Mercer Island Lake Line Permitting

  • Surveying nearshore habitat and documenting existing conditions.
  • Shoreline improvements create challenges for lake line replacement.
  • Existing lake line crossing sockeye spawning habitat.

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 to shoreline residents during construction, and the timing constraints for in-water work in Lake Washington.


Confluence’s Chris Cziesla led the effort to complete a shoreline fish and wildlife habitat inventory and prepare all environmental permit documents, including a full SEPA environmental impact statement, Shoreline Habitat Inventory, ESA biological assessment, Clean Water Act Section 404(b)(1) Analysis, and JARPA submittal (for Corps Section 404 and 10, Hydraulic Project Approval, 401 Water Quality Certification, Coastal Zone Management consistency, Shoreline permit). Mitigation and shoreline restoration, such as riparian improvements, bulkhead removal, invasive species removal, and substrate augmentation were also included as part of the project. Confluence’s technically sound analyses, timely response, and excellent working relationships with the client, regulators, and contractors paved the way for a dynamic team able to respond to changing project concerns and constraints. Strong relationships with the following regulatory agencies were critical in allowing the city and their construction contractor flexibility in their construction approach:

  • U.S. Army Corps of Engineers
  • Washington State Department of Ecology
  • Washington State Department of Natural Resources
  • Washington Department of Fish and Wildlife
  • National Marine Fisheries Service
  • U.S. Fish and Wildlife Service


This project’s complicated construction schedule was met due to Confluence’s diligent communications, regulatory compliance strategy, clear and accurate analyses, thorough documentation, and responsive delivery of permits and modifications.

Project Location
Lake Washington Shoreline
Mercer Island, Washington

City of Mercer Island

Project Timeline
2003 – Fall 2010