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City Council Special Meeting Minutes November 29, 1994 Page 2 • 1 pond, this plan provides for several filter strips in the grassy areas by Silver Lake Road, 2 to further treat the run-off. The first filter strip, a small area, will route the run-off into 3 a catch basin where the large trash and sediments will be removed and the water will 4 then go into the storm sewer system. The second filter strip, a larger area, is equipped 5 with three water quality manholes. The trash, oil and large sediments will be removed 6 and the water will then go to the storm sewer system. The last filter strip will be located 7 by the bank. There is not much room in the area so they have installed an oil, grit 8 chamber to remove debris and coarse items. This is the best drainage plan possible due 9 to the site constraints. It provides a significant addition in water quality treatment in 10 comparison to the first proposed drainage plan. The drainage plan is of higher quality 11 than ever conceived when the project was started. 12 13 Jim McNulty, St. Anthony resident, asked what a filter strip was and how the trash, oils 14 and sediments are removed. 15 16 Beduhn explained that a filter strip is a wide flat area of medium length grass, 17 approximately six inches high and the strip is four to five feet wide. The strips are 18 designed to treat run-off from small storm events. The water flows over these areas and 19 the sediments are trapped in the grass. Filter strips are similar to road side ditches that 20 are used in rural areas. The sediments accumulate and build up in the grass. When the 21 sediment reaches a certain percentage,.the area is then excavated and reseeded. It is 22 similar to the pondage system, whereas the ponds are allowed to fill up to 75% of • 23 original volume and are then cleaned out. The developers have submitted a maintenance 24 agreement in which they will survey the ponds yearly and then report the status to the 25 city. Another addition to the new proposal is that the maintenance agreement has been 26 strengthened. It will now include weekly sweeping'of the parking lot at Apache Plaza 27 and the developers will be required to report to the city on a quarterly basis. 28 29 Greg Carluca, St. Anthony resident, asked what the additional cost of the alternative 30 proposed plan would be. 31 32 Beduhn reported that the water quality manholes would be an additional $40,000 to 33 $50,000. The expansion of the third pond would be an additional $35,000. 34 35 Councilmember Marks stated that it appeared in the report that Barr Engineering had 36 prepared for the City Council, that the phosphates going into Silver Lake from Apache 37 Plaza parking lot would actually be reduced from what they presently are. He asked if 38 there was an estimate of how much phosphate was actually being contributed into Silver 39 Lake from the Apache Plaza parking lot. 40 41 Beduhn reported that Terry Noonan had prepared a report on the load of phosphorous 42 that was going into Silver Lake from the Apache Center parking lot. According to 43 Noonan, Apache Plaza currently contributes 14% of the load of phosphorous into Silver • 44 Lake per.year. With the proposed drainage plan, that number will be reduced by 5%.