Browsing by Author "Sander, Andrew"

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    Inventory of Road Salt Use in the Minneapolis/St.Paul Metropolitan Area
    (St. Anthony Falls Laboratory, 2007-12) Sander, Andrew; Novotny, Eric; Mohseni, Omid; Stefan, Heinz
    In the northern regions of the U.S. and in Canada a water contaminant of increasing concern is chloride. The source of chloride contamination is mostly sodium chloride (NaCl) which is used in large quantities for road de-icing and for water softening. Chloride enters into the environment easily in snowmelt runoff and in wastewater treatment plant discharges. Because it is a fairly conservative material it can travel long distances without assimilation. It affects the quality of aquatic ecosystems. Because of its adverse effects on plants and aquatic animals, MPCA standards of 230mg/L and 800 mg/L have been set for chronic and acute exposure. The Twin Cities Metropolitan Area (TCMA) is one of the regions where salt is used for winter road maintenance and for water softening. The TCMA is an urbanized area with a population of about 2.7 million people. It is located at about 45oN latitude and has a reputation of cold and long winters. The TCMA is traversed by the Mississippi River and several of its tributaries, and claims to have 949 lakes within its seven counties and over 186 cities and townships. There are over 26,000 lane miles of roadways with impervious surfaces in the TCMA. In this report an inventory of the amount of road salt (NaCl) applied in the TCMA each year is given. This study was not aimed at evaluating the effectiveness, suitability or cost of using NaCl as a de-icer. In addition to the total amounts of salt used, it is of interest to identify and quantify the metrics that determine the rates of road salt application. The spatial and temporal scales will be large enough so that the results of this study can be compared to other regions in northern climates. Many sources of information regarding the use of road salt in the TCMA and the state of Minnesota were consulted. In the TCMA, most municipalities and counties purchase salt through contracts offered by the Material Management Division (MMD) of the state of Minnesota. The average amount of reported salt use per winter season (2001 to 2006) was 236,800 tons per year and varied between 243,000 and 274,000 tons per year. Relative to the sum of the contract amounts, the actual reported use was on average 93% for the TCMA. Not all municipalities participate in the MMD contract or keep track of the actual road salt applications. The amount of road salt used by municipalities without information was estimated based on a per capita road salt use rate of 0.045 tons per season per person. The rate was determined from the reported road salt use in the TCMA covering about 90% of the population.
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    Potential for Groundwater Contamination by Road Salt in Minnesota
    (St. Anthony Falls Laboratory, 2008-11) Sander, Andrew; Novotny, Eric; Mohseni, Omid; Stefan, Heinz
    In northern states of the U.S. and in virtually all provinces of Canada sodium chloride is becoming a water contaminant of increasing concern. The source of contamination is mostly anthropogenic: Salt (NaCl) is used in large amounts for road deicing and water softening. Sodium chloride enters into the environment easily in snowmelt runoff and from wastewater treatment plant discharges. Sodium chloride is not removed by conventional waste water treatment. It is a fairly conservative material and can travel long distances without assimilation. It affects terrestrial and aquatic ecosystems. Because of its adverse effects on plants and aquatic animals, water quality standards for Cl have been set, e.g. by the Minnesota Pollution Control Agency (MPCA) at 230mg/L and 800 mg/L for chronic and acute exposure, respectively. The Minneapolis/St. Paul (Twin Cities) Metropolitan Area (TCMA) is one of the regions where sodium chloride is used for winter road maintenance and for water softening. The TCMA is an urbanized area with a population of about 2.7 million people in seven counties. It is located at about 45oN latitude and has a reputation of cold and long winters. The TCMA is traversed by the Mississippi River and several of its tributaries, and claims to have 949 lakes within its seven counties and over 188 cities and townships. There are over 26,000 lane miles of roadways with impervious surfaces in the TCMA. In previous reports of this study we have given a budget for road salt applications in the TCMA and field observations of salinity in lakes of the TCMA. The goal of this study is to give an overview of measured chloride and sodium concentrations in groundwater (wells) of the TCMA. The information will be compared to statewide observations in Minnesota, and to other regions in northern climates. Changes in groundwater salinity in the TCMA and Minnesota over time, particularly the last 50 years are of particular interest, because it is suspected that aquifers are the ultimate recipients (sinks) of some of the road salt applied at the ground surface. This study is not aimed at evaluating the effectiveness, suitability or cost of using NaCl as a deicer.
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    A Salt (Chloride) Balance for the Minneapolis/St. Paul Metropolitan Area Environment
    (St. Anthony Falls Laboratory, 2008-08) Novotny, Eric; Sander, Andrew; Mohseni, Omid; Stefan, Heinz
    There are no natural sources of NaCl in the geology of the Twin Cities Metropolitan Area (TCMA) of Minnesota. Salinity in surface water or groundwater of the TCMA must therefore be of anthropogenic origin. The largest salt uses in the TCMA are for water softening and for road de-icing. Water softening occurs in individual households, and in commercial and industrial establishments. Backwash is typically disposed of in sanitary sewers and discharged from wastewater treatment plants to major rivers. Road salt is used for public safety on winter roads. Road salt is a solute in snowmelt water, which runs into storm sewers, small streams, rivers, lakes and wetlands. In the TCMA watershed analyzed, approximately 267,000 short tons (242,000 metric tonnes) of road salt (NaCl) are applied annually for road de-icing. Within the political boundaries of the seven county TCMA, the numbers are 350,000 short tons (315,000 metric tonnes). It is important to understand how these applications influence the environment. Salt balances for the entire TCMA and for 10 smaller sub-watersheds reveal that a large portion of the local road salt applied in the TCMA is not carried away in the Mississippi River water. Streamflow and bi-weekly concentration measurements from 2000 to 2007 indicate that the Minnesota and Mississippi Rivers import 235,000 tonnes of chloride annually from upstream into the Twin Cities Metropolitan Area and 355,000 tonnes are exported by the Mississippi River downstream. 120,000 tonnes are being added to the rivers as they travel through the Twin Cities. Of these 120,000 tonnes, approximately 87,000 tonnes come from wastewater treatment plants as determined from flowrate and biweekly concentration measurements in 2007/2008. The remaining 33,000 tonnes are attributed to road salt, and represents 22% of the total of 148,000 tonnes of chloride that are applied to the roads in the TCMA watershed every year. The latter figure was obtained from a detailed survey and inventory of road salt uses from 2000 to 2006. Roughly, 78% of the road salt applied is staying in the watershed. From chloride balances in 10 small sub-watersheds, slightly lower values of 65 - 73% were calculated.
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    Study of Environmental Effects of De-Icing Salt on Water Quality in the Twin Cities Metropolitan Area, Minnesota
    (St. Anthony Falls Laboratory, 2008-09) Stefan, Heinz G.; Novotny, Eric; Sander, Andrew; Mohseni, Omid
    A 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.
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    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, Omid
    A 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.