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Planning Commission • Case No. 471-97: O'Neil Property March 28, 1997 Page 2 Discussion: A. Issues Addressed ■ Wetland The site contains a Minnesota Department of Natural Resources(DNR) protected wetland of approximately 8.5 acres. A wetland delineation study was done in September, 1996. No construction work is proposed in the wetland. Comments received from DNR state that if no work is done in the wetland, the proposed development will conform to this agency's requirements. A permit from Rice Creek Watershed District will be required. The proposal shows the necessary water quality ponds used to filter runoff before it enters the wetland. Wayne Jacobson, a wetland expert in the City Engineer's Office, has stated that the higher water levels in the wetland will improve its ecology, with the exception of floral diversity and integrity. Higher water elevations will tend to support more cattail growth and less reed canary grass and willow edge, until this type of vegetation is re-established along the new water edge. ■ Drainage The proposed drainage system is consistent with the City's local water management plan, and will • provide the necessary water quality filtering before runoff enters the wetland. Increased flows into the wetland will increase water surface elevations by 0.2 feet in a 10 year storm, and 0.3 feet in a 100 year storm. The increased water elevation will not have a negative impact on adjacent structures or roads; the water will remain on the site. The City Engineer recommends that the existing 15" pipe from the wetland into the Long Lake Road storm sewer remain as is, since enlarging it would cause capacity problems downstream and there is enough room to store water in the wetland. There should not be any impacts to existing groundwater table, and little change in the current recharge potential of the area. An engineered drainage design would be submitted at the developme� staff Residents south of the O'Neil property have expressed concerns that this development will increase existing problems with flooding in their backyards. The City Engineer reviewed this situation and responded that the localised flooding south of County Road 112 is not affected by the O'Neil property, even with development. Also, according to Al Sunderman, a groundwater specialist in the City Engineer's Office, there should not be any impacts to the existing groundwater table in the area. It is the City Engineer's view that flooding in the neighborhood is being caused by upstream drainage from the north side of Highway 10 overloading the existing storm drain system in the neighborhood. The size of the storm drains needs to be upgraded or a parallel line installed so water is diverted before it reaches the storm drain in County Road H2. • Soils • The soils on the O'Neil property are classified as having moderate limitations, in the area proposed for development, and severe limitations where the wetland is located. According to the