Minutes - Council - 02/24/2004 - Laserfiche WebLink

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trees due to the construction and damage to the roots. The trees closer to Highway 116, which would be part of the future development, would be a good natural buffer. There will be a good extensive landscaping plan that will be nice over time. In staffs perspective they are okay with the few remaining trees in this developed area being taken down, but defer the decision on the rest of the trees in the outlots until such time as those properties are developed. Councihnember Kurak inquired about the rain gardens that are planned. Assistant Public Works Director Olson explained there are limited areas that are signified by rain gardens, if a rain garden is done correctly it can infiltrate water into the ground and pre-treat the water before it gets to a regional basin. There have been a number of studies that have shown the rain gardens are not as efficient as they are designed for in that even With the sandy soil they tend to clog up after a number of years with silt and end up holding water. They are not supposed to hold water, but to be a temporary holding area of water so that it soaks into the ground. One of the reasons rain gardens were not mentioned specifically in the AUAR to a great deal is that staff did not want these types of devices to be used in lieu of the regional storm water system, which is a proven technique and decreases the amount of maintenance necessary. Within the development there are a number of storm water treatment techniques that will be used because the ponding areas within the parkways need to be extremely clean water and there will be storm scepters used that filter the water before it is discharged. Rain gardens are one alternative to use. He explained it would be staff's intention that the use of these smaller detention basins are basically just to catch the first flush of rain in an average summer storm, to try to take out as much sediment as possible. Future treatment would occur downstream and would be the association's responsibility to maintain. There would be language in the development agreement at the time of final plat approval. This language would state if there is standing water in the rain gardens the association would be required to dig out the bottom two to three feet of the rain garden and make sure it does not compact, and put it back together with new vegetation. Councilmember Kurak questioned if the rain gardens would be aesthetically pretty as well as useful. Assistant Public Works Director Olson replied there has been a lot of discussion about this and the development guidelines are still being worked on. There are about five different ways that storm water can be treated, one being raingardens. Staff has repeatedly expressed concern about the potential of the rain gardens looking like a weed patch. The developer has indicated there are 10 to 12 plant species out of the list of over 200 that can be successful in this environment and grow short and look manicured. Councihnember Kurak expressed concern with the association maintaining the rain gardens, which could affect the drain system in the whole development. Assistant Public Works Director Olson explained maintenance of the rain gardens is included in the association control. However, staff will have authority in that if the rain gardens do not continue to tktnction as designed, staff will have the ability to require the association to maintain them. If this is not done in the specified time frame it can be completed by staff and billed back City Council/February 24, 2004 Page 13 of 31