Fay, Spofford & Thorndike TOWN OF BELMONT WINN’S BROOK SEWER OVERFLOW MITIGATON Presentation to the BOARD OF SELECTMAN December 7, 2009

Fay, Spofford & Thorndike Presentation Objectives Project background Causes of sewer overflows Conceptual design and modeling Final Design Opinion of probable construction cost Funding Schedule

Fay, Spofford & Thorndike 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

Fay, Spofford & Thorndike The Problem Periodic sanitary sewer overflows and backups into basements of homes in the Winn’s Brook Area

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Reported Backups DatesNumberRainfall (inches) October June March May

Increased Hydraulic Grade Line Creates Sewer Backups HGL

Fay, Spofford & Thorndike Causes of an Increased Hydraulic Grade Line (HGL) System Capacity Constraints Infiltration/Inflow in Belmont –2007 Flow Monitoring Program Elevated downstream HGL –Flanders Road Connection to the MWRA

Fay, Spofford & Thorndike 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

Fay, Spofford & Thorndike 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

Fay, Spofford & Thorndike Mitigation Concepts Increase sewer capacity Flow diversion Storage Isolation and Pumping I/I Removal 13 Mitigation Alternatives Modeled

Fay, Spofford & Thorndike 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)

Fay, Spofford & Thorndike 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

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Predicted Impact at Key Manholes Outside Winn’s Brook Area (MH rim to HGL) HamiltonBakerOliverChanning Baseline (May 2006) Alt. 12 (15 % I/I red)

Fay, Spofford & Thorndike Flanders Road Predicted Discharge May 2006 Mother’s Day Storm Peak Discharge MGD 24-Hour Volume MG Baseline Alternative Difference1.98%-2.84%

Fay, Spofford & Thorndike

Opinion of Probable Construction Cost - Contract 3 Base Bid Winn’s Brook Sewer Overflow Mitigation Facilities $6.6 Million Additive Alternates Townwide I/I Removal $1.4 Million TOTAL$8.0 Million

Fay, Spofford & Thorndike 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

Fay, Spofford & Thorndike Winn’s Brook – Contract 3 Construction Schedule 11/25/ Advertised for Bid 12/21/ Bids Received 01/15/ Contract Execution 02/01/ Notice to Proceed 07/31/ Construction Complete (18 months)

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