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DESIGN AND CONSTRUCTION STANDARDS AND SPECIFICATIONS <br />Department of Ecology for stormwater facility design in Western Washington. Modeling shall be performed <br />using a 5-minute timestep. <br />Additional Requirement <br />Flow Control BMPs shall be selected, designed, and maintained in accordance with the City's adopted <br />Stormwater Management Manual and Section 4 of the DCSS, except as noted in this Section. The Flow <br />Control Performance Standard may be achieved through any combination of onsite stormwater management <br />techniques, flow control BMPs and selective site design which can be demonstrated to achieve the standard. <br />6-10.1 (2) DESIGN DOCUMENTATION <br />Development applicants shall provide documentation of compliance with the Combined Sewer Area <br />stormwater standards. Development applications shall include the following: <br />a. Stormwater Report which includes the following elements: <br />• Narrative description of the proposed project, existing & proposed conditions, and proposed <br />stormwater facilities to be implemented. <br />• Existing and proposed site maps identifying land cover types used in the stormwater analysis <br />• Numeric summary of existing and proposed surface areas within the site and contributing <br />offsite areas <br />• Determination of erosion control risks and proposed measures to control erosion and <br />sedimentation. <br />• Offsite analysis narrative description and figure describing upstream areas which contribute <br />runoff to the site and the downstream system which will receive runoff from the site. Describe <br />any identified issues which may affect or could be exacerbated by the project. <br />• Flow control design and sizing calculations <br />• Conveyance pipe sizing calculations <br />• Other reports and data required to prepare the stormwater facility design <br />b. Construction plans for proposed stormwater facilities <br />c. Operations and maintenance manual for all proposed stormwater facilities. <br />d. Maintenance covenant for owner conducted maintenance of all stormwater facilities. <br />6-10.2 COMBINED SEWER CONVEYANCE SYSTEM <br />6-10.2 (1) MATERIALS AND CONSTRUCTION <br />Elements of the combined sewer system which convey only stormwater, such as catch basins and <br />stormwater piping shall be constructed in accordance with the stormwater conveyance system requirements <br />in Section 4-2. <br />Elements of the combined sewer system which convey only sanitary sewage, or a combination of <br />stormwater runoff and sanitary sewage, shall be designed in accordance with Section 6-7 and 6-8. <br />SANITARY SEWERS 6-16 <br />