# Presentation: 118617

## Approach to Developing a Plan of Action for Scour Critical Bridges

- Presented at TRB annual meeting
- January 16, 2002
- by:
- J. Sterling Jones
- Jorge E. Pagán Ortiz

## A Plan of Action (POA) should be Developed for Each Existing Bridge Found to be Scour Critical

- A Plan of Action (POA) _***should***_ be Developed for Each Existing Bridge Found to be Scour Critical

- Per FHWA guidance contained in Technical Advisory T 5140.23, “Evaluating Scour at Bridges” dated October 28, 1991

##                 Scour Critical Bridge

-                 Scour Critical Bridge

- A Scour Critical bridge is one with foundation
- elements that are determined to be unstable for
- the calculated and/or observed stream stability/
- scour conditions.
- Includes the following categories from the NBI Coding Guide item 113:
- _Code_ 	_Description_
- 	3    	Assessed or calculated condition
- 	2   	Comparison of calculated and observed condition
- 	1	Comparison of calculated and observed; failure is imminent
- 	0	Bridge failed and is closed

## Goal of POA

- Provide guidance for Inspectors and Engineers
- that can be implemented before, during, and after flood events to protect the traveling public.

## Elements of the POA

- Management Strategies
- Inspection Strategies
- Closure Instructions
- Countermeasure Alternatives and Schedule
- Other Information

## Management Strategies

- Location of Bridge
- Bridge Identification
- Type of Foundation and Foundation Material
- Source of Scour Critical Rating
- Importance of Roadway to the Transportation Network
- ADT, Access Route to Emergency Facilities, Evacuation Route, Detour
- Programmed for Replacement (may suggest a risk- based analysis)

## Inspection Strategies

- Type and Frequency of Inspection
- Normal frequency is 2 years for superstructure and visual or probing underwater where applicable.
- 5 years for general underwater inspection.
- Need for continuous Monitoring
- When to start?
- When to stop?
- What Constitutes a Scour Critical condition?
- Instructions for Action when the Scour Critical Condition is Reached

## Closure Instructions

- Can be Load Restrictions,  Lane Closure or Complete Bridge Closure
- Criteria for Closure should be Established by Scour Team based on one or more of:
- Observed scour, movement of riprap, monitoring bed movement, water level, discharge, rainfall, flood forecasting, debris build-ups
- Identify Authority for Closing and Reopening a Bridge
- Communication and coordination

**DETOUR**

## Countermeasure Alternatives

- Alternatives Considered
- More intense monitoring can be one of the  alternatives
- Preferred Alternative
- Engineering Feasibility
- Schedule for Timely Design and Construction

## Other Information

- Author and sign–off on POA
- Media Alert Instructions
- Sources of Emergency Repair Materials
- Detour Instructions

## Generic POA 

**Generic POA**

**Bridge Identification:** _____; **Location of Bridge: **____; **Year Built: **____; **Replacement Plans (if scheduled):_____  Foundation Type: ____________________________ Foundation Soils Types: _______________________________**
**ADT: ________________; Service to Emergency Facilities or Evacuation (Y/N): ____________________________**
**Sources of scour critical rating (Assessment, Analysis, and/or Observation): _______________________________**
**Comments about rating (e.g., analysis did not account for erosion resistant material; emergency riprap placed after last flood, etc.): ________________________________________________________________**______________
**Inspection and Monitoring:**
**Increase inspection frequency: _________________________________________________________________**
**Types (Probing, diving, inspection of banklines): __________________________________________________**
**Special Inspection Criteria (after bankfull events, during major  events): ______________________________**
**Monitoring Type (Fixed instrumentation, Portable instrumentation): _____________________________________**
**Criteria for monitoring: ___________________________________________________________________________**
**Closure Plans (Limit loads; Lane closure; Full closure): ________________________________________________**
**Criteria for Closure (Discharge; Floodwater Elevation; Flood Forecast; Scour Soundings): ___________________ ________________________________________________________________________________________________**
**Authorization for Closure (Bridge Maintenance engineer; Inspector; Police; Statewide Bridge Closure Procedure): ______________________________________________________________________________________**
**Detour Route: ____________________________________________________________________________________**
**Criteria for reopening bridge: ______________________________________________________________________**
**Countermeasures considered: (1) ____________________________________; Cost: $ ________________________**
**                           **** ****(2)____________________________________ ; Cost: $ ________________________**
**                  ****(3)____________________________________ ; Cost: $ ________________________**
**Countermeasure Recommended: ____________________________________; Status: ________________________**
**Author(s) of POA:_________________________________________________; Date: _________________________**
**Concurrences on POA: _______________________, __________________________, _________________________**

## POA Examples from DOT’s

- Oregon
- Dave Bryson
- Florida
- Rick Renna
- Seta Koroitamudu
- Maryland
- Andy Kosicki
- Stan Davis

## Slide 13

## Oregon DOT Plan of Action for Scour Critical Bridges

**Oregon DOT Plan of Action for Scour Critical Bridges**

## I-84 Bridges over the Snake River near Ontario, Oregon

- I-84 Bridges over the Snake River near Ontario, Oregon

## Oregon Snake River POA Example

- Oregon Snake River POA Example

- Determined to be Scour Critical, Code 3.  Scour has been observed to shale layer.
- Foundation material is Shale that is continuously wet.
- Annual Underwater Inspection; Murky Water; All Inspection by Feel.
- Re-Evaluation by Annandale procedure might elevate Item 113 to Code 5.

## SR 44 Bridge over St. John’s RiverDistrict 5, Florida

- SR 44 Bridge over St. John’s RiverDistrict 5, Florida

## SR 44 Bridge over St. John’s RiverDistrict 5, Florida

- SR 44 Bridge over St. John’s RiverDistrict 5, Florida

## SR 44 Bridge over St. John’s RiverPOA Example

- SR 44 Bridge over St. John’s RiverPOA Example

- Bridge Number:		110063
- Location:			SR 44 over St. John’s River
- Foundation: 		Pile
- Scour Mode: 		Riverine
- Status:
- Phase I: Data Collection and Qualitative Analysis	         	Final
- Phase II: Hydrologic Assessment for Scour Analysis        	Final
- Phase III: Geotechnical & Structural Scour Assessment    	Final
- Phase IV: Recommended Plan of Action		          	Final
- Scour Rating: 		3  Critical

## SR 44 Bridge over St. John’s RiverPOA Example (Continuation)

- SR 44 Bridge over St. John’s RiverPOA Example (Continuation)

-  POA Summary
- To mitigate active scour, riprap was recently installed from Bent 5 to the West Side of bascule Pier 1.
- Although a temporary scour countermeasure, the riprap in conjunction with a monitoring program may be an effective permanent scour countermeasure.
- Should the monitoring program find significant degradation below the elevation of the riprap lined channel, a structural based countermeasure may be warranted.

## SR 44 Bridge over St. John’s RiverPOA Example (Continuation)

- SR 44 Bridge over St. John’s RiverPOA Example (Continuation)

- Countermeasure Alternatives
- _Alternatives_ 			_Cost_
- 	1. Permanent Monitoring Program/	$313 per monitoring event
- 	    Portable Instrument
- 	2. Permanent Monitoring Program/	$18,500
- 		 Fixed Instrument
- 	3. Install Crutch Bents		Not feasible, riprap in vicinity

## SR 44 Bridge over St. John’s RiverPOA Example (Continuation)

- SR 44 Bridge over St. John’s RiverPOA Example (Continuation)

- Closure Plan
- If a scour condition develops, it may be necessary to close the bridge.
- If bridge closures, immediate implement District 5 bridge closure plan for state bridges.

## SR 44 Bridge over St. John’s RiverPOA Example (Continuation)

- SR 44 Bridge over St. John’s RiverPOA Example (Continuation)

- Plan Developer
- Ayres Associates, Brian A. Acken, P.E., 01/30/98
- Consultant Recommendation
- Alternative #1
- Action taken by FDOT
- Routine monitoring/riprap already in place
- Work Program
- 238328 (2-98); Project file 8