COMMON
QUESTIONS &
ANSWERS
|
|
|
Volume 3, Number 1 (April 1998)
|
Q: |
Is the Pit water rising faster
or slower than expected? |
|
A: |
The water continues to
rise about one foot per month as expected. Because the Pit widens
toward the top, the rate of rise will eventually decrease. The
same volume of water (about 3 million gallons a day) will spread
over a larger surface area, meaning fewer inches of rise per
month.
Back to top |
|
Q: |
Has the Critical Water Level
been changed? |
|
A: |
No. The Critical Water
Level is still 5,410 feet. The regulatory officials remain convinced
that the situation is safe and under control as long as the water
stays below 5,410. Pumping and treatment of the water must be
well underway when the water approaches this elevation in the
Pit or in any of the bedrock monitoring wells and mine shafts.
If present trends continue, the water level in the Anselmo will
be the only point to approach 5,410.
Back to top |
|
Q: |
What is the water monitoring
program? |
|
A: |
Twenty-three wells and
14 mine shafts supply information about the deep bedrock aquifer.
Thirty-six wells provide similar data about the alluvial aquifer,
which is much closer to the surface. Each month, scientists manually
check and record the water levels in these wells. Twice a year,
they collect samples to analyze the water's chemistry. All of
this information helps scientists understand where the water
is coming from and how it is moving underground.
Back to top |
|
Q: |
Have the monitoring efforts
revealed any surprises? |
|
A: |
Yes. The latest one involves
changes in bedrock Well H. The water level of this well is usually
about 10 feet above the level of the Berkeley Pit, just like
other bedrock wells nearby. But last July, Well H's level started
falling, and by September it had dropped about 3 ½ feet.
Meanwhile, the Pit kept rising. From December through February,
the water levels of the Pit and Well H were just inches apart.
Well H is now gaining on the Pit again.
What is the significance of the surprise reading in Well H? It
appears to be an isolated incident caused by underground subsidence
(shifting of dirt) adjacent to the well. Well H is southeast
of the Pit in the middle of the old Pittsmont Mine workings where
the ground is known to be unstable. The water levels in all of
the surrounding bedrock wells remain high, indicating that flow
is still toward the Pit. It is important to look at the monitoring
well system as a whole, rather than focus solely on the performance
of a single well.
And Well H is not the only surprise to date. In 1989, the water
level in the Kelley shaft dropped two feet in one month, but
it, too, recovered (must confirm this). Well DDH-5 also occasionally
fluctuates. The monitoring program was set up specifically to
detect changes like these. When something unusual turns up, monitoring
is heightened at that spot, and scientists determine what action,
if any, needs to be taken. At Well H, water levels have been
checked weekly since October. On February 18, a special camera
was lowered 927 feet into the well to look for abnormalities,
and none were found.
Future years will bring many more monitoring well changes, especially
in the area between the Berkeley and Continental pits. See the
back page for details on how active mining will affect the monitoring
system.
Back to top |
|
|
