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CITY OF EVERETT SPECIAL PROVISIONS The Water Quality Treatment unit (s) shall be MWS Modular Wetland devices manufactured by: Bio Clean, Inc, of type and configuration indicated in the Drawings, or approved equivalent. 7-06.1(2) Performance Requirements Bypass Structure Type-C The device shall be designed to discharge the water quality flow rate to the treatment devices while conveying flows in excess of the water quality flow rate to a bypass conveyance system. Vortex Pretreatment Device Washington State Department of Ecology approval requirements: general use level designation for pretreatment. Treatment: The treatment unit shall be sized to treat the design flow rate designated in the plans. The treatment unit shall be capable of capturing and retaining 100 percent of pollutants greater than or equal to 2.4 millimeters (mm) regardless of the pollutant's specific gravity for flows up to the design flow rate. The treatment unit shall be designed to retain all previously captured pollutants addressed by this subsection under all flow conditions. The treatment unit shall be capable of capturing and retaining total petroleum hydrocarbons and shall be capable of achieving a removal efficiency of 92 and 78 percent when the device is operating at 25 and 50 percent of its rated-treatment capacity. These removal efficiencies shall be based on independent third-party research for influent oil concentrations representative of storm water runoff (20 ± 5 mg/L). The treatment unit shall be greater than 99 percent effective in controlling dry-weather accidental oil spills. The treatment unit shall be capable of treating the design flow specified without prematurely bypassing flows via an internal bypass or the bypass structure (SD05- 08A and SD01-15). The treatment unit shall be designed with a sump chamber for storage of captured sediments and other captured pollutants. Hydraulics: The treatment unit shall convey the flow from the peak storm event of the drainage network, in accordance with required hydraulic upstream conditions as defined by the Engineer. If a substitute treatment unit is proposed, supporting documentation shall be submitted that demonstrates equal or better upstream hydraulic conditions compared to the model specified. This documentation shall include a hydraulic gradeline for the upstream and downstream system and headloss though the treatment unit during the 100-year storm. This documentation shall be signed and sealed by a Professional Engineer registered in the State of Washington. All costs associated with preparing and certifying this documentation shall be born solely by the Contractor. Stormwater Biofiltration System Stormwater Biofiltrations Systems shall meet the Ecology General Use Level Designation (GULD) certification for enhanced treatment, be sized to meet Ecology Enhanced Water Quality Treatment requirements for the minimum Water Quality Flow Rates shown on the Drawings and specified herein. Exterior dimensions shall fit within the designed footprint of the facility. Hydraulics: ;t The treatment unit shall convey the flow from the peak storm event as discharged from the upstream CDS device and in accordance with required hydraulic conditions as defined by the Engineer. 7-06.1(3) Materials Bypass Structure Type-C Jackson Park Area Stormwater Separation September 2020 WO No. -UP3703 Division 7—STORM, SEWER,WATER SP-158