Ask the Builder: How to avoid geologic hazards when building
You probably don’t give much thought to the ground under or around your home. What follows are a few true stories that may change your perspective. If you’re in the market to buy land to build your dream home, or if you’re looking to buy an existing home, what I’m about to share could prevent financial ruin.
My college degree is in geology, and what I learned allows me to look at building lots through a different lens than you might use. Less than a week ago a woman hired me to do a one-hour video call. She recently bought raw land in the heart of the Bluegrass region of Kentucky just east of Lexington. I happen to know this part of Kentucky is one of the top places in the U.S. for Karst topography. This translates to sinkholes that can cause serious structural damage to homes.
Before the call, I asked for the address. I wanted to locate her land on a U.S. Geological Survey topographic map. You can get high-resolution PDF copies of these for free online for any land in the USA. Sure enough, within a half-mile radius of her land there were no fewer than 10 sinkholes. You can clearly see these on a topographic map as circles or ovals that have small lines pointing to the center of the circle or oval.
Does this mean her new home will sink into the ground? Not necessarily. That said, it might be a good idea to chat with the local building inspector or folks at the Kentucky Geological Survey. I’d also inspect the land to see if there was evidence that a sinkhole had been filled in to disguise it.
Topographic maps can shed light on many things. My friend Ed purchased a lot in a new subdivision in Cincinnati about 20 years ago. The developer had to do lots of cut and fill. Ed’s lot was land that was fill dirt. The dishonest excavator dumped dirt on fallen trees to bury them. Within a year after Ed’s house was built, it started to crack in half. The basement floor looked like a dough bubble on a pizza. The entire foundation was dropping but the floor was not falling at the same rate. Ed now knows to never again build on fill.
About 30 years ago, neighbors of mine were almost killed in a flash flood. They bought a home in a nice subdivision nestled on rolling land. Their home was right on top of an old dry creek. Under their driveway was a hidden 5-foot-diameter storm sewer that was installed when the farmland was converted to residential property. My neighbors had no idea this pipe was in the ground.
One day a huge storm caused storm water to completely fill the pipe and then run across the land to a depth of 8 feet in my friend’s driveway. It completely flooded their basement in a matter of minutes. Had they studied a topographic map before buying this home, they could have seen from the contour lines how much land above them collected water and then funneled it to their lot.
As most of us know, active geologic faults can be found all over the western United States. But the center of the USA is not immune from tremendous earthquakes. In 1811-12, the New Madrid earthquake caused massive damage where western Tennessee touches southeast Missouri and northeast Arkansas. If you live near here or intend to build there, talk to your insurance agent about an earthquake rider on your homeowner’s policy.
Landslides can also cause nightmares and death. Just three years ago, two friends of mine died when a propane explosion destroyed their home. Heavy rain caused a landslide that dislodged their propane tank resulting in a gas leak in their home. This was preventable to a large degree, but the average person would never think about the relationship of a propane tank to a hillside.
Humble Cincinnati is the epicenter of some of the highest landslide damage in the U.S. The media darling for landslides is California, where each winter we seem to see houses falling into the ocean during fierce winter storms. But in Cincinnati, the bedrock geology is such that thousands of homes are built on unstable clay soil that can be found on the hillsides all around the tri-state region.
How disappointed would you be if you had bought raw land only to discover there’s no water? Yes, this happened to friends of mine in Washington state. They had to stop drilling after boring a hole 700 feet. This might have been avoided had they talked to well drillers before buying the land. The drillers might have told them land to avoid and the places where water is discovered at a shallow depth.
You may place your trust on government officials in situations like this. That would be a grievous error. There are neighborhoods in many cities in the USA that get flooded in periods of heavy rain. These old creek beds should have never been allowed to be developed by not-so-wise government officials.
You can make the best decision when buying land by hiring a professional geotechnical engineer or a professional geologist. These folks can look at raw or developed land and produce a report indicating any potential issues that could affect your major investment. I wish you the best of luck!
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