The Uncertainty Of Working Underground

By Jim Anspach, UESI president

Editor’s Note: This is part one of an exclusive four-part series outlining the risks of modern underground utility infrastructure construction and rehabilitation work.

The world population is still growing. As population grows, so does the demand for basic resources including housing, transportation, access to potable drinking water, means for sanitary sewer collection and removal, means to provide heat and power, and the ability to communicate. In North America, these demands consequently result in new construction projects that involve moving dirt and rock.

In addition to new infrastructure, our existing infrastructure – roads and bridges, buildings, railroads, airports and seaports and utility systems – are in use beyond their intended design life and in the process of replacement, expansion and rehabilitation. Available right-of-way is increasingly more restricted and congested, especially in urban and suburban areas. That, in turn, challenges new construction, maintenance or replacement activities with efforts to identify and remediate conflicts with existing underground and above- ground utility infrastructure.

These hidden utility structures’ location, size, ownership, material type and even existence are uncertain. We may have records that were created at the time of their design or construction, but these records may not be accurate, may have references to locations that no longer exist, or may have been lost or transcribed incorrectly into a new format like GIS, etc. Utilities that still exist in the ground may be abandoned and their records destroyed or buried deep in an archive.

More uncertainty

It’s not only existing utility infrastructure that is uncertain. Depth to bedrock and water table, types of ground, existence and size of cobbles and rock, extent of rock fracturing, legacy construction rubble, and other hidden and non-visible structures of the underground environment are also uncertain. Add to that items like voids (a lack of structure) and potential hazardous environmental conditions (now termed “constituents of concern” in some contract documents). All this uncertainty leads to risks that the assumptions we make in planning and design might end up being wrong or not complete enough. That creates opportunities during construction for inflated bids, cost overruns, change orders, time delays, damages and claims.

Addressing uncertainty in infrastructure design is the engineers’ practice. They make choices of placement location, materials and design elements using applicable codes and standards, and significant professional judgment in order to protect the health, safety and welfare of the public. The more uncertain the existing conditions, the more engineers need to compensate by “over-designing” the structure. This has cost and time ramifications. A great resource for up-to-date research information on this topic is the ASCE-ASME Journal of Risk and Uncertainty in Infrastructure Systems.

When all facts, outcomes and scenarios are known and competently addressed, there is no risk or uncertainty. This is a rare occurrence, but one we attempt to achieve if the stakes are high. Most projects contain three basic sources of risk and uncertainty.

“Unknown Knowns” are facts that others may know, but we don’t, usually due to lack of communication or information investigation.

“Know Unknowns” are things we are aware of, but don’t have the details (yet?).

“Unknown Unknowns” are things we may have not even considered.

The engineer may recommend a certain course of action, but the project owner controls the purse strings. A great balancing act results from this relationship: how much of what the engineer wants to do is allowed by the owner, and what if it seems to create the possibility of negligence or not meeting standards and codes?

Role

Project owners, engineers and contractors all play a role in eliminating some risk by reducing uncertainty, and for uncertainty that cannot be reduced, managing the risks presented by the remaining uncertainty. There are many landmark court cases that set forth decisions regarding these uncertainties and the project owner-contractor relationship. There are far fewer that involve the relationship between project owner and engineers/architects.

According to these cases, during project development, the project owner (or its engineer, if part of the scope) is responsible for providing details of existing conditions on the site, or being financially responsible for the consequences of an inadequate investigation. Project owners usually accomplish this by hiring geotechnical engineers to investigate ground conditions and subsurface utility engineers to investigate existing utilities. The American Society of Civil Engineers has provided guidance documents to help project owners with these subsurface investigations and how to portray their results on contract documents. Geotechnical Base Line Reports, and ASCE 38-02 (Standard Guideline for the Collection and Depiction of Existing Subsurface Utility Data) are two prime documents for communicating the risks of existing condition investigations. The Engineers Joint Contract Documents Committee, a joint venture of ASCE, ACEC and NSPE, along with more than 20 other organizations, has set forth clear and unambiguous contract language for these responsibilities of the project owner, its engineer and the contractor.

In our next installment, we will look specifically at contracts, GBRs and ASCE 38 as means to reduce and manage uncertainty.

About the Author:
Jim Anspach is technical practice lead for Cardno Inc.’s Utility Engineering and Survey Practice. He serves as ASCE’s Utility Engineering and Surveying Institute President for 2018. He is the incoming chair for EJCDC, and chairs the ASCE 38 Standard Committee. He is also a member of ASCE’s Board Committee on Claims Reduction and Management.

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