HELP!

OK I have put it off long enough... 5 or 6 years... and the hole is growing so I need to mitigate it and secure it for safety / liability reasons.

So to start a conversation with the collective... hoping some one has experience or maybe even a geologists can chime in.

Sink hold showed up behind my construction shop / warehouse... a commercial property within city limits. It very gradually grows due to surface water draining into it.

I hesitate to contact the city engineer or county extension office because I fear they may require costly steps be taken. UT had at one time a program to map / assist with sinkholes in Tennessee but I'm reluctant to contact them as well.

The hole has no known bottom but no one had been down in it to look. It curves slightly as it gets deeper so you can only see about 20 feet down but a pickup truck load of field rocks went out of sight. Simply filling it is probabally not an option. It Is roughly about 12 to 15 feet opening at the top narrowing to half that at 20 feet down. You can hear water running in it somewhere out of sight in rainy weather.

Huge rocks make up a lot of the walls so erosion is partially stopped by that. During heavy rains surface water drains into the hole.

My plan is to cover the hole with fence wire, or heavy welded wire livestock panels, crossed in two or more directions to keep dogs cats and people from falling in. This will be stretched across the ground and secured by driving steel T post around the diameter and perhaps rebar stakes. Then I would fence around the T post circle with chain link fence as a first line of defense against animals and people. There is normally no people in the area but it does get cut for hay sometimes.

Next I would have a shallow ditch cut to redirect surface water better and use the removed soil to build a berm around the hole, placed over the fence wire on the ground to stop surface water from draining into the hole.

Then I would plant Multiflora rose or similar around the hole that would help with erosion and form a natural dense thorny barrier. I know that is invasive but there is already som on the property.

NOT necessarily looking for a permanent solution, no structures are in danger. I'm 65 yr old and retired so the property will probably be sold in the next 20 years or less but I don't want some exploring kid, or even a wandering pet falling in and getting someone hurt or me sued.

40 years ago we would have used it to dump construction debris... but they seem to frown on that anymore...

White circle is location of my sink-hole.
Yellow is drainage ditch and a small wet weather creek
Orange lines show lay of the land and current water flow.

The building closest to the hole is my shop... It is 50 x 100 feet for scale.

I'd call someone in before your shop collapses because you didn't see the erosion under the foundation. You never know, but be on the safer side and call a pro.

Most states have a geologist that will be happy to help you with this , if not the state, there are a half dozen Universities that you should/ could. consult.

Concealing it on the cheap could very well make the problem much worse, and a much greater liability, in the not too distant future

I’m assuming that you have insurance on the property and if so read the policy carefully to determine if sink hole coverage is excluded or not.

If it is not excluded then you should contact the state extension office or perhaps the University to determine what is your best method to mitigate the situation. Even if it’s excluded from coverage you probably should get a third party expert to inspect it.

You will never be able to sell the property with a growing sink hole in it...and the liability will continue to grow..

I think you need to have pros look into this. You really have no idea what's going on down there.

Even if you do have insurance to cover damage resulting from it, if such damage occurs and the insurance company finds out you knew about the sinkhole and failed to take precautions, they'll probably deny you coverage.

quote:

Originally posted by smlsig:
I’m assuming that you have insurance on the property

No insurance since built / self insured. Even if it fell in a hole today I expect I would still be money ahead... including contents... than if we had paid premiums for the last 48 years.

Not trying to HIDE it, just control the erosion and make it safe for people and animals. BIG holes falling in do happen but are EXTREMELY rare around here. Smaller one like mine are fairly common. For example my Father in Law and Brother in Law both have one equal to or bigger than mine on their respective farms but require no action due to their remote locations.

There is always a cause.

It could be a broken sewer line, an underground stream, or something geological.

Until you figure out the cause, you will have no clue how to fix it.

Call in an expert to look at it.

Short money now compared to a collapse down the road.

I worked on subsidence mitigation for 15 years. I agree with others who urge you to get professional advice.

I have no idea about liability issues, but the fact that you have taken measures to keep people/animals from falling in is evidence that you knew there is a risk.

Might want to contact a lawyer with all the money you saved on insurance.

Well, six votes so far for getting professional help... perhaps I should, that is why I asked the collective...

But NO one thinks I should just make it safe and watch it?

1) My Brother is married to the sister of the wife of the official Surveyor for the City and his Dad was the city Civil Engineer for decades.

2) I go to the same church as the county agent, A University of Tennessee Agriculture Extension Office.

Perhaps I could talk to one or the other for some guidance, hopefully off the record for starters.

I can give you my "geologist from afar" perspective based on your description. Given your location and the size of the hole, that is almost certainly related to karst. What you are seeing at the surface is likely the "tip of the iceberg", so to speak. Karst sinkholes will often narrow from the surface to a throat of stronger material and then open up again below. Think hourglass shape, but with the bottom part usually significantly bigger than the top part.

There is no getting rid of the sinkhole. If you're in middle Tennessee, there's not enough grout on God's green earth to fill it. Instead, the most common solution is to plug the top with an inverted filter of graded stones and geotextile that will allow any water that enters to filter through while keeping additional soil from washing in. Your idea of diverting water is good, but only if you can divert it far from the hole. Give it a wide berth, and direct the water away from any structures. If there is a large solution cavity beneath the hole, moving the water could just cause a new sinkhole to open up. Better to dance with the devil you know.

Those are general guidelines from a licensed engineer and geologist, but I'd be hesitant to make any more than general suggestions without actually laying eyes on the property. I would contact a local university or the state geology board and see if they have someone willing to come look at it. I've looked at sinkholes for people near my college, and usually there is someone willing to help. Local knowledge is always best in these situations.

You can get some pros to look at it, or wish you did.

Be careful about getting the government involved. My sister had one adjacent to her house & too close to the foundation. They were on the verge of condemning the property & putting her & our then 90 year old mother on the street THAT DAY! She told them in no uncertain terms they weren't leaving, and to get off the property immediately. The next day she had a concrete truck pour a shitload of concrete down the hole. It's been a coupla' years & still holding.

Get this, it was caused by a modification the state did to the road. She never was able to get them to admit to the fuck-up, nor reimburse her for the concrete, nor the subsequent work she did to berm the front of the property along the road.

Welcome to Tennessee’s karst topography.

Let me think on it. Try the TN Dept. of Agriculture for a referral or information.

Or TN Dept of Environment and Conservation.

One should be able to get you some info.

How deep can sinkholes be?

Yeah, I’d have some geologist look at it....best case it’s a city problem with a water line or the like....and they pay to fix it.

Otherwise you may find you can abate it using some kind of fill(Rock vs limestone)

quote:

Originally posted by Ripley:
How deep can sinkholes be?

This U TN extension article says as much as 100’ deep in some types of geology

OP is in Middle TN. To give you an idea of the extreme end - Mammoth Caves National Park is in Middle TN.

This post is the first I've heard of a Karst.

after reading this article, I tossed out my idea of filling the sinkhole with large rocks and concrete.

https://www.mtsu.edu/glade-center/karst.php

Dr. Evan Hart
Dept Chair of Geology at Tenn Tech seems like the guy you should call. He has done quite a bit of karst and erosion research and published several papers on karst.

His contact information is available via this link.
https://www.tntech.edu/directo...iences/evan-hart.php

Based on this map of TN sinkholes you seem to be out of the area where the known deep ones are located. So yours might be something new that the phd's would want to know about.
https://tnlandforms.us/landfor...9&scale=8&file=sinks

https://tnlandforms.us/landforms/sinks.php

I remember learning about karst topology in geology class, you could have a massive cave below it. I can't add anything above what a 200 level class would tell you, but I saw some insane pics in class.

Hopefully it's not worst case scenario.