Reservoir 3 replacement

Reservoir 3 is a key terminal reservoir constructed in 1923 and has exceeded its expected life. The 2020 Comprehensive Water Plan called for a structural assessment of Reservoir 3 to determine its resiliency to seismic events and current structural codes. The study found that the structure is susceptible to structural failure of the reservoir during a significant seismic event, and structural improvements would not address the overall seismic deficiency of the reservoir. Based on this structural analysis and inspection, the criticality of the reservoir, and the age of the reservoir (100 years), the City decided to replace the reservoir with new reservoir(s) designed to current standards, located at the current reservoir site or in its vicinity.

  1. Project description
  2. Project area
  3. Timeline

Reservoir No. 3 was originally constructed nearly 100 years ago as a below-grade square concrete open reservoir with a capacity of 20 million gallons (MG). A cover was constructed over the reservoir approximately 30 years ago. Taking the existing reservoir offline for an extended period of time for construction is not feasible. In addition, there is a significant risk that the existing reservoir’s embankments could not survive a large seismic event, causing a structural failure of the reservoir. 

The City decided to replace Reservoir No. 3 as quickly as possible because of the reservoir cover’s rapidly deteriorating structural condition, age and structural deficiency in a large seismic event. The objective of this project is to design and prepare plans, specifications and estimate (PS&E) for the construction of a minimum of two ground storage reservoirs (GSR) totaling a minimum of 20 MG storage to meet current seismic code requirements.

The project will be implemented in two separate design phases and performed under separate construction contracts with approximately half the required reservoir storage (10 MG) completed in Phase 1 while the existing 20 MG reservoir remains in service. Phase 2 will be constructed once the Phase 1 reservoir(s) has(ve) been placed in service and will include the demolition of the existing 20 MG reservoir and construction of the remaining 10 MG reservoir capacity. The final storage capacities of the replacement reservoirs are estimates only and may be adjusted based on the results of the system analysis that will be performed as part of this project.

The replacement reservoirs will be constructed within the City-owned site of the existing reservoir at 6107 Berkshire Dr, Everett, WA