The Washington State Department of Enterprise Services (DES) proposed to remove the 5th Avenue Dam on the Capitol Lake Deschutes Estuary at the Port of Olympia commissioners’ work session yesterday.
An overview of the proposal was a part of the Capitol Lake-Deschutes Estuary Draft Environmental Impact Statement (EIS), which provides long-term management alternatives to the property.
The project area extends from Tumwater Falls to the northern point of the West Bay and includes the 260-acre Capitol Lake.
Originally, the waterbody was an area where freshwater from the Deschutes River would mix with the saltwater coming from the Budd Inlet. In 1949 the state began the construction of a dam at 5th Avenue. The structure eventually changed the brackish water into fresh water, and later became known as Capitol Lake.
In their discussion, the DES staff provided three alternatives that are being evaluated, two of which would remove the 5th Avenue Dam.
1) Estuary Alternative
For the Estuary Alternative, the DES proposes to remove the 5th Avenue dam to make way for a 500 ft wide opening. This would reintroduce tidal flow to the Capitol Lake Basin and return it to its normal brackish state. The DES also noted that the removal of the dam will “significantly improve” the migration for anadromous fishes by providing a scarce estuary habitat.
Anadromous fish are those that hatch in rivers and spend much of their lives in marine waters, such as salmon, trout, steelhead and lamprey, before returning to fresh water to breed.
To maintain water quality, DES proposes maintenance dredging to remove accumulated sediments in the basin.
Some of the planners’ illustrations show several small islands that would be created in the Capitol Lake – Deschutes Estuary. The illustration above shows what the area would look like at high, mean and low tide.
2) Hybrid Alternative
The Hybrid Alternative is similar to the Estuary Alternative. This alternative also includes the removal of the 5th Avenue dam to make way for a 500-ft-wide opening.
What makes the Hybrid Alternative different from the prior model is the construction of a 2,600 ft wall which would serve as a saltwater reflecting pool. The model is considered a hybrid since it maintains a saltwater reflecting pool and the estuary’s natural water condition.
The Hybrid Alternative also provides fair to moderate habitat for salmon.
3) Managed Lake Alternative
Unlike the two other options, the Managed Lake Alternative would maintain the 5th Avenue Dam. If selected, the DES would make improvements to extend the serviceable life of the structure.
Based on their study, the DES claimed that during major tidal floods, the Hybrid and the Estuary Alternatives would have a higher water level against the Managed Lake. The high-water level is attributed to the absence of the dam.
However, if the flood comes from the Deschutes River, the Managed Lake Alternative would have the highest extent of flooding as the dam constrains the water.
All three models involve the construction of a dredging system. It will also include habitat areas, a boardwalk in the middle and South basins, a hand-carried boat launch in Marathon Park, a pedestrian and bike lane along the 5th Avenue bridge, as well as a decontamination center to prevent the transportation of invasive species.
During the presentation, Commissioner Joe Downing shared that he wanted to see a beach and a swimming area. However, Ann Larson, DES Director of Governmental Relations, responded that swimming activities are not in line with the agency mission. Larson added that they see boating as something that is more environmentally sustainable.
The area also holds historical importance as the Deschutes Estuary played an important role for local tribes such as the Squaxin Island Tribe.
For community feedback, the DES is conducting an online open house. A public hearing is set for Tue., July 27, from 6:30 to 8:30 p.m. and DES is encouraging residents to participate in the discussion.
UPDATE and CLARIFICATIONS: July 21, 2021, 3 p.m. Several corrections and clarifications were made to this story based on comments from DES.