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TOWN OF BELMONT

Presentation to the Board of Selectman outlining causes, design solutions, timeline, funding, and collaboration with Cambridge on Winn’s Brook sewer overflow mitigation project.

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TOWN OF BELMONT

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  1. TOWN OF BELMONT Presentation to the BOARD OF SELECTMAN December 7, 2009 WINN’S BROOK SEWER OVERFLOW MITIGATON

  2. Presentation Objectives • Project background • Causes of sewer overflows • Conceptual design and modeling • Final Design • Opinion of probable construction cost • Funding • Schedule

  3. Winn’s Brook Area • Low lying area in Northeast Belmont • Close proximity to MWRA connection on Flanders Road • 85% of Belmont tributary to Flanders Road • Extensive upstream sewer system • Two different sewer subsystems

  4. The Problem Periodic sanitary sewer overflows and backups into basements of homes in the Winn’s Brook Area

  5. Reported Backups

  6. Increased Hydraulic Grade Line Creates Sewer Backups HGL

  7. Causes of an IncreasedHydraulic Grade Line (HGL) • System Capacity Constraints • Infiltration/Inflow in Belmont • 2007 Flow Monitoring Program • Elevated downstream HGL • Flanders Road Connection to the MWRA

  8. Project Timeline • 2005 – Geographical Information System (GIS) • InfoWorks Sewer Model • Used by Cambridge & MWRA • 2006 – Winn’s Brook Area Study • 2007 – State (SRF) Loan Application • 2009 – Final Design

  9. Solution Constraints • No transference of the problem to Cambridge or significant increase in flow to MWRA interceptor • No transference of problem within Belmont • Continued I/I reduction will be required • 2009 Sewer System Evaluation Survey

  10. Mitigation Concepts • Increase sewer capacity • Flow diversion • Storage • Isolation and Pumping • I/I Removal • 13 Mitigation Alternatives Modeled

  11. Collaboration with the City of Cambridge • Cambridge integrated Belmont’s model into the complete downstream system model • Key in refining the selected Alternative • NO ADVERSE IMPACT TO CAMBRIDGE • NO INCREASED CSO RELEASE (MWRA)

  12. Selected Alternative No. 12 • Isolate Winn’s Book Area during elevated HGL conditions • New sewers and diversion structures • Divert flow to an off-line pumping station • Divert upstream flow • Dean Street • Leonard Street & Alexander Ave. • In-line storage conduit (Dean St) • Restricted discharge • 15% Townwide I/I reduction

  13. Predicted Impact at Key Manholes Outside Winn’s Brook Area(MH rim to HGL)

  14. Flanders RoadPredicted Discharge

  15. Opinion of Probable Construction Cost - Contract 3

  16. Project Funding • $11.6 M State Revolving Loan (SRF) • ARRA “Shovel Ready” Projects • Contract 1 – Wellington Brook Area Sewer and Storm Drain Improvements • Contract 2 – Stony Brook Road and Woodbine Road Pump Station Replacement • Contract 3 – Winn’s Brook Area Sewer Overflow Mitigation

  17. Winn’s Brook – Contract 3Construction Schedule 11/25/2009 - Advertised for Bid 12/21/2009 - Bids Received 01/15/2010 - Contract Execution 02/01/2010 - Notice to Proceed 07/31/2011 - Construction Complete (18 months)

  18. Questions? Justin Gould, P.E.Fay, Spofford & Thorndike

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