What alternative designs have been considered and why was the proposed design selected?

In addition to the alternative approaches addressed in the previous questions (repair dam and replace fish ladder, remove dam and construct a NLF like at Bradford) other alternatives have been evaluated, which were presented during the March 18 Public Information Meeting. Wetland permitting agencies (Rhode Island Department of Environmental Management and US Army Corps of Engineers) require an evaluation of alternatives that demonstrates that the selected alternative be the least impactful approach that meets the project purpose(s). The permit application materials that will be submitted to these agencies this fall will describe the project team’s evaluation of alternatives, which is briefly summarized below. 

● “Do Nothing” Approach
○ Dam, millrace gates and crumbling mill buildings near the dam would remain a significant public safety hazard
○ Mill building debris would remain in the river
○ No improvements to recreational boating/portage safety
○ No improvement to other recreational opportunities or public access
○ No upstream flood risk reductions
○ Continued risk of downstream flooding and loss of water to residents along river with shallow wells due to breach of dam remains
○ No water quality improvements
○ No ecological wetland/wildlife habitat restoration or enhancements
○ Fish ladder currently performs poorly due its layout - entranceway lies in the turbulent area below the dam’s spillway, and the fishway operates effectively only during a limited range of river flows
○ No ownership, no funding to repair or to maintain dam in future

● Repair/Replace Dam and Replace Fish Ladder
○ No funding is available to repair dams without safety improvement benefits
○ No upstream flood risk reduction for properties and roads
○ No improvement to recreational boating opportunities or risks
○ Same limitations in fish ladder capacity vs. full channel width for fish passage
○ Requires ongoing, long-term operation, maintenance and repairs
○ On-going public safety hazard in the vicinity of the dam

● Remove Dam and Construct Full-Height Nature-Like Fishway (maintain impoundment like at Bradford NLF)
○ No flood risk reduction for upstream properties and roads
○ Would increase flood risk to Maxson Street and adjacent residences
○ No water quality improvements
○ Limited increase in wildlife benefits
○ Reduced fish passage capacity versus full channel width for fish passage
○ Unlikely to be permitted due to greater direct wetland disturbance and significant amount of fill material required in river
○ No current funding for the increased cost to construct due to large size structures and fill in the river
○ Requires ongoing, long-term operation, maintenance and potential repairs

● Remove Dam Only (No Additional Channel Modifications)
○ Would not assure efficient fish passage or boating safety
○ Continued erosion of riverbanks and risk of undermining Maxson Street requiring future maintenance and repairs

● Remove Dam and Construct Nature-Like Roughened Channel or
Riffle-Pool Channel
○ Roughened Channel
■ Simplest approach to restore channel to pre-dam condition – lower construction cost, shorter construction duration
■ Enhances recreational boating opportunities and public safety
■ Reduces upstream flood risks
■ Improves upriver water quality and river ecology (lower water temperatures, higher dissolved oxygen levels)
■ No future operation, maintenance or repairs required
■ Resilient to potential climate change effects ○ Riffle-Pool Channel
■ Similar benefits as the roughened channel design but could potentially provide enhanced fish passage efficiency and recreational boating opportunities

While evaluations of the preferred alternative are currently ongoing, based on the engineering analyses completed to date, the option to fully remove the dam and construct a nature-like riffle-pool channel is most advantageous due to the more significant benefits it would provide to fish passage, flood risk reduction and recreational boating opportunities.

Show All Answers

1. Why is the dam being removed?
2. Could the dam be repaired or partially removed?
3. Could a design similar to that of the Bradford fish passage project be used for the Potter Hill project?
4. What alternative designs have been considered and why was the proposed design selected?
5. What safety hazards are associated with the mill and dam structures?
6. How will removing the dam affect water levels in the river?
7. Will my household well be affected?
8. Many properties along the Pawcatuck River have private drinking water wells, especially on the Hopkinton side of the river. How many homeowners’ wells could be affected by the predicted drop
9. Will Westerly’s municipal water wells adjacent to the Pawcatuck River be affected?
10. How will removing the dam reduce flood risk to upstream and downstream properties? Will larger flood events (i.e., the 500-year recurrence flood) be worse upstream or downstream following dam removal?
11. Will removal of the dam cause increased flooding to downstream areas, including downtown Westerly?
12. How will removing the defunct dam and mill affect public access to and uses of the river?
13. How will removing the dam affect fish and wildlife?
14. How will removing the dam affect wetland systems upstream of the dam?
15. Is the proposed design accounting for climate change projections and worst-case future hydrologic scenarios?
16. Who is the project team?
17. What are the next steps?
18. Where can I get more information on the project?