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RESPONSE TO HINED LAND RECLAMATION DIVISION HYDROLOGY CONCERNS AT THE ALHA PLACER MINE Memos have been issued by Mined Land Reclamation Division (NERD) 'ndicating concerns regarding pond embankments that will be used to contain he recirculating water for the Placer mining operation. In response to these concerns from the MLRD, pond embankments have been altered in the field, and office reassessment has been performed. Field work is continuing, and minor differences may occur from estimates contained herein. Hl~AHR~S9TS • History A brief history of the embankments is useful information. The po d embankments present in the field today have a core embankment tha has been in place for over 50 years. The relatively small historic embankmen s were used by several mining operations over the years. Usage of the ponds 'mpounded mine waters upstream of the embankment and fine materials, i.e., ilt and clays, (also known as slimes) settled into the bottom of the pond Reports indicate that these fines were bulldozed out of the pond bottoms nd pushed up on top of the historic berms. Some of this material slid down th downstream slope of the resulting embankment and impinged on some vegetation at the toe of the embankment. This raised the ire of regulatory agencies, a d the mine applicant was directed to remove the material From the vegetation. To achieve this goal, bulldozers were used to pull the downstream face of th loose embankment up the slope and discharge it into the impoundment are temporarily in order to clear the downstream toe. Additional concerns Erom t e HERD at the time this operation was taking place resulted in more extensi a embankment evaluation and reconstruction. As a result, the downstream face of the modified historic embankm nts has been cleaned to within zero to three feet of the apparent original gro nd level. The material was then replaced in approximately 12 inches loose 1'fts and compacted using a vibrating sheet roller. The downstream slope w s reconstructed in a slope of 3 horizontal to 1 vertical as shown o Plate lA. The earthwork movement became so extensive, that the removal and ompaction effort was repeated for the upstream face of the embankments as w 11 as the downstream face. • Soils Data As discussed above, the embankment section has been extensively r vised from that which previously existed. Soils tests were performed on the disturbed embankments and the material was found to fall into two classific tions, SW- SM end CL. The clay soils (CL) are relatively limited in extent nd appear to be the slimes that were pushed out of the pond. For the most par , a 1