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The soil horizons are predominately clayey silts (CL-ML)with some variation in structure. There is a relatively thin silty sand strata which was encountered in both deep borings at approximately 13 to 15 feet below existing grade. There are some changes in color, indicating changes in the geological formation of the horizons. The Morada area is known for a high cohesive content soil and consequently, a high density of septic system failures. There are three applications for septic system installations and six applications for septic system repairs/additions at the Morada Center(See attachments). This indicates the on-site soils have the propensity for failure under heavy wastewater flows. PERCOLATION TESTING Percolation testing was conducted in accordance with San Joaquin County Environmental Health Department and U.S.E.P.A. regulations. Prior to pre-saturation of the test borings, the sidewalls of all four borings were scarified the entire depth. This is a critical procedure in which smeared soil that occurs from the augering process, is opened to allow water infiltration. Four inches of gravel was placed at the bottom of each boring to prevent scour,then each test boring was sleeved with three-inch diameter perforated pipe. Pre-saturation consisted of filling the borings with clear water to approximately 90% capacity. This procedure induced saturated soil conditions so that perc rates could be obtained under"worst-case" circumstances. The shallow perc tests indicate marginal soils for percolation at the assumed leachline trench depth of 42 inches. The deep perc test borings which represent seepage pits indicate more favorable percolation. The following is a summarization of the perc rates: East- Shallow: 63 min/in East- Deep: 9 min/in West- Shallow: 31 min/in West - Deep: 5 min/in As can be noted from the deep perc test data,the perc rates fall off over time. At two hours into the test, the deep borings were refilled. There was a dramatic increase in the water drop after this addition of water. This can be attributed to the increase in head pressure forcing the water laterally through the referenced sand strata, as well as the remaining wetted sidewall surface area. CONCLUSIONS AND RECOMMENDATIONS It is our opinion the final perc rates after the four-hour test period are indicative of water percolation after achieving equilibrium. It is evident from the perc tests,that the 100% replacement area appears to have a greater percolative capacity than the primary drainfield. Although we do not know the estimated average daily wastewater flows, we are recommending that ultra-low flow toilet fixtures and spring-loaded sink fixtures be installed to minimize wastewater flow. 2 ©. Q.1i,