Built to Last

by sean O’keefe

Construction that stands the test of time is a combination of the right products, preparation, and installation; finding the exact sequence of each is often driven by the building site’s particular challenges. Such was the case for the Town of Jean Lafitte, La., in September 2008 when Hurricane Ike destroyed the town auditorium while flooding thousands of homes and businesses in Jefferson Parrish. The auditorium’s central location adjacent to Lafitte Library, plus elementary and middle schools, was critical to its success as a community landmark. The town was determined to rebuild in place, and resolving site flood plain issues was an obvious concern.

The Grasscrete embankment suits the engineering objectives FEMA outlined for the new Lafitte Auditorium. Bomanite of New Orleans’ 12-man crew applies hands-on craftsmanship to Grasscrete and other licensed processes to ensure highly durable, long life cycle slabs.

The Federal Emergency Management Agency committed to funding a new auditorium, but required that the site be raised out of the flood plain before new construction could begin. Filled with more than 9 feet of a local soil known as River Sand, the site was raised as required and a pile-supported building was designed for the new 18,000-sq.-ft. auditorium. Elevating the site ultimately resulted in some drainage complications along the parking lot where a steep embankment transitions down to a ball field at the original grade.

“The slope needed to be stabilized beyond the parking lot because of the steep grade and concerns about erosion,” says Robby Oswald, owner of Bomanite of New Orleans, the contractor hired to resolve the issue. He describes the hill as descending about 7 feet in just 12 feet of distance and, with rain runoff in Louisiana’s damp climate, the hill side would likely deteriorate fairly quickly. Once it did it would be an eyesore at least and potentially dangerous as well in a highly-trafficked area between the schools and library.

“Grasscrete was the ideal solution because it forms a concrete lattice that allows grass or other vegetation to grow within the voids. In this case it was covered with sod,” notes Oswald, who along with other Bomanite licensees across the country has exclusive rights to this innovative concrete system that has been in development since the mid-1970s. Beyond the ability to be planted naturally, a key to Grasscrete’s success is its overall strength and durability. Grasscrete is constructed using a molded-pulp former system that allows ready mixed concrete to be monolithically placed. When the forms are continuously reinforced with #4 rebar, the result is a compressive strength that can range from 4,500–12,000 psi depending on the specific mix used. Another important part of concrete’s strength is in the thickness of the slab. Grasscrete formers are designed for a 5-½ in. thick concrete pan.

As a Bomanite Licensed Contractor, Oswald has used Grasscrete on many applications and notes that it is especially useful in situations where the client wants a vegetated surface but municipal codes require access for emergency vehicles. “When a city fire truck has to drive, or worse, park on it you really want a strong solid surface below them,” quips Oswald, who speculates his firm must have installed more than 2 million square feet of Grasscrete over the years. He adds that overflow and industrial parking lots where surface drainage can be beneficial, as well as roadway shoulders and embankments, are all opportunities for engineers to consider this application.

In addition to Grasscrete, Oswald installs a wide range of Bomanite architectural cast-in-place concrete systems for clients across Louisiana’s’ Gulf Coast in a combination of indoor and outdoor environments. From large civic plazas and polished floors for commercial projects to decorative walks, patios and pool decks for residential clients, Bomanite of New Orleans covers almost everything owners could want in specialty flatwork.

Oswald credits Bomanite’s carefully developed proprietary systems and advanced technical resources as a critical component of what set his work apart from other local contractors. “Bomanite is a great company that provides technical support whenever we need it,” he concludes. “The ability to trouble shoot a project with Bomanite and our fellow vendors around the country is always there for us.” — Sean O’Keefe writes built environment stories for Bomanite Co., Granite Bay, Calif., 303/369-1115, www.bomanite.com, and many others in the design and construction industry.