Preparing Boston’s Water and Sewer Systems for Future Design Storms

John P Sullivan, P.E.Boston Water and Sewer CommissionNovember 22, 2019

DISCUSSION TOPICS

Present Condition & Upgrades to Existing Systems

Improved Stormwater and Inundation Modelling

Upland Control of Stormwater

Coastal Stormwater Discharge Analysis

Smart Sewers

STORMWATER

WATERSHEDS

TIDE GATES

MOUNTED ON

SEA WALL

NEW TIDE GATES

MT. WASHINGTON AVE

WHY ARE TIDE

GATES

IMPORTANT

Boston Stormwater

Management Total Maximum Daily Load (2007)

Phosphorus: Upper & Middle/Lower Charles River

Consent Decree (2012) Update Stormwater Model

Create BMP Implementation Plan

Implement 3 Pilot Green Infrastructure/Low Impact Development

(“GI/LID”) Projects

Central Square, Audubon Circle, City Hall Plaza

GI/LID Obstacles in Boston

Commission does not own land for GI/LID

• Need to work with other agencies and entities– Department of Public Works

– Department of Transportation

– Boston Parks and Recreation Department

– Boston Public Schools

– Boston Planning and Development Agency

• Need to work with private property owners

• Need complete understanding of who is responsible for continued maintenance

Year 2060 RainSea Level Rise, With Storm Surge

Today’s Extreme High Tides

Source: CHI Water

Develop improved models to show extent andduration of inundation in major wet weather

events

IMPROVED INUNDATION MODELLING

2030 STORMS

GARR SEPTEMBER 9TH,1999, W/ 2030 SLR

GARR JUNE 12TH,1998, W/ 2030 SLR

GARR AUGUST 2ND, 2017, W/ 2030 SLR

AIRMASS 2-YEAR W/ 2030 SLR

AIRMASS 10-YEAR W/ 2030 SLR

FRONTAL 10-YEAR W/ 2030 SLR

TROPICAL 10-YEAR W/ 2030 SLR

FRONTAL 50-YEAR W/ 2030 SLR

NOR’EASTER 10-YEAR W/ 2030 SLR

NOR’EASTER 50-YEAR W/ 2030 SLR

NOR’EASTER 50-YEAR W/ 2030 SLR + 100-YEAR STORM SURGE

TROPICAL 100-YEAR W/ 2030 SLR +100-YEAR STORM SURGE

NOR’EASTER 100-YEAR W/ 2030 SLR + 100-YEAR STORM SURGE

TROPICAL 500-YEAR W/ 2030 SLR + 500-YEAR STORM SURGE

2070 STORMS

GARR SEPTEMBER 9TH,1999, W/ 2070 SLR

GARR JUNE 12TH,1998, W/ 2070 SLR

GARR AUGUST 2ND, 2017 W/ 2070 SLR

AIRMASS 2-YEAR W/ 2070 SLR

AIRMASS 10-YEAR W/ 2070 SLR

FRONTAL 10-YEAR W/ 2070 SLR

TROPICAL 10-YEAR W/ 2070 SLR

FRONTAL 50-YEAR W/ 2070 SLR

NOR’EASTER 50-YEAR W/ 2070 SLR + 100-YEAR STORM SURGE

NOR’EASTER 100-YEAR W/ 2070 SLR + 500-YEAR STORM SURGE

TROPICAL 100-YEAR W/ 2070 SLR +100-YEAR STORM SURGE

TROPICAL 500-YEAR W/ 2070 SLR + 500-YEAR STORM SURGE

GARR – Gauge-Adjusted Radar Rainfall

Airmass – summer thunderstorm

Frontal Storms – advancing warm or cold airmasses

Tropical – Hurricanes

Nor’easters – Nor’easters

0

2

4

6

8

10

12

14

1948 1953 1958 1963 1968 1973 1978 1983 1988 1993 1998 2003 2008 2013

Rain

fall, in

Date

Twenty Largest Storms from 1948 to 2017using Logan Airport and BWSC Rain Gages

rainfall old 10 yr storm atlas 14 storm

Old 10 yr / 24 hr

Design Storm = 4.86 in.

Atlas 14 - 10 yr / 24 hr

Design Storm = 5.15 in.

NEW

INUNDATION

ANALYSIS

IMPROVED

ESTIMATES OF

FUTURE FLOODING

DEPTHS AND

EXTENTS

DETAILED FLOOD DEPTHS

AVAILABLE FOR

EXTREMELY SMALLER

SUB-AREAS

IMPROVED VISUALS FOR ENHANCED PUBLIC

UNDERSTANDING

STORMWATER

DETENTION

IDENTIFY AREAS TO DETAIN

STORMWATER DURING EXTREME

EVENTS AND POSSIBLY PROVIDE

TREATMENT DURING MINOR EVENTS

TOP AREAS FOR

POSSIBLE

STORMWATER

DETENTION

STORMWATER

DETENTION WITH

PHOSPHOROUS

TREATMENT

CAPABILITIES

FORT

POINT

CHANNEL

STORAGE

Smart Sewers

CONTINUING FORWARD

• INVESTIGATE PIPES THAT NEED TIDE GATES

• COORDINATE WITH CITY ON BARRIERS AND THE NEED FOR TIDE GATES TO ENSURE COMMISSION PIPES DO NOT ACT

AS BY-PASS TO BARRIER

• INVESTIGATE CATCH BASINS THAT MAY DISCHARGE TO COMBINED SYSTEMS IN AREAS THAT MAY BE PRONE TO

INUNDATION

• CONTINUE TO COORDINATE WITH CITY ON CLIMATE CHANGE STRATEGIES

• INVESTIGATE AREAS TO STORE STORMWATER DURING LARGE EVENTS

• CREATE INUNDATION MODEL TO IDENTIFY AREAS: THAT MAY NEED TO BE EVACUATED IN EXTREME EVENTS; DISRUPT

TRANSPORTATION; IMPACT POTENTIAL EVACUATION CENTERS; IMPACT HEALTH CARE FACILITIES

• INSPECT TIDE GATES AND OUTFALLS

• MONITOR RAIN DATA TO GATHER INFORMATION ON STORM EVENTS AND INTENSITY

• CONDUCT MONITORING ON DORCHESTER INTERCEPTOR

• IDENTIFY STRATEGIC MONITORING LOCATIONS AND INSTALL METERS TO GATHER INFORMATION ON HOW SYSTEM

RESPONDS TO CHANGING RAIN EVENTS