Roswell this week begins construction of a $4.2 million extension of Sun Valley Drive, intended to relieve traffic congestion on Alpharetta Highway (Ga. 9) by creating an eastern connector to Mansell Road.

The extension of Sun Valley to Warsaw Road will let motorists bypass the Alpharetta-Mansell intersection. The work is expected to take about 12 months, weather permitting.

The Roswell Department of Transportation already has completed Phase I grading and water quality work. The next phase entails actual road construction, with intersection improvements at Alpharetta Highway and a Finchley Drive/Timbercreek Circle (currently a cul-de-sac), and the creation of a roundabout at Sun Valley and Warsaw.

The extension will be a “complete street” with 11-foot travel lanes, 4-foot bicycle lanes, a 5-foot sidewalk on the street’s south side, and an 8-foot multi-use path on the north side. Vertical Earth Inc. is the city’s contractor. Funding will be provided by a Roswell bond referendum approved by voters in November 2012, as well as impact fees and the city’s general fund.