Total Trihalomethanes (TTHM) Maximum Contamination Level Tier 2 Violation

The Dedham-Westwood Water District Has Achieved Tier 2 Compliance for Total Trihalomethanes  

The Dedham – Westwood Water District is pleased to announce that we have achieved compliance and are no longer in violation of a Tier 2 Massachusetts Drinking Water Regulation. Together, our team of water professionals executed a plan to reduce the locational running annual average (LRAA) for total trihalomethanes (TTHM) in the public drinking water supply, including flushing the water distribution system, blending water from the Massachusetts Water Resources Authority (MWRA), and continually sampling and monitoring the levels of TTHM in the water to ensure our actions were having an impact and to protect public health and safety.

TTHM COMPLIANCE                     
Sample Location  Q2 (Apr – Jun)  Q3 (Jul – Sep)  Q4 (Oct – Dec)  Q1 (Jan – Mar)  OEL           Q1  LRAA 
Date  ppb  Date  ppb  Date  ppb  Date  ppb 
Dedham Medical Associates  4/6/2021  58  7/8/2021  89  10/7/2021  118  1/6/2022  24  64  73 
Getty Gas Station  4/6/2021  33  7/8/2021  46  10/7/2021  81  1/6/2022  57  60  54 
East Dedham Fire Station  4/6/2021  45  7/8/2021  64  10/7/2021  42  1/6/2022  24  39  44 
Far Reach Pump Station  4/6/2021  58  7/8/2021  89  10/7/2021  109  1/6/2022  23  61  70 
  MCL = 80 (ppb)  Was OEL exceeded  NO  Was the MCL exceeded  NO 


TTHMs are a group of disinfection byproducts that form when chlorine compounds, which are used to disinfect water, react with other naturally occurring chemicals in the water. They are colorless and will evaporate out into the air. There are four significant TTHM (chloroform, bromoform, bromodichloromethane, and dibromochloromethane) potentially found in disinfected drinking water and their combined concentration is referred to as total TTHM. 

The Dedham-Westwood Water District is working with the MWRA to continue to blend the water supply, while our consultant, Weston & Sampson is in the process of designing an enhance treatment process to our Bridge Street Water Treatment Plant that includes the installation of tank mixers, aerators, and vents. We anticipate implementing the procurement process to begin in the spring of 2022, with construction to follow later in the year.  

We will continue to monitor the public drinking water supply for all regulated inorganic substances, synthetic organics, volatile organic compounds (vocs), Total Coliform, e.coli bacteria, unregulated (secondary) substances, organic disinfection byproducts, radionuclides, as well as lead and copper. Our team is committed to providing clean, safe water. As stewards of this valuable resource, we take our job to protect public health and safety seriously. Our team of 30+ professionals work around the clock to provide reliable, cost-effective, high-quality water service that protects public health, promotes environmental stewardship, maintains customer confidence, and supports economic development and sustainability. 

We are here to answer your questions, call our water quality hotline to speak with a live representative Monday through Friday between the hours of 8 AM and 5 PM at (800) 279-8810 or email us at

Complete Web Solution by Pebblehaven