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SECTION 2 Study Area Characteristics • The extent of the open drainage system in the basin on a miles per square mile basis is in the mid -range when compared with other Eugene drainage basins. • At 34 percent, the basin currently has levels of imperviousness that are expected to degrade water quality. Projections at UGB buildout indicate that the impervious surface area will increase to 51 percent, which is the highest for all of the basins. 2.7 Rare, Threatened, and Endangered Plants, Animals, and Communities Stormwater management decisions and practices can affect rare, threatened, and endangered plant and animal species. Local populations can be reduced or even eliminated as a result of decisions to pipe a waterway, install upstream detention, or to allow significant increases in runoff due to new development. The purpose of this chapter is to describe the known rare species and communities located in the River Road Santa Clara basin so that the details of these resources can be consulted prior to any final decisions. Review of the Oregon Natural Heritage Program database reveals no records of rare plant, animal, or community observations. In March 1999, the National Marine Fisheries Service (NMFS) listed spring -run Chinook salmon as a threatened species under the Endangered Species Act (ESA). It includes all naturally spawned populations of Spring Chinook in the Clackamas River and in the Willamette River and its tributaries above Willamette Falls, Oregon. Because runoff from Eugene discharges either directly or indirectly to the Willamette River, the listing will affect the city's stormwater management program and practices. A species that is listed as threatened means it is likely to become endangered within the foreseeable future throughout all or a significant portion of its range. Protective regulations, known as 4(d) rules, have been developed that are deemed necessary and advisable to provide for the conservation of the species. These rules spell -out the take prohibitions that pertain to Spring Chinook and focus on the type of activities that are likely to lead to a "take." The City completed a review of its own processes, procedures, and development standards and identified those that may not be compatible with the 4(d) rules for potential adjustment. Lane County has established a Routine Road Maintenance Manual outlining procedures and standards for road maintenance activities designed to be compatible with the 4(d) rules. 2.8 Soils Soil characteristics are important factors in predicting the amount, rate, and quality of stormwater runoff and for selecting management measures for addressing the effects of runoff. This section describes the key soil parameters relative to stormwater issues and the distribution of those parameters in the River Road Santa Clara basin. All soils data were obtained from the USDA Soil Survey of Lane County. Refer to Tables 2 -6 to 2 -8 and Maps 6 to 10 for a description of the soil mapping units and relevant stormwater related data found in River Road Santa Clara basin. 0:A25695978 Eugene RR-SC Final Basin Plan \Master Plan\FINAL 2- 2010AMaster_ Plan _3 -11 -10 FINAL Word Version AW Sec 2 Corr.doc 2 -25