REP28887

• Permit No: M1985029
• IBM Index Class Name: Report
• Doc Date: 6/8/1990
• Doc Name: RESPONSE TO MLRD-HYDROLOGY CONCERNS AT ALMA PLACER MINE
• Media Type: D
• Archive: No

RESPONSE TO
MINED LAND RECLAMATION DIVISION
HYDROLOGY CONCERNS AT THE
ALMA PLACER ?SINE
\J
Memos have been issued by Mined Lend Reclamation Division (HERD)
concerns regarding pond embankments that will be used to contain 1
recirculating water for the Placer mining operation. In response
concerns from the MLRD, pond embankments have been altered in the
office reassessment has been performed. Field work is continuing,
differences may occur From estimates contained herein.
• 8lstor~
A brief history of the embankments is useful information. The poe
embankments present in the field today have a core embankment that
place for over 50 years. The relatively small historic embankment
by several mining operations over the years. Usage of the ponds i
mine waters upstream of the embankment and fine materials, i.e., e
clays, (also known as slimes) settled into the bottom of the ponde
indicate that these fines were bulldozed out of the pond bottoms
on top of the historic berms. Some of this material slid down the
slope of the resulting embankment and impinged on some vegetation
of the embankment. This raised the ire of regulatory agencies, ar
applicant was directed to remove the material from the vegetation.
this goal, bulldozers were used to pull the downstream Face of the
embankment up the elope and discharge it into the impoundment are:
in order to clear the downstream toe. Additional concerns from tt
the time this operation was taking place resulted in more extensi~
evaluation and reconstruction.
As a result, the downstream face of the modified historic embanks
cleaned to within zero to three feet of the apparent original gro
The material was then replaced in approximately 12 lnches loose 1
compacted using a vibrating sheet roller. The downstream slope w
reconstructed in a slope of 3 horizontal to 1 vertical as shown o
The earthwork movement became so extensive, that the removal and
effort was repeated for the upstream face of the embankments as w
downstream face.
• Soils Data
As dlscussed above, the embankment section has been extensively re
that which previously existed. Soils tests were performed on the
• embankments and the material was found to fall lnto txo classifica
SM and CL. The clay soils (CL) are relatively limited in extent a
be the slimes that were pushed out of the pond. For the most part
ndicating
he
to these
field, and
and minor
has been in
were used
pounded
It and
Reports
d pushed up
downstream
t the toe
the mine
To achieve
loose
temporarily
MLRD at
embankment
has been
level.
end
Plate IA.
as the
sad from
sturbed
ons, SW-
appear to
a
1