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

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COR Wetland Mitigation Memorandum October 7, 2021 Page 9 Shallow marsh performance standards are partially met, as the number of native species has been matched, as has the number of FAC or wetter species. This is likely a result of the restoration efforts completed in 2011, as there is a good abundance of native species present; presumably remnants of the seeding and plugs installed when the site was reestablished. The abundance however, as measured by percent cover of native species, is less than the presumed performance standard. While species richness is high for shallow marsh, the dominance of hybrid cattails is very high, and is not likely to change without intervention. Upland buffer performance standards are not met, although the native species richness is close, and the percent cover of native species is higher than anticipated for a site with no maintenance since 2012. Much like the presence of individual native species in the shallow marsh, the occurrence of native grasses and forbs in the upland buffer are likely remnants of the restoration initiated in 2011. It is anticipated that the native species will decrease in richness and percent cover as non-native and invasive species outcompete them over time. Overall, the vegetation quality observed in the two mitigation sites does not meet the presumed performance standards. This is not surprising, given the lack of maintenance although they were better quality than anticipated when compared to similar sites. Recommendations The quantity of wetland and associated stormwater treatment and upland buffer exceeds what we proposed. On the basis of credits, the two sites meet the quantity criteria. It is recommended that specific to the wetland credits, the sites are approved as is. The quality of the wetland mitigation sites does not meet the presumed performance standards. The number of native species present in the shallow marsh and upland buffer meets or nearly meets the standard, but the percent native cover does not. This is primarily because both sites are dominated by hybrid cattail. This species is very aggressive and will outcompete native species. The restoration of the site in 2011 had an initial site that met performance standards, but without intensive management, cattails have taken over. The scattered number of native species present indicate that some individuals have persisted, but overall, the site lacks diversity. While vegetation management could be initiated, including herbicide applications and reseeding, the dominance of hybrid cattails is not likely to be easily controlled. After 10 years of development, there is likely a hybrid cattail seedbank that cannot be effectively removed. Removal of the seed bank would require scraping of the entire site, including the stormwater treatment areas. This is not a feasible activity, as it is more extensive than a typical maintenance task. It is also not likely to be successful as hybrid cattails are still present in the area and stormwater runoff will still flow through the sites. As has been demonstrated with the need to reset the site in 2011 and the current conditions, the long-term prognosis of these sites without perpetual maintenance to meet very challenging performance standards is poor. Based on our assessment of the site, we advise that the City of Ramsey present these findings and recommendations to the LRRWMO and TEP with the following request: 1. Approve the two mitigation sites on the basis that the area of wetland credit exceeds the quantity required. 2. Approve the two mitigation sites performance standards on the basis that while the desired quality is not met it is unlikely to be significantly improved with remediation and the long-term