Agenda - Public Works Committee - 07/19/2011

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additional storage capacity in the system. The elevation of the outlet pipe under 156th Lane controls the water elevation of this pond and the one adjacent to the subject property. This would require removal of trees and export of soil. The estimated cost for this work is $60,000. Option 3 The elevation of the pipe under 156th Lane is controlled by the elevation of storm sewer installed as part of the Reilly Estates subdivision. The outfall of this pipe is approximately 14 feet below the elevation of the Pond B. Lowering the outlet elevation of Pond B would require removing and replacing all of the pipe. The pipe is covered in most areas by drainage and utility easements; however, additional easements would be required for removal and replacement of the pipe. There would be significant restoration costs associated with this option, the route passes through a park and landscaped yards, in addition to two street crossings. An alternate may be directional drilling a pipe along the right of way for 156th Lane and Juniper Ridge Drive then connecting to the existing pipe before it enters the river. This pipe would provide flow for smaller events, larger events would continue to flow through the existing storm sewer. The estimated cost for replacing the pipe is $150,000 plus easements. We are working on prices for directional drilling a pipe in the street right of way. Discussion Replacing the drainfield would address the immediate concerns of the resident. This could set a precedent for replacing drainfields adjacent to other ponding areas in the city. Enlarging Pond B would provide additional storage in the storm sewer system. Replacing the existing storm sewer or installing an additional pipe would provide long term relief and lower the water level in Pond B which would lower the water level adjacent to 5220 156th Lane. Funding Source: The funding source for these proposed improvements would be the storm water utilty fund. Staff Recommendation: This case was brought forward in response to a request from the residents at 5220 156th Lane NW. Staff recommends further investigation of each of these option before recommending one for construction. Options 2 or 3 if selected should be included in the Capital Improvement Program so they can be included in the budget. Committee Action: Committee action based on discussion. Area Overview Lot Detail Attachments Form Review Inbox Reviewed By Date Brian Olson MaryJo Warner 07/14/2011 03:21 PM Kurt Ulrich Kurt Ulrich 07/14/2011 03:44 PM Form Started By: Len Linton Started On: 07/14/2011 10:07 AM Final Approval Date: 07/14/2011