Review Updated Costs to Construct Sedimentation Basin Improvements at Sunfish Lake

Purpose:
The purpose of this case is to present updated estimated costs for constructing a stormwater sedimentation basin within the wetland south of Sunfish Lake, filling in a sedimentation swale on the south side of the property at 14520 Sunfish Lake Drive NW, and purchasing wetland credits from a wetland bank to mitigate the resulting wetland impacts at a 2:1 ratio.
 
Background:
Attached are copies of three AgendaQuick cases discussed with the Public Works Committee on September 15, 2015 (case #5674), May 17, 2016 (case #6299), and June 21, 2016 (case #6377.  All background information is included in these cases.
 
Also attached are copies of the meeting minutes from these meetings.
 
At the last PWC meeting where this issue was discussed, Staff was directed to bring back updated costs and potential funding mechanisms for the improvements.
 

Staff estimates 15 minutes will be needed to present and discuss this case.     

Observations:
Only one member of the current Public Works Committee was involved in earlier discussions regarding this case so Staff did not contact the property owner of 14520 Sunfish Lake Drive in advance of this meeting. If the Committee would like to discuss anything related to this case with the property owner, Staff will update them and invite them to the next regularly scheduled meeting. Otherwise, Staff will contact the property owner to inform them of the updated cost estimate and will relay any other information as directed by the Committee.    
 
Alternatives:
Based on discussion.
 

Staff has updated project cost estimates for the required work. The total estimated project cost is $83,160. Attached is a detailed cost estimate for reference.
 
This cost estimate includes all costs required to construct the settling basin, to construct required storm sewer modifications, to fill in the drainage swale across the rear of the private property, to remove the storm sewer structure at the end of the swale on the west side of the private property, to restore all disturbed areas (sod is proposed on the private property and a wetland seed mix on all other areas), and to vacate the easement the swale was located in. The estimated costs also include 5% contingency costs for unknowns and miscellaneous pay items not included in the cost estimate, as well as 15% indirect costs for administrative, engineering, finance, and legal fees.
 
If an improvement project were to be ordered, any City costs would be proposed to be taken from the Stormwater Fund. 
 

Staff recommends leaving the existing swale as is and not constructing a sedimentation basin.  Everything is working well as is and the private property owner has not contacted Staff since the last Public Works Committee meeting when this was discussed. If the private property owner requested this work to be completed, Staff would recommend that the property owner be required to pay for the requested work since it solely benefits the use of their property.  However, the City could consider contributing an amount commensurate with the estimated long-term savings associated with maintaining a settling basin next to a public street versus maintaining a linear drainage swale along the rear of a private property within a drainage easement.  Based on a 50-year maintenance schedule, this cost is estimated at $2,000 as the City would dredge and restore the turf in the swale every 25 years on average.  
 

Based on discussion.