U.S. Department of Transportation
Federal Highway Administration
1200 New Jersey Avenue, SE
Washington, DC 20590
202-366-4000


Skip to content U.S. Department of Transportation/Federal Highway AdministrationU.S. Department of Transportation/Federal Highway Administration

Bridges & Structures

   

Differing Site Conditions (23 CFR 635.109)

Formerly Federal-aid Policy Guide Non-Regulatory Supplement NS 23 CFR 635,
Transmittal 16
See Order 1321.1C FHWA Directives Management

  1. Differing Site Conditions (23 CFR 635.109)
    1. The 23 Federal Code of Regulations (CFR 635.109) contains policies, requirements, and procedures for standardized "changed conditions" clauses for Federal aid highway projects. In summary, unless prohibited by State law, part 635 requires that a "differing site condition" clause shall be made part of and incorporated into each highway project approved under Title 23.
    2. Geotechnical engineering Guideline #15 provides information on geotechnical aspects of differing site conditions, adequate site investigation, disclosure and presentation of subsurface information by highway agencies, and the use of such information in mitigating or resolving contractor claims of differing site conditions. Recommendations are provided for disclosure of factual, qualified and interpretive geotechnical information. The uses of geotechnical design summary reports are described and a typical report outline provided in the appendices. This guideline is available from HNG-31.
Updated: 06/27/2017
Federal Highway Administration | 1200 New Jersey Avenue, SE | Washington, DC 20590 | 202-366-4000