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SpecificationsSpecifications are used (1) to convey information concerning desired products from a buyer to a seller or potential seller, (2) as a basis for competitive bidding for the delivery of products, and (3) to measure compliance to contracts. Typically, four types of specifications; proprietary product, method, end-result and performance specifications; are generally recognized in the construction industry.
Figure 1: Some WSDOT Standard Specifications from 1963 - 2000 This section is largely taken from a series of three articles written for HMAT Magazine and a Washington State DOT research report as listed below:
Proprietary Product SpecificationsA proprietary product specification is used when a generic description of a desired product or process cannot be easily formulated. It usually contains an "or equivalent" clause to allow for some measure of competition in providing the product. It is generally acknowledged that such a specification severely limits competition, increases cost, provides little latitude for innovation, and puts substantial risk on the owner for product performance. Most agencies avoid this type of specification whenever possible, however private owners often use them.
Method SpecificationsA method specification outlines a specific materials selection and construction operation process to be followed in providing a product. In the past, many construction specifications were written in this manner. A contractor would be told what type of material to produce, what equipment to use and in what manner it was to be used in construction. In its strictest sense, only the final form of the structure can be stipulated (for instance, the thickness of the pavement layers). This type of specification allows for a greater degree of competition than the proprietary product specification, but as long as the structure is built according to the materials and methods stipulated, the owner bears the responsibility for the performance. Although widely used, method specifications have several key disadvantages. First, they tend to stifle contractor innovation because there is virtually no incentive to develop better, more efficient construction methods. Second, since they are not statistically based and 100 percent compliance is usually not possible, method specifications usually required “substantial compliance,” a purposely vague and undefined term that can lead to disputes. Finally, spot checks of material quality, which are often used in method specifications, do not reflect overall material quality because they are taken from subjectively determined non-random locations. Since they are not random, these spot checks have no statistical validity and therefore do not reflect overall material quality. Despite their flaws, method specifications are still widely used on the local agency level (e.g., counties, small cities, towns, etc.). In general, this is because they are familiar, straightforward to write and can be implemented with minimal agency involvement. Local agencies often lack the expertise and resources required to use statistical specifications or warranties.
End-Result SpecificationsAn end-result specification is one in which the final characteristics of the product are stipulated, and the contractor is given considerable freedom in achieving those characteristics. In their roughest form, they specify minimum, maximum or a range of values for any given characteristic and base acceptance on conformance to these specifications. For instance, they may state a minimum layer thickness or a range of in-place air voids. Since it is impractical to measure every square foot of constructed pavement, end-result specifications use statistical methods to estimate overall material quality based on a limited number of random samples. Therefore, end result specifications improve on methods specifications in two key areas: (1) they shift the focus away from methods and on to final product quality and (2) they do not rely on the nebulous "substantial compliance" because they clearly define acceptable quality. Today, most large State and Federal pavement contracts use statistically based end-result specifications
that incorporate some elements of method specifications (usually used to guard
against early failure of the product). These end-result specifications are
often referred to as a "quality assurance specifications", "QA/QC
specifications" or "QC/QA specifications". Essentially, these specifications specify the
end results and also specify certain minimum construction method requirements
(e.g., temperatures below which paving is not allowed, descriptions of initial
test sections, minimum number of rollers, conditions under which the agency may
halt paving operations, etc.).
Performance SpecificationsPerformance specifications are those in which the product payment is directly
dependent upon its actual performance. Typical of these specifications are
warranty, limited warranty and design-build-operate contracts. Contractors
are held responsible for the product performance within the context of what they
have control over. The contractor is given a great deal of leeway in
providing the product, as long as it performs according to established
guidelines. In this case, the contractor assumes considerable risk for the
level of service the product provides by paying for or providing any necessary
maintenance or repair within the warranty period. |
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