U.S. Department of Transportation
Federal Highway Administration
|Subject:||ACTION: Project Oversight Unusual Bridges and Structures||Date:||November 13, 1998|
|From:||/s/ Original signed by:
Director, Office of Engineering
|Reply to Attn. of:||HNG-30|
Resource Center Directors
The August 20, 1998, memorandum entitled "Implementation Guidance - Project Oversight under Section 1305 of the Transportation Equity Act for the 21st Century" (copy attached) provides guidance regarding project oversight. This supplements that guidance and details FHWA Headquarters and field responsibilities for the review and approval of preliminary plans for unusual bridges and structures. Federal-Aid Program Guide G 6012.1, Chapter 6, Preliminary Plan Review and Approval, is now superseded.
The Headquarters Bridge Division shall be responsible for the approval of preliminary plans for unusual bridges and structures on the Interstate System. However, engineers in some Division Offices may have substantial recent experience on certain types of unusual bridges and structures. In those cases, and upon agreement between the Division Administrator and the Chief of the FHWA Bridge Division, approval authority may be delegated to the Division for specific types of bridges or structures. The availability of specialized technical assistance to the Division from our Resource Centers will be considered in such delegation decisions.
For unusual bridges and structures on other Federal-aid and non-Federal-aid highways, project responsibilities shall be in accordance with the August 20, 1998, guidance. The Bridge Division will provide technical assistance when requested.
For the purpose of this guidance, unusual bridges are those the Divisions determine have: (1) difficult or unique foundation problems, (2) new or complex designs with unique operational or design features, (3) bridges with exceptionally long spans, or (4) bridges being designed with procedures that depart from currently recognized acceptable practices. Examples of unusual bridges include cable-stayed, suspension, arch, segmental concrete, movable, or truss bridges. Other examples are bridge types that deviate from AASHTO bridge design standards, or AASHTO guide specifications for highway bridges; major bridges using load and resistance factor design specifications; bridges requiring abnormal dynamic analysis for seismic design; bridges using a three-dimensional computer analysis; bridges with spans exceeding 152 m (500 feet); and bridges with major supporting elements of "ultra" high strength concrete or steel.
Unusual structures are tunnels, geotechnical structures featuring new or complex wall systems or ground improvement systems, and hydraulic structures that involve complex stream stability countermeasures, or designs or design techniques that are atypical or unique.
An important consideration is the timing of submittals for approval or assistance. The most benefit can be gained if the FHWA is involved as early as possible. This is especially true in the case of design-build contracts where decisions on structure types and size greatly affects the contract bidding process.
Preliminary documents submitted to Headquarters should include the preliminary design plans and supporting data along with the Division's review comments and recommendations. Supporting information should include bridge/structures related environmental concerns and suggested mitigation measures, studies of bridge types and span arrangements, approach bridge span layout plans and profile sheets, controlling vertical and horizontal clearance requirements, roadway geometry, design specifications used, special design criteria, special provisions and cost estimates. Hydraulic and scour design studies/reports should also be submitted showing scour predictions and related mitigation measures. Geotechnical studies/reports should be submitted along with information on substructure and foundation types. Early and complete submissions would be appreciated in order to facilitate meaningful and expeditious reviews and approvals.
For further information, please contact Mr. David H. Densmore, Chief, Bridge Division (HNG-30) at 202-366-4589.
/s/ original signed by
Henry H. Rentz
Henry H. Rentz