New Hampshire's Innovative Approach to Dam Removals

Environmental Services (DES) Dam Bureau had classified both dams as low hazard dams. A breach of either dam would cause damage to downstream roads. Regular dam safety inspections had identified numerous deficiencies which the dam owner had failed to address. The City of Rochester and the Society for Protection of New Hampshire Forests (SPNHF) were interested in obtaining the property but not interested in taking on the liability for the two earth dams which were both in poor condition. In 2005, the New Hampshire Department of Transportation -Bureau of Aeronautics was expanding the adjacent Skyhaven Airport and was required to mitigate wetland impacts. Through some creative inter-agency discussions and the implementation of new compensatory mitigation DES Wetlands rules, removal of both dams was used as mitigation for airport expansion impacts. The Champlin Dam was initially to be repaired while the Champlin Farm Pond Dam, approximately 2,000 feet downstream was to be removed. However, test borings revealed weak embankment and foundation soils at Champlin Pond Dam- making any potential repair of that structure more complicated and expensive, thus partial breaching was selected. The dam removal and partial dam breach included the use of bioengineered and on-site materials for channel restoration and stabilization. The measures included stone and log weirs, coir logs, boulder clusters, and planting of live stakes and wetland seed mix. During construction, real-time design modifications were implemented as the dynamic process of dam breaching and channel restoration was occurring. The project alleviated dam safety concerns, enabled the transfer of land to conservation purposes, and restored the stream channel to a natural and stable condition. 12 pp.