At first glance, it may look like the customer for Maryland’s Inter-County Connector (ICC) is wildlife and vegetation. With 15 percent of the $2.55 billion construction budget dedicated to environmental programs, the Maryland State Highway Administration (SHA) has made a resounding statement that large roadway projects will be conceived, built, and evaluated based on their environmental stewardship.
With certainty, a project of this scale and with specific environmental requirements has introduced design and construction innovation, which has helped make the ICC a model for how highway builders can deliver megaprojects in sensitive areas.
Stretching nearly 18 mainline miles when the first three segments are completed, the ICC will provide a much-needed east-west connection between Maryland’s populous Montgomery and Prince George’s counties. The six-lane, limited-access toll road will traverse multiple communities, parklands, and waterways following a great deal of effort to maintain these natural, human, and cultural environments. In some cases, projects such as stream and wetland restoration, bike trail creation, and reforestation will rectify the consequences of previous development.
Longer bridges, integrated designs One technique for addressing environmental sensitivity is to build longer-than-normal bridges, according to SHA’s ICC Project Director Melinda Peters. “This creates a narrower footprint and allows greater clearance for stream-stabilizing shrubs,” she said. Some bridges span a whole floodplain, and where appropriate, designers used precast concrete beams to avoid the un-environmental sandblasting, painting, and associated maintenance of structural steel beams.
On the 7-mile segment known as ICC-B, recognized as the most environmentally sensitive section, the five mainline crossings are dual bridges (and there are five cross-over spans). To ensure these structures and the overall roadway are minimally intrusive to surrounding communities, there is an extensive program of landscaping, sound barriers, and retaining walls. On ICC-B, there are eight interchanges supported by mechanically stabilized earth (MSE) retaining walls designed for global stability. Precast facing panels and wide, ribbed-steel strips enable taller walls with greater longevity, and different top-of-wall designs helped to achieve the desired diversity of appearances. Four architectural finishes and different sizes also contributed to the accommodation of preferences from nearby communities.
One MSE wall reaches 50 feet in height, which required designers to take into account the lateral loads from adjacent, caisson-supported sound walls. The panel facings were cast with special inserts at the front face to accommodate a cast-in-place protective wall.
In another effort to decrease the project’s footprint, according to Peters, the arches of a bridge on ICC-A avoid a stream altogether. “They are 70 feet above it and sit on the sidewalls of the valley with footings socketed into the sides,” she explained. ICC-A’s path also has a section below grade to reduce the noise and visual impact to existing communities. Sound barriers, landscaping, and berms line the highway for additional screening; walls, guardrails, and other features use browns and other earth tone colors that blend together well.
Stormwater management Concern about impacts to the environment and to communities figures prominently in the highway’s design, construction, and operation. In fact, it has taken planners nearly 50 years to reach agreement among stakeholders. Maintaining their support involves simply delivering what was promised in terms of customization. However, another significant factor is the technological innovation that has enabled those promises to be kept.
Stormwater management, for example, uses a system of underground tanks that collect road water through vegetative swales. The water cools in the concrete tanks before being slowly released to streams with temperature-sensitive fish. In areas where designers had to plan open ponds, the “dry” holes hold water as long as 72 hours to lower the temperature before release.
Especially during construction, managing the runoff, erosion, and sediment control falls to a combined system of automated and human water quality monitors. In-stream, automated monitors provide continuous data to determine degradation via measures such as pH, turbidity, and water level, and data are posted to the Web via telemetry. Environmental specialists also use handheld monitors for instant readings of discharges during storms or dewatering operations; any readings not compliant with water-quality standards generate e-mail alerts. The redundancy of these monitors, along with stormwater filtration, underground storage, and even the use of washing stations to clean mud from vehicles, combine to keep streams as healthy as possible during and after construction.
Innovation also is evident in stream crossings below grade. Special culvert designs include a maintenance-free, bottomless arch that enables aquatic, amphibian passage and small mammal passage, as well as deluges.
“We take the geomorphic approach where we take into account the existing stream geometry and design the culvert so that it can handle different flow rates for the whole flood plain,” said Bill Park, environmental manager for ICC-B contractor MD 200 Constructors.
Taking on unknowns with design-build Construction of the highway is an accomplishment that’s hard to understate, and it could not have been accomplished without a design-build approach where work could proceed in some areas without completion of a final design.
In one case, shallow rock layers could handle the spread footing for a bridge, and on others caissons and piles provided abutment support. In other instances, drilled shafts reduced the impact to wetlands (and improved the bridge’s performance with regard to flooding and scour). The variety of subsurface conditions prevents ironclad planning and costing. According to Park, “Design-build helped cut the schedule in half for ICC-B.”
ICC may be too good The ICC stands out as a great example of a project because of its environmental orientation, and the consensus achieved among the state, county, property owners, and other stakeholders. However, as a new, high-profile road, an enduring effect is that it draws attention to the state of other roads.
Many of Maryland’s roads and bridges need maintenance, repairs, and upgrades to meet current design standards. According to the transportation research group TRIP (www.tripnet.org) in its report, “Future Mobility in Maryland: Meeting the State’s Needs for Safe and Efficient Mobility,” roads in need of repair cost each Maryland motorist an average of $422 annually in extra vehicle operating costs — $1.6 billion statewide. It’s an issue not just for the immediate costs to consumers and businesses, but for overall economic development and prosperity: The tonnage of freight transported into, out of, within, and through Maryland will grow by 105 percent in roughly the next 20 years.
As governments strive to improve their transportation networks and highway builders seek to integrate projects with natural surroundings, the ICC serves as a model. It showcases environmental stewardship — even a certified arborist was hired to evaluate the critical root zones of trees along the limit of disturbance. Most importantly, it emphasizes engineering best practices that will ensure a long life for the habitat, the roadway, and the state’s transportation needs.
The players
Multiple phases of ICC construction
ICC totals
Eric Hilberath is national sales director for EarthTec, a division of design-build contractor GeoStructures.
Get more information about the ICC and view project photos at www.iccproject.com.
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