Drying and Oxidation Properties of Sediments from an Urban Lake Primary Researcher: Scott E. Castelli, 1998 Advised by: Dr. Aaron Jennings topics: LAKE REMEDIATION, SEDIMENT REMEDIATION, SEDIMENT OXIDATION, SEDIMENT DESICCATION, SEDIMENT VOLUME REDUCTION, SEDIMENT OXYGEN DEMAND, SEDIMENT CHEMICAL OXYGEN DEMAND The goals of this study were to predict sediment desiccation rates, volume changes and changes to the chemical oxygen demand (COD) and sediment oxygen demand (SOD) during a lake draining event. The study was initiated in response to the planned draining and dredging of Lower Shaker Lake, near Cleveland, OH. The Lower Shaker Lake is a 22 acre lake located in a highly urbanized area that is perceived of as being subject to eutrophication, high sedimentation rates and poor water quality, resulting in a lack of aquatic life. The draining and dredging of the lake was the proposed method of remediation and provided us with an opportunity to predict and study the effects of desiccation on sediment properties. As a result of this study we found that the long held notion of rapid sedimentation may be incorrect. A survey of the lake bottom, when compared to a survey performed in 1973, showed that the water depths have not changed significantly in the last 25 years (see Figure 1). This may be evidence that the lake depths are in a state of equilibrium and that no further significant sedimentation will occur. It is suspected that, during dry weather, the lake does experience some sedimentation, but that extremely elevated flows during wet weather (caused by the high percentage of impervious area in the watershed) scour sediments from the lake bottom. This cycle of sedimentation and scouring probably maintains the lake water depths at their current state. The study produced interesting results regarding the changes in sediment during desiccation. First, it was discovered that, because of the sedimentŐs high porosity and organic content, the drying process would take a very long time (on the order of 100Ős of days). The drying of the sediment was an important part of the lake draining and dredging process because dry sediment would be more easily removed by earth moving operations than the sediment as it currently exists: a high moisture content, gelatinous mass. Second, it was found that full sediment desiccation would result in a volume decrease of about 65%. Analysis indicates that a sediment reduction of this order will increase lake water volume by about 25%. This volume change process may have remedial implications on lakes and reservoirs where volume is an important consideration, such as water bodies used for drinking water storage or storm water retention. Third, it was observed that the sedimentŐs oxidative properties changed during the desiccation process. The COD decreased by up to 17% upon full desiccation while the organic content remained the same, implying that portions of the sediment chemical species have oxidized. Because oxidized chemical species usually control the phosphorous adsorption capability of sediments, this oxidation may have remedial implications regarding the lakeŐs ability to alleviate the eutrophication process. Observations show that the lake, commonly perceived of as being devoid of life, supports a surprisingly abundant and diverse population of turtles, fish and snails. Freshwater clams and sponges were also identified. A draining event is expected to kill much of the life in this lake that is already stressed by the urban surroundings. The nature of the surrounding environment may make repopulation of this animals slow, if not impossible. The driving force in this draining and dredging event was the notion that the lake may soon fill in if dredging does not occur. Our studies of the lake bottom topography show that this is not the case. With this evidence, we have recommended that the draining event be reconsidered to include plans for a partial water level drawdown if the event must still proceed. This may provide the animals with a place to live during the dredging process and hopefully will not stress the populations to a degree that they may never return. The unusual abundance and diversity of life in this heavily urbanized lake is something that should be valued and considered during this process. CWRU Department of Civil Engineering Main Menu | Sitemap | Department Activities | On-Campus Menu Communication Click to request a Graduate | Undergraduate Application Form. Click to get in touch with a Graduate | Undergraduate Student. Click to Schedule a Tour of the Department.