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h" KLEINFEL1) ER PRESENT AND PAST USE OF THE SITE / EXISTING AND PROPOSED SEPTIC TANK USAGE The following information was obtained by Mr. Neal Pollard, whose father previously owned the proposed church site. Apparently, in the mid-1950's an existing structure was remodeled and occupied by the 99 Christian Church. In approximately 1980, this church structure was destroyed by fire. According to Mr. Pollard, no other structure or facility has occupied this site. The site currently contains two concrete slabs, a well, and a graveled surface area. _ As you are aware, the Morada area of north Stockton is blanketed with an expansive black clay commonly known as "adobe." As a consequence, the long-term performance of shallow leach fields is often less than desirable and seepage pits are now the more common method of disposal in this area. The site plan attached on Plate 1 shows the presence of seepage pits at the end of each seepage trench in the northwest corner of the property. GROUNDWATER DEPTH AND TESTING There is an existing well at the Pollardville Restaurant located adjacent to the proposed site. A water sample was obtained from this well for nitrate testing, but the well was not sounded. According to the "Lines of Equal Depth to Groundwater," published in the Fall of 1999 by the San Joaquin County Flood Control and Water Conservation District, the depth to groundwater at this location is between 70 to 80 feet. A water sample obtained from this adjacent well was _ submitted to Sequoia Laboratories for analytical testing of nitrate as N. The result, which is attached, indicates a concentrJ ation_of 2.25 milligrams per liter (mg/1). PERCOLATION TESTS We have attached to this letter, the results of a percolation test observed by a representative of the San Joaquin County Environmental Health Division. An initial percolation test performed at the 8-foot depth on May 26, 2000, failed to meet San Joaquin County minimum standards. We note that the soils encountered in the percolation test hole at the depths of 7 to 8 feet consisted of silty fine sand. However, this sandy layer must have been a localized pocket. Three additional percolation tests were performed on June 9. The percolation test denoted P-3 was performed at a depth of approximately 9-1/2 feet and indicated a percolation rate of 15 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/l 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, is primarily for residential type structures versus the church facility as proposed. Since the intent of this mass balance equation is to evaluate the 20-3168-36.G01/2000L581 Page 2 of 4 Copyright 2000, Kleinfelder, Inc. June 21,2000