HomeMy WebLinkAboutTHE DISTRICT @ CAMPUS WEST - PDP - PDP120003 - SUBMITTAL DOCUMENTS - ROUND 1 - DRAINAGE REPORTPreliminary Drainage and Erosion Control Report
for
THE DISTRICT AT CAMPUS WEST
Fort Collins, Colorado
January 25, 2012
Prepared for:
Ft. Collins Student Housing, LLC
1302 Waugh Drive, PMB 305
Houston, TX 77019
Prepared by:
200 South College Avenue, Suite 100
Fort Collins, Colorado 80524
Phone: 970.221.4158 Fax: 970.221.4159
www.northernengineering.com
Project Number: 670-001
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.
ADDRESS:
200 S. College Ave. Suite 10
Fort Collins, CO 80524
PHONE: 970.221.4158
FAX: 970.221.4159
WEBSITE:
www.northernengineering.com
January 25, 2012
City of Fort Collins
Stormwater Utility
700 Wood Street
Fort Collins, Colorado 80521
RE: Preliminary Drainage and Erosion Control Report for
The District at Campus West
Dear Staff:
Northern Engineering is pleased to submit this Preliminary Drainage and Erosion Control
Report for your review. This report accompanies the 01.18.12 Project Development Plan
submittal for the proposed District at Campus West multi-family (student housing)
development. Comments from the Preliminary Design Review Letter dated 09.06.11 have
been addressed. Written responses thereto can be found in the comprehensive response to
comments letter on file with Current Planning.
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
District at Campus West student housing 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 T. Cvar, PE
Senior Engineer
Nicholas W. Haws, PE Kevin R. Brazleton, PE
Project Manager Project Engineer
The District at Campus West
Preliminary Drainage and Erosion Control Report
TABLE OF CONTENTS
I. GENERAL LOCATION AND DESCRIPTION ......................................................... 1
II. DRAINAGE BASINS AND SUB-BASINS ............................................................. 5
III. DRAINAGE DESIGN CRITERIA ......................................................................... 6
IV. DRAINAGE FACILITY DESIGN ........................................................................ 11
V. CONCLUSIONS ............................................................................................ 17
References ............................................................................................................. 19
APPENDICES:
APPENDIX A – Hydrologic Computations
APPENDIX B – Hydraulic Computations
B.1 – Storm Sewers (reserved for future use)
B.2 – Street Flow (reserved for future use)
B.3 – Inlets (reserved for future use)
B.4 – Detention Facilities
APPENDIX C – Water Quality Design Computations
APPENDIX D – HEC-RAS Input and Output Files
D.1 – Hard Copy
D.2 – Digital Copy (CD)
APPENDIX E – Operations and Maintenance Guidelines for Bioretention Planters
(reserved for future use)
APPENDIX F – Erosion Control Report
LIST OF TABLES AND FIGURES:
MAP POCKET:
C600-C601 – Drainage Exhibit
NOTE: TABLE OF CONTENTS WILL BE UPDATED/CORRECTED WITH SUBSEQUENT
REPORT ISSUANCES.
The District at Campus West
Preliminary Drainage and Erosion Control Report 1
I. GENERAL LOCATION AND DESCRIPTION
A. Location
1. Vicinity Map
2. The District at Campus West project site is located in the northeast quarter of Section
15, 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 north side of West Plum Street, and is bordered by
City Park Avenue on the west and Aster Street on the east. Bluebell Street runs
continuously north-south through the eastern third of the site, and will remain a
through public street. However, two existing dead-end streets (Columbine Street and
Daisy Street) will be vacated as part of this development. City Park, Daisy,
Columbine, Bluebell, and Aster all have 50’ right-of-ways. The existing right-of-way
(ROW) along Plum Street varies from 40’ to 66’. The District at Campus West project
proposes to dedicate additional right-of-way along Plum Street to create a consistent
north half-ROW width of 31.5’.
The District at Campus West
Preliminary Drainage and Erosion Control Report 2
4. There are no major drainageways or easements within or adjacent to the site. There is
a public storm sewer in Plum Street along the eastern third of the site with inlets at
Bluebell and Aster Streets. An off-site private storm sewer runs west to east in a drive
aisle north of the site, and discharges into the western curb and gutter of Bluebell
Street.
5. Sunstone Condos is located north of the project site between City Park Avenue and
Bluebell Street, and the Zeta Tau Alpha sorority house is located north of the project
site between Bluebell and Aster Streets. The remainder of the property is bound
entirely by public streets. For context, the Cambridge House apartments are located
on the south side of Plum Street near the eastern third of the project site.
B. Description of Property
1. The District at Campus West property is approximately 3.34 net acres.
Figure 1 – Aerial Photograph
2. The subject property currently consists of sixteen (16) single-family residential homes,
all of which are rental properties primarily leased to students attending nearby
Colorado State University. The age and condition of the residences varies; however,
none of them are eligible for historic designation, and many of them are in severe
disrepair. The ground cover varies from rooftops, concrete, asphalt, lawn, and bare
dirt. Numerous trees and shrubs are currently present (see Tree Mitigation Plan by
Ripley Design for additional information). Being already developed lots, the slopes are
rather gentle throughout (i.e., 2±%). General topography slopes from north to the
south towards Plum Street. Plum Street slopes west to east.
The District at Campus West
Preliminary Drainage and Erosion Control Report 3
According to the United States Department of Agriculture (USDA) Natural Resources
Conservation Service (NRCS) Soil Survey, the site consists of Nunn clay loam, which
falls into Hydrologic Soil Group C. More site-specific exploration found varying
materials including sandy lean clay and silty to clayey sand with varying amounts of
gravel. See the Geotechnical Engineering Report by Terracon (Terracon Project No.
20115026) for additional information.
3. There are no major drainageways within the vicinity of The District at Campus West
project.
Figure 2 – Existing Drainage Systems
The District at Campus West
Preliminary Drainage and Erosion Control Report 4
4. The proposed District at Campus West redevelopment project will completely raze all
of the existing structures currently occupying the property. As previously mentioned,
both Daisy and Columbine Streets are proposed to be vacated and redeveloped as part
of this project as well. The District at Campus West will contain approximately 192
multi-family dwelling units in three main buildings. Also included will be a parking
structure, secured bike storage, maintenance facilities, plazas, a clubhouse, and an
exquisite outdoor pool and courtyard area.
Figure 3 – Proposed Site Plan
5. There are no irrigation ditches or related facilities in the project’s vicinity.
6. The proposed land use is residential, multi-family dwellings. This is a permitted use
in the Community Commercial (C-C) Zone District, subject to a Type 1 administrative
review.
The District at Campus West
Preliminary Drainage and Erosion Control Report 5
C. Floodplain
1. The subject property is not located in either a FEMA regulatory or City of Fort Collins
designated floodplain. See Section III.E.4, below for a description of hydraulic
modeling conducted for the 100-year water surface elevations along Plum Street.
Figure 4 – Existing Floodplains
II. DRAINAGE BASINS AND SUB-BASINS
A. Major Basin Description
1. The District at Campus West project is located within the City of Fort Collins’ Old
Town Drainage Basin.
2. The majority of the Old Town Basin, including the portion where the subject property
is located, is already developed. There are certain provisions in the Old Town Basin
that properties can add up to 5,000 square feet of new impervious area without
providing on-site detention. This is because of the assumptions made in the drainage
master plan for percent imperviousness. However, this interpretation does not apply
to the District at Campus West property since the proposal calls for complete removal
of all existing structures and surface features. Additionally, the existing public
drainage deficiencies in this area warrant special consideration. Whereas both the
existing and proposed land uses themselves are consistent with the major drainage
basin’s assumed characteristics, additional site-specific analysis is necessary.
The District at Campus West
Preliminary Drainage and Erosion Control Report 6
3. As previously mentioned in Section I.B.5, there are no irrigation ditches or related
facilities in the immediate project vicinity. The Canal Importation Basin Drainage
Master Plan does identify spills from the Larimer Canal No. 2 and New Mercer Ditch
near Ram’s Village that flow east down Plum Street. However, these flows are being
addressed by regional City of Fort Collins stormwater improvement projects.
B. Sub-Basin Description
1. The subject property historically drains overland towards two inlets located on the
north side of Plum Street; one on the east side of Bluebell Street and the other on the
east side of Aster Street. The majority of the site sheet flows directly into the adjacent
curb and gutter of the public City streets. A very small portion of the site immediately
adjacent to the northern property line appears to sheet flow into the private storm
drain in the parking lot of Sunstone Condos; however, this storm drain discharges
back into the public right-of-way, where flows continue south to Plum Street. The
District at Campus West development aims to preserve the existing drainage patterns
as much as possible, and will have the same outfall locations. A more detailed
description of the project’s drainage patterns follows in Section IV.A.4., below.
2. The project site does not receive any notable runoff from off-site properties. With the
exception of the small area along the northern property line, the subject property does
not drain across any off-site private land either.
III. DRAINAGE DESIGN CRITERIA
A. There are no optional provisions outside of the FCSCM proposed with The District at
Campus West project. Explicit approval is requested for underground detention at the
parking structure, in accordance with Volume 2, Section 4.16 of the Manual. See Section
III.G.1., below, for deviations.
B. The overall stormwater management strategy employed with The District at Campus West
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. 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. The
second site planning component falling into this category is the preservation of the large
green ash tree at the northwest corner of Plum and Bluebell. Not only does this
encourage infiltration and evapotranspiration, but it also adds shade and a great site
amenity. Another consideration also comes by way of the site plan layout and an early,
integrated, and deliberate design goal of the project team. That is, distributed stormwater
planter boxes have been designed to emphasize multiple controls throughout the
development as opposed to a centralized treatment facility. These vegetated planters have
been closely coordinated between the Architect, Owner, Landscape Architect, and Civil
Engineer.
The District at Campus West
Preliminary Drainage and Erosion Control Report 7
The District at Campus West aims to reduce runoff peaks, volumes, and pollutant loads by
implementing Low Impact Development (LID) strategies. Wherever possible, runoff will be
routed through the aforementioned bioretention planter boxes. This LID practice reduces
the overall amount of impervious area, while minimizing directly connected impervious
areas (MDCIA) at the same time. All downspouts will be routed through the bioretention
planters; and since rooftops comprise a majority of the project’s impervious area, this
achieves an extremely high degree of MDCIA. The combined LID/MDCIA techniques will
be implemented throughout the development, thereby slowing runoff, increasing
infiltration, and otherwise helping to mimic the pre-development hydrologic regime.
Figure 5 – Stormwater Planter Box Concept Photographs
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 runoff; however, urban
development of this intensity will still have stormwater runoff leaving the site. However,
The District at Campus West project will capture and treat all rooftop runoff before
releasing it at a slow rate to downstream facilities. The primary WQCV will occur in the
distributed bioretention planter boxes. However, the stormwater vault within the parking
structure will also be fitted with a WQCV. Details of the on-site water quality facilities are
further described in Section IV.B, below.
Step 3 – Stabilize Drainageways. As stated in Section I.B.3, above, there are no major
drainageways in or near the subject property. While this step may not seem applicable to
The District at Campus West development, the proposed project indirectly helps achieve
stabilized drainageways nonetheless. Once again, site selection has a positive effect on
stream stabilization. By repurposing an already developed, under-utilized site with
existing stormwater infrastructure, combined with LID, MDCIA, and WQCV strategies, the
likelihood of bed and bank erosion is greatly reduced. 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.
The District at Campus West
Preliminary Drainage and Erosion Control Report 8
Step 4 – Implement Site Specific and Other Source Control BMPs. This step typically
applies to industrial and commercial developments; however, the District at Campus West
project does contain two components warranting site specific consideration for source
control. Those two components are the outdoor pool and parking structure. Chemicals
for the pool will be stored and handled in a manner so as to minimize the potential for
pollutants to enter the stormwater system. See the Hazardous Materials Impact Analysis
submitted with this project for additional information on the pool chemicals. The parking
structure will be equipped with a sand-oil separator to trap and collect pollutants
associated with the vehicles and maintenance functions contained therein. The lease
agreement will explicitly prohibit residents from performing fluid changes or similar vehicle
maintenance within the parking garage. Additionally, the overall operations and
maintenance procedures to be implemented by the District at Campus West’s professional
staff will be done with a conscious awareness of source control BMPs, including storage,
handling, spill containment, and control.
C. Development Criteria Reference and Constraints
1. The subject property is not part of any Overall Development Plan drainage study or
similar “development/project” drainage master plan. A Project Development Plan
(PDP) known as The Retreat at 1200 Plum was approved for a portion of the property
in April of 2009. While The District at Campus West PDP is neither subject to, nor
can fully rely upon, the drainage report as approved in 2009, there are certain items
that are desired to be carried forward. The deficiencies of the public storm sewer
system in Plum Street and the desire to not exacerbate the existing condition –
particularly the flooding at Aster Street – remain the same. There was a substantial
amount of vetting done working through the distributed stormwater planter box
concepts. Handling stormwater detention for the parking garage in a structural vault
is another strategy from the approved Retreat at 1200 Plum PDP that will replicated
with the District at Campus West development.
Figure 6 – Site Plan Approved with The Retreat at 1200 Plum PDP in 2009
The District at Campus West
Preliminary Drainage and Erosion Control Report 9
2. There are no known drainage studies for any adjacent properties that will have any
effect on The District at Campus West project.
3. The site plan will be constrained on three sides by public streets and by a private drive
on the fourth. As previously mentioned, the drainage outfall for the entire
development is the storm sewer in Plum Street. This storm sewer is very shallow
(2.5’±) and has extremely limited capacity. This serves as the most significant
drainage constraint for the project.
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 District at Campus West 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. 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.
5. Due to the deficiency of the existing storm sewer system in Plum Street, a hybrid
approach has been utilized to compute the maximum allowable release rate
associated with the FAA detention sizing calculations. The 100-year peak runoff rate
was calculated for the pre-development impervious areas. This essentially
“grandfathers” the existing impervious areas by allowing the respective 100-year peak
discharge to be added to the maximum allowable release rate. The release rate for the
remaining undeveloped land (existing pervious surfaces) was established by
calculating the 2-year peak runoff rate for these areas. The total of these two
discharges establishes the overall maximum allowable release rate utilized in the FAA
procedure detention storage computations. This hybrid approach ensures that all
increased impervious areas (not just those greater than 5,000 sq-ft) are over-detained
down to the 2-year undeveloped (historic) rate in the 100-year developed condition.
The District at Campus West
Preliminary Drainage and Erosion Control Report 10
E. Hydraulic Criteria
1. The option to reconstruct, and potentially increase the capacity of, the existing public
storm sewer in Plum Street was briefly analyzed. However, due to hydraulic
limitations downstream towards Elizabeth Street, there was no noticeable increase in
capacity (i.e., higher allowable discharge rate) realized by the District at Campus West
site. The only potential benefit would be a lower outfall elevation. Unfortunately, in
order to achieve the deeper gravity invert, the storm sewer would have to be
reconstructed all the way across Shield Street to the eastern parkway along the Moby
parking lot. The cost-benefit analysis does not justify said reconstruction of the public
storm sewer in Plum Street.
2. All drainage facilities proposed with the District at Campus West 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.
3. As stated in Section I.C.1, above, the subject property is located in neither a
FEMA regulatory nor a City of Fort Collins designated floodplain.
4. Even though this portion of West Plum Street is not an officially mapped
floodplain, it is identified in certain Fort Collins drainage master plan
documents as an area prone to stormwater problems. Therefore, as part of the
District at Campus West drainage study, a hydraulic analysis was conducted
along Plum Street using HEC-RAS.
The purpose of said analysis is twofold. First, it was desired to confirm that
the proposed District at Campus West development does not push 100-year
stormwater onto properties beyond that which current exists. Second, the
proposed finished floor elevations of the District at Campus West buildings are
set one foot above the modeled post-development 100-year water surface
elevations. While the pre-development versus post-development HEC-RAS
analysis shows a slight rise in some areas, it also shows a slight lowering in
others. A detailed topographic field survey was conducted along both sides of
Plum Street to ensure that; A) the extents of the 100-year water surfaces do
not extend onto properties beyond that which exists in the pre-development
condition, and B) the 100-year water surface elevations do not exceed any
minimum opening elevations for any structures located on properties within
the study area.
Table 1 – Plum Street 100-year WSEL’s and Proposed FFE’s
Structure
Controlling
HEC-RASa
Cross-Section No.
100-year
Water Surface
Elevation (ft)
Proposed
Finished Floorb
Elevation (ft)
Building 1 114 5035.80 5036.80
Building 2 108/107
c 5032.34 5033.34
Building 3 105/104
c 5030.34 5031.34
a. See Appendix D for complete HEC-RAS model.
c. A linear interpolation was applied to obtain the estimated 100-yr WSEL between these two cross-sections.
b. Listed elevations represent the lowest finished floor for each respective structure.
Additional information from the Plum Street HEC-RAS hydraulic analysis can be
found in Appendix D.
The District at Campus West
Preliminary Drainage and Erosion Control Report 11
F. Floodplain Regulations Compliance
1. As previously mentioned, this project is not subject to any floodplain
regulations. However, extra care has been taken (per Section III.D.5) to
ensure that neither existing nor proposed structures will suffer damage during
the 100-year storm as a result of the District at Campus West development.
G. Modifications of Criteria
1. A modification to Volume 2, Section 3.1.3 of the FCSCM is hereby requested
to allow the full storage capacity of the bioretention rain garden planters to be
utilized in an inclusive manner to satisfy the 100-year detention volume
requirements.
2. The modification requested above was already granted with the previously
approved Retreat at 1200 Plum PDP, and is critical to the viability of this
property to redevelop. While the FCSCM requires the 100-year detention
volume to be provided in addition to (i.e., on top of) the water quality capture
volume, UDFCD criteria provides the ability for the storage volumes to be
inclusive of one another. Additionally, there is a certain amount of storage
volume provided for in the bioretention sand media, drainage bedding, and
underdrain piping, all of which is ignored in the water quality and quantity
computations. On an already constrained site, the duplicative requirements of
Volume 2, Section 3.1.3 would be prohibitive to a project already going the
extra mile to help enhance and restore this area. There is not expected to be
any detriment to public health or safety, nor additional maintenance or cost
burdens born by the City, as a result of the requested modification.
IV. DRAINAGE FACILITY DESIGN
A. General Concept
1. The main objective of The District at Campus West’s drainage design is to maintain
existing drainage patterns, while not adversely impacting any adjacent properties or
exacerbating the existing drainage problems at Plum Street and Aster Street.
2. The only “off-site” runoff consideration is the aforementioned 100-year hydraulic
analysis conducted along Plum Street. No other off-site runoff flows directly through
the project site. Likewise, apart from the small landscaped area along the northern
property line that historically sheet flows towards the private inlets and storm sewer in
the Sunstone Condos drive aisle, no developed runoff from the District at Campus
West site flows across off-site private property.
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 project site has been divided into three (3) major drainage basins, designated as
Basins 1, 2, and 3. The drainage patterns anticipated for each basin are further
described below.
The District at Campus West
Preliminary Drainage and Erosion Control Report 12
Basin 1
Basin 1 consists of the block bound by City Park Avenue on the west, Plum Street on
the south, the Private Drive on the east, and Sunstone Condos on the north. This
basin is compromised almost entirely of proposed Building 1. The vast majority of
this basin is rooftop area, all of which will be routed via roof drains and downspouts
into fourteen (14) main stormwater planter boxes. Each planter box is designed as a
bioretention rain garden with underdrain pipes connecting into the new storm sewer
flowing east along the north side of Plum Street.
Basin 2
Basin 2 consists of the block bound by the Private Drive on the west, Plum Street on
the south, Bluebell Street on the east, and Sunstone Condos on the north. This basin
is compromised almost entirely of the proposed parking structure (Building 2). The
parking structure is lined on the south and east sides with “row home”-like apartment
units. While the vast majority of this basin is rooftop area, it drains to two separate
catchments. The bulk of the rooftop is the top parking deck itself. This area will be
collected in a series of drainage inlets, and will be conveyed via internal piping to a
stormwater vault located underneath the ramp from the first to second levels of the
structure. This vault discharges into a storm sewer located in the Private Drive to the
west, which conveys flow south into the new storm sewer paralleling Plum Street.
The multi-family residential dwelling units lining the parking structure all have pitched
roofs, which do not drain into the garage’s stormwater vault. Runoff from these roofs
will be routed via gutters and downspouts into five (5) main stormwater planter boxes.
Each planter box is designed as a bioretention rain garden with underdrain pipes
connecting into the new storm sewer paralleling Plum Street. The western-most
portion of Basin 2 consists of one-half of the Private Drive. The Private Drive
(including its other half located in Basin 1) sheet flows south into a trench drain
behind the public sidewalk, and drains into the new storm sewer flowing east along
the north side of Plum Street.
Basin 3
Basin 3 consists of the block bound by Bluebell Street on the west, Plum Street on the
south, Aster Street on the east, and the Zeta Tau Alpha sorority on the north. This
basin is compromised almost entirely of proposed Building 3. The vast majority of
this basin is rooftop area, all of which will be routed via roof drains and downspouts
into six (6) main stormwater planter boxes. Each planter box is designed as a
bioretention rain garden with underdrain pipes connecting into the Plum Street storm
sewer main. It should be noted that the storm sewer main in Plum Street is proposed
to be reconstructed from Aster Street to Bluebell Street, including the existing inlet at
Bluebell. Furthermore, Aster Street itself is proposed to be milled and overlaid to
remove the crown and create a west to east sheet flow pattern. This is to help
alleviate some of the existing drainage problems this street experiences.
A full-size copy of the Drainage Exhibit can be found in the Map Pocket at the end of
this report.
The District at Campus West
Preliminary Drainage and Erosion Control Report 13
B. Specific Details
1. The main drainage problem associated with this project site is the existing
deficiency of the public storm drainage system, which culminate at the
intersection of Plum and Aster Streets. The drainage strategies employed with
The District at Campus West development aim to match existing drainage
patterns and peak flow rates so as not to have an adverse impact at this
location. This will be achieved by providing on-site detention and water
quality in distributed stormwater planter boxes and a stormwater vault within
the parking structure.
Figure 7 – Flooding at 728 Aster Street
2. An FAA method computation has been performed for the three major drainage
basins to determine the detention storage volume required for each. For the
basins being treated by bioretention stormwater planters, the total detention
storage volume has been evenly distributed among the planter boxes servicing
that particular basin. It will be important to confirm at final design that the
roof areas draining to each bioretention box are proportionate to the planter
areas they discharge into. The architect and plumbing engineer will need to
ensure that all roof drainage is routed through the stormwater planters.
Horizontal check dams or weirs will also be considered during final design of
the larger planter boxes to ensure that the full storage depth is realized for any
sloped or stepped planters.
The District at Campus West
Preliminary Drainage and Erosion Control Report 14
Water quality computations have also been performed for each of the three
major drainage basins utilizing the UDFCD’s UD-BMP Version 3.01 “Rain
Garden (RG)” Design Procedure Form. As with the detention storage volume,
the required water quality capture volume (WQCV) for the overall basin is
distributed proportionally among the planter boxes serving the tributary area.
A maximum allowable depth of 1-ft is designed for the WQCV’s.
The 100-year detention storage volume is designed at a maximum depth of 2-
ft (inclusive of the 1-ft WQCV). The 2-ft deep 100-year water surface
elevations in each planter box will never be allowed to be closer than 1-ft from
the nearest window sill. In addition to the minimum 1-ft of freeboard provided
at each window sill, emergency overflow weirs will be notched into the planter
walls ensuring that water spills away from the building toward the adjacent
streets and does not enter the structure.
Figure 8 – Stormwater Planter Box Detail
The stormwater planter boxes do not have any physical outlet control beyond
the bioretention sand media and underdrain piping itself. The infiltration
capacity of the 18” growing media itself serves to restrict the peak discharge
to pre-development rates, more consistent with 2-year historic flows.
The District at Campus West
Preliminary Drainage and Erosion Control Report 15
The stormwater vault located within the parking structure will have a more
conventional outlet control utilizing orifices and/or weirs to restrict peak
discharge and provide a water quality capture volume. The parking garage will
have specific components to treat sand and oil from vehicles contained
therein. Said sand/oil separator will either be integrated into the main
stormwater storage vault, or inline as an independent facility. The final
drainage report for The District at Campus West will specify the required
detention storage volume, maximum allowable peak discharge rate, and
minimum water quality treatment requirements for the parking structure’s
stormwater vault. However, since this facility is located within the parking
garage, the final design details and construction documentation will be by
others (architect, structural engineer, plumbing engineer, etc.) as part of the
building permit plans for the parking structure. Preliminarily, Northern
Engineering computes a required storage volume of approximately 4,100 cu-ft.
There appears to be an available 100-ft long x 62-ft wide footprint underneath
the first floor ramp. This translates into a preliminary 100-year storage depth
of only 8-in. The discharge from this vault also passes through a manhole
equipped with a Snout water quality device located in the Private Drive as an
extra measure to provide superior water quality treatment for Building 2.
Although the final design details, construction documentation, and Standard
Operating Procedures (SOP) Manual may be supplied by others after PDP
approval, said information 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.).
The present assumption is that the stormwater vault located under the first
floor ramp of the parking garage falls into the “underground detention”
category. Therefore, this report shall also serve as official written request for
said facility, pursuant to Volume 2, Section 4.16 of the FCSCM. A surface-
based detention system or alternative BMP would be infeasible in this
instance. Stormwater storage tanks are not uncommon in urban parking
structures. This concept was previously approved with The Retreat at 1200
Plum after all other options had been thoroughly explored with City Staff.
This project also proposes a second Snout water quality device in the new
stormwater manhole to be constructed near Aster Street. This goes above and
beyond the development’s requirements by treating existing runoff from the
surrounding (off-site) public streets. It also will serve to provide one final BMP
for the District at Campus West’s runoff prior to heading east towards the
public storm sewer in Shields Street.
The District at Campus West
Preliminary Drainage and Erosion Control Report 16
3. Table 2, below, summarizes the detention storage and water quality
information for each main drainage facility.
Table 2 – Detention Storage and Water Quality Summary
Required Provided Required Provided
Building 1a 1 6,999 7,400 2.0 3.8 1,450 3,700 1.0
Building 2b 2 4,104 4,150 0.7 3.3 - - -
Building 3a 3 2,406 5,227 2.0 3.2 730 2,614 1.0
b. See Section IV.B.1.2. for a narrative further explaining the stormwater vault under the first floor ramp of the parking garage.
a. Total detention storage and water quality capture volumes listed will be equally distributed among the stormwater planter boxes.
"Elevations" listed are average "depths" relative to the top soil elevation of the planter. Actual elevations will vary.
WQCV
Water Surface
Elevation (ft)
100-year Detention
Storage Volume (cu-ft)
Water Quality
Structure Capture Volume (cu-ft)
Basin
ID
100-year Storage
Water Surface
Elevation (ft)
100-year
Peak Discharge
Rate (cfs)
4. Proper maintenance of the drainage facilities designed with The District at Campus
West is a critical component of their ongoing performance and effectiveness. The
stormwater planter boxes can be easily accessed by maintenance staff, and do not
require heavy equipment for routine upkeep, or even major overhauling. Operations
and maintenance of the planter boxes shall follow the recommendations for
bioretention (rain garden) facilities, as outlined in the UDFCD manual. Appendix E
contains applicable excerpts to serve as guidance for the professional maintenance
and subcontractors responsible for maintenance of these facilities at The District at
Campus West.
The drainage design for this Development provides for the evacuation of storm
drainage runoff in a reasonable amount of time out of the stormwater planters and into
the drainage outfall system. The bioretention facilities have been designed to
discharge stormwater runoff from frequent storms over a 12-hour period through the
underlying subdrain system. Under the intended operation of these drainage facilities,
there will not be standing water more than 48 hours after the end of a rainfall event. If
standing water conditions persist in these facilities; and if such conditions are beyond
what can be expected in accordance with the approved stormwater design, the Owner
shall promptly remedy the situation. The proposed corrective measures shall be
reviewed and approved by the City prior to implementation.
Maintenance of the stormwater vault (and any associated facilities) within the parking
structure is equally important. Access shall be provided by at least one man-door into
the stormwater collection area underneath the first floor ramp. The ability for
specialized service vehicles (vacuum-trucks, etc.), as well as their respective hoses
and appurtenances, needs to be ensured so that the stormwater vault can be properly
cleaned and maintained. As previously mentioned, the final design details will be
documented with the Architect’s building permit plans for the parking garage. The
stormwater component of the garage will be explicitly addressed in the project’s
Operations and Maintenance Manual provided to the Owner by the Architect.
The District at Campus West
Preliminary Drainage and Erosion Control Report 17
5. The drainage features associated with The District at Campus West project are all
private facilities, located on private property. The planter boxes and stormwater vault
only serve the respective buildings to which they are attached or located within.
Therefore, no drainage easements or separate tracts will be dedicated for these
facilities. However, the new storm sewer flowing west to east on the north side of
Plum Street does serve multiple buildings. Even though these buildings will be
located on the same lot, a private drainage easement will still be dedicated to ensure
that the stormwater conveyance outfall line is protected. Landscape features, site
amenities, and even structural elements associated with seat walls and planter boxes
are allowed within said private drainage easement.
6. As previously mentioned, the outfall for the entire District at Campus West project is
the public storm sewer in Plum Street. This storm sewer flows east across Shields
Street before heading south towards Elizabeth Street. Stormwater conveyed by this
City drainage system ultimately reaches Spring Creek. There are no additional
facilities or upgrades needed off-site in order to accommodate the developed runoff
from The District at Campus West.
V. CONCLUSIONS
A. Compliance with Standards
1. The modification request detailed in Section III.G provides the necessary information
for compliance with the Fort Collins Stormwater Criteria Manual. All other design
elements comply without variation.
2. The drainage design proposed with The District at Campus West project complies with
the City of Fort Collins’ Master Drainage Plan for the Old Town Basin.
3. There are no regulatory floodplains associated with The District at Campus West
development.
4. The drainage plan and stormwater management measures proposed with The District
at Campus West apartment community 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 any potential
damage associated with its stormwater runoff. Rather than utilizing the 5,000 sq-ft
allowance of increased impervious area allowed in the Old Town Basin, The District at
Campus West will over-detain all increased impervious areas to release at the 2-year
historic rate during the 100-year storm. Additionally, a HEC-RAS analysis has been
performed along Plum Street to ensure that all new structures are elevated above
expected 100-year water surface elevations, and that all existing structures adjacent to
the study area remain dry in the major storm event.
The District at Campus West
Preliminary Drainage and Erosion Control Report 18
Figure 9 – Rendering of Proposed District at Campus West Development
The proposed on-site stormwater facilities will offer substantial water quality
treatment, in addition to peak volume attenuation. The stormwater planter boxes will
serve multiple purposes, contributing to the urban design elements, allowing
pedestrian seat walls, and otherwise enhancing the overall function and aesthetic of
this first-class redevelopment project. The District at Campus West will be a LEED
certified project. While an initial has not yet been performed, it is anticipated that the
bioretention planter boxes will contribute towards the project’s LEED credits.
2. The proposed District at Campus West development will not have any impact on the
Master Drainage Plan recommendations for the Old Town Basin.
The District at Campus West
Preliminary Drainage and Erosion Control Report 19
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. Final Drainage and Erosion Control Report for The Retreat at 1200 Plum, April 22, 2009,
Northern Engineering (Project No. 410-002).
3. 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.
4. Geotechnical Engineering Report, The District at CSU, East of West Plum Street and City
Park Avenue, Fort Collins, Colorado, November 2, 2011, Terracon Consultants,
Inc.(Terracon Project No. 20115026).
5. Larimer County Urban Area Street Standards, Adopted January 2, 2001, Repealed and
Reenacted, Effective October 1, 2002, Repealed and Reenacted, Effective April 1, 2007
6. Soils Resource Report for Larimer County Area, Colorado, Natural Resources Conservation
Service, United States Department of Agriculture.
7. 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
The District at Campus West
Preliminary Drainage and Erosion Control Report
CHARACTER OF SURFACE:
Runoff
Coefficient
Percentage
Impervious Project: District at Campus West
Streets, Parking Lots, Roofs, Alleys, and Drives: Calculations By: K. Brazelton
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 73927 1.697 0.000 0.501 0.890 0.000 0.307 0.82 0.82 1.00 74%
2 52223 1.199 0.000 0.169 0.853 0.000 0.176 0.85 0.85 1.00 77%
3 39787 0.913 0.000 0.246 0.463 0.000 0.203 0.79 0.79 0.99 70%
TOTAL 165937 3.809 0.000 0.917 2.206 0.000 0.687 0.82 0.82 1.00 74%
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
January 25, 2011
The District at Campus West
Preliminary Drainage and Erosion Control Report
Overland Flow, Time of Concentration:
Project: District at Campus West
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)
The District at Campus West
Preliminary Drainage and Erosion Control Report
Rational Method Equation: Project: District at Campus West
Calculations By:
Date:
From Section 3.2.1 of the CFCSDDC
Rainfall Intensity:
1 1 1.70 8 8 8 0.82 0.82 1.00 2.46 4.21 8.59 3.4 5.9 14.6
2 2 1.20 9 9 8 0.85 0.85 1.00 2.35 4.02 8.38 2.4 4.1 10.0
3 3 0.91 5 5 5 0.79 0.79 0.99 2.85 4.87 9.95 2.1 3.5 9.0
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)
K. Brazelton
January 25, 2011
Q C f C i A
D:\Projects\670-001\Drainage\Hydrology\PDP\670-001_Proposed-Rational-Calcs\Direct-Runoff
The District at Campus West
Preliminary Drainage and Erosion Control Report
DESIGN
POINT
BASIN
ID
TOTAL
AREA
(acres)
C10 C100
10-yr
Tc
(min)
100-yr
Tc
(min)
Q10
(cfs)
Q100
(cfs)
1 1 1.70 0.82 1.00 7.9 7.6 5.9 14.6
2 2 1.20 0.85 1.00 8.6 8.2 4.1 10.0
3 3 0.91 0.79 0.99 5.4 5.0 3.5 9.0
DRAINAGE SUMMARY TABLE
D:\Projects\670-001\Drainage\Hydrology\PDP\670-001_Proposed-Rational-Calcs\SUMMARY-TABLE
APPENDIX B
HYDRAULIC COMPUTATIONS
B.1 – Storm Sewers (reserved for future use)
B.2 – Street Flow (reserved for future use)
B.3 – Inlets (reserved for future use)
B.4 – Detention Facilities
APPENDIX B.1
STORM SEWERS (reserved for future use)
APPENDIX B.2
STREET FLOW (reserved for future use)
APPENDIX B.3
INLETS (reserved for future use)
APPENDIX B.4
DETENTION FACILITIES
The District at Campus West
Preliminary Drainage and Erosion Control Report
CHARACTER OF SURFACE:
Runoff
Coefficient
Percentage
Impervious Project: District at Campus West
Streets, Parking Lots, Roofs, Alleys, and Drives: Calculations By: K. Brazelton
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.
Basin 1 - Impervious Area 27385 0.629 0.000 0.237 0.242 0.150 0.000 0.84 0.84 1.00 78%
Basin 1 - Pervious Area 46542 1.068 0.000 0.000 0.000 0.000 1.068 0.25 0.25 0.31 0%
Basin 1 - Total Area 73927 1.697 0.000 0.237 0.242 0.150 1.068 0.47 0.47 0.59 29%
Basin 2 - Impervious Area 22734 0.522 0.165 0.158 0.173 0.026 0.000 0.93 0.93 1.00 91%
Basin 2 - Pervious Area 29489 0.677 0.000 0.000 0.000 0.000 0.677 0.25 0.25 0.31 0%
Basin 2 - Total Area 52223 1.199 0.165 0.158 0.173 0.026 0.677 0.55 0.55 0.68 39%
Basin 3 - Impervious Area 15850 0.364 0.056 0.137 0.171 0.000 0.000 0.95 0.95 1.00 92%
Basin 3 - Pervious Area 23937 0.550 0.000 0.000 0.000 0.000 0.550 0.25 0.25 0.31 0%
The District at Campus West
Preliminary Drainage and Erosion Control Report
Overland Flow, Time of Concentration:
Project: District at Campus West
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)
The District at Campus West
Preliminary Drainage and Erosion Control Report
Rational Method Equation: Project: District at Campus West
Calculations By:
Date:
From Section 3.2.1 of the CFCSDDC
Rainfall Intensity:
1 Basin 1 - Impervious Area 0.63
23 23 21 0.84 0.84 1.00 1.51 2.58 5.46 0.8 1.4 3.4
1 Basin 1 - Pervious Area 1.07
23 23 21 0.25 0.25 0.31 1.51 2.58 5.46 0.4 0.7 1.8
1 Basin 1 - Total Area 1.70
23 23 21 0.47 0.47 0.59 1.51 2.58 5.46 1.2 2.1 5.4
2 Basin 2 - Impervious Area 0.52
20 20 19 0.93 0.93 1.00 1.63 2.78 5.84 0.8 1.3 3.0
20 20 19 025 025 031 163 278 584 03 05 12
Area, A
(acres)
Intensity,
i2
(in/hr)
100-yr
Tc
(min)
HISTORIC 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)
K. Brazelton
January 25, 2011
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
2 Basin 2 - Pervious Area 0.68
20 20 19 0.25 0.25 0.31 1.63 2.78 5.84 0.3 0.5 1.2
2 Basin 2 - Total Area 1.20
20 20 19 0.55 0.55 0.68 1.63 2.78 5.84 1.1 1.8 4.8
The District at Campus West
Preliminary Drainage and Erosion Control Report
KRB
Pond No : Basin 1
3
100-yr
1.00
Area (A)= 1.70 acres 6999 ft
3
Max Release Rate = 3.80 cfs 0.16 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 16.92 5075 1140.0 3934.5
10 600 7.72 13.12 7874 2280.0 5594.4
15 900 6.52 11.08 9976 3420.0 6555.6
20 1200 5.60 9.52 11424 4560.0 6864.0
25 1500 4.98 8.47 12699 5700.0 6999.0
30 1800 4.52 7.68 13831 6840.0 6991.2
35 2100 4.08 6.94 14566 7980.0 6585.6
40 2400 3.74 6.36 15259 9120.0 6139.2
45 2700 3.46 5.88 15881 10260.0 5621.4
50 3000 3.23 5.49 16473 11400.0 5073.0
55 3300 3.03 5.15 16998 12540.0 4458.3
60 3600 2.86 4.86 17503 13680.0 3823.2
65 3900 2.72 4.62 18034 14820.0 3213.6
70 4200 2.59 4.40 18493 15960.0 2532.6
75 4500 2.48 4.22 18972 17100.0 1872.0
80 4800 2.38 4.05 19421 18240.0 1180.8
85 5100 2.29 3.89 19854 19380.0 474.3
90 5400 2.21 3.76 20288 20520.0 -232.2
95 5700 2.13 3.62 20640 21660.0 -1020.3
100 6000 2.06 3.50 21012 22800.0 -1788.0
105 6300 2.00 3.40 21420 23940.0 -2520.0
110 6600 1.94 3.30 21767 25080.0 -3313.2
115 6900 1.89 3.21 22170 26220.0 -4050.3
120 7200 1.84 3.13 22522 27360.0 -4838.4
Design Point
Design Storm Required Detention Volume
Developed "C" =
DETENTION POND CALCULATION; FAA METHOD w/ Ft.Collins IDF
Project Number : 670-001
The District at Campus West
Preliminary Drainage and Erosion Control Report
KRB
Pond No : Basin 2
2
100-yr
1.00
Area (A)= 1.20 acres 4104 ft
3
Max Release Rate = 3.30 cfs 0.09 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 11.94 3582 990.0 2592.0
10 600 7.72 9.26 5558 1980.0 3578.4
15 900 6.52 7.82 7042 2970.0 4071.6
20 1200 5.60 6.72 8064 3960.0 4104.0
25 1500 4.98 5.98 8964 4950.0 4014.0
30 1800 4.52 5.42 9763 5940.0 3823.2
35 2100 4.08 4.90 10282 6930.0 3351.6
40 2400 3.74 4.49 10771 7920.0 2851.2
45 2700 3.46 4.15 11210 8910.0 2300.4
50 3000 3.23 3.88 11628 9900.0 1728.0
55 3300 3.03 3.64 11999 10890.0 1108.8
60 3600 2.86 3.43 12355 11880.0 475.2
65 3900 2.72 3.26 12730 12870.0 -140.4
70 4200 2.59 3.11 13054 13860.0 -806.4
75 4500 2.48 2.98 13392 14850.0 -1458.0
80 4800 2.38 2.86 13709 15840.0 -2131.2
85 5100 2.29 2.75 14015 16830.0 -2815.2
90 5400 2.21 2.65 14321 17820.0 -3499.2
95 5700 2.13 2.56 14569 18810.0 -4240.8
100 6000 2.06 2.47 14832 19800.0 -4968.0
105 6300 2.00 2.40 15120 20790.0 -5670.0
110 6600 1.94 2.33 15365 21780.0 -6415.2
115 6900 1.89 2.27 15649 22770.0 -7120.8
120 7200 1.84 2.21 15898 23760.0 -7862.4
Design Point
Design Storm Required Detention Volume
Developed "C" =
DETENTION POND CALCULATION; FAA METHOD w/ Ft.Collins IDF
Project Number : 670-001
The District at Campus West
Preliminary Drainage and Erosion Control Report
KRB
Pond No : Basin 3
1
100-yr
0.99
Area (A)= 0.91 acres 2406 ft
3
Max Release Rate = 3.20 cfs 0.06 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 8.96 2689 960.0 1729.2
10 600 7.72 6.95 4173 1920.0 2253.0
15 900 6.52 5.87 5286 2880.0 2406.5
20 1200 5.60 5.05 6054 3840.0 2214.0
25 1500 4.98 4.49 6730 4800.0 1929.7
30 1800 4.52 4.07 7330 5760.0 1569.7
35 2100 4.08 3.68 7719 6720.0 998.9
40 2400 3.74 3.37 8086 7680.0 406.5
45 2700 3.46 3.12 8416 8640.0 -223.8
50 3000 3.23 2.91 8730 9600.0 -870.3
55 3300 3.03 2.73 9008 10560.0 -1551.9
60 3600 2.86 2.58 9276 11520.0 -2244.3
65 3900 2.72 2.45 9557 12480.0 -2923.3
70 4200 2.59 2.33 9800 13440.0 -3640.0
75 4500 2.48 2.23 10054 14400.0 -4346.0
80 4800 2.38 2.14 10292 15360.0 -5068.1
85 5100 2.29 2.06 10522 16320.0 -5798.4
90 5400 2.21 1.99 10751 17280.0 -6528.7
95 5700 2.13 1.92 10938 18240.0 -7302.2
100 6000 2.06 1.86 11135 19200.0 -8064.9
105 6300 2.00 1.80 11351 20160.0 -8808.7
110 6600 1.94 1.75 11535 21120.0 -9584.9
115 6900 1.89 1.70 11749 22080.0 -10331.4
120 7200 1.84 1.66 11935 23040.0 -11104.9
Design Point
Design Storm Required Detention Volume
Developed "C" =
DETENTION POND CALCULATION; FAA METHOD w/ Ft.Collins IDF
Project Number : 670-001
APPENDIX C
WATER QUALITY DESIGN COMPUTATIONS
The District at Campus West
Preliminary Drainage and Erosion Control Report
Sheet 1 of 2
Designer:
Company:
Date:
Project:
Location:
1. Basin Storage Volume
A) Effective Imperviousness of Tributary Area, Ia Ia = 74.0 %
(100% if all paved and roofed areas upstream of rain garden)
B) Tributary Area's Imperviousness Ratio (i = Ia/100) i = 0.740
C) Water Quality Capture Volume (WQCV) for a 12-hour Drain Time WQCV = 0.24 watershed inches
(WQCV= 0.8 * (0.91* i3 - 1.19 * i2 + 0.78 * i)
D) Contributing Watershed Area (including rain garden area) Area = 73,927 sq ft
E) Water Quality Capture Volume (WQCV) Design Volume VWQCV = 1,450 cu ft
Vol = (WQCV / 12) * Area
F) For Watersheds Outside of the Denver Region, Depth of d6 = in
Average Runoff Producing Storm
G) For Watersheds Outside of the Denver Region, VWQCV OTHER = cu ft
Water Quality Capture Volume (WQCV) Design Volume
H) User Input of Water Quality Capture Volume (WQCV) Design Volume VWQCV USER = cu ft
(Only if a different WQCV Design Volume is desired)
2. Basin Geometry
A) WQCV Depth (12-inch maximum) DWQCV =12in
B) Rain Garden Side Slopes (Z = 4 min., horiz. dist per unit vertical) Z = 0.00 ft / ft
(Use "0" if rain garden has vertical walls)
Design Procedure Form: Rain Garden (RG)
Kevin Brazelton
Northern Engineering Services
January 25, 2012
The District at Campus West
Basin 1
C) Mimimum Flat Surface Area AMin = 967 sq ft
D) Actual Flat Surface Area AActual = 3550 sq ft
E) Area at Design Depth (Top Surface Area) ATop = 3550 sq ft
F) Rain Garden Total Volume VT= 3,550 cu ft
(VT= ((ATop + AActual) / 2) * Depth)
3. Growing Media
4. Underdrain System
A) Are underdrains provided?
B) Underdrain system orifice diameter for 12 hour drain time
i) Distance From Lowest Elevation of the Storage y = 1.0 ft
Volume to the Center of the Orifice
ii) Volume to Drain in 12 Hours Vol12 = 1,450 cu ft
iii) Orifice Diameter, 3/8" Minimum DO = 1.01 in
Choose One
Choose One
18" Rain Garden Growing Media
Other (Explain):
YES
NO
BLDG 1 Rain Gardens, RG 1/25/2012, 10:09 AM
The District at Campus West
Preliminary Drainage and Erosion Control Report
Sheet 2 of 2
Designer:
Company:
Date:
Project:
Location:
5. Impermeable Geomembrane Liner and Geotextile Separator Fabric
A) Is an impermeable liner provided due to proximity
of structures or groundwater contamination?
PROVIDE A 30 MIL (MIN) PVC LINER WITH CDOT CLASS B
GEOTEXTILE ABOVE IT. USE THE SAME GEOTEXTILE BELOW THE
LINER IF THE SUBGRADE IS ANGULAR
6. Inlet / Outlet Control
A) Inlet Control
7. Vegetation
8. Irrigation
A) Will the rain garden be irrigated?
Notes:
January 25, 2012
The District at Campus West
Basin 1
Design Procedure Form: Rain Garden (RG)
Kevin Brazelton
Northern Engineering Services
Choose One
Choose One
Choose One
Sheet Flow- No Energy Dissipation Required
Concentrated Flow- Energy Dissipation Provided
Plantings
Seed (Plan for frequent weed control)
Sand Grown or Other High Infiltration Sod
Choose One
YES
NO
YES
NO
BLDG 1 Rain Gardens, RG 1/25/2012, 10:09 AM
The District at Campus West
Preliminary Drainage and Erosion Control Report
Sheet 1 of 2
Designer:
Company:
Date:
Project:
Location:
1. Basin Storage Volume
A) Effective Imperviousness of Tributary Area, Ia Ia = 70.0 %
(100% if all paved and roofed areas upstream of rain garden)
B) Tributary Area's Imperviousness Ratio (i = Ia/100) i = 0.700
C) Water Quality Capture Volume (WQCV) for a 12-hour Drain Time WQCV = 0.22 watershed inches
(WQCV= 0.8 * (0.91* i3 - 1.19 * i2 + 0.78 * i)
D) Contributing Watershed Area (including rain garden area) Area = 39,787 sq ft
E) Water Quality Capture Volume (WQCV) Design Volume VWQCV = 730 cu ft
Vol = (WQCV / 12) * Area
F) For Watersheds Outside of the Denver Region, Depth of d6 = in
Average Runoff Producing Storm
G) For Watersheds Outside of the Denver Region, VWQCV OTHER = cu ft
Water Quality Capture Volume (WQCV) Design Volume
H) User Input of Water Quality Capture Volume (WQCV) Design Volume VWQCV USER = cu ft
(Only if a different WQCV Design Volume is desired)
2. Basin Geometry
A) WQCV Depth (12-inch maximum) DWQCV =12in
B) Rain Garden Side Slopes (Z = 4 min., horiz. dist per unit vertical) Z = 0.00 ft / ft
(Use "0" if rain garden has vertical walls)
Design Procedure Form: Rain Garden (RG)
Kevin Brazelton
Northern Engineering Services
January 25, 2012
The District at Campus West
Basin 3
C) Mimimum Flat Surface Area AMin = 486 sq ft
D) Actual Flat Surface Area AActual = 2090 sq ft
E) Area at Design Depth (Top Surface Area) ATop = 2090 sq ft
F) Rain Garden Total Volume VT= 2,090 cu ft
(VT= ((ATop + AActual) / 2) * Depth)
3. Growing Media
4. Underdrain System
A) Are underdrains provided?
B) Underdrain system orifice diameter for 12 hour drain time
i) Distance From Lowest Elevation of the Storage y = 1.0 ft
Volume to the Center of the Orifice
ii) Volume to Drain in 12 Hours Vol12 = 730 cu ft
iii) Orifice Diameter, 3/8" Minimum DO = 0.72 in
Choose One
Choose One
18" Rain Garden Growing Media
Other (Explain):
YES
NO
BLDG 3 Rain Gardens, RG 1/25/2012, 10:10 AM
The District at Campus West
Preliminary Drainage and Erosion Control Report
Sheet 2 of 2
Designer:
Company:
Date:
Project:
Location:
5. Impermeable Geomembrane Liner and Geotextile Separator Fabric
A) Is an impermeable liner provided due to proximity
of structures or groundwater contamination?
PROVIDE A 30 MIL (MIN) PVC LINER WITH CDOT CLASS B
GEOTEXTILE ABOVE IT. USE THE SAME GEOTEXTILE BELOW THE
LINER IF THE SUBGRADE IS ANGULAR
6. Inlet / Outlet Control
A) Inlet Control
7. Vegetation
8. Irrigation
A) Will the rain garden be irrigated?
Notes:
January 25, 2012
The District at Campus West
Basin 3
Design Procedure Form: Rain Garden (RG)
Kevin Brazelton
Northern Engineering Services
Choose One
Choose One
Choose One
Sheet Flow- No Energy Dissipation Required
Concentrated Flow- Energy Dissipation Provided
Plantings
Seed (Plan for frequent weed control)
Sand Grown or Other High Infiltration Sod
Choose One
YES
NO
YES
NO
BLDG 3 Rain Gardens, RG 1/25/2012, 10:10 AM
APPENDIX D
HEC-RAS INPUT AND OUTPUT FILES
D.1 – Hard Copy
D.2 – Digital Copy (CD)
City of Fort Collins
Stormwater Utility
700 Wood Street
Fort Collins, CO 80521
January 17, 2012
RE: HEC-RAS summary
The District
Dear Staff,
This Memo is to summarize HEC-RAS modeling that we have done for the proposed development
referred to as The District, which is located on Plum Street between Shields St. and City Park Ave. We
have run existing and proposed conditions models to represent 100-year water surface elevations prior to
the project and after completion of the project. The proposed conditions model is based on preliminary
grading plans for the project.
As shown on the attached Existing Conditions HEC-RAS Exhibit and Proposed Conditions HEC-RAS
Exhibit, we have placed cross-sections at key locations along the length of Plum Street. The majority of
our modeling is based on one-foot topography generated from field shots. However some augmentation
of data has been supplied by City two-foot aerial topography. All topographic information is related to City
of Fort Collins Vertical Datum (unadjusted NGVD-29).
The following table shows existing and proposed conditions modeling results. Please see the attached
HEC-RAS output for support of this data.
Existing
Cond. Proposed
100-yr Cond. Cond. Difference
Section Discharge Min Ch El W.S. Elev W.S. Elev W.S. Elev
(cfs) (ft) (ft) (ft) (ft)
114 232 34.22 35.73 35.8 0.07
112 232 33.62 35 35.04 0.04
110 232 32.73 33.79 34.03 0.24
108 232 31.24 32.54 32.79 0.25
107 232 30.38 31.87 31.89 0.02
106.5 232 30 31.61 31.48 -0.13
106 232 29.7 31.23 31.16 -0.07
105.5 232 28.85 30.41 30.52 0.11
105 232 28.55 30.48 30.43 -0.05
104 232 28.36 30.14 30.26 0.12
103.5 232 27.7 30.29 30.25 -0.04
103 232 27.45 30.3 30.3 0
102 232 27.7 30.14 30.14 0
100 232 28.49 29.75 29.75 0
‐ 1 ‐
The attached Finished Floor Elevation Exhibit 1 shows finished floor elevations at locations upstream of
cross-section 104. The apartment complex at Section 104 maintains 9-inches of freeboard from the
proposed condition water surface elevation. All other residences maintain12-inches or more of freeboard
from the proposed conditions 100-year water surface elevations.
The attached Finished Floor Elevation Exhibit 2 shows finished floor elevations at locations upstream of
cross-section 108. As shown in this exhibit, all residences maintain 12-inches or more of freeboard from
the proposed conditions 100-year water surface elevations.
Please feel free to contact me with any questions you may have.
Sincerely,
Northern Engineering Services, Inc.
Aaron Cvar, PE
‐ 2 ‐
T
T
T T T T T
T T
T T T
T T
T
T T
CTV
CTV
CTV
CTV CTV
CTV
TTT
X
X
X
X X
X
OHE OHE OHE
OHE OHE OHE
OHE
OHE
OHE
OHE
OHE
OHE
X X
X X
8" SS 8" SS 8" SS 8" SS
8" SS 8" SS 8" SS
8" SS
8" SS 8" SS 8" SS
8" SS 8" SS
8" SS 8" SS 8" SS
X
ST ST
ST
ST
ST
ST
X
X
CTV
CTV CTV
CTV
X X
X
8" SS
8" SS 8" SS 8" SS
8" SS
8" SS
8" SS
8" SS 8" SS 8" SS
CTV
CTV
CTV
CTV
G G
G
T
T
T T T T T
T T
T T T
T T
T
T T
CTV
CTV
CTV
CTV CTV
CTV
TTT
X
X
X
X X
X
OHE OHE OHE
OHE OHE OHE
OHE
OHE
OHE
OHE
OHE
OHE
X X
X X
8" SS 8" SS 8" SS 8" SS
8" SS 8" SS 8" SS
8" SS
8" SS 8" SS 8" SS
8" SS 8" SS
8" SS 8" SS 8" SS
X
ST ST
ST
ST
ST
ST
X
X
CTV
CTV CTV
CTV
X X
X
8" SS
8" SS 8" SS 8" SS
8" SS
8" SS
8" SS
8" SS 8" SS 8" SS
CTV
CTV
CTV
CTV
G G
G
107 106.5 106
105.5
105 104
DRAWN BY:ATC
SCALE:1"=40'
ISSUED:1/16/12
SHEET NO:
FINISHED FLOOR ELEVATION
EXHIBIT 1
1-STORY
WOOD 1-STORY
WOOD
FF=5037.48
FF=5037.35
1-STORY
WOOD
FF=5037.44
FF=5036.43
2-STORY
WOOD 1-STORY
WOOD
CARPORT
FF=5036.36
1-STORY
STUCCO w/
BASEMENT
FF=5035.82
1-STORY
WOOD
GARAGE
FF=5033.94
"NO PARKING"
"NO PARKING"
"NO PARKING"
"CAMPUS WEST
CONDOMINIUMS"
BRIDGE
3" ADS
ELEV=5034.74 FENCE ON
CONCRETE PAD
FENCE ON
CONCRETE
PAD
FENCE ON
CONCRETE
PAD
MOE=5033.57
MOE=5033.59
114 112 110
108
DRAWN BY:ATC
SCALE:1"=40'
ISSUED:1/16/12
SHEET NO:
FINISHED FLOOR ELEVATION
EXHIBIT 2
APPENDIX D.1
HEC-RAS INPUT AND OUTPUT FILES
Hard Copy
APPENDIX B.2
HEC-RAS INPUT AND OUTPUT FILES
Digital Copy (CD)
APPENDIX E
OPERATIONS AND MAINTENANCE GUIDELINES FOR BIORETENTION PLANTERS (reserved for future use)
APPENDIX F
EROSION CONTROL REPORT
The District at Campus West
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 Sheet C001 of 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 District at Campus West. 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.
The District at Campus West
Preliminary Erosion Control Report
MAP POCKET
C600-C601 – DRAINAGE EXHIBIT
OHE OHE OHE OHE OHE
OHE OHE OHE OHE
ST ST ST ST ST
ST ST ST ST ST
�
�
� �
���
���
OHE
FIRE
1
1.70 ac
CO
CO
CO CO
CO
CO
CITY PARK AVENUE
BUILDING 1
FFE=5036.80
BUILDING 1
FFE=5034.30
BUILDING 2
FFE=5033.34
CITY PARK AVENUE
(50' ROW)
WEST PLUM STREET
(ROW VARIES) WEST PLUM STREET
(ROW VARIES)
6.5' ADDITIONAL
ROW (SEE PLAT)
ADDITIONAL ROW
WIDTH VARIES
(SEE PLAT)
40' EXIST. ROW
50' EXIST. ROW
50' EXIST. ROW
66' EXIST. ROW
3.5' ADDITIONAL
ROW (SEE PLAT)
1
10.0' DRAINAGE
EASEMENT
4.0' DRAINAGE
EASEMENT
EXISTING DAISY STREET TO BE
VACATED
(50' ROW)
(1205)
(1303)
KIEL FAMILY
LIMITED
PARTNERSHIP
(1307)
DERNBERG,
ANN R.
(1311)
TAN,
SHIRLEE
4' MIN. WIDTH
24" MIN.
36" MAX.
2" MIN.
12" MAX. PONDING
OVER FFE
VARIES
NOTES:
�
�.�.
�.�.
�.�.
�.�.
�.�.
OHE OHE OHE OHE OHE
OHE OHE OHE OHE OHE
OHE OHE OHE OHE
OHE OHE OHE
OHE OHE
OHE OHE
ST ST ST ST ST ST
ST ST
ST
2
1.20 ac
3
0.91 ac
CO
CO
SCOTT AVENUE
BUILDING 2
FFE=5033.34
BUILGING 3
FFE=5031.34
FFE=5033.00
WEST PLUM STREET
(ROW VARIES)
WEST PLUM STREET
(ROW VARIES)
ASTER STREET
(50' ROW)
BLUEBELL STREET
(50' ROW)
11.5' ADDITIONAL
ROW (SEE PLAT)
6.5' ADDITIONAL
ROW (SEE PLAT)
66' EXIST. ROW
50' EXIST. ROW
40' EXIST. ROW
FFE=5032.00
2
1
3
4.0' DRAINAGE
EASEMENT
(1201)
(1205)
(809)
(813)
(1113)
CAMBRIDGE
HOUSE LOFTS
(733)
TAU OF GAMMA PHI BETA
SORORITY INC.
(728)
TAU OF GAMMA PHI BETA
SORORITY INC.
(700)
SUNSTONE CONDOMINIUMS
(1225)
ZETA TAU ALPHA
FRATERNITY
EXISTING COLUMBINE STREET TO
BE VACATED
(50' ROW)
(1209)
TOWN SQUARE
CONDOMINIUMS
(1209)
TOWN SQUARE
CONDOMINIUMS
No. Revisions:
By: Date:
REVIEWED BY:
N. Haws
DESIGNED BY:
DRAWN BY:
SCALE:
DATE:
01.25.12
PROJECT:
670-001
Sheet
Of 15 Sheets
THE DISTRICT AT CAMPUS WEST
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NOT FOR CONSTRUCTION
REVIEW SET
01/25/12
200 S���� C������ A�����, S���� 010
F��� C������, C������� 80524
E N G I N E E R I N G
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PHONE: 970.221.4158 FAX: 970.221.4159
���.�������������������.���
C601
DRAINAGE EXHIBIT
PRELIMINARY
K. Brazelton
K. Brazelton
1"=30'
City UTILITY of Fort PLAN Collins, APPROVAL Colorado
Date
Date
Date
Date
Date
Date
APPROVED:
City Engineer
Traffic Engineer
Parks & Recreation
Stormwater Utility
Water & Wastewater Utility
CHECKED BY:
CHECKED BY:
CHECKED BY:
CHECKED BY:
CHECKED BY:
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
K��� ����'� �����.
C��� ������ ��� ���.
R
( IN FEET )
1 inch = ft.
30 0 30 Feet
30
60 90
LEGEND:
NORTH
FOR DRAINAGE REVIEW ONLY
NOT FOR CONSTRUCTION
PROPOSED CONTOURS
80
79
EXISTING TREES
EXISTING ROW
EXISTING EASEMENT LINE
EXISTING CURB & GUTTER
PROPOSED SWALE
PROPOSED 2.5-FOOT VERTICAL CURB & GUTTER SECTION
PROPOSED CONCRETE
EXISTING CONCRETE
PROPOSED EASEMENT
A
A
1.23 ac
DESIGN POINT
FLOW ARROW
DRAINAGE BASIN LABEL
BASIN
DESIGNATION
BASIN
AREA (AC)
DRAINAGE BASIN BOUNDARY
PROPOSED DETENTION PLANTER
PROPOSED LANDSCAPE BED/PLANTER
PROPOSED ENHANCED PAVING
PROPOSED STORM SEWER
PROPOSED STORM INLET
PROPOSED STORM MANHOLE
NOTES:
1.REFER TO THE "PRELIMINARY DRAINAGE & EROSION CONTROL REPORT FOR THE DISTRICT AT CAMPUS WEST' BY NORTHERN ENGINEERING, DATED JANUARY 25, 2012 FOR ADDITIONAL INFORMATION.
DETENTION POND SUMMARY
VOLUME REQ'D (ac-ft) VOLUME PROVIDED (ac-ft) DETENTION METHOD WATER QUALITY METHOD
BASIN 1 0.16 0.17 DETENTION PLANTER PLD SOIL SECTION WITHIN DETENTION PLANTER
BASIN 2 0.09 0.09 DETENTION VAULT W/IN BUILDING 2 INTERNAL SAND/OIL SEPARATOR WITH STORM SEWER STRUCTURE EQUIPPED WITH SNOUT
BASIN 3 0.06 0.12 DETENTION PLANTER PLD SOIL SECTION WITHIN DETENTION PLANTER
DRAINAGE SUMMARY TABLE
DESIGN
POINT
BASIN
ID
TOTAL
AREA
(�����)
C10 C100
10-��
T�
(���)
100-��
T�
(���)
Q10
(���)
Q100
(���)
1 1 1.70 0.82 1.00 7.9 7.6 5.9 14.6
2 2 1.20 0.85 1.00 8.6 8.2 4.1 10.0
3 3 0.91 0.79 0.99 5.4 5.0 3.5 9.0
KEYMAP
NTS
WEST PLUM ST.
CITY PARK AVE.
BLUEBELL ST.
ASTER ST.
C600 C601
FLOW-THROUGH DETENTION PLANTER
{NTS}
MATCHLINE-SEE SHEET C600
(1315)
PANDO,
MATTHEW PAUL
(1319)
PANDO,
MATTHEW PAUL
(1323)
PANDO,
MATTHEW PAUL
(700)
SUNSTONE CONDOMINIUMS (700)
SUNSTONE CONDOMINIUMS
EXISTING COLUMBINE STREET TO
BE VACATED
(50' ROW)
(1209)
TOWN SQUARE
CONDOMINIUMS
(1209)
TOWN SQUARE
CONDOMINIUMS
BUILDING 1
FFE=5035.30
No. Revisions:
By: Date:
REVIEWED BY:
N. Haws
DESIGNED BY:
DRAWN BY:
SCALE:
DATE:
01.25.12
PROJECT:
670-001
Sheet
Of 15 Sheets
THE DISTRICT AT CAMPUS WEST
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� P����������� E������� ��
��� ������ �� N�������
E���������� S�������, I��.
NOT FOR CONSTRUCTION
REVIEW SET
01/25/12
200 S���� C������ A�����, S���� 010
F��� C������, C������� 80524
E N G I N E E R I N G
� � � � � � ��
PHONE: 970.221.4158 FAX: 970.221.4159
���.�������������������.���
C600
DRAINAGE EXHIBIT
PRELIMINARY
K. Brazelton
K. Brazelton
1"=30'
City UTILITY of Fort PLAN Collins, APPROVAL Colorado
Date
Date
Date
Date
Date
Date
APPROVED:
City Engineer
Traffic Engineer
Parks & Recreation
Stormwater Utility
Water & Wastewater Utility
CHECKED BY:
CHECKED BY:
CHECKED BY:
CHECKED BY:
CHECKED BY:
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
K��� ����'� �����.
C��� ������ ��� ���.
R
( IN FEET )
1 inch = ft.
30 0 30 Feet
30
60 90
LEGEND:
NORTH
FOR DRAINAGE REVIEW ONLY
NOT FOR CONSTRUCTION
PROPOSED CONTOURS
80
79
EXISTING TREES
EXISTING ROW
EXISTING EASEMENT LINE
EXISTING CURB & GUTTER
PROPOSED SWALE
PROPOSED 2.5-FOOT VERTICAL CURB & GUTTER SECTION
PROPOSED CONCRETE
EXISTING CONCRETE
PROPOSED EASEMENT
A
A
1.23 ac
DESIGN POINT
FLOW ARROW
DRAINAGE BASIN LABEL
BASIN
DESIGNATION
BASIN
AREA (AC)
DRAINAGE BASIN BOUNDARY
PROPOSED DETENTION PLANTER
PROPOSED LANDSCAPE BED/PLANTER
PROPOSED ENHANCED PAVING
PROPOSED STORM SEWER
PROPOSED STORM INLET
PROPOSED STORM MANHOLE
NOTES:
1.REFER TO THE "PRELIMINARY DRAINAGE & EROSION CONTROL REPORT FOR THE DISTRICT AT CAMPUS WEST' BY NORTHERN ENGINEERING, DATED JANUARY 25, 2012 FOR ADDITIONAL INFORMATION.
DETENTION POND SUMMARY
VOLUME REQ'D (ac-ft) VOLUME PROVIDED (ac-ft) DETENTION METHOD WATER QUALITY METHOD
BASIN 1 0.16 0.17 DETENTION PLANTER PLD SOIL SECTION WITHIN DETENTION PLANTER
BASIN 2 0.09 0.09 DETENTION VAULT W/IN BUILDING 2 INTERNAL SAND/OIL SEPARATOR WITH STORM SEWER STRUCTURE EQUIPPED WITH SNOUT
BASIN 3 0.06 0.12 DETENTION PLANTER PLD SOIL SECTION WITHIN DETENTION PLANTER
DRAINAGE SUMMARY TABLE
DESIGN
POINT
BASIN
ID
TOTAL
AREA
(�����)
C10 C100
10-��
T�
(���)
100-��
T�
(���)
Q10
(���)
Q100
(���)
1 1 1.70 0.82 1.00 7.9 7.6 5.9 14.6
2 2 1.20 0.85 1.00 8.6 8.2 4.1 10.0
3 3 0.91 0.79 0.99 5.4 5.0 3.5 9.0
No. Revisions:
By: Date:
REVIEWED BY:
N. Haws
DESIGNED BY:
DRAWN BY:
SCALE:
DATE:
01.25.12
PROJECT:
670-001
Sheet
Of 15 Sheets
THE DISTRICT AT CAMPUS WEST
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KEYMAP
NTS
WEST PLUM ST.
CITY PARK AVE.
BLUEBELL ST.
ASTER ST.
C600 C601
MATCHLINE-SEE SHEET C601
G G
G
G
G G G
G
G
G
G
G
G G
G G G
G
G
G
G G
G
G G G G G
G
G
G G
E
E
E
E
E
E E
E
E E E
20" W 20" W
20" W 20" W 20" W
20" W
20" W
20" W 20" W
20" W 20" W
20" W
20" W 20" W 20" W 20" W
6" W 6" W 6" W
6" W 6" W 6" W
FO FO
FO
FO FO
FO
FO
FO FO
FO FO
FO
FO FO FO FO FO FO
FO FO
FO
FO
FO
FO
FO
FO FO FO FO
FO
T T T
T
T T
T
T T T T T
T T T
T
T
T T T
ST ST
ST
ST
ST
ST
ST
ST
ST
6" SS
6" SS
6" SS
W W W
W
W
W
W
W
X
X
X
X
OHE
SHIELDS STREET
ASTER STREET
BLUEBELL STREET
W. PLUM STREET
COLUMBINE STREET
CITY PARK AVE.
114 112 110
108
107 106.5 106
105.5
105 104
103.5 103
102 100
DRAWN BY:ATC
SCALE:1"=150'
ISSUED:1/16/12
SHEET NO:
PROPOSED CONDITIONS
HEC-RAS EXHIBIT
G G
G
G
G G G
G
G
G
G
G
G G
G G G
G
G
G
G G
G
G G G G G
G
G
G G
E
E
E
E
E
E E
E
E E E
20" W 20" W
20" W 20" W 20" W
20" W
20" W
20" W 20" W
20" W 20" W
20" W
20" W 20" W 20" W 20" W
6" W 6" W 6" W
6" W 6" W 6" W
FO FO
FO
FO FO
FO
FO
FO FO
FO FO
FO
FO FO FO FO FO FO
FO FO
FO
FO
FO
FO
FO
FO FO FO FO
FO
T T T
T
T T
T
T T T T T
T T T
T
T
T T T
ST ST
ST
ST
ST
ST
ST
ST
ST
6" SS
6" SS
6" SS
W W W
W
W
W
W
W
X
X
X
X
OHE
SHIELDS STREET
ASTER STREET
BLUEBELL STREET
W. PLUM STREET
COLUMBINE STREET
CITY PARK AVE.
114 112 110
108
107 106.5 106
105.5
105 104
103.5 103
102 100
DRAWN BY:ATC
SCALE:1"=150'
ISSUED:1/16/12
SHEET NO:
EXISTING CONDITIONS
HEC-RAS EXHIBIT
Project Location : Ft Collins
Input Variables Results
Calculations By:
Project Location : Ft Collins
Input Variables Results
Calculations By:
Project Location : Ft Collins
Input Variables Results
Calculations By:
3 Basin 3 - Impervious Area 0.36
10 10 10 0.95 0.95 1.00 2.21 3.78 7.88 0.8 1.3 2.9
3 Basin 3 - Pervious Area 0.55
10 10 10 0.25 0.25 0.31 2.21 3.78 7.88 0.3 0.5 1.4
3 Basin 3 - Total Area 0.91
10 10 10 0.53 0.53 0.66 2.21 3.78 7.88 1.1 1.8 4.8
* Pond Release Rates for each basin include the 100-year flow rate from the historic impervious area plus the 2-year release rate from the historic pervious area.
D:\Projects\670-001\Drainage\Hydrology\PDP\670-001_Historic_Rational_Calcs\Hist Direct-Runoff
2-yr
Tc
(min)
10-yr
Tc
(min)
100-yr
Tc
(min)
1 Basin 1* No
0.25 0.25 0.31 164 1.14% 19.5 19.5 18.1 351 0.92% 1.92 3.0 0 N/A N/A N/A 23 23 21
2 Basin 2* No
0.25 0.25 0.31 164 1.30% 18.7 18.7 17.3 93 0.35% 1.18 1.3 0 N/A N/A N/A 20 20 19
3 Basin 3* No
0.25 0.25 0.31 40 4.44% 6.1 6.1 5.7 342 0.47% 1.37 4.2 0 N/A N/A N/A 10 10 10
* Time of Concentrations are calculated for the entire basin and used for both the Impervious and Pervious portions of the basins.
HISTORIC TIME OF CONCENTRATION COMPUTATIONS
Gutter Flow Swale Flow
Design
Point
Basin
Overland Flow
K. Brazelton
January 25, 2011
Time of Concentration
(Equation RO-4)
3
1
1 . 87 1 . 1 *
S
Ti C Cf L
D:\Projects\670-001\Drainage\Hydrology\PDP\670-001_Historic_Rational_Calcs\Hist Tc-10-yr_&_100-yr
Basin 3 - Total Area 39787 0.913 0.056 0.137 0.171 0.000 0.550 0.53 0.53 0.66 36%
TOTAL 165937 3.809 0.221 0.532 0.586 0.176 2.295 0.51 0.51 0.63 34%
HISTORIC 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
January 25, 2011
D:\Projects\670-001\Drainage\Hydrology\PDP\670-001_Historic_Rational_Calcs\Hist C-Values
2-yr
Tc
(min)
10-yr
Tc
(min)
100-yr
Tc
(min)
11No0.95 0.95 1.00 20 2.00% 1.0 1.0 0.7 586 0.50% 1.41 6.9 0 N/A N/A N/A 8 8 8
22No0.25 0.25 0.31 15 2.00% 4.9 4.9 4.5 440 1.00% 2.00 3.7 0 N/A N/A N/A 9 9 8
33No0.95 0.95 1.00 38 2.00% 1.4 1.4 0.9 345 0.50% 1.41 4.1 0 N/A N/A N/A 5 5 5
DEVELOPED TIME OF CONCENTRATION COMPUTATIONS
Gutter Flow Swale Flow
Design
Point
Basin
Overland Flow
K. Brazelton
January 25, 2011
Time of Concentration
(Equation RO-4)
3
1
1 . 87 1 . 1 *
S
Ti C Cf L
D:\Projects\670-001\Drainage\Hydrology\PDP\670-001_Proposed-Rational-Calcs\Tc-10-yr_&_100-yr
D:\Projects\670-001\Drainage\Hydrology\PDP\670-001_Proposed-Rational-Calcs\C-Values