The Thorgren Basin, located in Valparaiso, IN, was created as a component of the stormwater management system for the city. The basinâ€™s primary function is to collect stormwater from two separate regions of the Salt Creek Watershed after large storm events, that is then discharged through a single outlet. In its current state the basin has limited infiltration capabilities due to a lack of vegetation and pervious surfaces. The Save the Dunes Conservation Fund, a local non-profit group, provided a cost share opportunity to naturalize Thorngren basin. The goal of the summer 2011 project was to create a monitoring strategy for the basin, collect baseline water quality data to later evaluate the effectiveness of the retrofit, and provide public education and awareness of the project. Water quality and quantity parameters were evaluated on weekly sampling events within the interior and exterior of the basin. The water quality parameters analyz ed include Total Suspended Solids (TSS), nitrates, Total Phosphorus (TP), Dissolved Oxygen (DO), pH, temperature, and conductivity. Benthic macroinvertebrates were also collected to assess the extent of biologic degradation. Water quantity was evaluated using discharge rates from the inlets and outlets of the basin, along with evaluating the retention rates after storm events. After examining the water quality parameters, the northern most inlet (21F and 21B) had the most inconsistent water chemistry values and was the main contributor to water pollutants such as nitrates, Total Suspended Solids (TSS), and E. coli bacteria. By the time pollutants reached the outlet, the data reflects a mild dilution of nutrients and sediment, whether it be absorbed by plant or macroinvertebrate life. The effectiveness of the retrofit will be noted by the decrease in these pollutants and water chemistry after future data is collected post-implementation caused by alterations in plant species and the internal structure of the basin.
Argyilan, Erin; Birchfield, Jennifer; Goyne, Tom; Grabos, Nicole; Soley, Caitlin; and Wunsch, Jennifer, "Baseline Data Analysis of the Throgren Basin Retrofit" (2011). Symposium on Undergraduate Research and Creative Expression (SOURCE). 87.