A buried utility takeoff should account for approximate service locations, separate voltage plans and cables owned by other bodies.
Key takeaways
- Mark plan-based quantities and keep uncertainty allowances separate.
- Check every utility sheet before pricing excavation.
- Confirm excavation scope before counting another trench.
- Record ownership questions and confirm your coordination scope.
When you measure trench lengths, widths and depths from a set of utility plans, you are measuring what the plans show, and the plans show less than the ground holds. The gap between the two is where unpriced cost tends to hide.
This post covers three limits that should change how you price a dig, not only how you measure it. Each one is tied to a linked source below. Where a source covers one country, one agency or one contract form, the text says so. Read the linked pages yourself before you rely on any of this in a bid, because a summary can leave out a condition that matters on your job.
Plans give only an indication of buried services
Plans give only an indication of the location, configuration and number of underground services at a particular site, according to the Health and Safety Executive guidance on underground electricity cables. That single sentence contains three separate limits, and each one can change a dig quantity.
Location is the most visible. A line on a plan shows an approximate position. When you scale a run off the drawing and use that length as your trench length, you have assumed the drawing is right to the precision your quantity needs. Check the scale on the sheet before you measure, and use the sheet's own notes and legend if it has them. Then mark plan-scaled lengths as plan-based in the takeoff, so that nobody reading it later mistakes them for field-verified figures. For related checks, see takeoff scale setup and stated limits.
Configuration is the second limit. The layout of cables, meaning how runs branch and where they meet, bears directly on how many separate trench segments you need and how many crossings you must work around. A plan can place a route correctly and still leave out a branch. Walk each route on the plan and ask where it could split. Record possible splits as uncertainties or allowances, and confirm excavation scope before counting them as measured trench quantities.
Number is the third. The plan's count of services is the count it indicates. Because the sheet gives only an indication of number, an allowance for services you have not seen belongs in the price itself, not in a note that gets skipped when the bid is reviewed.
Three habits follow from this. First, keep plan-based lengths and allowances on separate lines. Mixing them hides the risk from whoever reviews your numbers, and it makes the allowance look like measured quantity. Second, ask for field locating before you commit to trench lengths on any route where a wrong position would change the scope. Third, write the assumption next to the quantity in a sentence a reviewer can read at a glance, such as "trench length from plan, not yet field-verified."
A lump-sum contingency for buried services is easy to add and hard to defend. A reviewer looking at one round figure cannot tell whether it covers location, configuration, voltage or ownership, so cannot judge whether it is enough. An allowance tied to a specific route and a specific uncertainty is easier to explain to a client, and easier to revise when field information arrives. Set the figure from your own records and from the site in front of you.
When field locating does disagree with the plan, treat the field position as the new basis for that route and measure the trench again from it. Keep the original plan length beside the new one, with the date and the name of whoever recorded the field position, so the change is visible in the takeoff and not buried in a revised total. An error on one part of a sheet is also a reason to look again at the rest of that sheet and at the other routes that depend on it.
High-voltage cables may be shown on separate plans
Remember that high-voltage cables may be shown on separate plans from low-voltage cables, according to the HSE guidance on underground electricity cables. The word "may" is the point. Do not assume the split is there, and do not assume it is absent. Check the set you have in front of you.
The risk for a takeoff is straightforward. If you build dig quantities from one utility sheet, you can miss an entire class of cable.
The check is short compared with the cost of missing a route. Before you finalize quantities, list every utility sheet in the set. For each sheet, note which voltage class it shows, using what the sheet itself says rather than what you expect it to say. Then take each measured trench route and confirm it against every sheet, not only the one you started from. Where a high-voltage route and a low-voltage route run near each other, record both services and confirm whether they require separate trenches, share excavation or only affect work around existing services. If a route appears on one sheet and nowhere else, record that as well, because it is a question to ask.
When two sheets show the same corridor differently, the difference is a question for the designer or the owner. It is not a choice for you to make by picking the sheet that gives the cheaper dig. Write the discrepancy into your clarification list with the sheet references and the location, so the answer can be tied to the right drawing and the right revision.
Pricing follows from the check. If high-voltage routes add trench length, give them their own lines so the client can see the effect of each voltage class. If they change the working method, the crew or the safety measures, that belongs in your method statement and in your pricing discussion. Settle those changes with the owner and with your own safety planning, not with a rate from memory.
Carry the voltage class into the quantity itself. A trench line labelled only "service run" gives a reviewer nothing to check against the sheets. Label each line with its route, the voltage class where the sheet states it, and the sheet reference. A label like that turns a quantity into something that can be traced, and traceable quantities are the ones that hold up under a second check. Use the trench takeoff measures before pricing shoring alongside those route records.
Some buried cables may belong to other bodies
It is possible that some cables belong to other bodies, for example a highways authority, the Ministry of Defence or Network Rail, according to the HSE guidance on underground electricity cables. That sentence changes who you need to ask. One owner's plan should not be treated as the full picture of a corridor, because it may not show a cable owned by a highways authority, a defence cable, or a railway cable that shares your corridor.
Start with an owner list for each route, not one contact for the whole project. Walk the corridor and ask who could own something within it. The HSE page names three kinds of other body, which is a starting point for the question, not a complete list.
When you contact an owner, ask specific questions. Ask whether the owner holds records for the corridor, what format those records come in, how long a response takes, and whether the owner needs to attend or inspect before work begins. Record the answer, the date and the name of the person who gave it. Owner information that arrives by phone and is never written down is information you will have to argue about later.
That way a delayed answer from one owner shows up as one visible item, not as a vague overrun spread across the whole job.
The UK's construction regulations assign coordination to a named role. Under Regulation 13 of the Construction (Design and Management) Regulations 2015, "The principal contractor must plan, manage and monitor the construction phase and coordinate matters relating to health and safety during the construction phase to ensure that, so far as is reasonably practicable, construction work is carried out without risks to health or safety." If you are not the principal contractor on your job, confirm who holds that role before you price coordination time, and confirm which part of the coordination your scope includes. Distinguish your contractual coordination costs from the principal contractor's health-and-safety coordination duty.
Disconnections are coordination too. The HSE page states that "Electricity companies are required to give five days' notice to customers whose supply is to be disconnected." If a dig depends on a supply being disconnected, put that notice period into the programme, and confirm who is giving the notice and when. A dig that waits on a supply change should not be scheduled as if the supply were already off. Build the notice period into the start date, not into a note about possible delay.
Price the three limits as separate lines
Price each limit as its own line with its own assumption, so the client can see what each one costs and what would change it. Separate lines show the reasoning and let you revise one limit without reopening the whole estimate.
Separate lines also make the bid easier to defend after the work starts. If the field shows a route is somewhere other than the plan showed, you can point to the line that carried that uncertainty and the assumption written beside it. If the change is in ownership rather than location, the coordination line is where it belongs.
The table below summarizes how each limit enters the takeoff.
Illustrative example: confirm excavation before adding length
Suppose a dig route has a plan-based trench length. The electricity plan shows a low-voltage run, and a separate high-voltage sheet shows another service nearby. The owner of that service is not yet known.
Keep the length labelled as plan-based, not yet field-verified. Record the high-voltage cable as a service to assess. Add another trench quantity only if confirmed excavation scope requires it. Keep a coordination line for the unknown owner and an allowance for services the plans do not show. Each line can then be priced, questioned and revised on its own, and the client can see which line would move if the field disagrees with the drawings.
Today, choose one measured route and write down its sheet references, excavation assumption and unresolved ownership question before reviewing the bid.
Settle these questions before you submit
Before you submit, get field locating on the routes where a wrong position would change scope, collect every utility sheet in the set, and compile an owner list for each route. Those three steps answer most of the questions this post raises, and settling them now is easier than settling them after the trench is open.
Put these questions to the client or designer in writing:
Which routes have field locating, and which are plan-based only?
Label each route according to whether its quantities use field information or plans.
Which utility sheets are in the set, and does any sheet show a voltage class that another sheet does not?
List every sheet and the voltage class it states, then compare routes across the set.
Where two sheets disagree about a corridor, which sheet governs?
Ask the designer or owner to resolve the discrepancy in writing.
Who owns each service on each route, and who will request its information?
Record the owner and the person responsible for requesting records against each route.
Who holds the principal contractor role on the job, and what coordination does your scope include?
Confirm the named role and your contractual coordination scope before pricing that work.
If a dig depends on a supply disconnection, who gives the notice and when?
Confirm responsibility and timing with the electricity company before fixing the dig's start date.
Each question should be answered in writing and tied to a sheet number or a route name. If the answer is "to be confirmed," record that as an open item with an owner and a date, and price the line with the assumption you used.
Ask before the bid closes, not after. A request that names the sheet, the route and the service is one a designer can act on. A request that asks generally about "buried services" tends to get a general reply that does not help you price.
Write clarifications that hold up
A good clarification has four parts. It names the document and its sheet number or revision. It names the route, the stretch of ground or the service in question. It states the assumption you have priced, in one sentence. And it asks for a specific reply by a stated date.
That can be answered in one line. Compare it with a note that says "please confirm utilities," which invites a yes that tells you nothing.
Keep a log of clarifications and answers with the bid file. When a reviewer or a client asks why a line is priced the way it is, the log shows the question, the answer and the date. Without it, you are relying on memory, and memory is poor evidence about drawings that changed several revisions ago.
Check contract requirements before relying on a summary
Check unit rates and percentage allowances against your own records and your job's documents.
One U.S. contract clause has the same subject in its title. The Federal Acquisition Regulation clause 52.236-9 is titled "Protection of Existing Vegetation, Structures, Equipment, Utilities, and Improvements." The title is the only part of that clause this post quotes. If a U.S. federal contract applies to your work, read the clause itself, because this post does not describe what it requires.
The three limits are not reasons to avoid a dig. They are reasons to write down what you know, what you assumed and who you need to ask. A takeoff that does that is easier to defend, and easier to correct when the ground shows what the plans did not.