San Juan Islands Conservation District Re-Connects Tidal Flow and Restores Beach Vegetation at the Port Stanley Lagoon

Location: Port Stanley Lagoon, Swifts Bay, Lopez Island

On July 2, 2006 San Juan Islands Conservation District (SJICD) completed a three-year effort to improve water quality in the Port Stanley Lagoon on Lopez Island. Installation of a new, hydraulically-operated tide gate at the lagoon outlet in June 2006 restored daily tidal flow into the lagoon for the first time since the early 1960s. With the completion of the project, SJICD and its project partner the San Juan County Department of Public Works (DPW) have seen improvement in the lagoon water quality as well as improved wildlife habitat and reduction in flooding during severe winter storms. It replaces a tide gate that was installed in the 1960s, the lagoon gradually filled with sediment and it became so shallow that only a stagnant puddle remained each summer.

At the request of the lagoon owners, the Mattson Family, SJICD received a US Fish and Wildlife Service grant in 2003 to complete an engineering study to evaluate ways to restore some degree of tidal exchange while improving the winter drainage and flooding situation. After completing a hydraulic modeling study and field-testing, SJICD presented several options to local community members. The Mattsons and other neighbors favored a plan to allow partial tidal exchange into the lagoon, but only up to a level that would not impact lawns, drain fields, and other property.

SJICD next received a grant from the Washington Department of Fish and Wildlife to design and implement the plan. The project began with dredging the outlet channel and modifying the beach out-fall pipe. Then installing a new type of tide gate that would open and close at pre-set tidal elevations.

DPW’s Lopez Island road crew installed the new tide gate in June 2006, during which the upland portion of the beach was disturbed and compacted by heavy machinery. We completed the project by restoring the original beach vegetation in April 2007 by planting 700 plants to cover the 2500 square foot site (500 Dune Wild Rye (Leymus mollis) and 200 Beach Pea (Lathyrus maritimus) from 4th Corner Nursery in Bellingham. Plant choice was based on species currently present along undisturbed areas of the beach and from suggestions by beach restoration specialist Jim Johannessen of Coastal Geologic Services Inc. Funding for this project was provided by Ducks Unlimited as well as the San Juan Islands Conservation District and San Juan County Public Works.

The tide gate is managed by San Juan County Public Works Lopez Road Crew and can be viewed inside a grated vault along Port Stanley Road, Lopez Island. For questions about the project contact us at (360) 378-6621.

Press Release by D. N. Kinsey, San Juan Islands Conservation District


© San Juan Islands Conservation District 2016