Tampa Port Authority Spoil Island 2D
Tampa, Florida

Client
Tampa Port Authority

Project Value
$8,000,000

Project Type
Construction Management and Levee Improvements

History


WRScompass was contracted by the Tampa Port Authority (TPA) to perform construction management and levee improvements on their 2D Dredge Spoil Disposal Island. The 2D Dredge Spoil Island is a 500 acre island located in Hillsborough Bay in Tampa, Florida.  The island is primarily used as an area for material that is generated from both maintenance dredge activities and from the construction of new facilities within the TPA theater of operations.  
 

Project Scope


At the start of the project the levee elevation was at approximately 19 feet above the National Geodetic Vertical Datum (NGVD) and virtually over grown with vegetation.  The scope of work required that the levees be raised to an elevation of 31 feet, NGVD and be constructed with a 22-foot wide crest.  Also included in the scope of work was the construction of a new decant structure, the closure of twelve existing decant structures, the construction of an American Oyster Catcher Habitat and the dredge spoil management on the southern half of the island. 

 

One of the unique challenges associated with the operations of the island is that the island is closed between the months of April through August due to the use of the island as a nesting ground for several species of birds.  Some of these species include the American Oyster Catcher, the Least Tern and the Black Skimmer, to name a few.  For this reason, the project schedule had to be accelerated to fit within the given window of operations.  Stormwater run-off and control of turbidity was also another challenge for island operations due to the vicinity of environmentally sensitive waters.

Levee Construction


The island levees had been virtually covered in vegetation and inaccessible to all but foot traffic.  The interior of the island was somewhat inundated and consisted of what was thought to be mostly undesirable material for the use in construction of containment levees. In order to construct the levees, the proposed footprint had to be cleared and a bridge lift, 85 feet wide, had to be constructed.  The bridge lift was installed to bring the surrounding footprint up to the elevation of the existing levee, at the time of the start of the project. 

To facilitate construction of the North Levee system, WRScompass performed borrow excavation activities of the material on the north side of the island.  WRScompass estimated that approximately 3.84 MM cubic yards of material were located above elevation 10.5 on the north side of the island.  Suitable materials above and below elevation 10.5 were excavated and utilized for levee construction.  Unsuitable materials were segregated and placed in areas designated by the engineer.

WRScompass utilized 75,000 pound excavators for the removal and quarry of suitable materials.  Suitable and unsuitable materials were loaded into off-road articulated dump trucks and hauled to levee areas and or dump areas.  In addition, haul and placement of material was utilized to increase production and run times to and from the borrow pit.

Suitable materials were then placed in the footprint on the levee in approximate 24 inch loose lifts as required by the specifications.  Materials then were graded with D-6 dozers and compacted with sheepsfoot compactors in order to obtain 95% compaction of the standard proctor maximum dry density to the lines and grades in the construction documents. 

Island Structure


The most difficult task was the planning of the construction of the new decant structure and outfall pipe.  This structure consisted of installing 16, 8-foot long, steel pipe piles, the installation of 2,
40-cubic yard concrete pile caps, the construction of a 25-foot tall decant structure, the installation of 1,500 feet of 60-inch inside diameter, high density polyethylene pipe and the installation of 3 large, pre-cast concrete junction boxes.  The decant structure itself was designed as part of a value engineering option in the WRScompass contract with the TPA. 

 

The overall cost savings to the TPA was approximately $850,000.  By far, the most logistically challenging part of this project was the transportation of concrete to the island for the construction of the pile caps supporting the decant structure.  The concrete mix design constraints and transportation time to the island presented WRScompass with an extremely short window for completing this task.  This task was completed in 2 days, with the first pile cap installed on the first day and the second cap poured the following week.  This concrete pour exceeded the largest remote pour performed for TPA activities to date.
 

American Oyster Catcher Habitat


The American Oyster Catcher is one of the top ten listed “At Risk” species that the Audubon Society is focusing on.  The new habitat was constructed as part of a study performed by the Regional Audubon Society.  WRScompass was instrumental in locating and increasing the size of the habitat according to a design completed by a joint/team effort between WRScompass, Tampa Port Authority, the Audubon Society, and the Florida DEP.  These habitats are large sea-side rip-rap groins placed in shallow water, and aid in the protection of sensitive nesting areas that have been historically damaged by waves generated from large sea-going vessels.