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Geocethnlcal 1 Emlronmental Enalneerina • Maerlab Tertlna December L, 1997 Seneca Coal Company 36600 County Road 27 P.O. Drawer D Hayden, CO 80477 Atm: Mr. Mike Altavilla, P.E. Job No. 97-3000 Subject: Summary Report, Pond Ol I Construction, Yoest Mine, Routt County, Colorado. Gentlemen: This letter bas been prepared m sum~~* =.+~P the test results and our observations made during the construction of the Pond 011 embankment and a review of the final as-built drawing for the Pond 011 site located at the Yoast Mine in Routt County, Colorado. As requested, Northwest Colorado Consultants, Inc. visited the project site on a part-time basis between August 26 and September 30 , 1997 to conduct density tests on the embankment fills constructed, as well as observe the conditions and construction operations at the project site. Clearing and grubbing of the site were initiated on approximately August 26 and we visited the site to verify the removal of topsoil and organics from the embankment site. It appeared that at least 3 feet of topsoil and organic materials were removed from the embankment and pond site. A key-way was excavated near the embankment centerline approximately 5 to 6 feet below the stripped surface and backfilled with compacted on-site materials. The embankment site was prepared to receive fill by thoroughly ripping the ground surface to a depth of approximately 2 to 3 feet, adding moisture and recompecting. The soils exposed at this depth appeared to be stable and were able to support heavily loaded construction equipment. The drainage blanket and toe drain were installed from the cutoff trench to the tce of the downstream side of the fill. The drainage blanket was constructed with I.5-inch washed r«k and wrapped in Mirafi 140N filter fabric. The tce drain was constructed with 6-inch perforated PVC pipe meeting ASTM 3034 requirements and daylighted with solid pipe at the south edge of the embankment fill. Our observations and testing of the fill operations were conducted between August 27 and September 30, 1997 and the reports indicate that the embankment fills were constructed in general accordance with the original design report. The daily construction reports are attached. An as-built drawing was prepared by the client following completion of the grading operations. We • understand that the pond excavation upstream of the embankment was deepened to provide the required storage capacity. The as-built drawing reflects this and other deviations from the original pond design including changes in spillway elevations. The pond embankment was constructed with an upstream (970) 879.7888 • Fax (970) 87&7891 29585 U.S. 40 West Box 775226 • Steamboat Springs, CO 80477