Vertical Lift Bridges

Face lift at the Woodruff Dam

Work began on May 23 to replace the steel rails across the top of the Jim Woodruff Dam.

These steel rails allow the gantry crane to ride along from gate to gate. It opens and closes the huge vertical lift gates that regulate the amount of water allowed over the dam. A huge barge, a push boat and a large crane are all working hard to replace the rails.

While the work is going on there will be no draw down of water from Lake Seminole. All of the work being done is above the lake.

Here are a few facts about the Woodruff Dam that may help you. The dam consists of a fixed spillway, a lock, a gated spillway, a powerhouse and an earthen dike.

The Jim Woodruff Dam is a gravity dam. This is the type that is built of solid concrete and depends primarily on its own weights for stability. Concrete 15 feet thick is in the foundation. This gradually becomes 3 feet thick at the top. No other structure has more permanence or requires less maintenance than this type darn.

The gated spillway is 766 feet long consists of 16 vertical lift gates that are 40 feet wide and 30.5 feet high. The gates are operated by a 75-ton gantry crane that runs on rails atop the service bridge. The 16 gates are used to maintain a minimum upper water pool of 76 feet. The gated spillway also provides controlled release of water.

The water levels on each side of the dam are very important to the structure and were determined by studies made by engineers when it was constructed. They based these depths on the force exerted on the dam, which is called head rating. The water on the low side needs to be maintained as close to 33 feet as possible. The lakes ideal depth is 76 feet.

There have never been any problems at Woodruff Dam at any time since its initial startup in February of 1957. It is well maintained and it has inspections daily. In the past, the dam has shut down for two weeks every two years for routine maintenance. It has run 24 hours a day, seven days a week for almost 55 years.

The routine maintenance inspections are done on a certain schedule all of the time. Everything is checked. A geologist studies the bed rock of the area and architects discuss what needs to be attended to so as to ensure the integrity of the dam.

Divers regularly check the dam structure. This is because the concrete gets scoured by the constant movement of water at the discharge area. When it becomes too eroded new concrete is then added. Later, when it dries it is checked one more time before opening for use.

Army Corps of Engineers will Dredge Chelsea Creek by 2012 ...

The U.S. Army Corps of Engineers, New England District is proposing to perform maintenance dredging of the Federal navigation channel in the vicinity of the Chelsea Street Bridge in East Boston and Chelsea by 2012.

The replacement of the existing Chelsea Street Bridge with a new vertical lift bridge will allow the Corps to modify the existing Federal navigation channel in the vicinity of the bridge. The Chelsea Creek navigation channel was authorized to a width of 225 feet by the River and Harbor Act of 1962, but because of the restrictions caused by the Chelsea Street Bridge, the channel was never widened to its authorized width.

“The project area is located approximately 125 feet downstream of the bridge to approximately 350 feet upstream of the bridge,” said Project Manager Mike Keegan, of the Corps’ New England District, Programs/Project Management Division. “There are two alternatives currently under consideration to widen the channel. Both alternatives are located in disturbed areas where previous vehicular or railroad bridges, and utilities were constructed.”

The first alternative would create a minimum 140-foot-wide channel in the vicinity of the new Chelsea Street Bridge. The second alternative is the creation of a minimum 175-foot-wide channel. The 175-foot-wide channel alignment is dependent on bulkhead modifications that must be designed and implemented by non-Federal interests. These bulkhead modifications must be completed before the navigation channel can be widened to 175 feet. Both alternatives would widen the channel to the channel depth of -38 feet Mean Lower Low Water (MLLW) which was authorized in the Water Resources Development Act of 1990.

Fuel tankers transiting the existing Chelsea Creek have less than six feet of clearance between the existing Chelsea Street fenders. The new vertical lift bridge that is currently under construction will eliminate any constriction of the navigation channel. The purpose of this Federal navigation project is to widen the navigation channel in the area of the Chelsea Street Bridge quickly after the new bridge is finished.

Widening the channel will potentially allow a larger class of vessels to safely enter the oil terminals upstream of the bridge, which could increase the volume and reduce the transportation cost of home heating oil and various other commodities available in Massachusetts.

The project is also needed to reduce potentially hazardous navigation conditions. Dredging is expected to begin as soon as possible after completion of the new bridge, sometime in the beginning of 2012.

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