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SUBSURFACE UTILITY ENGINEERING IN WASHINGTON STATE

Washington State Department of Transportation/WST2.  Issue 71, July 2001

What is subsurface utility engineering?

Subsurface Utility Engineering (SUE) is a relatively new interdisciplinary approach to managing the risks that existing underground utilities create on projects involving excavation.  Many of these risks are a direct result of inaccurate, incomplete, or imprecise information on the location or existence of existing utilities.  Just as important are the timing and distribution of this utility information.  Subsurface utility engineering utilizes new and existing technology to collect and manage utility data, and transmits this data to the right parties, at the right times, in order to decrease project risks.  SUE is now accepted and promoted by engineering organizations, and federal and state agencies, as a means of reducing overall project costs and liabilities.

A pending ASCE standard titled Standard Guidelines for the Collection and Depiction of Existing Subsurface Utility Data defines subsurface utility engineering as:

A branch of engineering practice that involves managing certain risks associated with: utility mapping at appropriate quality levels, utility coordination, utility relocation design and coordination, utility condition assessment, communication of utility data to concerned parties, utility relocation cost estimates, implementation of utility accommodation policies, and utility design.

An engineer has many sources of information on existing utilities.  Utility owner records, public records, private records, interviews with knowledgeable sources, visual site indications, historical books and newspaper archives, surface geophysical information, test holes, and GIS systems are some examples.

Utility owners keep many different kinds of records.  Large-scale transmission/distribution system maps may show presence of utilities, but because of their scale they may not be horizontally accurate or show details of material type, size, etc.  On the other end of the spectrum may be field notes, where field personnel made accurate measurements to existing topographic features during installation or maintenance activities (sometimes all those topographic references will be long gone, rendering these drawings less useful for location purposes).  Service record cards, valve drawings, and circuit schematics are examples of other kinds of records.  These utility records may exist on all kinds of formats, such as mylar, aperture cards, computer files, index cards, wall maps, paper sheets, and so on.

How Do These Records Differ?

There is one obvious difference between these records. Quality!  Different types of records have different quality.  Some records have very high quality, and tell us everything we need to know about a particular utility at a known point.  Other records may have a very low quality, and tell us next to nothing about the utility, other than its potential presence somewhere in the general area.

Until recently, there was no mechanism for engineers or surveyors to differentiate these differences in quality on design or construction plans, or in GIS databases.  All utility information was depicted as being the same.  The end result of low quality information being portrayed the same as high quality information resulted in all the information sinking to the lowest common denominator of quality, in other words, untrustworthy information.

Engineers and surveyors recognize this and completely disclaim responsibility for utility information that they depict on documents.  They attempt to push liability to the utility owner or the constructor.  Some court rulings uphold these disclaimers.  Others do not.  In a Commonwealth of Pennsylvania ruling (PennDot v. I.A. Cataldo), the owner of the construction plans (PennDot) was found to be responsible for any costs associated with poor or missing utility information on the plans.  This prompted the following statement from William D. Pickering, P.E., PennDot State Utilities Engineer, on a 1995 Federal Highway Administration film: 

“In Pennsylvania, the project owner can be held legally responsible for the accuracy of the information on the bid documents.  Consequently we want a competent professional to obtain that information for us.”

Usually, the finger of blame points everywhere for problems associated with poor utility information and only the lawyers profit.  A recent Indiana (Lafayette) court case assessed damages at 30%, 30%, and 40% respectively to the City, the engineer, and the contractor.

How Can Responsibility Be Better Defined?

One of the advantages of applying subsurface utility engineering to a project is that responsibility for wrong or missing utility data on plans is better defined.  The subsurface utility engineer becomes individually and corporately responsible for negligent errors or omissions of the deliverables and no longer disclaims utility information, but instead, claims responsibility for it - within certain guidelines.  These guidelines involve defining and then obtaining and depicting the “Quality Level” of utility information.  In other words, if the engineer can verify that a particular utility depiction on the plans is very accurate, why not say so, rather than disclaim the good information along with the bad?  By taking responsibility for data, contractor bids are lowered and there is certainly a better incentive to get right information on the plans.

The American Society of Civil Engineers recognizes that national standards for these quality levels need to be developed and promoted.  They have therefore formed a national consensus standards activity to draft such standards.  Once in place, these standards may influence how the insurance industry and the courts view utility data liability.  Membership of the committee includes people from engineering, construction, insurance, utility owners, academia, federal agencies, the military, labor unions, equipment manufacturers, and providers of subsurface utility engineering.

What are Utility Quality Levels?

It would be quite easy to develop literally hundreds of different quality levels if one were so inclined.  However, such a large number would be unwieldy and therefore probably not effective.  In developing quality levels, a natural grouping emerged that addressed how data was collected and how that data could be endorsed by a licensed professional. 

Quality Level D utility data is that information that is collected and depicted on documents that comes solely from utility owner records, or conversations, or indirect visual indications.  It is the lowest quality level and everyone should be very careful when using it for any purpose.  The only aspect the engineer can be held accountable for is investigating appropriate sources of information and interpreting the records as best as can be done.  It has a good application for project planning/route selection, where the planner needs to get an overall “feel” for the utility congestion.  An example of its use and pitfalls is as follows: A water record from 1960 shows the water line two feet off the edge of the road, with one valve on the main. The road in 1960 was two narrow lanes; now it is two wider lanes with a turn lane.  The engineer plots the water line two feet off the edge of the road, but is not known whether i) the edge of the road is at the same place now as in 1960, ii) the water record was correct as far as its geometry, iii) the water line is still in service or abandoned, or iv) the water line underwent changes in conjunction with road improvements or other events.

Quality Level C utility data is better. It addresses the problem of where the old road edge might be by using the water valve as a survey point.  All visible utility structures that indicate a utility below the surface are surveyed to project control and placed on the plans at the right positions.  Then, the utility record’s geometry can be used to place it on the plans.  The water line that would have been plotted two feet off the edge of the road is now plotted through the surveyed water valve.  If the water valve is six feet inside the turn lane, then the water line is plotted parallel to the road (following the record geometry) but six feet inside the turn lane.  Of course, if the water valve can’t be found, this utility can only be plotted to quality level D standards.  Quality level C data still does not address utilities for which there are no records, utilities for which the records are wrong or incomplete or not updated, or utilities which have no visible features that can be surveyed.  The survey of the visible utility feature is endorsed by a licensed professional. Liability revolves around the appropriate utility records search, the survey, and the best interpretation of the records information.

Quality Level B utility data provides a significant upgrade in quality from QL C data.  It involves the use of surface geophysics to identify, interpret, and field-mark underground utilities, combined with a survey of the field markings, and subsequent reduction onto plans or into the digital database.  There are many different types of surface geophysics that will work under certain conditions to identify underground utilities.  The key to liability here is that the appropriate methods be used.  Appropriateness of method is part of the professional geologist’s or competent engineer’s role, along with interpretation of the data, and education of the client for budgetary purposes.  The key is to pick those techniques that, given the environmental and site conditions, will give the educated client the best “bang for the buck” in identifying the most, or the most critical, utilities for the project mission.  Not all utilities may be found through surface geophysics.

After utilities’ approximate locations are marked on the ground surface, the engineer/surveyor references them to project control and reduces them onto plans or into the database.  Other information might be interpreted from the surface geophysics, such as approximate depth and utility type.  Utilities for which records exist, but which could not be found through the surface geophysics, are depicted at a lower quality level.

In the water record example, if the water line had bends in it that the records did not reflect, the surface geophysics would detect them.  If the valve were paved over, the surface geophysics would detect it; survey would place it on the plans correctly.  If the water line was abandoned and in poor condition, the surface geophysics might detect the new waterline, and give clues to the condition of the abandoned one.

Liability for quality level B data is generally confined to surface geophysics method selection, education of the client, correct interpretation of the surface geophysics, correct marking of the utility on the ground surface, survey of those markings, depiction on the plans or in the database, and evaluation of all appropriate records to see if utilities must be depicted at a lower quality level.  The appropriate professional affixes his or her stamp on the deliverables; insurance covers all aspects of the end work deliverables.  QL B data is most useful in the preliminary design stage of projects.

Quality Level A data is the highest quality.  No matter how well the surface geophysics are applied and interpreted, precise information on elevation, size, material type, condition, configuration, and so forth of the utility cannot be verified without exposure.  So QL A data is that data that is gathered, surveyed, and depicted through excavation or exposure of the utility.  It takes all interpretation out of the utility information at that point.  In our water line example, the exact horizontal location, depth, condition and other data at the point where it is needed is gathered.

New excavation technologies such as air/vacuum methods protect the utility from damage during exposure, limit the work zone, and reduce costs.  Quality Level A measurement data is endorsed by the licensed professional.

What Are The Advantages Of Using Quality Levels?

Instead of all utilities depicted the same on a document, those utilities for which better data are available can be portrayed in such a manner that designers and constructors can minimize their impacts.  The subsurface utility engineer is responsible for depicting the utilities at the correct quality level, and following the established industry procedures for collecting and interpreting that data.  If the engineer makes a negligent error or omission, he or she may become responsible for the resultant problems with design or construction.

Being able to obtain higher quality utility information results in project savings through better design and construction.  The Federal Highway Administration has performed widespread studies that show average savings in excess of 462% for every $1 spent in upgrading utility information to its highest necessary quality.

Project owners and utility owners can select the amount of risk they want to underwrite on a project by selecting the quality level of utility information that they procure, or by requiring the project engineer to provide it to them.

How is SUE used in Washington?

WSDOT and TIB are actively promoting the use of subsurface utility engineering on their projects.  WSDOT has existing task-order contracts in place, and the TIB has issued several policies on the subject.  They also have an “approved roster” of subsurface utility engineers for the benefit of their member agencies.

The Washington State Technology Transfer Center will be hosting a series of 6 hour seminars on subsurface utility engineering in the Fall.  These seminars are applicable for design and construction engineers, public works directors and their staff, and utility owners.  It will cover the pending ASCE Standard and give specific examples on when and how to specify subsurface utility engineering in scopes of work and contracts.

Jim Anspach is Chairman of the ASCE’s Construction Standards Council and Chairman of the ASCE committee writing Standard Guidelines for the Collection and Depiction of Existing Subsurface Utility Data.  He is a Principal with So-Deep, Inc. and has been involved with the creation and development of subsurface utility engineering for the last twenty years.

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