Project Description:

This major transportation project in Sioux Falls, SD consisted of converting a rural gravel road into an urban four-lane divided section with a new bridge constructed over the BNSF Railroad.  Earthen embankments of up to 40 feet high were needed for the new bridge approaches and MSE retaining walls were constructed for the bridge abutments and grade separation due to restricted right-of-way.  A protected wetland is located immediately north of the roadway.


69th Street Embankment

Subsurface Conditions:

The geotechnical soil borings encountered 4 to 8 feet of clay fill and organic topsoil overlying soft to very stiff clay glacial till.  The exploration found soft to firm alluvial clay above the glacial till at some locations.  Groundwater was measured at depths varying from 2 ½ feet to 6 feet below existing ground surface. 


We worked with the design team to determine that the replacement Geopier GP3TM System would be an effective ground improvement solution to increase the bearing capacity, increase the factor of safety for global stability, and provide settlement control for the MSE walls and earthen embankments.


Geopier GP3 installation

The Geopier GP3 system provided significant cost savings over the more expensive over-excavation/refill option, and avoided major impacts to the adjacent protected wetland.  The Geopier approach also allowed the general contractor to build the project in a shorter time schedule during a stretch of wet weather.

MSE Wall Base - Note exposed GP3 elements

Project Team

Owner:  City of Sioux Falls

Geotechnical Engineer:  GeoTek Engineering & Testing Services, Inc.; Sioux Falls, SD

Civil Engineer:  HR Green, Inc.; Sioux Falls, SD

General Contractor: Grangaard Construction, Inc.; Watertown, SD

Construction Administrator:  Sayre Associates; Sioux Falls, SD

GFC Installer:  Peterson Contractors, Inc.; Reinbeck, IA

GFC Designer:  Ground Improvement Engineering (formerly Geopier Midwest)