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September 20,2001 <br /> Job Number: LGO1-098 <br /> Page 8 <br /> Table 6. Summary of Percolation Test. <br /> No. Percolation Test Depth (ft) Percolation Rate <br /> (minutes/inch) <br /> P-1 2 <1.6 min/inch <br /> In addition to the soil suitability study, a nitrate loading study was required for project <br /> approval by SJC PHS-EHD. <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/1 nitrate as N, 1000 ug/L nitrate as N,or 45 mg/1 nitrate as NO3. <br /> Because of the concern of nitrate leaching into ground water, a nitrate loading analysis <br /> was required by the County to estimate the average nitrate concentration of percolating water for <br /> the subject parcel. If a site is contributing excess nitrogen to ground water, ground water quality <br /> can be impacted. The nitrate sources considered for this project are percolating septic effluent <br /> from proposed facility, and deep percolation of rain water containing nitrate. <br /> The method utilized in this analysis is based on a simple mass balance formula discus)ha <br /> in a published article by Hantzsche and Finnemore7 that provides a convenient and simplified <br /> method to estimate long-term ground-water nitrate impacts on an area-wide basis. Hantzsche <br /> Finnemore found that over a long period of time,water quality in the upper saturated ground- <br /> water zone closely approximates the quality of percolating recharge waters. They have found <br /> their approach is a good planning tool and provides useful information to planners and local <br /> officials but with some real limitations. In Hantzsche and Fennemore's article, published in <br /> Ground Water, they mention that "...the equation ignores dispersion, lateral flow, and mixing <br /> with ground water flow from up-gradient areas. These processes would generally contribute <br /> additional reduction of nitrate-nitrogen concentrations in ground water to the extent that the <br /> nitrate-nitrogen concentration of ground-water flow from up-gradient areas is lower." <br /> i <br /> 7 Hantzshe N.N.,Finnemore,E.J. 1991,Predicating Ground-Water Nitrate-Nitrogen Impacts. Ground <br /> Water, Vol. 30,No.4. <br /> ?pERJO <br /> r S <br /> i r <br /> o � <br />