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KLEINFELDER replaced. At that time, new pipe was installed between the house and the tank. Currently, this is the only septic system on the 70-acre parcel. Mr. Heilmann indicated that the system has performed well. GROUNDWATER DEPTH AND TESTING The closest well to the proposed new septic system is located approximately 350 feet away at the existing house. According to the "Lines of Equal Depth to Groundwater,"published in the fall of 1998 by the San Joaquin County Flood Control and Water Conservation District, the depth to groundwater at this location is between 60 to 70 feet. We understand that a water sample was obtained from the well at the existing house and submitted to Far West Laboratories in Riverbank for analysis of nitrate and nitrogen. The results of these analyses are attached. The nitrate as NO3 was reported as 27 milligrams per liter (mg/1). It appears that an analysis for TKN was performed by a different laboratory and reported as non- detect. TKN measures ammonia and organic nitrogen. Although not measured in the laboratory, we estimate that nitrate as N would be approximately 6 to 7 mg/l. PERCOLATION TESTS We have attached to this letter, the results of a percolation test observed by Mr. Rodney Estrada on November 15, 1999. The soil conditions apparently encountered at this location consisted of sandy loam and the measured percolation rate was approximately 3.6 minutes per inch. NITRATE LOADING CALCULATIONS We have been requested by Mr. Mike Huggins of the San Joaquin County Public Health Services Department Environmental Health Division (PHS/EHD) to calculate the nitrate loading for the proposed leach field. As you are aware, the drinking water standard for nitrate is 45 milligrams per liter (NO3) and 10 mg/1 as Nitrogen (N). In our evaluation of nitrate loading, we have used the Hantzsche mass balance equation, which is presented below with an explanation for each factor and the value used in our study. We note that the Hantzsche mass balance equation, as well as the literature available for our review, are primarily for residential type structures versus a commercial facility such as a produce stand. Since the intent of this mass balance equation is to evaluate the impact on groundwater over a large area, we have assumed that the usage of one bathroom by two employees basically during daytime fiours would be at most approximately 1/4 of a typical household. In otherwords there would be no bathing, laundry, dishes etc. The entire property encompasses approximately 70 acres and there is currently one septic system on the property. If we assume that the employee restroom would be the second system on 70 acres, an argument could be made to define `A' (the number of dwelling units per acre on septic tanks) as equal to .25 dwelling units divided by 35 acres or .007. With the term `A' so low, the only parameter that has any influence on the Hantzsche mass balance equation is Nb. Unfortunately, 20-1210-99/2019RIO86 Page 2 of 4 Copyright 1999 Kleinfelder, Inc. December 14, 1999