WATER QUALITY TEST RESULTS LAKE REBECCA, HASTINGS, MINNESOTA

PLEASE CLICK ON IMAGES OR DOWNLOAD TO ENLARGE

The below report was recently provided by Travis Thiel, Watershed Specialist Vermillion River Watershed Joint Powers Organization, Dakota County Water Resources Department.

Travis is responding to the test conducted on potential water pollution incidents reported at this site. We wish to thank Travis for his investigative and coordinative efforts over the last year on this matter.

Let us hope the wild life and fish pictured here will continue at the lake in health and abundance.

REPORT

"I have received all of the lab results on the sample you were concerned about. I didn’t include the raw data as I felt it would be better understood by everyone involved if I touched on the results versus sending raw lab results out that likely wouldn’t make much sense to most people without guidance and research.

Here’s what I’ve found: Upon my initial review, nitrogen values looked a bit higher than normal with the exception of Ammonia. These nitrate values are higher than what I’ve personally seen in other urban settings from storm water pipes I’ve monitored in the past. After consulting Travis Bistodeau, Water Resource Specialist at the Dakota SWCD, who has extensive experience with monitoring around the County, he indicated that the levels detected were similar to levels he has detected while sampling the Vermillion River near the Falls and other locations upstream in the watershed. This level of nitrate detected was not in exceedance of the drinking water standard. I would expect nitrogen values to be slightly higher as well considering the time of year and use of nitrogen on lawns and fields. The ammonia value detected appeared to be relatively normal. My guess is any elevated nitrogen levels are a reflection of warm season nitrogen application and current background nitrogen levels found in this area of the County.
Metals values detected were less than any toxicity levels stated in the MN ch. 7050 water quality standards.

MBAS (Methylene Blue Activated Substances) is a test for surfactants that the lab ran and helped me interpret the results since I’m not familiar with it. I was hoping this test would address any foaming that was present in the water. The text below indicates the lab’s opinion on what was detected. It appears that a situation like someone washing a car or cars may have contributed to this surfactant level as it does not appear to be a wastewater issue.

From Standard Methods:

"At current detergent and water usage levels the surfactant content of raw domestic wastewater is in the range of about 1 to 20 mg/L. Most domestic wastewater surfactants are dissolved in equilibrium with proportional amounts absorbed on particulates. Primary sludge concentrations range from 1 to 20 mg absorbed anionic surfactant per gram dry weight. In environmental waters the surfactant concentration generally is below 0.1 mg/L except in the vicinity of an outfall or other point source of entry."

Based upon this and the 0.1mg/L in waters, the 0.527 mg/L would seem to indicate a slightly elevated surfactant level. Plus, remember that the sample was already about a week+ old (hold time 48 hours) before it was analyzed.

I hope that provides some clarity about this potential discharge concern. We greatly appreciate having some "eyes and ears" within the watershed to help us potentially locate and fix problems that might exist on the upland areas that drains to our water resources. Please let us know if we can further assist you with this matter and also let us know if other potential concerns arise.

Regards,

Travis Thiel
Watershed Specialist
Vermillion River Watershed Joint Powers Organization
Dakota County Water Resources Department
14955 Galaxie Avenue, Apple Valley, MN 55124
Phone: 952-891-7546 Fax: 952-891-7588
travis.thiel@co.dakota.mn.us
http://www.co.dakota.mn.us"