IMCO General Construction 5/9/2022

City of Everett,Washington I Water Filter Plant- Phase 2 Capital Upgrades PDB Project Progressive Design-Build Contract I Exhibit B.Owner's Project Criteria improvements to the flow capacity of the flocculation basin outlet channel. Scope descriptions for each of the sub tasks follow. A physical inspection of the flocculation basin mixers during the WFP Facilities Plan project determined that the mixing paddles, motors, and bearings are in poor physical condition and should be replaced. While the plant can meet current water quality standards without using the flocculation basin mixers, the use of this equipment may become more frequent if there is a change in raw water quality (either a long-term degradation of water quality or a short-term adverse water quality event). For these reasons, the City desires a full replacement of the existing flocculation basin mixing system. The replacement mixing system shall consist of readily available, current technology equipment that will meet the capacity needs of Filter Plant today and into the year 2046. The Design-Builder shall determine the best, cost effective technologies and present the options to the City. Structural inspection of the flocculation basin identified signs of structural joint sealant degradation and a need for coating and resealing the interior walls of the basins and flocculated water channels. Approximately 45,500 square feet of basin area will need to be cleaned using a high-pressure wash and coated with an epoxy approved for potable water application. It's anticipated this work will be performed through bypassing sections of the flocculation basin via the existing gates and additional temporary measures. In the current basin configuration, the flocculation basin inlet channel bulkhead gate cannot be installed without a rental crane and therefore is not readily available for immediate short-term use or emergency operation. As such, the City desires the installation of a davit crane at the head of the flocculation basin to enable rapid deployment of the bulkhead gate whenever necessary without relying on an offsite crane service for gate installation. Flow distribution in the flocculation basin outlet channel is impacted by high flow velocities during periods of high WFP flow rates resulting in potential floc shear. Additionally, there are operational deficiencies in the flocculation basin outlet channel that restrict the ability of WFP operators to isolate portions of the outlet channel or isolate the outlet channel from individual flocculation channels. The City intends to improve the flocculation basin outlet channel to meet the following criteria. • Increase capacity of the flocculation basin outlet channel(s) such that the velocity and headloss in the channel(s) are reduced, upstream flow distribution in the flocculation channels is improved, and floc shear is minimized during periods of high WFP flow rates. • Connect the improved outlet channel(s) to the existing flocculated water pipeline. • Improve operational ability to isolate select portions of the outlet channel(s) and to isolate individual flocculation channels from the outlet channel(s). The Page 5 of 16