2006-02-28_PWETC_AgendaPacket - Laserfiche WebLink

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Page 10 of 26 PennitNo: MNRIOOOOI 4. The temporary (or pemlanent) basins mnst be constructed and made operational concnnent with the stmt of soil disturbance that is npgradient of the area and contributes runoff to the pond. 5. Where the temporary sediment basin is not attainable due to site limitations, eqnivalent sediment controls snch as smaller sediment basins, and/or sediment traps, silt fences, vegetative buffer strips, or any appropriate combination of measures are required for all down slope boundaries of the construction area and for those side slope boundaries deemed appropriate as dictated by individual site conditions. In detennining whether installing a sediment basin is attainable, the Permittee must consider public safety and may consider factors such as site soils, slope, and available area on site. This determination must be documented in the SWPPP. C. PERMANENT STORM WATER MANAGEMENT SYSTEM All storm water must be discharged in a manner that does not cause nuisance conditions, erosiou in receiving channels or on downslope properties, or inundation in wetlands cansing a significant adverse impact to the wetlands. W11ere a project's ultimate development replaces vegetation and/or other pervious surfaces with one or more acres of cumulative impervious surface, a water quality volume of Y, inch of runoff from the new impervious surfaces created by the project must be treated by one of the methods outlined in Part IILC.1 tln'ough Part III.C.5 prior to the runoff leaving the construction site or entering surface waters (excluding drainage systems that convey storm water to a constructed pennanent storm water management facility designed to treat the water quality volnme from the project). For those areas of a project where there is no feasible way to meet the treatment requirement for the water quality volume, other treatment such as grassed swales, smaller ponds or grit chambers is required prior to discharge to surface waters. A cumulative maximum of (3) three acres or 1% of project size whichever is larger can be treated in this mmll1er. Where the proximity to bedrock precludes the installation of any of the pennanent storm water management practices outlined in Part III.C., 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 pennanent storm water management practices outlined in Part III.C., other treatment such as grassed swales, smaller ponds, or grit chambers, is required prior to discharge to surface waters. I. Wet Sedimentation Basin a. The basin must have a permanent volume of 1800 cubic feet of storage below the outlet pipe for each acre that drains to the basin. The basin's pennanent volume must reach a minimum depth of at least 3 feet and must have no depth greater iliaJJ 10 feet. The basin must be configured such that scour or resuspension of solids is minimized. b. The basin's water quality volume is calculated as Y, inch of runoff from the new impervious surfaces created by the project. c. Basin outlets shall be designed such that the water quality volume is discharged at no more thaJJ 5.66 cubic feet per second (cfs) per acre of surface area of the pond. wq-stnn2-51