HomeMy WebLinkAboutCOLLEGE & TRILBY MULTIFAMILY COMMUNITY - PDP220009 - SUBMITTAL DOCUMENTS - ROUND 3 - RESPONSE TO STAFF REVIEW COMMENTS (3)
EPA-SWMM Model Review Comments Project: Core Spaces (Trilby & College)
Reviewer: Dan Evans
Model Submittal Date: November 2, 2022
Model File: SWMM Ultimate Model – 100 Year Proposed.inp
NOTE: JR has responded to these comments in red for the updated College and Trilby Multi-Family Submittal
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.
SWMMM 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].
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)
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
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.
6) Several of the basins have parameters that are inconsistent with other basins:
JR Response: Updated. Basins inputs have been updated for composite basins.
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
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.
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 it capacity in SWMM.
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.
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.
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.
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.
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.
14) Looks like three conduits are surcharging. Please determine if these need to be resized. JR Response: Model has been updated.
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.
16) Simulation Options were unchanged from the corrected effective and proposed conditions
models.
JR Response: Noted
Input file: SWMM Interim Model – 100 Year Proposed.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