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Apri1.25,2001 ,. , ' • . . , - lob Number: LGOI-098 Page 8 addition to the soil suitability study which includes the percolation testing, a nitrate loading study rwas required for project approval by the County. VII. NITRATE LOADING STUDY ` A build up of nitrates in ground water can cause a temporary blood disorder in infants F€ called methemoglobinemia(blue baby syndrome).- Serious and occasionally fatal poisonings of ; infants have.occurred following the ingestion of water containing nitrate concentrations greater than 10 mg/l nitrate as N or 45 mgll nitrate as NO'. Because of the concern of nitrate leaching into ground water, a nitrate loading analysis was required by the County to estimate the average nitrate concentration of percolating water for the subject parcel. .lf a site is contributing excess nitrogen to ground water, ground water quality can be- impacted: The nitrate sources considered for this project are percolating septic effluent, from the proposed residences constructed on each of the new 2-acre parcels, agriculture, and " deep'percolation of rain water containing nitrate. The method utilized in this analysis is based on a sim mass balance ' ul discussed in a published article.by Hantzsche and Finnemore'that.provides a convenient and simplified E method to estimate long-term ground-water nitrate impacts on an area-wide basis. Hantzsche and Finnemore found that over'a long'period of time,water quality in the upper saturated ground- water zone closely approximates the quality of percolating recharge_waters. They have found that their approach is a.good planning tool and provides useful information to planners and local officials but with some real limitations.• In Hantzsche and Fennemore s article, published in Ground Water, they mention that,......the equation ignores dispersion, lateral flow,and mixing with ground water:flow from up-gradient:areas. These processes would generally contribute to additional:reduction of nitrate-nitrogen concentrations in groundwater to the extent that the ` nitrate-nitrogen concentration of ground-water flow from up-gradient areas is lower_." The Hantzsche and Fennemore equation' provides "...a conservative (worst case) first ss approximation of ground-water nitrate-nitrogen.concentration resulting from the combined effect- of on-site sewage disposal systems and.precipitation. This (the equation and approach)'is for estimation of long-term effect (i.e., over years) on ground-water quality, and is not intended for prediction of seasonal changes." `! Hantashe N.N.,Finnemore,E.J. 1991,Predicating Ground-Water Nitrate-Nitrogen Impacts. Ground Water, Vol. 30,No:4. , x F�lr