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BMP and Infeasibility description <br /> applicable lists Infeasibility criteria and rationale for each <br /> BMP not selected <br /> T5.30 ❑ Site setbacks and design criteria provided in BMP T5.30 <br /> Full Dispersion (SWMMWW,Section V-4.1)cannot be achieved. <br /> ❑ A 65 to 10 ratio of forested or native vegetation area to impervious <br /> area cannot be achieved. <br /> ❑ A minimum forested or native vegetation flowpath length of 100 <br /> feet(25 feet for sheet flow from a non-native pervious surface) <br /> cannot be achieved. <br /> T5.15 Citation of any of the following infeasibility criteria must be based on <br /> Permeable an evaluation of site-specific conditions and a written <br /> Pavement recommendation from an appropriate licensed professional(e.g., <br /> engineer,geologist,hydrogeologist): <br /> ❑ Where professional geotechnical evaluation recommends <br /> infiltration not be used due to reasonable concerns about erosion, <br /> slope failure,or downgradient flooding. <br /> ❑ Within an area whose ground water drains into an erosion hazard, <br /> or landslide hazard area. <br /> ❑ Where infiltrating and ponded water below the new permeable <br /> pavement area would compromise adjacent impervious <br /> pavements. <br /> ❑ Where infiltrating water below a new permeable pavement area <br /> would threaten existing below grade basements. <br /> ❑ Where infiltrating water would threaten shoreline structures such <br /> as bulkheads. <br /> ❑ Down slope of steep,erosion prone areas that are likely to deliver <br /> sediment. <br /> ❑ Where fill soils are used that can become unstable when saturated. <br /> ❑ Excessively steep slopes where water within the aggregate base <br /> layer or at the subgrade surface cannot be controlled by detention <br /> structures and may cause erosion and structural failure,or where <br /> surface runoff velocities may preclude adequate infiltration at the <br /> pavement surface. <br /> ❑ Where permeable pavements cannot provide sufficient strength to <br /> support heavy loads at industrial facilities such as ports. <br /> ❑ Where installation of permeable pavement would threaten the <br /> safety or reliability of pre-existing underground utilities,pre- <br /> existing underground storage tanks,or pre-existing road <br /> subgrades. <br /> City of Everett Public Works <br /> Small Project Stormwater Site Plan Report-Dec 2019 30 <br />