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78 Conclusions The primary objective of NCHRP Project 10-86 was to develop a Recommended Practice to assist transportation agencies and industry in implementing a performance-based process for design and selection of alternative culvert and storm water drainage pipe systems on highway projects. The procedure developed has been described as a Recommended Practice in standard AASHTO format. This Recommended Practice was trialed using nine different agency policies across the United States and Canada and was proven to allow incorporation of the wide variety of factors required to successfully bid alternative pipe systems within a single framework. The successful trials of the Recommended Practice illustrated that the framework facilitates an alter- native pipe system selection procedure that is flexible, com- prehensive, and technically sound. This was demonstrated clearly when previously unspecified pipe system alternatives were identified when the Recommended Practice was applied to trial projects. The Recommended Practice will have the following functions: â¢ Provide a systematic, rational, and technically sound process for the evaluation of pipe systems (incorporating pipe and backfill materials and their interaction); â¢ Aid designers and bidders in selecting appropriate and cost-effective pipe systems for specific applications and site locations. The Recommended Practice is considered suitable for use in conventional design-bid-build contracts and also in alternative delivery mechanisms, such as design-build; â¢ Incorporate a comprehensive evaluation of site character- istics (environmental, geotechnical, hydrogeological); â¢ Evaluate hydraulics, structural performance, and durability in a streamlined and technically sound manner; â¢ Use a novel matrix approach that facilitates clarity and transparency; â¢ Allow confidence in and tracking of post-construction performance; â¢ Be mindful of constructability, operational, and maintenance requirements; â¢ Have an expandable framework enabling modifications as new methods and materials are developed; â¢ Have an underlying framework that is flexible, which enables extensive customization to address individual agency needs; and â¢ Handle routine drainage pipe system design issues in an efficient manner and provide options for special design cases. An agencyâs implementation of the Recommended Practice will require some customization. An inventory of approved pipe systems needs to be prepared and associated fill height tables developed for each pipe system option. The methods for estimated services life calculation need to be selected and, where possible, calibrated against local practice. The Recom- mended Practice has been developed with software automa- tion in mind. This can be done by way of spreadsheets or more sophisticated database software. Widespread implementation of the Recommended Practice will require access to such an automated software tool so that the full process, from proj- ect data input to generation of quantity sheets for bidding, is streamlined and requires less engineering intervention than current drainage system design processes. This project was intended to develop a national procedure for alternative bidding of highway drainage systems and has also put forward a range of standardization opportunities to additionally streamline and optimize drainage system design across the nation. The proposed Recommended Practice for Alternative Bidding of Highway Drainage Systems is intended to provide the following: â¢ Comprehensive framework for increasing competition in pipe system selection with a resulting reduction in overall costs to the agency â¢ Streamlined, technically sound, and consistent approach to pipe system selection C H A P T E R 1 6
79 â¢ Integrated use of best available practices â¢ Expandable framework enabling modifications as new methods and materials are developed â¢ Flexible framework enabling customization to address individual agency needs The Recommended Practice provides a standardized frame- work to ensure technical robustness, completeness, and trans- parency, while maintaining the ability of agencies to use their local experience to assist in alternative pipe system selection. Risk associated with using new products and practices is mitigated through the use of such a framework. The clarity in evaluation criteria provided by the recommended matrix approach should facilitate an agencyâs ability to more easily update policies in line with changes in applicable codes and material advances.