Navigation structures are necessary to make inland waterways viable, year-round transportation corridors.  The U.S. Army Corps of Engineers builds, maintains and improves navigation structures on Pittsburgh’s three rivers – the Allegheny, Ohio and Monongahela!

The Lower Monongahela River Project
will keep river transport reliable and economical through the lower part of the Monongahela River.

 Locks and Dams 2, 3 and 4 on the Monongahela River in Allegheny, Washington and Westmoreland counties in southwestern Pennsylvania, are the three oldest currently operating navigation facilities on the Mon River.  These locks experience the highest volume of commercial traffic on the entire Monongahela River Navigation System and the pools created by these dams are also popular with recreational boaters.

The Lower Mon Project replaced the nearly 100 year-old fixed-crest dam at Braddock Locks and Dam with a gated dam, and will remove Locks and Dam 3 in Elizabeth and construct two new larger locks (Charleroi Locks) at Locks and Dam 4 in Charleroi.

These improvements will visibly affect the Monongahela River.  Removing Locks and Dam 3 will create a single pool and cause the river to rise 5’ between Braddock and Elizabeth.  From Elizabeth to Charleroi, the river will drop 3.2’.  Even though normal river levels will be different from Braddock to Charleroi, flooding will be no worse because of the new gated Braddock Dam.

The Lower Mon Project will fund the design and relocation of municipal facilities along the Monongahela and Youghiogheny Rivers adversely affected by the project pool changes.  However, changes to private or commercial facilities must be made by the owner.  Although this will involve some expense in the short term, cost-effective long-term advantages will result from a 30-mile unimpeded section of river from Braddock to Charleroi.

Charleroi Locks
View the current construction of the new Charleroi Locks on the Charleroi Webcam 

The new Charleroi Locks, with both lock chambers 84’ wide by 720’ long, are an essential component of the “two-for-three” replacement plan that will lower the downstream operating pool by 3.2’ after the removal of Locks and Dam 3.  This pool lowering, driven by major structural problems at Locks and Dam 3, will result in major impacts to existing Locks 4.  Major impacts to Lock 4 include differential loading on the lock walls increasing to unacceptable levels and water depths over the lock chamber sills and struts becoming lower than required.

Existing Locks 4 are 70 years old with thin, unreinforced, non-air entrained concrete sections founded on wood piles.  Concrete struts were constructed across the floor of the locks to stabilize the walls prior to raising the upper pool by 6’ in 1967 when the new gated dam was built.  At that time, the up-river Maxwell Locks and Dam were constructed to replace several old middle Monongahela River projects, and a new dam was constructed at Locks and Dam 4 to raise the pool to the new Maxwell project.  

There are six facilities upstream of Locks and Dam 4 and all have 84’ wide lock chambers.  Maxwell Locks, the first upstream project, has twin 720’ long by 84’ wide chambers.  When Locks and Dam 3 is removed, all locks downstream of Locks and Dam 4 will have a 110’ wide main chamber.  All downstream locks have a 110’ wide main chamber and auxiliary chambers.  Since the existing chambers at Locks and Dam 4 are each only 56’ wide, constructing larger chambers would remove a bottleneck from the system that forces the complicated and hazardous process of tow disassembly and reassembly in order to “double lock” typical tows through Locks and Dam 4.  Larger chambers would also provide additional capacity to process traffic.  In sum, the plan to construct new and larger locks at Locks and Dam 4 is driven by the age and condition of the existing locks as affected by the planned lowering of the downstream pool and the raise in the upstream pool that was made in the 1960s, and in the benefits of removing a bottleneck (i.e., the last remaining 56’ wide chamber) to transportation on the Monongahela River.

Construction of the new locks began in the fall of 2003 with a $7.9 million contract to prepare the site by construction of a new access road, bridge and parking areas as well as operations and service buildings.  Another contract for demolition of the river lock chamber was awarded in the fall of 2004 for $12.9 million.  This contract included removing the river lock chamber floor struts, timber and steel piles and installing stabilizing struts and coffercells to prepare for the eventual construction of the new lock’s middle wall within the area of the existing river chamber.  Continuing the Lower Mon Project’s award winning trend, the design for this contract earned the 2006 Grand Award for Engineering Excellence from the American Council of Engineering Companies of Ohio.

The current contract for construction of the new river wall was also awarded in the fall of 2004.  Construction began in the spring of 2005 and is scheduled to be complete in 2010.  Construction of the remainder of the locks will be completed in several separate phases with the new locks scheduled for completion in 2019.

Braddock Dam
reflects the Corps of Engineers’ initiative to apply innovative technologies to the design and construction of navigation structures!

In June 2002 when Dam Segment #2 was set-down onto its foundation, Act One of the Braddock Dam “In-the-Wet” construction project was completed to rave reviews.  For the 1^st time in civil engineering history, an inland navigation dam was created using innovative float-in technology, wherein two massive concrete dam segments, fabricated on land, were launched, floated into place and submerged onto a previously constructed large diameter drilled shaft foundation.

On July 26, 2001 Braddock Dam Segment #1, weighing 16,800 tons, floated out of its casting basin in Leetsdale and into the Ohio River to begin a groundbreaking 27.5 river mile trek.  On February 27, 2002 Segment #2, weighing 13,500 tons, embarked on its maiden voyage.  The segments were towed with precision through Dashields and Emsworth Locks on the Ohio River, nearly filling the lock chambers.  After passing through what was then Lock 2 on the Monongahela River, the segments were moored at an outfitting pier in Duquesne to prepare them to be sunk onto the drilled shaft foundation at the Braddock project site. Their 15-hour trips were major media events in western Pennsylvania.  The flotilla – dam segment, 3,300 HP primary tow boat, two assistance tow boats and escort vessels – traveled in the heavily used waters of the Port of Pittsburgh as thousands of on-lookers lined the riverbanks and cheered while others tracked their progress through periodic television and radio updates.

On December 5, 2001 Segment #1 was transported to the Braddock Dam site, positioned and set down on its prepared underwater foundation.  On June 19, 2002 Segment #2 reached its final destination.  Safely set-down on their foundations, Segments #1 and #2 formed the lower third of the pier bases and overflow sections of the five-bay gated navigation dam.  The balance of the dam was constructed from floating plant above the water.  The new Braddock Dam became fully operational in April 2004.

The $107.4 million Braddock Dam project incorporates significant new and innovative business practices with respect to design, construction, procurement and contract management that have received notable interest and endorsement not only with the federal government, but the engineering community as well.  The Braddock Dam has been recognized in many engineering periodicals, including Civil Engineering magazine, and Engineering News-Record named it one of the top 25 newsmakers of the year in 2002.  In 2003 the Engineers’ Society of Western Pennsylvania honored Braddock Dam as its Project of the Year, in 2004 the project was a finalist for the American Society of Civil Engineers’ Outstanding Civil Engineering Achievement Award and in 2005 it received the Civil Engineering Achievement Award from the Pittsburgh Section of the American Society of Civil Engineers.  And finally, the History Channel’s Modern Marvels highlighted the Braddock Dam construction in its 1-hour documentary on the history of the U.S. Army Corps of Engineers.

Relocation of Municipal Facilities

The Lower Monongahela River Project, authorized for construction by the Water Resources Development Act of 1992, will raise existing Pool 2, between Braddock and Elizabeth, by 5’ and lower existing Pool 3, between Elizabeth and Charleroi, by 3.2’.  These pool changes will require the relocation of shore side facilities.  In accordance with the discretionary authority afforded the Chief of Engineers under Section 111 of the River and Harbor Act of 1958, the Lower Mon Project will fund the design and relocation of municipal facilities along the Monongahela and Youghiogheny rivers adversely affected by the project pool changes. Shore-side municipal facilities owned by the following 20 public entities will be adjusted at an estimated cost of approximately $25 million.

The government and the Norfolk Southern Corp. will share in the cost of adjusting the Port Perry railroad bridge.

All privately-owned facilities along the Monongahela and Youghiogheny rivers adversely affected by the project pool changes are required to perform any needed adjustments at their own expense according to the navigation servitude powers of the federal government as specified in their Section 10 permits.  The Feasibility Report estimated these costs at approximately $111 million, based on gross estimates provided by the owners.  Congressional representatives from these areas have been personally involved in discussions with the Pittsburgh District and affected local businesses concerning possible federal assistance for these private relocations.

The Corps of Engineers and the Port of Pittsburgh Commission have established a forum to continue dialogue with these affected owners on likely impacts, technical assistance available from the Corps and potential sources of non-project financial assistance.  The Corps routinely interacts with the public on these private relocations during formal presentations to civic groups, participation in community awareness events and publication of the project's newsletter.

Frequently Asked Questions
What is the target date for the permanent raising of the Braddock pool?
The target date is the summer of 2009.  We are working to complete all federally-funded relocations between Braddock and Elizabeth before establishing the new Braddock Pool.  Although the new Braddock Dam is now operational not all of the relocations are complete.  However, the new gated dam is capable of maintaining a stable pool lower than the permanent future normal pool level of elevation 723.7 NGVD.  Until all the relocations are completed in 2009, we will maintain the pool no higher than elevation 721.8.  This is the constraining elevation determined by the required clearance under the Port Perry railroad bridge at mile 11.7.

When will Dam 3 be removed?
When one new lock chamber is operational at the new Charleroi Locks and the dredging of Pool 3 is complete.  Although these activities started in the spring of 2005, the construction has been separated into several contracts and Dam 3 may have to remain in service through 2016.  There is an opportunity to compress the current schedule by at most three years and begin removal of Dam 3 in 2013.

When will the dredging of the river between Locks 3 and 4 start?
It already has started.  In May 2000, we awarded a $6.4 million contract to GASA, Inc. to dredge between river miles 40 and 41. This is the first dredging effort.  Much more work remains to be completed.  The remaining dredging may be done in increments as funds become available beginning in 2008, but will have to be complete no later than 2016 so Dam 3 can be removed.

What will the health concerns for recreational boating be during the dredging?
The dredging work will not create any water quality problems.  Recreational boaters will have to be mindful of the location of dredging equipment and operations in the interest of safe boating.

What will be the approximate loss of river bank?
The new normal pool will be 3.2’ lower than the existing normal pool of elevation 726.9 or elevation 723.7.  Here's what that means in relation to what you would normally see.  For instance, say the upper gage at Locks 3 Elizabeth was at 9.7’.  This means that the elevation of pool was 0.7’ above "normal" or at elevation 727.6 (9’ on the gage is normal pool).  Therefore, the new normal pool level will be 3.9’ below the river level you see right now.  On average, this will result in the river receding about 15’ to 25’ from the current shoreline.

How can I find out about any funds available to retrofit my docks after the project is completed?
The authorized Lower Mon Project does not include any funds for the adjustment of privately-owned facilities.  The Port of Pittsburgh Commission has investigated other potential funding sources to assist private owners.

Are the floating pieces of the new Braddock Dam structurally sound?
Yes.  As you probably saw when Braddock Dam Segments #1 and #2 were floated up the Ohio and Monongahela Rivers from Leetsdale to Duquesne, they performed as they were designed.  They floated!  Each floating dam segment is designed similar to the hull of a large ship.  The only difference is that ships are manufactured with an inner super structure of steel members and a heavy plated steel outer skin, while our dam segments' superstructure and skin are made of concrete that is reinforced with steel bars.  When floating, the segments flex like a ship's hull.  So we place our heaviest reinforced concrete members at the places where we expect the segment to flex the most and cause the most force to be exerted on the structure.  There's plenty of steel inside all of the concrete to resist the forces and pressures that each segment is expected to experience.  If an accident had occurred during transport that would have caused a puncture in the outer wall of a dam segment, like a ship's hull, the arrangement of internal walls are designed so that only limited compartments would have flooded, which would have prevented the segment from sinking.

How did we make the floating pieces sink in the right place?
Prior to set-down, each dam segment had positioning winches and other important equipment attached to it at the Outfitting Dock at Duquesne.  In addition, at the Braddock Locks and Dam, mooring lines were connected to fixed anchor piles located in various positions in the river.  These fixed anchor piles are located very close to the new dam's final set-down location.  Also, many of the exact survey points were established and re-verified at this time, along with checks of the accuracy and preparedness of the survey equipment.  Once all of this initial preparation work was finished, the contractor ensured that weather and river forecasts were favorable.  When the forecasts were favorable, two towboats towed the dam segment downstream from the Outfitting Dock at Duquesne to the Braddock Locks and Dam.  When the dam segment reached Braddock, the two towboats carefully positioned the segment at a predetermined location in close proximity to the final set-down area.  Then the mooring lines from the fixed anchor piles were attached to the positioning winches on the dam segment.  The towboats then disconnect themselves from the dam segment, thus the winches and mooring lines had control of the dam segment's final positioning movements.  Once the towboats were disconnected, the winches were operated according to a winching plan which had been developed for each dam segment.  In addition to the winches, the land wall of Braddock Locks had a guide attached to it where Dam Segment #1 meets the lock wall.  This guide helped align Dam Segment #1 in the proper position before final set-down.  Dam Segment #1 was also fitted with this guide at the opposite end where Dam Segment #2 connects to it.  While the dam segment was being positioned, its location was extensively surveyed and crews directed the positioning of the dam segment to a tolerance of plus or minus 2 inches.  Once the dam segment was positioned properly in the river, water was very slowly pumped into the compartments in the dam segment.  By pumping water into the compartment, the weight of the dam was increased to a point where it no longer displaced enough water to float, and began to sink.  The pumping was accomplished according to a specific ballasting procedure, and this procedure ensured that each dam segment sunk in a slow, level and safe manner.  Once the dam segment was set down, several hydraulic jacking devices that were installed during construction were used to make any final adjustments that were needed in the dam segment's position.  Finally, each dam segment is concreted into its final position.

How did the dam segments float?  Aren't the pieces too heavy to float?
The two dam segments were assembled from 438 reinforced concrete pre-cast panels.  These panels weigh from four to 70 tons each and would not float individually.  But they were interconnected in gridlock fashion and provided with a continuous concrete slab underneath, creating a boat-like structure with watertight interior cells.  With these cells and the use of transport bulkheads (temporary steel walls that close an opening), the segments float because of the Law of Buoyancy.  The Law of Buoyancy, which was formulated by the ancient Greek mathematician Archimedes, simply states that "The upward force on an immersed object is equal to the weight of the displaced fluid."  So Segment #1, which weighed about 11,000 tons, would need to displace about 11,000 tons of water to stay afloat.  Because water weighs 62.4 pounds per every cubic foot of volume, 11,000 tons of water would occupy a space about 10’ high if spread over a footfall field.  And, coincidently, Dam Segment #1, at 333’ by 104’, is about the size of a football field.  So, when surrounded by water, Dam Segment #1 would theoretically float in about 10’ of water.  In actuality, Segment #1 floated at approximately 11’.  Dam Segment #2, at 265’ by 104’ and about 9,000 tons, would also theoretically float in about 10’ of water.  In actuality, Segment #2 also floated at approximately 11’.

The next logical question would be: "Well, so much for theory, how much did the dam segments really weigh?"  The construction and design team carefully monitored the weight of every piece of the segments as they were being built at the Leetsdale Casting Facility.  We calculated precise volumes and weights of materials incorporated into each piece and keep a running tally of the actually weight of each segment as work progressed.  Based on the final tally, the segments weighed:

v       Dam Segment #1 weighed 22,369,000 pounds (11,184.5 tons)
v       Dam Segment #2 weighted17,169,980 (8,585.0 tons)

With this actual weight information, we can more precisely predicted how deep into the river each dam segment will float for their 27.5 mile trip from the Leetsdale Casting Facility to the outfitting dock at Duquesne.  This depth into the water is commonly known to ship builders and operators in the navigation industry as the term "draft."  The predicted drafts we

v       Dam Segment #1 would draft at 10.4’.  (It actually drafted at a little less than 11’.)

v       Dam Segment #2 would draft at 10.0’.  (It actually drafted at a little over 11’.)

The navigation channel in the Ohio River and the Monongahela River from the Leetsdale Casting Facility to the outfitting dock at Duquesne, and through the Dashields, Emsworth and Braddock locks is deep enough to accommodate these segment drafts.

Did each floating piece fit through the locks?
Yes.  The floating dam segments fit through all the locks.  Each segment passed through three locks in route to Braddock.  Lockages occurred at Dashields Locks and Dam and Emsworth Locks and Dam on the Ohio River and Locks and Dam 2 on the Monongahela.  Each facility is equipped with two lock chambers, with the larger of the two being 110’ wide.  Each segment was 104’ wide at its base, but there was an additional 1’6” of concrete that projected from the downstream end of each segment.  So the maximum width of each segment was actually 105’-6”, but as we can see, each segment was able to enter and leave the large lock chambers and still have about 2-1/2’ of clearance on each side.  This may seem very close, but this is the type of side clearance that most towboats and barges normally operate with as they pass through our locks.  The length of our larger lock chambers is also suitable to hold each dam segment.

How long did it take to transport the floating pieces to the dam site?
The distance from the Leetsdale Casting Facility to the Outfitting Pier at Duquesne is about 27 miles.  The general contractor was limited to a transport speed of no more than 4 knots.  Based on this speed and considering the time necessary for the lockages at Dashields, Emsworth and Braddock, we predicted it would take between 18 to 20 hours to make the complete journey.

Segment #1 left Leetsdale about 7:30 a.m. on July 28, 2001 and arrived at Duquesne at 9:15 p.m. that same day.  Segment #2 left Leetsdale at 6:55 a.m. on February 27, 2002 and arrived at Duquesne at 9:30 p.m. that same day.

Were timbers being used in the construction of the dam segments?
Wood and timbers were used as temporary formwork that shapes the concrete members and slabs in each dam segment.  This material was removed once the concrete was adequately hardened.  Otherwise, there is no other timber or wood permanently incorporated into the finished work.

Why did we build the floating dam segments at Leetsdale and not closer to Braddock?
Pittsburgh District elected not to provide a mandated government-furnished fabrication site for the float-in concrete segments since an array of options were possible; the method and location of the fabrication site, which would provide the "best value for the government" was impossible to predict at the time of requesting proposals.  The source selection method was by the Best Value Trade-Off methods, wherein offerors submitted both technical and price proposals.  The Joint Venture leased approximately 30 acres of land in Leetsdale, Pa., prior to submitting a proposal to the district for the construction of Braddock Dam.