DNAPL or Dissolution? Mercury Transport to Riverbed Fractures at a Former Chlor-Alkali Facility

Tuesday, September 24, 2013: 9:50 a.m.
Jennifer Lambert, P.G. , Nobis Engineering, Inc., Concord, NH
James Doherty, PhD, P.E., LSP , Nobis Engineering, Lowell, MA
Liyang Chu , Nobis Engineering, Inc., Lowell, MA
Darryl Luce, PhD , U.S. Environmental Protection Agency, Boston, MA

Significant quantities of mercury migrate from the former Brown Company’s Chemical Plant (a chlor-alkali facility) into the adjacent Androscoggin River. The former Chemical Plant is located in Berlin, New Hampshire immediately downstream of the hydroelectric Sawmill Dam. The local bedrock consists of quartz monzonite gneiss and granitic pegmatite with lenses of chlorite schist, all of which are extensively folded and irregularly fractured.

Between 1999 and 2004, approximately 170 pounds of mercury and mercury-contaminated debris were removed from the riverbed. Mercury, both as liquid droplets and semi-solid and solid amalgam, continues to accumulate in bedrock fractures along the river almost 50 years after the cessation of the Chemical Plant operations. A CERCLA Remedial Investigation was completed to help identify the mercury source location and possible mechanisms for mercury transport and discharge to the River. 

Local hydrology is complicated by several factors: an impermeable source area cap; a partially confining slurry wall in the overburden upgradient of the primary source area which diverts overburden groundwater into the bedrock; and the schedule of water releases from the dam, which may not coincide with local precipitation. The means of mercury transport to the surface may be the simple migration of non-aqueous phase mercury through bedrock fractures driven by hydraulic gradients.  However, geochemical conditions in the subsurface may allow the dissolved transport of mercury with subsequent precipitation in liquid and amalgam forms once exposed to surface water conditions.  The Plant’s past operational practices have resulted in unusual geochemistry in groundwater underlying the former Chemical Plant’s footprint, including elevated pH and high concentrations of organic compounds and metals.  Defining these conditions and their effect on mercury speciation are critical in understanding the conditions for mercury transport and guiding future remedial actions.

Jennifer Lambert, P.G., Nobis Engineering, Inc., Concord, NH
Jennifer Lambert is a geologist with approximately 10 years of experience in environmental consulting. She received her Bachelor’s degree from Hamilton College in New York and her Master’s degree from the University of Waterloo in Ontario. Ms. Lambert has primarily worked on environmental projects in New England and the mid-Atlantic region for federal and industrial clients. She has lead field investigations and performed geological, hydrogeological, and chemical analyses to determine chemical fate and transport and to support remediation planning. Ms. Lambert is currently working in New Hampshire on environmental investigation and remediation projects, as well as municipal water supply projects.



James Doherty, PhD, P.E., LSP, Nobis Engineering, Lowell, MA
James Doherty is a senior project manager and senior technical specialist for environmental investigation and remediation projects. He has worked with commercial and industrial clients and federal, state and local government clients under state and federal programs. He has performed fractured bedrock investigations; dense non aqueous phase liquids (DNAPL) investigations; assessments of chlorinated volatile organic compound migration; subsurface mercury migration investigations; and groundwater, soil, surface water and indoor air investigations for metals and organic chemicals. He developed and implemented approaches to remediate soil and groundwater contaminated with DNAPL, metals, and organic chemicals.


Liyang Chu, Nobis Engineering, Inc., Lowell, MA
Liyang Chu is an engineer with over 30 years of experience in environmental consulting. He received a Bachelor in Engineering in civil engineering from The Cooper Union in New York, NY, and a Master of Science in civil engineering from Carnegie-Mellon University in Pittsburgh, PA. Mr. Chu has been a project manager for Superfund sites in New England and the mid-Atlantic states involving industrial, commercial, and military sites. Mr. Chu has managed and implemented treatability studies and pilot tests, hazardous waste site investigations, feasibility studies, and remedial design and remediation.


Darryl Luce, PhD, U.S. Environmental Protection Agency, Boston, MA
Darryl Luce has been a Superfund project manager at EPA for 24 years. He received a Bachelor's degree in Geology from the University of Missouri-Kansas City, a Master's degree in Geophysics from Boston College, and a Ph.D. in Environmental Science from the University of Massachusetts in Boston. In addition to directing the investigations and cleanups at seven Superfund sites, Darryl has provided technical assistance in hydrogeology and geophysics to other project managers in EPA Region 1.