Home>Discussions>HEALTH & SAFETY>COLLAPSE HAZARD? Unused, cement/cinder block SEPTIC SYSTEM.
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Debbie I
COLLAPSE HAZARD? Unused, cement/cinder block SEPTIC SYSTEM.

There is an unused, cement or cinder block septic system under our yard that dates back to 1947 when the house was built. When we bought our home in August of 2013, the back yard was level. Now that we've been through a few freeze/thaw cycles, the yard above or near the system is indented in several areas by around six or so inches.

What type of professional should be called in to investigate and remediate the situation to ensure that our yard is safe from collapse?

Our home is a twin, and our attached neighbor has the same system in her yard. Her yard is showing no signs of change.

As an aside, our attached neighbor's father built the twin home using the frame from an old barn that he moved from a few streets over. It's a neat old house.

Re: COLLAPSE HAZARD? Unused, cement/cinder block SEPTIC SYSTEM.

Since it is showing signs of possible collapse and isn't being used, the best thing would be to remove it or open it and fill it with sand or gravel. There is also a product called flowable fill, but for this small scale it probably isn't economical. To fill it properly the top may need to be broken open to be sure the fill is on both sides of any baffles. Septic tanks back in the day are probably 500 gal or less. Not a huge thing if you want to DIY and don't mind a little manual labor.

Debbie I
Re: COLLAPSE HAZARD? Unused, cement/cinder block SEPTIC SYSTEM.

Thank you for responding!
I'm not sure we're qualified to break open our tank without breaking open our skulls in the process.
Do you think an excavating or concrete professional would take this on?

A. Spruce
Re: COLLAPSE HAZARD? Unused, cement/cinder block SEPTIC SYSTEM.

Someone familiar with septic systems would be the ones to call.

Re: COLLAPSE HAZARD? Unused, cement/cinder block SEPTIC SYSTEM.

Anyone with a backhoe (plumber, landscaper, grading contractor etc) can deal with this and it should be done immediately. Use the bucket to cut the sod away in chunks, either lift or break the top off, then fill with gravel only, not sand ir soil which can settle. Tamp the gravel a bit with the backhoe to ensure compaction, cover with permeable landscape fabric, add topsoil if needed, then replace the sod. It will become the greenest spot on the lawn but it will be safe and that's what matters most.

I don't know why but I've seen a few septic tanks that were covered with plywood (yikes!) which failed and fell in as you'd expect them too. We discovered that my Mom had one of these when my brother parked his VW in the wrong spot- luckily only one rear wheel went in and the muscle-power of a few friends got it out. Glad it wasn't a Caddy and centered on the tank! She's got a concrete cover there now but it was quite a surprise in the discovery.


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