Climate Adaptation Challenges for Boston s Water and Sewer Systems

National Association of Flood & Stormwater Management Agencies Climate Adaptation Challenges for Boston s Water and Sewer Systems John P Sullivan P.E. October 15,2014

Boston 1630

Boston 1630-2012

Boston 2100?

Boston Water and Sewer Commission Provides water and sewer services to more than one million residents, workers, students, shoppers, conventioneers, hospital patients and visitors each and every day. Owns and operates a system for the distribution of potable water to approximately 88,000 active accounts throughout the City of Boston. Owns and operates a system for the collection and transport of wastewater and storm drainage in the City of Boston. Copyright 2014 Boston Water and Sewer Commission 980 Harrison Ave. Boston, MA 02119 617-989-7000

BWSC Infrastructure: Wastewater and Storm Drainage Systems 1,455 linear miles of sewers: 622 miles of sanitary sewers 595 miles of storm drains 235 miles of combined sewers 3 miles of combined sewer overflow outfalls 8 pumping stations 35,934 catch basins 47,413 manholes 174 combined sewer regulators 430 CSO and stormwater outfalls 202 tide gates 8 rainfall gauges Tide gates on CSO outfalls in Fort Point Channel prevent high tides from entering combined sewers Copyright 2014 Boston Water and Sewer Commission 980 Harrison Ave. Boston, MA 02119 617-989-7000

Climate Change Risks Increased Rainfall Average annual rainfall will increase Storms will become more intense Storm drains and combined sewer systems will have to convey more runoff 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 Storm surge with hurricanes and nor easters will flood city streets now. Sea level rise will increase the elevation of the storm surge and the areas that will flood. Sewer systems may be inundated in flooded areas. Pump stations may be flooded and disabled. More streets may be flooded if the water has nowhere to go. Copyright 2014 Boston Water and Sewer Commission 980 Harrison Ave. Boston, MA 02119 617-989-7000

Sewer and River Monitoring Systems Sewer Metering: Six permanent metering stations located near the downstream end of BWSC s sanitary sewer system prior to discharge to the MWRA system. More than 20 other metering stations moving around the City to identify problems and plan solutions. Characterize flow throughout the system and determine how it reacts to climate change conditions. Identify and eliminate extraneous flow to increase capacity to convey increased storm flows. River Data Analysis Rivers are regulated by dams and water levels by pumping. As annual rainfall and the intensity of storms increase, the frequency of river flooding may increase as well. Account for more frequent and higher future river stages in planning. Copyright 2014 Boston Water and Sewer Commission 980 Harrison Ave. Boston, MA 02119 617-989-7000

Climate Change Scenarios for Planning Using information consistent with the IPCC and National Climate Assessments Managing the uncertainty of the risks by considering at the range of climate change scenarios Looking ahead 25, 50 and 100 years in the future Forecasted Greenhouse Gas Emissions Forecasted Sea Level Rise Source: Vermeer & Rahmstorf, 2009 Copyright 2014 Boston Water and Sewer Commission 980 Harrison Ave. Boston, MA 02119 617-989-7000

Increased Monitoring

Changes in Rainfall Average annual rainfall is increasing, it is now about 52 inches per year could be 65 inches by 2100. The Commission designs its storm sewers and combined sewers based on a design storm. The design storm is statistically calculated based on historical data. The current design storm is 4.8 inches in 24 hours, which conveys 90% of daily storms in an average year. Climate change is increasing the size and intensity of this statistical storm and it could be 6.65 inches by 2100. Copyright 2014 Boston Water and Sewer Commission 980 Harrison Ave. Boston, MA 02119 617-989-7000

Evaluating Flooding Risks to Infrastructure Running 2-dimensional computer inundation models of current and future storm surge conditions Identifying pump stations and other critical BWSC infrastructure at risk of inundation Copyright 2014 Boston Water and Sewer Commission 980 Harrison Ave. Boston, MA 02119 617-989-7000

Boston Harbor Sea Level Rise Trend Historical sea level rise is 0.1 inch/year Sea levels could rise from 3.8 to 7.2 feet by 2100. Copyright 2014 Boston Water and Sewer Commission 980 Harrison Ave. Boston, MA 02119 617-989-7000

Risks Of Flooding With Sea Level Rise And Storm Surge Year 2060 Year 2060 Rain Sea Level Rise, No Storm Surge Year 2060 Rain Sea Level Rise, With Storm Surge Copyright 2014 Boston Water and Sewer Commission 980 Harrison Ave. Boston, MA 02119 617-989-7000

Risks Of Flooding With Sea Level Rise And Storm Surge Year 2100 Year 2100 Rain Sea Level Rise, No Storm Surge Year 2100 Rain Sea Level Rise, with Storm Surge Copyright 2014 Boston Water and Sewer Commission 980 Harrison Ave. Boston, MA 02119 617-989-7000

Boston Harbor Hotel

Boston Back Bay

Mean High High Water +2.5 feet Projected to occur by mid-century Similar to flooding from Hurricane Sandy 28

Mean High High Water +5 Projected to occur by mid- to late-century Equivalent to flooding from Hurricane Sandy if it hit during high tide 29

Mean High High Water + 7.5 Could occur by late-century Charles River Dam is over-topped Sandy at mid-century 30

High Tide, 2011 Long Wharf Winter Storm Hercules, 2014 Christopher Columbus Park Hurricane Sandy, 2012 Long Wharf & Morrisey Blvd 31

Communication with the Public

The Beginning