1981-11-27 Septic System Design Report

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#615 Ringer Subdivision Page 6 Lot 6, Block 2 Peres PA61 thru PA66. Borings BA61 thru BA63. Slopes are nearly level. Mottling occurred below 1.5', with actual water encountered below 5.7'. (Note that soil appears saturated below 2.51) Perc rates were acceptable, although 2 of 6 taken at depth very very slow. Both primary and secondary sites should use mound systems. 100 Lot 1, Block 3 Peres PC11 thru PC14. Boring BC11 and BC12. This lot contains an existing house, garage and barn. The existing septic system is unknown and was not located during my routine inspection in July 1981, although no evidence of failure was noted. A future drainfield site has been tested to the south of the house. Average percolation rate is 21 minutes per inch; soil borings indicate soils suited for a shallow trench or mound system, with mottling beginning at a depth of 5'. This is the highest elevated point in the entire subdivision and appears to be the only lot possibly suited for a shallow trench system. An attempt should be made to locate the existing system to ensure it is within the lot boundaries, although there i3 only a -remote possibility that it isn't. Lot 2, Block 3 Peres PC21 thru PC24. Borings BC21 and BC22. This lot contains an existing house and small shed. The existing septic system is unknown and was not located during my inspection last July. No evidence of system failure is noted. While the existing system undoubtedly consists of trenches, soils data provided for a future drainfield site indicates mottling at a 3.5' depth. This indicates that the replacement system, should it ever be necessary, would probably have to be a mound. Percolation rates averaged 56 mpi. It would alto be advisable to locate the existing system to ensure it is within the new lot boundaries. B. Discussion of Mound Systems Since the proposed Ringer subdivision appears to need mound systems throughout, it might be worthwhile to review the conditions which favor use of mound systems over conventional trench systems. As you are aware, a biomat norms at the rock -soil interface in a standard trench system. This biomat acts as a "valve" to slow the downward percolation of septic tank effluent to a rate where the flaw is unsaturated, i.e. air in the soil pores is in contact with -che percolating effluent. Under these essential conditions, adequate sewage treatment will occur. However, in many soils, either a seasonal saturated condition or extremely fine, impermeable soil texture (or both) tends to eliminate the air/effluent contact and also severely limits the soils capacity to absorb large amounts of effluent. To ensure that a standard trench system is not