Protection for Merrimack River Radial Collector Well
Since 1874, Manchester Water Works (MWW) has been committed to providing safe drinking water to over 160,000 customers in the greater Manchester area. To address the growing demands in southern New Hampshire that houses 40% of the state's population, we introduced a new supplemental water source: the state’s first Radial Collector Well (RCW) for drinking water supply along the Merrimack River in Hooksett, New Hampshire.
With a permitted daily capacity of 7.2 million gallons (which is 12.6% of our total capacity), our primary goal is to protect the quality of the water at the source. To achieve this, a comprehensive Source Water Protection Plan (SWPP) was developed to keep this vital resource clean.
How It Works: The Radial Collector Well
The MWW Radial Collector Well is the first of its kind used for a public water supply in New Hampshire. Unlike a standard well, this system features a 16-foot-diameter, 70-foot-deep vertical concrete cylinder on the riverbank. From the bottom of this structure, six screen pipes fan out horizontally up to 240 feet underneath the riverbed. As water is drawn in, the sand and gravel act as a giant, built-in filter (hence the term “bank filtration”), cleaning the water before it even reaches our treatment plant. Once collected, the water is sent to the Merrimack River Water Treatment Plant for final purification and disinfection.
For more information, see the video "That's how bank filtration works."
Our Source Water Protection Plan
The Merrimack River Watershed & Protection Zones
A watershed is simply an area of land where all water, when it touches the land surface, flows downhill into a single source. The Merrimack River watershed is vast, covering 2,814 square miles. Because it is impossible to monitor this entire area with a single approach, our SWPP strategically breaks the watershed into four zones based on risk. For details, refer to the attached SWPP document.
Read the Documents:
Full SWPP Document (Letter to NHDES):
2025 Annual Report:
- Table of Contents
- Section 1
How You Can Help Protect Our Water
(Best Management Practices)
You can play a vital role in protecting our regional drinking water by utilizing Best Management Practices (BMPs) to minimize polluted runoff. Browse our quick tips below:
In Your Yard,
Limit your use of fertilizers and pesticides, which can wash directly into the river. Adopt the “Fertilize in the Fall. That’s All!” approach. Additionally, leave grass clippings on the lawn, consider planting native plants that require less water and fertilizer, and dispose of pet waste promptly, all to significantly reduce harmful bacteria and nutrient pollution.
With Your Vehicle,
Check your vehicles regularly for fluid leaks and properly recycle motor oil. During the winter months, reduce your use of deicing road salt. We recommend hiring snow removal contractors certified under the NHDES Green SnowPro Program.
At Your Home or Business,
Never dump household chemicals, paint, or grease down the drain or storm grates. If you have a septic system, routine maintenance is critical; have your system inspected every three years and pumped as necessary to prevent raw sewage from contaminating the groundwater.
Additional Resources:
- Three Ways to Protect Your Drinking Water (PDF)
- Clean Drinking Water: It's Up to You! (PDF)
- Road Salt and Water Quality (PDF)
Emergency Response & Contact Information
See a Spill? Report It!
If you witness a chemical spill, illegal dumping, or an emergency near the river, please act quickly. Rapid reporting is critical to stopping pollution before it reaches our treatment plant.
First, contact 911 or local fire department.
Second, call NHDES Spill Response at (603) 271-3899, Monday to Friday, 8 a.m. to 4 p.m., or call New Hampshire State Police Dispatch at (603) 223-4381 for weekends and evenings.