ARCHIVED REPORTS_1999 - Laserfiche WebLink

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Once the Petromat layer was installed, soil was compacted over the Petromat and brought up approximately 7 feet above the original grades. At an elevation of about 48 feet msl a slope stability synthetic, Supac 6WS, was placed over the top portion of the vertical berm to prevent cracking and sloughing of the upper sections of berm. Additional layers of soil were compacted over the stability synthetic and Phase 1 construction of the eastern berm was completed at elevation of approximately 50 feet msl. At the time the vertical expansion of the eastern berm was completed, the sides of berm were trimmed, resulting in a final berm width of 12 feet. The sloughed material was removed from east side of the berm down to an elevation of about 41 feet msl and from the ash pit side of the berm to an elevation of approximately 43 feet, leaving a small amount of soil in the ash Pit. The purpose of leaving some soil in the ash pit was to avoid trimming the sluff too far down and disrupting the Petromat liner positioned at the base of the berm. The filling of the ash on the west side and waste on the east side of the berm progressed concurrently to prevent undue horizontal stresses on the berm and the possibility of lateral slipping or stability failures. Phase II Expansion - The second phase of expansion of the eastern berm was done in October and began with lightly scarifying the upper layers of the Phase 1 expansion. Soil was placed in 5 inch thick horizontal lifts and compacted using a sheepsfoot compactor. The berm was built to an elevation of 56 feet msl, at which point a second layer of Supac 6WS was positioned to ensure sidewall stability. Additional layers of compacted soil were placed over the stability synthetic, resulting in a final berm elevation ranging from 57.93 feet to 58.76 feet msl. Again, once the design elevation was reached, the sloughed material was removed from both sides of the berm and waste disposal operations commenced concurrently on both sides of the berm. Expansionconstruction along• boundary of pit tookplace. in August 1990,simultaneouslyinitial phase of construction • eastern expansion berm.•sure sidewall. was constructed in lifts of • more than 5 inches in thickness and extends along the southern berm from the southeast comer of the pit for a distance of .► • 11 feet. The final configuration is a 1.5:1 slope extending from the original grades to an elevation of about 50 feet msI. The expansion berm located along the southern boundary was constructed to a widthof •• i feet, with soil• • southern 1 - 12 feet and compacted ash makingr the remainderberm. .! t !' i t .• ! ct ii' ` t •sit 0