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09/19/2008 FRI 11:44 FAX 651 770 2552 EMMONS&OLIVIER RESOURCES ~006/008 Permit Application No. 08-054 City ofCenterviIle are satisfied at each of the project discharge points (via the BMPs proposed). Although the water quality / volume standard is not satisfied for all subwatersheds within the project, proposed BMP locations are consistent with an onsite meeting that was held in July 2006, at which time RCWD staff, DistIict engineers and City staff walked the site and identified potential BMP opportunities throughout pal1s of the project corridors. Additional con'espondence on the project occUlTed between City and RCWD staff and engineers both in 2007 and 2008 and through these early discussions, this application informally underwent altemative compliance sequencing as identified in the rules. While water quality treatment / volume control is not provided for 1,500:1: LF of the 6,200:1: LF of reconstructed roads, 650:1: LF of roadway not requiIing treatment (BI;an Drive and Twin Lakes Avenue) is treated via the filtration raingardens proposed along 73rd Street. In addition, excess volume credit for oversizing of BMPs (up to two inches of runoff over the tributary drainage areas) per RCWD Rule C, Subpart 5(f)(3) criteria is proposed. Sufficient pretreatment is provided for all proposed BMPs via 3-foot grass filter strips. The treatment of additional areas and oversizing of BMPs, in combination, satisfies the water quality and volume control standard for the overall project. Subwatersheds not provided with volume control BMPs are either tributary to existing wetlands and stormwater features or served by proposed sumps to provide TSS removal pI;or to discharge to Peltier Lake or Clearwater Creek. It should be noted that this project proposes re-construction of stOlmsewer along Peltier Lake Drive re-routing runoff from 475:1: LF back to DNR Public Wetland 2-546W rather than directly to Peltier Lake. Although water quality / volume requirements are not satisfied for this segment of roadway, the proposed modifications will provide an overall improvement to the system. The existing weir structure at the DNR Public Wetland 2-546W outlet historically provided skimming capability but is currently in disrepair. Since areas of this project discharge to this wetland untreated, this weir will be replaced to provide skimming capability up to the I-year event. Additionally, there is a slight overall reduction in volume to this wetland under both the 2- and 100-year events, so there is no concem regarding bounce and inundation as a result of the proposed drainage alteration. It appears that eliminating CBMH 17-A and other structures along Emmons & Olivier Resources, Inc. - 5 - 9/19/08