1988-03-29 Septic System Evaluation

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To: Street File - 888 Dakota Avenue oil <,•IIIa From: Michael P. Gaffron, Asst Planning & Zoning Administrator Date: March 29, 1988 Subject: Proposed Repairs to Septic System This afternoon I met with Jerry Johnson, Steve Schirmers and property owner Dave Woodward on the site to discuss the various possibilit-es for repairing Mr. Woodwards's septic system, which is currently failing. Because this is an extremely small lot, it is impossible to re -,lace the existing system within the confines of minimum code requirements. Schirmers has completed a site evaluation of the site, including percolation tests and borings, and has indicated that due to a heavy clay layer there is a high seasonal wat _ table ioL:ated at 18-24" as evidenced by mottling. Based on prior discussions with me and based on the existance of a loam to sandy -loam layer underlying '_he clay loam, 3chirmers Proposed a pressurized bed system which would remove the heavier clay layers and add sand and rock, essentially being a mound system constructed below existing grade level. Septic system installer Jerry Johnson is proposing to constr•..ct a normal, above grade mound sys"em in the same location, basing his pronosal on the idea that there is a iairly deep layer of good loam top soil that would accept effluent, and that although the mound system might be smaller in size than would normally be required (due to the small lot area -vailable), he feels that would be the most workable system. Schirmers' proposal eliminates the concern about a clay pan layec that .ffluent hp,,- to go through, but does not account for potential seasonal water table problems that may exist below the clay layer but are not confirmable, and does not account for any continuity of the sander layers Below the clay pan that might outlet along the hillside to the :south and ..test. Schirmers' proposal also negates any future possibil=ty of a secondary site for a mound to be located over the trenches, since tha soil would be disturbed. On the other hand, a mound system placed on the site and meeting at least a minimum 5' setback from the lot line, 50' setback from neighboring wells, and 10' setback from the house would .iot have the necessary 2,500 s.f. of basal area required to treat 600 gallons per day (for a 4 i.edroom home), using the allowable loading rate of 0.24 gallons per day per s.f. as shown in the P.C.A. Design Manual. Johnson's mound proposal would probably have no more than 2,000 s.f. of basal area which would presumably handle somewhat less than 500 gallons per day. The other factor to take into account is that this is a 4 bedroom home with only 4 occupants currently, although the design late is for 2 people per bedroom or 8 people for this house, and 600 gallons er day, the actual usage may be somewhat less in actuality.