Erosion Control March/April 2017 : Page 40

Beginning the project in April 2015, “As is often the case, the development For related articles: Team Elmer’s had a completion date site had a slope to it,” says Stan Hamil-www.erosioncontrol.com of July 2, 2015, just in time for Cherry ton, president of ReCon Wall Systems in Festival traffic. Midway through, St. Louis Park, MN. “To accommodate changes were made that required lowering a manhole the new store and the surrounding parking requirements, structure, moving a fire hydrant, and incorporating a few the site needed to be level. That meant that on one side of other challenges. In spite of the two-week extension that was the site, excavation of the existing slope would be required to required, Team Elmer’s finished the project on the morning lower the elevation, while on the other side of the site, new of July 2. The ribbon-cutting ceremony for Lafranier Road’s soil needed to be added to raise the site elevation. A storm-opening was held in time for holiday traffic and the Traverse water detention pond was a requirement. This resulted in the City National Cherry Festival that week. need for retaining walls.” Todd Sternfeld, chief executive officer and owner of Supe-Rockwall, TX, Gains Ground rior Concrete in Euless, TX, which manufactured the blocks When Kroger’s opened its first grocery store in 1883 in Ohio, for the project, explains that the utility company had expressed its founder Bernard Kroger had one philosophy: “Be particu-some concern about where the “fill” side was. In addition, he lar. Never sell anything that you would not want yourself.” notes, “If a pavement is close to a retaining wall, we have to That dictum and a $372 savings account began what is now be real cognizant of that. We cut down about 14 or 15 feet on the third-largest retailer in the world. that east side, on the back of where the store would be. But it’s In 2015, the $109.83-billion super giant was, by revenue, the hard to reuse that [excavated material]. We use select fill. It has largest chain in the country, and the second-largest general a certain density. And it has to be pre-tested for adhesion, and retailer behind Walmart. With headquarters still in Cincin-there’s some wetting that has to be done.” nati, the chain now has stores in 34 states, recently adding one Winkelmann & Associates of Dallas, TX, was the civil in Rockwall, TX. Rockwall, population 37,490, is a suburb of engineering firm on the project. As Maria Bonilla reviewed Dallas and part of the Dallas and Fort Worth metropolis. designs, she went searching for specific products that would The Rockwall area has an archaeological site that dates meet the customer’s needs. She was initially looking for a back 13,500 years called the Brushey Creek Clovis site. Early geogrid wall and a taller—over 17 feet—gravity wall for the occupations included Caddo and Creek Indians. But the “fill” and “cut” sides of the lot. name came when the settlers dug wells in the area and found There were some challenges, though. Utility and property large underground rock displays, described as “sandstone lines would be butting up to the backside of the wall, too rock walls with jointed wall-like features.” The US Soil Con-close for the footprint a geogrid wall would need. And the servation Service lists Rockwall as having fine, silt soil with products chosen need to have a degree of long-term durabil-0 to 5% limestone and chert gravels with calcium carbon-ity with respect to water, because the walls would support ate equivalents equal to 40 to 70%, derived from mudstone. detention ponds. These were the foundation for the area that became known When Superior Concrete and Winkelmann and Associ-as Rockwall. ates got together on the Kroger’s project, they found exactly what was needed—a tall wall with a small footprint. One of ReCon’s retaining walls manufactured by Superior is a rather tall gravity wall built with large wet-cast retaining wall blocks. Completing the requirement for a small footprint, Superior also manufactured and installed 5,000 square feet of concrete privacy fence that was mounted directly on top of the retaining wall. Using ReCon’s 24-inch-deep Superior Cobblestone block, the “fill” walls reached a maximum height of 16 feet. Atop a leveling pad with the drain tile, Recon’s reinforced walls typi-cally layer the 24-inch blocks and geogrid and backfill with increasingly wider layers of drainage aggregate. “Because of the mass of the ReCon blocks, you don’t need to use as much geogrid, depending on conditions, such as distance from buildings or fire lanes. You don’t have to go as far back and use as much,” says Sternfeld. “It’s just such a robust system.” The “cut walls” were designed as gravity walls to get that minimum footprint from the very beginning. The depth of the base block on a gravity wall generally needs to be from 35 to 50% of the height of the wall, compared to a geogrid length of 60 to 80% of the height of the wall. The retaining wall on this Large blocks at the side of the site reached a minimum height of 17 feet, 4 inches, base of a wall on the and an 84-inch-deep block was required at the base. “These Kroger’s site blocks weigh from 1,250 to 5,000 pounds,” says Sternfeld. 40 EROSION CONTROL WWW.EROSIONCONTROL.COM RECON

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