Is it reasonable to build a new driveway on top of an old, eroded one?
August 8, 2018 12:57 PM   Subscribe

We have an old asphalt driveway partially washed out in a flood. Construction company put a layer of milled recycled asphalt on top and compacted it, as a temporary fix while we worked out what was to be done more permanently; they're now proposing to pave over that to finish the job. I'm concerned that the uneven base below the milled layer will be a problem, they're telling me it's fine, the milled layer will be the solid base. Am I overthinking this, or am I right to be concerned?

So the high school next door installed their brand new parking lot, and two days later a major rainstorm caused a flood that mostly wound up running through our barn and along the driveway out to the main road. Dang.

What was there before the flood was fairly old pavement with a tar-and-chip surface, plus some recycled asphalt as a later repair over some potholes. That washed out pretty thoroughly. We're now negotiating with the construction company responsible about how best to repair it more permanently.

This morning they came and put down a layer of milled recycled asphalt and compacted it, without removing what was left of the existing roadway. This was described to us as a temporary fix just to hold things together until they can get the job done for real; we're still having a lot of rain so this seems reasonable -- I expected that they'd take this out when they came back to fix it for real.

Now, as the permanent solution, they've proposed using that new milled layer as the base for asphalt paving. The base itself looks solid enough, and paving atop that would protect it from washing away in the next rain -- my concern is that underneath it is some areas which still have the old pavement, other parts don't, and that that uneven base is going to make it more likely that we'll end up with weird potholes and frost heaves. They say, nah, frost heaves are a fact of life but the partial old asphalt underneath there won't make a difference either way.

I really don't know whether my concerns are valid or not (I've learned more about paving techniques over the past couple days than the whole rest of my life, but that's still not much.) So: reality check me plz? Is their plan reasonable or are they cost-cutting?
posted by ook to Home & Garden (7 answers total) 2 users marked this as a favorite
I think your concerns are warranted. I worked on paving crews doing driveways and freeways (albeit 20+ years ago) and I would also be concerned about those areas in the photo that are full of water. Once the water was gone, was that ground as firm as the surrounding road? If not, the recycled mix in the holes is not compacting as well the rest of the road. It might feel solid now but it will sag very quickly under the weight of cars.

The firmness of the ground under the cold mix is the biggest issue, not the unevenness. When we built driveways we would roll and re-roll and re-roll the gravel base until it was as solid as concrete. It doesn’t take much of a soft spot in the base to get a pothole.

There are devices that can test asphalt density without taking a core sample. I don’t if something like that would work on cold mix or if your paving company even has one. Either way, I would insist on them fixing it before paving. It’s not a lot of work to dig those spots out, fill them with gravel and compact it.
posted by not_the_water at 2:37 PM on August 8, 2018 [3 favorites]

I don't know if this is considered OK or not, but I do know that you need to talk to an independent company about this, not just the company that ruined your driveway and which will want to fix it as cheaply as possible. You are not even that company's customer, they have no incentive to do more than the bare minimum to make you go away.

Tell the people fixing your driveway that you are going to have a consultation with a third party, and that you will send them the bill for that along with their recommendations.
posted by Anticipation Of A New Lover's Arrival, The at 3:42 PM on August 8, 2018 [4 favorites]

They need to fix the drainage, have they done that? And no the proposed fix is no good, it'll erode under the new paving and collapse eventually.

You need site specific advice from another company here about how to proceed. And they must fix the drainage.
posted by fshgrl at 9:30 PM on August 8, 2018 [2 favorites]

Thanks guys! This has already been really helpful. Some hopefully-not-threadsitting followups:

fshgrl, my understanding from the school admins is that the drains had silt filters in them as pollution control during the construction work, which got overloaded by what was a badly timed and genuinely torrential storm. This seems plausible, and they are doing additional work on site to improve the drainage above and beyond that, so I'm reasonably comfortable on that front (though of course we're keeping everyone on speed dial in case this does happen again...)

You're almost certainly right, AoaNLA,T that we should have insisted on a third party doing the repairs in the first place -- it's a small town and and the school's been a great neighbor for years and I don't want to be That Guy, and they were so responsive during the flood and everybody was saying all the right things and it would be so much easier for everyone if we all acted in good faith and so I allowed myself to hope. ¯\_(ツ)_/¯ At this point I'm mostly asking about the physical structure of what they've done so far, just to get a sense of where on the spectrum of [totally normal --> imperfect but meh --> totally unacceptable] it is.

not_the_water, (and anyone else who's familiar with this kind of work), would you say it's standard practice when repaving a badly damaged driveway to remove the old one first? When you say "dig it out" do you mean just the cold mix, or break up the old paving enough that it can be compacted properly?
posted by ook at 4:41 AM on August 9, 2018

So.... Paving or chip seal sits on top of a layer of compacted fines, which sit on a base of compacted coarser material. Under that is usually dirt but there may be some drainage or other material depending on your soils like, rocks fabric etc. The thickness of each layer depends on the kind of dirt, height of the road and the expected traffic loads. You had significant erosion of your driveway but the question is how many of those layers it eroded through. If it just took the top chip seal layer off patching is likely appropriate. If it eroded the base all the way to the dirt then it may need a complete redo. Digging it all up, grading the dirt, applying a new base etc. Failure to do so means you will most likely have soft spots in your driveway down the road. You will also probably be on the hook for it yourself at that point having accepted the companies terms.
posted by fshgrl at 7:33 AM on August 9, 2018 [3 favorites]

If I were you I'd definitely get a neutral third party opinion as to extent of repairs.
posted by fshgrl at 7:37 AM on August 9, 2018 [1 favorite]

We are definitely bringing in a third party to assess at this point, yes; this is just information gathering ahead of that so I know I'm asking the right questions.
posted by ook at 8:14 AM on August 9, 2018

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