HomeMy WebLinkAboutSTANFORD SENIOR LIVING - PDP200022 - SUBMITTAL DOCUMENTS - ROUND 2 - DRAINAGE REPORT
PRLIMINARY DRAINAGE REPORT
STANFORD SENIOR LIVING
Fort Collins, Colorado
March 31, 2021
Prepared for:
United Properties
1331 17th Street
Denver, CO 80202
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: 1530-002
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.
March 31, 2021
City of Fort Collins
Stormwater Utility
700 Wood Street
Fort Collins, Colorado 80521
RE: Preliminary Drainage Report for
Stanford Senior Living
Dear Staff:
Northern Engineering is pleased to submit this Preliminary Drainage Report for your review. This
report accompanies the Preliminary Development Review submittal for the proposed Stanford Senior
Living.
This report has been prepared in accordance with the Fort Collins Stormwater Criteria Manual
(FCSCM) and Urban Storm Drainage Criteria Manual. This report serves to document the
stormwater impacts associated with the proposed Stanford Senior Living 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.
Blaine Mathisen, EI Stephanie Thomas, PE
Project Engineer Project Manager
Stanford Senior Living
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 ......................................................................................................................... 7
E. Hydraulic Criteria .............................................................................................................................. 7
F. Floodplain Regulations Compliance .................................................................................................. 8
G. Modifications of Criteria ................................................................................................................... 8
IV. DRAINAGE FACILITY DESIGN .................................................................................... 8
A. General Concept ............................................................................................................................... 8
B. Specific Details ................................................................................................................................ 10
V. CONCLUSIONS ...................................................................................................... 11
A. Compliance with Standards ............................................................................................................ 11
B. Drainage Concept ............................................................................................................................ 11
References ....................................................................................................................... 12
APPENDICES:
APPENDIX A – Hydrologic Computations
APPENDIX B – Hydraulic Computations
B.1 – Storm Sewers (For Future Use)
B.2 – Inlets (For Future Use)
B.3 – Detention Facilities
APPENDIX C – Water Quality Design Computations
APPENDIX D – Erosion Control Report
APPENDIX E – Additional References
Stanford Senior Living
Final Drainage Report
LIST OF TABLES AND FIGURES:
Figure 1 - Vicinity Map ........................................................................................................ 1
Figure 2 – Aerial Photograph ................................................................................................ 3
Figure 3 – Existing FEMA Floodplains .................................................................................... 4
Figure 4 – Existing City Floodplains ....................................................................................... 5
Table 1 - Pond Summary ................................................................................................... 11
Table 2 - Chamber Count Summary ..................................................................................... 11
MAP POCKET:
Existing Drainage Exhibit
DR1 - Drainage Exhibit
Stanford Senior Living
Preliminary Drainage Report 1
I. GENERAL LOCATION AND DESCRIPTION
A. Location
1. Vicinity Map
Figure 1 - Vicinity Map
2. Stanford Senior Living project is located in the southwest quarter of Section 25,
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 at the southwest corner of the Stanford Road and Monroe
Drive intersection.
4. Currently the site is vacant on the north side of the lot with native grasses and
patches of gravel. The south half of the project site is currently an asphalt parking lot
with landscaped medians that the Marriot Hotel is currently utilizing for guest parking.
The undeveloped portion of the site drains via overland flow at an average grade of
3.50% to the south towards the existing parking lot. In general, the site conveys
stormwater runoff from the north to the south where it is collected by a customized
inlet in the southeast corner of the existing parking lot.
5. In the existing condition most of the site is being captured by a custom inlet in the
southeast corner of the parking lot that was designed per Strachan Subdivision 3rd
Filing. A small portion of the existing drive entrance aisle is being conveyed via curb
and gutter to existing inlets at the northwest corner of the Stanford Road and
Horsetooth Road intersection. Both the custom inlet in the parking lot and inlets at
Stanford Senior Living
Preliminary Drainage Report 2
the intersection tie into existing 30”x36” HERCP pipes. From there the runoff is
routed via the HERCP pipes into Warren Lake which is located at the southeast corner
of the Stanford Road and Horsetooth Road intersection.
6. “Stanford Senior Living is in the Foothills Drainage Basin Master Plan that was
prepared by Resource Consultants, Inc. and dated July 1980. The Strachan
Subdivision Third Filing was developed in 1980 and was divided into two basins.
The Southerly Basin, which contains 17.9 acres and drains to the corner of
Horsetooth Road and Stanford Road. Mitchell and Co. were the developers, and they
paid the Warren Lake Company for storm water detention rights in Warren Lake for
Strachan Subdivision 1st, 2nd, and 3rd Filings. These filings correspond to the area
between Monroe Drive and Horsetooth Road and between College Avenue and
Stanford Road. They also developed the Strachan Continental Subdivision at the
southwest corner of Horsetooth Road and J.F.K Parkway. Its detention was also paid
for in Warren Lake.” – Final Drainage Report for J.F.K. Office P.U.D
7. According to the Final Drainage Report for J.F.K. Office P.U.D the HERCP pipes in the
southeast corner of the parking lot were sized to carry the 10-year event (48 cfs) for
the Strachan Subdivision while the 100-year event overtopped Horsetooth Road and
sheet flowed to Warren Lake. Due to the report being 40 years old it is important that
the Stanford Senior Living project does not adversely impact downstream
infrastructure but is still allowed to utilize the Warren Lake Company agreement to
some degree. Therefore, the Stanford Senior Living project will detain the difference
between the historic 10-year runoff and the proposed 100-year runoff. By utilizing
this approach, the Stanford Senior Living center will be reducing the historic flows to
the existing inlet at the corner of the parking lot because the current FCSCM
Standards are more conservative than they were when the original report was first
published. Additionally, the downstream infrastructure will not be adversely impacted,
and the Stanford Senior Living center will no longer contribute to the 100-year flows
that currently overtop Horsetooth Road during the major event.
B. Description of Property
1. The Stanford Senior Living project has a total acreage of 3.28 acres. However, the
Stanford Senior Living project only plans on developing 2.50 acres and leaving the
existing parking lot in place. The existing parking lot historically sheet flows to the
southeast to the custom inlet box as previously described. Therefore, Stanford Senior
Living will only be detaining and treating 2.50 acres. The proposed flows to the
existing inlet will be reduced because the Stanford Senior Living Center is detaining
the difference between the 10-year historic and 100-year developed. The 10-year
historic rate is also a conservative release because it assumed that there is no
pervious area currently on the 2.50 acres that are being developed and that is not the
case. There is currently a drive aisle and some gravel roads that are currently being
undetained and untreated. Please refer to Appendix A for the runoff calculations.
Stanford Senior Living
Preliminary Drainage Report 3
Figure 2 – Aerial Photograph
2. The Stanford Senior Living project will consist of a new assisted living and memory
care center. It will be a four-story building with underground parking. There is an
existing parking lot that is currently being used by the Marriot Hotel for guest parking
which will now serve as the Stanford Senior Living parking lot.
3. According to the United States Department of Agriculture (USDA) Natural Resources
Conservation Service (NRCS) Soil Survey, 100 percent of the site consists of Nunn
clay loam, which fails into Hydrologic Soil Group C
4. No irrigation facilities or major drainageways are within the property limits.
5. The project site is within a General Commercial District (C-G) 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 08069C0987G illustrates that this project site is not near any FEMA
delineated regulatory floodplain.
Stanford Senior Living
Preliminary Drainage Report 4
Figure 3 – Existing FEMA Floodplains
Stanford Senior Living
Preliminary Drainage Report 5
Figure 4 – Existing City Floodplains
II. DRAINAGE BASINS AND SUB-BASINS
A. Major Basin Description
1. The Stanford Senior Living project is in the Foothills Basin which is centrally located
in Fort Collins. The basin is mostly developed with commercial development along
College Avenue and mixed-use residential in the remainder of the basin. The basin
drains from west to east through open channels or a storm sewer system to the Fossil
Creek Reservoir.
B. Sub-Basin Description
1. The property historically drains from the northwest to the southeast corner of the
existing parking lot via overland flow. The existing parking lot was developed as a part
of the Strachan Subdivision 3rd Filing and is currently being used by the Marriot Hotel
and Merrill Lynch Wealth Management. As previously described, there is a custom
inlet in the southeast corner of the parking lot that has three 30”x36” HERCP that
currently routes the 10-year storm event east across Stanford Road to a junction box
that then routes the runoff south across Horsetooth Road where it is ultimately
discharged into Warren Lake. The 100-year event has historically overtopped
Horsetooth Road and overland flowed south to Warren Lake. There are two on-grade
inlets at the northwest corner of the intersection of Horsetooth Road and Stanford
Road that collects additional flows. These additional flows are then routed to the
existing 30”x36” HERCP pipes crossing Stanford Road.
2. A historic rational calculation was performed for the 2.33 acres of the 3.79 acres that
are being platted for the Stanford Senior Living project. According the FCSCM Chapter
6 developments are only responsible for detaining any newly installed impervious
areas. Since the parking lot is existing, and downstream of the new development, the
Stanford Senior Living project will not be detaining or treating any runoff that has
historically drained to the custom inlet at the southeast corner of the parking lot.
Additionally, the Stanford Senior Living project is maintaining the existing drainage
patterns within Stanford Road and Monroe Drive. Therefore, no runoff generated on
the adjacent streets will be routed through the proposed detention and water quality
facility.
3. Following FCSCM requirements for rational calculations the 10-year runoff generated
by the existing 2.33 acres is 2.33 cfs. Therefore, Stanford Senior Living can have a
max release rate of 2.33 cfs. Traditionally, Fort Collins requires the 2-year event
dictate the max release rate but since there is a historic agreement in place with
Warren Lake Company to detain all runoff from Strachan Subdivision Third Filing this
new development can release at a higher release rate than current FCSCM
requirements. By releasing at the historic 10-year event it ensures that downstream
infrastructure is not adversely impacted while also allowing the developers to use their
agreement with Warren Lake Company to some extent. See Section IV.A.4 below for a
more detailed description of the project’s proposed drainage patterns.
4. No offsite drainage is being routed through the property.
5. Please refer to the Appendix for additional information about the existing conditions.
Stanford Senior Living
Preliminary Drainage Report 6
III. DRAINAGE DESIGN CRITERIA
A. Regulations
There are optional provisions outside of the FCSCM proposed with the Stanford Senior
Living project. Stanford Senior Living project will be detaining the difference between the
historic 10-year event and proposed 100-year event. This deviates from the standard
existing 2-year and proposed 100-year difference for detention requirements set forth in
the FCSCM.
B. Four Step Process
The overall stormwater management strategy employed with Stanford Senior Living 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:
Providing vegetated open areas along the north, south, east and west portion of the
site to reduce the overall impervious area and to minimize directly connected
impervious areas (MDCIA).
Routing runoff through the drain rock within the underground detention facility to
increase time of concentration, promote infiltration, and provides water quality via the
isolator rows.
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 and provide the necessary
BMPs required for water quality. All runoff that is captured on site will be routed through
isolator rows within Stormtech chambers. The isolator rows will remove sediment and
other pollutants through filtration.
Step 3 – Stabilize Drainageways
As stated in Section I.B.4, above, there are no major drainageways in or near the subject
site. While this step may not seem applicable to Stanford Senior Living, the proposed
project indirectly helps achieve stabilized drainageways nonetheless. Once again, site
selection has a positive effect on stream stabilization. By detaining the difference between
the 10-year and 100-year events there will be less stress on the downstream
infrastructure. Combining detention with LID it reduces the likelihood of bed and bank
erosion within Warren Lake. 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
necessarily applicable for this project. However, a localized trash collection system that is
stored internally to the building will reduce the potential impacts of garbage making its
way downstream.
Stanford Senior Living
Preliminary Drainage Report 7
C. Development Criteria Reference and Constraints
1. There are existing drainage studies for this area. They were completed as part of the
Strachan Continental Subdivision as well as the J.F.K Office P.U.D. These reports
can be found in the Appendix and serve as the basis for the 10-year release rate.
2. The subject property is 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 northern and eastern right-of-way lines make it
difficult to capture all the flow along these edges. However, it should be noted that
the areas that are freely discharging to either Monroe Drive or Stanford Road are
associated with the vegetated parkways. Therefore, runoff impacts are minor, and
it still maintains the existing conveyance path for these areas.
As previously mentioned, overall drainage patterns within the Master Drainage
Plan for Strachan Continental Subdivision will be maintained. The conveyance
path that runoff is using is the same as it historically has been. There are issues
with the Strachan Continental master plan as it is no longer compliant with code.
However, at the time of this report there are no known issues with this existing
master drainage plan. The city has not identified the intersection of Horsetooth
Road and Stanford Road as a problem intersection and there are currently no
future plans to revitalize this intersection. However, the Stanford Senior Living
Center is proposing detaining and treating 2.50 acres of runoff in order to help
alleviate some of the downstream infrastructure. For additional information on
detention and water quality please see Section IV.B of this report.
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. The first event analyzed is the “Minor,” or “Initial” Storm, which has a 2-
year recurrence interval. The second event considered is the “Major Storm,” which
has a 100-year recurrence interval. The third storm computed, for detention
requirements, is the 10-year recurrence interval.
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 drains into the custom inlet at
the southeast corner of the existing parking lot. From there, the runoff is routed via a
series of elliptical pipes to Warren Lake where it has been historically detained and
treated for water quality.
Stanford Senior Living
Preliminary Drainage Report 8
2. All drainage facilities proposed with Stanford Senior Living project are designed in
accordance with criteria outlined in the FCSCM and/or the Mile High Flood Control
District’s 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. Stanford Senior Living 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
1. The proposed Stanford Senior Living development is requesting a modification at this
time. As previously stated, the original Strachan Thrid Filing included this area as part
of the agreement with Warren Lake Company to detain and provide water quality
treatment for developed stormwater runoff. However, to meet current FCSCM
requirements Stanford Senior Living can no longer allow the 100-year event to overtop
Horsetooth Road. Therefore, to meet current FCSCM criteria while also utilizing the
Warren Lake agreement to the fullest extent possible Stanford Senior Living will be
detaining the difference between the historic 10-year event and proposed 100-year
event.
IV. DRAINAGE FACILITY DESIGN
A. General Concept
1. The main objectives of Stanford Senior Living drainage design is to improve the
surrounding stormwater infrastructure while also maintaining existing drainage
patterns.
2. As previously mentioned, there are no off-site flows draining onto the existing
property.
3. A list of tables and figures used within this report can be found in the Table of
Contents at the front of the document. The tables and figures are located within the
sections to which the content best applies.
4. The Stanford Senior Living project is composed of nine minor drainage basins,
designated as Basins A, B, C, D, E, F, G, H, and OS. The drainage patterns for each
major basin are further described below.
Basin A
Basin A represents the area in the northwest corner of the site. It consists of a small
portion of concrete walk but most of the area is landscaping. Runoff from this basin
will enter the storm sewer and be conveyed to the Stormtech chambers.
Basin B
Basin B encompasses a small area near the trash enclosure. Runoff generated in
Basin B will enter the storm sewer system via an area inlet and be conveyed to the
Stormtech chambers.
Stanford Senior Living
Preliminary Drainage Report 9
Basin C
Basin C is associated with the memory care garden near the northeast corner of the
site. Runoff in Basin C will be collected via area inlets and be routed via storm sewer
to the Stormtech chambers.
Basin D
Basin D consists of a small amount of concrete walk and the rest being landscaping
with a swale conveying stormwater runoff to an area drain near the drive entrance to
the site. Runoff from Basin D will be conveyed to the Stormtech chambers via a storm
sewer.
Basin E
Basin E shown as the area in front of the building. This area consists of concrete
walks, asphalt drive aisles, and landscaped islands. Runoff from Basin E is collected
via a series of area drains. Once runoff is collected in the area drains the runoff is
routed to the Stormtech chambers via the storm sewer.
Basin F
Basin F is associated with the drive entrance that will flow east and be captured by an
on-grade inlet. Runoff will then be routed to the Stormtech chambers via the storm
sewer.
Basin G
Basin G is a swath of land along southwest boundary near the Marriot Hotel. Runoff
generated in Basin G will flow along the property line in a landscape swale and then
be routed to an area inlet that is located at the entrance to the garage. From there the
runoff will be conveyed via the storm sewer to the Stormtech chambers.
Basin H
Basin H encompasses the entire building. Most of the runoff from Basin H will be
collected in roof leaders and conveyed to the Stormtech chambers via the storm
sewer. There is also an internal courtyard in the center of the building which will
generate a small amount of runoff. Runoff from the courtyard will be collected by area
drains which will convey the stormwater to the storm sewer that runs through the
building. This run of storm sewer will connect to the outside storm sewer where the
runoff will then be conveyed to the Stormtech chambers.
Basin OS
Basin OS is a small amount of landscaping and concrete area that cannot be captured
on site because of topographic constraints. Runoff from Basin OS sheet flows north
offsite to Monroe Drive where it then flows east towards Stanford Road. Once in
Stanford Road it flows south to the inlet at the northwest corner of the Horestooth
Road and Stanford Road intersection. This flow has historically contributed to the
Stanford Senior Living
Preliminary Drainage Report 10
100-year overtopping spill at Horsetooth Road. However, the Stanford Senior Living
project has throttled the max release rate by the 100-year runoff from Basin OS to
help alleviate this issue. The 100-year runoff from Basin OS is 0.50 cfs, therefore the
max release rate from the Stormtech chambers has been reduced an additional 0.50
cfs.
A full-size copy of the Drainage Exhibit can be found in the Map Pocket at the end of
this report.
B. Specific Details
1. The release rate for the proposed development was established by calculating the 10-
year historic runoff rate of the area proposed for development minus the 100-year
developed flow from Basin OS as previously discussed. As mentioned in section III.G
this is a modification to the FCSCM. By utilizing a reduced historic 10-year peak
runoff the Stanford Senior Living project will maintain downstream infrastructure while
also utilizing their agreement with Warren Lake Company to detain this site’s runoff.
2. The Stanford Senior Living project area will no longer be contributing to the spill that
overtops Horsetooth Road during the major event because the project is detaining the
difference between he historic 10-year and developed 100-year runoff.
3. These release rates were utilized in the FAA method for design of the pond. (Refer to
Appendix B for these calculations).
4. Detention Pond Calculations
Pond
Calculations were completed for the underground pond, based on the proposed land
use characteristics of Basins A, B, C, D, E, F, G, and H with a release rate of 1.73
cfs, indicates a detention volume of 23,652 cu. ft. Based on Stormtech specifications
in order to achieve 23,652 cu. ft. of detention it will require 127 MC-3500
chambers. However, based on the Stormtech system layout Stanford Senior Living
will be providing 24,609 cu. ft. of detention.
5. Water Quality Pond Calculations
Pond
The Stanford Senior Living project will be providing 100% of their water quality
capture volume in the form of isolator rows within the Stormtech system. Isolator
rows qualify as a BMP measure and therefore 100% of the water quality capture
volume will be provided in the form of low impact development (LID). Isolator rows
are designed to retain sediment and filter out the first flush of any storm event. At the
end of each isolator row is a Nyloplast Basin that allows for routine and easy
maintenance so that the entire system can be maintained for its design life. Even
though Basin OS can not be captured the Stanford Senior Living project will still be
providing WQCV for that area.
Following FCSCM requirements yields a WQCV of 2,538 cu. ft. Utilizing available
chamber sizing and infiltration data provided by Stormtech requires 22 additional
MC-3500 chambers to meet the required WQCV.
Stanford Senior Living
Preliminary Drainage Report 11
6. Pond Summary
Pond 1
The Stanford Senior Living project will be utilizing 147 MC-3500 Stormtech
chambers to fulfill their stormwater detention and treatment requirements. Stanford
Senior Living will be providing 100% WQCV using LID measures.
Reuired
Detention
(cu. ft.)
Provided
Detention
(cu. ft.)
Required
WQCV
(cu. ft.)
Provided
WQCV
(cu. ft.)
Required
Total
Volume
(cu. ft.)
Provided
Volume
(cu. ft.)
23,652 24,609 2,538 2,625 26,190 27,234
Table 1 - Pond Summary
MC-3500 Chamber Counts
Detention WQCV Total
127 22 149
Table 2 - Chamber Count Summary
V. CONCLUSIONS
A. Compliance with Standards
1. The drainage design proposed with Stanford Senior Living project complies with the
City of Fort Collins’ Stormwater Criteria Manual.
2. The drainage design proposed with Stanford Senior Living project complies with the
City of Fort Collins’ Master Drainage Plan for the Foothills Basin.
3. The drainage design proposed with Stanford Senior Living project complies with the
Master Drainage Plan for Strachan Continental Subdivision.
4. There are no regulatory floodplains associated with the Stanford Senior Living
development.
5. The drainage plan and stormwater management measures proposed with the Stanford
Senior Living 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 drainage design proposed with this project
will be utilizing the agreement with the Warren Lake Company to some extent.
2. The Stanford Senior Living project will detain the difference between the historic 10-
year event and the developed 100-year event.
3. The Stanford Senior Living project will be providing 100% WQCV using an LID
measure.
Stanford Senior Living
Preliminary Drainage Report 12
References
1. City of Fort Collins Landscape Design Guidelines for Stormwater and Detention Facilities,
November 5, 2009, BHA Design, Inc. with City of Fort Collins Utility Services.
2. Fort Collins Stormwater Criteria Manual, City of Fort Collins, Colorado, as adopted by Ordinance No.
174, 2011, and referenced in Section 26-500 (c) of the City of Fort Collins Municipal Code.
3. Larimer County Urban Area Street Standards, Adopted January 2, 2001, Repealed and
Reenacted, Effective October 1, 2002, Repealed and Reenacted, Effective April 1, 2007.
4. Soils Resource Report for Larimer County Area, Colorado, Natural Resources Conservation
Service, United States Department of Agriculture.
5. Urban Storm Drainage Criteria Manual, Volumes 1-3, Urban Drainage and Flood Control
District, Wright-McLaughlin Engineers, Denver, Colorado, Revised April 2008.
6. Final Drainage Report For J.F.K Office P.U.D, January 9, 1995, Vaught-Frye Architects
7. Strachan Continental Subdivision Storm Drainage Report, July 3, 1981, James H. Stewart &
Associates, INC
APPENDIX A
HYDROLOGIC COMPUTATIONS
CHARACTER OF SURFACE1:
Percentage
Impervious
2-yr Runoff
Coefficient
10-yr Runoff
Coefficient
100-yr Runoff
Coefficient
Developed
Asphalt .…………………………..……………………………………………….…………………………..……………………………………………….…………………………..……………………………………………….…………………………..………………………………………………100%0.95 0.95 1.19
Concrete .…………………………..……………………………………………….…………………………..……………………………………………….…………………………..……………………………………………….…………………………..………………………………………………100%0.95 0.95 1.19
Rooftop .…………………………..……………………………………………….…………………………..……………………………………………….…………………………..……………………………………………….…………………………..………………………………………………90%0.95 0.95 1.19
Gravel .…………………………..……………………………………………….…………………………..……………………………………………….…………………………..……………………………………………….…………………………..………………………………………………40%0.50 0.50 0.63
Pavers .…………………………..……………………………………………….…………………………..……………………………………………….…………………………..……………………………………………….…………………………..………………………………………………40%0.50 0.50 0.63
Landscape or Pervious Surface
Playgrounds .…………………………..……………………………………………….…………………………..……………………………………………….…………………………..……………………………………………….…………………………..………………………………………………25%0.35 0.35 0.44
Lawns Clayey Soil .…………………………..……………………………………………….…………………………..……………………………………………….…………………………..……………………………………………….…………………………..………………………………………………2%0.25 0.25 0.31
Lawns Sandy Soil .…………………………..……………………………………………….…………………………..……………………………………………….…………………………..……………………………………………….…………………………..……………………………………………….…………………………..……………………………………………….…………………………..………………………………………………2%0.15 0.15 0.19
Notes:
Basin ID Basin Area
(ac)
Area of
Asphalt
(ac)
Area of
Concrete
(ac)
Area of
Rooftop
(ac)
Area of
Gravel
(ac)
Area of
Pavers
(ac)
Area of
Playgrounds
(ac)
Area of Lawns
(ac)
Composite
% Imperv.
2-year
Composite Runoff
Coefficient
10-year
Composite
Runoff
Coefficient
100-year
Composite
Runoff
Coefficient
H 2.50 0.00 0.00 0.00 0.00 0.00 0.00 2.50 2%25%25%31%
HISTORIC BASIN % IMPERVIOUSNESS AND RUNOFF COEFFICIENT CALCULATIONS
2) Runoff Coefficients are taken from the Fort Collins Stormwater Criteria Manual, Chapter 3. Table 3.2-1 and 3.2-2
1) Percentage impervious taken from the Fort Collins Stormwater Criteria Manual, Chapter 5, Table 4.1-2 and Table 4.1-3
Overland Flow, Time of Concentration:
Channelized Flow, Time of Concentration:
Total Time of Concentration :
T c is the lesser of the values of Tc calculated using T c = T i + T t
C2 C100
Length,
L
(ft)
Slope,
S
(%)
Ti2 Ti100
Length,
L
(ft)
Slope,
S
(%)
Roughness
Coefficient
Assumed
Hydraulic
Radius
Velocity,
V
(ft/s)
Tt
(min)Tc (Eq. 3.3-5) Tc2 = Ti +Tt Tc100 = Ti +Tt Tc2 Tc100
h H 0.25 0.31 310 2.75% 20.0 18.6 0 N/A N/A N/A N/A N/A 11.7 20.0 18.6 11.7 11.7
HISTORIC TIME OF CONCENTRATION
Channelized Flow
Design
Point Basin
Overland Flow Time of Concentration
Frequency Adjustment Factor:
(Equation 3.3-2 FCSCM)
(Equation 5-5 FCSCM)
(Equation 5-4 FCSCM)
(Equation 3.3-5 FCSCM)
Table 3.2-3 FCSCM
Therefore Tc2=Tc10
Rational Method Equation:
Rainfall Intensity:
h H 2.50 11.7 11.7 0.25 0.31 2.09 3.57 7.29 1.31 2.23 5.65
HISTORIC RUNOFF COMPUTATIONS
Design
Point Basin(s)Area, A
(acres)
Tc2
(min)
Flow,
Q2
(cfs)
Flow,
Q100
(cfs)
C2 C100
IDF Table for Rational Method - Table 3.4-1 FCSCM
Intensity,
i10
(in/hr)
Flow,
Q10
(cfs)
Tc100
(min)
Intensity,
i2
(in/hr)
Intensity,
i100
(in/hr)
()()()AiCCQf=
BASIN
TOTAL
AREA
(acres)
Tc2
(min)
Tc100
(min)
C2 C100
Q2
(cfs)
Q10
(cfs)
Q100
(cfs)
H 2.50 11.7 11.7 0.25 0.31 1.31 2.23 5.65
Rational Flow Summary | Historic Basin Flow Rates
3/25/202112:44 PM P:\1530-002\Drainage\Hydrology\1530-002_Historical Rational Calcs (FCSCM).xlsx\Summary Tables
CHARACTER OF SURFACE1:
Percentage
Impervious
2-yr Runoff
Coefficient
10-yr Runoff
Coefficient
100-yr Runoff
Coefficient
Developed
Asphalt .…………………………..……………………………………………….…………………………..……………………………………………….…………………………..……………………………………………….…………………………..………………………………………………100%0.95 0.95 1.19
Concrete .…………………………..……………………………………………….…………………………..……………………………………………….…………………………..……………………………………………….…………………………..………………………………………………100%0.95 0.95 1.19
Rooftop .…………………………..……………………………………………….…………………………..……………………………………………….…………………………..……………………………………………….…………………………..………………………………………………90%0.95 0.95 1.19
Gravel .…………………………..……………………………………………….…………………………..……………………………………………….…………………………..……………………………………………….…………………………..………………………………………………40%0.50 0.50 0.63
Pavers .…………………………..……………………………………………….…………………………..……………………………………………….…………………………..……………………………………………….…………………………..………………………………………………40%0.50 0.50 0.63
Landscape or Pervious Surface
Playgrounds .…………………………..……………………………………………….…………………………..……………………………………………….…………………………..……………………………………………….…………………………..………………………………………………25%0.35 0.35 0.44
Lawns Clayey Soil .…………………………..……………………………………………….…………………………..……………………………………………….…………………………..……………………………………………….…………………………..………………………………………………2%0.25 0.25 0.31
Lawns Sandy Soil .…………………………..……………………………………………….…………………………..……………………………………………….…………………………..……………………………………………….…………………………..……………………………………………….…………………………..……………………………………………….…………………………..………………………………………………2%0.15 0.15 0.19
Notes:
Basin ID Basin Area
(ac)
Area of
Asphalt
(ac)
Area of
Concrete
(ac)
Area of
Rooftop
(ac)
Area of
Gravel
(ac)
Area of
Pavers
(ac)
Area of
Playgrounds
(ac)
Area of Lawns
(ac)
Composite
% Imperv.
2-year
Composite Runoff
Coefficient
10-year
Composite
Runoff
Coefficient
100-year
Composite
Runoff
Coefficient
A 0.12 0.00 0.02 0.00 0.00 0.00 0.00 0.11 17%0.36 0.36 0.45
B 0.05 0.00 0.04 0.00 0.00 0.00 0.00 0.01 82%0.82 0.82 1.03
C 0.09 0.00 0.09 0.00 0.00 0.00 0.00 0.00 100%0.95 0.95 1.19
D 0.41 0.00 0.07 0.00 0.00 0.00 0.00 0.34 18%0.37 0.37 0.46
E 0.27 0.21 0.02 0.00 0.00 0.00 0.00 0.05 84%0.83 0.83 1.04
F 0.05 0.03 0.01 0.00 0.00 0.00 0.00 0.01 79%0.80 0.80 1.00
G 0.19 0.03 0.02 0.00 0.00 0.00 0.00 0.15 26%0.42 0.42 0.52
H 1.15 0.00 0.00 1.15 0.00 0.00 0.00 0.00 90%0.95 0.95 1.19
OS 0.15 0.00 0.00 0.00 0.00 0.00 0.00 0.14 5%0.27 0.27 0.34
Basins A-OS 2.50 0.27 0.27 1.15 0.00 0.00 0.00 0.81 64% 0.72 0.72 0.91
DEVELOPED BASIN % IMPERVIOUSNESS AND RUNOFF COEFFICIENT CALCULATIONS
2) Runoff Coefficients are taken from the Fort Collins Stormwater Criteria Manual, Chapter 3. Table 3.2-1 and 3.2-2
1) Percentage impervious taken from the Fort Collins Stormwater Criteria Manual, Chapter 5, Table 4.1-2 and Table 4.1-3
Combined Basins
Overland Flow, Time of Concentration:
Channelized Flow, Time of Concentration:
Total Time of Concentration :
T c is the lesser of the values of Tc calculated using T c = T i + T t
C2 C100
Length,
L
(ft)
Slope,
S
(%)
Ti2 Ti100
Length,
L
(ft)
Slope,
S
(%)
Roughness
Coefficient
Assumed
Hydraulic
Radius
Velocity,
V
(ft/s)
Tt
(min)Tc (Eq. 3.3-5) Tc2 = Ti +Tt Tc100 = Ti +Tt Tc2 Tc100
a A 0.36 0.45 50 11.00%4.4 3.9 0 N/A N/A N/A N/A N/A 10.3 4.4 3.9 5.0 5.0
b B 0.82 1.03 25 5.20%1.5 0.4 0 N/A N/A N/A N/A N/A 10.1 1.5 0.4 5.0 5.0
c C 0.95 1.19 30 4.00%1.0 -0.6 0 N/A N/A N/A N/A N/A 10.2 1.0 -0.6 5.0 5.0
d D 0.37 0.46 20 15.00%2.5 2.2 260 2.23%0.025 0.45 5.23 0.8 11.6 3.3 3.0 5.0 5.0
e E 0.83 1.04 37 4.76%1.8 0.4 19 0.50%0.013 0.15 2.29 0.1 10.3 2.0 0.5 5.0 5.0
f F 0.80 1.00 25 2.24%2.1 0.7 35 3.43%0.013 0.15 5.99 0.1 10.3 2.2 0.8 5.0 5.0
g G 0.42 0.52 25 12.00%2.8 2.4 75 5.00%0.025 0.45 7.83 0.2 10.6 2.9 2.5 5.0 5.0
h H 0.95 1.19 15 0.67%1.2 -0.7 0 N/A N/A N/A N/A N/A 10.1 1.2 -0.7 5.0 5.0
os OS 0.27 0.34 10 21.00%1.8 1.6 0 N/A N/A N/A N/A N/A 10.1 1.8 1.6 5.0 5.0
Stormtech Basins A-OS 0.72 0.91 20 2.25% 2.4 1.2 15 1.20% 1.30% 15.00% 0.35 0.7 10.2 3.1 1.9 5.0 5.0
Combined Basins
DEVELOPED DIRECT TIME OF CONCENTRATION
Channelized Flow
Design
Point Basin
Overland Flow Time of Concentration
Frequency Adjustment Factor:
(Equation 3.3-2 FCSCM)
(Equation 5-5 FCSCM)
(Equation 5-4 FCSCM)
(Equation 3.3-5 FCSCM)
Table 3.2-3 FCSCM
Therefore Tc2=Tc10
Rational Method Equation:
Rainfall Intensity:
a A 0.12 5.0 5.0 0.36 0.45 2.85 4.87 9.95 0.13 0.22 0.56
b B 0.05 5.0 5.0 0.82 1.03 2.85 2.85 9.95 0.12 0.12 0.55
c C 0.09 5.0 5.0 0.95 1.19 2.85 2.85 9.95 0.24 0.24 1.07
d D 0.41 5.0 5.0 0.37 0.46 2.85 2.85 9.95 0.43 0.43 1.89
e E 0.27 5.0 5.0 0.83 1.04 2.85 2.85 9.95 0.65 0.65 2.84
f F 0.05 5.0 5.0 0.80 1.00 2.85 2.85 9.95 0.11 0.11 0.50
g G 0.19 5.0 5.0 0.42 0.52 2.85 2.85 9.95 0.23 0.23 1.00
h H 1.15 5.0 5.0 0.95 1.19 2.85 2.85 9.95 3.12 3.12 13.66
os OS 0.15 5.0 5.0 0.27 0.34 2.85 2.85 9.95 0.11 0.11 0.50
Stormtech Basins A-OS 2.50 5.0 5.0 0.72 0.91 2.85 2.85 9.95 5.13 6.48 22.64
DEVELOPED RUNOFF COMPUTATIONS
Design
Point Basin(s)Area, A
(acres)
Tc2
(min)
Flow,
Q2
(cfs)
Flow,
Q100
(cfs)
C2 C100
IDF Table for Rational Method - Table 3.4-1 FCSCM
Intensity,
i10
(in/hr)
Flow,
Q10
(cfs)
Combined Basins
Tc100
(min)
Intensity,
i2
(in/hr)
Intensity,
i100
(in/hr)
()()()AiCCQf=
BASIN
TOTAL
AREA
(acres)
Tc2
(min)
Tc100
(min)
C2 C100
Q2
(cfs)
Q100
(cfs)
A 0.12 5.0 5.0 0.36 0.45 0.13 0.56
B 0.05 5.0 5.0 0.82 1.03 0.12 0.55
C 0.09 5.0 5.0 0.95 1.19 0.24 1.07
D 0.41 5.0 5.0 0.37 0.46 0.43 1.89
E 0.27 5.0 5.0 0.83 1.04 0.65 2.84
F 0.05 5.0 5.0 0.80 1.00 0.11 0.50
G 0.19 5.0 5.0 0.42 0.52 0.23 1.00
H 1.15 5.0 5.0 0.95 1.19 3.12 13.66
OS 0.15 5.0 5.0 0.27 0.34 0.11 0.50
Basins A-OS 2.50 5.0 5.0 0.72 0.91 5.13 22.64
Rational Flow Summary | Developed Basin Flow Rates
Combined Basins
3/25/202112:42 PM P:\1530-002\Drainage\Hydrology\1530-002_Proposed Rational Calcs (FCSCM).xlsx\Summary Tables
APPENDIX B
HYDRAULIC COMPUTATIONS
B.1 – Storm Sewers
B.2 – Inlets
B.3 – Detention Facilities
APPENDIX B.1
STORM SEWERS (FOR FUTURE USE)
APPENDIX B.2
INLETS (FOR FUTURE USE)
APPENDIX B.3
DETENTION FACILITIES
Pond No :
Pond
100-yr
0.91
5.00 min 23652 ft3
2.50 acres 0.543 ac-ft
Max Release Rate =1.73 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 6791 1.00 1.73 519 6272
10 7.720 10538 0.75 1.30 779 9759
15 6.520 13350 0.67 1.15 1038 12312
20 5.600 15288 0.63 1.08 1298 13991
25 4.980 16994 0.60 1.04 1557 15437
30 4.520 18509 0.58 1.01 1817 16693
35 4.080 19492 0.57 0.99 2076 17416
40 3.740 20420 0.56 0.97 2336 18085
45 3.460 21253 0.56 0.96 2595 18658
50 3.230 22045 0.55 0.95 2855 19190
55 3.030 22748 0.55 0.94 3114 19634
60 2.860 23423 0.54 0.94 3374 20050
65 2.720 24133 0.54 0.93 3633 20500
70 2.590 24747 0.54 0.93 3893 20855
75 2.480 25389 0.53 0.92 4152 21237
80 2.380 25990 0.53 0.92 4412 21578
85 2.290 26570 0.53 0.92 4671 21899
90 2.210 27150 0.53 0.91 4931 22219
95 2.130 27621 0.53 0.91 5190 22431
100 2.060 28119 0.53 0.91 5450 22670
105 2.000 28665 0.52 0.91 5709 22956
110 1.940 29129 0.52 0.90 5969 23161
115 1.890 29668 0.52 0.90 6228 23440
120 1.840 30139 0.52 0.90 6488 23652
*Note: Using the method described in FCSCM Chapter 6 Section 2.3
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
1530-002
Stanford Senior Living
Project Number :
Project Name :
Stormtech Detention
Page 1 of 1
1530-002_FAAModified Method.xls
User Inputs
Chamber Model: MC-3500
Outlet Control Structure: Yes
Project Name: The Stanford
Engineer: Blaine Mathisen
Project Location: Colorado
Measurement Type: Imperial
Required Storage Volume: 23652 cubic ft.
Stone Porosity: 40%
Stone Foundation Depth: 9 in.
Stone Above Chambers: 12 in.
Average Cover Over Chambers: 18 in.
Design Constraint Dimensions:(100 ft. x 100 ft.)
Results
System Volume and Bed Size
Installed Storage Volume: 24608.62 cubic ft.
Storage Volume Per Chamber: 109.90 cubic ft.
Number Of Chambers Required: 127
Number Of End Caps Required: 22
Chamber Rows: 11
Maximum Length:96.24 ft.
Maximum Width: 78.18 ft.
Approx. Bed Size Required: 7289.80 square ft.
System Components
Amount Of Stone Required: 955.88 cubic yards
Volume Of Excavation (Not Including
Fill):
1484.96 cubic yards
APPENDIX C
WATER QUALITY DESIGN COMPUTATIONS
Project Title Date:
Project Number Calcs By:
City
Basins
1
WQCV = Watershed inches of Runoff (inches)71%
a = Runoff Volume Reduction (constant)
i = Total imperviousness Ratio (i = Iwq/100)0.280 in
A =2.50 ac
V = 0.0583 ac-ft
V = Water Quality Design Volume (ac-ft)
WQCV = Water Quality Capture Volume (inches)
A = Watershed Area (acres)
The Stanford March 25, 2021
1530-002 B. Mathisen
Fort Collins
Stormtech Detention
2538 cu. ft.
Drain Time
a =
i =
WQCV =
Figure EDB-2 - Water Quality Capture Volume (WQCV), 80th Percentile Runoff Event
0.231
0
0.05
0.1
0.15
0.2
0.25
0.3
0.35
0.4
0.45
0.5
00.10.20.30.40.50.60.70.80.91WQCV (watershed inches)Total Imperviousness Ratio (i = Iwq/100)
Water Quality Capture Volume
6 hr
12 hr
24 hr
40 hr
()iii78.019.10.91aWQCV 23 +-=
()iii78.019.10.91aWQCV 23 +-=
AV*
12
WQCV
=
40 hr
Pond No :
Pond 1
WQ
0.91
5.00 min 2333 ft3
2.50 acres 0.05 ac-ft
Max Release Rate =0.53 cfs
Time (min)
Ft Collins
WQ
Intensity
(in/hr)
Inflow
Volume
(ft3)
Outflow
Adjustmen
t Factor
Qav
(cfs)
Outflow Volume
(ft3)
Storage Volume
(ft3)
5 1.425 973 1.00 0.53 158 815
10 1.105 1508 1.00 0.53 315 1193
15 0.935 1914 0.67 0.35 315 1599
20 0.805 2198 0.63 0.33 394 1804
25 0.715 2440 0.60 0.32 473 1967
30 0.650 2662 0.58 0.31 552 2110
35 0.585 2795 0.57 0.30 630 2164
40 0.535 2921 0.56 0.30 709 2212
45 0.495 3041 0.56 0.29 788 2252
50 0.460 3140 0.55 0.29 867 2273
55 0.435 3266 0.55 0.29 946 2320
60 0.410 3358 0.54 0.28 1025 2333
65 0.385 3416 0.54 0.28 1103 2313
70 0.365 3488 0.54 0.28 1182 2305
75 0.345 3532 0.53 0.28 1261 2271
80 0.330 3604 0.53 0.28 1340 2264
85 0.315 3655 0.53 0.28 1419 2236
90 0.305 3747 0.53 0.28 1497 2250
95 0.290 3761 0.53 0.28 1576 2184
100 0.280 3822 0.53 0.28 1655 2167
105 0.270 3870 0.52 0.28 1734 2136
110 0.260 3904 0.52 0.27 1813 2091
115 0.255 4003 0.52 0.27 1891 2111
120 0.245 4013 0.52 0.27 1970 2043
*Note: Using the method described in FCSCM Chapter 6 Section 2.3
DETENTION POND CALCULATION; MODIFIED FAA METHOD w/ Ft Collins IDF
Input Variables Results
Required Detention Volume
Fort Collins, Colorado
1530-002
The Stanford
Project Number :
Project Name :
Pond 1
A =
Tc =
Project Location :
Design Point
C =
Design Storm
Page 2 of 5
1530-002 Chamber Summary.xlsx
Vault IDTotal RequiredWQ Volume(cf)Flow,WQ(cfs)ChamberTypeChamber Release Ratea(cfs)ChamberVolumeb(cf)Installed Camber w/ Aggregatec(cf)Mimimum No. of ChambersdTotal Release Ratee(cfs)Required Storage Volume by FAA Method(cf)Mimimum No. of ChambersfStorage Provided within the Chambersg(cf)Total Installed System Volumeh(cf)Pond1 2538 2.24 MC-3500 0.038 109.90 175.00 15 0.56 2333222418 2625a. Release rate per chamber, limited by flow through geotextile with accumulated sediment.b. Volume within chamber only, not accounting for void spaces in surrounding aggregate.c. Volume includes chamber and void spaces (40%) in surrounding aggregate, per chamber unit.d. Number of chambers required to provide full WQCV within total installed system, including aggregate.e. Release rate per chamber times number of chambers.f. Number of chambers required to provide required FAA storage volume stored within the chamber only (no aggregate storage).g. Volume provided in chambers only (no aggregate storage). This number must meet or exceed the required FAA storage volume.h. System volume includes total number of chambers, plus surrounding aggregate. This number must meet or exceed the required WQCV.Chamber Configuration SummaryP:\1530-002\Drainage\WatQual\1530-002 Chamber Summary.xlsx
Chamber Dimensions SC-160 SC-310 SC-740 MC-3500 MC-4500
Width (in)34.0 34.0 51.0 77.0 100.0
Length (in)85.4 85.4 85.4 90.0 52.0
Height (in)16.0 16.0 30.0 45.0 60.0
Floor Area (sf)20.2 20.2 30.2 48.1 36.1
Chamber Volume (cf)6.9 14.7 45.9 109.9 106.5
Chamber/Aggregate Volume (cf)29.3 29.3 74.9 175.0 162.6
Flow Rate* 0.35 gpm/sf
1 cf =7.48052 gal
1 gallon =0.133681 cf
1 GPM = 0.002228 cfs
*Flow rate based on 1/2 of Nov 07 QMAX in Figure 17 of UNH Testing Report
SC-160 SC-310 SC-740 MC-3500 MC-4500
Flow Rate/chamber (cfs) 0.015724 0.015724 0.023586 0.037528 0.028159
end caps have a volume of 108.7 cu. ft.
StormTech Chamber Data
Chamber Flow Rate
Chamber Flow Rate Conversion (gpm/sf to cfs)
end caps have a volume of 45.1 cu. ft.
P:\1530-002\Drainage\WatQual\1530-002 Chamber Summary.xlsx
APPENDIX D
EROSION CONTROL REPORT
Stanford Senior Living
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.
APPENDIX E
ADDITIONAL REFERENCES
This unofficial copy was downloaded on Jun-30-2020 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 Jun-30-2020 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 Jun-30-2020 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 Jun-30-2020 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 Jun-30-2020 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 Jun-30-2020 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 Jun-30-2020 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 Jun-30-2020 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 Jun-30-2020 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 Jun-30-2020 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 Jun-30-2020 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 Jun-30-2020 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 Jun-30-2020 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 Jun-30-2020 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 Jun-30-2020 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 Jun-30-2020 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 Jun-30-2020 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 Jun-30-2020 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 Jun-30-2020 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 Jun-30-2020 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 Jun-30-2020 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 Jun-30-2020 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 Jun-30-2020 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 Jun-30-2020 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 Jun-30-2020 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 Jun-30-2020 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 Jun-30-2020 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 Jun-30-2020 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
MAP PACKET
EXISTING DRAINAGE EXHIBIT
DR1 – DRAINAGE EXHIBIT
D
VAULTF.O.
D
H
ex
D
D
TCONTROLIRR
D
MONROE DRIVE
(PRIVATE ROAD)STANFORD ROADPORTION OF LOT 3 STRACHAN
SUBDIVISION THIRD FILING
REC. NO. 20190052896
36" RCP
3
6
"
R
C
P
EX STRM MH 1
RIM = 5009.54
INV. IN = 5002.30 (W)
INV. IN = 5002.55 (N)
INV. IN = 5002.77 (NW)
INV. OUT = 5022.27 (SE)
EXISTING STORM STRUCTURE
PER STRACHAN 3RD FILING
EXISTING
30"X36" HERCP
EX STRM MH 2
RIM = 5005.30
BTM BOX = 5002.21
PORTION OF LOT 3 STRACHAN
SUBDIVISION THIRD FILING
REC. NO. 20180064205
TRACT J
FOOTHILLS MALL
REDEVELOPMENT SUB.
FILING NO. 3
LOT 6
FOOTHILLS MALL
REDEVELOPMENT SUB.
LOT 2 PRIVATE ROAD
REC.NO. 88042989 &
PORTION OF PARCEL 1
EXISTING
INLET
EXISTING INLET HORSETOOTH ROAD(3.7%)(2
.7%
)
(1
.
9%
)
(2
.1%
)
(4
.0%
)(2.5%)(6.4%)NORTH
( IN FEET )
0
1 INCH = 80 FEET
80 80 160 240
GRAPHIC SCALE:
LEGEND:
PROPERTY BOUNDARY
EXISTING STORM INLET
EXISTING CURB & GUTTER
EXISTING SLOPE
EXISTING MAJOR CONTOUR
RUNOFF SUMMARY:
A2
a3DESIGN POINT
DRAINAGE BASIN ID
DRAINAGE BASIN MINOR/MAJOR COEFF.
EXISTING STORM SEWER
BASIN DELINEATION
1. REFER TO "PRELIMINARY DRAINAGE REPORT FOR STANFORD SENIOR LIVING"
PREPARED BY NORTHERN ENGINEERING ON 03/31/2021 FOR ADDITIONAL
INFORMATION.
2. FOR HISTORIC RUNOFF CALCULATION ALL IMPERVIOUS AREA WAS ASSUMED TO
BE PERVIOUS.
NOTES:
GRAVEL
CONCRETE
ASPHALT
EXISTING DRAINAGE
EXHIBIT
FORT COLLINS, CO
STANFORD SENIOR LIVING
E N G I N E E R N GI
EHTRON R N
03.31.2021
P:\1530-002\DWG\DRNG\1530-001_EX-DRNG.DWG
DRAINAGE BASIN AREA
(2.0%)
BASIN
TOTAL
AREA
(acres)
Tc2
(min)
Tc100
(min)
C2 C100 Q2
(cfs)
Q10
(cfs)
Q100
(cfs)
H 2.50 11.7 11.7 0.25 0.31 1.31 2.23 5.65
UDUDUDMONITOR
I
N
G
W
E
L
L
TRAFFI
C
R
A
T
E
D
MONITORING WELLTRAFFIC
R
A
T
E
D
D
D
D
D
VAULT
ELEC
VAULT
ELECELEC
T S
D
a
C
A
E
D
d
149 MC-3500
STORMTECH
CHAMBERS
EXISTING STORM
STRUCTURE BUILT
PER STRACHAN SUBDIVISION
THIRD FILING
EXISTING 36" RCP
PROPOSED
STORM MH
EXISTING 36" RCP
EXISTING
STORM MH
ISOLATOR ROWS
(22 MC-3500 STORMTECH
CHAMBERS)
100-YR OUTFALL
BASIN
WQ BASIN
WQ BASIN
CURB CUT
CURB CUT
INLET
INLET
INLET
INLET
INLET
NYLOPLAST BASIN
NYLOPLAST BASIN
NYLOPLAST BASIN
NYLOPLAST BASIN
NYLOPLAST BASIN
30"x36" HERCP
MONROE DRIVE
(PRIVATE ROAD)STANFORD ROADINLET
INLET
F
STORM DRAIN OUTFALL
f
D
D
D
BASIN C WILL BE REDESIGNED
TO FULLY CAPTURE FLOWS ONCE
THE MEMORY CARE COURTYARD
DESIGN IS COMPLETE.
PORTION OF LOT 3 STRACHAN
SUBDIVISION THIRD FILING
REC. NO. 20190052896
PORTION OF LOT 3 STRACHAN
SUBDIVISION THIRD FILING
REC. NO. 20180064205
UNPLATTED
REC. NO.
2015002744
G B
H
OS
g
STORM DRAIN
CONNECTION
TO COURTYARD
b
e
INLET
os
REFER TO LANDSCAPE
PLANS FOR COURTYARD
DESIGN AND DRAINAGE
SheetSTANFORD SENIOR LIVINGThese drawings areinstruments of serviceprovided by NorthernEngineering Services, Inc.and are not to be used forany type of constructionunless signed and sealed bya Professional Engineer inthe employ of NorthernEngineering Services, Inc.NOT FOR CONSTRUCTIONREVIEW SETENGINEERNGIEHTRONRNFORT COLLINS: 301 North Howes Street, Suite 100, 80521GREELEY: 820 8th Street, 80631970.221.4158northernengineering.comof 07
DR1 DRAINAGE EXHIBIT07
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'sbelow.
before you dig.Call
R
NORTH
( IN FEET )
0
1 INCH = 30 FEET
30 30 60 90
PROPOSED CONTOUR
EXISTING STORM SEWER
PROPOSED STORM SEWER
PROPOSED SWALE
EXISTING CONTOUR
PROPOSED CURB & GUTTER
OVERLAND FLOW
PROPOSED STORM INLET
EXISTING LOT LINE
BASIN AREA
RUNOFF SUMMARY:
A
a
EXISTING RIGHT OF WAY
DESIGN POINT
BASIN ID
BASIN MINOR AND MAJOR C COEFFICIENTS
PROPERTY BOUNDARY
LEGEND:
1.REFER TO THE "PRELIMINARY DRAINAGE REPORT FOR STANFORD SENIOR LIVING"
BY NORTHERN ENGINEERING DATED 03/31/2021 FOR ADDITIONAL INFORMATION.
2.STANFORD SENIOR LIVING PROJECT WILL BE DETAINING THE DIFFERENCE BETWEEN
THE HISTORIC 10-YEAR EVENT AND THE DEVELOPED 100-YEAR EVENT.
3.LID MEASURES ARE PROVIDED VIA ISOLATOR ROWS.
4.ALL PROPOSED STORM SEWER AND STORMTECH SYSTEM ARE TO BE PRIVATELY
OWNED AND MAINTAINED.
NOTES:
CONCENTRATED FLOW
BASIN DELINEATION
BASIN
TOTAL
AREA
(acres)
Tc2
(min)
Tc100
(min)
C2 C100 Q2
(cfs)
Q100
(cfs)
A 0.12 5.0 5.0 0.36 0.45 0.13 0.56
B 0.05 5.0 5.0 0.82 1.03 0.12 0.55
C 0.09 5.0 5.0 0.95 1.19 0.24 1.07
D 0.41 5.0 5.0 0.37 0.46 0.43 1.89
E 0.27 5.0 5.0 0.83 1.04 0.65 2.84
F 0.05 5.0 5.0 0.80 1.00 0.11 0.50
G 0.19 5.0 5.0 0.42 0.52 0.23 1.00
H 1.15 5.0 5.0 0.95 1.19 3.12 13.66
OS 0.15 5.0 5.0 0.27 0.34 0.11 0.50
Combined Basins
Basins
A-OS 2.50 5.0 5.0 0.72 0.91 5.13 22.64