This sinkhole opened up after Hurricane Debby made landfall in Florida’s Big Bend region on August 5, 2024. Image source: Suwannee River Water Management District.
Sinkholes are a natural part of Florida’s landscape, especially in areas where limestone lies close to the surface. If a sinkhole appears on your property, knowing how to respond is key. This article outlines important first steps, available resources, and expert contacts to help you assess the situation and determine what to do.
How do sinkholes form?
Sinkholes form when surface sediments collapse into empty spaces, or cavities, within the limestone bedrock beneath the ground. These cavities develop over time as slightly acidic groundwater slowly dissolves the limestone. When a cavity becomes too large to support the weight of the ground above it, a sudden collapse can occur, creating a noticeable hole at the surface. In some cases, sinkholes can form gradually as sediments slowly settle into cavities over long periods of time, resulting in shallow, bowl-shaped depressions without a sudden collapse.
Limestone underlies our entire state but there are regions where the risk of sinkholes is higher, such as where the limestone is closer to the surface. Although cavities and voids are a feature of carbonate rocks like limestone, few collapse and directly impact roads or buildings.
Where can you find help if you have a sinkhole on your property?
Sinkhole in Union County, FL. Image source: Suwannee River Water Management District
The Florida Geological Survey (FGS), has a Sinkhole Helpline (850 245-2118) as well as a sinkhole website and extensive Sinkhole FAQ to answer residents’ questions. You can speak with someone on the helpline for guidance about what to do (you may not need to do anything) and they can help clarify information found in the FAQ. The FGS also has a leaflet available, A Homeowner’s Guide to Sinkholes in Florida.
Here are a few important tips to keep in mind, summarized from the Florida Geological Survey Sinkhole FAQ. Much more detailed information is found on the website. Call the sinkhole helpline or your Water Management District for further clarification on steps to take.
Call your local law enforcement agency if there is any risk of physical harm.
For sinkholes under or near structures: Stay out of your house if you suspect the hole is causing or could cause any impact to the structure. In some counties, local government agencies, the sheriff’s office or emergency management office may offer help when a home is endangered.
Contact your property insurance to see if they cover assessment and repair of damage caused to structures. It’s recommended to mark the hole’s approximate boundaries and document its size by taking photographs and monitoring changes. Do this from a safe distance. Keep children and pets away.
For sinkholes in your yard, small holes can often be filled with clean sand or soil.
On large properties, sinkholes that are not actively developing and are not affecting a structure can usually be left alone. If there’s a risk of people or animals falling in, fence or cordon off the sinkhole or you can usually fill the hole with clayey sand (which is preferred) although clean fill material can also be used. Don’t throw anything into a sinkhole or use any fill material that can decompose or leach toxins into groundwater. Call the Sinkhole Helpline for further clarification (850 245-2118).
Although no permit is usually needed to fill a new sinkhole, sinkholes in wetland areas or those that may change water flow or add to groundwater pollution if filled may need an environmental resources permit (ERP) before filling. Contact your Water Management District or FL Department of Environmental Protection (FDEP) District Office for guidance.
Keep in mind that other factors besides sinkholes can cause settling on the land surface. These include decomposing stumps, compressed or decomposing garbage and other debris, collapsed or broken sewer pipes and septic systems, soil that wasn’t compacted properly after excavation was completed, among others.
Private well system in Florida. Image: UF/IFAS, C. Wofford
UF/IFAS Extension and Mississippi State University are offering a workshop about the fundamentals of private well and onsite wastewater systems (septic systems) on October 24, 2024 from 6-8:30 pm CST. Join us virtually or in-person at the UF/IFAS Walton County Extension Office for an informative session that will cover everything you need to know about these essential systems. Whether you’re a homeowner, realtor, or simply interested in the topic, this event is perfect for gaining valuable insights. Don’t miss out on this chance to expand your knowledge!
Flooding due to heavy rains can cause septic systems to fail. Image: B. White NASA. Public Domain
About 30% of households in Florida rely on septic systems to treat and dispose of household wastewater. This includes all water from bathrooms and kitchens, and laundry machines.
Conventional septic systems are made up of a septic tank (a watertight container buried in the ground) and a drain field, or leach field. The septic tank’s job is to separate out solids (which settle on the bottom as sludge), from oils and grease, which float to the top and form a scum layer. Bacteria break down the solids (the organic matter) in the tank. The liquid wastewater or effluent, which is in the middle layer of the tank, flows out through pipes into the drain field and underlying soil, where most of the treatment takes placeDuring floods or heavy rains, the soil around the septic tank and in the drainfield become saturated, or water-logged, and the effluent from the septic tank can’t properly drain though the soil. Special care needs to be taken with your septic system during and after a flood or heavy rains.
Diagram of a conventional septic system. Courtesy of the Leon County Public Works Department.
What should you do after flooding occurs?
The U.S. Environmental Protection Agency (EPA) offers these guidelines:
If your water supply comes from a private well, have it tested for bacteria (total coliform bacteria and E. coli) to make sure it’s safe for consumption, which includes drinking, brushing teeth and cooking. Contact your local County Health Department for testing information. Use an alternate water source or boil your water (bring it to a rolling boil for at least 1 minute) before using it.
Relieve pressure on the septic system by using it less or not at all until floodwaters recede and the soil has drained. For your septic system to work properly, water needs to drain freely in the drainfield. Under flooded conditions, water can’t drain properly and can back up in your system. Remember that in most homes all water sent down the pipes goes into the septic system. Clean up floodwater in the house without dumping it into the sinks or toilet.
Avoid digging around the septic tank and drainfield while the soil is water logged. Don’t drive heavy vehicles or equipment over the drainfield. By using heavy equipment or working under water-logged conditions, you can compact the soil in your drainfield, and water won’t be able to drain properly.
Don’t open or pump out the septic tank if the soil is still saturated. Silt and mud can get into the tank if it is opened and can end up in the drainfield, reducing its drainage capability. Pumping under these conditions can cause a tank to pop out of the ground.
If you suspect your system has been damage, have the tank inspected and serviced by a professional. How can you tell if your system is damaged? Signs include: settling, wastewater backs up into household drains, the soil in the drain field remains soggy and never fully drains, a foul odor persists around the tank and drain field.
Keep rainwater drainage systems away from the septic drainfield. As a preventive measure, make sure that water from roof gutters doesn’t drain into your septic drainfield – this adds an additional source of water that the drainfield has to manage.
Green stormwater infrastructure at Cascades Park in Tallahassee, Florida. Image: T. Jones, UF/IFAS.
Join us for a two-part webinar series on Managing Stormwater in a Changing FL Panhandle on May 1, 2024 from 8:30-11:30 am CST (9:30-12:30 pm EST), and May 15, 2024 from 8:30-11:30 am CST (9:30-12:30 pm EST).
We are also offering two optional no-cost field tours of stormwater management sites in northwest Florida. The first will be held on May 3 in Pensacola to the Escambia County Central Office Complex, and the second on May 22 in Tallahassee to the Upper Lake Lafayette Nutrient Reduction Facility (aka Weems Pond). Detailed information as well as how to register for both the webinars and the field tours is found below.
Webinar series: Information and registration
Please register for the webinar series here: Eventbrite link Once in the registration site, you will have to register for both dates separately.
May 1: Day 1 will focus on Green Stormwater Infrastructure (GSI) and its maintenance, as well as presentations and discussion on the ecological function of GSI+LID.
May 15: Day 2 will focus on implementing GSI and LID at the community level, with presentations about ongoing research on extreme sea levels and effects on flooding events, a resiliency case study on Cedar Key and funding opportunities for GSI and LID through FDEP.
PDHs and CEUs offered:
4 Professional Development Hours (PDH) will be offered through the Florida Board of Professional Engineers. Two PDHs will be offered for Day 1 and two for Day 2.
4 Continuing Education Units (CEU) will be offered for Pesticide Applicators through FDACS in these categories: Ornamental & Turf, Private Applicator Ag, Right-of-Way, Aquatic, Natural Areas, Commercial Lawn & Ornamental, Limited Commercial Landscape Maintenance, Limited Lawn & Ornamental and Limited Urban Fertilizer.
The webinar is free for those not seeking PDHs or CEUs. For those seeking PDHs or CEUs, the cost is $50 for Day 1, and $50 for Day 2.
Field Tours: Information and registration
Please register for each tour separately through the Eventbrite links provided.
May 3 Pensacola Tour: Join us for a tour of the Escambia County Central Office Complex, a LEED Gold certified building with pervious pavement, energy efficient design, and the largest green roof in Florida. Registration: Pensacola Field Tour
May 22 Tallahassee Tour: Join us for a tour of the Upper Lake Lafayette Nutrient Reduction Facility (aka Weems Pond) which captures sediment and trash from a large upstream drainage basin and uses modern treatment methods to filter the stormwater before it enters a natural system. The tour will be led by the City of Tallahassee Stormwater Planning team. Registration: Tallahassee Field Tour
We look forward to your attendance! Please contact Andrea Albertin if you have any questions at (850) 875-7111 or via email: albertin@ufl.edu
Private well system in Florida. Image: UF/IFAS, C. Wofford
About 2.5 million Floridians rely on private wells for home consumption, which includes water for drinking, cooking, and personal hygiene. Private wells are not regulated by the EPA Clean Water Act, and well users are responsible for ensuring their water is safe to drink.
What should you have your well water tested for?
The Florida Department of Health (FDOH) recommends that well users test their well water once a year for bacteria at a minimum. Another important contaminant to test for is nitrate.
Bacteria: Labs generally test for total coliform (TC) bacteria and fecal coliforms (like E. coli).
Coliform bacteria are a large group of bacteria and most are harmless. But a positive test result indicates that if they are in your water, other pathogens that cause diseases may also be present. They are used as indicator organisms.
Fecal coliform bacteria are a subgroup of coliform bacteria found in human and other warm-blooded animal feces. E. coli are one species and some strains can cause diarrhea, food poisoning and other illnesses.
If your water sample tests positive for only total coliform bacteria or both TC and fecal coliform (E. coli), FDOH recommends your well be disinfected through shock chlorination. You can either hire a well contractor to do this or you can do it yourself. Information for how to shock chlorinate your well can be found at EDIS Private Wells 101: Bacterial Contamination and Shock Chlorination
Take a water sample at the kitchen faucet if this is where you get most of the water that your household consumes. Image: F. Alvarado
Nitrate: The U.S. EPA set the Maximum Contaminant Level (MCL) allowed for nitrate in drinking water at 10 milligrams per liter of water (mg/L). Values above this are a particular concern for infants less than 6 months old because high nitrate levels can cause a type of “blue baby syndrome” (methemoglobinemia), where nitrate interferes with the capacity of hemoglobin in the blood to carry oxygen. It is especially important to test for nitrate if you have a young infant in the home that will be drinking well water or when well water will be used to make formula to feed the infant.
If test results come back above 10 mg/L, never boil nitrate contaminated water as a form of treatment. This will not remove nitrates. Use water from a tested source (bottled water or water from a public supply source) until the problem is addressed. Nitrate in well water can come from multiple sources, including fertilizers, animal waste and/or human sewage, such as from a septic tank.
You should also have your well water tested at any time when:
The color, taste or odor of your well water changes or if you suspect that someone became sick after drinking your well water.
A new well is drilled or if you have had maintenance done on your existing well
A flood occurred and your well was affected
Remember: Bacteria and nitrate are by no means the only parameters that well water is tested for. Call your local health department to discuss what they recommend you should get the water tested for. FDOH also maintains an excellent website with many resources for private well users which includes information on potential contaminants and how to maintain your well to ensure the quality of your well water.
Where can you have your well water tested?
UF/IFAS Extension will be hosting a private well and water quality workshop on April 11 in Blountstown, with a Zoom option. We will cover well and septic system function and maintenance, water testing and how to prepare for hurricane season. We will also offer facilitated water testing. For more information and to register go to our Eventbrite link or you can also register by visiting the Calhoun County Extension Office, (850-674-8323). Last week’s post about the workshop provides more information as well.
In general, many county health departments accept samples for water testing. You can also submit samples to a certified commercial lab near you. Contact your county health department for information about what to have your water tested for. If they don’t offer testing, they often provide the name of certified laboratories near you. Or you can search for FDEP certified laboratories here.
If you have any questions, you can also reach out to me at albertin@ufl.edu or (850)875-7111.
