HomeMy WebLinkAboutTHE SLAB - FDP - FDP160022 - SUBMITTAL DOCUMENTS - ROUND 1 - DRAINAGE REPORTFINAL DRAINAGE REPORT
The Slab
Fort Collins, Colorado
May 3, 2015
Prepared for:
Maxiiimo Development Group
706 S. College Avenue, Suite 201
Fort Collins, CO 8024
Prepared by:
301 North Howes Street, Suite 100
Fort Collins, Colorado 80521
Phone: 970.221.4158 Fax: 970.221.4159
www.northernengineering.com
Project Number: 1033-001
P 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.
May 3, 2015
City of Fort Collins
Stormwater Utility
700 Wood Street
Fort Collins, Colorado 80521
RE: Final Drainage Report for
The Slab
Dear Staff:
Northern Engineering is pleased to submit this Preliminary Drainage and Erosion Control Report for
your review. This report accompanies the Final Development Review submittal for the proposed
The Slab. Comments from the Final Review Letter dated August 26, 2015 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 The Slab 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.
Nicholas W. Haws, PE Cody Snowdon
Project Manager Project Engineer
The Slab
Final Drainage Report
TABLE OF CONTENTS
I. GENERAL LOCATION AND DESCRIPTION ................................................................... 1
A. Location ....................................................................................................................................... 1
B. Description of Property ................................................................................................................ 2
C. Floodplain .................................................................................................................................... 3
II. DRAINAGE BASINS AND SUB-BASINS ....................................................................... 5
A. Major Basin Description ............................................................................................................... 5
B. Sub-Basin Description .................................................................................................................. 5
III. DRAINAGE DESIGN CRITERIA ................................................................................... 6
A. Regulations .................................................................................................................................. 6
B. Four Step Process ........................................................................................................................ 6
C. Development Criteria Reference and Constraints ......................................................................... 7
D. Hydrological Criteria .................................................................................................................... 8
E. Hydraulic Criteria ......................................................................................................................... 8
F. Floodplain Regulations Compliance .............................................................................................. 8
G. Modifications of Criteria .............................................................................................................. 8
IV. DRAINAGE FACILITY DESIGN .................................................................................... 9
A. General Concept .......................................................................................................................... 9
B. Specific Details ........................................................................................................................... 10
V. CONCLUSIONS ...................................................................................................... 13
A. Compliance with Standards ........................................................................................................ 13
B. Drainage Concept ...................................................................................................................... 13
References ....................................................................................................................... 14
APPENDICES:
APPENDIX A – Hydrologic Computations
APPENDIX B – Hydraulic Computations
B.1 – Storm Sewers
B.2 – Inlets
B.3 – Detention Facilities
APPENDIX C – Water Quality Design Computations
APPENDIX D – Select Information from Previous Analysis
APPENDIX E – NRCS Soils Report
APPENDIX F – Conceptual Analysis of Future Drainage within Lot 2
APPENDIX G – Erosion Control Report
The Slab
Final Drainage Report
LIST OF TABLES AND FIGURES:
Figure 1 – Aerial Photograph ................................................................................................ 2
Figure 2– Proposed Site Plan ................................................................................................ 3
Figure 3 – Existing FEMA Floodplains .................................................................................... 4
Figure 4 – Existing City Floodplains ....................................................................................... 4
Table 1 – Low Impact Development Summary Table ................................................................ 7
Table 2 – Northern Pond Summary Table ............................................................................. 11
Table 3 – Southern Pond Summary Table ............................................................................. 12
MAP POCKET:
C8.00 - Drainage Exhibit
Sheet 1 – Historic Drainage Exhibit (by DMW Civil Engineers)
The Slab
Final Drainage Report 1
I. GENERAL LOCATION AND DESCRIPTION
A. Location
1. Vicinity Map
2. The Slab project is located in the southwest quarter of Section 14, 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 west of South Whitcomb Street on the north side of West
Prospect Road.
4. Currently the existing lot does not have any stormwater or water quality facilities. The
project was previously designs and the slab of the proposed building was constructed.
The entire site was overlot graded, but no other improvements were constructed. The
site now consist of native vegetation. The area north of the existing slab drains
towards the northeast corner of the site. The area south of the slab drains south into
Prospect Road.
The project is currently bordered to the north by a multi-family building, west by a single
family residence, east by a single-family residence and south by Prospect Road.
The Slab
Final Drainage Report 2
B. Description of Property
1. The Slab is approximately 1.436 net acres.
Figure 1 – Aerial Photograph
2. The Slab consists of one property, but some improvements required for this
development are planned to occur within the properties to the north and east. The lot
has an existing basement and first concrete floor of the previously designed multi-
family building. The remaining area consist of native vegetation. The area planned to
be used for an emergency access consists of native vegetation. The area planned to
be used for some detention consists of a manicured front yard.
3. According to the United States Department of Agriculture (USDA) Natural Resources
Conservation Service (NRCS) Soil Survey, 100 percent of the site consists of Altvan-
Satanta loam, which falls into Hydrologic Soil Groups B.
4. The proposed development will include the reuse of the existing structure. The
proposed site plans to mimic the previously approved construction plans and
concepts. The access to the site will come from Prospect Road west of the existing
building leading to a parking area located north of the existing building. The drive will
include permeable pavers to supply water quality for the northern half of the site.
There is a proposed detention pond located at the northeast corner and another
located east of the proposed site.
The Slab
Final Drainage Report 3
Figure 2– Proposed Site Plan
5. No irrigation facilities or major drainageways are within the property limits.
6. The project site is within the High Density Mixed-Use Neighborhood District (HMN)
Zoning District. The proposed use is permitted within the zone district.
C. Floodplain
1. The subject property is not located in a FEMA or City regulatory floodplain.
2. The FEMA Panel 08069C0979H illustrates the proximity of the project site to the
nearest FEMA delineated regulatory floodplain. It is noted that the vertical datum
utilized for site survey work is the City of Fort Collins Benchmark #28-92
Elevation = 5010.65 (NAVD 88) – Project Datum
Elevation = 5007.48 (Fort Collins NVGD 29 – Unadjusted)
The Slab
Final Drainage Report 4
Figure 3 – Existing FEMA Floodplains
Figure 4 – Existing City Floodplains
The Slab
Final Drainage Report 5
II. DRAINAGE BASINS AND SUB-BASINS
A. Major Basin Description
1. The Slab is located within the Old Town Basin, which is located primarily in Old Town
Fort Collins.
B. Sub-Basin Description
1. This property and project were previously analyzed in August, 2007 by DMW Civil
Engineers. To honor the historic drainage patterns, the historic analysis from that
report will be preserved throughout this analysis. Within that analysis, the site was
divided into three on-site historic basins (E1-3) and one off-site historic basin (EO1).
Basin E1 consisted of the northern half of the site and routed stormwater via overland
flow to the northeast corner of the site. E2 consisted of the southern portion of the
site and routed stormwater via overland flow to the southern property line. Basin E3
consisted of the area within Prospect Road public right-of-way and routed stormwater
via gutter flow to the east. Off-Site Basin EO1 consist entirely of the off-site
emergency access easement and routes stormwater via overland flow north to Lake
Street. A more detailed description of the projects proposed drainage patterns follows
in Section IV.A.4., below.
2. There is a portion of the single family residence neighboring the project to the west
that drains onto this property. The area is 0.370 acres and consists mostly of the
backyard between the house and the garage, as well as a portion of both the house
and garage. Drainage is routed via overland flow and sheet flows across the western
boundary of the project. The proposed design will preserve this route and plans to
pass the flow through the project. This basin has been delineated as Basin OW1 and
discharges 0.66 cfs and 1.2 cfs for the 2-year & 100-year event, respectively.
A full-size copy of the Historic and Proposed Drainage Exhibit can be found in the
Map Pocket at the end of this report.
The Slab
Final Drainage Report 6
III. DRAINAGE DESIGN CRITERIA
A. Regulations
There are no optional provisions outside of the FCSCM proposed with the The Slab project.
B. Four Step Process
The overall stormwater management strategy employed with the The Slab project utilizes
the “Four Step Process” to minimize adverse impacts of urbanization on receiving waters.
The following is a description of how the proposed development has incorporated each
step.
Step 1 – Employ Runoff Reduction Practices
Several techniques have been utilized with the proposed development to facilitate the
reduction of runoff peaks, volumes, and pollutant loads as the site is developed from the
current use by implementing multiple Low-Impact Development (LID) strategies including:
Selecting a site that has been previously developed and currently consist an existing
building pad located in middle of the property.
Providing vegetated open areas along the south and east portion of the site to reduce
the overall impervious area and to minimize directly connected impervious areas
(MDCIA).
Routing flows, to the extent feasible, through drain rock to increase time of
concentration, promote infiltration and provide initial water quality.
Providing permeable paver areas with underground detention area to increase time of
concentration promote infiltration and provide water quality.
Routing runoff from the proposed roofs into either a grass lined swale or permeable
pavers to promote infiltration, biological uptake, and evapotranspiration.
Step 2 – Implement BMPs That Provide a Water Quality Capture Volume (WQCV) with
Slow Release
The efforts taken in Step 1 will facilitate the reduction of runoff; however, this
development will still generate stormwater runoff that will require additional BMPs and
water quality. Stormwater generated from the northern portion of the site will be routed
over permeable pavers and discharge into a bio-swale with and underdrain system prior to
being collected within the proposed detention pond. All of the roof area draining to the
north will be collected in roof leaders and discharged directly into the paver system sub-
grade. The area that is draining off-site to the north will be treated by use of permeable
pavers and a dry well. Stormwater generated from the southern portion of the site will be
routed through either a grass lined swale or the privately owned storm sewer system. The
runoff from this area will be treated through use of extended detention within the proposed
detention pond.
Below is a table that summarizes the Low impact Design practices being utilized within
this project to not only reduce the amount of runoff generated from the site through
infiltration, but also treat the runoff prior to releasing it from the site.
The Slab
Final Drainage Report 7
Design
Point Basin ID Basin Area Treatment Type
LID
System
Area
Treated by
LID System
Percent of Site
Treated by LID
System
Area of
Pavers
Area of
Aphalt
Parking
Percent
Pavers
Run-on Area
for Paver
Section
Run-on Area
Ratio (3:1
Max)
n1 N1 0.230 ac. Bio-Swale
(Off-Site) Yes 0.230 ac. 13% 0.000 ac. 0.083 ac. N/A N/A
n2 N2 & N3 0.780 ac. StormTech
Chambers Yes 0.780 ac. 45% 0.000 ac. 0.458 ac. N/A N/A
s1 S1 0.100 ac. Extended Detention No N/A 0% 0.000 ac. 0.000 ac. N/A N/A
s2 S2 0.210 ac. Bio-Swale Yes 0.210 ac. 12% 0.000 ac. 0.000 ac. N/A N/A
s3 S3 & S4 0.150 ac. StormTech
Chambers Yes 0.150 ac. 9% 0.000 ac. 0.048 ac. N/A N/A
on ON1 0.250 ac. TrueGrid Retention
Section Yes 0.250 ac. 15% 0.000 ac. 0.000 ac. N/A N/A
Total 1.720 ac. 1.620 ac. 94% 0.000 ac. 0.589 ac. 0.00%
Table 1 – Low Impact Development Summary Table
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 The Slab, 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, 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 Citywide drainageway stability.
Step 4 – Implement Site Specific and Other Source Control BMPs.
This step typically applies to industrial and commercial developments and is not
applicable for this project.
C. Development Criteria Reference and Constraints
1. A drainage study was prepared for this property by DMW Civil Engineers, dated
August 27, 2007, but only the building foundation was constructed. That report will
be utilized throughout this analysis.
2. There are no known drainage studies for any adjacent properties that will have any
effect on The Slab project.
3. The subject property is essentially an "in-fill" development project as the property is
surrounded by currently developed properties. As such, several constraints have been
identified during the course of this analysis that will impact the proposed drainage
system including:
Existing elevations along the southern property line adjacent to the West Prospect
The Slab
Final Drainage Report 8
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 this 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 Modified Federal Aviation Administration (FAA)
procedure has been 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. No other assumptions or calculation methods have been used with this development
that are not referenced by current City of Fort Collins criteria.
E. Hydraulic Criteria
1. As previously noted, the subject property historically in two different directions, north
to Lake Street or south to Prospect Road. The majority of the site drains stormwater
via overland flow.
2. All drainage facilities proposed with The Slab 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 not located within any
regulatory floodplain.
4. The Slab project does not propose to modify any natural drainageways.
F. Floodplain Regulations Compliance
1. As previously mentioned, all structures are located outside of any FEMA 100-year or
City floodplain, and thus are not subject to any floodplain regulations.
G. Modifications of Criteria
The proposed Slab development is not requesting any modification to the standards,
but will be requesting an exception to be granted by the Utilities Executive Director or
his designee to Section 4.15(b). The project is proposing to use the parking area for
additional detention volume with depths that exceed the 12-inch maximum. These
depths will not exceed 18-inches in the parking area and the area exceeding the 12-
inches of ponding will occur within less that twenty-five percent (25%) of the total
parking spaces provided. Please see the full-size copy of the Proposed Drainage
Exhibit within Map Pocket to see the extents of these ponding areas.
The Slab
Final Drainage Report 9
IV. DRAINAGE FACILITY DESIGN
A. General Concept
1. The main objectives of The Slab drainage design are to maintain existing drainage
patterns and ensure no adverse impacts to any adjacent properties.
2. The existing site does have off-site flows from the west that historically drain onto the
property. The existing routing of this runoff of will remain and pass through the
proposed project.
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 Slab project is composed of three major drainage basins, designated as Major
Basins N, Major Basin S and Major Basin O. Major Basin N is further subdivided into
three (3) sub-basins, designated as Basins N1-N3. Major Basin S is further
subdivided into four (4) sub-basins, designated as Basins S1-S4. Major Basin O is
further subdivided into three (3) sub-basins, designated as Basins ON, OW, and OS.
The drainage patterns anticipated for Major Basins N, S and OS and associated sub-
basins are further described below.
Basin N
Basin N consists of all of the on-site improvements being proposed north of the
existing concrete building slab. The major basin was divided into three (3) sub-basins
to better size the LID concepts proposed on the northern side of the property. Sub-
Basin N1 encompasses the furthest downstream reach of Major Basin N and consists
of a portion of the parking area and the entire Northern Detention Pond. The runoff
from this basin is routed via overland flow and discharges directly into the proposed
detention pond through a curb cut located at the eastern edge of the proposed
parking. Basin N2 encompasses the northern portion of the parking area and consist
primarily of asphalt parking and drains via overland flow into the proposed bio-swale.
This bio-swale is proposed to have an underdrain system and be composed of
mitigated soils to promote infiltration. Runoff not captured by the bio-swale will be
discharged directly into Sub-Basin N1 through a curb cut located in the median. Sub-
Basin N3 encompasses the southern portion of the parking area and is composed of
the northern half of the building and some asphalt parking area and the proposed
pavers. The runoff from the roof will be routed via underground pipe into the paver
section. The runoff from the remaining area will be routed via overland flow across
the permeable pavers. The runoff not capture by the paver system will be discharged
directly into Sub-Basin N2 through a series of curb cuts within the proposed median.
Basin S
Basin S consists of all of the on-site improvements being proposed west, east, and
south of the existing concrete building slab. The major basin was divided into four (4)
sub-basins to better size the LID concepts proposed on the west, east and south sides
of the property. Sub-Basin S1 encompasses the furthest downstream reach of Major
Basin S and consists of east of the proposed building. The runoff from this basin is
routed via overland flow across a grass buffer yard and discharges off-site, directly into
the proposed southern detention pond. Basin S2 encompasses the southern portion of
the building and the area surrounding the building to the south. This area consists of
The Slab
Final Drainage Report 10
the proposed building and the surrounding landscape areas. The runoff from this area
will be routed via overland flow and roof leaders into a grass lined swale. The runoff
conveyed through the grass lines swale is intercepted by an area inlet and routed
directly into the proposed detention pond. Sub-Basin S3 encompasses the western
portion of the parking area and is composed of a small portion of the proposed
building, some asphalt parking area and permeable pavers. The runoff from the roof
will be routed via underground pipe into the paver section. The runoff from the
remaining area will be routed via overland flow across the permeable pavers. The
runoff not capture by the paver system will be intercepted by two combinations inlets
and routed into the proposed storm sewer system. Sub-Basin S4 encompasses the
furthest upstream reach of Major Basin S and consists of western portion of the
project. The runoff from this basin is routed via overland flow into a small depression
located at the southwest corner of the property. Runoff from this basin is intercepted
by a flared end section and routed through the proposed storm sewer.
Basin O
Basin O consists of all of the off-site improvements being proposed. The major basin
was divided into three (3) sub-basins all draining undetained in three different
directions. Sub-Basin OW1 encompasses the area along the western edge of the site
that historically drains across the site from the west. This includes a portion of the
existing single family residences, associated backyard and existing garage buildings.
The stormwater is routed via overland flow and sheet flow onto the property along the
western property line. This stormwater is planned to pass through the site
undetained. Sub-Basin OS1 encompasses the existing public right-of-way within
Prospect Road. Other than the proposed entrance and the master planned public
sidewalk, no other improvements are proposed. The stormwater is routed via overland
and gutter flow and is released off-site, undetained east on Prospect Road. Sub-Basin
ON1 encompasses the emergency access drive located to the north of the site. The
stormwater is routed via overland and swale flow. A portion of the runoff is planned to
be detained within a TrueGrid and drain rock section and released partially through
infiltration and partial through an underdrain system. Another portion of the runoff is
planned to be captured through infiltration within the bi-swale and the use of a dry
well. Emergency overflow is planned to over top and be routed through a sidewalk
chase and into Lake Street.
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. One of the main drainage problems associated with this project site is the deficiency
of water quality present within the existing site. Currently the entire site drains
overland and discharges directly into either Lake Street or Prospect Road without
water quality. The proposed site will mitigate this issue by instituting the following
water quality devices:
All of the runoff generated from the proposed building will be routed through a
landscape area or filtered through drainage rock.
Most of the improvements generated from the parking lot will be routed either
through a permeable paver system and sub-surface drainage rock or bio-swale.
Low Impact Design will be implemented to break up the impervious areas and
promote infiltration.
The Slab
Final Drainage Report 11
The southern detention pond is designed with a water quality element and is
designed to slowly release the minor storm into Prospect Road.
2. Since the site was partially developed since 2007, the release rate for the
undeveloped land (pre-development) was established through using the previously
approved quantities as reported by DMW Civil Engineers (Refer to Appendix D for
supporting documentation). The historic 2-year peak runoff rate was established for
the entire project area excluding the portion of public right-of-way that contains the
front landscape area designated as Basin OS1 and excluding the off-site emergency
access drive to the north. The total establishes the overall maximum allowable release
rate, 1.1 cfs, from the on-site improvements, in which 0.8 cfs drains to the north into
Lake Street and 0.3 cfs drains to the south into Prospect Road. These release rates
were utilized in the FAA procedure detention storage computations (Refer to Appendix
B for these calculations).
3. Within the original report, it was assumed that porous concrete would not change or
generate more runoff than historic conditions. Since that time, it has been proven
that porous concrete is not a viable solution and will in fact change the characteristic
and quantity of runoff from historic conditions. Through subsurface exploration, it
was determined that the soils in this area have an infiltration rate of 0.63
inches/hour. Through the use of TrueGrid, drain rock subsection and the bio swale,
the entire area (10,820 sq. ft.) will allow infiltration. This results in an overall release
of 0.16 cfs. Infiltration will be required to drain the entire subsurface rock section
(2054.5 cu. ft.) and will completely drain in 3.5 hours. The on-site basin was
required to reduce the overall amount of runoff to be less than the combined 2-year
peak runoff rate from Basin OS1 of 0.1 cfs and the 2-year peak runoff rate from Major
Basin N of 0.8 cfs resulting in an overall release of 0.9 cfs. The detention pond
within Major Basin N was designed to over detain and release at a release rate of 0.8
cfs, leaving 0.1 cfs to be released from the off-site Basin ON1. By releasing the
developed on site basin, Basin N1, at the historic 2-year peak runoff rate and the off-
site basin, Basin ON1, at the 2-year peak runoff rate, the runoff entering into Lake
Street during the 100-year event is reduced below the current conditions.
4. The FAA method was used to size both of the ponds for quantity detention.
Calculations for the northern pond, based on the characteristics of Basin N and
adjusted release rate, indicate a detention volume of 9,688 acre-feet. In addition to
the detention volume, additional storage was supplied to include adequate Water
Quality Capture Volume (WQCV) for the overall Major Basin resulting in an overall
volume of 0.245 acre-feet. During the water quality events, additional water quality
capture volume will release into and through the permeable paver section over 12-
hours. This section is considered an infiltration section because the in-situ soils in
this area are Altvan-Satanta loam. Below is a table summarizing the results for the
northern detention pond.
North Pond 0.025 5025.710 0.22 0.25 5027.07 5028.00
Required Water
Quality Storage
(ac-ft)
Water Quality
Surface
Pond ID Elevation (ft)
High Water
Surface
Elevation (ft)
Top of Pond
Elevation (ft)
Total Detention
Volume (ac-ft)
Required 100-year
Detention Volume
(ac-ft)
Table 2 – Northern Pond Summary Table
The Slab
Final Drainage Report 12
Calculations for the southern pond, based on the characteristics of Basin S and
adjusted release rate, indicate a detention volume of 0.10 acre-feet. In addition to
the detention volume, additional storage was supplied to include adequate Water
Quality Capture Volume (WQCV) for the overall Major Basin and some assumed runoff
generate from future use of Lot 2, resulting in an overall volume of 0.12 acre-feet.
Below is a table summarizing the results for the southern detention pond. For a
conceptual analysis of future drainage patterns of Lot 2, refer to Appendix F.
South Pond 0.0116 5023.186 0.1039 0.1472 5025.72 5025.80
Required Water
Quality Storage
(ac-ft)
Water Quality
Surface
Basin ID Elevation (ft)
High Water
Surface
Elevation (ft)
Top of Pond
Elevation (ft)
Total Detention
Volume (ac-ft)
(w/ 0.0317 ac-ft
Required 100-year
Detention Volume
(ac-ft)
Table 3 – Southern Pond Summary Table
5. The emergency spillway for the northern pond will be located on the eastern wall. In
the event that emergency overflows occur, the drainage will flow into off-site bio-swale
and into Lake Street. The emergency spillway for the southern pond will be located
on the southern wall. In the event that emergency overflows occur, the drainage will
flow directly into Prospect Road.
The Slab
Final Drainage Report 13
V. CONCLUSIONS
A. Compliance with Standards
1. The drainage design proposed with The Slab project complies with the City of Fort
Collins’ Stormwater Criteria Manual. The project is requesting an exception to be
granted by the Utilities Executive Director or his designee to Section 4.15(b). The
project is proposing to use the parking area for additional detention volume with
depths that exceed the 12-inch maximum. These depths will not exceed 18-inches
within the parking area and the area exceeding 12-inches of ponding will occur within
less that twenty-five percent (25%) of the total parking spaces provided. Please see
the full-size copy of the Proposed Drainage Exhibit within Map Pocket to see the
extents of these ponding areas.
2. The drainage design proposed with The Slab 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 Slab development.
4. The drainage plan and stormwater management measures proposed with The Slab
development 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. The Slab will detain for the pervious area
converted to impervious areas by releasing all on-site areas to the 2-year existing rate
during the developed100-year storm. The off-site basin, Basin ON1, will also be
released at the existing 2-year yate during the developed 100-year event. By
releasing the developed on site basin, Basin N1, at the historic 2-year peak runoff
rate, the runoff entering into Lake Street during the 100-year event is reduced from
the current conditions.
2. The proposed Slab development will not impact the Master Drainage Plan
recommendations for the Old Town major drainage basin.
The Slab
Final Drainage Report 14
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 Report for Observatory Park Fort Collins Colorado, August 27, 2007, DMW
Civil Engineers.
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. Larimer County Urban Area Street Standards, Adopted January 2, 2001, Repealed and
Reenacted, Effective October 1, 2002, Repealed and Reenacted, Effective April 1, 2007.
5. Soils Resource Report for Larimer County Area, Colorado, Natural Resources Conservation
Service, United States Department of Agriculture.
6. Urban Storm Drainage Criteria Manual, Volumes 1-3, Urban Drainage and Flood Control
District, Wright-McLaughlin Engineers, Denver, Colorado, Revised April 2008.
The Slab
Final Drainage Report 15
APPENDIX A
HYDROLOGIC COMPUTATIONS
CHARACTER OF SURFACE:
Runoff
Coefficient
Percentage
Impervious Project: The Slab
Streets, Parking Lots, Roofs, Alleys, and Drives: Calculations By:
Asphalt ……....…………………....……….....…...……………….………………………………….0.95 . 100% Date:
Concrete …….......………….……….….……….………………..….………………………………… 0.95 90%
Gravel ……….………………..…...…….….…………………………..……………………………….0.50 . 40%
Roofs …….…….………...….....…..…..……………….…………………………………………….0.. 95 90%
TrueGrid………………………........…...………………..…………………………………………….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
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.
N1 9989 0.229 0.083 0.039 0.000 0.004 0.000 0.104 0.58 0.58 0.73 52%
N2 25067 0.575 0.332 0.050 0.152 0.000 0.000 0.041 0.89 0.89 1.00 89%
N3 8727 0.200 0.126 0.027 0.000 0.000 0.000 0.047 0.76 0.76 0.95 75%
S1 4450 0.102 0.000 0.021 0.040 0.000 0.000 0.042 0.62 0.62 0.78 53%
S2 9211 0.211 0.000 0.011 0.137 0.000 0.000 0.063 0.71 0.71 0.89 63%
S3 3403 0.078 0.017 0.034 0.021 0.000 0.000 0.006 0.89 0.89 1.00 85%
S4 3248 0.075 0.031 0.015 0.000 0.000 0.000 0.029 0.64 0.64 0.80 59%
Overland Flow, Time of Concentration:
Project: The Slab
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: The Slab
Calculations By:
Date:
From Section 3.2.1 of the CFCSDDC
Rainfall Intensity:
n1 N1 0.23 6 6 5 0.58 0.58 0.73 2.67 4.56 9.95 0.36 0.61 1.66
n2 N2 0.58 5 5 5 0.89 0.89 1.00 2.85 4.87 9.95 1.46 2.50 5.73
n3 N3 0.20 5 5 5 0.76 0.76 0.95 2.85 4.87 9.95 0.43 0.74 1.90
s1 S1 0.10 5 5 5 0.62 0.62 0.78 2.85 4.87 9.95 0.18 0.31 0.79
s2 S2 0.21 5 5 5 0.71 0.71 0.89 2.85 4.87 9.95 0.43 0.73 1.87
s3 S3 0.08 5 5 5 0.89 0.89 1.00 2.85 4.87 9.95 0.20 0.34 0.78
s4 S4 0.07 5 5 5 0.64 0.64 0.80 2.85 4.87 9.95 0.14 0.23 0.59
on ON 0.25 7 7 7 0.49 0.49 0.61 2.52 4.31 9.06 0.30 0.52 1.37
os OS 0.31 5 5 5 0.74 0.74 0.93 2.85 4.87 9.95 0.66 1.13 2.89
ow OW 0.37 11 11 11 0.34 0.34 0.43 2.17 3.71 7.57 0.27 0.47 1.20
C. Snowdon
May 3, 2016
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 Notes
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)
Q = C f ( C )( i )( A )
Page 3 of 7 D:\Projects\1033-002\Drainage\Hydrology\1033-002_Rational-Calcs.xlsx\Direct-Runoff
CHARACTER OF SURFACE:
Runoff
Coefficient
Percentage
Impervious Project: The Slab
Streets, Parking Lots, Roofs, Alleys, and Drives: Calculations By: C. Snowdon
Asphalt ……....……………...……….....…...……………….………………………………….. 0.95 100% Date: May 3, 2016
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
Design Point Basin IDs
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
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.
n1 N1-N3 43783 1.005 0.541 0.116 0.152 0.004 0.000 0.192 0.80 0.80 0.99 78%
n1 N1-N3 & OW1 59900 1.375 0.541 0.146 0.202 0.024 0.000 0.462 0.67 0.67 0.84 63%
n2 N2-N3 33794 0.776 0.458 0.077 0.152 0.000 0.000 0.088 0.86 0.86 1.00 86%
s1 S1-S4 20312 0.466 0.048 0.081 0.198 0.000 0.000 0.140 0.71 0.71 0.89 64%
s3 S3-S4 6651 0.153 0.048 0.049 0.021 0.000 0.000 0.035 0.77 0.77 0.96 73%
COMBINED DEVELOPED COMPOSITE % IMPERVIOUSNESS AND RUNOFF COEFFICIENT CALCULATIONS
**Soil Classification of site is Sandy Loam**
10-year Cf = 1.00
Overland Flow, Time of Concentration:
Project: The Slab
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)
Upstream
Time Tu
(min)
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
Rational Method Equation: Project: The Slab
Calculations By:
Date:
From Section 3.2.1 of the CFCSDDC
Rainfall Intensity:
n1 N1-N3 1.01 6 6 5 0.80 0.80 0.99 2.76 4.72 9.95 2.2 3.8 9.9
n1 N1-N3 & OW1 1.38 12 12 15 0.67 0.67 0.84 2.09 3.57 6.52 1.9 3.3 7.5
n2 N2-N3 0.78 5 5 5 0.86 0.86 1.00 2.85 4.87 9.95 1.9 3.2 7.7
s1 S1-S4 0.47 8 8 6 0.71 0.71 0.89 2.46 4.21 9.63 0.8 1.4 4.0
s2 S3-S4 0.15 5 5 5 0.77 0.77 0.96 2.85 4.87 9.95 0.3 0.6 1.5
C100
Intensity,
i2
(in/hr)
Intensity,
i10
(in/hr)
Intensity,
i100
(in/hr)
COMBINED DEVELOPED RUNOFF COMPUTATIONS
C. Snowdon
May 3, 2016
Rainfall Intensity taken from the City of Fort Collins Storm Drainage Design Criteria (CFCSDDC), Figure 3.1
Design
Point
Basin(s)
Area, A
(acres)
2-yr
Tc
(min)
10-yr
Tc
(min)
100-yr
Tc
(min)
Flow,
Q2
(cfs)
Flow,
Q10
(cfs)
Flow,
Q100
(cfs)
C2 C10
Q = C f ( C )( i )( A )
Page 6 of 7 D:\Projects\1033-002\Drainage\Hydrology\1033-002_Rational-Calcs.xlsx\Comb-Direct-Runoff
DESIGN
POINT
BASIN
ID
TOTAL
AREA
(acres)
C2 C100
2-yr
Tc
(min)
100-yr
Tc
(min)
Q2
(cfs)
Q100
(cfs)
n1 N1 0.23 0.58 0.73 6 5 0.36 1.66
n2 N2 0.58 0.89 1.00 5 5 1.46 5.73
n3 N3 0.20 0.76 0.95 5 5 0.43 1.90
s1 S1 0.10 0.62 0.78 5 5 0.18 0.79
s2 S2 0.21 0.71 0.89 5 5 0.43 1.87
s3 S3 0.08 0.89 1.00 5 5 0.20 0.78
s4 S4 0.07 0.64 0.80 5 5 0.14 0.59
on ON 0.25 0.49 0.61 7 7 0.30 1.37
os OS 0.31 0.74 0.93 5 5 0.66 2.89
ow OW 0.37 0.34 0.43 11 11 0.27 1.20
DESIGN
POINT
BASIN
ID
TOTAL
AREA
(acres)
C2 C100
2-yr
Tc
(min)
100-yr
Tc
(min)
Q2
(cfs)
Q100
(cfs)
n1 N1-N3 1.01 0.80 0.99 6 5 2.21 9.94
n1 N1-N3 & OW1 1.38 0.67 0.84 12 15 1.93 7.55
n2 N2-N3 0.78 0.86 1.00 5 5 1.90 7.72
s1 S1-S4 0.47 0.71 0.89 8 6 0.81 3.98
s3 S3-S4 0.15 0.77 0.96 5 5 0.33 1.46
Developed Runnoff Summary Table
Combined Developed Runnoff Summary Table
Page 7 of 7 D:\Projects\1033-002\Drainage\Hydrology\1033-002_Rational-Calcs.xlsx\SUMMARY-TABLE
APPENDIX B
HYDRAULIC COMPUTATIONS
B.1 – Storm Sewers
B.2 – Inlets
B.3 – Detention Facilities
APPENDIX B.1
STORM SEWERS
APPENDIX B.2
INLETS
APPENDIX B.3
DETENTION FACILITIES
Pond No :
n1
100-yr
1.00
5.00 min 9688 ft3
0.99 acres 0.22 ac-ft
Max Release Rate = 0.90 cfs
Time (min)
Ft Collins
100-yr
Intensity
(in/hr)
Inflow
Volume
(ft3)
Outflow
Adjustment
Factor
Qav
(cfs)
Outflow Volume
(ft3)
Storage
Volume
(ft3)
5 9.950 2943 1.00 0.90 270 2673
10 7.720 4567 0.75 0.68 405 4162
15 6.520 5786 0.67 0.60 540 5246
20 5.600 6626 0.63 0.56 675 5951
25 4.980 7365 0.60 0.54 810 6555
30 4.520 8022 0.58 0.53 945 7077
35 4.080 8448 0.57 0.51 1080 7368
40 3.740 8850 0.56 0.51 1215 7635
45 3.460 9211 0.56 0.50 1350 7861
50 3.230 9554 0.55 0.50 1485 8069
55 3.030 9859 0.55 0.49 1620 8239
60 2.860 10152 0.54 0.49 1755 8397
65 2.720 10459 0.54 0.48 1890 8569
70 2.590 10726 0.54 0.48 2025 8701
75 2.480 11004 0.53 0.48 2160 8844
80 2.380 11264 0.53 0.48 2295 8969
85 2.290 11515 0.53 0.48 2430 9085
90 2.210 11767 0.53 0.48 2565 9202
95 2.130 11971 0.53 0.47 2700 9271
100 2.060 12187 0.53 0.47 2835 9352
105 2.000 12424 0.52 0.47 2970 9454
110 1.940 12625 0.52 0.47 3105 9520
115 1.890 12858 0.52 0.47 3240 9618
120 1.840 13063 0.52 0.47 3375 9688
*Note: Using the method described in Urban Storm Drainage Criteria Manual Volume 2.
A =
Tc =
Project Location :
Design Point
C =
Design Storm
DETENTION POND CALCULATION; MODIFIED FAA METHOD w/ Ft Collins IDF
Input Variables Results
Required Detention Volume
Fort Collins, Colorado
Project Title Date:
Project Number Calcs By:
Client
Pond Designation
1
WQCV = Watershed inches of Runoff (inches) 66.00%
a = Runoff Volume Reduction (constant)
i = Total imperviousness Ratio (i = Iwq/100) 0.258 in
A = 0.99 ac
V = 0.0254 ac-ft
V = Water Quality Design Volume (ac-ft)
WQCV = Water Quality Capture Volume (inches)
A = Watershed Area (acres)
1.2 = 20% Additional Volume (Sediment Accumulation)
The Slab March 5, 2016
1033-002 C. Snowdon
Maxiiimo
North Pond
Drain Time
a =
i =
WQCV =
Figure EDB-2 - Water Quality Capture Volume (WQCV), 80th Percentile Runoff Event
0.258
0
0.05
0.1
0.15
0.2
0.25
0.3
0.35
0.4
0.45
0.5
0.00
0.10
0.20
0.30
0.40
0.50
0.60
0.70
0.80
0.90
1.00
WQCV (watershed inches)
Total Imperviousness Ratio (i = Iwq/100)
Water Quality Capture Volume
6 hr
12 hr
24 hr
40 hr
WQCV = a ( 0.91 i 3 - 1 . 19 i 2 + 0 . 78 i )
WQCV = a ( 0.91 i 3 - 1 . 19 i 2 + 0 . 78 i )
* * 1 . 2
12
V WQCV A
÷
ø
Project Title Date:
Project Number Calcs By:
Client
Pond Designation
Invert Elevation
Water Quality Volume
100-yr Detention Volume
Total Pond Volume
Min Sc
D = Depth between contours (ft.)
A1 = Surface Area lower contour (ft2) t
A2 = Surface Area upper contour (ft2) Area/Row
No. of Rows
5025.00 277.25 0.17 15.71 15.71 0.0004
5025.20 1033.62 0.20 123.08 138.79 0.0032
5025.40 1757.84 0.20 275.96 414.75 0.0095
5025.60 2254.05 0.20 400.16 814.91 0.0187
5025.80 3102.87 0.20 533.44 1348.35 0.0310 WQCV
5026.00 3868.57 0.20 695.74 2044.09 0.0469
5026.20 5303.53 0.20 913.45 2957.53 0.0679
5026.40 8308.12 0.20 1349.97 4307.51 0.0989
5026.60 11315.55 0.20 1954.64 6262.14 0.1438
5026.80 14530.71 0.20 2577.93 8840.08 0.2029
5027.00 17725.19 0.20 3220.30 12060.38 0.2769 100-yr Vol
5027.20 21189.39 0.20 3886.31 15946.69 0.3661 Total Vol
5027.40 25256.73 0.20 4638.66 20585.36 0.4726
5027.60 21867.81 0.20 4708.39 25293.74 0.5807
5027.80 24284.52 0.20 4613.12 29906.86 0.6866
5028.00 14440.00 0.20 3830.04 33736.91 0.7745
Elevation Depth Volume
WQCV 5025.71 0.88 0.0254
100-yr Detention 5026.85 2.02 0.2200
Overall Detention 5027.07 2.24 0.3081
Maxiiimo
The Slab March 5, 2016
1033-002 C. Snowdon
North Pond
5024.83 ft
0.0254 ac-ft
0.2200 ac-ft Circular Perforation Sizing
2
0.2454 ac-ft Dia (in.)
n
1/4
0.08
Required Area
Per Row 0.130 sq-in
2
Total Outlet
Area 0.16 sq. in.
North Pond Volume
Elevation
(ft)
Surface
Area (ft2)
Incremental
Depth (ft)
Incremental
Vol. (ft3)
Total Vol.
Project Title Date:
Project Number Calcs By:
Client
Pond Designation
Q = 0.90 cfs
C = 0.621
Q = Release Rate (cfs) Eh = 5027.07 ft
C = Discharge Coefficients (unitless) Ei = 5024.83 ft
Aa = Area Allowed of Opening (ft2)
g = Gravity (32.2 ft/s2) 0.120665 ft2
Eh = High Water Surface Elevation (ft) 17.37571 in2
Ei = Elevation of Outlet Invert (ft)
H = Height of Opening (in.)
R = Inner Radius of Outfall Pipe (in.)
Δ = Top of Plate to Center of Pipe (in.)
S = Arc Length of Open Area (in.)
Ac = Area of Opening (in2)
θ = Angle of Plate on Pipe to Center Pipe (radians)
Calculated Area of Opening (Ac)
Design Height of Opening (H)
Proposed Outfall Pipe Diameter
2.94 sq. in.
C. Snowdon
March 5, 2016
Aa =
3/4 in
12 in
Maxiiimo
1033-002
The Slab
North Pond
[ ( ( ) ) ]
2
2
R
Sin S
R
R S
K
-
=
Q = CA 2 g ( E h - E i )
S = R q
( ) Cos ( R )
Cos R
D ® = D
2 = 2 -1
q q
Ac = p R 2 - K
Project Title Date:
Project Number Calcs By:
Client
Pond Designation
Q = 0.90 cfs
C = 0.65
Q = Release Rate (cfs) Eh = 5027.07 ft
C = Discharge Coefficients (unitless) Ei = 5024.83 ft
Aa = Area Allowed of Opening (ft2) Ec = 5025.02 ft Circular
g = Gravity (32.2 ft/s2) Ec = 5025.00 ft Rectangular
Eh = High Water Surface Elevation (ft)
Ei = Elevation of Outlet Invert (ft) 0.115281169 ft2
Ec = Elevation of Outlet Centroid (ft) 16.600488 in2
Orifice Size (in.) 4 -19/32 in.
Area (in2) 16.60 sq-in
Q 0.86 cfs
Orifice Height (in.) 4 - 1/8 in.
Orifice Width (in.) 4 in.
Area (in2) 16.60 sq-in
Q 0.86 cfs
Circular Orifice
100-Year Orifice
Rectangular Orifice
100-Year Orifice
The Slab March 5, 2016
1033-002 C. Snowdon
Maxiiimo
North Pond
Aa =
Required Water Quality Storage (ac-ft) 0.03
Water Quality Surface Elevation (ft) 5025.71
North Pond 0.025 5025.710 0.22 0.25 5027.07 5028.00 Required 100-year Detention Volume (ac-ft) 0.22
Total Detention Volume (ac-ft) 0.25
High Water Surface Elevation (ft) 5027.07
Top of Pond Elevation (ft) 5028.00
Required Water
Quality Storage
(ac-ft)
Water Quality
Surface
Pond ID Elevation (ft)
High Water
Surface Elevation
(ft)
Top of Pond
Elevation (ft)
Detention Pond Summary
Total Detention
Volume (ac-ft)
Required 100-year
Detention Volume
(ac-ft)
Pond No :
s1
100-yr
0.88
5.60 min 4524 ft3
0.49 acres 0.10 ac-ft
Max Release Rate = 0.30 cfs
Time (min)
Ft Collins
100-yr
Intensity
(in/hr)
Inflow
Volume
(ft3)
Outflow
Adjustment
Factor
Qav
(cfs)
Outflow Volume
(ft3)
Storage
Volume
(ft3)
5 9.950 1274 1.00 0.30 90 1184
10 7.720 1977 0.78 0.23 140 1837
15 6.520 2504 0.69 0.21 185 2319
20 5.600 2868 0.64 0.19 230 2638
25 4.980 3188 0.61 0.18 275 2913
30 4.520 3472 0.59 0.18 320 3152
35 4.080 3657 0.58 0.17 365 3291
40 3.740 3831 0.57 0.17 410 3421
45 3.460 3987 0.56 0.17 455 3532
50 3.230 4136 0.56 0.17 500 3635
55 3.030 4268 0.55 0.17 545 3722
60 2.860 4394 0.55 0.16 590 3804
65 2.720 4527 0.54 0.16 635 3892
70 2.590 4643 0.54 0.16 680 3962
75 2.480 4763 0.54 0.16 725 4038
80 2.380 4876 0.54 0.16 770 4105
85 2.290 4985 0.53 0.16 815 4169
90 2.210 5093 0.53 0.16 860 4233
95 2.130 5182 0.53 0.16 905 4276
100 2.060 5275 0.53 0.16 950 4325
105 2.000 5378 0.53 0.16 995 4382
110 1.940 5465 0.53 0.16 1040 4424
115 1.890 5566 0.52 0.16 1085 4480
120 1.840 5654 0.52 0.16 1130 4524
*Note: Using the method described in Urban Storm Drainage Criteria Manual Volume 2.
DETENTION POND CALCULATION; MODIFIED FAA METHOD w/ Ft Collins IDF
Input Variables Results
Required Detention Volume
Fort Collins, Colorado
1033-002
The Slab
Project Number :
Project Name :
South Pond
A =
Project Title Date:
Project Number Calcs By:
Client
Pond Designation
1
WQCV = Watershed inches of Runoff (inches) 60.00%
a = Runoff Volume Reduction (constant)
i = Total imperviousness Ratio (i = Iwq/100) 0.236 in
A = 0.49 ac
V = 0.0116 ac-ft
V = Water Quality Design Volume (ac-ft)
WQCV = Water Quality Capture Volume (inches)
A = Watershed Area (acres)
1.2 = 20% Additional Volume (Sediment Accumulation)
The Slab May 3, 2016
1033-002 C. Snowdon
Maxiiimo
South Pond
Drain Time
a =
i =
WQCV =
Figure EDB-2 - Water Quality Capture Volume (WQCV), 80th Percentile Runoff Event
0.236
0
0.05
0.1
0.15
0.2
0.25
0.3
0.35
0.4
0.45
0.5
0.00
0.10
0.20
0.30
0.40
0.50
0.60
0.70
0.80
0.90
1.00
WQCV (watershed inches)
Total Imperviousness Ratio (i = Iwq/100)
Water Quality Capture Volume
6 hr
12 hr
24 hr
40 hr
WQCV = a ( 0.91 i 3 - 1 . 19 i 2 + 0 . 78 i )
WQCV = a ( 0.91 i 3 - 1 . 19 i 2 + 0 . 78 i )
* * 1 . 2
12
V WQCV A
÷
ø
Project Title Date:
Project Number Calcs By:
Client
Pond Designation
Invert Elevation
Water Quality Volume
100-yr Detention Volume
Min Sc
D = Depth between contours (ft.)
A1 = Surface Area lower contour (ft2) t
A2 = Surface Area upper contour (ft2) Area/Row
No. of Rows
5022.60 67.03 0.12 2.68 2.68 0.0001
5022.80 474.51 0.20 47.99 50.67 0.0012
5023.00 1230.74 0.20 164.63 215.30 0.0049
5023.20 1925.36 0.20 313.03 528.33 0.0121 WQCV
5023.40 2226.46 0.20 414.82 943.15 0.0217
5023.60 2358.58 0.20 458.44 1401.59 0.0322
5023.80 2358.83 0.20 471.74 1873.33 0.0430
5024.00 2359.07 0.20 471.79 2345.12 0.0538
5024.20 2359.32 0.20 471.84 2816.96 0.0647
5024.40 2359.57 0.20 471.89 3288.85 0.0755
5024.60 2359.82 0.20 471.94 3760.79 0.0863
5024.80 2360.07 0.20 471.99 4232.78 0.0972
5025.00 2360.32 0.20 472.04 4704.82 0.1080 100-yr Vol
5025.20 2360.57 0.20 472.09 5176.91 0.1188
5025.40 2360.82 0.20 472.14 5649.05 0.1297
5025.60 2361.07 0.20 472.19 6121.23 0.1405
5025.80 2361.33 0.20 472.24 6593.47 0.1514 Total Vol
Elevation Depth Volume
WQCV 5023.19 0.71 0.0116
100-yr Detention 5024.92 2.44 0.1039
Overall Detention 5025.72 3.24 0.1472
Maxiiimo
The Slab May 3, 2016
1033-002 C. Snowdon
South Pond
5022.48 ft
0.0116 ac-ft
0.1039 ac-ft Circular Perforation Sizing
1
0.1472 ac-ft Dia (in.)
Total Pond Volume (w/ Additional
0.0317 ac-ft assumed for Lot 1)
n
1/4
0.05
Required Area
Per Row 0.067 sq-in
2
Total Outlet
Area 0.10 sq. in.
South Pond Volume
Elevation
(ft)
Surface
Area (ft2)
Incremental
Depth (ft)
Incremental
Project Title Date:
Project Number Calcs By:
Client
Pond Designation
Q = 0.30 cfs
C = 0.65
Q = Release Rate (cfs) Eh = 5025.72 ft
C = Discharge Coefficients (unitless) Ei = 5022.48 ft
Aa = Area Allowed of Opening (ft2)
g = Gravity (32.2 ft/s2) 0.031938 ft2
Eh = High Water Surface Elevation (ft) 4.599105 in2
Ei = Elevation of Outlet Invert (ft)
H = Height of Opening (in.)
R = Inner Radius of Outfall Pipe (in.)
Δ = Top of Plate to Center of Pipe (in.)
S = Arc Length of Open Area (in.)
Ac = Area of Opening (in2)
θ = Angle of Plate on Pipe to Center Pipe (radians)
Calculated Area of Opening (Ac)
Design Height of Opening (H)
Proposed Outfall Pipe Diameter
4.50 sq. in.
C. Snowdon
May 3, 2016
Aa =
1 in
12 in
Maxiiimo
1033-002
The Slab
South Pond
[ ( ( ) ) ]
2
2
R
Sin S
R
R S
K
-
=
Q = CA 2 g ( E h - E i )
S = R q
( ) Cos ( R )
Cos R
D ® = D
2 = 2 -1
q q
Ac = p R 2 - K
Project Title Date:
Project Number Calcs By:
Client
Pond Designation
Q = 0.30 cfs
C = 0.65
Q = Release Rate (cfs) Eh = 5025.72 ft
C = Discharge Coefficients (unitless) Ei = 5022.48 ft
Aa = Area Allowed of Opening (ft2) Ec = 5022.59 ft Circular
g = Gravity (32.2 ft/s2) Ec = 5022.56 ft Rectangular
Eh = High Water Surface Elevation (ft)
Ei = Elevation of Outlet Invert (ft) 0.031938232 ft2
Ec = Elevation of Outlet Centroid (ft) 4.599105 in2
Orifice Size (in.) 2 -17/32 in.
Area (in2) 5.08 sq-in
Q 0.33 cfs
Orifice Height (in.) 2 - 1/16 in.
Orifice Width (in.) 2 - 1/2 in.
Area (in2) 5.08 sq-in
Q 0.33 cfs
Circular Orifice
100-Year Orifice
Rectangular Orifice
100-Year Orifice
The Slab May 3, 2016
1033-002 C. Snowdon
Maxiiimo
South Pond
Aa =
South Pond 0.0116 5023.186 0.1039 0.1472 5025.72 5025.80
Required Water
Quality Storage
(ac-ft)
Water Quality
Surface
Basin ID Elevation (ft)
High Water
Surface Elevation
(ft)
Top of Pond
Elevation (ft)
Total Detention
Volume (ac-ft)
(w/ 0.0317 ac-ft
Required 100-year
Detention Volume
(ac-ft)
Pond No :
n1
100-yr
0.61
7.00 min 1639 ft3
0.25 acres 0.04 ac-ft
Max Release Rate = 0.10 cfs
Time (min)
Ft Collins
100-yr
Intensity
(in/hr)
Inflow
Volume
(ft3)
Outflow
Adjustment
Factor
Qav
(cfs)
Outflow Volume
(ft3)
Storage
Volume
(ft3)
5 9.950 455 1.00 0.10 30 425
10 7.720 706 0.85 0.09 51 655
15 6.520 895 0.73 0.07 66 829
20 5.600 1025 0.68 0.07 81 944
25 4.980 1139 0.64 0.06 96 1043
30 4.520 1241 0.62 0.06 111 1130
35 4.080 1307 0.60 0.06 126 1181
40 3.740 1369 0.59 0.06 141 1228
45 3.460 1425 0.58 0.06 156 1269
50 3.230 1478 0.57 0.06 171 1307
55 3.030 1525 0.56 0.06 186 1339
60 2.860 1570 0.56 0.06 201 1369
65 2.720 1618 0.55 0.06 216 1402
70 2.590 1659 0.55 0.06 231 1428
75 2.480 1702 0.55 0.05 246 1456
80 2.380 1742 0.54 0.05 261 1481
85 2.290 1781 0.54 0.05 276 1505
90 2.210 1820 0.54 0.05 291 1529
95 2.130 1852 0.54 0.05 306 1546
100 2.060 1885 0.54 0.05 321 1564
105 2.000 1922 0.53 0.05 336 1586
110 1.940 1953 0.53 0.05 351 1602
115 1.890 1989 0.53 0.05 366 1623
120 1.840 2020 0.53 0.05 381 1639
*Note: Using the method described in Urban Storm Drainage Criteria Manual Volume 2.
A =
Tc =
Project Location :
Design Point
C =
Design Storm
DETENTION POND CALCULATION; MODIFIED FAA METHOD w/ Ft Collins IDF
Input Variables Results
Required Detention Volume
Fort Collins, Colorado
Project Title Date:
Project Number Calcs By:
Client
Pond Designation
0.8
WQCV = Watershed inches of Runoff (inches) 33.00%
a = Runoff Volume Reduction (constant)
i = Total imperviousness Ratio (i = Iwq/100) 0.128 in
A = 0.25 ac
V = 0.0032 ac-ft
V = Water Quality Design Volume (ac-ft)
WQCV = Water Quality Capture Volume (inches)
A = Watershed Area (acres)
1.2 = 20% Additional Volume (Sediment Accumulation)
Drain Time
a =
i =
WQCV =
Figure EDB-2 - Water Quality Capture Volume (WQCV), 80th Percentile Runoff Event
The Slab May 3, 2016
1033-002 C. Snowdon
Maxiiimo
Emergency Access Drive
0.128
0
0.05
0.1
0.15
0.2
0.25
0.3
0.35
0.4
0.45
0.5
0.00
0.10
0.20
0.30
0.40
0.50
0.60
0.70
0.80
0.90
1.00
WQCV (watershed inches)
Total Imperviousness Ratio (i = Iwq/100)
Water Quality Capture Volume
6 hr
12 hr
24 hr
40 hr
WQCV = a ( 0.91 i 3 - 1 . 19 i 2 + 0 . 78 i )
WQCV = a ( 0.91 i 3 - 1 . 19 i 2 + 0 . 78 i )
* * 1 . 2
12
V WQCV A
÷
ø
Project Title Date:
Project Number Calcs By:
Client
Pond Designation
Invert Elevation
Water Quality Volume
100-yr Detention Volume
Total Pond Volume
Total Adjusted
Volume
5,021.82 0.08 N/A N/A 0 0 N/A N/A N/A 0 0
5,021.92 517.34 0.1 25.87 17.46 6.984 N/A N/A N/A 0 6.984
5,022.02 1,155.88 0.1 83.66 99.01 39.604 N/A N/A N/A 0 39.604
5,022.12 1,794.76 0.1 147.53 245.38 98.152 N/A N/A N/A 0 98.152
5,022.22 2,433.99 0.1 211.44 456 182.4 N/A N/A N/A 0 182.4
5,022.32 3,026.56 0.1 273.03 728.49 291.396 N/A N/A N/A 0 291.396
5,022.42 3,347.72 0.1 318.71 1047.07 418.828 N/A N/A N/A 0 418.828
5,022.52 3,667.69 0.1 350.77 1397.72 559.088 N/A N/A N/A 0 559.088
5,022.62 3,987.79 0.1 382.77 1780.38 712.152 N/A N/A N/A 0 712.152
5,022.72 4,308.03 0.1 414.79 2195.07 878.028 N/A N/A N/A 0 878.028
5,022.82 4,628.42 0.1 446.82 2641.8 1056.72 N/A N/A N/A 0 1056.72
5,022.92 4,948.96 0.1 478.87 3120.58 1248.232 N/A N/A N/A 0 1248.232
5,023.02 5,051.14 0.1 500.01 3620.58 1448.232 N/A N/A N/A 0 1448.232
5,023.12 5,051.92 0.1 505.15 4125.73 1650.292 N/A N/A N/A 0 1650.292
5,023.22 5,052.69 0.1 505.23 4630.96 1852.384 N/A N/A N/A 0 1852.384
5,023.32 5,053.47 0.1 505.31 5136.27 2054.508 N/A N/A N/A 0 2054.508
2020 cu. ft.
Total Volume
(ft3)
Total Vol.
(ft3)
Paver Volume
2020 cu. ft.
Surface
Area (ft2)
May 3, 2016
C. Snowdon
Surface Volume
Incremental
Depth (ft)
Incremental
Vol. (ft3)
1033-002
Maxiiimo
Emergency Access Drive
139 cu. ft.
5021.82 ft
The Slab
Elevation
(ft)
Surface
Area (ft2)
Incremental
Depth (ft)
Incremental
Vol. (ft3)
Total Vol.
100% Capacity(ft3)
Total Vol.
40% Capacity(ft3)
B 138.719 0.003 2020.00
Basin ID
Pond Volume
(cu. ft.)
Provided Water
Quality (ac-ft)
Required Water
Quality Storage
(ac-ft)
APPENDIX C
WATER QUALITY DESIGN COMPUTATIONS
1008
Project Title Date:
Project Number Calcs By:
Client
Basins
0.8
WQCV = Watershed inches of Runoff (inches) 86.00%
a = Runoff Volume Reduction (constant)
i = Total imperviousness Ratio (i = Iwq/100) 0.296 in
A = 0.78 ac
V = 0.0191 ac-ft
V = Water Quality Design Volume (ac-ft)
WQCV = Water Quality Capture Volume (inches)
A = Watershed Area (acres)
Lake Street Apartments May 3, 2016
1232-001 C. Snowdon
Basins N2 & N3
833 cu. ft.
Drain Time
a =
i =
WQCV =
Figure EDB-2 - Water Quality Capture Volume (WQCV), 80th Percentile Runoff Event
0.296
0
0.05
0.1
0.15
0.2
0.25
0.3
0.35
0.4
0.45
0.5
0.00
0.10
0.20
0.30
0.40
0.50
0.60
0.70
0.80
0.90
1.00
WQCV (watershed inches)
Total Imperviousness Ratio (i = Iwq/100)
Water Quality Capture Volume
6 hr
12 hr
24 hr
40 hr
WQCV = a ( 0.91 i 3 - 1 . 19 i 2 + 0 . 78 i )
WQCV = a ( 0.91 i 3 - 1 . 19 i 2 + 0 . 78 i )
V * A
12
WQCV
÷
ø
Project:
Chamber Model - SC-160
Units - Imperial
100
Number of chambers - 56
Voids in the stone (porosity) - 40 %
Base of STONE Elevation - 0.00 ft
Amount of Stone Above Chambers - 6 in
Amount of Stone Below Chambers - 4 in
Height of
System
Incremental Single
Chamber
Incremental
Total Chamber
Incremental
Stone
Incremental Ch
& St
Cumulative
Chamber Elevation
(inches) (cubic feet) (cubic feet) (cubic feet) (cubic feet) (cubic feet) (feet)
22 0.00 0.00 27.68 27.68 839.15 1.83
21 0.00 0.00 27.68 27.68 811.48 1.75
20 0.00 0.00 27.68 27.68 783.80 1.67
19 0.00 0.00 27.68 27.68 756.12 1.58
18 0.00 0.00 27.68 27.68 728.45 1.50
17 0.00 0.00 27.68 27.68 700.77 1.42
16 0.05 2.87 26.53 29.40 673.10 1.33
15 0.13 7.53 24.66 32.19 643.70 1.25
14 0.29 16.27 21.17 37.44 611.51 1.17
13 0.44 24.75 17.78 42.52 574.07 1.08
12 0.54 30.19 15.60 45.79 531.54 1.00
11 0.62 34.51 13.87 48.38 485.75 0.92
10 0.68 38.12 12.43 50.55 437.37 0.83
9 0.74 41.21 11.19 52.40 386.82 0.75
8 0.78 43.87 10.13 54.00 334.41 0.67
7 0.82 46.19 9.20 55.39 280.42 0.58
6 0.86 48.18 8.40 56.58 225.02 0.50
5 0.89 50.10 7.64 57.74 168.44 0.42
4 0.00 0.00 27.68 27.68 110.70 0.33
3 0.00 0.00 27.68 27.68 83.03 0.25
2 0.00 0.00 27.68 27.68 55.35 0.17
1 0.00 0.00 27.68 27.68 27.68 0.08
StormTech SC-160 Cumulative Storage Volumes
The Slab - Basins N2 & N3
Include Perimeter Stone in Calculations
Click Here for Metric
1008
Project Title Date:
Project Number Calcs By:
Client
Basins
0.8
WQCV = Watershed inches of Runoff (inches) 73.00%
a = Runoff Volume Reduction (constant)
i = Total imperviousness Ratio (i = Iwq/100) 0.231 in
A = 0.15 ac
V = 0.0030 ac-ft
V = Water Quality Design Volume (ac-ft)
WQCV = Water Quality Capture Volume (inches)
A = Watershed Area (acres)
129 cu. ft.
Drain Time
a =
i =
WQCV =
Figure EDB-2 - Water Quality Capture Volume (WQCV), 80th Percentile Runoff Event
Lake Street Apartments May 3, 2016
1232-001 C. Snowdon
Basins S3 & S4
0.231
0
0.05
0.1
0.15
0.2
0.25
0.3
0.35
0.4
0.45
0.5
0.00
0.10
0.20
0.30
0.40
0.50
0.60
0.70
0.80
0.90
1.00
WQCV (watershed inches)
Total Imperviousness Ratio (i = Iwq/100)
Water Quality Capture Volume
6 hr
12 hr
24 hr
40 hr
WQCV = a ( 0.91 i 3 - 1 . 19 i 2 + 0 . 78 i )
WQCV = a ( 0.91 i 3 - 1 . 19 i 2 + 0 . 78 i )
V * A
12
WQCV
÷
ø
Project:
Chamber Model - SC-160
Units - Imperial
100
Number of chambers - 10
Voids in the stone (porosity) - 40 %
Base of STONE Elevation - 0.00 ft
Amount of Stone Above Chambers - 6 in
Amount of Stone Below Chambers - 4 in
Height of
System
Incremental Single
Chamber
Incremental
Total Chamber
Incremental
Stone
Incremental Ch
& St
Cumulative
Chamber Elevation
(inches) (cubic feet) (cubic feet) (cubic feet) (cubic feet) (cubic feet) (feet)
22 0.00 0.00 4.94 4.94 149.85 1.83
21 0.00 0.00 4.94 4.94 144.91 1.75
20 0.00 0.00 4.94 4.94 139.96 1.67
19 0.00 0.00 4.94 4.94 135.02 1.58
18 0.00 0.00 4.94 4.94 130.08 1.50
17 0.00 0.00 4.94 4.94 125.14 1.42
16 0.05 0.51 4.74 5.25 120.20 1.33
15 0.13 1.34 4.40 5.75 114.95 1.25
14 0.29 2.91 3.78 6.69 109.20 1.17
13 0.44 4.42 3.17 7.59 102.51 1.08
12 0.54 5.39 2.79 8.18 94.92 1.00
11 0.62 6.16 2.48 8.64 86.74 0.92
10 0.68 6.81 2.22 9.03 78.10 0.83
9 0.74 7.36 2.00 9.36 69.07 0.75
8 0.78 7.83 1.81 9.64 59.72 0.67
7 0.82 8.25 1.64 9.89 50.07 0.58
6 0.86 8.60 1.50 10.10 40.18 0.50
5 0.89 8.95 1.36 10.31 30.08 0.42
4 0.00 0.00 4.94 4.94 19.77 0.33
3 0.00 0.00 4.94 4.94 14.83 0.25
2 0.00 0.00 4.94 4.94 9.88 0.17
1 0.00 0.00 4.94 4.94 4.94 0.08
StormTech SC-160 Cumulative Storage Volumes
The Slab - Basins S3 & S4
Include Perimeter Stone in Calculations
Click Here for Metric
Sheet 1 of 1
Designer:
Company:
Date:
Project:
Location:
1. Design Discharge for 2-Year Return Period Q2 = 0.43 cfs
2. Hydraulic Residence Time
A) : Length of Grass Swale LS = 124.0 ft
B) Calculated Residence Time (based on design velocity below) THR= 3.1 minutes
3. Longitudinal Slope (vertical distance per unit horizontal)
A) Available Slope (based on site constraints) Savail = 0.010 ft / ft
B) Design Slope SD = 0.010 ft / ft
4. Swale Geometry
A) Channel Side Slopes (Z = 4 min., horiz. distance per unit vertical) Z = 4.00 ft / ft
B) Bottom Width of Swale (enter 0 for triangular section) WB = 0.00 ft
5. Vegetation
A) Type of Planting (seed vs. sod, affects vegetal retardance factor)
6. Design Velocity (0.413 ft / s maximum for desirable 5-minute residence time) V2 = 0.67 ft / s
7. Design Flow Depth (1 foot maximum) D2 = 0.40 ft
A) Flow Area A2 = 0.6 sq ft
B) Top Width of Swale WT = 3.2 ft
C) Froude Number (0.50 maximum) F = 0.26
D) Hydraulic Radius RH = 0.19
E) Velocity-Hydraulic Radius Product for Vegetal Retardance VR = 0.13
F) Manning's n (based on SCS vegetal retardance curve E for seeded grass) n = 0.073
G) Cumulative Height of Grade Control Structures Required HD = 0.00 ft
AN UNDERDRAIN IS
8. Underdrain REQUIRED IF THE
(Is an underdrain necessary?) DESIGN SLOPE < 2.0%
9. Soil Preparation
(Describe soil amendment)
10. Irrigation
Notes:
Bio-Swale Soil Media
Design Procedure Form: Grass Swale (GS)
C. Snowdon
Northern Engineering
May 3, 2016
The Slab
Basin S2
Choose One
Temporary Permanent
Choose One
Grass From Seed Grass From Sod
Choose One
YES NO
Basin S2 - Grass Swale UD-BMP_v3.03.xlsm, GS 5/3/2016, 7:33 AM
Design
Point Basin ID Basin Area Treatment Type
LID
System
Area Treated
by LID
System
Percent of Site
Treated by LID
System
Area of
Pavers
Area of
Aphalt
Parking
Percent
Pavers
Run-on Area
for Paver
Section
Run-on Area
Ratio (3:1
Max)
n1 N1 0.230 ac. Bio-Swale
(Off-Site) Yes 0.230 ac. 13% 0.000 ac. 0.083 ac. N/A N/A
n2 N2 & N3 0.780 ac. StormTech
Chambers Yes 0.780 ac. 45% 0.000 ac. 0.458 ac. N/A N/A
s1 S1 0.100 ac. Extended Detention No N/A 0% 0.000 ac. 0.000 ac. N/A N/A
s2 S2 0.210 ac. Bio-Swale Yes 0.210 ac. 12% 0.000 ac. 0.000 ac. N/A N/A
s3 S3 & S4 0.150 ac. StormTech
Chambers Yes 0.150 ac. 9% 0.000 ac. 0.048 ac. N/A N/A
on ON1 0.250 ac. TrueGrid Retention
Section Yes 0.250 ac. 15% 0.000 ac. 0.000 ac. N/A N/A
Total 1.720 ac. 1.620 ac. 94% 0.000 ac. 0.589 ac. 0.00%
APPENDIX D
Select Information from Previous Analysis
APPENDIX E
EROSION CONTROL REPORT
This unofficial copy was downloaded on Mar-02-2015 from the City of Fort Collins Public Records Website: http://citydocs.fcgov.com
For additional information or an official copy, please contact City of Fort Collins Utilities 700 Wood Street Fort Collins, CO 80524 USA
This unofficial copy was downloaded on Mar-02-2015 from the City of Fort Collins Public Records Website: http://citydocs.fcgov.com
For additional information or an official copy, please contact City of Fort Collins Utilities 700 Wood Street Fort Collins, CO 80524 USA
This unofficial copy was downloaded on Mar-02-2015 from the City of Fort Collins Public Records Website: http://citydocs.fcgov.com
For additional information or an official copy, please contact City of Fort Collins Utilities 700 Wood Street Fort Collins, CO 80524 USA
This unofficial copy was downloaded on Mar-02-2015 from the City of Fort Collins Public Records Website: http://citydocs.fcgov.com
For additional information or an official copy, please contact City of Fort Collins Utilities 700 Wood Street Fort Collins, CO 80524 USA
This unofficial copy was downloaded on Mar-02-2015 from the City of Fort Collins Public Records Website: http://citydocs.fcgov.com
For additional information or an official copy, please contact City of Fort Collins Utilities 700 Wood Street Fort Collins, CO 80524 USA
This unofficial copy was downloaded on Mar-02-2015 from the City of Fort Collins Public Records Website: http://citydocs.fcgov.com
For additional information or an official copy, please contact City of Fort Collins Utilities 700 Wood Street Fort Collins, CO 80524 USA
This unofficial copy was downloaded on Mar-02-2015 from the City of Fort Collins Public Records Website: http://citydocs.fcgov.com
For additional information or an official copy, please contact City of Fort Collins Utilities 700 Wood Street Fort Collins, CO 80524 USA
This unofficial copy was downloaded on Mar-02-2015 from the City of Fort Collins Public Records Website: http://citydocs.fcgov.com
For additional information or an official copy, please contact City of Fort Collins Utilities 700 Wood Street Fort Collins, CO 80524 USA
This unofficial copy was downloaded on Mar-02-2015 from the City of Fort Collins Public Records Website: http://citydocs.fcgov.com
For additional information or an official copy, please contact City of Fort Collins Utilities 700 Wood Street Fort Collins, CO 80524 USA
APPENDIX E
NRCS Soils Report
400 North Link Lane | Fort Collins, Colorado 80524
Telephone: 970-206-9455 Fax: 970-206-9441
March 9, 2016
Maxiiimo Development Group
706 South College Avenue
Fort Collins, Colorado 80524
Attn: Christian Bachelet
Subject: Subsurface Investigation and
Hydraulic Conductivity Testing
808 West Prospect Road
Fort Collins, Colorado
CTL|T Project Number: FC07161-125
CTL|Thompson, Inc. has conducted a subsurface investigation and hydraulic
conductivity testing at 808 West Prospect Road. The purpose of our investigation was to
determine relevant soil and infiltration characteristics at the project location to inform
possible construction of a dry well drain system. This letter presents the results of our
investigation.
Subsurface Investigation
Our investigation included drilling three exploratory borings and six hydraulic
conductivity test holes at the locations shown on Figure 1. Our exploratory borings were
drilled to a depth of approximately 20 feet. Hydraulic conductivity test holes were drilled
to depths between 7½ and 15 feet as needed to test different soil layers. The hydraulic
conductivity test holes were fitted with slotted PVC pipes to facilitate testing. A
representative from our firm observed drilling, logged the soils encountered and
collected samples. Samples were taken at 2½ to 5 foot intervals by driving a 2.5-inch
O.D. modified California sampler 12 inches. This method is similar to the standard
penetration test and is typical of local practice. Summary logs of the borings, including
results of field penetration testing, are shown on Figure 2.
Samples were return to our laboratory and examined by the geotechnical
engineer for this project. Laboratory tests were assigned, including moisture content, dry
density, gradation and Atterberg limits tests to classify the soils. Results of laboratory
tests are given on Figure 3 and summarized in Table 1.
Subsurface Conditions
Soils encountered in our borings consisted of 12 to 20 feet of sandy clay with
layers of clayey sand overlying cleaner sands with occasional gravel. The upper 1 to 2
feet of material in all three borings was identified as probable fill. Groundwater was
encountered in one boring during drilling at a depth of 19 feet, and was measured in two
borings several days after drilling at depths of 18½ and 19 feet.
0
5
10
15
20
25
30
35
40
0
5
10
15
20
25
30
35
40
17/12
19/12
17/12
14/12
16/12
17/12
WC=78.0
DD=114
LL=32 PI=15
-200=78
WC=5.6
-200=15
WC=78.0
DD=114
LL=32 PI=15
-200=78
WC=5.6
-200=15
TH-1
10/12
11/12
14/12
13/12
19/12
11/12
WC=18.3
DD=110
LL=32 PI=15
-200=69
WC=5.7
-200=15
WC=18.3
DD=110
LL=32 PI=15
-200=69
WC=5.7
-200=15
TH-2
14/12
19/12
14/12
16/12
Sample of SAND, CLAYEY (SC) GRAVEL 8 % SAND 77
%
From TH - 1 AT 14 FEET SILT & CLAY 15 % LIQUID LIMIT %
PLASTICITY INDEX %
Sample of SAND, CLAYEY, GRAVELLY (SC) GRAVEL 11 % SAND 74
%
From TH - 2 AT 14 FEET SILT & CLAY 15 % LIQUID LIMIT %
PLASTICITY INDEX %
MAXIIIMO DEVELOPMENT GROUP
808 WEST PROSPECT ROAD
CTL | T PROJECT NO. FC07161-125
FIGURE 3
Gradation
Test Results
0.002
15 MIN.
.005
60 MIN.
.009
19 MIN.
.019
4 MIN.
.037
1 MIN.
.074
*200
.149
*100
.297
*50
0.42
*40
.590
*30
1.19
*16
2.0
*10
2.38
*8
4.76
*4
9.52
3/8"
19.1
3/4"
36.1
1½"
76.2
3"
127
5"
152
6"
200
8"
.001
45 MIN.
0
10
PASSING
MOISTURE DRY LIQUID PLASTICITY NO. 200
DEPTH CONTENT DENSITY LIMIT INDEX SIEVE
BORING (FEET) (%) (PCF) (%) DESCRIPTION
TH-1 7 78.0 114 32 15 78 CLAY, SANDY (CL)
TH-1 14 5.6 15 SAND, CLAYEY (SC)
TH-2 7 18.3 110 32 15 69 CLAY, SANDY (CL)
TH-2 14 5.7 15 SAND, CLAYEY, GRAVELLY (SC)
TH-3 7 11.0 112 23 6 55 CLAY, SANDY (CL)
TH-3 14 16.1 113 27 11 53 CLAY, SANDY (CL)
TABLE I
SUMMARY OF LABORATORY TESTING
ATTERBERG LIMITS
Page 1 of 1
* NEGATIVE VALUE INDICATES COMPRESSION.
MAXIIIMO DEVELOPMENT GROUP
808 WEST PROSPECT ROAD
CTL|T PROJECT NO. FC07161-125
United States
Department of
Agriculture
A product of the National
Cooperative Soil Survey,
a joint effort of the United
States Department of
Agriculture and other
Federal agencies, State
agencies including the
Agricultural Experiment
Stations, and local
participants
Custom Soil Resource
Report for
Larimer County
Area, Colorado
The Slab
Natural
Resources
Conservation
Service
October 6, 2015
Preface
Soil surveys contain information that affects land use planning in survey areas. They
highlight soil limitations that affect various land uses and provide information about
the properties of the soils in the survey areas. Soil surveys are designed for many
different users, including farmers, ranchers, foresters, agronomists, urban planners,
community officials, engineers, developers, builders, and home buyers. Also,
conservationists, teachers, students, and specialists in recreation, waste disposal,
and pollution control can use the surveys to help them understand, protect, or enhance
the environment.
Various land use regulations of Federal, State, and local governments may impose
special restrictions on land use or land treatment. Soil surveys identify soil properties
that are used in making various land use or land treatment decisions. The information
is intended to help the land users identify and reduce the effects of soil limitations on
various land uses. The landowner or user is responsible for identifying and complying
with existing laws and regulations.
Although soil survey information can be used for general farm, local, and wider area
planning, onsite investigation is needed to supplement this information in some cases.
Examples include soil quality assessments (http://www.nrcs.usda.gov/wps/portal/
nrcs/main/soils/health/) and certain conservation and engineering applications. For
more detailed information, contact your local USDA Service Center (http://
offices.sc.egov.usda.gov/locator/app?agency=nrcs) or your NRCS State Soil
Scientist (http://www.nrcs.usda.gov/wps/portal/nrcs/detail/soils/contactus/?
cid=nrcs142p2_053951).
Great differences in soil properties can occur within short distances. Some soils are
seasonally wet or subject to flooding. Some are too unstable to be used as a
foundation for buildings or roads. Clayey or wet soils are poorly suited to use as septic
tank absorption fields. A high water table makes a soil poorly suited to basements or
underground installations.
The National Cooperative Soil Survey is a joint effort of the United States Department
of Agriculture and other Federal agencies, State agencies including the Agricultural
Experiment Stations, and local agencies. The Natural Resources Conservation
Service (NRCS) has leadership for the Federal part of the National Cooperative Soil
Survey.
Information about soils is updated periodically. Updated information is available
through the NRCS Web Soil Survey, the site for official soil survey information.
The U.S. Department of Agriculture (USDA) prohibits discrimination in all its programs
and activities on the basis of race, color, national origin, age, disability, and where
applicable, sex, marital status, familial status, parental status, religion, sexual
orientation, genetic information, political beliefs, reprisal, or because all or a part of an
individual's income is derived from any public assistance program. (Not all prohibited
bases apply to all programs.) Persons with disabilities who require alternative means
2
for communication of program information (Braille, large print, audiotape, etc.) should
contact USDA's TARGET Center at (202) 720-2600 (voice and TDD). To file a
complaint of discrimination, write to USDA, Director, Office of Civil Rights, 1400
Independence Avenue, S.W., Washington, D.C. 20250-9410 or call (800) 795-3272
(voice) or (202) 720-6382 (TDD). USDA is an equal opportunity provider and
employer.
3
Contents
Preface....................................................................................................................2
How Soil Surveys Are Made..................................................................................5
Soil Map..................................................................................................................7
Soil Map................................................................................................................8
Legend..................................................................................................................9
Map Unit Legend................................................................................................10
Map Unit Descriptions........................................................................................10
Larimer County Area, Colorado......................................................................12
3—Altvan-Satanta loams, 0 to 3 percent slopes.........................................12
Soil Information for All Uses...............................................................................14
Soil Properties and Qualities..............................................................................14
Soil Qualities and Features.............................................................................14
Hydrologic Soil Group (The Slab)................................................................14
References............................................................................................................19
4
How Soil Surveys Are Made
Soil surveys are made to provide information about the soils and miscellaneous areas
in a specific area. They include a description of the soils and miscellaneous areas and
their location on the landscape and tables that show soil properties and limitations
affecting various uses. Soil scientists observed the steepness, length, and shape of
the slopes; the general pattern of drainage; the kinds of crops and native plants; and
the kinds of bedrock. They observed and described many soil profiles. A soil profile is
the sequence of natural layers, or horizons, in a soil. The profile extends from the
surface down into the unconsolidated material in which the soil formed or from the
surface down to bedrock. The unconsolidated material is devoid of roots and other
living organisms and has not been changed by other biological activity.
Currently, soils are mapped according to the boundaries of major land resource areas
(MLRAs). MLRAs are geographically associated land resource units that share
common characteristics related to physiography, geology, climate, water resources,
soils, biological resources, and land uses (USDA, 2006). Soil survey areas typically
consist of parts of one or more MLRA.
The soils and miscellaneous areas in a survey area occur in an orderly pattern that is
related to the geology, landforms, relief, climate, and natural vegetation of the area.
Each kind of soil and miscellaneous area is associated with a particular kind of
landform or with a segment of the landform. By observing the soils and miscellaneous
areas in the survey area and relating their position to specific segments of the
landform, a soil scientist develops a concept, or model, of how they were formed. Thus,
during mapping, this model enables the soil scientist to predict with a considerable
degree of accuracy the kind of soil or miscellaneous area at a specific location on the
landscape.
Commonly, individual soils on the landscape merge into one another as their
characteristics gradually change. To construct an accurate soil map, however, soil
scientists must determine the boundaries between the soils. They can observe only
a limited number of soil profiles. Nevertheless, these observations, supplemented by
an understanding of the soil-vegetation-landscape relationship, are sufficient to verify
predictions of the kinds of soil in an area and to determine the boundaries.
Soil scientists recorded the characteristics of the soil profiles that they studied. They
noted soil color, texture, size and shape of soil aggregates, kind and amount of rock
fragments, distribution of plant roots, reaction, and other features that enable them to
identify soils. After describing the soils in the survey area and determining their
properties, the soil scientists assigned the soils to taxonomic classes (units).
Taxonomic classes are concepts. Each taxonomic class has a set of soil
characteristics with precisely defined limits. The classes are used as a basis for
comparison to classify soils systematically. Soil taxonomy, the system of taxonomic
classification used in the United States, is based mainly on the kind and character of
soil properties and the arrangement of horizons within the profile. After the soil
scientists classified and named the soils in the survey area, they compared the
5
individual soils with similar soils in the same taxonomic class in other areas so that
they could confirm data and assemble additional data based on experience and
research.
The objective of soil mapping is not to delineate pure map unit components; the
objective is to separate the landscape into landforms or landform segments that have
similar use and management requirements. Each map unit is defined by a unique
combination of soil components and/or miscellaneous areas in predictable
proportions. Some components may be highly contrasting to the other components of
the map unit. The presence of minor components in a map unit in no way diminishes
the usefulness or accuracy of the data. The delineation of such landforms and
landform segments on the map provides sufficient information for the development of
resource plans. If intensive use of small areas is planned, onsite investigation is
needed to define and locate the soils and miscellaneous areas.
Soil scientists make many field observations in the process of producing a soil map.
The frequency of observation is dependent upon several factors, including scale of
mapping, intensity of mapping, design of map units, complexity of the landscape, and
experience of the soil scientist. Observations are made to test and refine the soil-
landscape model and predictions and to verify the classification of the soils at specific
locations. Once the soil-landscape model is refined, a significantly smaller number of
measurements of individual soil properties are made and recorded. These
measurements may include field measurements, such as those for color, depth to
bedrock, and texture, and laboratory measurements, such as those for content of
sand, silt, clay, salt, and other components. Properties of each soil typically vary from
one point to another across the landscape.
Observations for map unit components are aggregated to develop ranges of
characteristics for the components. The aggregated values are presented. Direct
measurements do not exist for every property presented for every map unit
component. Values for some properties are estimated from combinations of other
properties.
While a soil survey is in progress, samples of some of the soils in the area generally
are collected for laboratory analyses and for engineering tests. Soil scientists interpret
the data from these analyses and tests as well as the field-observed characteristics
and the soil properties to determine the expected behavior of the soils under different
uses. Interpretations for all of the soils are field tested through observation of the soils
in different uses and under different levels of management. Some interpretations are
modified to fit local conditions, and some new interpretations are developed to meet
local needs. Data are assembled from other sources, such as research information,
production records, and field experience of specialists. For example, data on crop
yields under defined levels of management are assembled from farm records and from
field or plot experiments on the same kinds of soil.
Predictions about soil behavior are based not only on soil properties but also on such
variables as climate and biological activity. Soil conditions are predictable over long
periods of time, but they are not predictable from year to year. For example, soil
scientists can predict with a fairly high degree of accuracy that a given soil will have
a high water table within certain depths in most years, but they cannot predict that a
high water table will always be at a specific level in the soil on a specific date.
After soil scientists located and identified the significant natural bodies of soil in the
survey area, they drew the boundaries of these bodies on aerial photographs and
identified each as a specific map unit. Aerial photographs show trees, buildings, fields,
roads, and rivers, all of which help in locating boundaries accurately.
Custom Soil Resource Report
6
Soil Map
The soil map section includes the soil map for the defined area of interest, a list of soil
map units on the map and extent of each map unit, and cartographic symbols
displayed on the map. Also presented are various metadata about data used to
produce the map, and a description of each soil map unit.
7
8
Custom Soil Resource Report
Soil Map
4490720 4490740 4490760 4490780 4490800 4490820 4490840 4490860 4490880 4490900
4490720 4490740 4490760 4490780 4490800 4490820 4490840 4490860 4490880 4490900
492270 492290 492310 492330 492350 492370 492390
492270 492290 492310 492330 492350 492370 492390
40° 34' 7'' N
105° 5' 29'' W
40° 34' 7'' N
105° 5' 23'' W
40° 34' 1'' N
105° 5' 29'' W
40° 34' 1'' N
105° 5' 23'' W
N
Map projection: Web Mercator Corner coordinates: WGS84 Edge tics: UTM Zone 13N WGS84
0 45 90 180 270
Feet
0 10 20 40 60
Meters
Map Scale: 1:946 if printed on A portrait (8.5" x 11") sheet.
MAP LEGEND MAP INFORMATION
Area of Interest (AOI)
Area of Interest (AOI)
Soils
Soil Map Unit Polygons
Soil Map Unit Lines
Soil Map Unit Points
Special Point Features
Blowout
Borrow Pit
Clay Spot
Closed Depression
Gravel Pit
Gravelly Spot
Landfill
Lava Flow
Marsh or swamp
Mine or Quarry
Miscellaneous Water
Perennial Water
Rock Outcrop
Saline Spot
Sandy Spot
Severely Eroded Spot
Sinkhole
Slide or Slip
Sodic Spot
Spoil Area
Stony Spot
Very Stony Spot
Wet Spot
Other
Special Line Features
Water Features
Streams and Canals
Transportation
Rails
Interstate Highways
US Routes
Major Roads
Local Roads
Background
Aerial Photography
The soil surveys that comprise your AOI were mapped at 1:24,000.
Warning: Soil Map may not be valid at this scale.
Enlargement of maps beyond the scale of mapping can cause
misunderstanding of the detail of mapping and accuracy of soil line
placement. The maps do not show the small areas of contrasting
soils that could have been shown at a more detailed scale.
Please rely on the bar scale on each map sheet for map
measurements.
Source of Map: Natural Resources Conservation Service
Web Soil Survey URL: http://websoilsurvey.nrcs.usda.gov
Coordinate System: Web Mercator (EPSG:3857)
Maps from the Web Soil Survey are based on the Web Mercator
projection, which preserves direction and shape but distorts
distance and area. A projection that preserves area, such as the
Albers equal-area conic projection, should be used if more accurate
calculations of distance or area are required.
This product is generated from the USDA-NRCS certified data as of
Map Unit Legend
Larimer County Area, Colorado (CO644)
Map Unit Symbol Map Unit Name Acres in AOI Percent of AOI
3 Altvan-Satanta loams, 0 to 3
percent slopes
1.9 100.0%
Totals for Area of Interest 1.9 100.0%
Map Unit Descriptions
The map units delineated on the detailed soil maps in a soil survey represent the soils
or miscellaneous areas in the survey area. The map unit descriptions, along with the
maps, can be used to determine the composition and properties of a unit.
A map unit delineation on a soil map represents an area dominated by one or more
major kinds of soil or miscellaneous areas. A map unit is identified and named
according to the taxonomic classification of the dominant soils. Within a taxonomic
class there are precisely defined limits for the properties of the soils. On the landscape,
however, the soils are natural phenomena, and they have the characteristic variability
of all natural phenomena. Thus, the range of some observed properties may extend
beyond the limits defined for a taxonomic class. Areas of soils of a single taxonomic
class rarely, if ever, can be mapped without including areas of other taxonomic
classes. Consequently, every map unit is made up of the soils or miscellaneous areas
for which it is named and some minor components that belong to taxonomic classes
other than those of the major soils.
Most minor soils have properties similar to those of the dominant soil or soils in the
map unit, and thus they do not affect use and management. These are called
noncontrasting, or similar, components. They may or may not be mentioned in a
particular map unit description. Other minor components, however, have properties
and behavioral characteristics divergent enough to affect use or to require different
management. These are called contrasting, or dissimilar, components. They generally
are in small areas and could not be mapped separately because of the scale used.
Some small areas of strongly contrasting soils or miscellaneous areas are identified
by a special symbol on the maps. If included in the database for a given area, the
contrasting minor components are identified in the map unit descriptions along with
some characteristics of each. A few areas of minor components may not have been
observed, and consequently they are not mentioned in the descriptions, especially
where the pattern was so complex that it was impractical to make enough observations
to identify all the soils and miscellaneous areas on the landscape.
The presence of minor components in a map unit in no way diminishes the usefulness
or accuracy of the data. The objective of mapping is not to delineate pure taxonomic
classes but rather to separate the landscape into landforms or landform segments that
have similar use and management requirements. The delineation of such segments
on the map provides sufficient information for the development of resource plans. If
intensive use of small areas is planned, however, onsite investigation is needed to
define and locate the soils and miscellaneous areas.
Custom Soil Resource Report
10
An identifying symbol precedes the map unit name in the map unit descriptions. Each
description includes general facts about the unit and gives important soil properties
and qualities.
Soils that have profiles that are almost alike make up a soil series. Except for
differences in texture of the surface layer, all the soils of a series have major horizons
that are similar in composition, thickness, and arrangement.
Soils of one series can differ in texture of the surface layer, slope, stoniness, salinity,
degree of erosion, and other characteristics that affect their use. On the basis of such
differences, a soil series is divided into soil phases. Most of the areas shown on the
detailed soil maps are phases of soil series. The name of a soil phase commonly
indicates a feature that affects use or management. For example, Alpha silt loam, 0
to 2 percent slopes, is a phase of the Alpha series.
Some map units are made up of two or more major soils or miscellaneous areas.
These map units are complexes, associations, or undifferentiated groups.
A complex consists of two or more soils or miscellaneous areas in such an intricate
pattern or in such small areas that they cannot be shown separately on the maps. The
pattern and proportion of the soils or miscellaneous areas are somewhat similar in all
areas. Alpha-Beta complex, 0 to 6 percent slopes, is an example.
An association is made up of two or more geographically associated soils or
miscellaneous areas that are shown as one unit on the maps. Because of present or
anticipated uses of the map units in the survey area, it was not considered practical
or necessary to map the soils or miscellaneous areas separately. The pattern and
relative proportion of the soils or miscellaneous areas are somewhat similar. Alpha-
Beta association, 0 to 2 percent slopes, is an example.
An undifferentiated group is made up of two or more soils or miscellaneous areas that
could be mapped individually but are mapped as one unit because similar
interpretations can be made for use and management. The pattern and proportion of
the soils or miscellaneous areas in a mapped area are not uniform. An area can be
made up of only one of the major soils or miscellaneous areas, or it can be made up
of all of them. Alpha and Beta soils, 0 to 2 percent slopes, is an example.
Some surveys include miscellaneous areas. Such areas have little or no soil material
and support little or no vegetation. Rock outcrop is an example.
Custom Soil Resource Report
11
Larimer County Area, Colorado
3—Altvan-Satanta loams, 0 to 3 percent slopes
Map Unit Setting
National map unit symbol: jpw2
Elevation: 5,200 to 6,200 feet
Mean annual precipitation: 13 to 15 inches
Mean annual air temperature: 48 to 50 degrees F
Frost-free period: 135 to 150 days
Farmland classification: Prime farmland if irrigated
Map Unit Composition
Altvan and similar soils: 45 percent
Satanta and similar soils: 30 percent
Estimates are based on observations, descriptions, and transects of the mapunit.
Description of Altvan
Setting
Landform: Benches, terraces
Landform position (three-dimensional): Side slope, tread
Down-slope shape: Linear
Across-slope shape: Linear
Parent material: Mixed alluvium
Typical profile
H1 - 0 to 10 inches: loam
H2 - 10 to 18 inches: clay loam, loam, sandy clay loam
H2 - 10 to 18 inches: loam, fine sandy loam, silt loam
H2 - 10 to 18 inches: gravelly sand, gravelly coarse sand, coarse sand
H3 - 18 to 30 inches:
H3 - 18 to 30 inches:
H3 - 18 to 30 inches:
H4 - 30 to 60 inches:
H4 - 30 to 60 inches:
H4 - 30 to 60 inches:
Properties and qualities
Slope: 0 to 3 percent
Depth to restrictive feature: More than 80 inches
Natural drainage class: Well drained
Runoff class: Low
Capacity of the most limiting layer to transmit water (Ksat): Moderately high to high
(0.60 to 2.00 in/hr)
Depth to water table: More than 80 inches
Frequency of flooding: None
Frequency of ponding: None
Calcium carbonate, maximum in profile: 10 percent
Available water storage in profile: Very high (about 13.2 inches)
Interpretive groups
Land capability classification (irrigated): 3e
Land capability classification (nonirrigated): 3e
Hydrologic Soil Group: B
Custom Soil Resource Report
12
Description of Satanta
Setting
Landform: Terraces, structural benches
Landform position (three-dimensional): Side slope, tread
Down-slope shape: Linear
Across-slope shape: Linear
Parent material: Mixed alluvium and/or eolian deposits
Typical profile
H1 - 0 to 9 inches: loam
H2 - 9 to 18 inches: loam, clay loam, sandy clay loam
H2 - 9 to 18 inches: loam, clay loam, fine sandy loam
H2 - 9 to 18 inches:
H3 - 18 to 60 inches:
H3 - 18 to 60 inches:
H3 - 18 to 60 inches:
Properties and qualities
Slope: 0 to 1 percent
Depth to restrictive feature: More than 80 inches
Natural drainage class: Well drained
Runoff class: Low
Capacity of the most limiting layer to transmit water (Ksat): Moderately high to high
(0.60 to 2.00 in/hr)
Depth to water table: More than 80 inches
Frequency of flooding: None
Frequency of ponding: None
Calcium carbonate, maximum in profile: 10 percent
Available water storage in profile: Very high (about 27.4 inches)
Interpretive groups
Land capability classification (irrigated): 1
Land capability classification (nonirrigated): 3c
Hydrologic Soil Group: B
Custom Soil Resource Report
13
Soil Information for All Uses
Soil Properties and Qualities
The Soil Properties and Qualities section includes various soil properties and qualities
displayed as thematic maps with a summary table for the soil map units in the selected
area of interest. A single value or rating for each map unit is generated by aggregating
the interpretive ratings of individual map unit components. This aggregation process
is defined for each property or quality.
Soil Qualities and Features
Soil qualities are behavior and performance attributes that are not directly measured,
but are inferred from observations of dynamic conditions and from soil properties.
Example soil qualities include natural drainage, and frost action. Soil features are
attributes that are not directly part of the soil. Example soil features include slope and
depth to restrictive layer. These features can greatly impact the use and management
of the soil.
Hydrologic Soil Group (The Slab)
Hydrologic soil groups are based on estimates of runoff potential. Soils are assigned
to one of four groups according to the rate of water infiltration when the soils are not
protected by vegetation, are thoroughly wet, and receive precipitation from long-
duration storms.
The soils in the United States are assigned to four groups (A, B, C, and D) and three
dual classes (A/D, B/D, and C/D). The groups are defined as follows:
Group A. Soils having a high infiltration rate (low runoff potential) when thoroughly
wet. These consist mainly of deep, well drained to excessively drained sands or
gravelly sands. These soils have a high rate of water transmission.
Group B. Soils having a moderate infiltration rate when thoroughly wet. These consist
chiefly of moderately deep or deep, moderately well drained or well drained soils that
have moderately fine texture to moderately coarse texture. These soils have a
moderate rate of water transmission.
14
Group C. Soils having a slow infiltration rate when thoroughly wet. These consist
chiefly of soils having a layer that impedes the downward movement of water or soils
of moderately fine texture or fine texture. These soils have a slow rate of water
transmission.
Group D. Soils having a very slow infiltration rate (high runoff potential) when
thoroughly wet. These consist chiefly of clays that have a high shrink-swell potential,
soils that have a high water table, soils that have a claypan or clay layer at or near the
surface, and soils that are shallow over nearly impervious material. These soils have
a very slow rate of water transmission.
If a soil is assigned to a dual hydrologic group (A/D, B/D, or C/D), the first letter is for
drained areas and the second is for undrained areas. Only the soils that in their natural
condition are in group D are assigned to dual classes.
Custom Soil Resource Report
15
16
Custom Soil Resource Report
Map—Hydrologic Soil Group (The Slab)
4490720 4490740 4490760 4490780 4490800 4490820 4490840 4490860 4490880 4490900
4490720 4490740 4490760 4490780 4490800 4490820 4490840 4490860 4490880 4490900
492270 492290 492310 492330 492350 492370 492390
492270 492290 492310 492330 492350 492370 492390
40° 34' 7'' N
105° 5' 29'' W
40° 34' 7'' N
105° 5' 23'' W
40° 34' 1'' N
105° 5' 29'' W
40° 34' 1'' N
105° 5' 23'' W
N
Map projection: Web Mercator Corner coordinates: WGS84 Edge tics: UTM Zone 13N WGS84
0 45 90 180 270
Feet
0 10 20 40 60
Meters
Map Scale: 1:946 if printed on A portrait (8.5" x 11") sheet.
MAP LEGEND MAP INFORMATION
Area of Interest (AOI)
Area of Interest (AOI)
Soils
Soil Rating Polygons
A
A/D
B
B/D
C
C/D
D
Not rated or not available
Soil Rating Lines
A
A/D
B
B/D
C
C/D
D
Not rated or not available
Soil Rating Points
A
A/D
B
B/D
C
C/D
D
Not rated or not available
Water Features
Streams and Canals
Transportation
Rails
Interstate Highways
US Routes
Major Roads
Local Roads
Background
Aerial Photography
The soil surveys that comprise your AOI were mapped at 1:24,000.
Warning: Soil Map may not be valid at this scale.
Enlargement of maps beyond the scale of mapping can cause
misunderstanding of the detail of mapping and accuracy of soil line
placement. The maps do not show the small areas of contrasting
soils that could have been shown at a more detailed scale.
Please rely on the bar scale on each map sheet for map
measurements.
Source of Map: Natural Resources Conservation Service
Web Soil Survey URL: http://websoilsurvey.nrcs.usda.gov
Coordinate System: Web Mercator (EPSG:3857)
Maps from the Web Soil Survey are based on the Web Mercator
projection, which preserves direction and shape but distorts
distance and area. A projection that preserves area, such as the
Albers equal-area conic projection, should be used if more accurate
calculations of distance or area are required.
This product is generated from the USDA-NRCS certified data as of
the version date(s) listed below.
Soil Survey Area: Larimer County Area, Colorado
Table—Hydrologic Soil Group (The Slab)
Hydrologic Soil Group— Summary by Map Unit — Larimer County Area, Colorado (CO644)
Map unit symbol Map unit name Rating Acres in AOI Percent of AOI
3 Altvan-Satanta loams, 0
to 3 percent slopes
B 1.9 100.0%
Totals for Area of Interest 1.9 100.0%
Rating Options—Hydrologic Soil Group (The Slab)
Aggregation Method: Dominant Condition
Component Percent Cutoff: None Specified
Tie-break Rule: Higher
Custom Soil Resource Report
18
References
American Association of State Highway and Transportation Officials (AASHTO). 2004.
Standard specifications for transportation materials and methods of sampling and
testing. 24th edition.
American Society for Testing and Materials (ASTM). 2005. Standard classification of
soils for engineering purposes. ASTM Standard D2487-00.
Cowardin, L.M., V. Carter, F.C. Golet, and E.T. LaRoe. 1979. Classification of
wetlands and deep-water habitats of the United States. U.S. Fish and Wildlife Service
FWS/OBS-79/31.
Federal Register. July 13, 1994. Changes in hydric soils of the United States.
Federal Register. September 18, 2002. Hydric soils of the United States.
Hurt, G.W., and L.M. Vasilas, editors. Version 6.0, 2006. Field indicators of hydric soils
in the United States.
National Research Council. 1995. Wetlands: Characteristics and boundaries.
Soil Survey Division Staff. 1993. Soil survey manual. Soil Conservation Service. U.S.
Department of Agriculture Handbook 18. http://www.nrcs.usda.gov/wps/portal/nrcs/
detail/national/soils/?cid=nrcs142p2_054262
Soil Survey Staff. 1999. Soil taxonomy: A basic system of soil classification for making
and interpreting soil surveys. 2nd edition. Natural Resources Conservation Service,
U.S. Department of Agriculture Handbook 436. http://www.nrcs.usda.gov/wps/portal/
nrcs/detail/national/soils/?cid=nrcs142p2_053577
Soil Survey Staff. 2010. Keys to soil taxonomy. 11th edition. U.S. Department of
Agriculture, Natural Resources Conservation Service. http://www.nrcs.usda.gov/wps/
portal/nrcs/detail/national/soils/?cid=nrcs142p2_053580
Tiner, R.W., Jr. 1985. Wetlands of Delaware. U.S. Fish and Wildlife Service and
Delaware Department of Natural Resources and Environmental Control, Wetlands
Section.
United States Army Corps of Engineers, Environmental Laboratory. 1987. Corps of
Engineers wetlands delineation manual. Waterways Experiment Station Technical
Report Y-87-1.
United States Department of Agriculture, Natural Resources Conservation Service.
National forestry manual. http://www.nrcs.usda.gov/wps/portal/nrcs/detail/soils/
home/?cid=nrcs142p2_053374
United States Department of Agriculture, Natural Resources Conservation Service.
National range and pasture handbook. http://www.nrcs.usda.gov/wps/portal/nrcs/
detail/national/landuse/rangepasture/?cid=stelprdb1043084
19
United States Department of Agriculture, Natural Resources Conservation Service.
National soil survey handbook, title 430-VI. http://www.nrcs.usda.gov/wps/portal/
nrcs/detail/soils/scientists/?cid=nrcs142p2_054242
United States Department of Agriculture, Natural Resources Conservation Service.
2006. Land resource regions and major land resource areas of the United States, the
Caribbean, and the Pacific Basin. U.S. Department of Agriculture Handbook 296.
http://www.nrcs.usda.gov/wps/portal/nrcs/detail/national/soils/?
cid=nrcs142p2_053624
United States Department of Agriculture, Soil Conservation Service. 1961. Land
capability classification. U.S. Department of Agriculture Handbook 210. http://
www.nrcs.usda.gov/Internet/FSE_DOCUMENTS/nrcs142p2_052290.pdf
Custom Soil Resource Report
20
APPENDIX F
Conceptual Analysis of Future Drainage within Lot 2
1
Drainage Letter Report
Date: October 21, 2013
Project: Lot 2, Observatory Park Subdivision Project No. 1033-002
Fort Collins, Colorado
Attn: Mr. Brian Hood
Colorado State University Research Foundation
2537 Research Boulevard, Suite 200
Fort Collins, Colorado 80526
Purpose
This letter serves to provide adequate documentation of the existing and conceptual drainage
patterns of Lot 2, Observatory Park Subdivision. Within this study, we will document the historic
discharge locations and historic runoff rates for both the minor and major storm events. We will
also document conceptual discharge locations, developed runoff rates and the detention required to
restrict the developed release to the historic 2-year runoff rate.
Project Location
The drainage study area is located in the southwest Quarter of Section 14, Township 7 North,
Range 69 West of the 6th Principle Meridian, City of Fort Collins, County of Larimer, State of
Colorado, more specifically Lot 2, Observatory Park Subdivision. The project is located west of
Whitcomb Street on the north side of Prospect Road and is currently addressed 714 and 730 West
Prospect Road.
Historic Drainage Patterns
Currently there are two existing single family residences with a couple of out buildings. There is an
existing gravel drive that runs between the two residences supplying access. There is currently a
natural ridge line running through the middle of the lot from west to east. Lot 2 historically drains
both north and south and historically discharges in both the southeast and northeast corners of the
property; therefore two basins (Basin HN1 and HS1) were delineated to calculated existing
stormwater generated from the site. The northern historic basin (Basin HN1) routes stormwater via
overland flow and discharges at the northeast corner at a 2-year release rate of 0.29 cfs and a 100-
year release rate of 1.29 cfs. The southern historic basin (Basin HS1) routes stormwater via
overland flow and discharges at the northeast corner at a 2-year release rate of 0.41 cfs and a 100-
year release rate of 1.85 cfs. All existing stormwater is currently released from the site undetained
and untreated. An exhibit illustrating the historic drainage patterns and associated calculations
have been attached to this memo.
Lot 2, Observatory Park Subdivision
Conceptual Drainage
Analysis 2
Proposed Drainage Patterns
A conceptual sketch of the site layout was received from CSU Research Foundation and is attached
to this memo for reference. The conceptual layout includes the restoration of the two existing single
family residences and the relocation of three additional single family residences to be placed on site.
It also shows a shared drive access running down the middle of the site from south to north with
associated sidewalks connecting the buildings to the access drive. With the current City of Fort
Collins Standards, it is assumed that 25% of the overall access drive and parking area would be
composed of permeable pavers. For this analysis it was assumed that the existing ridgeline running
west to east would be maintained, creating two developed major basins (Basin S and Basin N)
similar to historic the historic basins mentioned above. Basin N1 is assumed to drain stormwater
via overland flow and discharge into a proposed detention pond located in the northeast corner of
the site. Currently Lot 1 is being processed through the City to resurrect the previously approved
design plans for a multi-family residences. Through this design, the increased runoff rate generated
from the proposed improvements are to be detained at the southwest corner of Lot 2. It was
assumed that a portion of the southern basin would drain to this pond subdividing the southern
basin into two basins, (Sub-Basin S1 and S2). Sub-Basin S1 is assumed to drain stormwater via
overland flow and discharge into the detention pond proposed for the improvements being proposed
for Lot 1 and out fall into W. Prospect Road. Sub-Basin S2 is assumed to drain stormwater via
overland flow and discharge into a conceptual detention pond located in the southeast corner of the
site and is assumed to outfall into W. Prospect Road.
Detention
There were three conceptual ponds that were analyzed for this project. Conceptually, one would be
located in the northeast corner, second would be located in the southwest corner and the third
would be located in the southeast corner. The pond located in the northeast corner would capture
the increased runoff from sub-basin N1 and would require 0.06 acre-feet of detention volume. An
outfall for this pond is unknown at this time and therefore a conceptual grading analysis was not
performed. The pond located in the southeast corner would capture the increase in runoff from sub-
basin S2 and would require 0.0345 acre-feet of detention pond. In assuming the outfall to be the
gutter of W. Prospect Road, a conceptual grading analysis was performed to better understand the
capacity of a conceptual pond located in the southeast corner of Lot 2. Below is a table
summarizing the results of the southeast detention pond.
Off-Site
Southeast Pond
0.005 5020.72 0.0300 0.0345 5021.89 5023.00
Required Water
Quality Storage
(ac-ft)
Water Quality
Surface
Basin ID Elevation (ft)
High Water
Surface
Elevation (ft)
Top of Pond
Elevation (ft)
Total Detention
Volume (ac-ft)
Required 100-year
Detention Volume
(ac-ft)
Table 1 – Southeast Detention Pond Summary
The pond located in the southwest corner was analyzed to capture the increase in runoff from sub-
basin S1 and the proposed increase in runoff from the improvements being proposed within Lot 1.
The increase in runoff from sub-basin S1 would require 0.0345 acre-feet of detention volume. The
increase in runoff from Lot 1 would require 0.1155 acre-feet of detention volume. For both Lot 1
and 2 to utilize this pond, the southwest pond would require a total detention volume of 0.1472
acre-feet. A grading plan is currently under review with the City for Lot 1 to adequately handle the
Lot 2, Observatory Park Subdivision
Conceptual Drainage
Analysis 3
Off-Site
Southeast Pond 0.0042 5022.960 0.0275 0.1472 5025.72 5025.80
Required Water
Quality Storage
(ac-ft)
Water Quality
Surface
Basin ID Elevation (ft)
High Water
Surface
Elevation (ft)
Top of Pond
Elevation (ft)
Total Detention
Volume (ac-ft)
(w/ 0.1155 ac-ft
from Lot 1)
Required 100-year
Detention Volume
(ac-ft)
Table 2 – Southwest Detention Pond Summary
Conclusion
In concluding, the design of Lot 1 and current configuration of the southwest pond should be
adequately sized to handle increased runoff from Lot 1 and the assumed drainage patterns of Lot 2.
It has been assumed the historic ridge line will be remain. The southeast pond, through the use of
walls, should have adequate space to supply the required detention for the southeastern portion of
Lot 2. The northern pond should have adequate space to detention the required detention volume,
but outfall has not been determined and therefore, a grading analysis was not performed.
If you should have any questions as you review this report, please feel free to contact us.
Sincerely,
Northern Engineering Services Inc.
Cody Snowdon
Project Engineer
4
APPENDIX A
HISTORIC DRAINAGE ANALYSIS
CHARACTER OF SURFACE:
Runoff
Coefficient
Percentage
Impervious Project: Off-Site Drainage
Streets, Parking Lots, Roofs, Alleys, and Drives: Calculations By:
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
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.
HN1 24467 0.562 0.000 0.005 0.030 0.063 0.000 0.464 0.24 0.24 0.30 10%
HS1 27585 0.633 0.000 0.020 0.057 0.088 0.000 0.467 0.30 0.30 0.37 17%
TOTAL 52052 1.195 0.000 0.018 0.087 0.152 0.000 0.939 0.26 0.26 0.33 13%
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.
HISTORIC % IMPERVIOUSNESS AND RUNOFF COEFFICIENT CALCULATIONS
C. Snowdon
October 20, 2015
Overland Flow, Time of Concentration:
Project: Off-Site Drainage
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: Off-Site Drainage
Calculations By:
Date:
From Section 3.2.1 of the CFCSDDC
Rainfall Intensity:
hn1 HN1 0.56 11 11 10 0.24 0.24 0.30 2.17 3.71 7.72 0.29 0.50 1.29
hs1 HS1 0.63 11 11 10 0.30 0.30 0.37 2.17 3.71 7.88 0.41 0.70 1.85
C100
Intensity,
i2
(in/hr)
Intensity,
i10
(in/hr)
Intensity,
i100
(in/hr)
DEVELOPED RUNOFF COMPUTATIONS
C. Snowdon
October 20, 2015
Rainfall Intensity taken from the City of Fort Collins Storm Drainage Design Criteria (CFCSDDC), Figure 3.1
Design
Point
Basin(s)
Area, A
(acres)
2-yr
Tc
(min)
10-yr
Tc
(min)
100-yr
Tc
(min)
Flow,
Q2
(cfs)
Flow,
Q10
(cfs)
Flow,
Q100
(cfs)
C2 C10 Notes
Q = C f ( C )( i )( A )
Page 3 of 7 D:\Projects\1033-002\Drainage\Hydrology\1033-002_Off-Site Rational-Calcs.xlsx\Historic Direct-Runoff
APPENDIX B
CONCEPTUAL DRAINAGE ANALYSIS
CHARACTER OF SURFACE:
Runoff
Coefficient
Percentage
Impervious Project: Off-Site Drainage
Streets, Parking Lots, Roofs, Alleys, and Drives: Calculations By:
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
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.
N1 24400 0.560 0.043 0.034 0.106 0.000 0.016 0.361 0.42 0.42 0.52 30%
S1 16315 0.375 0.045 0.009 0.022 0.000 0.008 0.291 0.32 0.32 0.40 19%
S2 11337 0.260 0.032 0.027 0.048 0.000 0.010 0.143 0.49 0.49 0.61 38%
TOTAL BASIN S 27652 0.635 0.077 0.035 0.071 0.000 0.018 0.452 0.39 0.39 0.49 27%
OVERALL TOTAL 52052 1.195 0.120 0.069 0.176 0.000 0.034 0.830 0.41 0.41 0.51 28%
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: Off-Site Drainage
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: Off-Site Drainage
Calculations By:
Date:
From Section 3.2.1 of the CFCSDDC
Rainfall Intensity:
n1 N1 0.56 11 11 10 0.42 0.42 0.52 2.17 3.71 7.88 0.51 0.87 2.30
s1 S1 0.37 8 8 7 0.32 0.32 0.40 2.46 4.21 8.80 0.29 0.50 1.31
s2 S2 0.26 8 8 6 0.49 0.49 0.61 2.46 4.21 9.31 0.31 0.53 1.48
DEVELOPED RUNOFF COMPUTATIONS
C100 Notes
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)
C. Snowdon
October 20, 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 )
Page 6 of 7 D:\Projects\1033-002\Drainage\Hydrology\1033-002_Off-Site Rational-Calcs.xlsx\Direct-Runoff
DESIGN
POINT
BASIN
ID
TOTAL
AREA
(acres)
C2 C100
2-yr
Tc
(min)
100-yr
Tc
(min)
Q2
(cfs)
Q100
(cfs)
n1 N1 0.56 0.42 0.52 11 10 0.51 2.30
s1 S1 0.37 0.32 0.40 8 7 0.29 1.31
s2 S2 0.26 0.49 0.61 8 6 0.31 1.48
DESIGN
POINT
BASIN
ID
TOTAL
AREA
(acres)
C2 C100
2-yr
Tc
(min)
100-yr
Tc
(min)
Q2
(cfs)
Q100
(cfs)
hn1 HN1 0.56 0.24 0.30 11 10 0.29 1.29
hs1 HS1 0.63 0.30 0.37 11 10 0.41 1.85
Page 7 of 7 D:\Projects\1033-002\Drainage\Hydrology\1033-002_Off-Site Rational-Calcs.xlsx\SUMMARY-TABLE
APPENDIX C
CONCEPTUAL DETENTION ANALYSIS
Pond No :
n1
100-yr
0.52
10.00 min 2727 ft3
0.56 acres 0.06 ac-ft
Max Release Rate = 0.29 cfs
Time (min)
Ft Collins
100-yr
Intensity
(in/hr)
Inflow
Volume
(ft3)
Outflow
Adjustment
Factor
Qav
(cfs)
Outflow Volume
(ft3)
Storage
Volume
(ft3)
5 9.950 869 1.00 0.29 87 782
10 7.720 1349 1.00 0.29 174 1175
15 6.520 1709 0.83 0.24 218 1491
20 5.600 1957 0.75 0.22 261 1696
25 4.980 2175 0.70 0.20 305 1871
30 4.520 2369 0.67 0.19 348 2021
35 4.080 2495 0.64 0.19 392 2104
40 3.740 2614 0.63 0.18 435 2179
45 3.460 2720 0.61 0.18 479 2242
50 3.230 2822 0.60 0.17 522 2300
55 3.030 2912 0.59 0.17 566 2346
60 2.860 2998 0.58 0.17 609 2389
65 2.720 3089 0.58 0.17 653 2437
70 2.590 3168 0.57 0.17 696 2472
75 2.480 3250 0.57 0.16 740 2510
80 2.380 3327 0.56 0.16 783 2544
85 2.290 3401 0.56 0.16 827 2574
90 2.210 3475 0.56 0.16 870 2605
95 2.130 3535 0.55 0.16 914 2622
100 2.060 3599 0.55 0.16 957 2642
105 2.000 3669 0.55 0.16 1001 2669
110 1.940 3729 0.55 0.16 1044 2685
115 1.890 3798 0.54 0.16 1088 2710
120 1.840 3858 0.54 0.16 1131 2727
*Note: Using the method described in Urban Storm Drainage Criteria Manual Volume 2.
A =
Tc =
Project Location :
Design Point
C =
Design Storm
DETENTION POND CALCULATION; MODIFIED FAA METHOD w/ Ft Collins IDF
Input Variables Results
Required Detention Volume
Fort Collins, Colorado
Pond No :
s1
100-yr
0.40
7.00 min 1199 ft3
0.37 acres 0.03 ac-ft
Max Release Rate = 0.20 cfs
Time (min)
Ft Collins
100-yr
Intensity
(in/hr)
Inflow
Volume
(ft3)
Outflow
Adjustment
Factor
Qav
(cfs)
Outflow Volume
(ft3)
Storage
Volume
(ft3)
5 9.950 442 1.00 0.20 60 382
10 7.720 686 0.85 0.17 102 584
15 6.520 868 0.73 0.15 132 736
20 5.600 995 0.68 0.14 162 833
25 4.980 1106 0.64 0.13 192 914
30 4.520 1204 0.62 0.12 222 982
35 4.080 1268 0.60 0.12 252 1016
40 3.740 1328 0.59 0.12 282 1046
45 3.460 1383 0.58 0.12 312 1071
50 3.230 1434 0.57 0.11 342 1092
55 3.030 1480 0.56 0.11 372 1108
60 2.860 1524 0.56 0.11 402 1122
65 2.720 1570 0.55 0.11 432 1138
70 2.590 1610 0.55 0.11 462 1148
75 2.480 1652 0.55 0.11 492 1160
80 2.380 1691 0.54 0.11 522 1169
85 2.290 1728 0.54 0.11 552 1176
90 2.210 1766 0.54 0.11 582 1184
95 2.130 1797 0.54 0.11 612 1185
100 2.060 1829 0.54 0.11 642 1187
105 2.000 1865 0.53 0.11 672 1193
110 1.940 1895 0.53 0.11 702 1193
115 1.890 1930 0.53 0.11 732 1198
120 1.840 1961 0.53 0.11 762 1199
*Note: Using the method described in Urban Storm Drainage Criteria Manual Volume 2.
A =
Tc =
Project Location :
Design Point
C =
Design Storm
DETENTION POND CALCULATION; MODIFIED FAA METHOD w/ Ft Collins IDF
Input Variables Results
Required Detention Volume
Fort Collins, Colorado
Project Title Date:
Project Number Calcs By:
Client
Pond Designation
1
WQCV = Watershed inches of Runoff (inches) 19.00%
a = Runoff Volume Reduction (constant)
i = Total imperviousness Ratio (i = Iwq/100) 0.111 in
A = 0.38 ac
V = 0.0042 ac-ft
V = Water Quality Design Volume (ac-ft)
WQCV = Water Quality Capture Volume (inches)
A = Watershed Area (acres)
1.2 = 20% Additional Volume (Sediment Accumulation)
The Slab October 21, 2015
232-035 C. Snowdon
CSU Research Foundation
Off-Site Southwest Pond
Drain Time
a =
i =
WQCV =
Figure EDB-2 - Water Quality Capture Volume (WQCV), 80th Percentile Runoff Event
0.111
0
0.05
0.1
0.15
0.2
0.25
0.3
0.35
0.4
0.45
0.5
0.00
0.10
0.20
0.30
0.40
0.50
0.60
0.70
0.80
0.90
1.00
WQCV (watershed inches)
Total Imperviousness Ratio (i = Iwq/100)
Water Quality Capture Volume
6 hr
12 hr
24 hr
40 hr
WQCV = a ( 0.91 i 3 - 1 . 19 i 2 + 0 . 78 i )
WQCV = a ( 0.91 i 3 - 1 . 19 i 2 + 0 . 78 i )
* * 1 . 2
12
V WQCV A
÷
ø
Project Title Date:
Project Number Calcs By:
Client
Pond Designation
Invert Elevation
Water Quality Volume
100-yr Detention Volume
Min Sc
D = Depth between contours (ft.)
A1 = Surface Area lower contour (ft
2
) t
A2 = Surface Area upper contour (ft
2
) Area/Row
No. of Rows
5022.60 67.03 0.12 2.68 2.68 0.0001
5022.80 474.51 0.20 47.99 50.67 0.0012
5023.00 1230.74 0.20 164.63 215.30 0.0049 WQCV
5023.20 1925.36 0.20 313.03 528.33 0.0121
5023.40 2226.46 0.20 414.82 943.15 0.0217
5023.60 2358.58 0.20 458.44 1401.59 0.0322 100-yr Vol
5023.80 2358.83 0.20 471.74 1873.33 0.0430
5024.00 2359.07 0.20 471.79 2345.12 0.0538
5024.20 2359.32 0.20 471.84 2816.96 0.0647
5024.40 2359.57 0.20 471.89 3288.85 0.0755
5024.60 2359.82 0.20 471.94 3760.79 0.0863
5024.80 2360.07 0.20 471.99 4232.78 0.0972
5025.00 2360.32 0.20 472.04 4704.82 0.1080
5025.20 2360.57 0.20 472.09 5176.91 0.1188
5025.40 2360.82 0.20 472.14 5649.05 0.1297
5025.60 2361.07 0.20 472.19 6121.23 0.1405
5025.80 2361.33 0.20 472.24 6593.47 0.1514 Total Vol
Elevation Depth Volume
WQCV 5022.96 0.48 0.0042
100-yr Detention 5023.51 1.03 0.0275
Overall Detention 5025.72 3.24 0.1472
CSU Research Foundation
The Slab October 21, 2015
232-035 C. Snowdon
Off-Site Southwest Pond
5022.48 ft
0.0042 ac-ft
0.0275 ac-ft Circular Perforation Sizing
1
0.1472 ac-ft Dia (in.)
Total Pond Volume (w/ Additional 0.1155
ac-ft from Lot 2)
n
1/4
0.05
Required Area
Per Row 0.049 sq-in
1
Total Outlet
Area 0.05 sq. in.
Off-Site Southwest Pond Volume
Elevation
(ft)
Surface
Off-Site Southwest
Pond 0.0042 5022.960 0.0275 0.1472 5025.72 5025.80
Required Water
Quality Storage
(ac-ft)
Water Quality
Surface
Basin ID Elevation (ft)
High Water
Surface Elevation
(ft)
Top of Pond
Elevation (ft)
Total Detention
Volume (ac-ft)
(w/ 0.1155 ac-ft
from Lot 1)
Required 100-year
Detention Volume
(ac-ft)
Pond No :
s2
100-yr
0.61
6.00 min 1307 ft3
0.26 acres 0.03 ac-ft
Max Release Rate = 0.21 cfs
Time (min)
Ft Collins
100-yr
Intensity
(in/hr)
Inflow
Volume
(ft3)
Outflow
Adjustment
Factor
Qav
(cfs)
Outflow Volume
(ft3)
Storage
Volume
(ft3)
5 9.950 473 1.00 0.21 63 410
10 7.720 735 0.80 0.17 101 634
15 6.520 931 0.70 0.15 132 798
20 5.600 1066 0.65 0.14 164 902
25 4.980 1185 0.62 0.13 195 989
30 4.520 1290 0.60 0.13 227 1064
35 4.080 1359 0.59 0.12 258 1101
40 3.740 1424 0.58 0.12 290 1134
45 3.460 1482 0.57 0.12 321 1160
50 3.230 1537 0.56 0.12 353 1184
55 3.030 1586 0.55 0.12 384 1202
60 2.860 1633 0.55 0.12 416 1217
65 2.720 1682 0.55 0.11 447 1235
70 2.590 1725 0.54 0.11 479 1246
75 2.480 1770 0.54 0.11 510 1260
80 2.380 1812 0.54 0.11 542 1270
85 2.290 1852 0.54 0.11 573 1279
90 2.210 1893 0.53 0.11 605 1288
95 2.130 1926 0.53 0.11 636 1289
100 2.060 1960 0.53 0.11 668 1292
105 2.000 1998 0.53 0.11 699 1299
110 1.940 2031 0.53 0.11 731 1300
115 1.890 2068 0.53 0.11 762 1306
120 1.840 2101 0.53 0.11 794 1307
*Note: Using the method described in Urban Storm Drainage Criteria Manual Volume 2.
A =
Tc =
Project Location :
Design Point
C =
Design Storm
DETENTION POND CALCULATION; MODIFIED FAA METHOD w/ Ft Collins IDF
Input Variables Results
Required Detention Volume
Fort Collins, Colorado
Project Title Date:
Project Number Calcs By:
Client
Pond Designation
1
WQCV = Watershed inches of Runoff (inches) 38.00%
a = Runoff Volume Reduction (constant)
i = Total imperviousness Ratio (i = Iwq/100) 0.174 in
A = 0.26 ac
V = 0.0045 ac-ft
V = Water Quality Design Volume (ac-ft)
WQCV = Water Quality Capture Volume (inches)
A = Watershed Area (acres)
1.2 = 20% Additional Volume (Sediment Accumulation)
Drain Time
a =
i =
WQCV =
Figure EDB-2 - Water Quality Capture Volume (WQCV), 80th Percentile Runoff Event
The Slab October 21, 2015
232-035 C. Snowdon
CSU Research Foundation
Off-Site Southeast Pond
0.174
0
0.05
0.1
0.15
0.2
0.25
0.3
0.35
0.4
0.45
0.5
0.00
0.10
0.20
0.30
0.40
0.50
0.60
0.70
0.80
0.90
1.00
WQCV (watershed inches)
Total Imperviousness Ratio (i = Iwq/100)
Water Quality Capture Volume
6 hr
12 hr
24 hr
40 hr
WQCV = a ( 0.91 i 3 - 1 . 19 i 2 + 0 . 78 i )
WQCV = a ( 0.91 i 3 - 1 . 19 i 2 + 0 . 78 i )
* * 1 . 2
12
V WQCV A
÷
ø
Project Title Date:
Project Number Calcs By:
Client
Pond Designation
Invert Elevation
Water Quality Volume
100-yr Detention Volume
Total Pond Volume
Min Sc
D = Depth between contours (ft.)
A1 = Surface Area lower contour (ft2) t
A2 = Surface Area upper contour (ft2) Area/Row
No. of Rows
5020.20 4.86 0.03 0.05 0.05 0.0000
5020.40 236.86 0.20 18.38 18.43 0.0004
5020.60 651.62 0.20 85.42 103.85 0.0024
5020.80 985.44 0.20 162.56 266.41 0.0061 WQCV
5021.00 1051.55 0.20 203.66 470.07 0.0108
5021.20 1099.14 0.20 215.05 685.12 0.0157
5021.40 1146.24 0.20 224.52 909.64 0.0209
5021.60 1192.71 0.20 233.88 1143.52 0.0263
5021.80 1238.47 0.20 243.10 1386.63 0.0318 100-yr Vol
5022.00 1283.51 0.20 252.18 1638.81 0.0376 Total Vol
5022.20 1327.89 0.20 261.13 1899.94 0.0436
5022.40 1371.83 0.20 269.96 2169.90 0.0498
5022.60 1415.74 0.20 278.75 2448.64 0.0562
5022.80 1460.54 0.20 287.62 2736.26 0.0628
5023.00 1510.03 0.20 297.04 3033.30 0.0696
Elevation Depth Volume
WQCV 5020.72 0.55 0.0045
100-yr Detention 5021.73 1.56 0.0300
Overall Detention 5021.89 1.72 0.0345
Total Outlet
Area 0.05 sq. in.
Off-Site Southeast Pond Volume
Elevation
(ft)
Surface
Area (ft2)
Incremental
Depth (ft)
Incremental
Vol. (ft3)
Total Vol.
(ft3)
Total Vol.
(ac-ft)
n
1/4
0.05
Required Area
Per Row 0.030 sq-in
1
Off-Site Southeast Pond
5020.17 ft
0.0045 ac-ft
0.0300 ac-ft Circular Perforation Sizing
1
0.0345 ac-ft Dia (in.)
CSU Research Foundation
Off-Site Southeast
Pond 0.005 5020.72 0.0300 0.0345 5021.89 5023.00
Required Water
Quality Storage (ac-
ft)
Water Quality
Surface
Basin ID Elevation (ft)
High Water
Surface Elevation
(ft)
Top of Pond
Elevation (ft)
Total Detention
Volume (ac-ft)
Required 100-year
Detention Volume
(ac-ft)
1421 S. College Ave
W. Prospect Ave
1417 S. College Ave
Stone Wall - 1417 S. College Ave
1435 S. College Ave
Existing Buildings to Remain
New Fence
Pedestrian Connetion 12’ Drives
8 Parking
Spaces Total
Drive Connection to
Access Easement
0 15 30 60
NORTH
730 W. PROSPECT ROAD
1 CONCEPTUAL SITE PLAN
APPENDIX G
Erosion Control Report
Brownes on Howes
Final 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 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 CS2 of the Utility Plans. The Utility
Plans at final design 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 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,
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.
MAP POCKET
DR1 – OVERALL DRAINAGE EXHIBIT
re
5028
5028
X
X
X
X
X X
VAULT
ELEC VAULT
ELEC
VAULT
ELEC
VAULT
CABLE
GAS
VAULT
CABLE
VAULT
ELEC
X
X X X X X X
X
X X X
X
X
X X X X
X
OHE OHE
OHE
OHE
OHE OHE
T
RAFFIC
VAULT
VAULT
ELEC
VAULT
ELEC
E
E
E
E E
E
E E
E
E
E E
E E
VAULT
CABLE
VAULT
ELEC
VAULT
ELEC
VAULT
CABLE
VAULT
ELEC
VAULT
ELEC
VAULT
ELEC
UD UD UD UD
UD
UD UD
UD
UD UD
UD
UD
UD UD
UD
UD
UD
G
G
UD
CO
CO
CO
UD UD UD
UD UD UD UD UD
UD UD
UD
UD
CO
CO
CO CO
CO
UD
UD
UD UD
UD
UD
CO
WEST PROSPECT ROAD
(81' PUBLIC ROW)
OWNER: DONALD R. &
LINDA R. WENZEL
OWNER: COLORADO FARM
HOUSE ASSOCIATION
METES & BOUNDS TRACT
OWNER: RIDGE GATE
PARTNERS, LLC
OWNER: RIDGE GATE
PARTNERS, LLC
acres
N1
0.58 0.23
0.73
acres
N2
0.89 0.58
1.00
acres
N3
0.76 0.20
0.95
acres
S1
0.62 0.10
0.78
acres
S2
0.71 0.21
0.89
acres
S3
0.89 0.08
1.00
acres
S4
0.64 0.07
0.80
acres
OS1
0.74 0.31
0.93
acres
OW1
0.34 0.37
0.43
acres
ON1
0.49 0.25
0.61
n2
n1
n3
ow1
os1
s1
s2
s3
s4
POND
OUTLET
STRUCTURE
NORTH DETENTION
POND
HWSE = 5027 (HATCHED)
2' TRICKLE PAN
CURB CUT
2' CROSS PAN
OVERFLOW BEYOND
WATER QUALITY
CAPTURE VOLUME
2' CROSS PAN
CURB CUT
CURB CUT
SOFT PAN
SOFT PAN
PIPE END
CURB
CUT
SOUTH
DETENTION
POND
HWSE = 5025.8 (HATCHED)
POND OUTLET
STRUCTURE CONCRETE
CHASE
SIDEWALK
CHASE
RIPRAP
(TYPICAL)
AREA
INLET
BIO-SWALE
BIO-SWALE
DRY WELL
2' TRICKLE PAN
AREA OF PONDING
EXCEEDING 12"
AREA
INLET
CURB
CUT
STORMTECH
VAULTS
STORMTECH
VAULTS
CURB CUT
DRAIN
BASIN
DRAIN
BASIN
WQ
STRUCTURE
WQ
STRUCTURE
n3
ELEC
V.P.
X
X
VAULT
ELEC
C VAULT
ELEC
X
E
E
E
E
E E
X
X X X
UD
UD
UD
CO
UD UD UD
CO
OWNER: RIDGE GATE
PARTNERS, LLC
OWNER: COLORADO FARM
HOUSE ASSOCIATION
METES & BOUNDS TRACT
WEST LAKE STREET
on1
2' SIDEWALK
CHASE
BIO-SWALE
C7.00
DRAINAGE EXHIBIT
C. Snowdon
B. Ruch
1"=20'
No. Revisions:
By: Date:
REVIEWED BY:
N. Haws
DESIGNED BY:
DRAWN BY:
SCALE:
DATE:
5.4.16
PROJECT:
1033-002
Sheet
Of 16 Sheets
THE SLAB PROPERTY
These drawings are
instruments of service
provided by Northern
Engineering Services, Inc.
and are not to be used for
any type of construction
unless signed and sealed by
a Professional Engineer in
the employ of Northern
Engineering Services, Inc.
NOT FOR CONSTRUCTION
REVIEW SET
5.4.16
200 South College Avenue, Suite 010
Fort Collins, Colorado 80524
E N G I N E E R I N G
N O R T H E RN
PHONE: 970.221.4158
www.northernengineering.com
Date
Date
Date
Date
Date
Date
APPROVED:
CHECKED BY:
CHECKED BY:
CHECKED BY:
CHECKED BY:
CHECKED BY:
City Engineer
Water & Wastewater Utility
Stormwater Utility
Parks & Recreation
Traffic Engineer
Environmental Planner
City of Fort Collins, Colorado
UTILITY PLAN APPROVAL
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
Know what's below.
Call before you dig.
R
NORTH
( IN FEET )
1 inch = ft.
20 0 20 Feet
20
40 60
NOTES:
5013
PROPOSED CONTOUR 93
PROPOSED SWALE
EXISTING CONTOUR
PROPOSED INFLOW VERTICAL
PROPOSED OVERLAND FLOW DIRECTION
CURB & GUTTER
EXISTING STORM SEWER LINE
PROPERTY BOUNDARY
EXISTING INLET GRATE
PROPOSED UNDERDRAIN UD
PROPOSED STORM DRAIN
PROPOSED RIBBON CURB
PROPOSED PERMEABLE PAVERS
acres
B1
0.69 1.79
0.86
f2
BASIN ACREAGE
DESIGN POINT
BASIN DELINEATION
MINOR RUNOFF COEFFICIENT
MAJOR RUNOFF COEFFICIENT
PROPOSED BASIN LINES
1.THE SIZE, TYPE AND LOCATION OF ALL KNOWN UNDERGROUND UTILITIES ARE APPROXIMATE WHEN SHOWN ON
THESE DRAWINGS. IT SHALL BE THE RESPONSIBILITY OF THE CONTRACTOR TO VERIFY THE EXISTENCE OF ALL
UNDERGROUND UTILITIES IN THE AREA OF THE WORK. BEFORE COMMENCING NEW CONSTRUCTION, THE
CONTRACTOR SHALL BE RESPONSIBLE FOR LOCATING ALL UNDERGROUND UTILITIES AND SHALL BE RESPONSIBLE
FOR FOR ALL UNKNOWN UNDERGROUND UTILITIES.
2.REFER TO THE FINAL DRAINAGE REPORT FOR OBSERVATORY PARK BY DMW CIVIL ENGINEERINGS, DATED AUGUST
27, 2007 FOR ADDITIONAL INFORMATION.
APPROXIMATE LIMITS OF DEVELOPMENT LOD
PROPOSED OUTFALL VERTICAL
CURB & GUTTER
PROPOSED BIO-SWALE
BENCHMARK/BASIS OF BEARING
{PROJECT DATUM: NAVD88
CITY OF FORT COLLINS BENCHMARK 28-92
SOUTHWEST CORNER OF WEST PROSPECT RD. AND CENTRE AVE., ON A
WATER VALVE PIT.
ELEVATION=5010.65
CITY OF FORT COLLINS BENCHMARK 29-92
APPROXIMATE 300 FEET SOUTH OF WEST PROSPECT RD. AND SHIELDS
ST., ON THE NORTH END OF THE
WEST BRIDGE PARAPET WALL.
ELEVATION=5025.67
PLEASE NOTE: THIS PLAN SET IS USING NAVD88 FOR A VERTICAL DATUM.
SURROUNDING DEVELOPMENTS HAVE USED NGVD29 UNADJUSTED FOR
THEIR VERTICAL DATUMS.
IF NGVD29 UNADJUSTED DATUM IS REQUIRED FOR ANY PURPOSE, THE
FOLLOWING EQUATION SHOULD BE USED:
NGVD29 UNADJUSTED = NAVD88 - 3.17'.
BASIS OF BEARINGS
BASIS OF BEARINGS IS THE SOUTH LINE OF LOT 1 AS BEARING NORTH 89
22' 14" WEST (ASSUMED BEARING).}
LEGEND:
MATCHLINE - SEE BELOW
MATCHLINE - SEE ABOVE
The Slab October 21, 2015
232-035 C. Snowdon
( )
3
V D * A 1 A 2 A 1 * A 2
= + +
ö
ç
è
= æ
40 hr
1033-002
The Slab
Project Number :
Project Name :
Off-Site Southeast Pond
Page 1 of 1
1033-001_Off-Site Southeast_DetentionVolume_FAAModified Method.xls
Area (ft
2
)
Incremental
Depth (ft)
Incremental
Vol. (ft
3
)
Total Vol.
(ft
3
)
Total Vol.
(ac-ft)
( )
3
V D * A 1 A 2 A 1 * A 2
= + +
ö
ç
è
= æ
40 hr
1033-002
The Slab
Project Number :
Project Name :
Off-Site Southwest Pond
Page 1 of 1
1033-001_Off-Site Southwest_DetentionVolume_FAAModified Method.xls
1033-002
The Slab
Project Number :
Project Name :
Off-Site North Pond
Page 1 of 1
1033-001_Off-Site North_DetentionVolume_FAAModified Method.xls
Tt
(min)
2-yr
Tc
(min)
10-yr
Tc
(min)
100-yr
Tc
(min)
n1 N1 No 0.42 0.42 0.52 62 2.00% 8.0 8.0 6.8 N/A N/A N/A 175 0.50% 1.06 2.7 11 11 10
s1 S1 No 0.32 0.32 0.40 30 2.00% 6.4 6.4 5.7 120 0.50% 1.41 1.4 N/A N/A N/A 8 8 7
s2 S2 No 0.49 0.49 0.61 40 2.00% 5.7 5.7 4.6 160 0.50% 1.41 1.9 N/A N/A N/A 8 8 6
DEVELOPED TIME OF CONCENTRATION COMPUTATIONS
Gutter Flow Swale Flow
Design
Point
Basin
Overland Flow
C. Snowdon
October 20, 2015
Time of Concentration
(Equation RO-4)
( )
3
1
1 . 87 1 . 1 *
S
Ti C Cf L
-
=
Page 5 of 7 D:\Projects\1033-002\Drainage\Hydrology\1033-002_Off-Site Rational-Calcs.xlsx\Tc-10-yr_&_100-yr
October 20, 2015
**Soil Classification of site is Sandy Loam**
C. Snowdon
Page 4 of 7 D:\Projects\1033-002\Drainage\Hydrology\1033-002_Off-Site Rational-Calcs.xlsx\C-Values
Tt
(min)
2-yr
Tc
(min)
10-yr
Tc
(min)
100-yr
Tc
(min)
hn1 HN1 No 0.42 0.42 0.52 165 2.54% 12.0 12.0 10.2 N/A N/A N/A N/A N/A N/A 11 11 10
hs1 HS1 No 0.32 0.32 0.40 124 3.33% 10.9 10.9 9.8 N/A N/A N/A N/A N/A N/A 11 11 10
DEVELOPED TIME OF CONCENTRATION COMPUTATIONS
C. Snowdon
October 20, 2015
Design
Point
Basin
Overland Flow Gutter Flow Swale Flow Time of Concentration
(Equation RO-4)
( )
3
1
1 . 87 1 . 1 *
S
Ti C Cf L
-
=
Page 2 of 7 D:\Projects\1033-002\Drainage\Hydrology\1033-002_Off-Site Rational-Calcs.xlsx\Historic Tc-10-yr_&_100-yr
**Soil Classification of site is Sandy Loam**
10-year Cf = 1.00
Page 1 of 7 D:\Projects\1033-002\Drainage\Hydrology\1033-002_Off-Site Rational-Calcs.xlsx\Historic C-Values
overall detention volume. Below is a table summarizing the results of the detention pond.
Survey Area Data: Version 9, Sep 22, 2014
Soil map units are labeled (as space allows) for map scales 1:50,000
or larger.
Date(s) aerial images were photographed: Apr 22, 2011—Apr 28,
2011
The orthophoto or other base map on which the soil lines were
compiled and digitized probably differs from the background
imagery displayed on these maps. As a result, some minor shifting
of map unit boundaries may be evident.
Custom Soil Resource Report
17
the version date(s) listed below.
Soil Survey Area: Larimer County Area, Colorado
Survey Area Data: Version 9, Sep 22, 2014
Soil map units are labeled (as space allows) for map scales 1:50,000
or larger.
Date(s) aerial images were photographed: Apr 22, 2011—Apr 28,
2011
The orthophoto or other base map on which the soil lines were
compiled and digitized probably differs from the background
imagery displayed on these maps. As a result, some minor shifting
of map unit boundaries may be evident.
Custom Soil Resource Report
9
20
30
40
50
60
70
80
90
100
CLAY (PLASTIC) TO SILT (NON-PLASTIC)
SANDS
FINE MEDIUM COARSE
GRAVEL
FINE COARSE COBBLES
DIAMETER OF PARTICLE IN MILLIMETERS
25 HR. 7 HR.
HYDROMETER ANALYSIS SIEVE ANALYSIS
TIME READINGS U.S. STANDARD SERIES CLEAR SQUARE OPENINGS
PERCENT PASSING
0
10
20
30
50
60
70
80
90
100
PERCENT RETAINED
40
0.002
15 MIN.
.005
60 MIN.
.009
19 MIN.
.019
4 MIN.
.037
1 MIN.
.074
*200
.149
*100
.297
*50
0.42
*40
.590
*30
1.19
*16
2.0
*10
2.38
*8
4.76
*4
9.52
3/8"
19.1
3/4"
36.1
1½"
76.2
3"
127
5"
152
6"
200
8"
.001
45 MIN.
0
10
20
30
40
50
60
70
80
90
100
CLAY (PLASTIC) TO SILT (NON-PLASTIC)
SANDS
FINE MEDIUM COARSE
GRAVEL
FINE COARSE COBBLES
DIAMETER OF PARTICLE IN MILLIMETERS
25 HR. 7 HR.
HYDROMETER ANALYSIS SIEVE ANALYSIS
TIME READINGS U.S. STANDARD SERIES CLEAR SQUARE OPENINGS
PERCENT PASSING
PERCENT RETAINED
0
10
20
30
40
50
60
70
80
90
100
13/12
11/12
WC=11.0
DD=112
LL=23 PI=6
-200=55
WC=16.1
DD=113
LL=27 PI=11
-200=53
WC=11.0
DD=112
LL=23 PI=6
-200=55
WC=16.1
DD=113
LL=27 PI=11
-200=53
TH-3
DEPTH - FEET
2.
DRIVE SAMPLE. THE SYMBOL 17/12 INDICATES 17 BLOWS OF A 140-POUND HAMMER
FALLING 30 INCHES WERE REQUIRED TO DRIVE A 2.5-INCH O.D. SAMPLER 12 INCHES.
FILL; CLAY, SAND, GRAVEL, MOIST, DARK BROWN
1.
NOTES:
WATER LEVEL MEASURED SEVERAL DAYS AFTER DRILLING.
CLAY, SANDY WITH LAYERS OF CLAYEY SAND, MOIST, STIFF TO VERY STIFF, BROWN,
RED-BROWN (CL, SC)
3.
LEGEND:
SAND, RELATIVELY CLEAN TO CLAYEY WITH OCCASIONAL GRAVEL, MOIST TO WET,
MEDIUM DENSE, BROWN (SP, SC)
DEPTH - FEET
WATER LEVEL MEASURED AT TIME OF DRILLING.
THESE LOGS ARE SUBJECT TO THE EXPLANATIONS, LIMITATIONS AND CONCLUSIONS IN
THIS REPORT.
Summary Logs of
Exploratory Borings
THE BORINGS WERE DRILLED ON FEBRUARY 18, 2016, USING 4-INCH DIAMETER
CONTINUOUS-FLIGHT AUGERS AND A TRUCK-MOUNTED DRILL RIG.
FIGURE 2
WC
DD
SW
-200
LL
PI
UC
SS
-
-
-
-
-
-
-
-
INDICATES MOISTURE CONTENT (%).
INDICATES DRY DENSITY (PCF).
INDICATES SWELL WHEN WETTED UNDER OVERBURDEN PRESSURE (%).
INDICATES PASSING NO. 200 SIEVE (%).
INDICATES LIQUID LIMIT.
INDICATES PLASTICITY INDEX.
INDICATES UNCONFINED COMPRESSIVE STRENGTH (PSF).
INDICATES SOLUBLE SULFATE CONTENT (%).
MAXIIIMO DEVELOPMENT GROUP
808 WEST PROSPECT ROAD
CTL | T PROJECT NO. FC07161-125
ö
ç
è
= æ
12 hr
ö
ç
è
= æ
12 hr
ö
ç
è
= æ
12 hr
1033-002
The Slab
Project Number :
Project Name :
Emergency Access Drive
Page 1 of 1
1033-001_Emergency Drive_DetentionVolume_FAAModified Method.xls
Vol. (ft3)
Total Vol.
(ft3)
Total Vol.
(ac-ft)
( )
3
V D * A 1 A 2 A 1 * A 2
= + +
ö
ç
è
= æ
40 hr
Tc =
Project Location :
Design Point
C =
Design Storm
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1033-001_South_DetentionVolume_FAAModified Method.xls
(ft3)
Total Vol.
(ac-ft)
( )
3
V D * A 1 A 2 A 1 * A 2
= + +
ö
ç
è
= æ
40 hr
1033-002
The Slab
Project Number :
Project Name :
North Pond
Page 1 of 1
1033-001_North_DetentionVolume_FAAModified Method.xls
(min)
2-yr
Tc
(min)
10-yr
Tc
(min)
100-yr
Tc
(min)
n1 N1-N3 No 0.80 0.80 0.99 0.00 73 2.95% 3.4 3.4 1.2 257 0.69% 1.66 2.6 N/A N/A N/A 6 6 5.0
n1 N1-N3 & OW1 No 0.67 0.67 0.84 10.90 17 1.00% 3.3 3.3 2.0 257 0.69% 1.66 2.6 N/A N/A N/A 12 12 15.5
n2 N2-N3 No 0.86 0.86 1.00 0.00 50 101.00% 0.7 0.7 0.3 158 0.50% 1.41 1.9 N/A N/A N/A 5 5 5.0
s1 S1-S4 No 0.71 0.71 0.89 0.00 65 2.34% 4.4 4.4 2.4 426 1.28% 2.26 3.1 N/A N/A N/A 8 8 5.6
s2 S3-S4 No 0.77 0.77 0.96 0.00 77 3.36% 3.6 3.6 1.5 N/A N/A N/A N/A N/A N/A 5 5 5.0
COMBINED DEVELOPED TIME OF CONCENTRATION COMPUTATIONS
C. Snowdon
May 3, 2016
Design
Point
Basin IDs
Overland Flow Gutter Flow Swale Flow Time of Concentration
(Equation RO-4)
( )
3
1
1 . 87 1 . 1 *
S
Ti C Cf L
-
=
Page 5 of 7 D:\Projects\1033-002\Drainage\Hydrology\1033-002_Rational-Calcs.xlsx\Comb-Tc-10-yr_&_100-yr
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.
Page 4 of 7 D:\Projects\1033-002\Drainage\Hydrology\1033-002_Rational-Calcs.xlsx\Comb-C-Values
Tt
(min)
2-yr
Tc
(min)
10-yr
Tc
(min)
100-yr
Tc
(min)
n1 N1 No 0.58 0.58 0.73 63 2.89% 5.4 5.4 3.9 92 0.89% 1.89 0.8 N/A N/A N/A 6 6 5
n2 N2 No 0.89 0.89 1.00 50 2.36% 2.1 2.1 1.0 158 0.50% 1.41 1.9 N/A N/A N/A 5 5 5
n3 N3 No 0.76 0.76 0.95 63 5.06% 2.9 2.9 1.3 N/A N/A N/A N/A N/A N/A 5 5 5
s1 S1 No 0.62 0.62 0.78 44 6.39% 3.2 3.2 2.2 N/A N/A N/A N/A N/A N/A 5 5 5
s2 S2 No 0.71 0.71 0.89 60 12.00% 2.5 2.5 1.3 N/A N/A N/A 150 2.00% 2.12 1.2 5 5 5
s3 S3 No 0.89 0.89 1.00 77 3.36% 2.3 2.3 1.1 N/A N/A N/A N/A N/A N/A 5 5 5
s4 S4 No 0.64 0.64 0.80 20 2.20% 3.0 3.0 1.9 N/A N/A N/A 68 3.81% 2.93 0.4 5 5 5
on ON No 0.49 0.49 0.61 28 5.61% 3.4 3.4 2.7 N/A N/A N/A 335 0.94% 1.45 3.8 7 7 7
os OS No 0.74 0.74 0.93 29 2.14% 2.8 2.8 1.3 237 1.32% 2.30 1.7 N/A N/A N/A 5 5 5
ow OW No 0.34 0.34 0.43 160 1.00% 17.9 17.9 15.9 N/A N/A N/A N/A N/A N/A 11 11 11
DEVELOPED TIME OF CONCENTRATION COMPUTATIONS
Gutter Flow Swale Flow
Design
Point
Basin
Overland Flow
C. Snowdon
May 3, 2016
Time of Concentration
(Equation RO-4)
( )
3
1
1 . 87 1 . 1 *
S
Ti C Cf L
-
=
Page 2 of 7 D:\Projects\1033-002\Drainage\Hydrology\1033-002_Rational-Calcs.xlsx\Tc-10-yr_&_100-yr
ON 10820 0.248 0.000 0.091 0.000 0.000 0.044 0.113 0.49 0.49 0.61 33%
OS 13642 0.313 0.140 0.092 0.000 0.000 0.000 0.081 0.74 0.74 0.93 71%
OW 16117 0.370 0.000 0.030 0.050 0.020 0.000 0.270 0.34 0.34 0.43 22%
TOTAL BASIN N 64095 1.005 0.541 0.116 0.152 0.004 0.000 0.192 0.80 0.80 0.99 78%
TOTAL BASIN S 20312 0.466 0.048 0.081 0.198 0.000 0.000 0.140 0.71 0.71 0.89 64%
TOTAL 88557 2.033 0.729 0.018 0.400 0.004 0.044 0.883 0.61 0.61 0.76 54%
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
May 3, 2016
**Soil Classification of site is Sandy Loam**
C. Snowdon
Page 1 of 7 D:\Projects\1033-002\Drainage\Hydrology\1033-002_Rational-Calcs.xlsx\C-Values
Road will be maintained. Existing elevations along the north and west will also be
maintained. Areas along the western property line will be modified through
grading off-site within a drainage easement.
Existing elevations and vegetation on the western and northern sides of the subject
property will be preserved.
As previously mentioned, overall drainage patterns of the existing site will be
maintained.