Mansfield Hollow Hydro Electric

Penstock, Mansfield Hollow, CT

Project Details

  • Customer:Sealand Environmental
  • Category: foundation
  • Job Type:Rock Dowels and Anchors
  • Location: Penstock, Mansfield Hollow, CT
  • Schedule: On time

Scope of Work

To remove rock for installation of pipe and structures to support a new water-driven turbine.


The rock removal needed to be completed for 500 feet adjacent to an existing river, 300 feet for a USACOE dam, and 6 feet from a smaller dam built in the 1800's. The protection of the smaller dam was critical to maintain the river height for the intake feeding the turbine. The nature of the geology made protecting the dam difficult, as it was hard granite with dirt seams that ran horizontally through the rock.


To protect the rock from shifting and breaking the dam, MD&B used a combination of line drilling, rock perforation and rock dowels. Twenty rock dowels were drilled, installed and grouted at the direction of the licensed geotechnical representing the project. The combination of drilling and pinning allowed for the remainder of rock removal to be completed without causing any damage to the dam. This kept the project on schedule and under budget, since there was no need to remediate the dam. Once the rock was excavated, we put in 6 rock anchors to hold down the concrete penstock.

Customer Comment

The crew who performed the drilling and blasting work at the Mansfield Hollow project exceeded all of our expectations. Their hard work, attention to detail and ability to adjust to changing conditions kept our project on schedule and completed the rock removal portion without incident. The professionalism and safety-first mindset demonstrated by the crew made them a pleasure to work with. Thanks again for the hard work and we will be calling MD&B for all of our drilling and blasting needs."

Steve Gordon