ARE YOU GOING TO VACUUM SOON? ESTABLISHING UNBIASED SPECIFICATIONS AND DESIGN CRITERIA FOR A VACUUM SEWER SYSTEM DESIGN-BUILD PROJECT

The Problem When the construction costs for proposed gravity sewer system improvements were estimated to be double the amount budgeted for the project, the leadership of St. Johns County, Florida sought alternative solutions. Delays resulting from the difficulties with the original project put Ponte Vedra community and County officials in the challenging position of quickly addressing widespread non-functioning septic tanks in this “old Florida” community. The County elected to utilize the State Revolving Fund (SRF) loan program, vacuum sewer technology, and a recent program amendment allowing design-build implementation to move the project forward. When complying with the open and competitive procurement requirements of the State, establishing fair and unbiased design criteria that balances differences in technology between the various manufacturers and promotes competition in the design-build procurement presents several challenges. Goals and Objectives The goals of this project were to address the challenges of establishing unbiased design criteria for the vacuum sewer system equipment and competitive bidding among the design-build teams. The objectives of this project were:To address the major technology differences between the various vacuum sewer system suppliers and establish unbiased design criteria.To prepare a flexible, yet comprehensive design-build procurement package to protect the community while preserving competitive bidding.Identifying the Problem Under the facilities planning requirements of the SRF program, CDM conducted an alternatives analysis that concluded the use of vacuum sewer technology would be a lower cost alternative to conventional gravity sewers. Further, it was determined that the vacuum sewer system costs could meet community affordability requirements. As a result, the County elected to proceed with the implementation utilizing the design-build provisions to expedite the project. Within the SRF program, however, the procurement must be open and pricing must be considered. Therefore, the design and construction requirements must be clear and the equipment specifications must be unbiased.Although the fundamental operating principles of a vacuum sewer system are same among manufacturers, there are significant differences in the components of vacuum sewer system equipment. Differences include:The requirements for an external air vent.Collection chamber volume and arrangementAccessibility and load bearing requirements of the valve chamber.Piping profilesThese differences can potentially create a bias to particular vacuum sewer equipment that limits the openness of the competitive bidding between the major equipment providers, in deference to the public procurement process.To further promote design-build competition, the design criteria package also had to very clearly establish minimum requirements; and provide sufficient information for the complex hydraulic design of the vacuum sewer system, and the construction in the congested right of way of an established neighborhood. The Solution A thorough understanding of the differences between the equipment of various manufacturers provides the knowledge to develop specifications that remove the biases created by the various vacuum sewer system manufacturers through proprietary components. By working with both the vacuum sewer system suppliers and the end user, specifications and design criteria can be established that meet the end user's requirements while promoting competition between vacuum sewer system manufacturers in the procurement process.Establishing appropriate design criteria for the placement of collection chambers, the vacuum piping network, the pump station arrangement and hydraulic conditions creates a competitive environment in which design-build teams have the opportunity to exercise flexibility in design and construction approaches to seek the lowest project implementation cost, without exposing loopholes in which the owner loses control of the project standard of quality and system integrity.This paper will outline the critical elements of unbiased equipment specifications and important design criteria used to procure design-build services for a large 700 home neighborhood septic tank phase-out program.