Infrastructure BoA Presentation 2017Apr27 reduced — File 203293

Mayor Joseph A. Curtatone Presented by Richard E. Raiche, PE, PMP, Director of Engineering Robert T. King, PE, Director of Capital Projects Spring 2017

Delivering on SomerVision: 3 key commitments GLX Zoning Infrastructure 2

Infrastructure Information Part One: Somerville’s Urban Hydrology

Somerville Geography 4.2 square miles – every square foot is valuable!

Somerville: Geography 101 Hills, wetlands, and rivers 1852

Fill, Development, and MDC pipes Present day

Water flows downhill, and to MWRA pipes Elevation 100 to 150 feet 65 to 100 feet 40 to 65 feet 20 to 40 feet -11 to 20 feet

Urban Hydrology Where does water go, and why doesn’t it go there sometimes?

Hydrologic Cycle

Storm drains, sanitary sewers and combined systems

Somerville’s System State of the Art water handling… in 1890

Collection System 502 1305 694 915 18 153 64 1860 to 1880 1880 to 1900 1900 to 1920 1920 to 1940 1940 to 1960 1960 to 1980 1980 to present Sewer & Drain Lines Built

Combined sewers Combined 68 miles Sanitary 62 miles Storm Drain 35 miles * Sanitary & Storm in shared trench

Combined 68 miles Sanitary 62 miles Storm Drain 35 miles * Sanitary & Storm in shared trench Two pipe roads … but not really separate

Smaller pipes flow to larger ones – 3 major interceptors Beacon-Washington-Somerville Cambridge Branch McGrath Somerville Marginal Tannery Brook  Alewife Brook Conduit

Major Subsystems

Subsystem statistics 19 33 98 76 10-Year Flood Volume (mgd) High level estimates of sanitary flow based on 2017 assessors data for bedrooms and building square footage time typical wastewater generation rates. High level estimates for flood volume based on 24-hour precipitation, calculated area, imperviousness per EPA source data and factors for runoff reaching the system. 0.53 1.02 2.67 1.82 Sanitary Flow (mgd)

Problems • Why do things go wrong?

311 Reports • Call types include: sewage, sewer, water inquiries, water issues, water leak in house, water emergency 0 50 100 150 200 250 300 350 July August September October November December January February March April May June July August September October November December January February 2015 2016 2017 311 Water & Sewer Related Calls,* 2015-2017

Heat Map: CY2016 311 W&S Calls

Blockages and Collapses Maintenance and Repairs • Blockages can be cleared • Collapses require emergency repairs

Systematic Flooding • Load exceeds capacity

Flood Hazards • Twelve events noted 1968 to 2010 • Twelve high risk areas defined • Model predicts damages between $38.5M and $192.5M

Constraints • What is out of Somerville’s control?

Regulatory & Permit Restrictions Our use is regulated by permits issued by: • MWRA Municipal Sewer • EPA/DEP NPDES CSO • EPA/DEP NPDES MS4 Separate Stormwater Discharge Combined Sewer Overflows Sewer Discharge

Physical limitations • MWRA interceptors

Union Square – Nexus of Flows • Uphill / Up-pipe areas all contribute to flooding 60% of Somerville’s flow Cambridge flow MWRA System

Rain from above.. trouble from below

Past Planning These aren’t new problems, what has been done to find solutions?

Millers River Drainage - Capacity in MBTA System 1990s - present

Sewer Separation – Cost Prohibitive CDM Reports 1994 – 2009 • Marginal sewer separation $74M 2009$ • Tannery Brook partial sewer separation $33M 2006$ • Cambridge Branch partial sewer separation $115M plus $?? stormwater pumping & outfall 2009$ • No projects resulted

SomerVision 2009 - present • Increase level of service • Remove stormwater from system • Reduce flooding and CSOs

Stormwater Management MWH Report 2013 • Shifted focus • Previous solutions ▫Bottom of hill ▫End-of-pipe ▫Increase capacity • New solutions ▫Intercept rain ▫Distributed throughout catchment ▫Preserve capacity

Stormwater Management Strategies • Runoff management • Surface storage • Underground storage • Pipe capacity

Combined 68 miles Sanitary 62 miles Storm Drain 35 miles * Sanitary & Storm in shared trench Locally separate stormwater pipes

Project identification and evaluation • Concept designs – 8 areas / 11 sub-alternatives • Cost estimates • Hydraulic modeling

Project ranking • Flood Reduction ▫What is the total benefit of the project? • Cost-Effectiveness ▫What is the cost per gallon of benefit? • Conclusions ▫Lincoln Park is most cost-effective, but has smaller impact ▫Somerville Ave Drain has most impact, but expensive ▫Nunziato most balanced, with high impact and cost-effective ▫Conway half as beneficial at similar cost range • No other projects provide substantial benefits cost-effectively

System Problems – Systematic Solutions Flooding occurs because the system moves water downhill. Solutions need to be system-wide.

Complex problem without simple solution

Requires suite of targeted control measures Sewer separation & infiltration / inflow mitigation Green stormwater infrastructure Stormwater storage tanks New stormwater discharges

Ongoing and evolving strategy • Past – Present – Future • Large scale and small scale Beacon St. Tank Western Somerville Ave Drain Cedar St. Sewer Separation Symphony Park Chuckie Harris Park Lincoln Park CP2/CP3 Somerville Ave Drain GLX Connection Nunziato Tank Citywide Development 4:1 I/I Requirement Targeted Separation

Data-driven planning and design • State of the Art for the 21st Century

Infrastructure Information Part Two: Proposed Major Infrastructure Projects

3 Project Overview Nunziato Field Redbridge PS USQ Infrastructure

Nunziato Field Stormwater Storage Green Infrastructure Field Upgrades

Stormwater Storage Facility UNDERGROUND TANK PUMP STATION DIVERSION STRUCTURE ADDING CATCH BASINS

Tank Excavation

Sewer & Drain Vaults

Park Improvements

Existing Example Beacon Street (1 MG Storage)

Construction Estimate Nunziato Field Stormwater Storage and Park Upgrades Estimated construction timeframe: • 27 months of phased construction • Storage Tank • Diversion Structure • Putnam and Vinal Improvements • 9 months of park work. • Field • Dog Park • Plaza Estimated construction cost: • $14, 600,000 (construction and construction oversight)

USQ - Somerville Ave Sewer Separation and Streetscapes Restoration

Box Culvert and Utilities – Cross-Section New 16" Water Main Line Existing 39" by 26" Brick Sanitary Sewer New 14' by 6' Stormwater Box Culvert Line Existing 72" Brick Combined Sewer New Communications Duct Bank Existing Communications, Electric, and Gas New 12" Water Main Line Existing 12" Clay Sanitary Sewer

Streetscapes – Typical Section Stormwater Green Infrastructure Silva Cells 6.5' Fully Protected Bike Lanes 11' Travel Lanes 7' Parking Lane (where space available) 51 New Trees

Streetscapes

Construction Estimate Somerville Avenue Sewer Separation and Streetscape Upgrades Estimated construction timeframe: • 3 full construction seasons (3 years if we start in March/April) • Anticipated construction includes the infrastructure constructed from Bow Street to Medford Street with the Streetscape to follow behind. Estimated construction cost: • $50,350,000 (currently working to finalize estimate) • MassWorks as partner will save the City $13,000,000 • MassWorks has deadlines

Redbridge Pump Station

Separation Opportunities

Proposed Connection

Construction Estimate Redbridge Pump Station Design has not been started (work pending Board approval) Estimated design timeframe: • Secure OPM • Secure Architect • 1 year design. Estimated construction timeframe: • 1.5 – 2 years of construction • Building / Pump Station / Wetwell • Force main connection Estimated design & construction cost: • $19,600,000

Questions?

Mayor Joseph A. Curtatone Presented by Richard E. Raiche, PE, PMP, Director of Engineering Robert T. King, PE, Director of Capital Projects Spring 2017