Hennepin County

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PROJECT QUESTION: It is our opinion that there is not enough geotechnical information to complete a final design of the permanent tieback anchors. With the exception of a few shallow hand auger borings at some of the walls, there were no SPT or CPT borings drilled in the tieback anchor zones for these retaining walls. The bond lengths that we have estimated are based on the soil borings drilled along the wall alignment, which may not be representative of the soil conditions present in the tieback zone. We strongly recommend that soil borings be drilled in the tieback anchor zone of each retaining wall to better characterize the soil conditions prior to final design.

Question:
It is our opinion that there is not enough geotechnical information to complete a final design of the permanent tieback anchors. With the exception of a few shallow hand auger borings at some of the walls, there were no SPT or CPT borings drilled in the tieback anchor zones for these retaining walls. The bond lengths that we have estimated are based on the soil borings drilled along the wall alignment, which may not be representative of the soil conditions present in the tieback zone. We strongly recommend that soil borings be drilled in the tieback anchor zone of each retaining wall to better characterize the soil conditions prior to final design.

Answer:
Available geotechnical information developed for the project has been included with the bid documents. We believe past borings in the aggregate/sand pit with the driveway at CSAH 61 centerline station 53+10 left of the roadway, ST-308, ST-309 and ST-310 are representative of the soil type in the bond zone for all anchors. We do not believe anchors will be bonded in cohesive soils or rock.