U.S. Department of Transportation
Federal Highway Administration
|Subject:||ACTION: Compliance with the National Bridge Inspection Standards; Scour Evaluation of Bridges over Waterways||Date:||October 20, 1998|
|From:||Director, Office of Engineering||Reply to Attn. of:||HNG-31|
We have completed reviewing the April 15, 1998, biannual progress report of bridge scour evaluations submitted by each State department of transportation (DOT). The current status is shown by total, Federal-aid highway, and non-Federal-aid highway bridges in Tables 1 through 3, which are attached. The bridge scour evaluation summary, sorted by Evaluations Needed, is shown in Table 4. Most DOTs (32) have made substantial progress towards completing their evaluations and another 14 have submitted reasonable action plans for completing their evaluations. However, six DOTs have not submitted a revised action plan for completion of their evaluations. We request that Massachusetts, Kentucky, Louisiana, Oklahoma, New Mexico and Nebraska submit a revised action plan with their November report that indicates their current status and projected completion date.
The current status report shows that there are over 18,000 bridges determined to be scour critical. Since the primary purpose of the scour evaluation program is to ensure safety for the public users of our Nation's bridges, each DOT should have a plan of action for each scour critical bridge, as recommended in the FHWA technical advisory TA 5140.23. The plan of action should include, as appropriate, the design and timely installation of scour countermeasures to protect the bridge foundations from scour. We encourage you to work with your corresponding DOT to develop a plan of action for each scour critical bridge.
As a reminder, DOTs that have identified bridges over tidal waterways (code "T" for item 113 of the Coding Guide) should be conducting scour evaluations on these bridges. In addition, DOTs that have identified bridges with unknown foundations (code "U" for item 113) should be conducting scour evaluations on these bridges if the engineer has been able to identify the type and/or depth of the bridge foundation. The FHWA Geotechnical Notebook Issuance, number 16, issued in September 1998, summarizes the technology contained in the NCHRP project 21-5 pertaining to techniques available for identifying bridge foundations.
/s/ original signed by
Henry H. Rentz
Henry H. Rentz
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