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Marshfield Reservoir Gate House Vent Shaft and Penstock Rehabilitation

Warren's epoxy coating system helps Green Mountain Power rehabilitate penstock and vent shaft under budget

Client Type



Power generation


Marshfield, VT

Map of United States

At a Glance

  • Aggressive schedule
  • I&I issues
  • Large diameter pipe
  • Penstock and vent shaft rehabilitation
  • Repeat client
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During inspections in late 2018, Green Mountain Power (GMP) detected significant erosion of their dam. Erosion was believed to be caused by exfiltration while the penstock and gatehouse were under operation. GMP and PC Construction selected Warren Environmental’s epoxy and our master applicator, A&W Coatings, to rehabilitate the penstock in the winter of 2018. 

The A&W team prepared the concrete pipe by power washing it using a pressure level between 4,000-6,000 psi. Once prepped, A&W lined 140 LF of the six-foot diameter pipe with 375 mils of Warren’s 301-14 epoxy coating.

GMP and PC Construction were so impressed with the product and quality of work that they requested the Warren and A&W team to repair the shaft as well.

Warren’s epoxy coating system created a solid lining from above the waterline to beyond the dam. Before lining the shaft, the A&W crew had to mitigate inflow and infiltration. The project required 17 gallons of Warren’s 151 grout to stop the inflow. A&W Coatings applicators sprayed 250 mils of Warren’s 301 epoxy inside the gatehouse shaft, a total of 861 SF. 

The crew relied on confined space training to ensure safe workspace entries and exits at all times. They worked diligently and efficiently to complete the job under budget and within GMP’s timeline.


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