07-28-1980 Council Minutes - Laserfiche WebLink

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• Page 34 _ Telephone 973-7357 • � _/ • �� c�TY o� oRo�To .� Post Office Box 66•Crystal Bay, Minnesota 55323•Municipal Offices ...�(�� �t�,-� On the North Shore of Lake Minnetonka � �� j�� July 30 , 1980 � � r..--- Mr. Norman W. Paurus, Chairman and Board Members Lake Minnetonka Conservaton District , 402 .East Lake Street Wayzata, Minnesota 55391 � Mr. David H. Cochran, Chairman and Managers Minnehaha Creek Watershed District P.O. Box 387 Wayzata, Minnesota 55391 Dear Ladies and Gentlemen: Ten years have past since the results of the Harza Study, which were based on data collected in 1968, have been known. The findings of the Harza Study confirmed earlier indications that the cause of pollution to Lake Minnetonka was from excess nutrients, primarily phosphorus, in Lake Minnetonka. The Harza Study determined that the largest cause of phosphorus discharged to Lake Minnetonka was from the effluent from the seven sewage treatment plants located within the Lake Minnetonka Watershed. The conclusions of the Harza Study were that the sewage treatment plants should be phased out and the sewage removed from the Watershed to a central facility located on the Minnesota River . To date, six of the seven sewage treatment plants have been closed ` with the construction of interceptors removing the sewage from the Lake Minnetonka Watershed. The seventh plant, located in Maple Plain, will have phosphorus removal equipment and additional filters installed to reduce the phosphorus content of the effluent to acceptable levels. The Harza Study also determined that the second largest source of nutrient loading to Lake Minnetonka came from run-off from the 123 square mile Watershed, which provides the sole source of make-up water for Lake Minnetonka. In addition, it indicated that the nutrients contained in this run-off would increase as the Watershed became more densely developed. The Harza Study indicated that this increase may be four-fold, but later studies have indicated that this increase can be as much as ten times.