Ordinance No. 20513 - Laserfiche WebLink

Home Browse Search

In addition to the two major storm drainage systems noted above, there is a minor 12 -inch public storm drain beginning near the terminus of the Hilyard Street railroad crossing, and extending east directly across the Riverfront property to an outfall at the Willamette River. That system conveys drainage from the Hilyard Street turn - around located on the EWEB side of the railroad tracks, and may become obsolete with the proposed Hilyard Street railroad crossing relocation. It is assumed that the two existing major public storm drainage systems will generally remain in place, continuing to provide stormwater conveyance for their respective upstream drainage basins. The existing public system originating in 4th Avenue will likely be displaced by the development within the block enclosed by 4th, 5th Avenue Extension, Ferry Lane, and Mill Street, and may need to be relocated to 4th Avenue. System Capacity In the context of the Riverfront project, the City of Eugene standards concerning stormwater runoff rate control and capacity of receiving systems are set forth in Eugene Code (EC) Section 6.6791 - "Destination ". Under that code section, developers are required to document that stormwater runoff from the proposed development will be discharged to a receiving system with adequate capacity to handle all upstream development. As an alternative, the developer may employ stormwater management measures to ensure the development does not increase runoff rates entering the public systems. Compliance with the City's "Destination" code requirements is not expected to be problematic for the Riverfront development for the following reasons: The proposed drainage concept will disconnect large areas from the piped public drainage system and will redirect those areas directly to the Willamette River through either the proposed 5th Avenue Swale or the proposed Millpond Swale. The proposed development will result in a net reduction of impervious surface, resulting in lower overall runoff rates. The Riverfront property is located within the Willamette Major Basin which, according to the 2002 City of Eugene Stormwater Basin Master Plan (SBMP), is generally designated as not having any major flooding problems. Furthermore, the SBMP has not identified any specific capacity - related concerns with the public systems located within the EWEB property. It should be noted that the SBMP evaluation is based on observed system performance during the February 1996 flood. Drainage Basin Delineation The Riverfront property is located within three separate minor delineated subbasins within Willamette River Major Basin '' On a large scale, the actual drainage basins are similar to the delineated subbasins. However, neither the existing drainage patterns or the proposed build -out drainage concept are in full agreement with the existing subbasin delineations. Since capacity is not expected to be a concern, as described above, the disagreement in basin delineation is not anticipated to be problematic. Existing Public Capital Improvement Projects The Eugene SBMP does not identify any capital improvements within the Riverfront project area to address flood control issues. However, the SBMP does identify one relevant capital improvement project associated with the goal of water quality. Project WR101 - "Millrace Enhancement" has potential to overlap with the proposed Millpond Swale element of the Riverfront project. The objective of the Millrace Enhancement project is to implement water quality treatment recommendations that were prepared for the City in a 1990 Study'. Although the millrace enhancement options presented in the 1990 study do not specifically address the lowest reach of the Millrace within the EWEB property, there is a possibility that some of the Page 2 of 4