Land and W ater July/August 2005•57 by Shannon Renz Project Overview THE two existing U.S. Highway 17 bridges over the Cooper River in antebel- lum Charleston, S.C., are functionally obsolete, characterized by too-narrow lanes, limited capacity and substandard vertical and horizontal ship channel clear- ance. In an effort to improve traffic safety while increasing overall capacity, the South Carolina Department of Transportation (SCDOT) began the mon- umental effort of designing and con- structing a replacement crossing. The ultimate solution – a $631-million -2.5- mile-long bridge with a 1,546-foot cable- stayed main span – is the single largest project in SCDOT history. The replace- ment is essentially five major projects in one: two interchanges, two approaches and the cable-stayed main span – nearly 75 percent of which is constructed over or adjacent to sensitive wetlands and water bodies of the Cooper River system. HDR was hired to provide environmental man- agement as the owner’s representative through a Construction, Engineering and Inspection services contract for the mas- sive bridge replacement project. NEPA Compliance and Permitting From the earliest testing through design and construction, important envi- ronmental activities were also taking place in anticipation of the project. No bridge or road is built today without first weighing its impact on the surrounding environment, and then making sure potentially adverse impacts are lessened during construction. Before anyone knew exactly what the new Ravenel Bridge would look like or how it would be fund- ed, the project team had to make sure their construction wouldn’t harm the har- bor, wetlands or wildlife. As the early financial and design discussions contin- ued, the final environmental impact statement (FEIS) required by the Environmental Protection Agency and the WETLANDS Protecting Wetlands and Wildlife on the Americas’ Longest Cable-Stayed Bridge Nearly 75 percent of the new Arthur Ravenel Jr. Bridge, Charleston, S.C., is constructed over or adjacent to sensitive wetlands and water bodies of the Cooper River system.
Transcript
Land and Water July/August 2005•57
by Shannon Renz
Project OverviewTHE two existing U.S. Highway 17
bridges over the Cooper River in antebel-lum Charleston, S.C., are functionallyobsolete, characterized by too-narrowlanes, limited capacity and substandardvertical and horizontal ship channel clear-ance. In an effort to improve traffic safetywhile increasing overall capacity, theSouth Carolina Department ofTransportation (SCDOT) began the mon-umental effort of designing and con-structing a replacement crossing. The ultimate solution – a $631-million -2.5-
mile-long bridge with a 1,546-foot cable-stayed main span – is the single largestproject in SCDOT history. The replace-ment is essentially five major projects inone: two interchanges, two approachesand the cable-stayed main span – nearly75 percent of which is constructed over oradjacent to sensitive wetlands and waterbodies of the Cooper River system. HDRwas hired to provide environmental man-agement as the owner’s representativethrough a Construction, Engineering andInspection services contract for the mas-sive bridge replacement project.
NEPA Compliance and PermittingFrom the earliest testing through
design and construction, important envi-ronmental activities were also takingplace in anticipation of the project. Nobridge or road is built today without firstweighing its impact on the surroundingenvironment, and then making surepotentially adverse impacts are lessenedduring construction. Before anyone knewexactly what the new Ravenel Bridgewould look like or how it would be fund-ed, the project team had to make suretheir construction wouldn’t harm the har-bor, wetlands or wildlife. As the earlyfinancial and design discussions contin-ued, the f inal environmental impact statement (FEIS) required by theEnvironmental Protection Agency and the
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Protecting Wetlands and Wildlifeon the Americas’ Longest
Cable-Stayed Bridge
Nearly 75 percent of the new Arthur Ravenel Jr. Bridge, Charleston, S.C., is constructed over or adjacent to sensitive wetlands and waterbodies of the Cooper River system.
Land and Water58•July/August 2005
National Environmental Policy Act(NEPA) was drafted in 1995, completedin 1998 and re-evaluated in 2001 as con-struction began. Once the re-evaluationFEIS was approved, the next step wasobtaining the required permits to do the
work, an extremely important task of theproject schedule. In today’s environmen-tal arena, without the proper permits inplace construction cannot begin.
Environmental permitting was more complicated than normal becausethe design-build nature of this project putit on a faster track than usual. Obtaining
permits usually requires a completedesign (60 percent at a minimum), whichwas not available using this deliverymethod. In addition, because permits hadto be obtained during the Request forProposal (RFP) stage, both dual and sin-
gle structures had to be permitted becausethe decision had not yet been made as towhether there would be one or tworeplacement structures. To expedite thepermit process, an interagency task forcewas formed early on, with upper manage-ment from the state and federal resourceand regulatory agencies. Realizing thatthis was a design-build project, it wasmade clear that any permit modificationswould have to be acted on quickly. Tomanage this, the interagency task forceestablished an agreed-upon method towork through issues in an effort to quick-ly address concerns through face-to-facemeetings.
Efforts to Minimize Impacts to SpeciesOn either side of the Cooper River
are environmentally sensitive, low-eleva-tion wetland areas. The Santee-CooperRiver Basin comprises the second largestAtlantic coast watershed in the UnitedStates and is home to more than 125 f ish species – including the federally
protected shortnose sturgeon – and anabundance of waterfowl. Additionally,concerns exist about impacts to thebehavior of migratory birds and nestingloggerhead turtles. For these and otherreasons, environmental monitoring and
mitigation on the project site is particular-ly important.
The Cape Romain National WildlifeRefuge 25 miles north of Mount Pleasanthas the nation’s second largest loggerheadsea turtle nesting ground, averaging 1,000nests per year. The loggerheads areamong South Carolina’s most belovedpart-time residents. The turtles also liketo nest on nearby Sullivan’s Island andFolly Beach. Migrating loggerheads laytheir eggs on the beaches near Charlestonand find their way back to sea via moon-light. Because a bridge adorned with toomany lights could directly and negativelyimpact the turtles’ migration pattern,designers have planned limited and direc-tional lighting for the new structure. Lightpollution poses a threat to this endan-gered species, because newly hatched turtles can become disoriented by brightlight on land, confusing it with the brightlight of the surf. As a result, the hatch-lings die when they don’t get to the waterin time.
The original plans for lighting designon the new bridge called for nearly threetimes the wattage as the existing lightingon the Grace and Pearman bridges—174,000 watts compared to 58,500 watts.After the U.S. Fish and Wildlife Service(USFWS) raised concerns about potentialharmful impacts to the sea turtles, a seriesof meetings was held to arrive at a solu-tion. Total wattage was finally reduced to142,000 watts. Specifics design changesincluded reducing the cable lighting from1,000-watt bulbs to 250-watt bulbs, elimi-nating the high-mast lighting on theCharleston and Mount Pleasant inter-changes (short mast lighting will be usedin place) and using reflective sheetinginstead of lights on overhead signage.
Restoring Wetlands and MitigationBanking
The Webster dictionary defines miti-gation as “To cause to become less harshor hostile, or to make less severe.” Onprojects such as the Cooper River Bridgereplacement, it means restoring the natu-ral environment as much as possible, orcausing the least possible amount of harmto wildlife and their habitat. Makinglighting changes to accommodate sea tur-tles is an example of mitigation. Otherexamples include restoring wetlands to
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Rip-rap (rock) was used to filter runoff and control erosion near the trestles.
Environmental permittingwas more complicatedthan normal because thedesign-build nature ofthis project put it on afaster track than usual.
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their natural condition after the bridgeand interchanges are built. Most of thewetland mitigation for the project is tak-ing place in Mount Pleasant. In additionto removal of all temporary accessinstalled by the contractor, as the oldbridges are removed the existing GraceBridge causeway will be excavated andrestored to wetlands.
The preference is always to mitigateonsite, but since this isn’t always possible,sometimes an agency will agree to pro-vide off-site mitigation. SCDOT actuallyhas a mitigation bank for this purpose.The mitigation bank works like a realbank, with deposits and withdrawals.Credits are deducted when an agency,such as SCDOT, is unable to mitigate allthe required acres, or credit is applied forprojects where the agency restored moreacres than were required.
The Charleston District office of theU.S. Army Corps of Engineers (Corps)establishes the required mitigationacreages. In South Carolina, the Corpsuses factors including existing conditionsand adverse impacts to calculate therequired replacement acreage. For theCooper River Bridge replacement project,4.92 wetland acres were impacted andrequired mitigation. Using the Corpsguidelines, 2.93 acres are being mitigatedonsite, and 4.88 acres will be mitigatedoffsite using credits from the mitigationbank.
Environmentally ConsciousConstruction
The high-level approaches connect-ing the interchanges to the bridge had tobe constructed over environmentally sen-sitive wetlands. To protect them, the proj-ect team departed from the conventionalapproach. To lessen permanent impacts toseveral acres of wetlands in Charleston,the contractor was encouraged by theinteragency task force to use temporarywork trestles for their access to the proj-ect. These structures are constructedabove wetlands and are permitted as tem-porary impacts through the Corps’s404/401-permit process.
The typical process is to place tem-porary fill in these areas to provide accessfor construction. This option provides asolid working surface but destroys thewetland’s ability to filter surface water
runoff. While temporary access roadswere used in a few areas, the contractorbuilt four temporary trestles, whichallowed them to move heavy materialsand equipment and place foundationswithout harming the wetlands. The tres-tles were built at the Charleston inter-change, the Mount Pleasant interchangeand the western and eastern edges ofDrum Island.
The cost to construct the trestles was
roughly $11 million, compared to roughly$3 million for dredging and filling to cre-ate temporary access roads. The timbersused to construct the trestles were recy-cled as much as possible by moving themto different areas of the project. Forexample, when the foundations werecompleted on the Charleston interchange,the pilings and surface timber mats fromthis trestle were removed and used to con-struct the trestle for the Morrison Driveramp in Charleston. Reusing the trestlesin this manner saved roughly $1 million.They suffered too much wear and tear tobe used on future projects, but theyserved their purpose well, greatly reduc-ing environmental impacts to the wet-lands. At the completion of constructionactivity, the trestles will be removed andthe area will be restored to pre-construc-tion conditions.
Because much of the construction
and inspection took place on the water,precautions were taken on the contractorcrew boats, barges, islands, tug boats,trestles and piers to prevent oil, fuel andother contaminants from making theirway into groundwater and surface waterssuch as the Cooper River. These precau-tions include implementation and inspection of best management practices(BMPs), enforcement of spill preventionand accident prevention plans, and regular
radio communication between f ieldcrews.
Proper permitting and storm waterpollution prevention plan (SWPPP)review and implementation also wereintegral to the success of the environmen-tal efforts. One of the more time-consum-ing permit requirements was the weeklysediment and erosion control inspectionsrequired by the joint Corps 404/401 per-mit. These inspections took place at 60monitoring stations in Charleston and 25in Mount Pleasant. In addition to weeklyinspections, the permit also requiredinspections after every half-inch rainevent. The Charleston area averages 52inches of annual rainfall.
Life After Grace - What the FutureHolds
Although the John P. GraceMemorial and Silas N. Pearman Bridges
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Endangered loggerhead sea turtles will benefit when the decorative bridge lighting is turnedoff during prime migrating months. Photo courtesy of Cape Romain Wildlife Refuge, takenby Karen Beshears on Cape Island.
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have ended their useful lives as a meansof transport, they will be reincarnated asmuch-needed marine habitat when theyare dismantled and the concrete is turnedinto approximately 77 acres’ worth ofartif icial reefs. In some sections, theexisting bridges will be wrapped (to mini-mize loose debris), dropped into the riverthrough the use of carefully placed explo-sive charges, and the material used toconstruct artificial reefs both inshore andoffshore. More than 230,000 tons of con-crete from the old bridges will become
underwater habitat for f ish and othermarine life. The Grace Bridge has enoughenvironmentally friendly concrete for26.5 acres of reef, and the PearmanBridge can create a 50.7-acre reef. Theadditional habitat will help ensure thedevelopment and survival of marine crea-tures, as a single reef can support up to 50species. Artificial reefs have become amainstay in supporting sea life, in SouthCarolina and elsewhere. According to theSouth Carolina Department of NaturalResources (SCDNR), only 5 to 10 per-cent of the continental shelf off of thesoutheast coast has the proper geologicmakeup to support natural reefs.
Artificial reefs attract both bottom-dwelling fish like black seabass, snappersand groupers, and pelagic species (fishthat live closer to the surface).Amberjack, King and Spanish mackereland even some Tuna will school over arti-ficial reef structures. Artificial reefs don’tjust benefit sea life; they also benefit thebottom line through increased recreation-al spending. According to SCDNR, theSouth Carolina artificial reef program
generates roughly $20 million from recre-ational fishing alone, and fishing isn’t theonly recreational option. A study con-ducted by HDR for SCDOT calculatedthe annual “recreational user value” ofeach new artificial reef at $98,000. Ifeight artificial reefs are created usingmaterial from the Grace and Pearmanbridges, the total recreational value is$784,000.
The Town of Mount Pleasant plans toplace a reef around a pier that will bebuilt from the existing Pearman Bridgepiers as the focal point of a new water-front park, in the area once occupied bythe Grace and Pearman Bridges. Not allof the reefs using material from thebridges may be in the Charleston area.South Carolina has 44 artificial reefs inits artificial reef program. At the time ofthis writing, 14 of them have applied toreceive material from the old bridges.Twelve currently permitted sites probablywill receive concrete from the bridgedemolition, according to SCDNR.
As of June 2005, all of the project’sfoundations are in place, the ship colli-sion islands have been constructed, thetwo diamond towers are complete, andmost of the temporary trestlework hasbeen removed allowing for precious wet-lands to begin natural recruitment.
The next year will bring about con-tinued work on demolishing the existingGrace and Pearman Bridges. With agrand opening for the new RavenelBridge scheduled for July 16, 2005 – andthe new demolition project scheduled tobegin approximately a month after that –many challenges no doubt still lie ahead.Of equal certainty is that the environmen-tal issues experienced and resolved in astreamlined approach on the CooperRiver Bridge replacement project willprove invaluable on the upcoming demo-lition project and future design-buildmega projects. L&W
For more information contactShannon Renz, HDR, Community BridgeOffice, 212 Huger Street, Charleston, SC 29403, (843)534-5000, e-mail: [email protected].
Shannon Renz is an environmentalscientist with HDR, and environmentalmanager for the Cooper River Bridgereplacement project for the SouthCarolina Department of Transportation.
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Permits were required from the fol-lowing agencies:• The U.S. Coast Guard (USCG).Because the bridge crosses navigablewaters, the USCG was involved in per-mitting the bridge’s span, width andheight, and the depth and dimensions ofthe rock islands built for pier protection.The USCG also required notification forany work in the waterway requiringalerts to mariners and others in the area.• The U.S. Army Corps of Engineers.The Corps is responsible for dredgingand filling in U.S. waters, including wet-lands.• The South Carolina Department ofHealth and Environmental Control(DHEC), which has responsibility forstormwater permits and water qualityissues. This activity is permitted underthe National Pollutant DischargeEliminating System (NPDES), the per-mit program under the EPA Clean WaterAct.• The South Carolina Office of Oceanand Coastal Resource Management(OCRM), an off ice of DHEC, wasinvolved in permitting along a “criticalarea” of the Cooper River, whichincludes neighboring wetlands. Theseitems are permitted jointly with theCorps for dredge and f ill and waterquality.
More than 230,000 tonsof concrete from the oldbridges wil l becomeunderwater habitat forfish and other marinelife. The Grace Bridgehas enough environmen-tally friendly concrete for26.5 acres of reef, andthe Pearman Bridge cancreate a 50.7-acre reef.
