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I I I I I I I . I I I, I I I I I I I I 0\ Massey Draw and SJCD Update Project Meeting Minutes February 18. 2004 Page 2 of 2 OLSSON ASSOCIATES 4. Justin Werdel provided copies of the culvert information and calculations for the culverts located along C-470. 5. Paula also provided a copy of a land use map for southern Jefferson County. She noted that the community plan for South Jefferson County would be updated later this year. The changes are anticipated to be minor and will not have a significant impact on the master plan update. It was agreed that the master plan update will use the current land use map ENGINEEIlS' f'lANNERS' SCIENTISTS' SURVEYORS 143 Union Blvd. Suite 700 Uikewood. CO 80228720.962-6072 MEETING MINUTES Massey Draw and SJCD (South) Update OA Project No. 02-2003-1321 February 18, 2004 Attendees: 6. The next meeting will include a preliminary discussion existing problems and alternatives. The meeting will be on March 2, 2004, 9:00 at Olsson Associates' office. Ben Urbonas - Urban Drainage and Flood Control District Paula Lundquist - Jefferson County Alecia Cope - Jefferson County Bob Deeds - City of Littleton Justin Werdel - CDOT Region 6 Hydraulics Bruce Buttner - Olsson Associates David Krickbaum - Olsson Associates Dana Carter - Olsson Associates cc: Attendees via e-mail Russ Clayshulte via e-mail Paul Winkle Kent Wiley Larry Lang via e-mail Gene Reetz John Liou Bill Kieck via e-mail Melissa Chew via e-mail Tim Carey via e-mail Larry MU91er via e-mail Rick McLoud via e-mail Scott Franklin via e-mail Sean Warren via e-mail Discussion Items: 1, Preliminary results of the modeling were reviewed. By adjusting the depression loss and soil infiltration parameters to those used for the Ken Caryl models. prepared by Muller Engineering in 1984, the 1 OO-year discharges at the hogback are within 2% of the target values from the 1985 Urban Drainage and Flood Control District memorandum. However, in the lower reaches of Massey Draw, the North Tributary of Massey Draw and SJCD (South) the 1 OO-year discharges are significantly higher than those contained in the original master plan, A comparison of the watershed areas and composite imperviousness between the original master plan and the update was presented, The imperviousness values match reasonably well. The areas of the North Tributary of Massey Draw and SJCD (South) are 16% and 28% greater, respectively, than those shown in the master plan. Olsson Associates (OA) is reviewing the watershed delineations to reconcile this difference. OA is also reviewing the modeling parameters to determine why the discharges are different. 2, Ben noted that an imperviousness of 0% or 0,5% for open space areas could be used instead of the typical 2% imperviousness, 3. OA is preparing fees to extend the study west of the hogback. Ben noted that the Ken Caryl Master Association would contribute funds to extend the study. Paula stated that Jefferson County is agreeable to extending the study, provided the extension does not come at the sacrifice of lower parts of the watershed located in public areas. If the master plan is extended, it is anticipated that it will be primarily a stabilization plan. Ben noted that any improvements shown in the Ken Caryl area would need to take into account maintenance access, similar to the rest of the study area.