Utilities & Site Services

Hewitt Avenue Sewer Line and Roadway Reconstruction—Everett, WA

Tree roots caused severe blockage in the Hewitt Avenue Sewer system, which spread to branch lines along intersecting cross streets. This blockage caused flooding in buildings along the sewer route.

The project scope included analyzing alternatives, developing solutions, and preparing plans and specifications to resolve the failing condition of the existing sanitary sewers. Since Hewitt Avenue is the primary east-west “gateway” to the downtown core of the City of Everett, the sewer replacement technical issues were addressed in parallel with strong community involvement and vision.

Phase one involved preparing a design report to evaluate the subsurface materials for soil conditions and provide computer modeling of existing utilities. A field survey was developed to create a base map of existing conditions and an analysis of sewer replacement alternatives. The report allowed the city to evaluate the alternative methods for sewer replacement and review the community’s vision of the existing streetscape replacement. The design included plans and specifications for the replacement of the failing sewers and streetscape.

A design charrette was hosted by the city to encourage design concepts for the redevelopment of Hewitt Avenue between Rucker Avenue and Broadway. Although some utility replacement issues were evaluated prior the replacement of the sewers, participants were encouraged to provide input on the physical design aspects of the surface of the street—including travel lanes, parking lanes, bus stops, bus shelters, loading zones, driveways, sidewalks, landscaping, street furniture, historical and gateway features, and signage.

Plans and specifications for the downstream sanitary sewer improvements were prepared during phase two. These improvements included approximately 1880 feet of sewer within Hewitt Avenue, Broadway Avenue and Wall Street.

During the third phase of the project, we planned the sanitary sewer replacement along Hewitt Avenue between Rucker and Broadway. Construction began in 2002 and cost $10 million.

Cemetery Creek Trunk Sewer Improvements—Snohomish, WA

Since 1997, Perteet has assisted the City of Snohomish with the development of a major 15-21 inch trunk sewer and lateral sanitary sewer collection system that serve newly annexed areas and locations within the city’s urban growth area.

We developed full build-out sewer flow rates, taking into account substantial sensitive areas and wetlands. Determination of future sewer flow rates was complicated by the potential construction of residential developments that allow clustered units and bonus densities. Alternative routes, facilities and pipe sizes were explored and developed for the sewer system. We also identified costs, connection fees and potential funding sources.

Wetlands crossing required more than 15 different permits and approvals, including the application of a Corps of Engineers nationwide permit, NEPA/SEPA documents, biological assessment, wetlands mapping and investigations, as well as wetland restoration and monitoring plans.

We also provided design and PS&E services to move a previously proposed sewer to fall within the Bickford Avenue ROW, to an alignment that follows a grade and alignment similar to Cemetery Creek. The relocated alignment is approximately 220 feet long.

Lynnwood Convention Center LID Drainage Design—Lynnwood Public Facilities District

Perteet provided storm drainage design, surveying services, site development, traffic analysis, and on-site circulations for the new $30 million Lynnwood Convention Center.

Using low-impact development techniques, Perteet designed the storm water system for the Convention Center that provided a $300,000 cost savings when compared to conventional drainage techniques.

The Lynnwood Fire Department has some of the heaviest fire trucks available. Because they could sink into the ground if a conventional vault was used for storm drainage management, our staff had to find an innovative solution. A preliminary geotechnical report performed at the site determined that permeable soils existed 22 feet below the clay-like “Alderwood Soils.” Perteet engineers suggested that, instead of a reinforced vault, a low-impact development technique be applied and an underground gravel gallery used to allow for stormwater infiltration. The gravel gallery would infiltrate all stormwater off current and future development of the Lynnwood Convention Center. This solution saved the client $280,000, and the project recently received a silver award from ACEC for Original or Innovative Application of New or Existing Techniques.