Climate Risk and Resilience Planning for Wastewater Infrastructure: Miami-Dade s Facility Hardening Planning Process and Design Guidelines

Transcription

1 Climate Risk and Resilience Planning for Wastewater Infrastructure: Miami-Dade s Facility Hardening Planning Process and Design Guidelines Bertha Goldenberg 1, Virginia Walsh 1, Laurens van der Tak 2, 1: Miami-Dade Water and Sewer Department; 2: CH2M 5 th University of Florida Water Institute Symposium Panel: Actionable Science for Water Resources Management Planning and Decision Making February 16, 2016

2 Acknowledgements Bertha M. Goldenberg, Miami-Dade Water and Sewer Department, FL Dr. Virginia Walsh, Miami Dade Water & Sewer Department, FL Dr. Doug Yoder, Miami Dade Water & Sewer Department, FL Dr. Peter B. Urich, CLIMsystems Ltd, NZ Evelio Agustin, CH2M, FL Matt Alvarez, CH2M, FL Chris Niforatos, CH2M, FL Dr. Say-Chong Lee, CH2M, FL Paul Robinson, CH2M, CA Dr. Swamy Pati, CH2M, FL

3 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

4 Findings/Recommendations: Climate Projections Facility Hardening Design Guidelines

5 Precipitation IDF Projections Impacts: 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) Precipitation (Inches) Updated Historical NOAA Atlas RCP % RCP % RCP % RCP % 2100 RCP % RCP % Return Period (Years) Source: CH2M / CLIMsystems, January 2015

6 2-year 24-hour Precipitation Projections (Design Criteria for Peak Sewer Flows): Implications for PS 187 Horizon RCP, % nonexceedance 2-Year 24- hr Rainfall (inches) % Change in 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% % % 2075 RCP6.0, 90% % % 2075 RCP8.5, 90% % % 5.42 inch, 2040 projection selected based on service life of PS 6

7 Precipitation for 2075: Flooding Impacts, Particularly Coupled with Coastal Storm Surge 100-yr storm projected to increase from 14.5 to * Representative Concentration Pathways (RCP) 7

8 Sea Level Rise Impacts: Coastal Flooding and Increased I/I (due to higher GW and rainfall) Surge and inundation modeling run with 1.23 m (48 ) SLR (2075 NOAA High). Surge modeling also run with 0.93 m (37 ) SLR (2075 USACE High), to test linearity assumption if smaller SLR design criteria are selected based on risk. All SLR scenarios in risk cost analysis are based on 1.23m (48 ), so 11 higher than 2075 USACE high projection for Source: SE FL Climate Compact, DRAFT April 2015

9 Surge Modeling: Comparison of Peak Surge Elevation: modeled with MIKE21 vs observations for Hurricane Andrew (mngvd)

10 Hurricane Andrew Storm Surge Impacts: Coastal Flooding Hurricane Andrew (1992) flooding extents WASD Critical Facilities Source: CH2M, DRAFT 2015

11 Storm Surge: 2075 Sea Level Rise (4 ft) and Extreme Rainfall Impacts: Coastal Flooding 100-yr 100-yr + SLR 11

12 Findings/Recommendations: Climate Projections Facility Hardening Design Guidelines

13 Factors in Setting Risk-based Design Criteria 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 13

14 Factors in Setting Risk-based Design Criteria 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 14

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

16 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 Equipment on pads or platforms, to a higher floor, to the roof, or to a new elevated building. Flood-Proof Equipment by replacing pumps with submersible pumps and installing watertight boxes around electrical equipment. Install Static Barrier across critical flood pathways or around critical areas. Seal Building with water-tight doors and windows, elevating vents and secondary entrances for access during a flood event. Sandbag Temporarily around doorways, vents, and windows before a surge event. Install Backup Power via generators nearby or a plug for a portable generator. Does not protect equipment but facilitates rapid service recovery. Source: NYCDEP

17 Facility Hardening Costs - WWTPs Scenario 1 (Design Elevation 16.0 ft) Scenario 2 (2075 SLR + FB + SF) CD OOL (Existing Total CD OOL (Existing Facilities) Total CDWWTP $ 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.

18 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. ft NGVD29 Existing WWTP Facility Assets Basis ft NGVD29 New WWTP Facility Assets Basis CDWWTP 16.0 FEMA BFE + 3ft SLR from SEFLCC(2011) +FB +SF SDWWTP 16.0 FEMA BFE + 3ft SLR from SEFLCC(2011) +FB +SF Surge+1.23m(48")SLR + FB +SF+21 (100-yr, 72-hr rainfall) Surge+1.23m(48")SLR + FB +SF+21 (100-yr, 72-hr rainfall) NDWWTP 16.0 Same as CDWWTP and SDWWTP 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)