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Frequently Asked Questions


Capitol Lake is a 260-acre man-made reservoir in Olympia and Tumwater, Washington. The Department of Enterprise Services manages the lake as part of the Capitol Campus.

The lake was created in 1951 when the state constructed an earthen dam and concrete spillway at 5th Avenue in Olympia. The same year the state built Deschutes Parkway, a nearly two-mile long road that parallels the western shore of the lake.

The original idea for creating a lake came from the 1911 master plan for the design of the Legislative (Capitol) Building and the Capitol Campus. The plan called for the “submerging of the mud flats by the creation of an artificial lake through the construction of a dam, bulkhead or spillway near the Fourth Avenue Bridge.” The goal was to create a reflecting pool for the Capitol.

When the final approval was given for construction of the dam, following World War II, a new reason emerged for creating the lake. It would help revitalize a part of the community along the shores of Budd Inlet that was in a state of urban decay.

In 1997, a committee made up of state, local and tribal government officials was formed to study lake management issues. This group met for many years, delivering a recommendation in 2009 on the future of the basin.

Long-term management planning for Capitol Lake - Deschutes Estuary

Why was long-term management planning resumed in 2016, and who participated?

The Washington State Legislature, through proviso in the capital budget for the 2015–17 biennium, directed the Department of Enterprise Services (DES) to “make tangible progress on reaching broad agreement on a long-term plan” for the Capitol Lake-Deschutes Estuary. Work throughout calendar year 2016 is referred to as Phase 1 and culminated in submission of a report to the Legislature in response to the proviso. Phase 1 laid the groundwork for Phase 2 (project-specific Environmental Impact Statement (EIS)) and Phase 3 (design, permitting, and construction of a long-term management option).

The work occurred in collaboration with the community, governmental entities, and coordinating state agencies, many of which also participated in earlier efforts.

Representatives from the following entities comprised an Executive Work Group, a Technical Committee (to review natural resource issues), and a Funding and Governance Committee (to consider future shared funding and governance).

  • Squaxin Island Tribe
  • City of Olympia
  • City of Tumwater
  • Thurston County
  • Port of Olympia
  • Washington State Department of Natural Resources
  • Washington State Department of Ecology
  • Washington State Department of Fish and Wildlife

What are the goals for long-term management of Capitol Lake - Deschutes Estuary?

As part of the Phase 1 process in 2016, the stakeholders and community identified common goals that should be satisfied by any long-term management option that would be considered for implementation. A long-term management project should identify and implement an environmentally and economically sustainable watershed approach that:

  • Improves water quality
  • Enhances ecological functions
  • Manages sediment accumulation and future deposition
  • Restores community use of the resource

How can I learn more about the Environmental Impact Statement (Phase 2 of long-term management)?

To learn more, please visit


Background and Current Conditions in Capitol Lake - Deschutes Estuary

Is there a problem with Capitol Lake?

Capitol Lake is a popular destination in Olympia because of its beauty and accessible trails. Large numbers of birds, salmon and bats use the lake, offering a unique opportunity for watching wildlife in an urban setting. The hillsides surrounding the area offer magnificent views of the lake, Puget Sound, the Olympic Mountains and Mount Rainier.

But Capitol Lake has some problems.

Every year more than 35,000 cubic yards of sediment comes down the Deschutes River and settles into the lake. That's enough soil to cover a city block to a depth of three feet. Today, the lake is about 21 percent smaller and it holds roughly 60 percent less water than it did in 1951. Capitol Lake is turning into a marsh.

A shallow lake heats quickly in the summer. High water temperatures can stress fish and other aquatic species. Warm water also encourages the growth of aquatic weeds.

Capitol Lake does not meet water quality standards because of high levels of phosphorus, which causes algae blooms. When algae and weeds die in late summer, some of it washes out into Budd Inlet where it decomposes, using up oxygen essential for fish and other aquatic life.

The lake also has high levels of fecal coliform bacteria, which can pose a health risk if ingested. The bacterium is washed into the lake through the stormwater system.

Non-native weeds, such as Eurasian milfoil, are found in the lake and along the shoreline. These weeds crowd out native vegetation, reducing fish and wildlife habitat. Invasive species, like the New Zealand Mudsnail, are also found in Capitol Lake and can dominate lakebed habitat by outcompeting native aquatic snails and insects that other species depend on for food.

Before Capitol Lake was created, this area was an estuary, where freshwater from the Deschutes River mixed with the saltwater of Budd Inlet, part of Puget Sound. At the time the lake was created, the existing estuary had water quality problems and had been greatly modified by urbanization.

What is an estuary?

It is an area where freshwater from a river mixes with the saltwater of the ocean. An estuary is influenced by tides but protected from large waves. Generally, estuaries are among the most productive habitats on earth, according to the Environmental Protection Agency. Estuaries also provide flood control and filter out pollutants. More information about estuaries can be found on the Environmental Protection Agency's website.

Can an estuary be restored by keeping the Capitol Lake Dam open?

No. Deschutes Parkway and other infrastructure around the lake were not built to withstand tidal action. It isn't possible to move the large volume of water that is part of a high tide through the narrow opening – 85 feet – at the dam. The original Deschutes estuary opening, before the development of the city, was estimated to be about 2,000 feet wide. Estuary restoration will require construction of a new 5th Avenue Bridge with a 500 foot opening.

Which habitat would be better for fish and wildlife?

An estuary would provide habitat for species that depend on saltwater or brackish water, while a lake provides habitat for freshwater species. Some species use both habitats, preferring the one that provides the most food and protection from predators.

For example, an estuary may benefit salmon, crabs and some types of ducks, but there would probably be fewer bats, swallows and other types of ducks.

Is Capitol Lake polluted?

The lake has water quality problems, including high levels of phosphorus which can cause algae blooms, but it does not appear to be contaminated with industrial pollutants or toxic chemicals. The Thurston County Environmental Health Division monitors the lake for toxic algae blooms from May through October, and measures oxygen levels in the water. The lake's oxygen levels are normal throughout much of the year, but can be higher than normal during the summer, which can harm fish.

The lake is off limits to swimming because of fecal coliform bacteria. The water is murky because of the sediment and algae.

Would an estuary cause odor problems?

A restored Deschutes River estuary would probably smell like any other area adjacent to Puget Sound. The unpleasant odors reportedly coming from this area in the early part of the 20th century, as noted in some historical accounts, may have been due to the discharge of raw sewage. Wastewater is now treated before it goes into Puget Sound.

What about mosquitoes?

Most species of mosquitoes breed in freshwater, not saltwater. A restored Deschutes estuary would likely produce far fewer of these insects than Capitol Lake does. In fact, it is the large number of mosquitoes and other aquatic insects that hatch in the lake that draws thousands of bats, swallows and swifts to feed on them.

Who was on the committee looking at this issue?

The future of Capitol Lake was studied by the Capitol Lake Adaptive Management Plan (CLAMP) Steering Committee. The committee consisted of representatives from the Squaxin Island Tribe; the cities of Olympia and Tumwater; Thurston County; the Port of Olympia; and the departments of Fish and Wildlife, Natural Resources, Ecology and General Administration. The Legislature included a proviso in the 2010 Supplemental Capital Budget that mandated the suspension of the Capitol Lake adaptive management planning process, which then resulted in the CLAMP Steering Committee being brought to a close in May 2010.

The committee considered four alternatives for the future of Capitol Lake:

  • Status quo – Do not dredge the lake and continue current dam operations, weed control and other maintenance procedures.
  • Managed lake – Conduct a large initial dredge to restore the depth of the lake and then periodically dredge the new sediment coming down the river.
  • Estuary – Restore tidal action by dredging sediment; removing the dam and constructing a new 5th Avenue Bridge.
  • Dual basin estuary – Same as the Estuary alternative but with a barrier dividing the north part of the lake into a saltwater reflecting pool adjacent to Heritage Park, and an estuary adjacent to Deschutes Parkway.

In 2009, the members of the Advisory Committee recommended as follows:

  • Comprehensive Estuary Restoration: Thurston County, Squaxin Island Tribe, departments of Ecology, Fish & Wildlife and Natural Resources
  • Managed Lake: City of Tumwater, Port of Olympia
  • Undecided: City of Olympia

Common goals were also identified from the CLAMP process:

  • The need for development of an implementation plan which recognizes the placement of the lake within the larger watershed, the need for long-term solutions which are economically durable and community interests through coordinated and collaborative approaches;
  • Protection of fish passages for the Deschutes River;
  • Development of an equitable cost sharing structure between all relevant stakeholders and beneficiaries;
  • Development of a sediment management strategy for the lake basin; and
  • Identification of potential funding opportunities.

For more information

Linda Kent, DES Communications
(360) 407-7921,

Carrie Martin, DES Facilities Division
(360) 407-9323,