Our Projects

North Mercer Island Interceptor and Enatai Interceptor Upgrade Project

King County Wastewater Treatment Division is upgrading the King County sewer system from the North Mercer Island Pump Station to Sweyolocken Pump Station in Bellevue. Phase 1 included a multi-stage alternative analyses process. For this project, Confluence provided technical expertise related to wastewater conveyance and infrastructure work in sensitive habitats such as the Mercer Island […]

SR520 Bridge Replacement Program – Permitting/ESA/Mitigation/Cultural Resources

Washington State Department of Transportation (WSDOT) is replacing the State Route (SR) 520 bridge. The work is divided into three projects: West Side/Floating Bridge, East Side Transit and HOV, and Pontoon Construction. Confluence’s leadership in implementing the environmental strategy has enabled WSDOT to meet a very aggressive schedule for environmental project delivery on one of […]

Regulatory Compliance and Permitting for Shellfish Aquaculture

Confluence Environmental Company staff have worked with shellfish growers for many years, individually and collectively. Our scientists have provided regulatory compliance and permitting strategies; developed biological assessments, habitat plans, and permitting documents; researched shellfish ecology; and created study designs for a wide range of shellfish aquaculture projects. Confluence’s work with growers at the individual project […]

Offshore Wind Energy Environmental Services

Offshore wind farms are gaining ground as a source of renewable energy in the United States. Applicants developing such projects must seek approval from the federal Bureau of Ocean Energy Management (BOEM), initially to assess impacts of wind energy leasing and site assessment, then to assess impacts of installation, operation, and decommissioning as farms move […]

Mid-Barataria Sediment Diversion Project

The Mid-Barataria Sediment Diversion project is a component of the Coastal Louisiana restoration strategy that proposes to divert sediment-laden water from the Mississippi River to restore natural deltaic processes and increase land area in the Barataria Basin. Over a 50-year time frame, the project will build and maintain 10,000 to 30,000 acres of upland and […]

Comparative Habitat Use of Estuarine Habitats with and Without Cultch-on-Longline Gear Present

Few studies have addressed how and whether off-bottom oyster culture affects species use and abundance, or whether these differences affect the overall food web ecology of the system. Confluence designed and is leading a grant-funded study to research comparative habitat use of estuarine habitats with and without cultch-on-longline gear present. The project addresses the goal […]

Japanese Gulch Creek Fish Passage Design and Habitat Restoration

Confluence Environmental Company led a team to address fish passage and habitat restoration on Japanese Gulch Creek. The original scope of the project was to improve fish passage in a concrete junction box between upstream and downstream culverts, where streamflow was spread over a concrete apron in a very thin layer that was a severe […]

Mercer Island Lake Line Permitting

Confluence Environmental Company staff provided regulatory compliance support, environmental review, permitting, and strategic input integral for the construction of a 2.5-mile, in-lake sewer line segment along the Lake Washington shoreline. The project was particularly challenging because of the sensitive shoreline resources including Endangered Species Act (ESA)-listed species, the technical challenges of maintaining reliable sewer service […]

Mapes Creek Stream Restoration

Confluence Environmental Company assisted the City of Seattle and SvR Design Company in developing draft and final engineering plans and specifications, as well as conducting construction oversight, to restore a piped section of Mapes Creek to an open-channel condition. The habitat restoration project is part of a larger stormwater drainage improvement project conducted by Seattle […]

Marina Redevelopment Biological Evaluation

Confluence Environmental Company assisted Yachtfish Marine NW, Inc. (Yachtfish Marine), in preparing a Biological Evaluation (BE) for the redevelopment of their marina in Port Orchard, Washington. The redevelopment included replacing the existing 50-foot wood piers with new 100-foot grated decking piers; replacing 12,664 square feet of covered moorage area with 11,814 square feet of covered […]