PHYSICAL AND CHEMICAL PROPERTIES OF DREDGED, CONFINED DISPOSAL FACILITY SEDIMENTS AT JOHN REDMOND RESERVOIR, BURLINGTON, KANSAS

Many of Kansas’s flood control reservoirs are nearing the end of their lifespans as they are filling with sediment. In 2016, the state of Kansas pilot tested the feasibility of reclaiming dredged sediments for crop production from one of the largest reservoirs, John Redmond. Nearly 3,000,000 cubic yards of lake-bottom sediment was vacuum dredged and placed into five foot deep confined disposal basins. Given the presence of nitrogen and phosphorous, and trace amounts of arsenic, nickel, chromium, and lead in the lake sediments, we evaluated their concentrations in materials at two locations in one basin, along with the development of soil properties (texture, structure, and color). The goal of our study was to evaluate the suitability of the dredged material for future crop growth. Continuous 5-ft vertical soil profiles were obtained using a modified vacuum coring method. The mucky material consists of 2-10% sand, 28-40% silt, and 50-70% clay, with the coarsest material at depth. The upper 70cm are blocky and deeper samples are structure-less. The top 25cm are very dark greyish brown (2.5Y 3/2), with darker hues such as 2.5YR 2/1 observed in deeper samples. Phosphate, potassium, nitrate concentrations were measured using the mehlich-3 extraction method and range from 4.5-10.3, 550-840, and 0.5-4.0ppm, respectively. Phosphate concentration generally increased and nitrogen generally decreased with depth. The potassium concentrations generally decreased with depth, with the exception of two high concentration samples. The measured concentrations of phosphate and nitrate are lower, and potassium are higher, than is optimum for the growth of typical Kansas crops, but similar to those of surrounding soil. Phosphate and nitrate are both lower than those found in lake sediments. Potassium levels in the sediments were elevated compared to native soils. The analysis of trace metal concentrations is underway. Metals will be extracted from the soil using nitrogen digestion, then analyzed using the Atomic Absorption Spectrophotometer (AAS) and the Inductively Coupled Plasma Spectrophotometer (ICP). The results of this study will further assess the ability to grow crops on the reclaimed, dredged material of the confined disposal facilities.