Resolution No. 4814 - Laserfiche WebLink

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For Eugene, the local drainage basins managed include both those within the City limits as well as the unincorporated areas west of Interstate 5, both within and outside the UGB. The total drainage basin management area is about 49,000 acres. There are about 540 miles of storm water drainage pipes, mostly within city limits, that convey storm water to receiving waters such as Amazon Creek and the Willamette River. There are also about 30 miles of open drainage channels maintained by the City and additional private storm water drainage infrastructure that is not maintained by the City. The general characteristics of the Springfield storm water drainage system are outlined in the City of Springfield Stormwater Management Plan. The drainage area managed by the City of Springfield includes about 14,000 acres, with about 213rds of the total area within City limits and 1/3rd outside of City limits within the UGB. Springfield's storm water drainage includes two major drainages, which flow to the McKenzie and Willamette Rivers, and 15 separate drainage subbasins. Springfield's built system includes 170 miles of piped drainage system and 13 miles of open channel watencvays, as well as 4,000 catch basins and two municipally-owned storm water detention ponds. As in Eugene, Springfield's storm water system also includes private storm water infrastructure such as detention ponds that have been included in new development since the 1980s to reduce the volume and pollutant content of storm water entering the public storm water system and/or local rivers and streams. Historically, the focus of local storm water maintenance practices has been limited to drainage and flood control. More recently, the focus has widened to include management of riparian vegetation by allowing it to remain in streams and channels for the beneficial effects of slowing runoff for filtration and sedimentation. Performance of the local storm water drainage systems has generally been very good. The system handled the February 1996 flood event with relatively few problems, even though much of the system was designed for 5-year or 10-year events and the February 1996 event was approximately a 25-year event. Historical experience and hydrologic/hydraulic modeling suggests that the most problematic areas for storm water drainage in Eugene are the Amazon Creek, Willow Creek and Laurel Hill basins in the South Hills. Drainage problems in these areas are exacerbated by relatively thin, impermeable soils. Many areas of Springfield are served by somewhat inadequate storm water drainage systems, as shown by the limited capacities of some systems to accommodate new development and to control flooding. The City's assessment of storm water system capacity needs and corresponding recommendations for future capital improvements is in process with the new Stormwater Facility Master Plan, which is scheduled for completion in 2004. A partial, preliminary list of sites in the Eugene/Springfield Metro Area, outside of the mapped floodplains, that have been subjected to repetitive flooding is given below in Table 6,3 Public Review Draft: August 6, 2004 6-10