HomeMy WebLinkAboutDrainage Reports - 08/29/2012August 1, 2012
Mr. Wes Lamarque
Stormwater Department
City of Fort Collins Utilities
700 Wood Street
Fort Collins, CO 80521
BLUE SKY
Engineering
City of Ft. Collins AR ov ' Plans
Approved By
Date R-a ci -sue.
Re.: Drainage Study Addendum #2
Registry Ridge Sixth Filing (First Replat of Fifth Filing)
Proiect #1312020
Dear Wes,
We have prepared Addendum #2 for the "Drainage Study for Registry Ridge 51h Filing" completed
by Northern Engineering on October 25, 2007. Addendum #1 was completed by Interwest
Consulting Group for the park area to the southwest on February 17, 2010. The original study for
the entire Registry Ridge development was completed June 14, 1999.
The approved Fifth Filing drainage study was based on a site plan that included 27 single family
lots. The new site layout proposes 28 single family lots and more open space within the same
boundary. The following is a summary of the impacts to the drainage systems on and off the site.
In addition, supporting calculations and a revised drainage exhibit have been attached.
Runoff
Basin C from the original study is the only basin that has any changes. The rest of the site,
—--including-the-main-road -and -lots-to-the -south-are-remaining-the-same—Basin-C-was-re-analyzed -_ for the new site plan and broken into two separate sub -basins C1 and C2 in order to calculate a
separate flow for the proposed swale between Lots 21 and 22.
The runoff coefficients for Basin C increased from 0.53 to 0.54 for the. 2-year storm and 0.66 to
0.67 for the 100-year storm. This increased the peak flows from Basin C from 4.67 cfs to 4.79 cfs
in the 2-year storm and 20.39 cfs to 20.89 cfs in the 100 year storm. -
1.
The two most recent drainage reports showed that the proposed runoff from the entire Fifth Filing
site was actually less than was planned in the original 1999 study. This minor increase in runoff
still keeps the proposed runoff well below the planned runoff for this area.
Onsite Systems
A new swale (Swale B) was designed between Lots 21 and 22 to convey drainage fiom sub -basin
C1. The swale was designed to convey 133% of the 100 year flow shown at design point C1.
The sidewalk chase at the downstream is designed to convey the 2 year flow.
Swale C will also see an increase in flow due to the increased runoff from Basin C. This swale
was designed to convey 133% of the difference between the 100 year storm and 2 year storm at
Design Point B2. As previously planned the 2 year storm will be conveyed by the underlying
storm sewer.
529 CRESTMORE PLACE I FORT COLLINS, CO 80521 1 970-217-7420 1 www•bluesky-engineer.com
BLUE SKY
Engineering
Water Quality and Erosion Control
The changes proposed have no impact on the original water quality or erosion control measures,
therefore no changes are proposed with this new site layout.
Summary
The proposed changes to the site will have minimal impact to the stormwater runoff that was
previously planned on and off the site. The onsite stormwater conveyance systems have been
adequately sized to convey the increases in runoff. The increase in runoff from the site is still
less than what was originally planned, therefore no downstream improvements are necessary.
I appreciate your time and consideration in reviewing this submittal. Please contact me at 970-
217-7420 or seliasonC@bluesky-engineer.com if you have any questions.
Sincerely,
Samuel M. Eliason, P.E.
Blue Sky Engineering, LLC
Attachments:
- - - -. --Runoff-Summary ---- - - - -- - - - _ . - - - — - ---- ---- - -- - - - -
Runoff Coefficients and % Impervious Calculations
• Time of Concentration
• Rational Method Peak Runoff Calculations
• Swale B
• Swale C
• Drainage Exhibit
r
529 CRESTMORE PLACE I FORT COLLINS, CO 80521 1 970-217-7420 1 www.bluesk-y-engineer.com
Registry Ridge Fifth Filing - Add. #2 BLUE SKY
Fort Collins, CO Runoff Summary E n g i n e e ring
Upstream
Basins ,.
Design
-.=:Point
Area '
.,(acres) :.-.
CZ
�i00 . r
.
ief;)
-1 Qioo
A
A
1.23
0.34
0.43
0.83
3.61
B
B
1.59
0.72
0.90
2.68
11.71
C1
C1
2.17
0.39
0.49
1.82
7.95
C2
2.20
0.68
0.85
2.96
12.94
C1, C2
C
4.36
0.54
0.67
4.79
20.89
B,C1,C2
B2
7.47
32.60
D
D
0.67
0.39
0.49
0.61
2.64
OSl
OSl
0.98
0.25
0.31
0.48
2.08
OS2
OS2
7.35
0.25
0.31
3.53
15.42
1
Calculations by: SME
Date: 513012012 C: iUsersiSom�DropboxI B12020-RegistryRidgel DrainageiB12020-Runoff xlsx
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Channel Report
Hydraflow Express Extension for AutoCAD® Civil 3D® 2012 by Autodesk, Inc.
Swale B at Design Point C1
User -defined
Highlighted
Invert Elev (ft) = 84.75
Depth (ft)
Slope (%) = 0.50
Q (cfs)
N-Value = 0.027
Area (sqft)
Velocity (ft/s)
Calculations
Wetted Perim (ft)
Compute by: Known Q '
Crit Depth, Yc (ft)
Known Q (cfs) = 10.57
Top Width (ft)
EGL (ft)
Cg%,eLj;Qp8340�(5.00, 84.75, 0.013}(6.00, 84.83, 0.013}(10.00, 85.63, 0.030)
Elev (ft)
86.00
85.50
85.00
84.50
a
Section
Tuesday, May 29 2012
= 0.85
= 10.57
= 4.58
= 2.31
= 9.86
= 0.68
= 9.70
= 0.93
1 0 1 2 3 4 5 6 7 „8 9 10 1
Sta (ft)
Depth (ft)
1.25
0.75
0.25
-0.25
-0.75
Channel Report
Hydraflow Express Extension for AutoCAD® Civil 3D® 2012 by Autodesk, Inc.
Tuesday, May 29 2012
Swale C at Design Point B
User -defined
Highlighted
Invert Elev (ft) = 83.16
Depth (ft)
= 0.57
Slope (%) = 1.60
Q (cfs)
= 33.43
N-Value = 0.025
Area (sqft)
= 7.75
Velocity (ft/s)
= 4.31
Calculations
Wetted Perim (ft)
=-17.25
Compute by: Known Q
Crit Depth, Yc (ft)
= 0.62
Known Q (cfs) = 33.43
Top Width (ft)
= 17.15
EGL (ft)
= 0.86
C`g�� 8�61.LAOOc93.25�0 (8.00, 83.16, 0.030}(14.00, 83.22, 0.013}(17.00,
f e e
83.28, 0.030}(20.00, 84.04, 0.030)
Elev (ft)
85.00
84.50
84.00
E:BIN1I7
83.00
1.30 OM
Section
2 0 2 4 6 8 10 12 14 16 18 20 22
Sta (ft)
Depth (ft)
1.84
1.34
0.84
0.34
-0.16
_n as
SWALE SECTIONS 80
79 78 77 76
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/ FEBRUARY 17, 2010 FOR ADDITIONAL
/ DRAINAGE DETAIL IN OS2 (REGISTRY , ' / 7 ! \ _ _ STOR
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GRAPHIC SCALE:
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Engineering
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LEGEND: szB aePhT,Dre Pbm
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EXSTING STORM SEWER 'RM"/bNe°ky<IpinCOt.l%fm
UISTNG STORM SEWER INLET
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DEVELOPED DRANAGE BOUNOXW µEl
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PROPOSED RUNOFF COERICIENT Z O
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RIPRAP OMET PROTECTION 1..�
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H2 EXISTING EASIN DESIGNATOR 2
IN
EXISTING RUNOFF COEFFICIENT 1`
•e (Mm. MNR) X T
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City of Fort Collins, Colorado
UTILITY PLAN APPROVAL
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