Civil Engineering: October 2009

Thursday, October 29, 2009

Steel bridge kicks off infrastructure stimulus program

Steel bridge kicks off infrastructure stimulus program

In late February, an $8.5 million steel replacement bridge in Miller County near Tuscumbia, Mo., was approved under the new federal economic stimulus package for construction as a top priority for the state of Missouri. Because of the desire for rapid and economical construction, steel was selected for the bridge's main span.

"Today, the Show Me State again showed the nation we are leaders in transportation by having the first economic recovery act project in the country under construction," said Missouri Department of Transportation director Pete Rahn. "We promised we would be ready to go to make the best use of every dollar we receive through the economic recovery act to create jobs and make our highways safer. We delivered on that promise and then some."

The new 1,000-foot-long, 28-foot-wide steel bridge will replace the existing 75-year-old Osage River Bridge, which is the same length and just 20 feet wide. The bridge crosses a Missouri River tributary near the middle of the state, where the average daily traffic is more than 1,000 cars per day. However, it has been off-limits to large trucks since 2007 because of its poor structural condition.

The new bridge, built by general contractor APAC of Kansas City, will use 395 tons of structural steel for the bridge's 570-foot main span and will be positioned just upstream from the existing bridge.

Short and Medium Span Bridge Conference

Short and Medium Span Bridge Conference

Sponsors of the 8th International Conference on Short and Medium Span Bridges—2010 issued a first announcement and call for papers. The conference, Aug. 3-6, 2010, in Niagara Falls, Ontario, has been held every four years in Canada. Sponsors include the Canadian Society for Civil Engineering and the International Association for Bridge and Structural Engineering.

Individuals wishing to contribute a technical paper or poster presentation are invited to submit an abstract (maximum of 300 words) relating to the conference themes:

Innovative design and construction;
Inspection, evaluation, and rehabilitation;
Advanced materials in bridges;
Accelerated bridge construction;
Research and development;
Management of bridge assets;
Bridge aesthetics; and
Engineering history.
The deadline for abstract submission is Sept. 15, 2009. More information is available on the conference website (www.bridgeconference2010.com); or contact Kwong-Yiu Chu at 905-704-2371 or via e-mail at smsb2010@ontario.ca.

Woodrow Wilson Bridge wins Lindenthal Medal

Woodrow Wilson Bridge wins Lindenthal Medal

The Woodrow Wilson Bridge (WWB) Project, which spans the Potomac River connecting Virginia and Maryland, won the 2009 Gustav Lindenthal Medal. It was honored for resolving a renowned transportation bottleneck through technical innovation, environmental stewardship, capacity and efficiency improvements, and transit alternatives. The project was completed in 2008 on-time and within its $2.5 billion budget.

The award, sponsored by Bayer MaterialScience LLC, was presented to the Maryland State Highway Administration (MSHA) and the Virginia Department of Transportation (VDOT) by Karsten Danielmeier, Ph.D., vice president, business development, Coatings, Adhesives and Specialties, Bayer MaterialScience LLC, during the annual International Bridge Conference (IBC) in Pittsburgh.

Potomac Crossing Consultants (PPC), a joint venture of Parsons Brinckerhoff, URS, and Rummel, Klepper & Kahl, LLP, provided program and construction management support to the primary partners—MSHA and VDOT—as well as the project's many other sponsors and consultants.

The bridge is noteworthy structurally, as well as aesthetically. Structurally, the bridge features the largest movable span in the world, and each of the structure's eight drawspans is designed to close within a 1/8-inch tolerance. Aesthetically, the design of the river crossing features an arch appearance that calls to mind other bridges in the Washington, D.C. area, as well as other "monumental" structures in the area. The V-piers maintain the arch theme, while functionally serving to minimize horizontal loads.

The bridge is environmentally significant, as well. As part of the project, five artificial reefs were created in the Chesapeake Bay. Additionally, more than 52 acres of new wetlands were created and more than 94 acres were restored or preserved. Also, the project reestablished streams for fish spawning and developed a contained bubble-curtain system to eliminate fish mortality during pile driving.

The culmination of the WWB Project is a functioning six-lane highway spanning the Potomac, reduced traffic congestion, renewed wetlands, and an on-time, on-budget signature structure.

"The Woodrow Wilson Bridge Project is an excellent example of how approaching a mega-project such as this one holistically—from a social, economic, and sustainable design perspective—can result in an achievement that is successful on many fronts," said Danielmeier. "For all its achievements, we are pleased to add the Woodrow Wilson Bridge Project to the elite group of this prestigious award's past winners."

One of five awards given annually at the IBC, the Gustav Lindenthal Medal was created in 1999 to honor a recent outstanding achievement that best demonstrates technical and material innovation together with aesthetic merit, harmony with the environment, or successful community participation.

Gustav Lindenthal was one of America's most celebrated bridge engineers, and is widely admired for his innovative ideas, vision, and foresight during the technology boom of the late 19th and early 20th centuries.

Researchers test bridge resilience

Researchers test bridge resilience

Researchers at the University at Buffalo's (UB) Multidisciplinary Center for Earthquake Engineering Research (MCEER) and Calspan, an independent aviation and transportation testing firm, plan to capitalize on the region's much-maligned climate through a partnership and testing program that will subject two full-scale bridges and their advanced protective technologies to a full range of naturally occurring environmental and climatic conditions, as well as earthquake vibrations.

The purpose of the partnership and the studies is to combine the talents of both organizations to meet effectively the nation's growing needs for the intelligent renewal and improved resilience of its infrastructure, in this case bridges, from natural-occurring phenomena and extreme events. The partnership expects to leverage the infrastructure-research skills of MCEER with the testing expertise of Calspan.

"This partnership puts each of our organizations into exciting new worlds," said Andre Filiatrault, Ph.D., MCEER director and professor of civil, structural, and environmental engineering at UB. "There is a tremendous synergy in the ability of Calspan to apply its testing expertise to develop full-scale experimental capabilities that enable MCEER to test large infrastructure components, such as roads and bridges, under multiple hazards including earthquakes and other extreme events."

Filiatrault also noted that Calspan's Ashford facility near Springville, N.Y., provides ample acreage to conduct such full-scale tests, as well as a wide array of naturally occurring weather conditions to expose infrastructure test specimens to the natural elements.

"Structural engineers traditionally have sought solutions to infrastructure problems in the confines of a laboratory," he said. "Calspan's Ashford Facility provides an opportunity to test new technologies and infrastructure remedies in the great outdoors, where they will have to perform over time and in varying climatic and other conditions."

Thomas Pleban, executive vice president of Calspan, said that the new relationship not only has the potential to enhance Calspan's current test capabilities, but will also benefit Western New York as a whole, by making it the world's premier destination for full-scale infrastructure testing.

Filiatrault said that the aging infrastructure in the U.S. is reaching a critical point. "As infrastructure approaches the end of its lifespan, it becomes increasingly susceptible to tremendous damage, especially during extreme events," he said. "Our nation needs to renew its infrastructure, but how shall we go about it? Do we simply replace the old with the new, or do we rebuild it more intelligently so that it is designed and built to withstand multiple hazards throughout its lifetime? The MCEER-Calspan partnership will focus on finding ways to protect our growing population and way of life by renewing and preserving our infrastructure through the development and validation of the most innovative and cost-effective methods available."

The initial focus of the partnership is development of a full-scale bridge test at Calspan's 700-acre Ashford facility. The Ashford facility, about 35 miles south of Buffalo, will enable MCEER researchers to subject two adjacent single-lane bridges equipped with state-of-the-art seismic isolation technologies to harsh, real-world conditions—and earthquake vibrations.

Construction of the 72-foot-long bridges will begin this fall, with a five-year test program scheduled to begin on July 1, 2010. Eleven concrete bridge girders donated by Hubbell Concrete of Utica, N.Y., already have been transported to the Ashford site.

Testing will chronicle the performance of seismic isolation technology over time and over a wide spectrum of temperatures and other environmental conditions. Seismic isolation decouples a structure from its foundation, effectively isolating it from damaging ground vibrations. The initial test program will examine the change in properties of elastomeric or rubber isolation bearings in a wide range of temperature settings. Bearings are being provided by Dynamic Isolation Systems, Inc.

The project is supported by funding from New York State and industry donations.

Michael Constantinou, professor of civil, structural, and environmental engineering at UB, acknowledged that "while seismic isolation technology is widely accepted in the civil engineering field, expanded understanding and continued development can only help to further its use—and the resilience of structures that it protects."

--------------------------------------------------------------------------------

Recycled plastic bridge carries tanks

Recycled plastic bridge carries tanks

Axion International Holdings, Inc., a technology company in infrastructure markets including bridges, railways, and marine applications, completed construction of two, 100-percent recycled-plastic bridges for the U.S. Army. The bridges were designed to allow for the crossing of M-1 Abrams tanks.An M-1 Abrams tank, which weighs more than 70 tons, is too heavy to drive across most standard bridges and roadways. However, Axion's composite technology, developed in conjunction with scientists at Rutgers University, allowed the tank to make multiple crossings over a bridge made entirely from recycled consumer and industrial plastics. The event took place on June 11, 2009, as a crowd of approximately 30 engineers and military personnel watched at Fort Bragg, N.C. These new bridges were less expensive to build than the wood timber bridges they replaced and were engineered to carry the necessary 70-plus tons of military hardware.According to Axion, the new bridges at Fort Bragg are innovative structures because of the following attributes:
patented structural materials made from 100-percent recycled plastic;
patent pending I-beam design;
speed of installation; and
reduced cost to construct and maintain.
The bridge achieved excellent performance reviews with regard to both live and static loads, the company said, and withstood the impact of the M-1 tank braking on the bridge. Construction of the two thermoplastic composite bridges used more than 170,000 pounds of recycled plastic, the equivalent of more than 1.1 million 1-gallon milk jugs.

Kanawha River Bridge main span completed

T.Y. Lin International (TYLI) announced completion of the closure segment on the 760-foot-long main span of the Kanawha River Bridge, a new segmental bridge over the Kanawha River between Dunbar and South Charleston, W.V. With the main span closure, this is now the longest box girder span in the United States.

TYLI designed the record segmental span for the West Virginia Department of Transportation, Division of Highways and is currently providing construction support services. The new bridge will carry I-64 eastbound traffic on an improved curved alignment as part of the widening of I 64 in Kanawha County, for which TYLI also provided civil design services. Westbound traffic will remain on the existing steel plate girder bridge.Transportation officials celebrated the historic moment during a ceremony on June 17 in which workers cast the final segment. Project Manager Santiago Rodriguez said that at the peak of the main span's construction, four 16-foot-long segments were cast per week, using two pairs of form travelers.

The challenge for Rodriguez, as the designer, was to design a bridge with expansion joints at the abutments only, resulting in a distance of 2,975 feet between expansion joints. Of the total superstructure, three cantilevers remain to be completed, along with the bridge parapets, overlay, and roadway—all due to be completed by October 2010.The new Kanawha River Bridge will have a total length of 2,975 feet, including the 760-foot river span, 460- and 540-foot side spans, and five additional approach spans, ranging from 144 to 295 feet. The 66-foot, 8-inch-wide deck will accommodate four lanes of traffic plus shoulders, all on a single cell box girder. The continuous girder has a varying depth of 16 to 38 feet at the main span and a constant 16-foot depth at the approaches. This low-cost design was selected instead of a steel alternative, saving $30 million and simplifying construction, according to TYLI. The final result is an elegant and distinct

Concrete sustainability hub launched at MIT

CAMBRIDGE, Mass. — Concrete is the most widely used building material on the planet; however, the production of some of its component materials accounts for up to 5 percent of global carbon dioxide emissions annually. To address the sustainability and environmental implications of the use of concrete as the backbone of our housing, schools, hospitals and other built infrastructure, including highways, tunnels, airports and rail systems, MIT announced the creation of the Concrete Sustainability Hub, a research center established at MIT in collaboration with the Portland Cement Association (PCA) and Ready Mixed Concrete (RMC) Research & Education Foundation.
The Concrete Sustainability Hub (CSH), established with the goal of accelerating emerging breakthroughs in concrete science and engineering and transferring that science into practice, will provide $10 million of sponsored research funding during the next five years. Researchers from MIT’s School of Engineering, School of Architecture and Planning and Sloan School of Management are expected to participate in the CSH’s research activities.
The launch of CSH incidentally coincides with last week’s announcement that the EPA is moving to enact rules that would curtail greenhouse gas emissions from power plants and large industrial manufacturers. If enacted, these rules would likely impose regulations on all 118 cement plants in the United States. The RMC and PCA leaders are hopeful that research results emerging from CSH projects will help ease the way for the industry to meet any changes that would be required by those new regulations.
“The concrete industry has the honor of producing the world’s most favored building material, but this honor comes with a responsibility for the industry to minimize its ecological footprint,” said Julie Garbini, executive director of the RMC Research & Education Foundation.
Brian McCarthy, CEO and president of PCA, added “The MIT research team is an exceptional group of dedicated interdisciplinary faculty and the CSH will take a holistic approach to research that allows science to feed seamlessly into today’s concrete applications like paving and wall systems. For ultimately, the greatest opportunity for the building industry to reduce greenhouse gas emissions may lay in the development of more durable and energy-efficient roads, houses, and buildings.”
“This collaboration is an excellent example of how MIT is addressing complex, interconnected issues of sustainability — and working to provide solutions,” said Subra Suresh, Dean of Engineering and Vannevar Bush Professor of Engineering at MIT. “Putting engineers together with economists, urban planners, architects and industry experts and practitioners on issues related to our built infrastructure will create truly novel opportunities for intervention.”
CSH research will initially be organized around three focus areas: concrete materials science, building technology and the econometrics of sustainable development. The first two projects, “Green Concrete Science,” and “The Edge of Concrete: A Life-Cycle Investigation of Concrete and Concrete Structures” are already underway. Franz-Josef Ulm, the Macomber Professor in the Department of Civil and Environmental Engineering, will serve as the CSH’s inaugural director and is the lead investigator on the Green Concrete Science project. The CSH will be co-directed by John Ochsendorf, Class of 1942 Career Development Associate Professor of Building Technology in the Department of Architecture and the Department of Civil and Environmental Engineering.
“It is rare that one has an opportunity to have a positive environmental impact on the most prevalent building material in the world,” said Ulm. “This means working closely with industry partners over time to ensure that our ideas and research are sustainable economically, as well as environmentally, and are a source of job creation.”

FRA receives 45 applications for high-speed rail funding

WASHINGTON, D.C. — The Federal Railroad Administration (FRA) said that it received numerous applications from states and groups of states for the development of high-speed and intercity passenger rail programs for grant funding from the American Recovery and Reinvestment Act. These include 45 applications from 24 states totaling approximately $50 billion to advance high-speed rail corridor programs. FRA also received 214 applications from 34 states totaling $7 billion for corridor planning and smaller projects.
FRA said that because of the overwhelming response and its desire to lay the groundwork for a truly national high-speed and intercity passenger rail program, the agency will be announcing all awards this winter. Selections will be merit-based and will reflect President Obama’s vision to remake America’s transportation landscape.

I-35W Bridge selected as 2009 best transportation project

PALM DESERT, CALIF. — The American Association of State Highway and Transportation Officials (AASHTO), AAA, and the U.S. Chamber of Commerce announced that the I-35W Bridge in Minneapolis was selected as the 2009 America's Transportation Awards Grand Prize winner. Florida Department of Transportation's (FDOT) 95 Express Miami Project won the People's Choice Award. The awards were presented at the AASHTO Annual Meeting.
The competition recognizes outstanding transportation projects in three categories: On Time, On Budget, and Innovative Management. The 10 projects that scored the highest during four regional contests competed for both the Grand Prize and the People's Choice Award.
In the aftermath of the catastrophic Aug. 1, 2007, collapse of the I-35W bridge over the Mississippi river in downtown Minneapolis, the Minnesota Department of Transportation implemented a plan to detour 140,000 vehicles, address public concerns, and begin immediate construction of the new $234 million replacement bridge. The massive design-build project — which included 10 lanes for traffic, several local side streets, and interchanges — was completed in 13 and half months; three months ahead of schedule.
"This is truly symbolic of triumph over tragedy," said John Horsley, AASHTO executive director. "We know how difficult the past two years have been for the citizens of the entire state, but this outstanding project can be seen as a victory for citizens and a legacy for the loved ones lost."
More than 200,000 online votes helped decide this year's People's Choice Award winner. FDOT's 95 Express Miami Project is a $62.9 million High Occupancy Toll (HOT) lanes project.
The winners will receive a $10,000 cash award to be used by the winning transportation department to support the charity or academic scholarship program of its choice.
Fifty projects were entered in this year's America's Transportation Awards competition. Complete details about each of these projects are included in “Smart Solutions: 50 Ways America Just Got Better,” a new report released by AASHTO and available at

EPA proposes one-year extension for NPDES 2008 Construction General Permit

WASHINGTON, D.C. — In an Oct. 19, 2009, Federal Register notice, the U.S. Environmental Protection Agency (EPA) announced that it is seeking public comment on its proposal to extend the 2008 NPDES general permits for stormwater discharges associated with construction activity, the 2008 Construction General Permit (CGP), by one year. The 2008 CGP applies only where EPA is the permitting authority, which is in five states; Washington, D.C.; most U.S. territories; many federal facilities; and most Indian country lands.…

President Obama announces $3.4 billion investment to spur transition to smart energy grid

ARCADIA, FLA. — Speaking at Florida Power and Light’s (FPL) DeSoto Next Generation Solar Energy Center, President Barack Obama announced the largest single energy grid modernization investment in U.S. history, funding a broad range of technologies that are intended to spur the nation’s transition to a smarter, stronger, more efficient and reliable electric system. The end result, according to the Administration, will promote energy-saving choices for consumers, increase efficiency, and foster the growth of renewable energy sources such as wind and solar.…

Top 100 Global Infrastructure Projects announced

WASHINGTON, D.C. — CG/LA Infrastructure LLC released the Top 100 Global Strategic Infrastructure Projects, with a total estimated value of nearly $550 billion. The Top 100 List was released prior to the 3rd Annual Global Forum in New York City, Dec. 9-11, 2009. According to Norman F. Anderson, president and CEO of CG/LA Infrastructure LLC, “The aim of the Global Forum is to fix a spotlight on the most important infrastructure projects in the world — and to give the men and women who lead those projects an opportunity to build long-term assets critical to their country’s future, at world-class levels of quality and velocity.”

Dutch Sea Barrier - Holland

Name: Dutch Sea Barrier
Location: Holland
Date Completed: 1990
Height:
Images: Altavista collections; Google collections
Facts:Part of Dutch Sea Protection project, the movable barrier preserves the estuary as a commercial fishery, but can be closed during storms to prevent flooding.
Links: The North Sea Protection Works

Thames Barrier - England

Name: Thames Barrier
Location: London, England
Date Completed: 1984
Height: 520 meters
Images: Altavista collections; Google collections
Facts:The world's largest movable flood barrier, protects Britain's capital city from tidal flooding.
Links: The official Thames Barrier Website

Dujiangyan Irrigation System - China

Name: Dujiangyan Irrigation System
Location: Sichuan, China
Date Completed: 240 B.C.
Height:
Images: Altavista collections; Google collections
Facts:Thanks to the project, it made, and still makes today, the Chengdu plain the most fertile area in all of China.
Links: Arteries of the Empire Saltbook

Trans-Arabian Pipeline

Name: Trans-Arabian Pipeline
Location: Persian Gulf
Length: 1068 miles
Images: Altavista collections; Google collections
Facts:
Links: Building of TAPline

Trans-Alaska Pipeline

Name: Trans-Alaska Pipeline
Location: USA, Canada
Length: 800 miles
Images: Altavista collections; Google collections
Facts:At the height of construciton in the summer of 1975, some 20,000 men and women worked 12-hour days, 7 days a week, in a race against winter.
Links: Facts of Trans-Alaska Pipeline The Alaska Pipeline

World Trade Center Twin Towers

Name: World Trade Center Twin Towers
Location: New York City, USA
Date Completed: 1973
Material: Steel
Height: 1368 feet and 1362 feet
Images: Altavista collections; Google collections
Facts:The twin towers collapsed due to the terrorist attacks of September 11, 2001.
Links: World Trade Center NOVA Video at Amazon - Why the Towers Fell (2002) Posters from Art.com: World Trade Center

Sears Tower - Chicago, USA

Name: Sears Tower
Location: Chicago, USA
Date Completed: 1974
Material: Steel
Height: 1454 feet
Images: Altavista collections; Google collections
Facts:Known as the "bundled tube" approach, the innovative tubular system requires much less steel than did traditional designs while maintaining stiffness against wind loads.
Links: The Official Site of Sears Tower

John Hancock Center - USA

Name: John Hancock Center
Location: Chicago, USA
Date Completed: 1970
Material: Steel frame
Height:
Images: Altavista collections; Google collections
Facts:It is a direct descendant of the Eiffel Tower. The diagonals lace the vertical columns together and thus distribute the gravity loads equally among them.
Links: Great Buildings

Trans-Canada Highway - CANADA

Name: Trans-Canada Highway
Location: Canada
Length: 7,821 Kilometers
Images: Altavista collections; Google collections
Facts:World's longest national road.
Links: Encyclop�dia Britannica: Trans-Canada Highway Adventure on the Trans-Canada Highway Trans-Canada Highway

T-REX - USA

Name: T-REX
Location: Denver, Colorado, USA
Length: 7,821 Kilometers
Images: Altavista collections; Google collections
Facts:World's longest national road.
Links: T-REX Project Page T-Rex Highway Project

Pan-American Highway

Name: Pan-American Highway
Location: North America and South America
Length: 48,000 kilimeters (30,000 miles)
Images: Altavista collections; Google collections
Facts:The network of highways connecting North America and South America.
Links: Pan-American Highway

The National Road - USA

Name: The National Road
Location: USA
Length:
Images: Altavista collections; Google collections
Facts:The first highway project funded by US federal government. It is usually considered the beginning of US federal interstate highway system.
Links: The National Road History of Route 40 and the National Road The National Road The National Road National Road

Alaska Highway

Name: Alaska Highway
Location: USA and Canada
Length: 2423 Kilometers
Images: Altavista collections; Google collections
Facts:The highway links Alaska, USA and Yukon, Canada through British Columbia.
Links: National Historic Civil Engineering Sites: THE ALASKA HIGHWAY History of the Alaska Highway

Design Complete For Tallest Building In Asia

Design Complete For Tallest Building In Asia

The project of what will be the tallest skyscraper in Asia is one step closer to completion. This week New York City-based Kohn Pedersen Fox Associates finished its conceptual design for the Lotte Super Tower 123.

Bay Bridge Span Designed To Endure Major Quake

Bay Bridge Span Designed To Endure Major Quake

Caltrans released a computer-generated simulation of how the new East Bay segment of the bridge - set to be completed in 2013 - is expected to respond when jolted by a large quake.

Researchers Testing Nanotech for Hazardous Waste Cleanups

Researchers Testing Nanotech for Hazardous Waste Cleanups
Scientists and environmental regulators are hoping that some extremely tiny materials might make a huge difference in hazardous waste cleanups.

Researchers are exploring whether nanoscale materials -- so named because they are as small as 1/100,000 the width of a human hair -- can be cleanup assets. They have two reasons for optimism: Nanomaterials' size lets them penetrate otherwise impossible-to-reach groundwater or soil, and their engineered coatings allow them to stay suspended in groundwater, a major asset in cleanups.
If they work, nanomaterials could slash cleanup prices by avoiding the extraordinary costs and risks of hauling materials away for burning or burial.
"There is significant potential to target a number of very complicated sites that to date we have been unable to remediate adequately," said Denis O'Carroll, an assistant professor of civil and environmental engineering at the University of Western Ontario.
The Woodrow Wilson Center's Project on Emerging Nanotechnologies (PEN) has identified 45 sites in several countries that are currently using nanomaterials for waste cleanups. But there is little data on cost and performance of nano-remediation, since most projects are in their infancy. Moreover, companies involved in the work are tight-lipped, concerned about releasing cost and performance information they consider proprietary.
"It's difficult to quantify operational costs," said Jeffrey Marqusee, executive director of the Defense Department's Strategic Environmental Research and Development Program and the Environmental Security Technology Certification Program. Marqusee's programs are tasked with researching and developing environmental cleanups.
Most DOD nano-remediation research projects are focused on cleaning up groundwater contaminated by chlorinated solvents such as trichloroethylene, Marqusee said. His teams have used nano-scale emulsified zero-valent iron at the Marine Corps base in Parris Island, S.C., among others.
Iron is a key element in cleanups, both traditional and nano, because it strips down toxic compounds and leaves behind individual, nontoxic elements. It has been used for some time at cleanups to form permeable barriers that keep contaminants from being carried off the site with groundwater. In nano-cleanups, nano-scale zero-valent iron is injected in toxic "hot spots," the source of contamination.
So far, results are promising, Marqusee said. In most demonstrations, he said, most of the contaminant has been destroyed, a finding that has been replicated by researchers elsewhere.
But there are complications. For one, iron also reacts with nontargeted materials, making it degrade too quickly -- before remediation is complete, O'Carroll said. Another problem: Iron particles clump after they are released, making it difficult for them to travel beyond where they are injected.
"Mobility is a really big deal," O'Carroll said. "With any sub-surface remediation technology, the big deal is getting it to the contaminant. You can't see it, so knowing where it is is a challenge."
So scientists are trying coatings that might enable nano-particles to travel. Researchers are also trying to learn how to make the nano-iron react only with target contaminants and not the surrounding environment. They are also trying to get it to self-destruct after it has done its job.
Such "smarter" nanomaterials will ultimately make the technology less risky, according to a paper published recently by U.S. EPA and the Wilson Center's PEN in the journal Environmental Health Perspectives.
Major hurdles
But nanotechnology won't be a silver bullet for cleanups because most contaminated sites are fouled by more than a single contaminant, O'Carroll said. Scientists will probably always need to have a phased approach, in which one technology is used to get rid of certain pollutants, followed by a different approach and then another as the site requires, he said.
And there is still a long way before nanotechnology becomes a mainstay at hazardous waste cleanups -- if it ever does. For one thing, regulatory uncertainties abound.
"It can save years of time and billions of dollars in estimates for cleanup for some Superfund sites," said Jane Warren, a lawyer at McCarter & English. "The problem is, as with any new technology, it hasn't been studied enough. There aren't even reliable ways to measure whether nanomaterials are achieving the goals they claim to be able to achieve."
And companies that do use nanomaterials in cleanups have been reluctant to discuss their efforts openly.

Subscribe to: Posts (Atom)

© Blogger templates Psi by Ourblogtemplates.com 2008

Back to TOP