KEARNEY LAKE DAM IDF UPGRADE USING A BURIED WEIR

摘要

The Annapolis Group engaged Hatch Ltd to undertake a condition assessment and dam safety review of the Kearney Lake Dam on the Paper Mill River in Bedford, Nova Scotia. The site consisted of a concrete overflow structure and a low wing dam near the main dam. It was found that rehabilitation work was required to address deterioration of the concrete overflow dam and to improve the stability of the structure. The consequence assessment found that the required design flood (IDF) was the Probable Maximum Flood, considerably larger than the capacity of the existing structure, which was estimated at less than the 1/100 Annual Exceedance Probability (AEP) event.This paper presents the unique approach that was undertaken in the rehabilitation work to address the owner's concern that the changes to the dam to handle the design flood could not appear to significantly alter or enlarge the footprint of the existing dam, and the rehabilitated structure had to blend in with the landscape. The approach taken was to construct a buried weir at a location downstream of the existing wing dam which would link the dam abutment to high ground. The existing dam was modified so that most floods (up to about 1/1000 AEP) would be contained within the existing abutments, and extreme floods (up to the design flood) would go over the buried weir and down an old channel.