April 1997

Bird Protection Plan is Working
PitWatch Issue Volume 2, Number 1

In response to and following the deaths of 342 snow geese in the Pit in November 1995, Montana Resources' has devised and implemented a plan to deter birds from landing in the Pit. The plan was recently granted official approval by EPA and MDEQ. For about a year now, the company has been using a combination of Phoenix Wailers (noise-making devices that scare birds), rockets, spotlights, flares, and shell crackers to shoo mainly geese and ducks away from the toxic water. When necessary, mine workers also travel by boat into the Pit to scare the birds. An estimated 4,000 birds were hazed away during 1996.

The Company will continue its efforts each year during the spring and fall migration seasons.

---

October 1997

A Tale of Two Aquifers
PitWatch Issue Volume 2, Number 2

Aquifers are places where water is found in rocks and soils underground. The area around the Berkeley Pit contains two main underground aquifers - the alluvial aquifer and the bedrock aquifer.

The alluvial aquifer is closest to the surface. Water flows freely through the layer of ground called the alluvium, a porous mixture of sands, gravels, and clays. Near the east wall of the Pit, the alluvium is saturated with water from this aquifer.

The bedrock aquifer runs deep below the ground. It's a "confined aquifer," trapped within fractured bedrock which water cannot easily pass through. In areas adjacent to historic mining activities, this aquifer was dewatered by large pumps located underground to allow for underground mining. The pumps were turned off in 1982, and since then, the dewatered area has been filling back up again.

These two aquifers are independent systems, separated by a thick layer of weathered bedrock that hinders water from the alluvial aquifer from seeping down into the bedrock aquifer. Instead, water from both aquifers is flowing toward the Pit because it's the lowest spot in the area.

Monitoring wells installed throughout the area are used to closely track the water levels and the water quality of both aquifers. Since the monitoring began, the alluvial aquifer has remained pretty much constant, fluctuating only a few feet here and there depending on seasonal precipitation. In contrast, the bedrock aquifer in areas of historic dewatering has been steadily rising to restore itself to pre-mining levels.

The monitoring wells also allow the scientists to measure the pressure differential between the two aquifers, expressed in pounds per square inch (psi). The downward pressure of the alluvial aquifer is much greater than the upward pressure of the bedrock aquifer. Even if the weathered bedrock weren't there, the water migration would still be downward, from the alluvium into the bedrock, because of this stronger downward pressure (technically referred to as the downward gradient).

The downward gradient will keep the water confined within the Berkeley Pit even when the water reaches the bedrock-alluvial interface at about the 5,260-foot level. At that level, the two aquifers will start to come in contact, but the force moving the water will continue to be downward and toward the Pit.

The gradient would eventually reverse if the Pit water were to exceed the 5,410-foot critical water level, but that will not be allowed to happen. Remember, pumping and treatment of the water must be well underway when the water in the Pit—or in any of the monitoring wells—approaches the critical level. If present trends continue, the Anselmo shaft (the one with the highest current water level reading) will be the first and only point to approach 5,410 feet.

---

Horseshoe Bend Contigency Plan Taking Shape
PitWatch Issue Volume 2, Number 2

Right now, the Horseshoe Bend diversion project is successful. It's diverting more water than expected from the Pit, and Montana Resources (MR) has encountered no problems with reusing a portion of the treated water at its concentrator. The Horseshoe Bend Contingency Plan spells out various options for handling the flow (3.8 million gallons per day) in the event that 'business as usual' has to stop—due to suspended mining operations, for example.

If the stoppage is for six months or less, MR and ARCO will be allowed to let the water once again flow into the Pit. If long-term problems are encountered, they will be required to find another way to treat the water. Options explored in the contingency plan include building a new treatment plant, converting the concentrator into a treatment plant, or using the Yankee Doodle Tailings Pond as a treatment facility. We'll continue to update you on the contingency plan as it is further developed.

---

Meet Our Science Fair Winners
PitWatch Issue Volume 2, Number 2

The Committee awarded $50 savings bonds to each of these students. Their science fair projects all explored important topics related to the Berkeley Pit. Congratulations, and keep up the good work! In fact, the Committee intends to offer awards again at the 1998 Science Fair, and students are encouraged to choose projects related to the Pit for next year's competition.

	Joe Metesh 4th grade, Kennedy Elementary What Makes Acid in the Berkeley Pit?
	Becky Patton 5th grade, Longfellow Elementary Can You Cleanse Polluted Water by Boiling or Freezing?
	Jamie Rozan 6th grade, Longfellow Elementary Taking Minerals out of Pit Water
	Alec Macgregor 7th grade, East Middle School The Effects of Lime Addition into the Warm Springs Ponds Systems
	Brian Wheeler 8th grade, Ramsay School Remediation of Berkeley Pit Water using Chemical Adjustment of pH Levels

Back to PITWATCH News Archive

---