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Wireless Networks Thread, Disaster planning: how much to repair a cut fibre? in Technical; We have some major building works on site over the next year, and in the half term a contractor will ...
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    AngryTechnician's Avatar
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    Disaster planning: how much to repair a cut fibre?

    We have some major building works on site over the next year, and in the half term a contractor will be digging a trench directly over the path of one of our underground fibre ducts. I believe the intersection point is currently beneath tarmac.

    I have been asked by Facilities to give an estimate of how much it would cost to repair said fibre if the contractors screwed up and dug through it, so that they know what sort of financial penalty to specify in the contract.

    I have given them the impression it would be pretty damned expensive. Anyone have a close-ish idea of what sort of figure we'd be talking about?

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    john's Avatar
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    Best bet AT is phone your fibre installers and ask them, as it will be a fusion splice repair that they do and sink it in a waterproof splice box. I'd estimate you should hurt them for £500 as if its a 24 core fibre it will be 48 splices to do and the kit for each splice can be between £2 and £5 depending on the fibre type and tooling used. Its not a cheap thing to do digging through fibre, we're just planning some building works which involves fitting fibre and other services so are discussing the order of install and who's in first and last to avoid damage.

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    AngryTechnician (13th May 2011)

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    maniac's Avatar
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    Whenever we've had fibre accidently damaged, we've always had the entire run replaced rather than repaired, as repairs just increase the db loss on the fibre. To be honest it's un-necessary to put specific figures in the contract. As I understand it, if a contractor is working on-site and causes damage to your infrastructure, then they are under obligation to arrange repair or replacement or to foot the bill for the repair or replacement, unless the school specifically accepts liability.

    If you want to be doubly sure, rather than put a specific figure in, you could put a clause that states in the event of damage being caused to the fibre optic cable, the contractor is liable for all costs associated with the replacement or repair of the cable and just leave it at that. The problem with putting a specific penalty figure in is you might get it wrong and be grossly under or over even if you do get an estimate, where as leaving it open ended like this gives more flxibility in both directions.

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    AngryTechnician (13th May 2011), plexer (13th May 2011)

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    plexer's Avatar
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    The actual technique used to splice depends on what your contractors a geared up to use.

    I agree with the above about just putting in a clasue that requires the contractors to fix the problem allthough if you give them the option of repair versus replacement I'd guess they'd go for the cheaper option of repair.

    Maybe word it like "in the event of any damage caused to the fibre infrastrucutre the contractor will be responsible for the costs incurred by the school to reinstate the infrastructure to its undamaged state" or something.

    Ben

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    AngryTechnician (13th May 2011)

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    Cost it as replacing the run entirely.

    Oh, and if they do break into the ducting, they'll fill it with soil / rubble / sand. Rain and ground water rises will wash this down the duct and make running future cabling problematic.

    Include exposing and replacing ductwork as necessary and ensuring the whole duct is free of rubble.

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    AngryTechnician (13th May 2011)

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    AngryTechnician's Avatar
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    The problem I have here is that the fibre was installed well before my time and I think the company that did it has gone bust, so I don't have any contacts to ask. I definitely would NOT want to have to replace the entire run, as it is the longest run on site (several hundred meters) and traverses more than one building before it even gets to the duct.

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    plexer's Avatar
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    Whereabouts are you? I'm sure someone can recommend an installer in your area.

    Ben

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    plexer's Avatar
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    Once you have a recommendation maybe a good idea to get them out to have a look over your site and get them to quote up some details, you can then keep this on file and not neccessarily put it in the contract with the builders.

    Ben

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    AngryTechnician (13th May 2011)

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    We use Home - Data Cabling, Lincoln, Lincolnshire. When our fibre was broken it was about £1,200 to do two 110 metre runs and terminate and test.

    They were very understanding with regard to billing for extra work when they turned up to find that the "repaired" ducting was actually full of rubble at a choke point, came back with a snake and still couldn't do it and then had to come back again after the culprits attacked the tarmac with pneumatic drills, cleared the rubble and redid the draw ropes.
    Ask for Dave Purnell.

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    AngryTechnician (13th May 2011)

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    When our builder snapped our fibre on the jaws of a dozer (boy is it stretchy - and it really goes TWANG after it snaps) - they were liable to get it all going again - though some mention of a timescale might be helpful, if you've important stuff on the other end.

    The kids also dug up one of the other runs and cut it with some tin snips - that cost in the region of £1500 to have respliced (afair)

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    AngryTechnician (13th May 2011)

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    AngryTechnician's Avatar
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    Quote Originally Posted by plexer View Post
    Whereabouts are you? I'm sure someone can recommend an installer in your area.
    Reading/Berkshire area.

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    GrumbleDook's Avatar
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    For DR you have 3 options.

    Splice the existing line as a repair and hope it doesn't get damaged. This is suitable for an emergency repair and most of the costs from John are similar to my experience, but add 25% on for emergency callout on any labour costs.
    Splice from the nearest 'safe' points. If you have long runs then you cut into the nearest point to the duct where the fibre run goes on either side. You then run a replacement line via the shortest and safest route bypassing the area of risk. It is a medium term option to keep things running and reduces the risk of the line being damaged again. As part of the DR the costs will be 2x splicing plus the cost of the fibre run plus the labour costs plus 25% on labour if an emergency ... and then the cost of replacing the full run at the end of the building works. There are problems with this, as mentioned by others, but builders like this option as it gives a shared risk where you accept a degraded replacement in the short term whilst they accept a cost penalty to get things going again.
    A new run via an alternative route which bypasses any area of risk. Most Heads and Bursars prefer this one as it transfers pretty much all the risk (and cost) onto the builders ... but they may put up their costs in return.

    When trying to decide which is the most appropriate option (there is no best option ... they are all best for different circumstances) you might find that the middle option works out most expensive as you still have to replace the run of fibre anyway. This second chunk of work would need to be costed into the option anyway (as mentioned) so it will really depend on the builder / foreman / project manager and how they manage the costs and risk.

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    This thread has made me laugh as I rememeber a construction firm cutting through our installed fibre...of course they denied it.
    Once on site we carried out an OTDR which gave us a pretty accurate idea of where the fibre was damaged, walking the installed run of fibre we got closer and closer to the location yup right next to a chap working a JCB digger lol.
    the underground trench had been smashed and there was our fibre it appeared to be in one piece though :-/ hmmmmm after pulling on the fibre it came clean out of the trench with what looked like electrical tape wrapped round it to "hide/make good" the damaged fibre INCREDIBLE! of course the building contractor paid up for a complete new fibre install :-D

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    AngryTechnician's Avatar
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    Well, they started work on Friday and when the Bursar and I went down for a look this morning, they have indeed managed to smash through the ducting, but luckily for them, the fibre isn't damaged.

    Yet.

    I'll post a photo on my blog later when I've calmed down.

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    plexer's Avatar
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    So they now need to clean and reinstate the duct?

    Ben



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