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Study findings indicate that Mill Lake is mesotrophic in that phosphorus levels are low, bottom water oxygen is low, and chlorophyll-a and transparency is moderate. Currently, the overall water quality of Mill Lake is good. However, in order to protect the lake over the long term, it is recommended that the management plan for Mill Lake include the following elements. Aquatic Plant Surveys and Nuisance Aquatic Plant Control: Annual surveys of Mill Lake should be conducted to determine the type and distribution of aquatic plants, with particular attention paid to invasive non-native species. The current aquatic plant control program should continue to focus on non-native plants and only those native plants growing at nuisance densities. Water Quality Monitoring: Water quality monitoring of Mill Lake should be continued in order to gauge the overall health of the lake. Monitoring should consist of annual E. coli measurements. Every fifth year in spring and late summer, Mill Lake should be sampled from top to bottom at the deepest point for temperature, dissolved oxygen, total phosphorus, chlorophyll-a, and Secchi transparency. Watershed Management: Study findings indicate that watershed management is essential to preserving the quality of Mill Lake over the long term. To this end, it is recommended that a watershed management program for Mill Lake be implemented that consists of the following: A Homeowners Guidebook: Lake protection guidelines should be prepared and mailed to all lake residents. The guidelines should include information on the physical characteristics of Mill Lake and its watershed, aquatic plants, lake water quality, invasive species, and watershed management techniques (i.e. wetland protection, septic system maintenance, lakeside landscaping and lawn care, and low impact development practices). Septic Systems: Shoreline septic systems are a substantial source of phosphorus loading to Mill Lake. Until such time as the Mill Lake area is serviced with sanitary sewer system, proper construction and maintenance of area septic systems will be critical to water quality protection. Lake residents should advocate for a septic maintenance ordinance that requires that septic systems be inspected and meet sanitary code requirements at the time a property is sold. In addition, residents should establish a community septic pumping program wherein all systems around the lake are pumped on a regular basis. Planning and Zoning: Lake residents should advocate for zoning regulations designed to minimize the impact of future development in the Mill Lake watershed. Approaches that may prove useful include open space zoning, a shoreland overlay district, and low impact development regulations. Phosphorus Fertilizer Regulations: Phosphorus in lawn fertilizers is often a primary source of phosphorus input to lakes. To help address this problem, many communities across Michigan have adopted ordinances to regulate the application of phosphorus lawn fertilizers. Mill Lake residents should advocate for phosphorus fertilizer ordinance for Bloomingdale Township (Appendix E). Wetland Protection: In addition to fish and wildlife habitat, wetlands in the Mill Lake watershed provide several valuable functions including pollution prevention, flood control, and groundwater recharge. Mill Lake residents should continue to monitor development in the watershed and cooperate with DEQ to ensure encroachment into area wetlands does not occur. Agricultural Best Management Practices: Agricultural landowners should employ best management practices to protect downstream water quality.
Executive Summary Mill Lake is located in Bloomingdale Township in van Buren County, Michigan. In March of 2007, Progressive AE was retained by Bloomingdale Township to conduct a lake improvement feasibility study and to prepare a management plan for Mill Lake. Based on the water quality data collected to date, Mill Lake is categorized as a mesotrophic lake. That is, the lake is moderate between a lake that is deep and clear with little plant growth and one that is shallow, nutrient-enriched and supports abundant plant growth. Phosphorus levels, chlorophyll-a levels, and Secchi transparency in Mill Lake are moderate. However, the depletion of dissolved oxygen and the build-up of phosphorus in the deep waters in late summer are early signs that "eutrophication" (or nutrient enrichment) is occurring in Mill Lake. As part of the study, a theoretical nutrient budget was constructed for Mill Lake. A nutrient budget is a calculation of phosphorus inputs to the lake based on land use, soil types, and other conditions in the surrounding watershed. The nutrient budget focused on phosphorus because phosphorus is usually the nutrient that controls eutrophication and because phosphorus inputs are more subject to control through management practices. Phosphorus budget calculations indicate that current levels of input to Mill Lake are sufficient to push the in-lake phosphorus concentration above the eutrophic threshold. Above the threshold, plant growth would be expected to increase, water transparency and dissolved oxygen levels would decrease, and the quality of the lake would decline. The most significant sources of phosphorus to Mill Lake include septic systems (which account for 41% of phosphorus input), residential runoff (30%), and agricultural runoff (11%). In order to protect the quality of Mill Lake over the long term, phosphorus inputs should be reduced. As is often the case, an ounce of prevention is worth a pound of cure. The recommended management plan for Mill Lake includes aquatic plan surveys and nuisance aquatic plant control; water quality monitoring; and watershed management. The watershed management program includes preparation of a guidebook for homeowners; septic system management; planning and zoning; phosphorus fertilizer regulations; wetland protection; and agricultural best management practices. Although there is no crisis in the quality of Mill Lake, this period of time is critical to prevent water quality degradation and costly remediation. The Mill Lake Association should be commended for taking a proactive approach to protect that precious resource known as Mill Lake.
Full copy of Mill Lake Management Plan (pdf file)
This site was last updated 06/25/09 |
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