DOUGLAS COUNTY, Colo. (CBS4)– The Interstate 25 South Gap Project, which will add another lane in each direction to the interstate in a portion of Douglas County, is entering another phase. The project will add additional lanes for an 18-mile stretch.

The northern end of the project, which stretches from south of Castle Rock to Monument, began in September 2018. Crews will begin on the southern end which stretches between Monument and Greenland Road.

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Work on this seven-mile stretch will include three new wildlife crossings, reconstruction of the Greenland Road interchange and new ramps at County Line Road.

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Drivers can expect traffic shifts and extended ramp and frontage road closures.

“We can begin construction on this as weather allows, we have done some pre-construction work to get the pavement ready for the traffic shifts,” said CDOT spokeswoman Tamara Rollison.

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By this summer, construction of the middle section of the project between Greenland Road and Sky View Lane will begin. That will make the $350 million project the longest work zone in Colorado.