Hayward Baker worked with the designer to develop an innovative solution that prevents ash flow from polluting a nearby river during a seismic event while meeting the requirements of CCR regulations.

The project

This Midwest coal-fueled power facility runs with a net generating capacity of over 1,000 MW. Improvement to approximately 900 linear wall ft of the existing dike of the east ash pond levee was required in accordance with the CCR Compliance Management Program.

The challenge

Portions of the existing dike were constructed by filling over the top of ash. Borings performed in the area of the work indicated medium stiff to stiff embankment clay fill underlain by very loose to loose ash fill. Below the ash fill, stiff to very stiff lean clay was encountered. Improving the existing subsurface soils at the project site was necessary to achieve static and seismic stability; instability could have resulted in ash flowing into a nearby river.

The solution

The improvement zone was 30 ft wide on the west side and transitioned to 55 ft wide at the east end. Existing grades ranged from El. 337 to El. 355 in the area of ground improvement. As such, portions of the existing dike were excavated and others filled to create the work bench at El. 349.3. HBI installed over 25,000 cubic yd of 6-ft-diameter wet soil mix columns each with a design compressive strength of 150 psi, overlapping to create panels. These overlapping panels provided resistance to the existing ash from experiencing lateral spreading during the design seismic event.

Project Facts

Owner

Confidential

Main Contractor(s)

Hayward Baker, Inc.

Keller Business Unit(s)

Hayward Baker

Engineer

AECOM