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63 Final Check and Policy Application Phase 3 of the Recommended Practice is to perform final design checks on the output from Phase 2, and to compare the results of the Recommended Practice with existing agency policies. It is anticipated that only pipe system options meeting the requirements of all three technical evaluation stages will be carried forward into Phase 3 for completion of final design and policy checks. 11.1 Final Design Checks Output from Phase 2 should be reviewed by the engineer to ⢠Identify possible errors and inconsistencies. ⢠Develop alternative designs that are outside the scope of the standard Recommended Practice (e.g., multiple barrels, aquatic organism passage). ⢠If desired, hydraulic design checks can be considered during this final check phase if generalized Manningâs n, equivalency charts, or other generalizations were applied for efficiency in the initial technical evaluations. The engineer should record why any options considered technically valid through the technical evaluations are not being forwarded into Phase 4. The engineer should record why any options not proposed by the Recommended Practice are being added for inclusion in Phase 4. 11.2 Agency Policy Checks The engineer should compare the output from Phase 2 and any adjustments made during final design checks with the drainage pipe system options allowed by the agency for the given application. Policy may dictate or restrict pipe size, pipe class, pipe material, backfill type, minimum or maximum fill height, and so forth as a matter of policy and those systems evaluated to meet the technical design criteria but not meet policy guidelines will be eliminated from further consideration in this phase. If AASHTO or FHWA standards have not been implemented as agency policy for hydraulic, structural, and/or durability evaluations, the previous evaluations should be checked against current agency policy in this stage. The intent of separating agency-specific policy evaluations from the initial technical evaluations is to promote greater standardization and adoption of national standards, and/or to identify areas for refinement of national standards to meet the range of needs expressed by all AASHTO agencies. The reason for elimination of a pipe drainage system in the final policy check phase should be recorded to provide full transparency in the design process. It is recommended that adopting agencies regularly review the list of final check eliminations to allow for evaluation and optimization of agency policies. 11.2.1 Presentation of Results As with the technical evaluation steps, a results matrix is used to present the evaluation results from the final design and policy check stage. The final check matrix is denoted with âFâ identifiers within the box for each pipe system type and highlighted green in cases calculated to be suitable for inclu- sion in bid documents, or highlighted red and crossed out for pipe system options that do not meet all the design and policy criteria. C H A P T E R 1 1
