Mother Nature can alter the landscape well beyond a natural disaster. Case in point is the Town of Jean Lafitte, Louisiana, when in September 2008, Hurricane Ike destroyed the town auditorium while flooding thousands of homes and businesses in Jefferson Parrish. Critical to the existing auditorium’s success as a community landmark is its central location adjacent to Lafitte Library and both the elementary and middle schools. The Town was determined to rebuild and resolve site issues related to the floodplain.
Although the Federal Emergency Management Agency (FEMA) funded the new auditorium, before any new construction could begin, it required that the site be raised out of the floodplain. The site was raised as required by nine feet and filled with a local soil known as River Sand. A pile-supported building was designed for the new 18,000 sf auditorium. Because the elevation was raised so drastically it ultimately resulted in some drainage complications along the parking lot where a steep embankment transitions down to a ball field at the original grade. This was a complication just waiting for another, albeit entirely different in type, disaster.
The hill descends about 7 feet in just 12 feet of distance. With rain runoff in Louisiana’s damp climate, the hill side would likely quickly deteriorate. This could cause a potentially dangerous scenario in a highly-trafficked area between the schools and library. “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 Bomanite Licensee contractor hired to resolve the issue. “The Grasscrete Slope Protection System was the ideal solution because it allows grass or other vegetation to grow within the voids. In this case it was covered with sod,” continues Oswald. The chosen solution is called the Grasscrete Concealed System.
Beyond the ability to be planted naturally, a key to Grasscrete’s success is its overall strength and durability. The Grasscrete molded-pulp former was used to allow cast-in-place 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 psi to 12,000 psi depending on the specific mix used. That strength is identical to other flatwork concrete. Another important part of concrete’s strength is in the thickness of the slab. Grasscrete formers are designed for a 5 ½ inch thick concrete pan.
Grasscrete is especially useful in situations where the client wants a vegetated surface but municipal codes require access for emergency vehicles. Overflow and industrial parking lots where surface drainage can be beneficial, as well as roadway shoulders and embankments are all opportunities for engineers to select the perfect solution by using Grasscrete.
