Location

  • Austin, Texas

Client

  • Downtown Gateway Partners

Status

  • Completed November 2020

Capital Metropolitan Transportation Authority (CapMetro) expanded its Downtown Rail Station to service more customers in the area along 4th Street from Trinity to IH 35. With the rail expansion in the area, certain utilities were not allowed to be under the rail or platform stations, or were required to be steel encased where they crossed the tracks. With these requirements, the impacts to the existing underground utilities in 4th Street became a major component of the project with added complexity in designing the relocations to meet all governing regulations, including: CapMetro, Texas Department of Transportation, TCEQ, City of Austin, and Austin Water Utility.

CobbFendley provided Engineering, Bid, and Construction Phase Services for the relocation of approximately 4,000 linear feet of water line, wastewater line, and chilled water line for the proposed expansion of the existing CapMetro Downtown Platform Station. The sizes range from 6” to 21” and include all associated appurtenances: valves, fire hydrants, manholes, encasements, borings, service connections, and encased water line attached to the bridge at Waller Creek. CobbFendley also provided relocation services for approximately 800 linear feet of Austin Energy electric infrastructure in the project limits. The construction methods include open trench, boring, tunneling, coring the Hotel wall, bypass pumping, and interior installation of the chilled water lines in the parking garage. Constructability and phasing are of high priority and complexity since this area is highly traveled through all forms of transportation: cars, bikes, and pedestrians. Traffic, pedestrian, and bike routes were considered in all phases of the project to continue to allow access to these high-demand businesses as well as maintain a route for the general traveling public. Also, any utility shut-off to provide connections to proposed utilities was heavily analyzed as the work would affect the Hilton Hotel and Convention Center.

CobbFendley performed SUE Quality Level B and 15 Quality Level A SUE test holes in various locations to identify potential utility conflicts. In order to safely work in the railroad ROW, CobbFendley crews obtained safety training and coordinated with CapMetro and the City of Austin to schedule work at off-peak times. Significant challenges were identifying the excavating potable water and chilled water lines in 4th Street. CobbFendley used pipe and cable locators and ground penetrator radar (GPR) to find the sides of a 66-inch waterline on Sabine Street. This was confirmed by vacuum excavating 2 test holes; one on either side. The size and location of the line could then be documented without having to cut a 6-foot long trench in the street across the top of the pipe. Pipe and cable locators were also used to identify the chilled water lines crossing 4th at Red River. The concrete pavement was cored rather than jack-hammered to maintain as much pavement integrity as possible, and the hole was excavated to a depth of 15 feet to find the waterline. City of Austin specification flowable fill was used to backfill the hole and the same concrete core was replaced and sealed in place providing a smooth repair.