Completing a 900-ft HDD Under the Loop 101 Freeway in Arizona

Earlier this year, SSC Underground was contracted to install 900 ft of 24-in. casing to carry a 16-in. PVC waterline under the intersection of East Via De Ventura Road and the Loop 101 Freeway in Scottsdale, Arizona.

 

SSC was uniquely qualified to construct this large specialized project.

The water line needed to be installed underneath a very busy roadway at the on and off-ramp to a major freeway, Arizona State Route 101. The construction site was also directly adjacent to the OdySea Aquarium complex, a high-traffic entertainment venue. It was very important that the construction method did not involve open cutting or trenching the roadway, which would have added more time to the construction process and caused major impacts to traffic and businesses in the area. SSC executive vice president Arvid Veidmark III consulted on the design with the general contractor and owner for more than one year prior to construction. Veidmark consults with project owners regularly on trenchless constructability methods, while they are in the early stages of planning, to ensure the best possible outcome.

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After a thorough analysis, Veidmark recommended the horizontal directional drilling (HDD) method. This method allowed the entire installation phase to be completed in less than six weeks. HDD was also the most appropriate method because of the depth and distance the utility line needed to travel. This was feasible because of the good soil conditions in the area, which were mostly free of cobbles and caliche. Other methods of construction would have been much more time intensive.

This project was also complex due to the number of entities involved in the design, permitting, planning, and construction phases – including the general contractor, DPP-MGC Contractors, the City of Scottsdale, The Salt River Pima Maricopa Indian Community, and various specialty sub-contractors. Additionally, special sensitivity training, waste management, and traffic control were required for this project by tribal regulations.

Initially, SSC’s vacuum division was dispatched to core the intersection, locate existing utilities, and map them. This helped the project team verify that the path of the proposed bore was clear of utility conflicts and confirm the placement of entry and exit pits. SSC’s construction crews then began to pre-assemble the 900 ft of 24-in. steel casing by staging sections on wooden skids and welding them together. The 900 ft of PVC waterline was then fused together for installation and casing spacers were assembled.

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The Salt River Pima Maricopa Indian Community (SRP-MIC) allowed SSC crews to use a closed and undeveloped section of roadway, directly east of the job site as a staging area. This created an overall construction site footprint over three-quarters of a mile in length, which provided crews with enough space to pre-assemble the full length of casing and waterline. This was critical to the success of the project, and saved a significant amount of time, as the pre-assembly resulted in an extremely efficient pullback and installation process. SSC was able to utilize its drone throughout the installation process, to view and track progress across the entire jobsite. Additionally, the SRP-MIC allowed crews to dump dirt spoils and excess mud from the pits onto the unused section of roadway, which saved crews the time they would have otherwise spent traveling to dump off-site.

SSC was able to the complete the pullback by utilizing its two track hoes, two backhoes and pipe rollers to move the casing and waterline from the staging area to the pullback pit for install. This was a highly precise task, as both of SSC’s excavators had to work in tandem to move the casing and clear the pipe rollers, while staying within single lane of roadway, as traffic continued to flow. Once the installation was completed, the pits were backfilled, slurried and sealed and traffic flow returned to normal.

“This was one of the more exciting projects SSC completed this year, because of its size,” said Abe Veidmark, vice president of SSC and superintendent on this project. “We had a chance to utilize our drone and capture the overall size of this project on video, which cannot usually be seen from a ground level view. We are thankful to have been selected for this project, and we look forward to working on other projects for the City of Scottsdale and the Salt River Pima Maricopa Indian Community.”

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Steven Kaufman is business process analyst for SSC Underground.