Geotechnical Baseline Reports: Suggested Guidelines

The underground construction industry in North America has made significant advances in developing and implementing methods to avoid and resolve disputes during construction. These evolved in the wake of years of disruptive and antagonistic project disputes and ensuing time consuming and costly litigation. Projects involving subsurface excavation present many risks, all of which must be allocated to either the owner or the contractor during design development. The greatest risks are associated with the subsurface materials encountered and their behavior during excavation and installation of ground support. The main purpose of the general baseline report (GBR) is to clearly define and allocate these risks between the contracting parties. The principal purpose of the GBR is to set realistic, measurable, and observable baselines that represent the best estimate of subsurface conditions that will be encountered during construction.

The geotechnical data report (GDR) is a document developed by the designer and/or the designer's geologic or geotechnical engineer, which presents the information that has been gathered during the exploration and design phases of the project. Depending on the design approach and number of design iterations that occur, multiple geotechnical memoranda may be produced. The geotechnical baseline report (GBR) should be limited to interpretive discussion and baseline statements and should refer to, rather than repeat or paraphrase, information contained in the GDR, drawings, or specifications. The GBR will rely to a significant degree on the data contained in the GDR. However, the baselines will also reflect information from relevant projects and may need to fill gaps in the database that are the result of incomplete exploration that has created a nonrepresentative database, or the inability of the exploration program to detect certain conditions known to exist that need to be expressed in baseline statements. Other topics covered in this chapter include geotechnical memoranda for design, the GBR, and contractual hierarchy.

A primary purpose for the geotechnical baseline report (GBR) is to assist in the administration of a differing site conditions (DSC) clause that is a part of the contract. The first standardized “changed conditions” clause was developed by an Interdepartmental Board of Contracts and Adjustments on November 22, 1921, by the US Bureau of the Budget. A DSC clause is nearly always included as a standard clause in the general conditions or general provisions of a contract that will involve subsurface construction. Over the years, an impressive body of case law has emerged with respect to the application and interpretation of the federal DSC clause. While widely adopted in concept, the federal clause has been modified in some other public jurisdictions. The authors of a GBR should understand the contractual significance of such modifications and adjust the wording in the GBR accordingly.

The goal of baselines is to translate the results of geotechnical investigations relevant engineering geology and previous experience into clear descriptions of anticipated subsurface conditions that bidders may rely on in developing their bids. By establishing clear, verifiable baselines as a part of the contract documents, the parties are more likely to agree on the conditions indicated in the contract, without time consuming and costly arguments (or litigation) that become counterproductive to a successful project. A well-written baseline resolves, at least contractually, the uncertainty that may exist in the data, or may be provisional baselines that address conditions not identified in the database but have a high probability of being encountered. The baselines can be set for a given project and set of geotechnical data at different levels of perceived adversity or difficulty.

The geotechnical baseline report (GBR) should describe the project and work requirements by referring to other contract documents without restating them. This chapter provides a discussion that reflects development for design-bid-build delivery. Mitigation measures identified in the risk management process and captured in the risk register need to be considered for incorporation in the contract documents, including the GBR. When a tunnel passes through two or more geologic regimes that may have different impacts to the construction process, it is preferable to describe the anticipated conditions for each reach rather than try to combine or average all the conditions along the alignment. The GBR should be consistent with and complement the other documents. A high-quality GBR will not be achieved unless the proper time and budget are allocated for its development. The chapter emphasizes the importance of the owner being involved in the risk assessments carried out during project development.

This chapter describes how the geotechnical baseline report (GBR) process is typically developed under design-bid-build, addresses additional steps required to achieve the same outcomes for design-build delivery, and addresses GBR development approach options under variations of both delivery methods. Design-build delivery presents additional challenges that must be overcome for the GBR to be part of the “solution” rather than part of the “problem.” The owner’s team prepares a GBR for bidding that provides a project description, certain constraints and latitudes, the physical baselines based on the exploration completed to date, and limited baselines that address construction considerations based on the preliminary design, possible means and methods assumed by the owner’s team, and the owner’s preferred risk allocation profile. Progressive design-build delivery is a variation of delivery where the owner engages the design-build team at an earlier stage of design, before the construction methods are determined, and at the early stages of GBR development.

As the awareness of geotechnical baseline reports (GBRs) has grown because of their use in the tunneling industry, owners have used GBRs on projects involving subsurface excavations or installations that are different from tunneling. For any project that will involve construction in or through ground that is not visible pre-bid, the baseline concept can reduce uncertainty in the evaluation and pricing of the work, as well as help to avoid and resolve disputes. Examples of excavations that can benefit from a GBR include deep building and bridge foundations, open-cut pipelines, braced and tied-back excavations, and highway and other types of earthworks. For many of these types of projects, subcontractors will be involved and be subjected to the same provisions that apply to the prime contractor. The scope of the GBR should be consistent with the project’s size, complexity, and risks. Specific design requirements for certain construction components are generally summarized in design criteria documents, specifications, or reference codes.

Over time, several contractual/legal issues and disputes have arisen involving preparation, relevance, contractual priority, use and interpretation of geotechnical baseline reports (GBRs). Standard contractual provisions variously prescribe that differing site conditions (DSC) entitlement be evaluated and determined based on a comparison between encountered conditions and conditions that should have been reasonably anticipated at tender. This standard is different under different forms of the contract. The GBR should be the primary contractual basis for the evaluation of DSCs that relate to a subsurface condition indicated in the GBR. The GBR statements do not and should not carry the same level of a standard of implied warranty as to their accuracy or completeness. Some owners have taken a proactive role to promptly conduct a reasonably thorough investigation of existing conditions upon notice of a DSC; compare the existing conditions with those indicated in the contract and the GBR in particular; and confirm if reasonable reliance is demonstrated.

This chapter summarizes various roles and responsibilities of the parties. The owner should provide adequate funding and time to complete the subsurface exploration program prior to or while the geotechnical baseline report (GBR) is prepared. Under design-bid-build delivery, the design team (geotechnical engineer or engineering geologist, and design engineer) must possess appropriate experience in the type of design and construction involved in preparing and reviewing plans, specifications, and the GBR. The contractor must bid the work with a clear understanding of the GBR information, the contractual baselines, and the anticipated subsurface conditions. The construction manager should be given the opportunity to participate in the review of the GBR during its preparation and in a compatibility check with the other contract documents during GBR finalization. If called upon, the dispute adjudicators must deny the merit of a claim if encountered conditions are shown to be consistent with or less adverse than the conditions described in the GBR.

This chapter captures recent practices and lessons learned since the first book on this topic in 1997. A 2021 conference workshop was held that focused on dispute review boards and their effectiveness. The discussion shifted to a focus on the need to increase the quality of geotechnical baseline reports (GBRs) that with better written GBRs, the dispute review board process would work more smoothly. To be risk averse, some GBRs are prepared with the “baseline” as the full range of potential values, extending from the low extreme to the high extreme, with no average or typical values indicated. Bidders were given the “option” to avoid the bid penalty by agreeing to have the GBR and differing site conditions clause removed from the contract, resulting in significant risk transfer to the contractor relative to subsurface conditions. Construction case law in the United States supports the interpretation that planned contract payment quantities in the bid schedule are valid “indications” of physical conditions to be anticipated during construction.