SU0002680 SSNL - Laserfiche WebLink

Home Browse Search

"— In KL EINEELDER the Hantzsche mass balance equation (source: Predicting Ground-Water Nitrate-Nitrogen Impacts, Hantzsche and Finnemore (1992)), which is presented below with an explanation for each factor and the value used in our study. The selection of parameters was based on previous studies and investigations performed by our firm and others, San Joaquin County Sewage Standards, and information provided in a report dated March 19, 1997 prepared by the Questa Engineering Corporation and authored by Mr. Hantzsche for a development in the Stockton area. Ne=AWNw 1-D + bZr AW+r Where: Ne = Average calculated nitrate-nitrogen in groundwater resulting from domestic sources and precipitation—mg/l, as N A = Number of dwelling units per acre on septic tanks (unit/acre) = 0.89 (estimated based on an estimated water usage of 150 gal./day (see below) which is equivalent to the typical daily water usage for 3 bedroom residential home) W = Annual wastewater loading per dwelling unit per acre (inches) = 1.27 inches (based on 5 workers with a water usage of 30 gal./shift (San Joaquin County Sewage Standards for day workers at offices) assuming 5 work days/week) Nw = Nitrate concentration of nitrified leachfield effluent (mg/1) = 35 mg/1 typical (Hantzsche and Finnemore (1992)) D = Percent dentrification of leachfield effluent = 0.35 percent (0.1 to 0.35 percent typical per Hantzsche and Finnemore (1992). 0.35 selected given the large depth to groundwater (>75 feet) and a majority of the soils encountered consist of fine clays and silts that tend to increase denitrification) R = Annual deep percolation of precipitation (inches) = 6.0 inches (representing 50 percent of average annual rainfall in project area. Remaining 50 percent of rainfall is assumed to fall on on-site improvements and/or drain off-site into natural or manmade drainages) Nb = Background nitrate concentration of the deep percolating precipitation — mg/I = 2.2 mg/l as N Our calculation is as follows: Ne = 0.89(1.27)(35)(1 —0.35) +2.2(6) = 25.7 + 13.2 = 5.45 mg/1 as N .89(1.27)+6 1.13 +6 CONCLUSIONS Based on the above evaluation, we conclude that wastewater produced by the proposed office building should not cause the nitrate levels in groundwater below the site to rise above the state 204585-0LG01/2011 R602 November 21,2001 ©2001 Kleinfelder,Inc. Page 3 of 4