Contractor Alternate Design Policy

Contracting for Bridges at PENNDOT.
March 1998
By Heinrich O. Bonstedt, Executive Director

Central Atlantic Bridge Associates
1042 North Thirty Eighth Street
Allentown, Pennsylvania 18104-3420

As with most public bidding, the letting of construction contracts in Pennsylvania has been on the basis of the lowest responsible bid in a design–bid–build environment.

In 1960 the Pennsylvania Department of Highways modified this basic concept and started to allow contractors to bid alternate designs of their own creation on selected projects. The Federal Highway Administration, in 1979, recognized that competition between materials would improve quality and reduce costs; therefore, began to require at least two designs of competing materials for bidding when federal funds above a certain minimum were involved. Over the years, as Departments of Transportation became familiar with the capabilities of "new" materials, the Federal Highway Administration raised the minimum thresholds for this requirement.

During 1980, the first Special Provisions that today basically still govern the Pennsylvania Department of Transportation’s Contractor Alternate Design, were formally incorporated in the Department of Transportation’s construction contract. These provisions are essentially bid-design-build, except that the Pennsylvania Department of Transportation prepares at least one complete design for bidding. The first Contractor Alternate Design bid in 1981 was for a steel structure. Since 1982 the Pennsylvania Department of Transportation has routinely practiced "Contractor Alternate Design" bidding.

In 1986 the Federal Highway Administration studied the first 5 1/2 years of the Pennsylvania Department of Transportation Contractor Alternate Design policy and made the following findings:

• "The bridges built with contractor alternate designs still look like all other bridges, and they all meet the same load carrying capacity with the required factor of safety." And "… that designers and contractors have become more adept at using existing materials and technology resulting in overall cost reductions without compromising safety, load capacity or durability of the structure."
• Cost savings for major bridges were 10 percent and for minor bridges 7 percent.
• A change in the material used resulted; away from steel to concrete.

A subsequent study during 1992 by the Pennsylvania Department of Transportation noticed the following:

• The frequency of Contractor Alternate Designs peaked in 1985 when 22 projects let were Contractor Alternate Designs.
• Designers were incorporating the ideas generated through the Alternate Design policy.
• In a competitive environment prestressed concrete bridges proved to be more economical than steel bridges.
• Low bid bridge alternates involved all materials:

The Central Atlantic Bridge Associates, in reviewing the results of Contractor Alternate Designs over the years, has also noted the almost total lack of claims from such Contractor Alternate Design projects. The bidding results of two recent projects are illustrated and attached as Appendix A.

Back to Top

A Tool for Developing Standards

As a manufacturing industry the prestressed concrete industry is generally operating differently than the construction industry. It must satisfy both sides of an equation: provide what its consumers like and produce what creates a profit. Asset utilization, production economies of scale, and the sensitivity to the issue of labor versus material content, have a major impact on product development efforts. Another important element in developing standards is the manufacturer’s need to manage the risks inherent in adopting a new standard. Gradual product modification is a key to reducing the risks of product development. The prestressed concrete producers in Pennsylvania have utilized the Contractor Alternate Design policy as a tool to evolve the beam standards of today.

As a result, the designer, today, can select from 29 I-beams, 15 adjacent composite box beams 1220mm wide, 15 adjacent composite box beams 915mm wide, 15 spread box beams 1220mm wide, or 15 spread box beams 915mm wide, to fine tune the bridge requirements and achieve an optimum solution. This policy also allowed for the introduction and general acceptance of high performance concrete (8,000 psi), continuous design, bridge decks without joints, fix – fix piers, refined live load distribution and many more.

Investment in product research and product development in the United States construction industry is notoriously low and slow. Nevertheless, new high performance materials and designs are being developed. Practical research and development looks to have impact in four primary areas of interest to owners and contractors:

• Lowest possible initial cost
• Speed up construction
• Increase the life-cycle performance of the structures
• Reduce the public inconvenience and impact on the environment that is necessitated by any construction, especially in urban areas.

Yet, the worthy results of this research are even slower in being introduced as a mainstream solution because there is no simple way to changing the mindsets of those charged with design. It is virtually impossible to introduce new technology generated by research unless there is an opportunity to perform a "show and tell" demonstration. But, an essential part of a technology demonstration project should be a requirement to establish the competitive viability for the development. Demonstration should not occur in a non-compete environment.

The provisions for Contractor Alternate Design, while they prohibit experiments, do allow for new developments to be introduced in a competitive environment.

The PennDoT commitment to seek the best-engineered solution is basically expressed in Chapter 2 of its Design Manual. In Section 2 – Selection of Bridge Types (see Appendix B) it states:

"Unless approved by the Chief Bridge Engineer, alternate designs by contractors are permitted in all cases. Justification must be provided whenever alternate designs are not allowed."

When it comes to the actual contracting, the contractor is kept in check with the Special Provisions included in the bidding documents (see Appendix C). Part A covers the general rules that apply, while Part B allows the specification writer, on a case by case basis, to modify Part A or to specify additional restrictions. To aid the specification writer PennDoT has established this checklist of items that might be considered.

• Bid advertisement by owner.
• Contractor/Supplier team procures plans.
• Contractor/Supplier team selects a design consultant to prepare design alternatives and performs preliminary value engineering to determine best solution.
• Best solution is refined to enable computation of major quantities for bidding.
• Contractor/Supplier team prepares preliminary conceptual plans and quantities. (For common bridges the bidding contractor requires this about one week prior to bid.)
• Contractor performs final cost comparisons of available options.
• Contractor submits bid using the Alternate Structure block on the bid form.
• Within 6 days of the contract award the contractor submits the conceptual design for PennDoT approval. PennDoT must review/comment/approve/reject within 24 days. In any event, contract time will not be extended due to any delays in approval of the alternate design concept.
• Final construction plans are prepared, for in-depth review, by PennDoT or by a selected consultant.
• Alternate structure is constructed.

In the most recent past we have noticed a number of structures going to bid without the provisions that allow for Contractor Alternate Design bidding. It seems that during the environmental process, negotiations with special interest groups result in concessions by the Department of Transportation in order to get their approvals. Such concessions then limit the engineering options unnecessarily and increase the cost to the public at large. The Department of Transportation will need to hold to its expressed policy of Design Manual 4 (see Appendix B) that requires that all engineering options be maintained in the environmental documents and that justifications for deviations and their special approvals be well documented. Further, the Department of Transportation must ensure that specifications do not become so proscriptive that the introduction of new ideas is stifled.