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ARDEN HILLS CITY COUNCIL WORK SESSION — MAY 12, 2025 2 Public Works Director/City Engineer Swearingen said that will be part of Bolton and Menk's work through that feasibility study with the PMP. We got feedback and the recommendation from Karth Lake to investigate top level design alternatives for pumping operations. Council could consider this at the June work session when the feasibility report is bought to Council. Councilmember Monson asked if Staff is seeking direction to go get those. Public Works Director/City Engineer Swearingen said Staff will be looking for direction at the June work session, if there is interest in pursuing those designs. Tonight's discussion is informational. Renee Marino of the Karth Lake Improvement District Board said about three years ago the Karth Lake Board initiated an effort to understand how the lake level interacts with the pump. The lake level bounces quite a bit and there is a lot of erosion when that happens. The pump exacerbates that and there have been pump failures. Rice Creek Watershed came on board to help with Matt Kocian's support. He brought in some funding for a hydrologist to develop an additional model for the lake level that worked really well. This helps answer some questions regarding pump operations. The DNR were also involved. They contributed a gauge in the lake and they calibrate it every year. They offer some other expertise in regards to automation of the pumping process. Renee Marino shared photos of a retaining wall that was built 15 years ago. The City designed the wall with Rice Creek and they funded part of it. Scouts finished it. It was expected to have a 10-year life and now it's bowing out and will fail. There was $100,000 set aside to do that, 3 years ago. It was decided to hold off on spending that money until next year. The controlling station has vandalism and the pump is sitting out in the open. The pump has also been flipped over before and caused it to fail. It has to be manually brought out to the lake. Karth Lake Improvement District Board is encouraging City Council to include improvements to manage the Karth Lake Watershed as part of the 2026 PMP Street Utility Improvement Project. It was discovered that the lake operates simply. There is no natural inflow or natural outflow. Working with the DNR, it is clear that if the lake is not pumped, it would put the houses on one side of the lake underwater. It would rise to the street level and flow into the houses on the other side, as well. Councilmember Holden asked if there was one side of the lake that didn't want the pump. She asked what side of the lake wants the pump and what side doesn't. Renee Marino said the members of the Karth Lake Board who are on the higher end have noted erosion issues with foundations. Councilmember Holden asked what side of the lake did not want the pumping. Renee Marino said it's the higher end. She said since 1984, there has been 36 feet pumped out of the lake. There is only a 10 foot difference between the normal lake level and street level. That reinforces that the pumping is essential. She shared a graphic showing the water level before the development went in. The development cause the watershed to expand dramatically. It's up 350% of its original size. Every time an inch of rain falls within the watershed you get a nearly instant two inch rise in the lake. If there are six inches of rain, specifically a multi -day event, it multiplies