<br />2 <br /> <br />Braewood Hills | KPFF Consulting Engineers <br />STORMWATER ANALYSIS <br />Project Overview and Description <br />Drainage Report <br />This storm drainage report has been prepared to show that the proposed Braewood Hills Third Addition PUD <br />meets or exceeds the stormwater regulations of the City of Eugene and SLOPES V (Standard Local Operating <br />Procedures for Endangered Species, authorized or carried out by the US Army Corps of Engineers in Oregon). <br />This report has been prepared for the JPA, Final PUD review, Site Development Permit review and PEPI Permit <br />review. The report will discuss existing and proposed storm drainage and how the proposed facilities will <br />meet the following requirements: vegetated treatment for water quality, flood control, flow control and <br />source control. <br />Site Constraints <br />The project will be constructed on a site that has a 15 to 20 percent average slope and poorly infiltrating soils. <br />For these reasons, infiltration is not an option. Instead, detention will be used to provide flood control for <br />the site. This will be discussed further in the Proposed Stormwater System section. <br />Project Narrative <br />Existing Conditions <br />The site is surrounded by low-density residential or undeveloped lots. Hawkins Drive provides the western <br />border of the project, Randy Lane runs along a portion of the southern edge and existing single-family <br />residences border the east edge of the site. <br /> <br />The existing wetlands have several sources. Some of them are from Goal 5 season streams that cut through <br />the site, but at least one of the wetland areas was likely caused by a storm system outfall that was installed <br />as part of the housing development to the east. The outfall itself is just outside of the project boundary. See <br />Exhibit 1 in Appendix 1 for existing conditions, including the existing wetland extents. <br /> <br />The site is within the City of Eugene Amazon Basin, per the 2002 Stormwater Master Plan and the receiving <br />water body for this basin is Amazon Creek. Currently, there is no stormwater infrastructure on site. <br /> <br />Amazon Diversion Canal-Amazon Creek is classified as water quality with a TMDL developed for the <br />parameters of Dissolved Oxygen and E. coli and is listed on the Section 303(d) list of impaired water bodies <br />for the parameters of Arsenic, Inorganic, Dissolved Oxygen and Iron (total). There are no nearby active NPDES <br />Permits. The site and receiving water are not in a groundwater management area or EPA-designated sole <br />source aquifer. <br /> <br />Before European Development, the site would have been a wooded hillside. According to the USDA Web Soil <br />Survey (WSS), the site soils consist of a combination of Dixonville silty clay loam, Panther silty clay loam and <br />Philomath cobbly silty clay. All of those soils have a hydrologic soil group rating of D . The resulting runoff <br />curve number for the pre-development condition of this site is 76. This was used to calculate the pre- <br />development runoff rates (see Appendix 2). <br />