The 1.5-acre site will house two new circular clarifiers and a UV disinfection building. Ground conditions at the proposed site consisted of approximately 30 ft of sandy silt/clayey silt overlaying 10 ft of glacial till, with rock present at approximately 40 ft below grade. Groundwater was encountered at 14 ft below the existing grade. 

Keller was contracted to design and build an excavation support and deep foundation solution for the new structures. 

Keller installed 900 linear ft of driven sheet pile, internal bracing, and one row of tieback anchors to support the ~60 ft excavation. Further investigation revealed the rock was more permeable than expected and that additional mitigation would be required to provide a dry excavation. Keller installed a grout curtain within the permeable rock layer to cut off groundwater flow below the tip of the sheet pile wall. 

Once the excavation was completed, Keller installed 700 micropiles ranging from 30 ft to 50 ft deep across the site to provide deep foundations. The entire project work progressed as scheduled.