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CITY OF EVERETT SPECIAL PROVISIONS <br /> <br />Beverly Lake Water Quality Retrofit Division 7 – STORM, SEWER, WATER August 2023 <br />WO No. - UPUP3745 SP – 191 <br />Structure 1 Basic & Phosphorus <br />Structure 2 Enhanced <br />Structure 3 Enhanced <br /> <br />Water quality treatment structures shall be sized in accordance with the GULD <br />approved design requirements for the minimum water quality flow rates shown in <br />the Drawings and specified herein. Exterior dimensions shall fit within the <br />designed footprint of the facility. <br /> <br />Hydraulics: <br />The water quality treatment structure shall convey the flow from the peak storm <br />event as discharged from the upstream structures and in accordance with <br />required hydraulic conditions as defined by the Engineer. <br /> <br />7-06.2 Materials <br /> <br />Flow Splitters <br />Flow splitters shall be constructed of materials indicated in the Plans and the <br />applicable City of Everett Standard Drawings. <br /> <br />The structure housing the bypass components shall be a precast concrete <br />structure complying with the requirements for a Type 2 Catch Basin in <br />accordance with Section 9-05.50 of the Standard Specifications. <br /> <br />Internal components shall conform to the following: <br /> <br />1. Risers and internal piping shall be shop fabricated of aluminum pipe and sheet <br />metal complying with the requirements of City of Everett Standard Drawing <br />416. Galvanized Steel Pipe will not be accepted. <br />2. Lift Gate Assemblies shall be manufactured of aluminum and shall be in <br />general conformance with City of Everett Standard Drawing 416 <br />3. Lift handle rods shall be aluminum or stainless steel. Lifting chains will not be <br />considered an acceptable substitute. <br />4. Orifice/restrictor plates shall be made of aluminum or stainless steel and shall <br />be machined to the dimensions indicated in the Plans. Dimensional tolerance <br />for orifices is not to exceed 1/16th of an inch. Orifices shall fabricate in such a <br />manner as to produce a sharp edge with the plane of the orifice plate. Edges <br />should not be rounded off. <br />5. Riser assemblies shall be delivered to the job site as a single unit or pre- <br />installed in the structure. <br /> <br /> <br />Hydrodynamic Pretreatment Device Housing unit of stormwater treatment <br />device shall be constructed of pre-cast structural concrete. Precast concrete <br />components shall conform to applicable sections of ASTM C478, ASTM C857 <br />and ASTM C858 and the following: <br />1. Concrete shall achieve a minimum 28-day compressive strength of 4,000 <br />pounds per square-inch (psi); <br />2. Unless otherwise noted, the precast concrete sections shall be designed to <br />withstand lateral earth and AASHTO H-20 traffic loads; <br />3. Shipping of components shall not be initiated until a minimum compressive <br />strength of 4,000 psi is attained or five (5) calendar days after fabrication has <br />expired, whichever occurs first.