HomeMy WebLinkAboutUNION PARK - PDP230005 - SUBMITTAL DOCUMENTS - ROUND 1 - DRAINAGE REPORT
PRELIMINARY DRAINAGE REPORT
FOR
Union Park
Prepared by:
Highland Development Services
6355 Fairgrounds Ave, Suite 100
Windsor, Colorado 80550
Phone: 970.674.7550
Prepared for:
Landmark Real Estate Holdings, LLC
6341 Fairgrounds Ave, Suite 100
Windsor, Colorado 80550
Office: 970.460.0567
February 22, 2023
Job Number 21-1044-00
6355 FAIRGROUNDS AVE, SUITE 100, WINDSOR, COLORADO 80550 | PHONE 970.674.7550
February 22, 2023
Mr. Wes Lamarque
Fort Collins Utilities
700 Wood Street
Fort Collins, CO 80522
RE: Preliminary Drainage Report – Union Park
(Previously Ziegler-Corbett)
Dear Wes,
We are pleased to submit, for your review, the Preliminary Drainage Report for the Union Park
(Ziegler – Corbett) Preliminary Development Plan. This report describes the general drainage
design intent to be implemented with future development and in accordance with the criteria
in the City of Fort Collins Storm Drainage Manual.
I appreciate your time and consideration in reviewing this submittal. Please call if you have any
questions.
Sincerely,
Highland Development Services
Paul Schwindler, CFM
Page i
TABLE OF CONTENTS
Table of Contents ............................................................................................................................. i
Engineer’s Certification Block ..........................................................................................................ii
General Description and Location .................................................................................................. 1
Site Description and Location ...................................................................................................... 1
Site Soils ....................................................................................................................................... 1
Storm Drainage Criteria .................................................................................................................. 3
Existing Conditions ...................................................................................................................... 3
Hydrologic Criteria ....................................................................................................................... 4
Hydraulic Criteria ......................................................................................................................... 4
Drainage Basins ............................................................................................................................... 6
Drainage Facility Design .................................................................................................................. 7
Drainage Conveyance Design ...................................................................................................... 7
Detention/Water Quality Pond Design ....................................................................................... 7
Detention/Water Quality Pond Variance Request ...................................................................... 8
Low Impact Development ............................................................................................................... 9
Stormwater Pollution Prevention ................................................................................................. 11
Conclusions ................................................................................................................................... 12
References .................................................................................................................................... 13
Appendix ....................................................................................................................................... 14
Appendix A – Site Vicinity Map & References ............................................................................. A
Appendix B – Rational Calculations ............................................................................................. B
Appendix C – Detention Pond Calculations ................................................................................. C
Appendix D – Street Capacity Calculations ................................................................................. D
Appendix E – Low Impact Development Calculations ................................................................. E
Page ii
ENGINEER’S CERTIFICATION BLOCK
I hereby certify that this Preliminary Drainage Report for Union Park was prepared by me (or
under my direct supervision) for the owners thereof and meets or exceeds the criteria of the
City of Fort Collins Stormwater Design Standards.
________________________________________
Jason T. Claeys, PE
Registered Professional Engineer
State of Colorado No. 42122
Page 1
GENERAL DESCRIPTION AND LOCATION
SITE DESCRIPTION AND LOCATION
The Union Park property is located in the Southeast Quarter of Section32, Township 7 North,
Range 68 West of the Sixth Principal Meridian, City of Fort Collins, County of Larimer, State of
Colorado. More specifically, the Union Park property is located north of the Front Range Village
commercial area, east of the Affinity residences, south of the English Ranch residential
subdivision, and west of Ziegler Road.
The project site is approximately 32.78 acres currently and is undeveloped agricultural and rural
residential land, with one residence and multiple outbuildings. The site appears to be mostly
vegetated with grass harvested for livestock feed. The site generally slopes from the west to the
east at about 0.7% slope.
The intent of the Preliminary Development Plan (PDP) is to update the ODP with the anticipated
uses No improvements are being constructed with the PDP, but rather establishing future
expectations for development. The property is anticipated to be a high-density multi-use
development, mainly multi-family residential, with retail space and supporting amenities.
The Union Park property is located within the City’s Fox Meadows Drainage Basin. In addition to
the City of Fort Collins Stormwater Design Standards, drainage requirements are also described
in both the “Front Range Village Final Drainage and Erosion Control Study,” prepared by Stantec
Consulting Inc., dated February 2007, and the “Final Drainage Report for Affinity Fort Collins,”
prepared by JR Engineering, LLC, dated March 2, 2016.
No City or FEMA floodplains/floodways are located within the Union Park property.
SITE SOILS
The Union Park project site consists primarily of Nunn clay loam (0 to 1 percent slopes) that is
classified as Type-C hydrologic group. According to USDA/Natural Resource Conservation
“Group, Type C soils have 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.”
Page 2
Per the “Preliminary Geotechnical Subsurface Exploration Report, Proposed Ziegler-Corbett
Mixed-Use Development”, prepared by Soilogic, Inc., dated April 4, 2022:
“approximately 4 to 6 inches of vegetation and topsoil was encountered at the surface at the
boring locations, underlain by brown/beige/rust lean clay with varying amounts of sand which
varied to clayey sand in places. The apparently-natural lean clay/clayey sand varied from soft to
hard in terms of consistency or from very loose to medium dense in terms of relative density,
typically exhibited no to low swell potential at in-situ moisture and density conditions (however
one sample of sandy lean clay obtained from boring B-2 at a depth of about 9 feet below ground
surface exhibited moderate swell potential) and extended to the bottom of each of the borings
at a depth of approximately 15feet below present site grades.”
“Groundwater was observed during the subsurface soil exploration: “Groundwater was not
encountered in borings B-1, B-2, B-3 or B-5 to the depths explored (about 15 feet below ground
surface), but was measured at a depth of about 15 feet below ground surface in boring B-4
when checked immediately after completion of drilling. When checked about five (5) days after
drilling, borings B-1, B-2 and B-5 remained dry to the approximate depth explored, while
groundwater was measured at a depth of about 14 feet below ground surface at the locations
of borings B-3 and B-4 at that time. Groundwater information is indicated in the upper right-
hand corner of the attached boring logs.”
“Groundwater levels will vary seasonally and over time based on weather conditions, site
development, irrigation practices and other hydrologic conditions. Perched and/or trapped
groundwater conditions may also be encountered at times throughout the year. Perched water
is commonly encountered in soils overlying less permeable soil layers and/or bedrock. Trapped
water is typically encountered within more permeable zones of layered soil and bedrock
systems. The location and amount of perched/trapped water can also vary over time.”
Page 3
STORM DRAINAGE CRITERIA
This Preliminary Drainage Report was prepared to establish drainage basins, and required
detention volumes, that meet or exceed the City of Fort Collins storm water criteria. The City of
Fort Collin’s Storm Drainage Design Criteria and amendments to the Urban Drainage Flood
Control District’s (UDFCD) Drainage Criteria Manual (USDCM) Volumes 1, 2 and 3 were
referenced as guidelines for this design.
EXISTING CONDITIONS
The Union Park Property is a portion of a drainage basin that is situated north of Harmony
Road, and west of Ziegler Road, which runoff is conveyed east under Ziegler Road into the
existing drainage channel on the HP Harmony Campus property. It has been determined in the
Front Range Village Final Drainage Report that this area is allowed to contribute 76.7 cfs to the
HP Campus drainage channel during 100-year event peak discharge. More specific to this site,
20.1 cfs release rate was allocated to the Union Park & the Affinity Fort Collins properties. Per
The Final Drainage Report for Affinity Fort Collins, the Affinity site has a 100-yr peak release rate
of 2.1 cfs, allowing a 100-yr peak discharge of 18.0 cfs from the Union Park property.
The Harmony Village Manufactured Home Community does not provide adequate detention
facilities. During a 100-yr storm event, a portion of the site flows to the east into both the Front
Range Village development as well as the Affinity Fort Collins site. This runoff was evaluated in
the Front Range Village Final Drainage Report and was determined to be 116 cfs peak runoff
during the 100-yr event. This runoff will be collected in the Front Range Village Detention Pond
D, intended to collect but not detain his flow. During the 100-year event, this peak flow of 116
cfs will flow over the weir on the north side of Detention Pond D. It is conveyed via the private
drive aisles to a level spreading weir on the northeast side of the Affinity Fort Collins site, where
it is discharged into the Union Park property. This flow is then assumed to sheet flow east to be
inadvertently detained on the east side of the Union Park property along Ziegler Road.
In reference to the Front Range Village Final Drainage Report, a detention pond is planned to
be incorporated into the Union Park site, Detention Pond 298. The volume of Detention Pond
298 has been determined by detaining the 100-yr peak developed runoff to the 2-yr historic
runoff rate, adding the existing inadvertent detention volume (detention volume is currently
provided onsite due to existing constraints such as grade features and outlet restrictions).
Based on the topographic survey of the existing conditions, the inadvertent detention volume is
constrained for this site by the spill location along the north property line, at an approximate
elevation of 4928.0 ft. The inadvertent detention volume is estimated to be 7.5± acre-ft. The
Page 4
estimated volume did not account for the two existing culverts along the west side of Ziegler
Road that currently provide ponding relief for the Ziegler-Corbet site.
All supporting preliminary calculations are located in the Appendix.
HYDROLOGIC CRITERIA
The rational method was performed to calculate the peak runoff rates for each basin. Percent
impervious were estimated based on land use, and the associated runoff coefficients were
calculated. The time of concentration was calculated using the City of Fort Collins’s initial time
of concentration, and the intensity was calculated using the corresponding storm rainfall depth
and USDCM Equation 4-3. To account for the City of Fort Collins’ IDF Curve, Coefficient 3 of the
UDFCD’s intensity formula was adjusted to 0.7867. The City of Fort Collins area has a 2-yr 1-hr
rainfall depth of 0.82 inches and a 100-yr 1-hr rainfall depth of 2.86 inches. These depths
account for the 1999 adjusted rainfall depths.
HYDRAULIC CRITERIA
The hydraulic calculations provided in this report are limited to maximum street capacities
based on the minimum street slopes (0.5%) for the most restrictive sections.
The final Union Park storm drainage system will be designed to convey the minor and major
storm events through the combination of streets, inlets, storm sewer pipes, and swales. Per the
requirements provided by the City of Fort Collins Storm Drainage Design Criteria, all inlets and
storm pipes will be designed such that, during the minor initial storm event, the 2-yr storm, the
flows for the streets will not top the curb and may only rise to the street crown elevation, and
for the entrance (with Median) will not top the curb and the flow spread will leave at least one
12 ft lane width free of water in each direction. During the major storm event, the 100-yr
storm, the water depth for the streets will be held to a maximum depth of 6” at the street
crown, 12” at the gutter flow line, and/or flow must be contained within right-of-way or
easements paralleling the right-of-way.
Within the Final Drainage Report, peak basin runoff flows from the rational calculations will
then be used to determine the street flows, and on-grade inlet locations. The on-grade and
sump inlet capacities will be calculated using UDFCD’s spreadsheet UD-Inlet_v4.05.xlsm. The
inlet capacities will be analyzed, and the necessary adjustments will be applied to the street
runoff flows based on the amount of runoff collected by on-grade inlets. The sump inlets will
be sized using the previously mentioned street capacity allowances, with overtopping if
needed.
Page 5
The captured flows will then be analyzed using EPA’s SWMM program to design pipe size and
slopes. UD-Inlet applies a clogging factor while sizing the inlets, but while sizing the storm pipes,
it is assumed that the inlets are free of clogging debris and capture the maximum amount of
street runoff. Orifice rating curves will be utilized for the inlet capture capacities and route the
captured runoff through the storm drain system. The program accounts for head losses within
manholes and bends and head losses associated with pipe friction.
Hydraflow will be used to compute the open channel hydraulics and check the capacities of the
drainage swales throughout the site. Flow velocities within these swales will be reviewed and
where flows are found to be supercritical, the swales will be protected with turf reinforcement
mat.
All swale and pipe outlets will be protected with riprap or suitable erosion protection methods.
Storm sewer pipe outlets will be protected using the requirements set by the USDCM to protect
downstream of culverts.
All supporting calculations for street sections are located in the Appendix.
Page 6
DRAINAGE BASINS
The Union Park developed drainage basins are delineated by areas draining to major drainage
elements. The Union Park property is divided into four developed drainage basins. The final
drainage report will further detail the drainage basins. For the purpose of this Preliminary
Drainage study impervious areas have been calculated and applied.
Drainage Basin D1 consists entirely of pond 298A, having an area of 2.96 acres. This
basin will convey flow to pond 298B in a system of pipes, with overflow being routed
through a swale and streets to pond 298B. No water quality will be provided for this
basin. (0% impervious)
Drainage Basin D2 consists of 9.42 acres of single-family attached and apartment
residential lots, attached garages, streets, private drives, and the club house recreation
area. Flows from this basin are mainly conveyed along roadways and will be collected by
inlets and conveyed to detention Pond 298B. Low Impact Development (LID) will be
used to address water quality in this basin through the application of ADS Stormtech
MC-3500 Filtration Chambers.
Drainage Basin D3 consists of 11.17 acres of attached single-family and apartment
residential lots, attached garages, streets, and private drives. Flows from this basin are
mainly conveyed along streets and will be collected by inlets and conveyed to detention
Pond 298B. LID will be used to address water quality in this basin through the
application of ADS Stormtech MC-3500 Filtration Chambers.
Drainage Basin D4 consists of 8.32 acres of attached single-family and apartment
residential lots, commercial and mixed-use lots, attached garages, streets, and private
drives. Flows from this basin are mainly conveyed along streets and will be collected by
inlets and conveyed to detention Pond 298B. Standard water quality will be used to
address water quality in this basin with the inclusion of extended detention for the
WQCV.
Page 7
DRAINAGE FACILITY DESIGN
DRAINAGE CONVEYANCE DESIGN
Storm infrastructure to convey runoff will include, concrete trickle pans, inlets, storm sewer
and culverts. Stormwater detention and water quality enhancement will be achieved using
extended detention and low impact development (LID). Storm inlets, storm sewers and the
roadway culverts will be appropriately sized with the final drainage design.
DETENTION/WATER QUALITY POND DESIGN
The FAA Method was utilized to estimate the required detention to be 7.3± acre-ft for the
developed conditions in accordance with the City of Fort Collins requirements (the 100-year
developed peak runoff detained to the 2-year historical peak runoff). Combining the
inadvertent detention (7.5 ac-ft), the 2-yr standard Storm Water Capture Volume (SWCV) for
drainage basin D4 (0.185 ac-ft) and the detention volume (7.3 ac-ft), a total of 15.0± ac-ft is
required to accommodate the developed site, as well as account for the displacement of the
historical inadvertent detention. Due to the limited grades on the site, and the profusion of
detention volume, multiple ponds are planned, with the main detention pond located in the
northwest corner of the site (298A), and the minor detention pond (298B) located adjacent to
the eastern property line. Pond 298A outlet connects to an underground storm drain leading to
pond 298B. Overflow from pond 298A will flow via an internal swale and streets to pond 298B.
The outlet for pond 298B will connect to an existing 30-inch storm drain that passes stormwater
east under Ziegler Road. The ultimate outfall will be the existing HP Harmony Campus storm
channel system, which ultimately flows into the Cache La Poudre River. EPA SWWM will be
utilized for the final drainage design.
As mentioned, the detention volume described above is designed to be provided in two on-site
detention facilities:
Pond 298A detention basin (DB) will be used as site detention and account for the
displacement of the historical inadvertent detention. The DB will provide an estimated
detention volume of 14.4 ac-ft, accounting for the historical inadvertent detention
volume of 7.5 ac-ft, and along with pond 298B, the additional detention of 7.3 ac-ft
required to accommodate the site in its developed condition.
Pond 298B extended detention basin (EDB) with a dry bottom will be utilized as site
detention and standard water quality (SWQ) facility for basin D4. The EDB will provide
an estimated detention volume of 4.7± acre-ft, accounting for additional detention, in
Page 8
addition to pond 298A, required to accommodate the site in its developed condition.
UDFCD is referenced for the water quality capture volume (WQCV) of 0.185 ac-ft with a
40-hr drain time. Pond 298B will release to an existing 30” storm drain under Ziegler
Road leading to the HP Harmony Campus storm channel.
Pond 298A has a potential storage volume of 14.4± ac-ft, and pond 298B has 4.7± ac-ft of
available storage. The combined available storage from ponds 298A & 298B is 19.1± ac-ft.
Adjustments should be expected in future submittals as the design is settled.
The final design will ensure the pond overflows, and outlet structures, are designed to release
flows as outlined above in accordance with the City of Fort Collins requirements.
Reference the appendix for estimated calculations and the drainage plan.
DETENTION/WATER QUALITY POND VARIANCE REQUEST
The Union Park site has several challenges that have limited the ability to meet the requirement
in Chapter 8, Section 3.1 Geometry of Stormwater Detention Facilities for the site’s various
detention ponds embankments and side slopes to “vary and undulate.” The site is flat with very
limited geographical relief (0.7% avg slope). Additionally, the site must account for inadvertent
detention that more than doubles the detention storage volume required. Accommodating for
the flat site and the large volume of detention, the ponds had to be maximized for volume. In
order to maximize the ponds for volume, pond side slopes are augmented with stepped
landscape walls and 4:1 slopes.
We request a variance to the requirement to “vary and undulate” the site’s detention ponds
embankments and side slopes to maximize detention pond volumes. This variance will not be
detrimental to public health, welfare, and safety, and will have no impact on the capital and
maintenance costs of the City of Fort Collins. It is respectfully requested that this variance be
granted.
Page 9
LOW IMPACT DEVELOPMENT
The City of Fort Collins updated the Low Impact Development ordinance in 2016 (Ordinance No.
007, 2016) to require:
· Treat at least 75% of any newly developed or redeveloped impervious area using one or
a combination of LID techniques, or
· Treat at least 50% of any newly developed or redeveloped impervious area using one or
a combination of LID techniques when 25% of private drivable surfaces are permeable.
To satisfy the required implementation of Low Impact Development (LID), the Union Park
property will utilize below-grade filtration galleries (ADS StormTech chamber system model
MC-3500). Other LID techniques were explored, but due to the limited grade available and the
amount of detention volume required, shallow filtration galleries assisted in maintaining storm
drain grades and detention volumes. Pavers within the private drives did not treat enough
contributing areas to justify their use. Filtration galleries will promote filtration while capturing
fine sediment that drains off the impervious areas. Isolator rows will be implemented at the
headworks to the filtration galleries to allow larger sediment particles to settle before entering
the gallery. The isolator rows will be accessible to remove sediments. A Standard Operations
Procedure will be provided at the final design to ensure these BMPs adequately perform over
time.
For this preliminary design, the impervious area was calculated in each drainage basin. Basins
D2 and D3, which will be treated using filtration chambers (LID), represent 35.5% and 39.6% of
the impervious area, respectively, resulting in 75.1 % of the developed impervious area being
treated using LID best practices. The remainder 24.9% of the impervious area within basin D4
will be treated using an extended dry detention pond (pond 298B) with a 40-hour drain time of
the WQCV.
Below is a description of the 4-step process for selecting structural BMPs:
Urban Drainage and Flood Control District (UDFCD) recommends a Four Step Process for
receiving water protection that focuses on reducing runoff volumes, treating the water quality
capture volume (WQCV), stabilizing drainage ways, and implementing long-term source
controls. The Four Step Process applies to manage more minor, frequently occurring events.
Step 1: Employ Runoff Reduction Practices
Page 10
To reduce runoff peaks, volumes, and pollutant loads from urbanizing areas, implement Low
Impact Development (LID) strategies, including Minimizing Directly Connected Impervious
Areas (MDCIA).
Captured runoff from strategic areas are routed through below grade filtration galleries,
bioretention pond/rain gardens, and/or permeable pavers. Filtration galleries, rain gardens, and
permeable pavers will slow runoff, promote filtration, and filter runoff prior to being released
into the adjacent storm drain system.
Step 2: Implement BMPs that Provide a Water Quality Capture Volume with Slow Release
The infiltration galleries, rain gardens, and permeable pavers are designed to provide water
quality capture volume per Urban Drainage’s recommendations and calculations. The captured
runoff is design for a 12-hr drain time.
Step 3: Stabilize Drainageways
Natural Drainageways are subject to bed and bank erosion due to increases in frequency,
duration, rate, and volume of runoff during and following development. Because the site will
drain to an existing storm system, bank stabilization is unnecessary with this project.
Step 4: Implement Site Specific and Other Source Control BMPs
Proactively controlling pollutants at their source by preventing pollution rather than removing
contaminants once they have entered the stormwater system or receiving waters is important
when protecting storm systems and receiving waters. This can be accomplished through site-
specific needs such as construction site runoff control, post-construction runoff control, and
pollution prevention / good housekeeping. It will be the contractor’s responsibility to develop a
procedural best management practice for the site.
Page 11
STORMWATER POLLUTION PREVENTION
Erosion and sedimentation can be controlled on-site by use of sediment control logs, inlet
protection, a gravel construction entrance, seeding, mulch, and turf. The measures are
designed to limit the overall sediment yield increase due to construction as required by the City
of Fort Collins. During overlot and final grading the soil will be roughened and furrowed
perpendicular to the prevailing winds.
During the performance of the work required by these specifications or any operations
appurtenant thereto, whether on right-of-way provided by the City or elsewhere, the
contractor shall furnish all labor, equipment, materials, and means required. The Contractor
shall conduct proper efficient measures wherever and as necessary to reduce dust nuisance,
and to prevent dust nuisance that has originated from his operations from damaging crops,
orchards, cultivated fields, and dwellings or causing a nuisance to persons. The Contractor will
be held liable for any damage from dust originating from his operations under these
specifications on a right-of-way or elsewhere.
It is unlawful to track or cause to be tracked mud or other debris onto city streets or rights-of-
way. Wherever construction vehicles access routes or intersect paved public roads, provisions
must be made to minimize sediment transport by runoff or vehicles tracking onto the paved
surface. Stabilized construction entrances are required with base material consisting of 6”
coarse aggregate. The contractor will be responsible for clearing mud tracked onto city streets
daily.
All temporary and permanent erosion and sediment control practices must be maintained and
repaired as needed to ensure the continued performance of their intended function. Silt fence
and sediment control logs will require periodic replacement. Maintenance is the responsibility
of the contractor.
All disturbed areas must be seeded and mulched within 30 days of the project’s start.
Vegetation shall not be considered established until a ground cover is achieved, which is
demonstrated to be mature enough to control soil erosion to the satisfaction of the City
Inspector and to survive severe weather conditions.
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CONCLUSIONS
This Preliminary Drainage Report for the Union Park property has been prepared to comply
with the stormwater criteria set by the City of Fort Collins. The proposed development’s
drainage system will be designed to convey the developed peak storm water runoff through the
site to the existing storm drain system and to the development’s detention, water quality, and
LID facilities. Storm drains will be sized to provide the required roadway relief in both the 2-yr
and 100-yr storm events, and to adequately convey the released runoff from the detention
ponds disbursed throughout the site. Overland relief will be provided at all sump locations. The
calculated 100-yr peak flows released from the Union Park property will adhere to the allowed
rates as established in the Front Range Village & Affinity Fort Collins drainage studies. This
Preliminary drainage report anticipates the implementation of best management practices for
erosion control, temporary and permanent, and on-site construction facilities that will be
further designed and detailed in future Preliminary and Final Drainage Reports.
It can therefore be concluded that the development of the Union Park property will comply
with the stormwater jurisdictional criteria and will not adversely affect the adjacent properties,
streets, storm drain system and/or detention/water quality facilities. Controlling the developed
runoff from these improvements will improve the current situation currently existing on the
site. Therefore, this preliminary report satisfies the burden of proof needed to proceed to the
Final Drainage Report.
Page 13
REFERENCES
1. Urban Storm Drainage Criteria Manual (Volumes 1, 2, and 3), Urban Drainage and Flood
Control District, Revised August 2018.
2. Fort Collins Stormwater Criteria Manual, Fort Collins Utilities, City of Fort Collins,
Colorado, Dated November 2018
3. “Final Drainage Report for Affinity Fort Collins,” prepared by JR Engineering, LLC, Dated
March 2, 2016.
4. “Final Drainage and Erosion Control Study for Front Range Village, Fort Collins,
Colorado,” Prepared by Stantec Consulting, Inc., dated February 2007.
5. “Preliminary Geotechnical Subsurface Exploration Report Proposed Ziegler-Corbett
Mixed-Use Development” Prepared by Soilogic, Inc., dated April 4, 2022.
Page 14
APPENDIX
Appendix A – Site Vicinity Map & References
Appendix B – Rational Calculations
Appendix C – Detention Pond Calculations
Appendix D – Street Capacity Calculations
Appendix E – Low Impact Development Calculations
Appendix A
APPENDIX A – SITE VICINITY MAP & REFERENCES
ZIEGLER RDE. HARMONY RD
PADDINGTON RD
CORBETT DRKINGSLEY DRSITE
Vicinity Map
Scale: 1" = 1000'
PROJECT DATUM: NAVD88
CITY OF FORT COLLINS BENCHMARK #14-94
NORTHWEST CORNER OF HEWLETT PACKARD PROPERTY ON EAST SIDE ZIEGLER RD., ON THE NORTHWEST
CORNER OF THE CONCRETE BASE OF A NATURAL GAS UNIT HOUSING.
ELEV= 4927.83
CITY OF FORT COLLINS BENCHMARK #6-07
SOUTHEAST CORNER OF HARMONY RD. AND ZIEGLER RD. 50 FEET +/- SOUTH OF THE EDGE OF ASPHALT ON THE
WALL OF A CONCRETE IRRIGATION DROP STRUCTURE.
ELEV= 4931.08
PLEASE NOTE: THIS PLAN SET IS USING NAVD88 FOR A VERTICAL DATUM. SURROUNDING DEVELOPMENTS HAVE
USED NGVD29 UNADJUSTED DATUM (PRIOR CITY OF FORT COLLINS DATUM) FOR THEIR VERTICAL DATUMS.
IF NGVD29 UNADJUSTED DATUM (PRIOR CITY OF FORT COLLINS DATUM) IS REQUIRED FOR ANY PURPOSE,
THE FOLLOWING EQUATIONS SHOULD BE USED:
NGVD29 UNADJUSTED DATUM (PRIOR CITY OF FORT COLLINS DATUM) = 4927.83 (NAVD88 DATUM) - 3.19'
NGVD29 UNADJUSTED DATUM (PRIOR CITY OF FORT COLLINS DATUM) = 4931.08 (NAVD88 DATUM) - 3.19'
PRELIMINARY GEOTECHNICAL SUBSURFACE EXPLORATION REPORT
PROPOSED ZIEGLER-CORBETT MIXED-USE DEVELOPMENT
4105 ZIEGLER ROAD, FORT COLLINS, COLORADO
SOILOGIC # 22-1062
April 4, 2022
Soilogic, Inc.
3522 Draft Horse Court • Loveland, CO 80538 • (970) 535-6144
April 4, 2022
Landmark Homes
6341 Fairgrounds Avenue, Suite 100
Windsor, Colorado 80550
Attn: Mr. Andrew Quest
Re: Preliminary Geotechnical Subsurface Exploration Report
Proposed Ziegler-Corbett Mixed-Use Development
Larimer County Parcel #’s 8732400010, 8732400009 and 8732000002
4105 Ziegler Road, Fort Collins, Colorado
Soilogic Project # 22-1062
Mr. Quest:
Soilogic, Inc. (Soilogic) personnel have completed the preliminary geotechnical subsurface
exploration you requested for the proposed mixed-use development to be constructed on a
combined property consisting of Larimer County Parcel Numbers 8732400010,
8732400009 and 8732000002, located at 4105 Ziegler Road in Fort Collins, Colorado. The
results of our subsurface exploration and pertinent geotechnical engineering
recommendations are included with this report.
In summary, approximately 4 to 6 inches of vegetation and topsoil was encountered at the
surface at the boring locations, underlain by brown/beige/rust lean clay with varying
amounts of sand which varied to clayey sand in places. The apparently-natural lean clay/
clayey sand varied from soft to hard in terms of consistency or from very loose to medium
dense in terms of relative density, typically exhibited no to low swell potential at in-situ
moisture and density conditions (however one sample of sandy lean clay obtained from
boring B-2 at a depth of about 9 feet below ground surface exhibited moderate swell
potential) and extended to the bottom of each of the borings at a depth of approximately 15
feet below present site grades.
Groundwater was not encountered in borings B-1, B-2, B-3 or B-5 to the depths explored
(about 15 feet below ground surface), but was measured at a depth of about 15 feet below
ground surface in boring B-4 when checked immediately after completion of drilling.
When checked about five (5) days after drilling, borings B-1, B-2 and B-5 remained dry to
the approximate depth explored, while groundwater was measured at a depth of about 14
Preliminary Geotechnical Subsurface Exploration Report
Proposed Ziegler-Corbett Mixed-Use Development
4105 Ziegler Road, Fort Collins, Colorado
Soilogic # 22-1062
4
from boring B-2 at a depth of about 9 feet below ground surface exhibited moderate swell
potential) and extended to the bottom of each of the borings at a depth of approximately
15 feet below present site grades.
The stratigraphy indicated on the included boring logs represents the approximate
location of changes in soil types. Actual changes may be more gradual than those
indicated.
Groundwater was not encountered in borings B-1, B-2, B-3 or B-5 to the depths explored
(about 15 feet below ground surface), but was measured at a depth of about 15 feet below
ground surface in boring B-4 when checked immediately after completion of drilling.
When checked about five (5) days after drilling, borings B-1, B-2 and B-5 remained dry
to the approximate depth explored, while groundwater was measured at a depth of about
14 feet below ground surface at the locations of borings B-3 and B-4 at that time.
Groundwater information is indicated in the upper right-hand corner of the attached
boring logs.
Groundwater levels will vary seasonally and over time based on weather conditions, site
development, irrigation practices and other hydrologic conditions. Perched and/or trapped
groundwater conditions may also be encountered at times throughout the year. Perched
water is commonly encountered in soils overlying less permeable soil layers and/or
bedrock. Trapped water is typically encountered within more permeable zones of layered
soil and bedrock systems. The location and amount of perched/trapped water can also
vary over time.
ANALYSIS AND RECOMMENDATIONS
General
Based on the subsurface conditions encountered in the completed site borings, results of
field and laboratory testing and type of construction anticipated, we expect relatively
lightly-loaded commercial/retail and residential structures could be constructed with
conventional footing foundations and floor slabs bearing on natural site lean clay/clayey
sand with no to low swell potential or a suitable zone of properly moisture conditioned
Hydrologic Soil Group—Larimer County Area, Colorado
Natural Resources
Conservation Service
Web Soil Survey
National Cooperative Soil Survey
10/1/2021
Page 1 of 444863604486420448648044865404486600448666044867204486360448642044864804486540448660044866604486720497700497760497820497880497940498000498060498120498180498240498300
497700 497760 497820 497880 497940 498000 498060 498120 498180 498240 498300
40° 31' 53'' N 105° 1' 38'' W40° 31' 53'' N105° 1' 11'' W40° 31' 39'' N
105° 1' 38'' W40° 31' 39'' N
105° 1' 11'' WN
Map projection: Web Mercator Corner coordinates: WGS84 Edge tics: UTM Zone 13N WGS84
0 100 200 400 600
Feet
0 40 80 160 240
Meters
Map Scale: 1:2,940 if printed on A landscape (11" x 8.5") sheet.
Soil Map may not be valid at this scale.
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:
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
Survey Area Data: Version 16, Sep 2, 2021
Soil map units are labeled (as space allows) for map scales
1:50,000 or larger.
Date(s) aerial images were photographed: Aug 11, 2018—Aug
12, 2018
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.
Hydrologic Soil Group—Larimer County Area, Colorado
Natural Resources
Conservation Service
Web Soil Survey
National Cooperative Soil Survey
10/1/2021
Page 2 of 4
Hydrologic Soil Group
Map unit symbol Map unit name Rating Acres in AOI Percent of AOI
73 Nunn clay loam, 0 to 1
percent slopes
C 26.6 91.7%
74 Nunn clay loam, 1 to 3
percent slopes
C 2.4 8.3%
Totals for Area of Interest 29.0 100.0%
Description
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.
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.
Rating Options
Aggregation Method: Dominant Condition
Hydrologic Soil Group—Larimer County Area, Colorado
Natural Resources
Conservation Service
Web Soil Survey
National Cooperative Soil Survey
10/1/2021
Page 3 of 4
Component Percent Cutoff: None Specified
Tie-break Rule: Higher
Hydrologic Soil Group—Larimer County Area, Colorado
Natural Resources
Conservation Service
Web Soil Survey
National Cooperative Soil Survey
10/1/2021
Page 4 of 4
Union Park Site
Flow Rate to Union Park
site from Affinity=116.0 cfs
Union Park SiteAffinity Pond D 100-yrOverflow = 116.0 cfs
TRACT H
FRONT RANGE VILLAGE
LOT 11
FRONT RANGE VILLAGE
LOT 16
FRONT RANGE VILLAGE
LOT 12
FRONT RANGE VILLAGE
TRACT B
ENGLISH RANCH SOUTH P.U.D.
ENGLISH RANCH SOUTH HOA
PARCEL #8732100001
BARTRAN FAMILY LLC.
TRACT A
ENGLISH RANCH SOUTH P.U.D.
ENGLISH RANCH SOUTH HOAENGLISH RANCH
SOUTH P.U.D. THIRD FILING
LOT 1
AFFINITY SUBDIVISION
LOT 15
FRONT RANGE VILLAGE
ENGLISH RANCH SOUTH P.U.D.CORBETT DRIVEPAD
D
I
N
G
T
O
N
R
O
A
D CARRICK ROADEDMONDSROADZIEGLER ROAD(ROW VARIES)KINGSLEY COURT NEWBURY COURT HARRINGTON COURT
PARCEL 2
3.879± acres
PARCEL 1
27.430± acres
PROPOSED DETENTION POND 1
VOLUME PROVIDED=10.7± ACRE-FT
2.4± SURFACE ACRES
AVAILABLE WATER
CONNECTION
AVAILABLE WATER
CONNECTION
AVAILABLE WATER
CONNECTION
AVAILABLE SANITARY
OUTFALL
AVAILABLE SANITARY
OUTFALL AREA OF INADVERTENT DETENTION
7.5± ACRE-FT
LOT 10
FRONT RANGE VILLAGE
INADVERTENT DETENTION SPILL LOCATION
OFFSITE AFFINITY
SPILL LOCATION
FULL MOVEMENT ACCESS
(SIGNALIZED)
BIKE & PEDESTRIAN
ACCESS ONLY
PARCEL 3
1.466± acres
STORM DRAIN OUTFALL
(CONNECT TO EX)
PROPOSED DETENTION POND 2
VOLUME PROVIDED=5.6± ACRE-FT
1.4 ± SURFACE ACRES
HIDDEN POND DRIVE REVISIONNO.BYDATEHIGHLANDDEVELOPMENT SERVICES6355 FAIRGROUNDS AVENUE, SUITE 100 | WINDSOR, CO 80550PHONE: 970.674.7550 | EMAIL: Info@Highland-DS.com | www.Highland-DS.comPREPARED BY OR UNDER THE
DIRECT SUPERVISION OF:
FOR AND ON BEHALF OF HIGHLAND
DEVELOPMENT SERVICES
OFSHEET
DRAWN BY
CHECKED BY
DATE
SCALE (H)
HDS PROJECT #
SCALE (V)ZIEGLER-CORBETTAMENDED OVERALL DEVELOPMENT PLANMASTER UTILITY & OVERALL DRAINAGE PLAN11/11/22
1" = 80'
N/A
JTC
JTC
21-1044-00
ODP
1 1
N
W E
S
0
SCALE: 1" = 80'
160804080
NOTES
1.TOTAL SITE AREA IS 32.78± ACRES.
2.BOUNDARY, UTILITY AND TOPOGRAPHICAL INFORMATION PROVIDED BY ALTA LAND TITLE SURVEY
PREPARED BY MAJESTIC SURVEYING, DATED 9-24-21.
3.PROJECT VERTICAL DATUM IS ON NAVD88.
4.WATER SERVICE TO BE PROVIDED BY THE CITY OF FORT COLLINS UTILIZING MAIN WITHIN CORBETT DRIVE
AND ZIEGLER ROAD.
5.SEWER SERVICE TO BE PROVIDED BY THE CITY OF FORT COLLINS UTILIZING 30" MAIN ALONG THE WEST
SIDE OF ZIEGLER ROAD AND/OR THE 8" MAIN ALONG EAST SIDE OF CORBETT DRIVE.
6.STORMWATER OUTFALL PROVIDED BY THE EXISTING 24" STORM DRAIN STUB, IN COMBINATION WITH
ADEQUATELY SIZED SPILLWAYS.
7.ALL POINTS OF ACCESS, POINTS OF UTILITY CONNECTIONS, AND STORMWATER DETENTION LOCATIONS
ARE CONCEPTUAL AND ARE SUBJECT TO CHANGE WITH SUBSEQUENT PROJECT DEVELOPMENT
APPLICATIONS.
Ziegler-Corbett
Inadvertent Detention Volume
Design Engineer:
Design Firm:
Project Number:
Date:
DESIGN CRITERIA
Stage Storage
Volume (pond volume calculated using the prismoidal formula):
CONTOUR (FT)AREA
(FT2)
AREA
(ACRE)
VOLUME
(ACRE-FT)
DEPTH
(FT)
CUMULATIVE VOLUME
(ACRE-FT)
4925.00 0 0.00 0.00
0.00 0.00
4926.00 3144 0.07 0.02
1.00 0.02
4927.00 164156 3.77 1.45
2.00 1.48
4928.00 377427 8.66 6.05 3.00 7.53
J.Claeys
Highland Development
21-1044-00
November 9, 2022
*Inadvertant spill elevation = 4928.00 ft
Urban Storm Drainage Criteria Manual, Urban Drainage and Flood Control District, Revised August 2018
()
3
2121 DepthAAAAV++=
21-1044-00 Inadvertant Detention.xls Page 1 of 1 Highland Development Services
Appendix B
APPENDIX B – RATIONAL CALCULATIONS
MECH MECHMECHOFFSITE AFFINITY
SPILL LOCATION
POND 298A
KINGSLEY COURT
NEWBURY COURT HARRINGTON COURT
CORBETT DRIVESTREET-04LOT 1AFFINITY SUBDIVISIONLID D2
STORMTECH MC-3500
(48 CHAMBERS)
POND 298A
AREA=2.81 AC
VOLUME=14.4 AC-FT
SPILLWAY ELEV=4935.25
STREET-05STREET-03
STREET-02
STREET-01
MATCHLINESEE SHEET 7TRACT A
PRIVATE ACCESS
&UTILITY EASEMENT
AFFINITY OUTFALL
ROUTED THROUGH
POND & SITE
BLOCK 1BLOCK 9
LOT
1 1BLDG
ENVELOPE
A2
LOT 1
LOT 2
LOT 3
LOT 4 BLOCK 2LOT 1
LOT 2
LOT 3
LOT 4 BLOCK 3LOT 1
LOT 2
LOT 3
LOT 4 BLOCK 4LOT 1
LOT 2
LOT 3
LOT 4 BLOCK 5LOT 1
LOT 2
LOT 3
LOT 4 BLOCK 7LOT 1
LOT 2
LOT 3
LOT 4 BLOCK 8LOT 1
LOT 2
LOT 3
LOT 4BLOCK 6LOT 1
LOT 2
LOT 3
LOT 4
LOT
2
LOT
3
LOT
4
LOT
5
BLOCK 10
LOT
1
LOT
2
LOT
3
LOT
4
LOT
5
LOT
6
LOT
1
LOT
2
LOT
3
LOT
4
LOT
5
BLOCK 11 BLOCK 12
LOT
1
LOT
2
LOT
3
LOT
4
LOT
5
LOT
6
BLDG
ENVELOPE
A7
BLDG
ENVELOPE
A8
BLDG
ENVELOPE
A1
BLDG
ENVELOPE
A3
BLDG
ENVELOPE
A4
BLDG
ENVELOPE
R1
BLDG
ENVELOPE
F1
BE G5
BE G9 BE G10BE AG1 BE AG2 BE AG3
BLDG
ENVELOPE
F5 REVISIONNO.BYDATEHIGHLANDDEVELOPMENT SERVICES6355 FAIRGROUNDS AVENUE, SUITE 100 | WINDSOR, CO 80550PHONE: 970.674.7550 | EMAIL: Info@Highland-DS.com | www.Highland-DS.comPREPARED BY OR UNDER THE
DIRECT SUPERVISION OF:
FOR AND ON BEHALF OF HIGHLAND
DEVELOPMENT SERVICES
REVIEW SET
NOT FOR
CONSTRUCTION
OFSHEET
DRAWN BY
CHECKED BY
DATE
SCALE (H)
HDS PROJECT #
SCALE (V)UNION PARKGRADING & DRAINAGE PLAN02/22/23
1" = 40'
N/A
PHS
JTC
21-1044-00
C2.00
6 9
BASIN COEFFICIENT (100-YR)
BASIN DESIGNATION
BASIN AREA
DESIGN POINT
DRAINAGE FLOW ARROW
DRAINAGE BASIN BOUNDARY
DRAINAGE BASIN FLOW PATH
LEGEND
EXISTING MAJOR CONTOUR
EXISTING MINOR CONTOUR
PROPOSED MAJOR CONTOUR
PROPOSED MINOR CONTOUR
N
W E
S
0
SCALE: 1" = 40'
80402040
CALL UTILITY NOTIFICATION
CENTER OF COLORADO
CALL 2-BUSINESS DAYS IN ADVANCE BEFORE YOU
DIG, GRADE OR EXCAVATE FOR THE MARKING OF
UNDERGROUND MEMBER UTILITIES.
before you dig.CallKnow what's below.
R
MECHMECHMECH MECHMECHMECHMECHMECHMECHMECH MECH
TRAFFIC SIGNAL
TRAFFIC SIGNALTRAFFIC SIGNALTRAFFIC SIGNALINADVERTENT DETENTION SPILL LOCATION
LID D3
STORMTECH MC-3500
(50 CHAMBERS)STREET-06STREET-01
STREET-02
STREET-06STREET-03 ZIEGLER ROAD(ROW VARIES)MATCHLINESEE SHEET 6POND 298B
AREA=1.22 AC
VOLUME=4.7 AC-FT
SPILLWAY ELEV=4929.0
POND 298B
AREA=1.22 AC
VOLUME=4.7 AC-FT
SPILLWAY ELEV=4929.0
TRACT A
PRIVATE ACCESS
&UTILITY EASEMENT
STORM OUTFALL
20.1 CFS LIMITED
BE G6
BLDG
ENVELOPE
A9
BLDG
ENVELOPE
A10
BLDG
ENVELOPE
A11
BLDG
ENVELOPE
A4
BLDG
ENVELOPE
A5
BLDG
ENVELOPE
A6
BLDG
ENVELOPE
R2
BLDG
ENVELOPE
F1
BLDG
ENVELOPE
F2
BLDG
ENVELOPE
F3
BLDG
ENVELOPE
F4
BLDG
ENVELOPE
F5
BLDG
ENVELOPE
F6
BLDG
ENVELOPE
C3
BLDG
ENVELOPE
C1
BLDG
ENVELOPE
C2
BLOCK 13LOT 2
LOT 3
LOT 1
BLOCK 14LOT 2
LOT 3
LOT 1
BE G7BE G5 BE G8
BE
G1
BE
G3
BE
G2
BE
G4
BE AG3 BE G11 BE AG4 BE G12 BE AG5 BE G13
BE MU1 BE MU2
BLDG
ENVELOPE
F5 REVISIONNO.BYDATEHIGHLANDDEVELOPMENT SERVICES6355 FAIRGROUNDS AVENUE, SUITE 100 | WINDSOR, CO 80550PHONE: 970.674.7550 | EMAIL: Info@Highland-DS.com | www.Highland-DS.comPREPARED BY OR UNDER THE
DIRECT SUPERVISION OF:
FOR AND ON BEHALF OF HIGHLAND
DEVELOPMENT SERVICES
REVIEW SET
NOT FOR
CONSTRUCTION
OFSHEET
DRAWN BY
CHECKED BY
DATE
SCALE (H)
HDS PROJECT #
SCALE (V)UNION PARKGRADING & DRAINAGE PLAN02/22/23
1" = 40'
N/A
PHS
JTC
21-1044-00
C2.01
7 9
BASIN COEFFICIENT (100-YR)
BASIN DESIGNATION
BASIN AREA
DESIGN POINT
DRAINAGE FLOW ARROW
DRAINAGE BASIN BOUNDARY
DRAINAGE BASIN FLOW PATH
LEGEND
EXISTING MAJOR CONTOUR
EXISTING MINOR CONTOUR
PROPOSED MAJOR CONTOUR
PROPOSED MINOR CONTOUR
N
W E
S
0
SCALE: 1" = 40'
80402040
CALL UTILITY NOTIFICATION
CENTER OF COLORADO
CALL 2-BUSINESS DAYS IN ADVANCE BEFORE YOU
DIG, GRADE OR EXCAVATE FOR THE MARKING OF
UNDERGROUND MEMBER UTILITIES.
before you dig.CallKnow what's below.
R
Design Engineer:
Design Firm:
Project Number:
Date:
%
Impervious
Runoff
Coefficient C
Return
Period
Frequency
Adjustment
Factor (Cf)
100% 0.95
2-year to
10-year 1.00
90% 0.95 100-year 1.25
90% 0.95
40% 0.50
2% 0.20
C2 to C10 C100
H1 1,427,720 32.78 3,427 9,737 6,176 39,454 1,368,926 4.3% 0.22 0.27
Agravel/pavers
(sq feet)
Alawn
(sq feet)
Weighted %
Impervious
COMPOSITE
Union Park
EXISTING IMPERVIOUS AREA CALCULATION
Fort Collins Stormwater Criteria Manual, December 2018
DESIGN CRITERIA:
BASINS:
% Impervious values from Table RO-11 in the Fort Collins Amendments to the Urban Drainage and Flood Control District Criteria Manual
Sub-basin
Designation
Atotal
(sq feet)
Atotal
(acres)
Apaved
(sq feet)
Aroof
(sq feet)
Awalk/RAP
(sq feet)
Lawns
(Clayey Soil)
J.Claeys
Highland Development Services
21-1044-00
February 15, 2023
Runoff Coefficients and Frequency Adjustment Factors for City of Fort Collins - Storm Water Criteria Manual
Land Use
Paved
Roof
Walks/RAP
Gravel/Pavers
21-1044-00 Rational Calcs.xlsx Page 1 of 8 Highland Development Services
Design Engineer:
Design Firm:
Project Number:
Date:
EQUATIONS:
-Equation 6-2 -Equation 6-4 -Urbanized Check Equation 6-5
- CoFC Overland Flow
CONSTRAINTS:
300 ft - Overland flow shall not exceed for developed condition
500 ft - Overland flow shall not exceed for undeveloped condition
Final t c = minimum of t i + t t and urbanized basin check
recommended minimum t c = 5 min for urbanized basins
Time of Concentration (2-yr to 10-yr)
Type of Travel
Surface Cv
H1 H1 4.3% 0.22 32.78 500 0.0074 40.75 1453 0.0074
Tilage/Field 5 0.43 56.30 97.06 0.0074 46.41 46.41
February 15, 2023
Union Park
HISTORIC TIME OF CONCENTRATION
J. Clayes
Highland Development
21-1044-00
DESIGN CRITERIA:
SUB-BASIN DATA INITIAL/OVERLAND TIME
(ti)TRAVEL TIME (tt)
tc=ti+tt
(min)
Urban Check Final
tc
(min)DESIGN
POINT Sub-basin %
Impervious C2-10
AREA
(acres)
Fort Collins Stormwater Criteria Manual, December 2018
tt
(min)
OVERALL SLOPE
(ft/ft)
LENGTH
(ft)
tc
(min)
SLOPE
(ft/ft)
ti
(min)
LENGTH
(ft)
SLOPE
(ft/ft)
Table RO-2 VELOCITY
(ft/s)
ticttt+=5.0
wvSCV=
V
Ltt60
=
=18 − 15 +
60 24 +12
=
1.87(1.1 − )
21-1044-00 Rational Calcs.xlsx Page 2 of 8 Highland Development Services
Design Engineer:
Design Firm:
Project Number:
Date:
EQUATIONS:
-Equation 6-2 -Equation 6-4 -Urbanized Check Equation 6-5
- CoFC Overland Flow
CONSTRAINTS:
300 ft - Overland flow shall not exceed for developed condition
500 ft - Overland flow shall not exceed for undeveloped condition
Final t c = minimum of t i + t t and urbanized basin check
recommended minimum t c = 5 min for urbanized basins
Time of Concentration (100-yr)
Type of Travel
Surface Cv
H1 H1 4.3% 0.27 32.776 500 0.0074 38.23 1453 0.0074
Tilage/Field 5 0.43 56.30 94.53 0.0074 46.41 46.41
February 15, 2023
Union Park
HISTORIC TIME OF CONCENTRATION
J.Claeys
Highland Development
21-1044-00
DESIGN CRITERIA:
SUB-BASIN DATA INITIAL/OVERLAND TIME
(ti)TRAVEL TIME (tt)
tc=ti+tt
(min)
Urban Check Final
tc
(min)DESIGN
POINT Sub-basin %
Impervious C100
AREA
(acres)
Fort Collins Stormwater Criteria Manual, December 2018
tt
(min)
OVERALL SLOPE
(ft/ft)
LENGTH
(ft)
tc
(min)
SLOPE
(ft/ft)
ti
(min)
LENGTH
(ft)
SLOPE
(ft/ft)
Table RO-2 VELOCITY
(ft/s)
ticttt+=5.0
wvSCV=
V
Ltt60
=
=18 − 15 +
60 24 +12
=
1.87(1.1 − )
21-1044-00 Rational Calcs.xlsx Page 3 of 8 Highland Development Services
Design Engineer:
Design Firm:
Project Number:
Date:
EQUATIONS:I = rainfall intensity (in/hr)
Q n = n -yr peak discharge (cfs)P 1 = one-hour point rainfall depth (in)
C n = n -yr runoff coefficient t c = time of concentration (min)
I n = n -yr rainfall intensity (in/hr) P 1-2yr =0.82 in
A n = Basin drainage area (ac)P 1-100yr =2.86 in
BASIN SUMMARY:
tc (min)Runoff Coeff
(C5)C(A) (acres)Intensity
(in/hr)Q (ft3/s)tc (min)Runoff Coeff.
(C100)C(A) (acres)Intensity
(in/hr)Q (ft3/s)
H1 H1 32.78 46.41 0.22 7.16 0.98 7.01 46.41 0.27 8.95 3.42 30.57
February 15, 2023
Union Park
HISTORIC PEAK RUNOFF
J.Claeys
Highland Development Services
21-1044-00
DESIGN CRITERIA:
Design
Point Sub-basin Area (acres)
2-yr Peak Runoff 100-yr Peak Runoff
Fort Collins Stormwater Criteria Manual, December 2018
nnnnAICQ=
(0.786651)
1
)10(
5.28
ct
PI
+
=
21-1044-00 Rational Calcs.xlsx Page 4 of 8 Highland Development Services
Design Engineer:
Design Firm:
Project Number:
Date:
%
Impervious
Runoff
Coefficient C
Return
Period
Frequency
Adjustment
Factor (Cf)
100% 0.95
2-year to
10-year 1.00
90% 0.95 100-year 1.25
90% 0.95
40% 0.50
0% 0.25
C2 to C10 C100
D1 128,895 2.959 0 0 0 0 128,895 0.0% 0.25 0.31
D2 410,142 9.416 112,697 137,182 55,397 0 104,866 69.7% 0.77 0.96
D3 486,716 11.173 120,220 163,837 56,166 0 146,494 65.4% 0.74 0.92
D4 362,282 8.317 89,395 91,541 33,617 0 147,729 55.8% 0.66 0.83
D total 1,388,035 31.865 322,311 392,560 145,179 0 527,984 58.1% 0.68 0.85
Union Park
DEVELOPED IMPERVIOUS AREA CALCULATION
DESIGN CRITERIA:
Fort Collins Stormwater Criteria Manual
BASINS:
Highland Development Services
% Impervious values from Table 3.2.2 in the Fort Collins Stormwater Criteria Manual
J.Claeys
21-1044-00
February 15, 2023
Land Use
Paved
Roof
Walks
Runoff Coefficients and Frequency Adjustment Factors for City of Fort Collins - Storm Water Criteria Manual
Gravel/Pavers
Lawns
(Heavy, 2-7% Slope)
Sub-basin
Designation
Atotal
(sq feet)
Atotal
(acres)
Weighted %
Impervious
COMPOSITEApaved
(sq feet)
Aroof
(sq feet)
Awalk
(sq feet)
Agravel/pavers
(sq feet)
Alawn
(sq feet)
21-1044-00 Rational Calcs.xlsx Page 5 of 8 Highland Development Services
Design Engineer:
Design Firm:
Project Number:
Date:
EQUATIONS:
-Equation 5-3 -Equation 5-4 -Urbanized Check Equation 3.3-5
- CoFC Overland Flow
CONSTRAINTS:
300 ft - Overland flow shall not exceed for developed condition
500 ft - Overland flow shall not exceed for undeveloped condition
Final t c = minimum of t i + t t and urbanized basin check
recommended minimum t c = 5 min for urbanized basins
Time of Concentration (2-yr to 10-yr)
D1 D1 0.0% 0.25 2.959 35 4.0000 1.28 136 0.0200 0.14 0.024 2.37 0.96 5.00 171 10.95 5.00
D2 D2 69.7% 0.77 9.416 52 0.0200 3.53 633 0.0050 0.10 0.016 1.42 7.44 10.98 686 13.81 10.98
D3 D3 65.4% 0.74 11.173 100 0.0200 5.35 647 0.0050 0.10 0.016 1.42 7.61 12.96 747 14.15 12.96
D4 D4 55.8% 0.66 8.317 35 0.0200 3.85 1107 0.0100 0.10 0.016 2.01 9.20 13.04 1142 16.35 13.04
February 15, 2023
Union Park
DEVELOPED TIME OF CONCENTRATION
J.Claeys
21-1044-00
Highland Development Services
LENGTH
(ft)
DESIGN CRITERIA:
City of Fort Collins Stormwater Criteria Manual
Overland Flow Equations for City of Fort Collins Stormwater Criteria Manual
SUB-BASIN DATA INITIAL/OVERLAND TIME
(ti)TRAVEL TIME (tt)
tc=ti+tt
(min)
Urban Check Final
tc
(min)DESIGN
POINT Sub-basin %
Impervious C2-10
AREA
(acres)
tt
(min)
OVERALL LENGTH
(ft/ft)
tc
(min)
SLOPE
(ft/ft)
ti
(min)
LENGTH
(ft)
SLOPE
(ft/ft)
VELOCITY
(ft/s)
ROUGHNESS
COEFFICIENT
HYDRAULIC
RADIUS
(ft)
ticttt+=
V
Ltt60
==
1.87(1.1 − )
10
180
+=LtcV=.R2/3 S 1/2
21-1044-00 Rational Calcs.xlsx Page 6 of 8 Highland Development Services
Design Engineer:
Design Firm:
Project Number:
Date:
EQUATIONS:
-Equation 5-3 -Equation 5-4 -Urbanized Check Equation 3.3-5
- CoFC Overland Flow
CONSTRAINTS:
300 ft - Overland flow shall not exceed for developed condition
500 ft - Overland flow shall not exceed for undeveloped condition
Final t c = minimum of t i + t t and urbanized basin check
recommended minimum t c = 5 min for urbanized basins
Time of Concentration (100-yr)
D1 D1 0.0% 0.31 2.959 35 4.0000 1.18 136 0.0200 0.14 0.024 2.37 0.96 5.00 171 10.95 5.00
D2 D2 69.7% 0.96 9.416 52 0.0200 1.46 633 0.0050 0.10 0.016 1.42 7.44 8.91 686 13.81 8.91
D3 D3 65.4% 0.92 11.173 100 0.0200 2.61 647 0.0050 0.10 0.016 1.42 7.61 10.22 747 14.15 10.22
D4 D4 55.8% 0.83 8.317 35 0.0200 2.38 1107 0.0100 0.10 0.016 2.01 9.20 11.58 1142 16.35 11.58
February 15, 2023
Union Park
DEVELOPED TIME OF CONCENTRATION
J.Claeys
21-1044-00
Highland Development Services
LENGTH
(ft)
DESIGN CRITERIA:
City of Fort Collins Stormwater Criteria Manual
Overland Flow Equations for City of Fort Collins Stormwater Criteria Manual
SUB-BASIN DATA INITIAL/OVERLAND TIME
(ti)TRAVEL TIME (tt)
tc=ti+tt
(min)
Urban Check Final
tc
(min)DESIGN
POINT Sub-basin %
Impervious C100
AREA
(acres)
tt
(min)
OVERALL LENGTH
(ft/ft)
tc
(min)
SLOPE
(ft/ft)
ti
(min)
LENGTH
(ft)
SLOPE
(ft/ft)
VELOCITY
(ft/s)
HYDRAULIC
RADIUS
(ft)
ROUGHNESS
COEFFICIENT
ticttt+=
V
Ltt60
=
=
1.87(1.1 − )
10
180
+=LtcV=.R2/3 S 1/2
21-1044-00 Rational Calcs.xlsx Page 7 of 8 Highland Development Services
Design Engineer:
Design Firm:
Project Number:
Date:February 15, 2023
EQUATIONS:I = rainfall intensity (in/hr)
Q n = n -yr peak discharge (cfs)P 1 = one-hour point rainfall depth (in)
C n = n -yr runoff coefficient t c = time of concentration (min)
I n = n -yr rainfall intensity (in/hr) P 1-2yr =0.82 in
A n = Basin drainage area (ac)P 1-10yr =1.40 in
P 1-100yr =2.86 in
BASIN SUMMARY:
tc (min)Runoff Coeff
(C2-10)C(A) (acres)Intensity
(in/hr)Q (ft3/s)tc (min)Runoff Coeff
(C2-10)C(A) (acres)Intensity
(in/hr)Q (ft3/s)tc (min)Runoff Coeff.
(C100)C(A) (acres)Intensity
(in/hr)Q (ft3/s)
D1 D1 2.959 0.0% 5.00 0.25 0.74 2.85 2.11 5.00 0.25 0.74 4.87 3.60 5.00 0.31 0.92 9.95 9.20
D2 D2 9.416 69.7% 10.98 0.77 7.26 2.13 15.48 10.98 0.77 7.26 3.64 26.43 8.91 0.96 9.07 8.07 73.25
D3 D3 11.173 65.4% 12.96 0.74 8.26 1.99 16.41 12.96 0.74 8.26 3.39 28.01 10.22 0.92 10.33 7.66 79.07
D4 D4 8.317 55.8% 13.04 0.66 5.53 1.98 10.95 13.04 0.66 5.53 3.38 18.69 11.58 0.83 6.91 7.28 50.26
10-yr Peak Runoff 100-yr Peak Runoff
Union Park
DEVELOPED PEAK RUNOFF
DESIGN CRITERIA:
Design
Point Sub-basin Area (acres)
J.Claeys
Highland Development Services
21-1044-00
2-yr Peak Runoff
City of Fort Collins Stormwater Criteria Manual
% Impervious
nnnnAICQ=(0.786651)
1
)10(
5.28
ct
PI
+
=
21-1044-00 Rational Calcs.xlsx Page 8 of 8 Highland Development Services
Appendix C
APPENDIX C – DETENTION POND CALCULATIONS
Design Engineer:
Design Firm:
Project Number:
Date:
DESIGN CRITERIA
0.68
1.25
0.85 ft3 acre-ft
32.78 acres 318,601 7.31
7.01 cfs
Time
(min)
100-yr
Intensity
(I , in/hr)
Q100
(cfs)
Accumulative
Runoff Volume
(ft3)
Release
Volume
(ft3)
Detained
Volume
(ft3)
Detained
Volume
(acre-ft)
0 0.00 0.00 0 0 0 0.00
5 9.95 277.19 83,158 2,103 81,055 1.86
10 7.72 215.07 129,042 4,206 124,836 2.87
15 6.52 181.64 163,475 6,309 157,166 3.61
20 5.60 156.01 187,211 8,412 178,799 4.10
25 4.98 138.74 208,105 10,515 197,590 4.54
30 4.52 125.92 226,659 12,618 214,041 4.91
35 4.08 113.66 238,694 14,721 223,973 5.14
40 3.74 104.19 250,060 16,824 233,236 5.35
45 3.46 96.39 260,256 18,927 241,329 5.54
50 3.23 89.98 269,951 21,030 248,921 5.71
55 3.03 84.41 278,560 23,133 255,427 5.86
60 2.86 79.68 286,834 25,236 261,598 6.01
65 2.72 75.78 295,526 27,339 268,187 6.16
70 2.59 72.15 303,047 29,442 273,605 6.28
75 2.48 69.09 310,904 31,545 279,359 6.41
80 2.38 66.30 318,258 33,648 284,610 6.53
85 2.29 63.80 325,362 35,751 289,611 6.65
90 2.21 61.57 332,466 37,854 294,612 6.76
95 2.13 59.34 338,233 39,957 298,276 6.85
100 2.06 57.39 344,334 42,060 302,274 6.94
105 2.00 55.72 351,020 44,163 306,857 7.04
110 1.94 54.05 356,703 46,266 310,437 7.13
115 1.89 52.65 363,306 48,369 314,937 7.23
120 1.84 51.26 369,073 50,472 318,601 7.31
Ziegler-Corbett
100-yr Detention Volume - FAA Method
Highland Development Services
February 22, 2023
21-1044-00
J.Claeys
Area (A )
Allowed Release Rate
Fort Collins Stormwater Criteria Manual, December 2018
Runoff Coefficient (C )
Frequency Factor (C f )Required Detention
Adjusted Runoff Coefficient (CC f )
Developed Detention Volume Calculation
Union Park
Critical Pond Elevations
Design Engineer:
Design Firm:
Project Number:
Date:
DESIGN CRITERIA
Urban Storm Drainage Criteria Manual, Urban Drainage and Flood Control District, June 2001 (Revised January 2016)
Stage Storage - Pond 298a
Volume (pond volume calculated using the prismoidal formula):
CONTOUR (FT)AREA
(FT2)
AREA
(ACRE)
VOLUME
(ACRE-FT)
DEPTH
(FT)
CUMULATIVE VOLUME (ACRE-
FT)
4926.25 0.000 0.000
0.00 0.000
4927.0 5,858 0.134 0.034
0.75 0.034
4928.0 24,925 0.572 0.328
1.75 0.362
4929.0 45,998 1.056 0.802
2.75 1.163
4930.0 70,642 1.622 1.329
3.75 2.492
4931.0 93,965 2.157 1.883
4.75 4.375
4932.0 97,929 2.248 2.202
5.75 6.578
4933.0 100,509 2.307 2.278
6.75 8.855
4934.0 107,819 2.475 2.391
7.75 11.246
4935.0 110,390 2.534 2.505
8.75 13.751
4935.25 9.00 14.392 Spillway
4936.0 112,971 2.593 2.564
9.75 16.315
4937.0 122,267 2.807 2.699
10.75 19.014
Northwest POND
J. Clayes
Highland Development
21-1044-00
February 22, 2023
()
3
2121 DepthAAAA
V
++=
21-1044-00 PondCalcs - NW Pond Stage Storage Page 1 of 1 Interwest Consulting Group
DESIGN CRITERIA
Urban Storm Drainage Criteria Manual, Urban Drainage and Flood Control District, June 2001 (Revised January 2016)
Water Quality Capture Volume (WQCV):
Tributary Area, A 8.317 acres Basin D4 (not treated by LID)
Composite. Imperviousness, I 55.8%
WQCV (watershed inches)0.223 inches 40-Hour Drain Time (Fig SQ-2)
Required WQCV 0.185 acre-feet Including 20% for Sedimentation
Stage Storage - Pond 298b
Volume (pond volume calculated using the prismoidal formula):
CONTOUR (FT)AREA
(FT2)
AREA
(ACRE)
VOLUME
(ACRE-FT)
DEPTH
(FT)
CUMULATIVE VOLUME (ACRE-
FT)
4922.30 0.000 0.000
0.00 0.000
4923.0 4,852 0.111 0.026
0.70 0.026
4924.0 22,431 0.515 0.289
1.70 0.315
4925.0 33,771 0.775 0.641
2.70 0.955
4926.0 36,420 0.836 0.805
3.70 1.761
4927.0 41,824 0.960 0.897
4.70 2.658
4928.0 45,101 1.035 0.998
5.70 3.656
4929.0 49,692 1.141 1.088
6.70 4.743 Spillway
4930.0 53,287 1.223 1.182
7.70 5.925
Southeast POND
()
3
2121 DepthAAAAV++=
21-1044-00 PondCalcs - SE Pond Stage Storage Page 1 of 2 Highland Development Services
Appendix D
APPENDIX D – STREET CAPACITY CALCULATIONS
Channel Report
Hydraflow Express Extension for Autodesk® Civil 3D® by Autodesk, Inc.Wednesday, Feb 22 2023
26' Inverted Street
User-defined
Invert Elev (ft) = 100.00
Slope (%) = 0.50
N-Value = Composite
Calculations
Compute by: Q vs Depth
No. Increments = 20
(Sta, El, n)-(Sta, El, n)...
( -15.67, 100.76)-(2.00, 100.17, 0.013)-(15.00, 100.43, 0.013)-(15.67, 100.76, 0.013)
Highlighted
Depth (ft) = 0.76
Q (cfs) = 73.08
Area (sqft) = 14.88
Velocity (ft/s) = 4.91
Wetted Perim (ft) = 31.51
Crit Depth, Yc (ft) = 0.76
Top Width (ft) = 31.34
EGL (ft) = 1.13
-5 0 5 10 15 20 25
Elev (ft)Depth (ft)Section
99.75 -0.25
100.00 0.00
100.25 0.25
100.50 0.50
100.75 0.75
101.00 1.00
Sta (ft)
Channel Report
Hydraflow Express Extension for Autodesk® Civil 3D® by Autodesk, Inc.Wednesday, Feb 22 2023
36' Crowned Street
User-defined
Invert Elev (ft) = 100.00
Slope (%) = 0.50
N-Value = Composite
Calculations
Compute by: Q vs Depth
No. Increments = 20
(Sta, El, n)-(Sta, El, n)...
( 0.00, 100.50)-(2.00, 100.17, 0.013)-(18.00, 100.49, 0.013)-(34.00, 100.17, 0.013)-(36.00, 100.00, 0.013)-(36.00, 100.50, 0.013)
Highlighted
Depth (ft) = 0.50
Q (cfs) = 19.12
Area (sqft) = 7.10
Velocity (ft/s) = 2.69
Wetted Perim (ft) = 37.02
Crit Depth, Yc (ft) = 0.50
Top Width (ft) = 36.00
EGL (ft) = 0.61
-5 0 5 10 15 20 25 30 35 40 45
Elev (ft)Depth (ft)Section
99.75 -0.25
100.00 0.00
100.25 0.25
100.50 0.50
100.75 0.75
101.00 1.00
Sta (ft)
Appendix E
APPENDIX E – LOW IMPACT DEVELOPMENT CALCULATIONS
Design Engineer:
Design Firm:
Project Number:
Date:
DESIGN CRITERIA
Low Impact Development Summary
Sq-Ft Acres
Impervious Area
(sq-ft)
% of Impervious
Area Requiring
Treatment
Impervious Area
Requiring
Treatment
1,427,723 32.78 860,051 75% 645,038
LID
Facility
Contributing
Basins
Area Drainage
to LID
(sq-ft)
% Impervious
Impervious
Area Treated
(sq-ft)
WQCV12-hr
(watershed inches)
WQCV12-hr
(cu-ft)
Treatment
Method
D2 D2 410,142 69.7% 305,275 0.22 7,488 Filtration Gallery
D3 D3 486,716 65.4% 340,222 0.20 8,294 Filtration Gallery
EDB Pond Contributing
Basins
Drainage Area
(sq-ft)
Drainage Area
(sq-ft)% Impervious WQCV40-hr
(watershed inches)
WQCV40-hr
(ac-ft)
Pond 298B D4 362,282 8.317 55.8% 0.22 0.185
645,038
645,497
100.1%
Area (sq-ft) Area (acres) Treatment Ratio
896,858 20.59 62.8%
362,282 8.32 25.4%
1,259,140 28.91 88.2%
168,583 3.87 11.8%
1,427,723 32.78Total Improvement Area
Water Quality Area Treatment Summary
Description
Total Area Treated by LID
Total Area Treated by EDB
Description
Development Area
Total Untreated Area (includes Pond 298A)
Total Treated Area
Union Park
Low Impact Development
Total % of Required Treatment
Development Area Breakdown
City of Fort Collins - Ordinance No. 007, 2016
- Treat at least 75% of any newly developed or redeveloped impervious area using one or a combination of LID techniques, or
- Treat at least 50% of any newly developed or redeveloped impervious area using one or a combination of LID techniques when 25% of private driveable surfaces are
permeable.
Total Impervious Area Treated (sq-ft)
Total Impervious Area Required for LID Treatment (sq-ft)
LID Treatment Summary
LID Treatment Areas
J.Claeys
Highland Development Services
21-1044-00
February 22, 2023
Urban Storm Drainage Criteria Manual by Urban Drainage and Flood Control District, June 2001 (Revised January 2016)
Standard Water Quality Areas
Allowed FilterFabric Flow Ratea(cfs)0.35 gpm/sq-ftSC-106LP 14 10 6 6 85.4 25 12 14.8 0.012 6.9 15.0SC-310 18 8 6 6 85.4 34 16 20.2 0.016 14.7 31.0SC-740 18 8 6 6 85.4 51 30 30.2 0.024 45.9 74.9DC-780 18 12 6 9 85.4 51 30 30.2 0.024 46.2 78.4MC-3500 24 8 12 9 90 77 45 48.1 0.038 109.9 178.9 14.9 46MC-4500 24 7 12 9 52 100 60 36.1 0.028 106.5 162.6 35.7 108.7LIDFacilityChamberTypeTotalRelease Ratef(cfs) WQ Flowg(cfs)Req'd StorageVolumeh(cu-ft)Minimum No. of ChambersiChamberStoragej(cu-ft)No. ofEndcapskEndcapStoragel(cu-ft)Total ChamberVolumem(cu-ft)Total InstalledSystem Volumen(cu-ft)WQCV12-hr(cu-ft)D2 MC-3500 1.80 7.565,240 48 5,275 8 119 5,394 9,389 7,488D3 MC-3500 1.88 2.095,251 50 5,495 10 149 5,644 9,860 8,294Max Cover(ft)Min Cover(in)ChamberModelJ.ClaeysHighland Development Services21-1044-00February 22, 2023Min InstalledChamber/AggregateVolumec(cu-ft)Union ParkLow Impact DevelopmentStormTech Chamber Configuration SummaryStormTech Chamber DataDesign Engineer:Design Firm:Project Number:Date:Length(in)Width(in)Height(in)Floor Area(sq-ft)ChamberVolumeb(cu-ft)MinAggregate Base(in)Min Aggregate Cover(in)NegligibleEndcapVolumed(cu-ft)Min InstalledEndcap/AggregateVolumee(cu-ft)NegligibleNegligibleNegligibleNote:a. Release rate per chamber, limited by flow through geotextile with accumulated sediment. City acceptable flow rates determined to be approximately 1/2 of the Nov-07 Qmaxfrom Figure 17 of the "Final Report on Field Verification Testing of the StormTech Isoloator Row Treatement Unit", prepard by the University of New Hamphire Stormwater Center, dated Setpember 2010.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. Volume within endcap only, not accounting for void spaces in surrounding aggregate.e. Volume includes endcap and void spaces (40%) in surrounding aggregate, per chamber unit.f. Release rate per chamber times number of chambers. This is used as the allowed release rate for the FAA calculations.g. WQ flow, equal to 1/2 of the 2-yr peak runoff rate, referenced to size flow control structure.h. Required detention volume determined using the FAA Method based on the acceptable release rate of sediment accumulated filter fabric of the chambers and the 1/2 of the 2yr in flow rate.i. Number of chambers required to provide required FAA storage volume stored within the chamber and endcaps only (no aggregate storage).j. Total volume provided in chambers only (no aggregate storage).k. Number of endcaps based on desired chamber layout.l. Total volume provided in endcaps only (no aggregate storage).m. Total chamber and endcap storage (not aggregate storage). This number must meet or exceed the required FAA storage volume.n. System volume includes total chambervolumeplus surrounding aggregate volume,assumes a 40% void ratio for aggregate storage.This totalis provided from ADS Design Tool.
DESIGN CRITERIA
0.77
1.00
0.77 (ft3)acre-ft
9.42 acres 5,240 0.12
1.80 cfs
Time
(min)
1/2 2-yr
Intensity
(I , in/hr)
Q100
(cfs)
Accumulative
Runoff Volume
(ft3)
Accumulative
Release Volume
(ft3)
Detained
Volume
(ft3)
Detained
Volume
(acre-ft)
0 0.000 0.00 0 0 0 0.00
5 1.425 10.33 3,099 540 2,559 0.06
10 1.105 8.01 4,807 1,081 3,726 0.09
15 0.935 6.78 6,101 1,621 4,480 0.10
20 0.805 5.84 7,003 2,162 4,842 0.11
25 0.715 5.18 7,776 2,702 5,074 0.12
30 0.650 4.71 8,482 3,242 5,240 0.12
35 0.585 4.24 8,907 3,783 5,124 0.12
40 0.535 3.88 9,309 4,323 4,986 0.11
45 0.495 3.59 9,690 4,864 4,826 0.11
50 0.460 3.33 10,005 5,404 4,601 0.11
55 0.435 3.15 10,407 5,944 4,463 0.10
60 0.410 2.97 10,701 6,485 4,216 0.10
Union Park
WQ Treatment Volume - FAA Method
- City of Fort Collins accepts 1/2 of the 2-yr runoff as the WQ inflow rate
WQ Treatment Volume Calculation - D2 Filtration Gallery
Runoff Coefficient (C )
J.Claeys
Highland Development Services
21-1044-00
February 22, 2023
- City of Fort Collins - Storm Water Criteria Manual
Design Engineer:
Design Firm:
Project Number:
Date:
- Drainage Basins A1 thru A12
Allowed Release Rate
Frequency Factor (C f )Required Detention
Adjusted Runoff Coefficient (CC f )
Area (A )
DESIGN CRITERIA
0.66
1.00
0.66 ft3 acre-ft
11.17 acres 5,251 0.12
1.88 cfs
Time
(min)
1/2 2-yr
Intensity
(I , in/hr)
Q100
(cfs)
Accumulative
Runoff Volume
(ft3)
Accumulative
Release Volume
(ft3)
Detained
Volume
(ft3)
Detained
Volume
(acre-ft)
0 0.000 0.00 0 0 0 0.00
5 1.425 10.51 3,153 563 2,590 0.06
10 1.105 8.15 4,889 1,126 3,763 0.09
15 0.935 6.90 6,206 1,689 4,517 0.10
20 0.805 5.94 7,124 2,252 4,872 0.11
25 0.715 5.27 7,909 2,815 5,095 0.12
30 0.650 4.79 8,628 3,378 5,251 0.12
35 0.585 4.31 9,060 3,940 5,119 0.12
40 0.535 3.95 9,469 4,503 4,965 0.11
45 0.495 3.65 9,856 5,066 4,790 0.11
50 0.460 3.39 10,177 5,629 4,548 0.10
55 0.435 3.21 10,586 6,192 4,394 0.10
60 0.410 3.02 10,885 6,755 4,130 0.09
Adjusted Runoff Coefficient (CC f )
Area (A )
Allowed Release Rate
- City of Fort Collins - Storm Water Criteria Manual
- City of Fort Collins accepts 1/2 of the 2-yr runoff as the WQ inflow rate
WQ Treatment Volume Calculation - D3 Filtration Gallery
Runoff Coefficient (C )
Frequency Factor (C f )Required Detention
- Drainage Basins B10 thru B12
Union Park
WQ Treatment Volume - FAA Method
J.Claeys
Highland Development Services
21-1044-00
February 22, 2023
Design Engineer:
Design Firm:
Project Number:
Date:
User Inputs
Chamber Model: MC-3500
Outlet Control Structure: No
Project Name: Union Park - LID D2
Engineer: Paul Schwindler
Project Location: Colorado
Measurement Type: Imperial
Required Storage Volume: 9000 cubic ft.
Stone Porosity: 40%
Stone Foundation Depth: 9 in.
Stone Above Chambers: 12 in.
Average Cover Over Chambers: 18 in.
Design Constraint Dimensions:(60 ft. x 110 ft.)
Results
System Volume and Bed Size
Installed Storage Volume: 9389.10 cubic ft.
Storage Volume Per Chamber: 109.90 cubic ft.
Number Of Chambers Required: 48
Number Of End Caps Required: 8
Chamber Rows: 4
Maximum Length:95.88 ft.
Maximum Width: 29.17 ft.
Approx. Bed Size Required: 2796.57 square ft.
System Components
Amount Of Stone Required: 370 cubic yards
Volume Of Excavation (Not Including
Fill):
570 cubic yards
Total Non-woven Geotextile Required:930 square yards
Woven Geotextile Required (excluding
Isolator Row):
168 square yards
Woven Geotextile Required (Isolator
Row):
419 square yards
Total Woven Geotextile Required:587 square yards
Impervious Liner Required:0 square yards
User Inputs
Chamber Model: MC-3500
Outlet Control Structure: No
Project Name: Union Park - LID 3 (5
rows)
Engineer: Paul Schwindler
Project Location: Colorado
Measurement Type: Imperial
Required Storage Volume: 9400 cubic ft.
Stone Porosity: 40%
Stone Foundation Depth: 9 in.
Stone Above Chambers: 12 in.
Average Cover Over Chambers: 18 in.
Design Constraint Dimensions:(50 ft. x 80 ft.)
Results
System Volume and Bed Size
Installed Storage Volume: 9860.04 cubic ft.
Storage Volume Per Chamber: 109.90 cubic ft.
Number Of Chambers Required: 50
Number Of End Caps Required: 10
Chamber Rows: 5
Maximum Length:81.55 ft.
Maximum Width: 36.08 ft.
Approx. Bed Size Required: 2942.57 square ft.
System Components
Amount Of Stone Required: 391 cubic yards
Volume Of Excavation (Not Including
Fill):
600 cubic yards
Total Non-woven Geotextile Required:958 square yards
Woven Geotextile Required (excluding
Isolator Row):
67 square yards
Woven Geotextile Required (Isolator
Row):
88 square yards
Total Woven Geotextile Required:155 square yards
Impervious Liner Required:0 square yards