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Construction of Longmont’s $3 million County Line Road improvements project is to begin Monday, city officials announced.

The work is to continue between Ninth and 17th avenues the rest of this summer and fall, with an anticipated shutdown over the winter months. Completion is expected in April, city staff said in a news release.

The project will widen County Line Road to accommodate auxiliary turn lanes and on-street bike lanes, as well as to construct various intersection improvements. The project’s cost has been estimated at about $3 million, primarily being paid from Longmont’s 3/4-cent street fund sales and use tax.

DeFalco Construction is Longmont’s contractor for the planned improvements, which will include limited widening of County Line Road, installation of left turn lanes for the length of the project, trail connections at Jim Hamm Nature Area and sidewalk improvements along the west side of County Line Road from the Spring Gulch No. 2 Greenway — which also is under construction — to 17th Avenue.

Longmont officials said in their news release the city intends to use a phased construction approach to allow one lane of traffic to be maintained in each direction during the project. At this time, no full road closures are anticipated.

To the extent possible, the County Line Road work will be coordinated with Phase 2 of the Spring Gulch No. 2 Drainage and Trail Improvement project, using existing traffic patterns. A bicycle detour route already in place for the Spring Gulch No. 2 project will be maintained for the County Line Road project.

Longmont is encouraging the public  to use alternate routes to avoid construction delays and lane closures. Current project information and traffic impacts can be found on the project website,

People with questions or concerns about the project can call the project hotline at 720-491-1167 or email

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