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November 1978 KEPORT TO THE ORONO CITY COUNCIL <br />West Shore Lafayette Bay Dredging Project <br />From July 7th to August 29th a dredging project was monitored on the <br />West shoreJ.ine of Lafayette Bay, Lake Miinetonka. Approximately 16,000 <br />cubic yavda of silt was dredged from the existing boat channel using a <br />suction dredging technique operated by Dewey Lindsey, UAWAPADCO. The <br />spoils were retained in two dans which were prepared adjacent to the wetlands <br />on Freshwtaer Biological Research Foundation property at Navarre. <br />A report on the Engineering part of the project has already been <br />submitted by Mr. Lindsey. This report deals with a study of water quality <br />in Lafayette Bay and in the Wetlands. This study was conducted before. <br />during and after the dredging project was completed. The effect of both <br />suction dredging and traditional dredging on the water quality of Lafayette <br />Bay is compared. Analyses were conducted during the period for total <br />phosphorus, total carbon, and total nitrogen. In addition, turbidity. <br />chlorophyll levels, and secchi disk measurei.'ents were made throughout the <br />summer season. The results of this study are presented in Table 1 (Lafayette <br />^ • <br />* <br />Bay), II (Foundation Marsh) and III (Seascout Survey of Lake Minnetonka, 1978). <br />The detailed technical methodology used in this study can be obtained from <br />the Freshwater Biological Research Foundafion upon request. <br />Conclusions <br />Suction dredging caused very little change in Lafayette Bay during the <br />Entire project. At all times the nutrient balance was seen to be significantly <br />better than the natural conditions in the bay reported in 1972 by R.O. Megard, <br />Journal of Limaology and Ocenaography, Volume 17, p. 68-87. However, in the