A New Application of Roller Compacted Concrete: Reconstruction of the Upper Damon Reservoir Dam, Rindge, New Jersey

Dams are neglected and failing infrastructure across the U.S. The number of high hazard dams in the U.S. is increasing, as is the cost to repair the dams. The Association of State Dam Safety Officials (ASDSO) estimates that $36.2 billion is needed to rehabilitate all dams across the nation, with about $10 billion needed just for the most critical dams over the next 10 years. This project illustrates efforts by the private sector in conjunction with public regulators to explore cost effective and new applications of existing construction methods and materials for repair of dams.
The Upper Damon Reservoir dam was a 100-year old structure (consisting of an earth embankment and a stone gravity spillway) that impounded a 55-acre lake. In 2008, the NH Dam Bureau determined the spillway had deteriorated to the point where, for public safety reasons, it needed to be removed and the lake temporality drained until a new spillway could be constructed.
The owner decided to reconstruct the spillway, rehabilitate the earth embankment and refill the reservoir. His requirements included a spillway design that could; 1) cost-effectively utilize an abundance of on-site construction material (aggregate), 2) be constructed by local construction labor and standard equipment, and 3) reasonably match the look of the original structure. Following preliminary investigations (survey, subsurface, H&H), a number of suitable alternative replacement structure types were evaluated.
A Roller Compacted Concrete (RCC) structure to serve as the active spillway was recommended by the Design Engineer as the best alternative to meet the owner’s requirements. The spillway was designed as a gravity structure (trapezoidal shape), and was sized to support applied loads as defined in the Engineering Guidelines for the Evaluation of Hydropower Project, FERC, Chapter 3. Critical design issues included RCC freeze-thaw considerations, permeability, wear and associated loss of section, stability of a potentially reduced cross-section, hydraulic capacity and field quality control of foundation preparation, dental concrete, and RCC manufacturing, placement and compaction. This is the first known application of RCC as an active spillway in New England, and perhaps in the northeast United States.
In November 2009, the RCC spillway, consisting of approximately 3,500 cubic yards of RCC, was successfully placed in about 21-days. The RCC spillway was insulated for a winter curing period, and in-situ testing in late April 2010 confirmed the RCC had acquired adequate strength. The remainder of the project was completed in May - June 2010, and following final inspection, the NH Dam Bureau authorized impoundment of water. The reservoir was subsequently filled and the spillway placed into service in October 2010.
Subsequent reviews of the RCC spillway by the Design Engineer and NH Dam Bureau indicate that the RCC is performing as expected to date. Monitoring of the spillway performance, particularly as it relates to the wearing of the RCC surface will be on-going. The project has significant value to the dam community as it represents a unique and original application of RCC that, under appropriate site conditions, can be a cost-effective alternative for active spillway replacement / rehabilitation in the Northeast. 8 pp.