Before




After

The Constance Marina on the Ohio River in Hebron, Ky., wanted to create a more attractive riverside entrance that would withstand the waters of the river. The solution was a gravity wall that doubles as a floodwall. The new brown and gray gravity wall improved the look of the marina from the water and incorporated an installation that required no excavation, preserving the marina's outdoor living area. Project challenges included an unsightly, sloping terrain, and maintaining the marina's outdoor living space as a gathering spot.

David Landwehr, owner of Constance Marina on the Ohio River, wanted to create a more attractive riverside entrance to his facility that could withstand the riverbank's harsh environment. The 10' gravity wall was recently put to the test when it withstood a 20-year flood event, with waters cresting less than 6" below the top of the wall and no resulting signs of distress or degradation of the wall system.

Finding the Solution to Project Challenges
Just around the river's bend from downtown Cincinnati, Constance Marina is a 45-boat, dry dock storage facility in Hebron, Ky., with a vision to become a social gathering space for boating enthusiasts. The first obstacle in the marina's evolution, however, was an unusable and unsightly hillside. The slope was challenging to maintain - so steep, its grass could only be tamed by a hand-held weed-whacker. From the water's view, the land was unkempt and unwelcoming. While a typical solution would be a segmental retaining wall, the marina had an additional consideration: Adjacent to the hill is an outdoor living space with a patio and outdoor fireplace use by guests. A segmental retaining wall installation would require excavation of that land to stabilize the wall, destroying the patio and adding time and expense. Instead, Landwehr chose a wall that required no excavation for installation, offered the visual appeal of a natural stone appearance, and created an extra 1,890 square feet of outdoor space for the marina. The wall also offered the additional protection of functioning as a floodwall. Belgard Mega-Tandem Mass Segmental Retaining Wall (MSRW) was selected for the project. The size and structure of the MSRW allows for walls up to 15' high and gravity walls up to 10' without reinforcing. Patent-pending positive mechanical connectors in the system allowed for high gravity walls without a surcharge, so no excavation was needed. This provides a major advantage for project sites where utility lines or property lines abut the project. For Constance Marina, it meant the existing outdoor living space was spared.

On March 9, 2015, shortly after the wall was completed, the Ohio River crested a foot above flood stage, approximately halfway up the Constance Marina's new gravity wall, putting the floodwall to the test.




After additional heavy rains, the river rose to its highest level since 1997, where it stayed for two days before beginning to recede. The floodwall functioned as designed, with no degradation or signs of distress.

Light Weight Panels Pack a Big PSI Punch
The wall system panels were 12"x 24" and weighed in at 65 pounds per panel, which benefitted the project, according to Landwehr, who owns the marina and Structures Hardscapes Specialists, the national civil design specialty construction firm that built the wall.

"The lighter units were cheaper to ship, and the weight made them easier to use on site," Landwehr said. Because of its weight, the block could also be installed by hand, eliminating the need for bigger equipment. The system has a running bond configuration, so no pattern was required, which sped installation. The wall incorporates reinforced polypropylene connecting members to create structural integrity. Meeting ASTM standards (C-1372 and C-1262), the system was constructed of 8,500-psi compressive strength concrete and can offer in excess of up to 10,000 psi. The new floodwall incorporates a blend of grays and browns, reflecting tones found in the natural landscape. The textured surface emulates the look of natural chiseled stone. The cap offers the coordinating look of rugged cut stone.

Structures Hardscapes Specialists built the 126' long, 10' high gravity wall with no reinforcement, using Belgard's Mega-Tandem Mass Segmental Retaining Wall (MSRW) system, which includes three parts:

A. The MSRW unit with dovetail connection.
B. Polypropylene connection members, designed for non-reinforced walls of 6' and up to 10' in height.
C. Mega-Tandem wall jigs for wall or corner installation.

Putting the Flood Wall to the Test
The snow laid down by winter storm Thor was hit by a wave of warmth in March 2015, causing the Ohio River to flood, cresting a foot above flood stage, approximately halfway up the marina's new gravity wall. With the addition of heavy rains over the following week, the river eventually crested at its highest level since 1997, completely submerging the wall except for the cap. The water remained at this level for two days before beginning to recede. Though the manufacturer's research and development division conducted internal testing, this was the first real world flood test of the relatively new product.

"Anytime you get into these types of applications with a new product, there is always an unknown factor until it's tested in a real-life situation," said Al Pfannenstein, national retaining wall manager for Belgard. "Mega-Tandem was designed as a floodwall, and now we have solid evidence of its strength and durability in the field.