Westside Water Main

The majority of Mountlake Terrace’s water system was originally installed in the 1950s and 1970s. This system generally experiences significant water loss due to leakage from these aged pipes and also has areas that do not satisfy current firefighting needs. Several water mains were selected for replacement based on:

The City’s Water Comprehensive Plans
Public Works engineers’ evaluation of risks of failure (their likelihood and magnitude of consequences)
Recent break history
Known failing conditions
Potential for cost savings when coordinated with other projects
Opportunities to address deficiencies in capacity and fire flow demand
Grouping locations within a general region within the city

The Westside Water Main Improvements identified for various locations west of I‑5 and designed by Public Works engineers include:

226^th Place SW from 70^th Avenue W – 73^rd Place W
68^th Place W from 226^th Place SW – Cul-De-Sac
67^th Place W from Cul-De-Sac – 224^th Street SW
224^th Street SW from 65^th Avenue W – 66^th Avenue W
65^th Avenue W from 224^th Street SW – Cul-De-Sac
67^th Avenue W from 222^nd Street SW – Cul-De-Sac
61^st Place W from 212th Street SW – 215^th Street SW
213^th Place SW from 61^st Place W – Cul-De-Sac
64^th Avenue W from 219^th Street SW – 220th Street SW
219^th Street SW from 60^th Avenue W – 64^th Avenue W
60^th Avenue W from 21503 Block – 219^th Street SW
66^th Avenue W from 216th Street SW – 220th Street SW
The intersection of 236^th Street SW and 49th Place W

Across these locations, the project includes construction of approximately:

9,500 linear feet of earthquake-resistant 8- and 12-inch diameter ductile iron water main pipe
The replacement or addition of:
- 69 gate valves assemblies
- 24 fire hydrants
- 3 Blow-off Assemblies
- 2 Combination Air Release/Air Vacuum Valve Assemblies
- 108 water service connections
- Pressure reducing valve assemblies

The project also rehabilitate or upgrades 35 linear feet of Sanitary Sewer Main across the project sites that are impacted by the primary work. The works include minor restoration of concrete traffic curb and gutter, concrete sidewalk, asphalt pavement and landscaping, as well as traffic and erosion control.