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15999 W CORRAL HOLLOW RD Project No.2019-00027 Page 18 For the site,the total daily toilet use contributing wastewater quantity is 2,566 gallons per day.The average total nitrogen concentration of domestic wastewater is normally considered to be 20-85 m�- N_with 35 to 45 mg/L-N being typical (Crites and Tchobanoglous, 1998). To be conservative, >'we have esti m ted that for this site a commercial wastewater concentration will be approximately 85 mg/L-N. 4.4.2 :Denitrification Estimate 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 percent. Soils with higher clay content,moist soil conditions,high pH,and organic material denitrify by about 35 percetp-arid'sgils with high sand content and fast percolation rates are estimated to denitrify at a low�r,rate,about 10 percent to 15 percent.To be conservative,and based on the sandy soils,w have used,a 10 percent denitrification value. 4.5 Nitrate Loading A nitrate loading scenario was performed to determine the impact from the proposed project. The scenario utilizes the variables discussed previously which represent the estimated conditions and uses associated with this project. The following table presents a summary of the nitrate loading calculation for the parcel. Table 4. Summary of Nitrate Mass Balance Anal sis. Parcel Result Acres Average Daily Effluent Leachfield Deep (Nc)* (A) Flow(Q) Concen- Denitrifi- Percolation of (mg/L-N) (gpd) tration cation(d) Rainfall (R) (Nw) (Plate 9) (in.) (mg/L-N) 1 1.2 5,753 2,566 85.00 1 10% 1 2.52 * Maximum contaminant level (MCL) for nitrate in drinking water is 10 mg/L-N. 4.6 Impact of Nitrate Loading to Nearby Water Sources Based on the methods and assumptions described, in addition to our professional judgement and geologic setting,we believe the proposed projects will not cause a build-up of nitrate in the ground water above 10 mg/L-N over the long term. Based on the relatively flat topography of the site,we do not foresee percolating effluent affecting any surface water resources. �V" Petralogix Engineering,Inc. rt , 26675 Bruella Road,Galt,Ca 95632k, �1 a��r (209)-406-5729 !A{�tb4ieF;` .phr^ wwwetralogix.corn tk "