Bellevue’s network of natural trails and open-space areas received a boost Monday with the formal annexation of 146 acres in the Coal Creek Natural Area.

Annexation of the unincorporated acreage, approved by the City Council, brings the total size of the natural area to 446 acres, making it the largest single area in the city’s park system. It also adds nearly five miles to the city’s natural trails system.

The city has over 80 miles of trails.

The Coal Creek Natural Area, which the city acquired from King County in 2004, is part of a nearly contiguous corridor of public lands for wildlife, natural areas preservation and public use. It connects to the 3,000-acre Cougar Mountain Regional Wildland Park, which is the county’s largest park.