The Port purchased the Biringer Farm property in the early 90's to use as wetland mitigation for Port projects. Biringer Farm is located on North Spencer Island and is currently in agricultural production. It is bounded to the west by Interstate 5, to the north and east by Steamboat Slough, and to the south by Union Slough. The site was identified in the Snohomish Estuary Wetland Integration Plan (SEWIP) and in the Draft WRIA 7 Salmon Conservation Plan as an area of high potential value for estuarine salmon habitat restoration. The Biringer Farm Mitigation Bank project, now called Blue Heron Slough,  would breach the existing dikes in one or more places and return the area into an intertidal marsh environment. Approximately 300 acres of freshwater wetlands and brackish marsh habitat would be created. The mitigation bank would provide mitigation for Port projects elsewhere, as well as, provide mitigation credits to third parties. Under the policies of SEWIP and the SEWIP Salmon Overlay, use of this site as a mitigation bank would result in a net increase in salmon habitat area and quality in the lower Snohomish Estuary.

The Port has negotiated a contract with Wildlands, and expects to convert the property back to its pre-developed state by 2009.