The URL can be used to link to this page

Home My WebLink AboutCOLLEGE & TRILBY MULTIFAMILY COMMUNITY - PDP220009 - SUBMITTAL DOCUMENTS - ROUND 4 - Responses EPA-SWMM Model Review Comments Project: Core Spaces (Trilby & College) Reviewer: Dan Evans - Updated Comments in BLUE Model Submittal Date: November 2, 2022 DLE Response: December 20, 2023 Model File: SWMM Ultimate Model – 100 Year Proposed.inp Model name change to Proposed College and Trilby SC_100YearPROP.inp NOTE: JR has responded to these comments in red for the updated College and Trilby Multi-Family Submittal for 5/1/24 Comments: 1) Error message when opening the model: “Error occurred while reading SWMM5 Project: SWMM Ultimate Model - 100 Year Proposed.inp [XSECTIONS]: Unrecognized keyword (STREET) at line 1268: 50 STREET Trilby_Road Frontage Unrecognized keyword ([STREETS]) at line 1294: [STREETS]” Please correct. JR Response: The JR ultimate SWMM model was run in a newer version SWMM 5.2, which supports this function. JR Engineering created a Transect of the Trilby Frontage Road to address this comment. DLE-EPA SWMM website indicates that the most current version is 5.2.4. They do not recommend using early versions due to bug fixes. JR Response: JR is now running the proposed model in EPA STORM WATER MANAGEMENT MODEL - VERSION 5.2 (Build 5.2.4). SWMM 5.1 SWMM 5.2 2) Model does not run. Screenshot of the error screen below: JR Response: JR ran the model in EPA STORM WATER MANAGEMENT MODEL - VERSION 5.2 (Build 5.2.1). JR added a Transect of the Trilby Frontage Road and deleted the [STREET]. DLE-EPA SWMM website indicates that the most current version is 5.2.4. They do not recommend using early versions due to bug fixes. JR Response: JR is now running the proposed model in EPA STORM WATER MANAGEMENT MODEL - VERSION 5.2 (Build 5.2.4). 3) This model was run in EPA-SWMM version 5.2.1 and the corrected effective and proposed conditions models were run in version 5.1.015. The reviewer ran the model in both versions and there appears to be no differences so the model review continued. JR Response: JR ran the model in EPA STORM WATER MANAGEMENT MODEL - VERSION 5.2 (Build 5.2.1) DLE-EPA SWMM website indicates that the most current version is 5.2.4. They do not recommend using early versions due to bug fixes. JR Response: JR is now running the proposed model in EPA STORM WATER MANAGEMENT MODEL - VERSION 5.2 (Build 5.2.4). 4) It appears that there is a part of basin B820 that has been removed from the model. Please readjust the basin boundary and areas for B820 and B850. JR Response: Updated DLE – JR removed Basin B820 and readjusted B850. 5) How were the basin parameters (width, length, slope, % impervious, etc.) determined for the SWMM basins (subcatchments)? It appears that the width and length are not calculated per City Standards, please see Chapter 5 of the City of Fort Collins Stormwater Criteria Manual and excerpt below regarding basin width calculation. JR Response: Updated. Impervious values were calculated based on roofs, pavement, and grass for the onsite College and Trilby Basins. The lengths were calculated as the concentrated flow paths. The widths were calculated using the formula in Equation 5-7 below. See the table provided in Appendix B of the report with basin widths and lengths. DLE – JR has completely changed the way they have modeled the development from the previous submittal. Previously they had modeled all the subbasins in EPA-SWMM as shown on the drainage plan. In the current submittal, they only have four basins called CT-1 through CT-4. The comment above indicates that the basin width and length calculations are in Appendix B; however, Appendix B only has parameters for the basins on the drainage plan. To address this comment, we need to see the concentrated flow path and impervious calculations for basins CT-1 thru CT-4. JR Response: Impervious calculations for basins CT1 through CT-4 have been added to Appendix B. An Exhibit showing the SWMM basin Lengths for basins CT1 through CT-4 has been added to Appendix F. 6) Several of the basins have parameters that are inconsistent with other basins: JR Response: Updated. Basins inputs have been updated for composite basins. DLE- These have been corrected. 7) JR indicates that the arrow for L840_SF is pointed in the wrong direction. The model has the flow going in the correct direction, so the figure needs to be corrected in the College and Trilby Intersection Final Design Report. JR Response: Noted DLE- addressed 8) JR used a rating curve for the outfall to Pond P363 based on an MHFD spreadsheet. A printout of the spreadsheet and rating curve could not be found in the drainage report. Recommend allowing the model to calculate outfall rates because the rating curve shows discharges going down after a head of 1.49 feet. JR Response: Noted. JR is currently modeling the pipe based on its capacity of 60 cfs as a conduit in SWMM. DLE - addressed 9) Compare volumes and outfall rates of interim vs ultimate rates for P366. Interim Model Ultimate Model Ultimate Model Outfall Rate = 51.55 cfs – Interim Model Outfall Rate = 60 cfs. If the ultimate model outfall rate is at 60 cfs then this would reduce the volume needed in Pond P363. JR Response: The pond release rate is below 60 cfs since there is also some undetained flow that enters the outfall pipe via an on-grade inlet on South College Ave. JR is now modeling the conduit at its capacity in SWMM. DLE -addressed 10) Junction Check – How were the depths determined? There are no profiles provided in the drainage report so the invert elevations and depths could not be checked. There are also some junctions with zero depth. Depths in the model seem arbitrary and not calculated based on the design. JR Response: The SWMM model has been updated to contain composite basins. JR Engineering is sizing the onsite pipes, drains, and inlets with the rational method. The model is currently being used to model offsite flow through the site and size the WQ pond (P366), channel, and detention facility (P363). Ultimately, the hydraulics of the site will be modeled within StormCAD for storm sewer capacity at the time of Final CDs under the City of Fort Collins Criteria, and profiles will be shown in the Final Drainage Report in StormCAD with corresponding peak inflows and head loss coefficients in StormCAD. DLE - addressed JR Response: The model has been simplified to composite basins. Currently, the onsite pipes have been preliminarily sized. Pipe sizes for the onsite basins and inlets will be calculated with the rational method at time of final and will be sized within StormCAD. DLE - addressed 11) Conduit Check – Looks like most of the conduits are pipe so Manning’s of 0.013 is appropriate. However, none of the pipes have entrance or exit losses. Please add this to the model and provide justification for these losses. JR Response: Entrance and exit losses have been added to the conduits in the College and Trilby site within the model. DLE - addressed 12) Conduit 40 has a roughness of 0.01 for a 1-foot diameter pipe; however, it appears that it should be an irregular open channel (street section) based on the drainage map. Also, check the length of this conduit. JR Response: This basin has been updated to a composite basin. DLE - addressed 13) Cross Section C-C’ in the drainage report does not match SF840_SF in the model. JR Response: Updated. The proposed channels have been updated to transect sections from the grading in AutoCAD C3D. DLE - addressed 14) Looks like three conduits are surcharging. Please determine if these need to be resized. JR Response: Model has been updated. DLE - addressed 15) Rain Gages – Several rainfall events (time series) are shown in the model, but only the 100-year was simulated. The time series matches Fort Collins Criteria and is the same as the one in the corrected effective and proposed conditions models. JR Response: Noted. JR added the 25-YR time series to determine what event overtops the proposed overflow channel between P366 and P363. DLE - addressed 16) Simulation Options were unchanged from the corrected effective and proposed conditions models. JR Response: Noted DLE - addressed Input file: SWMM Interim Model – 100 Year Proposed.inp Name was changed to Interim SC_100YEarPROP.inp 1) Remove L366_SF3. It is also in the Proposed Conditions model but will be removed in the next submittal for the final design. JR Response: Updated DLE - addressed