How Can Subsurface Risks Be Managed?

by | Aug 22, 2022 | Topics | 0 comments

General Terms and Conditions, frequently referred to as “Boilerplate,” defines how the Client and Consultant will relate to each other in a business relationship without regard to a specific project. The following is a critical “Boilerplate” item that if not clearly and equitably stated will likely result in misunderstandings and confrontational situations:

Managing Subsurface Risks – A discussion regarding subsurface risks must begin with the definition of a surface.  It can be any surface behind which the Consultant intends to make changes.  It can be a retaining wall, a ceiling or wall within in a building, the ground surface, or any other surface. 

Certain investigative processes can determine, with some degree of certainty, the conditions that exist behind the surface in question.  However, the cost and feasibility of determining all conditions behind the surface makes the results of the investigation an approximation at best.  Accordingly, the process of coming to agreement with the Client as to how subsurface conditions will be determined and the risks attendant therewith becomes one of tradeoffs between the value and necessity of the more complete and accurate information and the cost of obtaining it. 

It becomes essential that the expected results of subsurface investigations are clearly defined, agreed to with the Client, and documented in the contract.  This may involve significant education of the Client.

The following are some thoughts about what should be included in the contract provision:

    • Acknowledgement by the Client that it is not feasible and often not possible to determine all subsurface conditions that can affect the design.
    • Identification of potential risks associated with not having complete subsurface information and agreement that those risks are acceptable to the Client.
    • Acknowledgement by the Client that extrapolation of data between actual points that are investigated may not be a precise indication of what exists between the points.
    • Acknowledgement by the Client that any investigation is valid only at the time of the investigation, as conditions may change between the investigation and actual construction.
    • Agreement with the Client that a contingency fund will be included in the construction budget to accommodate differing subsurface conditions that only become known during construction.

The Consultant should carefully consider and chose the professional Subconsultants who work on their projects; particularly those that are involved in performing geotechnical engineering investigations and evaluations.  It is strongly recommended that the Consultant utilize a Qualification Based Selection process for selection of all Subconsultants. 

The Consultant and Client should acknowledge that below ground risks, which can affect construction cost estimates and Contractor claims due to changed conditions, include the accurate identification of the location of any rock and/or hard cemented soil layers that lie within the planned depth of excavations.  The groundwater level at the time of construction along with likely fluctuations can also have a significant impact on the construction process and the potential for construction claims.

In order for the Geotechnical Engineering Subconsultant to provide a level of service that is normally expected by Consultants and Clients they should be provided with the following information prior to their development of the scope of work and budget for their services:

    • Site map showing property boundaries and all known existing natural features and prior development on the site.  Identification of any known hazardous materials on the site.
    • Adjacent property owners and contact information if access on their property is required during the site investigation.
    • Existing topographic data and proposed preliminary site grading plans.
    • Details regarding the proposed site improvements, including dimension of all proposed structures, preliminary dead and live load conditions, required depths of excavation within and/or outside of the proposed structures, such as pits and basements.  

It is almost impossible to avoid having subsurface conditions that differ from that which was expected.  Be prepared for this situation by having a well thought out and documented change management procedure in place before design and construction begins.

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Lowe Consulting, LLC
John M. Lowe, Jr., P.E.
Happy Valley, OR