Travelers using County Line Road north of 9th Avenue can expect traffic slowdowns beginning the week of March 9 as part of work on the Spring Gulch #2 Drainage and Trail Improvement project. Intermittent lane closures will take place in both directions as crews remove lane striping and install new lane markers ahead of a temporary road detour of County Line Road.

The temporary road detour, referred to as a shoofly, is anticipated to remain in place for approximately 6 months.

Later in the week, the speeds on County Line Road will be reduced and traffic will be diverted to the shoofly detour to allow for construction to start on the box culvert system underneath County Line Road, explained City of Longmont project manager Ellen Hilbig. Once complete, the box culvert system will allow cyclists and pedestrians to travel under County Line Road, as well as divert the Spring Gulch #2 stormwater flows that otherwise could overtop the road during heavy storms.

In addition to the box culvert installation under County Line Road, other project work includes relocating the Lower Oligarchy Ditch and installing a 10-foot wide concrete greenway trail with a 3-foot wide crusher fine trail from Stephen Day Park southeast to the Union Reservoir Nature Area at Weld County Road 26. The project began in September 2019 and is anticipated to conclude in late 2020.

During the period the shoofly detour is in place, work will also begin on the County Line Road Improvements project. The two projects will coordinate work where possible to minimize impacts to travelers along the road.

Improvements along County Line Road will include limited widening of the road from 17th Avenue to Spring Gulch #2 (near Trail Ridge Middle School) to accommodate on-street bike lanes and left-turn lanes along the entire segment. Intersection improvements will be made where needed, and sidewalks will be added along the west side of County Line Road.

As part of the County Line Road Improvements project, a large cottonwood tree along the west side of County Line Road about 1500 feet north of Spring Gulch #2 will be removed. A recent nesting bird survey confirmed there are no active nesting birds within the tree. Roadway construction is slated to start in April.

One traffic lane will remain open in each direction during much of the shoofly detour period. However, travelers are encouraged to seek alternate north-south routes, such as Pace, Main, Alpine or Lashley Streets.

Cyclists will be detoured around the construction zone, taking Deerwood Drive between 9th and 17th Avenues. Detour signs will mark the route.

(View renderings of the detour routes below. Click to open larger PDFs that may be saved or printed.)

To learn more about the Spring Gulch #2 Greenway, visit bit.ly/spring-gulch-2. To learn more about the County Line Road improvements, visit bit.ly/county-line-road. Those without internet access should call 303-651-8416.