Bancroft Contracting Corporation constructed the Union Gas Dam on the Mesalonskee Stream in Waterville, Maine for Maine Renewables of Annapolis, Maryland. This 32-foot high, 82-foot long reinforced concrete dam occupies a site where a granite-block dam had been breached and abandoned. Existing at the site was a powerhouse equipped with a 1.5 megawatt generator. The purpose of the dam is to capture the hydraulic head available at the site to power the generator.
The project involved placement of approximately 1,500 cubic yards of reinforced concrete and the installation of two hydraulically operated gates to allow the dam operator to control river flow. The dam is anchored to ledge at its base and to existing concrete piers at its ends.
Cost of the project was approximately $872,000. Project Manager for Maine Renewables was Arthur Hagood, engineering was by Andy Straz. Bancroft Contracting Corporation was general contractor, represented on site by Ernest Desroches, Project Superintendent.
Contribution to the Community
The Union Gas Dam project makes its most important contribution to the community as a source of clean hydroelectric power. This dam is one of the few, possibly the only, new hydro dams constructed in Maine in the recent past. Maine’s electric power needs are currently met in largest part by power generated from combustion of natural gas and imported oil. The Union Gas Dam is a new source of clean, locally produced electric power that lessens the community’s reliance on imported fossil fuels and their attendant carbon outputs, increasing cost, and potential availability issues.
Job Challenges & Innovation
This challenging project required Bancroft Contracting to begin and complete the work within time constraints imposed by river flow levels, to control normal river flow within the site, and to respond effectively to rapidly rising water levels that followed significant rain events during the course of construction. In order to de-water the site and facilitate movement of materials, Bancroft used large granite blocks existing on the site to construct an earth-filled granite cofferdam and crane pad. Bancroft constructed the project in two phases, routing the river flow initially into one-half of the river channel and then re-routing it through a gate structure in the base of the newly constructed first half of the dam. This project execution permitted the construction to go forward to completion within the required schedule and with minimal down-time despite repeated high water events.
In addition to the environmental advantages inherent in the project and outlined above, Bancroft Contracting was able to construct the project with minimal impact to the river by strictly controlling siltation and minimizing introduction of construction pollutants into the water flow. It is our belief that the construction of the dam had essentially no long-term impact on the river environment.
Response to Client Needs
This is a project that Bancroft initially priced on a competitive-bid basis two years before construction. Because of continuing regulatory challenges, the customer postponed construction. When the customer was ready to construct the project in 2008, Bancroft worked together with Synergics to adjust pricing and find cost savings that allowed the customer to construct the project. We believe this was possible, at least part, because of the trust built between the customer and contractor on previous projects.