Building A Better Basin.

By Steve Hudson

Here's how Gulf Shore Site Development tackled a challenging marina deepening project in Naples, Fla.

In Naples, Fla., a 50-year-old marina on Naples Bay is being reborn as a major new condominium, hotel and marina complex. Antaramian Development is spearheading the redevelopment project, which will turn the old marina into a new 15-acre site featuring not only 30 waterfront condominiums and an 85-unit hotel, but also commercial, retail and restaurant space and a significantly upgraded 2.3-acre yacht basin with close to 100 boat slips.

A key to the overall plan, notes Antaramian Development's Ken Schneider, was to demo and remove the existing Boat Haven Marina - and then deepen the marina basin by several feet accommodate deeper draft boats. Gulf Shore Site Development, Inc. won the contract to handle the demolition and deepening. It was project that brought unique construction challenges as well as close environmental scrutiny by a variety of agencies, by the Corps of Engineers and even by the governor of Florida - and an intriguing project it has proven to be.

Gulf Shore Site Development is a family business in every sense of the word. The company originated as Raiser Construction, Buffalo, N.Y., explains Jim Raiser, now treasurer of Gulf Shore.

"My grandfather started coming to Naples in the early 1960s," Raiser says, adding that the company began some work in the area in the late 1970s. In the early 90s, he adds, the company started the Naples operation and shifted its focus to south Florida.

Today, the company focuses on a market area that includes Collier, Lee and Charlotte counties as well as the Everglades. Jim's brother Richard Raiser is president of the firm, with brother Tom as vice president, Richard's son Mac as secretary, his brother Bob running a grading crew, and his brother Jim as treasurer and chief estimator. Additionally, their sister Mary DiPardo is controller.

Demolition

Demolition of the existing facility began in July 2004 and required about two months to complete. Demolition involved removal of an existing 150-foot-long boathouse, removal of numerous old timber piles, as well as removal of an existing sea wall.

"The old sea wall was constructed in the mid 1950s," Raiser says, "and it was a conglomerate of block on poured footers, some timber wall and some panels."

Because of the waters-edge location of the old marina, Gulf Shore handled most of the demolition from a 125-foot barge using a pair of excavators (including a Link-Belt 3400 and a Case 9030 with hydraulic thumb attachments) to pull out the old structures.

"We brought the barge up through the bay and wiggled it in here to the basin," Raiser says. "It just made the turn at the entrance to the basin."

The Damming Solution

With demolition complete, attention turned to cleaning out the basin - an ambitious and multi-faceted process that would be completed in stages. Stage one would be to isolate the basin from the rest of Naples Bay in order to allow the necessary dewatering; stage two would be to deepen the basin itself, with crews working in the dry - relatively speaking.

But nothing could get going until a way was found to isolate the marina basin from the rest of Naples Bay.

"We considered an earth dam," notes Jim Raiser. "But there were concerns over an earthen dam's impact on the bay waters, so that option was ruled out."

That's when Gulf Shores went searching for an alternate approach, and the solution turned up during an Internet search when the contractor ran across Portadam Inc. Portadam's approach utilizes a steel structure in conjunction with a continuously reinforced vinyl liner membrane to allow construction of portable dams in a variety of configurations. The support structure is designed to transfer the hydraulic loading from the water to a near vertical load, creating a freestanding structure which anchors itself to the underlying surface with no back bracing required. The liner system, which extends from the toe of the dam and under the impounded or blocked water for some distance, is flexible and readily seals over most irregular bottom contours.

Gulf Shores discussed the idea with Portadam. The decision was made to move ahead with dewatering in multiple phases, using an initial Portadam to isolate and dewater half of the basin, then using a second dam to isolate and dewater the rest. This division of the basin into sections made the dewatering operation much more manageable.

Installation of each Portadam was straightforward. First, the steel frames were assembled in pairs on land. A crane was then used to set each pair of frames into position, one pair at a time, until all frame sections were in place. The frames were positioned on a prepared base of #1 stone, which was placed underwater, smoothed with the excavator bucket and further smoothed as required by divers.

At that point liner installation began. The prefabricated liner was unfolded and pulled out into position using a crane, where it floated on the water's surface. The top of the liner was then attached to the frames, and divers working in the water then began to sink the liner down the frame's surface, securing it as they went. The liner extended about 30 feet beyond the toe of the frame, providing a good seal with the existing bottom.

"The trick," Raiser says, "is to leave enough slack. But the Portadam technicians are very good at it."

As liner installation neared completion, sandbags were hand-placed along the outer edge, by divers, to secure the liner and ensure a good seal.

Siltation Control

Using 10-foot-high frames, Portadam crews constructed the first dam - a 140-foot-long structure - across the midpoint of the basin. The contractor planned to utilize a 24-inch hydraulic pump from MWI to pump out the water. But the pumping would stir up many years of sediment, and environmental concerns would not allow sediment-laden water to be discharged directly into Naples Bay.

To deal with that challenge, Gulf Shore had also arranged for Portadam to construct an above-ground settlement pond in a level area along the east side of the job site. The pond, measuring about 175 feet long and 70 feet wide with a capacity of close to 1 million gallons, included a filtering and settling system utilizing three turbidity fences. Special additives helped clarify the water even further. Water was discharged from the far end of the pond, where a pair of "chimneys" drew water from the top of the final settling area, and twice-daily turbidity monitoring ensured that the system was doing its job.

The dewatering process worked well on the first half of the basin, and it was repeated (after installation of a second Portadam structure at the mouth of the basin) to dewater the remaining portion. The second dam, with a length of about 160 feet, worked equally effectively, allowing the remaining water to be pumped out and processed through the filtration pond, and after dewatering of the second section the first Portadam was removed so it would not impede subsequent work.

Moving Out The Muck

With the entire basin dewatered, deepening could at last begin. The first challenge was to remove several feet of silt, mud and organic matter - a layer that was as much as 3 feet deep in some areas. Working in the basin (while a 12-inch pump took care of seepage and kept things relatively dry) a fleet of New Holland dozers pushed the muck to the sides, where the excavators dug it out and loaded it into Terex off-road trucks. The material was hauled to an on-site holding area, where it was spread and allowed to dry for eventual re-use as fill. Overall, more than 3,000 cubic yards of muck was removed from the basin during this phase of the work.

During the de-mucking phase, Naples had to deal with the effects of three hurricanes - Charley, Frances and Ivan. Work was shut down prior to the arrival of each storm, with some water pumped back into the basin area to equalize pressure on the Portadam in case the area should experience a storm surge. The Portadam survived the storms in good shape, requiring only some retying of the fabric to the frames after each storm had passed.

Into The Rock

Once de-mucking was complete, Gulf Shore Site Development turned to the next phase of the operation - deepening of the basin to the final design level. Plans called for bringing the entire basin to a depth of minus 6 feet. However, the basin floor below the muck was hard lime rock - and that meant that the rest of the deepening operation would involve cutting through some very hard material to reach the specified depth.

The developer's permit allowed for removal of 2 feet of rock. Hammering and breaking of the rock was the first approach that came to mind, but the contractor considered that to be too imprecise.

"If we were to remove rock below the permitted level," Raiser said, "we would have been required to go back and fill any overcuts back to the 2-foot level."

In light of that concern (not to mention concerns from nearby condo owners over possible effects from any rock-breaking operation) Gulf Shore chose to go with an unusual approach to rock removal - use of a milling machine of the sort more commonly seen on highway projects.

Asphalt Milling Services was named to handle the milling operation and utilized a Roadtec milling machine for the purpose. The machine cut the lime rock to a depth of 6 inches to 8 inches on each pass, requiring three to four passes to achieve the desired change in bottom elevation. A Deere 650LGP dozer and a Komatsu WA-380 loader worked behind the milling machine to pick up the cuttings and transport them out of the basin area for eventual use in various on-site applications. This innovative approach to reconstructing the basin has gone well, Raiser says, effectively deepening the basin with a high degree of precision and minimal impact on the surrounding area and on the project's neighbors.

Has Gulf Shore Site Development been pleased with the performance of the Portadams?

"They are a little more expensive," Raiser says, "but if we'd had an earth dam up there for nine months and three hurricanes you can imagine the runoff."

He adds, "In an application such as this, the Portadam is so much cleaner than any earth dam would be."