Bank Stabilization

Route 35 (Grafton Road) south of Chester village has a long stretch of deteriorated roadway, characterized by uneven and broken pavement and unstable river banks immediately adjacent to the South Branch of the Williams River.  The conditions have worsened over time but the town has been unable to secure funding for needed improvements.

In 2016, M&W Soils completed a geotechnical evaluation of the worst section of roadway and reported the roadway failures were the result of inadequate drainage and subsurface water flow that exited on the steep river banks.  Dufresne Group designed a solution to collect the surface water as well as intercept groundwater flow with an underdrain, and discharge the controlled water through culverts to the stream.  The roadbed was rebuilt and bank stabilization was accomplished with heavy rip rap.

Site challenges included:

1. Steep banks on both sides of the roadway.

2. A winding roadway that added to traffic control constraints.

3. The requirement to minimize inconveniences to the traveling public, as the project site is on the primary route between Grafton and Chester.

4. Silty soils that became very unstable when wet.

Despite these challenges, the improvements were constructed on time and on budget.