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46 Preparatory Agency Actions Prior to Implementation of the Recommended Practice To optimize the benefits of implementing the Recom- mended Practice, initial preparatory work and internal review is recommended. 6.1 Identification of Agency Goals, Requirements, Constraints, and Opportunities Before implementing a new or revised alternative pipe system bidding practice, it is recommended that an agency identify the requirements, constraints, and opportunities associated with any new or revised system, and select a system that will most effectively meet the agencyâs goals. 6.2 Pipe System Inventory To complete technical evaluations it is necessary to define the characteristics of each pipe system within the inventory including the following: â¢ Pipe size â¢ Pipe shape â¢ Pipe profile â¢ Pipe material type â¢ Pipe coating or lining condition â¢ Pipe structural class (presented as min and max allowable fill height) â¢ Pipe joint type â¢ Pipe roughness (Manningâs n value) â¢ Pipe abrasion resistance â¢ Installation type (embankment or trench) â¢ Installation class (as per AASHTO, ASTM, or agency-specific classifications defining backfill and bedding geometry, materials, and compaction requirements) An inventory of pipe systems within a jurisdiction may not be available and may have to be developed by the agency. Comparing the allowable pipe system inventory with other AASHTO agency inventories and with available pipe systems in the marketplace is recommended prior to Recommended Practice implementation and at regular intervals thereafter. Considering piggyback approvals based on research and pilot verification efforts by other AASHTO agencies and lever- aging of the NTPEP system are recommended to expand the inventory of approved pipe systems to include the widest possible range of pipe materials and installation conditions appropriate. 6.3 Pipe System Codes The adopting agency needs to maintain a detailed inventory of available pipe systems approved for use on agency projects. To help promote standardization and efficiency in dealing with the large number of pipe system variations available for use in highway drainage systems, the Recommended Practice recommends developing and integrating a pipe system iden- tification code (PSIC) for use in uniquely identifying each available pipe system alternative. The unique PSIC code for each available pipe system option can either be agency specific or follow from the example nomenclature presented below. The use of a PSIC to uniquely identify pipe systems is intended to allow for simpler and clearer presentation of pipe systems within the Recommended Practice matrix, on construction documents, and on as-built drawings to identify the full range of pipe system characteristics. 6.4 Inventory Database While not a requirement for implementation of the Rec- ommended Practice, it may be advantageous for the adopting agency to enhance the benefits of implementation by main- taining a detailed inventory of in-service drainage pipe systems. To help promote standardization and to allow for potential multi-agency data gathering and research, the Recommended C H A P T E R 6
47 Practice can be expanded to include an inventory database which would include the following items at a minimum, noting that many agency inventories may have additional items: â¢ Functional classification: arterial, collector, local, and so forth â¢ Roadway number â¢ Drainage system type: culvert or storm sewer â¢ Station of culvert inlet or station range for storm sewers â¢ Pipe system ID â¢ Installation date: month and year â¢ Original DSL in years â¢ Current estimated service life or achieved service life to failure â¢ Failure causation mechanism(s) This inventory could also form the basis for an asset man- agement system for drainage pipe systems to assist with estab- lishing long term pipe replacement and rehabilitation budgets. The tracking of original DSL, current estimated service life (from regular maintenance inspections), achieved service life to failure, and failure causation mechanisms is intended to allow for evaluation and improvement through calibration of durability prediction methods over time.