Within the Baker River watershed near the town of Warren is the former Ore Hill Mine site. This 10-acre site is the only known source of acid mine water impacting water quality in the Baker River watershed, and was intermittently mined for silver, lead, copper, and zinc starting in 1834.  The mine was reportedly one of the largest mines in the state before it was abandoned in approximately 1910.  The federal government acquired part of the site in 1937 for the White Mountain National Forest, and the federal Bureau of Mines studied the old workings during World War II.  A small amount of mica was subsequently mined from separate workings.  The remaining non-federal portion of the site was acquired by the National Park Service as part of the Appalachian Trail corridor in 1979.  The Park Service ceded management control and responsibility for Appalachian Trail corridor parcels in this area to the Forest Service in the 1980’s.

The Ore Hill deposit was a 48-foot wide massive sulfide-type vein at the surface, dipping steeply to the east.  The workings extended to more than 450 feet in depth. The ore was initially shipped to England for silver, but the operation was non-economic. Subsequent operations were also generally failures. The most active mining occurred between 1890 and 1910 when up to 35 men were employed at the site.  A custom smelter was imported from Belgium around 1904, but this venture failed by 1910.  The smelter was dismantled and shipped to Pennsylvania in the 1930’s.

No reclamation work was done on the mine site before it was abandoned, and there were approximately four acres of tailings (crushed and processed ore rock from which most of the metals have been removed) and waste rock piles that historically caused extremely poor water quality in Ore Hill Brook.  In 1984, the Forest Service re-routed the site surface water, and re-graded and capped the tailings, filling in a former small drainage channel that flowed through the site. Downstream surface water quality improved following this effort, but water quality problems remain.

Up to six seeps still discharge acidic water (pH 3.3) with high metals content from the waste rock pile and the tailings area.  One mile Ore Hill brook downstream from the site is essentially devoid of aquatic species due to aluminum precipitate in the streambed, and to low pH stream water with levels of dissolved zinc, copper, and cadmium that are toxic to aquatic organisms.  Water quality impacts are diluted further downstream, and impacts to the Baker River (4 miles from the Ore Hill site) are unknown but are not believed to be significant.

The Forest Service is currently addressing the site under its Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA) authority.  A Preliminary Assessment (PA) was completed in 2000 and a Site Inspection (SI) was completed in 2001. Additional site characterization and sampling was conducted and an Engineering Evaluation/Cost Analysis (EE/CA) was drafted in 2002 to evaluate alternatives.  More recent work includes a Treatability Study on the tailings and waste rock materials.  A Removal Action construction design was completed in 2005, and construction to mitigate the environmental impacts of the mine is planned for 2006.

The work will include excavating approximately 21,000 cubic yards of tailings and waste rock, hauling the material to an on-site repository area, performing phosphate-based treatment on the material to reduce metals availability, and placing the treated material in a designed repository.  It is anticipated that stream pH will increase, and that there will be more than a 98% reduction in metals leaving the site after the construction.  Ground water quality monitoring adjacent to the repository and site and downstream surface water monitoring is also planned.

More information on the Ore Hill Mine, including photos, is available through the White Mountain National Forest.