Napoli Luxury Condominium Seawall Repair Case Study

Napoli is a condominium community of 101 units set on a seven-acre parcel of land between Davis Blvd and the East County Barn Road. It lies at the heart of the vibrant community of Naples, Florida. Amenities include two heated swimming pools two all-weather tennis courts. Not incidental is the property’s proximity to some of the best dolphin and manatee watching in Southwest Florida.

The project has a 16 year old wood retaining wall constructed of CCA treated lumber with 3 x 8-inch whalers and 2 x 8-inch vertical boards. Placed in front of the wall to resist overturning pressures are 8 to 10-inch diameter wood piling embedded into ground. Each of the piling is assisted by a through bolt connection to a ½” cable tie-back rod which runs behind the wall to a concrete dead-man.  The wall has an exposed face of nine (9) foot.

The present state of the existing seawall is in fair condition. The age of the fasteners coupled with corrosive characteristics of the CCA treatment has caused certain fasteners to fail (specifically nails and cables). This has caused certain portions of the whalers to become disengaged from the bulkhead.

The failing conditions are predominately created by tie-back failure and slippage of concrete dead man. This causes the existing wood bulkhead to rotate out of alignment. The tie-back cables are essentially too small in diameter (½”) and are showing visual signs of rusting due their connection point to the CCA piling coupled with salt moisture content in immediate vicinity.

Florida Marine Construction was contacted by the property management company to repair the failing wood bulkhead. Our wood bulkhead repair experience is unparalleled in Southwest Florida.

Florida Marine Construction proposed a helical anchor pile that can be utilized with tension piling projects to support vertical wood bulkheads. The square shaft helical pile is impeccable in its load bearing capacity to maintain seawall alignment. The grouping of the square shaft lead section and extensions both work successfully for hard difficult soils conditions. The square-shaped shaft portion of the design assists with greater penetration through old construction debris, small cobbles and tight soil. We proposed to use a 10”/12”/14” lead square shaft helical anchor for maximum torque and holding capacity.

In addition, we presented a plan to cover the existing wood sheathing with new D.O.T. filter fabric to prevent future soil loss trough the wall. A new 2” x 6” pressure treated timber fastened with stainless steel screws was then to be placed over the existing wood. New 4” x 6” wood whalers would be attached to new helical tieback anchors.

Our proposed strategy progressed precisely according to our approach with no time delays. We successfully installed a total of forty-six (46) 1 in. square shaft helical anchors with 10”/12”/14” lead section, with an average pile length of 15 to 21 foot. The helical anchor pile extensions consisted SS5 Square Shaft Helical Pile (1-1/2” x 1-1/2”) .

The helical pile installation process took a total of four working days. The entire installation took place off one of our floating modular barges. Forge Engineering effectively monitored the entire structural helical pile installation process and provided all the certifications flawlessly. The piling loads included 15 tons ultimate load capacity but several pilings torqued up to 22 tons.

• Forty-six (46) “Chance Helical Anchor Pilings” SS5 Square Shaft Helical Pile (1-1/2” x 1-1/2”) new foundation pile with a 10”- 12”- 14” triple-helix lead section was installed into a compacted dense soil. A Komatsu MR 88 18,000-pound excavator with a specialized hydraulic drive head (16 Digga) was used to rotate anchors. Helical extensions progressed the tieback anchors to distances on the order of 15 to 21 feet to realize final installation torques. The ultimate capacities and design working tension load of 14 kips.
• Fifty-Nine (59) additional seven (7) foot SS5 Square Shaft Helical Pile (1-1/2” x 1-1/2”) extensions were utilized to reach required load capability due to sub-surface soil variations and debris.
• The helical tie back anchor was linked to a hot dipped galvanized steel channel, placed within the new seawall cap to provide lateral structural support. All tiebacks and anchors were load tested with a 30-ton center pull ram to secure required engineered load capacity of 14 KIPS.

Florida Marine Construction utilized a vast array of specialized equipment to complete the project. We maintain a fleet of long reach excavators, floating modular barges, hydraulic/pneumatic drills and significant support equipment. It has always been our protocol to possess the correct equipment to perform the work we contract.