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position brief #2

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Jordan Sedlock
Jordan Sedlock

Chloride concentrations in rivers in snow-affected urban watersheds are increasing in all seasons, outpacing the rate of urban growth. A study found that 29% of sites examined had chloride levels higher than the EPA chronic criteria on over 100 days per year. Increased road salt application due to expansion of impervious surfaces and de-icing is causing chloride to accumulate and be slowly released throughout the year. From the 1940s to 1980s, annual road salt usage doubled from 9.6 to 19.6 million metric tons and has increased 3.9% per year since while urban area grew 2.8% annually. Recommendations include training workers, pre-wetting salt, calibrated spreaders, and considering alternative de

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Prepared for: Dr. Joel Moore, Towson University Prepared by: Jordan Sedlock, Towson University, GEOL 305, Environmental Geology Topic: Increasing chloride trends in all seasons in snow-affected urban watersheds Date: April 22, 2015 Source: Corsi et al. (2015) River chloride trends in snow-affected urban watersheds: increasing concentrations outpace urban growth rate and are common among all seasons. Science of the Total Environment. 508: 488-497. Statement of Issue Increased river chloride concentrations are resultant of increased road salt application to impervious surfaces during deicing periods. A study conducted by Corsi et al. found that 29% of snow-affected urban watershed sites examined, exhibited on average more than 100 days per year with chloride concentrations higher than the EPA chronic criteria. The U.S. EPA defines chronic criterion for chloride exposure to be 230 mg/L on a 4-day average.1 Chloride concentration trends in urban watersheds are found to be increasing in deicing conditions as well as present, now, in non-deicing conditions, suggesting that chloride is being stored within hydrologic reservoirs (increasing baseline concentrations of chloride) and slowly released throughout the year. The increases in chloride concentrations are attributed to increased road salt application to the increasing urban land cover during deicing periods. The effects of increased chloride are damaging to the environment and hydrologic systems as well as aquatic life in affected areas. This excess sodium chloride increases salinity and threatens drinkability of surface water in affected areas; within the next century, scientists predict that this source of water will no longer be potable and fit for human consumption. Historical Background From the 1940s to the 1980s, rate of road salt application increased to an annual average of 9.6 million metric tons/year; from the 1980s to 2011, an annual average of 19.6 million metric tons/year.1 Also, from 1987 to 2010, road salt sales have increased by about 3.9%/year while urban land cover has only increased by about 2.8%/year.1 Road salt sales have outpaced urban land cover by more than 40%.1 More road salt is being applied to impervious surfaces for deicing than is necessary, either, in attempt to maintain longer, ice-free conditions, because density of impervious surfaces have increased per unit of urban land cover, or differences in weather between the 40s and now could warrant different application rates and different amounts of road salt. Also, increased usage of road salt has increased baseline concentrations of chloride in shallow groundwater systems, indicated by present and elevated levels of chloride observed throughout the entire year. Potential Solutions Potential solutions for this issue include reducing applications of road salt, providing training for most effective use, pre-wetting salt to maximize retention to road surfaces, using carefully calibrated applicators, implementing anti-icing techniques using organic glycols, for example, to facilitate plowing, or using alternative chemicals such as organic salts like calcium magnesium acetate or sodium acetate. It would be difficult to reduce application because of increased density of impervious surfaces however; using carefully calibrated dispensers to evenly distribute salt could help reduce excess amounts applied to roads. Pre-wetting is also an option that is effective and low in cost. Proper training for employees is very important as well as relatively low in cost and more effective than not providing any type of informative seminar prior to deicing. As far as alternative chemicals, organic compounds used for deicing tend to have negative impacts on the environment similar to inorganic compounds. Environmental assessment is recommended prior to implementing use of any new organic compounds for deicing. Recommendations 1) Provide information seminar to ensure employees understand importance of proper application 2) Implement a pre-wetting technique to ensure maximum retention to road surfaces/ reduce runoff 3) Utilize carefully calibrated dispensers to evenly disperse salt/ reduce excessive application/ reduce runoff 4) Assess environmental conditions and consider implementing different chemicals to slow/ lower increasing chloride concentrations

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position brief #2

  • 1. Prepared for: Dr. Joel Moore, Towson University Prepared by: Jordan Sedlock, Towson University, GEOL 305, Environmental Geology Topic: Increasing chloride trends in all seasons in snow-affected urban watersheds Date: April 22, 2015 Source: Corsi et al. (2015) River chloride trends in snow-affected urban watersheds: increasing concentrations outpace urban growth rate and are common among all seasons. Science of the Total Environment. 508: 488-497. Statement of Issue Increased river chloride concentrations are resultant of increased road salt application to impervious surfaces during deicing periods. A study conducted by Corsi et al. found that 29% of snow-affected urban watershed sites examined, exhibited on average more than 100 days per year with chloride concentrations higher than the EPA chronic criteria. The U.S. EPA defines chronic criterion for chloride exposure to be 230 mg/L on a 4-day average.1 Chloride concentration trends in urban watersheds are found to be increasing in deicing conditions as well as present, now, in non-deicing conditions, suggesting that chloride is being stored within hydrologic reservoirs (increasing baseline concentrations of chloride) and slowly released throughout the year. The increases in chloride concentrations are attributed to increased road salt application to the increasing urban land cover during deicing periods. The effects of increased chloride are damaging to the environment and hydrologic systems as well as aquatic life in affected areas. This excess sodium chloride increases salinity and threatens drinkability of surface water in affected areas; within the next century, scientists predict that this source of water will no longer be potable and fit for human consumption. Historical Background From the 1940s to the 1980s, rate of road salt application increased to an annual average of 9.6 million metric tons/year; from the 1980s to 2011, an annual average of 19.6 million metric tons/year.1 Also, from 1987 to 2010, road salt sales have increased by about 3.9%/year while urban land cover has only increased by about 2.8%/year.1 Road salt sales have outpaced urban land cover by more than 40%.1 More road salt is being applied to impervious surfaces for deicing than is necessary, either, in attempt to maintain longer, ice-free conditions, because density of impervious surfaces have increased per unit of urban land cover, or differences in weather between the 40s and now could warrant different application rates and different amounts of road salt. Also, increased usage of road salt has increased baseline concentrations of chloride in shallow groundwater systems, indicated by present and elevated levels of chloride observed throughout the entire year. Potential Solutions Potential solutions for this issue include reducing applications of road salt, providing training for most effective use, pre-wetting salt to maximize retention to road surfaces, using carefully calibrated applicators, implementing anti-icing techniques using organic glycols, for example, to facilitate plowing, or using alternative chemicals such as organic salts like calcium magnesium acetate or sodium acetate. It would be difficult to reduce application because of increased density of impervious surfaces however; using carefully calibrated dispensers to evenly distribute salt could help reduce excess amounts applied to roads. Pre-wetting is also an option that is effective and low in cost. Proper training for employees is very important as well as relatively low in cost and more effective than not providing any type of informative seminar prior to deicing. As far as alternative chemicals, organic compounds used for deicing tend to have negative impacts on the environment similar to inorganic compounds. Environmental assessment is recommended prior to implementing use of any new organic compounds for deicing. Recommendations 1) Provide information seminar to ensure employees understand importance of proper application 2) Implement a pre-wetting technique to ensure maximum retention to road surfaces/ reduce runoff 3) Utilize carefully calibrated dispensers to evenly disperse salt/ reduce excessive application/ reduce runoff 4) Assess environmental conditions and consider implementing different chemicals to slow/ lower increasing chloride concentrations