U.S. Department of Transportation
Federal Highway Administration
1200 New Jersey Avenue, SE
Washington, DC 20590
Federal Highway Administration Research and Technology
Coordinating, Developing, and Delivering Highway Transportation Innovations
This magazine is an archived publication and may contain dated technical, contact, and link information.
|Publication Number: FHWA-HRT-2006-005 Date: July/August 2006|
Publication Number: FHWA-HRT-2006-005
Issue No: Vol. 70 No. 1
Date: July/August 2006
A sediment storage system is helping preserve the pristine environment surrounding a scenic highway in the Rocky Mountains.
|This aerial photo shows two tight switchbacks of Berthoud Pass highway (U.S. 40) as it winds its way up the mountain. The construction work is not only widening and improving the roadway but also protecting the local environment and water quality. Photo: Gregg Gargan, CDOT.|
No one said it would be easy. Reconstructing a narrow highway that cuts through a mountain range, winds its way up 3,446 meters (11,307 feet), and passes through some of Colorado's most pristine alpine environment would have its share of challenges. At the least, the engineers would need to reconcile the frequently conflicting aspects of roadway geometry, safety, wildlife and forest impacts, aesthetic considerations, and water quality requirements.
The Berthoud Pass highway (U.S. 40) climbs through the Arapaho National Forest between the ski resort communities of Winter Park to the north and the towns that lie along I-70 to the south. In the mid-1990s, officials at the Colorado Department of Transportation (CDOT) determined that the road through the pass needed to be upgraded for a number of reasons. The tight curves, steep switchbacks, and narrow pavement made travel treacherous. From a safety perspective, with minimal shoulders, the highway offered few safe zones where drivers could pull over or recover from errors. Old highway cuts from past years were eroding, causing rock and mudslides in the summer and icy spots in the winter and making driving potentially treacherous year round.
Environmental considerations also factored into the equation. Wildlife following migratory routes across the highway interfered with traffic flow, endangering both animals and motorists. And the Berthoud Pass ecosystem suffered when sand and gravel applied to the roadway to improve traction eventually wound up in local rivers and on forest floors.
Work to improve the safety and capacity of 8 kilometers (5 miles) of U.S. 40 on the east side of Berthoud Pass focused on accomplishing the construction objectives with as little impact as possible on the Rocky Mountain environment. Ultimately, the project team not only provided a safer, modern mountain corridor but also improved water quality, reduced erosion, and took steps to protect local wildlife.
Because work zone-related congestion is a frustration for road users, CDOT implemented several measures to mitigate negative impacts on the traveling public. These included setting maximum allowable delays at 40 minutes, allowing no lane closures from 2 p.m. on Fridays until 10 p.m. on Sundays, requiring that the road be open to two-way traffic for the weekends and holidays, restricting the amount of time motorists would have to travel on a nonpaved road surface, and requiring that no lane closures occur between late fall and early spring while the Winter Park Resort ski area was in operation. In addition, CDOT created a Web site to provide up-to-date information to motorists and community members. The CDOT public relations (PR) staff was heavily involved in project communications and brought on a local PR firm to help with the development and distribution of information.
With the first two phases completed in 2002, and the final phase scheduled for completion in late 2006, the Berthoud Pass Mountain Access ProjectTM already has earned accolades for CDOT, its consultants, and Federal agency partners. (See "Project Awards to Date".)
|Year||Award||Organization Bestowing the Award|
|2003||Environmental Achievement Award of Distinction||International Erosion Control Association|
|2003||Globe Award||American Road & Transportation Builders Association|
|2003||Engineering Excellence Awards, Merit Award||American Council of Engineering Companies|
|2005||Environmental Excellence Award for Roadside Resource Management and Maintenance||Federal Highway Administration|
|2005||Best Practices in Context Sensitive Solutions, Notable Practice||American Association of State Highway and Transportation Officials Center for Environmental Excellence|
By the time the environmental assessment for the project was completed in 1997, CDOT engineers knew that the principles of context sensitive solutions would be significant components in the design and construction. In fact, says CDOT Landscape Architect Mike Banovich, "The project was designed with possibly the highest level of environmental sensitivity used on any CDOT project to date."
|In this photo from the 1930s, motorists are driving around a switchback on historic Highway 40, climbing toward Berthoud Pass.|
The Berthoud Pass highway carries some 7,000 vehicles per day, on average, a significant increase from its days as a wagon trail built in 1874. Prior to the reconstruction and widening project, which began in 1999, the two-lane road measured only 7.6 meters (25 feet) wide in places. The safety and capacity improvements notwithstanding, a major concern for project crews, and certainly the traveling public, has always been water in its myriad forms: rain, snow, ice, and runoff, all resulting in challenges for maintenance as well as impacts on the environment. Therefore, resolving roadway deficiencies associated with snow storage was a key element in reconstructing this stretch of highway.
|The newly widened highway provides ample space to store plowed snow, as shown here, without encroaching on the travel lanes. As the snow melts, the runoff, along with deposited traction sand, will flow into sedimentation basins, from which the sand can be retrieved and then reused for other purposes.|
Located in the heart of Colorado's ski resort region, Berthoud Pass receives more than 10 meters (400 inches) of snow annually. After heavy storms, which can arrive as early as September and continue into early June, maintenance crews had limited space for plowing and piling the mounds of snow cleared from the road.
|This illustration shows a profile drawing of a roadside sediment basin. Source: CDOT.|
In addition, CDOT typically places approximately 2,700 to 3,600 metric tons (3,000 to 4,000 tons) of sand on the roadway each winter to provide traction for motorists. Staff from the CDOT Environmental Program identified the sand mixture, which includes approximately 5 percent salt, in combination with ongoing erosion from the exposed slopes, as major factors contributing to sediment loading of nearby Hoop Creek and the West Fork of Clear Creek. Accommodations for snow and sand storage, therefore, were important considerations. A primary component of the highway construction plan involved creating a highway template (a cross section of the roadway that includes all features such as retaining walls, drainage areas, shoulders, driving lanes, and sediment basins) that would ultimately recapture 60 to 70 percent of the sand.
|Above:A triple-tiered wall replaced a heavily eroded hillside. The widened roadway is shown here halfway through repaving.
Below: Traps such as this one capture sand from winter maintenance activities so CDOT workers can collect it for reuse elsewhere.
"The new system was loosely modeled on the existing sediment ponds we already have on the west side of the pass," says CDOT Area Maintenance Supervisor John Bordoni. "But a storage system on the east side needed to be compact enough to accommodate smaller spaces and a different highway geometry, yet large enough to accommodate our loading equipment."
To improve the safety of the highway, while also addressing the snow and sand challenge on the mountain pass, CDOT created a plan for roadside management and maintenance that involves several key features. The first was widening the highway to three lanes by adding a climbing lane and increasing the width of the roadway to 20 meters (66 feet). The resulting roadway template for the project includes three 3.7-meter (12-foot) lanes, 1.8- and 2.4-meter (6- and 8-foot) shoulders, and snow storage areas 1.5 and 3.4 meters (5 and 11 feet) wide.
|After years of erosion and sediment buildup caused by sand-laden runoff from the roadway, this wetland was restored during the Berthoud Pass Mountain Access Project.|
Next, CDOT installed concrete safety barriers to prevent vehicles from leaving the roadway. Finally, the department created snow storage areas between the road shoulders and safety barriers on both sides of the highway. A system of paved ditches and culverts, with numerous inlets, will ensure that leftover sand is transported with the snowmelt and runoff through a piped system to 12 strategically placed sediment basins along part of the highway. Furthermore, underdrains and cross culverts are now preventing clean, offsite drainage from mixing with highway surface drainage.
As a result of the widened highway, much of the traction sand applied in the winter months can be plowed away from the travel lanes without being pushed over the side. Maintenance workers then can collect and haul the sand away once the snow melts. Any sand that flows downhill with snowmelt will reach the concrete sedimentation basins and settle down to the bottom. The water runoff rises to the top to exit the basins through small "weep holes" in steel plates. The clean water reenters Hoop Creek and flows into Clear Creek, which supplies drinking water to approximately 300,000 people in the west Denver metropolitan area and also is used for a variety of agricultural and industrial purposes.
"The water in the sediment basin filters slowly," says CDOT Region 1 Environmental Specialist Holly Huyck, who collects and analyzes sand and water samples from the sediment ponds each spring. "In the last 4 years, we have tested used sand samples, and they are not hazardous."
Once the water drains from the sediment ponds, maintenance crews can recover the sand, entering down sloped ramps, which provide access to loaders that can easily remove the sand. Any leftover sand is removed by sweeping.
The current use and storage system is working well. In addition, to help control sediment loading in the creeks, cut-and-fill slopes from the original highway construction were terraced, stabilized, and replanted to prevent erosion.
CDOT's environmental team is currently researching the effective reuse of recaptured sand for purposes other than winter traction. "We know we cannot reuse the sand for highway traction," Huyck says. "The sand has been ground too finely and would contribute to the PM10 [airborne particulate matter less than 10 micrometers in diameter] pollution caused by fine dust entering the air."
|This worker is planting a tree upslope from the highway to help stabilize the roadbank.|
Instead, CDOT is using some of the sand to construct sound berms adjacent to highways. The rest is hauled away and put to other uses. "Maintenance crews haul the sand to [the town of] Empire, where it is effectively used to cap old mill tailings," says CDOT Project Engineer Brian Gilbert, a resident of Empire who proposed the storage idea. "It has been a win-win situation."
The reinforced concrete sediment basins are located in the switchbacks and along the edge of the snow storage flow lines in straighter roadway segments. This allows stormwater and snowmelt to be transported either directly into the basins or to flow into drop inlets that allow the water to outfall through culverts into the basins. Some of the basins were built early in the project phases and were used as erosion-control features during construction.
CDOT was committed to protecting water quality throughout the project's construction. Engineers are tracking and monitoring the amount of material being collected and removed from the sediment control structures and the roadway corridor. They will correlate these efforts with data from water quality monitoring to evaluate the overall efficiency of the system and ensure long-term protection of the Hoop Creek basin.
"We anticipate that as a result of the roadway improvements, sediment loading from the highway corridor will be significantly reduced," Huyck says. "It has taken years for the sand to work its way into the streams, so it will take some years to see major improvements."
A tributary of Hoop Creek also was shifted during the project to protect it from highway runoff. The small creek that had been approximately 3 meters (10 feet) from the road now is 15.2 meters (50 feet) away.
To date, the total project costs for the entire east side of the pass are about $76 million, according to CDOT's Office of Financial Management & Budget. For partners CDOT and the Federal Highway Administration, as well the U.S. Department of Agriculture's Forest Service, this has been an important investment. The project demonstrates that cost-effective management and maintenance activities can promote environmental protection and protect water quality near roadways.
"To work and be successful in alpine environments requires adequate resources to retain the mountain slopes, protect and preserve the forests, and create a safe mountain corridor," says CDOT Resident Engineer Ina Zisman. "This work also required strong teamwork, technical expertise, and a will to create a successful project for the public and the environment."
CDOT Program Engineer Brian Pinkerton echoes that sentiment. "CDOT raised the bar for environmental stewardship on this project," he says, "[setting] a new standard for erosion control, water quality, and wildlife access on Rocky Mountain highway projects."
|CDOT used stringent contractor specifications to maintain a construction schedule that would minimize inconvenience to motorists.|
CDOT took a number of measures to mitigate the impacts of 4 years of construction by stepping up its communication with community residents, businesses, elected officials, and the media in Grand County. First, CDOT's PR office assigned an employee to serve as a liaison between the project and the community. The agency also provided a budget to support a public information campaign about the project and hired a Grand County firm to do the work. These efforts provided the public with a variety of sources for information: the project liaison, stories in the media, displays in public offices and businesses, and the project's Web site. Slowly these efforts shifted the focus from the negative aspects of construction impacts to the more positive future benefits of the improvements to Berthoud Pass.
In addition, CDOT permitted work that could be performed effectively without lane closures to continue during times that would normally have been restricted as nonworking hours, including weekends, nighttime, and Friday afternoons. This practice allowed peak traffic flows to proceed while at the same time enabling the contractor to catch up or even get ahead on some wall-building operations.
The Berthoud Pass Mountain Access Project will wrap up in the fall of 2006, just before snow hits the region. Only 3.2 kilometers (2 miles) of the widened roadway, sediment basins, and concrete barriers remain unfinished. A wildlife underpass, which will measure 7.3 meters (24 feet) wide by 3.7 meters (12 feet) high, and adjacent deer fencing also will be installed.
CDOT and its contractors are committed to upholding the same environmental principles that they maintained during the first two phases of the project.
"CDOT was able to come to an environmentally sensitive area, upgrade and widen a narrow two-lane road, and leave with a sense that the environment and the traveling public are both winners," says CDOT Project Engineer Gilbert.
"There is truly no other project like this in the world," adds CDOT Region 1 Transportation Director Jeff Kullman. "We have spectacular features that correct erosion problems. We have preserved historical features and provided wildlife crossings and beautiful landscaping. These elements complement the safety and capacity improvements that have been made."
Nancy Shanks is a PR specialist with CDOT.