BRADDOCK DAM HAER PA-635 Braddock vicinity ......The U.S. Army Corps of Engineers, Pittsburgh...

PHOTOGRAPHS

WRITTEN HISTORICAL AND DESCRIPTIVE DATA

HAER PA-635HAER PA-635

BRADDOCK DAMBraddock vicinityAllegheny CountyPennsylvania

HISTORIC AMERICAN ENGINEERING RECORDNORTHEAST REGIONAL OFFICE

National Park ServiceU.S. Department of the InteriorU.S. Custom House, 3rd Floor

200 Chestnut StreetPhiladelphia, PA 19106

Location:

HISTORIC AMERICAN ENGINEERING RECORD

BRADDOCK DAM

Monongahela River Locks and Dams, Braddock Vicinity, Allegheny County, Pennsylvania UTM: 17.596795.4471515 QUAD: Braddock, Pennsylvania

HAER No. PA-635

Present Owner: Pittsburgh District, U.S. Army Corps of Engineers

Present Use:

Significance:

Description:

Lock and Dam Facility

The U.S. Army Corps of Engineers, Pittsburgh District, planned the construction of Braddock Dam in the 1990s and began it in 2000 as part of a $750 million (2004 price level) modernization of the lower Monongahela navigation system. Braddock Dam replaced Monongahela River Dam 2 and allows for the removal of Locks and Dam 3. In 1997, the Pittsburgh District decided to use innovative in-the-wet construction methods to build the Braddock Dam. These construction methods involved prefabricating the dam's base at a remote casting basin, with the base in the form of two hollow concrete segments that could be floated to the dam site (a "float-in" system). Once completed, the dam segments were floated up the Ohio and Monongahela rivers and set in place on a prepared foundation at the construction site. This construction method, developed from techniques used to build immersed tunnels and offshore oil-rig platforms, had not been used previously for an inland navigation dam in the United States. This innovative approach eliminated the need for extensive cofferdams and cofferboxes at the construction site and allowed construction to proceed simultaneously on both the foundations and the concrete base sections of the dam. These techniques accelerated the construction schedule of the dam, saved money, and eliminated the dangers associated with conventional in-the-dry construction. The construction of Braddock Dam has been published in several engineering journals and is recognized internationally for its use of new construction techniques and technologies.

Braddock Dam is a reinforced-concrete, gated dam measuring approximately 140' x 600'. The dam has four gated bays and two fixed-crestl weir sections. Five concrete piers support three large identical tainter2 gates that can be

1 A "fixed-crest" weir is a dam that has a height that does not vary; it has no gates or other moving parts to raise or lower the water level behind the dam. 2 Originally designed by Jeremiah Burnham Tainter in the late 1800s, the tainter gate is a convex gate mounted on radial arms and supported on two rockers. The gate is an economical water-control device that is able to instantly release a large amount of water; the rush of released water helps to both open and close the gates.

History:

BRADDOCK DAM HAER No. PA-635

Page 2

raised and lowered to regulate water flow; the fourth tainter gate is smaller and located over a gate bay with a raised sill that was designed to aerate low river flow to improve water quality. Each of the dam's five concrete piers contains a small structure at the top to accommodate machinery to operate the gate, and a steel footbridge runs across the entire length of the dam. The dam is connected on its north side to Braddock Locks, which were formerly known as Monongahela River Locks 2. The south end of the dam is composed of a section of fixed weir, consisting of two sheet-pile cells and three sheet-pile arcs, filled with concrete and attached to a reinforced concrete abutment.

The Monongahela Navigation Company built the earliest locks and dams on the Monongahela River in Pennsylvania between 1838 and 1887. Monongahela Navigation Company facilities in Pennsylvania that have been recorded for the Historic American Engineering Record include Locks and Dam 2 near Port Perry (PA-564), Locks and Dam 3 near Elizabeth (PA-565), and Locks and Dam 4 near North Charleroi (P A-566).

By the 1870s, the U.S. Army Corps of Engineers had begun constructing locks and dams on the upper Monongahela in West Virginia, and in the early years of the twentieth century, they began replacing old locks and dams on the lower portion of the river. First to be replaced was Lock and Dam No.2, which was rebuilt from 1902 to 1906.3 The next lock and dam replaced was old Lock and Dam No.3, from 1905 to 1908. Similar to new Lock and Dam No.2, the new Lock and Dam No.3 had two locks and a concrete dam with a movable Chittenden drum weir. Lock and Dam No.5 was rebuilt at a new site from 1907 to 1910, and Locks and Dams No 1 and No.4 were rebuilt at the original sites circa 1909-17. Replacement continued with the rebuilding of Lock and Dam No.6 from 1913 to 1923, Lock and Dam No.7 from 1923 to 1926 (HAER No. PA-299), and the replacement of Locks and Dams No. 8-9 by Point Marion Locks and Dam in 1923-1926.4

After a brief transition period immediately after the end of World War II, the Corps of Engineers resumed the job of improving the nation's rivers. The Pittsburgh District immediately began replacing the upper Monongahela's nearly fifty-year-old system of early twentieth-century locks and dams. The first facility to be built in the 1940s was Morgantown Lock and Dam, with construction beginning in 1948. Replacement of the old locks and dams on the Monongahela moved forward rapidly in the 1950s and 1960s, triggered in part by a new River and Harbors Act passed by the U.S. Congress on May 17,

3 Gannett Fleming, Corddry and Carpenter, Inc., A History o.fNavigation Improvements on the Monongahela River (March 1980), 16. 4 John Milner Associates, Inc., Monongahela River Navigation System Historical Engineering Evaluation (1999), 61-64.

5 Ibid., 19-20.


Page 3

1950, that authorized construction of new locks and dams on the Monongahela. Priority was given to replacing the upper Monongahela's locks and dams, most of which dated to circa 1903-15. Hildebrand Lock and Dam was built at river mile 108.2 from 1956 to 1960 to replace old locks and dams No. 12 and No. 13. Because the upper Monongahela saw less traffic than the lower part of the river, Hildebrand and the other replacement dams were built with only one large lock measuring 84' by 600.' Opekiska Lock and Dam was constructed from 1961 to 1964 to replace locks and dams No. 14 and No. 15.5

In 1958-59, concrete piers and six movable crest gates were also added to Lock and Dam No. 8.6

In 1960-1965, construction was completed on the middle Monongahela's first post-World War II replacement facility, Maxwell Locks and Dam. Maxwell was also a Tainter gate dam and was built to replace Lock and Dam No.6 at Rice's Landing. The facility was equipped with two locks, each measuring 84' by 720.'7

During the period from 1965 to 1990, no new locks and dams were built, but significant improvements were made to existing facilities. In 1967, a new gated structure was built at Dam No.4 that allowed the elimination of Lock and Dam 5. In 1986, the u.s. Congress passed a special act funding river improvements, including a lock and dam at Gray's Landing, Pennsylvania, to replace Lock and Dam No.7. Construction began there in 1986, the lock was placed into service in 1993, and the dam was completed in 1996.

By the 1980s, the u.s. Army Corps of Engineers recognized the need to replace Monongahela River Dam 2. The original construction of Dam 2 (HAER No. PA-558) had been authorized by the u.s. Congress in 1902, with construction completed by 1906. The dam was then composed of a fixed concrete weir capped by a movable section that used air-filled drums to raise and lower the movable portion of the dam. During low flow conditions, these movable drums added 3' of depth to the pool. After several years of problematic operation, the movable section was removed, and the existing concrete weir was permanently raised with a 3' cap of concrete. By the 1980s, Dam 2 was nearly eighty years old and had outlived its reliable lifespan, and the smaller, outmoded locks at Locks and Dams 3 and 4 were causing increased transportation costs. Because of their age, Dams 2 and 3 were viewed as a threat to the stability of the navigation pools. Since about 22

6 Leland Johnson, The Headwaters District: A History of the US Army Corps of Engineers Pittsburgh District, US Army Corps of Engineers (Pittsburgh: US Army Corps of Engineers, 1978),240. 7 John Milner Associates, Monongahela River Navigation System, 50.


Page 4

million tons of goods per year pass through the lower Monongahela River at Pittsburgh, making this navigation system very important to the national and local economies, some sort of action was required.

By December of 1989, the Pittsburgh District was completing a four-year feasibility study that recommended a two-for-three replacement of Locks and Dams 2,3, and 4. Locks and Dam 3 near Elizabeth, Pennsylvania, (HAER No. P A-559) could be removed if replacement structures were built for Dam 2 and Locks 4, and if Pool 2 were raised and Pool 3 lowered to equalize their elevations. This configuration would eliminate a significant bottleneck in the navigation flow through these older, undersized locks, permitting faster journeys up and down the Monongahela River. And because lock and dam sites are expensive for the federal government to maintain and operate, reducing the number of them would be of benefit.

In 1991, the Corps of Engineers submitted the final feasibility report and environmental impact statement to the U. S. Congress for approval. 8 Congress authorized the Lower Mon Project as the "Locks and Dams 2, 3, and 4, Monongahela River Project" in the Water Resources Development Act of 1992. This act authorized $556.4 million (1991 price level) to modernize the navigation system on the lower Monongahela, including the construction of Braddock Dam and the removal of Dam 2. The overall project also included new larger lock chambers at Locks and Dam 4 at Charleroi, Pennsylvania (HAER No. PA-560), pool elevation adjustments between Braddock and Charleroi, shoreside public facility relocations, one railroad bridge adjustment, and the removal of Locks and Dam 3 at Elizabeth, Pennsylvania. The new facilities would be renamed Braddock Locks and Dam and Charleroi Locks and Dam in honor of their nearby communities, following a postWorld War II practice used with the earlier modernizations on the upper Monongahela River.9

The feasibility study and planning undertaken for the Braddock Dam project during the 1988-91 timeframe determined that replacing the fixed crest weir Dam 2 with a gated dam was critical to the success of the two-for-three replacement plan. Removing the central facility, Locks and Dam 3, would require pool elevation adjustments, namely raising the normal elevation of Pool 2 by 5' and lowering Pool 3 by 3.2'. If the new dam were another fixedcrest dam instead of a gated dam, the crest elevation would have to be raised

8 Henry Edwardo, response to interview questions by Roy Hampton (e-mail communication, on file at Hardlines Design Company, Columbus, Ohio, June 25, 2004), 1. 9 William Miles, Robert Bittner, and William Karaffa, "In the Wet Construction of a New Gated Dam: Braddock Locks and Dam, Monongahela River" (unpublished article, on file at U.S. Army Corps of Engineers, Pittsburgh District Office, Pennsylvania, 2002), 1.


Page 5

to accommodate the rise in the ordinary high-water and flooding elevations behind the dam. New easements would be required, which would mean acquiring additional land and adjusting publicly owned facilities. In addition, with a fixed-crest dam, the navigation would be interrupted about 20 percent of the time because of the reduced clearance between the new operating pool and the tops of the existing lock walls. 1 0

U sing a gated structure resolves these disadvantages because the water level in the navigation pool can be more precisely controlled; the movable gates can be raised when the river is higher to prevent the pool elevation from rising. Although the gates cannot control extremely high water levels during flooding, their performance during more normal flow conditions justifies their higher cost.

Gated-dam technology had been used by Pittsburgh District engineers since the 1930s on the upper Ohio River and following World War II on the upper Monongahela River. The traditional in-the-dry construction technology used to build these dams, however, dated to the 1840s. By the mid-1990s, the Pittsburgh District was seriously considering departing from traditional methods of construction for the new dam. Previous navigation dams built by the U.S. Army Corps of Engineers on major inland rivers were constructed by establishing large cofferdams and cofferboxes that exposed portions of the riverbed for in-the-dry construction. Cofferdams and cofferboxes are expensive to build and can be dangerous in high-water conditions, and a construction method that does not use cofferdams would make for safer working conditions and lower costs.

The In-the-Wet Construction Method

By July 1997, the Pittsburgh District had decided on an innovative approach for construction of the new Braddock Dam that was known as "in-the-wet" construction. 1 1 The new dam was to be built without major cofferdams or cofferboxes. Instead, foundation preparations for the dam would be built on the site from a floating plant, while at the same time, the main body of the new dam structure would be prefabricated at a separate remote site, as two floating segments. Once the foundation preparations and floating dam sections were completed, the sections of the dam (known as Segments 1 and 2) would be towed to the construction site via the inland waterway system, then set in place and filled with concrete.

10 Pittsburgh District, Lower Monongahela River Navigation System Feasibility Study, Interim Report, Volume 2 0/6, Engineering Technical and Real Estate Appendices (on file at U.S. Army Corps of Engineers, Pittsburgh District Office, 1991), 3-8. 11 Miles et aI., "In the Wet Construction," 1.


Page 6

Henry Edwardo, Lower Monongahela Project Manager, indicated that a number of factors were involved in selecting the in-the-wet method of construction. Edwardo stated:

The prime mover was the goal of the government and its Inland Waterways partners to deliver a lower-cost project in the face of dwindling funding from the general treasury opposed to the growing need to address the crumbling inland waterways infrastructure. A general consensus existed that the in-the-wet techniques used routinely in tunnel, bridge, and off-shore oil construction projects might find application in lock and dam construction and lead to lower project costs. The pressure of shrinking federal funding for navigation projects was the overriding factor in taking the risk of the pioneering Braddock Dam Project. 12

Edwardo further stated that the biggest advantage to in-the-wet construction was" ... the elimination of the time and cost of cofferdams and the associated risks with flood surcharges."13

Design engineer Robert Bittner also listed some additional advantages of inthe-wet construction that may have influenced the selection process. Completing a large amount of construction at a casting basin site instead of in the riverbed allowed for less disruption of river navigation. Also, with much of the work performed on the shore, environmental hazards could be more easily contained. Overall, in-the-wet construction disrupted the river flow less than other methods, and the quality of the construction was higher because the dam segments were constructed in the controlled environment of the casting basin rather than in the riverbed. 14

The dam's innovative construction and design was the result of collaboration between the U.S. Army Corps of Engineers, the lead design firm of Bergman Associates, and the two subconsultants Ben C. Gerwick, Inc. (BCG) and D' Appolonia engineering and design consultants, who were consulted for the innovative construction features of the dam. According to Mr. Edwardo, the project was unique from a design standpoint. The design involved an unusually high degree of cooperation between private architecture/engineering design firms and the government. These organizations worked together to produce the completed design drawings and specifications necessary to issue a request for proposals for construction. The project also required a high level

12 Edwardo, response to interview questions, 1. 13 Edwardo, response to interview questions, 2. 14 Robert Bittner, response to interview questions by Roy Hampton (e-mail communication, on file at Hardlines Design Company, Columbus, Ohio, August 9,2004),3.

15 Ibid. 16 Ibid., 1.


Page 7

of public outreach because of the pioneering nature of the construction techniques and the project's location in a densely populated urban area. 15

In 1997, the private-sector design team of Bergmann Associates, BCG, and D' Appolonia engineering and design consultants was selected to evaluate the initial in-the-wet design concepts for Braddock Dam. After they reviewed and improved upon the U.S. Army Corps of Engineers' concept for the in-the-wet construction, the Bergman/BCG/D' Appolonia team was selected to take the concepts developed in the initial review of the in-the-wet proposals and assist the Pittsburgh District in developing the final design documents. 16 The task of completing the final analyses and designs of the two floating dam segments fell to the firm of BCG, which was founded over seventy-five years ago as a heavy-construction company specializing in marine projects. The company's expertise with in-the-wet construction played an important role in the planning, design, and construction administration of many aspects of the Braddock Dam project. 17

The technologies used for the in-the-wet construction at Braddock Dam were first developed for use with immersed tube tunnels, of which over 110 have been built in the last 100 years. According to Robert Bittner, President of BCG, one of the major projects that influenced the Braddock Dam in-the-wet technique was the Oresund Tunnel. This tunnel is an underwater concrete tube, 3.5 kilometers long, that connects Denmark and Sweden. Oresund is the largest immersed tube in the world, and its construction involved extensive use of in-the-wet construction techniques. Many concepts used at Braddock, such as the two-level casting basin, were originally developed for the Oresund Tunnel. Bittner mentioned too that the Bath-Woolwich Bridge Project on the Kennebec River in Maine also had an influence on Braddock Dam. For BathWoolwich, BCG designed a cofferdam system that was floated to the site that was used to construct six underwater pile caps for the bridge's main river piers. Construction methods and tolerances for mating a float-in structure to underwater pilings were developed and used for Bath-Woolwich and were an important component of the float-in aspects of Braddock Dam. 18

An important factor discussed during planning of the dam was the size of the segments that would be prefabricated and floated to the Braddock Dam site. One option considered was the construction of a segment 600' long, with multiple segments of smaller dimensions. During the planning discussion, Ben

17 Ben C. Gerwick, Inc., promotional material for Ben C. Gerwick, Inc. (on file at Hardlines Design Company, Columbus, Ohio, August 9, 2004), 1. 18 Bittner, response to interview questions, 6.


Page 8

C. Gerwick Jr. ofBCG recommended constructing two segments that were 250' to 300' in length instead of one larger segment. The two-segment option had a number of advantages. Since shorter segments would bend less while floating, less steel rebar could be used to reinforce the concrete shell, thereby reducing mass and material costs. Smaller segments would also be easier to maneuver through the locks and navigation channels of the Ohio and Monongahela rivers, and they would cause less interference for river navigation. 19 After considering the options, the Pittsburgh District decided on the two-segment configuration.

One unknown factor in planning in-the-wet construction was the availability of contractors who had experience in this type of construction and whether they would compete for the project.20 Proposals for construction of the dam were accepted in 1999, and a $107 million construction contract was awarded to a joint venture of the 1. A. Jones Construction Company of Charlotte, North Carolina, and Traylor Bros. Inc. of Evansville, Indiana. 1. A. Jones is one of the largest construction companies in the United States. Founded by James Addison Jones in 1890, the company has been involved in many large-scale construction projects, including the Petronas Towers in Malaysia, which now rank as the world's tallest buildings.21 Traylor Bros., Inc. was founded in 1946 by civil engineer and former Navy construction battalion officer William F. Traylor. The company specializes in marine and underground heavy construction, including ports, tunnels, and lock and dam facilities. Traylor's previous work for the U.S. Army Corps of Engineers includes projects on the Ohio River, such as extensive construction at McAlpine Locks and Dam in Louisville, Kentucky, and a 1200' lock at Lock and Dam 53 at Mound City, Illinois.22

19 Ben C. Gerwick Jr., response to interview questions by Roy Hampton (e-mail communication, on file at Hardlines Design Company, Columbus, Ohio, August 10, 2004), 1. 20 Bittner, response to interview questions, 3. 21 J. A. Jones Construction Company, company Web site at http://www.jajones.com (accessed Jun 17,2004; site now discontinued; paper copy on file at Hardlines Design Company, Columbus, Ohio). 22 Traylor Bros., Inc., company Web site at http://www.traylor.com/wps-htmIlAbout/History/ (accessed Jun 17, 2004).

Construction of the Dam

Overview of Construction


Page 9

By early 2000, construction on Braddock Dam was underway. The basic construction process was structured as follows. The new dam's foundations were completed on the bottom of the Monongahela River without the use of cofferdams, while at the same time, two reinforced concrete dam segments were fabricated within an offsite casting basin that was excavated adjacent to the Ohio River at Leetsdale, Pennsylvania. Once completed, each segment of the dam was floated up the Ohio and Monongahela rivers to an outfitting pier, which was located two miles upstream of the Braddock Dam site at Duquesne, Pennsylvania. Here, each segment was prepared for final positioning and setdown.

When outfitting was complete, the segments were then transported back to the dam site and set down on the prepared foundations. After the segments were set down and grouted onto their foundations, specially designed underwater concrete was placed into each hollow compartment of the segments to form a solid-mass concrete structure. Then from the floating plant, the dam piers were raised using conventional form-in-place concrete placement methods, and the dam's steel footbridges were installed. The downstream tailrace23 was constructed using prefabricated concrete panels. Four fully fabricated steel tainter gates were then floated into place and installed between the completed dam piers. The construction crew then finished the operating houses atop each pier and the mechanical systems that are used to operate the dam gates. The dam's left abutment and a small section of closure weir completed the construction sequence. Once the new dam was capable of maintaining the navigation pool, the existing 100-year-old Dam 2 was demolished.

Overall, this construction process differed greatly from traditional in-the-dry construction that used cofferdams and cofferboxes. Fabricating two segments at a remote casting basin, while simultaneously preparing the foundation on the river bottom, was a method that had never been used to construct a navigation dam in the United States. The in-the-wet installation of fully assembled tainter gates was also a pioneering construction technique. The following description of the construction of the dam seeks to explain and highlight significant aspects of the innovative construction methods and techniques.

23 A "downstream tailrace" is the concrete structural extension of the main weir that handles the erosive force of the water flowing below the dam gates.

Preparing for Construction


Page 10

By early June of 2000, the Pittsburgh District acquired and developed temporary easement lands along two miles of the left bank of the Monongahela River, on formerly industrialized property at Duquesne. Development consisted of project construction offices (see Photos 175-177), haul roads for placing dredged materials in the RIDC Duquesne Brownfield site, elevated railroad crossings, and a concrete plant for the project.

The large amount of concrete needed for the project was provided by a concrete plant that was built on the south (left) bank of the Monongahela River at Duquesne (see Photos 1, 84-85,214). The concrete plant included a bridge that allowed the concrete to be pumped over railroad lines to a barge moored on the south bank of the Monongahela River. From the barge, the concrete could be distributed to wherever it was needed on the construction site (see Photos 81, 82, 215). This plant continued to provide concrete for the construction of the tailrace and for the completion of the dam piers after Segment 1 had been filled with concrete. For the concrete plant, the U.S. government acquired approximately thirteen acres of land from Conrail (now Norfolk Southern Corporation) via a temporary work easement for a period of eight years to serve as the downstream work area for the batch plant, staging area, parking area, and access to the construction site. This plant has provided all concrete that was placed at the Braddock project site.

The concept originally called for a separate concrete plant to be built at the offsite casting basin; this plant would be used to complete the construction of the two floating dam segments. During proposal evaluations, the construction contractor suggested using an existing ready-mix facility located within ten miles of the proposed casting basin site. The government adopted this proposal and waived the requirement to build a new plant, subject to the condition that the contractor secure the necessary Pennsylvania Department of Environmental Protection permits for the existing ready-mix facility.

In addition to the aforementioned work, the construction contractor completed an offloadingloutfitting pier that would be used through the duration of the project. The offloadingloutfitting pier was a cellular dock located along the left descending bank at Monongahela River Mile 1208 at Duquesne, Pennsylvania. The dock's main purpose was to provide a staging and mooring area for outfitting Braddock Dam Segments 1 and 2,24 but it was also used to

24 Pittsburgh District, U.S. Army Corps of Engineers, Water Quality Management Planfor Construction of Braddock Dam, 2002 (on file at U.S. Army Corps of Engineers, Pittsburgh District Office, 2002), 5.


Page 11

carry dredged materials from the dam foundation and setdown excavations to the USX Duquesne Brownfield site, where the silt was used as a soil cap.

Constructing the Foundation

The foundation system for the dam was one of the first components of the dam to be constructed. The system is composed of upstream and downstream cut-off walls to prevent water from passing under the dam, a graded gravel base, and a grid of reinforced-concrete, drilled shafts that extend from the riverbed down into bedrock. The system has eighty-nine drilled shafts in all, each measuring 78" in diameter and about 30' to 40' in length. Each shaft was then drilled an additional 15' into bedrock with a 72" -diameter socket to carry the weight of the dam and the operating loads into the rock.25 The footprint of the foundation is 140' x 600' .26

To construct the dam foundation, the riverbed was excavated, starting at the existing river wall of Locks 2 and continuing toward the left bank abutment (see Photo 2). To prepare for the cut-off walls to be installed, piles were driven to determine how far they needed to go to reach the bedrock. The cutoff walls were then installed, using approximately 1,400 linear feet of steel sheet pile.27 Interlocking steel sheet pile was used to provide continuous upstream and downstream cut-off walls, and all pile driving was completed using drivers that were mounted on barges. The downstream cut-off wall also served to retain the riverbed when the dam's downstream scour protection system was placed. After the cut-off walls were completed, the riverbed between the walls was further leveled by adding a layer of specially formulated gravel mix. This gravel mix would provide a uniform surface beneath the floating segments for when the segments were set down onto their foundations.

A system of drilled shafts was then installed for the new dam foundation. This system included six set-down drilled shafts for each concrete segment that would be floated in and seventy-seven foundation shafts that would carry the operating loads on the dam to the bedrock. All of the drilled shafts were the tapered type with a permanently steel-cased 78" -diameter main shaft and 72"diameter rock socket. Each drilled shaft was located precisely using a pileanchored, two-level guide template.28 These templates allowed each shaft to be placed to a centerline tolerance of less than 112". Concrete for these heavily

25 Miles et aI., "In the Wet Construction," 3. 26 Pittsburgh District, Water Quality Management Plan, 2. 27 "Sheet pile" is a vertical column of steel, wood, or concrete driven into the ground alongside others to form an underground barrier impeding the movement of earth or water. 28 Miles et aI., "In the Wet Construction," 4.


Page 12

reinforced shafts was supplied from the left bank concrete plant that was located next to the project site. Concrete was conveyed by a system of belt conveyors from the plant to a discharge structure mounted atop a floating barge that was moored along the left bank. All foundation shafts were completed by the summer of 2000.

As part of a final maintenance program, silt, debris, and other materials that could interfere with the segment set-down process were dredged and removed within the cut-off wall footprint area of 140' x 600' .29

Constructing the Casting Basin for the Segments

Construction of the remote casting basin at Leetsdale, Pennsylvania, proceeded concurrently with the work on the dam's foundation system. In order to promote innovation and provide flexibility to contractors, the Pittsburgh District did not mandate a specific location or method for assembling the floating dam segments. Instead, contractors were allowed to select the site and method of assembly from a number of options. The dam's designers had envisioned a number of viable methods for assembling the float-in dam segments, including assembly within an existing dry dock, within a two-level casting basin, or atop a large special-purpose deck barge. Of six proposals submitted, four were based on land, while two used assembly atop a barge. The successful bidder, the Joint Venture of 1. A. Jones and Traylor Brothers selected an approach that used a two-level casting basin for construction of the dam segments.30 The site chosen by the contractor was located along the right descending bank of the Ohio River, about twenty-seven miles downstream of the Braddock Dam project site. The site was a large tract (approximately twenty-six acres) of vacant land in an industrial park area at Leetsdale.

On the contractors' selection of the casting basin option, Edwardo stated:

Most team members were of the opinion that the contractors who proposed on the Braddock Dam would elect to fabricate the segments in an existing commercially available dry dock with access to the inland waterway system. This turned out to be wrong. None of the six offerers proposed using a commercially available dry dock; each instead proposed developing from the ground up a new casting site/operation specifically designed for the two segments. As a result, the development of the Leetsdale Casting Site placed extraordinary demands on the

29 Pittsburgh District, Water Quality Management Plan, 7. 30 Miles et aI., "In the Wet Construction," 3

BRADDOCK DAM HAERNo. PA-635

Page 13

government and the contractor, with respect to obtaining and complying with NPDES [National Pollutant Discharge Elimination System] permits from the Pennsylvania Department of Environmental Protection, and more importantly, addressing the Section 106 [historic preservation compliance] issues which were not adequately forecast by either party.31

While initiating the site permits, the Joint Venture discovered that the selected Leetsdale site contained previously unidentified archaeological remnants of a nineteenth-century brick factory owned by the Harmony Society, a local communal religious group of German origins. The site also contained extensive archaeological deposits associated with prehistoric Native American inhabitants of the area. The Pittsburgh District, in consultation with the Pennsylvania Bureau for Historic Preservation (BHP), evaluated the archaeological site and determined that it was a significant site requiring avoidance and! or mitigation for the adverse effects that would be caused by the construction of the casting basin. To allow construction to proceed without delay, the Pittsburgh District formulated and implemented a $6.5 million mitigation plan. Forming this plan required a close partnership with the Joint Venture and BHP, and between February 2000 and July 2003, the archaeological data recovery by multiple government archaeological contractors proceeded concurrently with the construction.

With the necessary permit approvals obtained, the Joint Venture initiated construction of the basin by June 2000 (see Photos 4, 5). The two-level casting basin method would allow each segment to be assembled in the upper portion of the basin, which was located a few feet above the normal Ohio River pool elevation and was protected by an earth berm. A lower basin with additional depth was constructed next to the upper basin level. When each segment was floated, it would be positioned within this lower basin and then drawn out into the Ohio River for transport to the project site. The lower basin featured an opening into the Ohio River that was closed by a removable steel sheet-pile bulkhead structure that separated the casting facility from the river (see Photos 15, 16). The closure structure was composed of some 170 sheet piles with lengths of 50'-60' and 150 tons ofwalers32 and bracing. Total excavation of the two-level basin, the sedimentation control ponds, and the perimeter dikes amounted to approximately 120,000 cubic yards. All excavated materials were either used for development of perimeter dikes or were stockpiled locally at the site. Some 1,500 linear feet of roads and access was constructed.

31 Edwardo, response to interview questions, 3. 32 A "waler" is a horizontal timber or beam used to brace or support an upright member, such as sheeting.


Page 14

Once excavation and grading was complete, work began on constructing a system of reinforced-concrete grade beams that supported the weight of the segments as they were assembled (see Photos 130, 131 showing exposed grade beam system after removal of both dam segments). The grade beam system featured an integral drain system that would keep the base beneath the segments dry until they were ready to be floated. 33 By August 2000, Segment 1 was under construction in the completed casting basin.

Constructing the Segments

Each of the two dam segments formed a thin-shelled, hollow, reinforcedconcrete structure, flat on the sides and bottom with curved portions of the top that formed the ogee-shaped spillway34 of the fixed weir and of each gate bay (see Photo 23). Both segments included gate sills, a portion of the stilling basin35, and the lower portion of the five pier bases.36 Segment 1 measured 333' along the axis of the dam and 104' wide and included a fixed weir bay, a water quality gate bay to be used to aerate river water, and one standard gate bay. Segment 2 measured 256' along the axis of the dam and included two standard gate bays.37 Segment 1 had a total design weight of 11,600 tons, while Segment 2 weighed 9,000 tons.38 These dimensions and weights were constrained, in part, by the width of the navigation locks along the transportation route, as well as by the navigable depths in the channel and over the lock sills. Each of the gate bays between the piers measured 110' along the axis. The joint between the two segments occurred at Pier 3, and this pier was made 11' wider than the others to accommodate the connection joining the two segments.39

The construction method for the segments used a combination of precast concrete wall panels with cast-in-place concrete top and bottom slabs. Internal wall panels and the bottom slab of the segments were constructed of specially designed lightweight concrete (125 lbs/cubic foot) to conserve on weight and to control the depth to which the segments would sit in the water. Exterior wall panels and the top slabs of the segments were constructed of normal weight of concrete (145 lbs/cubic foot). An existing concrete ready-mix plant, located along the Ohio River near Beaver Falls, Pennsylvania, about ten miles

33 Miles et aI., "In the Wet Construction," 3. 34 A "spillway" is a passage for surplus water to run over or around an obstruction, such as a dam. 35 A "stilling basin" is a basin constructed to dissipate the energy of fast-flowing water, such as that from a spillway; it serves to protect the stream bed below a dam from erosion. 36 Miles et ai., "In the Wet Construction," 2. 37 Ibid., 3. 38 Pittsburgh District, Water Quality Management Plan, 2. 39 Miles et aI., "In the Wet Construction," 3.


Page 15

downstream of the casting basin, supplied all concrete for the dam segments. The concrete for the segments was manufactured at this plant and transported by truck to the casting basin for placement. Over 5,800 cubic yards of concrete was used in the construction of Dam Segment 1, while more than 4,300 cubic yards was used for Segment 2.

Design engineer Robert Bittner described the segments as a thin shell of the outer surface of the dam that was sealed off with bulkheads, floated to the construction site, and then filled with concrete. Because the segments were not constructed at the dam site, each segment had to be designed both for its ultimate function as part of a navigation dam and for its short-term role as a transportable structure that would float. As a result, each segment had to be analyzed for performance during launch, towing, positioning, ballasting, landing, and concrete filling.40

In early March 2000, the construction contractor began casting 438 reinforced panels of concrete that ranged from one to eighty tons in weight. These precast concrete units would form the interior and exterior walls of the floating segments. As units were completed, they were moved to the casting basin and stockpiled until they were erected. Precasting operations for the 438 units continued for approximately eight months. By August 2000, the precast concrete panels were being erected to begin building the two concrete dam segments, and in October 2000, the first concrete for the reinforced base slab for Segment 1 was placed. Concrete placement of the top and bottom slabs of Segment 1 continued through the winter of 2000-0 1 until the shell was complete (see Photos 6-14, 1 7-26). Internal bracing was then installed to structurally reinforce the segment for flotation and transport. By March 2001, the construction crew at the casting basin was erecting ten tons of steel bracing per week.41 Assembly of Segment 2 (see Photos 59, 70-77) began in early 2001, and work on completing Segment 1 continued through December 2001. In general, construction of the segments in the casting basin continued from August 2000 through December 2001.

40 Bittner, response to interview questions, 2. 41 Ivan Rostosky, remarks at dedication of Braddock Dam (transcript on file at U.S. Army Corps of Engineers, Pittsburgh District Office, May 27, 2004), 1.

Launching the Dam Segments


Page 16

Final checks of Segment 1 prior to its launch (flotation) were completed by a Naval Architect and Marine Engineer in June 2001.

Braddock Dam Segment 1 was floated from its casting platform on the morning of July 10, 2001. Three days earlier, the construction contractor began filling the casting basin with water from the adjacent Ohio River. Five large-capacity pumps ran continuously for this period so that the basin contained enough water to support the buoyant weight of the segment. During this period, engineers and contractor personnel held a continuous vigil of the launch operations to ensure that everything proceeded according to the detailed plans.

The segment, although composed of heavy concrete and steel rebar, had a hollow interior, and as the water level began to rise in the casting basin, the dam segment floated. Although mammoth in size, once afloat, it was relatively easy to position the segment over the lower basin with a simple system of air-operated winches and cables (see Photos 27-33). When positioning was completed and the segment secured, water was pumped back out of the casting basin by reversing the five large filling pumps. This emptying operating continued until the level in the lower basin was at the same level as the river level. At this point, the sheet-pile closure structure was removed, providing direct access to the Ohio River. Once Segment 1 had been removed from the casting basin, the construction contractor rebuilt the closure structure, and in January 2002 the process was repeated for Segment 2.

Transporting the Segments to the Outfitting Pier

The safe transport of Segment 1 required extensive planning and coordination efforts; beginning in January 2001, this process continued into July. To eliminate any high spots in the river that could interfere with the transport, the river channel was sounded and swept numerous times, and to identify potential problems with the towing process, a simulated dry run of the process was conducted, using a fleet of barges about the same shape and size as Segment 1.42 There was also extensive coordination with the towing industry and public media.

In the early morning of July 26,2001, transport of Segment 1 began. With the closure structure removed, crews began to draw the segment out of the lower basin and into the Ohio River using cables and winches. An assist towboat, MV Joe T, took control of the segment when its leading end entered the river.

42 Miles et aI., "In the Wet Construction," 5.


Page 17

The assist towboat continued to draw the segment out into the river until it could transfer its control to the primary towboat, the MV A. A. Vestal, a 3,200 hp diesel-powered twin-screw vessel.

With the segment successfully transferred from the basin into the river, the segment began its twenty-seven-mile journey from Leetsdale on the Ohio River to the Duquesne outfitting pier on the Monongahela River. The segment would be pushed up the Ohio and Monongahela Rivers by diesel-powered towboats, specifically the MV A. A. Vestal, assisted by the MV Joe T and MV Boaz, much as a series of coal barges would be transported. The transportation route required the segments to pass through the Dashields and Emsworth locks on the Ohio River, past the "Point" at Pittsburgh, and through the Monongahela Locks 2 at Braddock (see Photos 34-38, 39-42, 43-44, and 45-47, respectively). To ensure safe delivery of the segment, the towing speed was limited to an average of2.5-3.5 miles per hour during the entire journey, and river traffic was stopped on the sections of the river where the dam segment was to be transported.43 Transporting the segment up the Ohio and Monongahela rivers took most of one day, with Segment 1 moving through Monongahela Locks 2 late in the evening and mooring at the Duquesne outfitting pier after dark on July 26th. When the segment was successfully moored, the transport of Segment 1 was complete.

The transport of Segment 1 was a unique event, and advance press releases for it generated significant public interest. Spectators crowded the Sewickley Bridge on the Ohio River, the Smithfield Street Bridge on the Monongahela River, Pittsburgh's Point Park, and other public access points. The Pittsburgh District hired a helicopter with a mounted camera to videotape the transport between Dashields Locks and the Pittsburgh Point, and other video coverage was taken by local television stations. News reporters provided detailed media coverage of the event, stationing themselves at the various locks, as well as on a separate Pittsburgh District vessel that was following the segment.

While Segment 1 was being outfitted for setdown at the Braddock project site between July and December 2001, construction continued at the Leetsdale casting basin on Segment 2 (see Photos 70-77). The process for launching and transporting Segment 2 was identical to the process described above for Segment 1 (see Photos 86-97). The only difference was that Segment 2 was considerably shorter in length than Segment 1. The extraction and transport of Segment 2 to Duquesne took place successfully on February 27,2002, despite sub-freezing temperatures and winds gusting to over thirty miles per hour.

43 Dennis B. Roddy, "Big Dam Project Takes a River Journey to Braddock," Pittsburgh Post-Gazette (July 26, 2001): A-I.


Page 18

Media coverage and public turnout for this event was nearly non-existent, most likely because of the severe weather and the duplicative nature of a second transport.

Outfitting the Segments

Each segment was prepared for setdown at the Duquesne outfitting pier that was constructed during the initial phases of the project in 2000. For the outfitting process, the piers on each of the segments were extended vertically by 21 ' , and temporary steel bulkheads were installed on the upstream and downstream end of each gate bay and in the fixed weir bay (see Photos 48-58). Segments were equipped with positioning equipment, composed of cable winches and fixed horn guides, to provide alignment control as they were being set down onto the previously completed foundations. Outfitting also included the installation of an elaborate piping system that would be used for the controlled ballasting operation that would allow the segment to be set down in a controlled manner. In addition, work platforms, and vertical delivery pipes for filling the hollow segment with concrete after setdown were also included as part of the items added at the outfitting pier.44 All of the outfitting work increased the weight and draft of the segments to about 15.5'.

The process of outfitting the segments presented unique challenges for engineers and the construction contractor because the work platform was floating and not fixed. They had to use water ballast to keep the segments as level as possible as weight was added during outfitting. Outfitting work took approximately three months for each segment. After the dam was constructed, the outfitting pier was left in place for municipal use, in partnership with the City of Duquesne and the Regional Industrial Development Corporation.

Setting Down the Segments

Once outfitting was completed, each segment was transported downstream to the project site for set down. The transport of the segments was unique in that the towboat controlling the operation was positioned on the downstream side of the segment rather than the pushing side (see Photos 60-64). Transport to the dam site followed a tracking scheme that had been physically modeled by the Corps of Engineers' Waterways Experiment Station in Vicksburg, Mississippi. The model studies showed that towboat operators would have better control of the segment if attached in a "reverse" manner. The principal of the maneuver was to allow the current of the Monongahela River to do all of the work. The towboat maneuvered the segment from the outfitting pier



Page 19

into the river current, allowing the segment to drift downstream. The tow pilot applied power only to orient and position the segment safely under two railroad bridges and around the locks' upper guard wall and into its final setdown position. The Pittsburgh District mandated that the construction contractor and their towing subcontractor attend a demonstration of the Corps' physical modeling. Using a 1:100 scale model of the project site and automated towboat under various flow conditions, the contractor and their towing firm were able to conduct a mock run in October 2000 to "rehearse" the reverse maneuvers and tracking.

Once the segments were delivered to the project site for set down, cables from the winches that were installed during outfitting were extended to eight mooring piles that had been installed in the river months earlier. The mooring piles consisted of drilled shafts that were smaller but similar to the drilled shafts used for the dam's foundation system. Using barge-mounted cranes and divers, the cables were extended and attached to each of the eight mooring positions. The segments could then be adjusted precisely about their comers and along their axes by operating the winches affixed to the segments.

U sing the mooring/positioning system with assistance from the towboats, each segment was precisely positioned over its portion of the foundation (see Photos 65-67). Precise positioning and control was critical to the setdown operation. Each segment had to land exactly onto its six setdown drilled shafts so they would line up perfectly with the flat-jack operated steel pistons that were located in corresponding locations at the bottom of the segment. The flat-jack operated pistons were used to level the segment before it was locked onto its foundations. In addition, the numerous drilled shaft recesses cast within the bottom of each segment had to align exactly with each of the segment's foundation drilled shafts; each of the segment's drilled shafts had a 5' structural steel shear-pin extending from it, and each shear-pin had to extend into its corresponding recess, and the seal surrounding the recess had to make positive contact with the edge of the foundation drilled shafts. At a later date, the contractor could then fill the recess and surround the structural pin with high strength grout. This connection was essential to permit the structure to interact with the foundation system in the way the designers intended.

Once the segment was positioned, the slow process of set down began (see Photo 68). Water was pumped into the hollow compartments of the segments in a specifically designed sequence so the segment would sink in a controlled and level manner. If the segment became misaligned at any time during the set down, the pumps could be reversed to remove water from any compartment. The ballasting system consisted of pipes that ran to each ballast compartment


Page 20

and small submersible pumps that could draw water out of each compartment (see Photo 69). Water was pumped out of the river for ballasting by three pumps with a pump rate of 5,000 gallons per minute. Over 3 million gallons of water were used to ballast Segment 1, and about 2 million gallons were used for Segment 2.45

As the segment slowly sank onto its foundations, its alignment was kept in correct position through a guiding tool, the positioning/mooring lines, towboats, and land-based survey control. Surveyors used land-based survey equipment to continuously check the alignment of the segment as it was set down. They placed tall poles topped with survey targets on the highest points of the segment so that these key dimensional points would still be visible to the land surveyors as the segment sank beneath the water surface.

Once the segment was firmly resting on its setdown drilled shafts, additional water was added to the segment to achieve a negative buoyancy that would prevent the segment from accidentally floating off, a situation that could occur when the rise of water in the pool was not offset by a corresponding rise in the bays. This negative buoyancy had to be maintained until the segment was grouted to the foundation's drilled shafts.

Operations to set down Segment 1 began at 5:00 am on December 5,2001. The operation was scheduled to occur within a forty-eight-hour period, from 6:00 a.m. on December 5 to 6:00 a.m. on December 7. During this time, the locks at Braddock were closed to all traffic. The actual setdown of the segment was completed on December 7, 2001, at approximately 10:00 pm.

Similar operations to set down Segment 2 began at 6:00 a.m. on June 17, 2002, with the actual setdown completed at approximately 6:00 p.m. on June 19, 2002 (see Photos 102-129). With Segment 1 in place, river flow was partially diverted through the Locks 2 river chamber to remove pressure against Segment 2 during its transport and setdown (see Photos 124-125). This process was accomplished through the use of the maintenance bulkhead system.

Grouting and Jnji/l Operations

After each segment was firmly resting on its set-down drilled shafts, workers began the grouting and infilling of the segments. All grout and infill concrete for these operations was manufactured at the concrete plant located near the dam abutment on the left bank. The various concrete and grout mixes were transported from the concrete plant to the points of placement by conveyors

45 Pittsburgh District, Water Quality Management Plan, 9.

46 Ibid., 7.


Page 21

and pressurized pump lines. Some materials had to be conveyed as far as onefourth mile from the plant to the point of placement, all within the allotted time limit (see Photos 81, 82, 84, 85).

Once each segment was securely set down, the 9" to 15" gap between the underside of the segment and the prepared river bottom was filled with a specially formulated underwater grout that would eliminate water flow beneath the segment. A total of 2,500 cubic yards of underbase grout was placed beneath Segments 1 and 2. Inflatable nylon grout bags had been installed beneath the segments earlier at the Duquesne outfitting pier, and these served as bulkheads to hold the underbase grout while it was being placed and to divide the area into smaller sections that would make for more manageable pours. The inflatable bags divided the area under each segment into transverse strips 70' wide, with five areas for Segment 1 and four areas for Segment 2. Once the segment was leveled, the inflatable bags were deployed and filled with grout. Divers fed grout into the bags through tubes that extended nearly the full length of the grout bag. Each grout bag, constructed of tear-resistant, high-strength geotextile, inflated until it came into contact with the gravel base.46

Each dam segment was then anchored firmly to its foundations by pumping a high-strength grout into the recesses that surrounded the structural shear-pin. In order to accommodate the short working time of the grout, which ruled out transporting the material, high-strength grout was mixed centrally in a specialized mixer located on the work platform. Water was evacuated through pre-installed return ports as the high-strength grout was pumped under pressure into the recesses. Pumping continued until the stream of grout emitted from the returns indicated that all water had been completely removed.

When this grouting procedure was completed, the compartments in each segment were filled with concrete in a two-stage process. In all, forty-two main compartments in Segment 1 and twenty-eight main compartments in Segment 2 were filled. The first stage involved filling the lower 8' to 16' of each compartment with a specially designed underwater concrete mix while the segment was still filled with water. The concrete was placed by tremie method47 into each compartment, one at a time, in a balanced checkerboard

47 The "tremie method" of placing concrete allows continuous placement of concrete without creating a large amount of turbulence in the water. This method involves using a rigid steel pipe with a hopper (the tremie assembly). The tremie pipe is sealed at the end to prevent water from entering it and is then lowered into the water until the sealed end of the pipe rests on the point of placement. The specially designed underwater concrete is placed in the hopper, filling the pipe completely. The tremie assembly is then lifted off the bottom a short distance so that


Page 22

pattern (see Photos 78-79). A total of 13,800 cubic yards of this specially formulated concrete was placed in Segments 1 and 2. The concrete mixture included chemical admixtures that prevented any cement from being washed out as the material flowed underwater. The volume of individual concrete placements for this stage of the operation varied between 30 cubic yards for the smallest compartments to 250 cubic yards for the largest ones. The water inside each compartment was displaced by the special underwater concrete and evacuated out of the compartments through preinstalled ports. The amount of water displaced varied between 6,000 to 50,000 gallons per placement. 48

Once the first-stage concrete had been placed and cured, the remaining water was removed from each compartment. The latent concrete was then removed from the top of the first-stage concrete through high-pressure washing49 to enable a more secure joint between the tremie concrete and the in-the-dry concrete that would be soon be poured on top of it. The interior walls of each compartment were also pressure-washed to remove any deposits that could prevent a bond between the infill concrete and the shell of the dam segment. 50

Each remaining open space was then filled with concrete of a different formulation than the first-stage concrete, and this concrete was placed in the dry instead of in the wet. 51 A total of 6,100 cubic yards of infill concrete was placed in the dry for Segments 1 and 2.

Constructing the Tailrace

As the segments were being filled with concrete, a tailrace52 was constructed contiguous with the downstream edge of the dam to prevent scouring from the high-velocity water that comes through the dam gates. The tailrace was constructed in-the-wet using a series of thirty-one interlocking precast concrete panels, each 30'6" wide x 20'0" long x 15" deep and precast at the project work area on the south bank of the Monongahela River at Duquesne (see Photos 139-146). Once in place, the panels were supported along their upstream edge by the concrete float-in segments and along the downstream

the weight of the concrete in the pipe breaks the sealed end and flows outward, burying the end of the tremie pipe. More concrete is added to the hopper, keeping the pipe continuously full of concrete until the placement is complete. During this process, the tremie pipe is always embedded in the concrete so that no water can enter and compromise the quality. 48 Pittsburgh District, Water Quality Management Plan, 10. 49 "Latent concrete" is concrete of poor quality. The concrete at the top portion of the tremie concrete in each cell would have contained a layer of loose concrete, as well as concrete that had been exposed to dirt and river water. 50 Pittsburgh District, Water Quality Management Plan, 10-11. 51 Miles et aI., "In the Wet Construction," 6. 52 A "tailrace" is the downstream part of a dam where the water enters the river again.


Page 23

edge by the previously constructed sheet-pile cut-off wall. The area beneath the tailrace panels was then filled with underwater concrete. This entire structure was supported by a system of steel H-piles driven down to the bedrock. Placement of the tailrace panels was underway in November 2002.

The in-the-wet construction process for the thirty-one tailrace panels began when they were transported on a barge from the precast site to their setdown position, located between two barge-mounted cranes (see Photos 139-141). The cranes lifted each panel onto a temporary stand where steel dowels were installed on the underside so as to provide good bonding material for the infill concrete (see Photos 142, 143). After the dowels were installed, the cranes lifted each panel again, the transport barge withdrew, and the panel was lowered about 30' underwater into place, so that each panel would bear on the downstream edge of the pipe piles of the downstream cut-off wall (see Photos 144-146). The first panel was placed adjacent to the river wall of Locks 2, and each subsequent panel was positioned using a guide attached to the previously set panel. Divers assisted in setting the panels and in making the necessary tolerance checks underwater (see Photo 138). Once the panels were installed, underwater concrete was placed by tremie method to fill in the space between the precast panel and the river bottom; the tremie placement of concrete was similar to that used to fill in the dam segments. Bulkheads included on some of the tailrace panels transversely divided the concrete pour area into five compartments. Each compartment was filled with two lifts of underwater concrete. 53

Constructing the Piers

The upper 39' of each of the five piers were constructed after the dam segments were filled in with concrete. Original design plans had called for these piers to be extended using a combination of conventional cast-in-place concrete and a series of precast panels 8" thick, but the plans were later revised per the construction contractor, who suggested using only conventional cast-in-place methods (see Photos 132-137).

The construction contractor used a conventional steel formwork system that could be moved upwards as each layer of pier concrete was placed. For each pier, a total of nine separate lifts of concrete were placed. As each lift was placed, it was consolidated with hand-held vibrator equipment to ensure that the aggregates and cement paste were homogenously distributed. Shortly after each lift of concrete had been placed but before it had fully cured, a highpressure surface treatment, commonly referred to as "green cutting," was used

53 Pittsburgh District, Water Quality Management Plan, 18.


Page 24

to remove any latent concrete from the horizontal surface. The curing of the pier concrete lifts took approximately fourteen days. During the curing process, the surface of the newly poured concrete was kept wet through plastic sheeting and wet burlap, while soaker hoses kept the burlap continuously moist. 54

Massively reinforced-concrete trunnion girders were also completed as part of the pier work; the purpose of each girder is to transfer the operating loads from the dam's four steel tainter gates into the piers. These structures were placed in a cantilevered position on the downstream ends of each pier. The dam gates pivot in a circular pattern on a set of trunnions, which are connected to these girders (see Photos 134, 135).

Operating buildings were constructed on the top of each pier to accommodate electrical and mechanical equipment for operating the tainter gates (see Photos 156, 178, 197-200, 244-246), and steel footbridges were erected between each dam pier, as well as between the dam and new piers that were constructed on the land, middle, and river walls of the locks (see Photos 152, 170, 234, 239, 243).55

Installing the Tainter Gates

Once the dam piers were completed, installation of the four steel tainter gates began. Each of the gates is 110' wide, and three of the gates are 21' high, while the special water quality gate is 12' tall. 56 The gates are mounted by their arms to the trunnions, from which they pivot in an arc to regulate water flow. Normally, tainter gates would be fabricated in three to five sections for assembly later at the site within a dewatered gate bay. However, for this project, the construction contractor proposed to build and install the gates in one piece. This innovative approach was a bold step on the part of the contractor and required almost eight months of advance planning and engineering efforts to bring to fruition.

The tainter gates of Braddock Dam are powered not by a conventional winchand-cable system, but instead by a series of hydraulic cylinders, with each cylinder having a 21" bore and a stroke of approximately 33'. A steel rod with a diameter of 9-1/4" extends from each cylinder to each side of the tainter gate. 57

54 Pittsburgh District Water Quality Management Plan, 12---13. 55 Miles et aI., "In the Wet Construction," 6-7. 56 Pittsburgh District, Water Quality Management Plan, 3. 57 Ibid., 3.


Page 25

The tainter gates for Braddock Dam were manufactured in Birmingham, Alabama, and transported atop specially designed deck barges by river to the Duquesne outfitting pier. Here, they received final painting and preparations for installation (see Photos 147-149). As this work was being done, bulkheads were placed in each gate bay and the gate bay was de-watered (see Photo 159). A pair of temporary steel support stands was then installed at each pier near the gate trunnions (see Photo 160). A temporary support system was also installed around each girder at the trunnion connection. These systems would be used to provide temporary support for the gates during the installation and assembly process. 58 After these temporary supports were installed, the gate bays were refilled to the level of the upper pool.

Each gate was then moved into place on the deck barge and positioned using towboats (see Photos 161, 164). After barge-mounted cranes had removed the upstream bulkhead (see Photos 162, 163), the towboat maneuvered the gate into the opening of the upstream gate bay (see Photos 165-168). Once the gate was in the approximate position, the towboat withdrew, and the bulkhead was replaced. The gates were precisely positioned by using pumps to manipulate the water level within the gate bay, adjusting the level of the barge with ballast water. Each gate was then attached to the temporary support system surrounding the trunnion girders that were anchored to the dam piers (see Photos 171-174). Once final alignment and adjustments were made to the gate, it was tested for proper tracking. The sides and bottom-sealing surfaces of each gate were also tested for water-tightness. Once these checks were completed, the gate trunnions were securely grouted to the girders and the final connections at the yokes were completed. All temporary support systems were then removed.

Two hydraulic operating cylinders were then installed on each gate, one per arm, and anchored to the upper pier structures (see Photos 153-155).

Once the gate had been installed, bulkheads were removed and installed in the next bay in which a gate was to be installed. All three of the standard gates and the smaller water-quality gate were installed using this procedure. Mechanical equipment was then installed, including the hydraulic and electronic equipment for raising and lowering the gates (see Photos 199, 200). Tainter gate installation took place in the summer of2003 and was complete by November of that year.

Concrete baffle blocks were also completed during the summer of 2003 (see photos 184-187). These blocks were cast in place in the dewatered gate bays,

58 Miles et aI., "In the Wet Construction," 6-7.

59 Ibid., 21.


Page 26

where they will dissipate the erosive energy and slow the velocity of water in the dam's spillway.

Installing the Closure Weir

The final task of completing the dam was the installation of a section of closure weir on the south (left) portion of the dam (see Photos 202, 205, 211, 212,241). The closure weir was positioned in a space between Pier 5 of Braddock Dam and the left abutment wall. The closure weir was composed of two sheet-pile cells 52' in diameter, three connecting arcs located between each cell, and two closure sections between the cells (see Photos 192, 194). The circular cells, made of steel sheet piling, were driven into the riverbed down to the bedrock, using conventional pile-driving equipment. Existing mud and silt in the cells was removed or leveled off and jet-grouted to make the soil impermeable (see Photo 201). A series of underwater concrete placements then filled the cells and arcs, forming cylinders and arcs of concrete, banded with steel. A total volume of 15,000 cubic yards of underwater concrete was placed into the closure weir.59 After existing Dam 2 was demolished, a reinforced, cast-in-place, concrete cap of variable thickness was installed to complete the left closure weir.60

Construction of the closure weir also included completion of the abutment on the south (left) end of the dam. Initial work to construct the left abutment was completed under a separate construction contract in 1998. The remaining unfinished work at the left abutment included installing the remaining rock anchors, installing weep holes, and completing a reinforced-concrete wall facing. Sixty-three pre-stressed rock anchors were installed along the length of the left abutment wall, using a temporary cofferbox that the construction contractor had elected to use for this work (see Photos 179, 180, 188, 193). Ground water levels behind the abutment wall site were maintained at l' above the river elevation by a system of wells that drew water out of the backfill material and reduced the hydrostatic pressure on the back of the wall until the anchors could be completed. Holes for the rock anchors were drilled using conventional track-mounted drilling equipment (see Photos 189, 195, 196). After the rock anchor installation had been completed, ninety-three weep holes were drilled in the caisson wall at the abutment site, and the left abutment wall was faced with 12" of reinforced, cast-in-place concrete (see Photos 203, 204, 213).


Demolishing Dam 2


Page 27

Once the new Braddock Dam was able to maintain the navigation pool, the final task of demolishing the existing fixed-crest Dam 2 began. This process included removing the original 1902-06 concrete of the fixed -crest dam, the associated timber piles or crib work, the concrete poured in subsequent repairs and modifications, and the associated scour protection below the dam. A 120' section of the dam near the center was chosen for the initial breach. Controlled explosive charges were loaded into drilled holes that were lined with plastic sleeves extending above the river level (see Photos 205-207). Extensive public notifications were made in advance to the media, U.S. Coast Guard, and navigation industry, and large crowds lined all convenient vantage points on the scheduled demolition day, March 27, 2004. Although the notifications warned of a possible slight rise in river level as the water between the two dams was released through the breach, this phenomenon did not occur. The blast fractured the concrete in place for subsequent removal by excavating equipment. Instead of a dramatic rush of water through a breached hole, a brief dark staining of the flow over the dam was all that resulted (see Photos 208,209).

As the breach was opened by barge-mounted excavators, the river elevation behind the dam gradually lowered to the elevation of the lower pool, leaving old Dam 2 protruding above the river level. Sequential sections of the dam were similarly blasted and removed with heavy machinery (see Photos 210, 211,221), with the final blast of the dam occurring on April 19, 2004 (see Photos 222-223). Dam sections within 50' of the locks and abutment were drilled and fractured with heavy impact equipment. To re-use some of the disposal material in a beneficial manner, some of the concrete fragments were transported about one mile downstream (see Photo 219) and placed in the shallows of the left descending bank to improve fish habitat. 61

Once Dam 2 had been removed and the left abutment wall was completed, a new scour protection system consisting of large boulder-sized stones was placed downstream of the new dam and along the left abutment. 62 By May 2004, existing Dam 2 had been completely removed.

Reflections on the Project and Applications for the Future

A dedication ceremony for the new Braddock Dam was held aboard a riverboat on May 27,2004. The end of construction at Braddock Dam brought

61 Pittsburgh District, Water Quality Management Plan, 3. 62 Ibid., 26.


Page 28

to a close a very significant and innovative construction process that influenced and continues to influence the construction of lock and dam projects, as well as the planning for future navigation dams. The construction of Braddock Dam was the first use of in-the-wet construction for an inland navigation dam in the United States. As of2004, five additional U.S. Army Corps of Engineers construction projects currently in the design phase have decided to apply in-the-wet construction methods similar to those used at Braddock Dam. 63

Asked to reflect on the project, many of the construction team members had thoughts on what worked well in the project and what future dam builders could learn from this project. Kirk McWilliams, the government's project field engineer throughout the work, remarked on the prefabrication of the dam's tainter gates, as opposed to the traditional method of constructing the gates on the construction site. He stated:

Installation of the tainter gates themselves was something that was innovative, in my opinion, because the designers had envisioned building these gates in pieces, and then welding these big steel pieces of gate in place in the gate bays. And this contractor had come up with a method to actually completely fabricate them in the shop, load them onto a barge, float them into place, and just hang them in position, all in one unit. And again, it was something that we looked at kind of skeptically at first, but then we were impressed with their approach. Actually, it was a rather simple approach that they had come up with, but it worked beautifully.64

Mc Williams felt that steel tainter gates on future navigation dams would be prefabricated in a manner similar to Braddock Dam, and this technique would be one of the significant contributions of Braddock Dam to the development of future construction technology for dams.

There were many opinions expressed about the effectiveness of the in-the-wet construction techniques, the suitability for future projects, and the lessons learned. Kirk McWilliams felt that the set-down process was one of the most high-risk aspects of the Braddock Dam construction because of the severe consequences that could have resulted from any damage to, or loss of control of, one of the segments. McWilliams stated:

63 Edwardo, response to interview questions, 3. 64 Kirk McWilliams, interview by Roy Hampton, Pittsburgh (tape recording and transcript on file at Hardlines Design Company, Columbus, Ohio, July 1,2004),4.


Page 29

Setting it [a dam segment] down on its foundation to me involved the most risk because there was very little tolerance for error. The foundation was there, the drill shafts were constructed, and this segment had to be landed on that foundation very precisely, or it could be catastrophic. In addition, it is a very unusually shaped object. It is not symmetrical, so it involved a lot of coordination with the naval architects as this segment was being immersed, just to ensure that it stayed under control. And, we experienced a few minor problems with some leakage that we had to deal with, and so that, to me, could have been catastrophic. If anything had gone wrong at that point, there's a very good chance that the segment, piece of segment, would have been ruined and not repairable. And that could have just completely shot this job. As far as having to build another [replacement] segment, perhaps that was the riskiest part of all. 65

Robert Bittner also identified the positioning and setting down of the segments as the most risky part of the construction process. Bittner stated, "the highest risk was during positioning and landing of the segments. This operation required simultaneous threading of thirty-four tension anchors up into the pockets positioned in the bottom of the float-in segments. If anyone of the pre-installed tension anchors or pockets in the bottom of the dam shell had not been in the intended position, it would have been possible to punch a hole in the bottom of the float-in segment.66

William Karaffa, the Pittsburgh District's Project Engineer for Braddock Dam, also agreed that the construction, transportation, and setting down of the dam segments was the portion of the proj ect that had the highest level of risk.67 Bittner, McWilliams, Edwardo, and Karaffa all agreed that the transportation and setting down of the segments worked well and proceeded more smoothly than expected. Ben C. Gerwick Jr. felt that the success of the towing and transportation of the segments was completed as smoothly as it was because the Pittsburgh District and the joint venture contractors planned the operation in great detail before executing it. 68

The success of the transport of the Braddock Dam segments can be attributed to a number of factors. Because the Pittsburgh District had not completed a float-in construction project before, many experts were hired who had experience in these areas. The Jones-Traylor joint venture had experience

65 McWilliams, interview, 2. 66 Bittner, response to interview questions, 3. 67 William Karaffa, response to interview questions by Roy Hampton (e-mail communication, on file at Hardlines Design Company, Columbus, Ohio, July 7, 2004), 2. 68 Gerwick, response to interview questions, 2.


Page 30

dealing with float-in procedures for large structures. The naval architects involved with the project were also present when the segments were set down, and they constantly monitored their condition and the progress of the operation. 69

In-the-wet construction is being planned for a number of projects by the U.S. Army Corps of Engineers, and McWilliams thought that future projects could benefit from having smaller float-in segments than the ones used at Braddock. Mc Williams also felt that more space should have been left under the dam segments at the end of set-down process, since they had difficulties with the [under-foundation] grouting process for both segments after they were set down.7o However, in regards to segment size, Hemy Edwardo stated, "The scale of the Braddock Dam segments was dictated by the constraints of the lock chamber sizes downriver from Braddock. Larger segments are possible. Smaller is not necessarily better from a cost and/or quality standpoint."71

Most individuals associated with the design and construction of Braddock Dam that were contacted for this history thought that the in-the-wet construction methods used for Braddock Dam would have wide applications for future lock and dam construction. Ben C. Gerwick, Jr. and Robert Bittner both thought that the in-the-wet techniques used at Braddock would be more cost-effective on future inland navigation projects. Both felt that as future contractors become more familiar with and skilled at applying in-the-wet techniques to inland lock and dam projects, the efficiency of the construction effort would increase, leading to significant savings. Gerwick also thought that in-the-wet, float-in construction would be used on the majority of future river-control projects because of their potential to speed up construction and save costs.72

Karaffa thought that one of the main challenges of the project was related to the underwater, out-of-sight nature of the in-the-wet construction. Karaffa indicated that the Braddock Dam project required the same degree of construction accuracy as in-the-dry construction. However, since the in-thewet construction required much of the work to be done underwater, much of the precise work could not readily be seen by construction supervisors.73 Key surfaces of the segments were projected above the water surface with tell tails that could be read by land-based surveying equipment Sonar and manual

69 McWilliams, interview, p. 3. 70 Ibid. 71 Edwardo, response to interview questions, 3. 72 Gerwick, response to interview questions, 2. 73 Karaffa, response to interview questions, 2-3.

74 Ibid. 75 Ibid.


Page 31

sounding devices were also used to determine the alignment and elevation of the segments.

Karaffa also said that the structural reinforcement of the segments was a challenge. The segments had to be particularly strong to resist bending stresses that occurred while the segments were transported down the river. However, too much steel reinforcement could make the segments too heavy to travel successfully down the river. Each segment was basically limited to between 10' and 11' of draft due to depth constraints with the navigation channel and lock sills, so the weight of the segments had to be planned accordingly. Precise calculations were necessary to ensure the strength and floatability of the segments. In addition, engineers had to develop specialized materials and construction methods because of the pioneering nature of the project. Specialized concrete mixtures and placement techniques, for example, were developed specifically for Braddock Dam. The concrete that was to be placed inside and under the Braddock Dam segments had to be composed so it would not wash out, while still retaining a high level of strength once it had cured.74

Conclusion

The Braddock Dam project was significant as the first use of in-the-wet construction methods for an inland navigation dam in the United States. The project required cooperation between the U.S. Army Corps of Engineers and a large number of private consultants and contractors who played a vital role in design, planning, and coordination, as well as the actual construction of the dam. The Pittsburgh District's William Karaffa thought that one of the major achievements of the project was proving that multiple elements of a large dam construction proj ect could be completed concurrently, saving time and reducing costS.75 Bittner suggested that future development of a permanent U.S. Army Corps of Engineers central casting basin would eliminate the time and expense of building a new casting basin facility each time a new dam or lock was constructed using float-in construction.

The success of the two-level casting basin at Leetsdale for fabricating Braddock Dam has also influenced other projects, and a similar type of casting basin was chosen for the construction of floating pontoons for the New Hood Canal Bridge that is under construction on Puget Sound in Washington State. And, as further demonstration of the influence of Braddock Dam,

Sources:


Page 32

Canadian engineers have selected in-the-wet construction for a proposed dam and power plant on the S1. Lawrence Seaway in Montreal, Quebec.76

The completion of Braddock Dam has allowed the Pittsburgh District to eliminate the nearly 100-year old Dam 2, and once new locks at Locks and Dam 4 are completed, Locks and Dam 3 will be removed. This program of demolition and new construction will eliminate a navigation bottleneck by creating a thirty-mile unimpeded section of the Monongahela River from Braddock to Charleroi, which the Pittsburgh District maintains will be one of the most efficient waterways in the world. Edwardo compared the Lower Monongahela project to " ... turning an old country road into a superhighway. "77

Angelo, William 1. "Corps Goes 'In the Wet' to Replace Monongahela Dam." Inland Waterways 245, no. 9 (September 4,2000): 14.

Ben C. Gerwick, Inc. Promotional material for Ben C. Gerwick, Inc., August 9, 2004. On file at Hardlines Design Company, Columbus, Ohio.

Bittner, Robert. Response to interview questions by Roy Hampton, e-mail communication, August 9, 2004. On file at Hardlines Design Company, Columbus, Ohio.

Edwardo, Henry. Response to interview questions by Roy Hampton, e-mail communication, June 25, 2004. On file at Hardlines Design Company, Columbus, Ohio.

Edwardo, Henry. "U.S. Army Corps of Engineers Uses 'In the Wet' Construction Techniques for Braddock Dam to Save Time and Money." 2004. Unpublished article, on file at U.S. Army Corps of Engineers, Pittsburgh District Office, Pennsylvania.

Gannett Fleming, Corddry and Carpenter, Inc. A History of Navigation Improvements on the Monongahela River. March 1980. On file at U.S. Army Corps of Engineers, Pittsburgh District Office, Pennsylvania.

76 Bittner, response to interview questions, 5. 77 William 1. Angelo, "Corps Goes 'In the Wet' to Replace Monongahela Dam," Inland Waterways 245, no. 9 (September 4, 2000): 1.


Page 33

Gerwick, Ben C. Jr. Response to interview questions by Roy Hampton, email communication, August 10,2004. On file at Hardlines Design Company, Columbus, Ohio.

Harris, Cyril M., ed., Dictionary of Architecture and Construction (USA: McGraw Hill, 1975).

J. A. Jones Construction Company. Company Web site, http://www.jajones.com (accessed Jun 17, 2004; site now discontinued; paper copy on file at Hardlines Design Company, Columbus, Ohio).

John Milner Associates, Inc. Monongahela River Navigation System Historical Engineering Evaluation. 1999. On file at U.S. Army Corps of Engineers, Pittsburgh District Office, Pennsylvania.

Johnson, Leland. The Headwaters District: A History of the Pittsburgh District, Us. Army Corps of Engineers. Pittsburgh: US Army Corps of Engineers, 1978.

Karaffa, William. Response to interview questions by Roy Hampton, e-mail communication, July 7, 2004. On file at Hardlines Design Company, Columbus, Ohio.

Karaffa, William, Henry Edwardo, and Andreas Huesig. "Innovativer Wasserbau 1m Ohio Valley bei Pittsburgh: Braddock Locks & Dam, Inthe-Wet Construction. " Binnenschifffahrt, noA (2002). On file at U.S. Army Corps of Engineers, Pittsburgh District Office, Pennsylvania.

Mc Williams, Kirk. Interview by Roy Hampton, July 1, 2004, Pittsburgh. Tape recording and transcript on file at Hardlines Design Company, Columbus, Ohio.

Miles, William, Robert Bittner, and William Karaffa. "In the Wet Construction of a New Gated Dam: Braddock Locks and Dam, Monongahela River. " 2002. Unpublished article, on file at U.S. Army Corps of Engineers, Pittsburgh District Office, Pennsylvania.

Pittsburgh District, U.S. Army Corps of Engineers. Lower Monongahela River Navigation System Feasibility Study, Interim Report, Volume 2 of 6, Engineering Technical and Real Estate Appendices, p. 3-8. December 1991. On file at U. S. Army Corps of Engineers, Pittsburgh District Office.


Page 34

Pittsburgh District, U.S. Army Corps of Engineers. "Nomination for New Braddock Dam, 2004 Outstanding Civil Engineering Achievement Award Program." Nomination submitted to U.S. Army Corps of Engineers headquarters, on file at U.S. Army Corps of Engineers, Pittsburgh District Office.

Pittsburgh District, U.S. Army Corps of Engineers. "Memorandum for Record. Subj: Administrative and Contractual Procedures for the Fabrication of New Dam 2, Locks and Dams 2, 3, and 4, Monongahela River, PA." September 18, 1997. On file at U.S. Army Corps of Engineers, Pittsburgh District Office.

Pittsburgh District, U.S. Army Corps of Engineers. Water Quality Management Plan for Construction of Braddock Dam, 2002. On file at U.S. Army Corps of Engineers, Pittsburgh District Office.

Roddy, Dennis B. "Big Dam Project Takes a River Journey to Braddock." Pittsburgh Post-Gazette (July 26, 2001): A-I.

Rostosky, Ivan. Remarks at dedication of Braddock Dam, May 27,2004. Transcript on file at U.S. Army Corps of Engineers, Pittsburgh District Office.

Traylor Bros., Inc. Company Web site, http://www.traylor.com/wpshtmllAbout/Historyl (accessed Jun 17, 2004).

Supplemental Material:

The following HAER documents have been completed for the Monongahela River locks and dams:

HAERNo. PA-299 Monongahela River Lock & Dam No.7 River Mile No. 85 Greensboro Greene County Pennsylvania

HAER No. PA-385 Monongahela Navigation Company Lock & Dam No.7 River Mile No. 82.5 Greensboro vicinity Greene County Pennsylvania

HAER No. PA-558 CC No. PA3774 Monongahela River Locks & Dam No.2 Braddock Vicinity Allegheny County Pennsylvania

HAER No. PA-559 CC No. PA3775 Monongahela River Locks & Dam No.3 Elizabeth Vicinity Allegheny County Pennsylvania

HAERNo. PA-560 CC No. PA3776 Monongahela River Locks & Dam No.4 Monessen Vicinity Westmoreland County Pennsylvania

HAER No. PA-563 CC No. PA3785 Monongahela Navigation System Pittsburgh Vicinity Allegheny County Pennsylvania

HAER No. PA-564 Monongahela Navigation Company Locks & Dam No.2 Monongahela River Locks and Dams Port Perry Vicinity Allegheny County Pennsylvania

HAER No. PA-565 Monongahela Navigation Company Locks & Dam No.3 Monongahela River Locks and Dams Elizabeth Vicinity Allegheny County Pennsylvania


Page 35

Historian:

HAER No. PA-566 Monongahela Navigation Company Locks & Dam No.4 Monongahela River Locks and Dams North Charleroi Washington County Pennsylvania

HAERNo. PA-567 Charleroi Boatyard Monongahela River Locks and Dams North Charleroi Washington County Pennsylvania

HAERNo. PA-568 Pittsburgh Engineer Warehouse & Repair Shops (PEWARS) Monongahela River Locks and Dams Emsworth Vicinity Allegheny County Pennsylvania.

HAERNo. PA-635 Braddock Dam Monongahela River Locks and Dams Braddock Vicinity Allegheny County Pennsylvania

HAERNo. WV-75 Tygart Dam & Reservoir Monongahela River Locks and Dams Grafton Vicinity Taylor County West Virginia

Roy A. Hampton III Hardlines Design Company


Page 36

Braddock Dam, current site plan


Page 37

(On file at U.S. Army Corps of Engineers, Pittsburgh District Office)

BRADDOCK DAM HAER PA-635 Braddock vicinity ......The U.S. Army Corps of Engineers, Pittsburgh...

Documents

Transcript of BRADDOCK DAM HAER PA-635 Braddock vicinity ......The U.S. Army Corps of Engineers, Pittsburgh...