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7 <br />TO; <br />FROM: <br />DATE: <br />Jeanne Mabusth, Zoning Administrator Qj <br />Michael Gaffron, Septic System Inspector <br />January 8, 1980 <br />SUBJECT: #533 Stephen C. Curren, 110 Orono Orchard Road <br />VARIANCE <br />Mr. Curren proposes to create a two-bedroom home from his existing <br />one-bedroom home. The Hennepin County Soil Survey shows that the <br />soil type on the site is probably Erin Locun, which generally has <br />a slow percolation rate due to a high clay content. Although no <br />actual soil testing has been done on the site, we could probably <br />expect a percolation rate of from 30-60 minutes per inch or slower <br />based on the soil type. In this ranges Orono's Design Manual requires <br />330 s.f. of drainfield per bedroom. The Design Manual also requires <br />a minimum of 800 s.f. of drainfield per dwelling unit for this <br />percolation rate range, and a like amount (800 s.f.) installable in <br />the future. <br />Based on the existing and proposed site restrictions, probably no <br />more than 1250—1300 s.f. of drainfield meeting all code requirements <br />can be installed on the lot. On a per bedroom design basis, a <br />two-bedroom home could be acceptable on the lot, leaving enough <br />area for future drainfield. Based on the code requirement of 1,600 <br />s.f. total possible drainfield (primary and future needs) the lot <br />falls short by about 20%. <br />With these numbers in mind, and assuming no plans for sewer in this <br />area, my feeling is that we could allow the proposed room and garage <br />addition if the soils can be shown through percolation testing to be <br />able to support a standard septic system. Due to the extreme slopes, <br />we probably could not allow a mound system. <br />If soil testing indicates the use of standard or shallow trenches <br />would be allowable in the area available for drainfield use, I would <br />recommend approval of the addition. If soil testing indicates an <br />average percolation rate too slow for a standard system, I recommend <br />the application be denied on the grounds that the lot will not support <br />an acceptable on-site sewage treatment system for the proposed home. <br />If the addition is allowed, the owner should be required to bring the <br />existing septic system up to current standards for a two-bedroom home. <br />isi I