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Listed below are examples of case studies including best practices and/or innovative tools/approaches. This section will grow as entries are submitted or links to other sites with useful examples are provided. If you believe your agency has utilized a best practice/approach that others could learn from, please submit a short description to AASHTO (including any pertinent links) on the Share Info with AASHTO form. Please note that currently submissions are only being accepted from governmental entities.

California

Caltrans Uses Air Bubble Curtain Technology to Protect Wildlife During Bridge Implosions

The California Department of Transportation (Caltrans) is using cutting-edge technology to remove the marine foundations of the former East Span of the San Francisco-Oakland Bay Bridge while protecting area wildlife and reducing project cost and schedule.

The technology controls the blast sequence down to microseconds by using a computer system to precisely detonate hundreds of small individual charges to implode the foundations, thus greatly reducing impacts. At the same time, Caltrans is implementing a blast attenuation system that creates a shield of air bubbles to abate resulting sound waves and pressure.

Cutting edge technology helps protect the environment during implosion of this former bridge pier. (Photo: Caltrans)

“By employing leading edge technology, we have reduced the temporal environmental impact of our demolition work from years to seconds,” said Stefan Galvez-Abadia, Chief, Office of Environmental Analysis and San Francisco-Oakland Bay Bridge Environmental Manager. “Simultaneously, we are working more safely and efficiently and saving money.”

The agency’s other option would have been to build a cofferdam, he said, which is an enclosure around each foundation pumped dry to enable loud, heavy machinery to carry out the demolition work. With a limited construction window each year, it could have taken up to four construction years to remove each foundation, a very expensive undertaking. In addition, this approach can result in continuous environmental impacts and safety risks.

“Real-time results have exceeded those anticipated by the model,” Galvez-Abadia said. “Both in-water noise and pressure as well as water quality impacts were significantly less than anticipated. We view this cutting-edge technology as another valuable tool in our toolbox.”

Caltrans’ implosion technology supplements additional steps it routinely takes to protect wildlife. The marine foundations are located in a portion of the San Francisco Bay that contains several fish species protected by the Endangered Species Act as well as marine mammals protected by the Marine Mammal Protection Act. Caltrans avoids impacts to most of these species through seasonal work windows. However some species are present in the Bay year round and the agency has developed specific work windows to avoid impacts to these species to the greatest extent practicable.

History of Project

The reason for removal dates back to 1989, when a segment of the bridge partially collapsed during the Loma Prieta earthquake. Although it reopened later that year after extensive retrofitting, experts decided that the East Span needed to be more earthquake-resistant than would be possible by retrofitting the existing bridge. Construction of a replacement span began in 2002 and was opened to traffic in 2013. After beginning to dismantle the original span’s superstructure in 2013, Caltrans began to remove its foundations as stipulated in the final Environmental Impact Statement (EIS) for the replacement span.

The first of the former East Span’s 21 foundations, called Pier E3, was imploded in November 2015. Two more foundations followed suit in 2016, and an additional six to thirteen are slated for demolition in 2017 and 2018, when the project is slated for completion.

Permits, Protections

Caltrans’ engineers and environmental team spent years working closely with a variety of resource agencies to determine how best to minimize potential environmental impacts to area wildlife and habitat.

Before beginning the project, the agency received federal permits from the National Marine Fisheries Service (NMFS), the U.S. Army Corps of Engineers, the U.S. Coast Guard, and the U.S. Fish and Wildlife Service (USFWS). State agencies granting permits included the California Regional Water Quality Control Board, the California Department of Fish and Wildlife, and the San Francisco Bay Conservation and Development Commission. These permits covered the building of the new bridge as well as the removal of the original bridge by mechanical means.

As the implosion work advances, Caltrans will continue to implement its impact avoidance and minimization measures. In addition, marine mammal species in the area will be protected via monitoring of pre-established exclusion zones around each foundation. If marine mammal species such as harbor seal, sea lion, or harbor porpoise, are spotted, the implosion will be delayed until the individual has moved outside the zone. Water quality and air quality monitoring also will continue to be conducted.

Perhaps the most powerful piece of the protection arsenal is Caltran’s air bubble curtain. To activate the system, a compressor pumps air through a manifold of perforated pipes set in a steel frame. Multiple frames contiguously surround the foundation and are activated just before the implosion process begins. The escaping air bubbles create a continuous shield, or wall, that provides a robust acoustic barrier.

Lessons Learned and Advice

Caltrans has tweaked several of its procedures along the way, said Galvez-Abadia. For example, after analyzing the results of the Pier E3 Demonstration Project, then determining that potential impact areas were less than modeled and subsequently consulting with associated resource agencies, the expanse of the wildlife exclusion zone was reduced to reflect the minimized impacts.

He recommends that other state departments of transportation consider adopting a similar approach for their own underwater implosion work provided they adhere to the following guidelines:

  • Allow sufficient time to develop and tailor the technology and time of year to the particular locale and scenario – in Caltrans’ case, it took about two years;

  • Ensure that those carrying out the work possess a high level of expertise and will not cut corners;

  • Identify appropriate work windows when the least number of species may be affected;

  • Reach out early to local environmental stakeholder groups as well as resource agencies, and continue the dialogue throughout the process.

The technology behind the air curtain will be added to Caltrans’ Technical Guidance for Assessment and Mitigation of the Hydroacoustic Effects of Pile Driving on Fish. The current version provides guidance on the environmental permitting of in- and near-water pile driving projects. It includes an extensive collection of data on pile driving under a variety of conditions that can be used as an empirical reference for the permitting process.

For more information on Caltrans’ bridge marine foundation implosion work, contact Stefan Galvez-Abadia, Chief, Office of Environmental Analysis and San Francisco-Oakland Bay Bridge Environmental Manager, at stefan.galvez@dot.ca.gov. Information also is available from Dr. Brian Maroney, SFOBB Project Manager and Chief Engineer, at brian.maroney@dot.ca.gov.

Additional information and videos of the E-3 pier implosion are available at http://www.dot.ca.gov/e3implosion/. A video describing the environmental monitoring efforts is available here.

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Texas

TxDOT's Traffic Noise Toolkit Helps Streamline Compliance

Highway project developers in Texas responsible for compliance with traffic noise regulations now have a comprehensive collection of documents to turn to for reference, thanks to Texas DOT’s (TxDOT) online Traffic Noise Toolkit. The toolkit contains a dozen documents on topics including traffic noise regulations, compliance with the National Environmental Policy Act (NEPA), compliance with Federal Highway Administration (FHWA) requirements, and instructions for using FHWA’s Traffic Noise Model.

To assist with documentation, the toolkit includes a template letter to local officials about noise contours for land use planning as well as recommended text for documenting traffic noise analyses. And it provides direct links to relevant federal requirements and websites as well as a brochure about traffic noise abatement in both Spanish and English for public outreach.

Texas DOT's Noise Toolkit helps streamline requirements for projects such as this noise barrier in Austin. Photo: Texas DOT

One of a Group

The Traffic Noise Toolkit is one among a group of 17 environmental compliance toolkits developed by TxDOT’s Environmental Affairs Division. Subject matter ranges from air quality to Section 4(f) of the Department of Transportation Act to bicycle and pedestrian accommodation. Each toolkit contains background policy information, general guidance for compliance, procedures, and standards, and a variety of forms for conducting environmental compliance work and recording environmental decisions.

“Our goal in developing the toolkits was to provide a one-stop shop for information pertaining to compliance policy and guidance,” said Ray Umscheid, TxDOT’s Noise Specialist and lead for the Traffic Noise Toolkit. “These types of materials can be difficult enough to understand without having to scavenge the Internet to find them. By having all of the guidance in one location, related materials can clearly be linked and better understood.”

Compliance and the Toolkit’s Origins

Adherence to traffic noise regulations involves compliance with sections of the National Environmental Policy Act (NEPA) as well as the Federal Highway Aid Act. The latter Act mandated that FHWA develop and promulgate procedures to abate highway traffic noise and construction noise. Compliance with these procedures is a prerequisite for granting federal-aid highway funds or FHWA approvals for construction or reconstruction of a roadway. In Texas, regardless of the funding source, all projects must undergo the same process for a noise analysis and ultimately must be approved by TxDOT.

When developing the toolkit, TxDOT determined the contents and developed the draft documents. The documents then were sent to FHWA for input, revised as needed, and posted online. Umscheid said the toolkits already were under way when his agency was granted authority to assume federal NEPA responsibility from FHWA in December 2014. The toolkits will serve TxDOT well as it carries out that role, he added.

Using the Toolkit

“Traffic noise guidelines and modeling methodologies can vary widely from state to state. Because many of the consultants that perform our work are from other states, it is important to have this information readily accessible to facilitate quicker project turn-around,” explained Umscheid.

One of the toolkit’s benefits is that the documentation for complying with FHWA requirements now can be dropped directly into the documentation for complying with relevant portions of NEPA. Before the toolkit was developed, the TxDOT noise guidelines were posted online while there was an overall environmental manual posted elsewhere on the TxDOT intranet site. In the toolkit, the manual has been revised as a noise only manual which references the noise guidelines and the additional supporting documentation, which either didn’t exist or had to be e-mailed to consultants for specific situations.

Umscheid offered specific advice for those using the toolkit. He said there is an inherent hierarchy in the documents posted, with guidance documents having the most detail and therefore being the key documents for ensuring compliance. Next down in the hierarchy come the standard operating procedures documents, which ensure that procedures are performed and documented appropriately. The information posted has been specifically broken out to address the needs of many audiences and users including in-house users, TxDOT district personnel, local governments, and the public.

A substantial portion of the information in the toolkit is “Texas-specific.” FHWA’s Federal Aid Policy Guide 23 CFR 772 gives states considerable discretion on precisely how to abate construction and traffic noise. The Texas-specific information includes TxDOT policy, guidance, and procedures as well as standards for environmental studies and document production. It reflects the fact that TxDOT has several agreements with resource agencies that require certain formats for information submittals, procedures for consultation, and communication protocols.

Recently, said Umscheid, the toolkit was put to particularly good use on a US 290 project in Houston. Consultants were able to access the TxDOT Traffic Noise Model Manual online and use that reference material to help them update an older noise model so that it was consistent with the agency’s modeling methodology for its current projects. In general, the toolkit helps to ensure that all projects are as consistent as possible, that impacts are predicted accurately, and that abatement will be proposed in a similar fashion throughout the state.

Work in Progress

“While the toolkit clearly already has proven its worth, I still view the current version as a starting point… a work in progress,” said Umscheid.

From time to time, he receives feedback from TxDOT Districts and other users in the form of suggestions for additional toolkit components. The latest was a request for a blank letter template intended to inform local officials of noise impact contours. Although the requirement is directed in the federal rule, a consistent, easily accessible template aids in the effort for districts with little noise experience, he said.

In terms of whether other state DOTs can use the Traffic Noise Toolkit as a starting point for their own toolkits, Umscheid reiterated that much of the content is state-specific. However, he suggested that the general format of the kit (and its counterpart kits) may be useful.

The toolkit is continually under development as federal guidance evolves, best practices are incorporated, and questions and issues arise. Because much of the overall guidance is not prescriptive, associated documentation is easy to create and update within that structure.

One example of an anticipated change to the toolkit will be to post an updated Traffic Noise Model manual upon completion of the beta testing of the upcoming model. When available, it will include additional details regarding the modeling barriers for multilevel apartments or other special land uses.

For more information about the toolkit, contact Ray Umscheid, TxDOT Noise Specialist, at ray.umscheid@txdot.gov, or go to http://www.txdot.gov/inside-txdot/division/environmental/compliance-toolkits/traffic-noise.html.

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Federal Highway Administration

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Featured Case Study

  • Case Study Photo

    Caltrans uses air bubble curtain technology to mitigate noise impacts and protect wildlife during bridge pier implosions.

    Read Case Study >Photo: Caltrans

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