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Anthem 13-197 May 1,2014 <br /> Response to 2009 City Comments <br /> Drainage Comments by Jane Zimmerman on 5/11/2009 on construction plans sheets C4.1,C4.2, C4.3 and L1.0: <br /> C4.1 <br /> 1. HGL during the 6month-24hr storm: <br /> Response: The filter backwater HGL for each the north and south systems have been added on the profiles. <br /> 2. Calculation:Stormfilter-South ouflow+2.3'=design elevation <br /> 3. Calculation:Stormfilter-North ouflow+2.3'=design elevation <br /> 4. Do these systems function effectively under backwater conditions? <br /> Response to 2,3&4: <br /> HGL: <br /> The HGL for the 6mo-24hr storm and the 100yr storm have been added to the profiles. The Filter's HGL has also <br /> been added to the profile upstream of each respective filter. <br /> Filter: <br /> The filter outlet is located above thg 6mo-24hr_storage stage,thus the filters will flow freely during the 6mo-24hr <br /> events. Larger storm events will have stages that backwater into the filter,which reduce filter flow but do not <br /> impact the filter bypass functionality or the 6month functionality.The filters also have bypass capabilities for larger <br /> storm flows. <br /> The Contech Stormfilters in use here also contain a permanent pool,which is rim elevation minus two feet in this <br /> case(other filter products have an HGL of the filter cartridge height). The permanent pool causes a backwater to <br /> occur,and the backwater HGL has also been plotted on the drainage profile. <br /> C4.2 <br /> 5. Please show the 6 month, 24-hour water surface. The outlet pipes from the storm filter need to flow freely <br /> during the 6 month, 24-hour storm. <br /> Response: <br /> WQ stage is now shown in the vault and control structure. <br /> C4.3 <br /> 6. Re planting strip on top of the level spreader <br /> 7. Re wrapping drain rock associated with the level spreader <br /> 8. Re porosity of drain rock associated wit the level spreader <br /> Response: <br /> No more level spreader,Sheet"C4.3-Level Spreader"was replaced with Sheet'4.3-WSDOT Storm Outfall". <br /> Per current WSDOT review,WSDOT rejects their 2009 request for a level spreader and is instead requesting <br /> conveyance via buried stormpipe. We have removed the level spreader and added a discharge pipe sheet for plan <br /> and profile. Level spreader notes and details have been removed. <br /> C� --1---9 <br /> X:\Oak Harbor.13-197 Anthem Storage\C'li..DOCS'2009 City Comments'2014 05 01 Anthem Response to 2009 Comments-Drainage.docx <br />