US287 to Heritage Trace existed on the future southbound lanes and the roadway from Heritage Trace north to Golden Triangle was on the future northbound lanes, causing a switch over at the Heritage Trace intersection. The crews had green fields alongside the existing roadways to begin construction without impacting normal traffic flows. Working both northbound and southbound lanes simultaneously, the project was able to progress the critical path through the roundabouts and utility tie-ins. With each roundabout being completed in its own phase, Golden Triangle Boulevard brought the team the second substantial challenge in overall sequencing and planning - two main transmission waterlines servicing countless residents would need to be tied-in under a 48-hour shutdown window. Construction started March of 2021 and was to be completed by early summer of 2023 – leaving the team with one low demand season, December 1st to March 1st. Shortly after the notice to proceed was issued in March of 2021, three winter snowstorms within a two-week period crippled Texas roadways and electricity grid, shutting down supplier businesses and deliveries which multiplied pandemic-related supply issues. The storm caused unexpected timeline delays, greatly increasing lead times on various materials. The critical path of the project started in Phase 1 which was driven by the installation of various large storm drainage box culverts. Due to the storm impacts, the original material delivery was pushed out by a minimum of 11 weeks. The project team was able to mitigate critical impacts to the overall project schedule by shifting phases and working on the Heritage roundabout which had minimal storm piping. This allowed the overall sequencing to change but still maintain the optimal window for the Golden Triangle utility tie-in. Water Works The construction of Golden Triangle’s two main water transmission lines - Water Line A (24-inch water main) and Water Line B (36-inch water main) was a critical operation due to the complexities presented by the intersection itself. The two water mains had to be connected by a 36-inch butterfly valve inside a cast-in-place concrete vault - in the middle of an active intersection. Due to the Project’s phasing constraints, the operation was broken into two subparts to ensure traffic continued to flow smoothly along Harmon Road. Phase A constructed the Water Line A segment along Harmon Road from north to south splitting the existing intersection in half at the vault. Sequentially, Phase B constructed Water Line B from the vault westbound along Golden Triangle Boulevard. The team excavated, laid pipe, and constructed the vault for Phase A over a month starting in September of 2022. Quickly, the team swapped traffic control to construct the Phase B segment. It was critical that both phases be completed for the low-demand season due to one 48-hour window being allotted for the tie-in of both mainlines. Due to Water Line A tie-in point to Line B laying under existing pavement higher than the future roadway cut, the team had to excavate from existing ground 19-feet down to make the tie-in at the center of the future roundabout. This alone added a safety challenge and
Moving traffic through the Presidio Vista Roundabout
encompassed daily verification that the excavation remained sound, verification of elevations at the current roadway, and addition of concrete traffic barriers (CTB) and asphalt to allow the public to commute past the work area with a buffer layer. At the time of the tie-in, all locations were excavated and ready to go once the city shut down the valves. Three different crews rotated between each tie-in location cutting, laying, and welding in the new pipe. The lines were pressurized and active under the 48-hour window, making this a pivotal moment for the Harmon Road Project’s overall success.
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AUGUST 2023 csengineermag.com
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