FRSRWAPITI ERL Corrosion with Piping and Scour - Yellow Priority 2023 09 19.pdf

To: Paul Johnson

Public Works Director

From: Phillip Osborn, P.E.

Project Manager

Date: September 29, 2023

Essential Repair Finding – FRSRWAPITI

The following bridge is recommended for repairs as recently discovered by the bridge inspection program:

Responsible Party: Town of Fraser

Facility Carried: Wapiti Street

Feature Intersected: Fraser River

ERF Color Code Classification: Yellow (See definition at end of letter)

Structure Description: FRSRWAPITI is a culvert that consisted of (3) 10 foot wide by 7 foot high elliptical steel corrugated metal pipes.

Findings

The bridge inspectors noted that the invert of the north pipe (Pipe 3) exhibited large perforations up to

3 feet wide with exposed rock fill for an approximately 33-foot-long section in the middle of the pipe.

There was also R3 to R4 corrosion (minimum of 10% steel section loss, some small holes in metal) with up to 1/4-inch-diameter rust nodules below the waterline and flaking corrosion up to 2 feet above the invert throughout all pipes.

There was a 3-inch-wide gap at a joint in the bottom of the center pipe (Pipe 2) approximately 20 feet from the outlet with a 3 inch height differential between the channel bottom and invert of the pipe, allowing piping below the end 20 feet of the pipe. When struck with a hammer, the end 20 feet of Pipe 2 sounded hollow, indicating undermining voids from the gap to the outlet. At the outlet end, inspectors observed an undermining void measuring 7 inches high by 56 inches penetration. There was also undermining at the outlet end of Pipe 3 measuring up to 9 inches high with 33 inches of penetration.

Additionally, there was grout spalling in the inlet headwall along both sides of all pipes, allowing water to penetrate up to 51 inches from the inlet around the edges of the pipes (worst at the south side of Pipe 2).

The bottoms of all pipes at the inlet (below the invert) were not undermined.

See the attached photos.

Recommendations

It is our office’s recommendation to inject flowable fill into all areas of undermining and all pipes be slip lined to prevent additional corrosion and piping. As funds become available, we recommend installing engineered scour countermeasures per HEC-23 Volume II (http://www.fhwa.dot.gov/engineering/hydraulics/pubs/09111/09112.pdf). Once engineered scour countermeasures have been installed, we can change NBI Item 113 Scour and remove this bridge from the scour list. The Essential Repair for this structure has been given a Yellow Priority. The Item 113, Scour Critical, rating remains a 4, and the culvert will require monitoring during flood conditions, checked for scour damage after flooding and closed if settlement is noticed during flooding.

Let us know your Plan of Action

CDOT would like to know your plan of action to repair or mitigate the above conditions. Please respond to this ERL within 14 days with a very brief plan of action that includes what repairs are planned and a general timeframe for when you expect repairs will be made.

Please let me know if you have any questions or if I can provide any additional information regarding this inspection.

Thank you for your time, Phillip Osborn, P.E.

posborn@collinsengr.com

Inspector Printed Name:_____Phillip Osborn_________________________

Inspector Signature:_____________________________________________

Date of Inspection:__09/19/2023__

Senior Inspection Engineer Printed Name:_____Benjamin Brock_______________

Senior Inspection Engineer Signature:____________________________________

Date Reviewed:___09/29/2023__

By signing here, I have determined that the above description of Essential Bridge Repairs meets the established criteria set forth by CDOT Staff Bridge and that the repair is essential. Color code prioritization has been determined and notification of the above findings has been sent to the local agencies' public works or road and bridge departments.

Definition, Classification and Prioritization

Definition of Essential Bridge Repairs: Repairs necessary to ensure the safe and continued service of off-system major bridge structures. Examples of essential repair needs include but are not limited to: tension members identified as fracture critical members within the Structure File Data and which are damaged by natural or impact forces, a condition which results in a restriction of the maximum acceptable load carrying capacity of a structure to some value less than 27 Tons on the Type III, 3-axle truck at the Operating Rating level, three adjacent crushed stringers, three broken stringers in one span, two of which are adjacent to one another, stringers with rot at the ends, which may cause the stringer to fall off the timber cap, “mushrooming” for a depth of 2 inches on three adjacent stringers, rot in the top of 80 percent of all stringers in one span, which reduces the effective depth by 25 percent, rot in timber piles that affect the carrying-capacity of the structure, concrete girders with over 30 percent of the primary moment steel severed, loss of section in beam ends and/or spalls in concrete girder supports where girders have less than 80 percent bearing area remaining, steel members with over 30 percent section loss, steel or aluminum culverts including super spans with unusual section displacement and/or gaps at the point of overlap and cracks in bolt lines, steel or aluminum pipe culverts with perforations in the bottom 1/3, scour greater than one foot since the last inspection which has caused vertical or horizontal displacement, scour under a spread footing, which has caused a loss of 15 percent of the bearing area.

When identifying a needed repair as essential, the Bridge Inspection Program Manager will classify the repair based on the appropriate time frame for addressing the problem as follows:

cc:

Lynn E. Croswell, P.E., CDOT Bridge & Structure Inspection Engineer Natasha Butler, P.E., CDOT Bridge Asset Management Engineer Josh Dunbar, CDOT Structure Inspections Project Manager Andrew Brown, CDOT Bridge Inspections Project Manager Spencer Tucker, P.E., FHWA Division Bridge Engineer

Classification

Legacy

Color

Code

Target Time Frame for

Completion Priority

Federal

NBIS

Initial

Notification

E-Mail

Notification

Time Frame

Follow-up

Time Frame

Urgent Priority Repair Orange Within 30 days Urgent E-Mail

Notification

Within 10 working days of finding

14 Calendar days of E-Mail

High Priority Repair Yellow Within 90 days High E-Mail

Notification

Within 10 working days of finding

14 Calendar days of E-Mail

Moderate Priority Repair Green Within one year Moderate At presentation

As needed

(not required)

As needed or

At next inspection

Monitor Blue Specified in the letter Monitor E-Mail

Notification

Within 10 working days of finding

As suggested in the notification

Low Priority Repair

(maintenance item) No Color As funding allows Low

Included with transfer files to

Owner

N/A At next inspection

Culvert Inlet Looking West

Culvert Outlet Looking East

Typical Perforation with Exposed Rock Fill in Invert of Pipe 3 Looking North

Typical Perforations with Exposed Rock Fill in Invert of Pipe 3 Looking West

Typical R3 to R4 Corrosion with Small Holes and Rust Nodules in Invert of Pipe 1 Looking North

Typical R3 Flaking Corrosion Above the Waterline in Pipe 1 Looking Northwest

3-Inch-Wide Gap in the Invert of Pipe 2 Approximately 20 Feet from the Outlet Looking North

Undermining at the Outlet of Pipe 3 Looking Northeast

Undermining at the Outlet of Pipe 3 Looking Northeast

Typical Spalled Grout at Inlet Headwall (South Side of Pipe 2 Shown) Looking South