Alex Hall, ORISE Research Fellow c/o US EPA Office of Research and Development

Fran Kremer, PhD, USEPA Office of Research and Development

Using GIS to Assess Underground Storage Tank Vulnerability in Disasters with a Focus on Floodplains

Office of Research and DevelopmentNational Risk Management Research Laboratory.

May 1, 2019

Overview

• Scope of the problem

• Types of flooding

• Critical Infrastructure

• GIS – understanding the threats and vulnerable assets

• Improving preparedness

EPA Disclaimer: The findings and conclusions in this presentation have not been formally disseminated by the U.S. EPA and should not be construed to represent any agency determination or policy.

2019 Midwest Flooding

"There's a gas station here, and his tanks are floating down the river,"

https://www.marketplace.org/2019/03/18/business/its-mess

2019 Spring Flood Predictions and Actual Flooding

4/22/19 – 197 stream gauges in flood

https://waterwatch.usgs.gov/?id=ww_floodhttps://www.noaa.gov/media-release/spring-outlook-historic-widespread-flooding-to-continue-through-may

Types of Flooding

• Fluvial or river floods - excessive runoff from longer-lasting rainstorms or melting snow causes a slower water-level rise over a larger area

• Pluvial floods – extreme rainfall, precipitation cannot be absorbed in the soil

• Ground water floods - sub-surface water emerges to the surface or in structures due to persistent rainfall, high river levels or tides

• Coastal floods – occurs from storms where water driven onto land due to high winds, severe storms, and/or high astronomical tides

Ground Water Flooding

• Occurs when the water table rises due to• recharge to (or decreased abstraction from) aquifers with low storativity or

• propagation of the rising river stages into permeable, river‐connected alluvial aquifers.

• Can be significantly impacted by tidal surges• Expose tank infrastructure to brackish water

Areal Recharge and Diving Plumes

LeBlanc, D et al, https://doi.org/10.1029/91WR00241

Center of mass moved downward >3 m in 237 days with recharge having a significant affect

https://clu-in.org/download/contaminantfocus/mtbe/EPA-Plume-Dive-LL36DvPlm.pdf

Coastal FloodingPotential for Coastal Saltwater Intrusion

https://science.sciencemag.org/content/353/6300/705.full

Average Number of Coastal Flood Events per Year

https://tidesandcurrents.noaa.gov/publications/NOAA_Technical_Report_NOS_COOPS_073.pdf

Houston Case Study

• Houston and Harris County flat, low-lying region marked by high rainfall, poorly drained, clay soils, and sprawling development

• Harvey – Harris County Flood Control District estimated that 33” of rainfall over 4 day period was between a 3000 year and 20,000 year event• Lindner and Fitzgerald, 2018

• Half of impacted homes were outside the 500 year floodplain

Phil Bedient, Rice University

Spatial and Temporal Variability in Extreme Precipitation

An Assessment of the Impacts of Climate Change on the Great LakesReport Commissioned by Environmental Law and Policy Center and the Chicago Council on Global Affairs

• Annual precipitation averaged across the United States has increased by approximately 4% from 1901 to 2015 (USGCRP, 2017)

• There is a 9.6% increase in annual precipitation averaged over the Great Lakes while the Great Lakes Basin shows a comparable 10.0% increase.

• The largest increasing trends are for fall season (~15.8% for the bordering states), with summer (9.9%) precipitation also being larger relative to winter precipitation (7.7%) and spring precipitation (7.0%).

• Largest observed changes in extreme precipitation in the United States have occurred in the Midwest and Northeast.

http://elpc.org/wp-content/uploads/2019/03/Great-Lakes-Climate-Change-Report.pdf

Framing the Challenge of Urban Flooding in the United States, 2019

National Academy of Science

• Finding: A new generation of flood maps and visualizations that integrate predictions and local observations of flood extent and impact is needed to communicate urban flood risk. Improved methods for updating the maps to keep pace with urbanization and climate change are also needed.

• Tools to analyze and portray urban flood hazard in the United States are incomplete and inconsistent.• In many cases, the default tools are FEMA maps and analyses, which were not

developed to assess urban flood hazard• FEMA maps and analyses do not include

• Some aspects of pluvial flood hazard,• Flood hazard in small drainage areas (less than 1 square mile), • Flood hazard created by drainage and other urban infrastructure (FEMA, 2003).

Fueling Stations are Critical in Disaster Response

• Categories of Critical Facilities includes• Facilities involved in the production, storage and/or transport of

corrosives, explosives, flammable materials, radioactive materials and toxins.

• Systematically assess the storm risk and identifying protection strategies to “harden” facilities against damage for each location

• Essential for providing• Adequate fuel for evacuees• Assistance for first responders

• After Hurricane Harvey, responders found a convenience store on higher ground

“every one of the roughly 120 fueling pumps had an emergency response vehicle stationed at it”

• “Eye of the Storm, Report of the Governor’s Commission to Rebuild Texas”, 2018

Approach to Flood Resilience

• STEP 1 Understand the Threat of Flooding

• STEP 2 Identify Vulnerable Assets & Determine Consequences

• STEP 3 Identify & Evaluate Mitigation Measures

• STEP 4 Develop Plan to Implement Mitigation Measures

• ~500 UST Facilities were inundated

• ~1,200 USTs were inundated

• Up to 15.4 millions of gallons of Texas UST fuel/hazardous material were inundated

H U R I C A N E H A R V E Y

AGE OF FLOOD INUNDATED USTs DURING

HURICANE HARVEYGAS STATION AFTER HARVEY

6 USTs

H U R I C A N E H A R V E Y

0

5

10

15

20

25

30

35

40

<.5 1 2 3 4 5 6 7 8 9 11 12 13 15 19

UST

Co

un

t

Inundation Depth (ft)

Houston

• 202 tanks were inundated by the Brazos and San

Jacinto River, with a storage capacity of 1.5

million gallons of fuel. Estimated depth of

inundation ranged from .1-19 feet.

6 USTs

UST INUNDATION DEPTH

H U R I C A N E H A R V E Y

UST Facility

• ~33,0000 underground storage tanks within FEMA’s estimated 100 yr floodplain…

• Totaling 250 million gallons of fuel/hazardous substance capacity…

• With an average UST age of 25 years

N A T I O N A L U S T F L O O D V U L N E R A B I L I T Y

COUNT OF USTs WITHIN 100 YR FLOODPLAIN*—BY STATE

UST FACILITIES WITHIN 100 YR FLOODPLAIN NEAR ST. LOUIS

90 USTs~500k gallon storage capacity* Using estimated floodplain map for the conterminous

United States, produced by US EPA

Active UST Facility

100 yr Floodplain

N A T I O N A L U S T F L O O D V U L N E R A B I L I T Y

TOP 10 STATES WITH THE MOST FUEL CAPACITY

WITHIN 100 YR FLOODPLAINS—AND UST COUNT

N A T I O N A L F L O O D V U L N E R A B I L I T Y

• Spatial, intersessional, and annual heterogenous groundwater levels create challenges to LUSTs and USTs

• Saltwater intrusion can contribute to corrosion

• Groundwater flux can complicate/expand LUST plumes

F L O R I D A ’ S G R O U N D W A T E R V U L N E R A B I L I T Y

MODEL CROSS VALIDATION

(RMS=10 FT)

AVERAGE APRIL STATIC GROUNDWATER DEPTH

F L O R I D A ’ S G R O U N D W A T E R V U L N E R A B I L I T YSTUDY AREA’S AVERAGE GROUNDWATER DEPTH

• In the 13 FL county study area

there are 2,730 active LUST sites

• 42% of LUSTs have groundwater

depths of 15 ft or less

• ~3,000 private domestic wells

within 1,500 ft of an active LUST

F L O R I D A ’ S G R O U N D W A T E R V U L N E R A B I L I T Y

HISTOGRAM OF LUST DEPTH TO GROUNDWATER

HISTOGRAM OF ACTIVE USTs DEPTH TO GROUNDWATER

• In the 13 FL county study area

there are 11,500 active UST sites

• 42% of USTs have groundwater

depths of 15 ft or less

• ~4,600 private domestic wells

within 1,500 ft of an UST facility

F L O R I D A ’ S G R O U N D W A T E R V U L N E R A B I L I T Y

Active LUST

Well outside 1,500 ft of a LUST

Well within 1,500 ft of a LUST

Groundwater Depth (FT)119

0

50X vertical exaggeration

VISUALIZING THE INTERFACE BETWEEN GROUNDWATER, LUSTS, AND WATER WELLS

USEPA OUST Flood GuidePotential impacts on UST systems as a result of flooding

• buoyancy • Offset the restraint of backfill, pavement, or hold-down straps, cause tank to shift in the backfill from its location• If tank unanchored, may lift out of the ground and float resulting in a rupture or separation of the connecting pipes,

releasing product into the environment.

• erosion and scour • Rapidly moving water can cause soil erosion (soil above or around the UST being carried away by floodwaters) and scour

(velocity of flowing water removing soil cover and supporting backfill material around the UST system). • Expose the system to stressors from flood water pressure or floating debris even more vulnerable to being undermined

or collapse.• Cause underground piping to shift and become detached from the UST, releasing product into the environment.

• product displacement • During a flood, water or other debris can enter an UST through openings, e.g., fill pipes, vent pipes, gaskets, loose fittings,

covers, sumps, and damaged tank walls.• As water and debris settle on the bottom of the UST, product will rise and float on top until it exits the tank through

openings, releasing product to the environment.

• electrical system damage• Extended contact with floodwaters may cause damage to electrical equipment, e.g., ATG systems, panel boxes,

emergency shutoff switches, submersible turbine pumps, dispensers, motors, cathodic protection

https://www.epa.gov/sites/production/files/2014-03/documents/ustfloodguide.pdf

Roles of Federal, State, and Local Government in Preparing for Floods

National Response Framework, National Preparedness System

• Federal• Precipitation and flood forecasts

• Flood hazard and analysis maps

• Outreach/education

• State/Local• Infrastructure improvements

• Storm water system design and maintenance

• Land use policies and plans

• Building codes, development plans