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FDue ERCOLATION TESTING digenous surface and subsurface clay soil properties, and the fact that R.B. Constructionwn excavator, it was decided to proceed with the soil profiling and percolation testing by using this CAT 320L excavator. The test pit provides greater evaluation of the soil characteristics than with an augered boring. In addition to strata delineation, a trench pump-in test was done in lieu of the traditional eight-inch diameter augered boring (See Metcalf& Eddy - Wastewater Engineering - Treatment, Disposal. Reuse, p 1050). Since there will be seepage pits installed for effluent management, the trench pump-in test is more indicative of predicting percolation under the anticipated design conditions. Percolation testing was performed in accordance with San Joaquin County Department of Environmental Health regulations. The attached Site Plan denotes the location of the percolation trench pump-in test and the FIELD PERCOLATION TESTING REPORT illustrates the perc test results. The subsurface soil strata indicate that seepage pits will have to be installed at the end of each leachline. Additionally, the information obtained from the Environmental Health Department regarding the number of permits for repairs/additions also indicates the need for the installation of seepage pits. The perc test results reveal a comparatively slow infiltration and percolation rate (for seepage pits), which eventually decreases by approximately half over the four-hour test period. It is to be noted, however,that the test pit depth was terminated at 22 feet and not 25 feet. The Environmental Health Department allows seepage pits to terminate at a depth of 25 feet which will allow for significantly greater percolation of septic effluent. The excavator can reach to a 25 ft depth. The water drop for the last half-hour of the four-hour test period was 1.1 inches, which translates to a perc rate of 27.3 minutes/inch (min/in). This can be considered a comparatively slow perc rate since 30 min/in is considered failure for seepage pit tests. The trench pump-in test calculations demonstrate an acceptance rate (AR) in gals/sq ft/day as follows: ❑ Length of trench= 17 ft ❑ Width of trench=4 ft [should Depth of trench=22 ft Depth of water maintained on the floor of trench=4.5 ft Depth below bottom of trench at periphery of plume=4 ft(est) Total water volume= 1322 gals. Total water absorbed during test - 213 gals L Extent of water plume area: water surface=4 ft x 10 ft :. plume area is estimated to be: 12 ft width x 20 ft length=240 sq ft Acceptance Rate (AR)=total flow absorbed-(area)(time) AR=213 gals_ (240 sq ft)(4 hrs-24 hrs/day)=5.3 gals/sq ft/day oretical Effluent Acceptance (TEA): The bottom 4.5 feet of a 25 ft excavator-dug seepage pit have a TEA of: 1215 sq ft x 5.3 gals/sq friday= 6430 gals/day. 3 Nafky Ag Research