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NORTHERNENGINEERING.COM | 970.221.4158
FORT COLLINS | GREELEY 1 | 2
DATE: June 21, 2024
PROJECT: 316 Park Street
Fort Collins, Colorado
PROJECT NO. 24-0312
ATTENTION: Stormwater Staff
City of Fort Collins Stormwater
700 Wood Street
Fort Collins, CO 80521
Stormwater Staff
This letter serves to document the proposed drainage impacts for improvements at 316 Park Street in Fort
Collins, Colorado. The site is in the Capitol Hill neighborhood, and it is bounded by Park Street to the west, an
alley to the east and single-family homes to the north and south.
Project Overview
The proposed project is to build a two-story accessory building on the existing single-family property, with a
concrete walkway from the existing residence to the proposed accessory building. All other existing structures
and walks are to remain.
Existing Site/Drainage
The existing site has a single-family residence, a garage, a shed, a concrete driveway, and some concrete
patio/walk areas with portions of flagstone. The rest of the property is grass lawn with trees and landscaping.
The western half of the property drains north toward the adjacent lot, south toward the adjacent lot and west
toward Park Street, the eastern half of the property drains to the alley on the east side of the property. The
existing alley generally drains from south to north.
The total existing impervious area draining to the alley is 3,302 square feet.
Proposed Site/Drainage
The proposed site was designed to maintain existing drainage patterns as closely as possible. The proposed
accessory building is roughly 600 square feet at the finished floor with roughly 800 square feet of roof cover. A 3-
foot walk is proposed from the existing residence to the proposed accessory building. A 6-foot walk will run
along the west side of the proposed accessory building. The bottom floor of the proposed accessory building is a
garage that backs up to the alley on the east.
The total proposed impervious area for the lot is 4,220 square feet. This is a net increase of 918 square feet for
the entire site. The additional 918 square feet of impervious area drains towards the alley.
Five cross sections were evaluated within the alley, sections A-A, A1-A1, A2-A2, A3-A3, A4-A4 and section B-B.
Hydraulic computations for both the existing and proposed conditions for cross sections A-A and B-B have been
included in this report. In the existing condition, it was assumed both sections A-A and B-B would be inundated
by the 0.16 cfs runoff from the site. This was determined to be the most conservative approach considering the
runoff sheet flows almost uniformly from the site to the alley. In the proposed condition, section A-A was
evaluated at the discharge point from the north swale. Flows evaluated at this point include the runoff from
Basin N and Basin E. The total flow evaluated at section A-A was 0.26 cfs which resulted in a 0.01 ft increase in
depth within the alley. Section B-B was evaluated at the discharge point of the south swale. Flows evaluated at
this point include runoff from Basin S. The total flow evaluated at section B-B was 0.16 cfs which resulted in a
Grading/Stormwater Plan Accepted
(Building Permit Released)
Accepted by:
Date :
Dan Mogen
06/26/2024
NORTHERNENGINEERING.COM | 970.221.4158
FORT COLLINS | GREELEY 2 | 2
0.00 ft increase in depth within the alley. Under further analysis, it was determined flow primarily travels north
through the alley towards Cherry Street. The additional sections (A1-A1 through A4-A4) show the capacity of the
alley to handle the proposed runoff from the site and convey it to Cherry Street, where it will be further routed to
public drainage infrastructure. Grading and drainage exhibits detailing these basins and cross section locations
has been included in this report.
Erosion and Sediment Control
During construction, the contractor will follow the appropriate and applicable Fort Collins standards for erosion
and sediment control. Regardless that the project will disturb less than 10,000 square feet, the contractor will
be required to sweep and maintain the site to prevent dirt, saw cuttings, concrete wash, trash and debris,
landscape materials and other pollutants from leaving the site. City inspectors may require the installation of
erosion and sediment control measures dependent on site inspections or neighbor complaints.
Floodplains
There are no regulatory floodplains associated with the project.
Conclusions
The proposed grading concept closely matches the original drainage patterns and complies with the City of Fort
Collins Stormwater Manual. While there is a net increase of 0.06 cfs and 0.25 cfs in the 2-Yr and 100-Yr event
respectively there are no adverse impacts to downstream properties and City of Fort Collins infrastructure from
the proposed improvements for 316 Park Street.
Please feel free to contact me if you have any questions.
Sincerely,
NORTHERN ENGINEERING SERVICE, INC.
Reviewed by:
Jacob O'Banion, EIT Cassandra Ungerman, PE
Project Engineer Project Engineer
Runoff Coefficient1
Percent
Impervious1 Project:
Location:
0.95 100%Calc. By:
0.95 90%Date:
Flagstone 0.85 80%
0.50 40%
0.10 2%
Basin ID Basin Area
(sq.ft.)
Basin Area
(acres)Concrete (Sq. Ft.)Asphalt, Concrete
(sq.ft.)
Asphalt, Concrete
(acres)Rooftop (sq.ft.) Rooftop (acres) Flagstone (sq.ft.) Flagstone (acres) Gravel (sq.ft.) Gravel (acres)
Lawns, Sandy Soil,
Flat Slope < 2%
(sq.ft.)
Lawns, Sandy Soil,
Flat Slope < 2%
(acres)
Percent
Impervious
C2*Cf
Cf = 1.00
C5*Cf
Cf = 1.00
C10*Cf
Cf = 1.00
C100*Cf
Cf = 1.25
Alley 3,248 0.075 103.000 103.000 0.002 264.00 0.006 28.00 0.001 0.000 0.000 2,853.00 0.07 13% 0.20 0.20 0.20 0.25
N 1,305 0.030 95.310 95.310 0.002 306.78 0.007 28.00 0.001 0.000 0.000 874.92 0.02 32%0.38 0.38 0.38 0.47
E 511 0.012 0.000 0.000 0.000 427.45 0.010 0.00 0.000 84.000 0.002 0.00 0.00 82%0.88 0.88 0.88 1.00
S 1,432 0.033 168.783 168.783 0.004 355.18 0.008 0.00 0.000 0.000 0.000 907.67 0.02 35% 0.41 0.41 0.41 0.51
RUNOFF COEFFICIENT CALCULATIONS
Asphalt, Concrete
Rooftop
Lawns, Sandy Soil, Flat Slope < 2%
Streets, Parking Lots, Roofs, Alleys, and Drives:
Character of Surface:316 Park Street
Fort Collins
Jacob Obanion
June 12, 2024
Lawns and Landscaping:
2) Composite Runoff Coefficient adjusted per Table 3.2-3 of the Fort Collins
Stormwater Manual (FCSM).USDA SOIL TYPE: C
Gravel
Composite Runoff Coefficient2
1) Runoff coefficients per Tables 3.2-1 & 3.2 of the FCSM. Percent impervious per Tables 4.1-2 & 4.1-3 of the FCSM.
Proposed Runoff
Exisitng Runoff
Page 1 of 1
Where:
Length
(ft)
Elev
Up
Elev
Down
Slope
(%)
Ti
2-Yr
(min)
Ti
10-Yr
(min)
Ti
100-Yr
(min)
Length
(ft)
Elev
Up
Elev
Down
Slope
(%)Surface n
Flow
Area3
(sq.ft.)
WP3 (ft)R (ft)V
(ft/s)
Tt
(min)
Max.
Tc
(min)
Comp.
Tc 2-Yr
(min)
Tc
2-Yr
(min)
Comp.
Tc 10-Yr
(min)
Tc
10-Yr
(min)
Comp.
Tc 100-
Yr
(min)
Tc
100-Yr
(min)
alley Alley 32 24.20 23.60 1.87%7.70 7.70 7.26 50 23.60 23.40 0.40% Swale (8:1)0.035 8.00 16.12 0.50 1.69 0.49 10.46 8.19 8.19 8.19 8.19 7.76 7.76
A-A N 28 24.20 23.76 1.57%6.15 6.15 5.34 36 23.76 23.33 1.19%Swale (4:1)0.035 4.00 8.25 0.48 2.87 0.21 10.36 6.35 6.35 6.35 6.35 5.55 5.55
A-A E 5 23.91 23.36 11.00%0.42 0.42 0.19 0 N/A N/A N/A N/A N/A N/A N/A N/A 0.00 10.03 0.42 5.00 0.42 5.00 0.19 5.00
B-B S 32 24.20 23.60 1.87%5.91 5.91 5.03 50 23.60 23.40 0.40% Swale (8:1)0.035 8.00 16.12 0.50 1.69 0.49 10.46 6.40 6.40 6.40 6.40 5.52 5.52
Proposed Runoff
Existing Runoff
Design
Point Basin ID
Overland Flow Channelized Flow Time of Concentration
TIME OF CONCENTRATION COMPUTATIONS
Location:
Maximum Tc:Overland Flow, Time of Concentration:
Channelized Flow, Velocity: Channelized Flow, Time of Concentration:
316 Park Street
Fort Collins
Jacob Obanion
June 13, 2024
Project:
Calculations By:
Date:
Notes
S = Longitudinal Slope, feet/feet
R = Hydraulic Radius (feet)
n = Roughness Coefficient
V = Velocity (ft/sec) WP = Wetted Perimeter (ft)
(Equation 3.3-2 per Fort Collins Stormwater Manual)𝑇=1.87 1.1 −𝐶∗𝐶𝑓𝐿
𝑆
𝑉=1.49
𝑛∗𝑅/∗𝑆(Equation 5-4 per Fort Collins Stormwater Manual)
𝑇𝑐=𝐿
180 + 10 (Equation 3.3-5 per Fort Collins
Stormwater Manual)
𝑇𝑡=𝐿
𝑉∗ 60
(Equation 5-5 per Fort Collins
1) Add 4900 to all elevations.
2) Per Fort Collins Stormwater Manual, minimum Tc = 5 min.
3) Assume a water depth of 6" and a typical curb and gutter per
Larimer County Urban Street Standard Detail 701 for curb and
gutter channelized flow. Assume a water depth of 1', fixed side
slopes, and a triangular swale section for grass channelized flow.
Assume a water depth of 1', 4:1 side slopes, and a 2' wide valley
pan for channelized flow in a valley pan.
Page 1 of 1
Tc2 Tc10 Tc100 C2 C10 C100 I2 I10 I100 Q2 Q10 Q100
Existing Runoff
alley Alley 0.07 8.2 8.2 7.8 0.2 0.2 0.3 2.4 4.1 8.6 0.04 0.06 0.16
Proposed Runoff
A-A N 0.03 6.4 6.4 5.5 0.4 0.4 0.5 2.7 4.6 9.6 0.03 0.05 0.14
A-A E 0.01 5.0 5.0 5.0 0.9 0.9 1.0 2.9 4.9 10.0 0.03 0.05 0.12
B-B S 0.03 6.4 6.4 5.5 0.4 0.4 0.5 2.7 4.6 9.6 0.04 0.06 0.16
Date:
Fort Collins
Project:
Location:
Calc. By:
DIRECT RUNOFF COMPUTATIONS
Intensity Flow (cfs)
316 Park Street
Jacob Obanion
June 12, 2024
Design
Point Basin
Intensity, I, from Fig. 3.4.1 Fort Collins Stormwater Manual.
Rational Equation: Q = CiA (Equation 6-1 per MHFD)
Area
(acres
)
Runoff CTc (Min)
Page 1 of 1
Project Number:24-0312 Calc. By:J. Obanion
Project Name:316 Park St.Date:6/12/2024
Project Location:Fort Collins, Colorado
Description Surface Area (sf) Percent Impervious Impervious Area (sf)
Concrete 1501 100% 1501
Rooftop 1976 90% 1779
Flagstone 28 80% 22
3302
Description Surface Area (sf) Percent Impervious Impervious Area (sf)
Concrete 1661 100% 1661
Rooftop 2781 90% 2503
Flagstone 28 80% 22
Gravel 84 40% 34
4220
918
Total Impervious Area
Net Increase Impervious Area
Existing Impervious Areas
Developed Impervious Areas
Impervious Area Calculations
Total Impervious Area
Channel Report
Hydraflow Express Extension for Autodesk® Civil 3D® by Autodesk, Inc. Wednesday, Jun 12 2024
ALLEY XS A-A EXST
User-defined
Invert Elev (ft) = 22.91
Slope (%) = 1.00
N-Value = 0.023
Calculations
Compute by: Known Q
Known Q (cfs) = 0.16
(Sta, El, n)-(Sta, El, n)...
( 0.00, 23.32)-(0.67, 23.19, 0.023)-(3.86, 22.95, 0.023)-(7.68, 22.98, 0.023)-(10.54, 22.91, 0.023)-(16.80, 23.02, 0.023)-(19.71, 23.02, 0.023)
Highlighted
Depth (ft) = 0.07
Q (cfs) = 0.160
Area (sqft) = 0.30
Velocity (ft/s) = 0.53
Wetted Perim (ft) = 11.07
Crit Depth, Yc (ft) = 0.06
Top Width (ft) = 11.06
EGL (ft) = 0.07
-2 0 2 4 6 8 10 12 14 16 18 20 22
Elev (ft) Depth (ft)Section
22.00 -0.91
22.50 -0.41
23.00 0.09
23.50 0.59
24.00 1.09
Sta (ft)
Channel Report
Hydraflow Express Extension for Autodesk® Civil 3D® by Autodesk, Inc. Wednesday, Jun 12 2024
ALLEY XS A-A PROP
User-defined
Invert Elev (ft) = 22.91
Slope (%) = 1.00
N-Value = 0.023
Calculations
Compute by: Known Q
Known Q (cfs) = 0.26
(Sta, El, n)-(Sta, El, n)...
( 0.00, 23.32)-(0.67, 23.19, 0.023)-(3.86, 22.95, 0.023)-(7.68, 22.98, 0.023)-(10.54, 22.91, 0.023)-(16.80, 23.02, 0.023)-(19.71, 23.02, 0.023)
Highlighted
Depth (ft) = 0.08
Q (cfs) = 0.260
Area (sqft) = 0.42
Velocity (ft/s) = 0.62
Wetted Perim (ft) = 11.77
Crit Depth, Yc (ft) = 0.07
Top Width (ft) = 11.76
EGL (ft) = 0.09
-2 0 2 4 6 8 10 12 14 16 18 20 22
Elev (ft) Depth (ft)Section
22.00 -0.91
22.50 -0.41
23.00 0.09
23.50 0.59
24.00 1.09
Sta (ft)
Channel Report
Hydraflow Express Extension for Autodesk® Civil 3D® by Autodesk, Inc. Friday, Jun 21 2024
ALLEY XS A1-A1 PROP
User-defined
Invert Elev (ft) = 21.69
Slope (%) = 2.60
N-Value = 0.023
Calculations
Compute by: Known Q
Known Q (cfs) = 0.26
(Sta, El, n)-(Sta, El, n)...
( 0.00, 22.30)-(0.95, 22.06, 0.023)-(21.28, 21.69, 0.023)-(26.34, 21.83, 0.023)
Highlighted
Depth (ft) = 0.08
Q (cfs) = 0.260
Area (sqft) = 0.29
Velocity (ft/s) = 0.89
Wetted Perim (ft) = 7.31
Crit Depth, Yc (ft) = 0.08
Top Width (ft) = 7.31
EGL (ft) = 0.09
-5 0 5 10 15 20 25 30 35
Elev (ft) Depth (ft)Section
21.00 -0.69
21.50 -0.19
22.00 0.31
22.50 0.81
23.00 1.31
Sta (ft)
Channel Report
Hydraflow Express Extension for Autodesk® Civil 3D® by Autodesk, Inc. Friday, Jun 21 2024
ALLEY XS A2-A2 PROP
User-defined
Invert Elev (ft) = 19.61
Slope (%) = 4.20
N-Value = 0.023
Calculations
Compute by: Known Q
Known Q (cfs) = 0.26
(Sta, El, n)-(Sta, El, n)...
( 0.00, 20.84)-(3.50, 20.31, 0.023)-(7.60, 19.93, 0.023)-(10.64, 19.97, 0.023)-(16.45, 19.91, 0.023)-(20.23, 19.80, 0.023)-(23.70, 19.61, 0.023)
-(26.19, 20.32, 0.023)
Highlighted
Depth (ft) = 0.12
Q (cfs) = 0.260
Area (sqft) = 0.16
Velocity (ft/s) = 1.63
Wetted Perim (ft) = 2.68
Crit Depth, Yc (ft) = 0.13
Top Width (ft) = 2.66
EGL (ft) = 0.16
-5 0 5 10 15 20 25 30 35
Elev (ft) Depth (ft)Section
19.00 -0.61
19.50 -0.11
20.00 0.39
20.50 0.89
21.00 1.39
Sta (ft)
Channel Report
Hydraflow Express Extension for Autodesk® Civil 3D® by Autodesk, Inc. Friday, Jun 21 2024
ALLEY XS A3-A3 PROP
User-defined
Invert Elev (ft) = 17.89
Slope (%) = 4.70
N-Value = 0.023
Calculations
Compute by: Known Q
Known Q (cfs) = 0.26
(Sta, El, n)-(Sta, El, n)...
( 0.00, 19.13)-(5.37, 18.15, 0.023)-(11.32, 18.20, 0.023)-(16.31, 18.12, 0.023)-(21.45, 17.97, 0.023)-(22.72, 17.89, 0.023)-(26.77, 18.19, 0.023)
Highlighted
Depth (ft) = 0.10
Q (cfs) = 0.260
Area (sqft) = 0.15
Velocity (ft/s) = 1.73
Wetted Perim (ft) = 3.30
Crit Depth, Yc (ft) = 0.12
Top Width (ft) = 3.30
EGL (ft) = 0.15
-5 0 5 10 15 20 25 30 35
Elev (ft) Depth (ft)Section
17.00 -0.89
17.50 -0.39
18.00 0.11
18.50 0.61
19.00 1.11
19.50 1.61
20.00 2.11
Sta (ft)
Channel Report
Hydraflow Express Extension for Autodesk® Civil 3D® by Autodesk, Inc. Friday, Jun 21 2024
ALLEY XS A4-A4 PROP
User-defined
Invert Elev (ft) = 16.21
Slope (%) = 3.70
N-Value = 0.023
Calculations
Compute by: Known Q
Known Q (cfs) = 0.26
(Sta, El, n)-(Sta, El, n)...
( 0.00, 17.38)-(2.61, 16.50, 0.023)-(7.49, 16.36, 0.023)-(14.23, 16.38, 0.023)-(20.56, 16.21, 0.023)-(22.91, 16.36, 0.023)
Highlighted
Depth (ft) = 0.09
Q (cfs) = 0.260
Area (sqft) = 0.22
Velocity (ft/s) = 1.20
Wetted Perim (ft) = 4.82
Crit Depth, Yc (ft) = 0.09
Top Width (ft) = 4.82
EGL (ft) = 0.11
-5 0 5 10 15 20 25 30
Elev (ft) Depth (ft)Section
15.50 -0.71
16.00 -0.21
16.50 0.29
17.00 0.79
17.50 1.29
18.00 1.79
Sta (ft)
Channel Report
Hydraflow Express Extension for Autodesk® Civil 3D® by Autodesk, Inc. Wednesday, Jun 12 2024
ALLEY XS B-B EXST
User-defined
Invert Elev (ft) = 23.08
Slope (%) = 0.50
N-Value = 0.023
Calculations
Compute by: Known Q
Known Q (cfs) = 0.16
(Sta, El, n)-(Sta, El, n)...
( 0.00, 23.59)-(1.35, 23.39, 0.023)-(5.27, 23.08, 0.023)-(10.98, 23.19, 0.023)-(19.66, 23.22, 0.023)
Highlighted
Depth (ft) = 0.10
Q (cfs) = 0.160
Area (sqft) = 0.32
Velocity (ft/s) = 0.50
Wetted Perim (ft) = 6.46
Crit Depth, Yc (ft) = 0.07
Top Width (ft) = 6.46
EGL (ft) = 0.10
-2 0 2 4 6 8 10 12 14 16 18 20 22
Elev (ft) Depth (ft)Section
22.75 -0.33
23.00 -0.08
23.25 0.17
23.50 0.42
23.75 0.67
24.00 0.92
Sta (ft)
Channel Report
Hydraflow Express Extension for Autodesk® Civil 3D® by Autodesk, Inc. Wednesday, Jun 12 2024
ALLEY XS B-B PROP
User-defined
Invert Elev (ft) = 23.08
Slope (%) = 0.50
N-Value = 0.023
Calculations
Compute by: Known Q
Known Q (cfs) = 0.16
(Sta, El, n)-(Sta, El, n)...
( 0.00, 23.59)-(1.35, 23.39, 0.023)-(5.27, 23.08, 0.023)-(10.98, 23.19, 0.023)-(19.66, 23.22, 0.023)
Highlighted
Depth (ft) = 0.10
Q (cfs) = 0.160
Area (sqft) = 0.32
Velocity (ft/s) = 0.50
Wetted Perim (ft) = 6.46
Crit Depth, Yc (ft) = 0.07
Top Width (ft) = 6.46
EGL (ft) = 0.10
-2 0 2 4 6 8 10 12 14 16 18 20 22
Elev (ft) Depth (ft)Section
22.75 -0.33
23.00 -0.08
23.25 0.17
23.50 0.42
23.75 0.67
24.00 0.92
Sta (ft)
Channel Report
Hydraflow Express Extension for Autodesk® Civil 3D® by Autodesk, Inc. Wednesday, Jun 12 2024
PROPOSED SWALE NORTH
User-defined
Invert Elev (ft) = 23.40
Slope (%) = 1.00
N-Value = 0.035
Calculations
Compute by: Known Q
Known Q (cfs) = 0.14
(Sta, El, n)-(Sta, El, n)...
( 0.00, 23.91)-(6.15, 23.40, 0.035)-(7.11, 23.64, 0.035)-(9.43, 23.73, 0.035)
Highlighted
Depth (ft) = 0.16
Q (cfs) = 0.140
Area (sqft) = 0.21
Velocity (ft/s) = 0.68
Wetted Perim (ft) = 2.60
Crit Depth, Yc (ft) = 0.12
Top Width (ft) = 2.57
EGL (ft) = 0.17
-1 0 1 2 3 4 5 6 7 8 9 10 11
Elev (ft) Depth (ft)Section
23.00 -0.40
23.25 -0.15
23.50 0.10
23.75 0.35
24.00 0.60
Sta (ft)
Channel Report
Hydraflow Express Extension for Autodesk® Civil 3D® by Autodesk, Inc. Wednesday, Jun 12 2024
PROPOSED SWALE SOUTH
User-defined
Invert Elev (ft) = 23.38
Slope (%) = 0.50
N-Value = 0.017
Calculations
Compute by: Known Q
Known Q (cfs) = 0.16
(Sta, El, n)-(Sta, El, n)...
( 0.00, 23.91)-(1.95, 23.46, 0.035)-(2.95, 23.38, 0.013)-(3.95, 23.46, 0.013)-(4.44, 23.63, 0.035)
Highlighted
Depth (ft) = 0.12
Q (cfs) = 0.160
Area (sqft) = 0.17
Velocity (ft/s) = 0.97
Wetted Perim (ft) = 2.31
Crit Depth, Yc (ft) = 0.10
Top Width (ft) = 2.29
EGL (ft) = 0.13
-.5 0 .5 1 1.5 2 2.5 3 3.5 4 4.5 5
Elev (ft) Depth (ft)Section
23.00 -0.38
23.25 -0.13
23.50 0.12
23.75 0.37
24.00 0.62
Sta (ft)
NORTH CHRIS S,
324 PARK STREET,
FORT COLLINS
X
X
X
X
X
X
X
X X X X X X X X X X X
X X X X X X X X X X
GG
G G
E
E E E E
AC
W
20' ALLEYPA
R
K
S
T
R
E
E
T
CZERWINSKI
MICHELLE,
312 PARK STREET,
FORT COLLINS
5' SETBACK
5' SETBACK
AA
BB
EXISTING SINGLE
FAMILY RESIDENCE
w/ BASEMENT
FF=5026.14
EXISTING GARAGE
FF=5024.34
EXISTING SHED
FF=2024.00
EXISTING WOOD FENCE
EXISTING WOOD FENCE
EXISTING PROPERTY
LINE (TYP.)
EXISTING CHASE
EXISTING BRICK WALL
EXISTING BRICK WALL
EXISTING WET WELL
RIM = 5025.20
EXISTING WALK
EXISTING BRICK WALL
EXISTING GATE
EXISTING CHASE
EXISTING WET WELL
RIM = 5025.02
EXISTING TREE (TYP.)
EXISTING DRIVEWAY
EXISTING PATIO
EXISTING FRENCH
DRAIN (TYP.)
EXISTING
FRENCH DRAIN
RIM = 5024.23
EXISTING
FRENCH DRAIN
RIM = 5023.89
EXISTING WALK
PROPOSED
ACCESSORY
BUILDING
TF=5024.66
PROPOSED 3' WALK
PROPOSED 6' WALK
PROPOSED ROOF
OVERHANG (TYP.)
PROPOSED SWALE
(NORTH)
EXISTING
FLAGSTONE
WALK
PROPOSED SWALE
(SOUTH)
PROPOSED 2'
CONCRETE PAN
EXISTING GATE
0.01 ac.
E
0.03 ac.
S
0.03 ac.
N
D1
DR
A
I
N
A
G
E
E
X
H
I
B
I
T
CALL 2 BUSINESS DAYS IN ADVANCE BEFORE YOU
DIG, GRADE, OR EXCAVATE FOR THE MARKING OF
UNDERGROUND MEMBER UTILITIES.
CALL UTILITY NOTIFICATION CENTER OF
COLORADO
Know what'sbelow.
before you dig.Call
R
NORTH
( IN FEET )
1 inch = ft.
Feet01010
10
20 30
GEXISTING GAS
EEXISTING ELECTRIC
EXISTING TREES
PROPOSED CONCRETE PAVING
EXISTING CONCRETE PAVING
EXISTING FLAGSTONE PAVING
SWALE SECTIONS
SWALE SUMMARY TABLE
Sheet
KO
L
L
A
R
S
R
E
S
I
D
E
N
C
E
31
6
P
A
R
K
S
T
R
E
E
T
PROPOSED CONTOUR
PROPOSED SWALE
EXISTING CONTOUR
PROPERTY BOUNDARY
PROPOSED SPOT ELEVATION
PROPOSED SLOPES
1.THE SIZE, TYPE AND LOCATION OF ALL KNOWN UNDERGROUND UTILITIES ARE
APPROXIMATE WHEN SHOWN ON THESE DRAWINGS. IT SHALL BE THE
RESPONSIBILITY OF THE CONTRACTOR TO VERIFY THE EXISTENCE OF ALL
UNDERGROUND UTILITIES IN THE AREA OF THE WORK. BEFORE COMMENCING
NEW CONSTRUCTION, THE CONTRACTOR SHALL BE RESPONSIBLE FOR LOCATING
ALL UNDERGROUND UTILITIES AND SHALL BE RESPONSIBLE FOR FOR ALL
UNKNOWN UNDERGROUND UTILITIES.
2.REFER TO THE PLAT FOR LOT AREAS, TRACT SIZES, EASEMENTS, LOT DIMENSIONS,
UTILITY EASEMENTS, OTHER EASEMENTS, AND OTHER SURVEY INFORMATION.
3.ALL PROJECT DATA IS ON VERTICAL DATUM; NAVD88.
4.ALL CURB SPOTS SHOWN ARE FLOWLINE ELEVATIONS. ALL OTHER SPOTS ARE
FINISHED GRADE ELEVATIONS.
5.LOT GRADING IS DESIGNED FOR TYPICAL RECTANGULAR FOOTPRINT WITH
DIMENSIONS AS SHOWN HEREON. SHOULD BUILDING FOOTPRINT CHANGE,
GRADING SHALL BE ADJUSTED BY PLOT PLAN FOR THE SPECIFIC FOOTPRINT. ALL
MINIMUM OPENINGS SHALL BE A MINIMUM OF 18" ABOVE FRONT LOT ELEVATIONS
AND PLOT PLAN DESIGN SHALL MEET FHA GRADING GUIDELINES AND BUILDING
CODE REQUIREMENTS.
6.REFER TO THE DRAINAGE LETTER, DATED JUNE 12, 2024 FOR ADDITIONAL
INFORMATION.
NOTES:
2.0%
(47.45
)
EXISTING SPOT ELEVATION
EXISTING LOT LINE
33.43
LEGEND:
EXISTING SLOPES (2.0%)
PROPOSED CONCRETE PAN
Impervious Area Calculations
Existing Impervious Areas
Description Surface Area (sf)Percent Impervious Impervious Area (sf)
Concrete 1501 100%1501
Rooftop 1976 90%1779
Flagstone 28 80%22
Total Impervious Area 3302
Developed Impervious Areas
Description Surface Area (sf)Percent Impervious Impervious Area (sf)
Concrete 1661 100%1661
Rooftop 2781 90%2503
Flagstone 28 80%22
Gravel 84 40%34
Total Impervious Area 4220
Net Increase Impervious Area 918
C2 C100 Q2
(cfs)
Q100
(cfs)
NORTH CHRIS S,
324 PARK STREET,
FORT COLLINS
X
X
X
X
X
X
X
X X X X X X X X X X X
X X X X X X X X X X
GG
G G
E
E E E E
AC
W
20' ALLEYPA
R
K
S
T
R
E
E
T
(24
.
1
9
)
(24
.
1
9
)
24.2
3
24.04
24.07
24.15
24.16
24.16
24.07
24.07 24.1
6 23.9
1
(23.31)
23.35
1.0%
0.
0
%
0.
0
%
1.5%
1.8%
0.5%
1.
4
%
1.0%
1.0%
11.1%
1.5%
1.5%
1.0
%
1.7
%
8.
2
%
(23.40)
(23
.
6
0
)
CZERWINSKI
MICHELLE,
312 PARK STREET,
FORT COLLINS
5' SETBACK
5' SETBACK
(1
.
7
%
)
(1
.
5
%
)
(2
.
4
%
)
(1
.
4
%
)
(1.
4
%
)
(2
.
1
%
)
(20
.
0
%
)
(4
.
5
%
)
(2.2%)
(6.
4
%
)
(6
.
0
%
)
(8.2%)
(1
.
2
%
)
(4.
0
%
)
5.3%1.6%2.0%
4:
1
2.0
%
10:1
1.0%
23.66
23.6
0
23.95
24.14
24.1
8
24.2
1
24.0
7
23.
6
4
23.53
(23.34)
23.62
23.6
2
23.50
23.3
8
23.4
0
23.9
1
4:
1
0.5%
1.0%AA
BB
EXISTING SINGLE
FAMILY RESIDENCE
w/ BASEMENT
FF=5026.14
EXISTING GARAGE
FF=5024.34
EXISTING SHED
FF=2024.00
EXISTING WOOD FENCE
EXISTING WOOD FENCE
EXISTING PROPERTY
LINE (TYP.)
EXISTING CHASE
EXISTING BRICK WALL
EXISTING BRICK WALL
EXISTING WET WELL
RIM = 5025.20
EXISTING WALK
EXISTING BRICK WALL
EXISTING GATE
EXISTING CHASE
EXISTING WET WELL
RIM = 5025.02
EXISTING TREE (TYP.)
EXISTING DRIVEWAY
EXISTING PATIO
EXISTING FRENCH
DRAIN (TYP.)
EXISTING
FRENCH DRAIN
RIM = 5024.23
EXISTING
FRENCH DRAIN
RIM = 5023.89
EXISTING WALK
PROPOSED
ACCESSORY
BUILDING
TF=5024.66
PROPOSED 3' WALK
PROPOSED 6' WALK
PROPOSED ROOF
OVERHANG (TYP.)
PROPOSED SWALE
(NORTH)
EXISTING
FLAGSTONE
WALK
PROPOSED SWALE
(SOUTH)
PROPOSED 2'
CONCRETE PAN
EXISTING GATE
A1A1
A2A2
A3A3
A4A4
CHERRY STREET
Sheet
KO
L
L
A
R
S
R
E
S
I
D
E
N
C
E
31
6
P
A
R
K
S
T
R
E
E
T
G1
GR
A
D
I
N
G
P
L
A
N
CALL 2 BUSINESS DAYS IN ADVANCE BEFORE YOU
DIG, GRADE, OR EXCAVATE FOR THE MARKING OF
UNDERGROUND MEMBER UTILITIES.
CALL UTILITY NOTIFICATION CENTER OF
COLORADO
Know what'sbelow.
before you dig.Call
R
NORTH
( IN FEET )
1 inch = ft.
Feet01010
10
20 30
PROPOSED CONTOUR
PROPOSED SWALE
EXISTING CONTOUR
PROPERTY BOUNDARY
PROPOSED SPOT ELEVATION
PROPOSED SLOPES
1.THE SIZE, TYPE AND LOCATION OF ALL KNOWN UNDERGROUND UTILITIES ARE
APPROXIMATE WHEN SHOWN ON THESE DRAWINGS. IT SHALL BE THE
RESPONSIBILITY OF THE CONTRACTOR TO VERIFY THE EXISTENCE OF ALL
UNDERGROUND UTILITIES IN THE AREA OF THE WORK. BEFORE COMMENCING
NEW CONSTRUCTION, THE CONTRACTOR SHALL BE RESPONSIBLE FOR LOCATING
ALL UNDERGROUND UTILITIES AND SHALL BE RESPONSIBLE FOR FOR ALL
UNKNOWN UNDERGROUND UTILITIES.
2.REFER TO THE PLAT FOR LOT AREAS, TRACT SIZES, EASEMENTS, LOT DIMENSIONS,
UTILITY EASEMENTS, OTHER EASEMENTS, AND OTHER SURVEY INFORMATION.
3.ALL PROJECT DATA IS ON VERTICAL DATUM; NAVD88.
4.ALL CURB SPOTS SHOWN ARE FLOWLINE ELEVATIONS. ALL OTHER SPOTS ARE
FINISHED GRADE ELEVATIONS.
5.LOT GRADING IS DESIGNED FOR TYPICAL RECTANGULAR FOOTPRINT WITH
DIMENSIONS AS SHOWN HEREON. SHOULD BUILDING FOOTPRINT CHANGE,
GRADING SHALL BE ADJUSTED BY PLOT PLAN FOR THE SPECIFIC FOOTPRINT. ALL
MINIMUM OPENINGS SHALL BE A MINIMUM OF 18" ABOVE FRONT LOT ELEVATIONS
AND PLOT PLAN DESIGN SHALL MEET FHA GRADING GUIDELINES AND BUILDING
CODE REQUIREMENTS.
6.REFER TO THE DRAINAGE LETTER, DATED JUNE 12, 2024 FOR ADDITIONAL
INFORMATION.
NOTES:
2.0%
(47.45
)
EXISTING SPOT ELEVATION
EXISTING LOT LINE
33.43
LEGEND:
GEXISTING GAS
EEXISTING ELECTRIC
EXISTING TREES
PROPOSED CONCRETE PAVING
EXISTING CONCRETE PAVING
EXISTING FLAGSTONE PAVING
EXISTING SLOPES (2.0%)
SWALE SECTIONS
SWALE SUMMARY TABLE
PROPOSED CONCRETE PAN
Impervious Area Calculations
Existing Impervious Areas
Description Surface Area (sf)Percent Impervious Impervious Area (sf)
Concrete 1501 100%1501
Rooftop 1976 90%1779
Flagstone 28 80%22
Total Impervious Area 3302
Developed Impervious Areas
Description Surface Area (sf)Percent Impervious Impervious Area (sf)
Concrete 1661 100%1661
Rooftop 2781 90%2503
Flagstone 28 80%22
Gravel 84 40%34
Total Impervious Area 4220
Net Increase Impervious Area 918
C2 C100 Q2
(cfs)
Q100
(cfs)
SEE BOTTOM RIGHT
SEE ABOVE