| p>The first project manager we visited in this series | | | | base is too technically complex for me to explain |
| was General Leslie Richard Groves, the project | | | | here. Just bear in mind that this was all unexplored |
| manager responsible for the successful completion of | | | | territory for bridge building, Roebling and his team had |
| the Manhattan project. For our next remarkable | | | | to improvise these solutions on the fly, without |
| project manager we're going to go back a little | | | | having an opportunity to prove his methods with |
| further in time to the period just after the American | | | | pilots. If you're interested in the technique that |
| Civil War when the Brooklyn Bridge was built, directly | | | | Roebling used to sink his towers, there is a great |
| connecting Brooklyn with Manhattan. In those days, | | | | article in the Catskill Archives on the subject. Just visit |
| Brooklyn was the suburbs and Manhattan was the | | | | their website at: |
| business district so most people had to cross the | | | | The construction of the towers above the water line |
| East River to get to work. Up until the bridges | | | | was a much simpler process and the first tower was |
| completion in 1883, people crossed the East River in | | | | completed in May of 1875 and the second was |
| ferries; fine in the summertime but more problematic | | | | finished in July of 1876. The next challenge was the |
| in wintertime when ice could stop the ferries. By 1867 | | | | cables that transfer the weight of a suspension |
| New Yorkers had had enough inconvenience and | | | | bridge to its towers. |
| called on the New York Bridge Company to put | | | | Washington Roebling fell ill at this time to health |
| together plans for a bridge. The New York Bridge | | | | issues stemming from what divers call "the bends". |
| Company assigned a senior engineer to the project, | | | | The bends are caused by nitrogen bubbles in the |
| John A. Roebling, and made him responsible for the | | | | blood that don't dissolve as a diver returns to the |
| plans and the project. | | | | surface of the water too quickly. Compressed air |
| The Brooklyn Bridge took 16 years to build (from | | | | was used to keep the water from flowing into the |
| project initiation to completion) and our story spans | | | | caissons as the digging proceeded to the river |
| two generations of Roeblings - John and Washington, | | | | bottom. The use of the compressed air duplicated |
| father and son. John Roebling died as a result of an | | | | the problems that divers have when making deeper |
| injury he suffered while supervising the project work | | | | dives. We know now that a limit to the time a diver |
| in 1869. His foot was crushed by a ferry as he was | | | | spends at depth and a slow ascent are the two key |
| fixing the location of the first tower and he died 16 | | | | strategies to defend against the bends, but this |
| days later of lockjaw. His son, Washington Roebling, | | | | knowledge wasn't prevalent at the time Roebling was |
| took over the project and completed it. At the time | | | | building the bridge. Although Washington Roebling was |
| the bridge was built, it was customary for the | | | | incapacitated, he enlisted the help of his wife to act |
| engineer who designed a structure to take | | | | as lieutenant. Mrs. Roebling studied mathematics and |
| responsibility of managing the project which built it. | | | | engineering until she was able to carry Roebling's |
| The Roeblings were not only remarkable and forward | | | | instructions to the work site and oversee their |
| thinking engineers (the design and many technical | | | | implementation through project engineers. He never |
| innovations were the father's ideas), they were | | | | completely recovered from his case of the bends, |
| remarkable, persevering, and effective project | | | | suffering ill effects from it for the rest of his life. |
| managers. This article focuses on the project | | | | Roebling was lucky; fires, explosions, and the bends |
| management aspect of this project, but because | | | | would take the lives of 20 workers before the |
| Roebling senior was actually responsible for the plan, | | | | caissons were completed. |
| we give credit to both. | | | | Roebling made use of another significant innovation in |
| The construction of a bridge over such a long span | | | | constructing the bridge: steel for the 4 massive |
| (remember this was 1867) was the first technical | | | | cables that support the bridge. These 4 cables run |
| challenge that had to be overcome. The bridge has a | | | | from both sides of the river and over the two |
| total span of 6,016 feet and a main span length of | | | | towers. Up to that time no-one had ever used steel |
| 1,595.5 feet. To put this challenge into perspective, it | | | | to create cables for suspension bridges, they used |
| was not until 1890 that a bridge with a longer main | | | | iron. Roebling was constructing a longer, heavier |
| span was built over the Firth of Forth in Scotland. | | | | bridge than had been constructed to that point and |
| The technical challenges are the most interesting | | | | knew (or suspected) that iron would not be strong |
| aspect for the technical crowd, but the Roeblings | | | | enough to suit the purpose. He bucked conventional |
| also faced political challenges and safety challenges. | | | | wisdom, and the project budget, and chose to |
| The political challenges were mainly caused by the | | | | construct the cables from steel. As to whether iron |
| fact that the bridge started in one municipality and | | | | cables would have been sufficient, we'll never know |
| finished in another so the Roeblings were faced with | | | | but we do know that Roebling's steel cables were. |
| satisfying two key stakeholders with sometimes | | | | The bridge was initially designed for foot traffic, |
| competing interests. Further challenges were provided | | | | horse drawn traffic, and trains. The trains would run |
| by increasing jealousy from competing engineering | | | | on two elevated tracks, the horse drawn traffic on |
| firms. The project started with a budget of | | | | four lanes below, and the foot paths were on an |
| $7,000,000 (excluding land) which was a huge sum in | | | | elevated promenade above the train tracks. The two |
| those days. As the project moved forward the | | | | train tracks meant the bridge had to be constructed |
| budget gradually increased to $12,000,000. Safety at | | | | to carry heavy loads so each cable was constructed |
| construction sites doesn't become a major issue until | | | | to carry a maximum of 11,200 tons. Each cable was |
| a completely new and untried approach to building is | | | | 15" in diameter and consisted of 19 strands containing |
| used for the first time. Inventing the technical solution | | | | a total of 5,434 individual wires! Roebling used vertical |
| is one challenge. Now find a solution that produces | | | | cables suspended from the 4 main cables to suspend |
| the deliverable that can be performed safely! | | | | the bridge and then added stiffening trusses to make |
| Another problem faced by Roebling was the financing | | | | the bridge wind proof. |
| of the bridge. The financing came from a rather | | | | Construction of the bridge proper began in 1879 after |
| complex set of subscriptions from both municipal | | | | completion of the two towers and rigging of the 4 |
| governments and private industry. Financing was not | | | | main cables. By 1883 the bridge was completed and |
| always received according to the project plan which | | | | ready for its grand opening. Though Washington |
| not only made completion of the project to any sort | | | | Roebling was unable to attend, his wife represented |
| of schedule difficult, it also increased the cost of the | | | | the Roebling interests and officially opened the bridge. |
| project. | | | | The project was to have one last brush with tragedy |
| John Roebling was assigned the project in May of | | | | that day. A lady pedestrian ascending the stairs to |
| 1867 and submitted his plans, surveys, and estimates | | | | the walkway tripped and fell, screaming as she did. |
| for the bridge in September of that year. The plans | | | | Her screams set off a panic amongst the rest of the |
| were turned over to a team of consulting engineers | | | | pedestrians on the bridge who thought her screams |
| provided by the army. The consulting engineers were | | | | were an indication the bridge was in trouble. In the |
| engaged to ensure the plans were properly done and | | | | ensuing panic, 12 people were killed and 35 seriously |
| that the project was feasible. The consulting | | | | injured. |
| engineers approved Roebling's plans with one minor | | | | The Roeblings, father and son, not only exhibited a |
| modification, that the height be increased by 5 feet | | | | remarkable degree of engineering skill in designing and |
| to a height of 135 feet, to ensure that marine traffic | | | | engineering the longest suspension bridge to have |
| would not be interfered with. Work commenced on | | | | been built to that date, they also exhibited a |
| the bridge on January 3, 1870. Unfortunately John | | | | remarkable degree of project management skill in |
| was not around to see work start on his project as | | | | seeing the project through to the end. Let's take a |
| he died the previous year but the work was passed | | | | look at a few of their project management |
| off to his son, another engineer, who had been | | | | accomplishments: |
| involved in one capacity or another from the outset. | | | | - Planning the project The Roeblings planned the |
| Washington Roebling received the first change | | | | successful completion of, what to that point was the |
| request for the project before work had actually | | | | longest suspension bridge. The plan was solid as |
| started. In the world of bridge construction your | | | | proven by its successful execution. |
| customers can easily understand the impact of asking | | | | - Customer management Don't forget that the |
| for a doubling in the bridges size after 80% of the | | | | Roebling's had two individual municipal governments to |
| work is completed. The change request was to | | | | satisfy. These governments did not necessarily share |
| increase the carrying capacity of the bridge to | | | | a common set of interests, and when they did share |
| anticipate future demand. This change was estimated | | | | a common interest, such as limiting the money spent |
| by Roebling to cost an additional 8% over the original | | | | on the bridge, these interests were not always in the |
| budget. The additional cost was accepted, the | | | | best interests of the project. The Roeblings |
| change accepted and Roebling changed the bridge | | | | persevered through the times when money was |
| plans accordingly. The next change originated with | | | | tight and succeeded in securing sufficient budget to |
| the project: it was determined that the original plan | | | | build the bridge the way they knew it should be built. |
| to use pilings as foundations for the twin towers of | | | | - Managing Change There were several sources of |
| the bridge was not feasible, the foundations would | | | | change during construction of the bridge. Some came |
| need to rest on bedrock which was 78 feet below | | | | from the stakeholders of the project, such as the |
| grade on the one side and 45 feet on the other. | | | | increase in scope of the bridge to handle an |
| The first project phase involved creating the two | | | | anticipated increase in traffic, or the increase in the |
| towers that form the structural base of the bridge. | | | | minimum required height, and others came from the |
| As mentioned, these towers are not only below the | | | | project such as the change from iron cables to steel. |
| water (approx. 80 feet) but between 45 and 80 feet | | | | The Roeblings handled the changes well, rejecting |
| below the river bed because they have to be set on | | | | changes that did not add value to the project and |
| solid bedrock rather than on pilings because of the | | | | implementing the ones which did with a minimum of |
| tremendous weight they bear. The problem to be | | | | disruption to deliverables and schedules. The |
| solved was how to dig an 80 foot hole 80 feet | | | | Roeblings were particularly adept at dealing with the |
| underwater? The solution Roebling chose was | | | | upsets that the bridge financing threw their way. The |
| caissons. Caissons are water tight structures that | | | | bridge was 90% funded by Brooklyn and Manhattan |
| carry workers who do the excavating. The caissons | | | | (New York) and 10% funded by private capital. The |
| are lowered into the water until they rest on the | | | | Roeblings survived a stock manipulation scandal, |
| river bottom. Compressed air is then pumped into the | | | | numerous budget increases, and the threat of a |
| caisson to create a breathable atmosphere. The | | | | discontinuation of funding altogether and still delivered |
| inspiration for this solution came from the diving bell | | | | the project. |
| which was the submersible of its day. The diving bell | | | | - Lessons Learned/Corrective Action/Changing the |
| worked on the same principal: a diver was locked in | | | | Plan Washington Roebling learned from mistakes on |
| the bell; compressed air pumped in then the diver | | | | the Brooklyn Bridge project, and other projects, took |
| was lowered into the water. | | | | corrective action when needed and did not hesitate |
| The caissons used for the Brooklyn bridge tower | | | | to make changes to the plan when it was clear to |
| were constructed of wood calked with pitch and | | | | him that they were warranted. A good example of |
| lined with steel and fit the footprint of the bottom of | | | | his ability to learn quickly and avoid unnecessary |
| the tower, 102 feet by 172 feet, plus 11 feet on | | | | mistakes on the project was his use of compressed |
| each side. This massive structure was lowered into | | | | air to enable work at the bottom of the deep |
| the water until it rested on the bottom, and then the | | | | caissons. The technology was fairly new but was in |
| construction workers began excavation of the river | | | | use at the time in diving bells. Washington Roebling |
| bottom. When they had reached the bedrock 80 | | | | adapted the technology to his purpose to enable the |
| feet (or 45 feet depending on which tower was | | | | men to work in the caissons. Keep in mind that as |
| being worked on) they began the construction of the | | | | the men excavated the silt at the bottom of the |
| actual tower which then rested on the caisson. | | | | caissons the water would want to rush in the |
| Manual excavation would have taken forever and | | | | opening this created. The compressed air served to |
| there were no machines which they could lower with | | | | keep that water out. |
| the caisson which could do the job so Roebling | | | | - Managing the Risks The first risk to be managed |
| decided to use dynamite to speed the process. | | | | during the construction of the bridge were the risks |
| Imagine the combination he was dealing with here. | | | | to the workers' safety. Although the record shows |
| The interior of the caisson had to be lit so the | | | | that 20 workers died while working on the bridge, |
| workers could see what they were doing and the | | | | the fatalities all occurred around the building of the |
| only light available at the time was gas light. The | | | | caissons, a new venture. Mitigation strategies were |
| atmosphere in the caisson was charged with | | | | implemented in an attempt to avoid accidents, such |
| compressed air and, to top it all off, the caisson was | | | | as the lining of the wooden caissons with iron but the |
| constructed from wood! Not what I would call a safe | | | | combination of compressed air, open flame and |
| working environment and, in fact, explosions and fires | | | | explosives were clearly more than this strategy could |
| did happen. That's why Roebling had the caissons | | | | deal with. Other project risks, which could be better |
| lined with steel to protect the wood and pitch from | | | | predicted, based on other bridge projects and other |
| open flame. | | | | municipal projects were well mitigated. An example of |
| Once the caissons reached bedrock, cement was | | | | those risks and mitigation strategies is the risk of a |
| hydraulically inserted beneath its floor to provide a | | | | stress fracture in any of the steel trusses or girders |
| solid, level platform for the tower and then the | | | | used to build the bridge. The mitigation strategy used |
| platform was built in place using the caissons as its | | | | was the testing of samples of all the components |
| foundation. The process that Roebling devised to | | | | using a hydraulic press. |
| build the tower in place and sink it onto the caisson | | | | |