Developing a Project Technical Criteria Document - Design-Build for Water and Wastewater Projects - page 163

diagrams or preliminary drawings, industry standards, standard specifications, and other
owner-mandated design, drafting, or documentation standards.
The design criteria document is typically organized by project elements or systems,
and in most cases, it contains both prescriptive and performance requirements. Prescrip-
tive design criteria are precise specifications for project elements, including treatment
process, equipment, system sizing, materials of construction, and so on. Performance
design criteria establish the required output performance for a defined input, such as the
flow and water quality of a WWTP. They can also define a functional requirement with-
out precise specification of the means, method, or solution.
Some owners use prescriptive design criteria as a means to control the design and the
selection of components that are installed. This is most common for large owner organiza-
tions with multiple facilities, because of their desire for standardization between facilities.
Alternatively, the use of performance criteria gives the proposers more flexibility to be
innovative when developing solutions, while achieving the same functionality but within
a shorter schedule or at a lower cost.
Table 13-1 can be used to compare and contrast prescriptive and performance-based
criteria for a basic pumping application.
Performance Requirements and Guarantees
Owners may elect to establish performance requirements or performance guarantees to
validate the performance of the completed project. The use of performance guarantees
represents performance-based contracting, which is based on the owner's definition of the
input and expected output. A performance test is then required to demonstrate that the
treatment plant performs to the stipulated output. Performance guarantees, sometimes
also called process guarantees , can be classified as either primary performance guarantees
secondary performance guarantees.
Because most water and wastewater project procurements reflect a mix of both pre-
scriptive and performance-based criteria, the validity of performance guarantees must be
scrutinized relative to the prescriptive design criteria. This is very important because the
owner may not get a guarantee from the proposer if the owner has made all the control-
ling design decisions and has included them as prescriptive design criteria. Proposers may
only be willing to guarantee performance when they are allowed a reasonable degree of
design control. Performance guarantees represent a level of assurance above and beyond
the normal standard of professional care; thus, the impacts of performance guarantees on
cost and risk should be carefully reviewed.
When properly written and executed, performance guarantees are a useful vehicle
for establishing project performance expectations for DB projects. Owners and proposers
should, however, be pragmatic when establishing performance guarantees for a project.
Guarantees are appropriate to demonstrate performance relative to critical design param-
eters but be wary of placing guarantees on unit processes or individual pieces of equip-
ment, unless they are deemed critical for the operation of the WTP or WWTP. Excessive
guarantees may be met with qualifications to proposals and extra contingency in price
proposals. In most cases, a review of the engineering calculations around individual unit
processes may be more appropriate than field testing.