Laurens van der Tak, PE, D

Climate Risk and Resilience Planning for Wastewater Infrastructure

Laurens van der Tak, PE, D.WRE

VWEA Education Seminar –Managing Risk through Process and Organizational Innovation

May 12, 2016

2

Presentation Outline

Climate Change Threats

Adaptation Strategy Framework

Climate Change Adaptation Case StudiesMiami-Dade Water and Sewer Department

Boston Water and Sewer Commission

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Climate Change Threats: Rainfall, Extreme Storms and Sea Level Rise - Impacts Vary Based on System Function and Source (Drainage, Riverine, and Coastal)

Precipitation

Precipitation timing,

Sea level rise Storm surge

2- to 10-year storms

100-year storms

Stormwater/DrainageManagement

Localized floodingIncreased CSOs

Riverine Floodplain Management

Regional flooding

Tidal flooding Tropical storms

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Climate Change will make storms we design for more intense, and increase the frequency (ie risk) of exceeding design criteria for flood protection.

Precipitation

Precipitation timing,

10-year storm depth will increase by

about 1 inch

A 100-yr becomes 50-yr recurrence

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Adaptation Framework:When dealing with future uncertainty an adaptive planning process provides needed flexibility.

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Continually Monitor and

Re-assessMonitor sea

level rise, revisit assessments and

re-assess priority

strategies to continually

inform future actions to adapt

to changes in sea level.

Identification of

Vulnerabilities and Risk

Identify and assess

infrastructure that may be

impacted by sea level rise.

Develop a list of potential adaptation strategies

Determine the range of

strategies that will provide the best adaptation

to changing future

conditions based on identified

vulnerabilities.

Link adaptation

strategies to current processReview

adaptation strategies to

identify those that only require

an adjustment or modification

to current policies or programs.

Implement Adaptation Strategies

Identify priority strategies for

implementation: those strategies

that are best aligned with the

values, goals and objectives

of the implementing organization .

Steps to identify strategies to increase resilience to sea level rise:

2 3 4 5 6

Frame the Problem

“What are the overarching questions to

answer and sea level rise

scenarios to plan for, with the

goal of increasing

resilience to sea level rise?”

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Frame the Problem

“What are the overarching questions to answer and sea level rise scenarios to plan for, with the goal of increasing resilience to

sea level rise?”

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A problem well-defined, is a problem half solved. ~Charles Kettering

• Are facilities near tidal waters, subject to sea level rise and storm surge?

• Are my operations at risk of riverine flooding or greater I/I from sea level rise and higher rainfall?

• Are my operations at risk from power outages?

• What is the planning horizon for evaluating climate change:

– Service life of assets

– CIP planning cycle, based on growth, land use change, finances

• Select climate scenarios based on your risk tolerance:

– Consider low, medium and/or high future scenarios

1

Frame the Problem

“What are the overarching questions to answer and sea level rise scenarios to plan for, with the goal of increasing resilience to

sea level rise?”

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Scenario analysis…accounting for future uncertainty

0

20

40

60

80

100

120

140

160

2010 2020 2030 2040 2050 2060 2070 2080 2090 2100

Sea

leve

l abo

ve 2

010,

cm

YearExtrapolated Historic Trend Line Curve 1 (2100 End Point = 70 cm)Curve 2 (2100 End Point = 100 cm) Curve 3 (2100 End Point = 140 cm)

Curves adapted from the NC Coastal Resources Commission Science Panel on Coastal Hazards 2010NC Sea Level Rise Assessment Report (March 2010)

Historic Trend40-cm (1.3-ft)

PrecautionaryTrend100-cm (3.3-ft)

Sea Level Rise Scenarios

9

Continually Monitor and

Re-assessMonitor sea

level rise, revisit assessments and

re-assess priority

strategies to continually

inform future actions to adapt

to changes in sea level.

Develop a list of potential adaptation strategies

Determine the range of

strategies that will provide the best adaptation

to changing future

conditions based on identified

vulnerabilities.

Link adaptation

strategies to current processReview

adaptation strategies to

identify those that only require

an adjustment or modification

to current policies or programs.

Implement Adaptation Strategies

Identify priority strategies for

implementation: those strategies

that are best aligned with the

values, goals and objectives

of the implementing organization .

Frame the Problem

“What are the overarching questions to

answer and sea level rise

scenarios to plan for, with the

goal of increasing

resilience to sea level rise?”

Steps to identify strategies to increase resilience to sea level rise:

1 4 5 6

Identification of Vulnerabilities

and RiskIdentify and assess

infrastructure that may be impacted by sea level

rise.

2

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Asset Inventory and Risk Evaluations provide a strong foundation for CC Vulnerability Assessments

• Identify major asset types of interest, e.g.:

– Wastewater treatment plants

– Wastewater pump stations

– Gravity sewers and manholes

– Force mains

• Define the critical elevations for these assets

• Identify vulnerable assets.

• Define probability of inundation events and likelihood of damage.

• Determine consequence of failure.

• Determine risk level: high, medium, and low risk groupings.

Identification of Vulnerabilities

and RiskIdentify and assess

infrastructure that may be impacted by sea level

rise.

2

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Climate risk builds on asset management information to understand critical assets

Sea Level Rise ScenariosExtreme Events

Hazard Characterization

Susceptible AssetsVulnerable ElevationsDamage Thresholds

Consequence of Failure

Asset Characterization

Vulnerability:Risk = P(Event)*

[P(Damage)*P(Consequence)]Adaptation

Options

Driven by Asset Management program data

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Options

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Climate Vulnerability Assessment Relies on Asset Inventory and Risk Assessment

Manhole Risk Identification

WWTP Electrical Building At Risk from 100-yr storm surge and 100 cm SLR

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Options

• SLR Hazards = SLR scenario x event• SLR scenarios

40 cm rise – historic trends scenario100 cm rise – precautionary scenario

• EventsMean higher high water (MHHW)10-year flood elevation100-year flood elevation

SLR Impacts on Wilmington NC

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Adaptation Strategies for Improving Flood Resilience

Water Street GI, Onondaga NY

Adaptation Strategies for Stormwater Management and Flood Protection Systems Grey Solutions:

• Raising electrical and mechanical equipment• Sealing wall penetrations• Water tight doors• Adding tide gates to outfalls• Backup generators• Barriers or local surge walls• Adding capacity to the drainage network• Moving flows from one part of the system to another• Emergency response planning

Green Solutions:• Green infrastructure• Coastal wetlands• Renewable energy and Co-generation• Zoning and Land Use Planning

Phasing adaptations to account for uncertainty in projections and risk tolerance

DC Water Blue Plains Flood WallSource: Umair Irfan, eenews.net

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Climate Change Case Studies• NACWA: Confronting Climate Change Report to Congress

• City of Wilmington, NC

• NYCDEP – Wastewater Resiliency Plan

• Boston Water and Sewer Commission

• North Carolina Sea Level Rise Risk Management

• USEPA Climate Adaptation Strategies Guide

• City of Alexandria, VA

• Fairfax VA, Master Plan

• LA Bureau of Sanitation

• California Bay-Delta

• Colorado River Basin Study

• Berwick, ME

• Miami-Dade Water and Sewer Department

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Miami-Dade Water and Sewer Department

Ocean Outfall Legislation Program

MIAMI-DADE COUNTY WATER AND SEWER DEPARTMENT

Preliminary Facility Hardening Plan

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OOL Compliance Projects

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Climate Resilience/Facility Hardening- Objectives and General Approach• Assess projected climate change for key climate variables (sea level rise,

precipitation, wind, inundation due to surge)

• Define critical wastewater assets and risk due to climate change

• Define design criteria to minimize risk

• Develop facility hardening plans and design guidelines for WASD design teams

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Findings/Recommendations:

•Climate Projections •Facility Hardening Design Guidelines

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Precipitation IDF ProjectionsImpacts: Peak Flows and Flooding

WASD Pump Station Peak Flows Are Based on 2-yr Storm:• Historically: 4.5” (SFWMD, 2001)• Updated: 4.9” (2014)• Projected: 5.4” to 6” (2040 to 2100)

Source: CH2M / CLIMsystems, January 2015

4.69

8.26

14.51

4.89

8.03

14.48

4.77

8.57

15.49

4.80

8.68

15.84

4.84

8.82

16.26

4.93

9.18

17.42

4.88

9.00

16.83

5.04

9.60

18.74

0

2

4

6

8

10

12

14

16

18

20

2 10 100

Prec

ipita

tion

(Inch

es)

Return Period (Years)

Updated HistoricalNOAA Atlas 142040 RCP 6.0 50%2040 RCP 8.5 50%2075 RCP 6.0 50%2075 RCP 8.5 50%2100 RCP 6.0 50%2100 RCP 8.5 50%

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2-year 24-hour Precipitation Projections (Design Criteria for Peak Sewer Flows): Implications for PS 187

HorizonRCP, % non-exceedance

2-Year 24-hr Rainfall

(inches)% Changein Rainfall

Peak Flow Rate

(mgd)

% Change in flow

“Current” 4.5 0% 151 0%

2040 RCP6.0/8.5, 50% 4.8 7% 155 3%

2040 RCP8.5, 90% 5.42 20% 167 11%

2075 RCP6.0, 90% 5.58 24% 171 13%

2075 RCP8.5, 90% 6.05 34% 180 19%

5.42 inch, 2040 projection selected based on service life of PS

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Precipitation for 2075: Flooding Impacts, Particularly Coupled with Coastal Storm Surge

100-yr 24hr storm projected to

increase from 14.5” to

17.4” – 20”

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Stressor: Sea Level RiseImpacts: Coastal Flooding and Increased I/I (due higher GW)

Source: SE FL Climate Compact, DRAFT April 2015

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Surge Modeling: Modeled Result

Comparison of Peak Surge Elevation (mNGVD)

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Surge Modeling: Modeled Result

Distribution of boundary Peak Surge Elevations:

Blue:

100yr condition

Red: 100yr

+ 1.23m SLR

Bay

Ocean

Tran

sect

Loc

atio

n123456789

1011121314151617181920212223

0 1 2 3 4 5 6Peak Surge Elevation (mNGVD)

1O2O3O4O5O6O7O8O9O10O11O12O13O14O15O16O17O18O19O20O21O26O29O

CDWWTP CDWWTP

SDWWTP

NDWWTP

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100-yr 100-yr + SLRProjected Stillwater Elevations:

Surge+2075 SLR+2075 Extreme Rainfall

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Findings/Recommendations:

•Climate Projections •Facility Hardening Design Guidelines

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Factors in Setting Risk-based Design Criteria will be used to evaluate cost/benefit of facility hardening

• Planning Horizon to establish the service life:

– 2075 for Critical Long-Term Facilities (e.g. WWTPs)

– 2040 selected for pump station flows (e.g. PS-1)

• Criticality, based on wastewater or pumping facility function, such as:

– Maintenance of facility hydraulics

– Maintenance of equivalent primary treatment, liquid train

– Maintenance of secondary treatment, liquid train

– Maintenance of solids treatment

– Ancillary facilities, such as administration and laboratory buildings

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Factors in Setting Risk-based Design Criteria will be used to evaluate cost/benefit of facility hardening

• Level of protection:

– NOAA (High) SLR curve

– USACE (High) SLR curve

• Level of Freeboard:

– 2 ft for WWTP vs Pump Stations in Coastal Flood Zones, ie. FEMA Zone V (ASCE Standard 24-05/2010 FBC Category IV)

– 1 ft for WWTP vs Pump Stations in Inland Flood Zones, ie. FEMA Zones A, AE (ASCE Standard 24-05/2010 FBC Category III)

• Level of Safety Factor:

– 0 ft for low risk facilities, or

– 1 ft as set by WASD at CDWWTP

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Facility Hardening Costs were Developed for Critical Facilities above Design Flood Elevation

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Adaptation Strategies / Protective Measures

Identified site-specific protective measures to minimize prolonged service interruption and flood risk, while balancing feasibility, resiliency, and cost.

Establish robust design guidelines for future wastewater infrastructure upgrades/designs that assist in mitigating flood risk.

Elevate Equipmenton pads or platforms, to a higher floor, to the roof, or to a new elevated building.

by replacing pumps with submersible pumps and installing watertight boxes around electrical equipment.

Flood-Proof Equipment

Install Static Barrieracross critical flood pathways or around critical areas.

Seal Buildingwith water-tight doors and windows, elevating vents and secondary entrances for access during a flood event.

Sandbag Temporarilyaround doorways, vents, and windows before a surge event.

Install Backup Powervia generators nearby or a plug for a portable generator.

Does not protect equipment but facilitates rapid service recovery.

Source: NYCDEP

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Facility Hardening Costs - WWTPs

Scenario 1 (Design Elevation 16.0 ft)

CDOOL

(Existing Total CDOOL (Existing

Facilities) TotalCDWWTP 4,576,200$ 4,576,200$ 39,947,600$ 39,947,600$ SDWWTP 1,533,000$ 3,980,000$ 5,513,000$ 16,053,000$ 7,650,000$ 23,703,000$ NDWWTP 9,213,000$ 9,213,000$ 14,578,000$ 14,578,000$ Note: 19,302,200$ 78,228,600$ OOL Facility hardening was only estimated for retrofitting existing facilities. New OOL facilities would be hardened to same design criteria.

Scenario 2 (2075 SLR + FB + SF)

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Facility Hardening Design Guidelines for Existing and New WWTP Assets

WWTP Summary of Design Criteria for Hardening against Flooding from Surge, Sea Level Rise and Extreme Storm Events.

Existing WWTP Facility Assets New WWTP Facility Assetsft

NGVD29Basis ft

NGVD29Basis

CDWWTP 16.0 FEMA BFE + 3ft SLR from SEFLCC(2011) +FB +SF

20.3 2075 Surge+1.23m(48")SLR + FB +SF+21”(100-yr, 72-hr rainfall)

SDWWTP 16.0 FEMA BFE + 3ft SLR from SEFLCC(2011) +FB +SF

19.0 2075 Surge+1.23m(48")SLR + FB +SF+21”(100-yr, 72-hr rainfall)

NDWWTP 16.0 Same as CDWWTP and SDWWTP 17.1 2075 Surge+1.23m(48")SLR + FB +SF+21”(100-yr, 72-hr rainfall)

FB= Freeboard = 2.0 ft per ASCE Standard 24-05/2010 FBC Category IV

SF= Safety Factor = 1.0 ft per 2014 MWH study at CDWWTP

SLR = 1.23m = 48" per NOAA High projection for 2075 (USACE High projection is 0.93m)

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Boston Water and Sewer Commission

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Climate Change Risks

• Increased Rainfall

• Increased river flows and flooding

– Charles River, Neponset River and Mystic River may flood areas of the City during storms

• Sea Level Rise and Storm Surge

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Forecasted 10-year, 24-hour Design Storm Volumes and Peak Hourly Intensities

Total Storm Volume(inches)

Peak Hourly Intensity(inches per hour)

Scenario 2035 2060 2100 2035 2060 2100

Medium (B2) 5.55 5.76 6.08 1.76 1.83 1.93

Precautionary (A1FI)

5.60 6.03 6.65 1.78 1.91 2.11

BWSC’s current design standard is 4.8 inches

Climate change is increasing the size and intensity of this design storm and it could be 6.65 inches by 2100.

A recalculation of historical rainfall through 2012 indicated that their 4.8-inch design storm has increased to 5.2 inches

Copyright © 2014 Boston Water and Sewer Commission 980 Harrison Ave. Boston, MA 02119 617-989-7000

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Sea Level Rise Projections

Medium SLR Projections through 2100

Component 2035 2060 2100

Global (feet) 0.79 1.54 3.51

Subsidence (feet) 0.08 0.16 0.30

Regional (feet) 0 0 0

Total (feet) 0.87 1.70 3.81

Precautionary SLR Projections through 2100

Component 2035 2060 2100

Global (feet) 1.21 2.20 6.20

Subsidence (feet) 0.08 0.16 0.30

Regional (feet) 0.23 0.39 0.66

Total (feet) 1.52 2.75 7.16

Source: Vermeer & Rahmstorf, 2009

Return Period (years) Boston (mm) Boston (m) Boston (ft)

2 868 0.87 2.85

5 1,067 1.07 3.50

10 1,194 1.19 3.92

20 1,311 1.31 4.30

50 1,457 1.46 4.78

100 1,562 1.56 5.12

200 1,664 1.66 5.46

500 1,793 1.79 5.88

1,000 1,887 1.89 6.19

Storm Surge Heights held Constant with Today


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Evaluated Flooding Risks to Sewer Systems

• Models of the Storm Drain and Sewer Systems (SWMM) to Calculate Flows Now and in The Future

• 2-dimensional computer models (CH2M’s Flood Modeler-FAST) to map surface flooding due to drainage and storm surge


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Flood Modeler Simulation of Hurricane Sandy

Source: Douglas, et. al. 2013.


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Risks Of Flooding With Sea Level Rise And Storm Surge –Year 2060 with 10-year/24-hour Rainfall

Year 2060 Rain

Sea Level Rise, No Storm Surge

Year 2060 Rain

Sea Level Rise, With Storm Surge


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Pump Station Risk Scoring for Precautionary 2100 Scenario with Storm Surge

0

10

20

30

40

50

60

70

80

90

100

MW

RA C

otta

ge F

arm

(MW

RA00

1)

Sulli

van

Squa

re(2

9JPS

1)

Com

mon

wea

lth A

ve(2

2IPS

1)

MW

RA P

rison

Poi

nt(M

WRA

003)

Caru

so(2

9NPS

4)

Trill

ing

Way

(22M

PS2)

Publ

ic A

lley

701

(21J

PS52

6)

Sum

mer

Str

eet

(22M

PS5)

Uni

on P

ark

(21K

PS2)

MW

RA D

eLau

ri(M

WRA

002)

Sym

phon

y H

all

(21I

PS1)

Aust

in S

tree

t(2

7JPS

1)

Port

Nor

folk

(11L

PS31

6)

TOTA

L RIS

K (0

-100

)

PUMP STATION (FACILITY ID)

Pump Station Total Risk Score for P2100 with Storm Surge (23.50 feet)

BWSC MWRA


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Future Condition Without and With Flood Walls

Precautionary 2060 Precautionary 2060 With Flood Walls

Flooding due to SLR and storm surge only, no rainfall in these calculations


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Drainage Would Still Have to be Addressed

Precautionary 2060 With Flood Walls and 10-year/24-hour rainfall

Additional mitigations beyond flood walls along shorelines would be needed to prevent street flooding should a significant rainfall occur during a storm surge event in the future


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Update Design Storm for Drainage and Conveyance Engineering, Planning and Design

• 10-year/24-hour design storm

– 5.20 inches (instead of 4.80 inches)

– Peak hourly intensity of 1.65 inches per hour

• For life cycles through the year 2100:

– Consider range from 5.55 inches to 6.65 inches

– Depending on the life cycle starting and end date.

• Other Recommendations

– Annual rainfall should range from 50.0 to 55.4 inches by the year 2100

– Apply to CSO control and TMDL planning

– Apply to operations and maintenance planning

– Continually monitor and update rainfall statistics


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Design Flood Elevations (DFEs) to Protect Facilities and Operations

Recommended DFEs for Pump Stations and other Structures

Design Condition

Project Life cycles up to the Year(feet – Boston City Base)

2035 2060 2100

Minimum 18.22 19.06 21.16

Higher Risk Mitigation 18.88 20.11 24.50

Recommended DFEs are based on:• The current MHHW elevation of 11.23 feet• Sea Level Rise• 100-year storm surge of 5.12 feet • 1-foot freeboard

Apply to:• Construction of new infrastructure • Capital improvements to existing infrastructure• Tide gates


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New York City DEP

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NYC Wastewater Resiliency Plan

Strategy: Protect wastewater treatment facilities

Adopt a wastewater facility design standard

Harden pumping stations and wastewater treatment plants

Explore opportunities to expand cogeneration

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Critical Flood Elevations

26th Ward 12.6 13.5 12.9 Brooklyn-Sewer

Bowery Bay 11.6 15.5 13.9 Queens

Coney Island 10.1 15.5 14.0 Brooklyn-Highway

Hunts Point 10.2 17.5 16.0 Bronx

Jamaica None 13.5 11.9 Queens

Newtown Creek 10.0 13.5 12.0 Brooklyn-Highway

North River 9.7 12.5 10.8 Manhattan

Port Richmond 12.1 14.5 12.4 Staten Island

Oakwood Beach 13.1 16.5 14.4 Staten Island

Owls Head 13.5 14.5 13.0 Brooklyn-Highway

Red Hook 11.7 14.5 13.0 Brooklyn-Highway

Rockaway 11.4 14.5 12.9 Queens

Tallman Island 10.1 15.5 13.9 Queens

Wards Island 10.7 17.5 15.8 Manhattan

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Building-Level Risk Assessment

Performed site visits and analyzed each facility for flood pathways and threshold elevations.

Locations identified as at-risk if threshold elevations are below the assigned flood elevation (100-yr ABFE + 30-inches SLR).

Electrical Conduits and ManholesTunnels Grates

Rollup Doors Doorways & Windows Areaways

Common Flood Pathways:

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Asset-Level Risk Assessment

Target Assets include:

• Equipment associated with primary treatment

• Electrical equipment

• Pumps and motors

Target asset identified as at-risk- situated below the assigned flood elevation (100-yr ABFE + 30 inches SLR), and are not submersible.

Electrical assets located underground in the RAS Gallery at 26th Ward WWTP are at risk of flood damage.

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NYCDEP Wastewater Resilience Plan Comparison of Mitigation Costs and Cost of No Action (ie Benefits of Mitigation)

Source: NYCDEPAll estimates are based on AACE Level 5 Cost Estimate guidelines as noted in the NYCDEP BEDC Cost Estimating Manual

Adaptation Cost No Action Cost Risk Avoided Over 50 years

Thank You

Laurens van der Tak, PE, D

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