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Sticky Wickets: Lifting Device Developed to Remove Stoplogs at Ivanhoe Lake Dam

The seven spillway bays at Ivanhoe Lake Dam are controlled by stoplogs, with frequent installation and removal from March through November to control the lake level. The old system of manipulating the stoplogs using a an overhead gantry system was difficult and dangerous for personnel during high flow events. Dam owner the Ontario Ministry of Natural Resources (OMNR) worked with Hatch Energy to develop an electric overhead stoplog lifting device that can be remotely operated.

The situation at the dam

Ivanhoe Lake Dam, on the Ivanhoe River in northern Ontario, was built in 1962 to regulate water levels on Ivanhoe Lake for recreational use and to prevent flooding of the community of Foleyet.

Ivanhoe Lake Dam is a 10-meter-high reinforced concrete gravity structure with a raised sill and seven 4.27-meter-wide spillway bays controlled by stoplogs. Each bay contains a maximum of six 0.3-meter-deep wood stoplogs and two 0.6-meter-deep steel stoplogs. Installation and removal of these stoplogs occurs frequently during the operating season (from March through November) to provide control of the water level in the lake.

The electric overhead stoplog lifting device being used at Ivanhoe Lake Dam allows Ontario Ministry of Natural Resources personnel to safely install and remove stoplogs remotely from the dam deck.

Conventional rail "crab" winches were implemented during a system redesign in 1962 to handle the stoplogs. The big, bulky winches were slow to move around the deck and were physically demanding for OMNR staff to operate.

In 1999, OMNR installed a single monorail overhead gantry system with two manual 2-ton hoists. This system was used to maneuver the stoplogs during regular operations and flood events. However, dam configuration presented an obstacle to the use of this system. The dam deck is 2 meters above the top stoplog in each spillway bay. During high flow events, this large distance between the deck and stoplogs made it difficult and dangerous for personnel to remove and install the stoplogs.

In 2006, a flood passage improvement study provided options to improve the overall effectiveness of flood passage capabilities of the dam. The first option was to implement a high-speed, low operator fatigue overhead gantry system that would be capable of removing all the stoplogs in a safe and time-efficient manner.

Developing the lifting device

Hatch and OMNR worked to develop the lifting device, called a log lifter, in 2006. It consists of an electric overhead crane with a lifting beam (called a follower) that is lowered through the stoplog guides and into the water to remove and install the stoplogs. This follower is equipped with hooks. Typically, these hooks must be manually actuated to remove or install the stoplogs. Once a stoplog is removed from the guides, it must be moved to the storage location on the deck of the dam.

Because of the fast-moving water flowing over the stoplogs, one of the greatest risks involved in removing the stoplogs is detecting engagement of the follower hooks. Thus, the lifting device features submersible proximity sensors that allow the operator to detect engagement of the hooks with the stoplogs. In addition, the device contains independently actuated hooks, to give the operator separate information on each end of the follower.

John Gaffney Construction built and installed the log lifter in 2007. To adjust the dam to use of the log lifter, OMNR also replaced the existing stoplogs. Cost to complete the work was $575,840.

Since that time, the stoplog lifting machine has operated as intended.

- By Pat Cantin, engineering technologist, Northeast Regional Engineering Unit, Ontario Ministry of Natural Resources

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