06-26-2017 Council Packet - Laserfiche WebLink

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address disease or invasive species, mowing for purposes of public safety, temporary disturbance for placement or repair of buried utilities. Pesticides and herbicides may be used in accordance with Minnesota Department of Agriculture rules and guidelines. No new structure or hard surface will be placed within a buffer, except that construction of a trail or path of no more than 4 feet in width to provide riparian access through the buffer is acceptable. No fill, debris or other material will be excavated from or placed within a buffer. b. Permanent wetland buffer monuments or markers will be maintained in the locations shown on the approved site plan. Monument or marker language will indicate the purpose of the buffer, restrictions and the name and phone number of the Minnehaha Creek Watershed District. 2. WATERBODY CROSSINGS & STRUCTURES. CITY, at its cost, will maintain waterbody crossings and structures in accordance with the following: a. Crossings and structures in contact with the bed or bank of a waterbody will be inspected at least once a year and maintained in good repair in perpetuity to ensure continuing adequate hydraulic and navigational capacity is retained in accordance with approved plans, to ensure no net increase in the flood stage beyond that achieved by the approved plans, to prevent adverse effects on water quality, changes to the existing flowline/gradient and increased scour, erosion or sedimentation, and to minimize the potential for obstruction of the waterbody. 3. STORMWATER FACILITIES. CITY, at its cost, will maintain stormwater facilities in accordance with the following: a. Stormwater retention and treatment basin(s). Stormwater retention and treatment basin(s) must be inspected at least once a year to determine if the basin's retention and treatment characteristics are adequate and continue to perform per design. Culverts and outfall structures must be inspected at least annually and kept clear of any obstructions or sediment accumulation. Sediment accumulation must be measured by a method accurate to within one vertical foot. A storage treatment basin will be considered inadequate if sediment has decreased the wet storage volume by 50 percent of its original design volume. Based on this inspection, if the stormwater basin(s) is identified for sediment cleanout, the basin(s) will be restored to its original design contours and vegetation in disturbed areas restored within one year of the inspection date. b. Raingardens, infiltration basins and filtration basins. Raingardens, infiltration basins and filtration basins will be inspected annually to ensure continued live storage capacity at or above the design volume. Invasive vegetation, excess sediment and debris will be removed as needed and healthy plant growth will be maintained to ensure that the facilities continue to perform per design. Iron -enhanced sand filters. Iron -enhanced sand media must be inspected every three years to determine if the iron's binding capacity has been reached. The phosphorus binding capacity of the iron -sand bed is exhausted and must be replaced to the original specifications when the total -phosphorus -to -total -iron ratio exceeds 5 milligrams of phosphorus per I gram of elemental iron or when the total phosphorus at the outlet of the iron -sand filter consistently exceeds 60 to 70 micrograms per liter.