U.S. Department of Transportation
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Federal Highway Administration Research and Technology
Coordinating, Developing, and Delivering Highway Transportation Innovations
This magazine is an archived publication and may contain dated technical, contact, and link information.
|Publication Number: FHWA-HRT-2006-006 Date: September/October 2006|
Publication Number: FHWA-HRT-2006-006
Issue No: Vol. 70 No. 2
Date: September/October 2006
A walk-through of the SEIS on the demolition of the old Jamestown Bridge over Narragansett Bay demonstrates how debris can be reused as habitats for marine life.
|Rhode Island's new Jamestown-Verrazzano Bridge parallels the old span, shown here partially demolished. The two bridges are only 30.4 meters (100 feet) apart.|
In the early 1980s, the Rhode Island Department of Transportation (RIDOT) and Federal Highway Administration (FHWA) approved replacement of the Old Jamestown Bridge, which was built in 1940 and had weathered the storms of Narragansett Bay for 66 years while carrying Route 138 over the west passage of the bay to link Jamestown and North Kingstown. Although construction of the new Jamestown-Verrazzano Bridge was completed in 1992, the Old Jamestown Bridge was not removed until 14 years later.
During the intervening years, removal of the old bridge remained a condition of the permit granted by the United States Coast Guard for construction of the new structure that replaced the old bridge. In 2003, the Coast Guard ordered RIDOT to remove the old bridge due to safety concerns, and the towns of North Kingstown and Jamestown also requested that RIDOT demolish the obsolete structure. Because removal of the old span remained a commitment under the environmental impact statement for the new bridge, RIDOT was legally obligated to proceed.
"The question was not whether it was to be removed, but what would be the easiest, most environmentally friendly, and most cost-effective method of removal," says RIDOT Chief Engineer Edmund T. Parker Jr., P.E. When demolition of the Old Jamestown Bridge finally began in 2006, the contractor used explosives to demolish the structure in two initial stages, which took place exactly 1 month apart in April and May 2006.
In accordance with the National Environmental Policy Act, RIDOT prepared a supplemental environmental impact statement (SEIS) to address the effects of removing the old span and to identify and evaluate alternatives for the ultimate disposition of the bridge materials. Because the structure had to be removed for legal reasons, a no-build (or "no-action" in this case) alternative was not applicable. Accordingly, the project alternatives were all identical in terms of demolition but differed in the disposition of the resulting debris. The contractor would need to dispose of approximately 5,442 metric tons (6,000 tons) of steel and 32,895 cubic meters (43,000 cubic yards) of concrete. The debris will be reused to create fish habitats, plus it will provide beneficial recreational and economic opportunities for the towns near it.
|This image shows the through truss span of the Old Jamestown Bridge, just before it hits the water following the April 18, 2006, first controlled explosive demolition.|
In the draft SEIS, the agency identified three viable alternatives. Each option was evaluated in terms of its comparative merits and anticipated social, economic, and environmental consequences:
|Old Jamestown Bridge prior to demolition.|
The agency estimated that the most expensive alternative, landfill disposal, would cost between $20 million and $24 million, of which approximately $4.5 million would be incurred in landfill disposal fees alone. Barges would transport the concrete debris to an unloading site, and then trucks would take the debris to a landfill. The trucks would produce air quality, noise, and traffic impacts for the duration of the removal operations. Given that this alternative would result in the permanent consumption of a significant volume of landfill space and would provide little social or environmental benefits to the community, landfill disposal was not considered a prudent alternative.
The remaining two options differed primarily in the ultimate disposition of the steel debris. The artificial reef alternative would deploy all of the steel and concrete to construct the reef, while the hybrid alternative would recycle the steel and build the reef using only the concrete.
The two alternatives were expected to have similar impacts and benefits. Given the successes of artificial reef initiatives in other States, RIDOT believed that the placement of suitable bridge structure at selected barren ocean bottom areas would represent a unique opportunity to enhance marine habitat. This use would offer potential long-term recreational and economic benefits through the creation of new fishing and sport-diving opportunities.
In terms of impacts, both reuse alternatives would result in minor localized noise and air quality effects from the transport of materials to the artificial reef site, and short-term disturbances to bottom sediments. The hybrid alternative would offer material conservation and economic benefits through steel recycling, but also would result in short-term impacts from the processing and transport of the metal to a recycling facility.
"Under both alternatives, the short-term impacts would be outweighed by the potential long-term benefits of the creation of the artificial reef," says Parker. Both alternatives, at an estimated cost of $16 million to $20 million each, would represent significant economic and environmental benefits when compared to conventional landfill disposal.
|These workers are removing the deck of Old Jamestown Bridge during the preparatory work that preceded the first demolition.|
Section 1805 of the Safe, Accountable, Flexible, Efficient Transportation Equity Act: A Legacy for Users (SAFETEA-LU)—directs States to make debris from bridge demolitions available for beneficial use by a Federal, State, or local government, unless such use obstructs navigation. This directive applies to structures that are eligible for Federal assistance under the Highway Bridge Replacement and Rehabilitation Program. "Beneficial use" is defined as use of the debris for shore erosion control or stabilization, ecosystem restoration, or creation of marine habitat.
According to a March 2006 memorandum issued by M. Myint Lwin, P.E., S.E., director of FHWA's Office of Bridge Technology, "The recipient of the debris shall bear the additional cost of processing, delivery, placement, and use of the materials, and shall assume all legal responsibility for the placement of the debris. Preconstruction agreement should be established between the States and recipients of the debris, outlining responsibility, cost, and compliance with environmental laws and regulations. The agreement should include such language holding the owner of the demolished structures harmless in any liability action."
In 2003, RIDOT and FHWA approved the draft SEIS for distribution, identifying the second option—the artificial reef—as the preferred alternative. At the time, the two agencies preferred that alternative to the hybrid option because restriction of the reef material to concrete rubble would limit the opportunity to create a diverse series of artificial reefs for different purposes and user groups. Reef materials are evaluated based on their durability, stability, and nonpenetration. Old bridge structures with combinations of high truss, deck truss, and girders provide substrata for a variety of epifaunal organisms including barnacles, mussels, and hydroids. They also provide refuge habitat for the benefit of juvenile finfish. Concrete rubble from the bridge is ideal material for establishing benthic (sea bottom) lobster habitat.
|This drawing of RIDOT's original concept for the artificial reef project shows how the sections of girder spans could be used to form the reef.|
Preliminary analyses also indicated that any savings from the salvage of structural steel would likely be offset by the additional costs incurred in the materials separation, handling, and mobilization required for transporting the steel by barge to an unloading site for subsequent sale to a scrap metal salvage facility. Although steel of this vintage has higher carbon content than newer steel and therefore is potentially more valuable, it was not until the sharp rise in steel prices in 2004-2005 that the value of the metal components became great enough to justify the additional costs of handling.
RIDOT held a public hearing in 2003 to solicit comments on the draft SEIS. The hearing was followed by a 1-month public comment period, during which agencies, organizations, and individuals could submit written comments. After the comment period, RIDOT undertook an extensive reassessment of the proposed project and the preferred alternative.
In 2004, RIDOT and FHWA approved the final SEIS for distribution, with the hybrid alternative now selected as the preferred choice. The decision to redesignate the preferred alternative and recycle the steel was based primarily on the presence of lead-based paints on the structural steel elements.
Although there are no definitive studies or data documenting the long-term stability of lead-based paints in a marine environment, empirical evidence suggests that such material would not pose an environmental hazard if deployed as reef material. Nevertheless, based on the level of concern expressed by the public, the agencies decided that the omission of a potential (albeit unlikely) source of contamination would outweigh the potential benefits offered by steel debris in terms of reef diversity.
|A construction barge is approaching the old bridge to salvage the steel for recycling.|
During the public hearing and comment period following release of the draft SEIS, local commercial fishing organizations and individuals raised substantial concerns regarding three proposed near-shore locations for the artificial reef: Gooseberry Island, Black Point, and Sheep Point. The stakeholders were concerned about the potential for a reef to adversely affect bottom trawling and trap fisheries in those areas. After careful deliberation on the merits of near-shore reef development, the three sites were eliminated from consideration.
During the public comment period for the final SEIS, RIDOT received further comments from the Rhode Island Commercial Fishermen's Association regarding the proposed Block Island site. Again, the concern was that creating a reef at this location would interfere with commercial fishing operations.
Conversely, natural resource agencies expressed a preference for creation of reefs at the largest feasible number of appropriate sites so that the environmental benefits could be extended as broadly as possible. Reconciliation of these competing interests was left to the Federal and State agencies responsible for issuing permits for artificial reefs. In the end, none of the sites selected were within the bay area; however, numerous deep water sites were used in the Rhode Island Sound.
Another public concern was potential impacts from the use of explosives. The final SEIS was revised further to address that concern. Other revisions involved avoidance and minimization of potential impacts on the local communities from construction noise and other impacts.
|Alternative||Estimated Total Cost||Advantages||Disadvantages|
|Landfill Disposal||$20-24 million||
|Artificial Reef||$16-20 million||
During preparation of the final SEIS, RIDOT conducted a comprehensive inspection of the trestle portion of the bridge. The agency had proposed that this portion, consisting of 305 meters (1,000 feet) from the West Abutment to Pier 28W, be retained for future development of a public recreational fishing pier. The inspection revealed, however, that this part of the bridge was extremely deteriorated, with critical deficiencies in the concrete deck and trestle portion of the bridge. After evaluating the inspection data, RIDOT concluded that the existing trestles were structurally unfit for a pier and that rehabilitation was neither practical nor economically feasible. Accordingly, the scope of the proposed demolition and removal was broadened to include the entire bridge.
Through further coordination between RIDOT and the Coast Guard, the original requirements for removal of the bridge piers, as stipulated in the permit for construction of the new Jamestown-Verrazzano Bridge, also were modified. The Coast Guard allowed for the pier footings to be cut off at elevations at or above the natural bay bottom, as opposed to 0.6 to 1.5 meters (2 to 5 feet) below the seabed, as originally specified. The modification still provides adequate navigational clearances but offers several benefits:
|The pier column shown here next to a girder span will be cut off at an elevation at or above the natural bay bottom.|
The agencies and contractors identified several steps that would minimize impacts on the human and marine environments to the greatest extent possible. In addition, a major consideration was that the blast force and flying debris from demolition of the old bridge should not damage the new replacement bridge. RIDOT incorporated the following specific measures in the project:
During development of the final SEIS, several agencies raised additional issues about the reef sites. Once again, the Rhode Island Commercial Fishermen's Association believed that the offshore reef locations would affect commercial marine fisheries because the proposed Block Island site is located well within the boundaries of regularly used commercial fishing grounds. Usage of these fishing grounds was well documented by the Rhode Island Coastal Resources Management Council and the Rhode Island Commercial Fishermen's Association.
The Rhode Island Department of Environmental Management (RIDEM) noted that the final SEIS did not mention the presence of eelgrass along the western shore of Conanicut Island, near the old bridge. The spatial extent of this resource needed to be identified and mapped prior to initiating the project so that the eelgrass could be protected.
The U.S. Environmental Protection Agency (EPA) supported the pro--posed changes to the project plan because the modifications would help reduce impacts on existing aquatic habitats by recycling the steel members and avoiding the placement of concrete in shallow water areas. EPA officials also supported measures to monitor and modify the new artificial reefs to clarify the steps that might be needed if the reef does not function as intended.
|The first blast ("event 1") removed the center through truss superstructure so the steel could be recycled. The second blast ("event 2") took place 1 month later and removed the deck truss and girder spans on either side of the center section as well as the two center piers.|
RIDEM officials noted that in the model used to predict the estimated larval mortality from a 1.4-kilogram (3-pound) confined blast, the researchers only studied the effects on cunner, tautog, and goby, under the assumption that these are the only species with swim bladders, which are subject to impacts from explosions. The most abundant larval species, bay anchovy, was not included in the model because it was incorrectly assumed that this species does not have a swim bladder. RIDEM officials determined that the greatest impact on important fisheries resources in Narragansett Bay, including lobster larvae, would occur if blasting took place during the warmer months of May through September, but that period also represents the best construction season.
In terms of blast impacts on other animals, seals are not threatened or endangered, although covered under the Marine Mammal Protection Act, and whales and dolphins are rarely seen in Narragansett Bay. All species of sea turtles are either threatened or endangered. Several species occasionally are spotted in the bay during the summer months. Although EPA officials agreed that changes to the artificial reef component of the project would help alleviate many concerns, RIDOT also agreed to limit both underwater charge sizes and the number of allowable blast days in order to minimize disturbance to the ecology of Narragansett Bay.
Since the initial planning on the Jamestown Bridge replacement in 1992, some advances had occurred in research on the effects of resuspended sediments on marine organisms, specifically fish (including eggs, larvae, juveniles, and adults). Much of this research was derived from studies on dredging and resulting resuspension of sediments. The dredging research, although viewed with caution, can provide at least some insight for potential impacts on fish due to sediment resuspension.
EPA and RIDEM did not expect that adult and juvenile fish would be severely disrupted by sediment resuspension during demolition, as these motile organisms are capable of vacating disturbed areas. Fish eggs and larvae incapable of moving out of disturbed areas were potentially much more susceptible to harmful impacts. Recent literature suggests that some estuarine species may be particularly sensitive to suspended sediments. In a 2000 paper published by the U.S. Army Corps of Engineers' Dredging Operations and Environmental Research Program (DOER) in DOER Technical Notes Collection, D.G. Clarke and D.H. Wilber summarized the research. "The eggs and larvae of estuarine and coastal fish exhibit some of the most sensitive responses to suspended-sediment exposures of all the taxa and life history stages for which data are available," the authors reported.
This susceptibility appears to be highly species-specific. For example, experiments have shown lethal effects at suspended sediment dosages as low as several hundred milligrams per liter (mg/L) over a 24-hour exposure in certain species of larvae, while no effects were observed in some species at concentrations of more than 10,000 mg/L for 7 days. Two of the species in Narragansett Bay, Atlantic silverside (Menidia menidia) and white perch (Morone americana), are fish with the most sensitive lethal responses, exhibiting 10-percent mortality at concentrations less than 1,000 mg/L for 1- and 2-day durations, respectively, according to the findings of Clarke and Wilber.
Using a wide variety of published data, C.P. Newcombe and J.O.T. Jensen developed mathematical models to quantify the potential impacts of suspended sediment on a variety of freshwater and estuarine fish species. The empirical equations they developed and reported in a 1996 article in the North American Journal of Fisheries Management employed a "severity scale of ill effects associated with excess suspended sediments," which divided impacts into a 14-point scale, with 0 being no impact and 14 representing 80- to 100-percent mortality. RIDOT undertook an extensive reevaluation of the estimated fish mortality associated with underwater blasting and used more detailed information on the number of blast events, the timing of the blasts, and the size of the blasts allowed. Based on this evaluation, RIDOT projected total fish mortality between 1,600 and 4,700 fish. Although it is too soon to determine the actual impacts on the fish population, visual inspections noted very little impact from the current blasts.
|Severity||Description of Effect||Predicted Suspended Sediment Concentration (mg SS/L)|
|2||Abandonment of cover||0|
|4||Short-term reduction in feeding rates||0|
|5||Minor physiological stress||0|
|6||Moderate physiological stress||0|
|7||Moderate habitat degradation||0|
|8||Indications of major physiological stress||2|
|9||Reduced growth rate; delayed hatching||54|
|This table shows predicted concentrations of suspended sediment per liter after a 39-hour exposure for the eggs and larvae of salmonids and nonsalmonids.
Source: Newcombe, C.P. and J.O.T. Jensen. 1996. "Channel suspended sediments and fisheries: A synthesis for quantitative assessment of risk and impact." North American Journal of Fisheries Management, 16(4): 693-727.
Demolition of the Jamestown Bridge involved two major controlled explosions and about a dozen smaller ones. In April 2006, the contractor demolished the center truss section with its two adjoining deck truss sections using a blast that cut them into 6-meter (20-foot) sections. A series of explosions 1 month later removed the two long, low truss sections on either side of the center span. A third blast was planned to remove the two large center piers that held up the center span, but instead that demolition was combined with the second blast.
The contractor used two types of charges. The first were linear shaped charges—devices that resemble thin, flexible lengths of copper pipe—wrapped around key connecting points. The heat from the charges essentially burns through the steel, allowing the sections to separate and fall into the water. The bridge segments were fitted with a cable and buoy system to facilitate safe and efficient removal of the steel debris for salvaging.
The two main concrete piers and smaller piers were removed by boring holes into the concrete and inserting conventional blasting charges. Because the charges were confined within the concrete, the explosions emitted little flying debris and did not produce fireballs. Clearing the debris so that marine traffic could pass safely was scheduled to take about 4 weeks. A portion of the main channel under the Jamestown-Verrazzano Bridge was reopened 1 week ahead of schedule because RIDOT worked with the U.S. Coast Guard to establish a temporary channel after clearing a major portion of the 671 meters (2,200 feet) of deck steel.
"Taking the bridge apart using controlled demolition required less time and was safer and more cost effective than manual disassembly," says Parker. "The use of explosives in bridge demolition is a proven technology that has been used throughout the United States."
All the demolitions were weather-dependent, and the first blast was delayed 2 weeks in April because of poor weather conditions. Approximately 6 days of clear weather were needed before each blast to set the charges, precut the steel, and check the wiring.
During the major controlled demolitions, the adjacent new Jamestown-Verrazzano Bridge (Route 138) was closed for 2 hours (a plan was in place for up to a 4-hour closing), and during the minor controlled demolitions, it was closed for about 30 minutes. To avoid affecting commuting periods and weekend events, the closures were restricted to 10 a.m. to 2 p.m. on Tuesdays, Wednesdays, and Thursdays. Local roads in Jamestown were closed as well, and the police and contractor employees maintained a clear zone for spectators to view the demolition blasts. Motorists were encouraged to avoid the area, and emergency vehicles, such as ambulances, were permitted access just prior to and after the controlled demolition.
"Rhode Island residents approached this project like it was a giant Fourth of July fireworks display," says Parker. RIDOT deployed fixed and portable electronic message boards to indicate detours, and disseminated traffic information and announcements through the State's Highway Advisory Radio System. Motorists also were notified of the road closures through RIDOT's Web site, www.dot.state.ri.us, and newspaper notices appeared in the The Providence Journal and other local newspapers. "Overall, the demolition and artificial reef creation was accomplished without a hitch," says Parker.
|These citizens are watching the demolition from a safe distance.|
The successful demolition of the Old Jamestown Bridge is the first large-scale Rhode Island project to implement FHWA's policy for the "Use of Debris from Demolished Bridges and Overpasses," issued in the March 2006 memorandum mentioned earlier. The demolition of the Old Jamestown Bridge (including the ultimate disposal of the demolition material) required an unprecedented amount of coordination and cooperation from very unlikely groups of interested parties. The permitting and environmental process required time to collect relevant data and develop the most acceptable approach, not only to State and Federal interests but also to the local fishing and boating concerns.
Creating a marine reef in this manner involves a number of challenges. Responding to citizens needs should be the overarching goal and may require the State to accept positions that may not be backed by science. For example, although the risk of lead-based paint contamination may be minimal, it is a key aspect in the eyes of many environmental permitting agencies. For this reason, this risk may be unacceptable for any amount of lead-based paint on bridge elements in New England.
Finally, the creation of marine reefs effectively meets the needs and commitments of more than one Federal and State government agency. Although not everything will be constructed as designed, by providing access to shared information, training, and financial resources, these facilities can be a cornerstone for research on marine mitigation.
After the first two explosions in April and May 2006, the demolition moved into a new phase in June and continued through to the fall. All of the steel sections were removed from the bay bottom, and the concrete pier columns were brought down to the water level. Using a demolition device called a hoe ram, which employs a long arm with a jackhammer-like head, the contractor broke apart the columns without using above-water explosives. The use of mechanical demolition avoided the need to close the adjacent Jamestown-Verrazzano Bridge. Mechanical demolition does generate some noise, but the decibel level was lower than pile driving. Where dust was an issue, the contractor incorporated a water line mist spray into the operation. Now that the piers are demolished to the waterline, underwater explosive charges will remove the pier sections to a depth safe for navigation.
|The new bridge dwarfs the remains of the old one.|
Although the lessons learned in establishing relationships and developing procedures for material disposal will be valuable in the future, more followup studies by biologists and marine fisheries experts will be necessary to determine the actual success of the new artificial reef areas. RIDOT, working with the RIDEM, is committed to monitoring the reefs, and only time will tell regarding their success. Nevertheless, because of the RIDOT's sensitivity to the bay's importance, Rhode Island fisherman and recreational boaters will continue to enjoy the benefits of Narragansett Bay.
Dan Berman has served as assistant division administrator for FHWA's Rhode Island Division for the past 10 years. He has worked for FHWA for 32 years in transportation engineering, planning, and management at the regional level and at several division offices. From 1991-1996, he served as FHWA's first project manager for the $14.5 billion Central Artery/Tunnel (CA/T) Project in Boston, MA. He has a bachelor's degree in civil engineering from Lamar University in Beaumont, TX. He was a 1995 recipient of FHWA's Superior Achievement Award in recognition of his outstanding accomplishments on the CA/T Project.
For more information, contact Daniel J. Berman at 401-528-4560 or email@example.com.