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1246 N Fine Road Project No. 2021-00025 Page 17 <br />(100 gallons per 1st bedroom per <br />1 100 365 day x 1 bedroom x 365 days) / <br />Proposed 365 days = 100 gal <br />2nd Unit Dwelling - 3 <br />Bedroom (50 gallons per bedroom per day <br />2 SO 365 x 2 bedrooms x 365 days) / 365 <br />days = 100 gal <br />* Based on EHD request with previous studies <br />TOTAL AVERAGE GALLONS PER DAY 450 gallons <br />For the site, the total daily toilet use contributing wastewater quantity, considering the <br />existing and planned residential dwellings is 450 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 sandy loam and clay soil types for the subject property, denitrification is <br />estimated to be 25 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 />Table 4. <br />Summary of Nitrate Mass Balance Analysis. <br />Parcel Result Acres Average Daily Flow Effluent Leachfield Deep Percolation <br />(Nc) * (A) (Q) Concen- Denitrifi- of Rainfall (R) <br />(mg/L-N) (gpd) tration (Nw) cation (d) (Plate 7) (in.) <br />(mg/L-N) <br />1 13.2 2.00 450 35.00 25% 3.21 <br />* Maximum contaminant level (MCL) for nitrate in drinking water is 10 mg/L-N. <br />Petralogix Engineering, Inc. <br />26675 Bruella Road, Gait, Ca 95632 <br />(209)-400-5729 <br />www.petralogix.com