 percent, and soils with high sand content and fast <br />percolation rates are estimated to denitrify at a lower rate, about 10 percent to 15 percent. <br />Based on the clayey loam soil types for the subject property, denitrification is estimated to <br />be 30 percent. <br />5.5 Nitrate Loading <br />A nitrate loading scenario was performed to determine the impact from the proposed <br />project. The scenario utilizes the variables discussed previously which represent the <br />estimated conditions and uses associated with this project. The following table presents a <br />summary of the nitrate loading calculation for the parcel. <br />TOTAL AVERAGE GALLONS PER DAY 350 gallons