11-03-1980 Planning Packet - Laserfiche WebLink

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• > L‘ j ■y V-. TO: FROM: Jeanne Mabusth, Zoning Administrator I" Michael Gaffron, On-Site Systems Manager DATE:October 30, 1980 SUBJECT:#582 H. R. Johnston, 925 Willow Drive South - SUBDIVISION On-Site Systems Review On October 28, 1980, I reviewed the five proposed new building sites for the above referenced subdivision as per the attached survey. Each lot {save Lot 4, Block 1 with existing house) appears to have 2.0 acres of dry buildable land. However, due to proximity to adjacent wetlands and the accompanying water table a portion of e^'^h lot is unsuitable for use as drainfield. All lots had areas touted which meet the requirements for standard trench drainfield systems. These designated tested drainfield areas on certain lots are the only available acceptable sites for drainfield. In every case, assuming a long term water table exists at approximately the 930* elevation, no drainfield trenches (2* depth standard) should be allowed below elevation 935* in order to ensure a 3* separation between trench bottoms and water table. In addition, where individual lot testing indicates a water table depth, the above 3* separation must be adhered to. Following is a detailed review of each lot. Lot 1, Block 1 Testing indicates soil and water table conditions are suitable for a standard trench drainfield system. This lot has some alternate house location possibilities. However, the tested site and in fact the entire lot should be left undisturbed until a final house location is determined. Lot 2, Block 1 As in Lot 1, testing found sandy soils suitable for a standard drainfield system. Various house locations may be possible. An excavation crossing the lot has not severely damaged drainfield areas, but no further excavation or disturbance should be allowed until final house location is determined. Lot 3, Block 1 This is probably the most critical lot of the subdivision in that a limited area is available for use as drainfield. The tested area is at the highest point of the lot due to extreme slopes. An excavation near the northwest corner of the lot may have affected the extent of the area available for drainfield. By creating an outlet for sidehill seepage from trenches above the excavation. However, due to the extremely fast percolation rates and sandy soils and the existence of untested but probably suitable area for drainfield to the east on the lot, the effect of this excavation is only slight.