09-11-1989 - Agenda Packet City Council - regular meeting

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Zoning File #1448 August 15, 1989 Page 2 of 5 Two drainfield sites were tested for the existing house ir_ 1978 during the subdivision that created the plat of Willow Run. Additional testing was done in 1978 to verify that a shallow trench system could be placed relatively near the house, and that system was constructed in 1978. An area northwest of the house but south of the existing pond would meet the setback and soil requirements for use as an alternate site. This site would require a mound system. A second alternate site was tested in 1978 to the southwest of the house, although a portion of that site is less than the required 75' setback from the well. Ample area exists further west on Lot 2 such that a number of future drainfield alternatives exist. The existing system appears to be functioning adequately. 3. The pond in proposed Lot 1 was shown on the original plat of Willow Run, and described on the plat as a "pond" within a squared -off survey line. The Conservation and Flowage Easement granted over that pond is described by a 180' diameter circle centered over the pond. This is shown on the staff sketch. The Conservation and Flowage Easement description generally follows the boundaries of the banks of the pond, and does not include the drainageway leading to the next lot to the west. The City Engineer has recommended that a 20' wide drainage easement be shown on the plat drawings over this drainageway. Alternatively, the applicant could re -direct the drainageway to the south lot line of Lot 1, which would allow him to do some filling in the existing drainageway in order to increase the size of the buildable envelope. However, if applicant does not choose to do that as part of the subdivision, any future intent to do so would require a conditional use permit. Staff has requested applicant's surveyor to provide elevations along this drainageway and tc provide hydrologic calculations for this watershed to O etermine the flood boundaries of the pond. Although such information has not been received as of `:,.is writing, staff would expect that the 1034 contour in t: area of the pond would provide the appropriate wetland boundary for determination of the 26' wetland setbacks. City Engineer Glenn Cook also noted that in his opinion, the City should not require the 26' setback from drainageway corridors, only from the boundaries of defined wetlands, since the two serve different functions. (Fonds and wetlands hold the run-off and provide flood storage as well as nutrient retention and significant wildlife habitat.