SR0073449 - Laserfiche WebLink

Home Browse Search

F7ATTACHMENT: Mike Brown NLS-SSS Addendum nitrate-nitrotr_en loading from 80 people on the subject property_ INw(1 -d)+RNb Nr= (I+R) Where: Nr = Resultant average concentration of nitrate-nitrogen in recharge water-(ppm NO,-N) 1 = Volume rate of wastewater entering the soil averaged over the gross developed area in inches per yr Nw = Total nitrogen concentration of wastewater in mg N/L d = Fraction(%)of nitrate-nitrogen loss due to denitrification in the soil R = Average recharge rate of rainfall-inches per yr Nb = Background nitrate-nitrogen concentration of rainfall recharge,exclusive of wastewater influences (ppm NO,--N). Values and Assumptions: 15 gals/person/day x 80 on-site people x 5 days/wk x 50 wks/yr=300,000 gals/yr I =300.000 pals=total WW/yr-40,107 cu ft = 1.87 in/yr 5.90 Ac x 43,560 sq ft/Ac x (I ft/12 in) Nw=62 mg N/L d = Assume 20%by substantially increasing the denitrification potential by the use of one ft of peat material within the floor of the filter bed. R = 11 in/yr. Nb= Assumed to be 0.1 ppm NO}N 1.87 in/yr(62 mg N/L) (I -0.20)+(11 in/yr x 0.1 mp/L) Nr = (1.87 in/yr+ 11 in/yr) Nr = 7.3 ppm as nitrate-nitrogen (NO3-N)or 32.5 ppm as nitrate(NO3) Calculated nitrate-nitrogen loading from the residential structure exclusively: I =75,000 gals=total WW/yr= 10.027 cu ft =0.47 in/yr 5.90 Ac x 43,560 sq ft/Ac x (1 ft/12 in) Nw=62 mg N/L d = Assume 10%due to low percentage of fine-grained clay/silt soil in upper soil profile. R = 11 in/yr. Nb= Assumed lobe 0.1 ppm NO,N 0.47 in/yr(62 my N/L) (I -0.10)+(11 in/yr x 0.1 mg/L) Nr = (0.47 in/yr+ 11 in/yr) Nr = 2.4 ppm as nitrate-nitrogen(NO3-N)or 10.6 ppm as nitrate(NO3) Therefore,the total theoretical nitrate-nitrogen contribution from the entire property=7.3 +2.4=9.7 ppm N0,-N, which is under the MCL of 10 ppm NO3-N. Chesney Consulting