-By John Lynds
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.
Approximately 34,700 cubic yards of material, which includes two feet of over depth dredging, would be removed by mechanical means to widen the channel to 140 feet.
Of this amount, approximately 5,100 cubic yards of surface material is unsuitable for ocean placement and will need to be placed into the existing Confined Aquatic Disposal (CAD) container that was constructed during the deepening of the Boston Harbor Navigation Improvement Project. This container is located at the upper end of the navigation channel in the Chelsea Creek.
The remaining 29,600 cubic yards of material will be placed in the U.S. Environmental Protection Agency-designated Massachusetts Bay Disposal Site (MBDS) located 20 miles offshore. This active disposal site is and has been used for the placement of dredged material that has passed chemical and biological testing.
An Environmental Assessment for this work is currently being prepared. To protect the endangered right whale, whale observers will be on board the scows transiting to the MBDS from Feb. 1 to May 31 to avoid potential ship strikes.
The Corps is also assessing the effects that the proposed project is likely to have on Essential Fish Habitat and has made a preliminary determination that there will be no significant impacts on the designated fisheries resources.
There is expected to be no impact on local traffic.