The Texas Department of Transportation (TXDOT) is moving forward with State Highway 161, an eight-lane, grade-separated toll road connecting western Dallas County’s three largest east-west freeways: I-20, I-30, and the Airport Freeway (State Highway 183).
TXDOT began work on the extension of SH 161 in July.
This included phase I of a five-level interchange at I-30 in Grand Prairie. The $28-million project will be the first step in building the interchange’s frontage roads, said Mike Bostic, TXDOT’s Southwest Dallas County area engineer.
“This is an important project for our office, the city of Grand Prairie and the state. It will tie in all of the new SH 161 extension frontage roads,” Bostic said.
The work consisted of excavation, embankment and drainage structures and paving. When finished, the SH 161, I-30 interchange will have continuous frontage roads that form a “box.” Work on the frontage roads from Spur 303 (Pioneer Parkway) to I-30 and from I-20 to Spur 303 also is under way.
State Highway 183 is a major east west thoroughfare in the Dallas/Fort Worth Metroplex, which carries traffic between the two largest cities in North Texas, as well as providing motorists with access to one of the busiest airports in the world, the Dallas/Fort Worth (DFW) International Airport.
To increase regional mobility through the western extents of Dallas County, TXDOT is building an extension to the President George Bush Turnpike (PGBT). This segment of highway, named Texas 161, will connect PGBT to Interstate 20, in the southern part of Dallas County.
Texas 161 connects to the Airport Freeway, which is currently undergoing a massive widening and reconstruction. This timing makes the phasing of construction on the interchange between the two highways difficult. In addition, traffic passing through this exchange is extremely heavy, as both passengers and cargo travel the Airport Freeway to connect from the Central Business District of Dallas to DFW Airport.
Since Texas 161 is a new road, direct connections between it and the Aiport Freeway are easier to build. As a result, the general contractor does not need to worry about traffic control during construction because piers for 161 have already been drilled, formed and finished. The hardest task of this operation was building the massive steel reinforcing cages and lowering them into the cavernous drill shafts, according to officials. These shafts are drilled by augurs, which have extension after extension added to the bit that cores through the expansive North Texas clays.
The Dallas/Fort Worth region is notorious for plastic fine clay soils, which causes large-scale cost escalations on public works projects. These clays shrink and swell drastically in response to changes in moisture, causing substantial earthen pressures on both natural and man-made structures. Additionally, much of the clay in the area has been deposited from cuts from when the airport was built in the 1970s.
Construction of DFW Airport resulted in millions of cubic yards of haul-off dirt, which was distributed throughout the area and continues to settle and shift. The drill shafts for the piers that support the overpasses for the 161/183 interchange are drilled through the clays, as deep as necessary to anchor them in rock, substantially below the finished grade of the proposed road.
Once these shafts are drilled, massive steel reinforcing cages are assembled on site and dropped into the shaft. The contractor then makes the concrete pour, in accordance with the recommendations of a geotechnical engineer. Due to the many slope failures, pavement cracks, and structural difficulties associated with building on clay, soil-stabilizing treatments are employed, such as cement, lime, and even gypsum.
As construction continues vertically, the process becomes more standardized, and similar in nature to construction projects in other parts of the country. The end result is a direct connection highway exchange that allows free movement through the western extents of Dallas County, to meet the explosive growth of the region.
Contractor Texas Sterling Construction L.P., of Dallas, headed up the project, which is expected to take 23 months to complete. CEG