Winter 2015 Chairman's Corner

By Dale Bacon

The 2014 VLAWMO Monitoring report is an interesting read.  Birch Lake continues to demonstrate excellent water quality, with nitrogen and phosphorous levels well below MPCA water quality limits. The lake level has been up for the past 3-4 years; the water is very clear; fish are thriving; no algae blooms and the rooted aquatic plant community is well behaved!  Life is good!!

Well almost!  The relatively high chloride level of 80 mg/l is cause for some concern.  Although the level is below current MPCA acute and chronic limits, the data are insufficient to predict future chloride levels. A more robust database is needed to validate current and future compliance.

Road salt is used in large quantities to de-ice roads during the winter season.  The MPCA estimates that the Twin Cities Metropolitan Area uses 365,000 tons of road salt each year.  A 2007 University of Minnesota report estimated that Ramsey County used 12+Tons of road salt per lane mile per winter season!  Higher volume, higher speed roads generally receive more road salt.  The City of White Bear Lake uses far less salt, limiting road salt treatment to intersections, curves and ice patches. 

Birch Lake is bounded on three sides by heavily used roads as well as a residential street. Runoff from these roads as well as side city streets and parking lots drains into Birch Lake. This results in a large amount of chloride ion accumulating in the lake.   Assuming a lake size of 110 acres with an average depth of 4 feet and the current chloride level of 80 mg/l, a back of the envelope calculation yields about 160,000 pounds of salt (expressed as
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NaCl) in the lake. The chloride ion is very soluble in water and increases in concentration over time.  If allowed to build up in a lake, it will reach a level that will have an adverse effect on the lake’s biota.

Road salt usage presents a dilemma in balancing the benefits of its use to its environmental consequences.  Total elimination is not practical.  Most of the current focus is on best management practices to reduce the amount of road salt use for deicing.  As an example, the City of White Bear Lake calibrates salt spreaders to better control its application.  Techniques such as pretreatment with a brine solution to prevent ice sticking to roadways have resulted in reductions in road salt use.  The MPCA is leading the Twin Cities Metropolitan Area Chloride Project.  One of its goals is to develop a chloride management that will include recommendations to reduce chloride input to metro area waters.   It is hoped that activities such as this will result in chloride level reduction in Birch Lake.

The BLID board is concerned about the elevated chloride level in Birch Lake and has taken steps to understand the long-term impact better.  Jim Grisim has taken the lead in following developments at the state and local level.  He reports on a recent conference in this newsletter. The board is also working with VLAWMO on this issue. The membership will be kept informed of these activities.   Feel free to contact Jim or me if you have any questions.