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5 <br />Drainage <br />25 <br />The Biopod GULD letter states that for Biopods downstream <br />Report <br />of detention, the water quality design flow rate is the full 2- <br />year release of the detention facility. Per the provided <br />modeling results, this is 0.094056 cfs for Vault #3 and <br />0.053198 cfs for Vault #4. Update the text on page 25 in the <br />drainage report. However, it appears that the Biopods are <br />sufficiently sized. <br />6 <br />Drainage <br />Per the Ecology GULD letter for the Biopods, each site plan <br />Report <br />must undergo manufacturer review and approval before site <br />installation to ensure that site grading and slope are <br />appropriate for use of the Biopods. Provide a letter from the <br />manufacturer addressing this, and attach it to the drainage <br />report. <br />7 <br />Drainage <br />CSWPPP, <br />It appears that the project will use BMPT5.13 where there <br />Report <br />Element 13 <br />are no steep slopes. Include Element 13 in the construction <br />SWPPP and include language/BMPs to protect those areas <br />from compaction. <br />8 <br />Civil Plans <br />T5.13 <br />Include a detail for BMPT5.13 or call out DCSS Standard Plan <br />202 or 203 by reference. <br />9 <br />Drainage <br />33-36 <br />A single event hydrograph method should be used to <br />Report <br />calculate Q for BMP C241, instead of WWHM. If the <br />construction area is < 1 acre, then the Rational Method Can <br />be used. <br />10 <br />Drainage <br />Appendix E <br />If pipes downstream of detention are smaller than pipes <br />Report <br />Conveyance <br />upstream of detention, provide calculations that the <br />Calculations <br />downstream pipes are sized for the 100-yr storm for <br />documentation purposes. <br />11 <br />Drainage <br />Appendix <br />• The Storm Chamber System #1 model is missing. Attach <br />Report <br />D, Models <br />this to the drainage report. <br />• Provide sizing calculations to demonstrate that the <br />chamber and stone void space was accounted for in sizing <br />the Storm Chamber system to meet the modeled <br />detention requirements. <br />Page 3 of 7 <br />