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UO North Campus June 15, 2018 Conditional Use Permit Stormwater, Sanitary Sewer, and Water Analysis Report may not be capable of serving the entire Riverfront Area. New outfalls to the Millrace and Willamette River may be required. Possible outfall locations are shown on Drawing C01. New outfalls may be subject to the US Army Corps (COE) / Oregon DSL permitting process. Outfalls permitted under the COE/DSL process are expected to be subject to the 2014 National Marine Fisheries Services (NMFS) document NWR-2013-10411, Standard Procedures for Endangered Species (SLOPES) for Stormwater, Transportation or Utilities. These standards involve more rigorous treatment, flow control, and LID requirements for new development contributing to the outfall. Exemptions to the NMFS flow control standards may apply for outfalls discharging directly to the Willamette River. Hilyard Street Outfall (Basin E / Destination Point E): The City has developed a concept plan for a future roundabout at the location of the existing cul-de-sac at the north terminus of Hilyard Street. The roundabout will provide access to the EWEB Riverfront property and possible access to the western edge of the UO Riverfront property. Public storm drain infrastructure may be reconstructed and extended as part of that project and may serve as a destination point for stormwater runoff from UO Riverfront property within this area. The existing outfall and public system is relatively shallow, so future extensions may not be feasible unless the public system is reconstructed at a greater depth. Stormwater Water Quality (EC 9.6792): Stormwater runoff from new or redeveloped impervious surfaces must be treated for water quality. Treatment methods must be selected in the following order: Priority 1: Onsite Infiltration using Vegetated / Low Impact Development (LID) Methods. Priority 2: Onsite Filtration using Vegetated / Low Impact Development (LID) Methods. Priority 3: Onsite Mechanical Treatment with Payment of 50% LID Fee. Priority 4: No Onsite Treatment with Payment of 100% LID Fee (for Offsite Mitigation) Onsite infiltration must be utilized where feasible. Lower priority methods may be utilized if required due to site constraints, poor infiltration rates, shallow groundwater, steep topography, or space constraints. Treatment methods and onsite infiltration feasibility will be evaluated on a project-by- project basis, and will depend on the findings of the geotechnical investigations. Treatment methods will conform to the standards of the SWMM. Notable stormwater treatment exemptions and alternatives are summarized below: Treatment of existing equivalent onsite areas may be utilized in lieu of treatment for new development. City standards do not require stormwater treatment for synthetic turf fields unless the athletic fields incorporate an impervious surface into the field cross section. However, redevelopment projects may voluntarily elect to include stormwater treatment through infiltration or other means. Treatment is not required for new or replaced impervious surfaces less than 1,000 square feet, constructed within a 12-month period. Stormwater treatment is not required for projects that replace existing impervious surface for the purpose of maintenance or repair of the continuance of the current function, provided that less than 50% of the storm drainage system is replaced. |6