Tunnel Business Magazine

OCT 2018

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Page 23 of 47

TUNNELINGONLINE.COM TBM: TUNNEL BUSINESS MAGAZINE // OCTOBER 2018 that baselines the permanent design basis in the specific context of antici- pated subsurface conditions. • The GBR (and/or DBR) will be a part of the Contract Documents. • The objective of the IRAB approach is to include in the GBR (and/or DBR) the relevant baseline statements in a unitary, consolidated, cohesive and integrated fashion that adequately address the DII Factors in the context of both subsurface conditions and de- sign adequacy risk allocation. • The IRAB provisions contained in the GBR (and/or DBR) should objectively and clearly articulate, and define (a) the anticipated subsurface condi- tions (based on underlying data and evaluations) (b) the contemplated permanent final design basis, and (c) the expectations as to the suitabil- ity, compatibility and constructabil- ity of the final design in the specific context of the baselined subsurface conditions. The IRAB should also address the anticipated behavior of subsurface conditions in the specific contexts of (a) the permanent design basis approach and (b) the design- builder's contemplated construction means and methods. This approach, of necessity, would address the DII Factors as they relate to both subsur- face conditions and the permanent design basis. • Under the IRAB approach, the Con- tract Documents – which include the GBR (and/or DBR) – should pro- vide a clear and objectively defined foundation to address how risk is allocated between the owner and design-builder, and whether the latter is entitled to a cost or time ad- justment when: Identified/encountered sub- surface conditions during post-bid design or construc- tion processes are materially different from those condi- tions baselined in the GBR; or The permanent design basis needs to be substantially al- tered or revised due to mate- rial variations in identified/ encountered subsurface con- ditions (from those baselined in the GBR (and/or DBR). To achieve the objective of the IRAB approach will require the collaborative involvement of both the owner (and its consulting engineers) and the design- builder (and its consulting engineers) in the joint preparation of the GBR (and/or DBR). The IRAB (and other portions of the GBR and/or DBR) provisions would need to be prepared when, during the tender phase, the design-builder (and its consult- ing engineers) has had a reasonable oppor- tunity to (1) conduct its own subsurface investigations and evaluations required to support its final design approach, (2) validate subsurface data and evaluations furnished by the owner, (3) perform a suf- ficient level of preliminary development of the permanent design basis; and when the owner has given initial acceptance of a preliminary permanent design basis sub- mittal prepared by the design-builder (and its consulting engineer). Some commentators have suggested a sequential but collaborative approach in DB to GBR development: (1) a GBR for bid- ding ("GBR-B"), prepared by the owner and furnished during procurement with a fo- cus on the anticipated physical conditions; and (2) a GBR for Construction, prepared by the design-builder, that augments the GBR-B and primarily addresses anticipat- ed ground behavior based on the design- builder's proposed construction means and methods, reviewed by the owner for concurrence and reasonableness. The IRAB approach is distinguished from the preceding approach in explic- itly and specifically requiring that the permanent design basis be expressly ad- dressed in the GBR (and/or DBR) for risk allocation purposes. The IRAB approach contemplates that the GBR (and/or DBR) will (a) be jointly and collaboratively pre- pared by the owner and design-builder, (b) define the appropriate risk allocation baselines as to both subsurface condi- tions and the permanent design basis and (c) constitute an integral part of the Contract Documents. Significantly, the GBR (and/or DBR) in the IRAB approach is not limited to only subsurface condi- tions risk allocation and statements as to anticipated constructability (e.g., con- struction means and methods) consider- ations, but also addresses risk allocation pertaining to permanent design basis. The collaborative process for prepara- tion of the GBR (and/or DBR) facilitates and supports the fusion, contractual alignment, and documentation of the mutual understandings and expecta- tions of the owner and design-builder as to anticipated subsurface conditions and permanent design basis, relative to the DII Factors. ess sign- c Progressive DB provides a framework for utilization of the IRAB approach. Pro- gressive DB is intended to improve the process by which final contractual deci- sions as to subsurface conditions and de- sign adequacy risk allocation may be in- formed and reasonably determined. The improvement is accomplished by provid- ing a meaningful and interactive approach in which the owner and design-builder may more effectively synchronize their contractual and (design and construction) performance expectations pertaining to the DII Factors. In progressive DB, the par- ticularization, clarity and documentation of contractual risk allocation decisions are enhanced through the owner and design- builder's collaboration in the joint prepara- tion of a GBR. Progressive DB provides the opportu- nity within a contractual framework to defer final risk allocation decisions relat- ing to subsurface conditions until the design-builder has the ability to (a) learn more about the reasonably anticipated subsurface conditions, (b) conduct an ap- propriate level of design development; and (c) validate the compatibility, suitability and constructability of its design approach in the specific context of the reasonably anticipated subsurface conditions. In conjunction with progressive DB, the IRAB approach could function to pro- vide a concerted series of consolidated and composite statements in the Contract Documents (i.e., the GBR and/or DBR) rel- evant to cohesive and comprehensive risk allocation for subsurface conditions and design adequacy risks that adequately ac- count for the DII Factors. The objective of the IRAB approach is to capture, define and contractually baseline the mutual expectations of the owner and design-builder as to (a) subsurface condi- tions, (b) the permanent design basis, and (c) the relevant DII Factors, all of which may impact the compatibility, suitability and constructability of that design in those conditions. That objective is principally accomplished in a manner that allows for more informed, refined and collaborative risk allocation agreements between the owner and the design-builder. The essence of the IRAB approach is the achievement of transparency and the ascertainment, concerted refinement and definition, and documentation of mutual contractual expectations pertaining to subsurface conditions and design adequa- cy risks respectively, and specifically in relation to the DII Factors. This approach should significantly reduce the prospect of DSC and breach of implied warranty claims on major DB subsurface projects. Above all of those attributes, the IRAB ap- proach is premised on, and an extension of, the sound principle of risk sharing which 2 4 F E AT U R E S T O R Y

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