Neighbors expressed concern that the proposed PUD design crowds the waterway and will aggravate <br />waterway pollution and impede the flow in the waterway. Staff asserts that the applicant's stormwater <br />plan does not demonstrate that stormwater discharges from this site will be outside of the /WR <br />conservation area, or demonstrate that the proposed crossing design will aNoid erosion and provide <br />free water flow through the culvert during peak storm events. <br />The applicant responds that, while the riparian corridor is identified as a Goal 5 resource, it is not a <br />"natural drainage course" within the meaning of EC 9.8320(9), because it has been significantly <br />altered by excavation and by agricultural activities on the site. In the event the hearings official <br />disagrees with that characterization, the applicant argues that its design includes setbacks from the <br />conservation area and addresses the city's stormwater standards. To the extent this standard concerns <br />additional stormwater-related effects, the applicant contends that the applicable development standards <br />will adequately assure that development on this site will not create significant negative impacts. The <br />applicant argues that staff's concerns regarding culvert and crossing designs can be addressed by <br />conditioning approval based on the submittal of an appropriate crossing design: In any event, the <br />applicant argues, even if the application does not satisfy all stormwater standards, the standard set out <br />in EC 9.8320(9) is a "significant impact" standard, a much less demanding standard than the general <br />stormwater standards. <br />EC 9.8320(9) requires a showing that the proposed PUD design will not increase peak stormwater <br />flows or velocity to an extent that the stormwater will create "significant negative impacts" on natural <br />drainage courses. The site was included on the Goal 5 inventory because it includes riparian vegetation <br />and is a "natural area" near a water feature. The hearings official concludes that while there may be <br />some dispute as to the "naturalness" of this drainage way, the reasons the council included the site on <br />the city's Goal 5 resource inventory are sufficient to demonstrate that it is a "natural drainage course" <br />within the meaning of this standard. , <br />Turning to the parties' other arguments, the applicant supplied a stormwater design that shows that <br />stormwater from the 15 lots located to the east of the easternmost arm of the riparian corridor will be <br />diverted into storm drains and treated prior to release into Gilliam Creek dii-ch southeast of the site. <br />The applicant also submitted stormwater calculations that show that the existing peak stormwater flow <br />through the drainage ditch is 93 cfs, which will increase to 95 cfs after development of this PUD. With <br />respect to the proposed culverted crossing, the applicant's engineer considered two culvert alternatives <br />(a 78" x 60" elliptical culvert and a 60" round culvert), concluding that either one of those culvert <br />designs would be able to accommodate the peak 100-year flow of 95 cfs. With respect to the soakage <br />trenches proposed for Lots 5 and 6, the applicant submitted data that the trenches can accommodate <br />stormwater flows from those lots. Finally, the applicant argues that conditions of approval can be <br />imposed to ensure the crossing design will not fail during storm events. <br />Staff's concerns regarding compliance with this criterion flow from their assertions that the proposal <br />does not satisfy applicable /WR conservation area and stormwater standards. The applicant's evidence <br />responds to those concerns by providing testimony regarding culvert capacity and'soakage trenches. <br />As noted above, the hearings official concludes that the /WR conservation boundaries need to be <br />modified and the modification to those boundaries may reduce the developable area on those lots. The <br />changes in the boundaries of the /WR conservation area may also require modifications to the location <br />and design of the soakage trenches and/or culvert size. Therefore, the hearings official concludes that <br />it is appropriate to condition development west of the riparian corridor to remove lots 5 and 6 from the <br />final plan or require a showing that a revised lot layout can satisfy the stormwater standards. <br />Alder Woods PUD (PDT 07-5 & SDR 08-2) Page 26 <br />Laurel Ridge Record (Z 15-5) Page 1154 <br />