Hospital renovation requires extensive retaining walls

By: Kevin Loe

When the St. Cloud Hospital was expanding its facility in a $225 million project, it required 25,000 sq ft of new retaining walls to support a new access road and parking structure.

The St. Cloud Hospital in St. Cloud, Minn., is located on the banks of the Mississippi River which presented some unique challenges to the project including steep grade changes and existing structures that could not be disturbed.

The new roadway required walls standing 33 ft tall in some areas in addition to gravity walls in other areas. Searching for a wall solution that could meet both of these construction needs led hospital designers to Redi-Rock , a wall system that utilizes massive, one-ton, interlocking concrete blocks with the look of natural stone.

Redi-Rock wall systems were the solution of choice for this project based on the natural-looking quarried limestone texture in addition to the engineering behind the massive block’s design.

Local Redi-Rock producer Hardrives Inc. provided blocks for the project that was installed by Joe’s Excavating and Structures Hardscapes. The majority of the wall was built using Redi-Rock 28 in. series blocks and was reinforced with geogrid in every course.

About 200 sq ft of the wall was constructed using Redi-Rock 41 in. series gravity blocks to minimize excavation at the hospital’s property line. The blocks weigh one ton or more each, which allows walls to harness the power of gravity and minimizes the need for reinforcement. By utilizing Redi-Rock’s gravity system, the wall’s construction did not disturb the neighboring property and also saved the neighbor’s mature trees.

The most recent phase of construction began in spring of 2009 and included Redi-Rock 28-in., zero-batter blocks, which allowed construction to take place close to an adjacent building and underground utilities. The blocks are ideal for areas where walls meet up with buildings or other structures with zero batter. The blocks have the same appearance and functionality as other blocks, but have an alternative batter to accommodate construction needs.

All of the walls on site were originally designed with cable fencing along the top to act as a pedestrian barrier. However, when hospital officials saw the freestanding blocks, they decided the blocks provided a nicer looking structural barrier. Freestanding blocks top the retaining walls throughout the project.

A unique facet of these walls is the uncommon bond pattern utilized. While most retaining walls have a ½-bond pattern, meaning that each course of block is offset by half the length of the block below, the St. Cloud Hospital walls have a 1/3-bond pattern. This means that each course of block is offset by 1/3. This required installation crews to custom cut a portion of the blocks in each course to create a unique look for the hospital’s walls.

At the terminus of the walls stand two reinforced concrete bridge piers. To make the look of the project blend together, contractors used form liners to give the cast-in-place bridge piers the look and texture of the walls. In the next phase of construction, a bridge deck will be placed atop the piers to provide access to the parking garage.