Dear PoP – Sinkholes!

“Dear PoP,

So, I have a little dispute with our landscape/hardscape contractor about a two sinkholes in our Columbia Heights backyard. I believe the sinkholes have occurred due to a lack of soil compaction but they think its plumbing related. I’m wondering if there are any soils engineers or geotech experts in the POP viewing area that would be willing to take a look and provide some opinion. This has been a multi-year saga with one trip already to the DC Courts Dispute Resolution Center. I’d jump at the chance for and expert opinion to put this issue to rest. Any help would be appreciated!”

If we have soils engineers or geotech experts I’ll be seriously impressed. If not, perhaps others have dealt with a similar situation? If so, how was responsible and how was the issue resolved?

9 Comment

  • I’d venture to say they are correct.

    1. To do the initial hardscaping, I would be surprised if they disturbed more than a foot of soil as you aren’t doing anythign serious like drilling caissons, so this really isn’t a compaction thing. It isn’t like they dug a 10″ hole and then just backfilled the hole with uncompacted soil.

    2. If anything, hardscaping the ground would make it LESS likely to sinkhole as it blocks additional water infiltration, which is ultimately the cause of sinkholes.

    I am a little curious as to what the DC Resolution Center result was? And last but never least you could hire a geotechnical engineer to come out to your house and specifically identify the problem for probably 300-400 dollars.

  • Homeowner here – I should clarify that the location of the sinkholes are in the same exact location as the holes that were dug for a water line replacement. The water line work was done in conjunction & in cooperation with the landscape company. They were both there at the same time and were working together on the project. The dirt in the holes just wasn’t compacted.

    DC Resolution Center was great. Less stressful than court!

  • how green is your back lawn?

  • You leave out far too much relevant information. If it’s a “multi-year” problem, and the holes are still getting bigger (you don’t say) then it’s pretty likely a plumbing problem, or a genuine sinkhole caused by underlying rock erosion. Obviously soil type & settling time is variable (houses can sink slowly over 100+ years if they’re built on poor soil or the water table changes), but even if your landscaper did nothing to compact the soil it will have mostly settled in ~3 years. Many areas of DC were built over filled in ravines and creek beds and can have ongoing problems.

    • The sink holes keep happening in the same exact place every year or so. They landscape company begrudgingly came out once to “fix” the problem. The holes don’t get any larger and they are less severe each year. After the first sinkhole happened, I begged the landscape company to hire an expert to provide advice to permanently solve the problem. Unfortunately, they refused and then then refused to even try to fix the problem the second time. That’s when we went to the dispute resolution center. They were ordered to fix the problems which has now failed for a third time. Now they are full of more excuses and I just want an expert opinion.

      • If back fill was the problem, you’d expect the ground to sink all along the trench, not just in spots.

        • There was no trench. Nowadays, they dig a hole at the water meter, dig a hole at the house and shoot a pneumatic tool from one hole to the other and feed the new waterline through.

  • Off topic, but there are a bunch of sinkholes on Mozart Place, just south of Columbia Road. I love the bike lanes and all, but DOT ought to try to fix things like this. Seems like they just spray some tar and move on, but it keeps recurring. I talked to a woman last week whose car had become stuck on the concrete, with the wheels lifted off the ground. She was stuck, literally, on the road. There are all sorts of dips in the concrete, and I guess it’s a plumbing problem that keeps recurring.

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