HomeMy WebLinkAboutREGISTRY RIDGE SIXTH FILING (FIFTH FILING, FIRST REPLAT) - MAJOR AMEND. - MJA120002 - SUBMITTAL DOCUMENTS - ROUND 1 - DRAINAGE REPORT529 CRESTMORE PLACE | FORT COLLINS, CO 80521 | 970-217-7420 | www.bluesky-engineer.com
May 30, 2012
Mr. Wes Lamarque
Stormwater Department
City of Fort Collins Utilities
315 East Mountain Avenue, Suite 100
700 Wood Street
Fort Collins, CO 80521
Re.: Drainage Study Addendum #2
Registry Ridge Fifth Filing First Replat
Project #B12020
Dear Wes,
We have prepared Addendum #2 for the “Drainage Study for Registry Ridge 5th 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.
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 from 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 | FORT COLLINS, CO 80521 | 970-217-7420 | www.bluesky-engineer.com
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 seliason@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
Registry Ridge Fifth Filing - Add. #2
Fort Collins, CO Runoff Summary
Area Q2
Q100
(acres) (cfs) (cfs)
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
OS1 OS1 0.98 0.25 0.31 0.48 2.08
OS2 OS2 7.35 0.25 0.31 3.53 15.42
C100
C2
Upstream
Basins
Design
Point
Calculations by: SME
Date: 5/30/2012 C:\Users\Sam\Dropbox\B12020-RegistryRidge\Drainage\B12020-Runoff.xlsx
Registry Ridge Fifth Filing - Add. #2
Fort Collins, CO Runoff Coefficients and % Impervious
Character of Surface % Impervious
(2)
Streets, Parking Lots, Roofs, Alleys, and Drives:
Asphalt 100%
Concrete driveways and sidewalks 90%
Gravel 40%
Roofs 90%
Lawns and Landscaping
Clayey Soils between 2% and 7% 0%
Total Total
Area of
Asphalt
Streets
Area of
roofs and
concrete
Area of
Gravel
Paths
Area of
Lawns/
Landscaping
acres sf sf sf sf sf C2 C100
C (2007 Study) 4.365 190127 32620 40886 7728 108893 38.14% 0.53 0.66
C1 2.165 94317 0 17561 5170 71586 18.95% 0.39 0.49
C2 2.199 95810 32501 25337 2080 35892 58.59% 0.68 0.85
C = C1+C2 4.365 190127 32501 42898 7250 107478 38.93% 0.54 0.67
Notes:
(1) Recommended Runoff Coefficients for 2-year to 10-year storms from Table 3-3 of City of Fort Collins Design Criteria
(2) Recommended % Imperviousness Values from USDCM Vol 1 - Ch 5 - Table RO-3. Increased Lawns from 0% to 2% Impervious.
(3) C100
= C2
* 1.25
(4) Lot assumptions: 1600 sf roof, 600 sf concrete driveway, 200 sf back patio, 300 sf gravel path
0.95
0.25
Runoff Coefficient
(1)
0.95
0.95
0.5
Composite Runoff
Basin Coefficients (3)
Areas
Composite
Imperviousness
(%I)
Design
Pt.
Calculations by: SME
Date: 5/30/2012 C:\Users\Sam\Dropbox\B12020-RegistryRidge\Drainage\B12020-Runoff.xlsx
Registry Ridge Fifth Filing - Add. #2
Fort Collins, CO Time of Concentration
ti+tt Final
Length Slope ti
(2)
Length Slope Velocity
(3)
tt
(4)
Length Slope Velocity
(3)
tt
(4) Check
tc?
Total
Length
tc
(5)
ft % min ft % fps min ft % fps min min
u =
urban
ft min min
C (2007
Study)
0.25 179 5.2 12.3 110 2.8 3.3 0.5 187 0.8 1.3 2.3 15.2 u 476 12.6 12.6
C1 0.25 75 6 7.6 236 0.9 1.9 2.1 192 3 2.6 1.2 10.9 u 503 12.8 10.9
C2 0.25 30 2 6.9 880 1.5 2.4 6.0 12.9 u 910 15.1 12.9
C = C1+C2
Notes:
(1)
C5
based initial ground type and Table RO-5
(4)
tt
=L/(V*60 sec/min)
(2)
ti
= [1.87(1.1-C5
)L
1/2
]/S
1/3
, S= slope in %, L=length of overland flow (400' max)
(5)
tc
check (for urban or developed areas only) = total length/180 + 10
(3)
V=Cv
S
0.5
, S=watercourse slope in ft/ft, UDFCD Equation RO-4
(6)
min tc
= 5 min
Basin
Overland Flow (ti) Gutter Flow Swale Flow tc Check for Urbanized
C5
(1)
Calculations by: SME
Date: 5/30/2012 C:\Users\Sam\Dropbox\B12020-RegistryRidge\Drainage\B12020-Runoff.xlsx
Registry Ridge Fifth Filing - Add. #2
Fort Collins, CO Rational Method Peak Runoff
Final
tc
(6) I2 I100 Q2 Q100
acres min in/hr in/hr cfs cfs
C (2007 Study) 190,127 12.6 0.53 0.66 2.02 7.04 4.67 20.39
C1 94,317 10.9 0.39 0.49 2.14 7.45 1.82 7.95
C2 95,810 12.9 0.68 0.85 1.99 6.94 2.96 12.94
C = C1+C2 190,127 4.79 20.89
Design
Pt.
Peak Discharge
Area
Basin
Runoff Coefficients Rainfall Intensity
C2 C100
Calculations by: SME
Date: 5/30/2012 C:\Users\Sam\Dropbox\B12020-RegistryRidge\Drainage\B12020-Runoff.xlsx
Channel Report
Hydraflow Express Extension for AutoCAD® Civil 3D® 2012 by Autodesk, Inc. Tuesday, May 29 2012
Swale B at Design Point C1
User-defined
Invert Elev (ft) = 84.75
Slope (%) = 0.50
N-Value = 0.027
Calculations
Compute by: Known Q
Known Q (cfs) = 10.57
(Sta, El, n)-(Sta, El, n)...
( 0.00, 85.63)-(4.00, 84.83, 0.030)-(5.00, 84.75, 0.013)-(6.00, 84.83, 0.013)-(10.00, 85.63, 0.030)
Highlighted
Depth (ft) = 0.85
Q (cfs) = 10.57
Area (sqft) = 4.58
Velocity (ft/s) = 2.31
Wetted Perim (ft) = 9.86
Crit Depth, Yc (ft) = 0.68
Top Width (ft) = 9.70
EGL (ft) = 0.93
-1 0 1 2 3 4 5 6 7 8 9 10 11
Elev (ft) Depth (ft)
Section
84.00 -0.75
84.50 -0.25
85.00 0.25
85.50 0.75
86.00 1.25
Sta (ft)
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
Invert Elev (ft) = 83.16
Slope (%) = 1.60
N-Value = 0.025
Calculations
Compute by: Known Q
Known Q (cfs) = 33.43
(Sta, El, n)-(Sta, El, n)...
( 0.00, 84.06)-(4.00, 83.25, 0.030)-(8.00, 83.16, 0.030)-(14.00, 83.22, 0.013)-(17.00, 83.28, 0.030)-(20.00, 84.04, 0.030)
Highlighted
Depth (ft) = 0.57
Q (cfs) = 33.43
Area (sqft) = 7.75
Velocity (ft/s) = 4.31
Wetted Perim (ft) = 17.25
Crit Depth, Yc (ft) = 0.62
Top Width (ft) = 17.15
EGL (ft) = 0.86
-2 0 2 4 6 8 10 12 14 16 18 20 22
Elev (ft) Depth (ft)
Section
82.50 -0.66
83.00 -0.16
83.50 0.34
84.00 0.84
84.50 1.34
85.00 1.84
Sta (ft)
H2
H1
H4
H3
C1
A
D
B
B
C2
SEE ADDENDUM #1 TO REGISTRY RIDGE
5TH FILING DRAINAGE REPORT DATED
FEBRUARY 17, 2010 FOR ADDITIONAL
DRAINAGE DETAIL IN OS2 (REGISTRY
RIDGE PARK AREA)
NORTH
GRAPHIC SCALE:
OS2
LEGEND:
H2
PREPARED FOR: DATE SUBMITTED:
The engineer preparing these plans will not be responsible for, or
liable for, unauthorized changes to or uses of these plans. All
changes to the plans must be in writing and must be approved by
the preparer of these plans.
CAUTION
REGISTRY RIDGE FILING 5 LLC 5/30/2012
REGISTRY RIDGE FIFTH FILING, FIRST REPLAT
18
B12020
PRELIMINARY
PLANS
NOT FOR CONSTRUCTION
Civil Engineering & Consulting
529 Crestmore Place
(970) 217-7420
Fort Collins, CO 80521
www.bluesky-engineer.com
BLUE SKY
E n g i n e e r i n g
DRAINAGE EXHIBIT
DR1
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