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June 10,2002 <br /> Job Number: LG02-164 <br /> Page 8 <br /> A satisfactory percolation rate is less than or equal to 60 minutes per inch(drop)per <br /> County requirements. The percolation test conducted on Parcel 1 was found to be satisfactory. <br /> VII. NITRATE LOADING STUDY <br /> A build up of nitrates in ground water can cause a temporary blood disorder in infants <br /> called methemoglobinemia(blue baby syndrome). Serious and occasionally fatal poisonings of <br /> infants have occurred following the ingestion of water containing nitrate concentrations greater <br /> than 10 mg/L nitrate as N or 45 mg/L nitrate as NO3. <br /> Because of the concern of nitrate leaching into ground water, a nitrate loading analysis <br /> may be required by the County to estimate the average nitrate concentration of percolating water <br /> for the subject parcel. If a site is contributing excess nitrogen to ground water, ground-water <br /> quality can be impacted. The nitrate sources considered for this project are percolating septic <br /> effluent from the proposed residences constructed on each of the parcels, agriculture, and deep <br /> percolation of rain water containing nitrate. <br /> The method utilized in this analysis is based on a simple mass balance formula discussed <br /> in an article published in Ground Water by Hantzsche and Finnemore'that provides a convenient <br /> and simplified method to estimate long-term ground-water nitrate impacts on an area-wide basis. <br /> Hantzsche and Finnemore found that over a long period of time, water quality in the upper <br /> saturated ground-water zone closely approximates the quality of percolating recharge waters. <br /> They have found that their approach is a good planning tool and provides useful information to <br /> planners and local officials but with some real limitations. <br /> Hantzsche and Fennemore'mention that"...the equation ignores dispersion, lateral flow, <br /> and mixing with ground water flow from up-gradient areas. These processes would generally <br /> contribute to additional reduction of nitrate-nitrogen concentrations in ground water to the extent <br /> that the nitrate-nitrogen concentration of ground-water flow from up-gradient areas is lower." <br /> The Hantzsche and Fennemore equation'provides "...a conservative(worst case) first <br /> approximation of ground-water nitrate-nitrogen concentration resulting from the combined effect <br /> of on-site sewage disposal systems and precipitation. This(the equation and approach) is for <br /> estimation of long-term effect(i.e., over years) on ground-water quality, and is not intended for <br /> prediction of seasonal changes." <br /> ' Hantzshe N.N.,Finnemore,E.J. 1991,Predicating Ground-Water Nitrate-Nitrogen Impacts. Ground <br /> Water,Vol.30,No.4. <br /> PERS 1 <br /> N <br /> W <br /> �SSO GAP <br />