REP26671 - Laserfiche WebLink

Home Browse Search

By using the same rationale as shown e6ove, and using the 9.01 ac-ft existing storage • capacity, the pond has a current capacity of 2.1 MUSLE~s. T he equivalent sediment generated from approximately two 10-yr, 24-hr precipitation events Could be stored beneath the principal spillway elevation. This is an adequate amount of sediment storage; therefore, no remedial sediment clean out work is scheduled during the next year. Sedimentation Pond 006. Sedimentation 'Pond 008 was surveyed in 1990 for sediment accumulation during the scheduled pond sedimentation surveys. The survey information was utilized to develop a Contour map. This contour map was used to Calculate the sediment storage beneath the principal spillway. The sediment storage capacity was compared to the previous survey conducted in 1987. The results ere as follows: POND 008 1987 Survey 1990 Survey Capacity Cumulative Capacity Capacity Cumulative Capacity Elevation (AC-ft) (AC-ft) (Ac-ft) (Ac-ft) 7002 0 0 0 0 7004 0.42 0.42 0.12 0.12 • 7006 1.12 1.54 0.88 1.00 7008 1.86 3.40 1.64 2.64 7010 2.56 5.96 2.36 5.00 7011.4 2.20 8.16 2.14 7.14 The As-Built Report for this pond was done in April 1988. (See Appendix 7-be, Tab 7, volume 5). This report showed an available sediment storage of 8.16 ae-ft below the principal spillway elevation of 7011.4. Sediment inflow into the pond was based on the USLE. The rate was calculated at 1.8 ac-ft/year, or a total design capacity of approximately 4.5 years. By using the same rationale as shown above, and using the 7.14 ac-ft existing storage capacity, the pond now has a total life of 4 years. Peabody has commi tted to clean the pond when the sediment capacity reduces to 3.3 ac-ft of storage, which is 40X remaining sediment storage (based on 8.16 ec-ft initial storage). Therefore, no remedial sediment . cleanou[ work is scheduled during the next year. 8