Wastewater System Overview Brian L. Kubaska, P.E. Assistant Director - - PowerPoint PPT Presentation

Massachusetts Water Resources Authority

Presentation to the

MWRA Advisory Board Operations Committee

Wastewater System Overview

May 7, 2019

Brian L. Kubaska, P.E. Assistant Director of Engineering Operations Division, Engin. & Const. Department

• How the MWRA’s Wastewater Collection System Works
• What are the System Capacity Limitations
• How the System is Impacted by Wet Weather Flows
• MWRA’s ongoing Efforts and Tools to Manage Wet Weather

Flows

Wastewater System Overview Will Cover

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Wastewater Service Area

Over 2.5 million people and 5,500 businesses in 43 communities, send sewage through MWRA sewer system to the Deer Island Treatment Plant (DITP). System expanses over 25 miles E-W & N-S and include about 250 Miles of Sewer

• Pipeline. Wastewater entering

from Ashland takes 13 hours to reach NIHW. MWRA collects and treats an average of 330 million gallons

• f wastewater per day. This is

down from the average design flow of 361 MGD.

• Deer Island Treatment Plant Capacity: 1,270 MGD
• Combined Sewer Overflow Facilities Total Treatment Capacity: 1,006 MGD

– Cottage Farm CSO: 233 MGD – Prison Point CSO: 323 MGD – Somerville Marginal CSO: 150 MGD – Union Park CSO: 300 MGD

• CSO Overflow Storage Tunnels

– South Boston CSO storage tunnel: 18.7 MG – BOS019 storage tunnel: 673,000 gallons – Detention tanks at 3 CSO facilities: 4.5 MG

Wastewater Treatment & Storage Capacity

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MWRA’s System Can Treat or Store up to 2.3 Billion Gallons in a 24 Hour Period

Getting Wastewater to Deer Island Treatment Plant (DITP)

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Three Main Tunnels and One Gravity Sewer Feed DITP

• North Met Relief Tunnel
• 1951, 10-ft, 350MGD Cap
• Boston Main Drainage Tunnel
• 1952, 11.5-ft, 438MGD Cap.
• Inter-Island Tunnel
• 1994, 11.5’, 400MGD Cap.
• North Met. Sewer
• 1890, approx. 8.5-ft,

Capacity limit at Winthrop Terminal 125 MGD

Getting Wastewater to Deer Island Treatment Plant (DITP)

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Headworks Conveyance Capacities to Deer Island Total 1,318 MGD (slightly above treatment capacity of 1.27MGD) Getting Wastewater to DITP

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• Chelsea Creek Headworks:

350MGD

• Ward Street Headworks:

256MGD

• Columbus Park Headworks:

182MGD

• Nut Island Headworks:

360 MGD

• Winthrop Terminal Facility:

125MGD

• Braintree-Weymouth

Intermediate Pump Station: 45MGD

• Choking at CCHW, CPHW & WSHW during significant rain events

Exceeding Tunnel or Headwork Capacity Requires Choking

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How Flows Differ (Northern vs. Southern Collection Systems)

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Southern Collection System

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• Separate Community Systems
• Impacted by long period of wet

weather / high groundwater conditions.

• All Flow Through Nut Island

Headworks or IPS facility

• 8 Southern Pump Stations
• Braintree-Weymouth
• Framingham (wet weather)
• Hingham
• Hough’s Neck
• Intermediate Pump Station
• New Neponset (wet weather)
• Quincy
• Squantum

Southern Collection System Detail

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Contributing Factors to Rainfall Impacts on MWRA Collection System

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• Rainfall Volume (inches),

Intensity (inches/Hour), and Durations (Hours) “Every Storm is Unique”

• Antecedent Conditions

(How wet or dry has it been leading up to the event)

• Spatial Variation in Rainfall

(especially thunder storms)

Rainfall Impacts on MWRA Collection System

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Short Storm Report April 22-23, 2019

Description

• f Events:

Thunderstorms and rain passed though the service area on April 22-23, 2019, dropping 3.22 inches of rain at the Braintree/Weymouth PS, with a peak rainfall rate of 0.83 inches per hour. Rain Gauge@Braintree/Weymouth PS 3.22 Inches High @ 2:24 PM 10.3 FT

Choke Start Date Time End Date Time Length

MGD Cap. Chelsea No 350 Ward St. Yes 4/22/19 6:35PM 4/23/19 2:19AM 7 H 44 M 256 Col.Park Yes 4/22/19 2:59PM 4/23/19 4:51AM 13 H 52 M 182

CSO FACILITIES Facilities Discharges & Duration Sampling

Station Yes/No Hours Minutes Volume Discharged MG NPDES Inf & Eff Min TCR Post-Chlor Max TCR Post Dechlor

CottFarm Yes

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11 5.01 Yes 4.0 *9.6 Prison.Pt. Yes 9 35 41.21 No 4.0 0.0 SomMarg Yes 11 40 9.79 No 8.0 0.0 Union Pk Yes 7 58 6.52 No 4.0 1.0 BOS019 Yes 1 17 * = NPDES Sample Volume Stored In Gallons

Brookline Gate: Open 3:06PM 4/22/19

BOS019 Yes 683,328

Closed 3:32AM 4/23/19

S.B.Tunnel Yes 8,520,000 Other Monitored CSOs

CSO Facility Activation Levels

Location Activated Duration Max Height Over Weir Facility Activation Elevation

SOM205A Yes 5 H 22 M 1.14 FT Cottage Farm 98.0 CAM017 No Prison Point 104.0

MWR 018, 019, 020

No Somerville 108.0

MWR 003

No Union Park 98.8

Wet Weather Pumping Activated Start Date Time Stop Date Time Length

Framingham: Yes 4/22/19 8:28PM still on line New Neponset: Yes 4/22/19 7:10PM still on line

This is an informational report, data subject to change. **multiple starts and stops form revised 12/2/10

Recent Storm of April 22-23

• Rainfall mostly occurred over 12

hours (4/22 Noon – Midnight)

• 1-2 year recurrence interval

Wet period leading up to storm:

• March Total Rainfall = 3-4 inches
• April Total Rainfall through 21st =

2.5inches

MEASURED AREA RAINFALL Hayes PS: 1.63 inches Columbus Pk HW: 2.60 inches Ward Street HW: 2.68 inches Braintree/Wey PS: 3.22 inches

New Neponset PS 2.51 inches

South System Storm Response (NIHW)

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0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 50 100 150 200 250 300 0:00 2:00 4:00 6:00 8:00 10:00 12:00 14:00 16:00 18:00 20:00 22:00 0:00 2:00 4:00 6:00 8:00 10:00 12:00 14:00 16:00 18:00 20:00 22:00 0:00 2:00 4:00 6:00 8:00 10:00 12:00 14:00 16:00 18:00 20:00 22:00

PRECIPITATION (INCHES PER HOUR) FLOW (MGD) TIME

NUT ISLAND HEADWORKS

Apr 21-23 Rainfall Apr 21-23 Flow

South System Storm Response (BWRPS)

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0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 5 10 15 20 25 30 0:00 2:00 4:00 6:00 8:00 10:00 12:00 14:00 16:00 18:00 20:00 22:00 0:00 2:00 4:00 6:00 8:00 10:00 12:00 14:00 16:00 18:00 20:00 22:00 0:00 2:00 4:00 6:00 8:00 10:00 12:00 14:00 16:00 18:00 20:00 22:00

PRECIPITATION (INCHES PER HOUR) FLOW (MGD) TIME

BRAINTREE-WEYMOUTH REPLACEMENT PS

Apr 21-23 Rainfall Apr 21-23 Flow

Northern Collection System

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• 4 Combined Sewer Community

Systems with remaining separate

• Immediately Impacted by

Rainfall

• 4 Major Tributary Areas
• 6 Northern Pump Stations: Alewife,

Caruso, Delauri, Hayes, Prison Point (dry weather), Wiggins

• 4 CSO Facilities: Prison, Cottage,

Union Park, Somerville

• 2 CSO Storage Facilities: South

Boston, BOS019

Chealsea Creek Headwork & Screenhouse / Caruso PS Area

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North System Storm Response (CCHW)

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0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 50 100 150 200 250 300 350 0:00 2:00 4:00 6:00 8:00 10:00 12:00 14:00 16:00 18:00 20:00 22:00 0:00 2:00 4:00 6:00 8:00 10:00 12:00 14:00 16:00 18:00 20:00 22:00 0:00 2:00 4:00 6:00 8:00 10:00 12:00 14:00 16:00 18:00 20:00 22:00

PRECIPITATION (INCHES PER HOUR) FLOW (MGD) TIME

CHELSEA CREEK HEADWORKS

Apr 21-23 Rainfall Chelsea Creek Flow Nut Island Flow

North System Storm Response (Caruso PS)

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0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 10 20 30 40 50 60 70 80 90 100 0:00 2:00 4:00 6:00 8:00 10:00 12:00 14:00 16:00 18:00 20:00 22:00 0:00 2:00 4:00 6:00 8:00 10:00 12:00 14:00 16:00 18:00 20:00 22:00 0:00 2:00 4:00 6:00 8:00 10:00 12:00 14:00 16:00 18:00 20:00 22:00

PRECIPITATION (INCHES PER HOUR) FLOW (MGD) TIME

CARUSO PS

Apr 21-23 Rainfall Apr 21-23 Flow

Columbus Park Headworks / South Boston Area

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North System Storm Response (CPHW)

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0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 50 100 150 200 250 300 0:00 2:00 4:00 6:00 8:00 10:00 12:00 14:00 16:00 18:00 20:00 22:00 0:00 2:00 4:00 6:00 8:00 10:00 12:00 14:00 16:00 18:00 20:00 22:00 0:00 2:00 4:00 6:00 8:00 10:00 12:00 14:00 16:00 18:00 20:00 22:00

PRECIPITATION (INCHES PER HOUR) FLOW (MGD) TIME

COLUMBUS PARK HEADWORKS

Apr 21-23 Rainfall Columbus Park Flow Nut Island Flow

North System Storm Response (South Boston Tunnel Volume)

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0.00 0.10 0.20 0.30 0.40 0.50 0.60 0.70 0.80 1 2 3 4 5 6 7 8 9 0:00 2:00 4:00 6:00 8:00 10:00 12:00 14:00 16:00 18:00 20:00 22:00 0:00 2:00 4:00 6:00 8:00 10:00 12:00 14:00 16:00 18:00 20:00 22:00 0:00 2:00 4:00 6:00 8:00 10:00 12:00 14:00 16:00 18:00 20:00 22:00

PRECIPITATION (INCHES PER HOUR) VOLUME STORED (MG) TIME

SOUTH BOSTON CSO TUNNEL

Apr 21-23 Rainfall Current Tunnel Volume

Somerville / Cambridge Area

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North System Storm Response (Prison Point)

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0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 20 40 60 80 100 120 140 160 180 0:00 2:00 4:00 6:00 8:00 10:00 12:00 14:00 16:00 18:00 20:00 22:00 0:00 2:00 4:00 6:00 8:00 10:00 12:00 14:00 16:00 18:00 20:00 22:00 0:00 2:00 4:00 6:00 8:00 10:00 12:00 14:00 16:00 18:00 20:00 22:00

PRECIPITATION (INCHES PER HOUR) FLOW (MGD) ELEVATION (FEET MDC) TIME

PRISON POINT CSO

Apr 21-23 Rainfall Prison Point Flow Inlet Structure Level

Ward Street Headwork / Cottage Area

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North System Storm Response (WSHW)

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0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 50 100 150 200 250 300 0:00 2:00 4:00 6:00 8:00 10:00 12:00 14:00 16:00 18:00 20:00 22:00 0:00 2:00 4:00 6:00 8:00 10:00 12:00 14:00 16:00 18:00 20:00 22:00 0:00 2:00 4:00 6:00 8:00 10:00 12:00 14:00 16:00 18:00 20:00 22:00

PRECIPITATION (INCHES PER HOUR) FLOW (MGD) TIME

WARD STREET HEADWORKS

Apr 21-23 Rainfall Ward Street Flow Nut Island Flow

Combined Sewer Connections to MWRA’s System

• Combined Sewers exist

within Boston, Cambridge, Somerville & Chelsea

• 57 CSO Regulators split flow

between MWRA or Community Sewers and CSO

• verflow pipes.
• There are 44 permitted CSO

discharges.

• Some Regulators overflow to

pipes tributary to CSO treatment facilities.

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Dry Weather – All Incoming Flow Diverted to Interceptor

Tide Gate Overflow Weir Receiving Water (Ocean/River) Incoming Flow Underflow to Interceptor Dry Weather Flow

Start of Wet Weather Flow – All Incoming Flow Diverted to Interceptor, Weir Prevents Overflow

Tide Gate Overflow Weir Receiving Water (Ocean/River) Incoming Flow Underflow to Interceptor Initial Wet Weather Flow

Additional Wet Weather Flow – Water Level Exceeds Weir, Tide Gate Opens, Overflow Occurs

Underflow to Interceptor Incoming Flow Overflow Additional Wet Weather Flow

Wet Weather Flow at High Tide – Tide Level Prevents Discharge

Underflow to Interceptor Incoming Flow High Tide in Receiving Water Wet Weather Flow

Wet Weather Flow at High Tide – Higher Water Level in Regulator Needed to Discharge against the Tide

Underflow to Interceptor Incoming Flow Overflow

CSO Improvements Since MWRA begain

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Dramatic Improvements In Bacterial Water Quality

Average Enterococcus counts in Boston Harbor 1987-1998 (Before Secondary Treatment and South System transfer) Elevated bacteria around outfalls, rivers, Inner Harbor, shoreline 1999 - 2003 (After Secondary Treatment and New Outfall) Most of Harbor well within swimming criteria, most remaining problems in rivers

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Long Term Control Plan CSO Reduction Efforts

• Boston, Cambridge,

Chelsea and Somerville have combined sewer systems that connect to MWRA's sewer system.

• MWRA & the CSO

Communities have spent over $1B during the last 30 – years to reduce or eliminate CSO discharges.

Ongoing CSO Post-Construction Monitoring and Performance Assessment (Contract 7572)

• Demonstrate whether CSO

activations and volumes are consistent with the Long Term Control Plan.

• Demonstrate whether Water

Quality Standards are met at remaining CSOs to the Charles River and Alewife Brook/Upper Mystic River.

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Completed and Continuing Work

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• CSO structure inspections
• Temporary metering at all potentially active CSO regulators
• Collection of rainfall data
• Quantification of CSO discharges from meter data, and correlation

to rainfall

• Site specific CSO discharge investigations
• Hydraulic model updates and improved model calibration using

2018 meter data

• Second of five planned semiannual progress reports issued May

3, 2019

• Required to Show System Performance Against the LTCP
• Need to be able to Perform Model Simulation of “Typical Year

Rainfall”

• Will be used by MWRA to further evaluate and improve system

performance.

Hydraulic Model Update and Calibration

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What is the Hydraulic Model of Collection System?

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Example of Model Subcatchments

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Model Conduit Runoff Subcatchment tributary to model node

Influent from Rutherford Ave. Influent from Boston Marginal Conduit & Cambridge Marginal Conduit Treated effluent to Upper Inner Harbor Dry weather flow/tank dewatering to Cambridge Branch Sewer Sluice Gates Bar Screens Tanks Weirs Effluent Pumps DWF Pumps

Model Details for Prison Point CSO Pump Station

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Questions???