Castagna Consulting Group performed Program Management Services for the River Birch Marketplace in Peterborough, NH. One of the major design features of the project is a modern roundabout as the solution for access to the new development on NH Route 101 just west of Peterborough center. It is one of only a handful in the state, and the first to be permitted on a major state highway for access to a commercial development. Completed in November 2008, the roundabout will handle about 15,000 vehicles per day, many of which will be accessing the new marketplace.

The modern roundabout differs significantly from the traditional traffic circle prevalent on older New England highways. The main difference is travel speed–whereas the older designs can be traveled at speeds of 35 mph or more, the modern roundabout is designed to slow traffic to 20 or 25 mph. The slower circulating speed makes it easier for vehicles to enter the stream of traffic and keep it moving, which can help reduce delays and lengthy queues associated with signalized intersections. Because of this, roundabouts also reduce air pollution associated with congestion. These are among the primary reasons that the Peterborough Selectmen and Town Planners rallied in favor of a roundabout versus a traffic light.

The development brought a much needed Shaws Grocery Store back to Peterborough as well as a CVS pharmacy. The site was a former auto dealership and New England Telephone repair station. The telephone building was built over an old local dump site. Remediation of underground oil and gas tanks were required. The entire dump site encompassed 80% of the new Shaws footprint and had to be replaced with structural fill that in many places was over 15 feet deep. The site now has been restored to a useful, productive venue for the community and surrounding region.