HomeMy WebLinkAboutHEARTSIDE HILL RESIDENTIAL DEVELOPMENT - PDP210020 - DOCUMENT MARKUPS - ROUND 1 - DRAINAGE REPORT
PRELIMINARY DRAINAGE REPORT
FOR
Heartside Hill
Prepared by:
Highland Development Services
6355 Fairgrounds Ave, Suite 100
Windsor, Colorado 80550
Phone: 970.674.7550
Prepared for:
CARE Housing, Inc.
1303 W. Swallow Road
Fort Collins, CO 80525
Office: 970.282.7522
December 22, 2021
Job Number 21-1045-00
Highland Development Services, Inc.
6355 Fairgrounds Avenue, Suite 100 | Windsor, CO 80550 | 970.674.7550
December 22, 2021
Mr. Matt Simpson, P.E.
Fort Collins Utilities
700 Wood Street
Fort Collins, CO 80522
RE: Preliminary Drainage Report for Magnolia Dwellings
Dear Dan,
We are pleased to submit for your review, the Preliminary Drainage Report for the Heartside
Hill affordable residential housing project. This report describes the drainage design intent to
be in accordance with the City of Fort Collins Stormwater Criteria Manual.
We appreciate your time and consideration in reviewing this submittal. Please call if you have
any questions.
Sincerely,
Highland Development Services
Andrew C. Bartel, EI Jason T. Claeys, P.E., LEED AP
Page i
TABLE OF CONTENTS
Table of Contents ............................................................................................................................. i
Engineer Certification ......................................................................................................................ii
General Description and Location .................................................................................................. 1
Site Description and Location ...................................................................................................... 1
Site Soils ....................................................................................................................................... 2
Storm Drainage Criteria .................................................................................................................. 3
Hydrologic Criteria ....................................................................................................................... 3
Hydraulic Criteria ......................................................................................................................... 3
Drainage Basins ............................................................................................................................... 4
Drainage Facility Design .................................................................................................................. 6
Drainage Conveyance Design ...................................................................................................... 6
Low Impact Development ............................................................................................................... 7
Stormwater Pollution Prevention ................................................................................................... 9
Conclusions ................................................................................................................................... 10
References .................................................................................................................................... 11
Appendix ....................................................................................................................................... 12
Appendix A – Site Descriptions, Characteristics, & References .................................................. A
Appendix B – Rational Calculations ............................................................................................. B
Appendix C – Low Impact Development Calculations ................................................................. C
Appendix D – Pond Calculations .................................................................................................. D
Page ii
ENGINEER CERTIFICATION
I hereby certify that this report (plan) for the preliminary drainage design of Heartside Hill was
prepared by me (or under my direct supervision) in accordance with the provisions of the City
of Fort Collins Stormwater Criteria Manual and Construction of Public and Private
Improvements for the Responsible Parties thereof. I understand that the City of Fort Collins
does not and shall not assume liability for drainage facilities designed by others.
________________________________________
Jason T. Claeys, PE
Registered Professional Engineer
State of Colorado No. 42122
Page 1
GENERAL DESCRIPTION AND LOCATION
SITE DESCRIPTION AND LOCATION
The project site is situated in the southeast quarter of Section 12, Township 6 North, Range 69
West of the 6th Principal Meridian, City of Fort Collins, County of Larimer, in the State of
Colorado. The property consists of Lots 1 and 2, Block 1 of the Heart of the Rockies Second
Subdivision, dated June 9, 1999. Heartside Hill is located within Lot 2, at the northwest corner
of the intersection of S. Lemay Ave. and E. Trilby Rd. Lot 1 contains the existing Heart of the
Rockies Christian Church. It is bounded by private residential lots to the north and west, E.
Trilby Rd. to the south, and S Lemay Ave to the east.
The existing church facilities are anticipated to remain. The site area is currently undeveloped
and is approximately 8.84 acres. The development would consist of up to 72 CARE Housing for
rent apartment units ([1] 8-unit with an attached clubhouse, [5] 8-unit and [2] 12-unit
buildings), 9 Habitat for Humanity single-family detached lots, 2 L’arche group homes, and a
planned shared community center to be designed and constructed at a future date. The project
is anticipated to be completed in a single phase.
The project site generally slopes from the southwest to the northeast at approximately 4%
toward an existing pond at the northeast of the property. Storm runoff is currently conveyed
from a grate inlet in the pond to a ditch along the east side of the property and into the existing
storm drain sewer. The existing project site is approximately 0.0% impervious. No wetlands are
located within the area of proposed development.
The project site is not located within the FEMA floodway or floodplain and is within the non-
printed FEMA FIRM panel 08069C1200F, effective 12/19/2006. The site is also not located
within the City of Fort Collins floodplain.
The proposed development includes eight multi-family buildings with a clubhouse along with
eleven low income housing lots. The required parking areas, driveways, sidewalks, and open
space are also included in the development. A rain garden is proposed to provide the
stormwater quality enhancement requirement as a low impact development technique.
The site was previously analyzed within the “Drainage Investigation for Heart of the Rockies
Christian Church,” prepared by Messner Engineering, Inc., dated June 29, 1999.
Page 2
SITE SOILS
The Heatside Hill project site consists primarily of Renohill clay loam and a small portion of
Longmont clay and are both classified as Type D hydrologic group. According to USDA/Natural
Resource Conservation Group, Type D soils a have very slow infiltration rate when thoroughly
wet. These soils 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 also have a very slow rate of water
transmission.
Per the “Preliminary Geotechnical Subsurface Exploration Report, Proposed Residential
Development Lots 1 and 2, Heart of the Rockies Second Subdivision”, prepared by Soilogic, Inc.
dated August 13, 2021:
“The subsurface materials encountered in the completed site borings were quite variable across
the site, but generally consisted of a thin mantle of vegetation and topsoil underlain by
brown/beige/rust lean clay with varying amounts of sand. A portion of the near-surface lean
clay encountered at the location of boring B-2 extending to a depth of about 3 to 4 feet below
ground surface was somewhat mottled in color, appeared to contain bedrock fragments and
was identified as possible existing fill material which may have been placed to develop present
site grade. In general, the lean clay varied from medium stiff to very stiff in terms of consistency,
exhibited variable swell potential (ranging from none to very high) at current moisture and
density conditions and extended to depths between 2½ to 18 feet below present site grade,
where it was underlain by brown/olive/beige/gray/rust interbedded claystone/siltstone/
sandstone bedrock of varying composition. The bedrock varied from weathered to very hard in
terms of hardness, also exhibited variable swell potential (ranging from low to high) at in-situ
moisture and density conditions and extended to the bottom of each boring at depths ranging
from approximately 15 to 30 feet below present site grades. In general, we judge the bedrock
unit underlying the site to possess moderate to high swell potential overall.”
Groundwater was also observed during the subsurface soil exploration:
“Groundwater was measured in borings B-1, B-2, B-3 and B-6 at depths between about 13 and
27 feet below ground surface, but was not encountered in any of the remaining site borings to
the depths explored when checked immediately after completion of drilling. When checked
seven (7) days after drilling, groundwater was measured in all borings with the exception of
boring B-3 at depths between about 5 and 15 feet below ground surface. The ground surface in
the area of boring B-3 had been disturbed, such that subsequent groundwater level
measurements could not be completed.”
Page 3
STORM DRAINAGE CRITERIA
This preliminary drainage report was prepared to meet or exceed the City of Fort Collins
Stormwater Criteria Manual. The Criteria Manual 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.
HYDROLOGIC CRITERIA
The rational method was performed to calculate the peak runoff rates for each basin. Percent
imperviousness and runoff coefficients were calculated for each basin using the surface
characteristics of each basin. The time of concentration was calculated using City of Fort Collins
initial time of concentration and the intensity was calculated using the corresponding storm
rainfall depth and the City of Fort Collins’ Intensity-Duration-Frequency Curve. 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 do account for the 1999 adjusted rainfall depths.
HYDRAULIC CRITERIA
The final Heartside Hill storm drainage system will been designed to convey the minor and
major storm events through the combination of private drives, storm sewer pipes and swales.
Runoff flows determined with the rational method will be attenuated through the site. Inlet
capacities will be calculated using UDFCD’s spreadsheet UD-Inlet_v4.05.xlsm.
The Autodesk Hydraflow Express program 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
lined 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 for the
protection downstream of culverts.
All supporting calculations are located in the Appendix.
Page 4
DRAINAGE BASINS
The Heartside Hill developed drainage basins are delineated by areas draining through the site.
The drainage basins are placed to limit the runoff flowing from the site into Brittany Street. The
site is broken into 10 main drainage systems:
Drainage Basin D1:
Drainage Basin D1 has an approximate area of 1.05 acres and is approximately 36.7%
impervious. This basin consists of a future community center and open space. Runoff is
conveyed via swales to a curb cut and is conveyed through Rain Garden D1 to detention Pond
D.
Drainage Basin D2:
Drainage Basin D2 has an approximate area of 2.47 acres and is approximately 50.9%
impervious. This basin consists of half of the existing church building, nine of the low income
housing lots, private drives, parking areas, and a majority of the open space/amphitheater area.
The area along the low income housing lots draining to Type R inlet, Ex Inlet-03, is negligible
and the capture rate is assumed to be the same as the approved. Runoff is conveyed via private
drives, through two curb cuts, into Rain Garden D1 and is ultimately discharged to detention
Pond D.
Drainage Basin D3:
Drainage Basin D3 has an approximate area of 0.75 acres and is approximately 34.1%
impervious. This basin consists of two of the multi-family buildings, the attached clubhouse,
and Rain Garden D1. Runoff is conveyed via swales to Rain Garden D1 and is discharged to
detention Pond D.
Drainage Basin D4:
Drainage Basin D4 has an approximate area of 1.09 acres and is approximately 27.3%
impervious. This basin consists of three multi-family buildings and open space. Runoff is
conveyed via swales and is discharged to detention Pond D.
Drainage Basin D5:
Drainage Basin D5 has an approximate area of 0.42 acres and is approximately 97.1%
impervious. This basin consists of private drives and parking areas. Runoff is conveyed via
private drives, storm drains, and swales to a type R inlet and is ultimately discharged to
detention Pond D.
Page 5
Drainage Basin D6:
Drainage Basin D6 has an approximate area of 0.13 acres and is approximately 78.6%
impervious. This basin consists of the private drive access from Trilby Rd. Runoff is conveyed to
a curb cut and is ultimately discharged to detention Pond D.
Drainage Basin D7:
Drainage Basin D7 has an approximate area of 0.79 acres and is approximately 35.2%
impervious. This basin consists of three multi-family buildings and open space. Runoff is
conveyed via swales and is ultimately conveyed to detention Pond D.
Drainage Basin D8:
Drainage Basin D8 has an approximate area of 0.70 acres and is approximately 92.3%
impervious. This basin consists of private drives and parking areas. Runoff is conveyed via
private drives to a curb cut, where it is discharged into detention Pond D.
Drainage Basin D9:
Drainage Basin D9 has an approximate area of 1.42 acres and is approximately 20.6%
impervious. This basin consists of a part of a multi-family building, private drives, parking areas,
two low income lots, open space, and detention Pond D. Runoff is conveyed via private drives
and swales to detention Pond D.
Drainage Basin OS1:
Drainage Basin OS1 pertains to the drainage from the existing improvements in Lot 1. This basin
has an approximate area of 1.89 acres and is approximately 69.8% impervious. This basin
consists of half of the existing church building, private drives, parking areas, and open space.
Runoff is conveyed via roadways to a swale and is ultimately conveyed through Rain Garden D1
to detention Pond D.
Page 6
DRAINAGE FACILITY DESIGN
DRAINAGE CONVEYANCE DESIGN
Storm infrastructure to convey runoff will include swales, inlets, and storm sewer pipes.
Stormwater detention and water quality enhancement are achieved through the use of
detention Pond D and Rain Garden D1.
DETENTION/WATER QUALITY POND DESIGN
An extended detention basin, Detention Pond D, will be utilized as the detention and water
quality facility for Heartside Hill. For the preliminary drainage study, the FAA method was used
to determine the detention volume needed. UDFCD is referenced for the standard water
quality capture volume (WQCV) with a 40-hr drain time. Below is a brief summary of the
proposed design for the pond:
Pond D:
Extended detention basin for both Lots 1 and 2 with standard water quality treatment. A 100-yr
orifice plate maximizes volume in the pond and restricts release rate into the existing
stormwater system. The existing 100-yr release rate into the existing stormwater system is 13.2
cfs according to the Drainage Investigation for Heart of the Rockies Christian Church, prepared
by Messner Engineering, Inc (Revised June 29, 1999). The 100-yr water surface elevation is
4911.05 feet, with a maximum depth in the pond of 3.35 feet. During an event that exceeds the
100-yr storm, or the pond outlet should be obstructed, overtopping will occur through a 66-ft
spillway on the east side of the pond with an overflow depth of 0.45 feet. The top of berm
elevation is at 4912.50 ft, providing 1-ft of freeboard over the spill depth. The 100-yr
emergency spillway will flow into Lemay Avenue public ROW.
Page 7
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 driveable surfaces are permeable.
To satisfy the required implementation of Low Impact Development (LID) techniques, Heartside
Hill utilizes a bioretention pond/Rain Garden D1. Due to site constraints and the inability to
treat the required amount of newly developed impervious area, the rain garden is designed to
treat a portion of the newly developed impervious area along with the existing church
impervious area. The rain garden is designed to treat the total drainage area being directed to
the rain garden. The result is that the rain garden treats 105.9% of the impervious area required
to be treated. The water quality capture volume provided within the rain garden (LID) is 3,802
cu-ft and the pond (standard WQCV) is 0.087 ac-ft.
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 drainageways and implementing long-term source controls.
The Four Step Process applies to the management of smaller, frequently occurring events.
Step 1: Employ Runoff Reduction Practices
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 bioretention pond/rain gardens. Rain
gardens will slow runoff, promote infiltration, 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
Page 8
The bioretention pond/rain gardens are designed to provide water quality capture volume per
Urban Drainage’s recommendations and calculations. The captured runoff is designed 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
The proposed project will improve upon site specific source controls compared to historic
conditions by providing localized trash enclosures within the development for disposal of solid
waste; a rain garden for water treatment prior to flows entering storm systems; and additional
water quality measures to protect and prolong the design life of BMPS delineated in Step 1.
All calculations are attached for reference.
Page 9
STORMWATER POLLUTION PREVENTION
Erosion and sedimentation will be controlled on-site by use of sediment control logs, inlet
protection, and gravel construction entrances. 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 carry out 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 nuisance to persons. The Contractor will be
held liable for any damage resulting from dust originating from his operations under these
specifications on right-of-way or elsewhere.
It is unlawful to track or cause to be tracked mud or other debris onto public streets or rights-
of-way. Wherever construction vehicles access routes or intersect paved public roads,
previsions must be made to minimize the transport of sediment 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 public streets on a daily basis.
All temporary and permanent erosion and sediment control practices must be maintained and
repaired as needed to assure continued performance of their intended function. Maintenance
is the responsibility of the contractor.
All disturbed areas must be seeded and mulched within 30 days of project 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 condition.
Page 10
CONCLUSIONS
This Preliminary Drainage Report for Heartside Hill has been prepared to comply with the
stormwater criteria set by the City of Fort Collins. The proposed drainage system will be
designed to convey the developed peak 100-yr storm water runoff through the site to the
proposed detention pond, and ultimately to the existing storm system. Drainage conveyance
systems will be designed to convey drainage to the proposed roadways and collect onsite
drainage and treat it in accordance with LID requirements before discharging it into the
proposed detention pond. This preliminary drainage report anticipates the implementation of
best management practices for erosion control, temporary and permanent, and on-site
construction facilities.
It can therefore be concluded that development of Heartside Hill will comply with the storm
water jurisdictional criteria and the approved City of Fort Collins Stormwater Criteria Manual
and will not adversely affect the adjacent properties, streets, storm drain system and/or
detention/water quality facilities.
Page 11
REFERENCES
1. Urban Storm Drainage Criteria Manual (Volumes 1, 2, and 3), Urban Drainage and Flood
Control District, June 2001, Revised January 2016.
2. Fort Collins Stormwater Criteria Manual, Fort Collins Utilities, City of Fort Collins,
Colorado, Dated December 2018, Adopted January 2019.
3. “Hydrologic Group Rating for Larimer County Area, Colorado”, USDA-Natural Resources
Conservation Service, National Cooperative Soil Survey. Web Soil Survey URL:
http://websoilsurvey.nrcs.usda.gov. [11/15/2021]
4. “Preliminary Geotechnical Subsurface Exploration Report, Proposed Residential
Development Lots 1 and 2, Heart of the Rockies Second Subdivision”, prepared by
Soilogic, LLC, Dated August 13, 2021.
5. “Drainage Investigation for Heart of the Rockies Christian Church”, prepared by Messner
Engineering, Inc., Dated June 29, 1999.
Page 12
APPENDIX
Appendix A – Site Descriptions, Characteristics, & References
Appendix B – Rational Calculations
Appendix C – Low Impact Development Calculations
Appendix D – Pond Calculations
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)
OS1 OS1 69.8% 0.75 1.891 240 0.0381 6.53 330 0.0177 0.10 0.016 2.67 2.07 8.60 570 13.17 8.60
D1 D1 36.7% 0.46 1.053 225 0.0268 12.89 98 0.0834 0.10 0.030 3.09 0.53 13.42 323 11.79 11.79
D2 D2 50.9% 0.61 2.471 88 0.0413 5.39 506 0.0292 0.10 0.016 3.43 2.46 7.85 594 13.30 7.85
D3 D3 34.1% 0.52 0.751 36 0.0500 3.85 237 0.0625 0.10 0.030 2.68 1.48 5.33 274 11.52 5.33
D4 D4 27.3% 0.46 1.092 55 0.0278 6.28 388 0.0453 0.10 0.030 2.28 2.84 9.12 443 12.46 9.12
D5 D5 97.1% 0.93 0.421 90 0.0510 1.75 215 0.0428 0.10 0.016 4.15 0.86 5.00 306 11.70 5.00
D6 D6 78.6% 0.81 0.125 51 0.0654 2.06 20 0.0065 0.10 0.016 1.62 0.20 5.00 71 10.39 5.00
D7 D7 35.2% 0.52 0.786 44 0.0100 7.15 378 0.0407 0.10 0.016 4.05 1.56 8.70 422 12.34 8.70
D8 D8 92.3% 0.90 0.695 108 0.0549 2.20 388 0.0357 0.10 0.030 2.02 3.20 5.40 496 12.76 5.40
D9 D9 20.6% 0.39 1.421 101 0.0331 8.90 63 0.0109 0.10 0.016 2.09 0.50 9.40 164 10.91 9.40
December 21, 2021
Heartside Hill
DEVELOPED TIME OF CONCENTRATION
A. Bartel
21-1045-00
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
=1.871.1
10
180
+=LtcV.R2/3 S 1/2
21-1045-00 Rational Calcs (2021-12-21).xlsx Page 2 of 4 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)
OS1 OS1 69.8% 0.93 1.891 240 0.0381 3.07 330 0.0177 0.14 0.016 3.34 1.65 5.00 570 13.17 5.00
D1 D1 36.7% 0.58 1.053 225 0.0268 10.56 98 0.0834 0.14 0.030 3.87 0.42 10.98 323 11.79 10.98
D2 D2 50.9% 0.76 2.471 88 0.0413 3.74 506 0.0292 0.14 0.016 4.29 1.96 5.70 594 13.30 5.70
D3 D3 34.1% 0.64 0.751 36 0.0500 3.00 237 0.0625 0.14 0.030 3.35 1.18 5.00 274 11.52 5.00
D4 D4 27.3% 0.58 1.092 55 0.0278 5.14 388 0.0453 0.14 0.030 2.85 2.27 7.41 443 12.46 7.41
D5 D5 97.1% 1.00 0.421 90 0.0510 1.03 215 0.0428 0.14 0.016 5.19 0.69 5.00 306 11.70 5.00
D6 D6 78.6% 1.00 0.125 51 0.0654 0.72 20 0.0065 0.14 0.016 2.03 0.16 5.00 71 10.39 5.00
D7 D7 35.2% 0.65 0.786 44 0.0100 5.52 378 0.0407 0.14 0.016 5.06 1.24 6.77 422 12.34 6.77
D8 D8 92.3% 1.00 0.695 108 0.0549 1.10 388 0.0357 0.14 0.030 2.53 2.56 5.00 496 12.76 5.00
D9 D9 20.6% 0.49 1.421 101 0.0331 7.66 63 0.0109 0.14 0.016 2.62 0.40 8.06 164 10.91 8.06
December 21, 2021
Heartside Hill
DEVELOPED TIME OF CONCENTRATION
A. Bartel
21-1045-00
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
=1.871.1
10
180
+=LtcV.R2/3 S 1/2
21-1045-00 Rational Calcs (2021-12-21).xlsx Page 3 of 4 Highland Development Services
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
105,661 2.43 63,509 0% 0
363,964 8.36 178,480 75% 133,860
443,462 10.78 241,989 - 133,860
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
D1 OS1+D1+D2+D3 268,585 52.2% 141,812 0.17 3,802 Rain Garden
EDB Pond Contributing
Basins
Drainage Area
(sq-ft)
Drainage Area
(acre)% Impervious WQCV40-hr
(watershed inches)
WQCV40-hr
(ac-ft)
Pond D D4+…+D9 197,737 4.539 44.4% 0.19 0.087
133,860
141,812
105.9%
Area (sq-ft) Area (acres) Treatment Ratio
268,585 6.17 57.2%
197,737 4.54 42.1%
3,303 0.08 0.7%
469,625 10.78
December 21, 2021
Urban Storm Drainage Criteria Manual by Urban Drainage and Flood Control District, June 2001 (Revised January 2016)
Heartside Hill
Low Impact Development
J.Claeys
Highland Development Services
21-1045-00
Total Improvement Area
Water Quality Area Treatment Summary
Description
Total Area Treated by LID
Total Area Treated by EDB
Total Area Not Treated
Total % 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
Totals
Standard Water Quality Areas
Description
Existing Church Site
Proposed Site
Sheet 1 of 2
Designer:
Company:
Date:
Project:
Location:
1. Basin Storage Volume
A) Effective Imperviousness of Tributary Area, Ia Ia =52.2 %
(100% if all paved and roofed areas upstream of rain garden)
B) Tributary Area's Imperviousness Ratio (i = Ia/100)i = 0.522
C) Water Quality Capture Volume (WQCV) for a 12-hour Drain Time WQCV = 0.17 watershed inches
(WQCV= 0.8 * (0.91* i3 - 1.19 * i2 + 0.78 * i)
D) Contributing Watershed Area (including rain garden area) Area = 268,585 sq ft
E) Water Quality Capture Volume (WQCV) Design Volume VWQCV =cu ft
Vol = (WQCV / 12) * Area
F) For Watersheds Outside of the Denver Region, Depth of d6 =0.43 in
Average Runoff Producing Storm
G) For Watersheds Outside of the Denver Region, VWQCV OTHER =3,802 cu ft
Water Quality Capture Volume (WQCV) Design Volume
H) User Input of Water Quality Capture Volume (WQCV) Design Volume VWQCV USER =cu ft
(Only if a different WQCV Design Volume is desired)
2. Basin Geometry
A) WQCV Depth (12-inch maximum)DWQCV =12 in
B) Rain Garden Side Slopes (Z = 4 min., horiz. dist per unit vertical) Z = 4.00 ft / ft
(Use "0" if rain garden has vertical walls)
C) Mimimum Flat Surface Area AMin =2804 sq ft
D) Actual Flat Surface Area AActual =sq ft
E) Area at Design Depth (Top Surface Area)ATop =sq ft
F) Rain Garden Total Volume VT=cu ft
(VT= ((ATop + AActual) / 2) * Depth)
3. Growing Media
4. Underdrain System
A) Are underdrains provided?1
B) Underdrain system orifice diameter for 12 hour drain time
i) Distance From Lowest Elevation of the Storage y =ft
Volume to the Center of the Orifice
ii) Volume to Drain in 12 Hours Vol12 =cu ft
iii) Orifice Diameter, 3/8" Minimum DO = in
Design Procedure Form: Rain Garden (RG)
A. Bartel
Highland Development Services
December 22, 2021
Heartside Hill
Fort Collins, CO
UD-BMP (Version 3.07, March 2018)
Choose One
Choose One
18" Rain Garden Growing Media
Other (Explain):
YES
NO
UD-BMP_v3.07.xlsm, RG 12/22/2021, 10:22 AM