Agenda - Public Works Committee - 01/20/2015

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Public Works Committee Meeting Date: 01/20/2015 Submitted For: Len Linton, Engineering/Public Works By: Len Linton, Engineering/Public Works 6. 2. Title: Historical Background on High Water Issues in Ramsey Purpose/Background: This is an informational presentation on historical high water concerns in Ramsey. There have been several years where residents have come to the City requesting assistance with high water adjacent to their homes. Several residents contacted staff and Council members during 2014. Staff is preparing a case for the February 17, 2015 Public Works Committee meeting to address these specific concerns. This presentation looks at historical incidents and how the City responded. Storm Water Overview Ramsey is located on the Anoka Sand Plain and the soils are generally sandy and free draining There are areas of heavier soils that retain water and support wetland vegetation. Approximately 20% of the surface area of Ramsey is classified as wetlands. Some of these wetlands are isolated pockets and the remainder are loosely connected by channels or swales. The water level in wetlands is generally static from year to year; however, the levels can fluctuate. The water levels can drop during longer periods of less rainfall and rise during longer periods of additional rainfall. This is more apparent in isolated areas that do not readily drain. All isolated areas will overflow given enough precipitation. The early developments in Ramsey were most often constructed without evaluation of the adjacent wetland and potential overflow elevations. Storm water management consisted of road side ditches adjacent to rural sections with a few culverts under the roads and possibly a small dry detention area. The storm water management requirements have increased until the present time. The current requirements include infiltration of the first 1" of runoff from new impervious (pavement and roof tops) surfaces and rate control for the 2 year, 10 year and 100 year events. Rate control means the flow from the site cannot exceed the pre -development rate for each storm. This is accomplished through construction of detention facilities on site. High water concerns are generally reported from older developments that were installed prior to storm water management being required. This presentation covers several historical periods when the residents brought problems forward and the City responded. 1985 The city received over 34 complaints about high water. Several were related to high groundwater flooding basements, several were water flooding basement from adjacent wetland. There was discussion at several Council meetings about how to resolve the situation. A resident said Andover had pumped water for its residents and asked what Ramsey would do. The City Engineer indicated it may be possible to pump some areas. The City Attorney cautioned that the City would be liable for damage to downstream properties of the increased flow from pumping caused damage. The City Engineer and the Public Works director were instructed to prepare a pumping plan and present it to the Council. The records show the city planned to pump water from 10 properties. 1997 The Mississippi River and Rum River experienced high flows. The City compiled a list of property owners who contacted the City. A small berm was constructed on one property along the Mississippi River. 2007