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Considering that runoff reaches a wetland both from a storm sewer and <br />from adjacent uplarxJs, the followir>g three issues will be managed to <br />minimize impact from runoff: <br />❖ Bounce - deals with the volume of stormwater input, in terms of the <br />change in water levels and the duration of that change. Ponds will <br />be designed to manage bounce associated with runoff from storm <br />sewers. Based a runoff event with a 100-year recurrence interval. <br />❖ Phosphorous (P) - addresses the amount of phosphorous being <br />delivered to a given wetland via runoff from storm sewers. <br />❖ Buffer - addresses both the quality and quantity/rote of runoff <br />entering a wetlarxj as surface flow from adjacent uplands. <br />Protection <br />Classification Protection Strategy <br />®®nnce: Maintain bounce at or below existing conditions <br />: Protect I1 P‘: Limit loadings to predevelopment loading (0.14 Lbs/Ac/Yr) <br />« <br />L_Buffer: 50 feet wide <br />1 <br />Bounce: Maintain bounce at or below existing conditions plus 0.5 foot <br />Protect II P: Umit loadings to predevelopment loadings times 2 (0.28 Lbs/Ac/Yr) <br />Buffer: 35 feet wide <br />Bounce: Maintain bounce at or below existing conditions plus l.O foot <br />Protect III <br />f P: Umit concentration to predevelopment concentrations (200 ppb) <br />i Buffer: 25 feet wide ”* <br />1 <br />•Bounce: No quantity requirement <br />! utilize P: Umit concentration to 225 ppb ~ <br />^ P a ohosohoraus <br />Buffer: 15 feet wide <br />The City of Orono has taken a somewhat different approach to the sizing <br />and location requirements for wetland buffers, for a couple of reasons: <br />1. It is generally known that, assuming all things equal, a larger <br />waterbody has a greater assimilative capacity than a small <br />wetlaryj. i.e. some given amount of phosphorous can be more <br />easily ‘absorbed ’ by a 14 acre marsh than by a 0.8 acre fen. <br />2. A given wetland's runoff susceptibility rating is a good indicator of it's <br />overall quality in terms of its functions and values. Sensitive <br />communities with a diverse assemblage of plants, provide scarce <br />and/or Ngh quality habitat (remember. Protection Classifications are <br />tied to runoff susceptibility). <br />Otyo/Orone <br />SUrfte Witer Managemnt PImt 5-Z <br />ml