Work begins May 8 to enhance public safety and stabilize a section of the hillside above Heritage Park by removing hazardous trees and a smothering carpet of invasive plants.

Once the trees are felled and invasive weeds removed, the area will be replanted with more than 1,500 native plants. Invasive plants, such as ivy, can out-compete native species without providing stabilizing benefits. The new vegetation will better absorb rain water and hold loose soils in place.

Some of the hazardous trees slated for removal are near the north end of the Governor's Residence parking lot and pose a risk of falling on parked vehicles. Other trees, farther down the slope, could fall on to the nearby hillside switchback trail. If any of the trees fall there is a risk of destabilizing the hillside. There have been several small slides in this area in the past.

This $60,000 project is part of a multi-year effort by the state to monitor and manage the stability of the west Capitol Campus hillsides. Two years ago, the department installed sensors at several hillside locations to track hydraulic movement. The Puget Sound area is among the most slide-prone regions in the U.S., according to U.S. Geological Survey, the federal agency that monitors natural hazards. This project won't guarantee there are no future slides, but it will reduce the risk.

Arbor Care Tree Service will cut the trees but leave stumps and roots behind to provide support for replacement plantings. Some trees will be cut about 10 feet above the ground to serve as wildlife snags, critical habitat for many species.

The company will also trim some ailing but salvageable trees. The branches will be chipped and reused on-site as mulch. The tree work is scheduled to be completed by May 19.

Inmates aid habitat restoration

A Department of Natural Resources correctional camp crew, consisting of 10 inmates, will remove the invasive plants, replant the area, spread mulch and install temporary irrigation. A Department of Natural Resources supervisor will oversee the crew. Only those inmates who have exemplary records of behavior while incarcerated and are near their release dates are eligible to work on these crews. The Department of Corrections carefully screens all offenders who apply to work on the crews.

Impacts to campus tenants

The project will be noisy at times, although Enterprise Services will minimize disruptions by scheduling the tree removal work to occur quickly. The tree felling will require a one-day closure of the hillside switchback trail.

The project is scheduled to be complete by the end of June, although irrigation will continue throughout the summer.

Full restoration of natural conditions will require several years, but the results will be improved stability, habitat and aesthetics.

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