HomeMy WebLinkAboutRIVER DISTRICT BLOCK ONE MIXED-USE (ENCOMPASS) - PDP - PDP120020 - REPORTS - DRAINAGE REPORTJuly 17, 2012
PRELIMINARY DRAINAGE AND
EROSION CONTROL REPORT
RIVER DISTRICT BLOCK ONE MIXED USE
Fort Collins, Colorado
Prepared for:
Encompass Technologies
324 Jefferson Street
Fort Collins, CO 80524
Prepared by:
200 South College Avenue, Suite 10
Fort Collins, Colorado 80524
Phone: 970.221.4158 Fax: 970.221.4159
www.northernengineering.com
Project Number: 685-002
3 This Drainage Report is consciously provided as a PDF.
Please consider the environment before printing this document in its entirety.
When a hard copy is absolutely necessary, we recommend double-sided printing.
July 17, 2012
City of Fort Collins
Stormwater Utility
700 Wood Street
Fort Collins, Colorado 80521
RE: Preliminary Drainage and Erosion Control Report for
RIVER DISTRICT BLOCK ONE MIXED USE
Dear Staff:
Northern Engineering is pleased to submit this Preliminary Drainage and Erosion Control Report
for your review. This report accompanies the 07.17.12 Project Development Plan submittal for
the proposed River District Block One Mixed Use development.
This report has been prepared in accordance to Fort Collins Stormwater Criteria Manual (FCSCM),
and serves to document the stormwater impacts associated with the proposed project. We
understand that review by the City is to assure general compliance with standardized criteria
contained in the FCSCM.
If you should have any questions as you review this report, please feel free to contact us.
Sincerely,
NORTHERN ENGINEERING SERVICES, INC.
Aaron Cvar, PE Kevin R. Brazleton, PE
Project Engineer Project Engineer
River District Block One Mixed Use
Preliminary Drainage Report
TABLE OF CONTENTS
I. GENERAL LOCATION AND DESCRIPTION ................................................................... 1
A. Location .................................................................................................................. 1
B. Description of Property............................................................................................... 2
C. Floodplain ................................................................................................................ 3
II. DRAINAGE BASINS AND SUB-BASINS ....................................................................... 4
A. Major Basin Description ............................................................................................. 4
III. DRAINAGE DESIGN CRITERIA ................................................................................... 5
A. Regulations .............................................................................................................. 5
B. Four Step Process ..................................................................................................... 5
C. Development Criteria Reference and Constraints ............................................................ 6
D. Hydrological Criteria .................................................................................................. 6
E. Hydraulic Criteria ...................................................................................................... 6
F. Floodplain Regulations Compliance ............................................................................. 6
G. Modifications of Criteria ............................................................................................. 7
IV. DRAINAGE FACILITY DESIGN .................................................................................... 7
A. General Concept ....................................................................................................... 7
B. Specific Details ......................................................................................................... 8
V. CONCLUSIONS ........................................................................................................ 9
A. Compliance with Standards ........................................................................................ 9
B. Drainage Concept ...................................................................................................... 9
References ....................................................................................................................... 10
APPENDICES:
APPENDIX A – Hydrologic Computations
APPENDIX B – Hydraulic Computations
B.1 – Storm Sewers (reserved for future use)
B.2 – Inlets (reserved for future use)
APPENDIX C – Water Quality Design Computations
APPENDIX D – Erosion Control Report
APPENDIX E – FEMA FIRMette
River District Block One Mixed Use
Preliminary Drainage Report
LIST OF TABLES AND FIGURES:
Figure 1 – Aerial Photograph ................................................................................................ 2
Figure 2 – Proposed Site Plan ............................................................................................... 3
Figure 3 – Existing Floodplains ............................................................................................. 4
Table 1 – Water Quality Pond Summary ................................................................................. 8
MAP POCKET:
Drainage Exhibit
River District Block One Mixed Use
Preliminary Drainage Report 1
I. GENERAL LOCATION AND DESCRIPTION
A. Location
1. Vicinity Map
2. The project site is located in the northwest quarter of Section 12, Township 7 North,
Range 69 West of the 6th Principal Meridian, City of Fort Collins, County of Larimer,
State of Colorado.
3. The project site is located on the east side of Linden Street, and just north of Willow
Street. The Cache La Poudre River runs just to the north of the project site.
4. The project site lies within the Downtown River District study area (Ayres, 2012), and
is located within Basin 115. This basin has a master planned outfall directly to the
Cache La Poudre river, which runs just north of the project site. However, based on
direction by the City, a new outfall to the river is not desired. The site will outfall to
the existing Linden Street storm system. Due to the project site proximity to the river,
no detention is required for onsite runoff.
5. Downtown development exists to the south and west of the site.
River District Block One Mixed Use
Preliminary Drainage Report 2
B. Description of Property
1. The subject property is approximately 1.03 net acres.
Figure 1 – Aerial Photograph
2. The subject property currently consists of open area. The ground cover generally
consists of gravel and some native seeding. Existing ground slopes are steep (i.e.,
10±%) along the boundaries of the property and relatively gentle (i.e., 2±%) through
the interior of the property. General topography slopes from southwest to the
northeast towards the Cache La Poudre River.
3. According to the United States Department of Agriculture (USDA) Natural Resources
Conservation Service (NRCS) Soil Survey, the site consists of Paoli fine sandy loam,
which falls into Hydrologic Soil Group B. More site-specific exploration found varying
materials including sandy clay with occasional sand layers and sandy gravel. See the
Geotechnical Engineering Report by Earth Engineering Consultants, Inc. for additional
information.
4. The proposed project will develop the majority of the existing site, constructing a
commercial building of several stories in height. Parking areas and associated utilities
will be constructed. A water quality pond will be constructed at the northeast corner
of the site.
River District Block One Mixed Use
Preliminary Drainage Report 3
Figure 2– Proposed Site Plan
5. There are no irrigation ditches or related facilities in the vicinity of the project site.
6. The proposed land use is commercial.
C. Floodplain
1. A portion of the subject property is encroached by the FEMA 100-year floodplain
(Cache La Poudre River).
River District Block One Mixed Use
Preliminary Drainage Report 4
Figure 3 – Existing Floodplains
2. FEMA FIRM Panel Number 979 for Larimer County, Dated May 2, 2012 is referenced
in this study.
3. The base (100-year) flood elevation in the vicinity of the proposed structures is
4953.6, which is referenced to the City of Fort Collins NGVD 29.
4. The proposed structures are located outside of the 100-year floodplain but are within
the 500-year floodplain.
5. The Cache La Poudre half-foot floodway is located outside of the property boundary
with the exception of very minor encroachment along the southeast boundary of the
site. The maximum floodway encroachment into the property is 6-feet. No fill is
proposed within the half-foot floodway. Proposed grading will tie-in with existing
grades outside of the floodway boundary.
6. It is noted that the vertical datum utilized for site survey work is the City of Fort
Collins Benchmark #4-00 (Elevation=4960.55, Ft. Collins NGVD 29).
II. DRAINAGE BASINS AND SUB-BASINS
A. Major Basin Description
1. The project site is located within the Downtown River District study area (Ayres,
2012), and is located within Basin 115.
River District Block One Mixed Use
Preliminary Drainage Report 5
B. Sub-Basin Description
1. The subject property historically drains overland towards the Cache La Poudre River,
which runs northeast of the site. A more detailed description of the project drainage
patterns follows in Section IV.A.4., below.
2. Developed areas to the southwest of the site historically drain through the project site.
These off-site drainage flows and patterns will be maintained and accounted for with
the proposed development.
III. DRAINAGE DESIGN CRITERIA
A. Regulations
There are no optional provisions outside of the FCSCM proposed with the proposed
project.
B. Four Step Process
The overall stormwater management strategy employed with the proposed project utilizes
the “Four Step Process” to minimize adverse impacts of urbanization on receiving waters.
The following is a description of how the proposed development has incorporated each
step.
Step 1 – Employ Runoff Reduction Practices
Several techniques have been utilized with the proposed development to facilitate the
reduction of runoff peaks, volumes, and pollutant loads as the site is developed from the
current use as athletic facilities by implementing multiple Low Impact Development (LID)
strategies including:
Conserving existing amenities in the site including the existing vegetated areas.
Providing vegetated open areas throughout the site to reduce the overall impervious
area and to minimize directly connected impervious areas (MDCIA).
Routing flows, to the extent feasible, through vegetated swales to increase time of
concentration, promote infiltration and provide initial water quality.
Step 2 – Implement BMPs That Provide a Water Quality Capture Volume (WQCV) with
Slow Release
The efforts taken in Step 1 will facilitate the reduction of runoff; however, urban
development of this intensity will still generate stormwater runoff that will require
additional BMPs and water quality. All stormwater runoff from the site will ultimately be
routed to the northeast corner of the site, where it is intercepted and treated in the main
water quality pond prior to exiting the site.
Step 3 – Stabilize Drainageways
There are no major drainageways within the subject property. While this step may not
seem applicable to proposed development, the project indirectly helps achieve stabilized
drainageways nonetheless. By providing water quality where none previously existed,
sediment with erosion potential is removed from the downstream drainageway systems
and Cache La Poudre River. Furthermore, this project will pay one-time stormwater
development fees, as well as ongoing monthly stormwater utility fees, both of which help
achieve City-wide drainageway stability.
River District Block One Mixed Use
Preliminary Drainage Report 6
Step 4 – Implement Site Specific and Other Source Control BMPs.
The proposed project will require the need for site specific source controls including:
Several localized trash enclosures throughout the site for the disposal of waste
products.
C. Development Criteria Reference and Constraints
The subject property is essentially an "in-fill" development project as the property is
surrounded by currently developed properties. As such, several constraints have been
identified during the course of this analysis that will impact the proposed drainage
system including:
Existing elevations along the west and south property lines will be maintained.
As previously mentioned, overall drainage patterns of the existing site will be
maintained.
Elevations of existing downstream facilities that the subject property will release to
will be maintained.
D. Hydrological Criteria
1. The City of Fort Collins Rainfall Intensity-Duration-Frequency Curves, as depicted in
Figure RA-16 of the FCSCM, serve as the source for all hydrologic computations
associated with the proposed development. Tabulated data contained in Table RA-7
has been utilized for Rational Method runoff calculations.
2. The Rational Method has been employed to compute stormwater runoff utilizing
coefficients contained in Tables RO-11 and RO-12 of the FCSCM.
3. Three separate design storms have been utilized to address distinct drainage
scenarios. A fourth design storm has also been computed for comparison purposes.
The first design storm considered is the 80th percentile rain event, which has been
employed to design the project’s water quality features. The second event analyzed is
the “Minor,” or “Initial” Storm, which has a 2-year recurrence interval. The third
event considered is the “Major Storm,” which has a 100-year recurrence interval.
The fourth storm computed, for comparison purposes only, is the 10-year event.
4. No other assumptions or calculation methods have been used with this development
that are not referenced by current City of Fort Collins criteria.
E. Hydraulic Criteria
1. As previously noted, the subject property maintains historic drainage patterns.
2. All drainage facilities proposed with the project are designed in accordance with
criteria outlined in the FCSCM and/or the Urban Drainage and Flood Control District
(UDFCD) Urban Storm Drainage Criteria Manual.
3. As stated above the subject property is located in a FEMA regulatory floodplain.
4. The proposed project does not propose to modify any natural drainageways.
F. Floodplain Regulations Compliance
1. As previously mentioned, all structures are located outside of the Cache La Poudre
100-year floodplain, and thus the structures are not subject to any floodplain
regulations. However, extra care has been taken to ensure that neither existing nor
proposed structures will suffer damage during the 100-year storm as a result of the
River District Block One Mixed Use
Preliminary Drainage Report 7
proposed development.
G. Modifications of Criteria
1. The proposed development is not requesting any modifications to criteria at this time.
IV. DRAINAGE FACILITY DESIGN
A. General Concept
1. The main objectives of the project drainage design are to maintain existing drainage
patterns, ensure no adverse impacts to any adjacent properties, and to maintain the
drainage concepts as outlined in the Downtown River District study (Ayres, 2012).
2. Developed areas to the southwest of the site historically drain through the project site.
These off-site drainage flows and patterns will be maintained and accounted for with
the proposed development.
3. A list of tables and figures used within this report can be found in the Table of
Contents at the front of the document. The tables and figures are located within the
sections to which the content best applies.
4. The drainage patterns anticipated for proposed drainage basins are described below.
Basin 1
Basin 1 consists of landscaped and concrete areas to the south and west of the
proposed building. The basin drains to the adjacent Linden Street.
Basin 2
Basin 2 consists entirely of the rooftop of the proposed building. The basin drains into
an existing “Bay Saver” water quality treatment unit, which outfalls to the existing
Linden Street storm sewer.
Basin 3
Basin 3 consists of landscaped and concrete areas to the north of the proposed
building. The basin drains as sheet flow into the Poudre River.
Basin 4
Basin 4 consists mainly of the proposed parking area. The basin drains into the
proposed water quality pond to be constructed with the development.
Basin 5
Basin 5 consists of landscaped areas to the northeast of the proposed building. The
basin drains as sheet flow into the Poudre River.
Basin 6
Basin 6 consists of landscaped areas to the east of the proposed building. The basin
drains as sheet flow into the Poudre River.
Basin OS1
Basin OS1 consists of developed areas to the south of the project site. Runoff from
this basin will follow existing drainage patterns, as stormwater from this basin will be
directed via sheet flow to curb and gutter which will direct flows to Linden Street.
River District Block One Mixed Use
Preliminary Drainage Report 8
Basin OS2
Basin OS2 consists of developed areas to the south of the project site. Runoff from
this basin will follow existing drainage patterns, as stormwater from this basin will be
directed via sheet flow through the site and into the Poudre River.
Basin OS3
Basin OS3 consists of developed areas to the south of the project site. Runoff from
this basin will follow existing drainage patterns, as stormwater from this basin will be
directed via sheet flow through the site and into the Poudre River.
A full-size copy of the Drainage Exhibit can be found in the Map Pocket at the end of
this report.
B. Specific Details
1. Water quality treatment is being provided for the proposed development in the form of
extended detention as previously described. Further documentation of treatment
volumes and removal rates of stormwater BMPs will be documented with the Final
Drainage Report prepared during the City FCP process.
Final design details, construction documentation, and Standard Operating
Procedures (SOP) Manual shall be provided to the City of Fort Collins for
review prior to Final Development Plan approval. A final copy of the approved
SOP manual shall be provided to City and must be maintained on-site by the
entity responsible for the facility maintenance. Annual reports must also be
prepared and submitted to the City discussing the results of the maintenance
program (i.e. inspection dates, inspection frequency, volume loss due to
sedimentation, corrective actions taken, etc.).
2. Table 1, below, summarizes the water quality information for the proposed water
quality pond.
Table 1 – Water Quality Pond Summary
Water Quality Water Quality
Pond
Spillway Top of Pond
Capture Volume WSEL Elevation Elevation
(AC-FT) (FT) (FT) (FT)
0.010 4952.85 4953.50 4953.50
3. Proper maintenance of the drainage facilities designed with the proposed
development is a critical component of their ongoing performance and effectiveness.
The water quality pond may be easily accessed by maintenance staff via the gentle
slope provided to the bottom of the pond from the south side.
4. The drainage features associated with the proposed project are all private facilities,
located on private property, with the exception of the pond outfall. An easement will
be dedicated for the portion of the pond outfall that lies within City property.
5. The proposed outfall pipe will outfall to the existing storm line in Linden Street, which
drains north to the Cache La Poudre River.
River District Block One Mixed Use
Preliminary Drainage Report 9
V. CONCLUSIONS
A. Compliance with Standards
1. The drainage design proposed with the proposed project complies with the City of Fort
Collins’ Stormwater Criteria Manual.
2. The drainage design proposed with this project complies with the Downtown River
District Final Design Report (Ayres, 2012).
3. There are no regulatory floodplains within the proposed development.
4. The drainage plan and stormwater management measures proposed with the
proposed development are compliant with all applicable State and Federal regulations
governing stormwater discharge.
5. The proposed development is in compliance with Chapter 10 of City Code.
B. Drainage Concept
1. The drainage design proposed with this project will effectively limit any potential
damage associated with its stormwater runoff by providing an extended detention
water quality pond.
2. The drainage concept for the proposed development is consistent with the Downtown
River District Final Design Report (Ayres, 2012).
River District Block One Mixed Use
Preliminary Drainage Report 10
References
1. City of Fort Collins Landscape Design Guidelines for Stormwater and Detention Facilities,
November 5, 2009, BHA Design, Inc. with City of Fort Collins Utility Services.
2. Fort Collins Stormwater Criteria Manual, City of Fort Collins, Colorado, as adopted by Ordinance No.
174, 2011, and referenced in Section 26-500 (c) of the City of Fort Collins Municipal Code.
3. Larimer County Urban Area Street Standards, Adopted January 2, 2001, Repealed and
Reenacted, Effective October 1, 2002, Repealed and Reenacted, Effective April 1, 2007.
4. Soils Resource Report for Larimer County Area, Colorado, Natural Resources Conservation
Service, United States Department of Agriculture.
5. Urban Storm Drainage Criteria Manual, Volumes 1-3, Urban Drainage and Flood Control
District, Wright-McLaughlin Engineers, Denver, Colorado, Revised April 2008.
6. Downtown River District Final Design Report, February 2012, Ayres Associates.
7. Subsurface Exploration Report, 418 Linden Street, October 25, 2011, Earth Engineering
Consultants, Inc.
APPENDIX A
HYDROLOGIC COMPUTATIONS
CHARACTER OF SURFACE:
Runoff
Coefficient
Percentage
Impervious Project: 685-002
Streets, Parking Lots, Roofs, Alleys, and Drives: Calculations By: ATC
Asphalt ……....……………...……….....…...……………….……………………………… 0.95 100% Date:
Concrete …….......……………….….……….………………..….…………………………… 0.95 90%
Gravel ……….…………………….….…………………………..…………………………… 0.50 40%
Roofs …….…….………………..……………….……………………………………………. 0.95 90%
Pavers…………………………...………………..…………………………………………… 0.40 22%
Lawns and Landscaping
Sandy Soil ……..……………..……………….…………………………………………….. 0.15 0%
Clayey Soil ….….………….…….…………..………………………………………………. 0.25 0% 2-year Cf
= 1.00 100-year Cf = 1.25
Basin ID
Basin Area
(s.f.)
Basin Area
(ac)
Area of
Asphalt
(ac)
Area of
Concrete
(ac)
Area of
Roofs
(ac)
Area of
Gravel
(ac)
Area of
Lawns and
Landscaping
(ac)
2-year
Composite
Runoff
Coefficient
10-year
Composite
Runoff
Coefficient
100-year
Composite
Runoff
Coefficient
Composite
% Imperv.
1 1826 0.04 0.042 0.000 0.000 0.000 0.000 0.95 0.95 1.00 100%
2 13413 0.31 0.000 0.000 0.308 0.000 0.000 0.95 0.95 1.00 90%
3 935 0.02 0.000 0.002 0.000 0.000 0.021 0.34 0.34 0.42 8%
4 23321 0.54 0.230 0.080 0.000 0.000 0.225 0.66 0.66 0.82 56%
5 2074 0.05 0.000 0.000 0.000 0.000 0.048 0.25 0.25 0.31 0%
6 3271 0.08 0.000 0.000 0.000 0.000 0.075 0.25 0.25 0.31 0%
OS1 23041 0.53 0.113 0.000 0.236 0.092 0.087 0.76 0.76 0.94 69%
OS2 21024 0.48 0.124 0.000 0.066 0.179 0.113 0.62 0.62 0.77 53%
OS3 5238 0.12 0.038 0.000 0.000 0.038 0.045 0.55 0.55 0.68 44%
DEVELOPED COMPOSITE % IMPERVIOUSNESS AND RUNOFF COEFFICIENT CALCULATIONS
Overland Flow, Time of Concentration:
Project: 685-002
Calculations By:
Date:
Gutter/Swale Flow, Time of Concentration:
Tt = L / 60V
Tc = Ti + Tt (Equation RO-2)
Velocity (Gutter Flow), V = 20·S½
Velocity (Swale Flow), V = 15·S½
NOTE: C-value for overland flows over grassy surfaces; C = 0.25
Is Length
>500' ?
C*Cf
(2-yr
Cf=1.00)
C*Cf
(10-yr
Cf=1.00)
C*Cf
(100-yr
Cf=1.25)
Length,
L
(ft)
Slope,
S
(%)
Ti
2-yr
(min)
Ti
10-yr
(min)
Ti
100-yr
(min)
Length,
L
(ft)
Slope,
S
(%)
Velocity,
V
(ft/s)
Tt
(min)
Length,
L
(ft)
Slope,
S
(%)
Velocity,
V
(ft/s)
Tt
(min)
2-yr
Tc
Rational Method Equation: Project: 685-002
Calculations By:
Date:
From Section 3.2.1 of the CFCSDDC
Rainfall Intensity:
1 1 0.04 5 5 5 0.95 0.95 1.00 2.85 4.87 9.95 0.1 0.2 0.4
2 2 0.31 5 5 5 0.95 0.95 1.00 2.85 4.87 9.95 0.8 1.4 3.1
3 3 0.02 5 5 5 0.34 0.34 0.42 2.85 4.87 9.95 0.0 0.0 0.1
4 4 0.54 5 5 5 0.66 0.66 0.82 2.85 4.87 9.95 1.0 1.7 4.4
5 5 0.05 5 5 5 0.25 0.25 0.31 2.85 4.87 9.95 0.0 0.1 0.1
6 6 0.08 7 7 6 0.25 0.25 0.31 2.60 4.44 9.31 0.05 0.08 0.22
OS1 OS1 0.53 5 5 5 0.76 0.76 0.94 2.85 4.87 9.95 1.1 1.9 5.0
OS2 OS2 0.48 5 5 5 0.62 0.62 0.77 2.85 4.87 9.95 0.9 1.5 3.7
OS3 OS3 0.12 5 5 5 0.55 0.55 0.68 2.85 4.87 9.95 0.2 0.3 0.8
Intensity,
i10
(in/hr)
Rainfall Intensity taken from the City of Fort Collins Storm Drainage Design Criteria (CFCSDDC), Figure 3.1
C10
Area, A
(acres)
Intensity,
i2
(in/hr)
100-yr
Tc
(min)
DEVELOPED RUNOFF COMPUTATIONS
C100
Design
Point
Flow,
Q100
(cfs)
Flow,
Q2
(cfs)
10-yr
Tc
(min)
2-yr
Tc
(min)
C2
Flow,
Q10
(cfs)
Intensity,
i100
(in/hr)
Basin(s)
ATC
July 10, 2012
Q C f C i A
APPENDIX B
HYDRAULIC COMPUTATIONS
B.1 – Storm Sewers (reserved for future use)
B.2 – Inlets (reserved for future use)
APPENDIX B.1
STORM SEWERS (reserved for future use)
APPENDIX B.2
INLETS (reserved for future use)
APPENDIX C
WATER QUALITY DESIGN COMPUTATIONS
WATER QUALITY POND DESIGN CALCULATIONS
Water Quality Pond
Project: 685-002
By: ATC
Date: 6.1.12
REQUIRED STORAGE & OUTLET WORKS:
BASIN AREA = 0.540 <-- INPUT from impervious calcs
BASIN IMPERVIOUSNESS PERCENT = 56.00 <-- INPUT from impervious calcs
BASIN IMPERVIOUSNESS RATIO = 0.5600 <-- CALCULATED
WQCV (watershed inches) = 0.223 <-- CALCULATED from Figure EDB-2
WQCV (ac-ft) = 0.010 <-- CALCULATED from UDFCD DCM V.3 Section 6.5
WQ Depth (ft) = ** <-- INPUT from stage-storage table
AREA REQUIRED PER ROW, a (in
2
) = ** <-- CALCULATED from Figure EDB-3
CIRCULAR PERFORATION SIZING:
dia (in) = ** <-- INPUT from Figure 5
n = ** <-- INPUT from Figure 5
t (in) = ** <-- INPUT from Figure 5
number of rows = ** <-- CALCULATED from WQ Depth and row spacing
**To be completed at final design
APPENDIX D
EROSION CONTROL REPORT
Block One
Preliminary Erosion Control Report
EROSION CONTROL REPORT
A comprehensive Erosion and Sediment Control Plan (along with associated details) will be included
with the final construction drawings. It should be noted, however, that any such Erosion and
Sediment Control Plan serves only as a general guide to the Contractor. Staging and/or phasing of
the BMPs depicted, and additional or different BMPs from those included may be necessary during
construction, or as required by the authorities having jurisdiction.
It shall be the responsibility of the Contractor to ensure erosion control measures are properly
maintained and followed. The Erosion and Sediment Control Plan is intended to be a living
document, constantly adapting to site conditions and needs. The Contractor shall update the
location of BMPs as they are installed, removed or modified in conjunction with construction
activities. It is imperative to appropriately reflect the current site conditions at all times.
The Erosion and Sediment Control Plan shall address both temporary measures to be implemented
during construction, as well as permanent erosion control protection. Best Management Practices
from the Volume 3, Chapter 7 – Construction BMPs will be utilized. Measures may include, but are
not limited to, silt fencing along the disturbed perimeter, gutter protection in the adjacent roadways
and inlet protection at existing and proposed storm inlets. Vehicle tracking control pads, spill
containment and clean-up procedures, designated concrete washout areas, dumpsters, and job site
restrooms shall also be provided by the Contractor.
Grading and Erosion Control Notes can be found on the Utility Plans. The Final Plans will contain a
full-size Erosion Control sheet as well as a separate sheet dedicated to Erosion Control Details. In
addition to this report and the referenced plan sheets, the Contractor shall be aware of, and adhere
to, the applicable requirements outlined in the Development Agreement for the development. Also,
the Site Contractor for this project will be required to secure a Stormwater Construction General
Permit from the Colorado Department of Public Health and Environment (CDPHE), Water Quality
Control Division – Stormwater Program, prior to any earth disturbance activities. Prior to securing
said permit, the Site Contractor shall develop a comprehensive StormWater Management Plan
(SWMP) pursuant to CDPHE requirements and guidelines. The SWMP will further describe and
document the ongoing activities, inspections, and maintenance of construction BMPs.
APPENDIX E
FEMA FIRMETTE
Block One
Preliminary Erosion Control Report
MAP POCKET
DRAINAGE EXHIBIT
F
E
S
OWNER:
RANCH-WAY INC.
OWNER:
CITY OF FORT COLLINS
OWNER:
CITY OF FORT COLLINS
OWNER:
KEIFER
MARJORIE R.
OWNER:
KIEFER BLAIR A
FAMILY TRUST
OWNER:
KIEFER BLAIR A
FAMILY TRUST
LINDEN STREET
(100' ROW)
CACHE LA POUDRE RIVER
T
T
RD
PROPOSED
BUILDING
PROPOSED
BUILDING
PROPOSED
BUILDING
PROPOSED
BUILDING
EXISTING 100'
LINDEN
STREET
RIGHT-OF-WAY
FFE=65.00
(FIRST FLOOR)
2
0.31
2
FFE=65.00
(FIRST FLOOR)
1
0.04
3
0.02
4
0.54
6
0.08
5
0.05
OS1
0.53
OS2
0.48
OS3
0.12
4
5
6
OS2
OS3
OS1
3
100-YR FLOOD ELEV.=4953 (FT.COLLINS NGVD29)
4956 (NAVD88)
FEMA CROSS-SECTION "CA"
EXISTING 36" STORM DRAIN
DRAINAGE SUMMARY TABLE
DESIGN
POINT
BASIN
ID
TOTAL
AREA
(�����)
C10 C100
10-��
T�
(���)
100-�
�
T�
(���)
Q10
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Q100
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1 1 0.04 0.95 1.00 5.0 5.0 0.2 0.4
2 2 0.31 0.95 1.00 5.0 5.0 1.4 3.1
3 3 0.02 0.34 0.42 5.0 5.0 0.0 0.1
4 4 0.54 0.66 0.82 5.3 5.0 1.7 4.4
5 5 0.05 0.25 0.31 5.0 5.0 0.1 0.1
6 6 0.08 0.25 0.31 6.6 6.1 0.1 0.2
OS1 OS1 0.53 0.76 0.94 5.0 5.0 1.9 5.0
OS2 OS2 0.48 0.62 0.77 5.0 5.0 1.5 3.7
OS3 OS3 0.12 0.55 0.68 5.0 5.0 0.3 0.8
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REVIEWED BY:
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DESIGNED BY:
DRAWN BY:
SCALE:
DATE:
07/17/12
PROJECT:
685-002
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REVIEW SET
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E N G I N E E R I N G
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C500
DRAINAGE EXHIBIT
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CALL 2 BUSINESS DAYS IN ADVANCE BEFORE YOU DIG, GRADE, OR EXCAVATE FOR THE MARKING OF UNDERGROUND MEMBER UTILITIES.
CALL UTILITY NOTIFICATION CENTER OF
COLORADO
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FOR DRAINAGE REVIEW ONLY UTILITY PLAN APPROVAL
NOT FOR CONSTRUCTION
WATER QUALITY POND SUMMARY
VOLUME REQ'D (��-��) VOLUME PROVIDED (��-��) POND INVERT WQ WATER SURFACE POND SPILL ELEV.
0.01 0.01 4951.50 4952.65 4953.50
PROPOSED STORM SEWER
PROPOSED STORM DRAINAGE INLET
PROPOSED CONTOURS
80
79
EXISTING STORM SEWER
PROPERTY BOUNDARY
EXISTING MAJOR CONTOUR
EXISTING MINOR CONTOUR
5015
5013
EXISTING TREES
A
DESIGN POINT
FLOW ARROW
DRAINAGE BASIN LABEL
BASIN
DESIGNATION
BASIN
AREA (AC)
DRAINAGE BASIN BOUNDARY
B2
1.45 ��
EXISTING RIGHT-OF-WAY
EXISTING TOP OF BANK
PROPOSED RETAINING WALL
EXISTING 100-YEAR FLOODPLAIN
EXISTING 0.5-FOOT FLOODWAY
EXISTING RIVER'S EDGE
(min)
10-yr
Tc
(min)
100-yr
Tc
(min)
11No0.95 0.95 1.00 17 2.00% 0.9 0.9 0.6 0 0.00% N/A N/A 0 N/A N/A N/A 5 5 5
22No0.95 0.95 1.00 92 0.50% 3.4 3.4 2.3 0 0.50% N/A N/A 0 N/A N/A N/A 5 5 5
33No0.34 0.34 0.42 15 2.00% 4.4 4.4 3.9 0 0.50% N/A N/A 0 N/A N/A N/A 5 5 5
44No0.66 0.66 0.82 94 3.50% 5.3 5.3 3.4 0 0.50% N/A N/A 0 N/A N/A N/A 5 5 5
55No0.25 0.25 0.31 27 14.00% 3.4 3.4 3.2 0 0.00% N/A N/A 0 N/A N/A N/A 5 5 5
66No0.25 0.25 0.31 68 8.00% 6.6 6.6 6.1 0 0.00% N/A N/A 0 N/A N/A N/A 7 7 6
OS1 OS1 No 0.95 0.95 1.00 150 1.00% 3.4 3.4 2.3 85 0.40% 1.26 1.1 0 N/A N/A N/A 5 5 5
OS2 OS2 No 0.95 0.95 1.00 150 1.00% 3.4 3.4 2.3 37 0.40% 1.26 0.5 0 N/A N/A N/A 5 5 5
OS3 OS3 No 0.95 0.95 1.00 133 1.00% 3.2 3.2 2.2 0 0.00% N/A N/A 0 N/A N/A N/A 5 5 5
DEVELOPED TIME OF CONCENTRATION COMPUTATIONS
Gutter Flow Swale Flow
Design
Point
Basin
Overland Flow
ATC
July 10, 2012
Time of Concentration
(Equation RO-4)
3
1
1 . 87 1 . 1 *
S
Ti C Cf L
Runoff Coefficients are taken from the City of Fort Collins Storm Drainage Design Criteria and Construction Standards, Table 3-3. % Impervious taken from UDFCD USDCM, Volume I.
10-year Cf = 1.00
July 10, 2012