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Commissioning: Design-Build Vs. Design-Bid-Build

For commissioning agents, the difference is nuanced but significant.

It has been a number of years since I addressed commissioning of D-B projects. In my September 2000 column, I reflected on how commissioning is at least, and probably more, applicable and important to D-B projects as it is to traditional design/bid/build (D-B-B) projects. In addition, I noted that the overall commissioning process is the same for both D-B and D-B-B.

This month, I will address aspects of the commissioning process which, although fundamentally the same, differ in their execution details between D-B-B and D-B. The commissioning team is still made up of the same key players: owner’s project manager, owner’s O&M representative, design team, construction team, and commissioning professionals. Contractually, it just happens that the design team and construction team are both under a single D-B contractor’s umbrella in a D-B project.

Commissioning Plan and Owner’s Project Requirements

For the best chance of project success, I recommend that the commissioning plan and owner’s project requirements (OPR) be prepared by or on behalf of the owner prior to procuring the D-B contractor’s services. The OPR will define the system performance the owner expects from the D-B contractor’s design, installation, and startup effort. The commissioning plan will outline the process by which the owner (with help from the commissioning professional) will validate and accept the systems at the end of the construction.

Commissioning Specification

The use of written specifications in D-B projects varies extensively from nothing but notes on drawings to fully developed multi-division specification books prepared by the design team. The commissioning professional needs to ask about the intentions for specifications early in the design phase and coordinate the inclusion of a commissioning specification within the format and deliverables planned by the D-B contractor. If it is the case that there will be no written specifications at all, the detailed commissioning requirements, checklists, and test procedures may best be appended to the commissioning plan during the design phase.

Submittal Reviews

Equipment shop drawing and submittal reviews are handled very differently in most D-B projects, because there is no “approval” of the documents by the design team. When the design team and construction team are under the same contractual umbrella, the concept of review for approval does not typically apply; it is assumed that the design team has been part of selecting the submitted equipment and, thus, has inherently approved it. The commissioning–focused review of selected equipment shop drawings, however, remains very important (see this column in Engineered Systems, April 2008).

In a traditional D-B-B commissioning project, the commissioning professional reviews the shop drawings and provides comments to the design team for consideration in the design team’s formal approval process. In a D-B project, the commissioning professional should submit their comments directly to the D-B contractor’s design team as, essentially, another round of design review. The design team provides written responses to each commissioning comment, just like they do during the design phase review process.

Under the D-B model, the commissioning professional should never be put in a position of “approving” the shop drawings on behalf of the owner. The D-B contractor has taken full responsibility for the final performance of the systems, and no one outside of the design and construction teams can provide design and construction direction without the assumption of some of that responsibility and risk.

Pre-Functional Checklist and FPT Procedure Development

In D-B-B projects, I always recommend incorporating as much project-customized technical commissioning requirements in the bid specification as practical. This is intended to improve communication with and understanding by the bidding contractors and to avoid disputes about level of rigor and acceptance criteria at the end of the construction.

In D-B projects, most of the benefit of this early development — primarily of prefunctional checklists (PC) and FPT procedures — is lost by the fact that the construction team is under contract long before the design has evolved to the point of being able to customize the technical commissioning documents. Therefore, I recommend that the D-B commissioning professional wait until after at least shop drawings (and, for some systems, after operations and maintenance manuals) have been reviewed and approved prior to preparing the PCs and FPTs. To compensate for this, the commissioning plan should include examples of typical PCs and FPTs for the type of facility being constructed; this will help communicate the technical level of rigor for commissioning at the time the D-B contractor is hired.

 

Commissioning: Getting It Right

Engineered Systems, May, 2008

by
Rebecca Ellis, PE, LEED AP, CCP, CxA
President
Questions & Solutions Engineering
1079 Falls Curve
Chaska, MN  55318
rteesmag@QSEng.com