Agenda - Public Works Committee - 09/15/2015

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Motion carried. Voting Yes: Chairperson Riley, Councilmembers Johns and Kuzma. Voting No: None. 5. COMMITTEE BUSINESS 5.01: Consider Drainage Options for 173rd Avenue and Gibbon Street Area Civil Engineer II Linton reviewed the staff report and each of the options, noting that option 4 was added since this case was last discussed which would involve constructing a storm sewer outlet pipe south along the Gibbon Street ROW then west in the 173rd Avenue right of way to County Ditch 66. He said the wetland cannot be drained to make the water level lower than the homes lowest level. He explained that while option 4 may provide some relief, the groundwater levels might still rise high enough on occasion to result in wet basement issues for the Miske's and other homes in the area. Chairperson Riley asked why it would not work to dig a hole. Civil Engineer II Linton noted the natural level of the wetlands is a result of the groundwater table. If a hole was dug, the water level would be the same elevation as is expressed in the wetlands; it would not drop down. He stated it could provide more storage area. He related the action of the water in the hole to a cup and a serving bowl. Four inches of water in a little cup would fill it up, while the water level would be much lower in the serving bowl. The water is more spread out and shallow. Councilmember Shryock arrived at 6:05 p.m. Councilmember Johns inquired if the water will always be an issue in this area. Civil Engineer II Linton responded in the affirmative. Councilmember Johns asked how much water could be drained with piping added. Civil Engineer II Linton answered he could not be sure. The existing elevations will remain and make water drainage difficult. Chairperson Riley inquired whether the water table has risen over the course of time. Civil Engineer II Linton responded it has changed. City Engineer Westby noted the water level was very high in 2014. It does fluctuate. He said this issue will likely be a recurring problem without the pipe. He said the pipe will at least provide relief on a more routine basis. Civil Engineer II Linton stated if there is a heavy rain, the water could back up before it runs off. Councilmember Kuzma asked what the anticipated cost would be. Public Works Committee / June 16, 2015 Page 2 of 8