HomeMy WebLinkAboutWEBERG PUD - PRELIMINARY - 76-88F - SUBMITTAL DOCUMENTS - ROUND 1 - DRAINAGE REPORTPreliminary Drainage Report
for
Weberg Furniture
March 6, 1989
PRELIMINARY DRAINAGE REPORT
FOR
WEBERG FURNITURE
PREPARED FOR:
WEBERG FURNITURE
442 WEMBLEY COURT
COLORADO SPRINGS, COLORADO 80906
PREPARED BY:
RBD, INC. ENGINEERING CONSULTANTS
2900 SOUTH COLLEGE AVENUE
FORT COLLINS, CO 80525
T:IINC
Engineering Consultants
2900 South College Avenue
Fort Collins, Colorado 80525
303/226-4955
March 6, 1989
Ms. Susan Hayes
Storm Drainage Department
City of Fort Collins
P.O. Box 580
Fort Collins, Colorado 80522
RE: PRELIMINARY DRAINAGE REPORT FOR
WEBERG FURNITURE
Dear Susan:
We are pleased to submit to you this
preliminary drainage report
for Weberg Furniture.
Should you have any questions, please
feel free to contact us.
Sincerely,
RBD, Inc.
\`�»�e�uut�lrpu�r��
\,\6�4 GLq
r('�
Brian Cole, P.E.
Project Engineer
_ 24993 a —
_°
e
:'i. �'r
nn �
Stan A. Myers, P.E.
Project Manager
cc: John Weberg
Murray and Stafford Inc.
Other Offices: Vail, Colorado 303/476-6340 e Colorado Springs, Colorado (719) 598-4107
INTRODUCTION
LOCATION a
DESCRIPTION i
DESIGN REQUIREMENTS 1
DESIGN PROCEDURE
CONCLUSIONS AND RECOMMENDATION 3
REFERENCES 4
APPENDIX
VICINITY MAP Al
100 YEAR HISTORY A2
HISTORIC FLOWS TO HIGHWAY 287 (BASIN "H") A3
FLOWS IN A MAJOR ARTERIAL STREET A4-A5
BASIN "A" A6
BASIN "B" A7
BASIN "C" A8
BASIN "D" A9
INTR011UCTION
LOCATION
The Weberg Furniture site is located about 1/2 mile south of Har-
mony Road on the west side of Highway 287 (College Avenue in Fort
Collins) in Larimer County Colorado. Annexation is currently un-
derway to bring this site within City limits. More specifically
this location is in the east hai.f of Section 2, Township 6 North,
Range 69 West of the 6th Principal Meridian.
nF.GC PTPTTnN
This site currently is occupied by a residence with a large open
grass field between it and College Avenue. The general slope of
the property is at about 1% to 3% in a southeasterly direction.
Existing drainage from this site flows in two directions. Basin
H1 (on plan in pocket) drains to a drainageway that exists just
south of this basin. Drainage from Basin H2 drains directly into
Highway 287. Calculations for the existing flows from Basins H1
and H2 are shown in the Appendix.
Offsite flows from a portion of the Burlington Northern Railroad
right of way currently drain into proposed Basin A. The path
that the flows will take and the drainage facilities necessary to
safely pass them through the site will need to be considered
during final design.
Offsite flows from the north currently are captured into a
drainage swale near the north property line. This drainage swale
meanders on and off this property but exists primarily north of
property line. The development of this area will require re-
defining this swale north of this site or make provisions for the
offsite flows to safely pass through this site.
DESIGN REQUIREMENTS
This property is a part of the Fossil Creek Major Drainage Basin
which is explained in the Fossil Creek Drainage Basin Master
Drainageway Planning Study, by Simons, Li and Associates, Inc.
August, 1982. Based on the above report, The City of Fort Col-
lins does not require any storm water detention from this site in
a totally developed condition. Under this condition, however,
the City Stormwater Utility Department requires as agreement with
the downstream property owners to accept the additional runoff
generated without detention. Such an agreement would involve all
property owners between this site and Fossil Creek. It should
also be pointed out that the Colorado State Highway Department,
in a letter to the City of Fort Collins, dated October 7, 1988,
stated that on -site detention is to be required to limit flows
onto Highway 287 to the historic runoff rate.
The City Stormwater Utility Department's alternative to the above
approach and the alternative that this report pursues is to
release flows from this site at existing rates. This would
require some storm water detention to keep the developed flows
from exceeding existing flow rates. The preliminary design
1
� I
proceeded based on this design requirement.
' Design Approach
The first design step is to calculate existing flows in Highway
287 to ensure that these existing flows do not already exceed the
' City of Fort Collins criteria during a 10 year and 100 year
design storm. The existing flows in Highway 287 are calculated
to be acceptable to city criteria. The slope of Highway 287 is
' steeper south of this site, thus the flow capacity of the street
increases south of this site.
The next design step is to develop detention ponds for the
developed basins in order to reduce developed flows to historic
rates. This is shown for the 100 year storm only because it is
considered to be the major storm event.
The calculations for Basins A and B, show that two ponds will be
necessary to reduce flows to the historic rates of Basin H1. The
calculations for Basins C and D also show that two additional
ponds will be necessary to reduce flows to historic rates of
Basin H2. The results of the calculations are shown in the table
below:
(cfs)
100 Year Design
Storm Maximum
Release Rate
Basin "A" 3.64
Basin "B" 1.06
Basin H1 --
Basin "C" 4.42
Basin "D" 3.06
Basin H2 --
(cfs) (Ac.-Ft.)
100 Year Historic Proposed
Storm Maximum Detention Pond
Flow Rate Volume
-- 0.35
-- 0.10
4.7 --
-- 0.38
-- 0.27
7.5
All of the basins have surface detention ponds, however, Basin C
lacks the area for the required detention storage to be on the
surface. This is due to the grading and site layout. For this
reason, building roof top storage and underground storage may be
necessary. The preliminary calculations show that 0.16 acre feet
of volume can be achieved on the ground surface. This leaves
0.22 acre feet of the required total detention volume (0.38 acre
feet) to be detained by other means. If underground storage is
used, about 340 lineal feet of 6 ft. diameter pipe is required.
If roof top storage is used, and the roof drains towards the
south at a typical slope of one percent a maximum depth of 0.82
ft. is needed to attain the required 0.22 acre feet of storage
(Note: A depth of 0.47 ft. of water is approximately equal to a
snow load of 30 lb/ft2). This, of course, would require struc-
tural upgrading of the building as well as additional sealing of
the roof from leakage. A third alternative would be to allow the
Weberg facility to be stepped downward to the east. This would
allow the possibility of attaining the required detention on the
surface of the east parking lot. These alternatives will be
2
evaluated during the final design. In any case the required
detention for Basin C will be achieved.
The pond grading, sizing of inlets pipe sizes, storage
facilities, orifice openings and emergency overflow structures
will be accomplished during final design.
CONCLUSIONS AND RECOMMENDATIONS
1) This preliminary drainage report identifies the proposed
design approach as detaining drainage flows to release into
Highway 287 and the adjacent properties at the 100 year ex-
isting rates.
2) Sizing and grading of drainage facilities will be covered in
final design.
.i
REFERENCES
1) Fossil Creek Drainage Basin Master Drainageway Planning
Study, by Simons, Li and Associates, Inc. August, 1982.
2) Storm Drainage Design Criteria and Construction Standards,
by the City of Fort Collins, May, 1984.
3) Letter to Ms. Linda Ripley of the City of Fort Collins Plan-
ning Department from the State of Colorado Division of High-
way (DOH File 45100), Octcber 7, 1988.
4
1
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APPENDIX
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FORM 5
CLIENT
INC PROJECT
Engineering Consultants MADEBY
- ___ JOB NO.
CALCULATIONS FOR
DATE CHECKEDBY _ DATE _____-_. __SHEET
HISTORIC FLOWS TO HIGHWAY 287
BASIN "H"
P �- v v o & k r- c c.->
- a R C)
I
T,co-
A
OF
FLOWS IN A MAJOR ARTERIAL STREET
T:IINC
Engineering Consultants
CLIENT _
PROJECT
MADEBY
CALCULATIONS FOR
DATE CHECKED BY DATE
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���&��N�� w�&m
��mq��"mm`� m�u
MASS DIAGRAM
METHOD
for
N�
DETENTION VOLUMES
PROJECT:
WEBERG
~~
COMMENTS:
100 YEAR STORM
MAXIMUM ALLOWABLE RELEASE (CF8)
=
3.64
RATIONAL
EQUATION: Q =
CIA
N�
C =
1
A(area)
2.84
TIME OF CONCENTRATION
=
m�
TIME
CA
I
INFLOW
OUTFLOW
STORAGE
(min)
(in/hr>
(cu ft)
(cu ft)
(cu ft)
(ac ft)
N�
______________________________________
5
2. 84
9
7668
10��2
6576
O. 150964
10
2.84
7.3
12439.2
2184
10255.2
0.235426
U�
15
20
2.84
2.84
6
5.2
15336
17721.6
3276
4368
12060
13353.6
0.276859
0.306556
25
2.84
4.6
19596
5460
14136
0.324517
30
2.84
4.15
21214.8
6552
14662.8
0.336611
N�
35
2.84
3.8
22663.2
7644
15019.2
0. 344793
m�
4O
2.84
3.5
23856
8736
15120
0. 347107
45
2.84
3.25
24921
9828
15093
0.346487
50
2.84
3
25560
10920
14640
0.336088
N�
~�
55
2.84
2.8
26241.6
12012
14229.6
0.326666
60
2.84
2.6
26582.4
13104
13478.4
0.309421
N�
70
80
2.84
2.84
2.3
2.05
27434.4
27945.6
15288
17472
12146.4
10473.6
0.278842
0.240440
90
2.84
1.85
28371.6
19656
8715.6
0.200082
100
2.84
1.7
28968
21840
7128
0.163636
110
2.84
1.55
29053.2
24024
5029.2
0.115454
N�
120
2.84
1.45
29649.6
26208
3441.6
0,079008
� I
����N�N�� =��"
��m=um�mm� ��
MASS .0IAGRAM METHOD
for
DETENTION VOLUMES
COMMENTS: 100 YEAR STORM
MAXIMUM PA t OWAUL.E1.06
RATIONAL EQUATION: Q = CIA
C " = 1 A(area> = 0.83
TIME OF CONCENTRATION
=
n�
TIME
CO,
I
INFLOW
OUTFLOW
STORAGE
(min>
(in/hr}
(cu ft)
(cu ft>
(cu ft)
(ac ft)
�N-------------------------------------------------------------------
N�
5
0.83
9
2241
318
1923
0.044146
10
0.83
7.3
3635.4
636
2999.4
0.068856
U�
15
20
0.83
0.83
6
5.2
4482
5179.2
954
1272
3528
3907.2
0.080991
0.089696
25
0.83
4.6
5727
1590
4137
0.094972
30
0.83
4.15
6200.1
1908
4292.1
0.098533
U�
35
0.83
3.8
6623. 4
2226
4397.4
0. 10O950
40
0.83
3.5
6972
2544
. 4428
0' 101652
45
0.83
3.25
7283.25
2862
4421.25
0.101497
50
0.83
3
7470
3180
4290
0.098484
N�
55
0.83
2.8
7669.2
3498
4171.2
0.095757
60
0.83
2.6
7768.8
3816
3952.8
0.O90743
U�
70
80
0.83
0.83
2.3
2.05
8017.8
8167.2
4452
5088
3565.8
3079.2
0.081859
0.070688
90
0.83
1.85
8291.7
5724
2567.7
0.058946
100
0.83
1.7
8466
6360
2106
0.048347
110
0.83
1.55
8490.9
6996
1494.9
0.03431G
U U�
120
0.83
1.45
8665.2
7632
1033.2
0.0231 79
'
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���&N�N�� w��=
��m=���mm`� ��
11ASS DIA6RAM METHOD
for
DETENTION VOLUMES
PROJECT: WEBERG
COMMENTS: 100 YEAR STORM
4.42
RATIONAL EQUATION: Q = CIA
C = 1 A(area} = 3.25
TIME OF CONCENTRATION =
TIME
CA
I
INFLOW
OUTFLOW
STORAGE
(min)
(in/hr)
(cu ft)
<cu ft)
(cu ft>
(ac ft>
U�
5
3.25
9
8775
1326
7449
0.171005
10
3.25
7.3
14235
2652
11583
0.265909
15
3.25
6
17550
3978
13572
0.311570
U�
20
3.25
5.2
20280
5304
14976
0.343801
25
3.25
4.6
22425
6630
15795
0.362603
30
3.25
4.15
24277.5
7956
16321.5
0.374690
35
3.25
3.8
25935
9282
16653
0.382300
U�
40
3.25
3.5
27300
10608
16692
0.383195
45
3.25
3.25
28518.75
11934
16584.75
0.380733 '
50
3.25
3
29250
1326O
15990
0.367079
U�
55
3.25
2.8
30030
14586
15444
0.354545
60
3.25
2.6
30420
15912
14508
0.333057
70
3.25
2.3
31395
18564
12831
0.294559
N�
80
3.25
2.05
31980
21216
10764
0.247107
~~
90
3.25
1.85
32467.5
23868
8599.5
0. 197417
100
3.25
1.7
33150
26520
663O
0.152203
110
3.25
1.55
33247.5
29172
4075.5
0.093560
U U�
120
3.25
1 .45
33930
31824
2106
0.048347
11
AS
11
�
�
���&W�N�� ���'
����°�mm`� ��
MASS DIAGRAM METHOD
for
DETENTION VOLUMES
~~
PROJECT:
COMMENTS:
WEBERG
100 YEAR
STORM
MAXIMUM ALLOWABLE
RELEASE (CFS)
=
3.06
RATIONAL
EQUATION:
Q = CIA
N�
C =
1
A(area) =
2.25
m�
TIME OF CONCENTRATION
TIME
CA
=
I
INFLOW
OUTFLOW
STORAGE
(min>
(in/hr)
(cu ft)
(cu ft)
(cu ft}
(ac ft)
N�
5
2'25
9
6075
918
5157
0.118388
10
2.25
7.3
9855
1836
8019
0.184090
15
2.25
6
12150
2754
9396
0.215702
��
20
2.25
5.2
14040
3672
10368
0.238016
25
2.25
4.6
15525
4590
10935
0.251033
�
30
35
2.25
2.25
4.15
3.8
16807.5
17955
5508
6426
11299.5
11529
0.259400
0.264669
40
2.25
3'5
18900
7344
1 1556
0.265289
45
2.25
3.25
19743.75
8262
11481.75
0.263` 84
50
2.25
3
20250
9180
11070
0.254132
N�
55
2.25
2.8
20790
10098
10692
0.245454
�
60
2.25
2.6
21060
11016
10044
0.230578
U�
70
80
2.25
2.25
2.3
2.O5
21735
2240
1
12852
14688
8883
7452
0.203925
0. 171074
N�
90
2.25
1.85
22477.5
16524
5953.5
0.136673
100
2.25
1.7
22950
18360
4590
0.105371
110
2.25
1.55
23017.5
'20196
2821.5
0.064772
2.25
1.45
23490
22032
1458
0.033471
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