Culvert Risk Mitigation Planning

Lizzie Kemp, CDOT Resiliency Program Manager

August 29, 2019

AASHTO CTSSR Meeting

1. Background – Why a mitigation plan for minor culverts?

• CDOT Resiliency Program

• I- 70 Risk and Resiliency Pilot

• Prioritizing Risks Based on Study Results

2. Method for Identifying Highest Risk Minor Culverts

3. Goal: Developing a Mitigation Plan for Highest Risk Culverts

Overview

CDOT Resiliency Program

Lessons Learned

1976 and 2013 floods destroyed many of the same facilities

What can we do now ….

… To avoid this in the future?

Colorado Resiliency Framework

Created by the Colorado Resiliency Office (DOLA)

Defines re·sil·ience for Colorado

“The ability of communities to rebound, positively adapt

to, or thrive amidst changing conditions or challenges—

including human-caused and natural disasters—and to

maintain quality of life, healthy growth, durable systems,

economic vitality, and conservation of resources for

present and future generations.”

CDOT Resiliency Program

• Created in 2018, with Policy Directive

1905.0 – the vision for resilience at CDOT

• Works to integrate resilience in CDOT

functions

• Coordinates resilience activities at CDOT

• Conducts research to support resilience

• Provides resilience knowledge and

resources to CDOT staff

I 70 Risk and Resiliency Pilot

I-70 Corridor Risk & Resiliency Pilot

• Analysis of risk potential from physical threats on I-70 from Kansas to Utah

• Looked at – all assets – roads, bridges, culverts, etc.– Wide range of threats – flood, avalanche,

rockfall, etc.

• Proactive look at optimal investments we can make now, in advance of future events, to improve system resilience

• Builds on the 7-step RAMCAP process utilized in flood recovery effort

I 70 Pilot Results

Asset Criticality – Some Roadways are More Critical Than Others

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• Usage: AADT + Roadway Classification

• Economic Impact: Freight value ($) + Tourism value ($)

• Social Impact: SoVI

• System Impact: System Redundancy

Equal weight assigned to each of the six selected variables.

SOCIAL ENVIRO ECON

✓ ✓ ✓

✓

✓

✓ ✓ ✓

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Criticality Map for System Resilience

AADT 16.7%ASHTO Road Classification 16.7%Freight $ (County) 16.7%Tourism $ (County) 16.7%SoVI 16.7%Redundancy 16.7%

Reminder: Criticality reflects the importance of each asset to overall operations within CDOT’s network as related to system resilience only. Criticality is part of Step 1 in a 7-step Risk and Resilience Analysis process.

Equal Weight

53.8% Low

25.5% Moderate

20.7% High

Consequence Analysis ($ per threat-asset pair)

Given the worst reasonable event, what are the consequences? ($)

Owner Cost• Asset Replacement

Cost

User Cost• Value of time

(delay/detour)

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Prioritizing Which Risks to

Mitigate

Prioritizing I 70 High Risk

Assets

• Highest owner risk on all of I-70 is rockfall (63%). Rockfall also presents a pretty big portion of the corridor wide user risk (22%).

• Flood is the largest corridor user risk (72%) with most of that related to minor culverts (80%).

• Direction from Executive Committee –Focus first on Rockfall and Minor Culverts

I 70 Pilot Results

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$6,136,494

$164,667,186

$-

$20,000,000

$40,000,000

$60,000,000

$80,000,000

$100,000,000

$120,000,000

$140,000,000

$160,000,000

$180,000,000

Owner Risk (OR) User Risk (UR)

All Threats

Owner Risk (OR) User Risk (UR)

User Risk -- Share of Each Threat

Flood $118,190,629 Rockfall $35,781,405 Avalanche $8,516,650

Landslide $2,161,863 Wind $9,738 Bridge Strike $6,901

$-

$20,000,000

$40,000,000

$60,000,000

$80,000,000

$100,000,000

$120,000,000

ApproachFlood

BridgeFlood

MinorCulvertFlood

NBI CulvertFlood

Road Flood Wall Flood

User Risk Related to Flood

Prioritizing At Risk Culverts

• With nearly 60,000 culverts under 4 feet across the state, which subset should we create a maintenance plan for first and when should the plan be completed?

• Proposal: Focus first on culverts in poor condition that are also on critical routes

• First Tier (approx 18 k)– culvert scores 6-9 plus all unrated Target completion -- ?

• Second Tier (approx 14.5 k) – culvert scores 3-4 Target completion -- ?

• Third Tier (approx 24 k)- culvert scores 1-2 – no plan, accept the risk?

GIS At Risk Culverts tool

• Created by Gerry Shisler, CDOT GIS Team

• In development – data available statewide

• Able to identify culverts and their condition and whether they are located on “critical” roadways

CULVERTS CONDITIONS,LESS THAN 48” (4 FEET)TOTAL = 54,716 PIPES

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Criticality Map for System Resilience

AADT 16.7%ASHTO Road Classification 16.7%Freight $ (County) 16.7%Tourism $ (County) 16.7%SoVI 16.7%Redundancy 16.7%

Reminder: Criticality reflects the importance of each asset to overall operations within CDOT’s network as related to system resilience only. Criticality is part of Step 1 in a 7-step Risk and Resilience Analysis process.

Equal Weight

53.8% Low

25.5% Moderate

20.7% High

CULVERTS CONDITION POORHIGHWAY CRITICALITY HIGH

Proposed Culvert Mitigation Plans

Step 1: maintenance patrols complete an inspection of identified high-risk culverts (update condition in database)

Step 2: identify and document specific proposed mitigation action for each culvert based on inspection

* e.g. replace culvert, slip line, etc.

Step 3: if no mitigating treatment is possible or is too costly, identify and document a specific operations plan

* e.g. increased cleanout frequency, install technology to monitor flows, etc.

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HIGHWAY CRITICALITY

ONLY POOR CONDITION CULVERTS

Extra slides

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COLOR MATRIX

Three vehicles lie in a creek after raging

floodwater undercut Dillon Road near

U.S. 287 in Broomfield on Sept. 12,

2013. The three motorists were rescued

after emergency workers secured the

vehicles with ropes and the motorists

scrambled up the banks of the creek.

Credit: Andy Cross, The Denver Post

The 2013 Flood Was…

A Human

Disaster

• 10 fatalities

• 28,000 people force from home

• 2nd largest airlift in U.S. History

• 32 CDOT Permanent Repairs

required

The 2013 Flood Was…

A Costly

Disaster

• $555 billion impact to economy

• $4 billion in total damages statewide

• $736 million damage to infrastructure

– $130 million Emergency Repair

– $616 million Permanent Repair

– $708 from FHWA Emergency Fund

I-70 Corridor Risk & Resilience Pilot

• “Pilot” the data, assumptions, and methodology needed to quantify:– What are CDOT’s assets?

• Location, value, condition, criticality

– What are relevant physical threats?• Likelihood and location

– What impact would they have on our system?• Consequences and vulnerability

– What are the optimal investments we can make now to improve resiliency in advance of future events?

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Key Concepts – Risk Definition

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Risk (R) C x V x TRisk (R) ($) Potential cost of asset losses in a threat-filled environmentConsequence (C) ($) Result of asset failureVulnerability (V) (%) Susceptibility to the threatThreat Likelihood (T) (%) Potential of threat occurrence

Risk – potential cost of losses to CDOT assets (direct and indirect)Resilience – ability to remain functional even in presence of risks

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Threats Assets

Avalanche Bridges

Flood (scour) Bridge Approaches

Flood (Overtopping / debris) Roadway Prism

Fire (wildland) Post Tension Concrete Slabs

Landslide Tunnels

Rockfall NBI Culverts

High wind (special wind zone)

Minor Culverts

Tornado Walls

Bridge strike ITS Devices