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4. Ramsey County Public Works Inv. # PUBW-009107 <br />Analyses of Lake Owasso water samples $2,548.75 <br />Root moved, Westerberg seconded approval for the four invoices to be paid as <br />presented. Vote: Ayes - 4 Nays - 0 <br />D Other Business <br />D-1 Lake Owasso Study Update <br />Scott Sobiech presented a summary of the draft study on water clarity in Lake <br />Owasso. In a lake user survey conducted in 2007, residents identified water <br />quality and direct discharge to the lake as major concerns. There are 55 different <br />discharge points into Lake Owasso. Water quality that would fully support <br />swimming is one of the goals of the study. <br />Water samples have been taken every two to three weeks at a depth of 1 meter at <br />the four monitoring sites. Quality indicators include the level of phosphorous, <br />chlorophyll and algae. In the two-year period of the study, the amount of <br />phosphorous at the northern site has remained about the same. At the southern <br />site, the treatment of macrophytes caused a spike in phosphorous content. <br />Kelsey suggested other factors, such as weather and lawn care could also be part <br />of the problem. <br />Curly leaf is anon-native invasive species that seeds at the bottom of the lake, <br />propagates and grows through the winter. It dies in early July and releases <br />nutrients. Treatments do not appear to influence its presence. Removal can only <br />occur at the surface because the seeds are at the bottom of the lake. While it <br />releases a low amount of phosphorous, there is a high organic content which can <br />increase sediment. In the deeper portions of the lake, there is a high potential to <br />release phosphorous. <br />Ferrington noted on page 75 of the report that because the lake thermally <br />stratifies, sediments become anoxic during the summer. It is likely that there is <br />internal loading from sediments. There is a relatively low release comparison to <br />other lakes, but the potential is there. <br />Westerberg stated that internal loading is key. He suggested introducing oxygen <br />into the lower part of the lake when the anoxic phosphorous is released and <br />monitor from shallow areas. <br />Westerberg asked if there is ditching. Sobiech stated that the City of Roseville <br />built Legion Pond to remove sediment. The study shows that in 2007, there was <br />more phosphorous because it was a dry year and there was no flow from the <br />