HomeMy WebLinkAboutDrainage Reports - 06/01/1983Z1161110h M01
FINAL STORM DRAINAGE REPORT
for
PINEVIEW P.U.D.
PHASES I AND II
CITY OF FORT COLLINS
COUNTY OF LARIMER
STATE OF COLORADO
June, 1983
Prepared by: Parsons & Associates Consulting Engineers
432 Link Lane Plaza
Fort Collins, Colorado 80524
Project Number 83.14 PIN
Utilities
light & }power • stormwater e wastewater • water
City of Fort Collins
Date: December 15, 1999
To: Mark Taylor — Civil Engineer II
Memorandum
From: Susan Hayes — Senior Stormwater Engineer n`*'
Matt Fater— Master Planning Engineer�j'
RE: Pineview PUD
This memorandum is to provide you the information I found regarding the Pineview PUD.
First, I was asked to determine how the Pineview Pond would function as shown on the
approved Pineview PUD drainage under the new 3.67" rainfall criteria. I updated the
most current version of the Mail Creek Basin Model to reflect the new rainfall criteria and
any problems the new rainfall caused for the model. The modeling results showed a
100-year discharge, storage, and water surface elevation of 81.2 cfs, 3.9 ac-ft, and
5084.5 ft, respectively. These results are an increase over the original design plans
(designed under old rainfall criteria and modeling methods) that showed a 100-year
discharge, storage, and water surface elevation of 62.3 cfs, 2.72 ac-ft, and 5083.2 ft,
respectively. It should also be noted that with a 100-year water surface of 5084.5 ft, the
pond will overtop the intersection of Shields and Harmony by approximately six inches.
This overtopping condition would be a violation of arterial street criteria.
After the existing condition analysis, I proceeded to evaluate the possibility of slightly
modifying the Pineview PUD plan to contain the revised 3.67" rainfall without
overtopping. I conceptualized a six inch high berm along Harmony and Shields and
modified the pond analysis accordingly. The results of the analysis showed a 100-year
discharge, storage, and water surface elevation of 66.0 cfs, 4.14 ac-ft, and 5084.25 ft,
respectively. This condition would require an extension of the pond drainage easement
into the adjacent parking lot as well as raising three of the adjacent buildings by a half
foot and one of the adjacent buildings by a quarter of'a foot. The raising of the building
is to get one foot of freeboard from the 100-year water surface. However, the City may
be willing to consider a variance from the parking lot and freeboard criteria in order to
eliminate the overtopping of the street.
In addition, I will note the development agreement references 2.13 acres to be
purchased by the City. This area appears to include the detention pond easement and
the channel easement carrying flows from the upstream Regency Pond. These
easements are shown on the Pineview Phase 1 and 2 plats.
I also spoke to Dave Stringer about the status of Pineview PUD. He said the utility plans
are still valid because the developer constructed some of the site utilities giving the
developer vested rights. However, if the developer chooses to construct something
different than the approved utility plans, then the development would be subject to
current City criteria including: Land Use Code and rainfall criteria. I think if the developer
chooses to build based on the approved plans, we should encourage the minor changes
to the pond to eliminate the road overtopping.
700 Wood St. - P.O. Box 580 - Fort Collins, CO 80522-0580 - (9701 221-6700 - FAX (970) 221-6619 • FAX (970) 221-6593 - TDD (970) 224-0 III:,
e-mail: utilitiest(I-ci.fort-collins.co.iis - N,,,N ii :.ci.fort-colliiis.co.us/UTILITIES
I
PARSONS &
IA ASSOCIATES
r_ n
CONSULTING ENGINEERS
June 6, 1983
Mr. Bob Smith
City of Fort Collins
P.O. Box 580
Fort Collins, Colorado 80522
Re: Pineview P.U.D. Drainage Report
Dear Mr. Smith:
Please find attached the storm drainage report for Pineview P.U.D.,
Phases I and II. Included in the report is a discussion on regional
detention ponds No: 1 and 5 and the relocation of a portion of the
Pleasant Valley and Lake Canal as recommended by the "McClellands and _
Mail Creek Major Drainageway Plan."
The City of Fort Collins' Storm Drainage Design Criteria, dated
January, 1980, has been utilized as a guideline for analyzing
the stormwater runoff and required improvements..
If you have any questions or need additional information, please
contact me.
Sincerely,
ivl G' Michael C. Ketterling, P.E.. \��.`�PFLC.oKETTFgvi,,��
%S T EgFO
0016299 W `
i i. ids U e
9j .TONAL ;.
• 432 Link Lane Plaza • Ft. Collins, Colorado 80524 • [3031221-2400
FINAL STORM DRAINAGE REPORT
` PINEVIEW P.U.D.
FORT COLLINS, COLORADO
ABSTRACT
This report, in combination with Sheets 13 and 14 of the Pineview
P.U.D. Phase I final design plans, Sheets 8 through 11 of the Phase
II final design plans, and Sheets 1 and 2 of the Regional Detention
Pond Number 1 design plans, is intended to describe the procedures
and results of a drainage study of stormwater runoff generated by
this project and subsequent development west of the Pleasant Valley
and.Lake Canal. The historic conditions and proposed development
along with the required drainage improvements are analyzed in
accordance with the guidelines established by the City of Fort
Collins' Storm Drainage Criteria Manual.
INTRODUCTION
The intent of thi's study is to determine the quantity of stormwater
runoff generated from Phases I and II of the Pineview P.U.D., along
with potential adj�,cent upstream developments, the manner in which
thia runoff will be'accommodated by the Pineview development, and
ho� it relates to the storm drainage plan as determined in a study
entitled "McClellands and Mail Creek Major Drainageway Plan",
prepared by Cornell ConSulting Company and John S. Griffith, dated
December, 1980.,
SITE DESCRIPTION
The site is located in the southeast 1/4 of Section 34, Township 7
North, Range 69 West, of the 6th Principal Meridianr State of
Colorado, County of Larimer, in the southwestern portion of the City
of Fort Collins. Phase I of Pineview consists of 7.50 acres, and
Phase II consists of 19.45 acres. The project is bounded by Shields
Street on the east, � Harmony Road on the south, proposed Wakerobin
Lane on the north, and Lhe proposed relocation of a portion of the
Pleasant Valley and Lake Canal on the west (Figure 1).
The site, as well as adjacent upstream properties, is presently
undeveloped and used for agricultural purposes. The existing
dra�nage is to the southeast at a slope of approximately 1.5%. The
Mail Creek Drainageway flows through the Pineview project.
PROPOSED LAND USE
The project has received preliminary approval as the Pineview P.U.D.
The proposed development for the site will consist of townhomes
clustered around central plazas. Detached garages will be located
along the private drives throughout the project. The gross density
of the development will be approximately 12 units per acre.
• L�ki%�t .X�.
• I i cak e to
• V)
■
• �_ NTS_ ■ — -
-
. s
83
T . I II 48 47. 20.7 44
■ ' • \\
3 L • ° I� D ; r�
1.34. . — 50
I ` 79 I 52.6 \ �46 �45
84
11100 �,I2 4 CT 28:3 1
� I
0
29.2
- UJaKe ro'o n•i Ln.
+ \ De1ar,Tlen Por.c.
4- No. I
I � 2 3 I 22 `� . ! • 32.8 /', 19i ;
/25 Redocallon
75 8
\\ _ Area c. 37.3 1` '- �•: �%�4 - � 107
—�
a my Roa'\— _ -.-.. 2-r_ ■ _1f
° Phase o 20 11; i9
74 O�� �� 87 22.2 i
38.5
ti
HYDROLOGIC ANALYSIS
` The Rational Method has been
� used to generate stormwater runoff
flows for the 100-year return period storm for Phases I and II of
` Pineview., The design plans define sub -basins A through G, and Table
1 summarizes the results of the hydrologic analysis of these
sub -basins.
The Rational Method was also utilized for determining the 100-year
developed runoff from the portion of Basin 76 (Figure 1) north of
proposed Wakerobin Lane which will flow into Pineview Phase I.
Additionally, the 100-year developed flow from that portion of Basin
85 north of proposed Wakerobin Lane and west of the Pleasant Valley
and Lake Canal has been calculated by this method.
The Colorado Urban Hydrograph Procedure (CUHP) was used to determine
the 100-year developed inflow flood to be used in the design of
Regional Detention Pond Number 1. As a result of the Mail Creek
Major Drainageway Plan, a system of detention ponds to accommodate
runoff from the Southern half of Section 34 was recommended. The
contributing area to Detention Pond Number 1 is 195.4 acres (Basins
75, 80, 79 and (35). The contributing area to Detention Pond Number
`5 is 38.89 acres (Phases I and II of Pineview P.U.D. along with
15.92 acres of Basin 76).
DETENTION STORAGE
Stormwater generated upstream from the Pineview P.U.D. project will
be detained in Regional Detention Pond Number 1. The 100-year
developed inflow design flood for this contributing area will have a
peak flow of approximately 654 cfs at a time to peak of 40 minutes.
This storm generates an estimated 37.02 acre-feet of runoff.
(Figure 3 in Appendix). Figure 4 has been prepared to show the
stage -capacity curve for proposed Detention Pond Number 1.
The 100-year historic discharge from the contributing area to this -
pond has been determined to be 22 cfs. Using this as the discharge
of Pond Number 1, the accumulated runoff method gives a required
detention volume of 25.8 acre feet. Planimetering the area between
the inflow hydrograph and an outflow hydrograph for an 18''
R.C.P. outlet pipe (Figure 5) results in a storage volume
requirement of 33.45 acre-feet. The water su�face elevations
corresponding to these storage volumes are 509q.95 and 5101.0. This
pond, as proposed, will be constructed to elevation 5102 to provide
one foot of freeboard. �
Detention Pond Number 1 will be constructed immediately west of the
proposed relocation of the Pleasant Valley and Lake Canal. As an
additional safety factor, when a storm with return period greater
than a If0-year occurs which exceeds the additional storage volume
available, the runoff from the pond will flow into the canal and
along the west side of the canal to the southr where it will flow
into the drainage provided along the north side of Harmony Road.
Detention Pond Number 5 is proposed for the northwest corner of
Harmony Road and Shields Street. The intent of this pond is to
detain runoff from Pineview P.U.D. along with a portion of Basin 76
as well as'routing the 22.8 cfs released from Pond Number 1 through
the system.
The 100--year high water surface elevation for this pond has been
calculated to be 5083.2 with a storage volume of'.'72 acre feet.
The release rate at this level is 62.3 cfs. The stage -storage curve
for Pond Number 5 is shown in Figure 5. The discharge -elevation
curve for the 36" R.C.P. outlet pipe for this pond is shown on
Figure 7.
The recommended improvements to the Mail Creek Drainageway as
discussed in the study of that drainageway have been made along
Harmony Road to the east of Shields Street. These improvements have
the capacity to discharge th,e 62.3 cfs released from Pond Number 5.
The detention storage required for the Pineview Phase I development
is 0.76 acre-feet with a peak discharge of 23.1 cfs. It is our
recommendation, however, that upon construction of this phase, that
Detention Pond Number 5 be rough -graded. to its final configuration.
HYDRAULIC ANALYSIS
All the streets within the Pineview P.U.D. are designated as private
drives. A few of these drives have a single cross pan located to
one side of the drive. The transverse slopes away from these pans
are a minimum of 2%. In areas where the runoff dictates, an
additional cross pan has been added on the opposite side of the
drive to provide additional capacity. Reduction factors depending
on longitudinal street slope have been incorporated into the
anaylsis to determine the allowable street flows.
Culverts are proposed under Private Drive "A" in Phase I (30"
R.C.P.', and at 0+75 under Wakerobin Lane. (2----29" X 45"
R.C.P. horizontal elliptical). The 301' R.C.P. will discharge 30.3
cfs (desi(:.in flow X 1.33) with a headwater depth of 3.1 feet. The
horizontal elliptical culverts beneath Wakerobin Lane are designed
to carry the 100--year developed runoff from 15.92 acres of land
situated north of Wakerobin Lane between the Pleasant Valley and
LakeCanal and Shields Street. These two culverts will pass 93.2
cfs with a headwater depth ot 3-0 feet. The proposed 29" X 45"
R.C.P. horizontal elliptical culvert located approximately 100 feet
west of the Pleasant Valley and Lake Canal beneath Wakerobin Lane is
designed to discharge the 100-year developed runoff of 43.5 cfs
generated from 12.04 acres north of Wakerobin Lane between proposed
Seneca Street and the Pleasant Valley and Lake Canal. This flow
will discharge directly into Detention Pond Number 1
Presently, the P sant Valley and Lake Canal has a normal flow
estimated to be 3 cfs at a depth of 2.5 feet, a slope of 0.0002
ft/ft. and a vel ty of 0.8 fps. The approximate bank full
capacity of the existing canal is 37.2 cfs at a depth of 4.1 feet.
/
AsSuming Basin 77 were to flow into the canal at e 100-year historic
rate, the design flow for sizing the relocated canal would be 37.2 +
` 20.1 cfs or 57.3 cfs. ~The proposed relocated canal will have a 7
foot bottom widtyp 2:1 side slopes, depth of 3.25 feet, slope of
0.0004 ft/ft.and velocity of 1.4 fps under peak flow conditions. A
one -foot freeboard has also been incorporated into the design.
CONCLUSION
Drainage from Pineview P.U.D. Phases I and II has been accomplished
by street and open channel conveyance to Detention Pond Number 5.
The 100-year developed runoff from the area north of Wakerobin Lane
also flows to_this detention pond. The area contributing runoff to` -
Mail Creek west of the relocated Pleasant Valley and Lake Canal will
be detained in Detention Pond Number 1.
APPENDIX
it
u-.
C 4�
O C
•r •r
o O
0) m
en
I� mt t0 m N- MT ch M Ln
O Ln Ln 00 00 d 00 O Ln r`
O1 d• O W to O 00 -
Un CD Ln Lf) Ln U) U) In In C�
LP) tO t0 t0 r� tO O O tO
r1 e r r N • N N
O O M O O O O M O O
L.n w I*- U) U) LO Ln M Ln t0
O O O O O O O O O O
L� m tO N N Gt M r M M
0p Ln tO Ln t0 O m 0) .--i
N C) Lo N r` Ln N n •-'�
r :Zl- Ln
0) O
O 00
M V
O M
� N
Cl O
N Ln
O O
n n
O1 m
N N
N N
� 0
O CL
U 0)
3 .r 3 0
N i d
r O •r r
> 1 > 0)
Q m U (n W L' CD 0) •r C>
•r S •r �
Cl- D_
Pnevte-w P.Lk-U. Ph. a3.17
De-+cn*or, Pon,ci 1
S/z518.3
Mc- K
Color ac,o Ur Dan d o 0n ne /oo-yeas deb. runoi�
Area 195.+ acres L$as1n5 75, 80.> 79 anci 85 from IAcCaIl ay\As and
►ka,l cre-ey- 1la,or Drfl na�e ulay Plan ")
L la.�4\ dratna, e Way -Pron s'ika' P{`, io uQsi�earr� I m� of bash
39f7o' ±
Lca : d sl from s4ucky Pi. alon� s.+rearvl to tie cent-otA of he- basin
a_sume So 7� PCfViDI).�i area
l0 /" Im eCrV�OU,g
(7.81
ct colt, rai lec� no I he +o, eea�. = CSa)B. Ta > Qefv okAs
Ct - 7.EI/(-eO)0, o.37
5138.5 - So4E
Se 317/0� D.o13 1
o,01 < :5 S 0.0 noe. . Sloe - co rc` C-1. to Y'\ > Ci = Cto
\0.3 \ 0.3
p7 C.79A.33 Z4 hr
say Is minu"{"e5
to Pear ra+e, OT rv.n0
o, 41?
0.SR Cci)
(�
0, 09 ( o, 37) o.a
.56
tr� 640 Cp 640
%P = Qcak ra+e. vT Atsci\ar�e-. = 1-P o.z4 1493 c..*g
L Vey 591 mi.,
Q? = max. un, { hycirograeh ?C-aK for basin = 9P A - 1493 �95,4
i � 690) = 456 �-�S
Z/
Y nevte,)j
De++en-�ton Pon.L� 1
S�z5�83
AC-Y-
D<-+e.rm%rte_ Vjk + k of unl+" hYJrogra �V\ @ 50 `% aYtci
11-6 QP 50/9P - .500/1493 = .33 hr = ZO min.
'11_ Z60 2fo0
v5% QP �P - 493 a 17 hr /O m r\,
7= + R e. i t P e-;3 rm to E:o n o t tt�o 0-� rat n-Fa l �
0,5+�
+u i'irr.e of u�t� rdtr\ial� dLkratlon as£umC
�,o(.z4) + %Z - 17 min.
dclurne. o-� ur\t4- hydro�raph svtov-kCL 6e
P onlh E leced are2 - 3 5�6 x /00 {�eC x ZO m n X �m n
-T —Ime. W,Ir%.
o ao 60 5n
-i, C. MIr.
UNIT 14YDROGRAP14
1 , JS
O
fIo
Z93
4
410
?7�
�3
12b
55
0
SC
39
17
O
/00
IZO
Figure 2
Loc ATI 0 N : Sec. 34 -T' -7 M, RA69W DESIGN STORM: ioo - Yr-AP, P R OTE C-T No, sz. 17 DET
Lt
rK
T
co
4- j
o
�
_ ��
o
..
�
N
�
0
0
0
0
� 0
0
0-
o
o
� o
�
0
0
O
4pl
o
p
o
0�
J
w
\A
00
cc
ILI w
VI
0
%A
0.
c c
c
C�
43ci
a-
o
of
0
CMI,
10-
of
M!
oI o, of 0'
VI ru
cri
C)
Iu
0
It
c
CO
\Aj
lq
43
0
1`0'
6
of
cc,
0
00
0 4u
qT
0 0.
CO
(Y\
\n
IA
m
:
N
N
N
N
N
(�
N
N
N
N
N
N
r4
T-
Ir
VZ5 /8-3
Mc K
woc •
. •
•Film
' D
_ I N.T.S. _ ■
� i 49 tea. II •
T • — • 8 II - 48 ci 47.. - ` 20.7 44
, 90.3 — �\ Z34
\_
I' L . •
( 508I
79 I 52.8 \�46 �45
17.9 �� \ 84
11100 \�p124 tT 28.3 1
\ I 29 2 Pro used
LL1aK�robrt� Ln,7
<4 DetenT[or\ Pond
I ;23' .. 22 No.l 19.;
Bas No.
ProPOs
GD.P.
\ i 7 rJ 2 5 Relocation ;% Ilo. S
Area ac. 37.3 i — -.� Q �`/ 8 :�/ I .107
74
Ha nr RO a — — — — -
-� ° Phase 20/" i 19
D
2.2
38.5
PRo'JECT No. &B. 1-7 D(5-r SrAfLs3 14C r-
0
r
LI:
"D
ol
Tz
\n
MIT
CA
+
43
Ni
i 1 —1
—1
tA
NtTi
01
I.
jj
i D
c,-4,
'd-
til
ff
r-�i
coI!
J
4-
Cq,
11
_791---
U
I I
'd N
D;
T! rq1
0
a!
i
\n
It
i
CL
\of)! dcA
Njr
a:
'n.
�2;
C"j
r-
I ID
Vi
N
al
col
ro-
0
CO
N
2
cc
z
"A
1*
CAI
rp
N
I
I
L
\n
q-
Ln
L�
w
'D
'D
I-
cn
O
tX
ff
CQ
0.
In
(Rj
"An
O'A
.m
n
fl�sci�arg2.> c�5
i J
Fgur� 3
tY
%-1
O
L1
1 �
Li.
..1
i
fa
7
9
uaf,.}_nn-a13-aae��r�c�, .��,.�.>zr(1 �•.�o,� uol�.u��a�
H $ W
F-�
F,gare: s
V)
N
0
Of
Dei eni ion Pond Wa+er Surface. Elevation
LA
c
2
Z c
c
a
c
4-
i
4-
d
C
m
4-
ro
ro
+T
�j
ro
a_
N
U
ni
Z
D_O
c
O
C
4-
d
�}
o
lD O co
m m m
OD r
Detention Pond Water Surface Elevation
0
r
0
Is
a
0
v
N
0
6j
rq ro
s
0
q
CD
m 0 m 8 m
0 0
m a V) b
Detention Pond Wa+er Surface Eleva+ion