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2. Water Oualii:v <br />a. Developments must incorporate effective ion- point source pollution <br />reduction BMPs to achieve 90% total suspended solids removal from <br />the runoff generated by a NURP water quality storm (2.5" rainfall). <br />Runoff.. volume _P:1411uion_._rulurrement_ „nly, 1?e_,c_crosidercci,_mtd. <br />included in the calculations showing compliance with achieving the <br />90% TSS removal requirement. Water quality calculations, <br />documentation and/or water quality modeling shall be submitted to <br />verify compliance with the standard, <br />runoff rate control — hydrologic calculations -A hvdrograph method <br />based on sound hydrologic theory shall be used to analyze runoff for the <br />desirm or analysis of flows and water levels,. , _ _ ... _ _ . <br />4. Runoff rate control - design standards - ,Runoff rates for the proposed <br />activity shall. not exceed existing nmolff rates for the 2- vearIQ -yeaj and <br />100-year critical storm events, and runoff rates may he restricted to less <br />than the existing razes when the capacity of downstream conveyance <br />systems is limited,. <br />5. Outlets - Discharges from new construction sites must have a stable <br />outlet capable of carrying designed flow at a non - erosive velocity. <br />Outlet design must consider flow capacity and flow duration. This <br />requirement applies to both the site outlet and the ultimate outlet to <br />stormwater conveyance or waterbody. <br />6. ,Pond Requirements For all projects creating more than one acre of' <br />impervious surface, ponding shall be required. At a minimum all pond <br />design specifications shall conform to the current version of the approved <br />City Design Manual and the current requirements found in the NPDES <br />construction permit. In addition the following are required: <br />a. A bench shall be provided starting at the normal water novel and <br />ending 1 foot below normal water level with side slopes no less than <br />10 feet horizontal to 1 foot vertical (10:1) for safety considerations, <br />Pond side slopes shall not exceed 4 feet horizontal to I foot vertical <br />(4:1) without a1proval of the City. <br />b. All public and private owned stormwater management facilities shall <br />provide an unobstructed access path (minimum of 10 feet) capable of <br />supporting light truck traffic during normal weather for the purpose of <br />conducting inspections of the facility and maintenance thereof. No <br />private stormwater facility may be approved unless an easement is <br />provided to (:itv allowing for access for maintenance and inspection. <br />Maintenance agreements before, during, and after development are <br />also required. <br />c_ To provide proper protection for adjacent property within the first tier <br />from the pond, the design storm interval for the ponding area is a 100 - <br />year, 24 -hour storm with correctly sized conveyances for 100 -yr, 24- <br />Model Stonnwater Ordinance Page 8 <br />- 1 2 - <br />Deleted: At a minimum, the first half - <br />inch of runoff from a 24 -hour storm is <br />infiltrated unless the site is within 2,000 <br />feet of a special water where the first f- <br />inch of runoff from a 24 -hour storm event <br />shall be infiltrated. Calculations shall use <br />the appropriate Hydrologic Soil Group <br />Classification and saturated infiltration <br />rates unless specific rates are measured <br />by a registered soil scientist. <br />Deleted: <sp>Sediment Control <br />Deleted: For new M .:..:........:...M..�'.��.. <br />- _ Deleted: construction, design practices <br />to retain soil particles greater than 5 <br />microns on the site (80% reduction) <br />resulting from a one -year 24 -hour storm <br />event, according to approved procedures, <br />and assuming no sedimmd resuspensionif <br />For redevelopment and street <br />reconstruction resulting in exposed <br />surface parking lots and associated traffic <br />areas, design practices to retain soil <br />particles greater than 20 microns on the <br />entire site (40% reduction) resulting from <br />a one -year 24 -hour storm event, <br />according to approved procedures, and <br />assuming no sediment resuspension. <br />Under no circumstances shall the site's <br />existing sediment control level or <br />trapping efficiency be reduced as a result <br />of the redevelopment. <br />Deleted: <# >Oil and grease control - <br />For all stonnwater plans for commercial <br />or industrial developments and all other <br />uses where the potential for pollution by <br />oil or grease, or both, exists, the first 0.5 <br />inches of runoff will be treated usi <br />{Deleted: All <br />Deleted: runoff calculations shall be <br />according to the methodology described <br />in the Natural Resources Conservation <br />' Service's Technical Release 55, ' <br />NEMO Ordinance Project <br />Deleted: Where practices have been <br />implemented to restore soil structure to <br />pre - developed conditions, no <br />.1 permeability class modification is �€ <br />Deleted. Ail <br />r Deleted: stormwater facilities shall be <br />designed, installed and maintained to <br />effectively accomplish the following :1i <br />Maintain predevelopment peak ru <br />lift <br />Deleted: < # >Minimize impervious <br />surface area and maximize infiltration <br />- The project shall use existing natural <br />drainage ways and vegetated soil <br />( Deletetl Community .m... <br />Deleted: All stonnwater ponds shall be <br />provided with a forebay area to provide <br />for the settlement of fine sand sized <br />particles.5 <br />mil <br />Deleted: 20 <br />Deleted: cmmnuni <br />