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application or diffused aeration. In addition, artificial circulation is the only in-lake improvement <br />option in which the units could initially be rented, to verify their performance, before purchase. <br />The predicted total phosphorus concentration should he reduced from 62 • g/L to 43 • g/L following <br />implementation of the combination of artificial circulation with iron addition, rain water gardens, and <br />additional wet detention ponding in Subwatersheds CLC-3, CLC-4 and SB-2. The predicted <br />chtorophyll-a concentration should be reduced from 41 • g/L to 28 • g/L. and the Secchi depth should <br />incicose from 0.66 meters (2.2 feet) to 0 82 meters (2 7 feet) with this improvement option <br />combination. This should increase the maximum depth of aquatic plant colonization from <br />approximately 4.2 to 5.0 feet, according to Canfield ct al. (1985). The severe and very severe <br />nuisance algal bloom frequencies, as a percentage of the summer, should be reduced from <br />approximately 100 to 45 percent and from 44 to 18 percent, respectively. Tliis combination of <br />improvement options would result in somewhat higher annualized costs, but would result in the best <br />water quality for Stubbs Bay. In addition, this option combines the more feasible and constructibic <br />options that would have lower land acquisition costs. A bathymetric survey of the pond in <br />Subwatershed CLC-4 should be completed to verify that the existing treatment volume is <br />significantly .ess than the volume assumed for improvement option #8. <br />Other potential BMPs (nut modeled for this feasibility analysis) that should be considered fur <br />implementation in the Stubbs Bay watershed include: <br />Street/parking lot sweeping <br />Permeable pavement for driveways <br />Public education concerning waste disposal, litter control, pet waste and lawn care practices <br />Bank stabilization and vegetative bulfcrs for watershed ponds, wetlands, lakes and streams <br />Implementation of the recommended improvement options will ensure that the Stubbs Bay <br />phosphorus concentr.ations will meet the goals in MCWD’s Water Resource Management Plan (1997) <br />and the Hydrologic/Hydraulic, and Pollutant Loading Study (2003b). The predicted phosphorus <br />concentration very nearly meets the full use support designation and would fall in the review <br />category for listing eutrophication impairments, based on phosphorus concentrations for the North <br />Central llardworxl forest Ecoregion (MPCA. 2004). The MPCA intends to further review <br />P \23\37\FIO\Oi<ft Stubfc* tUy Fcaiibitily Study ii <br />^ ' <br />' r <br />N