Norman Water Treatment Plant

October 7, 2022 Melanie Chaney


  • Owner // City of Norman, Oklahoma
  • EOR // Frankfurt-Short-Bruza
  • General Contractor // BRB Contractors
  • Average Drive Torque // 5,500 ft-lb
  • Test Load // 30kips


The growing pains of most cities are felt first in the utility sector and Norman Oklahoma was not exempt. The expansion of the water treatment plant had a few obstacles to overcome the greatest of which was how to excavate 15′ below grade without undermining existing equipment and structures.


 The water treatment plant was located near the south Canadian river and though Oklahoma is known for its red clay that was not what was encountered. The soil report showed sand to a depth of over 50′. The Standard Penetration Blow Counts for the sand ranged from 13 to 18. Based on the geotechnical data a multi-flight 8”-10”-12” helical tieback configuration was designed to provide the required resistance in the loose to medium sands. This tieback anchor design provided easy and rapid penetration to a sufficient depth to achieve the 30 kip tension capacity required.


As excavation progressed, helical tieback anchors were used to stabilize the Sheet-pile wall shoring surface. The helical tieback anchors were installed through an opening cut in the sheet piling and the sheet piling was then secured with a short steel I-beam whaler. The helical tiebacks were installed quickly and immediately ready to load resulting in rapid project completion.

Per the EOR design the Piles were installed at the required angle. The design required that 33% of the Piles be proof loaded to the Ultimate Design Capacity before being locked off at the working load. Each helical tieback anchor was driven to a pre-determined installation torque. The sketch (to the right) shows the excavation and the proper angle specified to install the helical anchors.

Once the helical anchors were installed a steel I-beam whaler was attached and proof loading was preformed to confirm capacity.

Earth Retention Systems: Types of Shoring for Piles & Anchors