Work Speeds Ahead on Replacing Century-Old Bridges With Tunnel

COSMIX Rebuilds Colorado Springs’ I-25

Tue June 12, 2007 - West Edition
Richard Miller



When Interstate 25 In Colorado Springs, Colo. was opened in 1960 it originally handled traffic volume of 8,500 vehicles per day. Forty-seven years later the same two-lane corridor now handles over 100,000 vehicles daily.

In 1999, Colorado voters approved the Transportation Revenue Anticipation Notes (TRANS Bonds) to accelerate critical transportation projects. The same year the Colorado Department of Transportation (CDOT) began an environmental assessment to determine ways to ease the congestion that developed in the Colorado Springs corridor. This study was submitted to the Federal Highway Administration (FHWA) who subsequently gave notice to CDOT to proceed with the work.

In January 2005, the Colorado Springs Metro Interstate Expansion (COSMIX) name was announced and the $130 million contract was awarded to Rockrimmon Constructors, a joint venture of CH2M Hill Cos., Ltd. of Englewood, Colo., and Sema Construction Inc., of Centennial, Colo.

COSMIX goals are to maximize capacity and mobility improvements in the corridor within the program budget, minimize inconvenience to the public during construction, provide a quality product and make the improvements with the project deadlines.

When completed in December 2007, the COSMIX project will widen I-25 to three lanes in each direction along a 12-mi. (7.2 km) corridor south of the Bijou Street interchange to just south of the North Academy Boulevard interchange. Improvements also include numerous bridge replacements and several interchange enhancements.

Additionally, bridges and other infrastructure are being constructed to allow construction of a future fourth lane in each direction. Current estimates anticipate the need for a fourth lane around 2016.

“Commuters in the Pikes Peak region will enjoy three lanes of traffic in each direction through the heart of Colorado Springs,” said Dave Poling, CDOT project manager. “Visitors to downtown will be welcomed by a beautiful gateway bridge and commuters on the north side of town will find greatly improved access between the interstate and primary surface roads.”

According to Poling, COSMIX uses a new approach in highway construction to Colorado Springs: the ambitious and innovative concept of design-build, which provides flexibility to get the most improvements possible out of an existing budget.

“Design-build allows us to reduce the duration of the project, minimizing the impact of construction on the community,” said Poling. “By combining both the design work and the construction work into one contract, it facilitates cost effective, time efficient and innovative ideas, allowing CDOT and Rockrimmon Constructors to pursue creative approaches to scheduling, phasing and traffic handling during construction and, ultimately, condense the length of construction time.”

Construction is proceeding by location rather than defined phases. “Rather than proceed with defined phases, the project is divided into four geographic segments,” said Poling. “Two of those segments (Fillmore to Garden of the Gods, Woodmen to North Academy) are already complete, and the most complex segments are speeding toward completion.”

According to Poling, mainline pavement depth will be 12.5 in. (31.75 cm). Configurations from Fillmore Street to the Garden of Gods interchange will be asphalt because they are temporary configurations and additional work will be completed when additional funding becomes available. The other two segments are concrete and are in their final alignment, and need only minor inside widening to increase the highway from six lanes to eight when additional funding becomes available. The concrete mainline panels have doweled transverse contraction joints and longitudinal contraction joints reinforced with tie bars.

The pavement will have a presumed life expectancy of ten years for sections paved in asphalt, with the concrete pavement having a design life of 20 years. Preventive maintenance and rehabilitation may extend the lives of these pavement structures.

Sixteen of the mainline and overhead bridges will be replaced with reinforced concrete superstructures and class H concrete decks. Three additional bridges are being rehabilitated and widened to accommodate the I-25 widening of four lanes to six but will ultimately need to be replaced in the next phase of widening from six lanes to eight.

More than 1.12 million cu. yds. (856,301 cu m) of dirt will be excavated, relocated and used as backfill throughout the COSMIX project limits. Approximately 15,000 tons (13,607 t) of rock will be imported to line drainage ditches.

Nearly 100 percent of the old infrastructure (concrete and asphalt from the mainline, ramps and bridges) is crushed and recycled into the fill of the new infrastructure. Metal and rebar are removed and recycled at local recycling plants. Only the debris from clearing and grubbing activities and trash is disposed of in landfills.

Nearly 30 percent of the project involved the complex task of relocating multiple utilities including storm and sanitary sewer, water, gas, electric, communications and fiber. Critical to the project’s success has been to maintain service of the utilities during relocation in a heavily urbanized area.

The Environmental Assessment (EA) looked into several different transportation alternatives to ease congestion on I-25, including various types of mass transit and a bypass around the city. The study showed that while the other options may be necessary in the future, approximately 85 percent of traffic on I-25 is local, so adding capacity to the highway through the urbanized area of Colorado Springs was the logical choice to alleviate congestion.

However, one future addition will be High Occupancy Vehicle (HOV) lanes. They are part of CDOT’s future plans, but not during this phase of COSMIX.