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CTL 1 Thompson, Inc. should observe and test placement of the embankment fill <br />during placement. <br />SURFACE DRAINAGE <br />Good surface drainage around the tailings pond is essential to protect the <br />embankment and reduce water infiltration. The underlying soils are sandy, clayey <br />gravels that are permeable. Snow melt should not be allowed to pond adjacent to <br />the embankment. Onsite drainage should be directed away from the embankment. <br />The surface and near surface soils are vulnerable to erosion especially from <br />concentrated flows. The Civil Engineer should address control of surface drainage. <br />In any case, concentrated surface runoff should not occur on unprotected natural <br />soils or near the embankment area. <br />CONSTRUCTION OBSERVATION <br />An earthen embankment is built of materials that are variable. The best pre - <br />design investigation and design activities cannot foresee all the conditions that will <br />arise during construction. Variations in the soils not indicated by our exploratory <br />borings and previous permeability test pits will occur. <br />Observations by experienced geotechnical engineers and /or technicians are, <br />in our opinion, essential during construction to discover conditions that may impact <br />the design of the embankment. The proper handling of soil will be important to the <br />final quality of the embankment. We believe it is essential to have a qualified <br />geotechnical technician observe the processing and placement methods used by <br />the contractor and test materials during embankment construction. <br />We recommend full -time construction observation and testing by <br />geotechnical personnel experienced in tailings -pond embankment construction to <br />verify the appropriate use of soils and rock and construction procedures and that <br />adequate compaction is achieved. <br />LIMITATIONS <br />Our boring locations were selected to provide a general characterization of <br />subsurface conditions to supplement previous exploration. Drilling access was <br />limited. We believe this investigation was conducted in a manner consistent with <br />that level of care and skill ordinarily used by geotechnical engineers practicing in <br />this area at this time. No warranty, express or implied, is made. <br />THE UNION MILLING COMPANY <br />TAILINGS POND EMBANKMENT AND FUTURE TAILINGS SLOPE <br />UNION MILL <br />CTL 1 T PROJECT NO. DN45,584 -130 <br />S: IPROJECTS415500 1DN45584.000113013. Letters1L11DN45584- 130- L1.doc <br />10 <br />