The Lake County Forest Preserve District (LCFPD) is investigating the possibility of modifying the dam on Rasmussen Lake in Ethel’s Woods Forest Preserve. The lake is of low water quality with an eroding shoreline. Sediments have been deposited in the impoundment over the last 50 years. Twenty-eight sediment sampling locations were identified along seven transects over a 51.4 acre area in Rasmussen Lake to determine sediment thickness and obtain sediment material for physical and chemical analyses. The maximum sediment thickness was consistently 3.0-4.5 feet (ft) from the dam to the upper end of the lake. The sediment thickness was less than 2.5 ft near the shore and in transect 5, near the northern part of the lake. Sediment thickness did not increase either in the upstream or downstream direction. The average-transect sediment thicknesses ranged from 1.8 to 2.7 ft. The approximate total sediment volume that has accumulated in the 51.4 acres of the lake over the past 50 years is 115.1 acre-feet.