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NEWS > MAR 2020

Our Oldest Wire Suspension Bridge
Helps Visualize the Past

Spanning the Delaware River from Lackawaxen, PA to Minisink Ford, NY, Roebling’s first suspension bridge is the oldest in the United States. By Pete Hildebrandt WWII

by Peter Hildebrandt

Published in the February Issue of Wire Rope & Sling Technology

Roeblings.
The Delaware River calmly flows under the bridge in this view from the New York side.

What we saw above our heads was something which came to be known as Roebling’s Delaware Aqueduct, also known as the Roebling Bridge: the oldest existing wire suspension bridge in the United States. Built in 1848 by John Roebling, the structure measures 535 feet, crossing over the Delaware River, from Minisink Ford, New York, to Lackawaxen, Pennsylvania. When first opened in 1849 as an aqueduct connecting two parts of the Delaware and Hudson Canal, it has since been converted to carry automotive traffic and pedestrians.

We tend to remember certain events from our past quite selectively at times, as if certain experiences were highlighted with a marker in our mind – whether we mean to do this or not. For myself, a certain summer job at a camp in the hills above the Delaware River stands out vividly for me. At the time, it was not something I was wanting to be doing. But the college program I was in required an internship of some kind; at the time that was my position of last resort.

As with Dickens’ opening line, it was the best of summers — and the worst. I survived, myself and my young charges somehow intact. In the course of learning about the topic of this latest article, I was brought back once again to that time in my life. The staff, as part of our training, took a grand canoe trip down the Delaware River above Port Jervis, New York. The best of times. River trips to new places are the best. As with life, every turn in the river became a new experience. Calmer waters gave way to furious whitewater, then back again, all with Nature’s beauty throughout. Thinking back, I can recall a brooding, dark structure in the distance, looming as we approached not far above our heads. But hawks, shorebirds, and keeping a lookout for rapids or shallow waters may have let the structure soon fade from conversation.

We may have pulled up our canoes and feasted on peanut butter sandwiches and Kool aid not far from the bridge. One thing I do know is few if any in the group had a clue what this artifact above us was, why it was there, or what it had been built for out here in rural land, bridging a river separating New York and Pennsylvania. But the rudimentary bridge soon would be important enough to be incorporated into a recreational and historical park system.

ORIGINAL INTENTION

We may find it hard to believe that this structure originally carried not vehicles, wagons, or trains, but water. Two types of fuel and materials, timber and anthracite were in motion at the time. This also caused a bottleneck. Precious time was wasted waiting for the chance to transport the different materials. Anthracite coal, mined in the mountains of eastern Pennsylvania, traveled the 108 miles of the Delaware & Hudson Canal where it was transferred to barges traveling farther up the Hudson River or down to New York City and locations up and down the Atlantic seaboard.

The transported coal ended up where the Delaware River was before being picked up on the other side after a ferry trip across the Delaware. A slack water dam that allowed the canal boats to be ferried across and enter the canal on the New York side, had been operating from 1829 until 1848. But when timber rafts floated down the river, the ferryboats containing the coal came to a standstill. The timber was heading down the Delaware for Philadelphia where it found use in the shipping industry.

Also in the 1840s the Erie Railroad came on the scene and started to weigh in on building a railroad up the river valley. In order to compete with the railroad, the rope ferry across the river reached the decision to construct an aqueduct across the river at the same junction.

Due to the fact that a landowner wanted too much money for the purchase of land in the vicinity when those involved went to firm up negotiations, two aqueducts ended up being constructed where the Lackawaxen and Delaware merged. The aqueduct across the Lackawaxen had two abutments.

Roebling also built aqueducts across the Neversink and at High Falls for a total of four, all for the Delaware & Hudson Canal. Just one of these structures – the crossing at the Delaware – remains today. At that time, the new system of aqueducts shortened the travel time for the coal-filled barges from 10 days down to eight days. Also eliminated was the bottleneck with the railroad tracks, brought on by competing transports of coal and timber.

The Delaware & Hudson Canal totaled 108 miles, including an astounding 108 locks in the system. In those days the anthracite coal, which was a much “cleaner’ and less sooty coal found uses in the varied industries up and down the east coast of the new country. Heating and fuel being the primary use until later, when coal ended up being utilized for more industrial usages. There was no steel industry then in Pennsylvania and New York, nothing like what would emerge in western Pennsylvania.

The aqueduct’s construction took some three years and technically it was a suspension aqueduct. “We don’t have a whole lot of documentation about the canal itself aside from a few drawings,” says Ingrid Peterec, Chief of Interpretation at the National Park Service’s Upper Delaware Scenic and Recreational River. “West of this site, in the mountains of central Pennsylvania, is the Allegheny Portage Railway National Historic Site.”

Here, hemp rope was first used on the railroad before the change was made to John Roebling’s first attempt at wire rope cable. And on the gravity railroad they used John Roebling’s cables as well. Roebling and others had seen the disastrous results of using hemp ropes, sudden injuries and deaths that came with the snap of the unpredictable nature of rope crafted from an organic fiber — no matter how thick. The Allegheny Portage Railway Historic Site contains another first, the first railroad tunnel in the country.

MODERN ENGINEERING IN ITS TIME

Finished in two years, the 901 foot tunnel took an incredible amount of labor, rock blasting, and breaks from the blasting while the rock dust settled. The Park Service has restored the tunnel and visitors are able to enter this 1830s engineering feat. I recently met some visitors to the park who chose not to attempt travel into the tunnel, which apparently has maintained its 19th century mystery while at the same time being reinforced for at least the next 100 years.

Back at the Roebling Bridge on the Delaware River, the nearby Zane Grey Museum contains other items of cultural interest from the 19th and 20th centuries. The aqueduct was purchased in 1980, while the park itself was established in 1978 under the Wild and Scenic Rivers Act. The Upper Delaware System preserves a stunning 73 miles of the historic river.

“The restoration of the bridge — originally an aqueduct — took some 15 years of restoration work to bring back its original appearance,” explains Peterec. “At the same time the work also included converting the structure to its function as a bridge. What is amazing is that most of the iron in the structure is original, though obviously the woodwork has been restored and replaced. “Just about all our visitors come up from the metropolitan area of New York and New Jersey. They also may not have heard of the Roebling Bridge when they see it. But they’ve certainly heard of the Brooklyn Bridge. This makes a nice connection for them.” As I try to recall my canoe trip down the Delaware, way back when, Peterec helps me with my recollection. “You would certainly not have missed the bridge from the river, traveling by canoe or raft. The bridge’s three icebreakers at water level would have kept you paddling so you avoided a collision.

“Viewers will then see what looks more like a wooden structure crossing the river as the cables are behind the wood, instead of how they originally looked. When the structure was an aqueduct the primitive wire rope suspension cables were clearly visible.”

The cables were crafted of iron, not steel, which was in its infancy as a constituent in wire rope cable. “What they did was to take single strands and they created seven bundles. Those bundles were then wrapped together to create one big cable; iron strands all twisted together to make up each of the cables on the two sides.

“It looks like one big cable but it is composed of over 2,000 strands of iron wires. Cables at that time were constructed onsite, just as was done with the Brooklyn Bridge. The iron came from Roebling’s “new” factory at Trenton, New Jersey.”

A MATTER OF NECESSITY

The canal opened in 1828, was enlarged after the 1840s, and finally closed in 1898. Russell F. Lord and John A. Roebling designed the bridge and supervised its construction. As mentioned above, two important local industries with conflicting needs brought about construction of Roebling’s Delaware and Lackawaxen Aqueducts: canal traffic and timber rafting. Since the mid-18th century, timber from the Delaware valley had been floated down the river to shipyards and industries in Trenton and Philadelphia.

The canal’s rope ferry crossing of the Delaware at Lackawaxen created a blockade, and there were actually numerous collisions with timber rafts headed downstream. In 1846, to alleviate both problems, the D&H Canal Company approved Russell F. Lord’s plan to substitute two new aqueducts in place of the rope ferry. Once several options were evaluated, Lord recommended designs submitted by Roebling, who had previously built a wire suspension aqueduct at Pittsburgh in 1845.

To raise the canal enough to allow the passage of ice floes and river traffic, Lord’s plan called for three locks to be built on the eastern side. An immediate success, the Delaware Aqueduct — which cost $41,750 — and the Lackawaxen Aqueduct — which cost $18,650, and of which only the abutments remain — reduced canal travel time by one full day, saving thousands of dollars annually.

After the canal closed in 1898, the aqueduct was drained and converted into a vehicular bridge. Eventually, the canal sides and towpaths (walkways for those pulling barges) were removed. It operated as a toll bridge for wagons and, later, motor vehicles until 1979. Portions of the D&H Canal, including the Delaware Aqueduct, were designated as a National Historic Landmarkin 1978. The Delaware Aqueduct is also designated a National Civil Engineering Landmark.

Roebling Bridge
The narrow road shows its intended use was not designed for today's traffic.

FROM PAST TO PRESENT

Today the National Park Service owns and maintains the Roebling Bridge as a vehicular bridge between Lackawaxen, PA and Minisink Ford, NY but it’s story spans over 160 years. Roebling’s Delaware Aqueduct, the oldest existing wire cable suspension bridge in the United States, was built in 1848 by the iconic engineer John A. Roebling, who later designed the Brooklyn Bridge. The aqueduct once carried the Delaware and Hudson Canal above the Delaware River.

The aqueduct, a national historic landmark and a national historic civil engineering landmark, underwent adaptive reuse restoration, and received the Presidential Design Award for its design as a one-lane vehicular bridge, referred to as Roebling Bridge. Other portions of the Delaware & Hudson Canal, also nationally significant, are located in the river corridor.

John Roebling’s plan to “build the canal above the river,” did compare in some sense to a conventional bridge, but his suspension design allowed more room for ice floes and river traffic. An immediate success, the $41,750 Delaware Aqueduct and the $18,650 Lackawaxen Aqueduct (no longer standing) reduced canal travel time by one full day, saving thousands of dollars annually.

The aqueduct operated for 50 years until the closing of the canal in 1898, and its conversion to a private toll bridge. As time passed the structure underwent a series of modifications. In around 1900, a new owner Charles Spruks, built a tollhouse abutting the New York side of the crossing. And through the years towpaths were sawn off and the wooden trunk walls were dismantled. The protective icebreakers, through lack of proper maintenance, disintegrated into the Delaware in time.

The Delaware Aqueduct continued to function as a vehicular bridge right up until 1979; the following year the National Park Service purchased the aqueduct to be preserved as part of Upper Delaware Scenic and Recreational River. During the course of restoration work, just about all of the Delaware Aqueduct’s existing ironwork — cables, saddles, and suspenders — remained the same materials as installed when the structure was first built.

The two suspension cables are made of wrought iron strands, spun on site under the direction of John Roebling in 1847. Each 8½-inch diameter suspension cable carries 2,150 wires bunched into seven strands. Laboratory tests in 1983 concluded that the cable was still “viable;” some of the wires even exceeded Roebling’s original specifications. The cable strands are held in place by wrapping wire, which was replaced in 1985, after almost 140 years of use. Roebling’s cast iron “pier saddles” still sit astride the cables as they cross original stone piers.

“Cable saddles” each hold a wrought-iron “suspender rod,” a bar with both ends hanging vertically from the saddle. Suspenders support part of the aqueduct/bridge flooring by means of a hanger plate.

The wooden superstructure, made of white pine, was replaced about every 25 years by the D&H Canal Company. The last surviving canal-era timbers were removed in the 1930s.

After the purchase in 1980, The National Park Service rebuilt the bridge’s superstructure from Roebling’s original plans, drawings, notes, and specifications in 1986, and in 1995, the wooden icebreakers, towpaths and aqueduct walls were reconstructed, restoring the bridge’s original appearance as an aqueduct. The bridge is now part of the Upper Delaware Scenic and Recreational River.

Today, visitors stroll across the former aqueduct, following the path taken by canal sojourners with their mules some 200 years ago. Where canal boats once slowly floated, modern vehicles now cross the Delaware River effortlessly.

ON REFLECTION

And just as I passed silently underneath the structure decades ago, not knowing anything about what the structure above my head had been, others today probably do not know this interesting fact from the past: That is that the builder of the bridge they are very familiar with, over New York’s East River, Washington Roebling also had vivid memories of the time his father involved himself with the Delaware Bridge’s construction.

At that time, John Roebling had recently suffered a debilitating accident to his hand and arm at his wire mill. The teenaged Washington Roebling in turn assisted his father with everything from writing to dressing — serving as nurse, secretary, and general aide-de-camp. During the winter and spring, the younger Roebling also accompanied his father as he toured and inspected canal bridge job sites, a risky venture Washington recalled years later.

“The country at that time was very wild and unsettled,” he wrote. Wolves could be heard howling at night ... I was only 12½ years old.”

The open sleigh ride should have seemed a perfect time for singing Christmas carols. Such was not the case. “A driving Northern sleet storm,” challenged them, “having no overcoat or underclothes I nearly perished from cold,” he recalls. “Never shall I forget that ride.” ... as I will never forget that canoe ride down the Delaware River when I first encountered that unknown structure that Roebling built.

 

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