07-22-1985 Council Packet - Laserfiche WebLink

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UNIVERSITY OF MINNESOTA TWIN CITIFI, March 27, 1985 Ms. Jeanne Mabusth City of Orono Box 66 Crystal Bay, MN 55323 Dear Jeanne: Gray Freshwater Biological Inslitt;lc, College of Biologu,al Sciences P O Box 100 County Roads 15 and 19 Navarre. Minnesota 55392 (612) 47T-8476 r -- V h, M�iR 2 81985 CITY OF ORO am responding to a request for my comments concerning water quality issues as they relate to dredging for establishment of a formal pond and wildlife pond for the Gregory residence. I understand that the dredged material from the wildlife pond will be removed from the site and that the silt control fences will be in place during construction to prevent suspended material from entering Lake Minnetonka. In general I favor the construction of ponds that increase water retention capacit;; and thus opportunities for sedimentation and nutrient removal in the Lake Minnetonka watershed provided that construction does not cause erosion of materials into the Lake. Mature marshes and wetlands generally release as many nutrients as enter the wetlands. Removal of previously sedimented materials increases the capacity for nutrient remo-al. I would like to see more of a buffer area at the edge of the wildlife pond adjacent to the proposed erosion control fence. If the grading in this area were at 929 for a distance of 50-100 feet on the edge of the pond, emergent vegetation would filter sediment and other materials before it entered Browns Bay. The formal pond and wildlife pond will inevitably become choked with aquatic vegetation and algae. Odors from decaying algae will be objec- tionable and it is likely that control measures will be used. I do not object, and in fact favor, aeration of the formal pond. Because the ponds will communicate with groundwater I would like to see some restrictions on the use of chemical agents to control algae and aquatic vegetation. These restrictions, however, are hard to police.