FLH PDDM Chapter 9 - Eastern Federal Lands Highway Division

9.4.D. Earth Retaining Structures. (continued)c. Design Guidelines: All alternatives permitted in FLH contracts shall be designed in accordance with theGuidelines for the Design of Retaining Wall Systems. These guidelines are a summary, mainly by reference,of acceptable design criteria and other information for each wall system which may be considered for use inFLH contracts. These guidelines assure consistent FLH designs and encourage competition by permitting asmany Contractor designed alternatives in the contract as possible. These guidelines shall be used by the FLHin its designs, by A&E firms in designs done for FLH, and by the construction Contractor for alternativedesigns.In addition to design criteria, the guidelines contain other information, including wall system limitations,materials specifications, and construction specifications necessary for a construction contract. A checklist ofall retaining structure geometric and design data (original and final vertical profiles, beginning and endingstations, foundation capacity, backfill criteria, soils angle, etc.) needed for the design of each alternate wallsystem is included in the guidelines. This checklist will help insure the Project Manager provides all designdata for consultant and Contractor designed wall systems in the contract package. The FLH guidelines permitconsistent design and review of retaining walls. The guidelines will be updated as new retaining wall systemsare added to the list of alternative wall systems which may be considered for use on FLH projects.Each FLH division shall have a process to insure that any wall used on FLH projects is designed using theprocedures in the design guidelines. The process must include a review of designs of proprietary walls andthose prepared by A&E firms to insure the procedures in the Guidelines for the Design of Retaining WallSystems have been used.d. Selection of Wall Types: Once it has been determined that a wall is needed, the Project Manager shalldetermine which wall system alternatives shall be permitted. The Project Manager shall coordinate with theland-owning agency and a Federal Lands Highway (FLH) inter-disciplinary team. The team shall normallybe made up of Geotechnical, Highway Design, and Bridge Design Engineers. The level of involvement of theindividual team members will vary depending on the type and function of the wall. The Project Manager shallconsider spatial, behavioral, and economic factors in determining the alternatives to be permitted. Theseevaluation factors include: 1) Constructability, 2) Maintenance, 3) Schedule, 4) Aesthetics, 5) Environment,6) Durability or proven Experience, and 7) Cost.The Project Manager shall document the selection process. The documentation may be especially useful whenselection and non-selection of proprietary retaining wall systems are challenged. The Project Manager maylimit the number of alternative wall systems to be permitted based upon an analysis of the specific constraintsand conditions. The analysis shall consider the complexity of the site, and the estimate of the cost of the wallsystem in addition to the technical suitability of the wall system to the site.The Project Manager normally will consider only retaining wall systems included as part of the Guidelines forthe Design of Retaining Wall Systems, unless an unusual situation, or an experimental wall system is proposedby the interdisciplinary team. In these situations, the Project Manager must insure the design guidance andspecifications are made available. The wall systems which are normally considered are listed in the Guidelinesfor the Design of Retaining Wall Systems. This list shall be updated as new wall systems are added, asprovided in Section 9.4.D.5.d. below.9 - 79