2007-03-20_PERMIT FILE - C1996083

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M03106GE • 4.1 Foundation Preparation The foundation area of the gob pile site, top soil storage pile site and the cover material storage pile site should be cleared of all vegetable, organic or deleterious material prior to placement of the fill materials. The clearing operations should extend beyond each edge of the proposed fill area a distance sufficient to insure that the embankment fill materials are not placed on any deleterious material or at least five (5) feet, whichever is greater. This concept is shown on Figure 3. The soil material exposed in the clearing operations should be moisture conditioned, mixed and proof compacted prior to placement of the embankment fills. Any loose, low density or pumping areas exposed during the proof compaction operations should be removed and replaced with compacted fill material. Areas to receive fill should be con- structed with a toe key and benched into competent foundation material. The key and bench concept is shown on Figure 3. We should be called to observe the soil materials exposed during the clearing operations to verify the foundation conditions. Suggested guidelines for specifications for placement of compacted fill are provided in Appendix C. 4.2 Foundation Drain We recommend that the gob pile design and construction include a foundation drain. The purpose of the foundation drain is to intercept and collect water which may infiltrate through the gob material and collect at the natural foundation soil contact. The foundation drain is to help lower the phreatic surface and reduce hydrostatic pressures in the gob embankment toe area which will then increase the integrity of the slope. The drain system should be included at the bottom back of the toe key and at the back of several benches. This concept is shown on Figure 4. We should observe the key and bench preparation to verify that the key and bench extends into competent material. The drain system should consist of a drain pipe about three (3) to four (4) inches in diameter and surrounded by about three (3) to four (4) cubic feet per linear foot of drain of a free draining aggre- gate which is surrounded by an appropriate geotextile filter fabric. The drain should be graded to drain to positive gravity outlets. The outlets should be maintained to prevent them from becoming frozen or plugged and equipped with guards to prevent access by rodents or other animals. The drain system concept is shown on Figure 4. We did not observe springs or seepages in the gob pile foundation area during our field study. If seepages or springs are exposed u 4 ~Lam6ert ana ~,o~ociateo CGNSULTING GEOTECN NICAL ENGRIEERS ANO MATERIAL TESTING