INSPEC21099

• Permit No: C1981038
• IBM Index Class Name: Inspection
• Doc Date: 9/23/1997
• Doc Name: MINE SITE EVALUATION INSPECTION REPORT
• Inspection Date: 8/19/1997
• Media Type: D
• Archive: No

professional engineer's (PE) stamp on future inspection reports, which it did in the
second quarter of 1996. With one exception however. resorts s~~h~~rro~ s ...,, Duly
1990 through the first quarter of 1_997 didn't include a PE's certification that ihP~(s
had been constructe ass eci 'Pd in thP~cian agprove~i br,y DMG as required in
4.09.1(11)(b). The exception was a February 1990 PE's certification of the late 1989
WRWDA reconstruction as approved in technical revision TR-7.
Engineer's certifications that features of the WRWDA were constructed as designed
were available in two cases. First, an August 29, 1983, engineer's report certified that,
among other things, topsoil was removed from the WRWDA site, the area was
prepared, refuse layers were placed and compacted, and surface drainage systems
were constructed as specified in revised waste disposal area designs approved by
DMG. Second, an engineer certified on January 1, 1997, that construction approved
for the northeast area of the WRWDA in technical revision TR-25 was completed in
accordance with the approved revision. Though the east underdrain was not
specifically mentioned in that certification, TR-25 approved its construction. The
engineer who directed the underdrain's construction was at the mine office during part
of our review. She confirmed that the east underdrain was built according to the
approved design. We reviewed a number of photographs that were taken of the
underdrain's construction in compliance with 4.09.1(11)(c). Though not associated with
a specific engineer's inspection report for the drain construction, the photos were
available at the mine office.
I also reviewed 3 reports of compaction test results that were submitted to DMG.
Compaction results were available in reports of tests conducted during the period of
September 1989 through November 1990, in September 1995, and in September 1996.
Of 235 samples taken from the WRWDA, results showed that all but six attained at
least 90% relative compaction of the maximum dry density. The six locations in
question were checked at varying depths to 30 feet and all achieved at least 90%
compaction at some depth down to that level, and none were less than 78%
compacted. Subsequent engineer's reports described continuing efforts to increase
compaction by excavating uncompacted material, allowing it to dry, and replacing and
recompacting it. The OWDA apparently wash t sam led r compaction.
We reviewed results of piezometric monitoring at the mine office. Our review focused
on the static water levels in piezometers B~ and B-8 as monitored semi-annually in
May and November 1996. B~ was installed in October 1981 at the southwest end of
the OWDA. B-8 was installed in 1982 and is located just south of the WRWDA pond.
Though critical target depths were not available, the static water levels measured in
May and November 1996 in piezometer B~ were 5.7 feet and 4.8 feet, respectively,
above the 99-feet-deep bottom. Static water levels measured in piezometer B-8 were
three inches above, and 8'/. inches below (in the mud, apparently), respectively, the
bottom at 38.7 feet-deep in the May and November 1996 monitoring.
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