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CASE STUDYTHE DUNES OF NAPLES

AMENITY CENTER HELICAL INSTALLATIONPROJECT INFORMATION

In July of 2018, Coastal Foundation Solutions was contracted to install supplemental helical tiebacks and bolster plates to sustain an existing bulkhead structure for the Amenity Center located in The Dunes Of Naples, one of Southwest Florida’s premier housing communities.

EXISTING ISSUES

The owner was concerned about their existing wood bulkhead due to the construction of a 11-million-dollar new amenity center and upgrades to the existing pool. The expansion included all new pavers and railings adjacent to the wood bulkhead.

The Dunes has 402 lineal feet of wood bulkhead that is sustained by seventy-nine C.C.A. wood treated pilings. Upon initial inspection, the existing seawall was in fair condition. There were certain fasteners (nails, bolts etc.) along the bulkhead that were failing, which was ultimately causing the wood whalers to become disengaged.

The existing tie-back anchors were considered to be in fair to poor condition. Upon visual inspection the existing tie-back anchors were deemed too small in diameter with visual signs of significant rust. Throughout the bulkhead there were several locations were tie-backs were exposed and failing. Additionally, there were multiple locations along the wall that were slightly out of alignment.

PROJECT RECOMMENDATIONS

Installation of new galvanized steel anchor and new intermediate whalers at each span between pilings. Mechanical fasteners shall be fitted at each whalers/piling connection to improve longevity of existing seawall. With proper repairs the seawall will extend its’ lifespan upwards of 20 years.

Helical tie-backs are recommended to sustain existing bulkhead and helical anchors between each existing piling. Galvanized angle brackets were attached to existing whalers for support. Install Seawall drains to reduce the hydrostatic pressure from upland side of seawall.

BULKHEAD HELICAL INSTALLATIONTHE SOLUTION

Dunes of Naples located in North Naples, Florida in July 2018 awarded Coastal Foundation Solutions a contract for the installation of eighty-two (82) helical tieback anchors. CHS along with Turrell Hall and Associates designed a system to prevent any further movement to the wood bulkhead alignment. A CHANCE Helical Tie-Back anchor system was chosen by the owner, contractor, and engineer as the desired method to stabilize the seawall structure. The system was installed by Coastal Foundation Solutions (CFS), a Certified Installer of CHANCE Helical Foundations Systems. Coastal Foundation Solutions is located in Matlacha, Florida their service areas include Lee and Collier Counties.

Forty-five (45) CHANCE SS150 (1.5-inch square bar) helical tiebacks with an 8”-10” double-helix lead section was installed through ten-inch diameter core holes in a wood bulkhead using a Kubota KX040 excavator with a specialized mast system powered by a 6K Pro-Dig drive head. Helical extensions advanced the tieback anchors to lengths on the order of 15 to 21 feet to achieve final installation torques, The ultimate capacities of at least twice the design working tension load of 12 kips

Thirty-Seven (37) CHANCE SS150 (1.5-inch square bar) helical Anchors were installed through a combination of 3” thick wood bulkhead and 8” of solid reinforced concrete behind existing wall. Coastal Foundation Solutions utilized combinations of specialized core bits to gain access through existing vertical wall. Anchors were installed to corresponding capacities of working tension load of 12 kips.

Twenty-two (22) additional SS150 extensions were used to achieve required load capacity due to sub-surface soil variations.

The helical anchor was connected to a galvanized steel channel at the outside wall face. The channel bridged 24” with a wood 4” x 6” timber spanning 4’6” from between pilings. The tiebacks anchors were installed approximately two (2) foot down from the top of the wall and at a typical spacing of about five feet O.C. All tiebacks and anchors were load testing with a 30-ton center pull ram to secure required engineered load capacity.

Eighty-Two (82) seawall drains were installed to reduce hydrostatic pressure from upland side of bulkhead.

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