Bartlett & West delivers time and cost savings for TxDOT on Spur 303 while enhancing construction safety

Spur 303 (East Pioneer Parkway) is a principal arterial through Arlington and Fort Worth, Texas. Under an existing contract, Bartlett & West was issued a Work Authorization for the replacement of the Rush Creek Relief on-system bridge. The substantial traffic generators in the vicinity of the project included Interstate 820 (I-820), located approximately 3 miles west of the project, and SH 157, located 3.8 miles east. The annual average daily traffic at the bridge is currently 23,539 vehicles and is expected to exceed 33,000 by 2041.

Challenge

The first challenge the team faced was regarding hydraulics. The two downstream reaches — Rush Creek main channel and Rush Creek relief stream — were both within the 100-year floodplain. The flow distribution between the two reaches varies from inflow discharges. As such, the Hydrologic Engineering Center – River Analysis System (HEC-RAS) unsteady flow model was the best option for floodplain analysis. However, the unsteady flow model can trigger both upstream and downstream water surface elevation fluctuations, which makes the model simulation hard to control. An additional consideration was that the City of Arlington had a zero-rise policy for the development of this area.

The next challenge the team faced was right-of-way. Front slopes and header banks needed to remain within existing right-of-way. The proposed bridge would need to be widened for additional travel lanes and pedestrian sidewalks on both sides to satisfy Texas Department of Transportation’s (TxDOT) Design Manuel requirements and limit approach roadway work to 300 feet to meet Federal Highway Administration (FHWA) Category 6 funding requirements.

Finally, the existing bridge carried three lanes of traffic in each direction, separated by a raised median. Two lanes would need to be maintained during construction with no temporary construction easements allowed.

Solution

Throughout the project, our team worked closely across disciplines to develop a proposed bridge option that would nearly replicate the existing conditions of a bridge length and low chord elevation. A key concern in using unsteady flow modeling was stabilizing the pressure flow pattern. While the existing bridge over Rush Creek Relief was a 122-foot wide by 209-foot long five-span concrete slab and pan girder bridge, our proposed bridge was a 128-foot wide by 220-foot long three-span prestressed I-girder bridge. The combination of providing more efficient beams and a reduced number of spans offset the effects of a longer bridge while maintaining the existing low chord elevation needed for hydraulic modeling.

This complied with TxDOT Hydraulic Design Manuel criteria, as well as the City of Arlington’s zero-rise policy, which removed the added step of a CLOMR (Conditional Letter of Map Revision) application.

To address the right-of-way concerns, the team held the existing centerline and specified 3:1 front slopes to catch existing ditches. To maintain traffic during construction, a four-phase Traffic Control Plan (TCP) was implemented that remained within the right-of-way. Roadway transitions are designed to allow the existing pavement tie-in to occur before reaching the existing Rush Creek Bridge 450 feet away.

To resolve construction detour concerns, the team developed a four-phase TCP. In Phase 1 the existing raised median on the bridge will be removed, embankment added in the approach, grass median, and temporary pavement constructed to detour the east-bound traffic to the west-bound existing structure. The new east-bound bridge is constructed in Phase 2, after which traffic is shifted to the new east-bound bridge in Phase 3, allowing for the west-bound bridge to be built. The twin bridges were designed and separated by a 1-inch open joint. Construction of the raised median follows in Phase 4. To overcome unsafe conditions during construction, the team needed to provide an innovative approach to the limited space they were facing. During Phase 2, a portion of the existing westbound bridge would need to be removed to allow construction to proceed on the new eastbound bridge at the same elevation. This would mean all four lanes on the bridge would be reduced to less than 10 feet-wide, even with pinning the temporary barriers. To overcome this unsafe condition, the team designed precast overhangs on the inside to eliminate the need for traditional overhand supports. Use of precast overhangs, precast deck panels and precast I-girders will accelerate bridge construction.

Value

Bartlett & West’s approach using accelerated bridge construction techniques will save TxDOT time and money, and enhance safety during construction by providing 12-foot lanes during construction. Constructing the new bridge within the existing right-of-way was imperative to avoid costly and time-consuming impacts. Throwaway costs for the future replacement and widening of the Rush Creek bridge were reduced with the proposed transition, and FHWA Category 6 funding was not affected. Pedestrian walkways and shared-use bike lanes will be provided on each bridge for added safety and to meet TxDOT requirements.