Environmental Review Toolkit
Accelerating Project Delivery

Transportation Expansion (T-REX) Multi-Modal Transportation Project

Colorado DOT / Regional Transportation District
Denver, Colorado


The 19-mile Transportation Expansion or T-REX Multi-Modal Transportation Project (formerly known as the Southeast Corridor Project, and for this report referred to as such) involves sections of I-25 and I-225, the most heavily used roadways in Colorado, providing access to the region's major east-west freeway, I-70. The corridor carries more than 230,000 vehicles per day and connects the two largest employment centers in the region, downtown Denver and the Southeast Business District.

Project Area Demographics

Denver Population: 2,109,282
Racial and Ethnic Composition:
  • Hispanic or Latino: 18.8%
  • White: 70.4%
  • African American: 5.5%
  • Other: 5.3%
Source: 2000 US Census

The study area addressed is predominantly urban and suburban, with very little vacant or developable land. The northern portion of the study area includes the downtown and central areas of Denver, primarily consisting of single-family residential development with some commercial. In contrast, the southern portion of the study area is primarily suburban, and had recently experienced substantial residential and commercial development. Overall, the study area is highly developed.

Southeast Corridor T-REX Project Limits Map - decorative
Southeast Corridor TREX Project Limits
Source: TREX project website

In 1992, the Denver Regional Council of Governments (DRCOG) commissioned a region-wide congestion study. While the Southeast Corridor had been a likely candidate for highway expansion since the early 1970s, the DRCOG study brought the severity of congestion in the corridor to the forefront. In response to this study, the Colorado Department of Transportation (CDOT), in conjunction with the Regional Transportation District (RTD), began studying the corridor and, in 1995, commissioned the Southeast Corridor Major Investment Study (MIS), which was completed in 1997. Shortly thereafter, CDOT and RTD initiated the Southeast Corridor EIS process. Given that the project consists of highway and transit improvements, the EIS was jointly sponsored by both FHWA and the Federal Transit Administration (FTA).

Project Purpose

The primary purpose of the Southeast Corridor Multi-Modal Project is to improve travel time and enhance safety along I-25 and I-225. With major employment centers at both ends of the corridor, traffic congestion occurs in both directions during the morning and evening rush hours. Along I-25, the traffic volumes are evenly split in the two directions during both rush hours as commuters travel to the Denver CBD in the north and a number of major business parks in the south during the morning peak and then return during the evening peak. Traffic volumes have continued to grow even faster than the increasing population and employment within the region. The length of the peak rush hours has also grown over the years and the volumes have been found to be consistently high for up to 12 or 13 hours each day.

In addition to improving motorist travel time and reliability in the Southeast Corridor, it is also intended to improve transit travel time and reliability. Other goals of the project are to attract new transit riders, enhance safety for motorists, replace aging infrastructure and support the rapidly growing residential and commercial areas served by the corridor.

How Project Development Advanced Through NEPA

Project Chronology
  • DRCOG Congestion Study: 1992
  • Major Investment Study: 1995-1997
  • Notice of Intent Issued: Feb. 1998
  • Draft EIS Approved: Aug. 1999
  • NEPA Public Hearing: Sept. 1999
  • Final EIS Approved: Dec. 1999
  • Record of Decision: March 2000
Source: T-REX project website

The NEPA process for the Southeast Corridor project took 25 months, from Notice of Intent to Record of Decision. As previously mentioned, earlier studies had indicated the need for the project. These studies also helped to identify and refine some of the alternatives, thereby setting the stage for the environmental review process.

Congestion Study

In 1992, the DRCOG commissioned a congestion study for the Denver region. The study highlighted the most congested corridors in the Denver metropolitan area and identified whether travel demand reduction and operational management strategies implemented within those corridors would alleviate congestion through the year 2015. The study concluded that the Southeast Corridor was one of the most congested corridors in the region and that expected traffic growth along the corridor would exceed capacity by 15 percent by 2015. It was further concluded that travel demand management (TDM) strategies alone would not be sufficient to alleviate the congestion, and that a package of capital improvements including rapid transit, high occupancy vehicle (HOV) lanes or general widening should be considered in greater detail.

Subsequent to completion of this study, CDOT implemented ramp metering and interchange improvements within the corridor while the RTD has increased park-and-ride capacity and increased bus service to both the CBD and the Southeast Business District. Although these improvements helped in the short term, the Southeast Corridor continued to be the most congested corridor in the region.

Major Investment Study

In 1995, CDOT and the RTD jointly commissioned the Southeast Corridor Major Investment Study (MIS). CDOT had previously developed internal agency guidelines for the preparation of MISs, with the goal of ensuring a level of consistency in the approach that the agency took to such studies. The purpose of the MIS was to find the best solution to the ever-growing problem of congestion in the corridor. To accomplish this, the MIS examined the entire length of the corridor (including sections of I-25 and I-225) and recommended a combination of new light rail, highway improvements, pedestrian and bicycle facility improvements and enhanced TDM measures. The MIS was completed and DRCOG adopted these recommendations in 1997.

Policy Committee
  • Local elected & appointed officials
  • Focused on policy issues
  • Monitored public agency decision-making process
Technical Committee
  • Technical experts from state &
    local agencies
  • Focused on planning, engineering &
    environmental issues
  • Provided technical input to MIS study
    and NEPA process
  • Provided technical input to MIS study
    and NEPA process.
Source: Southeast Corridor MIS.

An important element of the MIS process was the formation of two committees. A Policy Committee provided input on policy-related issues and monitored project progress relative to the overall public agency decision-making process. Committee members primarily consisted of elected and/or appointed policy/decision-making officials from the affected areas.

A Technical Committee focused on all planning, engineering and environmental issues and assisted in the development and refinement of alternatives. Members of this committee were individuals from the various cities and jurisdictions within the study area who had a technical background.

The two committees used project goals to refine and evaluate each alternative. Public meetings and numerous workshops were held during NEPA scoping and at key milestones during the study to present the definition of alternatives and to guide CDOT and RTD in the development and evaluation of a Preferred Alternative. A project newsletter was published at key project milestones to keep the public informed. The committees remained intact during the NEPA and preliminary engineering process, and monthly meetings were held to keep them involved. This also helped with maintaining a constant public process and ongoing relations with the public.

With the MIS study drawing to a close, CDOT knew that the funding earmarked for the project by TEA-21 would be lost if they did not act quickly. CDOT was seeking $700 million in funding through the FTA's New Starts program, and knew that competition for the funding was strong. CDOT's Executive Director gave the project his full support, and made the project a priority for the agency.

In several respects, the 1995-97 MIS study laid the groundwork for the NEPA process. CDOT's in-place process kept the MIS study moving smoothly, the policy and technical committees brought together elected officials and government agency staff, while outreach activities served to introduce the project to the public. "Because of the MIS process, knowledge of the project to the public had become well established and contributed positively to the EIS efforts," according to Project Manager, Jim Bumanglag of CDOT.

NEPA EIS Process

Key Factors of the NEPA Process
  • DRCOG Congestion Study
  • MIS previously introduced project to
    agencies and public
  • Continued involvement of MIS study's
    Technical and Policy Committees
  • Proactive Public/Political Involvement
  • Co-location of project team
  • Interagency coordination

The NEPA process was kicked off with the Notice of Intent in February 1998. All of the alternatives for the Draft EIS were originally identified during the MIS study and then further evaluated to determine if there were any changed conditions that might alter the findings.

One of the major contributors to an accelerated NEPA process for this project was a cooperative and collaborative effort between CDOT and the RTD, as well as FTA and FHWA. This collaborative spirit extended to the physical location of the project team, as CDOT and RTD staff was "co-located" in an office building with NEPA consultant, Carter-Burgess and its subconsultants. With all project team members under one roof, meetings were easier to arrange, as travel time was not a factor. Spontaneous working sessions became the norm, thus fostering a sense of teamwork among the various agencies and firms working on the project. Internal reviews of EIS sections were performed while the sections were "hot off the presses." With little time lost to these internal reviews, the project team was able to immediately share draft work products with reviewing agencies upon completion. This resulted in substantial time savings over the typical NEPA EIS cycle of preparing a complete draft, distributing internally for comments, then revising, then sending out to resource agencies for their input.

Weekly federal coordination meetings were held with managers and staff from FHWA's divisional office and FTA's regional office, as well as from CDOT, RTD, and the consultant. As part of the weekly coordination meetings, the critical path schedule was reviewed, thereby allowing the technical leaders to focus attention on the critical path items that could delay the overall project schedule. FHWA and FTA worked hard to build a partnership that would help advance the Southeast Corridor project in a timely manner. Although both agencies had already been working cooperatively from the project outset, they officially documented their partnership with a signed project-specific interagency agreement on October 7, 1999.

Key Agencies Involved in the NEPA Process
  • Colorado DOT
  • Regional Transportation District
  • Colorado Department of Public Health and the Environment
  • Colorado Division of Wildlife
  • U.S. Army Corps of Engineers
  • Federal Highway Administration
  • Federal Transit Administration
  • U.S. Fish & Wildlife Service
  • U.S. Environmental Protection Agency

FHWA made a major commitment of its staff in order to facilitate reviews and ensure ongoing coordination on NEPA issues. FHWA staff took ownership of various sections of the EIS document and worked hard to complete reviews on time and keep the NEPA process going. "For two and a half years, we went down to the State offices to meet on the (Southeast Corridor) project," said Vince Barone of FHWA.

CDOT also organized task force groups for the various issue areas, including air quality, noise, and wetlands. The purpose of the task force groups was to give appropriate staff from relevant agencies the opportunity to brainstorm on project issues and to review analyses and sections of the EIS as they were prepared. The task force groups ensured that the project was pursued within the respective agencies, and fast-tracked the process by getting reviews done as they were needed. The task force groups met on a set schedule and addressed the critical path project schedule established by the primary interagency project team. In addition to CDOT, RTD, FHWA and FTA, agencies involved in the task force groups included DRCOG, Colorado Department of Public Health and the Environment, Colorado Division of Wildlife, Army Corps of Engineers, Fish & Wildlife Service and the Environmental Protection Agency.

The task force groups worked diligently on their review of EIS sections and analyses, resulting in substantial time savings to the project. One specific and important achievement of this effort was the air quality task force's completion of the project's air quality conformity analysis in one month. The various task force groups also made use of the consultant's series of technical memos on each of the project issues to be covered in the EIS. The technical memos served as resource papers for the federal and resource agencies and project team.

Photo of I-25 at Yale, showing location of proposed Yale Avenue LRT Station
I-25 at Yale, showing location of proposed
Yale Avenue LRT station.
Source: T-Rex project website.

A series of public events served as a platform to introduce the project's NEPA process to the public. In March and April of 1998, three public open houses were held as part of the NEPA process. In December of 1998, a second round of public open houses was held to solicit input on the NEPA process completed to date, as well as preliminary engineering. A third round of four public open houses was held in May and June of 1999 to present the Preferred Alternative and allow the public to comment on it. Finally, two Public Hearings pursuant to NEPA were held in September 1999, following the signing and distribution of the Draft EIS in August 1999. During the course of the four separate rounds of meetings, a total of more than 1,000 people attended. As a result of these meetings, some of the alternatives were expanded to include additional transportation elements not previously included. These expanded alternatives were subsequently considered throughout the remainder of the NEPA process.

Project Publication Cover
Project Publication Cover

In addition to the open houses, CDOT continued its public involvement activities through the release of project newsletters, which discussed the project, listed milestone dates and invited the public to attend open houses and provide comments. Press releases and a media tour were utilized to keep the project in the media, and project displays were placed in public buildings to keep the public informed. A project website was continuously updated with the latest documents and information. CDOT and project team members met 215 times with community groups.

Perhaps because of CDOT's extensive public involvement efforts, the public was generally in favor of the project. There was, however, some opposition from property owners who opposed the outright taking of, or encroachment onto their property. Public input did result in minor changes to the project, including LRT alignment and station locations

Political support may also have been a factor in the expediting of the project. Colorado Governor Roy Romer supported the project from the outset, and there was local political support for the LRT. However, some local politicians were against the highway.

The Final EIS was signed in December 1999, followed by the Record of Decision in March 2000. The total NEPA process had taken 25 months from its filing of Notice of Intent in February 1998 to its Record of Decision date.

Preferred Alternative

Project Snapshot
  • Highway / light rail combination
  • 1709 mile project corridor
  • 16055 mil expansion of I-25 and I-225
  • Bridge replacements & interchange reconstruction
  • 19.12 miles of double-tract LRT
  • 13 LRT stations
  • LRT maintenance facility
Source: T-REX project website

The actual selection and refinement of the Preferred Alternative did not occur until January 1999, during the Draft EIS process. The Preferred Alternative for the Southeast Corridor included a new light rail system and various highway improvements. The new light rail line would run adjacent to I-25 and I-225, connecting the community of Lone Tree in Douglas County to Downtown Denver, and would consist of 13 stations. The highway improvements would include 16 1/2 miles of widening and reconstruction.

Based on modeling results comparing a No-Build Alternative to the Preferred Alternative for the year 2020, these strategies would notably improve highway travel times and reduce congestion. Specifically, the Preferred Alternative would reduce highway travel times by 11 minutes and transit travel times by 32 minutes. Given these notable improvements, implementation of the Preferred Alternative was recommended.

Proposed Lane Configurations I-25 looking southbound, from Evans to Yale
Proposed Lane Configurations for I-25 looking south, from Evans to Yale (Source: TREX project website)

Other Alternatives Considered

Aside from the Preferred Alternative, three other alternatives were seriously considered. They included a No-Build Alternative, a Transportation Management Alternative, and a Bus/High Occupancy Vehicle (HOV) Lane Facility Alternative.

Based on an evaluation of the No-Build Alternative, which included minor improvements due to routine maintenance and safety operations, it would not meet the project purpose and need of reducing travel times and accommodating future demand. The No-Build Alternative was used as the baseline to evaluate improvements resulting from the other two alternatives, along with the Preferred Alternative.

Similarly to the No-Build Alternative, the Transportation Management Alternative was determined to fall short of meeting the project purpose and need, resulting in minimal reductions in travel time and minimal operational improvements compared to the No-Build Alternative. This alternative consisted of local intersection improvements, other safety and operational improvements (such as signing and additional turning and acceleration/deceleration lanes), and traffic management strategies to provide relatively low cost refinements to the existing transportation system.

While the Bus/HOV Lane Facility Alternative would provide notable improvements in travel time and increases in vehicle capacity, it would also result in greater physical, noise, and air quality impacts; greater bus and auto congestion and air quality problems in downtown; and reduced transit ridership when compared to the Preferred Alternative.

Since none of these alternatives would adequately meet the project purpose and need while sufficiently minimizing environmental impacts, they were not selected as the Preferred Alternative.

Environmental and Other Issues

Environmental Issues
  • Residential and Business Displacements
  • Increase in Noise Levels
  • Loss of Wetlands
  • Adverse Impacts to Historic Sites
  • Increase in Noise Levels
  • Loss of Wetlands
Source: Southeast Corridor Final EIS

There were several issues associated with the Preferred Alternative. These included residential and business displacements, adverse impacts to historic sites,an increase in noise levels and loss of wetlands.

A total of six single-family residences, 112 residential units in three multi-family buildings, and 119 individual businesses / offices in 20 commercial buildings would be impacted by the Preferred Alternative. While the inhabitants of these buildings, both residential and commercial, would be fairly relocated or compensated, it was recognized that the displacements would negatively affect community cohesion. Additionally, in some cases, it was concluded that there may not be adequate replacement housing or business locations within the community where the displacements would occur, which could further disrupt community cohesion.

Cultural resource issues were prominent on the project. The Colorado State Historic Preservation Office (SHPO) wanted to place all of Interstate 25 on the National Register of Historic Places because of the historic bridges that crossed the highway and the Highline Canal that run underneath through a box culvert. CDOT and FHWA, who were both opposed to the designation, met with SHPO regularly to resolve the issue and determined that no adverse effect would result. It was determined that six of seven historic properties evaluated would be impacted and two historic sites - bridges at I-25/225 interchange as well as the General Iron Works - would be minimally impacted. As a result of these issues, a Section 4(f) Evaluation was also required. The CDOT worked closely with the SHPO to minimize impacts to these sites and mitigate unavoidable adverse impacts.

1 of 13 Proposed LRT Stations Locations included in the Preferred Alternatives Left: Existing condition of a proposed station location.
1 of 13 Proposed LRT Stations Locations included in the Preferred Alternatives
Above: One of 13 proposed light rail stations included as part of the Preferred Alternative

The Preferred Alternative would also result in notable noise level increases, which would be effectively mitigated with the construction of noise walls, and loss of 3.2 acres of wetlands, which would be mitigated with replacement wetlands.

Current Status

CDOT awarded a design-build contract to the joint venture firm of Southeast Corridor Constructors in May 2001. It was at this stage that the Southeast Corridor Multi-Modal Transportation Project had its name changed to the "Transportation Expansion Project", or "T-REX" for short. This change was due to an extensive creative research and development process. Research surveys indicated that the Southeast Corridor name held very little value to the focus groups studied. Officials wished the name to capture the enormity of the project, as well as to add a touch of personality. Of all the names, T-REX received the most positive feedback in terms of appealing to many demographics, and being memorable and interesting.

Design is currently underway, and construction has begun. A full-time staff of 70 persons from CDOT, RTD, and T-REX consultant support is now co-located in the same building with the design-build contractor, and continues its work on the project. The project is scheduled to be completed in June 2008.

Lessons Learned

The newly named T-REX Project showed that the NEPA process for a complex urban project could be expedited by:

  • Utilizing previous studies to build momentum for the NEPA process,
  • Promoting aggressive public involvement;
  • Engaging the EIS consultant in NEPA interagency coordination activities, and
  • Co-locating the project team and consultants.

These factors are discussed in detail below.

Capitalize on Earlier Studies to Build Momentum for the NEPA Process

The earlier MIS study and region-wide congestion study gave CDOT and RTD the opportunity to explore project alternatives, form policy and technical committees, establish a rapport with the public, and begin the process of advancing the Southeast Corridor project. These studies presented the need for the project and identified appropriate alternatives in advance of the NEPA process. They also served to build momentum by bringing together the agencies that would later form the nucleus of the NEPA process - CDOT, RTD, FHWA Colorado Division, and FTA Region 8. The formation of policy and technical committees for the MIS study helped bring on board the local elected officials and agencies by engaging key personnel on specific project study tasks. As these committees remained intact throughout the NEPA process, there was a consistency to the team effort across both the MIS and the EIS. Public involvement efforts on the MIS served to first announce and then sustain the project in the eyes of the public. When the NEPA process began, introductions weren't necessary - agencies were already involved, and the public was already familiar with the project because of the detail in the earlier prepared studies.

US 25 Highway Corridor with Overpass View
US 25 Highway Corridor with Overpass

Aggressive Public Involvement

There was an extensive process of public and agency involvement that was implemented to guide and provide input. The process included meetings with neighborhood groups, agencies, business groups, land owners, developers, and the general public to discuss and evaluate alternatives, issues, and mitigation. A total of over 215 meetings were held with the public and/or community representatives. In addition to meetings, there were a number of open houses, interviews, a mailing list of over 5,400 individuals, twelve newsletters, press releases, a project office and phone line to display and discuss material, and a website. The involvement included the policy and technical committees created to advise the EIS project team and make specific recommendations on the direction of the project. The public involvement process in general was open, interactive, and proactive in its efforts to avoid unforeseen hurdles and keep the NEPA process in a forward momentum.

Engage the EIS Consultant in NEPA Interagency Coordination Activities

CDOT and RTD's environmental consultant, Carter-Burgess, helped channel interagency coordination during the NEPA process through the preparation of a series of technical memos on issues under consideration. Interagency coordination tasks were specified in the EIS contract, thus ensuring that the consultants were aware of CDOT's requirements at the outset and could allocate adequate staffing and material resources. In addition, the consultant's involvement in arranging and facilitating interagency meetings ensured that the agencies remained focused on the issues at hand and not on the logistics of the meetings. The important element here is that the contract clearly defined the roles and expectations of both agency and consultant with respect to interagency coordination, thus avoiding operational overlap or potential conflicts.

"(Carter-Burgess) really drove the coordination process."
– Vince Barone, FHWA

Co-locate the Project Team and Consultants

Having the sponsoring agencies, EIS consultants, and sub-consultants under the same roof allowed for a level of interaction not often seen during typical NEPA processes. Project team meetings were planned with only the shortest of lead times, and spontaneous working sessions became the norm. Delivery times for documents and materials were eliminated, thus saving critical time for preparing analyses and completing reviews. This arrangement worked so well for CDOT and RTD that they are now co-located with the design-build contractor for the current phase of the project.


Vince Barone, P.E.
FHWA New York State Division
(Formerly of FHWA Colorado Division)
Leo W. O'Brien Federal Bldg
719 Clinton Avenue
Albany, NY 12207

Jim Bumanglag
Colorado Department of Transportation
7200 S. Alton Way
Centennial, CO 80112

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