Building the Future: A multi-modal solution to congestion

Highway and transit agencies join forces to complete Denver’s Transportation Expansion (T-REX) design-build project.

A 500-foot-long, cut-and-cover tunnel for the light-rail system reduced the overall height of the I-25/I-225 interchange by 30 feet.

Denver needed the Transportation Expansion (T-REX) project. The five-year, design-build project improved 17 miles of I-25 and added 19 miles of light rail through Southeast Denver, Aurora, Greenwood Village, Centennial, and Lone Tree, Colo. As the only north-south interstate in Colorado, the I-25 corridor links two, high-employment areas—the Denver Central Business District (downtown) and the Southeast Business District, which includes the Denver Tech Center, Greenwood Village, Inverness, Meridian, and the city of Centennial. More than 180,000 people work in these two employment centers, and another 30,000 or so work along the corridor. On average, 162,800 vehicles a day pass through the I-25/I-225 interchange, and both highways were constantly congested during daylight hours. Once Colorado’s most heavily congested corridor, the area had been studied for 20 years to find solutions.

"It was looked at as a light rail-only solution [or as] a highway-only solution, but the optimal approach was determined to be multi-modal," said T-REX Project Director Rick Clarke. Clarke, formerly assistant project director with Denver’s transit agency, the Regional Transit District (RTD), replaced long-time T-REX Project Director Larry Warner of the Colorado Department of Transportation (CDOT) when he retired in March 2006.

Along I-25, T-REX added one through lane in each direction from Logan Street to I-225, and two through lanes in each direction from I-225 to the C470/E470 interchange. On I-225, the project added one through lane in each direction from Parker Road in Aurora to I-25. T-REX reconstructed eight interchanges, including I-25/I-225; built or rehabilitated 65 bridges; improved drainage; enhanced safety; added and improved shoulders; improved ramps and acceleration/deceleration lanes; and installed 3 million square feet of retaining walls—either mechanically stabilized earth, poured in place, or drilled shaft.

The rail portion of the project added 19 miles of double-track light rail, connecting to the existing system at Broadway in Denver; built 13 stations, with park-and-ride lots at 12 of the stations; added 34 light rail vehicles to RTD’s fleet; and constructed a new light-rail maintenance facility in Englewood.

T-REX is the first project in Colorado on which CDOT joined with a local mass transit agency to both fund and manage a single effort. CDOT and RTD formally entered a working relationship when Tom Norton, CDOT executive director, and Cal Marsella, RTD general manager, signed an Intergovernmental Agreement on Sept. 9, 1999. It was also the first time that two federal agencies—the Federal Highway Administration (FHWA) and the Federal Transit Administration (FTA)—partnered to oversee a project. FHWA and FTA officials signed their Interagency Agreement on Oct. 7, 1999.

The T-REX Team, an integrated management team—comprising personnel from CDOT, RTD, and engineering firm Carter & Burgess, the project’s program manager—was responsible for procuring the design-build team and managing contract implementation. Under the design-build concept, the owner team designed about 30 percent of the project and the winning project team was responsible for the remaining 70 percent of the design, as well as for construction.

The total projected cost of the project was $1.67 billion, with construction worth $1.18 billion. The remaining portion of the money was earmarked for relocating utilities and buying right of way. The highway component cost $795 million, and the light rail component cost $879 million. At $1.67 billion, the project is the second most expensive public works project in Colorado’s history; Denver International Airport, which cost $4 billion, holds the record.

T-REX selected its final team member on May 22, 2001. Southeast Corridor Constructors (SECC), a joint-venture group led by Kiewit Construction Co., and Parsons Transportation Group, was chosen through a best-value process in which CDOT and RTD equally evaluated and weighed technical and price aspects. Previously, the joint venture had completed the 17-mile, $1.3 billion I-15 reconstruction in Salt Lake City, on budget and on time for the 2002 Olympics; as well as Colorado’s I-70 Glenwood Canyon project. SECC agreed to finish the T-REX project in September 2006—22 months ahead of schedule.

Less than three weeks before bid date, however, Kiewit’s then-partner Washington Construction, a subsidiary of Washington Group International, withdrew from the team because the parent company was headed for bankruptcy. Washington’s place was taken by Parsons Transportation Group, a lower team member that moved up. Sub-consultants involved in various aspects of the T-REX project include DMJM Harris; Jacobs Civil; Turner, Collie & Braden; Terracon; Kleinfelder, Inc.; Shannon & Wilson; Schnabel Foundations; David Evans Associates, Inc.; and Kilgore Consulting and Management.

Design challenges
Existing soil conditions were one of the first major challenges on the project. "There were groundwater issues and expansive soils throughout the alignment," said Field Engineer Randy Carri with the Wheat Ridge, Colo., office of geotechnical engineer Terracon. "We had to do quite a bit of sub-excavation to maintain the project specs for post-construction movement. The owners weren’t satisfied with lime treatment." The Denver office of geotechnical engineer Kleinfelder, led by Eric Pond, also faced similar design challenges on the project. More than 3 million cubic yards of dirt were moved during construction.

Another major design team challenge was the more than 350 retaining walls and sound walls that were required, especially in the north end of the project site. Normally, walls are advanced more toward the back end of design, but a lot of the walls had to be advanced very early. "Some of them were quite tall—15 to 20 feet—and had to be installed first so that we could widen the corridor to build the highway and light rail improvements," said SECC Design Manager Jim Klemz of Parsons. The team used a combination of mechanically stabilized earth walls supplied by Reinforced Earth Company, and drilled-shaft cantilever walls with precast facings.

The T-REX project required design and installation of almost 3 million square feet of mechanically stabilized earth and drilled-shaft cantilever retaining walls.

Adding to the challenge was the limited right of way, especially in the section between Broadway and University Boulevard known as the Narrows, said Greg Fischer, president of the Denver office of geotechnical engineer Shannon & Wilson. "We had to put in high retaining walls with no room for inclusions, such as soil nails or tiebacks. We also had to add a lot of cantilevered retaining walls because we didn’t have the right of way."

The Aurora, Colo., office of Schnabel Foundations handled much of the wall construction in the Narrows section. "We did permanent, double-corrosion-protected tiebacks with a permanent, structural shotcrete facing for retaining walls built with top-down construction where they weren’t able to excavate behind because of active roads," said Construction Manager Todd Duncan. He added that with varying soil conditions, ranging from clean sand to stiff clay, "every wall was different."

An aerial view prior to construction in the northern part of the T-REX project site—a section called the Narrows—shows the limited right of way.

One innovation that helped SECC win the T-REX contract was a reconfiguration of the original design for the new I-25/I-225 interchange. "The owner had proposed to put a big flyover bridge over the intersection," said SECC Project Manager Tom Howell of Kiewit. "Through some value engineering, we [instead] took the light rail underground through the intersection." SECC built a 500-foot-long, cut-and-cover tunnel to accommodate the rail, which reduced the overall height of the interchange by 30 feet.

Also challenging the project’s design engineers was the owner’s proposal to construct tunnels to allow the new light rail tracks to pass through the interchange of I-25 and C470 and the grade separation at Yosemite Street, said Robert Clevenger, vice president with the Denver office of DMJM Harris. But, he said, "With the careful use of engineering innovation, a new light rail track alignment was developed to allow the tracks to be placed around the various bridge columns, abutments, and retaining walls in the interchange and separation."

Another technology used on the project was shredded-tire ballast layers placed under portions of the light rail to mitigate vibration. Parsons’ Pasadena office had used the technology on another project. "It did a better job than a conventional ballast mat," Klemz said.

Installed quantities on any mega-project are impressive, and T-REX was no exception. The project used 6.9 million pounds of structural steel, 2.6 million square feet of retaining wall and sound wall, 27 miles of drainage pipe, 865,000 tons of asphalt, about 7,500 tons of steel for the light rail track (about 30 percent of this was recycled from the old Mile High Stadium), and 830,000 cubic yards of concrete.

And high volumes of materials created high volumes of traffic. According to Howell, traffic control was one of the toughest challenges in getting the job done. "For any type of work during the day, we had to figure out the phasing, and how to work outside those three lanes," he said. "We really worked 24 hours a day. We also spent a lot of time and effort to get as much work done during the day, when people are more productive."

Goals achieved
Early in the project, CDOT, RTD, FHWA, and FTA agreed to the following project goals, which ultimately dictated priorities to all project participants:
• minimize inconvenience to the public;
• stay within the project’s $1.67 billion budget;
• design and construct a quality project; and
• complete the project on or before June 2008 (which SECC changed to September 2006).

To strictly adhere to the first goal, SECC was required to keep open three lanes of traffic in each direction on I-25 from 5:30 a.m. to 8:30 p.m. every weekday. Clarke said that the team may have been able to finish the project even sooner without the restriction. However, "we decided it was more critical to maintain traffic and work with the public, even if it cost us on the schedule."

Night work became a priority, added Clarke. "You could drive the corridor any night and see the workers," he said. "During summer months, it was not unusual to have 40 percent of the [work] hours done at night."

A key part of that night work was bridge demolition, and the inevitable noise that violated Denver’s restrictive noise ordinance. To alleviate the noise, SECC devised truck trailers fitted with noise-dampening skirts as mobile sound barriers. SECC also implemented a hotel voucher program that provided residents living closest to the demolition the opportunity to stay in hotels.

"It was a very popular program that really allowed those bridges to be demolished at night and keep the traffic open during the day," said Clarke.

Another key component that kept traffic moving was the project’s Intelligent Transportation System (ITS). "We installed an ITS system to give people real-time information, including variable-message boards, ramp metering, and arterial detection to help control intersections through the city," said SECC’s Howell.

During construction, the ITS system monitored traffic on the interstates and on roads that drivers used as alternate routes. ITS also helped agencies respond to emergencies on and off the highways, both during and after construction. During construction, the ITS elements included the following:
• expanded ramp metering to regulate traffic entering I-25;
• an enhanced network of closed-circuit cameras and vehicle detectors to monitor traffic on the interstates and on major feeder roads;
• highway advisory radio messages and variable-message signs to provide travelers with up-to-date construction and traffic information; and
• an interim traffic operations center operated by SECC to monitor traffic conditions and to coordinate response with state and local agencies.

An early goal was to establish a traffic management center with ITS technologies—such as the Autoscope wide-area vehicle detection system—deployed in the field to support a creative public information plan that helped motorists select the best routes, to curb congestion, to boost safety, and to speed coordinated response to incidents.
Technology also played a big part in adhering to the project’s third goal—design and construct a quality project. Program manager Carter & Burgess subcontracted with Delcan, a Markam, Ontario, Canada-based software vendor to implement a Compliant Audit System to ensure that everything stayed on track.

"We took the requirements right out of the contract," said SECC’s Klemz. "Design was audited as much as construction. In a nutshell, they took each individual sentence out of the RFP for design criteria, and that ended up being an audit item against which performance was measured. Each item was ultimately issued a conforming audit or a non-conforming audit. It was a web-based system, so it was easy to use by all parties. It was also easy to roll up into monthly metrics."

Howell concurred. "It was a great management tool that allowed us all to [know] in real time where we were in terms of getting the project completed," he said. "And not just in the field; there are all sorts of documentation requirements that have to be fulfilled on a project of this magnitude. So it also helped us keep track of which documents had been turned over to the owner. And as of today, there are no claims on this project."

In a recent FHWA publication, Larry Warner, former T-REX project director, offered the following advice when replacing an outdated, aging, problem-plagued highway system with one that increases mobility and improves safety, while meeting demanding goals for quality, schedule, and budget:
• Iron out the details of risk assessment or assignment of risk with the design-build contractor early in the process to determine which risks are best carried by the owner and which should be borne by the design-build contractor. Proper allocation of risk will result in lower overall risk for the project.
• Cost-validate early estimates to guarantee realistic cost estimating going into the process.
• Develop realistic project goals.
• Co-locate staff. For T-REX, the owner team shared office space with the design-build contractor team. The mingling of owner and contractor resources ensures the right skills mix and facilitates communications and partnering.
• Partner to produce faster, more cost-effective methods of designing and building projects and to provide support for innovations and higher quality.
• Create an effective public-information program.

In another issue of that same publication, the FHWA’s Colorado Division Administrator Bill Jones wrote about T-REX, "The sense of cooperation between highway and transit has been the backbone of this project. In my 30-plus years of experience, I have never seen any project with such high levels of cooperation."

In 2004, the Colorado Performance Excellence (CPEx) program honored T-REX for its sound management and systems practices. CPEx is a nonprofit effort based on the Malcolm Baldrige National Quality Program. During the CPEx assessment process, T-REX was evaluated on its key management processes developed for the project, which include project direction, quality audit program, project controls, public information program, contract change control, and partnering.

"Most of the competition was private companies," said Clarke. "The assessors had never seen an organization like the one we created."

And perhaps even more amazing was the fact that the job has been executed without a single claim. When asked for an explanation, Senior Project Manager Robert Ostermiller with Carter & Burgess’s program management team attributed it to "partnering, a fair and reasonable audit process, and the degree of pride we all felt of being a part of one of the most successful projects the state has ever done. We had the initiative to not combat each other."

Matthew Phair, principal of Phair Communications, is a New York-based writer and editor who has authored hundreds of articles about the application, marketing, and impact of technology in construction. He studied computer science and civil engineering at Polytechnic University, and holds a B.A. in English cum laude from Queens College. He can be contacted at .

T-REX: Resolving stormwater issues
Denver’s I-25 was a clogged highway in more ways than one. Development along the corridor—which had increased stormwater runoff—and the grossly undersized, 40-year-old stormwater system that served the north end of the T-REX project site between Broadway and University Boulevard, known as the Narrows, had contributed to highway flooding. Floods had shut down the highway at Logan Street every three to five years—so often that the area was nicknamed Lake Logan.

"The original drainage system was undersized, so Lake Logan essentially served as a detention facility," said drainage consultant Roger T. Kilgore, president of Kilgore Consulting and Management, Denver.

Fixing the existing stormwater drainage system along I-25 was a key goal of the T-REX project. The new, $40 million drainage system designed by SECC is built to handle rain from a 100-year flood. More than half of that, $21 million, was spent in the Narrows area, where a new box culvert trunk main storm sewer along the south side of the highway directs water to the South Platte River west of the interchange.

"Much of the T-REX corridor had the problem where, when you opened up drainage on the upstream side, you then risked flooding on the downstream side, so we had to balance the locations," said Kilgore. The eventual solution included dry ponds alongside the highway, one 20-acre pond at the intersection of I-225 and I-25, 15 new detention ponds, and seven underground sediment vaults for water quality.

A total of 200,000 feet of HDPE drain was used under the light-rail system. Rinker Materials, Hydro Conduit Division also provided precast concrete pipe and boxes for the project. Almost 8 miles (42,000 feet) of 18-inch-diameter to 90-inch-diameter concrete pipe was installed. Of this quantity, 1,500 feet was bored and jacked. In addition, the project required more than 2.5 miles (14,000 feet) of precast boxes in sizes as large as 12 feet by 8 feet.

Another storm sewer was constructed on Buchtel Boulevard. Most of the existing storm sewer in the median of I-225, from the I-25 interchange north to Parker Road, was relocated under the northbound shoulder of I-225 to accommodate the new light-rail line in the median. Additional storm sewers were constructed under Buchtel Boulevard, which parallels I-25 on the east and west in the Narrows. The new storm sewers connect to the drainage systems under Mississippi and Arizona avenues, which also empty into the South Platte River.

The most significant feature of the drainage project was the bored, 13-foot-diameter drainage tunnel to the South Platte River. In August 2002, crews completed the tunnel under Mississippi Avenue, from just west of Broadway to I-25 and Logan. The new tunnel replaces an existing, 42-inch pipe. Elmore Pipe Jacking of Terrace View, Calif., performed the work. For the needed clearance above the tunnel at the river outlet, the round tunnel was converted to a box culvert.

T-REX: Surveying the project
To gather the necessary design survey information, as well as construction staking and final right-of-way surveys, SECC Survey Manager Jim Bodi of Kiewit chose aerial mapping plus conventional terrestrial surveys using the latest technology. For the terrestrial work, Bodi turned to David Evans Associates, Inc. (DEA), of Denver. Using Cyrax laser scanning technology, DEA was able to survey 24 bridges in just 40 days without disrupting traffic on I-25.

The Cyrax system used by DEA was a self-contained unit that comprises a scanner the size and weight of a small computer monitor, a power supply, and a Dell laptop computer running Cyclone software. DEA Survey Manager Tom Service said that one problem with the system, which has since been corrected, was heat buildup caused by the lack of a fan inside the unit. Working in summer temperatures in the mid 90s, Service was forced to improvise. "I tied a piece of insulated bubble wrap from Home Depot on top of it to reflect the heat and get it to work," he explained.

In operation, the scanner swept a green, eye-safe laser over the area it surveyed. Each sweep gathered 1,000 points per second. It had a practical range of 594 to 660 feet, and it was calibrated to achieve survey-grade, 0.24-inch precision of each individual point for up to 165 feet. In a few minutes, the scanner captured as many as 1 million points and displayed them as a dense point cloud on the laptop’s screen.

The Cyclone software was used to stitch together individual scans when scans were taken from different angles to capture all sides of an object. Cyclone also converted point clouds into 3-D CAD objects, which in turn were exported to Microstation and AutoCAD, the required deliverable for SECC.

In the office, DEA employed six survey technicians to manage the Cyrax data—three to process the data, one to process the field survey data, and two drafters to produce the base maps. Two-person field crews collected control survey data and Cyrax scan data, which was then processed and loaded into Cyclone. Next, 3-D polylines of all key break lines and bridge features were created, including assigning colors and layers to line types for use in AutoCAD, then saved as an AutoCAD file. After a final review, the files were translated to Bentley’s Microstation/InRoads and delivered as 2-D planimetric drawing files and digital terrain models for contours. DEA took about 400 scans, and the office crew required about 50 days to model all of the data. But since the office personnel worked parallel to the field crews, they were able to finish modeling 10 days after the last scan day, said Service.

T-REX Project team perspectives
Project Director Rick Clarke
No one knows better than Project Director Rick Clarke just how big T-REX really is. "At $1.7 billion, it’s almost too big for us to think about it in [monetary] terms," he said. As an employee of the Denver Regional Transportation District (RTD), Clarke pares down its size to the light-rail view: "RTD has 16 miles in service and we’re adding 19 miles, so we’re [more than] doubling what we already have."

Clarke now leads the project with Deputy Project Director Dell Walker of the Colorado Department of Transportation (CDOT). Clarke was deputy project director for a number of years until March 2006, when former project director and CDOT employee Larry Warner retired, moving to Parsons Brinckerhoff.

Teamwork—For Clarke, building the half-road/half-rail T-REX project has been a challenge that could not have been accomplished without teamwork, and lots of it. Questions about paving have been answered by highway people, and questions about track construction by track engineers. "For things like right of way or public information, it’s very difficult to separate out the highway from the rail," he said. "There’s so much overlap in so many areas. The two are so interconnected that you really have to look at it as one project."

While the project design-build team was a joint venture, Clarke noted that the owner also was a joint venture. "In a lot of ways, it really is a joint venture between CDOT and RTD. A transit agency and a state DOT getting together and leveraging their resources is not typically something that is done."

Traffic control—"Our number one goal was to minimize inconvenience to the traveling public," said Clarke. "It was a goal that we did set as a standard. We didn’t just put it out there because it sounded good. It really affected how we did things."

As an example, Clarke said that when the contracting team was selected, how they were going to control traffic was one of the selection criteria. Then as the project proceeded, "when we went through something like closing a lane or a ramp, we really looked at how that is going to inconvenience the public," he said. "We set a criteria, for example, that we would keep at least three lanes of traffic open in each direction during the main traveling hours, from roughly 5:30 a.m. to 9:30 p.m."

Transit-oriented development—Building a light-rail system has a huge impact on the communities through which it runs. Instead of the project-typical, 30-percent design level that was achieved before construction began, "we took the stations to a much higher level of design because we wanted the community to get the sense that they knew what they were getting," Clarke said. "As we got underway we had a tremendous amount of interest in the stations."

And with more than 15 miles of rail running through populated urban areas, transit-oriented development—and the changes that come with it—became a huge theme for the project. To accommodate future transit-oriented development, change requests came from city officials and from developers for more than half of the stations, which led to multiple requests to change station layouts. "Doing that in the middle of a design-build project was very challenging," said Clarke.

But most challenging from a planning perspective was the redesign of the Arapahoe station area, he said. While the land-locked city of Greenwood was looking to develop a new city core, T-REX goals for the area near the station included building a parking garage for commuters, as well as a CDOT maintenance facility and laydown area, both of which would take up precious space.

"Greenwood proposed combining the [garage and maintenance facility] and using the excess land for development," Clarke said. "That was quite a challenge since we were already under construction." To keep the T-REX budget on track, Greenwood Village ultimately paid the extra cost to have it done. "Development hasn’t started yet," Clarke said, "but there are some pretty fantastic things that are going to happen in that space."

Project Manager Tom Howell
Project Manager Tom Howell has had his hands full since the T-REX project began in 2001. As the top team member from the managing partner of the Kiewit/Parsons Transportation joint venture, Howell is managing construction on the largest design-build project ever in the state of Colorado. Though the dollars for highway and light rail have been near a 50/50 split, Howell has been responsible for 80 percent of the massive T-REX Project. While no novice to design-build, Howell said that a project combining both highway and light rail in one is a first for him.

Planning and scheduling—In an effort to get design and construction going as quickly as possible in 2001, a specialty consultant was hired to laser-scan all of the project’s bridges (see "Surveying the project" on page xx). "It did work well for our team and got us a lot of information very quickly to get started," Howell said. Early data gathering also included photogrammetrically flying the project. "Flying over also helped us plan and manage the project," he said. "Our construction guys used those aerial photos almost daily."

Fast forward to May 2006, and the project is on track to be completed two years ahead of its original completion date. Looking back, Howell’s cost-loaded schedule was a big part of why that’s been achieved. Starting with a little more than 12,000 activities in the schedule, "we took our $1.2 billion, put a certain amount of dollars on each of the activities, then completed the activities to get paid," Howell explained.

But with the speed of construction on a design-build effort, coordination with the design group proved to be a crucial factor in making it happen. "Typically, we can get ahead of the design, so it was very important that the design team knew what was on our schedule and what was up next," said Howell. "It’s very important to have the designer work on something we’re close to working on, not something we’re going to build in three years."

Utility conflicts—In addition to keeping the design flowing, Howell said that working in a tight urban area always invites conflicts. "The challenge was to stay out in front of utility conflicts," he said, "so we had potholing crews that just went out locating utilities."

Utility relocation for T-REX involved many metro-area utility companies. Colorado Senate Bill 00-203 was passed and signed in spring 2000, providing for a master relocation agreement. The law required a new level of cooperation and coordination among utility companies and the contractor. To prepare the T-REX corridor for construction, utility experts had to complete numerous activities, including potholing and surveying 600 locations throughout the corridor. In an effort to locate utilities accurately without destroying property, 1,051 manholes were opened throughout the corridor to record the size and elevation of utility pipes.

Howell said that the team encountered more than 400 interferences with existing infrastructure, which in some cases took as long as three months to resolve. And as-built plans are not always accurate; some utility lines were not even on the plans. "Surprises are inevitable," he said, "and they can bring you to a screamin’ halt. You have to be prepared to change directions."

Design Manager Jim Klemz
Work for Design Manager Jim Klemz peaked in mid-2003. Starting in June 2001, the 24-month effort to design the majority of the T-REX project included more than 45 sub-consultants, including more than 300 people, working on nine design areas. Roughly 120 of the 300 people were from Parsons. To keep communication as simple as possible, about 80 percent of the design staff worked in downtown Denver in the same office tower, as did representatives from the T-REX staff, the Federal Highway Administration, and the city of Denver.

Workload—"We divided the project geographically into nine design areas," Klemz said. "There were three segments, and three design areas within each segment. Each firm had the responsibility to produce the package within its area." Parsons performed five of the design areas; DMJM Harris performed three; Jacobs Civil performed one; and Turner, Collie & Braden performed one. Assisting with geotechnical design were sub-consultants Terracon, Kleinfelder, and Shannon & Wilson.

Klemz said that the team used Bentley software products such as Microstation and In-roads, file management system ProjectWise, and FileNet as the overall project document-control system.

Working together was a key theme of this project, and proved to be a welcome challenge for the design team. "Integration of the highway works and light-rail works was an experience for me because I’m primarily a highway guy," Klemz said. While he acknowledged the two cultures of highway designers and rail designers, the tight site caused a sharing not often encountered.

Traffic control—For Klemz and the design team, traffic management through the 13th most formerly congested corridor in the nation proved to be a challenge and an opportunity. "Design had the responsibility for developing the traffic-control plans and the overall master phasing-sequence diagrams and advance traffic-impact plans," he said.

As part of the traffic-control plan that helped the Kiewit/Parsons joint venture win the job, Klemz said they developed an interim, high-occupancy vehicle lane in each direction for most of the congested, north end of the project. It was in place for about two years. "Adding a lane decreased the amount of work room," Klemz said, "and that was a constant phasing challenge of moving back and forth in the corridor."

Project products
Following are some of the significant products used during design and construction of Denver’s T-REX project.

Aggregate Industries, West Central Region, Golden, Colo., supplied more than 3 million tons of aggregates for asphalt and concrete for the T-REX project. In addition, the company set up a 12-cubic-yard, central-mix concrete plant on site to produce 625,000 cubic yards during the course of the project. When demand for concrete paving exceeded the plant’s 275 cubic-yard-per-hour capacity, volume was supplemented from the firm’s Riverview plant. In addition, the company’s quality control personnel tested more than 2,000 loads of concrete, conducted more than 1,000 aggregate tests, and provided quality assurance assistance on most concrete placements.

Anko Metals, Pueblo, Colo., initially received a T-REX contract in November 2001 for $1.04 million worth of non-structural ornamental handrail. The company subsequently received a change order to design-build three pedestrian bridges, followed by another contract to install the bridges. Anko eventually filled orders for more than 3 million pounds of steel for the six pedestrian bridges, plus shelter canopies for the 14 light-rail stations, including decorative work.

Banner Rebar, Denver, supplied reinforcing steel, both uncoated and epoxy-coated rebar, to strengthen the roughly 830,000 cubic yards of ready-mixed concrete used on T-REX for the concrete roadways, retaining walls, and bridges. Banner also fabricated all of the rebar on the project for ordinary structures such as bridges, as well as for unique elements such as soldier walls.

Bentley Systems‘ family of software programs helped engineers and others performing civil design work to create the T-REX Project. Microstation, InRoads, and ProjectWise were used by the design team, which at times exceeded 200 designers on site, plus remote workers. As a result of the success with T-REX and other recent projects in Colorado, the Colorado Department of Transportation decided to pursue an engineering software transition in 2003 and selected the Bentley Systems suite, which includes InRoads, MicroStation, and PowerSurvey, to provide an integrated software solution.
Image Sensing Systems, Inc., St. Paul, Minn., provided, through its distributor, Econolite Control Products, Anaheim, Calif., the Autoscope wide-area video detection system. The system comprised more than 300 Autoscope Solo Pro sensors for traffic monitoring on roads surrounding the construction area. Traffic on these roads had increased substantially because increased congestion on the freeways encouraged people to choose alternate arterial routes. Each Solo Pro sensor measured traffic mid-block along these arterials.

L.S. Gallegos and Associates (LSG), Englewood, Colo., supported the prime contractor’s IT staff in developing software for the Intelligent Transportation Systems/Traffic Operations Control Center. Specialists included computer programmers, software architects/engineers, and software testers. LSG also provided CADD technicians to support the design effort and served in a resource augmentation role, working alongside the prime contractor’s on-site IT development staff. LSG staff worked in multiple project offices in Colorado and Florida, where much of the software development and testing work was performed.

Plum Creek Structures, Littleton, Colo., produced precast, high-strength bridge girders for the T-REX project using specialized Port-a-Pour machines. The firm cast the girders on site with 10,000-psi concrete, which achieved strengths of 6,000 to 7,500 psi in 16 hours, with steam curing.

Reinforced Earth Company, Vienna, Va., met one of the biggest challenges on the T-REX project—the more than 350 retaining walls and sound walls, especially in the north end. Reaching 20 feet in height, the walls had to be installed first to widen the corridor to build the highway and light rail improvements. Parsons specified mechanically stabilized earth walls from Reinforced Earth, as well as drilled-shaft cantilever walls with a precast facing.

Rinker Materials, Hydro Conduit Division, Denver, supplied 42,000 feet (almost 8 miles) of 18-inch-diameter to 90-inch-diameter concrete pipe on the T-REX project. Of this quantity, 1,500 feet was bored and jacked. In addition, the project required 14,000 feet (more than 2.5 miles) of precast boxes in sizes as large as 12-feet by 8-feet.
Rocla Concrete Tie, Denver, manufactured prestressed concrete rail ties for the T-REX project. The company’s product line also includes ties for heavy-haul, ties for commuter rail, turnout ties, guardrail ties, and crossing ties.

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