Agenda - Council - 09/22/2020 - Laserfiche WebLink

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CC Regular Session 5. 19. Meeting Date: 09/22/2020 By: Bruce Westby, Engineering/Public Works Information Title Adopt Resolution #20-214 Accepting Quotes and Awarding Contract for 5751 164th Lane Drainage Improvements, Improvement Project #19-17 Purpose/Background: Purpose: The purpose of this case is to adopt Resolution #20-214 accepting the quote of and awarding a construction contract to Dryden Excavating, Inc. for 5751 164th Lane Drainage Improvements, Improvement Project #19-17. Background: The property owner at 5751 164th Lane first contacted Staff regarding drainage concerns on May 11, 2019. According to the property owner, stormwater runoff from the drainage ditch in City right-of-way in front of their house has been flowing directly across their property in a shallow swale for decades without any drainage easements in place. The property owner claimed that during the winter of 2018/19 the outer edge of the 14-foot by 16-foot floating concrete slab supporting their attached enclosed patio, which is directly adjacent to the drainage swale running across their property, lifted approximately 6-inches. Staff has not been provided with any evidence that the lifting of the slab actually occurred that winter, such as before and after pictures, but the lifting of concrete slabs can occur if the soils underneath a slab are wet and are subjected to numerous freeze -thaw cycles. After the property owner contacted Staff with their concerns, Staff began working to develop plans to route the stormwater runoff generated and conveyed within public right-of-ways through drainage ditches and storm sewer culverts located within existing City right-of-way and drainage easements, instead of through a swale on private property that is not encumbered by a public drainage easement as currently occurs. After collecting topographical survey and working with private utilities, including Northern Natural Gas who owns and operates two high pressure gas lines that traverse the private property, as well as City right-of-way including the ditches, Staff completed plans and recommends constructing the improvements this fall to help ensure no further claims of damage to private property will be received in the future. Existing drainage infrastructure includes a culvert crossing under 164th Lane located just west of the driveway to 5751 164th Lane. Runoff from the south side of 164th Lane flows though this culvert to the drainage ditch north of 164th Lane and adjacent to 5751 164th Lane. Then once the stormwater runoff reaches a certain elevation it starts flowing through the swale on the private property as previously noted. The attached plans show the proposed drainage improvements involve re -grading the ditch on the south side of 164th Lane, replacing the existing driveway culvert at 5800 164th Lane with a new culvert at a lower elevation, and adding a new culvert under 164th Lane at the western lot line of 5751 164th Lane where a drainage and utility easement currently exists and is the intended route for conveying stormwater runoff from this stretch of 164th Lane to the pond to the north. Northern Natural Gas owns two high pressure gas mains that are contained within a 50' wide easement which diagonally crosses 5751 164th Lane. Staff worked with Northern Natural Gas while designing the plans to avoid