3301 SEAWAY BLVD WHOLE SITE 2025-10-30

E.:Y.0_24"er -6-tyn Tioi0 •arrn fflivorinmit Ing41141 CITY OF EVERETT STORMWATER MANAGEMENT MANUAL 4. The maximum depth from finished grade to vault bottom or tank invert shall be 20 feet. 5. Ladders and hand-holds shall be provided at the outlet structure and inlet pipes and as needed to meet OSHA confined space requirements. 6. All access openings,except those covered by removable panels/access doors,shall have round, solid locking lids per City standards,or 3-foot square,locking diamond plate covers. 7. Rim elevations must match the finished grade. Ventilation requirements 1. Ventilation pipes(minimum 12-inch diameter or equivalent)must be provided in all four corners of vaults and at each end of tanks to allow for artificial ventilation prior to entry of maintenance personnel into the vault. 2. Vaults and tanks providing manhole access at 12-foot spacing need not provide corner/end ventilation pipes as specified above. 3. Vaults and tanks must comply with the Occupational Safety and Health Administration(OSHA) confined space requirements,which includes clearly marking entrances to confined space areas. This may be accomplished by hanging a removable sign in the access riser(s),just under the access lid Access criteria specific to vaults: 1. 1f more than one"V"is provided in the vault floor,access to each end of each"V"must be provided. 2. For vaults with greater than 1,250 square feet of floor area,a 5 x 10-foot removable panel shall be provided over the inlet pipe(instead of a standard frame,grate and solid cover). Alternatively,a separate access vault may be provided. 3. Internal structural walls of large detention vaults shall be provided with openings sufficient for maintenance access between cells. The openings shall be sized and situated to allow access to the maintenance"V"in the vault floor. 4. The minimum internal height of vaults must be 7 feet from the highest point of the vault floor (not sump),and the minimum width must be 4 feet. However,concrete vaults may be a minimum 3 feet in height and width if used as tanks with access manholes at each end,and if the width is no larger than the height. Also the minimum internal height requirement may not be needed for any areas covered by removable panels. Access criteria specific to tanks • 1. A 36-inch minimum diameter CMP riser-type manhole of the same gage as the tank material may be used for access along the length of the tank and at the upstream terminus of the tank in a backup system. The top slab is separated(1-inch minimum gap)from the top of the riser to allow for deflections from vehicle loadings without damaging the riser tank. 2.3 Ste El ankment Requirements .3.1 General Stonnwater facility berms and embankments shall satisfy the following criteria: 1. Pond berm embankments shall be constructed on native consolidated soil(or adequately compacted and stable fill soils analyzed by a geotechnical report),which is free of loose surface soil materials,roots and other organic debris. Volume III-Flow Control and Treatment _D)",)