06-09-1980 Planning Packet - Laserfiche WebLink

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TO; FROM; DATE; ir Jeanne Mabusth, Zoning Administrator Michael P. Gaffron, On-Site Systems Manager May 19, 1980 556 SUBJECT; Septic System - Subdivision #556, Richard Hawkinson 4625 West Branch Road INTRODUCTION This is a subdivision to create one new 4-5 acre buildable lot from an existing lot. Preliminary soil testing indicates heavy, seasonally saturated clay soils over most of the new lot. A mound-type drainfield would be required by our ordinances due to the high seasonal water table. Briefly, the owner wishes to install a shallow-trench drainfield which would be less costly than a mound due to lack of a pressure distribution system. The shallow trench system would not keep the 3-foot required vertical separation distance between the highest known zone of saturation and the bottom of the treatment system. Dr. Roger Machmeier and James L. Anderson of the University of Minnesota Extension Service, the property owner and I have discussed the possibility of using this site for an experimental shallow trench system. The University is willing to monitor the system and has made recommendations for system design and location on the site. However, they are making no assurance that the system will work correctly. This presents the City with an opportunity to be involved in some much- needed research as to the separation distances required between a drainfield and the seasonal zone of saturation in heavy clay soils, where the permanent water table is generally very deep. My main concern from the City's standpoint is to ensure that an adequate alternative method of sewage treatment can be provided should the experimental system fail. BACKGROUND In Orono, heavy clay soils are abundant, as you are aware. Soil scientists are fairly certain that sewage is adequately treated by filtration through dry clay soils, and that the most vexing problem is to move the effluent through the soil to assure filtration. Commonly, during periods that the soil is saturated, no additional water (or septic tank effluent) can be absorbed by the soil, hence effluent backs up into the house or seeps to the surface. On hilly ground this period of saturation often occurs only during the spring thaw or after heavy extended rains. On level ground the saturation may have a more prolonged effect (i.e. Medina Morningside's Cordova soils).