International Dredging Review

International Dredging Review

During a Nor'easter in March 2010 heavy surf and high winds devastated the dune system protecting beach front homes near the Hamptons on twin forks of Long Island in Quogue New York.

Instead of doing a “sand push” along the beach or trucking in sand to rebuild the dunes Maccaferri provided a different long-term solution. After the storm exposed steel sheeting remained which provided a temporary solution. The steel sheeting was put in years before after an earlier storm; however the Corps mandated that it must be removed.

Maccaferri installed MacTubes® and a single scour apron in front of the exposed bulkhead and used a dune core. The MacScour apron with a single three-inch anchor tube was put in place first. The MacTubes were then unrolled on top of the scour apron and covered with sand. Later the area was vegetated with native plants and a dune fence was put in place.

Macaferri completed construction within two to three weeks. Since then the dune had performed as designed and had also naturally accreted sand along the toe. On October 29 2012 the project area was hit by Super Storm Sandy.

Based on preliminary field observations and photo documentation of the post-storm conditions the geotextile tube structure maintained its structural integrity and design characteristics with little sand loss from within the bag and limited damage to the tubes from debris.

Some sediment and land losses behind the tube structure were observed due to overtopping of crest height from the storm surge. However visual inspection of the adjacent beaches to the north and south showed an average of 30 feet of additional landward recession in areas where no tube structure was in place.

While the losses directly landward of the tube were evident the landward extent of the erosion was less than that of neighboring shorelines. Maccaferri said the tube structure acted as a wave break as the water rose.

In the storm’s aftermath Maccaferri immediately repaired minor debris damage in the field. It worked with a local contractor to provide fabric patches fill the small voids within the tube where rips were apparent with sand and sew patches into the bags. Macaferri said it rehabilitated the dune structure to its original design capacity with minimal cost and labor.

Other Maccaferri coastal structures in New York installed to protect homes and natural shorelines from storm surge damage and erosion stood up against Super Storm Sandy. After the Nor’Easter in 2010 Maccaferri installed a gabion retaining wall on an oceanfront property in Staten Island New York.

The original wall design of PVC coated galvanized steel gabions spanned 100 feet parallel to the shore direction with a nine-foot vertical height and two 30-foot return walls at either end.

During Super Storm Sandy the storm surge pushed a large volume of sand and debris upland against the existing wall. While minimal damage was observed in confined places the wall structure remained intact and fully functional protecting the foundation of the home from the storm's surges and debris. Following the storm the property owner used the same contractor to perform clean up and maintenance on the gabion wall system.

Because the gabion wall performed so well the homeowner decided to add to the existing wall during storm clean up. By widening the footprint of the existing gabion wall its overall height increased from nine to 12 feet. The adjacent homeowner also decided to install a gabion wall after seeing how well it performed.