Malcolm Drilling was selected as the shoring contractor for Block 75 of the City Creek Center in Salt Lake City, UT. Block 75 was the center of the 3 city block Property. Malcolm’s scope of work included over 90,000sf of shoring and dewatering around a 2100LF site perimeter with cut heights of over 75 ft and a water table 25’ above the bottom of excavation. The project was completed over 2 phases to allow for existing structures at the north end of the site to be tenant occupied before relocating to new facilities on the south side of the project. Much of the shoring was done concurrent with the demolition of the existing ZCMI Shopping Center.

Malcolm’s shoring system directly or indirectly supported 4 existing structures surrounding the site and also provided a permanent foundation for one new structure.

iThis project highlighted the vast breadth of Malcolm’s capabilities as a shoring contractor due the unique constraints of the existing structures as related to the new construction.

Whenever possible, existing foundation walls from demolished structures were incorporated into the new shoring system.

One of the existing structures that were directly supported by Malcolm’s shoring system was the Historic Deseret Trust Building shown at the left. Malcolm installed vertical and battered micropiles through the buildings spread footings before installing a beam and shotcrete shoring system directly in front of the footings which extended beyond the building’s exterior walls. One of Malcolm’s Klemm Drill Rigs can also be seen installing well points for the dewatering system.

The Qwest Building provided a unique challenge as this building was a hub to telecommunication utilites and was supported by spread footings. The owner required a shoring system with cut heights of over 40’ to be installed within 30” of the existing structure. Malcolm chose to incorporate existing foundation elements from the old ZCMI center into its shoring system by pouring them into a grade beam. An “A-frame” micropile system was also utilized to aid in both lateral support and soil stabilization.

Micropiles were installed and incorporated into an gradebeam for the permanent foundation system of a new section of the project. This photo shows the shoring system being constructed “top down” as the new structure is being constructed above.

Because of its large Mat Foundation, a dewatering system would not have been practical underneath the 22 story Eagle Gate Tower. Malcolm chose to install a full cutoff system around the building. The combination of extremely high surcharge loads on the shoring system combined with presence of existing driven steel piles from the old ZCMI center located directly in line with the new shoring prevented the use of any standard cutoff system. Malcolm was able to install a secant pile shoring system in between groups of existing driven piles and fill the remaining areas with angled jet grouted columns.

Pre-drilling through the cobbles and boulders with jet grout operation closely following.

Exposed combination of secant pile wall with jet grouted infills.

Completed product.