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r KLEIN FELDER i I Following ou'r percolation testing a representative with our firm obtained a- sample of groundwater using clean procedures from the well located on 10834 Copperopolis Road f (northern parcel). The 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/1 as Nitrogen (N) 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 Finnerrzore (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, = AWN, (1-Dh (Nb AW-1- r Where: NC = Average calculated nitrate-nitrogen in groundwater resulting from domestic sources and precipitation— mg/l, as N � A = Number of dwelling units Derr acre on septic tanks (unit/acre) =.Z.OSestimated based on an estimated water usage of 300 gal./day for two homes (SJCPHS requirement). Typical daily water usages based on SJCPHS recommendations for a 3 bedroom residential home.) W = Annual wastewater loading per dwelling unit per acre (inches) = 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(>75 feet)) 4 R = Annual deep percolation of precipitation (inches) = 12.33 inches (representing 85 percent of average annual rainfall of 14.5 inches in project area. Remaining 15 percent of rainfall is assumed to drain off-site into natural or manmade drainages) 20-4684-0l.GO1/2011R1570 December 20,2001 0 2001 Kleinfelder,Inc. Page 3 of 4