SU0002183_SSNL - Laserfiche WebLink

Home Browse Search

KLEINFELDER Following our percolation testing, a staff engineer with our firm obtained a sample of groundwater using clean procedures from a well located at 30987 Highway 120, the neighboring property to the west. The well was located approximately 60 feet west and 80 feet north of that parcel's southwest corner. That same day, the water sample was submitted to Far West Laboratories using chain-of-custody procedures for DBCP and nitrate testing. The results of our tests and a copy of the chain-of-custody are attached. NITRATE LOADING CALCULATIONS Per San Joaquin County Public Health Services (SJCPHS) Department Environmental Health Division(PHS/EHD) requirements, the following summarizes our nitrate loading calculations for the proposed leach field. The drinking water standard for nitrate is 45 milligrams per liter (NO3) and 10 mg/l as Nitrogen (l) in groundwater. In our evaluation of nitrate loading, we have used 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. N, =A_WNw_(1-D)+(Nbj_r 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) = 0.13 (estimated based on an estimated water usage of 300 gal./day plus an avera a of 55 gal./day for • ) the clubhouse, typical water usages based on SJCPHS recommendations or two three-bedroom residences and approximately 2,060 attendees at 10 gal/attendee) W = Annual wastewater loading per dwelling unit per acre (inche§y�-2.0 inches (per year per dwelling unit assuming a flow of 150 gal./day/dwelling unit) 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(60+ feet)) R = Annual deep percolation of precipitation (inches) = 10.2 inches (representing 85 percent of average annual rainfall of 12 inches in project area. Remaining 15 percent of rainfall is assumed to drain off-site into natural or manmade drainages) Nb = Background nitrate nitrogen concentration of rainfall recharge at the water table = 20-4685-O1.G01/201 IR1543 December 12,2001 ©2001 Kleinfelder,Inc. Page 3 of 4