Midway Sewer District Submarine Outfall

Vanir’s constructability review, bid marketing campaign, and onsite construction management and inspection services led to the successful delivery of this complicated project. The marine outfall project included:

  • Installation of 2,100 lineal feet of owner-furnished 48-inch concrete cylinder pipe
  • 250 lineal feet of bored and jacked steel casing
  • Sheet pile shoring
  • Eelgrass harvesting, protection and replanting
  • Cathodic protection of the outfall pipeline
  • Beach and park protection and restoration

Overcoming Challenges

Marine projects (such as this) present unusual challenges due to the combination of constraints from permitting agencies, local jurisdictions and natural conditions. To help manage these difficulties, Vanir created a comprehensive table that identified all constraints and requirements in an abbreviated format that grouped constraints into specific areas of work. This was distributed to and discussed with the project team prior to starting construction.

In-water work had to be scheduled within the “fish window” timeframe established by the Hydraulic Project Approval (HPA) Permit and issued by the Washington State Department of Fish and Wildlife. Beach work had to be scheduled around tides and the beach had to be protected from damage during construction. Eelgrass had to be harvested prior to sheet pile installation in the eelgrass zone, maintained during construction, and re-planted after construction.

The upland and intertidal work took place in the summer of 2007 on a popular local beach park near a marina. The project team had to find the proper balance of safety and access to meet the needs of the public. Community relations was an important part of our onsite inspector’s job. The project was substantially complete on September 30, 2007 with the tie-in of the new outfall pipe to the wastewater treatment plant.


Des Moines, WA


Midway Sewer District

Design Team



General Construction Company

Construction Cost

$4.2 million