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I -35E Corridor Draft AUAR June 2, 2005 • considerations may include corridor width, appropriate vegetation structure, human access and use, and whether or not it is appropriate for a corridor to cross a particular type of roadway. • • New developments represent opportunities to plan and carry out ecological restoration and management. Ecological restoration, enhancement, and /or expansion will help mitigate potential impacts on wildlife and rare features, and if these activities are planned, scheduled, and carried out at the recommended broad scale, will likely result in a net increase in conservation and ecological benefits within the AUAR area compared with existing conditions. Various tools exist or can be developed to ensure the protection and stewardship of the preserved, restored, and enhanced natural resources in the AUAR area. These tools can be used to establish a consistent set of standards for treating the open space across different areas as they are developed. For example, the buffers shown on the Conservation Design Framework (Figure 10 -3) are conceptual and will allow the city the flexibility to consider several land protection and preservation tools in these areas. The variety of tools listed throughout this Draft AUAR will enable public and private sectors to cooperate in creating this network over time in a realistic market and regulatory context. Stormwater Management Effective stormwater management and planning within the AUAR area is a challenging pursuit, but one that is critical to prudent and environmentally sound development. The AUAR process presents an opportunity for logical and innovative stormwater management that integrates traditional stormwater detention and water quality requirements with environmental restoration and conservation objectives. This ideal can be implemented on both a regional and site scale to minimize the impact of development on runoff rates and volumes, water quality, and the region's aquatic resources. The stormwater analysis is fully discussed under Item 17 and Appendix D contains the Hydrologic Analysis The majority of the AUAR area faces many obstacles to effective stormwater management. In many cases agricultural ditch and tile networks have significantly altered drainage basins and changed sub - watershed divides. The drainage capacity of these existing tile networks will be insufficient to convey stormwater runoff from further residential, commercial, or industrial development. The recommendations made within this AUAR document are intended to improve post - development runoff water quality; attenuate runoff release rates below stream and drainage infrastructure capacities for both frequent and occasional rainfall events; and enhance groundwater recharge as the AUAR area is developed. Stormwater management areas (SMAs) will play a critical role in mitigating potential impacts from stormwater following development of the AUAR area. Appropriate design, construction, and maintenance of these areas will enable development to occur without compromising the integrity of the region's aquatic resources. The stormwater management approach outlined in this Draft AUAR provides adequate detention of runoff for post - development conditions. It also provides a framework for water quality enhancement and increased groundwater recharge. The stormwater detention facility design will provide hydraulic properties appropriate for native plant species to thrive. All of these factors will help mitigate potential water quality problems associated with development in the AUAR area. The most effective approach to addressing stormwater issues is by implementing an integrated system of stormwater management elements. The Conservation Design Framework provides an appropriate layout for the regional implementation of an integrated system (see Figure 10 -3). Within the greenway corridors shown in the Framework, bio- swales, wet prairie, and wetlands can be oriented in series to effectively retard runoff rates, reduce stormwater volume, and enhance water quality. Runoff rates and volumes are decreased due to increased infiltration, evapotranspiration, and increased friction imparted on the flow. These decreased rates also reduce the ability of runoff to generate and carry sediment and associated pollutants. xi