HomeMy WebLinkAboutHILL CREST PUD PRELIMINARY - 6 93A - SUBMITTAL DOCUMENTS - ROUND 1 - DRAINAGE REPORT100
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HILLCREST P.U.D.
THIS IS THE MASS DIAGRAM FOR THE DETENTION BASIN REQUIREMENT
0
1v.v GV.v JV.v W.v Jv.v W.v W.v 1W.v lkv.v liv.. 1.1W
TIME IN MINUTES
Total Runoff Vol. EE Allowable Discharge Vol.
NOTE: Discharge plot does not appear linear since time are not uniformly spaced
THIS MASS DIAGRAM TABLE IS FOR USE IN .ESTABLISHING THE STORAGE VOLUME
REQUIRED FOR THE 100 YR. STORM EVENT
PRELIMINARY HILLCREST DETENTION SIZING
n 4R = Runoff (c) 12.73 = Area (acres) 2.05 = Release Q(2)***
TIME
min
INTENSITY
in/hr
C*Cf*A
s .ft.
RUNOFF
cu-ft
OUTFLOW
cu-ft
STORAGE
cu-ft
5.0
7.00
7.64
16039.8
615.0
15424.8
10.0
7.00
7.64
32079.6
1230.0
30849.6
15.0
6.10
7.64
41932.6
1845.0
40087.6
20.0
5.20
7.64
47661.1
2460.0
45201.1
25.0
4.68
7.64
53618.8
3075.0
50543.8
30.0
4.15
7.64
•57055.9
3690.0
53365.9
35.0
3.83
7.64
61432.4
4305.0
57127.4
40.0
3.50
7.64
64159.2
4920.0
59239.2
45.0
3.25
7.64
67023.5
5535.0
61488.5
50.0
3.00
7.64
68742.0
6150.0
62592.0
55.0
2.80
7.64
70575.1
6765.0
63810.1
60.0
2.60
7.64
71491.7
- 7380.0
64111.7
70.0
2.33
7.64
74745.5
8610.0
66135.5
80.0
2.05
7.64
75157.9
9840.0
65317.9
90.0
1 L88
7.64
77541.0'
1107060.66471.0'
100.0
1.70
7.64
77907.6
12300.0
65607.6
110.0
1.58
7.64
79649.1
13530.0
66119.1
120.0
1.45
7.64
79740.7
14760.0
64980.7
135.0
1.331
7.64
82284.2
16605.0
65679.2
150.0
1.201
7.64
82490.4
18450.0
64040.4
165.0
1.131
7.641
85446.31
20295.0
65151.3
180.00
1.051
7.641
86614.91
22140.0
64474.9
*** NOTE: -if C * Cf > = 1 , then C * Cf = 1 is used
DEVELOPEDiCONTINUED
SUBBASIN TIME OF CONCENTRATION
D. Pnt.
Slope
°/,
C * Cf
verL Lengt
feet
Overt Tc
min.
han enght
f
Tc Chan.
min.
Tc Total
min.
COMMENTS
0-2
2.001
0.601
100.00
7.11
1 OVERLAND TIME ONLY
Tc
1.001
0.601
1 275.00
14.91
22.11
OVERLAND + CHANNEL
0.60 = C (Land) 0.60 = C Chan.
Pnt.
Area
C* Cf
I (2yr.)
1 (10yr.)
1 (100yr.)
Basin Q
Comb. Q
acres) -
(in/hr)
(in/hr
in/hr)
(cfs)
(cfs
—2
2.73
0.25
1.74
1.15
4i2
0.25
3.10
2.05
21'.
0.31
4.93
4.08
Al
0.60 = C . 1.00=Cf(2,10)
1.25=Cf(100)
5.50 = ACRES IN DEVELOPED BASIN, INCLUDING 50' ROW ALONG W. MULBERRY
COMMENTS
2 yr. runoff
10 vr. runoff
RUNOFF
FROM
ONSITE
11.61
2 yr.
historic runoff
20.21 10
yr. historic runoff
39.51 100
yr. historic runoff
7.23 = ACRES IN DEVELOPED BASIN, ADJACENT PROPERTY
OFFSITE
CONTRIBUTING
AREAS
_ 1.8
2 yr. historic runoff
3.2
-10 yr. historic runoff
6.31
100 yr. historic runoff
NOTE: ** These assumnption are for planning purposes only. Details will be added
when final design is under taken.
— Detention will be required in the Southeast and Northeast corner of the site.
— Release will be into the existing S.D. collection system in W. Mulberry St.
DEVELOPED CONTINUED
SUBBASIN TIME OF CONCENTRATION
D. Pnt.
Slope
C * Cf
verL LengthOvert
Tc
ha .Lengh
Tc Chan,
Tc Total
COMMENTS
feet
min.
f
min.
min.
4
2.00
0.60
60.00
5.5
OVERLAND TIME ONLY
Tc
1.00
0.60
185.00
12.2
17.8
OVERLAND + CHANNEL
0.60 = C (Land) 0.60 = C Chan.
D. Pnt.
Area
C * Cf
I,(2yr.)
1 (10yr.)
I (100yr.)
Basin Q
Comb. Q
UUMMLN 15
acres
in/hr
in/hr
in/hr)
(cfs)
(cfs
4
0.64
0.60
1.97
3.13
3`1l
2 yr. runoff
0.60
3.41
5.42
54
10 yr. runoff
0.75
5.48
10.89
109'
100 yr. runoff
0.60 = C 1.00=Cf(2,10)
1.25 =Cf 100
4
SUBBASIN TIME OF CONCENTRATION
D. Pnt.
Slope
%,
C * Cf
verL Length
feet
0-1
2.001
0.25
300.00
Tc
1.001
0.25
0.25 = C Land 0.25 = C Chan.
D. Pnt. Area
acres
0-1 1 4.
:f I (2yr.)
in/hr
0.25 0.93
0.25
0.31
1.00=Cf(2,10)
21.0
590.00 37.
0yr.) I (100yr.) Basin Q
Or in/hr cfs
0.6
1.66 1.1
2.65 2.1
125=Cf(100)'
Tc Total
min.
58.2
TIME ONLY
+ CHANNEL
2 yr. r
10 yr.
100 yr.
3ASIN TIME OF CONCENTRATION
Pnt. Slope C * Cf Ove
% I
1 2.00 0.60
Tc 1.00 0.60
0.60 = C (Land) 0.60 = C
Pnt. Area C * Cf I
acres
1 0.92 0.60
0.60
0.75
0.60=C 1.00=CI
gt OverL Tc han.Lenght
(min.) 0-�
00 6.4
320.00
I (10yr.) I (100yr.)
in/hr in/hr
72
3.00
4.31
1.25=Cf(100)
SUBBASIN TIME OF CONCENTRATION
D. Pnt.
Slope
C * Cf
Overt- Le gt
feet
2
2.00
0.60
130.00
Tc
1.00
0.60
0.60 = C Land 0.60 = C Chan.
D. Pnt.
C1x•'3M
n OverL Tc IChao.Lenghl
C * Cf I (2yr.)
in/hr
0.60 1.74
0.60
0.75
1.00=Cf(2,10)
SUBBASIN TIME OF CONCENTRATION
D. Pnt.
Slope
C * Cf
Overt- Length
feet
3
2.00
0.60
105.00
Tc
1.00
0.60
0.60 = C Land 0.60 = C Chan.
Chan.
nin.
16.1
isin Q
'cfs
2.7
240.001
13.9
)yr.)
'hr
I (100yr.)
in/hr
Basin Q
cfs
2.77
3.10
4.93
4.93
9.80
1.25 =Cf 100
rL Tc
in.
Chan Lenght
fe
Tc Chan.
min.
7.3
200.00
12.7
OVERLAND + CHANNEL
COMMENTS
2 yr. runoff
10 yr. runoff
100 vr. runoff
:al COMMENTS
OVERLAND TIME
22.1 OVERLAND + CHI
10
100
OVERLAND TIME ONLY
OVERLAND + CHANNEL
D. Pnt. Area
acres
C * Cf
I (2yr.)
in/hr
I (10yr.)
in/hr
1 (100yr.)
in/hr
Basin Q
cfs
Comb. Q
cfs
COMMENTS
3 0.94
0.60
1.85
2.94
29
2 r. runoff
0.60
3.22
5.12
51
10 r, runoff
0.75
5.17
10.28
10.311100
r. runoff
0.60 = C 1.00=Cf(2,10) 1.25 =Cf 100
3
HISTORIG:CONTINUED
SUBBASIN TIME OF CONCENTRATION
D. Pnt.
Slope
C * Cf
OverL Length
feet
Overt Tc
min.
h .Lenght
Tc Chan.
min.
Tc Total
min.
COMMENTS
HB-3
1.00
0.20
100.00
16.2
OVERLAND TIME ONLY
Tc
1.00
0.20
790.00
45.5
61.7
OVERLAND + CHANNEL
0.20 = C (Land)
0.20 = C Chan.
D. Pnt.
Area
C * Cf
I (2yr.)
1 (10yr.)
1 (100yr.)
Basin Q
Comb. Q
COMMENTS
acres
in/hr
in/hr
in/hr)
(cfs)
(cfs
HB-3
4.50
0.20
0.90
0.48
.:..::::.:.::::;OrS
2 yr. runoff
0.20
1.58
0.84
08
10 yr. runoff
0.25
2.51
1 66
i.7
100 yr. runoff
0.20 = C 1.00 =Cf 2,10
1.25 =Cf 100
HB _3:::
ACRES OF HISTORIC BASIN UNDER CONSIDERATION
*NOTES: This runoff rate does not include released storm water
from Impale Subdivision only site historic release
1.50
2 yr.
runoff
2.691
10
yr. runoff
5.371
100
yr. runoff
DATE: MARCH 1994
BASIN RUNOFF COMPUTATIONS FOR THE 2/ 10/ 100 YR. STORM EVENT
HILLCREST STORM RUNOFF RATES HISTORIC/DEVELOPED
FOR: FORT COLLINS HOUSING AUTHORITY
BY: Stewart & Associates
GENERAL NOTES:
If C x Cf > = 1 then C x Cf = 1 (constants listed below)
SUBBASIN TIME OF CONCENTRATION
D. Pnt.
Area
(acres)
C * Cf
I (2yr.)
(in/hr)
I (I 0yr.)
(in/hr)
I (100yr.)
(in/hr)
Basin Q
(cfs)
Comb. 0
(cfs) -
COMMENTS
HB-1
2.65
0.20
1.00
0.53
1
2 yr. runoff
0.20
1.80
0.95
10 yr. runoff
0.25
2.90
1.92
�z�:91�-
x-4.
100 yr. runoff
0.20 = C 1.00 =Cf(2,10) 1.25 =Cf(100
HB 1L11
SUBBASIN TIME OF CONCENTRATION
D. Pnt.
Slope
I (%)
C * Cf
Overl- Lengtfi
(feet)
HB-2
1.00
0.20
300.00
Tc
1.00
0.20
0.20 = C (Land) 0.20 = C (Chan.)
Tc �ha Lenght Tc Chan. Tc Total COMMENTS
1) (fee (min (min.)
28.11 OVERLAND TIME ONLY
1 320.00 29.0 57.0 OVERLAND + CHANNEL
D. Pnt.
Area
(acres)
C*Cf
I (2yr.)
(in/hr)
I (10yr.)
(in/hr)
I (1 00yr.)
(in/hr)
Basin Q
cfs;
Comb. Q
cfs
COMMENTS
HB-2
2.651
0.20
0.93
0
1
2 r. runoff
y
0.20
1 0.20
1.69
0.90
7.7770
10 yr. runoff
0.25
2.70
100 yr. runoff
0.20 = C 1.00 =Cf(2,10) 1.25 =Cf(100)
STEWARTRASSOCIATES 10 82 9 3DiRUM,FAX FO 938OLLINS, CO 80521
Consulting Engineers and Surveyors
By: Tl(� Date: -I - Iq Client: C _ U�a�, i Sheet No. 1 of
Project: �\Vtc O?.ac1- t'.r'( ice.
Subject:
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Storm Drainage Report
Hillcrest P.U.D.
Page 5
CONCLUSIONS
No apparent risk to property or human safety would result
from allowing this project to proceed. It does appear as though
the Storm Drainage Design and Construction Criteria Standards can
substantially be complying with at this cursory, preliminary
review.
Should questions regarding this project arise during your
review of this project please feel free too contact Alex Evonitz
or myself at your earliest convenience.
Respectfully,
�.....•, hey:,
Richard A. Rutherford, P.E. & L.S. #5028 z : 5 Q 2 30
• ••
hilcrest.rpt
Storm Drainage Report
Hillcrest P.U.D.
Page 4
DETENTION
Two ponds are indicated on the Preliminary Grading and
Drainage Plans. A detailed review of the contributing basins to
the East and North of the project site will be undertaken at
final design. Based on the aforementioned assumptions a detention
volume of 1.53 ac-ft appears to be adequate at this detail. The
two ponds indicated can provide that volume of detention.
A balance will have to be made between the two ponds and
•the allowable release from the southerly pond will be determined.
As mentioned the release structure from that Southerly pond has
not yet been determined.
Storm Drainage Report
Hillcrest P.U.D.
Page 3
Some general assumption have been included in this analysis
to establish areas of concern for final design. These are that
the developed runoff coefficient by zoning is C = 0.60, for the
project site, the coefficient for Impala Subdivision C = 0.48,
and detention sizing was based a release rate of 2.05 cfs. Slopes
for overland and channelized flows were assigned 2% and 1%
respectfully. Details of this preliminary review are attached in
the appendix of this report.
HYDRAULICS
There is an existing irrigation lateral crossing the project
from West to East. This feature has been the driving issue in
much of the horizontal design. Overland channelized flows will be
the primary method of direct runoff control and, it is not
anticipated that piped conveyance will be necessary. Connection
of the pan from the Impala Subdivision to the northerly detention
pond will be accomplished with a swale and concrete pan. The two
detention ponds, North and South will be connected by an earthen
swale and concrete pan. Release rates will be imposed at the
Southerly pond where either a swale would discharge into the curb
line of Mulberry or a pipe section will junction with the
existing piped collection system in Mulberry. Field data will
establish what option will be available for this detail.
S
Storm Drainage Report
Hillcrest P.U.D.
Page 2
HYDROLOGY
The site is currently covered in a heavy growth of rangeland
grasses and weeds. The topography is gently sloping to the East
with two distinct natural occurring swales on the North end and
the South ends of the project site. The direct runoff from this
site is toward the Tenth Green Subdivision on the East boundary.
This has not presented itself as a problematic circumstance,
though reduction of this undetained and undirected storm runoff
will be an objective of this project design.
This will be accomplished by undertaking a grading plan that
will serve to generally level the site. Also, two detention ponds
are proposed as part of the design proposal. This combination of
elements will accomplish the goal of correcting an undesirable
condition as it exists currently, while addressing the needs of
the proposed intensified usage.
The historic conditions on the site leads to a runoff
coefficient of C = 0.20 for use in the Rational Method. This in
accordance with the City of Fort Collins Storm Drainage Design
Criteria and Standards (SDDCCS). This assumption has led to a 2
year allowable release rate of 1.5 cfs, and does not consider the
flows directed toward this project from Impala Subdivision.
I
PRELIMINARY STORM DRAINAGE REPORT
FOR
HILLCREST P.U.D.
GENERAL SITE
The proposed multi -family development is located in the City
of Fort Collins in the Southeast 1/4 of Section 9, Township 7
North, Range 69 West of the 6th P.M. The site is approximately
500 feet west, of the intersection of West Mulberry Street
(Mulberry) and South Taft Hill Road (Taft). The P.U.D. is
proposing 14.duplex.buildings for a total of 28 dwelling units on
the approximately 5.5 acres. The tract lying North of the site
(± 4.5 acres) is under consideration for sale to the Poudre R-1
School District (District). For this report, the entire 10.02
acres will be included in the storm water management design with
the aforementioned 4.5 acres included as park & recreational use.
This is the use being contemplated by the District.
A second site specific detail will not be specifically
detailed for the preliminary analysis, the release from the
existing Impala Subdivision will require greater attention than
that put forth in a preliminary report. An existing concrete pan
directing storm flows from Impala Circle to the project site have
not been completely assessed at this stage of design. It is not
seen as a driving force for the overall project design however.
Preliminary Storm Drainage Report
for
Hillcrest P.U.D.
March 1994
STEWART&ksso ATES
Consulting En3ineers arx1 Surveyors
103 South l'le&lu m Si eet
To/it CoLti S, Co eolado 80521
3031482-9331