6502 EVERGREEN WAY ENHANCED SERVICE FACILITIES 2020-01-21

Page 4 of 6 3. MR #5:0n-Site Stormwater Management -must be addressed for the project using either the performance standard or the list method. If the list method is chosen document the feasibility/ infeasibility determination for the progression through the list. Specific infeasibility criteria must be cited. Note that if infeasibility is based on infiltration rate or potential, a PIT test will be required to document the infiltration rate. It appears that perched groundwater and/or impermeable layers may make some on-site BMPs infeasible. Storm water management is now handled with a detention system, report updated. Soils information also provided to support the use of non LID method due to lack of infiltration onsite. 4. MR#6: Water Quality Treatment -must be provided in accordance with the manual. Per Sep 5 of Section 2.1, Volume V of the Manual the project will be required to provide enhanced treatment as it is considered a commercial project. Two Filterra Units are proposed to treat runoff. See calculations provided by Contech for sizing. 5. If MR #7: Flow Control -is applied to replaced surfacing as well as new the site will need to provide stormwater flow control in accordance with Volume III of the Manual. The pre-developed conditions will be forested for all replaced pavement, rather than existing conditions. Chambermaxx detention system is proposed with a 54"control structure sized by WWHM2O12. See calculations for sizing. 6. Please provide the O&M manual as a standalone document (can also be included in the stormwater report for convenience.) Please include the following information on the cover page or other prominent location within the document: the party responsible for maintenance and operation, • the requirement for the O&M Manual to be retained on or within reasonable access to the site, the requirement to transfer the Manual to any new property owner along with the property, and • the requirement that a log of maintenance activity be kept and made available for inspection by the City upon request that indicates what M&O actions were taken shall be kept. O&M manual updated to current Everett Manual and provided as separate document. 7. Section 2 of the Storm Drainage Report notes that the NRCS classifies Alderwood soils as Class B. However, the Manual classifies Alderwood soils as a Class C soil (Volume III, Table 2.3.1). In the City's experience the soils in this area behave more like a Class C soil, Calculations for the site should be based on Class C or Till soil types. Soils information corrected. Soils report provided in appendix B. 8. The Offsite Analysis section of the report shall address run-on from the adjacent property. If runoff from areas outside the site flow to the treatment facilities., they must be included in the treatment calculations. Offsite analysis is updated in Section 3 to include Fleming and the onsite system along with the offsite runoff being bypassed. P:\2016\16153 ESF&Retail everett\P&E\Text\Correspondence\Everett 1st revlewrdo - (�