Starting Wednesday, Dec. 3, contractors hired by the Department of Enterprise Services will plant more than 3,000 shrubs and trees near the Legislative Building.

Contractors will also finish installing a new, cutting-edge stormwater management system to reduce polluted surface water runoff that washes into Capitol Lake and Puget Sound.

Both improvements are part of the final phase of the Sid Snyder Avenue Underground Utility Project, which replaces and repairs substandard electrical ducts, aged water lines, and other deficient utilities beneath the roadway that serves as a primary entry point to the Capitol Campus.

The $1.9 million project began in August and is scheduled to be finished in mid-December.

The landscape work starts with the planting of 16 Autumn Blaze maple trees along each side of the avenue, which over time will form a leafy gateway to the Capitol. Autumn Blaze is a fast-growing hybrid tree adaptable to a wide range of climate and soil conditions, according to Washington State University Extension. The leaves turn bright orange-red in the fall.

These will be followed by another 14 trees of various species and nearly 3,300 native plants planted along the street edge to serve a dual purpose: frame the view and filter surface water runoff through the new system.

The new landscaping meets Enterprise Services' long-term goal of reducing the amount of turf grass on the campus, which is labor and resource intensive to maintain. It is also consistent with original landscape plans for the Capitol Campus developed more than 80 years ago by the Olmsted Brothers landscape design firm.

Controlling surface water runoff

The new stormwater system consists of seven small bioretention cells that appear as shallow depressions along the north side of Sid Snyder Avenue.

The cells and the plantings in them will filter and clean surface runoff quickly during rain events before the water reaches Capitol Lake and eventually Puget Sound. The cells will be filled in with and surrounded by shrubs. After a few years growth, they will become a subtle feature of the west campus.

When it rains, the surface water that flows across urban yards and parking lots, streets and driveways often picks up and carries toxic chemicals and other pollutants. The contaminated runoff then washes, mostly untreated, into nearby lakes, rivers or coastal waters where it can harm plants, wildlife and habitat areas.

Enterprise Services maintains the state's Capitol Campus, which covers more than 486 acres, and includes four parks and the 260-acre Capitol Lake.

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