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I I I I I I II I I I I I I I I I I I I AGENDA TumerCelliel6Braden Ine. (I) (2) (3) (4) (6) (7) First Creek OSP and FHAD (2nd Progress Meeting) Time: 1:30 Date: October 5, 1999 Location: Urban Drainage & Flood Control District Subject: Lower First Creek and Direct Flow Area 0055 Outfall Study Job No.: 35.05096-040 Place: Urban Drainage and Flood Control District Offices Date & Time: 10/6/99 I :30 PM Hydrologic Analysis - Status Attendees: David Mallory (UDFCD) Edward Stafford (Commerce City) David Center (TCB) Tim Kilgannon (Rt'vIA) Exhibits (draft) for Report Pre parer: Rick Moser MEETING MINUTES Bill DeGroot (UDFCD) Rick Moser (TCB) Daren Duncan (Adams County) Jim Pearce (RNIA) Date: 10/20/99 Rainfall Data Unadjusted and Adjusted Depths The purpose of the meeting was to report on progress on the Outfall Planning and Flood Hazard Area Delineation Study for the lower First Creek watershed. DFA 55 Dave C. began the meeting by describing and distributing the hydrologic related drawings that bave been developed to date. Maps were displayed illustrating the study area, soils, land use, sub-watershed designations and SWMM routing elements. Hydrograph input into First Creek SWMM data set Sub watersheds/Routing into First Creek SWMM data set Problems Verifying input Hydrograph Contact List Dave pointed out that the subwatershed boundaries used in the MartinlMartin Study were checked against the two-foot contour interval mapping provided by the County. The boundaries looked reasonable and no changes were made to the subwatershed delineations. RMA personnel commented on both the existing and future percent impervious values assigned to the RMA. Based on these comments TCB will revise the percent impervious drawin~s along with the appropriate subwatershed CUHP characteristics to reflect a lower percent imperviousness for both the existing and future land use condition. Next Meeting/Adjournment The existing drainage system SWMM connectivity diagram will be revised to remove all detention elements (except 3 that are existing). DFA 0055 was added to the subwatershed delineation exhibit and the SWMM connectivity diagram to reflect integration of this area into the First Creek hydrologic model. Rick M. then presented rainfall depths and cJ.urations that will be used in the hydrologic modeling. A six-hour duration will be used for both the adjusted and unadjusted rainfall scenarios. A comparison ofTCB modeling results against the hydrograph values found in the Martinllvlartin SWMM tile for DFA 0055 was presented. The comparison was reasonable for the I O.yr event. However, for the 100-yr event, the TCB results were quite different than the MartinlMartin SWNIM hydrograph. The study contact list was expanded to include additional individuals to infonn about the project and send meeting minutes to. Meeting Schedule The next seheduled meetino is November 3 o , 1999 at I :30PM at the UDFCD. TC&B will present the draft hydrology report. Distribution: Study Contact List