Design a septic system with gravity flow subsurface soil adsorption for a three-bedroom house with two baths and a basement that is currently occupied by a family of four. The building site is depicted in topographic map A and in the cross sectional transects A3-C3, A2-C2, A1-C1. Based on an initial site investigation, soil percolation tests were conducted in areas C1 and A3 to assess their suitability as locations for the absorption bed. The pertinent data from these tests is given below. Area Cl Water Level Drop in Inches per 30 Minute Interval Percolation Rate (min/in Hole 1 13.56.57.361.24.221.221.211.2 65 .92.75.71 2.2 1.781.1.78 63 65 3 2.441.46 1.02 7 4 51.85 1.5 .92.87.8 1.76.781.6 1.441.36.28 1.26 1.26 .78 .78.78 Average: Area A3 Water Level Drop in Inches per 30 Minute Interval Percolation Rate (min/in Hole 1 3 5 1.340.940.900.88 0.840.78 0.76 0.75 2 1.45 1.18 0.98 0.92 0.90.88 0.880.86 3 0.980.88 0.840.81 0.820.800.790.77 1.140.960.90.870.850.84 0.82 0.83 1.211.02 0.920.880.85 0.830.82 0.81 4 Average:
Your solution to this exercise should include the following and should be in accord with the State of Virginia "Sewage Handling and Disposal Regulations" (A summary of the appropriate regulations is available within the course notes):.
a) The design of an appropriately sized septic tank. This design should include a fully labeled sketch that notes all appurtenances
b) The design for a complete gravity, subsurface trench drainfield system. Depict your system on the layout sketch for the site and note all setback distances. Discuss the reasons behind your choice of a location for the drainfield,
c) If you were to utilize a bed-based design, how would the surficial area of your drainfield change?