By Margaret M. Barondess

Click on a photo to view a larger image. Black/white photos Otto Sorgenfrei, color photos MDOT

Throughout history people have been challenged by a desire to get to the other side of a natural or manmade obstacle. It is no wonder then that a fascination about building bridges exists. Constructing monumental bridges, in particular, raises questions about how its designers and builders have managed to span large distances without the structure falling down. Most of us have approached these immense engineering marvels puzzling over the story behind the bridge’s construction.

At 6,535 feet long, the Blue Water Bridge over the St. Clair River, between Port Huron, Michigan, and Point Edward, Ontario, posed unique construction challenges during the 1930s. Nearly sixty years later, construction of a second bridge just south of the first presented a rare opportunity to compare past and present experiences for these two structures.

The first serious effort to build a bridge across the St. Clair River tried to connect Port Huron, Michigan, and Sarnia, Canada. During the 1920s construction activities for the Ambassador Bridge between Detroit and Windsor inspired other private interests to pursue a second international crossing. Although Detroit had far more traffic, Port Huron served as an international crossroads with its rail tunnel and busy ferryboats shuttling people and goods across the river. The automobile’s explosive popularity compelled Port Huron investors to recognize the economic potential of a toll bridge. They hoped to vie with Detroit for business. Completing plans for a new bridge sprang up, fueling the race to win necessary government approvals and obtain financing for a construction project.

The behind-the-scenes promotion of the big bridge ventures plays as important a role as the engineering. Many great bridges have resulted from a promoter-engineer partnership. Successful bridge engineers recognized the importance of marketing a design and promoters acknowledged the importance of working with an engineer capable of creating an economical and beautiful bridge.

The St. Clair River project in the 1920s did not lack promoters. Four competing proposals emerged—one from Lyle Harrington, a leading bridge engineer from Kansas; another from local businessman Maynard D. Smith; a third from the Port Huron-Sarnia Ferry Company; and a fourth from a group made up of a Toledo investment company and several Sarnia attorneys. All the promoters faced many hurdles. The project’s international nature complicated matters, with two governments involved in the bridge building. The U.S. Army Corps of Engineers insisted that the bridge clear the water by 150 feet and that construction not interfere with channel activity. This meant that floating platforms or falsework in the water cold not be used in building the bridge.

With politics heavily influencing the decision about where to place the bridge, all four proposals called for it to extend from downtown Sarnia to downtown Port Huron. City officials in both municipalities feared economic damage to their central business districts if the proposed bridge were located away from the downtown areas.

Local businessman Maynard Smith hired Modjeski and Masters, a well-known Pennsylvania firm, in 1928 to develop the bridge’s design. Frank Masters first designed a suspension bridge, but turned to a cantilever through-truss design similar to the one eventually used. Port Huron and Sarnia both endorsed Smith’s plans and authorized him to proceed. Smith also convinced Congress and Canadian officials to approve the necessary permits so he could begin construction. The ferry-service owners tried to stall his progress and he had difficulty finding financing. The Great Depression later forced him to abandon the bridge completely, although he succeeded in giving it momentum. The dream of spanning the St. Clair River evolved from a private venture into a government-sponsored project.

Congressional representatives extended the construction permits and then passed a bill granting a state bridge commission the power to build and run a bridge as well as buy out the competition—the Port Huron-Sarnia Ferry Company. In 1935 the State of Michigan created a bridge commission capable of issuing bonds to finance the bridge’s design and construction. Bridge toll revenues would repay the bonds.

The most practical location for the bridge was between the small community of Point Edward and the former village of Fort Gratiot, annexed by Port Huron in 1893. This permitted a shorter, less costly bridge and offered better soil for structure support. The Fort Gratiot neighborhood consisted of a Grand Trunk Railroad facility and a residential area. Real estate prices were lower here than in downtown Port Huron. The bridge would also connect with the proposed Montreal-Chicago international highway. Michigan Highway Commissioner Murray E. VanWagoner eagerly promoted the project through state channels.

Modjeski and Master continued to work on the bridge’s design. Their choices of bridge types were limited, given the length of the crossing and the U.S. Army Corps of Engineers’ height and construction requirements. The firm considered a suspension bridge, similar to the Ambassador Bridge, and a cantilever through-truss. The site conditions favored the latter type. Because suspension bridges require tall towers with massive cable anchorages on land, Port Huron’s notoriously poor soils made it difficult to anchor a suspension bridge. Modjeski and Masters chose he cantilevered through-truss.

Monsarrat and Pratley, a Montreal design firm, completed a technical review of the Modjeski and Masters’ plans to ensure that they conformed with Canadian standards. Monsarrat and Pratley designed the Canadian approach spans under a separate contract. Because of the job’s international nature, officials treated the bridge’s main span as a joint venture; work for the approach spans fell to each respective country under separate contracts.

In the 1970s, increased traffic volume inspired bridge planners to begin to study the need for a second bridge. Similar to the situation fifty years earlier, the politically sensitive issue of where to locate the bridge preceded who would build and pay for it. However, the established bureaucracies of the 1970s were familiar with transportation planning and had the experience to conduct the needed studies.

The Ontario Ministry of Transportation and Communications (OMTC) and the Michigan Department of Transportation (MDOT) assembled an international team of engineers and transportation and environmental planners to direct the St. Clair River Crossing Study. The team selected three locations to examine: one adjacent to the existing bridge; another to the south that would link Marysville, Michigan, and Sarnia; a third location between Marine City and Sombra, Ontario. The study team wanted to learn if a new bridge at any of these three locations would divert enough traffic from the Blue Water Bridge to significantly extend its life. The study also looked at a tunnel option, but exorbitant costs quickly caused the team to drop it.

The study offered several short-term improvements to the existing bridge, including repainting the pavement markings to create a truck-climbing lane and expanding the Michigan-side bridge plaza. After holding public meetings and studying several alternatives recommended construction of a second bridge just south of the existing bridge.

The Canadian Blue Water Bridge Authority, which owned and operated the existing bridge, had already purchased right-of-way immediately to the south side of the bridge. A new bridge located there would require less displacement of property and homes than one to the north. A southern location would accommodate the expansion of the bridge plaza on both the American and Canadian sides of the bridge.

Once the location was established, MDOT began planning a new toll and customs plaza. The original plaza crated a bottleneck, causing traffic to sit on the bridge rather than flow across it, which placed undue stress on the bridge, especially when heavy trucks backed up in a row. Keeping the traffic moving meant a healthier bridge for a longer time. The new plaza was completed in 1997.

In 1981 planners hoped a new bridge would not be needed until the year 2000. However, traffic increased dramatically during the 1980s after both countries completed major freeways leading to the bridge. Michigan’s I-69 and Canada’s Highway 402 provided attractive low-traffic alternatives to the Detroit-Windsor crossing. In 1991, 6.1 million vehicles crossed the Blue Water Bridge, compared to the 1939 total of 310,000 vehicles. The bridge had reached its capacity; the time had come to build a second bridge.

Past and present methods of deciding what type of bridge to build across the St. Clair River vary mainly because contemporary environmental laws have greater influence in both Canada and the United States. These laws require increased public input and a public record of the decision-making process. American and Canadian experts joined the team responsible for analyzing designs for the new bridge. They selected five bridge types for detailed analysis: a cable-stayed bridge; a duplicate of the Blue Water Bridge; a parallel-chord truss bridge; a continuous, tied-arch bridge, and a single-span tied-arch bridge. The team evaluated the designs for maintainability, durability, constructability, cost and aesthetics.

Historic preservation interests also influenced the analysis. Because the National Parks Service declared the Blue Water Bridge eligible for listing on the National Register of Historic Places in 1983, MDOT asked the Michigan State Historic Preservation Office (SHPO) to comment on the design selection process. The SHPO challenged the evaluation team to consider “how the bridge alternatives may affect the value of the existing bridge as a historic resource by including consideration of such aspects as changes to traditional views of the Blue Water Bridge and preserving or enhancing the uniqueness of the existing bridge.” As a consequence, the sixth evaluation criterion of “heritage” was added to the analysis.

The study team used a scoring method to evaluate the designs. A three-part rating system included scores from the bridge engineering team, the environmental team and the public. The visually unappealing parallel chord truss and the single-span, tied-arch bridges were dropped. Debate quickly heated up over the three remaining designs when public opinion and the study team’s conclusions clashed.

The engineering team preferred the cable-stayed design because of its superior performance in durability, maintainability, cost and aesthetic appeal. First popular during the 1950s, cable-stay bridges have increasingly replaced suspension bridges for long crossings. The environmental team also rated the cable-stayed bridge slightly higher than the continuous tied-arch bridge. However, the SHPO felt that the continuous tied-arch bridge better complemented the historic Blue Water Bridge. Citing federal historic preservation standards, the SHPO noted that although the continuous tied-arch bridge was different in appearance than the historic bridge, the two bridges would still be compatible. “The height of the tied arch bridge is also compatible with…the character of the surrounding area, allowing the historic bridge and its new partner to remain the tallest structures in the immediate vicinity.”

Construction of a duplicate bridge would be confusing since each historic property presents a physical record of its time, place and use. If there were no historic bridge at this location, engineers would design and construct a bridge using a contemporary design and modern materials rather than a duplicate historic design. It was imperative that the new bridge not bring a sense of false history to the St. Clair River crossing. The cable-stayed bridge’s size, scale, proportions and massing did not complement the old bridge. The cable-stayed design offered a high visual impact, but the strong vertical statement made by the towers competed with the rounded arches of the existing bridge.

Public opinion strongly favored construction of a duplicate Blue Water Bridge. The original dominates the local landscape and has become a symbol of local identity. The bridge’s image appears on the stationary of Port Huron’s tourist/visitor agency and on police and fire department patches. Port Huron and Point Edward residents maintain strong emotional ties to the bridge and felt only a duplicate structure would suffice. They did not want the cable-stayed design.

Ultimately, the parties involved reached a compromise. The team recommended construction of a continuous tied-arch bridge that complemented the historic bridge design. At first, the chosen design created a public uproar, but as the new bridge took shape, the controversy faded.

In the case of both bridges, engineers tried to balance visual concerns with practical considerations. In the late 1920s, after Modkeski and Masters had selected a cantilevered truss for the original bridge, they were faced with aesthetic drawbacks, including an awkward appearance, high, pointed towers supporting the cantilevered truss over the water and poor transition between the main and approach spans. Recognizing the challenge of designing a beautiful bridge, Modjeski and Masters consulted with Paul Cret, a well-known Philadelphia architect, who had collaborated with the firm on other bridge projects.

Modjeski and Masters proposed two designs for the piers. The first called for stone or concrete supports at the river’s edge, under the main span and flanking anchor spans. According to one of the engineers, “the main span looked good but the large anchor piers appeared bulky, the eye insisting on returning to this focal spot rather than contemplating the entire effect.” The second successful design called for the construction of a concrete pier at the water’s edge and a steel tower to support the anchor span. The tower appeared less massive and eased the difficult transition between the approach, anchor and main spans with steel rather than concrete supports.

At MDOT’s request, Modjeski and Masters also modified the approach spans’ lengths, incorporating Cret’s suggestion to use longer trusses than originally proposed, thus reducing the number of supporting piers and improving the approach spans’ look.

Modjeski and Masters made the main span attractive yet economical by using an innovative, low-arch design that merged the traffic deck with the bottom structural supporting steel of the arch. One engineer exclaimed, “We may congratulate ourselves that we have crated a happy marriage out of necessity and discover that this bond is a happy, long lasting union.”

Sixty years later Modjeski and Masters, with its Canadian partners, Buckland & Taylor, Ltd., returned to the drafting table to work out the details of the new bridge. The two firms prepared documents for the main span and the two separate approach spans, coordinating the three projects to ensure an overall, uniform appearance.

The two firms faced many of the same visual issues as the earlier designers, with the additional challenge of making the new bridge compatible with the old one. When they discovered the arch on the new bridge would be higher than the arch on the other they flattened the arch to more closely match the old bridge and raised the main piers near the water’s edge. This forced the designers to re-think their design for the main piers. They decided to keep the basic form of the old pier, but give it a simple, contemporary look.

The engineers selected concrete hammerhead piers for the anchor and approach-span piers. The designers also used three box-girder spans on either side of the main span rather than constructing deck trusses similar to those flanking the old bridge. Literally composed of steel boxes, the supporting members offer a compact appearance and contribute to the clean lines of the new bridge. The view of the old bridge’s deck trusses is uncluttered. The Americans and Canadian took different paths to construction the approach spans for the original Blue Water Bridge. The largest difference occurred in the composition of some steel members. Canadian steel mills could not roll beams of sufficient size to meet all requirements, so they used built-up sections of steel unlike the single member used on the American approach. Each country used available materials and familiar technologies to build the approach. The same scenario occurred with construction of the new bridge. This time the Americas used precast, I-shaped concrete beams to build their approach; the Canadians chose precast concrete box girders.

Other noteworthy differences between past and present exist. The new bridge uses fewer, more cleanly detailed steel members. To keep the weight of the original Blue Water Bridge within acceptable limits, much of the steel in the old bridge consists of open lacing. Affectionately referred to as “bird’s nests” by those who maintain the old bridge, this designs tens to trap road salt and debris and is difficult to inspect, clean and paint. The new bridge uses enclosed steel. Built mainly of steel boxes, the smaller sections are sealed and the larger box girders have access doorways and interior lighting for inspection and maintenance.

Because the bridge is shallow where the top arch intersects the bottom structural steel, large temporary towers supported construction activities suspended over the water. Without the towers, the steel would have bent as it stretched over the water. Cables extended from the towers to the arch to hold it up until both sections could be connected in the middle. Construction of the old bridge did not require such towers. Because of its substantial depth throughout the length, the truss was self-supporting as it extended over the water.

Construction workers used different connecting techniques on the two bridges. The old bridge’s steel was connected by rivets installed with hydraulic riveting machines. The rivet, a metal pin with a head at one end, was heated to red-hot temperature and passed to a worker who then inserted the pin through a hole in the steel and hammered down the plain end into the head, locking it in place. Bolts and welding have replaced rivets in bridge building. Workers need fewer bolts than rivets to connect the steel because bolts are stinger. Bolts therefore cost less and have the advantage of being easily replaced and safer to use.

Construction techniques for the main piers on the old and new bridges differed significantly. The original Blue Water Bridge required two round concrete caissons, from twenty-four to twenty-six feet in diameter to support each main pier. Workers sank the caissons one hundred feet into the bedrock to provide a sturdy foundation. As each caisson sank, workers added concrete sections on top. Cranes scooped dirt and debris from the caisson’s hollow core to help lower it. Work on the Canadian side went smoothly, but the American encountered twenty-thousand-year-old logs buried by the glaciers forty-five to ninety feet beneath the surface. Next they hit a layer of heavy clay twenty-five feet deep that halted the caissons’ descent. Divers worked with pneumatic chisels inside the caisson to clear the debris, delaying the job a month.

The engineers planning the second span of the Blue Water Bridge decided to use steel piles driven into the bedrock to support the bridge’s main piers. Although noisy, the pile driving did not require the messy excavations associated with the caissons. The Americans were forced to clear debris a second time when they hit the concrete foundation of the former Peerless Cement factory.

Workers completed the original Blue Water Bridge is mere sixteen months for $3.2 million. The second bridge, which opened in July 1997, was finished in twenty-four months and cost $79.3 million. Both projects maintained exceptional safety records—only one construction-related fatality occurring on the original bridge.

The major ingredients needed to successfully complete both the historic and new bridges across the St. Clair River included forceful and persistent sponsors, reliable financing, a proper location, the right design and effective implementation. Despite some differences in planning, design and construction, the 1938 Blue Water Bridge and its modern companion illustrate how little has changed in the building of monumental bridges.

Margaret M. Barondess was the cultural resource coordinator for the Michigan Department of Transportation. This article first appeared in the July/August 1997 issue of Michigan History.