1510 SE EVERETT MALL WAY 2018-01-01 MF Import

However, the westerly pond receives a significant amount of ofF-site drainage and a significant amount of detention may actually occur in the connected ponds. The ultiinate discharge location for the easterly and w�sterly ponds and off-:,ite pond is to a culvert under 100th Place SE, to the southwest of the Everett Mall. This culvert c'ischarges �nto Silver Lake Creek. This project shall not make modifications to the existing stormwater contro! facilities that would result in an increase of the rate of stormwater runoff entering the downstream drainage system. 8. The condition of the connecting pipe between the easterly and westerly ponds, and the outlet pipe from the westerly pond, must be determined. These pipes are bolh more than 35 years old, and are likely made of corrugated metal. If necessary, the pipes shall b� repaired or replaced as part of this project. 9. Because the site is located within the Silver Lake dreinage basin, a wetpond in series with vegetated swale is required to provide storm water treatment. Treatrc�ent of stormwater runoff is required from all new and redeveloped paved areas. The C',ty may waive the requirement for a vegetated swale if the stormwater management plan provides for an oversized wetpond that would provide adequate treatment of runoff from a significant amount of existing pavement that is not redeveloped as part of this project, or sediment removal from the o(f-site runoff in accordance with the Ciry of Everett pre-treatment standards. 10. The stormwater control facilities that are designed and constructed to meet the requirements of this project shall meet City standards for design and construction. The off-site flow must be received and discharged in a �vay that does not adversely affect the function of the ponds for treatment of the stormwater from the Everett Mall site. Sediment removal is required, prior to discharge to the vegetated iieatment cell of the wetpond, for all runoff entering the cell. 11. Maintenance access shall be providecl to stormwater control facilities in accordance with City standards. Ciry standards require me.intenance access to the primary sediment removing �acilities — either the first cell of a we;tpond, or a pre-treatment weNault. 12. A geotechnical engineer must evaluate the dam on the south side of the westerly detention pond for struclural integrity and safety. This dam appears to have been constructed more than 35 years ago, and contains a lo-inch cast-iron water main that is an important component of the City's water distribution system. The geotechnical engineer shall make recommcndations for structurel updates to the dam necessary to protect the water main and to bring the dam into compliance with current dam safety standards. Recommendations of the geotechical engineer must be implemented by the applicant. Maintenance of the dam is the ��espoRsibility of the Eve�ett Mall. 13. The plans do not appear to show the correct location of the 16-inch water main in the dam area, which, according to City information, is much closer to the north side of the berm than is currently shown. This water main must be located in the field and shown in the correct location on the plans. 14. The City would aliow the use of an SMI StormFilter instead of or in conjunction with a vaetpond. Additional criteria for the use of a StormFiiter would be as follows: . The StormFilter must be preceded by a pretreatment wetvault/tank containing at least 30% of the 6-month, 24-hour storm runoff volume from the contributing, developed dreinage area. 6/ !�