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j 7D. CALCULATED IMPACT FROM NITRATE-NITROGEN LOADING <br /> The calculated or estimated nitrate impact to the soil and ultimately to the groundwater is extremely <br /> difficult to determine due to the number of variables involved. For example, the number of people to <br /> inhabit the primary residence and possible second unit dwelling is unknown and variable. A value of <br /> four people per household has been used, which incorporates a safety factor. <br /> The nitrate-nitrogen loading will be calculated below under two different conditions: First, only the <br /> two acres of proposed Parcel 1,with the primary residence and a second unit dwelling will be <br /> assessed. With the second calculation, the total area of Parcel 1 and the Designated Remainder will <br /> both be taken into consideration. The nitrate loading will be quantified and compared with the <br /> current nitrate concentration in the groundwater in the Conclusions section of this Report. <br /> HANTZSCHEIFINNEMORE EQUATION TAKING INTO CONSIDERATION THE � <br />` ! PRIMARYRESIDENCEALONG WITH SECOND UNIT DWELLING ON PARCEL 1 <br /> AND EXCL UDING THE DESIGNATED REMAINDER AREA OF 4.5 ACRES: <br /> IN,(1 -d)+RNb <br /> Nr= (I+R) <br /> Where: <br /> Nr= Resultant average concentration of nitrate-nitrogen in recharge water-(ppm NO3-N) <br />€, I = Volume rate of wastewater entering the soil averaged.over the proposed Parcel 1 area in inches per yr <br /> Nw Total nitrogen concentration of wastewater in N mg/L(66 mg NIL/day) <br /> d = Fraction(%) of nitrate-nitrogen loss due to denitrification in the soil <br /> R = Average recharge rate of rainfall -inches per yr(9 in.) <br /> Nb= Background nitrate-nitrogen concentration of rainfall recharge, exclusive of wastewater influences <br /> E (ppm NO3-N) <br /> Values and Assumptions: <br /> 68 gals/person/day x 4 people per household x 2 houses ..2.00 Ac x 365 d/yr=3.6 in/yr <br /> I- 43,560 cu ft/Ac ft x 7.48 gal/cu ft x -(I ft/12 in) <br /> Nw— 66 mg/L - 10%reduction in each of 2 septic tanks in series=20%reduction total = 53 mg/L N <br /> d = 10% from biomat and 25% from clay soil under leachlines and from the observed nitrogen decrease. <br /> Nb = Assumed to be 0.1 ppm NO3-N <br /> 3.6 in/yr(53 mg N/L) {I -0.35)(9.0 in/yr x 0._1 m /L) <br /> Nr = (3.6 in/yr+9.0 in/yr) <br /> Nr = 9.9 ppm as NO3-N or 44.1 ppm as NO3 <br /> F <br /> Page -9- <br /> Chesney Consulting <br />