Iowa DOT Studies Erosion, Sediment Control Techniques

To determine the effectiveness of its erosion- and sediment-control techniques, the Iowa Department of Transportation recently teamed up with Iowa State University over two construction seasons to establish which ones worked the best and which ones needed improvement.

[Photo courtesy of Iowa Department of Transportation.]

According to an Iowa DOT blog post, Melissa Serio with the agency’s construction and materials group teamed up with Mike Perez, an Iowa State researcher, to examine alternative erosion and sediment control techniques and adaptations used successfully by other transportation agencies to see how well the Iowa DOT’s standard practices.

Some of Iowa DOT’s frequently used erosion and sediment control techniques include: fabric silt fences to slow water flow and collect sediment; porous mesh tubes (called wattles) filled with straw or other material to control storm water flow; sediment basins or small retention ponds to hold water until solid materials can settle; and rock check dams.

“While we were convinced these elements help control erosion and sediment, it wasn’t clear whether these were the most effective or whether there were other approaches that could be undertaken to achieve better or less expensive results,” Serio explained. “It was important to understand the feasibility of possible changes to practice and identify the right improvements that could be put in place at the right price.”

Photo courtesy of Iowa DOT

While some of Iowa’s existing techniques already performed well, several potential improvements became apparent over the course of the two-year study. For example, simple adjustments to silt fences included reducing the space between posts, adding wire support to the fence’s fabric backing, and cutting a notch, or weir, at the top of the fence so that overtopping of water could be directed to the most desired location.

The Iowa DOT detailed that and other improvements in its final report and technology transfer summary.

Even as the research pointed to potential new best practices, the Iowa DOT said this study “also challenged our expectations.” For example, sediment basins appeared not to be as effective a sediment control measure as had been previously thought. In fact, some data collected suggested that water leaving the basins might have more sediment than it had when entering.

“Further research in a controlled environment will provide more insight, but these initial findings are extremely valuable as we seek to maximize the effectiveness of our erosion and sediment control measures,” the agency noted. “We plan to include the most effective and cost-efficient erosion and sediment control treatments identified in this research project as part of standard road plans in the near future – mostly likely beginning the spring of 2021,” the Iowa DOT said.

Website Tool Created to Support Roadside Solar Array Establishment

The Ray – a corporate venture devoted to roadway technology testing – and the Webber Energy Group at the University of Texas-Austin are creating an interactive web-based tool to help state departments of transportation map out potential highway right-of-way (ROW) locations for solar energy arrays.

[Photo courtesy of the Federal Highway Administration]

According to the Webber Energy Group’s recent analysis, most states have more than 200 miles of interstate ROW suitable for solar energy development, which combined could generate up to 36 terawatt hours (TWh) per year of clean energy – providing approximately $4 billion in economic value to state DOTs.

The group analyzed the unpaved roadside areas at exits on the U.S. interstate system for solar energy generation potential and through this new interactive web-based tool hosted at, each of the lower 48-states now have access to projections of how much solar energy could be generated on their interstate exits.

“Interstate solar just makes sense,” said Harriet Langford, founder and president of The Ray, in a statement. “As our transportation systems become smarter and electrified, we will need more energy available, closer to the interstate and interstate exits, and more funding to support the infrastructure demands. By enabling renewable energy generation using the idle roadsides, our state DOTs can help to fill this gap.”

Photo courtesy of the Bureau of Land Management

“The aim of this project is to provide a report and mapping tool by which state DOTs or other interested parties can assess the potential for installing solar in the interstate ROW in all contiguous 48 states,” added Michael Webber, a professor of mechanical engineering at UT. “Our goal with this study: to help people understand the potential for interstate solar so that policymakers, developers, and investors have a clearer view of the opportunity.”

Interstate roadsides are appealing areas for renewable energy development for many reasons, he said, including: unshaded acreage; ease of access; public ownership status; and lack of competing development efforts. Because exits have more room to accommodate the transportation safety requirements, such as safety setbacks, they are ideal locations for solar development, Webber noted.

Individually, most states have interstate solar potential in the thousands of gigawatt hours (GWh) per year. At a typical retail price for electricity of roughly 10 cents per kilowatt-hour (KWh) and a wholesale price of two cents per KWh, this means states could generate carbon-free electricity with millions of dollars’ worth of value – anywhere from $2.5 million to $181.4 million annually, the group’s research indicated.

State DOTs can also take advantage of operational cost savings, the Webber Energy Group noted – such as through reduced roadside maintenance and reduced energy costs – and even build new revenue streams over the lifetime of such solar array projects, which could be 30 years or more.

“On day one of these projects, state DOTs win,” emphasized Laura Rogers, director of strategic partnerships at The Ray. “State DOTs have a lot of options when structuring ROW renewable energy projects.”

Depending on their priorities and goals, state DOTs can own the renewable energy system and use or sell the clean energy generated, she said – or they can work with a solar developer who owns the system and collect a land fee, while at the same time transferring land maintenance obligations to that developer. “No matter how they decide to structure the deal, state DOTs win on all fronts by optimizing underutilized land to generate clean renewable energy that benefits their communities, the environment, and their budgets,” Rogers added.

Broadband in the Right of Way: Ohio DOT’s Experience

Learning and working during the COVID-19 pandemic has made connectivity to the Internet more important than ever. That is why access to broadband service across the country is becoming essential for almost every communizing – providing critical virtual links to everything from online schooling to work-from-home opportunities. Those needs are not lost on the transportation industry.

[Photo courtesy of the Ohio DOT.]

That’s one reason why the Federal Highway Administration issued a notice of proposed rulemaking that would amend existing regulations governing the installation of broadband infrastructure on the right-of-way of Federal-aid or direct Federal highway projects.

According to the proposed rule, “highway rights-of-way are commonly used to accommodate public utilities, such as phone lines, electrical lines and pipelines. Expanding their use to include wireless broadband technology is a ‘critical next step’ in advancing connectivity in rural America.”

[Editor’s note: The FHWA is accepting comments on its proposed rule until September 14.]

Many state departments of transportation across the country are already participating in local efforts to improve and expand broadband access.

While states do not support a strict federal preemption on how states manage broadband deployment on their own properties, Carlos Braceras – executive director of the Utah Department of Transportation and the 2018-2019 president of the American Association of State Highway and Transportation Officials – noted in Congressional testimony that speeding up the federal permitting process would help facilitate “the merger of technology between motor vehicles and infrastructure.”

Photo courtesy of the Ohio DOT

To that end, InnovateOhio – in partnership with the Ohio Department of Transportation – issued a 16-page broadband access report in September 2019 to provide a strategic plan for providing more broadband access to citizens and businesses.  “Whether it’s connecting children to information at school or connecting smart vehicles to infrastructure, access to broadband is vital in the 21st Century,” said Jack Marchbanks, Ohio DOT’s director. “ODOT has always played a role in helping connect our state and this is just another opportunity to do that.”

That report highlighted that efforts to utilize right-of-way come with “special environmental” considerations. For example, the FHWA recommends the best practice of resource sharing in order to avoid repeated excavation. For instance, Dig Once initiatives have led to agreements between state DOTs and broadband contractors that allow use of right of way for fiber installation in exchange for broadband installation for highway message signs and autonomous and smart roadway transportation innovations. FHWA also encourages the use of trenchless technologies for broadband installation to minimize erosion and destruction of the area from construction.

When state DOTs need to issue permits for broadband installation on highway rights-of-way, categorical exclusions can typically be used when a request is for underground or above ground power, telephone, or pipelines, where no new structures, facilities, or major improvement to those facilities are required. Generally, buried communication lines fit this category. 

As part of Ohio DOT’s strategic plan for broadband, the agency launched an E-Permitting System for right-of-way access that aims to be more convenient for permit requesters; especially in terms of saving time when requesting to install broadband fiber optic cable. This centralized, digital system replaces a paper-only right-of-way permitting system that the Ohio DOT managed across all 12 of its district offices. 

[Details are available online at]

The agency also noted that partnerships in Ohio are fostering “environmental innovations” when increasing broadband installation in the right-of-way.

For instance, the City of Defiance proposed using sensors to monitor chemicals that can lead to harmful algal blooms in the local watershed. Yet those sensors needed a robust internet connection to allow researchers access to algal bloom data in real time. As a result, the city proposed installing concentric “fiber rings” connected to the monitoring stations via the existing infrastructure right-of-way – eventually expanding those fiber rings to provide high-speed internet services to residential and business customers.

That is an example of a right-of-way project that not only expanded broadband to underserved areas but also simultaneously helped solve real-world environmental problems, the Ohio DOT noted.

New Jersey DOT’s Role in State Transportation Electrification Plan

New Jersey Governor Phil Murphy (D) has set forth an aggressive goal of achieving 100 percent clean energy by 2050 for the state – and the New Jersey Department of Transportation will play a key role in helping attain that goal.

The agency is part of a broad statewide transportation electrification effort in line with the Rejoining the Regional Greenhouse Gas Initiative or RGGI; a multi-state, market-based program that establishes a regional cap on carbon dioxide or CO2 emissions.

In mid-April, the governor announced that RGGI auction proceeds will provide $80 million each year to programs that reduce greenhouse gas emissions, with a new, more all-inclusive Energy Master Plan outlining several state investment strategies that aim to electrify New Jersey’s transportation sector. 

Along with the Master Plan, the RGGI Strategic Funding Plan details how to move toward the goal of a greener transportation system. New Jersey’s plan for its RGGI revenue is designed to support legislation signed in January that calls for the state to have 330,000 registered electric vehicles or EVs by 2025 and 2 million by 2040. It also plans for 400 fast charging stations at 200 locations along major highways and communities by 2025.

To that end, the New Jersey DOT and several other state agencies –  NJ TRANSIT, the New Jersey Board of Public Utilities, the Department of Environmental Protection, the Department of Community Affairs, the Department of Labor and Workforce Development, and the Economic Development Authority – will work together within their respective areas to achieve the RGGI’s strategic goals. 

The specific strategies laid out for the New Jersey DOT within the plan include:

  • Promoting the use of the Logo Sign Program and Tourist-Oriented Directional Signing or “LOGOS” program to display the locations of EV charging stations on blue state highway exit signs. The state will also work collaboratively with local governments on transportation planning and land use/housing planning that will enable multi-modal transportation and EV-ready infrastructure.
  • Working to prioritize multi-modal accommodations in projects located in low- and moderate-income and environmental justice communities to promote more pedestrian and bicycle traffic as those two modes are part of the RGGI’s emission reduction strategies.
  • Looking at re-evaluating “Level of Service” metrics that measure the quality of transportation services and traffic flow and develop plans to mitigate congestion and reduce idling time for vehicles. 
  • Working with local governments to promote implementation of “Complete Streets” policies in municipalities, possibly with additional grants and incentives. As part of these efforts, the New Jersey DOT and NJ TRANSIT will continue to lead a multi-agency “Smart Growth” program called the Transit Village Initiative, which helps municipalities redevelop or revitalize their downtowns into dense communities within a half-mile of transit centers.
  • Deploying Transportation Systems Management & Operations or TSMO strategies to relieve road congestion through signal optimization technology; an effort funded via the federal Congestion Mitigation and Air Quality program to make traffic patterns more efficient and further reduce idling.

Yet even as New Jersey begins moving towards electrifying its transportation sector, the unintended consequences of funding shortages must also be considered.

The draft fiscal year 2020 New Jersey Transportation Capital Program, which funds both the New Jersey DOT and NJ TRANSIT for a total of $3.679 billion, depends on motor fuels tax revenues for funding – already significantly reduced due to the impact of the COVID-19 pandemic. As New Jersey encourages use of electric-powered vehicles, the state is also considering a replacement for lost fuel tax revenue and is participating in the I-95 Coalition Mileage Based User Fee study to see how such fees would affect different communities and how they would be collected.

Can Highway Construction Achieve “Net Zero” Carbon Emissions?

What does it mean to be “net zero” in the transportation world today?  When talking about carbon emissions, it refers to achieving an overall balance between emissions produced and emissions taken out of the atmosphere.

For example, the building industry has been working toward “net zero” infrastructure for years.  According to the World Green Building Council, buildings are currently responsible for 39 percent of global energy-related carbon emissions: with 28 percent coming from operational emissions – from the energy needed to heat, cool, and power the structures – and the remaining 11 percent from materials and construction. 

Though highway roads and structures do not have the same level of operating emissions as a building, “embodied” carbon from the construction process significantly adds to transportation’s carbon footprint. Embodied carbon is the carbon footprint of a material. It considers how many greenhouse gases (GHGs) are released throughout the supply chain. This includes the extraction of materials from the ground, transport, refining, processing, assembly, in-use and finally its end of life recycling of disposal.  

The building industry now believes that embodied carbon in projects can be reduced 10 percent to 20 percent without increasing capital costs. One new study out of Sweden believes net-zero carbon emissions in construction supply chains can be reached by 2045.

Photo courtesy Hawaii DOT

But what exactly does this mean for highway and bridge construction? Many believe that policy is the starting point for significant reductions in carbon in highway projects. Globally, many countries are already requiring “net zero” infrastructure design. In Sweden, for instance, large transport infrastructure projects (roads, rail, tunnels) are required to calculate and report embodied carbon and monetary incentives awarded if embodied carbon is below a specified target. 

Some state departments of transportation are already working toward similar goals. For example, the Hawaii Department of Transportation started a testing project in 2019 using a concrete mix injected with waste carbon dioxide (CO2). The CO2 is mixed into the concrete using CarbonCure technology. The resulting product traps carbon dioxide in mineral form within the concrete and improves the comprehensive strength of the material. 

The test project involves a pour of 150 cubic yards of carbon-injected concrete next to an equivalent pour of standard concrete mix on an access road for the Kapolei Interchange. This test will allow the Hawaii DOT to do a side-by-side comparison of the carbon reducing mix versus a standard mix to determine specifications for the use of carbon-injected concrete for road projects in the future.

“We’ve seen the benefits to CO2 mineralized concrete and will be using it when appropriate in Hawaii’s road and bridge projects,” explained Ed Sniffen, Hawaii DOT’s deputy director for highways. “The availability of environmentally friendly materials such as carbon injected concrete is necessary for us to move forward in reducing the carbon footprint of our construction projects.” 

In an interview with Smart Cities Dive, Sniffen added that the carbon-injected material has turned out to be stronger and more workable, with no increase in cost over traditional concrete. “The overall carbon savings is significant,” he said. “We reduce it overall about 1,500 pounds into the environment. Now, that doesn’t sound like a lot, but really, that equals up to one car driving 1,600 miles continuously. So, it builds up quite a bit.”

How can such “embodied” carbon in highway construction be reduced? In general, highway designers can use Life Cycle Analysis based tools to determine the environmental footprint of a whole project and search for ways to reduce life cycle GHG emissions and other impacts through strategies such as:

  • Ensuring efficient use of materials (i.e. “right-sizing”)
  • Selecting materials with more efficient manufacturing processes
  • Minimizing transportation impacts through use of local materials
  • Using robust materials that require less maintenance, repair, and refurbishment
  • Choosing materials that can be reused or recycled instead of landfilled

Although there may be a learning curve and increased costs initially to incorporate embodied carbon reduction into construction decisions, it appears that the incremental costs of incorporating this analysis is comparatively small for the potential benefit it could provide. Complicated decisions and life cycle analysis must be done from the planning phase of the project through design and construction to significantly reduce embodied carbon and hit the “net zero” goal. In the future, these efforts will be driven by government policy and environmental stewardship of firms and contractors. It is inevitable that the wave of “net zero” goals in the building industry will continue to transition into the highway industry as well.