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The earthen materials to be utilized at the location of Pond #2 (at the newer tailings pond) are presumed to
<br />distinct from those at the first holding pond site, but will also require adequate compaction and smoothness.
<br />For both Pond #1 and Pond #2 sites, please characterize the embankment and floor materials especially in
<br />terms of texture and compaction ability. Please describe the placement of these materials in terms of site
<br />preparation, i.e., lift thickness, compaction, and attaining an adequately smooth surface.
<br />The revision calls for using a 60- to 80 -mil HDPE membrane for the liner. Please provide a more specific
<br />description of the liner material to be used, and the name of the manufacturer, if known at this time.
<br />There is no secondary liner included in the proposed plan, which raises the importance of proper design,
<br />proper liner material, proper sub -base preparation, and proper installation. Please state whether the operator
<br />is planning to have the manufacturer or supplier onsite to observe and direct the preparation and/or
<br />installation, or have such outside party actually perform any of these activities. Please provide the name of
<br />the outside party who will perform these services, if applicable.
<br />Since there is no secondary liner, and since the intent of Pond #2 is for evaporation, losses from this pond
<br />may be difficult to track. Therefore the Division must know the quality of the water which will be placed
<br />there. There is a monitoring well on the 9700 portal road, from which the mine pool water was sampled on
<br />August 17, 2011. Prior to dewatering, the operator must provide the analysis results to this office. If proper
<br />sampling techniques are not possible from this well, such as failure to avoid stirring up sediment in the
<br />workings, additional samples will be needed, possibly from long - holing during the driving of the decline.
<br />(This sampling does not directly involve this TR -17, but will be a requirement under the future technical
<br />revision regarding the new decline and the dewatering. The operator is being informed now of this future
<br />requirement in order that sufficient time is given for performing the analyses.)
<br />Related to the future mine dewatering is the need for ensuring full containment of mine water in the holding
<br />ponds, in order that there is no adverse impact to the prevailing hydrologic balance. The operator has had
<br />an area -wide water sampling program for several years now, in order to establish baseline water quality
<br />conditions. Since the sampling has been performed outside of Bulldog Mine permit requirements, and
<br />analyses have not been submitted to the Division, our office has no current information on the specific sites,
<br />the parameters sampled, or the results. To assess whether future dewatering, pumping and impoundment
<br />activities impact water quality, the Division requires an adequate baseline. Please describe the current water
<br />sampling program (surface or groundwater), such as site locations, sampling frequency, and duration of
<br />baseline, that is pertinent to this project and could contribute to detecting hydrologic impacts from the
<br />proposed activities. If there are results from pertinent samples, please provide them to the Division. If a
<br />baseline is lacking or sampling is insufficient, please provide information concerning implementing a
<br />sampling program, pursuant to the rules cites above.
<br />The technical aspects of this technical revision will also be reviewed by another Division staff member, who
<br />is copied on this letter, and whose comments will be forwarded to you.
<br />The changes proposed under this technical revision involve several structures, which will require additional
<br />reclamation. Therefore, the bond amount must be recalculated when all technical issues are adequate. If a
<br />bond increase is indicated, the revision will not become final until the bond has been submitted and
<br />accepted.
<br />As always, please provide two hard copies of all response materials, addressed to me at the address below.
<br />If you have any questions, please contact me at the Division's Durango Field Office: 691 CR 233, Room A-
<br />2, Durango, CO 81301; telephone 970 - 247 -5193.
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