Remediating Groundwater Dioxane to Mitigate Marl Pond Degradation

Colebrook, New Hampshire

Featured image for the project, Remediating Groundwater Dioxane to Mitigate Marl Pond Degradation

Photo courtesy of the Town of Colebrook


The community of Colebrook, New Hampshire is a small, poor, rural community. It is a remote village located at the northern tip of New Hampshire. Colebrook has the highest unemployment in the State. Weather and climate is a factor.  It gets cold in Colebrook.  In January, temperatures will reach -40 degrees Celsius. 


The town’s closed municipal landfill has 1-4 Dioxane in the groundwater.  The levels present exceed Ambient Groundwater Quality Standards (AGQS).  The polluted groundwater has left the property boundary and is present on land of an abutter. 


The plume has resulted in groundwater degradation in the vicinity of Lime Pond located just across the municipal boundary in Columbia, New Hampshire.  This waterbody is an extraordinary example of a marl pond. Its bottom holds 6 feet of nearly pure, white marl, made up largely of shells of freshwater mollusks known as cyclas and planorbis that still live in the pond, usually under loose stones. The bedrock surrounding the pond is an impure, gray and blue limestone from which the calcium that defines the pond has leached over the past 10,000 years. 


To protect the pond, the Town was required to install a groundwater extraction system to collect groundwater.  This groundwater is then trucked across town to the municipal wastewater treatment system.  The Town then treats the groundwater as it does raw waste and discharges it into the Connecticut River.  The wastewater is treated with a system of aerators, SolarBees (mixers) and ultraviolet (UV) light. Locally, this system is referred to as a “pump and dump” method. 


Thus, the community has a groundwater dioxane problem associated with the landfill. Colebrook would like to know how they might determine a long-term, sustainable and cost-effective remedy.  The goal is to remediate the 1-4 Dioxane in situ (in place).


Becky and Dave will work together to provide a menu of remedies and costs for a “walk away” solution. The team anticipates that this project will take approximately 12 months. The primary deliverable(s) for this project will be a source characterization report and treatability studies.


Colebrook team has their first meeting

In their first meeting (via phone because Dave Ellerbroek, the scientific lead, is remote), the Colebrook team discussed the data the town has shared. They are now ready to move on to what the information means.  Becky had prepared a sheet of the different treatment options that the town is considering which proved useful to the team. Dave proposed that they will build upon this by developing a site conceptual model. They will use his masters students in the course he teaches on Groundwater Contaminant Transport at the Colorado School of Mines to have students illustrate what is known and not known of the hydrogeology of Colebrook site. The team would then use the site conceptual model as a decision-making tool/discussion format of what they propose to do with the site. Specifically, they will use this model to:

  • Hydraulic capture scenario
  • Look at trying to identify the source
  • Look at different scenarios
  • Use that info to evaluate different treatment technologies.

The team decided that they will have bi-weekly check-ins scheduled for an hour starting from 24 March. They also requested a shared folder in the TEX Google Drive. By their next meeting (in 2 weeks), the team will discuss:

  • Progress with students [Site conceptual model development and who might be able to be there in summer? ]
  • Funding [Identify sources of funding to have a student at the site in the summer of 2017.]
  • Becky’s webinar (Skype video) on April 4th. [Dave requested that Becky skype into the class to provide context for the students developing site conceptual models.]

By the time TEX checks in with Colebrook in April, the team aims to have Dave’s students in the midst of developing site conceptual models for Colebrook. By that point, Dave and Becky will have already answered the students’ first set of questions.

All updates for this project

Project Team

Community Lead

Becky Merrow, Esq. earned her Bachelor of Science Degree in Paralegal Studies from Woodbury College (now Champlain College) located in Burlington, Vermont.  She has been working in public administration since the 1990’s.  She has been the Town Manager of Colebrook New Hampshire since 2012. 


Vermont has a unique program that allows individuals with a bachelor degree to “Clerk” for the bar.  Commonly referred to as “reading the law,” the program is an apprenticeship platform which takes 4 years to complete.  Upon successful completion, she was deemed qualified to sit for the Vermont Bar Examination and was sworn in as a member of the Vermont Bar Association in June of 2009.  This is the same manner that President Abraham Lincoln and Vermont Supreme Court Justice Marilyn Skoglund were allowed to practice law. 


Becky enjoys kayaking and travel and is passionate about the community she serves.  She is the grandmother of 5 year old Maggie Lorraine Newton.

Scientific Lead

Dr. David Ellerbroek serves as the Denver Area Manager for AECOM and oversee operations related to transportation, water, environment and urban facilities. He is passionate about natural resource development and have spent significant portion of my career working on methods to mitigate environmental impacts and protect water resources during natural resource development. My career has included international work for O&G and mining companies (Australia, Argentina, Peru and Chile), several large remediation projects including serving as Client Service for the El Paso Corporation remediation program and developing water management solutions for unconventional Oil and Gas development.