11/30/2011 Env Bd Packet - Laserfiche WebLink

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• • • Hardwood Creek TMDL Goals: Attainment of aquatic life uses is determined by directly measuring fish and aquatic macroinvertebrate populations to see how they compare to reference areas. The MPCA has been using fish community data to assess water resource quality for the last decade. Minnesota uses a regional reference site approach based on a major river basin framework. Attainment benchmarks are established for each subbasin in the form of biocriteria (indices of biological integrities, or IBIs). For the Upper Mississippi Watershed, a separate IBI was developed for four stream size classes based on drainage area (Table 2). Hardwood Creek has a drainage area of approximately 27 square miles and therefore the applicable criterion is an IBI of 46 or greater. Hardwood Creek TMDL Goal:Total Suspended Solids Goal: TSS was selected as a surrogate to represent sedimentation and habitat quality in streams, and an in- stream TSS concentration goal was used to calculate the TMDL. Minnesota does not have numeric sediment criteria developed for rivers and streams in the state. Therefore, a numeric TSS goal was developed with the aim of improving and protecting in- stream habitat. The effects of recent stream restoration projects in Hardwood Creek were used to determine the in- stream TSS concentration as a result of these activities, and this concentration was used as the TSS goal. The restored habitat results in less erosion and a lower contribution of sediment. The goal was developed by using an in- stream sediment transport model, CONCEPTS, to predict the in- stream TSS concentration under different scenarios. CONCEPTS (CONservational Channel Evolution and Pollutant Transport System) is a computer model that simulates open channel hydraulics, sediment transport, channel morphology, and geotechnical processes of bank failure by tracking bed changes and channel widening. The restored channel modeled scenario represents the effects of the in- stream stabilization practices implemented in lower Hardwood Creek. The existing conditions modeled scenario (i.e., pre- restoration condition in 2002) predicts an average annual in- stream TSS concentration of 22 mg /L, and the restored channel scenario predicts an average annual in- stream TSS concentration of 19 mg/L. 19 mg /L TSS was used as the in- stream TSS goal for the Hardwood Creek TMDL. Hardwood Creek TMDL Goals: Biochemical Oxygen Demand Goal: BOD was used as the target parameter to address the DO TMDL. Minnesota does not have numeric BOD criteria developed for rivers and streams in the state. However, the state has data summaries by ecoregion in a technical report entitled "Selected Water Quality Characteristics of Minimally Impacted Streams from Minnesota's Seven Ecoregions" (McCollor and Heiskary 1993). The technical team for this TMDL considered these data and decided to set the BOD goal for the Hardwood Creek TMDL at the 75th percentile of the minimally impacted streams in the North Central Hardwood Forests ecoregion, which is 3.2 mg /L BOD. In the absence of more watershed - specific data, using historical ecoregion data with emphasis on the 75th percentile levels is an appropriate approach and is among the options recommended by EPA for water quality criteria (e.g., see USEPA, 2000 for nutrient criteria in rivers and streams) and was used recently by the MPCA for development of the state's lake eutrophication standards. 4.3. Natural Resources Issues Preservation of Natural Resources is a priority issue for the City,as established in the City Comprehensive - Plan. ,Exotic species_ are problematic ',because, when ;introduced into a - new environment they are__ _.- -- - - --- -- - -- -- - ---- -- usually free from the checks and balances experienced in their native environments. As a result, exotic species often grow very quickly to nuisance levels, and may overtake native plants and animals. Centerville, Peltier, Otter and Bald Eagle Lakes are examples of such problems. They have been identified by the MDNR as infested with Eurasian Water Milfoil. Problems such as these are recognized City of Lino Lakes SWMP j October 2011 1 7 { Formatted: Not Highlight { Formatted: Highlight