Since their first use in the mid 1970s, after some stellar claims for several notable tunneling projects in the United States, and the work of the groups like the United States National Committee on Tunneling Technology, some enlightened owners such as the Washington Area Metropolitan Transit Authority with its multiple modern underground mass transportation tunneling projects for the subways in the nation’s capital, and others led to a steady development over the ensuing years in to what is now generally called Geotechnical Baseline Reports (GBR).
The goal of baselines is to provide contractually binding and meaningful descriptions of geotechnical conditions to be encountered during tunnel construction. The objectives for establishing the baselines aim at:
- Presenting certain geotechnical and construction considerations and
information for the subsurface components (bored tunnel, portal structures
and appurtenant construction) of the project and for relating these to specific requirements that are included in the project Technical Requirements and Specifications.
- Enhancing the Constructor’s understanding of the key geotechnical features, and important requirements in the contract documents that need to be identified and addressed during bid preparation, preparation of technical and cost proposals, and during detailed design and construction.
- Assisting the Constructor in evaluating the anticipated ground behavior along the alignment, to better appreciate requirements for elements of the tunnel boring machine (TBM), and methods for excavating and supporting the ground, maintaining control of groundwater, and providing protection for adjacent or overlying structures, utilities or other facilities.
- Guiding the Owner in administering the contract, reviewing the Constructor’s submittals and design, and monitoring the performance during construction.
- Providing a basis for reducing uncertainty and the degree of contingency in Contractor bids, and to assist in administering the differing site conditions clauses contained in the Contract Documents. Encountering of conditions materially different or not normally encountered (type 1 and 2) would be grounds for a differing site conditions (DSC) claim and an equitable adjustment to the contract.
Taken with the other contracting reforms, including Geotechnical Data Reports (GDR) and Disputes Review Boards (DRBs) of this same time period, the objective was to improve contracting practice and minimize claims and disputes, as well as providing a means of settling disputes and claims on the job without costly and time consuming litigation which had pervaded the underground construction industry. These claims, and costly and lengthy litigations had lead to disenchantment for underground construction and generally a “bad rap” for the industry.
The conundrum today for the geotechnical professional, tasked with writing the GBR, as to what is to be baselined, if indeed baselined or not.
Consideration must be given to several aspects:
- Does the inclusion of a baseline, or lack of it, effect…. That is, does it influence cost, schedule, limit or require specific methods or precautions, conformance with environmental commitments…….
- Can the baseline be…….. measured, counted……..
- Can it be based on values determined relying on project specific data. That is, can it be determined by site field observation, pumping tests, down hole testing, laboratory test results, or on other relevant historic data….
- Can its extent or the range of values be easily definable or readily established in the field by either visual or in-situ testing.
Generally as applied today,
- There must be some recognition that behavior will vary and will also depend significantly upon, and be influenced by, the construction means and methods selected and used by the Constructor.
- In the interpretation of the data, assumptions generally are made regarding construction methods to be used by the Contractor. If significantly different methods are actually employed during construction, it must be expected that ground behavior will be different from that baselined and that risk must be taken by the Constructor.
- While it is preferred that the Constructor should be responsible for the choice of construction means and methods, due to specific ground conditions or toxic or hazardous conditions, contaminated materials, presence of adjacent or overhead susceptible utilities or infrastructure or project environmental commitments, prescribed means and methods may be imposed to restrict or specify construction techniques or methods.
The task then for the GDR preparation, is how best to describe the exiting conditions and how they may mesh with contractual provisions or other regulatory requirements, such as, for example, gassy or potentially gassy ground, and how are they provided for in the contract.
- How does the baseline get expressed or how to relate these baselines conditions to specific requirements that are included in the project’s Technical Requirements and Specifications.
- How does it get paid for, such as:
- expressed as a “contingent” or supplemental cost/unit price—per intervention, per obstruction, per crew hour…
- as a defined length, i.e. station to station for each class of ground, with the Contractor to determine the effect on the means of construction he has chosen and changes of production rate, support requirements, inclusion of conditioners, machine and spoil handling methods, etc.
- as part of the basis of bid.
- Is it fairly representative of the anticipated extent or quantity.
- Will it unbalance a bid or discourage/encourage the risk in bidding it.
Just as importantly, what are the Owners needs and tolerances and understanding of the baseline?
- What is the Owners appetite for risk and for project delays and overruns.
- Does the Owner not want to have ANY risk/contingencies.
- Which risks or contingencies is the owner want/willing to assume for themselves and which to assign to the Constructor.
- Does the Owner understand that baselines should not be understood or interpreted as a “guarantee” or “warranty” that the conditions encountered during construction will be exactly as described.
- Accept the idea that “Stuff Happens” and there is no absolute foolproof way to prevent claims.
- Bid contingencies or provisional sums become an “object of desire” for the Constructor.
With these things to consider the choice to baseline may not be as clear cut as it would appear, nor a simple engineering decision.
These few steps are offered to try to answer the question and provide guide the development of the baselines.
- Educate your Owner. To have a GBR is now current practice, but not all Owners have used the concept, and not all Owner’s can, by statute, or on advise of counsel, use them.
- Determine the Owner’s risk profile.
- Can he buy into the GBR and the associated assumptions of risk(s), and ownership to specific risks.
- Present the options for and against GBR and the associated contracting practices including Disputes Review Boards, contingent bid quantities, etc.
- With Owner concurrence develop the baselines based on the project conditions and tailored to the technical and specification requirements.
- Ensure that the GDR and contract technical data provide adequate detail and results to justify the baselines and allow Constructors independent evaluation.
- Have formal and formative discussions with Owner to establish the comfort level of the acceptance risks and of proposed baselines and the associated formative data and analysis.
- Provide rationale for and conditions requiring prescriptive specifications or construction requirements. These would include permissible equipment, muck conditioning, TBM cutterhead or tool requirements, handling of contaminated materials or instrumentation and monitoring of surrounding buildings, etc.
- Institute formal oversight during preparation and final review of the baseline report by experienced senior personnel, preferably with both design and construction experience.
- Tailor the specifications, measurement and payment and bid documents for the clear definition of the risk distribution, with the appropriate measurement and payment provisions consistent with the baselines, contract requirements, environmental protection or needs for protection of abutters, etc.
All this being said there is the assumption that good engineering judgment will be executed and that the needs and requirements of the Owner will be observed. The ASCE’s Underground Technology Research Council’s Geotechnical Baseline
Reports for Construction, provides a detailed and respected description and application of Baseline Reports which has been updated several times to keep up to current practice.
At all times it must be remembered that GBRs are not a panacea and do not by themselves guarantee a successful project. Difficult and complex ground conditions require an experienced, qualified, and conscientious Contractor, whose selected means and methods are appropriate and compatible with the anticipated ground conditions in addition to a complete GBR and good engineering design.
Debunking the baseline conundrum Dec 2015
Dr. Peter J. Tarkoy, USA
Pre-bid reports prepared for contractors preceded the advent of GBRs.
Independent geotechnical consultants have prepared these (pre-bid) reports for the last 70 years or more. I personally have prepared them for the past 40 years and find no conundrum in defining a baseline. We have also successfully defended the contractor’s differing site condition claims using our pre-bid reports. We relied on given physical properties, considered the contractor’s anticipated use of means, methods and equipment, and provided an experience-based expectation of progress.
The GBR should be limited to physical facts and cautionary statements, leaving interpretation up to the contractor or his consultant. If the engineer does not trust the contractor’s assessment, it should require a specialist to interpret the data. The problem of the perceived baseline conundrum is a result of the limited education, ability, and construction-specific experience of the person drafting the GBR.
Furthermore, I have often seen reports that are nebulous in order to avoid conveying specific information. Disclaimers have even crept into GBRs, which dilutes responsibility! Many large engineering firms have managed to undermine the concept. Ask the silent majority if you wish to have a clearer perspective that leads to neutralizing the conundrum.
Dr. Peter J. Tarkoy, USA