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Planning Commission 471-9i: O'Neil Property March 8, I997 Page 13 established aiong the new water edge. The amouni of groundwater interaction is not expect�d to change. Wetlar�d Buffer: The City of Mounds View has an adopted a wetland zoning disirici which establishes a 100-faofi buffer area abutting identified wetlands. Grading and construction in the buffer area requires approva.l of a wetland alteration permit. These permits may be granted as long as certain criteria were met, drainage conirolled and the adjacent wetland was protected from degradation. Th� applicant is proposing to build a portion of the theater buildir�� and both deiez�tzon ponds in the wetl�d bu�'er. The buffer area is shown wi�h a dotted line on ihe site p1an. Detention ponds are typically piaced °ua ihe buffer area since they need to be ciose to tl�e wetland. They usually revegetate so they continue to provide a"natural" buffer for the wetland. Encroachment of buildings into buffer areas creates less problems than parking lots because the runoff is cieaner. Staff regards the encroachment of the theater buiIding into ihe buffer as workable i�ihe area between the building and the wetland is left naturai, so the vegetation wili continue to provide a filterin� and screening effect. � Drainage The City Engineer has provided a review of drainage issues associated with this project {see Attachment 7}. The drainage system is designed to colleci the water fram the develaped partion af the site, run it through the detention ponds to allow settling of pollutants, and then discharge the water into the wetland. The wetland drains through a I 5" pipe into the storm sewer system in Long Lake Road. I�evelopment of the project wili result in higher water levels in the wetland (0.2 feet in a 10 year storm; 0.3 feet in a 100 year starm). The increased water elevation will not have a negative impact on adjacent s#ructures or roads;. the water will remain on the site. The rate of runoffinto the storm sewer on Long Lake Road is constricted by the size of the pipe. The Cify Engineer recommends that the pipe size be left as is, since enlarging if would cause capacity probiems downstream and there is enough room to store water in ihe wetland. Residents south of the 0'Neil properiy have expressed concerns that th�s developmeni will increase existing problems with flooding in their backyards. The City Engineer reviewed this situation and responded that the localized flooding south af Couniy Road HZ is not affected by the O'Nezl property, even with development. Also, accarding to A1 Sunderman, a groundwater specialist in the City Engineer's Office, there should not be a.ny impacts to ihe existing groundwater table in the area. '�he e�eci of converting woods or open space to impervious surfaces is ihat i� will reduce potential groundwater recharge areas. In this case, however, the water will be diverted. to the wetland and thus the net irnpact shouid be littie change in the current recharge potential of the area. It is th� City Engineer's view that flaoding in the neighborhood is being caused by upstream drainage from the north side of Highway 10 overIoading the existing storm drain system in the