10-10-11-WS Draft Minutes - Laserfiche WebLink

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ARDEN HILLS CITY COUNCIL WORK SESSION—OCTOBER 10, 2011 3 which is probably not worth the investment of $150,000 to $175,000 required to do all improvements. Option 4. Mr. Thomas explained that none of these options result in meaningful changes to the two low points in the development. So, they stepped out of that approach and considered doing something above and beyond the existing system. What they came up with would be adding a secondary storm sewer at the south end low point which would include adding another set of catch basins and a whole new piping system to an existing wetland pond area at a cost of $75,000 to $80,000. Their modeling with this addition showed that a 100 year event would probably be contained with both systems working together. However, even with that improvement, the system does not compare to an emergency overflow as it is still a landlocked area with no naturally graded overflow so there will always be that potential for flooding. Mr. Thomas stated that it is their opinion that such improvements would be considered private improvements because they are serving a private area within the association and the pipe itself would be constructed within private property. Mayor Grant questioned where the overland solution is for this property. Public Works Director Maurer stated that the overland solution would probably not be acceptable to the Association or the people who live there because significant grading and • retaining walls would be required to get the level low enough. He explained that essentially what the modeling completed by Bolton and Menk has shown is that if all the catch basins are operating at full efficiency in a 100 year storm event (6 inches of rainfall in 24 hours) the current system should be able to handle the drainage with minor flooding in the streets, driveways, and grass areas. Mr. Thomas pointed out that with no emergency overflow, whatever system is put in will have a finite capacity. Councilmember Tamble asked if there had been any modeling done that included taking the drainage straight west and connecting to the pond there. He asked if it was feasible to connect the storm sewer from where it ends on the north end to the pond to the west. He also asked if doing so would relieve more pressure than option 4. Public Works Director Maurer explained that they chose to go with a proposal that was a shorter distance. Mr. Thomas stated that Councilmember Tamble's suggestion might result in a minor reduction but would be the same benefit as their proposal. Mayor Grant asked if the pond to the north drains to the larger pond north of it and if they would consider enlarging the pond so it holds more water. Lani Leichty, Bolton and Menk, responded that it currently dumps into the north pond but then it all drains to the south.