Urban Stormwater Wetland Sampling Demonstration
Summit County Soil and Water Conservation District
Basin Program Funds:
Nonpoint source pollution from urban areas threatens the water resources of northeastern Ohio and the entire Great Lakes basin. Opportunities and technologies exist to reduce pollutant loads, such as installing constructed wetlands in new developments or modifying existing storm water detention basins. However, no data exists in northeastern Ohio that demonstrates the effectiveness of storm water wetlands.
This project continued with a previous project in which two storm water detention basins were converted into storm water quality improvement wetlands. The basins are located in an industrial park in different subwatersheds of the Cayuga River in Summit County, Ohio. They were originally designed as dry detention basins, which only store water immediately following a storm and release it at a slower rate to prevent downstream flooding. Many of the smaller storm events flow through these basins without being retained. Research has shown that many of these smaller but more frequent storm events are responsible for flushing pollutants such as oils and grease, fertilizers, pesticides, and heavy metals into our waterways.
In order to help remove pollutants from storm water runoff, the detention basins were modified in the previous project. The project team performed a low cost retrofit on Basin #1 by adding a water level control device to the outlet pipe, which allows various water levels to be achieved in the basin. They also brought in soil to create a longer flow path within the basin. Basin # 2 was retrofitted by adding many new wetland features recommended by the Center for Watershed Protection, such as sediment fore bays, wetland cells of varying depths, long flow paths and a micro pool at the outlet.
The Summit County Conservation District was to sample the inflow and outflow of the two wetlands. To oversee the wetlands sampling and to offer comments and technical assistance, the district would form a Technical Advisory Committee made up of private consultants, university professors, and federal and local employees. The district was also to construct two temporary weirs on each of the wetlands, to be used in combination with automated samplers and flow monitors to measure inflow and outflow of the wetlands. The samples would then beanalyzed by a professional laboratory for suspended solids, total phosphorus, total nitrogen, biological oxygen demand, total organic, copper, lead, zinc, oil/grease, and fecal coliform bacteria.
Water samples have been collected and analyzed, interim and final reports have been developed, and results have been presented at one workshop. Forty-two individual samples were collected and analysis for a variety of nonpoint source pollutants. The results have shown that the constructed wetlands overall have reduced the amount of pollutants in the runoff. The past two sampling seasons have been abnormally dry in northeast Ohio; as a result, sampling runoff events became rather difficult. The ideal storm event was determined to be approximately .25 inch of rainfall. Due to timing and infrequent storms samples were taken during rainfall events of less than .25 inches. This will not affect our data, but more samples would have been better during the study period. Actual flow monitoring in the open ditches and submerged inlet pipes did not yield usable numbers due to equipment failures and installation difficulties. As a result, the flow data will be calculated based on modeling the various runoff events. While actual flow data would be preferable, the estimated flow should provide consistent data results.
Work will continue on analyzing the data in order to submit findings to the National Storm Water Best Management Practice Database. The wetlands will continue to be monitored by JCU as an ongoing research project.
Contact: Dave Ritter, 330-929-2871