SU0008656 SSNL - Laserfiche WebLink

Home Browse Search

- Impact of Existing Nitrate Concentration in Ground Water The calculation above utilizes average values for nitrate concentration in the effluent, with no consideration as to the quality of the source water. However, as discussed on page 4 of this report, a water test found the domestic well at the on-site residence to contain nitrate at a concentration of 126 mg/L- NO3 (28 mg/L-N). Nitrate plumes may drift and/or attenuate, so this level may not rernain consistent. In addition, a new well is proposed for the church facility which may produce water lower in nitrate. Nevertheless, for the purposes of modeling, a second weighted average calculation has been run which incorporates the detected ni r�feve-I in the source water. -For the estimated waste water quality in this calculation, the detected concentration of" g mg/L-j N is added to the average concentration values from Crites and Tchobanoglous_,___� Table 6. Weighted Average Concentration Calculation with Existing Nitrate Use Average Daily Estimated Waste Water Weighted Average Flow Quality Product Residence 360 gpd 45 + 28 = 73 mg/L-N 26,280 gpd-mg/L-N Parishioners - Sunday 139.3 gpd 85 + 28 = 113 mg/L-N 15,741 gpd-mg/L-N Meetings 22.5 gpd 85 + 28 = 113 mg/L-N 2,542 gpd-mg/L-N Totals 521.8 gpd 44,563 gpd-mg/L-N Weighted Average 563 44, d-m /L-N / 521.8 Concentration: gp g gpd = 85.4 mglL-N Denitrification Reductions Denitrification is a process that occurs in the septic system drain field whereby certain bacteria oxidize the nitrate (NO3) in the waste water and release nitrogen gas (N2) to the atmosphere. Due to the biologic processes in the shallow-soils, nitrogen in the drain field will may undergo a reduction between 10 percent to 35 percerrV Soils with higher clay content, moist soil conditions, high pH, and organic material denitrify by about 35 percent, and soils with high sand content and fast percolation rates tend to denitrify at a lower rate of about 10 percent. A typical denitrification factor of 25 percent was selected for the Site because of the fine-grained nature of the soils. Nitrate Loading Estimate Two nitrate loading scenarios were employed to determine the impact from the proposed project to ground water. These scenarios utilize the variables discussed LOGE 1124 Page 12