Construction that stands the test of time is a combination of the right products, the right preparation and the right installation. Finding the exact sequence of product, preparation and installation is often driven by the building site’s particular challenges. Such was the case for the Town of Jean Lafitte, La, when in September 2008, Hurricane Ike destroyed the town auditorium while flooding thousands of homes and businesses in Jefferson Parrish. The existing auditorium’s central location adjacent to Lafitte Library and both the elementary and middle schools, was critical to its success as a community landmark. The Town was determined to rebuild in place, and resolving site issues related to the flood plain was an obvious concern.
The Federal Emergency Management Agency (FEMA) funded the new auditorium and required that the site be raised out of the flood plain before new construction could begin. Filled with more than nine 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-square-foot auditorium. Elevating the site so much 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. Oswald describes the hill as descending about seven 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,” continues 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-1970’s.
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 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 5.5-inch-thick concrete pan.
As a Bomanite Licensed Contractor, Oswald has used Grasscrete on many other 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,” laughs Oswald, who speculates his firm must have installed more than two 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.
