An assessment of the performance of federally regulated sedimentation ponds

Abstract

A study was undertaken to evaluate the performance of federally regulated sedimentation ponds, used in conjunction with surface mining operations in the semi-arid southwest. Emphasis was placed on the assessment of pond performance under conditions of hydrologic uncertainty represented by precipitation inputs of varying frequencies and durations. A hypothetical watershed with characteristics common to the study area functioned as the medium for surface water flux to the detention facility. Pond design was based on accepted hydrologic and engineering procedure and concurred with published federal reclamation statutes. Computer programs were utilized to model both the temporal characteristics of southwestern convective rainfall and the generation of water and sediment inflows resulting from the application of storms over the watershed. A previously developed sedimentation routine was then used to determine effluent sediment concentrations corresponding to the modeled events. Three watershed-pond conditions were investigated to assess the efficacy of the sedimentation pond in meeting effluent quality standards. Results indicated that poor pond performance ensured unless chemical treatment was maintained. Since variations in precipitation intensity influenced predicted pond performance, it was recommended that hydrologic uncertainty be considered in the drafting of regional reclamation statutes.