11-20-2006 Council Agenda - Laserfiche WebLink

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Where the proximity to bedrock precludes the installation of any of the permanent storm water management practices outlined in Appendix A, other treatment such as grassed swales, smaller ponds, or grit chambers is required prior to discharge to surface waters. For work on road projects where the lack of right of way precludes the installation of any of the permanent storm water management practices outlined in Appendix A, other treatment such as grassed swales, smaller ponds, or grit chambers is required prior to discharge to surface waters. 1. During construction. All exposed soil areas with a slope of 3:1 or steeper, that have a continuous positive slope to a special water must have temporary erosion protection or permanent cover within 3 days after the area is no longer actively being worked. All other slopes that have a continuous positive slope to a special water must have temporary erosion protection or permanent cover within 7 days after the area is no longer actively being worked. Temporary sediment basin requirements described in Part III.B.1 -5 must be used for common drainage locations that serve an area with five (5) or more acres disturbed at one time. 2. Post construction. The water quality volume that must be treated by the project's permanent storm water management system described in Part III.C. shall be one (1) inch of ntnoff from the new impervious surfaces created by the project. 3. Buffer zone. An undisturbed buffer zone of not less than 100 linear feet from the special water (not including tributaries) shall be maintained at all times. Exceptions from this requirement for areas, such as water crossings or limited water access, are allowed if the Permittee fully documents in the SWPPP the circumstances and reasons that the buffer encroachment is necessary. All potential water quality, scenic and other environmental impacts of these exceptions must be minimized and documented in the SWPPP for the project. 4. Enhanced runoff controls. The permanent storm water management system must be designed such that the pre and post project runoff rate and volume from the 1, and 2 -year 24 -hour precipitation events remains the same. 5. Temperature Controls. The permanent storm water management system must be designed such that the discharge from the project will minimize any increase in the temperature of trout stream receiving waters resulting from the 1, and 2 -year 24 -hour precipitation events. This includes all tributaries of designated trout streams within the section that the trout stream is located. Projects that discharge to trout streams must minimize the impact using one or more of the following measures, in order of preference: Minimize new impervious surfaces. Minimize the discharge from connected impervious surfaces by discharging to vegetated areas, or grass swales, and through the use of other non - structural controls. Infiltration or evapotranspiration of runoff in excess of pre - project conditions (up to the 2 -year 24 -hour precipitation event). - 3 6 -