The University LRT Line is a 2.3 mile, in-street-running, light rail project located in Salt Lake City, Utah. The dual trackwork ties into an existing light rail system via a half grand union and provides transit access to the University of Utah. It includes approximately 4.6 miles of concrete track slab with three special trackwork slabs, numerous retaining walls, and four transit stations. This was a design-build project led by SLC Rail Constructors, a joint venture consisting of Stacy and Witbeck, Inc. of Alameda, CA, Flatiron Structures Inc., of Longmont, CO, and Geneva Rock of Orem, UT. CHS Designers provided the design effort, a joint venture which included CH2M Hill, Hatch Mott McDonald, and STV Incorporated.

The reinforced track slab is eight feet wide by 18 inches thick with expansion joints at 100 feet. The 115 RE continuously welded rail is embedded in the slab and held in place by steel ties spaced at 10 feet. The use of concrete provides a unique trackway surface that allows it to be shared by light rail vehicles and automobiles at the intersections, as well as allowing the transit authority rubber tire maintenance vehicles to access all locations of the system. This design can be adapted to work in almost all light rail transit situations because of the infinite malleability of concrete. The original design specified AC pavement and was traded for the clean, modern look of concrete–one of the big selling points of this design. The owner was willing to invest more money up front in a product that they knew would continue to look and perform admirably for many years, as well as be easy to maintain, thus saving money in the long run. The riding public needed to be serenaded by the luxurious ribbon of concrete and rails in order to abandon their cars and take the train. This presents a long term economic advantage to the city as a whole by reducing the need for automobiles and the huge attendant costs of maintaining roads, as well as the hidden costs of pollution and traffic congestion. This project provides public transit access to a large shopping corridor along a major thoroughfare, as well as a means for 40,000 students and faculty to get to the University of Utah, replacing the automobile and related parking problems experienced by the school over the years.

Closely related to the track slab are the special trackwork slabs, which support the fully embedded half-grand union and the two double crossovers. Because one rail carries the negative return power and the other carries the signal system information, these rails need to be electrically isolated from one another. The solution was to use concrete with a micro-silica admixture, which provides a higher degree of electrical resistivity than normal concrete. This allowed the infill slab to provide a dual service of embedding the trackwork and isolating the rails at the same time, a cost saving benefit. This did require the addition of poly fibers to the concrete mix to counteract the higher shrinkage rates caused by the silica fume, but was an overall economic benefit when compared to other methods of providing rail isolation. This can be used in other special trackwork installations where electrical isolation is required. Additional benefits from the use of concrete are the aesthetic considerations of concrete versus paving with asphalt and the economic benefit of long facility life.

The retaining walls are typical cast-in-place walls utilizing T-footings and a fractured fin detail on the front face. This breaks up the blank face look and provides texture and interest to the wall. In several places the wall was high enough that the owner asked for additional masking. It was decided that vines would be trained to grow up the wall, providing further relief to the surface. Wall detailing is limited only by the imagination and is easily transferable to all types of transit projects. The ability to enhance the aesthetics of large areas of concrete with texture and vines and at a reasonable cost is one of the many benefits available to the concrete specifier.

The station platforms and high block ADA ramps are also cast-in-place concrete, portions of which make use polypropylene fibers to reduce the shrinkage and long term cracking and to improve the durability of the structures. The economic benefits of reduced maintenance costs and the aesthetic benefit of having a platform that keeps that “brand new” look are what make this a cost saving decision. As art is a part of most transit projects, the Trolley Square Station on the University LRT Line incorporates several types of tile work from local artists. The use of concrete allows the artwork to become a seamless part of the platform and ramps. Aesthetically, this gives the station visual interest and makes the riding experience more enjoyable. The economic benefits come from the increased ridership due to a more pleasing commuting environment. This is something that all transit agencies can benefit from.

The benefits from the use of concrete in the construction of the track slabs, retaining walls and station platforms on the University LRT Line have enabled the completion of a first class project that combines economy and aesthetics to provide a functional inner city transit system. The total project cost $105 million.

Project Credits:
Owner: Utah Transit Authority
Engineer: CHS Designers (J.V.)
Contractor: SLC Rail Constructors (JV)
Concrete Supplier: Geneva Rock