Agenda - Public Works Committee - 03/31/2015

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Public Works Committee Meeting Date: 03/31/2015 Submitted For: Len Linton, Engineering/Public Works By: Len Linton, Engineering/Public Works Title: Consider Options for Addressing Stormwater Drainage Issues in Low Lying, Land Locked Areas 5. 1. Purpose/Background: The City received several reports of high water on properties in 2014. The residents came to the September 16, 2014 and October 21, 2014 Public Works Committee meetings. The motion was made by the committee and ratified by City Council to direct staff to update the comprehensive stormwater model and prepare a feasibility study for addressing the concerns. Staff analyzed the drainage areas for three areas that reported flooding in 2014. The areas are listed with the highest priority first: 1. Gibbon Street north of 173rd Avenue 2. 162nd Lane West of Ramsey Boulevard 3. 156th Lane East of TH 47 There were several other property owners that contacted the City about standing water on their property during the 2014 spring snow melt. The three areas studied continued to experience high water long after the snow melt was finished. The other properties did not contact the City again. The attachments to this case include a City map showing the location of all three (3) areas studied, a neighborhood map for each area with the properties that contacted the City highlighted and plan and profile maps for each area showing the drainage routes considered and the elevation changes along the maps. Large scale colored maps of each neighborhood will be available at the meeting. They are too large to include in the agenda. The attachments also include emails from the residents, a neighborhood survey from Gibbon Street prepared by a resident and the list of property owners that contacted the City in 2014. The same process was used to analyze each area. Autocad Civil3D 2014 was used to create a surface model using the 2003 bare earth aerial topo points. The points were a product of the aerial mapping of the City completed in 2003. The vertical accuracy of the aerial mapping is adequate for preliminary analysis, it is not adequate for detailed design of projects. The surface was placed on the City base map. The drainage and utility easements were digitized and merged to show contiguous areas covered by easements. Alignments were created along easements down side lot lines and across the wetlands in the rear yards to evaluate drainage paths. Profiles were cut from the surface model along the alignments. A plan view and profile view sheets were created for each area. A summary of each area is presented below: Gibbon Street north of 173rd Avenue The area was platted in 1974. Drainage and utility easements were recorded over some of the wetlands in the plat and over the County Ditch that runs across the north side of the plat. The ditch runs through wetlands that were not encumbered with drainage and utility easements. Gibbon Street is in the Deerwood Plat. The area to the west was platted in 1991 as Wildwood Acres. This plat provided drainage and utility easements over the wetlands in the plat. There are also drainage and utility easements along the lot lines from the ROW to the wetlands. This area is relatively flat with minimum elevation change. The residents at 17421 Gibbon Street NW contacted the city about high water around their home and water coming into the basement. The home is a split level style with a 4 foot basement. The nearest wetland and easement recorded on the plat are on the north side of the next lot to the