SR0087834_NITRATE LOADING STUDY ADDENDUM

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Additionally, the soil organic percentage is comparatively high, increasing the denitrification potential, along with a high Cation Exchange Capacity(CEC) of 34.1 meq/100 g. The pH of the soil is 7.6 and 7.9. Neutrophilic denitrifying bacteria have an optimal pH ranging between 7.5 and 9.5. CALCULATED NITRATE-NITROGEN LOADING: HANTZSCHVFINNEMORE EOUATION INW(1 -d)+RNb Nr= (I+R) Where: Nr = Resultant average concentration of nitrate-nitrogen in recharge water-(ppm NO3-N) I = Volume rate of wastewater entering the soil averaged over the gross developed area in inches per yr. As referenced,the ADU=3 bd; Existing=2 bd. 100+50+50=200; 100+50=150. 200+150=350. Nw = Total nitrogen concentration of wastewater in mg N/L d = Fraction(%)of nitrate-nitrogen loss first in the septic tank and then due to denitrification in the soil environment. R = Average recharge rate of rainfall -inches per yr Nb = Background nitrate-nitrogen concentration of rainfall recharge,exclusive of wastewater influences (ppm NO3-N)- Values and Assumptions: I=350 gpd x 365 d/y= 127,750ag_ls/y= 17,079 cu ft = 8.88 in/yr 0.53 Ac x 43,560 sq ft/Ac x (1 ft/12 in) Nw=35 mg N/L d = Assume 50%due to heavy clay content soil. R = 8.82 in/yr. Nb= Assumed to be 0.1 ppm NO3-N l I _8.88 in/yr(35 mg N/L x(1-0.50))= 155.4 +(8.82 in/yr x 0.1 me/L)=8.8 ppm � Nr = (8.88 in/yr+8.82 in/yr) I 1 Nr = 8.8 ppm as nitrate-nitrogen (NO3-N) or 40 ppm as nitrate(NO3) I l ONSITE WASTEWATER TREATMENT SYSTEMS DESIGN i i This project fulfills the requirements of the EHD and addresses three main design factors. First, the replacement area for the existing onsite wastewater treatment system (OWTS) has been designated and illustrated on the attached Design Plans. Secondly, the primary OWTS for the ADU has been designed and is also illustrated. Thirdly, the replacement area for the ADU has I� also been designed and illustrated. I Page -3- Chesney Engineering, Inc.