Town materials say Cohasset’s drinking water remains safe for drinking, cooking, bathing and other ordinary household uses. The town’s current guidance says residents do not need to stop using the water or switch to bottled water and filters.

What TTHM means for Cohasset residents

TTHMs are disinfection byproducts that can form when chlorine reacts with naturally occurring organic material in source water. Cohasset uses Lily Pond as a source, and the town says the issue is measured through a locational running annual average, or LRAA, rather than a single short-term test.

The town’s second-quarter 2026 drinking-water notice said the federal Environmental Protection Agency maximum contaminant level for TTHMs is 80 micrograms per liter, equivalent to 80 parts per billion. Based on routine quarterly monitoring conducted May 19, the LRAA was 97 parts per billion at 208 Sohier Street and 92 parts per billion at 2 Whitehead Road.

The notice said the standard is based on potential health risks from long-term exposure over many years, not short-term or occasional use. It also said Massachusetts and federal health agencies advise that some people who drink water containing TTHMs above the standard over many years may face risks involving the liver, kidneys or central nervous system, as well as an increased risk of cancer. The notice said young children, pregnant people and those who may become pregnant may be more susceptible to risks from exposure to chemicals such as TTHMs.

The town describes the situation as not an emergency and says the water remains safe for everyday use. Residents with specific health questions can consult a health care provider or the state agencies identified in the notice.

Work already underway

The Water Department says treatment operations are being optimized to improve the removal of organic material before disinfection. The town is also continuing targeted hydrant flushing, expanded sampling and monitoring, and coordination with the Massachusetts Department of Environmental Protection and engineering consultants.

A water-system engineering analysis is complete. According to the town, the water-age study found that further reducing water age in distribution pipes is not expected to significantly reduce TTHMs, helping officials focus on other measures.

Source-water work is also underway. The town began updating a Lily Pond limnology study on July 16 to evaluate opportunities to improve source-water quality. Improvements to the sludge lagoon are in design and permitting and are intended to improve the plant’s ability to remove organic material before disinfection.

Possible treatment changes are not final decisions

Cohasset is evaluating alternative chemical treatment, including a possible conversion of filter media to granular activated carbon at the water-treatment plant. The town is also preparing an application for state infrastructure funding for water-storage-tank mixers.

A possible new treatment plant remains under review. The Water Department has received a proposal for a pilot study and preliminary design work, but the progress tracker states that no decisions have been made. The proposal should not be read as an approved, funded or scheduled construction project.

Rates and the next public step

The town’s TTHM information page says improving and maintaining Cohasset’s drinking-water system will require significant investment and that a future water-rate increase will be necessary. It does not establish a specific increase, project cost or construction timeline. Any proposed rate changes would go through public town processes.

Tuesday’s Select Board discussion is the next scheduled public point for residents seeking more detail about treatment alternatives, costs, timing and the status of the possible plant study. Any confirmed decisions should come through later meeting records or official town documents.

Sources

• Cohasset Water Department TTHM Solutions Progress Tracker

1) Mandatory drought-warning outdoor restrictions (Cohasset Water Department)

The Cohasset Water Department posted its mandatory outdoor watering restrictions on June 18, 2026 and last updated June 30, 2026. The posting says the rules are in effect until further notice.

• No irrigation systems at all (the posting says no irrigation systems may be used).
• Hand-held hose use is limited to ornamental plants and vegetable gardens.
• Allowed hours: daily from 5 p.m. to 9 a.m. (with no watering allowed on Sundays).

What the posting says about enforcement

The mandatory drought-warning posting lists specific penalties:

• $50 for the first violation
• $100 for each subsequent violation
• Each day of violation counts as a separate offense

It also says residents can report violations to the Cohasset Water Department.

2) Separate “total outdoor water ban” (North Cohasset / Weir River Water System)

Separately, the Weir River Water System—working with partner towns—issued a Total Outdoor Water Ban that the Cohasset posting describes as effective immediately as of June 16, 2026 for the towns of Hingham, Hull, and North Cohasset.

According to the ban notice, all outdoor water use is prohibited until further notice, including:

• Lawn and landscape irrigation
• Washing vehicles
• Filling swimming pools or hot tubs
• Using sprinklers or hoses for recreation
• Any other non-essential outdoor water use

The notice adds that the ban will remain in effect for the remainder of the season. It also says failure to comply may result in fines and/or shutoff of water service.

How to know which rules apply

Use this quick guide:

• If you rely on sprinklers or irrigation systems, the mandatory drought-warning posting says they are not allowed.
• If you’re watering ornamental plants or a vegetable garden under the mandatory drought-warning rules, use a hand-held hose only between 5 p.m. and 9 a.m.—and never on Sundays.
• If you’re in North Cohasset under the total outdoor water ban, don’t do outdoor watering of any kind, including lawn/landscape irrigation, vehicle washing, pool/hot tub filling, or using sprinklers/hoses for recreation.

What to do today

• Turn off irrigation systems immediately.
• For allowed hand-hose watering under the mandatory rules, adjust your schedule to the posted evening-to-early-morning window and avoid Sundays.
• If you’re in North Cohasset, pause all outdoor water use under the total outdoor ban and follow the posting’s instructions for reporting activity you believe is outside the restrictions.

Sources

• Cohasset Water Department/Civic Alerts — North Cohasset: TOTAL OUTDOOR WATER BAN ISSUED (Effective Immediately)
• Weir River Water System News Flash — Total Outdoor Water Ban Critical Alert

On the agenda: two dock special-permit requests for properties on Black Horse Lane (70–74 Black Horse Lane and 66 Black Horse Lane) and a variance request at 83 Spring Street for construction of a single-family home. The hearing is the place to review the relief being requested and the conditions that could be discussed.

Where to attend (in person or Zoom)

The hearing begins no earlier than 7:00 P.M. at Willcutt Commons (91 Sohier Street). A Zoom option is also available, using webinar ID 833 7857 6954 and passcode 752840.

What the ZBA does, in plain terms

In Cohasset, the Zoning Board of Appeals holds public hearings and handles zoning matters that include special permits, variances from zoning law, and certain appeals related to building-permit decisions.

Docket recap: dock special permits and the 83 Spring Street variance

Dock special permit — 70–74 Black Horse Lane
Applicant: Michael McGuinness. File #26.05.04a.

Dock special permit — 66 Black Horse Lane
Applicant: Michael Crowell. File #26.05.04b.

Variance — 83 Spring Street
Applicant: David Won. File #26.05.26. Listed pursuant to Zoning Bylaw Section 300-8.3.

What residents should listen for

Because the listed items are being heard before any decision is made, residents may want to track the specific relief being requested and any conditions discussed that could affect nearby properties—especially as described in the dock applications and addressed during the hearing.

Next checkpoint: August 3, 2026

The ZBA’s next scheduled meeting is Monday, August 3, 2026. If any of the July 6 items are continued, that meeting would be the next place to watch for follow-up discussion and additional public input.

Residents can review the posted July 6 agenda and attend in person or via Zoom during the public hearing window.

Sources

• Town of Cohasset — Zoning Board of Appeals Agenda (July 6, 2026) (PDF)

Cohasset Public Schools says bus registration is required for all riders and is handled through MySchoolBucks. The district’s fee-based system sets transportation at $450 per student for eligible K-6 students living within 2 miles of school and for all students in grades 7-12, with a family cap of $850.

Applications received after June 30 go on a waitlist, and the district says transportation cannot be guaranteed if a bus is full. A $50 late charge also applies after the deadline.

Bus passes will be available in the Aspen portal on or before Aug. 22, and routes are expected on or before Aug. 21.

The transportation notice lands while the School Committee keeps working through FY27 budget updates. At its June 24 meeting, the agenda included FY27 budget updates and authorization for an override exploratory process.

Cohasset Anchor reported that the committee wants Superintendent Sarah Shannon to prepare a five-year outlook covering personnel, utilities, transportation, enrollment and programming before deeper funding talks later this year.

For parents, the immediate takeaway is practical: sign up on time or risk losing a guaranteed seat. For the district, transportation costs are part of a broader budget conversation that is still in its early stages.

Sources

• Cohasset Public Schools — Transportation 2026-2027 School Year
• Cohasset School Committee — June 24, 2026 agenda
• Cohasset Anchor — district five-year outlook / override exploratory process report

The Water Department says the rules are meant to protect drinking-water supply and fire protection capacity. The notice also ties the local action to drought conditions affecting the wider region.

What is now banned

Irrigation systems cannot be used at all under the new rules. That is the biggest change for homeowners, landscapers, and property managers who rely on sprinklers, timers, or other automated watering setups.

The town is still allowing limited hand watering for ornamental plants and vegetable gardens, but only between 5 p.m. and 9 a.m. The restriction also says no watering is allowed on Sundays.

Violations come with fines: $50 for a first offense and $100 for each later offense. The town says each day of violation counts as a separate offense.

Why Cohasset acted now

Cohasset says the warning is tied to drought criteria in its water-supply planning, including below-normal precipitation, weak stream flow, and low storage levels. The state’s drought status page also shows a significant drought designation for the region.

For residents and landscapers, the practical message is simple: check what is still allowed before turning on a hose or irrigation system. For property owners, the order means outdoor maintenance plans may need to change immediately and stay changed until the town issues a new update.

The restrictions do not have a fixed end date. For now, Cohasset is asking residents to conserve water so the system can keep up with everyday use and emergency needs.

Sources

• Cohasset Water Department alert: Mandatory outdoor water restrictions
• Mass.gov drought status update
• WCVB: Massachusetts towns add outdoor water bans amid drought