Measuring 'Risk' from Utility Plans

Many users of the Dial Before You Dig (DBYD) service on National One Call (NOC) ask us about the accuracy of the utility and other asset owner plans they receive.

Our stock response is to we say that we cannot tell you how accurate they will be because; a) they are not our plans, b) we do not know the site, and c) we always recommend they be regarded as 'as-should-have-been-built' plans until verified.

But with over 25 previous years of experience of providing plant-information exchange services for utilities / pipelines / authorities before opening up the service for everyone else to use in 2007, it is not unreasonable that we should be able to take a stab at defining a methodology that may help some clients in making their own considerations about a) Accuracy and, from that, b) Risk.

Summary.

For anyone not wishing to spend an hour or so going through the issues, workings and outcomes, there is a methodology proposed for reviewing and measuring asset owner plans, useful if you needed to produce a very detailed evaluation for, for example, risk assessment.

It shows why it is that utility / asset owner plans present issues and risks and proposes a methodology of how they can be measured, managed and overcome.

I hope this is of use / interest.

Best regards,

Alan McMaster, Managing Director, National One Call.

Evaluating Plans and Responses; the Issues.

Each plan, and indeed response (e.g. 'Not Affected') from an asset owner (utility / pipeline / authority etc.) must be considered individually.

The Look of any Plan provided.

Some plans can be very alluring, produced to high specifications, drawn so well that the reader is very tempted to take them as 'as-built' plans.

And despite some ridiculous claims by our competitors, nobody gets any better a plan than anyone else; any request from any party will result in the same plan from the same systems, provided by the same people, at the same price (if they charge).

But even the neatest, most detailed plan (e.g. one that shows depths / size / capacity etc.) is no more likely to be accurate than a line drawing from someone else. Sure, it may be neater and contain more detail, but that does not make it any more accurate. This simple fact must throw all aspects of the plan into question.

So for example, an indicated depth (Z) is virtually immaterial if X and Y are held to be 'indicative only' - which is what they are most healthily treated as until they are physically verified on-site.

Why is this? 

Much of what utility planning systems contain are historical drawings, digitised from years-old paper plans at the time computerisation was undertaken. 

This historical data is what forms the majority of the drawings held by a utility, and you cannot know if it has ever been verified; certainly the asset owner will never state this. 

You have to assume it is unverified, and therefore hold the plan you see to be 'Indicative'; this is the healthy way to consider every plan and any other part of a response.

Not even new service installations are drawn up by engineers on-site as they install the services; they are done by CAD operators, planners / telemetry engineers / drawing office staff, and given to the installation team as instructions. 

These new installations are added to the historical drawings - and you cannot tell which part is old and which are new installations.

Underlying this is the problem that it is not always possible to install exactly as per instructions, e.g. having to go around other asset-owner services / avoid physical barriers such as large boulders, maybe simply laid in a slightly different place to that shown on the plan given in the installation instruction. 

This is seldom reported back if ever, so the plans remain as they were showing the services that are assumed to have been laid as planned.

External issues such as resurfacing by an authority / ground movement / unrecorded repairs / re positioning / renewals etc. can affect things, even if the service had been laid as planned in the first place.

All of which means that any plan you are sent is an unverified drawing of what that asset owner considers they have at your site. It is the 'best known information' they can provide at the time of your Enquiry.... it may or may not be correct.

Asset owners usually say this in their disclaimer, which also states they are not responsible for inaccuracies nor any consequences. Do not overlook it; always treat the plan accordingly.

The Date of the Response.

Plans never show the date of last update of the items shown in the drawing. And nobody - not even the asset owner themselves - can predict the date of the next update, this will happen only as required due to expansions / renovations etc.

What they show is the printed date; and that is all that can be known by anyone at the time of the Enquiry.

Plans are actually relatively static - but there is no guarantee of that for any specific site. What you receive is a snapshot of your site as the asset owner saw it on their planning system, as it stood right at the time that your enquiry was reviewed.

The plan you received this morning could well change this afternoon but you will not receive any update.

It is even possible that the 'Not Affected' response you were given this morning would be an 'Affected' one this afternoon if plans had been updated in-between times.

Because of these timing issues, asset owners assign a valid-for timescale to their plans, normally 30 elapsed days but some go as far as 120 days. This does not of course mean that they guarantee no changes will be made in that time.

Measuring each Asset Owner Response.

By reviewing a returned response, the client could begin to devise a notional 'Confidence Factor' to that response.

If asset owners were to state that their plan was 100% accurate and warranted it then there would be no problem. None of them do that though, in fact they disclaim accuracy and responsibility entirely. And you can now hopefully understand why they do that.

To devise some kind of purposeful measure, what the Dial Before You Dig client has to do is decide for themselves, on a response-by-response basis, how much reliance they are willing to attribute to that response. And this has to be based on their measures and values.

There are 3 components in this; the Accuracy of the Plan, any Known Omissions, and Validity (Timescale) of the Response.

1. Accuracy of a Plan.

By the fact they returned a plan, we know they consider that they have services at the site. We know they provided the latest information they had as at the print date of the plan.

We know that asset owner plans cannot be treated as 100% accurate - they even state that in the text that accompanies their plan. 

To begin to produce some form of measurement we must make a reasonable consideration of the level of accuracy we are prepared to attribute to that plan.

Let us say the client is prepared to assume 85% for Accuracy.

2. Known Omissions.

Positional and content accuracy issues apart, there are known omissions in utility plans, e.g. they do not show service lines and connections where they enter a property boundary, or site-internal structures such as septic-tanks etc.

These are considered 'private', installed by 3rd parties such as builders / developers and not usually recorded, certainly not by utility companies even though they connect to their services.

Depending on the client requirement and the nature of the site in their DBYD enquiry, this may or may not be too much of an issue. For example, green-field sites tend not to have 'private' connections at them, whereas in-town sites / specific properties more than likely do have these (electricity / gas / telecoms / water / sewerage etc.).

Either way, it is known that these items will not be on any plans received - we know them to be missing, hence 'Known Omissions'.

Let us say the client deducts a further 5% from Confidence due to Known Omissions, resulting in an 80% 'Confidence Factor' for accuracy and contents.

3. Validity of the Response.

The greater the time between the response-date and the time it is being read the less reliance can be put onto the Validity of the response. If a plan was provided a part of the response, then this of course also applies to that plan.

As time ticks away, day-by-day the response - and therefore any plan - loses more and more Validity, i.e. the greater the possibility that the response / plan may now be different to the one we currently hold.

Most asset owners put a timescale for validity to their response, sometimes up to 120 days.

But risk is not for each asset owner to decide; it is the Enquirer who has to decide if they consider they are working on 'best available information'.

We recommend that 30 days is the very maximum any response should be considered 'good for' unless it has been Verified (see below).

So if we were to divide the Confidence Factor by 30 we can find a measure of how much Validity we could say will be lost day-by-day.

Using the example of the 80% Confidence Factor for Accuracy and Known Omissions, we can subtract 2.66% (1/30th of 80) from our 'Confidence Factor' for every elapsed day from the date it was printed.

Bringing it Together.

So for the response in our example, we started out with an 80% Confidence Factor.

Every day that goes by that depreciates by 2.66% Confidence.

We could set Confidence Markers for Purposes that trigger unacceptability of risk, e.g.

• Set a Marker of 100% for Excavation (which would mean that Excavation is too risky using the utility plans alone - a great move, highly recommended!).
• Set a Marker of say 5% for Planning.

Using this approach, by Day-20 we have lost (20*2.66%) =53.2% due to decreasing Validity, resulting in a Confidence Factor for that response of (80%-53.2%) =26.8%.

Using our Markers, this is not acceptable for Excavation but is still acceptable for Planning.

At Day 31, we have reached a Confidence Factor of zero for that Response. This ties in exactly with the 30 elapsed days. Our Markers tell us that response is not now acceptable for either Excavation or Planning.

The Overall DBYD Enquiry.

 So far, we considered responses on an individual basis. But a DBYD enquiry is not about individual responses, it is about the responses from all known asset owners at that site.

An average DBYD enquiry on National One Call goes to 28 asset owners.

Of these, between 12 and 22 are 'Affected' (depending on where the site is within the UK), i.e. they will supply a plan. The rest will respond with a 'Not Affected' response.

Let us assume we receive 12 plans and 16 'Not Affected' statements, 28 responses in all. An individual 'countdown' could be started for each response (Affected or Not Affected), each reaching zero at its own 30 days from production by the asset owner.

Responses are generally received over 10 working days, so it is almost certain that some responses would 'time-out' before others.

How NOC Approaches this.

At National One Call, we cannot possibly know how a client will be using the plans and responses they receive, nor indeed their approach to 'risk'. 

We are a plan-obtaining service provider, nothing more; who are we to tell clients how and when they can and cannot use the plans and responses, nor how they apportion Risk.

To give some kind of guide we assign a 30-day 'Best Before Date' to every Dial Before You Dig Enquiry from the date that it is released. This is clearly shown in Enquiry documentation and certification.

We cannot of course guarantee that nothing will have changed even in this time, but this gives the client a reasonable window during which we suggest they could consider the information 'good', and from which they can decide how best to progress with their intentions using the received responses, using their own considerations of 'Risk'.

Conclusion.

It appears possible to put some element of 'science' into evaluating plans and responses received for a Dial Before You Dig enquiry.

This could be applied as part of a very detailed risk-assessment, perhaps define a 'Confidence Factor' per plan / response below which the use of any individual plan received is still acceptable for some situations (e.g. planning), but poses an unacceptable risk for others (e.g. excavation).

Too detailed?  Well, perhaps. Not even we at NOC do this. Although we record great detail about each response - dates / type / status / instructions / disclaimer etc., we evaluate at overall Enquiry level, and we recommend that clients regard the overall Enquiry as 'entirely unsafe' after 30 days if the responses it contains have not been Verified.

For clients who need to make these kinds of detailed evaluations we offer the approach as outlined, inserting their own values into the calculations. You are very welcome to use this should you so wish.

What about 'Fusion Plans'?

You will see some of our competitors strongly pushing you to buy an overall plan of received responses which is created by putting all plans into 1 overview drawing.

NOC also offers this to those clients who require it, we call it a 'Fusion Plan'.

By definition, a Fusion Plan or indeed any other plan produced in this way is a culmination of all received plans; therefore, it follows that it is also a compound of all Confidence Factors.

A Fusion Plan adds nothing to the validity of responses.

With just 5 plans copied into a single drawing, the resulting drawing, assuming an 80% Confidence Factor for each individual plan, compounds as:

Plan1:80%, + Plan2=64% + Plan3=51.2% + Plan4=40.96% + Plan5=32.76%.

And this too 'depreciates' over time as the Confidence Factor per plan reduces.

The Fusion Plan reflects any 'Not Affected' responses simply by omission of any plan in the drawing for that asset owner. 

A Fusion plan is useful for getting an initial overview of the site / for planning / for giving to surveyors for verification work, but give that plan to an excavator to work from as a statement of site contents and you are just asking for trouble.

NOC is very careful to point this out to Fusion Plan clients; our competitors on the other hand will not tell you this, they may not even understand it. 

But they will sell you their version of a Fusion Plan, promoting it to the point of seemingly being so good that you could do anything with it. 

It is not of course, and never could be due to the nature of its component parts.

If you must have a 'Fusion Plan' then by all means buy one, but it is a far wiser investment to spend your money getting professionals to verify the utility plans.

Who else would tell you that?

Overcoming these Issues and Limitations.

Every Dial Before You Dig Enquiry from National One Call comes with the warning:

'Please do not excavate or commit to expenditure based solely on the outcomes of a Dial Before You Dig enquiry'.

If more than just an initial site overview is required, the shortcomings of Accuracy, Known Omissions, and Validity of the outcomes of a DBYD enquiry must be overcome to an acceptable level, with that level of acceptability to be decided by the client.

If the Enquiry is out of date (more than 30 days old), or the intention has changed (gone from 'Planning' to 'Works Intended'), then re-running the Dial Before You Dig Enquiry is highly recommended.

But re-running the Enquiry will never overcome Accuracy, Known Omissions and Validity issues; re-running will however result in a higher 'Confidence Factor' as a start-point. 

Verification - the Next Step.

Only professionals can take a Dial Before You Dig Enquiry beyond these inherent risks, surveyors and other experts who will use the plans and responses resulting from the Dial Before You Dig enquiry as a basis for site investigations and verification.

National One Call does not offer surveying / trial pits / vacuum excavation / project management or any other services; our only business is in obtaining asset owner plans for clients, for any site, for any purpose. 

We do however have thousands of clients, some of whom DO offer these specialist services, using our Dial Before You Dig service for obtaining plans for their own requirements. 

Some Enquirers may already have arrangements for Verification but if any client needs these services we will happily put them in touch with one of these other clients, at no charge to either party.