In early January of this year, Florida experienced some unusually cold temperatures that forced Plant City area strawberry farmers to pump extra groundwater to try to protect their crops. Over the course of about 11 days, the groundwater table in areas of Plant City was lowered by as much as 60-ft.
Almost immediately as many as 80 sinkholes began opening up around that region. Including ones that jeopardized a 500,000-gallon water tower, several that shut down an elementary school and numerous ones that shut down roads and highways and affected individual property owners. Around 20 local homeowners were left homeless after sinkholes left their house uninhabitable. For comparison, based on data from Florida Department of Environmental Protection’s Sinkhole Database for the period of 1998 to 2008 (the last year for which data is available), 77 sinkholes were reported to have opened up in Polk, Pasco and Hillsborough counties combined.
Local officials are seeking help from the State and FEMA to cover the estimated $3 million in damages. That figure is double what Plant City received from FEMA for the particularly bad 2004 hurricane season. And that dollar amount does not include what individual homeowners and property owners will be seeking from their insurance carriers. (Photos by Tampa Bay Online)
Read on for maps of Plant City sinkhole locations and more information.
Groundwater withdrawal doesn’t cause the formation of the cavities in the limestone, but it does contribute to their collapse, forming what we think of as sinkholes. When the buoyant forces from the groundwater are no longer present after the withdrawal of the groundwater through pumping, the soil cover over the cavity can collapse.
In the case of the Plant City sinkholes, the period around which they occurred was marked by some unusually cold weather as mentioned above. The figure below shows the temperatures in the first and second week of January dropped down to freezing or below for 11 days (1/3 to 1/13).
December 2009 and January 2010 Temperatures in Tampa Bay, Florida (Source Data: Weather Underground)
Of course when many people think of Florida, one of the things that comes to mind is oranges. And the Plant City area does appear to have it’s share of citrus groves based on Google Earth imagery, but it is the strawberry farms that dominate the agriculture in the area, and it’s definitely an important part of the Plant City economy. This year marks the 75th anniversary of the Florida Strawberry Festival held in Plant City. It is actually running right now through March 14. So it’s understandable that the strawberry farmers would want to protect their crops.
One strategy to prevent damage to trees and crops in times of cold temperatures is to provide extra irrigation. I’m not sure what the goal is with the strawberries (ie. flood the fields or just keep the soil extra moist or something else), but I know if dry soil freezes, it can pull moisture from the roots damaging the plant or tree. So the growers and farmers in the area of Plant City pumped a billion gallons a day for 11 consecutive days to protect crops and actually lowered the groundwater table in the area by as much as 60-ft in some locations according to a spokeswoman for the Southwest Florida Water Management District.
Summary of Some of the Sinkhole News Stories
Most of what I’ve written here I’ve pieced together from news stories at Tampa Bay Online. Here are links to a few of them.