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Ore Hill Environmental Situation and Data
Prior to work in 2006, the circa 1984 tailings cap was failing, six pH 3.3 seeps with hazardous metals emerge from 18,000 cubic yards of seasonally saturated, high-metal content waste rock and tailings, and one mile of stream was essentially devoid of normal aquatic life due to Aluminum precipitate on the stream bottom and surface water with toxic concentrations of some hazardous metals. Ore Hill Brook water quality may have been impacted as far downstream as the Baker River (four miles).
Uncontaminated surface and shallow subsurface waters from wetland areas above the mine site, and from a small pond adjacent to the waste rock pile, flowed into the waste rock pile and the tailings, dissolving the metal sulfide minerals and generating acid mine drainage (AMD). Rain and snow falling directly on the capped tailings and uncapped waste rock also entered the piles and generated AMD. There were also somewhat elevated lead levels in soils immediately adjacent to the waste rock and tailings areas.
The table below indicates the average concentration of various metals in the tailings at the Ore Hill site prior to 2006 work, as well as in background samples from the area, and the State of New Hampshire standards for metals in soils. Lead and zinc concentrations in the tailings were each well above background and state soil standards.
Ore Hill Tailings
| Metal | "Avg" tailings (xBG) | Background | State soil std. |
|---|---|---|---|
| Arsenic | 15.9 (2.2) | 7.24 | 11 |
| Cadmium | 17.3 (270) | 0.064 | 230 |
| Copper | 2395 (22) | 107 | No standard |
| Iron | 113,025 (2.45) | 46,000 | No standard |
| Lead | 15,376 (111) | 138 | 400 |
| Mercury | 2.06 (6.6) | 0.31 | 13 |
| Zinc | 6356 (30) | 214 | 2500 |
All values in mg/kg (milligrams/kilogram), or parts per million ("ppm")
The table below indicates the average concentration of various metals in the seeps at the Ore Hill site prior to 2006 work, as well as background samples from the area, one mile downstream, and the State of New Hampshire standards for metals in streams. All the metals listed were well above both background sample concentration and above state standards in the seeps on site, and cadmium, copper, and especially zinc were above state surface water standards one mile downstream in Ore Hill brook.
Ore Hill Area Surface Waters
| Metal | "Avg" Seep (xNH std) | Background | 1 mile downstream | NH stream standard |
|---|---|---|---|---|
| Aluminum | 30,000 (40) | 101 | 117 | 750 (ac) |
| Cadmium | 375 (395) | nd | 1.2 | 0.95 (ac) |
| Copper | 1,550 (430) | 7 | 11.8 | 3.6 (ac) |
| Iron | 11,000 (11) | 165 | 34 | 1000 (ch) |
| Lead | 1,950 (139) | 2.1 | 8.7 | 14 (ac) |
| Zinc | 118,000 (3250) | 26 | 520 | 36.3 (ac) |
| pH | 3.3 | 5.87 | 6.13 | 6-9 (range) |
Metals values in microgram/liter, or parts per billion ("ppb"). ac = acute exposure standard, ch = chronic exposure standard