Commissioning and Acceptance Testing - Design-Build for Water and Wastewater Projects - page 280

COMMISSIONING
Commissioning is a critical transition point in the development of the project. It typically
occurs prior to substantial completion, which is a contractual milestone when the facility
is available for beneficial use. For WTPs and WWTPs, commissioning is usually one to
five months in duration, depending on the size and complexity of the plant.
During commissioning, the function of individual pieces is verified first, and then
groups of equipment are checked until the entire treatment facility functions properly.
The DBIA Manual of Practice (DBIA 2008a) states that commissioning “involves check-
out of all systems and components for functionality in accordance with specifications and
operating criteria.” Each functional component (e.g., valves, instruments, motors) must
be checked for safe operation before being used. These tests are primarily for mechani-
cal and electrical systems. They are complex but straightforward. By ensuring that each
component functions safely as designed, the system can be expected to function properly.
Once the components are determined to be functional, operational testing of the
overall facility can begin. Often at this stage, testing and optimizing the biology and
chemistry of treatment dominate the effort. This part of commissioning can be challeng-
ing if there were oversights in earlier commissioning steps or any design or construction
errors. If this occurs, correctly identifying and troubleshooting problems may require
days or weeks and can be a significant negative impact on the overall project schedule.
There are several reasons why modern treatment facilities require a thorough and
complete commissioning effort. First, the owner needs to gain confidence that the facility
meets the contractual obligations. There are also public safety and environmental con-
cerns regarding the quality of treated water. Further, the design-builder typically assumes
a large portion of risk associated with the proper function of the treatment plant before
it is turned over to the owner. They are eager to prove the plant operation so that the
substantial completion milestone can be reached. For these reasons, owners and design-
builders should plan careful commissioning activities for each project.
Planning for Commissioning
Planning for commissioning does not begin when plant construction ends. Design-
builders plan commissioning and acceptance testing tasks when responding to the RFP.
The time and effort to conduct the tests must be included in the cost of the project, and
this requires an understanding of how the tasks are to be completed. For example, there
may be a need to dispose of large quantities of off-spec water or to construct a bypass pipe
to allow the recycle of partially treated water to the head of the plant. Startup activities
can be complex, with multiple parallel tasks needing to be conducted, and they can be
influenced by the overall construction schedule (White, Larson, and Schebler 2009); thus,
thorough planning is critical.
While few RFPs contain much detail about the commissioning requirements of the
project, design-builders can gain an understanding of the overall objectives of the owner
and any constraints that might impact commissioning. As stated simply and directly in
The Municipal Water and Wastewater Design Build Handbook (WDBC 2010), “Project
planning must include the final stage of the project.”