Conclusions and Recommendations - Coal Waste Impoundments: Risks, Responses, and Alternatives - page 150

appears to be covered in general language authorizing investigation of all
relevant issues with respect to the impoundment. The committee recommends
that MSHA and OSM should have clear authority to review basin design. It
is not evident to the committee whether specific legislation to authorize more
detailed examination of basin issues is required or whether these issues can be
handled by additional rulemaking under existing authority.
The regulatory approach taken by MSHA and OSM with respect to the
design, construction, and operation of the embankment portion of
impoundments has been effective in general. The incidents that have occurred
involving impoundments have generally not been the result of significant
failures of the embankment structure. Similar guidance should now be provided
for the basin portion of impoundments. The committee recommends that
MSHA and OSM develop and promulgate guidelines for the site
evaluation, design, construction, and operation of basins. They should be
comparable in scope to the guidelines used in embankment design. The
guidelines should include methods for mitigation of any potential pathways for
release of coal slurry. Many of these mitigation measures will involve
established procedures for grouting, sealing of fractures, or construction of
embankments that line the basin rim, for example. At the same time, the
question of engineered bulkhead barriers used to isolate underground coal
mines from the coal slurry in the basin should be addressed. Current regulations
specify the design of bulkheads that are intended to protect miners from
underground explosions, but they do not provide for bulkheads intended to
support the high hydraulic heads that can arise in coal waste impoundments.
Hence, the committee recommends that MSHA review its current practice
and develop guidelines for the design of bulkheads intended to withstand
hydraulic heads associated with slurry impoundments.
While the embankments designed and constructed under the current
regulatory system have generally performed according to design, the committee
believes that prudence requires that MSHA and OSM continue to evaluate
worldwide experience with impounding structures, and to stay abreast of
lessons learned from failures experienced in other mining applications so that
their design criteria reflect the latest experience in all the mine sectors. The
committee recommends that MSHA and OSM continue to adopt and
promote the best available technology and practices with regard to the site
evaluation, design, construction, and operation of impoundments. MSHA
and OSM should commission periodic reviews of existing technical procedures
and practices, with particular attention to the basin. Results of the reviews
should be disseminated to industry. Based on