CC Morrison SRF 2026Jul09 — File 26-1156

Morrison Ave Linear Storage & Greater Davis Square Area Sewer Separation SRF Appropriation City Council File ID 26-1156 9 July 2026

Project elements 2

What is “linear storage”? 3

Challenge of the Cambridge / Alewife “CA” Sewershed 4

Project components 5

Project limits 6 • Morrison, Pearson, Highland Rd. Winslow, Clifton • Packard, Powder House • Jay Street

Project benefits 7

Flood Reduction Benefits (in MG)

Flood Reduction Benefits -10y, 24h 2030 Event Existing Conditions Proposed Conditions

CSO Reduction Benefits Hydraulic Model Predictions 2050 TY Receiving Water CSO Discharge Volume (MG) Activation Frequency Recommended Plan Current Conditions Recommended Plan Current Conditions 6.4 (25% reduction) 8.5 11 (15% reduction) 13 SOM001A Alewife Brook 170 (no increase) 171 41 (no increase) 41 SOM009 Union Square to Prison Point

Project schedule & funding Need Council action earlier in process than usual to secure 2% and possible loan forgiveness 11

Milestones & cost control July 2025 $130,392,395 SRF Application based on 30% $111,375,00 60% Design update June 2026 $130,392,395 SRF Council Authorization September 2026 90% Design update December 2026 Rescind delta Council Action* February 2027 Bidding May 2027 ~ 4 years Construction 12

To learn more… 13

One of two major sewer & drainage improvement projects in design • Concepts originated in the Citywide Drainage & Water Quality Master Plan • https://voice.somervillema.gov/citywide-drainage-and-water-quality- master-plan • Mystic River Outfall and Sewer Separation • https://voice.somervillema.gov/mystic-river-outfall • Morrison Avenue • https://voice.somervillema.gov/morrisonavenue 14

Questions 15

Morrison Ave Linear Storage & Greater Davis Square Area Sewer Separation SRF Appropriation City Council File ID 26-1156 9 July 2026

Examples of details 17