Cohasset Sewer System Overview Brian Joyce DPW DirectorTown

Cohasset Sewer System Overview Brian Joyce, DPW Director/Town Engineer

Presentation Purpose • Provide a general overview of the Cohasset Sewer System size, scale and operation • Collection System areas and history • Sewer Plant operation • Woodard & Curran to provide overview of regional discussions to date 2

Cohasset Sewer System History • 1971 - Cohasset Village and Harbor area (first centralized sewer system in Town) • 1998 – Expansion up the hillside to streets surrounding Cohasset High School • 1998 – North Cohasset Straights Pond area (discharge to Hull) • 2000 – Lilly Pond King Street/ Pond Street area • 2009 – Little Harbor and coastal areas (Connected North Cohasset to Central Cohasset) • Sewer Treatment Plant upgrades in 2000 • Approximately 14. 5 miles of collection system pipes 3

Cohasset Sewer System District Map Cohasset Sewer Operations • Plant is operated by a contractor under a long-term agreement (currently Woodard & Curran) • Town is divided into three sewer districts – Central, North, and Little Harbor • Agreement with Hull to send 80, 000 gpd for treatment (expires 2028) 4

Cohasset Sewer Collection System • Currently 1643 customers, both residential and commercial • 14. 5 miles of pipe • 9 centralized Town owned pump stations • Approximately 700 residential grinder pumps for pressurized collection system (force mains) in Little Harbor and North Cohasset 5

Cohasset Sewer Treatment Plant Treatment Challenges Capacity • Existing Cohasset Plant Capacity is 450, 000 gpd. • Current daily average flow is approximately 323, 000 gpd running average) (12 month Processing • Wastewater filtered through modular membrane cassettes • Treated effluent discharged into Cohasset Cove • Waste Sludge shipped to Brockton for incineration • Providing sewer service to all priority areas identified in the regional sewer discussion has an estimated design flow between 300, 000 to 550, 000 gpd • Existing plant is on a small fully utilized footprint and expansion would be challenging, likely vertical or increase in tank storage capacity. 6

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Cohasset Sewer • Plant Operating Permit Issues that require attention – Current NPDES Discharge Permit expired in 2012 – Awaiting a new permit to be issued by EPA which is likely to require a reduction in nitrogen discharge (Plant is currently permitted at 10 ppm) and require treatment plant upgrades – Regulators have been actively monitoring current regional discussions to determine the potential impact on nitrogen and other impacts 8

Recent Developments Sewer Plant membrane filtration system cassettes were replaced in May 2020, with projected operating life of 10 years Train 1 filter suffered an operating failure the day after membrane replacement was approved by Special Town Meeting in Nov 2019 An emergency temporary diversion of flow to Hull to ease burden on Cohasset Sewer plant Delays in installation of new filter required a second round of diversion this past spring 9

Cohasset Sewer • Environmental Impacts Issues that require attention – Cohasset Cove/Harbor water quality is heavily influenced by the Scituate Gulf and its tributaries – Cohasset’s southern South Main Street and North Scituate areas which drain into the Gulf are not connected to sewer service – Nitrogen and Phosphorous contributions to the harbor are largely influenced by tributary flows (Bound Brook, James Brook, Scituate gulf area flows) 10

Questions? 11

Thank you! 12