Sinkholes, Karst and Landslides: What to Check Before You Build in Kentucky

Before you plan an addition or a new home in Kentucky, look at the ground. The Kentucky Geological Survey says karst underlies about half the state. You can build on karst, but it costs more and takes extra precautions. The Survey's advice is plain: do not build inside a sinkhole, and avoid filling one.

Where karst is found

The Survey estimates that about 55 percent of Kentucky is underlain by rocks that could develop karst. It lists Louisville and Lexington among the Inner Bluegrass karst communities and Bowling Green among the Western Pennyroyal karst communities.

The hazards that damage buildings

• Cover-collapse sinkholes, where the ground gives way.
• Sinkhole flooding, when water collects in a depression.
• Relatively high radon levels, which the Survey also lists as a karst hazard.

What the Survey advises

• Building on karst is possible but costs more than building on non-karst ground, and it needs extra precautions.
• The safest strategy is not to fill a sinkhole. If filling is essential to the project, the Survey says there is a right way to do it.
• Building inside a karst sinkhole is never recommended.
• Review topographic and flood-prone area maps, and ask neighbors about past flooding.
• For projects in karst areas, the Survey points to the Kentucky Speleological Survey to help locate caves.

Slopes and landslides

The Survey says much of Kentucky is prone to landslides because of steep slopes. It advises keeping drainage working and watching for new cracks in the ground. Slope stabilization should be done by a licensed engineer or geologist.

Flood maps and local drainage review

FEMA's flood maps are the official source for flood hazard areas. Areas with a 1 percent or higher annual chance of flooding are considered high risk. In Jefferson County, MSD reviews land disturbance and issues floodplain permits, and it has a tool to check a property's flood status. In Bowling Green, disturbing 750 square feet to one acre of soil requires a professional plot plan, an erosion control plan and an EPSC-certified contractor.

Steps before design

1. Walk the lot and note any depressions, cracks or places where water pools.
2. Check the FEMA flood map and any local flood tool for your address.
3. Ask your local building office what site, drainage and floodplain reviews apply.
4. Bring in a licensed engineer or geologist when a lot has a sinkhole, a steep slope or signs of movement.
5. Place the footprint away from sinkholes and depressions.