Controlling floodwaters

The Orange County, Fla., Division of Roads and Drainage completed a project this summer that improved stormwater drainage and safety at a lake near the county correctional facility. The project replaced one of Lake Catherine’s drainage wells with three drainage wells at a different part of the lake.

Many areas in Orange County contain closed-basin lakes that either have no surface outflow or discharge only at high lake level. Most of the topography of the county is flat, and the surface areas of the lakes increase greatly when it rains.

Since the 1900s, the county has used drainage wells to control lake levels and to alleviate flooding. Many of the wells were installed as alternatives to positive outfall drainage systems that carry stormwater into a canal, pipe or other water body. When lake levels rise, the water flows into the wells, which carry water from the surface directly into the upper Floridian aquifer that is a source of drinking water for the state.

In 1999, the county began planning to expand its correctional facility, which is located on the northwest side of 88-acre Lake Catherine. Stormwater from the facility drained into the lake, the level of which was controlled by three drainage wells. The plans for the expansion edged the facility closer to the lake, which would have made it difficult for public works crews to access one of the three drainage wells for routine maintenance. Additional expansion of the facility would have prevented access to the well entirely.

Moreover, the facility had experienced localized flooding in the past, and failure of the drainage well would have been catastrophic. Because it would have been difficult to relocate inmates in case of a flood, the county needed to curb or completely prevent flooding of the lake.

In November 1999, the county Roads and Drainage Division contracted with Orlando, Fla.-based Civil Engineering Group and Orlando-based Devo Engineering to evaluate the feasibility of replacing the drainage well near the correctional facility. The consultant recommended constructing three small drainage wells in another part of the lake and closing off the existing well. Following project approval by the Florida Department of Environmental Protection, in October 2002, Orange County contracted with Tampa, Fla.-based Diversified Drilling to construct the replacement drainage wells.

The contractor built two 12-inch drainage wells and one six-inch well to replace the existing 18-inch well. A 36-inch intake pipe carries water from the lake to the center drainage well box, which is connected to the other two wells to distribute the stormwater. Water enters the three new drainage wells at the same invert elevation as the old well, and sediment settles out of the water at the bottoms of the well boxes to prevent pollutants from entering the aquifer. To close the old well, the contractors sealed it with grout and removed the headwall. With the installation of the three new drainage wells, Lake Catherine now has five wells to control its water level.

The $515,405 project was completed in May 2003. The new drainage wells are easy for crews to access for maintenance, and they remove floating debris much better than the previous well. The new wells also have wellhead enclosures with locking hatches to prevent tampering, and they are double-cased and grout-sealed to prevent cross-aquifer contamination. Since the wells were installed, the county has not had any reports of flooding at the lake, and the lake’s level has been controlled.

Deodat Budhu, manager, and Oscar Bermudez, engineer, Orange County, Fla., Roads and Drainage Division.