Agenda - Council - 06/28/1983 - Laserfiche WebLink

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I I I I I those site or soil conditions where a standard system cannot be installed or is not the most suitable type of sewage treatment system. The contents of this chapter do not approve of locating systems in such marginal sites, but rather offer procedures for upgrading existing systems so located. Subd. 2 FLUCTUATING GI~UNDWATER 1. 'Where natural drainage will not provide four (4) feet of separation between the bottom of the soil treatment area and the highest known' or calculated level of the water' table, agricultural drain tile may be used to intercept or lower the seasonal high water table, except within shore]ands of public waters. There shall be at least ten (10) feet of undJ. sturbed soil between the sidewall of the soil treatment unit and the agricultural drain tile. 2. Within shorelands of public waters, agricultural drain tile may be used to intercept the seasonal high water table, provided the groundwater table has a slope of at least two (2) feet per one hun- dred (100) feet toward the public water, and provided the drain tile are installed upslope of the soil treatment system. There shall be at least twenty (20) feet of undisturbed soil between the sidewall of the soil treatment unit and the agricultural drain tile. 3. In all cases, the greatest practicable vertical separation distance from the water table shall be provided. Subd. 3 SLOI'&Y PEF44EABLE SOILS 1. In no case shall filter material be placed in cbntact with original soil having a percolation rate slower than sixty (60) minutes per inch. 2. In no case shall construction equipment, wheels or tracks be placed in contact with the bottom of the excavation during the con- struction of a soil treatment system in soils having a percolation rate slower than fifteen (15) minutes per inch. 3. The size of soil treatment system shall be based on the required treatment area for a soil having a percolation rate of sixty (60) minutes per inch as specified in Table 4-1. Subd. 4 RAPIDLY PEP~\~ABLE SOILS 1. Filter material for a soil treatment unit using gravity distribution of effluent shall not be placed in contact with original soil having a percolation rate faster than one-ball (1/2) m~nute per inch. 2. For coarse soils having a percolation rate faster than one-bail (]./2) minute per inch, at least six (6) inches of sandy loam textnred soil having a percolation rate between five (5) and fifteen (15) minutes per inch after placement (loamy sand to sandy loam) shall be placed between the filter material and the coarse soil along the excavation bottom and sidewalls.