Geotechnical Baseline Report - The ultimate tool for dispute prevention in Tunnels

Introduction

The stated objective of a Geotechnical Baseline Report (GBR) is to define and allocate the risks associated with subsurface excavation. In theory, the GBR works in tandem with the Differing Site Condition (DSC) Clause in the Contract Documents to provide a mechanism for the contracting parties to identify any truly unanticipated conditions that may be encountered and pay the contractor an equitable adjustment for costs incurred to complete the work.

In a way the GBR is a knob which varies risk sharing between the client & contractor from 0 to 100 % based on the description and limits set by the definition of a baseline condition in the GBR. A GBR may transfer all risk to the contractor or cater for client to pay for all unforeseen circumstances. It’s the ultimate contractual tool for dispute prevention.

Baselines in a GBR need to be defined with precision and unambiguity to prevent disputes being referred to courts of law. ?It is pertinent that each site condition in a tunnel is baselined accurately and unambiguously so that clarity for risk sharing is established right from the tender stage itself.

Few examples and nuances of a tunnel GBR are discussed in succeeding paragraphs. ??????

Baselines for Boulders

How should boulder obstructions be baselined? Should rock strengths be given for boulders and/or cobbles?

The primary excavation risks associated with boulders depend on boulder size relative to the excavation diameter, the boulder and/or cobble quantities/frequency, and the unconfined compressive strengths of the boulders and/or cobbles.

In order to properly baseline boulders, a decision must be made by the Owner and/or Design Engineer regarding the size of the boulder that will be considered “out of contract.” It is important to note that, depending on the size of the boulder and the size of the machine, not all boulders may be obstructions. A boulder is only an obstruction if it stops the forward progress of the machine. If boulders of a particular size can be successfully excavated by a machine, it may not be necessary to baseline those boulders. However, if due to the restrictions on the machine size, boulders of a particular size cannot be excavated, these are the boulders that will obstruct the forward progress of the machine, and are extremely important to baseline as they markedly impact the bid price.

There are several indirect ways of determining quantity/frequency, including boulder volume ratio methods and probabilistic methods, but the selection of the method should include consideration of the quality and quantity of data available, as well as the size of the project. Both favourable and unfavourable determinations may have significant impacts to the project in terms of cost and risk.

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Rock strength determination, which is typically based upon unconfined compressive strengths from geotechnical testing, is often more complex to baseline. It should be noted that setting a baseline number for unconfined compressive strength of cobbles or boulders on trenchless projects (other than large diameter conventional tunneling) is very rare.

Setting rock strength baselines too low may lead to excessive back-end costs (i.e. change orders) for Owners. Setting baselines too high may lead to accusations regarding the constructability of projects. Deciding not to include rock strengths is also an option, but may lead to variable interpretation by the courts to what may be considered reasonable for the anticipated conditions. Please note that the Contractor’s interpretation of the indications represented in the Contract Documents need not necessarily be the best interpretation or the only interpretation, but a reasonable interpretation.

First, different geologic units can be baselined to have different boulder volume ratios. When combined with a profile, the contractor can expect to encounter higher frequencies of boulders when tunneling in a unit with a higher boulder volume ratio.

Second, cobble and boulder concentrations can be baselined. This might be done by proximity to bedrock (.e.g. within 10 feet), identification of a lag zone along the interface of two geologic units or at an end-moraine, or third by randomly indicating that a certain number of concentrations of a defined size and volume may be encountered within certain geologic units.

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Baselines for Dewatering

How should groundwater conditions be baselined to minimize misunderstanding and to facilitate risk sharing?

Baselining groundwater is difficult because there are many potential attributes to baseline. Hydrogeologic parameters, which include groundwater levels within one or more aquifers, permeability, storage coefficients and specific capacities, are independent of construction activity and do not vary based on a Contractor’s means and methods.

Groundwater behavior, including seepage velocities and inflow rates to excavations, are dependent on construction activities such as excavation size, depth, ground support system, ground improvement, dewatering. Generally, only one or the other of these two types of parameters would be baselined, as including both may lead to inconsistencies as Contractor’s means and methods vary.

Perhaps the two most commonly baselined groundwater attributes are hydraulic conductivity (permeability) and inflow rates. Hydraulic conductivity is a measurable hydrogeologic parameter independent of Contractor means and methods, while inflow rates are construction-dependent. For that reason, baselining both should be avoided.

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Some Design Engineers prefer to baseline hydraulic conductivity, as inflow rates may be calculated from the provided values for any given construction scenario after determining many other input parameters including: aquifer extent, groundwater heads, aquifer confinement, radius of influence, effects of ground improvement and ground support system/lining permeability, time to steady state flow, etc. Hydraulic conductivity is given as a velocity, and may be presented as a baseline value. Some designers prefer to baseline potential inflow rates.

To establish reasonable values the designer must make many parameter selections as discussed above including many that are related to contractor means and methods. Misunderstandings can occur if the assumptions in the baseline are not clearly stated so that the differences between the assumptions and actual conditions and means and methods can be assessed. One common misunderstanding is transient flow versus steady state flow. Most designers only compute the estimated stated steady flow and do not indicate that transient flows may be several times higher and last for days to over a week.

As may be expected, baseline values that are too adverse tend to inflate the bid price, while baseline values that are more favorable than anticipated may lead to decreased productivity and excavation instability as well as increased dewatering and water disposal costs, resulting in delays and claims.

From a legal standpoint, fewer conditions have created more uncertainty and resulted in more court cases than groundwater.

Key approach is the inclusion of a detailed and comprehensive dewatering specification identifying the Contractor’s post-bid engineering responsibilities and payment for same.

GBRs should not attempt to predict quantity or analyze how the stated groundwater conditions will behave during construction, or what means might be useful to mitigate or minimize water seepage or infiltration.

First, this is not the purpose of a GBR. Second, including this information will likely be interpreted by the Contractor as an implied or express warranty such quantities or volumes will not be exceeded. Third, mentioning potential ways to mitigate water infiltration may be interpreted by bidders as a warranty that implementing such measures will be successful.

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Baselines Significantly more Adverse than GDR

What should the contractor assume and what are the legal implications of that assumption if the conditions described in the GBR are extremely adverse and differ significantly from what is represented in the GDR?

Design Engineer may include statements in a GBR intentionally exaggerating the adversity of subsurface conditions in hopes of “protecting” an Owner from DSC claims.

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As Owners bear the risk of unanticipated surface conditions, they may think that inclusion of extremely adverse conditions may eliminate that risk. However, what they often do not realize is that statements that are significantly different from the remaining Contract Documents (the Geotechnical Data Report and boring logs) can be challenged in court, particularly when there is no effort made to explain the reason for the discrepancy.

Absent other factors or language in the GBR, the courts regard boring logs as “usually the best indicators of subsurface conditions and bidders ought to rely heavily on them” and that a “pattern of test borings is usually reasonably representative of the entire site.”

If a baseline statement contains information that may not be discerned from a reasonable interpretation of the boring logs, the validity of that statement can thus be challenged in court. Conversely, the Owner will most likely look to the GBR provisions as contractually superior to the data and will point out that the Contractor ignored the GBR clauses (and relied on the data) at his own peril.

From a legal standpoint: This is an important question because it requires us to address the essential purpose of the GBR and how achievement of that purpose impacts the participants in the construction process. It also requires us to think about facilitating risk allocation in a reasonable manner. First, the fact that the GBR might state conditions as being more adverse, or less adverse than those found in any given boring or set of borings is part of the nature of the GBR. GBRs therefore routinely go beyond the limits of conditions actually discovered (i.e. baselining boulders where none are actually encountered in drillings or borings). As a principle Baselines should be contractually binding regardless of the presence or absence of specific substantiating data.

Second, if the GBR does characterize the conditions in a more adverse manner than depicted in the borings, the mere fact of this discrepancy should not result in having the GBR language tossed out if the Contract Documents clearly rank the GBR as the superior document in the order of precedence. The cases in which courts consider the borings to be “usually the best indicators of subsurface conditions and bidders ought to rely heavily on them” are ones where the Contract Documents do not contain a GBR and/or where the Owner attempted to hide behind generic, ineffective disclaimer language.

By contrast, no court yet has disregarded a clear GBR baseline merely because it exceeds the conditions found in the specific data. As indicated, if the GBR is clearly written and has a hierarchy above the data report, then any conflicts between the two documents should be resolved in favour of the GBR.

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Advisable Length of the GBR

Should tunneling GBRs be lengthy and descriptive or more concise? Should there be a difference in the approach between tunneling and non-tunneling GBRs?

There is often a debate amongst GBR authors over length and written approach – should a GBR be more descriptive or more concise? Some authors feel that the GBRs for complex projects should provide as much information as possible about expected ground conditions, with the thought that Contractors will make the most educated decisions about means and methods.

Others feel that as little information as possible should be given, in hopes of “protecting” Owners from DSC claims based on minute differences between baseline statements and encountered conditions.

From a legal standpoint, while there is no off-the-shelf answer to this question for all projects, in most projects the GBR should be concise and clearly written. In fact, it is a misnomer to discuss advisable length of the GBR without also discussing the need for clarity, because lack of clarity – such as undefined terms, run-on sentences, excessive reliance of technical jargon and complex descriptions of geologic phenomena or history – contributes directly to over-length.

Writing with brevity is more difficult than the other way around and many professionals – lawyers included – tend to write too much out of habit or laziness. It is suggested to have a concise document that can be read and understood in 2 or 3 hours.

Keeping the GBR short is not an objective in itself, but rather a tool to reach the GBR’s ultimate purpose: a clearly, easily understood, not-open-to-second-guessing set of baselines. In that respect, writing a good GBR should be more akin to writing a tightly-crafted specification.

The benefits of brevity, from a legal standpoint, can be seen by considering the following factors:

1. In situations where the Prime Contractor will be subcontracting the tunneled work, it is important to provide the lower-tier participants with a document they can pick up and read efficiently. An overly long GBR may not be read by the subcontractors or may be read in a selective and self-serving way.

2. Keeping the GBR brief forces the Owner and its Design Engineers to limit the number of topics to be baselined. Limiting the number of baselined topics has legal advantages for the Owner because there are fewer opportunities for the Contractor to claim a deviation from the conditions indicated.

3. Length generally breeds inconsistency because a statement on Page 3 can be read as in conflict with a latter statement on Page 33. Such inconsistency in turn may lead the court to conclude the GBR is ambiguous and thereby not only defeat the purpose of the GBR as a technical tool, but also increase liability.

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4.??????? A concise document is easier to explain to the court. If the court can’t figure out what’s clearly intended to be stated in the GBR (either by reading the document or having it summarized by expert testimony), the court won’t have any way to enforce its content or, worse, may enforce it in unpredictable and incorrect ways.

5.??????? As a legal instrument, the intent of the GBR will be ascertained from its totality – that is, the entire GBR will be read with the objective to give meaning to each and every one of its parts.? A concise GBR will be less susceptible to manipulation and misreading during this scrutiny by the court.

6.??????? A concise GBR in turn should compel the author to reduce qualitative descriptions and increase the use of readily measurable quantifiable baselines.

7. ?????? Finally, the wider use of Defined Terms will be encouraged with concise GBRs. Use of Defined Terms is one of the main tools used by lawyers to achieve contractual clarity. They are currently underutilized in GBRs. GBRs need to have better worded definitions and consistently use these terms throughout the GBR and other contract documents.

?Conclusion

?The recommendations presented above are valuable for Owners, Contractors, and Design Engineers. It is important to consider while both writing and reading GBRs how baseline statements may be viewed by the courts should a claim become elevated to litigation.

?A thorough understanding of how courts typically stand on baseline statements will assist in the preparation of GBR documents which lead to an equitable risk distribution for the contracting parties.

Using this approach, one may reduce the need for antagonistic legal battles, leading to successful projects for Owners, Contractors and Design Engineers.

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