404 14TH ST BASE FILE 2024-12-09

7.5. MR#5—On-Site Stormwater Management The project will use List#3 located in Table 1-3.2 of the SWMMWW manual provide compliance with minimum requirement#5. No landscape areas are proposed with this project. Under a separate construction project,the Waterfront Place Central development will construct new landscape areas using BMP T5.13 Post-Construction Soil Quality and Depth. For other hard surfaces on site,the proposed finished ground will be graded such that stormwater runoff is not concentrated but is as evenly dispersed as practicable. Full infiltration is deemed to be infeasible due to high groundwater elevations and inadequate separation between any infiltration facility and the groundwater table.The groundwater elevation at the site mirrors tidal elevations.Anticipated sea level rise over the next 100 years ranges between +1'to +5'.The current Mean Higher-High Water elevation is 11.11' (NOAA Tides and Currents) and with an estimated 1'-5'due to sea level rise, future groundwater elevations are predicted to be within 3'of the ground surface. 7.6. MR#6—Runoff Treatment New runoff treatment facilities are not proposed as part of this project.There are existing runoff treatment vaults that the conveyance systems at Location A and Location B drain to.These treatment vaults will remain active during the construction project. The future WPC project will construct new stormwater treatment vaults that collect and treat stormwater from Location A and Location B. 7.7. MR#7—Flow Control The proposed project is Flow Control exempt,as it drains through an existing conveyance system to the Puget Sound,a water body listed as Flow Control exempt in Appendix I-A of the SWMMVWU manual. 7.8. MR#8—Wetlands Protection No wetlands are located on or downstream of the project site,therefore minimum requirement 8 does not apply. 7.9. MR#9—Operation and Maintenance No new facilities are proposed that require and Operation and Maintenance manual.