INTERRA, Inc. was the Geotechnical subconsultant to the design consultant Bowman Consulting. The goal was to build a retaining wall to retain the existing embankment material to the east of IL 31 near Plum Creek Road in South Elgin, IL.
The scope of work consisted of reviewing previous investigations, attending meetings, drilling three soil borings to bedrock, laboratory testing, and the preparation of SGR.
The retaining wall is tapered with the height varying between 5 feet and 13 feet, making it necessary to accurately determine the coordinates and elevations to capture soils information in the zone of interest. The presence of railroad tracks, overhead tree cover and railroad ballast created additional challenges in performing the field work. Additionally, shallow weathered bedrock created hard drilling conditions. INTERRA worked with the client, traffic control, railroad museum, and IDOT to ensure that the soil borings captured the necessary information.
Construction considerations played a major role in the development of recommendations. The need for a coffer dam, temporary ditches, sumps, granular drainage blankets for surface, and groundwater control were discussed in the report.