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Table 4.1: East Clearwell Performance and General Design Criteria <br /> CRITERION REQUIREMENT <br /> General <br /> Operability, • Provide for easy,safe and efficient operations and maintenance and access by <br /> Maintenance, personnel. <br /> and Repair • Structures,equipment,piping,and other facilities and systems shall provide for future <br /> maintenance and repair and inspection(to the extent practical)without requiring taking <br /> the East Clearwell off-line. <br /> Service Life and • All components shall be Utility Grade. <br /> Durability • Roof structure shall be designed consistent with a 50-year service life based on City and <br /> industry standard practices. <br /> • The roof fastener system shall be leak-proof and not require fastener maintenance or <br /> tightening of fasteners over time. <br /> Functionality • Provide a new roof system. <br /> • Roof systems,their connection to existing structure,and access hatches shall be water <br /> tight and shall be designed to prevent birds,animals, insects,excessive dust,and other <br /> potential vector and contaminant intrusion into the clearwell. <br /> • The roof slope shall allow for water drainage so that no water ponding occurs on any <br /> surface of the roof accounting for individual member structural deflection and historical <br /> precipitation intensity for the area. <br /> • The new roof structure support system shall not result in an overall clearwell storage <br /> volume reduction of more than [0%]or required change in operating water surface level. <br /> [NOTE TO PROPOSERS.%TO RE COMPI ETED RASED ON SEI ECTED PROPOSAL CITY <br /> STRONGLY PREFERS MINIMAL OR NO REDUCTION] <br /> • The roof shall be walkable. <br /> • Provide a roof access safety system,with safety connection points for personnel while <br /> on the roof and while accessing the roof. <br /> Architectural • The roof and support system shall completely integrate with existing infrastructure. <br /> Proposed architectural treatments,colors and textures of exterior materials shall be <br /> consistent with existing WFP facilities. Roof color shall match existing WFP blue as <br /> closely as reasonably possible,with color samples submitted for City approval. <br /> Ventilation • Vents shall be aluminum hoods that are tamper proof and protected from vandalism. <br /> • Design vents with hoods to minimize the potential for water intrusion. Design to prevent <br /> birds,animals, insects,excessive dust,and other potential vector and contaminant <br /> intrusion. <br /> • Design vents in accordance with AWWA D100-11. <br /> • Design vents with a maximum air velocity through each vent of 500 feet per minute. <br /> Vents shall be screened.Vents shall be sized to allow air into the clearwell at a rate <br /> greater than or equal to the assumed withdrawal rate under emergency(worst-case) <br /> conditions(full clearwell emptying through the largest pipe exiting the clearwell and <br /> discharging to atmosphere),whichever is greater. <br /> • Vents shall be easily accessible for inspection and cleaning by City staff. <br /> • Vents and screens shall be easily maintainable and replaceable by City staff. <br /> Roof Drainage • New roof downspouts shall be provided and shall discharge to new splash blocks. <br /> • Maintain existing drainage paths and elevations with positive drainage away from <br /> clearwell. <br /> • Drainage pipes and gutters shall not enter or pass through the clearwell interior. <br /> • Maintain slope to allow for walking along roof while also steep enough to encourage <br /> sloughing of snow accumulation. <br /> City of Everett January 29,2020 <br /> Water Filtration Plant East Clearwell Roof Replacement DB Project Supplementary Conditions Page 6 <br />