The Florida Keys Overseas Heritage Trail is a work in progress, as Phil and Debbie Jones of Virginia discovered during a hike earlier this month of the entire island chain, from Key Largo to Key West.

Serene paths along the ocean and bay all-too-frequently ended abruptly, leaving their only passage on a highway clogged with exhaust-spewing traffic.

``It's so much better where there is trail,'' Phil Jones said. ``You don't have to be on your guard from traffic. You can enjoy nature so much better, just space out and really look at everything.''

The project to create a scenic 106-mile, multi-use paved trail for bikers, hikers, runners, fishermen and picture-taking tourists began 10 years ago as part of a statewide system of trails established by the state Legislature.

After a lot of planning and environmental work, trail construction is now in high gear, with new sections being built to connect the existing 58 miles of trail. Several historic bridges -- a century old, built by Henry Flagler as part of his Overseas Railroad -- also are being restored. The trail runs parallel to the Overseas Highway, recently designated as a prestigious All-American Road.

About $21 million, including $1.3 million in federal stimulus money, is being spent on portions of the project scheduled for completion by June. Another $20 million in mostly federal funding will pay for most of the remaining trail by 2013.

``There have been huge challenges,'' said Trish Smith, construction projects manager for the Florida Department of Environmental Protection Office of Greenways & Trails. ``Nobody can just come out and build along a highway.''

Smith oversees 32 contracts for the project and has navigated local, state and federal laws regarding the environment, highways, historic designations and the Americans with Disabilities Act. One problem she ran into: the historic railroad tracks used as guardrails do not meet ADA standards for height.

At Bow Channel, 10 men from Pensacola-based Worth Contracting have been working for six months to restore one of the 23 Flagler bridges still standing in the Keys.

REPAIRS

To repair crumbling concrete under the bridge, crew members work from scaffolding hanging above the water. They have to be careful to make sure no concrete or other materials fall into the pristine water.

``The environment is a real big deal down here,'' said Mike Morgan, the superintendent for the project for Worth Contracting. ``It was so hot here in the summer, I had a lot of volunteers to do the diving for hammers and tools that fell in.''

Smith said even a Department of Environmental Protection project is monitored for environmental infractions by other agencies, including the Florida Keys National Marine Sanctuary.

Morgan has used the bridge as his own private fishing pier, getting up at 4:30 a.m. to catch dinner before starting work.

``I've seen schools of tarpon and spotted eagle rays,'' he said. ``It's just beautiful. And we eat good at night.''

On Ramrod Key, a new 4.3-mile section of trail is being paved that will link the island to Big Pine Key. It's not a simple task, with special concrete barriers built into the ground to separate the trail from environmentally sensitive wetlands.

In the next month, construction on other trail sections is scheduled to begin, including a stretch through the city of Marathon where local businesses over the years have used the designated trail space as parking.