Jefferson and Hood Street Surface Water Interceptor

The City of Tacoma’s Jefferson and Hood Street Surface Water Interceptor is a great example of the challenging infrastructure design projects KJ has undertaken for one of the firm’s oldest clients in the Pacific Northwest where KJ has performed many projects over a 50-year period. KJ’s role is as the design engineer with James W. Fowler as the design-build contractor. This project is being completed under a progressive design build delivery method.

The existing surface water system in Tacoma’s downtown core does not have sufficient capacity to convey the runoff generated from significant rain events. The Jefferson and Hood Street Surface Water Interceptor project will reduce flooding on downtown Tacoma streets during high rain periods by intercepting stormwater before it reaches the area that floods and piping it to an outfall through a large diameter interceptor. The project is one of the key capital investments the City is making to address an insufficient capacity in the downtown core surface water system.

The project will result in routing of upstream runoff through a new interceptor and marine outfall. Construction of a new outfall to the Thea Foss Waterway is also part of the scope of the project.

The work includes review and validation of reference documents, geotechnical evaluation, hydrogeological evaluation of groundwater conditions, surveying and mapping, hydrologic and hydraulic modeling, alternatives analysis, cost estimating, scheduling, permitting (including local, state, and federal), traffic control planning, stakeholder outreach, basis of design report, design drawings, specification preparation, all resulting in a design-build delivery with KJ in the role as the designer.

Planned project improvements specifically include:

• Up to about 3,200 feet of new 48-inch and 60-inch surface water conveyance pipe (diameter to be verified by the selected Design-Builder via hydraulic modeling). Utility and transportation corridor crossings using trenchless methods will be required in two locations.
• Trenchless crossing of Sound Transit’s Link Light Rail in downtown Tacoma
• Trenchless crossing of BNSF mainline tracks located between the downtown core and the Thea Foss Waterway
• A new marine outfall