Subsurface exploration authorized for third phase of F-48 West project

Before construction crews even begin working on the third phase of F-48 West — which won’t be until fiscal year 2027 at the very least — the Jasper County Board of Supervisors ordered soil borings be conducted for the twin box culverts that will be installed along the heavily traveled county highway.

County Engineer Michael Frietsch said the twin box culverts would be located near the first curve east of Polk County. Currently, the plan is to replace Bridge O10 with culverts. To determine what the underlying substructure is like, soil borings must be collected. TEAM Services of Des Moines will carry out the work.

Altogether, the soil borings will cost the county $4,980.

According to the contract included in the supervisors agenda, the two soil borings will be drilled to a depth of about 25 feet below the existing grades. The borings cannot be drilled within the stream area with a geotechnical drilling rig. Instead, they will be drilled alongside the nearby stream.

The third and final phase of the F-48 West resurfacing project extends from Colfax to Mitchellville. In addition to the road work and the bridge being replaced, a curve will also be relocated. The curve will be moved northwest, making the final product even wider. Design services have already been approved.

The county will have to acquire 6.3 acres of right-of-way easement and vacate about 9.2 acres to relocate the curve.

When the county vacates the old curve, Frietsch said the road surface will be taken out during the construction phase and then crews will restore the ground back to agriculture land. The concrete will likely be hauled off by the contractor to a landfill or reuse it as riprap provided there isn’t any rebar.