SU0002162 SSNL - Laserfiche WebLink

Home Browse Search

December 16,2002 Job Number: LG02-2I3 Page 8 "The method utilized in this analysis is based on a simple mass balance formula discussed in Ground Water by and Finnemore." This method provides a in a published article - convenient and simplified.method to estimate long-term ground-water nitrate •impacts on an area- wide basis. Hantzsche and Finne'More have found over a long period of-tiiiie, water quality in the upper.saturated ground-water zone closely approximates the quality of percolating recharge " 1 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, they mention that"...the equation ignores dispersion; lateral-flow,and mixing with ground water flow from up-gradient areas. These processeswould generally . contribute to additional reduction of nitrate-"nitrogen concentrations in ground water 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 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 a� prediction of seasonal changes." The Hantzsche and Fennemore' equation takes into account development area, soil 4 " denitrification factor, rainfall volume, rainfall nitrate concentration, the"waste effluent quantity, and waste effluent nitrate concentration. The formula, assumptions and calculations used for the analysis are shown on Plates 8 and 9.The units of nitrate used in the mass balance equation are nitrate-N whose maximum drinking water contarninate level is 10 mg/L. Nitrates from the Septic System and Rain Fall -The.average total nitrate concentration of.the"typical.septic waste is normally considered to be 45 mg/L-N. s Please note the concentration is not related to the maximum contaminate level for drinking water of 45,mg/L-NO3. The Phase Il church facility will contain 249 seats for up to 250 members. The average daily flow will vary during the days of the weeks. The optional use of a kitchen facility was.considered to estimate the daily flows. The SJC.PHS/EHD Sewage Standards allows 10 gallons per seat per day for a,church with ajdLc en. The average Haritzshe N.N_,Finnem_ ore,E.J. 1991,Predicating Ground-Water Nitrate-Nitrogen Impacts: Ground Water,Vol. 30,No.4. s.Otis,R.J.;Boyle;"W.C., 1980,Design manual,onsite wastewater treatment and disposal.systems:U.S. Environmental Protection Agency,EPA 625/1-80-012. (Seepage 100,table'6-1).