The City of Cincinnati believes in maintaining the historical integrity of the city throughout new construction projects. The downtown Cincinnati business district contains structures constructed of natural quarried stone, which engineers try to match as best they can while providing the structural support required in new building projects. A prime example of the city’s commitment to context sensitive design is the Riverside Drive Improvement Project that was completed in November 2008.

Construction on Riverside Drive in Cincinnati began June 4, 2007. The focus of the project was to improve safety and access for pedestrians and motorists using Riverside Drive between Eggleston Avenue and Bains Street. Widening and realignment of vertical and horizontal grades required the construction of a new retaining wall on the Ohio River side of the roadway that would replace an existing stone retaining wall that supported the roadway. The proposed widening began only several feet away from the existing wall, but then diverted up to 40 feet from the existing wall. Grades needed to be raised on the order of 18 feet. An existing parking lot and City Park prevented simple embankment construction, so a retaining wall was required to limit encroachment into the parking lot and park.

Redi-Rock Structures of OKI This Riverside Drive Project expressed cincinnati’s continuing commitment to improving neighborhood vitality through context sensitive design.

A segmental retaining wall constructed with Redi-Rock blocks was specified for the project. This wall system was selected on both its architectural and performance criteria, which met the unique characteristics of the project. The proposed wall would have a length of 1,013 feet and a maximum height of approximately 18 feet. The local Redi-Rock producer, Redi-Rock Structures of OKI, supplied blocks for this project that were installed by Ray Prus Construction.

The Redi-Rock split limestone texture closely matched the look and size of a portion of the existing wall which was constructed of quarried sandstone blocks. The dimensions of the limestone face enhanced the length and height of the wall.

The face of the proposed retaining wall ranged from 3 to 6 feet from the face of the existing wall for a distance of 400 feet. The maximum wall height along this length was 11 feet. Use of other types of segmental units would have required geogrid reinforcement with lengths extending beyond the existing wall requiring its removal, a costly and time-consuming task since the existing stone wall was in excellent condition. Redi-Rock blocks with limited backfill were the ideal solution to fill the area between the existing wall and the proposed face of wall. Redi-Rock 41-inch series blocks were specified along this length. Some portions required the width of the blocks to be modified to 35 inches because of the lack of space between the proposed and existing faces. Engineers from across the country can modify Redi-Rock blocks to fit site specific requirements.

As the new wall veered away from the existing wall and transitioned from a gravity structure to a geogrid reinforced wall, Redi-Rock 28-inch series blocks were specified. The maximum length of the geogrid was 11.5 feet and the maximum number of course blocks was ten. Select backfill, composed of a modified ODOT 304, which limited the amount of fines passing the No. 200 sieve, was used within the reinforced zone.

A set of stairs leading from the parking area to the street level was constructed in front of the wall. Construction of the stairs using Redi-Rock units allowed the stairs to be constructed as a separate entity. The wall indent was required in order to avoid placing the wall on top of a thrust block of a 60-inch diameter water main. Sheet piling was driven into bedrock at a depth of 30 feet in front of the wall in case the water main ever requires repair.

The Redi-Rock wall was capped with a concrete cap and sidewalk and a painted galvanized railing was anchored to the cap for pedestrian safety.

The bearing soil of the wall was fill material composed of cinders and soft lean clay. This soil was undercut to a depth of 4 feet below the bottom of the base course of block. The excavated soil was replaced with the same select backfill which was used in the reinforced zone.

The retaining wall is located within the floodplain of the Ohio River. In addition to the granular backfill, 6-inch-diameter perforated PVC drain pipes were place behind the wall. Redi-Rock Structures of OKI also custom made blocks that contained 4-inch by 4-inch weep holes which were placed in the lowest exposed course as every tenth block along the length of the wall. Other custom modifications that were done by Redi-Rock Structures of OKI included a vertical batter for the wall and a reduction in the dome height of the top blocks to allow clearance for the steel in the wall cap.

This Riverside Drive Project was an exciting and innovative project that expressed Cincinnati’s continuing commitment to improving neighborhood vitality through context sensitive design of our transportation facilities. The project enhanced the entrances and frontages of both Sawyer Point Park and Theodore M. Berry International Friendship Park, and improved the important gateway to the Central Business District/Riverfront and the exciting community re-development in the East End. Redi-Rock International was a major contributor to the success of the project.

Richard E. Pohana, P.E., is an engineering geologist/geotechnical engineer for the City of Cincinnati Department of Transportation & Engineering. For more information about Redi-Rock visit www.redi-rock.com.