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� w 7C. PERCOLATION 1 INFILTRATION TESTING AND TEST RESULTS Thhe three perc test borings were drilled on November 5 in the location of the leachfield, which is illustrated on the attached site plan. The test borings were then pre-saturated to 100% of total capacity. Percolation testing commenced the next day under U.S.E.P.A. and San Joaquin County Environmental Health guidelines. Before the start of testing, approximately 24 hours after pre-saturation, it was observed that the pre-saturation water had seeped away in all three test borings. At the start of the percolation tests, the 16 foot boring was filled with clew wa to a 13roximatelX one-third its ca acit , then the 7.2 foot test boring was filled to approximately one-third its ca acity, and then the 42 inch boring was filled with 6 inches of clear water. After every 30 minute interval, the test borings were refilled to the approximate beginning elevation. Each of the three tests were conducted over the standard four-hour time period. As illustrated on the attached FIELD PERCOLATION TEST DATA, the perc rate for the 7.2 + foot and 16 foot test borings showed excellent percolation rates at 4.6 and 7.9 minutes/inch, respectively, at the end of the four-hour test. The 42 inch test boring exhibited a slower.perc rate at 25 minutes/inch. Each of the three tests indicated slowing perc rates over the duration of the four-hour test, indicative of increasing soil saturation. k In addition to the conventional perc tests described above, a double ring infiltrometer test was conducted on the soil at 24 inches below existing grade. The double ring apparatus used for this test is illustrated in a photograph found in Appendix H. The infiltrometer test measures the incremental infiltration velocity, which is the quantity of flow per unit area, over an increment of time (cm3 - em' / sec). Infiltration is the downward entry of liquid into the soil and is measured by the infiltrometer. This test method involves driving two open cylinders, one inside the other, into the soil and then filling the rings with water, in this case to 14 inches. The purpose of the outer ring is to promote one-dimensional, vertical flow beneath the inner ring. The volume of water added to the inner ring to maintain the liquid level constant with the starting value, is the I measure of the volume of water that infiltrates the soil. Water volume infiltrated during the 30 minute intervals for five hours, is converted to an incremental infiltration velocity expressed in centimeters per hour(cm/hr). The infiltrometer test was conducted in the area where Infiltrator® Chambers are to be installed, as illustrated on the attached septic system schematic. The testing site was pre-saturated before r test initiation. Since septic effluent will infiltrate the soil surface at the bottom of the chambers, the double ring test is superior in determining effluent infiltration, in comparison to the standard perc test. The infiltration test was done at 24 inches below existing grade since this will be the { approximate depth of the chambers, which must be placed below the hardpan surface layer. A water head of 14 inches was used because this is the approximate storage head within each ' Infiltrator® chamber. The percolation tests results and double ring infiltration test results are summarized below: l 5 Chesney Consuking r