When plans for a new DHL facility in Allentown, Pa., were under way, security was a top priority for wall contractor Pickering Valley Landscape Inc., Glenmore, Pa., and construction manager, Opus Corp., Plymouth Meeting, Pa. The 290,000-square-foot distribution facility called for 3450 linear feet of retaining wall along the perimeter of its 72-acre site. “It is rarely understood by the client that fencing cannot be installed on thee top of perimeter walls without careful design considerations,” says Andre De Carville, vice president of Pickering Valley Landscape. “The grading plan noted a fence above every wall but did not provide a structural detail showing how to integrate our work with that of the fence contractor.”
The walls were to be constructed using a segmental retaining wall (SRW) system. The he most appealing quality of SRWs is how the dry stacked block face and geosynthetic reinforcement combine to form a retention system capable of holding back steep slopes and handling heavy loads. A limitation, however, is that the dry stacked wall face has minimal resistance to overturning in the upper two or three courses when such a load is applied to the block. This is precisely what happens when a horizontal load is placed on a fence post in close proximity to the wall face. Combined with tearing through the embedded soil reinforcement behind the wall with an auger, these two problems can compromise the integrity of both the wall and fence structure.
A decision was made to contact Strata Systems, Cumming, Ga., the manufacturer of a pre-engineered product called Sleeve-It 1224R. The product has a fence-ready and code-compliant design created to address the very issues the construction team was concerned about. Additionally, Strata provided test reports and additional calculations to the project engineer of record explaining how the Sleeve-It approach meets or exceeds the building code requirements for railings along the sides of elevated walking surfaces.
Each Sleeve-It 1224R is pre-assembled at the material staging area for the wall, then set in place with desired post spacing when the wall has reached 24 inches from the top. When the wall construction was completed, the fence installer arrived to complete the perimeter fencing. “We showed up ready to auger holes and much to our surprise the holes were already there,” says Scott Risbon from Earthcare Landscaping Inc., Honey Brook, Pa. “There was even a lid on every one that kept the topsoil from filling the holes during several rain storms after the wall was built.”
In all, more than 350 Sleeve-It units were installed during wall construction. Their use negated the need for a 36-inch offset of the fence on top of the wall. The 3-foot real estate savings translated into a total area savings of 10,000 square feet for the entire project. Traditional methods of integrating a railing at the wall face would have added two to three times greater cost to this portion of the project. The end result was a facility completed on time, within budget, and able to deliver the security that was needed.