Eastern Extension Features Natural Concrete

Retaining walls and bridge columns, caps, beams and decking are going up all along the President George Bush Turnpike (PGBT) Eastern Extension, giving residents in eastern Dallas County an idea of how the roadway will look when it opens in late 2011.

The goal of the NTTA and its contractors, however, is for these features to blend in so well they are hardly noticeable.

In 2003, the NTTA established System-Wide Design Guidelines, which require concrete elements to be consistent in appearance and to have minimal embellishments in order to blend in with the surroundings and reduce the need for maintenance, among other benefits.

Concrete features constructed before creation of these guidelines tend not to be uniform in appearance, so they have to be painted, or coated, and require periodic sandblasting and resurfacing. This process not only can be costly, but it can disperse volatile organic compounds into the air and cause traffic interruptions during the restoration. Also, before the work is done, the coated surfaces can peel and become unsightly.

The Eastern Extension, from Firewheel Town Center in Garland south to the north shore of Lake Ray Hubbard in Rowlett, is the first NTTA project that will be constructed entirely under the guideline's concrete requirements, referred to as the “850 specification” or “850 spec.”

The intent of the 850 spec is to ensure that the roadway’s concrete elements – whether precast or cast in place – are high quality enough to be attractive in their natural state.

To do that, the 850 spec was included in the Eastern Extension’s construction contracts, making the contractors aware that they won’t get paid if the appearance doesn’t meet expectations. Retaining wall panel mockups have been built to serve as examples, and products that are the wrong color, have pockmarks or have other undesirable components are rejected. In addition, visual quality inspectors are on hand at the plant where precast retaining wall panels are being made, and a team regularly visits the construction site to monitor the cast-in-place elements.

The System-Wide Design Guidelines are an example of the NTTA's commitment to the community it serves through strong visual guidelines that fuel growth and development.

The Eastern Extension will add 9.9 miles to the PGBT, traverse Lake Ray Hubbard via a bridge under construction by the Texas Department of Transportation and then connect with Interstate Highway 30.