Projects

Ore Hill Mine, White Mt. National Forest

An innovative in situ sulfate reducing bioreactor (SRB) system was used to treat acid mine drainage (AMD) from an abandoned New Hampshire copper, lead and zinc sulfide mine. Our client is the US Forest Service.

Background

The Ore Hill Mine is located on the White Mountain National Forest in Grafton County, New Hampshire. A CERCLA removal action was completed at the Site in 2006 to mitigate AMD from the Site that was impacting surface water quality in Ore Hill Brook. Approximately 36,000 cubic yards of metal sulfide tailings and waste rock were excavated down to the bedrock surface, stabilized, and placed in an on-site repository. During the removal action, a previously unknown adit was uncovered within the excavated area at the Site and water began discharging from the adit. Post-removal monitoring of surface water quality at the Site indicated the adit discharge is characteristic of AMD with a low pH and elevated concentrations of metals, particularly aluminum, cadmium, copper, magnesium, lead, and zinc.

Approach

MSE completed a supplemental Engineering Evaluation/Cost Analysis (EE/CA) to develop and evaluate several active and passive AMD treatment options including limestone dosing and dumping, mine inundation, anoxic limestone drains, aerobic and anaerobic wetlands, SRBs, open limestone channels, limestone ponds, limestone leach beds, and slag leach beds. The preferred alternative was determined to be an SRB combined with aerobic wetlands for polishing.

MSE, with support from Golder Associates, designed and conducted an SRB pilot study at the Site to evaluate the metals removal efficiency of various substrate mixtures and determine the optimum mix for the Site AMD. The pilot study determined that an SRB could significantly decrease metals concentrations in the AMD using a mixture of limestone chips, straw, and manure. MSE designed and constructed a full-scale SRB system and series of aerobic wetlands at the Site in August 2009.