Benefits, Feasibility, and Design Recommendations for a Proposed Constructed Wetland, Athens, Ohio
The project objective was to evaluate a proposal for a wetland at the Oxbow Stream site on the Ohio University campus. To determine the feasibility of a constructed wetland, the site was thoroughly evaluated, which involved analyzing: 1) soil morphology and sediment metal content; 2) hydrology and site flooding potential; 3) various water quality indicators; and 4) quantity and quality of aquatic life. The Udorthents soil type of Oxbow Stream was qualitatively determined as sandy loam having 10-15% pebble sized gravel. Based on these characteristics, the site soil is not expected to support the desired study objectives. The sediment metal analysis indicated possible lead and copper toxicity and water toxicity if the pH fell below two. The site flooding potential was determined to be the same as the surrounding landscape: it is within the 100-year floodplain. Water flow was estimated as 0.043-0.047 cfs, representing low flow while average annual flow was estimated as 0.36 cfs. Based on the sediment mass loading, a minimum of 9.92 tons of sediment is expected to accumulate within five years in the proposed wetland. In order for sedimentation to have minimal impact on the design detention period, volume lost to accumulation of sediment should be kept minimal. A three-foot deep wetland would require an area of 11,920 ft ^2 in order to treat the sediment, assuming a 20-year accumulation and 5% loss to volume. The summed concentration of nitrite and nitrate were the only chemical parameters exceeding benchmark values. Conductivity, averaging 805 ?s, exceeded the typical fresh water range, which may be explained by the high sodium concentration. Bioassessment results provided evidence that some impairment is occurring. Of the eighty macro invertebrates collected, none were the pollutant sensitive EPT taxa and 81% were tolerant species. Using the Modified Virginia Save Our Streams (SOS) method, Oxbow Stream was determined as unacceptable ecological condition. Based on the results from the feasibility study, it was determined that the site is an adequate site for a constructed wetland as long as considerations are made for the construction of two additional wetlands. The first wetland cell would serve as a sediment retention trap. The second wetland cell would primarily serve to treat the exceeding nutrient concentrations and moderate pollutants and to minimize the impact of runoff. The proposed wetlands will result in a wide range of beneficial outcomes. They will serve as a natural filter for contaminants, a water storage reservoir protecting the Ohio University Student Center, and a sedimentation trap to protect the quality of Ohio University's Emeriti Pond. In its role as an educational lab for Ohio University, the proposed wetlands will require continuous maintenance and future investments.
School Location:USA - Ohio
Source Type:Master's Thesis
Keywords:wetland constructed design athens ohio site selection
Date of Publication:01/01/2004