HomeMy WebLinkAboutREGISTRY RIDGE, 4TH FILING - PDP - 32-95G - SUBMITTAL DOCUMENTS - ROUND 1 - DRAINAGE REPORTDrainage Design Considerations
Registry Ridge P.U.D. Fourth Filing
September 11, 2000
Northern Engineering Services, Inc.
REFERENCES
1). Final Draina$e Report for Registry Ridge P U.D. First Filing, Fort Collins, Colorado,
Northern Engineering Services, Inc., May 19, 1997.
2.) Final Drainage Report for Registry Ridge P.U.D. Third Filing, Fort Collins, Colorado,
Northern Engineering Services, Inc., August 23, 2000.
3.) Fossil Creek Drainage Basin Master Drainage av Planning Study, City Of Fort
Collins, Simons, Li & Associates, Inc., August 1982.
4.) Storm Drainage Design Criteria and Construction Standards, City of Fort Collins,
Colorado, May, 1984.
5.) Drainage Criteria Manual Urban Drainage and Flood Control District, Wright -
McLaughlin Engineers, Denver, Colorado, March, 1969.
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Drainage Design Considerations
Registry Ridge P.U.D. Fourth Filing
September 11, 2000
Northern Engineering Services, Inc.
7.1 Compliance with Standards
All drainage design considerations are in accordance with the City of Fort Collins Storm
Drainage Design Criteria Manual (SDDCM) and the Urban Drainage and Flood Control District's
Drainage Criteria Manual. A variance is requested for the Mannings 'W' value of 0.060 which is
referenced in the SDDCM for the design of swales. A more realistic value for grass -lines swales
is 0.035, which is taken from the Urban Drainage Criteria Manual (See Page 132).
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Drainage Design Considerations
Registry Ridge P.U.D. Fourth Filing
September 11, 2000
Northern Engineering Services, Inc.
lined swales have been designed as a permanent onsite BMP and will be used to limit the extent of
directly connected impervious areas. Swales used for storm drainage and flood control have been
designed to be aesthetically pleasing and are located primarily between the southern walk -out lots.
Several swales are located throughout the site which will serve to convey stormwater to either a
large, grass -lined swale, or directly to detention Pond 603. Detention Pond 603 has been
designed with longitudinal slopes less than 1%. Shallow slopes in this facility will reduce the
velocity and provide water quality treatment by providing additional time for infiltration and
contact with vegetation. Moderate removal of suspended solids are expected with this type of
BUR
The Registry Ridge P.U.D. Fourth Filing residential development has implemented
adequate structural and nonstructural BMPs to provide an effective stormwater quality control
plan.
VI. EROSION CONTROL PLAN
6.1 Erosion Control Plan and Criteria
The erosion control plan presented here is intended to control rainfall erosion only. The
Erosion Control Reference Manual for Construction Sites (ECRM), City of Fort Collins, has been
referenced for this erosion control plan.
6.2 Rainfall Erosion Control Plan
The proposed rainfall erosion control plan during construction will consist of temporary
structural erosion control measures. Gravel inlet filters will be placed at all curb inlets. A
sediment trap will be placed at the outlet of existing Pond 603. Silt fencing will be installed at
along the southern, eastern, and western boundaries of the site to prevent sediment from
migrating into Lang Gulch and onto adjacent property.
Vegetative erosion control will be used in association with this project by using straw
mulch with temporary seeding. It has been clearly noted on the Grading Plan that no soils shall
remain exposed for more than thirty days before requiring temporary or permanent erosion
control measures, unless approved by Stormwater Utility.
Computation of the "Performance Standard" and "Effectiveness" of the Erosion and
Sediment Control Plan are presented in Appendix G of this report.
The proposed rainfall erosion control plan after construction will consist of permanent
riprap which will be provided at the outlet of the storm sewer.. All open space areas and grass -
lined swales will be seeded with a permanent dryland seed mix as specified on the Landscape Plan.
An erosion control cost estimate for "during construction" sediment control has been
provided for the Fourth Filing (See Appendix G).
VII. CONCLUSIONS
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Registry Ridge P.U.D. Fourth Filing
September 11, 2000
from basin 4e will drain directly to detention Pond 603.
4.6 SWMM Modeling
There will be no SWMM modeling performed as part of this Fourth Filing drainage study.
All SWMM modeling has been completed and approved by the City of Fort Collins as part of the
Registry Ridge First Filing submittal. The approved SWMM model has included a site plan with
areas of imperviousness and general layout equivalent to that being submitted with the Fourth
Filing.
4.7 HEC-2 Modeling
There will be no HEC-2 model performed as part of this Fourth Filing drainage study. All
HEC-2 modeling has been completed as part of the First Filing submittal and is contained in the
report entitled Final Drainage Report for Registry Ridge P.U.D. First Filing, Volume 2, Section I.
4.8 Off -site Improvements
No offsite drainage or roadway improvements are proposed as part of the Fourth Filing
development.
4.9 Construction Phasing
The construction of all utilities will be done at the same time.
V. WATER QUALITY
5.1 Water Quality Measures and Criteria
Structural and nonstructural Best Management Practices (BMPs) have been incorporated
into the design of storm drainage facilities for Registry Ridge P.U.D. Fourth Filing. The Urban
Storm Drainage Criteria Manual, Volume 3 Best Management Practices, by the Urban Drainage
and Flood Control District has been referenced as a guide in the selection of onsite BMPs.
Urban stonmwater runoff contains many types of pollutants. BMPs are designed to reduce
the concentration of pollutants that reach downstream receiving waters. Two types of BMPs,
structural and nonstructural, serve to mitigate the increase in pollutants which are generated by
development. Nonstructural BMPs limit the migration of pollutants at their source. Structural
BMPs control the migration of contaminants by providing facilities which remove pollutants from
stormwater.
Nonstructural BMPs which have been used within the Fourth Filing development include
stormwater quality control planning, erosion control during construction and vegetative practices.
Directly connected impervious areas have been minimized by routing stormwater runoff across
lots (which will in all likelyhood be vegetated with bluegrass), and into grass -lined swales and a
vegetated detention pond. Rainfall erosion control will be controlled during construction through
the use of a sediment trap at the outlet of Pond 603.
Structural BMW's will include grass -lined swales and a vegetated detention pond. Grass -
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Drainage Design Considerations
Registry Ridge P.U.D. Fourth Filing
September 11, 2000
Northern Engineering Services, Inc.
the intensities lie within 1.5% of each other.
SWMM modeling has also been performed as part of an overall hydrologic analysis of the
Registry Ridge development. The Final Drainage Report for Registry Ridge First Filing, Volume
1, Section A, contains all input and output files and supporting calculations pertaining to this
analysis. The SWMM model has accounted for the Fourth Filing being fully developed in the file
PD 1 OOFC.DAT.
4.4 Hydraulic Criteria
The City of Fort Collins Storm Drainage Design Criteria has been referenced for all
hydraulic calculations. In addition, the following computer programs have been utilized:
• The computer program "UDINLET" has been used to analyze inlet capacities,
0 The computer program "Flowmaster" has been used to analyze the capacity of the
proposed swale
• The computer program "Storm Sewer Modeling" has been used to analyze the
capacity of the proposed storm sewer
The hydraulic analysis of Lang Gulch was evaluated as part of the First Filing through the
use of the HEC-2 computer model. Input and output files of all HEC-2 runs are included in the
Final Drainage Report for Registry Ridge P.U.D. First Filing, Volume 3, Section I.
There are two storm inlets that have been sized to accommodate the 100-year event.
These inlets are numbered as Inlet IA and Inlet 113. The inlets are located at the low -point of
Bataan Drive. An emergency overflow swale has been proposed to safely convey runoff from the
100-year storm should the sewer system fail. The proposed grade of the overflow swale exceeds
2.0% (due to the grading for walkout basements) and therefore produces supercritical flows and
possible erosion. Since the inlets have been sized for the 100-year storm, the swale will not be
used except in an emergency.
4.5 Drainage Patterns
Detention is not a requirement within the Fossil Creek Major Drainage Basin. The
developer of Registry Ridge however, desires to incorporate both on and offsite detention
facilities into the drainage system to provide a water quality mechanism as well as negate the
possibility of further bank erosion along Lang Gulch and Smith Creek. Also, according to the
Master Plan, development would not be allowed in the floodplain.
The Registry Ridge development is divided into five (5) major drainage basins 401-405
(See Final Drainage Report for Registry Ridge P.U.D. First Filing). The Fourth Filing is
contained entirely in basin 403. The Fourth Filling site has been sub -divided into 5 basins, labeled
4a through 4e (See Sheet 7/14). Developed stormwater from basins 4a, 4b, and 4c will be
conveyed overland to curb and gutter, through the streets to proposed on -site storm drains, and
then travel to existing Pond 603 (part of the First Filing). Developed runoff from basin 4d will
drain into existing swale 603 (part of the First Filing) and be conveyed to Pond 603. Stormwater
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Drainage Design Considerations
Registry Ridge P.U.D. Fourth Filing
September 11, 2000
Northern Engineering Services, Inc.
III. PREDEVELOPMENT CONDITIONS
3.1 Major Basin Description
The site is located in the Fossil Creek Drainage Basin and is included in the report entitled
Fossil Creek Drainage Basin Master Drainageway Planning Study, by Simons, Li & Associates,
Inc., August, 1982. The S WMM model developed as part of this Master Study has been updated
by Northern Engineering as part of the First Filing Final Drainage Report to reflect proposed
developed conditions for the entire Registry Ridge site, which includes the Fourth Filing.
3.2 Predevelopment Drainage Patterns
The Fourth Filing site historically drains from the north to the south at slopes ranging from
2.2 to 9.7%. The entire Fourth Filing site is tributary to Lang Gulch which drains to an existing
culvert crossing at Shields Street. The existing culvert crossing under Shields Street at Lang
Gulch has been field verified as a sixty (60) inch RCP. During a 100-year storm, ponding occurs
along Lang Gulch at the following locations: upstream of South Shields Street, C&S Railroad
Crossing #3 and Trilby Road.
IV. POSTDEVELOPMENT CONDITIONS
4.1 Postdevelopment Conditions
The Fourth Filing development will include the following:
• residential duplex units;
• new local streets;
• utilities.
There are no off -site easements required for the Fourth Filing development.
4.2 Design Criteria and References
Drainage criteria outlined in both the City of Fort Collins Storm Drainage Design Criteria
Manual.(SDDCM) and Storm Drainage Criteria Manual by the Urban Drainage and Flood
Control District have been referenced for this study.
4.3 Hydrologic Criteria
The Rational Method has been used to estimate peak stormwater runoff within the
developed site. The initial 2-year and major 100-year design storms have been used in the design
of the proposed drainage system which include storm inlets, a storm drain and a swale. Rainfall
intensity data for the Rational Method has been taken from IDF curves and equations generated
specifically for the Registry Ridge P.U.D. site by the computer program "Watershed Modeling"
by Eagle Point. Input of precipitation amounts have been taken from the NOAA Atlas 2, Volume
III - Colorado. Compared to Figure 3-1 in the SDDCM, rainfall intensities generated for the
Registry Ridge site were approximately 15% higher than intensities given in Figure 3-1 (rainfall
intensity curves from 1997). When compared to the SDDCM rainfall intensity curves from 1999,
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Drainage Design Considerations
for
Registry Ridge P.U.D. Fourth Filing
Fort Collins, Colorado
September 11, 2000
I. INTRODUCTION
1.1 Objective
This report summarizes the results of a comprehensive analysis of both pre and
postdevelopment, hydrologic and hydraulic conditions, for the Registry Ridge Fourth Filing
development.
1.2 Mapping_and Survevine
Aerial topography of the site was provided by JR Engineering with a contour interval of
one (1) foot.
1.3 Site Reconnaissance
A site visit was conducted on June 28, 1996 by the project engineer. Based on the
topographic mapping, existing drainage basins and land use were confirmed as well as existing
structures. The location and dimensions of existing culverts were verified as well as their
condition and flow direction. An additional site visit was conducted on August 24, 2000 to verify
that no changes had been made to the area since the previous visit. It was determined that the
topography along Bon Homme Richard Drive and Shields Street may be different than what the
original topography shows. Additional survey will be conducted prior to final design to ensure
that design drawings correspond accurately to field conditions.
H. SITE LOCATION AND DESCRIPTION
2.1 Site Location
The site is located within the East Half of Section 15, Township 6 North, Range 69 West
of the 6th Principal Meridian in Fort Collins, Colorado. The project is bounded by Bon Homme
Richard Drive on the north, Shields Street on the east, existing swale 603 on the west, and
existing detention Pond 603 on the south (See Vicinity Map).
2.2 Site Description
Registry Ridge P.U.D. Fourth Filing ("Fourth Filing") is approximately 9.36 acres and has
historically been furrowed agricultural land. There are no existing structures located on the site.
The only existing utilities are a sanitary sewer line that runs along the southern property boundary
and a storm sewer line that runs along the eastern property boundary. These improvements are
part of Registry Ridge First and Third Filings. The Fourth Filing is located south of Registry
Ridge Second Filing which is currently beginning construction.
\d
VICINITY MAP
Table of Contents
VICINITY MAP
Page
I.
INTRODUCTION
1
1.1 Objective......................................................................................
1
1.2 Mapping and Surveying................................................................
..
1.3 Site Reconnaissance ...:........................... .... ...... ........................... I
II.
SITE LOCATION AND DESCRIPTION
1
2.1 Site Location................................................................................
2.2 Site Description............................................................................ 1
M.
PREDEVELOPMENT CONDITIONS
3.1 Major Basin Description................................................................ 2
2
3.2 Predevelopment Drainage Patterns ................................................
IV.
POSTDEVELOPMENT CONDITIONS
2
4.1 Postdevelopment Conditions.........................................................
2
4.2 Design Criteria and References......................................................
4.3 Hydrologic Criteria........................................................................ 2
4.4 Hydraulic Criteria.......................................................................... 3
4.5 Drainage Patterns......................................................................... 3
4
4.6 SWMM Modeling.........................................................................
4.7 HEC-2 Modeling........................................................................... 4
4
4.8 Off -site Improvements...................................................................
4
4.9 Construction Phasing.....................................................................
V.
WATER QUALITY
4
5.1 Water Quality Measures and Criteria .............................................
VI.
EROSION CONTROL PLAN
5
6.1 Erosion Control Plan and Criteria ..................................................
6.2 Rainfall Erosion Control Plan ........................................................ 5
VH.
CONCLUSIONS
6
7.1 Compliance with Standards...........................................................
REFERENCES..::.::................................................................................ 7
APPENDICES
APPENDIX A - Postdevelopment Hydrology
APPENDIX B - Street Capacity
APPENDIX C - Design of Inlets
APPENDIX D - Design of Swales
APPENDIX E - Design of Storm Sewers
APPENDIX F - Riprap Calculations
APPENDIX G - Erosion Control Calculations
ENGINEERING
S E R V I C E S I N C
September 11, 2000
City of Fort Collins
Stormwater Utility
700 Wood Street
Fort Collins, Colorado 80522
RE: Registry Ridge P.U.D. Fourth Filing
Fort Collins, Colorado
Project Number: 2040.00
Dear Staff -
Northern Engineering Services, Inc. is pleased to submit this Preliminary Drainage Report
for Registry Ridge P.U.D. Fourth Filing for your review.
We understand that review by the City of Fort Collins is to assure general compliance with
standardized criteria contained in the Storm Drainage Design Criteria and Construction
Standards.
This report was prepared in compliance with technical criteria set forth in the City of Fort
Collins Storm Drainage Design Criteria and Construction Standards manual.
If you should have any questions or comments as you review this report, please feel free
to contact me at your convenience.
Sincerely,
NORTHERN ENGINEERING SERVICES, INC.
Roger A. urtiss, P.E.
►736
420 SOUTH HOWES, SUITE 202, FORT (OLLINS, (OLORADO 80521, (970) 221-4158, FAX (970) 221-4159
Drainage Design Considerations
for
Registry Ridge P.U.D. Fourth Filing
Fort Collins, Colorado
September 11, 2000
Prepared for:
U.S. Home Corporation
Colorado Division
6000 S. Greenwood Plaza Blvd., Suite 200
Englewood, Colorado 80111
Prepared by:
Northam Engineering Services. Inc
420 S. Howes, Suite 202
Fort Collins, Colorado 80521
Phone:(970)2214158
Project Number: 2040.00
.J