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. a PUBLIC WORKS <br /> detailed analysis to support design development, indicating that the 1.5 in/hr <br /> rate was not intended for design purposes. <br /> o See comments in Section 6—Special Reports and Studies regarding the need <br /> to conduct infiltration feasibility and design assessment in accordance with <br /> the SWMM. The assessment must be documented in accordance with the <br /> report submittal requirements for Soils/Geotechnical Analysis. <br /> o Document specific design flows developed and used for sizing flow control, <br /> treatment, and conveyance facilities. <br /> k. Section 8.4—Stormwater Flow Control Plan <br /> o See above comments regarding infiltration rate and update discussion <br /> accordingly. <br /> o Document the infiltration pond and flow control structure design. Address <br /> the comments below for Sheet C-10 regarding the flow control structure <br /> design. <br /> 1. Section 8.5 —Stormwater Treatment Plan <br /> o Document what type(s)s of water quality treatment are required, and why: <br /> • Basic <br /> • Enhanced <br /> • Phosphorus <br /> • Oil control <br /> • Other(e.g., based on applicable basin plans, Total Maximum Daily <br /> Loads, etc.) <br /> • MR#4—Preservation of Natural Drainage Systems and Outfalls <br /> o Section 9.4 of the SSP (DEA, 2017) indicates that a Basin Balancing <br /> Analysis was performed to meet this requirement. Provide a more detailed <br /> narrative discussion of this analysis, including reference to supporting <br /> documents, to support the conclusion that this minimum requirement is met <br /> by the proposed designs. Include discussion of the applicable standards and <br /> requirements, methods, assumptions,results, and how those results support. <br /> the conclusion regarding satisfaction of this minimum requirement. <br /> • MR#5 - On-Site Stormwater Management <br /> o Modeling in Western Washington Hydrology Model (WWHM)used"C, <br /> Forest, Flat" for the pre-developed condition,representing a pre-developed <br /> forested condition on flat till soils. However,the soils are characterized as <br /> advance outwash(GeoEngineers 2015). Use the appropriate land surface <br /> type for the pre-developed condition and document the model inputs in the <br /> Drainage Report. <br /> r`'. Page 6 of 9` <br />