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We recently moved into a new to us house. There are a couple of depressions in the asphalt driveway that I thought I should try to level with some bagged asphalt patch.

Maybe unsurprisingly, when I swept the dirt and loose debris out of one of them, I found that there was a hole straight through the asphalt and into a void in the soil below. I am thinking this is an animal burrow, since I have found another void just under the soil surface nearby which I was able to confirm is a burrow.

My thought is that I could break away an opening in the asphalt large enough to gain greater access, fill the cavity to the best of my ability with crushed stone and then cover with and tamp the patch material.

I realize of course that if there is a burrow that close to the surface, it may manifest in other locations over time which I'll have to address too.

Otherwise, does this seem like an okay plan? Or should I be looking to do something else? (Short of tearing up the driveway, re-grading and repaving..) enter image description hereenter image description hereenter image description hereenter image description here

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  • I would get a light and make sure that’s not a clean out point I had a similar looking set of holes several houses back one was for downspouts and 1 was for the septic. Originally they had metal cans blocking them that rusted out. – Ed Beal May 21 at 13:27
  • If you don't expose the full void I would fill with round rock, it will settle into voids easier. – NoSparksPlease May 21 at 16:33
  • Is this on the apron that connects the road to your driveway? It may be the responsibility of the county to fix. Depending on your commissioner, they may take base failures seriously. – Aww_Geez May 28 at 14:41
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Possible causes: (not all of them equally likely)

  • Burrowing.
  • Poor compacting prior to paving.
  • Wood e.g roots, logs, garbage left under the gravel now decomposing.
  • Could be water erosion, perhaps a burst pipe. That would probably be obvious though.

I'd make a small effort to determine what's causing it, but at this stage I wouldn't make too much effort at that, and jump quickly to exactly what you are planning to do. If the situation returns I'd then dig it up and figure out what's causing it.

I wouldn't assume it's burrowing just because there is burrowing somewhere else. It's a clue. I have chipmunks, rabbits, groundhogs, voles, and hornets digging up my lawn constantly but I've never seen any of them burrow all the way under a paved driveway for no reason. Might be a question of Outdoors SE.

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  • Thanks for the feedback. Definitely not a burst pipe - no municipal water supply in the area, and no drain pipes in the vicinity either. I'd say that the other 3 are somewhat equally likely, though I see your point about burrowing that far under the driveway. Maybe it is warmer in the fall due to heat retention & this is appealing to neighborhood groundhogs - who knows. Could very well be decomposing wood too, we are in a heavily wood area with rocky soil. – renesis May 21 at 13:24
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I hope you weren't planning to dump some patch into the hole and forget about it.

The proper way to patch a hole is to cut out a clean square, add substrate if needed, and then apply the patch.

So if you do this properly then the cause of the issue will reveal itself at some point.

Here is a video which shows a very similar situation: How to Repair an Asphalt Pothole | Ask This Old House

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  • Just like in this video, I have attempted to begin my projects with "Honey, grab a shovel" but it's never gone so well for me. – jay613 May 23 at 17:01
  • The wet saw with diamond blade rather ruins the weekend warrior "grab a shovel" vibe of this project. – jay613 May 23 at 17:04
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    Yeah, I'm sure the wet saw is the best way to do it. I made do with a masonry chisel & a pinch point bar. Not the cleanest edges, but at least they are mostly vertical. I'll post pictures of what I did later. – renesis May 25 at 11:27
  • @renesis Yeah, the wet saw is the best way since it eliminates dust but you could just as easily use a segmented diamond blade which can do dry cuts. just make sure you're using a corded circular saw and position yourself upwind from the dust. – MonkeyZeus May 25 at 12:09
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So here is what I ended up doing.

Tools used:

  • Masonry Chisel & small sledge
  • Pinch Point Bar
  • Shovel
  • Trowel

Materials used:

  • 3 bags paver base sand
  • 2 bags crushed (drainage) rock
  • 2 bags cold asphalt patch

First, I used the chisel to lightly mark a perimeter outside the depression.

Then using the chisel & pinch point bar, I was able to open up the area and achieve fairly vertical walls. I wouldn't call them smooth, so certainly not as good as using a saw.

I dug down, clearing asphalt debris, base rock and some of the underlying stone & clay. Doing so I could follow the void (loosely filled with debris) down maybe 18" until it went underneath a small buried boulder. I'm now more than ever fairly certain it was a burrow. By this point I had removed 4 (or 5?) five-gallon buckets worth of material (asphalt, crushed rock, clay soil / stone).

Photo looking into the burrow under the boulder. enter image description here

I forgot to take pictures at this stage, but I filled the burrow with crushed stone, packing using the pinch point bar.

I then added & tamped down the paver sand. enter image description here

Followed by crushed stone, up to a level just below the existing asphalt. enter image description here

I then added 1 bag at a time of the cold patch, tamping flat between bags (I actually didn't need the whole second bag and used the rest elsewhere. enter image description here

Looking at it now, I probably should have removed a bit more of the asphalt, widening the hole. I say this because although it wasn't noticeably depressed (on the right side of the final picture) there is still a crack visible in the asphalt. So I guess I'll see if it stands the test of time...

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