HomeMy WebLinkAboutSOUTHGLEN PUD, 2ND FILING REPLAT - MAJOR AMENDMENT - 31-99A - SUBMITTAL DOCUMENTS - ROUND 1 - DRAINAGE REPORTm
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South Glen P.U.D. 2nd Filing Replat
Jim Sell Design, Inc.
22237/11/02 EMS
Table DA: Street capacity: Minor Event
Theoretical capacity: Revised Mannings equation
Q = 0.56'Z/n,S'*YW
where: Q = theoretical gutter capacity
Z = reciprocal of cross slope (ft/ft)
n = roughness coeff.
S = channel slope
y = depth of flow at face of gutter )ft)
Section
z
fVft
n
s
ft/ft
y
ft
Q
cfs
3.58
0.013
0.00526
0.396
0.945815
B
10.2
0.013
0.00526
0.396
2.694781
C
10.2
0.013
0.00526
0.281
1.079492
D
50
0.013
0.00526
0.281
5.291627
Total theoretical Q = Qe + QA - Qr,+ Qn — 7.85 cfs
Qa=al = Qtheoretical ; F
where F = Reduction Factor
from Fig 4-2 of the City of Fort Collins Drainage Criteria Manual, for S=0.00526ft/ft, F = 0.69
Total actual Q = 5.42 cfs
-7 6, -,;, (',o e
Oft 4 06 - 6(.
a
e-,ro
— A
3 sq 444
? C4
South Glen P.U.D. 2nd Filing Replat
Jim Sell Design, Inc.
2223 7/11 /02 EMS
Table CA: Summary of discharge calculations
Basin
ID
Description
Stewart I in/hr
Fort Collins I in/hr
Stewart I in/hr
Fort
Collins I in/hr
Q2
(existing)
cfs
Q2
(revised)
cis
,Percent.,:,
j'.t,Change,z
:>. 'VT(cfs)
Q2
(existing)
Q2
(revised)
cfs
Percent
.,.Change
:'" .=, ..
(e
+2.002.00
Percent
'Change
QIOO
(existing)
cfs
Q1oo
(revised)
(cis)
Percent
Change
A
0.64
0.64
,,, rt30.00.:..:
0.56
0.56
0.00
0.00
2.58
2.58
0.00
B
3.70
3.70
;u•-,0:00: , .:
3.28
3.28
...0.00.
13.87
13.87
0.00
15.47
15.47
0.00
C
3.06
3.14
,2.62.-,,:-
3.67
3.77
,.2;62 •
11.65
11.95
2.62
16.94
17.39
2.62
D
0.90
0.90
.::0.00e.;I ;
0.80
0.80
.,-,-,,0.00
2.69
2.69
0.00
3.72
3.72
0.00
E
0.38
0.38
< 0.00 ~ : ,
0.33
0.33
3, - 0.00'.
1.37
1.37
.0.00
1.47
1.47
0.00
F
0.68
0.86
;-,,26.40 ., ,
0.60
0.75
26.40 .. ,.
2.71
3.42
26.40
2.79
3.53
26.40
SUM OF
total going
9.35
9.61
, 2.77;.,=,
9.23
9.49
2.75 +1.
34.29
35.31
2.98
42.99
44.17
2.75
A -F
topond)
Difference
0.26
0.25
1.02
1.18
btwn existing
and revised
South Glen P.U.D. 2nd Filing Replat
Jim Sell Design, Inc.
2223 7/11/02 EMS
Table B.1: Runoff Coefficient Summary for existing condition (as referenced from 1996 JR report)
Sub -Basin
ID
Description
Area
(ac)
C2
C,M
(=Ci 1.25)
T2
min
12
(from Stewart)
(inlhr
12
(Ft. Collins
99)
Tim
min
I1W
(from Stewart)
IrN1r
l,m
(Ft. Collins
99)
02
(Stewart 1)
cfs
02
(Ft. Collins 1)
aim
(Stewart 1)
cfs
aim
(Ft. Collins I)
A
art
0.74
0.30
0.38
7.00
2.90
2.52
6.00
7.2
9.31
0.64
0.56
2.00
2.58
B
art
1.88
0.82
1.03
11
2.4
2.13
9
7.2
8.03
3.70
3.28
13.87
15.47
Brevisedfrom
C
rom
2.6
0.56
0.70
7
2.1
2.52
6
6.4
9.31
3.06
3.67
11.65
16.94
6D
rom
0.41
0.73
0.91
6
3
2.67
5
7.2
9.95
0.90
0.80
2.69
3.72
6E
art
0.7
0.3
0.38
21
1.8
1.56
20
5.2
5.6
0.38
0.33
1.37
1.47
994
F
from Stewartl
0.86
0.35
0.44
13
2.25
1.98
11
7.2
7.42
0.68
0.60
2.71
2.79
1994
Table B.2: Revised Runoff Coefficient Summary for Proposed Conditions, South Glen P.U.D. 2nd Filing Rapist
Sub -Basin
ID
Description
Area
(ac
C2
C1W
(=Cz 1.25)
T2
min
12
(from Stewart)
in/hr
12
(Ft. Collins
99)
Tim
min
11W
(from Stewart)
INhr
lim
(Ft. Collins
99)
O2
(Stewart 1)
cts
02
(Ft. Collins 1)
aim
(Ft. Collins 1)
kea
A
from Stewart
0.74
0.30
0.38
7.00
2.90
2.52
6.00
7.2
9.31
0.64
0.56
2.58
1994
B
from Stewart
1.88
0.82
1.03
11
2.4
2.13
9
7.2
8.03
3.70
3.28
15.47
1994
C
revised JSD
2.6
0.57
0.72
7
2.1
2.52
6
6.4
9.31
3.14
3.77
11.95
17.39
2002
D
revised from
0.41
0.73
0.91
6
3
2.67
5
7.2
9.95
0.90
0.80
2.69
3.72
JR 1996
E
from Stewart
0.7
0.3
0.38
21
1.8
1.56
20
5.2
5.6
0.38
0.33
1.37
1.47
1994
F
revised JSD
0.86
0.44
0.55
13
2.25
1.98
11
7.2
7.42
0.86
0.75
3.42
3.53
2002
South Glen P.U.D. 2nd Filing Replat
Jim Sell Design, Inc.
2223 7/11/02 EMS
Table A.1: Runoff Coefficient Summary
Sub -Basin
ID
Surface
Description
Area
(sq ft)
Area
(ac)
Total
Area
(ac)
Area
N
Runoff
Coefficienl
Cf
Weighted
Runoff
Coefficien
Cf
C
(revised by
Street
22906
0.53
20.22
0.90
0.18
R in 1996)
Parking
18305
0.42
16.16
0.90
0.15
Buildings
17480
0.40
15.43
0.90
0.14
Grass/Open Space
54583
1.25
48.19
0.20
0.10
2.60
100.00
0.56
F
(Stewart,'94)
Impervious Area
0.11
12.79
1.00
0.13
Pervious Area
0.75
87.21
0.25
0.22
0.86
100.00
0.35
Table A.2: Revised Runoff Coefficient Summary for South Glen P.U.D. 2nd Filing Replat
Sub -Basin
ID
Surface
Description
Area
(sq ft)
Area
(ac)
Total
Area
(ac)
Area
N
Runoff
Coefficient
Ct
Weighted
Runoff
Coefficien
C,
C
(revised by
Street
22906
0.53
20.22
0.90
0.18
SD in 2002)
Parking
18305
0.42
16.16
0.90
0.15
Buildings
17480
0.40
15.43
0.90
0.14
Grass/Open Space
52643
1.21
46.47
0.20
0.09
House
1200
0.03
1.06
0.90
0.01
Parking
740
0.02
0.65
0.90
0.01
2.60
100.00
0.57
F
(revised by
Impervious Area
0.11
12.79
1.00
0.13
SD in 2002)
Pervious Area
0.62
72.37
0.25
0.18
House
5240
0.12
13.99
0.90
0.13
Parking
320
0.01
0.85
0.90
0.01
0.86 1
100.00
0.44
E
Glen Schlueter
July 22, 2002
Page 3 of 3
G
Minimizing the overlot grading will be a primary source of erosion control; however, erosion
control, practices and devices will also be integrated with this plan so that the opportunities for'
further erosion will _be reduced. A vehicle tracking control pad (20-feet by 20-feet) will be
implemented at the access point to each lot. Silt fencing will be placed on the frontage of the
three lots between the vehicle tracking control pads. 'Inlet protection will be placed at the 8-foot.
Type R inlet north of the site on Albion Way south of the flowline. All erosion control measures
are presented on the Drainage and Erosion Control Plan in the plan set.
I hereby certify that this report (plan) for the drainage design of South Glen PUD 2nd Filing
Replat was prepared by me (or under my direct supervision) in accordance with the provisions of
City of Fort Collins Stormwater Utility Storm Drainage Design Criteria for the owners thereof.
Thank you for your time in reviewing this letter report. If you have any questions, or require
additional information, please do not hesitate,to call me.
9
Sincerely,
Jim Sell Design, Inc.
Kent Bruxvoort, P.E.
Senior Engineer
cc: Ed Stoner
r
E
0
F_VIROMCP MESV NM'223DOCADRAINAGE REPORTJ02.DOC
v
Glen Schlueter
July 22, 2002.
Page 2 of 3
year event (16.94 cfs to 17.39 cfs). Because the Rational Method cannot approximate runoff to
this degree of accuracy,- we consider this increase in runoff to be negligible. Basin F, however,
generates an additional 26 percent of runoff between the existing and proposed condition for
both the 2-year event.(0.68 cfs to 0.86 cfs) and the 100-year event (2.79 cfs to 3.53 cfs). The
increase in runoff for both Basins C and F are less than 1 cfs for the 2-year and 100-year events.
A summary table presenting these discharges is included in°the appendix.
A detention pond, as described in the 1994 Stewart report, collects runoff from the South Glen
and the Park South neighborhoods, and releases into the New Mercer Canal. The JR report
indicated that the contributing 2-year and 100-year discharge for the South Glen neighborhood is
reduced by 0.67 cfs and 2.54 cfs, respectively, as a result of the South Glen PUD:5 h. Filing. The
total increase in storm runoff from the South Glen neighborhood (Basins A, B; .C, D, E, and F)
for the 2-year and 100-year*discharges with the 'intgnsities used in the Stewart (1994) report are
0.26 cfs and 1.02 cfs, respectively. Therefore, the total contributing runoff to the pond from the
revised South Glen neighborhood (including the South Glen PUD 2°d Filing Replat) is less than
the anticipated 2-year and 100-year runoff from the South Glen neighborhood when the pond
was designed.
Even though we feel that an increase in runoff of less than 1 cfs is negligible for this site, we
analyzed Albion Way for -adequate street capacity for the minor and major events. The street has
a capacity of 5.42 cfs and 16.22 cfs for the 2-year and 100-year events, respectively. The 2-year
discharge for Basin C (3.77 cfs with 1999 Fort Collins intensity) is significantly less than the
minor event street capacity.. Basin C has a 100-year discharge of 17.39 cfs; however, a storm
inlet is placed roughly midway along Albion Way, so that significantly less than one-half of
Basin C contributes to the inlet from the south. As a result, significantly less than half of Basin
C 100-year runoff is expected to travel northward from the South Glen PUD 2°d Filing Replat
project in Albion Way. Thus, street capacity on the west side of Albion Way in front of the
replatted lots is acceptable.
An existing 15-inch storm sewer collecting'runoff from an apartment parking lot west of the site
will 'be relocated into a 10-foot drainage tract between Lots 1 and 2. The relocation of this line
will require a 10-foot by 5-foot concrete box to intercept a 15-inch storm line -from the cul-de-sac
at the end of Albion Way. The existing manhole located in the right-of-way in front of Lot 1 will
be removed. The 18-inch RCP pipe draining the manhole will be extended southward to drain
the 10-foot by 5-foot concrete box. The plan and profile drawings for the storm sewer
realignment are presented on sheet 6 of the adjoining plan set.
9
°• @NROR:cr ELM ANWUMD0(STRAINAGF. RFPORT] 02DOC
Ul
VJ
July 22, 2002
Glen Schlueter
-City of City of Fort Collins
Stormwater Utility
P.O. Box 580.
700 Wood Street
Fort Collins, CO 80522
4.
ImndrcnpeAn•biteehnr
Fixtinerinq _
Fraizvznmentnl 6- Cananmzity P(nnnu,y
RE: Drainage and Erosion Control Letter Report for South Glen PUD 2°d Filing Replat
Dear Glen:
The South Glen PUD 2"d Filing Replat consists of three single-family lots in lieu of an existing
pool and associated facilities. The three lots will face Albion Way and comprise a total area of
0.51 acres. The Storm Drainage Report for South Glen P.U.D. Fourth Filing (Stewart and
Associates, August 1994) and- the Final Drainage and Erosion Control Report for South Glen
PUD - 5th Filing (JR Engineering, Ltd., July 1996) were referenced for this report. ' The rational
method, used to calculate storm discharges in the Stewart and JR reports, was also used to
calculate the expected change in discharge as a result of the 2°d Filing Replat.
The replat site was originally contained within Basins C and F in the 1994 Stewart Report. Basin
C was revised in -the JR Engineering. 1996 report as a result of site layout changes for the South
Glen PUD Fifth Filing. Furthermore, runoff coefficients for Basins C and F were revised as part
of this replat to incorporate the decreased permeability of the proposed structures and driveways.
The revised runoff coefficient calculations are Included in the appendix.
The 1996 JR Engineering report referenced times of concentration from.the 1994 Stewart Report.
,pThe Stewart values for; time of concentration were also used in the modified South Glen PUD 2"d
Filing Replat Basins C and F calculations because the proposed site changes result in negligible
changes, in time of concentration paths. "Because the time, of concentration values did not change
with the revised basins, rainfall intensities presented in the Stewart report were also used to
calculate discharges. These discharges were then compared to determine the degree of impact to
Basins C and F.
The discharges.for Basins C and F were also calculated with revised intensities since the City of
Fort Collins intensity -duration frequency curves have been modified since the preparation of the
Stewart and JR reports. Additionally, revised intensities were used to calculate discharges from
the Stewart report for basins not disturbed by this project for comparison purposes.
Using 1999 City of Fort Collins intensities, runoff for Basin C increases by 2.62 percent between
the existing and proposed condition for both the 2-year event (3.06 cfs to 3.14 cfs) and the 100-
EAPROJECT FILES\LAND12M3\DOCS\DRAINAGE REPORT 7 M.DOC
AIM SELL DESIGN, INC. 153 WEST MOUNTAIN AVENUE FORT COLLINS, COLORADO 80524 970484.1921 FAX: 970484.2443 JIMSELLDESIGN.COM