Massachusetts Water Resources Authority Presentation to the MWRA Advisory Board Operations Committee Wastewater System Overview Brian L. Kubaska, P.E. Assistant Director of Engineering Operations Division, Engin. & Const. Department May 7, 2019
Wastewater System Overview Will Cover • 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 2
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 of wastewater per day. This is down from the average design flow of 361 MGD. 3
Wastewater Treatment & Storage Capacity • 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 MWRA’s System Can Treat or Store up to 2.3 Billion Gallons in a 24 Hour Period 4
Getting Wastewater to Deer Island Treatment Plant (DITP) 5
Getting Wastewater to Deer Island Treatment Plant (DITP) 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 6
Getting Wastewater to DITP Headworks Conveyance Capacities to Deer Island Total 1,318 MGD (slightly above treatment capacity of 1.27MGD) • 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 7
Exceeding Tunnel or Headwork Capacity Requires Choking • Choking at CCHW, CPHW & WSHW during significant rain events 8
How Flows Differ (Northern vs. Southern Collection Systems) 9
Southern Collection System • 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 10
Southern Collection System Detail 11
Contributing Factors to Rainfall Impacts on MWRA Collection System • 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) 12
Rainfall Impacts on MWRA Collection System Short Storm Report April 22-23, 2019 Recent Storm of April 22-23 Description of Events: • Rainfall mostly occurred over 12 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 hours (4/22 Noon – Midnight) 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 • 1-2 year recurrence interval Choke Time Start Date End Date Time Length MGD Cap. Chelsea No 350 4/22/19 6:35PM 4/23/19 2:19AM 7 H 44 M Ward St. Yes 256 4/22/19 2:59PM 4/23/19 4:51AM 13 H 52 M Wet period leading up to storm: Col.Park Yes 182 • CSO FACILITIES March Total Rainfall = 3-4 inches Facilities Discharges & Duration Sampling April Total Rainfall through 21 st = • Volume NPDES Inf & Station Yes/No Hours Minutes Min TCR Post-Chlor Max TCR Post Dechlor Discharged MG Eff 2.5inches 2 11 Yes 4.0 *9.6 CottFarm Yes 5.01 9 35 No 4.0 0.0 Prison.Pt. Yes 41.21 11 40 No 8.0 0.0 SomMarg Yes 9.79 7 58 No 4.0 1.0 Union Pk Yes 6.52 1 * = NPDES Sample BOS019 Yes 17 MEASURED AREA RAINFALL Brookline Gate: Open Volume Stored In Gallons 3:06PM 4/22/19 Hayes PS: 1.63 inches 683,328 Closed 3:32AM 4/23/19 BOS019 Yes Columbus Pk HW: 2.60 inches S.B.Tunnel 8,520,000 Yes Ward Street HW: 2.68 inches CSO Facility Activation Levels Other Monitored CSOs Braintree/Wey PS: 3.22 inches Max Height Over Facility Activation Elevation Location Activated Duration Weir New Neponset PS 2.51 inches 5 H 22 M Cottage Farm 98.0 SOM205A Yes 1.14 FT CAM017 Prison Point 104.0 No Somerville 108.0 MWR 018, 019, 020 No Union Park No 98.8 MWR 003 Wet Weather Pumping Activated Start Date Time Stop Date Time Length Yes 4/22/19 8:28PM still on line Framingham: New Yes 4/22/19 7:10PM still on line Neponset: This is an informational report, data subject to change. **multiple starts and stops 13 form revised 12/2/10
FLOW (MGD) 100 150 200 250 300 50 0 0:00 2:00 4:00 South System Storm Response (NIHW) 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 NUT ISLAND HEADWORKS 10:00 TIME 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 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 PRECIPITATION (INCHES PER HOUR) Apr 21-23 Flow Apr 21-23 Rainfall 14
FLOW (MGD) 10 15 20 25 30 0 5 0:00 2:00 4:00 South System Storm Response (BWRPS) 6:00 8:00 10:00 12:00 14:00 16:00 18:00 20:00 22:00 0:00 2:00 BRAINTREE-WEYMOUTH REPLACEMENT PS 4:00 6:00 8:00 10:00 TIME 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 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 PRECIPITATION (INCHES PER HOUR) Apr 21-23 Flow Apr 21-23 Rainfall 15
Northern Collection System • 6 Northern Pump Stations: Alewife, • 4 Combined Sewer Community Caruso, Delauri, Hayes, Prison Point Systems with remaining (dry weather), Wiggins separate • • Immediately Impacted by 4 CSO Facilities: Prison, Cottage, Rainfall Union Park, Somerville • 4 Major Tributary Areas • 2 CSO Storage Facilities: South Boston, BOS019 16
Chealsea Creek Headwork & Screenhouse / Caruso PS Area 17
North System Storm Response (CCHW) CHELSEA CREEK HEADWORKS 350 0.8 0.7 300 0.6 250 PRECIPITATION (INCHES PER HOUR) 0.5 200 FLOW (MGD) 0.4 Apr 21-23 Rainfall Chelsea Creek Flow 150 Nut Island Flow 0.3 100 0.2 50 0.1 0 0 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 TIME 18
FLOW (MGD) 100 10 20 30 40 50 60 70 80 90 0 0:00 2:00 4:00 North System Storm Response (Caruso PS) 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 TIME 12:00 14:00 CARUSO PS 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 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 PRECIPITATION (INCHES PER HOUR) Apr 21-23 Flow Apr 21-23 Rainfall 19
Columbus Park Headworks / South Boston Area 20
FLOW (MGD) 100 150 200 250 300 50 0 0:00 2:00 4:00 North System Storm Response (CPHW) 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 COLUMBUS PARK HEADWORKS 8:00 10:00 TIME 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 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 PRECIPITATION (INCHES PER HOUR) Nut Island Flow Columbus Park Flow Apr 21-23 Rainfall 21
North System Storm Response (South Boston Tunnel Volume) SOUTH BOSTON CSO TUNNEL 9 0.80 8 0.70 7 0.60 PRECIPITATION (INCHES PER HOUR) 6 VOLUME STORED (MG) 0.50 5 0.40 Apr 21-23 Rainfall 4 Current Tunnel Volume 0.30 3 0.20 2 0.10 1 0 0.00 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 0:00 2:00 4:00 6:00 8:00 10:00 12:00 14:00 16:00 18:00 20:00 22:00 TIME 22
Somerville / Cambridge Area 23
FLOW (MGD) ELEVATION (FEET MDC) 100 120 140 160 180 20 40 60 80 0 0:00 North System Storm Response (Prison Point) 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 PRISON POINT CSO TIME 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 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 PRECIPITATION (INCHES PER HOUR) Inlet Structure Level Prison Point Flow Apr 21-23 Rainfall 24
Ward Street Headwork / Cottage Area 25
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