Agenda - 10-21-1997 - 11a - Laserfiche WebLink

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1 21 EXECUTIVE SUMMARY (4) Management Options No single management option can meet all six of the water quality and non-water quality objectives. OWASA and the community must therefore consider scenarios that combine multiple forms of management(Chapter 3 and Appendix F). • Watershed Management. Achieving water quality objectives in Cane Creek Reservoir is best addressed through management actions in the watershed and tributary arms of the lake. Four alternative management approaches or scenarios, reviewed and refined by the Advisory Committee, are proposed for Mitlier review and evaluation.by the OWASA Board and community(See Table lil). The scenarios include different combinations of zoning; open-space preservation; buffer requirements; residential, agricultural, and forestry best management practices, land acquisition, and in-lake management options which are detailed in Exhibit E-1 at the end of the Executive Summary. Although each scenario is projected to meet water quality objectives, they differ in key areas for consideration, including political feasibility,certainty of effectiveness,potential for unintended adverse consequences, and ability to develop additional or retrofit solutions when unexpected conditions occur. Further input on community preferences and concerns should therefore be gathered and considered before deciding on a specific alternative (Chapter 4). Table E-1. Preferred Management Scenarios for Further Review Additional Best OWASA Orange Co. Opeo-space Management Aeon In-Lake Managentent Scenario zening PreaerTadm Butlers Practices (aces) Options 2. Tributary Detention Ponds 2-acre Voluntary current Dairies 86 4 tributary detention 4a. Open Space 2-a<ze Residential,forestry, 1 tributary Preservation and BMPa 5/2 Nearshore VOA agriculture,dairies 632 detention 5. Large Lot Zoning and 5/2 Voluntary current Forestry, 1265 None 6. Mandatory Cluster 2acm Mandatory I Current Residentiai,dairies 1377 2 tributary Devdopllt ClnRering detention • In-lake Management. Several in-lake management options were evaluated for addressing key risks, but were rejected because of high cost and uncertainty in effectiveness. These options included mechanical destratification,hypohmnetic aeration, alum and copper sulfate applications, and biomanipulation(changing biological community structure). Further evaluation of constructing impoutldments(large detention ponds) in one or more of the tributary arms of the lake to enhance removal of sediments and contaminants prior to reaching the intake area is recommended,however, as part of the four watershed management scenarios(Chapter 4 and Appendix F). • Water Supply Treatment. Attempting to address degradation of the raw water supply solely through enhanced processes at the treatment plant will not provide the desired level of assurance for providing high quality drinking water. Certain problems in raw water supply quality (e.g., periodic low levels of dissolved oxygen,high levels of iron and manganese, and high levels of total organic carbon) are, however, expected to continue even with the most restrictive watershed management options under E-6