The URL can be used to link to this page

Home My WebLink AboutWATERFIELD ODP - ODP130002 - SUBMITTAL DOCUMENTS - ROUND 1 - DRAINAGE REPORT1 Overall Drainage Report Date: July 31, 2013 Project: Waterfield Third Filing Overall Development Plan Fort Collins, Colorado Attn: Mr. Wes Lamarque Fort Collins Utilities 700 Wood Street Fort Collins, Colorado 80524 Mr. Lamarque: This letter report accompanies the submittal for the Waterfield Third Filing Overall Development Plan (ODP). Specifically, this letter report serves to document the overall drainage impacts associated with the proposed Waterfield Third Filing Development. The proposed development site is located northwest of the intersection of Timberline Road and Vine Drive in Fort Collins, Colorado. The overall Waterfield site is roughly 142 acres in size. The currently proposed Third Filing site involves roughly 117 acres. The site is not encroached by any FEMA or City floodplain. The proposed development site is in the City of Fort Collins Dry Creek Basin. Detention requirements for this basin are to detain the difference between the 100-year developed inflow rate and the historic 2-year release rate. The historic 2-year release rate for this basin is 0.20 cfs per acre. Previous submittals for the overall Waterfield site are briefly described below:  Waterfield P.U.D., First Filing, by Northern Engineering, October 1998. Existing development in the southeast corner of the overall Waterfield site was done with First Filing. Detention and water quality was provided in the pond at the southwest corner of the overall Waterfield site. 2  Waterfield P.U.D., Second Filing, by Nolte, Inc. March 2000. Was not constructed; focused on areas west of Merganser Drive, which are now included in the current Third Filing design. The existing First Filing development in the southeast corner of the site drains to the existing detention pond located at the southwest corner of the site. The outfall for this pond is a siphon storm line which conveys flows under the Lake Canal. This pond is to be modified with the currently proposed development to incorporate detention and water quality measures for the existing development, as well as the proposed Waterfield Third Filing development. It is understood that the siphon outfall for this pond is the responsibility of the development to maintain. A conceptual level SWMM model is provided in Attachment 1, showing concept level retention and detention volume requirements. This model shows 19.9 acre-feet of retention volume for “Basin 1” in the model (retention over the existing wetland area), and an addition of 5.2 acre- feet of detention volume for “Basin 2” in the model (modified existing detention pond at the southwest corner of the site). In summary, this Overall Drainage Report letter adequately addresses any potential stormwater changes associated with the proposed development. In general, there are no changes proposed at a major drainage level. The ODP complies with the governing City of Fort Collins Master Drainage Plans, and the previously approved drainage plans specific for the subject property. Please feel free to contact me with any questions you may have. Sincerely NORTHERN ENGINEERING Aaron Cvar, PE Project Engineer ATTACHMENT 1 Conceptual Stormwater Management Model (SWMM) 1 2 out1 out2 outfall pond1 pond2 FtCollins-100yr SWMM 5 Page 1 EPA STORM WATER MANAGEMENT MODEL - VERSION 5.0 (Build 5.0.022) -------------------------------------------------------------- ********************************************************* NOTE: The summary statistics displayed in this report are based on results found at every computational time step, not just on results from each reporting time step. ********************************************************* **************** Analysis Options **************** Flow Units ............... CFS Process Models: Rainfall/Runoff ........ YES Snowmelt ............... NO Groundwater ............ NO Flow Routing ........... YES Ponding Allowed ........ NO Water Quality .......... NO Infiltration Method ...... HORTON Flow Routing Method ...... KINWAVE Starting Date ............ NOV-21-2012 00:00:00 Ending Date .............. NOV-21-2012 06:00:00 Antecedent Dry Days ...... 0.0 Report Time Step ......... 00:15:00 Wet Time Step ............ 00:05:00 Dry Time Step ............ 01:00:00 Routing Time Step ........ 30.00 sec ************************** Volume Depth Runoff Quantity Continuity acre-feet inches ************************** --------- ------- Total Precipitation ...... 35.744 3.669 Evaporation Loss ......... 0.000 0.000 Infiltration Loss ........ 9.708 0.997 Surface Runoff ........... 25.846 2.653 Final Surface Storage .... 0.364 0.037 Continuity Error (%) ..... -0.489 ************************** Volume Volume Flow Routing Continuity acre-feet 10^6 gal ************************** --------- --------- Dry Weather Inflow ....... 0.000 0.000 Wet Weather Inflow ....... 25.846 8.422 Groundwater Inflow ....... 0.000 0.000 RDII Inflow .............. 0.000 0.000 External Inflow .......... 0.000 0.000 External Outflow ......... 1.863 0.607 Internal Outflow ......... 0.000 0.000 Storage Losses ........... 0.000 0.000 Initial Stored Volume .... 0.000 0.000 Final Stored Volume ...... 23.984 7.815 Continuity Error (%) ..... -0.001 ******************************** SWMM 5 Page 1 Highest Flow Instability Indexes ******************************** All links are stable. ************************* Routing Time Step Summary ************************* Minimum Time Step : 30.00 sec Average Time Step : 30.00 sec Maximum Time Step : 30.00 sec Percent in Steady State : 0.00 Average Iterations per Step : 1.00 *************************** Subcatchment Runoff Summary *************************** -------------------------------------------------------------------------------------------------------- Total Total Total Total Total Total Peak Runoff Precip Runon Evap Infil Runoff Runoff Runoff Coeff Subcatchment in in in in in 10^6 gal CFS -------------------------------------------------------------------------------------------------------- 1 3.67 0.00 0.00 1.04 2.62 6.49 490.74 0.713 2 3.67 0.00 0.00 0.86 2.79 1.93 159.43 0.760 ****************** Node Depth Summary ****************** --------------------------------------------------------------------- Average Maximum Maximum Time of Max Depth Depth HGL Occurrence Node Type Feet Feet Feet days hr:min --------------------------------------------------------------------- outfall OUTFALL 0.00 0.00 96.00 0 00:00 pond1 STORAGE 3.60 4.14 109.14 0 02:55 pond2 STORAGE 2.50 2.98 107.98 0 02:14 ******************* Node Inflow Summary ******************* ------------------------------------------------------------------------------------- Maximum Maximum Lateral Total Lateral Total Time of Max Inflow Inflow Inflow Inflow Occurrence Volume Volume Node Type CFS CFS days hr:min 10^6 gal 10^6 gal ------------------------------------------------------------------------------------- outfall OUTFALL 0.00 4.48 0 02:14 0.000 0.607 pond1 STORAGE 490.74 490.74 0 00:40 6.492 6.492 pond2 STORAGE 159.43 159.53 0 00:40 1.930 1.958 ********************** Node Surcharge Summary ********************** SWMM 5 Page 2 Surcharging occurs when water rises above the top of the highest conduit. --------------------------------------------------------------------- Max. Height Min. Depth Hours Above Crown Below Rim Node Type Surcharged Feet Feet --------------------------------------------------------------------- pond1 STORAGE 6.01 4.137 5.863 pond2 STORAGE 6.01 2.985 7.015 ********************* Node Flooding Summary ********************* No nodes were flooded. ********************** Storage Volume Summary ********************** -------------------------------------------------------------------------------------------- Average Avg E&I Maximum Max Time of Max Maximum Volume Pcnt Pcnt Volume Pcnt Occurrence Outflow Storage Unit 1000 ft3 Full Loss 1000 ft3 Full days hr:min CFS -------------------------------------------------------------------------------------------- pond1 721.068 14 0 865.923 17 0 02:54 0.20 pond2 181.165 7 0 232.745 9 0 02:14 4.48 *********************** Outfall Loading Summary *********************** ----------------------------------------------------------- Flow Avg. Max. Total Freq. Flow Flow Volume Outfall Node Pcnt. CFS CFS 10^6 gal ----------------------------------------------------------- outfall 97.09 3.87 4.48 0.607 ----------------------------------------------------------- System 97.09 3.87 4.48 0.607 ******************** Link Flow Summary ******************** ----------------------------------------------------------------------------- Maximum Time of Max Maximum Max/ Max/ |Flow| Occurrence |Veloc| Full Full Link Type CFS days hr:min ft/sec Flow Depth ----------------------------------------------------------------------------- out1 DUMMY 0.20 0 01:54 out2 DUMMY 4.48 0 02:14 ************************* Conduit Surcharge Summary ************************* SWMM 5 Page 3 No conduits were surcharged. Analysis begun on: Wed Jul 31 10:50:57 2013 Analysis ended on: Wed Jul 31 10:50:57 2013 Total elapsed time: < 1 sec SWMM 5 Page 4