2009 Road Salt Symposium. Eric Novotny, Andrew Sander, Omid Mohseni, Heinz Stefan St Anthony Falls Laboratory. (Funded by LRRB Mn/DOT)

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1 De-icing salt impact on Minnesota Waters 2009 Road Salt Symposium February 3, 2009 Eric Novotny, Andrew Sander, Omid Mohseni, Heinz Stefan St Anthony Falls Laboratory (Funded by LRRB Mn/DOT)

2 Agenda Impact of salt application on the environment Salt applications Cl- budget Twin Cities Metropolitan Area (TCMA) watershed Evidence of chloride retention

3 Road salt use has been rising across the country and in Minnesota

4 NaCl can negatively impact the environment Decreases the biodiversity of benthic and plant communities (1-4) Increases transport and bio-availabilty of heavy metals (5-7) Produces more toxic snowmelt runoff events (8) Chloride levels of 1000 mg/l can have lethal and sub- lethal effects on aquatic plants and invertebrates. Continuous chloride levels as low as 230 mg/l are harmful to aquatic life (9) Chronic standard of 230 mg/l based on a 4-day average can be exceeded once every 3 years on average Acute standard of 860 mg/l for a 1-hour duration can be exceeded once every 3 years on average

5 How much salt is retained in the Metropolitan Area?

6 (Sander et al. 2007) Inventory of Salt Applications

7 349,000 tons of road salt are applied in the TCMA every year by cities, counties and the state and private users. (Sander et al. 2007)

8 Chloride Budget for Minneapolis/St Paul Metropolitan Area (Novotny et al. 2008)

9 Methodology: Chloride Budget Inflow/Outflow Assembled flow data from the USGS and chloride grab sample data from the Metropolitan Council to determine the mass of chloride coming into the watershed and the amount leaving. Applications in the Metro Area/Loads Road Salt Estimated the amount of salt applied in the watershed by using road miles. WWTP effluent Metropolitan Council collected samples and flow rates from area waste water treatment plants (WWTPs) Other Estimated significance of other loads i.e. industries, fertilizers, and natural sources. Storage =Inflow +Loads Outflow

10 Chloride concentrations in the Mississippi River increase as it travels through the metro area (Novotny et al. 2008)

11 (Novotny et al. 2008) River Inflows and Outflow

12 Anthropogenic Loads Waste Water Treatment Plant Effluents 96,000 tons Cl- Road Salt Application (NaCl) 163,000 tons Cl- Other loads considered but determined to be insignificant: natural sources, fertilizers, industrial discharges

13 The amount of salt exported from the TCMA is greater then the input of chloride from point sources (inflow + WWTPs) (Novotny et al. 2008)

14 Export of chloride from road salt (Novotny et al. 2008)

15 128,000 tons of the chloride applied in the TCMA is not carried away by the Mississippi River. It is retained in the watershed. Inflows: 260,000 tons WWTP : 96,000 tons Road Salt: 163,000 tons Outflow: 391,000 tons Net Export : 35,000 tons Retained: 128,000 tons Percent exported: 22% Percent retained: 78%

16 What evidence is available for retention of salt in the Minneapolis/St. Paul Metropolitan Area?

17 Impacts were observed in 13 areas lakes 9 lakes were sampled between 1/15/2006 5/29/ lakes were sampled between 2/15/2004 4/13/2005 (Novotny et al., STOTEN 2008)

18 The chloride concentrations in lakes are highest at the bottom of the lake during the late winter and early spring causing a seasonal salinity cycle and monomictic behavior. (Novotny et al., STOTEN 2008)

19 Instrumentation was installed to study the accumulation of salt continuously in Tanners Lake

20 Elevated chloride concentrations are present in 9 metro area lakes near major roads (11) Sodium and chloride concentrations show greater differences between urban and other lakes than other major ions a From Wetzel (2001). b From Long Term Ecological Research (LTER) site (North Temperate Lakes (Trout) Region). C Averages from lakes in (Gorham, Dean et al. 1982). Minnesota d Median concentrations from area lakes studied during 2006/2007. Samples taken 11/15/1007. (Novotny et al., STOTEN 2008)

21 Seasonal patterns in chloride concentrations were observed. High concentrations at the end of winter were reduced by flushing events in the spring and summer. (Novotny et al., STOTEN 2008)

22 Lake chloride concentrations are increasing by 1.5 mg/l per year. Increasing trends were found in all 38 lakes analyzed regardless of location. (Novotny et al., STOTEN 2008)

23 High concentrations of sodium and chloride penetrate into the lake sediment pore water (Novotny et al., STOTEN 2008)

24 Chloride is accumulating in the shallow groundwater in the Twin Cities Metropolitan Area. Red well locations represent shallow wells (<50ft) Blue well locations represent wells >50ft Denotes Cl - concentrations above EPA secondary drinking water limit of 250 mg/l (Sander et al. 2008)

25 Concentrations are highest in the shallow surficial aquifers (Sander et al. 2008)

26 Conclusions 1) 349,000 tons of road salt are being added to the TCMA every year with 24% coming from private and commercial sources and 76% coming from cities, counties and the state. 2) A large portion of the chloride applied to the roads for deicing is being retained temporarily in nearby lakes and permanently in groundwater. 3) Lake concentrations near roadways in the TCMA have chloride and sodium concentrations 25 and 10 times higher respectively than other lakes located throughout Minnesota. 4) The added lake salinity is seasonal, causing some lakes to become monomictic, and affects lake sediments as well. 5) Salt retention in urban lakes has caused lake chloride concentrations to increase by 1.5 mg/l every year. 6) Chloride is also being retained in the groundwater with concentrations in shallow wells near major roadways above 250 mg/l.

27 More information Reports: ( Stefan, H., Novotny, E., Sander, A., Mohseni, O., Study of Environmental Effects of De- Icing Salt on Water Quality in the Twin Cities Metropolitan Area, Minnesota. Minnesota Department of Transportation, St. Paul, MN. Report No. MN/RC Sander, A., E. Novotny, O. Mohseni, H. Stefan, Inventory of Road Salt Uses in the Minneapolis/St. Paul Metropolitan Area. University of Minnesota, St. Anthony Falls Laboratory Report No. 503, December 2007, 46 pp. Novotny, E., Sander, A., O. Mohseni, H. Stefan, A salt (chloride) balance for the Minneapolis/St. Paul Metropolitan Area Environment. University of Minnesota, St. Anthony Falls Laboratory Report No. 513, August 2008, 23 pp. Novotny, E., Sander, A., O. Mohseni, H. Stefan, Road Salt Effects on the Water Quality of Lakes in the Minneapolis/St. Paul Metropolitan Area. University of Minnesota, St. Anthony Falls Laboratory Report No. 505, December 2007, 47 pp. Sander, A., E. Novotny, O. Mohseni, H. Stefan, Potential Groundwater Contamination by road Salt in Minnesota. University of Minnesota, St. Anthony Falls Laboratory Report No. 509, September Publication: Novotny, E.V.; Murphy, D.; Stefan, H.G. Increase of urban lake salinity by road deicing salt. Science of The Total Environment (STOTEN), 2008, 406,

28 Acknowledgments Local Road Research Board (LRRB) Minnesota Department of Transportation (Mn/DOT) Metropolitan Council Minnesota Pollution Control Agency Winter road maintenance personnel from counties and cities Minnesota Materials Management Division US Geological Survey Minnesota Geological Survey US Salt Institute

29 Questions

30 References 1) Marsalek J, Oberts G, Exall K, Viklander M. Review of operation of urban drainage systems in cold weather: Water quality considerations. Water Science and Technology 2003; 48: ) Richburg J A, Lowenstein W A P I. Effects of Road Salt and Phragmites Australis on the Vegetation of a Western Massachusetts Calcareous Lake Basin Fen. Wetlands 2001; 21: ) Panno S V, Hackley K C, Hwang H H, Greenberg S, Krapac I G, Landsberger S, et al. Source Identification of Sodium and Chloride Contamination in Natural Waters: Preliminary Results. 2002; 4) Talmage P J, Lee K E, Goldstein R M, Anderson J P, Fallon J D. Water Quality, Physical Habitat, and Fish-Community composition in Streams in the Twin Cities Metropolitan Area, Minnesota ; 18 5) Novotny V, Muehring D, Zitomer D H, Smith D W, Facey R. Cyanide and metal pollution by urban snowmelt: impact of deicing compounds. Water Science and Technology 1998; 38: ) Bauske B, Goetz D. Effect of deicing salts on heavy metal mobility. Acta Hydrochim. Hydrobiol 1993; 21: ) Warren L A, Zimmerman A P. Influence of temperature and NaCl on cadmium, copper and zinc partitioning among suspended particulate and dissolved phases in an urban river. Water Res. 1994; 28: ) Marsalek J, Rochfort Q, Brownlee B, Mayer T, Servos M. Exploratory study of urban runoff toxicity. Water Science and Technology 1999; 39: ) Environment Canada Health Canada (ECHC). Environment Protection Act Priority Substances List Assessment Report Road Salt. Ottawa, Canada. 1999