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Fowler #7 - Hydroelectric Dam, Power Plant & Sinkhole Repair

Client: Hydro Development Group, Inc. / ENEL North America, Inc. | Location: Fowler, NY | Completion Date: 2009 | Services Provided: Structural & Civil Engineering, Land Surveying

A&C was contacted in the fall of 2008 by Enel North America to assist with Engineering and permitting requirements related to emergency repair work at their Fowler #7 – Hydro Electric Plant. During a planned cofferdam installation and Plant shutdown, a catastrophic water loss within the Plant’s forebay impoundment occurred. All water behind Dam #1 within the forebay rushed through an unknown sinkhole and discharged sediment laden water downstream, into the Oswegatchie River.

A&C was initially brought in to prepare channel diversion and dewatering plans to allow for further analysis of sinkhole(s) and necessary repair, prior to the onset of winter. Services include the survey data collection and mapping of the impoundment area upstream of Dam #1, including the river bottom sediment, eroded sediment channels, stone cofferdam, Hydroelectric plant, surrounding access routes, dam locations, shoreline above and below the dam, river elevations, dam and weir locations and elevations, old dam and retaining wall locations, and surrounding rock outcroppings and islands. The DEC and the early arrival of winter postponed repairs.

Over the winter months Enel had A&C develop more detailed Site Restoration Plans to include Plan and Report preparation and submission to the DEC. The documents included the planning and Engineering of Cofferdam dewatering pumps and equipment, dewatering pump sedimentation tanks to provide sediment removal from pumping and discharges, sinkhole closure and repairs plans, Forebay sediment dredging plans and spoils location, summary of sediment and cofferdam soils testing results, plans for the removal of the stone Cofferdam, evaluation of the seasonal Oswegatchie River flows and elevations, and permit and consent order meeting and negotiations with the DEC. The Sinkhole repair work and rewatering of the forebay are currently schedule for the dryer months of Aug. and early Sept. 2009.

522 Bradley Street
Watertown, New York 13601


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