10-08-08 Council Agenda - Laserfiche WebLink

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ATTACHMENT 4 ~L~RIN6 ~ ~ASSOCI~AT~ES tau>i noaiu Memo TO: Honorable Mayor and City Council Members FROM: Lee Eifering, City Engineer DATE: October 2, 2008 RE: Savage Lake Action Plan Progress As you are aware resident concerns regarding the condition of Savage lake resulted in the development of an action plan to address and review the key issues. One of these factors was the water quality within the lake. The drainage area contributing runoff to Savage lake is shown by the green line on the attached aerial. The south and southwest portion of the drainage area is discharged to the wetland at the intersection of Jackson and Demont Avenue prior to discharge into Savage Lake, the remainder of the drainage area discharges into Savage Lake directly excluding some treatment ponds on private properties that do not utilize the City storm sewer system. The following is a summary of the items reviewed and the progress that is being made. Dredging wetland at Jackson/Demont As mentioned above the wetland in the northeast corner of Jackson and Demont Avenue is the discharge point for a significant portion of the drainage area to the south and southwest of the lake. Sediment has built up in this wetland to a Ievei that would warrant removal. Our office is developing plans for the sediment removal and it is anticipated that they will be competed by the end of the month with work anticipated to be completed over the winter of 08'I09'. it has been documented that there are some sediment blooms at the outlets that directly discharge into Savage Lake. The individual volumes of sediment at each outlet are relatively small and even the combined volume of these sediment blooms is significantly less than the volume of sediment proposed to be removed from the Jackson/Demont wetland area. We have previously indicated that the removal of these smaller sediment blooms would not be cost effective, however; to ensure that is the case, it may be beneficial to include them in the bid. These areas could be added as alternates to the bid and a decision made on whether to remove the sediment based on the actual numbers received. Treatment Techniques and Methods In order to improve the water quality from the remaining drainage area, which is currently entering Savage Lake untreated, a number of options have been reviewed. They are as follows: 10062 Flanders Court NE -Blaine, MN 55449 - Ph: (763) 780.0450 Fax (763) 780.0452 Memo•100206•CC (Savage ACtlon Plen Progr899) 17