Agenda - Public Works Committee - 06/21/2016

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estimated costs to the Committee for further discussion. Attached is an updated cost estimate which totals $46,782.75. This includes all estimated costs required to construct the settling basin shown in attached Figure 4,to construct required storm sewer modifications, to fill in the drainage Swale across the rear of the Bergevin property, to remove the storm sewer structure at the end of the Swale on the west side of the Bergevin property,to restore all disturbed areas using sod(Bergevin property only) and a wetland seed mix(all other areas), and to vacate the easement the Swale was located in. The estimated costs also include 10%contingency costs for unknowns and miscellaneous pay items not included in the cost estimate, as well as 23%indirect costs for administrative, engineering, finance,and legal fees. Staff previously estimated construction costs for the proposed settling basin and restoration of the Swale would cost between$15,000 and$45,000. A link to this case was sent to the property owner,who indicated they will be present at the meeting Tuesday evening. Timeframe: Approximately 25 minutes for presentation and discussion. Observations/Alternatives: Staff believes that the water observed in the bottom of the Swale in recent years is most likely not from storm water runoff but is rather groundwater rising in conjunction with the lake level rising. Permits from both the DNR and the Lower Rum River Watershed Management Organization would be required to complete the requested improvements as the settling basin and overflow would be located within wetland 114P (see attached Figure 3)which requires a WMO permit, and the work would be occurring below the Ordinary High Water Level which requires a permit from the DNR. In addition,wetland mitigation credits would need to be purchased at a 2:1 ratio to replace the impacted wetland due to construction of the settling basin. This is reflected in the attached estimated costs. May 17th Case Update Attached is a 30-year lake level chart for Sunfish Lake which shows that lake levels have varied by over 6 feet between the mid-1980's and today.As can be seen, lake levels were low at the time the property was developed and purchased by the Bergevin's,whereas lake levels are higher now and are hovering near or above the elevation of the bottom of the Swale(see gray line in chart)which tends to support staff s assertion that the Swale holds water for long periods of time only when lake levels are up and ground water elevations rise accordingly. Funding Source: Funding for the City's share of any ordered improvements would be paid from the Stormwater Fund. Recommendation: Staff recommends that the property owner be required to pay for the requested work since it solely benefits the use of his 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. Based on a 50 year maintenance schedule,this cost would be approximately$500 assuming the City would dredge and restore the turf in the Swale twice,once every 25 years. If the settling basin is constructed Staff also recommends filling in and sodding the Swale across the rear yard of the subject property,removing the storm sewer structure on the west end of the Swale, and vacating the existing drainage easement that encumbered the swale and drainage structure to prevent the need to maintain this infrastructure since a public purpose is no longer being served.However,the easement over the sanitary sewer line on the east side of the property would still be retained. Action: