HomeMy WebLinkAbout02/17/04
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16200 Eagle Creek Avenue S.E.
Prior Lake, MN 55372-1714
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Memo
DATE: February 9,2004
TO: Frank Boyles, City Manager
CC: Mayor and City Council
Bud Osmundson, Public Works Director
Lake Advisory Committee
FROM: Sue McDermott, City Engineer~
RE: Chloride Sampling Update
We are in the fourth year of the Prior Lake Chloride Monitoring Program. To date the
mean chloride content of Prior Lake is 43.2 ppm (or mg/l). Results and a map of the
sampling sites are attached. While the chloride levels measured in January of this year
are the highest we have seen to date, they are still within the acceptable standard.
Minnesota State Rule 7050.0222 assigns a quality standard for Class 2A waters, which
would include Prior Lake. The chronic standard for chloride in Class 2A waters is 230
milligrams per liter. The "chronic standard" is the highest water concentration of a
toxicant to which organisms can be exposed indefinitely without causing chronic toxicity.
If the standard is exceeded, it is considered indicative of a polluted condition which is
actually or potentially deleterious, harmful, detrimental, or injurious with respect to the
designated use.
A study done by MnDOT in 1994 lists an MPCA chloride standard for surface waters as
such:
High quality recreational waters (2A) = 50 mg/l chloride
High quality industrial waters (3A) = 50 mg/l chloride
Good quality industrial waters (3B) = 100 mg/l chloride
www.cityofpriorlake.com
Phone 952.447.4230 / Fax 952.447.4245
A five-year study conducted by MnDOT, which began in 1982, on 13 metro area lakes
that receive highway runoff resulted in a mean average of 88.3 ppm chloride content.
Typical chloride concentrations of various waters are:
Tvoe of Water
Chloride Content (oom or mvn
Rain Water
2
Spring Water
25
Deep Well Water
50
Sea Water
20,000
City Well Water Testing
3.2
The Minnesota Pollution Control Agency prepared a report entitled "Minnesota Lake
Water Quality Assessment Data: 2000", published October 1999. Prior Lake is located in
the North Central Hardwood Forests eco-region. The summer average Chloride content
(mg/l) for non-urban lakes in this region is 4-10 ppm.
Also last year we began testing for cyanide after staff attended a road salt symposium.
Cyanide is a hazardous by-product of road salt. Our initial years sampling for cyanide
showed only a trace (less than 0.02 mg/l cyanide), see attached results.
CONCLUSION
I think it is fair to conclude by looking at the various standards and concentrations that
have been established, that a mean of 43.2 ppm for Prior Lake is a good level for a highly
used metropolitan lake.
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City of Prior Lake
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This drawing is neither a IDgally record ,Or a survey
and is not inlended to be used as Ont rawing is a
compilation of records. info.....;;... ana. ;rom various
city, county and stale offices and other sources. This documer
should be used for reference only. No representation is made
that features presented lICCur~1y reflect true location. The
City of Prior l.ake, or any other entity from which data was
obtained, assumes no liability for any erICrs or omissions herei,
If discrepancies are found, please contact the City of Prior Lake
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CHLORIDE
MONITORING
PROGRAM
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SAMPLE LOCATION
Last Updated February 2004
City of Prior Lake Engineering Department
G ;\Waler _I nfo\LAC\Chloride sarnplinglcl-samples.apr
2800 0
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2800 Feet
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( SPRING LAKE
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SAMPLE LOCATION
ON CHLORIDE IN mg/L
PRIOR LAKE CHLORIDE MONITORING RESUL T~
Februarv 24. 2001 43.4 42.8 39.4 38.7 37.2 40.1 37.2 37.1 36.5 33.1 34.2 33.2 37.2 36.5 37.6
March 23.2001 39.6 42.5 44.3 35.4 40.5 38.9 39.6 36.3 37.6 43.3 39.1 33.4 30.8 71.3 63.2 42.6
May 1. 2001 32.9 31.8 30.8 31.6 30.9 31.4 30.8 29.9 30.6 28.4 28.6 28.8 28.5 30.7 30.7 30.3
I May 30. 2001 33.2 31.3 32.2 32.8 32.2 32.4 32.7 31.2 30.9 31.1 31.6 30.6 30.5 32.0 31.6 31.7
IJune 29. 2001 33.8 33.0 33.1 32.8 32.6 32.6 33.1 31.5 31.4 30.6 30.1 30.2 30.2. 30.2 30.6 31.6
IJuly 30. 2001 34.8 36.1 36.0 36.0 34.7 35.4 35.3 32.8 33.2 31.6 31.6 32.2 31.2 33.6 32.9 33.8
ISeptember 5. 2001 36.6 37.0 37.9 35.8 35.1 35.8 35.9 32.3 31.8 30.2 31.9 31.7 32.1 33.4 33.0 33.9
ISeptember 27,2001 34.5 52.7 37.3 36.3 34.2 34.6 35.8 31.2 33.0 30.6 30.8 30.6 31.6 30.3 30.0 34.2
November 1. 2001 37.9 44.9 41.7 37.6 38.2 38.0 38.3 34.8 34.4 34.8 34.3 34.2 34.7 33.8 34.3 36.7
November 30. 2001 36.8 37.6 49.2 36.4 36.6 37.1 36.6 32.7 32.4 32.6 32.6 33.4 33.2 33.6 35.7
Februa!V 1 . 2002 40.3 44.0 45.0 38.6 38.3 37.8 42.9 36.6 36.5 33.8 34.7 34.1 35.9 42.9 41.9 38.8
March 1. 2002 39.0 82.0 85.0 35.4 41.3 34.0 39.0 29.7 34.5 33.2 35.5 34.1 36.4 36.8 39.4 42.6
April, 2002 (No tests takenl 0.0
~y 8. 2002 3R.3 384 39.3 38.8 38.1 38.1 38.0 32.5 33.3 33.1 32.4 32.3 33.1 43.8 43.9 36.8
June 11. 2002 42.8 54.8 52.8 41.0 40.2 41.4 41.1 35.4 34.7 35.0 34.5 35.0 34.9 54.5 53.5 42.1
IJuly 17. 2002 40.1 40.1 40.0 38.6 38.5 37.5 38.1 33.5 33.5 32.0 32.3 32.1 32.3 56.3 55.9 38.6
IAuoust 9, 2002 39.3 38.7 38.6 37.8 37.9 37.5 37.6 32.7 32.6 32.5 32.7 34.2 32.6 46.5 38.1 36.4
I September 4. 2002 31.7 32.4 32.2 32.8 30.4 30.1 30.5 30.2 31.9 30.1 31.2
!October 2.2002 29.0 29.4 29.5 33.4 33.0 32.8 32.6 31.6 31.4 30.4 30.8 30.2 29.9 28.0 28.0 30.8
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I Februarv 3.2003 34.9 40.0 40.5 39.1 48.6 41.0 41.6 35.9 37.5 36.7 39.2 31.5 36.0 41.4 40.1 39.2
IMay 3.2003 37.3 37.5 38.7 36.9 37.5 39.6 38.2 34.5 33.8 33.2 33.8 34.5 33.7 43.7 44.9 37.2
IJuly 2,2003 36.9 36.6 36.6 37.7 37.4 37.6 37.9 34.3 34.5 33.9 37.1 33.6 42.3 42.4 37.1
IAuQust3. 2003 37.0 37.5 35.7 36.7 37.0 36.3 36.0 33.4 33.8 33.1 33.1 33.5 33.2 40.6 40.8 35.8
I September 3.2003 38.5 38.3 39.3 38.9 38.9 39.7 37.1 36.7 35.9 36.5 35.8 35.0 42.7 43.5 38.3
I October. 2003
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IJanuarv 18. 2004 46.1 44.2 41.7 43.0 43.5 42.8 40.9 39.9 39.4 39.8 38.2 52.1 53.2 43.2
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,PRIOR LAKE CYANIDE MONITORING RESULTS
SAMPLE LOCATION
ON CYANIDE IN mg/L
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May 3,2003 <0.02 <0.02 <0.02 <0.02 <0.02 <0.02 <0.02 <0.02 <0.02 <0.02 <0.02 <0.02 <0.02 <0.02 <0.02
June 2, 2003 <0.02 <0.02 <0.02 <0.02 <0.02 <0.02 <0.02 <0.02 <0.02 <0.02 <0.02 <0.02. <0.02 <0.02 <0.02
Auqust3,2003 <0.02 <0.02 <0.02 <0.02 <0.02 <0.02 <0.02 <0.02 <0.02 <0.02 <0.02 <0.02 <0.02 <0.02 <0.02
No Samples Taken
October 6, 2003 <0.02 <0.02 <0.02 <0.02 <0.02 <0.02 <0.02 <0.02 <0.02 <0.02 <0.02 <0.02 <0.02 <0.02