The retention area being stabilized developed from a naturally occurring depression, or sinkhole, that was present many years before I-4 construction began. Most of the numerous Central Florida ponds, lakes and wetlands so readily visible from the air were created by a sinkhole formation process. Sinkholes form in Central Florida because the geology is comprised of a deep layer of limestone that is filled with holes, caves and caverns.

At some locations, the soil over the limestone flows down into holes in the limestone creating a depression of the ground surface known as a sinkhole.  The sinkhole typically fills with water and becomes a pond or small lake.

To begin the stabilization process crews first removed water and muck from the retention area replacing it with sand.  For several months, workers have been drilling pipes into the ground down to the limestone layer and pumping a water, sand and cement mixture — called grout — through the pipes to fill holes and cracks in the limestone surface. This process of grout injection will seal the limestone surface.

Once grouting is complete, a retaining wall and a 28-foot high mound of soil called a “surcharge” will be placed over the project area for at least 24 months to further compact and strengthen the soil. The settlement of the soft soil will be monitored to determine when the soil within the area has been adequately compressed.

The entire construction should be completed by summer 2010.



Illustration of how a sinkhole is formed



Illustration of how workers are injecting grout into the limestone to stabilize the area

For more information on the Maitland Boulevard stabilization project, visit www.trans4mation.org.