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%000 ✓ Woodbridge Community Church Page 2 For approximate location of the test hole see the attached Parcel Map. The test hole was logged by an engineer and a description of the soils encountered is presented on the attached Log of Test Hole. The first 7 feet consisted of a silty fine to medium sand. This was underlain by a I foot stratum of slightly cemented clayey fine sandy silt. The cemented soil was underlain by various strata of silty sands and silts. For a more detailed description of the soils encountered see the log of test hole. A shallow percolation test was performed next to the profile hole. A 6-inch diameter by 36-inch deep test hole was excavated. Two inches of gravel was placed in the bottom of the hole. A 2-inch diameter perforated pipe was then placed in the hole and backfilled with gravel. The last half hour of the test readings was witnessed by a county health official and the test data obtained is attached. The percolation rates have been adjusted to account for the gravel and pipe backfill. Calculations for adjustments are on the test data sheets. A summary of the test results is presented next: Diameter of Depth of Test No. Hole in. Hole ft. Percolation Rate (min/in) PT-I 6.0 3.0 4.1 NITRATE LOADING STUDY The nitrate loading study was performed by using a mass balance equation to obtain a simplified prediction of groundwater nitrate buildup from the proposed installation of a septic system. Assumptions that were made and calculations arc attached. Due to approximately one- half of the future developed lot being covered with pavement and the other with landscaped vegetation, it was assumed that ground water recharge was equal to one-quarter of the yearly irrigation. It was also assumed that the yearly deep percolation of rainfall is 50 percent of the average yearly rainfall due to the above conditions and the presence of some subsurface cemented soils. A ground water sample from a well located in the adjacent mobile home park was obtained and tested for nitrate in order to determine a background level. Test results indicated a non-detected nitrate level (see attached laboratory results). Conservatively the minimum detection limit of 0.4 mg/1 was used for our analysis. Using a background level of 0.4 mg/1 for ground water nitrate and the proposed 6.5 acre lot density, a resultant average ground water nitrate level of 5.5 mg/1 was obtained. This level is well within acceptable limits. These calculations conservatively assume that all effluent percolates to the estimated ground water depth of approximately 40 feet,which based on the soil profile encountered in the test hole, is likely not the case. SDE RSO D '^ Z W O ` 9SSOC� P