06-10-1991 Council Packet - Laserfiche WebLink

Home Browse Search

iV' V )■' Zoning File #1642 May 15, 1991 Page 3 The westerly site (prirr.ary) contains a I5» slope and is 8uitable for a trench drainfield. The Orono Septic Code requires that for slopes of 12“18%f soil conditions must be carefully evaluated to ensure that no horizontal layering of soils will lead to side hill seepage. The applicant's site evaluator has performed a number of borings to depths of 6-8', and is recommending that while there is little likelihood of side hill seepage due to layering, there is some groundwater uphi 1 1 from the system that should be intercepted by a curtain drain. The drainfield proposal meets all required setbacks from lot lines. The other unique feature of this system is the need to pump over a distance of approximately 220', requiring a slightly larger than norma 1 pump. The alternate site, requiring a mound, is near the front of the lot and uphill from the house. With a slope of 10% and Average perc rate 15 minutes per inch or faster, this site meets criteria Orono has historically used for mound systems. The design submitted meets all setback and design criteria per the State of Minnesota Sewage Treatment Systems Standards, Chapter 7080. Orono's Code has always been somewhat ambiguous regarding the maximum allowable slope for mounds, and staff has in the past tried to limit mounds to slopes of no more than 6-8% wherever possible. State Code would allow mounds on slopes of 12% or even steeper if the area of the mound is increased. Staff has taken the position that where slopes exceed 6%, mound systems have a potential for affecting or being affected by structures or barriers immediately downslope. We therefore attempt to increase the separation between the downhill toe of the mound and any structures or driveways, to more than the minimum 20’ required setback. This extra setback allows more undisturbed area at the toe of the mound for expansion of the absorption area and reducing the potential for compaction or barriers to affect the mound. For the above reasons, it is staff's recommendation that a 10' side setback variance for the Swanson residence be allowed, leaving a 35' alternate drainfield setback from the house rather than 25' if no variance is granted. Setback Variance Effect on Neighborhood The other issue to discuss regarding uhe house setback variance, is the orientation of the house, the functional front and rear yards of the house, and whether the 10' variance will have a significant effect on neighboring properties. In a small lot situation, i.e. quarter acre lots, often the orientation of houses on corner lots leaves one resident's busy backyard