Browsing by Subject "Chlorides"
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Item Adaptive Management to Improve De-Icing Operations(Minnesota Department of Transportation, 2021-03) Baker, Lawrence A.; Wilson, Bruce; Klimbal, Doug; Furuta, Dan; Friese, Melissa; Bierman, JacobRoad de-icing is a major cause of chloride impairment in Minnesota's urban waters. The goal of our study was to develop an adaptive management (AM) strategy to reduce chloride impacts caused by de-icing operations. The AM process was informed by our analysis of chloride movement in a residential watershed, providing feedback to the street department of our collaborator, the City of Edina. A key finding was that most the chloride movement occurred during a small number of events, with half of annual chloride movement occurring in less than 50 hours during each of the two years of study. This observation means that targeting these events might be a more effective way to reduce chloride impacts than more generalized approaches. We also found that a significant amount of chloride added to streets during de-icing accumulated in roadside snow piles, likely contributing to groundwater contamination. To address this concern, we developed a spreadsheet tool to estimate steady-state (long-term) chloride concentrations in groundwater. Scenario analyses indicated that groundwater chloride levels in highly urbanized watersheds would eventually exceed water quality standards. We developed a second model, intended for use by urban planners, to estimate the impact of changing the percentage of salted impervious surface on chloride movement in re-developed watersheds.Item Durability of post-tensioning grout systems with mixed-In chlorides(2014-01) Thiesse, Benjamin LeeOne of the most important properties of concrete and grout is its ability to protect the structural steel that is essential to post-tensioned concrete. The purpose of this report is to determine the effect of various concentrations of chloride ions on the long term durability of pre-stressing strands embedded in grout. To achieve this objective, samples were created to mimic portions of a post-tensioned duct. Each duct was given a unique combination of chloride and water that would create an ideal environment for corrosion to take place. With the results of testing to date, it is clear that the amount of chloride is the only variable that was tested that had a significant effect on the rate of corrosion. The amount of water and characteristics of the specimen had a few trends but nothing that would lead to the conclusion that they play a significant role in the rate of corrosion.Item Investigating Wastewater Reuse at MnDOT Truck Stations(Minnesota Department of Transportation., 2019-05) Heger, Sara; Doro, Jessica; Rutter, Melissa C; Gustafson, Dave; Larson, SondraThe University of Minnesota (UMN) and the Minnesota Department of Transportation (MnDOT) conducted a study to determine whether implementing a wastewater reuse program would be a feasible option for MnDOT-owned truck washing stations. MnDOT has 137 truck stations in the state, where trucks are frequently washed to remove road salt build-up. MnDOT recognized an opportunity to potentially reuse the wastewater for appropriate greywater uses and recapture the salt for road use. Sampling was done to assess the wastewater contaminants in truck wash water at 11 truck-washing stations in Minnesota. Then technologies suited to removing organics and total suspended solids (TSS) but not chlorides were reviewed. The recommendation is that either a recirculating sand filter (RSF) or a membrane bioreactor (MBR) would be feasible technologies to use for this purpose. Using the MnDOT truck station in Arden Hills, Minnesota, an economic evaluation was done. Both systems could be used to effectively treat wastewater and produce brine for reuse, but the most economical solution for MnDOT would be to invest in a MBR. Compared with a RSF, an MBR is one-third less expensive over time, primarily due to low material and installation cost as well as a lower annual maintenance costs.Item Study of De-icing Salt Accumulation and Transport Through a Watershed(Minnesota Department of Transportation, 2017-12) Herb, William; Janke, Ben; Stefan, HeinzThe accumulation of chloride in surface waters and groundwater from road deicing and other sources is a growing problem in northern cities of the U.S., including the Minneapolis-St. Paul metro area. To inform mitigation efforts, the transport of chloride in surface waters of a metro-area watershed (Lake McCarrons) was studied in this project to characterize chloride transport by surface runoff, the residence time of chloride in surface water, and how variations in weather influence chloride transport and accumulation processes. Monitoring work over three winters showed that the residence time of chloride in small, sewered watersheds varied from 14 to 26 days, depending on winter weather conditions, with 37 to 63% of chloride applied as de-icers exported in snowmelt and rainfall surface runoff. In contrast, a monitored highway ditch exported less than 5% of chloride applied to the adjacent road. Stormwater detention ponds were found to act as temporary storage for chloride, with persistent layers of high chloride content at the bottom. Chloride monitoring data and runoff simulations were used to explore the possibility of snowmelt capture as a chloride pollution mitigation strategy. We found that capturing snowmelt runoff close to source areas (roads and parking lots) yields the highest chloride concentrations and removal potential.Item Study of Environmental Effects of De-Icing Salt on Water Quality in the Twin Cities Metropolitan Area, Minnesota(Minnesota Department of Transportation, 2008-09) Stefan, Heinz; Novotny, Eric; Sander, Andrew; Mohseni, OmidA study was conducted to generate knowledge on the environmental effects of de-icing salt, particularly sodium chloride (NaCl), on water quality in Minnesota, especially the Twin Cities Metropolitan Area (TCMA). The Mississippi River receives substantial sodium chloride inputs from the Minnesota River and waste water treatment plants as it passes through the TCMA. In addition, road salt applications in the TCMA use about 350,000 short tons of NaCl every year. A chloride budget at the scale of the TCMA and on individual sub-watersheds in the TCMA indicates that about 70% of the road salt applied in the TCMA is not carried away by the Mississippi River. Rates of seasonal road salt use are correlated with snowfall, road miles and population. Salinity in TCMA lakes increases in winter and decreases in summer. Ionic composition of dissolved substances in lakes of the TCMA suggests unnaturally high sodium and chloride concentrations compared to lakes and other water bodies in the Midwestern U.S. Data indicate a rising trend in urban lake water salinity over the last 30 years. Shallow groundwater in the TCMA, especially near major roadways, has started to show increasing chloride concentrations. Salinity trends in lakes and shallow aquifers of the TCMA are of concern.