# Presentation: 666609

## Changes to FHWA’s NBI Coding Guide               (Items 60 and 113)

***               *****Plan of Action Workshop**
**                              **January 16, 2002
-  Jorge E. Pagán-Ortiz
-   Senior Hydraulics Engineer
-   (e-mail: _[jorge.pagan@fhwa.dot.gov](mailto:jorge.pagan@fhwa.dot.gov)_)
-  Federal Highway Administration
-  Office of Bridge Technology
-  Washington, D.C.

## 	           Implementation

- Revisions implemented by April 27, 2001, memorandum (Mr. James D. Cooper)
- Coordinated with National Bridge Inventory Steering Committee

##                 Goal

- Provide new guidance for coding bridges over waterways for:
- Observed and assessed scour condition
- Scour and stream instability countermeasures

##             Objectives

- Make coding of Items 60 (Substructure) and 113 (Scour Critical) consistent when a rating of 2 or below is determined for Item 113
- Expand description of Item 113 codes 1, 2, 3, 4, 5, 7, 8, T and U

##    Objectives (Continuation)

- Encourage bridge owners to develop a plan of action for:
- Scour critical bridges (codes 1-3)
- Bridges coded “7” and “U”
- Improve communication between the engineer and inspector

##     Highlights of Changes to                Item 60

- Description changed to emphasize that rating factor given to Item 60 should be **consistent** with the one given to Item 113 when:
- Rating factor of 2 or below is determined for Item 113

##    Highlights of Changes to              Item 113

- Description changed to emphasize that:
- Rating factor of 2 or below requires revising Item 60 and other affected items (load ratings and superstructure rating)
- Plan of action should be developed for each scour critical bridge
- Coding is based on an engineering evaluation, which includes consultation of NBIS field inspection findings

##    Highlights of Changes to    Item 113 (continuation)

- Refers to FHWA’s Hydraulic Engineering Circulars 18 and 23 for guidance on scour and countermeasures.

##        Specific Changes to Rating Factors (Codes U and T)

- Code “U” – plan of action should be developed to reduce the risk of failure during and immediately after a flood event.
- Code “T” – tidal bridges should be monitored until an evaluation is performed

##                Code 8

- Expanded guidance for a bridge foundation determined to be stable:
- Assessment -- **bridge foundations on rock formations determined to resist scour within the service life of the bridge**
- Calculations
**Installation of** **properly designed countermeasures**

##               Code 7

- Countermeasures installed to **mitigate** an existing scour problem and to **reduce the** **risk** of bridge failure during a flood event
- Instructions in a **Plan of Action** have been **implemented** to reduce risk to users from a bridge failure during or immediately after a flood event

##               Code 5

- Foundation determined to be stable for the **assessed** or calculated scour condition
- Scour within the limits of footings or piles based on an **assessment**, calculation or **installation of properly designed countermeasures**

##               Code 4

- Bridge foundation stable for the a**ssessed** or calculated scour condition

##     Code 3 (Scour Critical)

- Bridge foundation unstable for the **assessed** or calculated scour condition

##     Code 2 (Scour Critical)

- Field review indicates that extensive scour has occurred at bridge foundations, which are determined to be **unstable** by:
- Comparison of calculated and observed scour during bridge inspection
- Engineering evaluation of the observed scour condition reported by the bridge inspector in Item 60

##     Code 1 (Scour Critical)

- Field review indicates that failure of bridge foundations is **imminent** based on:
- Comparison of calculated and observed scour during bridge inspection
- Engineering evaluation of the observed scour condition reported by the bridge inspector in Item 60

##   Current Status (04/15/01)

- Bridges over waterways:   481,530
- Screened by Categories:   481,319  (100% )
- Low risk (9, 8, 7, 5 or 4):          336,401  (69.9%)
- Unknown foundations (U):           89,611  (18.6%)
- Tidal (T):                                        987  (  0.2%)
- Scour susceptible (6):                 29,461  (  6.1%)
- Scour critical (3, 2, 1, or 0):        24,859   (  5.2%)
- Not Screened:                             211      ---

##    Scour Evaluation Status

##  Scour Evaluation Summary

- Evaluations Completed: 361,260   (92.4%)
- Evaluations Needed:     _  29,672   __(  7.6%)_
- Evaluations Total:         390,932  (100.0%)