Agenda - Council - 03/09/2004 - Laserfiche WebLink

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trees duc i~r~ lttt~ t:~msi.ructJon and damage to the roots. The trees closer to Highway 116, which would bc t~,t I ,~?l!~c fi~ture development, would be a good natural buffer. There will be a good extensive I;~(is;ca!~in!; plan that will be nice over time. In staffs perspective they are okay with thc t'ew rc~i~in~/, tr,_.'cs in this developed area being taken down, but defer the decision on the rest el'Ibc [~'..z~.:s i~ thc outlets until such time as those properties are developed. Councilm,'~l~,.:~' I( t.~'[tl~ inquired ahout the rain gardens that are planned. Assistant ~,'~!t'~ii~: ¥./~d~s l)irector Olson explained there are limited areas that are signified by rain gardens, ii' :~ ~'~i ~ .,,~trdc:n is done correctly it can infiltrate xvater into the ground and pre-treat the water bcl'(,~-:: ~l 5c[:; to a regional basin. There have been a number of studies that have shown the rain garttet~.~ ~ 1~ ,t zis efficient as they are designed for in that even with the sandy soil they tend to clog up :.~l'l~:! ;~ ~mmbcr of years with silt and end up holding water. They are not supposed to hold wale,'., i)~t tc~ be a temporary holding area of water so that it soaks into the ground. One of thc reasons: ~,it-~ ;~,.'~.~r,k:ns were not mentioned specifically in the AUAR to a great deal is that staff did not xv~nt ~l~,:~r: tTpcs of d cvices to be used in lieu of the regional storm water system, which is a proven t.-:x:i)~i~.l m~ :t~ld decreases the amount of maintenance necessary. Within the development tlac~-c arc :1 ~t~ r' el' stoma water treatment techniques that will be used because the pending ttrcas with i~ t!~c: !~}rl'3.'vays need to be extremely clean water and there will be storm scepters used that I'iltcr Iht; w:~;~' hcfi~re it is discharged. Rain gardens are one alternative to use. He explained it would bi; s l:_l?,~; intention that the use of these smaller detention basins are basically just to calcl~ thc iir:;-J [lu~;h et' rain in an average summer storm, to try to take out as much sediment as possible. ['tl:t~r(' treatment would occur downstream and would be the association's rcsponsibilil y' tt, ~t~::~i main. There would be language in the development agreement at the time of final plat :tl-~gr,.)x,~ti. 'l'hJs language would state if there is standing water in the rain gardens the associatio~ $',.,otdd i~c required to dig out the bottom two to three feet of the rain garden and make sure it (l~c:.: ~, ,i c;(,: n i)etct, and put il back together with new vegetation. questioned if' the rain gardens would be aesthetically pretty as well as Assistant t't~bti~: \,Vorks Director Olson replied there has been a lot of discussion about this and thc ctovolopm~::~t !.cfidclincs are still being worked on. There are about five different ways that StOrlll watt:~' Cml bt' treated, one being raingardens. Staff has repeatedly expressed concern about thc pott;nti~tl el' [hc rain gardens looking like a weed patch. The developer has indicated there are 10 t(~ 12 pl[t~t spt:.:ie.~ out of the list of over 200 that can be successful in this environment and Cotmciln~c~l-,,:~ I.':urttl( expressed concern with the association maintaining the rain gardens, which coulrl ~j ~:cl ~Jlc; d~-aJn system in the whole development. Assistam I'ui)i~ V~ t, rl(s Director O]son explained maintenance of the rain gardens is included in the ass('mi~ttio~ c(~ttml. Itowever, staff will have authority in that if the rain gardens do not continue to J~!~t!'t i(..n as designed, staff will have the ability to require the association to maintain them. I I' tl~i~ i:; i~(>i dom: in the spt. cited time frame it can be completed by staff and billed back City Council/February 24, 2004 Page 13 of 31