Innovative Transportable Dredges Maintain Canals in Cape Coral, FL

Typical of the Florida land boom in the 1950s, ’60s, and ’70s, the city now known as Cape Coral grew out of the swamps of southwest Florida. In the wake of development, the city was left with a multitude of unanticipated drainage problems. Although Cape Coral is unique with nearly 400 mi. of canals and waterways, the maintenance issues the city confronts are typical of many municipalities throughout the world. Drainage channels and canals that convey stormwater runoff from urban areas are often clogged with sediment buildup and/or are choked with vegetation. Forty years after the development boom in Cape Coral, the city is aggressively addressing its chronic drainage problems through a comprehensive dredging and vegetation removal program using four Innovative Material Systems (IMS) Versi-Dredges.

Program Development

Cape Coral initiated its dredging program in 1987 with a number of objectives, including:

• maintaining conveyance in canals by removing sediment buildup and vegetation,
• providing for a sounder ecological environment for marine life,
• improving the aesthetic and recreational quality of waterways.

The initial activity of the program was the assessment of options for removing sediment and unwanted vegetation. The city determined that conventional equipment, such as draglines and excavators, were impractical because of the scale of the project and because they could not work effectively in a highly populated environment. The city also considered contracting out the dredging work to private companies, but experience had shown contracting to be expensive and difficult to manage.

After considering many options, the city determined that the most cost-effective and efficient way to maintain the city’s waters was to purchase its own hydraulic dredging equipment and establish an “in-house” dredging program. The kickoff for this program was the purchase of a hydraulic dredge from IMS of Olathe, KS. This transportable dredge was used to excavate and pump sediment from the bottom of canals to spoil areas where the material was dewatered by settling and evaporation. The dried material was then removed by the city and stored for future use as fill. The dredge proved extremely effective as it pumped material to spoil areas 3,000-4,000 ft. away.

The dredging program has evolved to include a fleet of four 1545 Versi-Dredges operated by the city. Three key features differentiate this dredge system from other transportable dredge systems:

• a pump that is capable of moving higher volumes of thicker, more viscous material with less horsepower and far less wear than traditional turbulent flow pumps;
• a self-propulsion Starwheel Drive system consisting of two propulsion wheels independently mounted and driven by reversible hydraulic motors that enable the dredge to be completely maneuverable without the use of cables or spuds;
• the Weedmaster cutterhead attachment, which transforms the dredge into an aquatic vegetation harvester capable of removing both floating and rooted vegetation. The cutterhead chops the vegetation into small pieces that are pumped using the dredge pump to a spoils pile area.

These innovative design features have enabled the Cape Coral dredging program to be both productive and cost-effective. The present dredging program removes approximately 70,000 yd.³ of sand, silt, and vegetation annually at a cost of $700,000 as compared to an estimated contract cost in excess of $2 million.