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PERCOLATION TEST RESULTS FOR THE DISPOSAL AREA MOUND SYSTEM WITH CORRESPONDING APPLICATION RATES IN GALLONS / FT2 / DAY 36 INCH DEEP PERC TEST BORING PERCOLATION RATE / APPLICATION RATE 125 min/inch / 0.1 gallons/112 /day PERCOLATION TEST RESULTS SSS§ 6.2. To assess the permeability and the infiltration capabilities of the proposed mound system area, a percolation test boring was drilled in the location depicted on the Percolation Test Rate Form. As referenced, the test depth was 36 inches below existing grade. SSS§ 6.3. On December 29, 2020, the perc test boring was hand-drilled. The boring was scored with a pry-bar to open potentially smeared sidewalls. Two inches of pea gravel was placed at the bottom and three-inch perforated PVC pipe was inserted in the test boring to prevent potential cave- in. The boring was pre-saturated with 12 inches of water; 24 hrs before the start of testing. SSS§ 6.4, 6.5. On December 30, 2020, percolation testing commenced. No standing water was observed after the 24-hr soak period. Consequently, EHD Perc Test Procedure #2 was conducted in which testing was done over a four-hour period to induce maximum soil saturation. The test results indicate a very slow perc rate of 125 minutes/inch (mpi). A summary of the perc test results with corresponding application rates in gallons of effluent accepted per square foot of soil per day are found in Table 2: TABLE 2 Application Rates adapted from Water Quality Control Policy for Siting, Design, Operation, and Maintenance of Onsite Wastewater Treatment Systems. GROUNDWATER INFORMATION NLS§ 2.1, SSS§ 4.1, NLS§ 2.1. Groundwater depths and elevations throughout San Joaquin County are illustrated on maps published by the County Flood Control and Water Conservation District. However, due to the high degree of variability in groundwater elevations in the Tracy area, particularly north Tracy, lines of equal depth and equal elevation have not been determined for this area in close proximity to the Delta. This is due to the fact that seasonal water table variations occur that are primarily dictated by surrounding irrigation and Delta water volumes. The water table has been measured to be 5.5 ft below grade in this locale. With regard to groundwater directional flows, it is generally regarded that groundwater flows in a northeasterly direction, toward the Old River. This flow direction makes the mound systems crossgradient to this flow direction. NLS§ 2.2, 3.1, SSS§ 2.1, 4.2. Since surrounding properties have been intensely farmed for several decades, the potential for nitrate contamination in the underlying groundwater is significant. 4 Chesney Consulting