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Fobtaining er, to obtain a realistic and pertinent perc rate, the water level readings for the last half hour ken every ten minutes, as illustrated on the EHD Perc Test Form. Consequently, instead of the final reading for the last one-half hour of a four-hour test equal to: 30 minutes- 6.12 inches =4.9 min/in, the ten minute readings give a true perc rate of. 10 minutes_6.12 inches= 1.6 min/in. The test results indicate relatively equal perc rates between the 24 inch and 36 inch test depths. However, the rates are exceedingly rapid for EHD standards. Consequently, changes must be made to the native soil-effluent interface within the filter bed area. These changes are pursuant to EHD regulations and EPA regulations found in the EPA Design Manual- Onsite Wastewater Treatment and Disposal Systems. A summary of the perc test results with corresponding application rate in gallons of effluent accepted per square foot of soil, per day are found in Table 2 for proposed disposal area: TABLE 2 PERCOLATION TEST RESULTS FOR THE DISPOSAL AREA FILTER BED WITH CORRESPONDING APPLICATION RATES IN GALLONS / FT 2/ D Y 24 INCH DEEP PERC TEST BORING 1.7*n/inch / 1.2 gallons/ft2/day PERCOLATION RATE/APPLICATION RATE 38 INCH DEEP PERC TEST BORING 1.6 min/inch / 1.2 gallons/ft/day PERCOLATION RATE/APPLICATION RATE Application Rates adapted from California State Water Resources Control Board Guidelines for the Design of Sewage Systems. D. GROUWATER INFORMATION NLS§ 2.1, S S§ 4.1. Groundwater depths and elevations throughout San Joaquin County are illustrated onm p�_p lished by the County Flood Control and Water Conservation District. The mo t recent Lines of Equal Depth map (1999) indicates the groundwater depth to be approximately 22 feet. This groundwater depth corresponds with the sounding of the on-site domestic well. The 3 Lines of Equal Elevation Map illustrates the groundwater directional flow to be generally in a north-northwesterly direction. A well log for a domestic well near the subject property illustrates varied geological strata of clay, sand and some shale down to a depth of 180 feet. Standing well water levels measured in nearby wells in 1988 were found to be 20 ft; in 1986 - 16 ft, and in 1975 to be 18 ft. Groundwater research in the scientific literature suggests there may be significant denitrification potential within aquifers or saturated zones composed of a fine clay soil fraction. NLS§ 2.2, 3.1, SSS§ 2.19 4.2. ' Since surrounding properties have been intensely farmed for several decades, the potential Tor nitrate contamination in the underlying groundwater is significant. However, well water directly obtained from the underlying aquifers indicate medium nitrate impact. This relatively low concentration may be attributed to the denitrification potential within the underlying aquifers, as referenced. / 5 Chesney Consulting