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• _7 PREFACE During the past century, much of the lakeshore area now within the Boundaries of Orono was subdivided and developed in a relatively haphazard and unplanned fashion. Due to the lack of organized local governments during much of the period, little if any, planning to protect and preserve the quality of Lake Minnetonka was possible. The result has been pockets of small narrow lots totally incapable of supporting on-site sewage disposal systems. This led to lake pollution and public health problems from septic effluents on lots and in the groundwater supplies which problems have required Orono to complete three major municipal sewer projects, including the construction of a central sewage treatment plant. In 1955, Orono was incorporated as a Village and the first attempts were made at comprehensive planning and zoning. By 1965 the First Comprehensive Zoning Code, which established the principle of protecting and preserving Lake Minnetonka and the surrounding watershed and the groundwater supply, was adopted. In 1968, the Minnesota Pollution Control Agency, in cooperation with the Lake Minnetonka Conservation District, directed a study of Lake Minnetonka •by the Harza Engineering Company to determine the causes of pollution to the lake and to recommend a course of action. The Harza study completed in 1971 found the cause of pollution to the lake was a high input of nutrients, specifically phosporus. It further concluded that the single largest source of nutrient input at that time was effluent from the municipal sewage treatment plants, located within the Lake Minnetonka Watershed. The second single largest source of nutrients was contained in the storm water run-off from the watershed. Because Lake Minnetonka is fed by neither spring nor river tributary system, its sole source of replenishment comes from the storm water run-off of its own watershed. The recommendations of the Harza Study were to construct a system of metropolitan sewer interceptors, to -remove from the Minnetonka watershed the effluent of the seven municipal sewage treatment plants. The study also recommended that, because the storm water run-off could not be removed from the watershed, that the natural system of marshes and wetlands must be protected and preserved, as it is the only practical method of filtering'and removing the ever increasing nutrient load to the lake, the surrounding watershed, and the groundwater caused by increased urbanization within the Lake's Watershed District. The Harza Study, as well as several subsequent studies, has concluded that the nutrient input to the lake will increase as the level of urbanization increases. These studies show that greater land use density could raise the level of nutrients as much as ten times unless the present zoning, specifically the two to five acre minimum lot size in the Rural Service Area of Orono, is maintained. Other studies show that Lake Minnetonka has a slow 25 year "Flush -out" period second only to Lake Michigan in our region, which requires careful and continuous attention to the quality of the storm water run-off flowing into the lake. 1i