Project Profile: Replacing Undermined Florida Sea Walls With Vinyl Sheet Piling

July 1, 2000

When Eugene and Sandra Wieher retired and moved to Dunedin, FL, they bought a home on lot bordered by an 80-ft.-wide seawater canal flowing into the Gulf of Mexico. The canals running through their neighborhood were close to 40 years old and filling in with silt.

“So we had to have our canals dredged,” explains Sandy Wieher, “but after the dredging, some of the sea walls along the canal banks began to cave in and collapse. Almost all the neighborhood sea walls, including ours, were made of concrete that went down to the canal bottom. Apparently the dredges came too close in some cases and undermined the sea walls by removing bottom material. Our sea wall did not cave in and did not seem to be in immediate danger of collapsing, but it was old and we knew we should fix it. It turned out that when the sea walls were first built, the city thought they were made of 10-foot-long concrete sheet piling. Actually, the pilings were only 8 feet long, so they did not have the bottom penetration that the city thought was there.”

Gene Wieher, an industrial engineer, called Myron Gibson, a general contractor in nearby Palm Harbor. “We got quotes from Myron and several other sea wall contractors, but our original intention was just to have the concrete sea wall repaired. We also had an engineer come out and take a look. There were some short-term repairs that we could have done, but it was clear that for the long term we needed a new sea wall. We retired here for the long haul, so we decided to get a new one.”

One contractor gave the Wiehers a quote for an aluminum sea wall, but other aluminum sea walls in the neighborhood were not doing well. The canal’s salt water was apparently causing holes in the metal and allowing seepage. When the couple started talking with Gibson, they found he favored vinyl sheet piling instead of an aluminum sea wall. “And we couldn’t afford to do another concrete wall,” says Sandy. “It was just so prohibitively expensive, it really wasn’t even a consideration for us.”

Gibson installed C-LOC vinyl sheet piling from Crane Plastics Company in Columbus, OH. The 2-ft.-wide exterior-grade vinyl panels interlock to create curves that follow the natural contours of the terrain.

“Vinyl sheet piling is just coming into its own,” says Gibson. “I’ve been licensed on my own in Florida for about 15 years now, and I’ve been using C-LOC vinyl sheet piling down here for eight years. Although I’ve been using it since 1992, it’s taken a while for people to realize that plastic can do the job. For the Wiehers’ job we used the C-LOC 9000 series panels that are 24 inches wide, which normally speeds up installation since you need fewer panels. We experienced some installation problems, however, because we hit rock everywhere along the canal wall.

“The C-LOC panels drive in easily with a vibratory hammer that I use, but I had to make some adjustments to accommodate a rocky bottom. Our panels were 12 feet long, and my contract with the Wiehers called for them to go 6 feet into the canal bottom. So I drove them down as far as they would go, then drilled 18 inches into the rock and put a coated steel rod into the area where the foot of the piling was seated. Thereafter, I filled each panel with concrete. We left the old concrete sea wall in place, so the Wiehers have a seawall that is probably 20 inches thick consisting of a plastic wall backed with concrete and topped off with a concrete cap and anchor. Driving the C-LOC panels down against the rock took some doing, and although the panels received a lot of abuse, they didn’t shatter. It’s tough material.”

“Myron used a great big pile driver, and the thing that amazed me wasn’t that he succeeded in getting the panels in, but that the panels didn’t break,” Sandy remarks. “We also have a very heavy concrete cap on it, so this new sea wall is going to be here for the next millennium. Our canal runs right out to the Gulf of Mexico, and we figure sooner or later we’re going to be hit with a really nasty hurricane. And we figure the neighborhood might be gone, but this sea wall will still be here. We’re going to have the only really improved lot in the neighborhood after the storm hits.”