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Posted: Thu Jun 02, 2005 11:14 am
by pinkfoot
I'd be grateful for your opinion.
I had a private access road constructed last year. In general, I'm pleased with it. It takes relatively light traffic - a few cars and the odd tractor daily, a feed lorry a week, or whatever.
However, I am concerned about one section, about 1 m wide by 2m long, where there is a slight dip on one side (the road is about 3m wide). It's not very obvious - perhaps 5 - 10 mm deep. I'm not sure if it developed over recent months, or whether it was there before they laid the taramc (two layers, 70mm and then 30mm, over 300mm of hoggin and type 1 sub-base). Along one edge of the dip, about six inches in from the road edge (no kerb) there is a crack, half a metre long. It seems to me that the dip has caused this crack, by sinking down.
The contractor says the slight dip is not a problem - the road is well within being fit for purpose. He has filled the crack with poured bitumen. I asked him about patching the dip, but he says that might weaken the integrity of the whole road, and is unneccessary.
Now, the warranty expires in a couple of months. I don't want to be unreasonable, but this road has cost me a huge amount of money, which I paid without delay, and it needs to last. Should I insist that the contractor does something about the dip? If so, what?
Thanks for your help.
Posted: Thu Jun 02, 2005 9:59 pm
by Tony McC
Once again, all I can really say is that, without seeing the problem for myself, I can't make specific comment. How useless would I look if a client was to tell the contractor that "Tony McCormack says is ought to be re-done", but Tony McCormack hasn't actually visited the site and seen the problem at first hand? What's left of my reputation would be shredded immediately!
All I can say is that any dip that is collecting water ought not to occur, and, if this has occurred since completion of construction works, then that suggests some problem with the sub-base. Your contractor should be able to explain why the dip/hollow has occurred. Their claim that it is "not a problem" is subjective. Obviously, it's not a problem to them as they've been paid and don't want to get involved in any remedial works, but it is a problem to you, otherwise why write about it on this forum? So, as I said, ask the contractor to explain how it has come about, and what is likely to happen in the medium term, say the next 2-5 years. I can't call to mind any examples of dips in surfacing that have corrected themselves.
I'm not convinced by the claim that remedial patching would/could compromise the structural integrity of the pavement as a whole. That's not to say that the contractor is bull-shitting, but I'd prefer to hear why they believe the structure is threatened by repair work. Again, I can't call to mind any examples of projects where properly conducted remedial works have compromised pavement integrity there's plenty of examples of dodgy repairs and half-hearted remedial works have actually worsened the problem, but in all these examples, the problem was with the way in which the remedial work was carried out, not with the fact that remedial work was necessary.
Ask the contractor to explain why it's happened, and whether it is likely to deteriorate further. If they're convinced no further deterioration is likely, they should be willing to issue a further warranty on that spot.
HTH
Posted: Fri Jun 03, 2005 9:46 am
by pinkfoot
Many thanks. This is an incredibly useful site, as others have commented, and I am sincerely grateful for your input.
I measured th depth of the slight dishing this morning, and it is approx 12-15mm at its deepest. Now, I don't want to seem too anal about this - it's not very noticeble, and I'm pretty sure it hasn't worsened over the past 8 months. Because that section of the road is on a slight slope, the water does't collect in the dip. My real concern is whther the dip will get worse and then lead to premature failure of the surface. The only thing I can be certain of is the fact that the contractor won't want to sort out any problems then!
Incidentally, the original spec stated that the two bitmac courses would "comply with MOT series 900". Any idea what that actually means?
Posted: Fri Jun 03, 2005 9:12 pm
by moot de noo
Hi Pinkfoot,
The SHW 900 series is the part of the Specification for Highway Works that covers asphalt materials. Unfortunately the 900 series predominantly covers the materials you would use for various purposes rather than the design and construction of the pavement. This would be covered in Vol 7 of the (Design Manual for Roads and Bridges) DMRB.
However, this is probably overkill based on what you have said about your trafficking.
Regarding your problem with the "dishing" - Look for any adjacent features to the movement (old culverts etc) as to a possible reason. I would suggest the thing to do is keep a weather eye on the crack and make sure that it doesn't get any worse. These things can settle down and stabilise. The important thing is to keep the water out of the crack.
If the worst happens the area can be repaired by a full depth re -instatement. (It is unlikely that the crack is only in the top layer). Contact your Local Authority Highway Maintenance Department and ask them to recommend a contractor (who will at least be able to have a look at it for you and recommend a course of action.)
Hope this helps