28-14 Amend Chp. 1339 Storm Water Mgmt

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(j) Standards and Specifications: Post - construction runoff practices used to sat- isfy these standards shall meet the standards and specifications in the cur- rent edition of the Rainwater and Land Development manual, NRCS field office technical guide for the local county, or the guidance of the Ohio EPA, whichever is most stringent. The construction of new roads and roadway improvement projects by public entities shall implement post - construction BMPs in compliance with the current version of the Ohio Department of Transportation's Location and Design Manual, Volume Two: Drainage De- sign that has been accepted by Ohio EPA. (k) Water Quality Basins: (1) Pool Geometry: The minimum length -to -width ratio for the pond is 3:1 (the length will be three times the width). (2) Riser in Embankment: The riser shall be located within the embank- ment for purposes of maintenance access. Access to the riser will be by manholes. (3) Water Drains: Each retention basin shall have a drainpipe that can completely drain the pond. The drain shall have an elbow within the pond to prevent sediment deposition fi-orn plugging the drain. (4) Adjustable Gate Valves: Both the water quality and the storm water management basin drains shall have adjustable gate valves. Valves shall be located inside of the riser at a point where they will remain dry and can be operated in a safe and convenient manner. During the annu- al inspections the valves shall be fully opened and closed at least once, and the certifying official shall attest to this on the inspection form. To prevent vandalism, the handwheel shall be chained to a ringbolt or manhole step. (5) Principal Spillway: Each principal spillway shall be designed in ac- cordance with the Natural Resources Conservation Service (MRCS) standards and specifications for the office serving the local county. Each principal spillway shall have the capacity to pass the 100 year de- sign storm flows. The inlet or riser size for the pipe drops shall be de- signed so that the flow through the structure goes from weir flow con- trol to pipe flow control without going into orifice control in the riser. The crest elevation of the primary spillway shall be no less than one foot below the emergency spillway crest. Premium joint pipe is re- quired and a removable trash rack shall be installed at each location. Anti -seep collars shall be provided for all pipe conduits through an em- bankment. (6) Emergency Spillway: An emergency spillway shall be provided on each water quality and stonn water management basin. Emergency spillways shall convey flood flows safely past the embankment, and shall be designed in accordance with NRCS standards and specifica- tions for the office serving the local county. Emergency spillways shall have a 100 -year design storm capacity unless exempted in writing by the city engineer. (7) Embankments: Each dam embankment shall be designed in accordance with the NRCS standards and specifications for the office serving the 64