HomeMy WebLinkAboutHARMONY SAFEWAY MARKETPLACE, LOT 8 - PDP - 33-94G - SUBMITTAL DOCUMENTS - ROUND 1 - DRAINAGE RELATED DOCUMENTCif)of Ft. Collins. Colorado
MAJOR STORM
(I 00-YR) RUNOFF COMPUTATIONS
Overland Flow Time of Concentration:
T, = 1.870. I-05)L112 / 51/3
Flow, Time Concentration:
_Gutter/5wale of
Tt = L / GOV
T�=T.+Tt
Intensity (i), taken from Figure 3-1
Velocity (Gutter Flow), V = 20.3282'S'12
Calculate Tons Bv: f
WJC
Velocity (5wale Flow), V = 16. 1 345'5'12
PrQject:
LOT 8 - 5AFEWAY
Rational Equation: Q = GA
Date:
October 22, 2002
Overland Now
'60u-
:_.. .y,
I nten5ity,
Design
Area, A
Length, L
51ope, 5
T,
Length, L
51ope.,
I
V
it
Length, L
Slope, 5
v
It
T�
flow,
Point
625m5
(acre,)
C,00
C I0
(ft)
(%)
(min)
(ft)
(%)
(ft/5)
(min)
(ft)
(%)
(ft/5)
(min)
(min)
(in/hr)
(cft,;
I
N-1
0.54
0.97
0.78
105.0
2.00
4.9
180.0
I .65
2.61
1.1
0.0
0.00
0.00
WA
6.0
8.65
4.5
2
N-2
0.33
0.76
0.61
90.0
2.00
6.9
100.0
1.00
2.03
0.8
0.0
0.00
0.00
WA
7.7
8.10
2.0
3
N-18
2.16
0.58
0.46
140.0
2.00
11.2
1000.0
0.60
1.57
10.6
0.0
0.00
0.00
WA
21.8
4.90
6.1
4
5-1
0.91
1 0.80
0.64
60.0
2.00
5.3
250.0
1.50
2.49
1.7
0.0
0.00
0.00
WA
7.0
8.25
6.0
O
0
0.00
0.00
0.00
0.0
2.00
0.0
0.0
0.00
0.00
WA
0.0
0.00
0.00
WA
0.0
0.00
0.0
O
0
0.00
0.00
0.00
0.0
2.00
0.0
0.0
0.00
0.00
WA
0.0
0.00
0.00
WA
0.0
0.00
0.0
O
0
0.00
C.00
0.00
0.0
2.00
0.0
0.0
0.00
0.00
WA
0.0
0.00
0.00
WA
0.0
0.00
0.a
Runoff
Coefficient
Project: LOT 5 - HARMONY 5AFtWAY MAMF,:TLACE
Character of 5urface
Employee: W.J.0
.5treet5, Parking Lots, Roof5, Alleys, and Drives:
Ku ri t.5. ... a.r. c.. n-. -from the City of Fort Collins 5torm Drain
6je Dc5icln Criteriii
and Con5t
Area of Asphalt
Area of Concrete
Area of Gravel
I 0-year
I 00-year
5treet5, Parkinq
Walks,
Parkuuj
Area of
Area of Lawn
Composite
Composite
l3a5in Area
Lots, and Alleys
and Driveways
and Drives
Rooftops
and Landscape
Ru n off
Runoff
[5a5in ID
(acres)
(acres)
(acrc5)
(acres)
(acres)
(acres)
Coefficient
Coefficient
I
I 's� -tf- R�-\."� OrS
. • 1
I
M
. • 1
0
i
1 �
N-98
2.17 AC
(N- 1 s0
t
4 AC r
N-8
`%off .56 AC
79
•� YY rr V
.�
AP
_ N- 2 AP �
_ 0.39 AC '%% `
rN- 4
C
Those portions of this project located within basins N-1, N-2, N-18, and S-1 are small,
and the developed runoff coefficients are essentially identical to the ones assumed before.
Because of this they will not have any impact on the existing drainage conveyance
system or the existing detention pond located at the northwest corner of the site.
I have included a copy of the revised calculations for the composite runoff coefficient for
basins N-1, N-2, N-18, and S-1.
Please call us at 221-4158 if you have any questions regarding this project or require
additional information.
Sinncerely, �
William Chmelir, EIT
viewed by:
Aaron Cvar, PE
NORTHERN
ENGINEERING
NESERVICES, INC.
October 22, 2002
Mr. Basil Hamdan
City of Ft. Collins Stormwater Utility
Development Review Division
235 Matthews
Fort Collins, Colorado 80522-0580
RE: Lot 8 at Harmony Safeway Marketplace
Dear Basil,
As a part of the approved plan set for the Harmony Safeway Marketplace, there is one lot
located in the northwest comer of the property, designated as Lot 8. This letter is
intended to provide you with an overview of what the impacts development of this lot
will have on the existing drainage design, approved for the site.
As is typically the case with pad sites designed with this project, the ultimate user
generally likes to make minor changes to the approved plan. I have attached copies of
the plan that was the basis of our original runoff calculations, and what the proposed site
modifications include. As you can see, the changes they are requesting are minor in
nature, and the original intent of our engineering and drainage design has remained intact.
Our original runoff design calculations did account for areas if imperviousness at this
location. The differences are listed below.
Attached is a copy of a portion of the drainage basins that were associated with the
Harmony Safeway Marketplace site. As you can see lot 8 is located in sub -basins N-1,
N-2, N-18, and S-1. I have also attached the proposed improvements to lot 8, which
served as the basis for our original calculations. Also attached is a copy of the current
proposed improvements for Lot 8.
To recap, the sub -basins designated with an N prefix were designed such that developed
runoff would be directed towards the northeast corner of the site to a proposed detention
pond, and then ultimately to the Golden Meadows Regional detention pond. Basins
designated with an S prefix were designed to release into an open channel, through
proposed culverts under McMurray and Innovation Drive, and also ultimately to the
Golden Meadows regional detention facility. Sub -basins with an S prefix were not
designed to be detained on -site, should sufficient capacity exist in the downstream
conveyance system.
420 SOUTH HOWES, SUITE 202 / FORT COLLINS, COLORADO 80521 / 970.221.4158 / FAX 970.221.4159