Agenda - Council - 06/28/2022 - Laserfiche WebLink

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COR Wetland Mitigation Memorandum October 7, 2021 Page 8 likely related to an adjustment of the constructed area, but is within he platted area and is assumed to be the correct quantity to consider based on site conditions for the previous ten years. The wetland communities present are also different from what was proposed. The proposed wetland was anticipated to be comprised of wet meadow and shallow marsh. The current wetland is comprised of shallow marsh with smaller areas of deep marsh. The wet meadow component is generally not present, although small fringe areas do contain typical wet meadow species. This adjustment in wetland communities' correlates to the increase in wetland area, as both are a result if an increase in wetland hydrology. The areas of proposed storm water treatment are similar to what was proposed, however the treatment area in the Northwest wetland is larger. This appears to be from additional hydrology present, and an expansion of the treatment area into the sidelopes. The proposed upland buffers also differ a little in area from what was proposed. At the Charter site, there is additional buffer present, which was initially identified in 2011. It is unclear if this was a deliberate adjustment, but it was identified as an increased area in 2011, and it may have expanded slightly as the area was not mowed and perhaps expanded naturally. Conversely, at the Northwest site, the area of upland buffer is less than what was proposed, although the decrease appears to be related to an increase in the area of wetland and stormwater treatment. Overall, the total area of the Northwest site has decreased, based off the current property boundaries and limits of the current drainage and utility easements present on these parcels. On the basis of the quantity of credits generated, the objective of creating 149,634 square feet of wetland, stormwater treatment and upland buffer has been achieved. Vegetation Quality and Performance Standards An assessment of vegetation performance standards was completed to see if the sites meet the presumed success criteria identified in the 2011 monitoring report(Table 7). Wet Meadow criteria were determined to be not applicable, as that community is not present. No performance standards for deep marsh were identified as this was not an expected community, although the presence of only hybrid cattail would presumably not meet the anticipated standards. Table 7: Summary of Expected and Observed Vegetation Performance Standards—Charter Site Performance Standard Expected Observed Observed Standard p (Charter) (Northwest) Met? Wet Meadow No. of Native Species 12 N/A N/A N/A Wet Meadow Percent Native Cover 90% N/A N/A N/A Shallow Marsh No. of Native Species 8 8 8 Yes Shallow Marsh Percent Native Cover 75% <10% <10% No Deep Marsh No. of Native Species N/A 0 0 No Deep Marsh Percent Native Cover N/A <5 <5% No Percent FAC or Wetter 75% 100% 100% Yes Upland Buffer No. of Native Species 15 11 10 No [Upland Buffer Percent Native Cover 90% 75% 60% No