HomeMy WebLinkAbout320 MAPLE STREET - PDP - PDP150025 - SUBMITTAL DOCUMENTS - ROUND 1 - DRAINAGE REPORTNovember 18, 2015
PRELIMINARY DRAINAGE REPORT
MELDRUM MIXED USE
Fort Collins, Colorado
Prepared for:
Alex Schuman
Schuman Companies, Inc.
605 S. College Avenue, Suite 100
Fort Collins, Colorado 80524
Prepared by:
301 N. Howes Street Suite 100
Fort Collins, Colorado 80521
Phone: 970.221.4158
www.northernengineering.com
Project Number: 574-007
PThis 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.
November 18, 2015
City of Fort Collins
Stormwater Utility
700 Wood Street
Fort Collins, Colorado 80521
RE: Preliminary Drainage Report for
Meldrum Mixed Use
Dear Staff:
Northern Engineering is pleased to submit this Preliminary Drainage Report for your review.
This report accompanies the Preliminary Plan submittal for the proposed Meldrum Mixed
Use development.
This report has been prepared in accordance with the Fort Collins Stormwater Criteria
Manual (FCSCM), and serves to document the stormwater impacts associated with the
proposed Meldrum Mixed Use housing project. We understand that review by the City of
Fort Collins 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.
Andrew Reese
Project Engineer
Meldrum Mixed Use
TABLE OF CONTENTS
I. GENERAL LOCATION AND DESCRIPTION ......................................................... 1
II. DRAINAGE BASINS AND SUB-BASINS ............................................................. 4
III. DRAINAGE DESIGN CRITERIA ......................................................................... 5
IV. DRAINAGE FACILITY DESIGN .......................................................................... 7
V. CONCLUSIONS............................................................................................... 9
References ............................................................................................................. 10
APPENDICES:
APPENDIX A – Hydrologic Computations
APPENDIX B – Hydraulic Computations
B.1 – Hydraulic Computations (Reserved for Final)
B.2 – Detention Facilities
APPENDIX C – Water Quality Design Computations (Reserved for Final)
APPENDIX D – Erosion Control Report
APPENDIX E – Standard Operating Procedures (SOP’s) References (Reserved for Final)
MAP POCKET:
DR1 – Drainage Exhibit
DR2 – Existing Drainage Exhibit
Meldrum Mixed Use
Page|1
I. GENERAL LOCATION AND DESCRIPTION
A. Location
1. Vicinity Map
Figure 1 – Vicinity Map
2. The Meldrum Mixed Use project site is located in the southwest quarter of Section 11,
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 (refer to Figure 1) is bordered to the north by a single family
residence; to the south by Maple Street (100’ ROW); to the east by an existing public
alley (20' Right-of-Way); and to the west by Meldrum Street (100’ ROW).
4. There are no major drainageways within or adjacent to the site.
Meldrum Mixed Use
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B. Description of Property
1. Meldrum Mixed Use is comprised of ±0.65 acres.
2. The site is currently occupied by two commercial buildings, an single family residence
and several small outbuildings.
Figure 2 – Aerial Photograph
3. The existing groundcover consists of grasses, asphalt and gravel. The existing on-site
runoff generally drains from the southwest-to-northeast east across flat grades (e.g.,
<2.00%) into the existing alley. From there it is directed to Maple Street via the
alley, and then to an existing inlet via curb and gutter on Maple. The existing inlet is
located at the interseciton of Maple and Howes, at the northwest corner. From there,
the drainage continues through an existing storm system down Maple Street to a large
regional drainage culvert near Mason Street, and on to the Cache La Poudre River.
4. There are no major drainageways within or adjacent to the project site.
5. The proposed Meldrum Mixed Use development will consist of a single mixed-use
building. Other proposed improvements include: a new concrete parking area located
under the building, new sidewalks and new landscaping.
6. The proposed land use is mixed-use. This is a permitted use in the Downtown District
(D).
Project Site
Meldrum Mixed Use
Page|3
C. Floodplain
1. The subject property is not located in a FEMA regulatory floodplain. In particular, the
project site is not located within a FEMA designated 100-year floodplain per Map
Number 08069C0979H (Effective date: May 2, 2012).
The project site is located adjacent to a City of Fort Collins regulated Old Town
floodplain. As such, the project will comply with all regulations set forth in Chapter
10 of the City Municipal Code.
Figure 4 – FEMA Firmette (Map Number 08069C0979H)
Project Site
Meldrum Mixed Use
Page|4
II. DRAINAGE BASINS AND SUB-BASINS
A. Major Basin Description
1. Meldrum Mixed Use is located within the City of Fort Collins Old Town major drainage
basin. Specifically, the project site is situated in the north-central portion of this major
drainage basin. This basin is located in north-central Fort Collins and has a drainage
area of approximately 2,120 acres, including approximately 400 acres of the Colorado
State University campus. The Old Town major drainage basin generally drains from
west to east. It receives some runoff from the Canal Importation Basin directly west of
Old Town. Most of the runoff from the Old Town major drainage basin drains into the
Poudre River.
B. Sub-Basin Description
1. The outfall for the project site is the existing curb and gutter along Maple Street which
then flows to an existing curb inlet located at the intersection of Howes Street and
Maple Street, in the northwest corner.
2. The existing subject site can be defined with one (1) sub-basin. Refer to the Existing
Drainage Exhibit for additional information.
· Sub-basin EX1 delineates the proposed project site, which was used to
approximate the 2- and 100-year existing runoff.
The existing site runoff generally drains from northwest-to-southeast into the existing
alley along the eastern boundary of the site.
3. The project site does not receive notable runoff from contiguous off-site properties.
Meldrum Mixed Use
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III. DRAINAGE DESIGN CRITERIA
A. There are no optional provisions outside of the FCSCM proposed with Meldrum Mixed
Use.
B. The overall stormwater management strategy employed with Meldrum Mixed Use 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. The first consideration taken in trying to
reduce the stormwater impacts of this development is the site selection itself. By choosing
an already developed site with public storm sewer currently in place, the burden is
significantly less than developing a vacant parcel absent of any infrastructure.
Meldrum Mixed Use aims to reduce runoff peaks, volumes and pollutant loads from
frequently occurring storm events (i.e., water quality (i.e., 80th percentile) and 2-year
storm events) by implementing Low Impact Development (LID) strategies. Wherever
practical, runoff will be routed across landscaped areas or Bio-retention planters. These
LID practices reduce the overall amount of impervious area, while at the same time
Minimizing Directly Connected Impervious Areas (MDCIA). The combined LID/MDCIA
techniques will be implemented, where practical, throughout the development, thereby
slowing runoff and increasing opportunities for infiltration.
Step 2 – Implement BMPs That Provide a Water Quality Capture Volume (WQCV) with
Slow Release. The efforts taken in Step 1 will help to minimize excess runoff from
frequently occurring storm events; however, urban development of this intensity will still
have stormwater runoff leaving the site. The primary water quality treatment will occur in
the Bio-retention planters located in the second level courtyard.
Step 3 – Stabilize Drainageways. As stated in Section I.B.5, above, there are no major
drainageways in or near the subject site. While this step may not seem applicable to
Meldrum Mixed Use, the proposed project indirectly helps achieve stabilized drainageways
nonetheless. Once again, site selection has a positive effect on stream stabilization. By
developing an infill site with existing stormwater infrastructure, combined with LID and
MDCIA strategies, the likelihood of bed and bank erosion is reduced. Furthermore, this
project will pay one-time stormwater development fees, as well as ongoing monthly
stormwater utility fees, both of which help achieve Citywide drainageway stability.
Step 4 – Implement Site Specific and Other Source Control BMPs. This step typically
applies to industrial and commercial developments.
C. Development Criteria Reference and Constraints
1. The subject property is not part of any Overall Development Plan (ODP) drainage
study or similar “development/project” drainage master plan.
2. The site plan is constrained on two sides by public streets, as well as by existing
developments along the remaining two sides. As previously mentioned, the drainage
outfall for sub-basin A is the existing curb and gutter along Maple Street which then
flows to an existing curb inlet located at the intersection of Howes Street and Maple
Street, in the northwest corner.
Meldrum Mixed Use
Page|6
3. Peak runoff from the project site during the 2-year event will remain unchanged and
will decrease during the 100-year storm event. During the 2-year storm event, runoff
will remain at ±0.96 cfs; and during the 100-year storm event runoff will decrease
from ±4.28 cfs to ±0.96 cfs.
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 Meldrum Mixed Use 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. The Rational Formula-based Federal Aviation Administration (FAA) procedure has
utilized for detention storage calculations.
4. Two separate design storms have been utilized to address distinct drainage scenarios.
The first event analyzed is the “Minor,” or “Initial” Storm, which has a 2-year
recurrence interval. The second event considered is the “Major Storm,” which has a
100-year recurrence interval.
E. Hydraulic Criteria
1. The drainage facilities proposed with the Meldrum Mixed Use project are
designed in accordance with criteria outlined in the FCSCM and/or the Urban
Drainage and Flood Control District’s (UDFCD) Urban Storm Drainage Criteria
Manual.
2. As stated in Section I.C.1, above, the subject property is located in a City of
Fort Collins designated floodplain.
F. Floodplain Regulations Compliance
1. As previously mentioned, this project is adjacent to a City of Fort Collins
regulated floodplain. Discussions with City staff have indicated that more
accurate mapping information will likely remove all or part of the property from
the floodplain fringe. With this in mind, it is the intent of the project to
provide the additional data to modify the floodplain in this location.
2. Should additional data not have the anticipated effect on the floodplain
mapping, the building will be elevated or flood-proofed above the regulatory
floodplain as required by City Code. Additionally, all requirements set forth in
Chapter 10 of the City Municipal Code shall be met.
G. Modifications of Criteria
1. No modifications are requested at this time.
H. Conformance with Low Impact Development (LID)
Meldrum Mixed Use
Page|7
1. The project site will conform with the requirement to provide a minimum of
25% of new paving as permeable pavement. Since all parking for the project
is located under the structure, no permeable paving is required.
2. The project site will conform with the requirement to treat a minimum of 50%
of the project site using an LID technique. The total project area is 28,498 sf.
Of that area, 24,384 sf will be treated by LID techniques, primarily bio-
retention basins located in the second level courtyard. This means that ±
85% of the site will be treated by LID-type technology, exceeding the
minimum requirement of 50%.
IV. DRAINAGE FACILITY DESIGN
A. General Concept
1. The main objective of the Meldrum Mixed Use drainage design is to maintain existing
drainage patterns, while not adversely impacting adjacent properties.
2. No notable off-site runoff passes directly through the project site.
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. Drainage for the project site has been analyzed using two (2) drainage sub-basins,
designated as sub-basins A & B. The drainage patterns anticipated for the basins are
further described below.
Sub-Basin A
Sub-basin A encompasses approximately 85%the total site area. This sub-basin is
comprised primarily of roof area and the on-site parking area. The majority of the
parking area will be located below the building and will not be exposed to
precipitation. Detention will be provided within an underground vault located under
the parking area. This basin will release at an adjusted 2-year rate of 0.46 cfs through
an orifice plate. An outlet orifice cap located on the east wall of the proposed drain
basin will be used to control the flow rate. See Section IV.B.1 for discussion on how
the adjusted release rate was determined.
Sub-Basin B
Sub-basin B encompasses approximately 15%the total site area. This sub-basin is
comprised primarily of landscaped area surrounding the building. Sub-basin B will
leave the site undetained. This basin will release at 0.12 cfs in the 2-yr event and at
0.50 cfs in the 100-year event.
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. The release rate for the undeveloped land (pre-development) was established
Meldrum Mixed Use
Page|8
by calculating the 2-year peak runoff rate for the entire project area. The total
establishes the overall maximum allowable release rate, 0.96 cfs, from the
project site. The allowable release rate of 0.46 cfs utilized in the FAA
procedure detention storage computations (Refer to Appendix B for these
calculations) and was established by subtracting the total undetained release
from Basin B of 0.50 cfs from the overall maximum allowable release rate.
2. The FAA method was used to size the on-site detention vault for quantity
detention. Calculations for this area, based on the characteristics of sub-basin
A and adjusted release rate, indicate a detention volume of 4,557 cu. ft. This
does not include any volume for Water Quality Capture Volume (WQCV) as WQ
treatment is being provided in the bio-retention planters. There is no-
infiltration accounted for with this design.
3. All roof drain downspouts will discharge into the bio-retention planters section.
The exception to this are the small awning located over entrances, which will
release into landscaped areas.
4. The emergency spill path will be from the vault into the existing alley, where flows will
proceed along the historic path south along the alley and east to the existing curb
inlet.
Meldrum Mixed Use
Page|9
V. CONCLUSIONS
A. Compliance with Standards
1. The design elements comply without variation, and meet all LID requirements.
2. The drainage design proposed with Meldrum Mixed Use complies with the City of Fort
Collins Master Drainage Plan for the Old Town Basin.
3. There are no FEMA regulatory floodplains associated with the Meldrum Mixed Use
development. However the project is impacted by the Old Town Floodplain, which is
a City Regulated floodplain. All provisions within Chapter 10 of the City Municipal
Code shall be adhered to.
4. The drainage plan and stormwater management measures proposed with the Meldrum
Mixed Use project are compliant with all applicable State and Federal regulations
governing stormwater discharge.
B. Drainage Concept
1. The drainage design proposed with this project will effectively limit potential damage
associated with its stormwater runoff. Meldrum Mixed Use will detain for the pervious
area converted to impervious areas to release at the 2-year existing rate during the
100-year storm.
2. The proposed Meldrum Mixed Use development will not impact the Master Drainage
Plan recommendations for the Old Town major drainage basin.
Meldrum Mixed Use
Page|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. Soils Resource Report for Larimer County Area, Colorado, Natural Resources Conservation
Service, United States Department of Agriculture.
4. Urban Storm Drainage Criteria Manual, Volumes 1-3, Urban Drainage and Flood Control
District, Wright-McLaughlin Engineers, Denver, Colorado, Revised April 2008.
APPENDIX A
HYDROLOGIC COMPUTATIONS
CHARACTER OF SURFACE:
Runoff
Coefficient
Percentage
Impervious Project: Maple Mixed Use
Streets, Parking Lots, Roofs, Alleys, and Drives: Calculations By: A. Reese
Asphalt ……....……………...……….....…...……………….………………………………….0.95 . 100 Date:
Concrete …….......……………….….……….………………..….………………………………… 0.95 90
Gravel ……….…………………….….…………………………..……………………………….0.50 . 40
Roofs …….…….………………..……………….…………………………………………….0..95 90
Concrete 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
Concrete
Pavers
(ac)
Area of
Lawns and
Landscaping
(ac)
2-year
Composite
Runoff
Coefficient
10-year
Composite
Runoff
Coefficient
100-year
Composite
Runoff
Coefficient
Composite
% Imperv.
EX1 28,498 0.65 0.05 0.04 0.27 0.04 0.00 0.25 0.61 0.61 0.76 52.6
TOTAL ONSITE 28,498 0.65 0.05 0.04 0.27 0.04 0.00 0.25 0.61 0.61 0.76 52.6
EXISTING COMPOSITE % IMPERVIOUSNESS AND RUNOFF COEFFICIENT CALCULATIONS
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
November 18, 2015
Overland Flow, Time of Concentration:
Project: Maple Mixed Use
Calculations By:
Date:
Gutter/Swale Flow, Time of Concentration:
Tt = L / 60V
Tc = T
i + Tt
(Equation RO-2)
Velocity (Gutter Flow), V = 20·S
½
Velocity (Swale Flow), V = 15·S
½
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)
Rational Method Equation: Project: Maple Mixed Use
Calculations By:
Date:
From Section 3.2.1 of the CFCSDDC
Rainfall Intensity:
EX1 EX1 0.65 8.4 8.4 8.0 0.61 0.61 0.76 2.40 4.10 8.59 0.96 1.63 4.28
Area, A
(acres)
Intensity,
i2
(in/hr)
100-yr
Tc
(min)
EXISTING 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)
A. Reese
November 18, 2015
Intensity,
i10
(in/hr)
Rainfall Intensity taken from the City of Fort Collins Storm Drainage Design Criteria (CFCSDDC), Figure 3.1
C10
Q = C f ( C )( i )( A )
D:\Projects\574-007\Drainage\Hydrology\574-007_Rational Calcs_Existing.xlsx\Direct-Runoff
DESIGN
POINT
BASIN
ID
TOTAL
AREA
(acres)
C2 C10 C100
2-yr Tc
(min)
10-yr
Tc
(min)
100-yr
Tc
(min)
Q2
(cfs)
Q10
(cfs)
Q100
(cfs)
EX1 EX1 0.65 0.61 0.61 0.76 8.4 8.4 8.0 0.96 1.63 4.28
EXISTING RUNOFF SUMMARY TABLE
D:\Projects\574-007\Drainage\Hydrology\574-007_Rational Calcs_Existing.xlsx\Summary Table
CHARACTER OF SURFACE:
Runoff
Coefficient
Percentage
Impervious Project: Maple Mixed Use
Streets, Parking Lots, Roofs, Alleys, and Drives: Calculations By: A. Reese
Asphalt ……....……………...……….....…...……………….………………………………….0.95 . 100 Date:
Concrete …….......……………….….……….………………..….………………………………… 0.95 90
Gravel ……….…………………….….…………………………..……………………………….0.50 . 40
Roofs …….…….………………..……………….…………………………………………….0..95 90
Concrete 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
Concrete
Pavers
(ac)
Area of
Lawns and
Landscaping
(ac)
2-year
Composite
Runoff
Coefficient
10-year
Composite
Runoff
Coefficient
100-year
Composite
Runoff
Coefficient
Composite
% Imperv.
A 24,384 0.56 0.00 0.00 0.56 0.00 0.00 0.00 0.95 0.95 1.00 90.0
B 4,114 0.09 0.00 0.03 0.00 0.00 0.00 0.06 0.43 0.43 0.53 31.3
TOTAL ONSITE 28,498 0.65 0.00 0.00 0.56 0.00 0.00 0.00 0.81 0.81 1.00 77.0
DEVELOPED COMPOSITE % IMPERVIOUSNESS AND RUNOFF COEFFICIENT CALCULATIONS
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
Overland Flow, Time of Concentration:
Project: Maple Mixed Use
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: Maple Mixed Use
Calculations By:
Date:
From Section 3.2.1 of the CFCSDDC
Rainfall Intensity:
A A 0.56 5.0 5.0 5.0 0.95 0.95 1.00 2.85 4.87 9.95 1.52 2.59 5.57
B B 0.09 5.0 5.0 5.0 0.43 0.43 0.53 2.85 4.87 9.95 0.12 0.20 0.50
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)
A. Reese
November 18, 2015
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)
Q = C f ( C )( i )( A )
D:\Projects\574-007\Drainage\Hydrology\574-007_Rational-Calcs_Proposed.xlsx\Direct-Runoff
DESIGN
POINT
BASIN
ID
TOTAL
AREA
(acres)
C2 C10 C100
2-yr Tc
(min)
10-yr
Tc
(min)
100-yr
Tc
(min)
Q2
(cfs)
Q10
(cfs)
Q100
(cfs)
A A 0.56 0.95 0.95 1.00 5.0 5.0 5.0 1.52 2.59 5.57
B B 0.09 0.43 0.43 0.53 5.0 5.0 5.0 0.12 0.20 0.50
DEVELOPED RUNOFF SUMMARY TABLE
D:\Projects\574-007\Drainage\Hydrology\574-007_Rational-Calcs_Proposed.xlsx\Summary Table
APPENDIX B
HYDRAULIC COMPUTATIONS
B.1 – Storm Sewers
B.2 – Detention
Facilities
APPENDIX B.1
STORM SEWERS
APPENDIX B.2
DETENTION FACILITIES
Maple Mixed Use
Fort Collins, Colorado
A. Reese Date: November 18, 2015
Pond No.: A
A
100-yr
1.00 WQCV 0 ft
3
Area (A)= 0.59 acres Quantity Detention 4557 ft
3
Max Release Rate = 0.46 cfs Total Volume 4557 ft
3
Total Volume 0.105 ac-ft
Time Time
Ft.Collins
100-yr
Intensity
Q100
Inflow
(Runoff)
Volume
Outflow
(Release) Volume
Storage
Detention
Volume
(mins) (secs) (in/hr) (cfs) (ft
3
) (ft
3
) (ft
3
)
5 300 9.95 5.9 1761 138 1623
10 600 7.72 4.6 2733 276 2457
15 900 6.52 3.8 3462 414 3048
20 1200 5.60 3.3 3965 552 3413
25 1500 4.98 2.9 4407 690 3717
30 1800 4.52 2.7 4800 828 3972
35 2100 4.08 2.4 5055 966 4089
40 2400 3.74 2.2 5296 1104 4192
45 2700 3.46 2.0 5512 1242 4270
50 3000 3.23 1.9 5717 1380 4337
55 3300 3.03 1.8 5899 1518 4381
60 3600 2.86 1.7 6075 1656 4419
65 3900 2.72 1.6 6259 1794 4465
70 4200 2.59 1.5 6418 1932 4486
75 4500 2.48 1.5 6584 2070 4514
80 4800 2.38 1.4 6740 2208 4532
85 5100 2.29 1.4 6891 2346 4545
90 5400 2.21 1.3 7041 2484 4557
95 5700 2.13 1.3 7163 2622 4541
100 6000 2.06 1.2 7292 2760 4532
105 6300 2.00 1.2 7434 2898 4536
110 6600 1.94 1.1 7554 3036 4518
115 6900 1.89 1.1 7694 3174 4520
120 7200 1.84 1.1 7816 3312 4504
125 7500 1.79 1.1 7921 3450 4471
130 7800 1.75 1.0 8054 3588 4466
135 8100 1.71 1.0 8172 3726 4446
APPENDIX C
WATER QUALITY DESIGN COMPUTATIONS
APPENDIX D
EROSION CONTROL REPORT
Meldrum Mixed Use
EROSION CONTROL REPORT
A comprehensive Erosion and Sediment Control Plan (along with associated details) has
been 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 and/or wattles 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 Sheet C001 of the Utility Plans. The
Final Utility Plans will also contain a full-size Erosion Control Plan 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 any existing Development Agreement(s) of record, as well as the Development
Agreement, to be recorded prior to issuance of the Development Construction Permit. Also,
the Site Contractor for this project may 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, before commencing any earth
disturbing 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
STANDARD OPERATING PROCEDURES (SOPs) REFERENCES
MAP POCKET
DR1 – OVERALL DRAINAGE EXHIBIT
140 8400 1.67 1.0 8277 3864 4413
145 8700 1.63 1.0 8367 4002 4365
150 9000 1.60 0.9 8496 4140 4356
155 9300 1.57 0.9 8615 4278 4337
160 9600 1.54 0.9 8723 4416 4307
165 9900 1.51 0.9 8820 4554 4266
170 10200 1.48 0.9 8907 4692 4215
175 10500 1.45 0.9 8983 4830 4153
180 10800 1.42 0.8 9048 4968 4080
185 11100 1.40 0.8 9169 5106 4063
190 11400 1.38 0.8 9282 5244 4038
195 11700 1.36 0.8 9388 5382 4006
200 12000 1.34 0.8 9487 5520 3967
205 12300 1.32 0.8 9579 5658 3921
210 12600 1.30 0.8 9664 5796 3868
215 12900 1.28 0.8 9742 5934 3808
220 13200 1.26 0.7 9813 6072 3741
225 13500 1.24 0.7 9877 6210 3667
230 13800 1.22 0.7 9933 6348 3585
235 14100 1.21 0.7 10066 6486 3580
240 14400 1.20 0.7 10195 6624 3571
Input Variables Results
Design Point
Design Storm Required Detention Volume
Developed "C" =
Detention Pond Calculation | FAA Method
Project:
Project Location:
Calculations By:
D:\Projects\574-007\Drainage\Detention\574-007_Detention.xlsm\
(min)
10-yr
Tc
(min)
100-yr
Tc
(min)
A A No 0.95 0.95 1.00 25 1.0 1.4 1.4 0.9 83 2.1 2.90 0.5 83 2.1 2.18 0.6 5.0 5.0 5.0
B B No 0.95 0.95 1.00 15 1.7 0.9 0.9 0.6 0 0.0 0.00 0.0 0 0.0 0.00 0.0 5.0 5.0 5.0
DEVELOPED TIME OF CONCENTRATION COMPUTATIONS
Design
Point
Basin
Overland Flow
A. Reese
November 18, 2015
GutterConcentration Flow Swale Flow Time of
(Equation RO-4)
( )
3
1
1 . 87 1 . 1 *
S
Ti C Cf L
-
=
D:\Projects\574-007\Drainage\Hydrology\574-007_Rational-Calcs_Proposed.xlsx\Tc-2-yr_&_100-yr
November 18, 2015
D:\Projects\574-007\Drainage\Hydrology\574-007_Rational-Calcs_Proposed.xlsx\C-Values
Tt
(min)
2-yr
Tc
(min)
10-yr
Tc
(min)
100-yr
Tc
(min)
EX1 EX1 No 0.25 0.25 0.31 25 2.9 5.6 5.6 5.2 0 0.0 0.00 0.0 117 0.2 0.69 2.8 8.4 8.4 8.0
EXISTING TIME OF CONCENTRATION COMPUTATIONS
Design
Point
Basin
Overland Flow
A. Reese
November 18, 2015
GutterConcentration Flow Swale Flow Time of
(Equation RO-4)
( )
3
1
1 . 87 1 . 1 *
S
Ti C Cf L
-
=
D:\Projects\574-007\Drainage\Hydrology\574-007_Rational Calcs_Existing.xlsx\Tc-2-yr_&_100-yr
D:\Projects\574-007\Drainage\Hydrology\574-007_Rational Calcs_Existing.xlsx\C-Values