Chlorine Contact Basin Replacement

Project Summary (Project No. C2316)

This project will replace the existing chlorine contact basin at the Sudden Valley Water Treatment Plant with a new contact basin that will meet current seismic standards to ensure continuous operation during and after a major seismic event.

Project History

Water is provided to customers in the District’s South Shore water service area (made up primarily of the Sudden Valley and Geneva communities) by the Sudden Valley Water Treatment Plant, which filters and disinfects water pumped from Lake Whatcom.  The Chlorine Contact Basin (CCB), a 225,000 gallon steel reservoir, was installed in 1992 and is a critical component of the treatment process, providing sufficient detention time to allow for effective disinfection of the filtered water before it enters the distribution system.

In 2016, the District contracted with BHC Consultants to complete a seismic evaluation of the District’s steel water reservoirs, which included the CCB.  This evaluation determined that the CCB does not meet current seismic design standards and would not survive a major seismic event.

In 2021, in light of the findings by BHC, the District applied for and received a FEMA Hazard Mitigation Grant to design and construct improvements to the CCB to meet seismic standards.  The District evaluated numerous alternatives and determined that the most cost-effective alternative was to replace the CCB with a new CCB meeting seismic standards.

In 2023, the District advertised a request for proposals and selected Gray & Osborne Engineers to provide design and construction administration services for this project.

Schedule

Phase 1: Preliminary Design – Preliminary Design was completed by Gray & Osborne in early 2025 and a rectangular concrete reservoir was selected by the District as the preferred alternative for the new CCB.

Phase 2: Design – Gray & Osborne is 90% complete with preparation of design and bidding documents which will be used for advertisement of a public works contract for construction of the new CCB. Design is anticipated to be completed by mid-2026 and the construction contract will be advertised for bid in early 2027.

Phase 3: Construction – Construction of the new CCB is scheduled to begin in mid-2027 when the Lake Whatcom Watershed land disturbance window opens and construction will be completed over two construction seasons with completion planned for October 2028.

Project Cost

Project Contact

Greg Nicoll, P.E.
District Engineer
360.734.9224
greg.nicoll@lwwsd.org

Project Library