HomeMy WebLinkAboutDrainage Reports - 02/21/1995No Text
RCE
A Division of Ayres Associates
December 13, 1994
Mr. Basil Harridan
' Stormwater Utility
City of Fort Collins
235 Mathews Street
' Fort Collins, Colorado 80524
Re: Huntington Hills Filing 3 PUD
Dear Basil:
' Enclosed is the "Addendum No. 1 to the Revised Final Drainage and Erosion Control Report
of Huntington Hills Filing 3" for your review and approval.
' The purpose of the addendum is to change the overlot grading to lots 1 through 10 and
provide additional erosion control measures to the overflow Swale at lots 201 and 202
Huntington Hills Filing 2.
' If you have any questions, please call.
Sincerely, -
i
Resource Consultants & Engineers
A Division of Owen Ayres & Associates, Inc.
Paul R. Barker, P.E.
Manager, Civil Engineering
' PRB\bbv
Enclosure
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Resource Consultants & Engineers
Engineers/Scientists/Surveyors
3665 JFK Parkway, Building 2, Suite 300, P.O. Box 270460, Fort Collins, CO 80527
(303) 223-5556, Denver Metro (303) 572-1806, FAX (303) 223-5578
Printed on recycled paper
HAMDENI2.LTR
93-0103.03
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ADDENDUM NO. 1 TO THE
FINAL DRAINAGE AND EROSION CONTROL REPORT
FOR
HUNTINGTON HILLS PUD: FILING 3
Prepared for
Huntington Hills L.L.C.
650 S. Cherry Street Suite 435
Denver, Colorado 80222
To Meet the Final PUD Submittal Requirements for the
City of Fort Collins
256 West Mountain Avenue
Fort Collins, Colorado 80521
RCE
A Division of Ayres Associates
Resource Consultants & Engineers
A Division of Ayres Associates
3665. John F. Kennedy Parkway
Building 2, Suite 300
Fort Collins, Colorado 80525
December 1994
HH-F3.ADM
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' I. INTRODUCTION
' The purpose of this addendum is to document two proposed changes to the Final
Drainage Report of Huntington Hills Filing 3. The proposed changes are to (1) modify the
grading of lots 1 through 10, and (2) add a section of grouted riprap to the overflow swale
' behind lots 201 and 202, Huntington Hills Filing 2.
11. LOTS 1 THROUGH 10 OVERLOT GRADING
' Originally, the lots were proposed to be graded from the back of the lot to the front
of the lot so drainage water would flow onto the street. It is now proposed to crown the
' lots so that the front half of the lot drains to the street and the back half drains to the back
of the lot. A swale will be constructed adjacent to the back lot lines to collect the
drainage. The swale for lots 1 through 5 will collect the drainage and convey it to the
' drainage swale along the northern boundary of Filing 3, which discharges into the
drainageway on the Hahn property (see revised grading plan in back pocket). The swale
for lots 6 through 10 will collect the drainage and convey it to the detention pond in Filing
' 2. Both of these swales are located in Huntington Hills Filing 5. Easements will be
provided to the City.
' Basin A has been modified to include the back of lot areas for lots 1 through 10 and
an area just east of these lots in Filing 5 which will drain into the swale. This offsite area
,was determined from topographic maps used for Filing 5 which was mapped this fall by JR
' Engineers. This new topography is slightly different from the topography shown on the
grading plan. Basin B was also modified to exclude the back lot area of lots 1 through 10.
The new area for Basins A and B are 0.61 and 0.53 acre, respectively. New flowrates for
' the 2- and 100-year storms were computed at concentration points 10 and 12. At
concentration point 10, the new flowrates increased and are 0.39 and 1.40 cfs,
respectively for the 2- and 100-year events. At concentration point 12, the flowrates
' decreased to 0.85 and 3.26 cfs, respectively for the 2- and 100-year events.
Basin D was subdivided,into Basins D1 and D2 to reflect the changes in the grading
' of lots 6 through 10. The area of Basins D1 and D2 are 0.51 and 0.59 acre, respectively.
At concentration point 13, the flowrates decreased to 0.94 and 3.61 cfs, respectively for
the 2- and 100-year flood events. The flowrates at concentration point 15, increased to
0.42 and 1.54 cfs, respectively for the 2- and 100-year flood events. Table 4.1 was
revised based on the new areas. This table and detailed calculations are included in the
Appendix.
Both swales along the back lot lines will have 4 to 1 sideslopes and a minimum slope of 2
percent. The minimum full depth capacity of the swales will be 8.7 cfs which far exceeds
the required capacity. The swale along the northern boundary of the property which
connects to the back of lot swale for lots 1 through 5 has the same configuration and
capacity.
' No detailed calculations were completed of the street drainage structures (gutters,
inlets, and overflow swales) since the original street flowrates were larger than the
proposed street flowrates. The original calculations showed the design was adequate;
therefore, they will also be adequate with lower flowrates.
1 Resource Consultants & Engineers
A Division of Ayres Associates
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III. GROUTED RIPRAP SWALE BEHIND LOTS 201 AND 202
' Along the northern boundary of Filing 2 from lot 201 to the west, a 24-inch storm
drain was proposed and constructed to convey offsite drainage to the Hahn drainageway.
' Above the storm drain, an overflow swale was proposed and constructed to convey
excess offsite drainage and local drainage to the Hahn drainageway. Due to topographic
conditions at Manhole A between lots 201 and 202 (refer to sheet 8 of the construction
' drawings), a steep channel (21 percent slope) section is needed to convey the drainage
water to the Hahn. drainageway. The proposed channel will be a trapezoidal section with 3
to 1 s' lopes and 1.5-foot bottom width. This channel will be lined with grouted riprap
— 9
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2 Resource Consultants & Engineers
' A Division of Ayres Associates
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APPENDIX
Revised Table 4.1
and
Detailed Calculations
1
m m m m m m m m r m m m m m m m m m m
I
/BYRES
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h
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ASSOCIATES
DESIGN COMPUTATIONS
� /
fCom�Jo��:at:
O. /Oac %ou;e5, G,SiGc
.5ci� O, S/Dcc xT;�el�;<�c:...
ion Ler\
,,_ «.6 /o
G01.i::�t
71 Ov.� Lena �j t = �Z r
La. C 7o
1/
V =
ITS- of.
�q� /k
.-L 100 � G
V I 1 n/ ^r-
1
I.c j 0. 9 cis
C- o,s�
Overlic"d Lzf, ;tk = sS' s = a. � �7o
T = �
v= D.a
�luo- �,y min -Lloo' 490
cp \ 1
ut
Project No: Co
Remarks m ation b Date
Project Name i 1 J Checked by Date
Title/Rem V Sheet of
I /BYRES
ASSOCIATES
DESIGN COMPUTATIONS
�t :G
O L- 5- , .5
1
yy� ?
l
IX
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ayy r S = y.0 CPS
Too 9.00 ;
r.
Project No.G, — _ _ _ Remarks Computation by r Date
Project Name` Checked by �R �/� Date
Title/Rem Sheet of
i AyRES
ASSOCIATES DESIGN COMPUTATIONS
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_h..
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r, Q. CGc
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= O. 06 O
IUD0 .
V=
Project No. Remarks Computation by Date
Project Name I Checked b Date 1
nw� y Yeti
Title/item USheet of
Flow in Trapezoidal Channels
Swales on Basins A and D2
Given Depth
Compute Discharge
1 I 4.000 I 8.246 I 0.485 I 8.0 I 2.17 I 8.67
AVRES
ASSOCIATES DESIGN COMPUTATIONS
F- (' Z
A `4y
�c
Vy
V
3
`j s = Z I �/O '�Y— �'(.c.r,clr1 = 87. 1
Project No.
Remarks 14 ! `r a_
Computation by �2 ?
Date
Project Name
i! i
Checked by
Date
Title/Item
Sheet of
NML_CRIT.XLS Normal —Depth 12/13/94 11:44 AM
Compute Normal Depth for a Trapezoidal or Triangular Channel
mannings n
0.06
sideslope (_H:1 V)
5
bottom width
0
bedslope
0.21
Riprap Sizing Factor
for use with Table 8.2
Fort Collins SDDC
Known
wetted hydraulic Computed
difference:
Discharge Depth
Area
perimeter radius discharge
velocity known q -computed q VSo.17/(S.- 1)0.ea
17.06 0.76
2.90
7.77 0.37 17.06
5.88 0.00 3.24
Normal Depth = 0.76
Page 1 of 1
M M M M M M M s M M M M MMM MMMM
Critical —Depth
Compute Critical Depth for a Trapezoidal or Triangular Channel
sideslope (_H:1 V)
3
bottom —width
1.5
bedslope
0.015
Riprap Sizing Factor
for use with Table 8.2
Fort Collins SDDC
Known Assumed
Specific Energy
Discharge Critical Depth
Area Topwidth
velocity Depth + V2/2g
VSo.17/(SS 1)o.66
17.06 0.93
4.00 7.09
4.26 1.21
1.50
Critical De th = 0.93
Page 1
Flow in Trapezoidal Channels
Channel,
Side
Bottom •
`MaMn�ng's,
Given Depth
R F
Slope`
;,Slo es
1Niath,""
N `
Compute Discharge
,'
0.21
3
1.5
0.06
Depth _
Area
W P,
R =
Topwidth
UefOct
Q
feet 3 `
.,
s
1.5
9.000
10.987
0.819
10.5
9.96
89.67
n
AVRES
ASSOCIATES DESIGN COMPUTATIONS
G
v,/)
P� -Fv o
V1�%lon� \ Y hvc 5,86 s
9
Project No. 9 3 _ 1 03 , 0
Remarks �� -�L3
Computation by � i13
Date I,1
y 7
Project Name 1 I t7i-,
tb
Checked by
Date
Title/Item
Sheet of
1
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SIZE OF RIPRAP TO BE USED DOWNSTREAM FROM STILLING BASINS
4
12
6
re -
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1 •. 1 1 1 1 1
.ME,
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mirl
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its 1 . 1
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:
mm
duo
MEN
BOTTOM VELOCITY IN FEET PER SECOND
rl('-UI!L ]G5.--Curve to delerntine Maxintum store size in rihrap mixlure.
- 5000
- 4000
- 3500
F-
0
- 3000 O
U-
U
- 2500 In
U
2000 W
a
0
1500
O
d
N
(D
- 1000
900
600
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700 z
600
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a
500
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400 W
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300 FO
250 N
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200 Q
U
ISO W
IL
-100 N
75 u'
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0
25 W
3
10
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209
p MALE I S gk-j- -
01 F_ �� p \/
SWALE00 e AC PICKY yi �40' ORA GE r LOR,
RIP RAP WITH 40. ORA MA \ A Q•QS9 it
RL4XREi EASEME 1 / �E15FMEHi as) 04 A 1 THIS
p S10
MANHOLE / tiro L N2E E/
a _e18F1 TI L
„ We 2. 4�Sa -2c b ADS
`e
Sn As Nonvoters
up4m p pRN
EASEMENT
I Fi A 635 T
OVERFLOM BCITLE %"
[0 NLAP CITY E ET 02 ' 4•AO! : F663 666 'yd 667
f.f]9i 'TYP/E
12' TYPE X 4 10.86 [1e MA•O SS
--- --L 613 sale I
WSTALL CMM E`6S'O Y6 9
WLET FILTER 13• RCp E
EXISTING w%,
M Fi /1
IOX oft 0� 5.32 cis I L.
f 10y 10.2OSIS CIO
Proposed change to approves
Filing 2 drainage ta<Itos by
TST Inc. Su Sheet 6 for siRow MULCH
\
aelaile. I Ai 2 TLANS/A B
•OR 53a- \ FM6
aeFO
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III II II See I
II I I II I \
I I
T INSTALL STRAW MVLGH
AT TON IL .aye
A
1019 \r Sep
ail•
It
\ reposed
his
ye
\�Carder
F1683 \
�LINE 9
SWALE 54.'/e OCTO pCi0BE6 1994 90 LOPO.
G
G ew
�E t DRAINAGE
[Mf Ni %
S
F1699 /(
1 1
I I I I L
LII I1 1��FL 899 /
y I (ITO !
Huntington Hills / gA
Filing No. 2 SATURN DRIVE
- - -
T-
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IDab ST efil
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ExsTINO
Owl OR�
.
f_
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Kore
INSTALL cURs �L S /
INLET FILTER V"
EVSi H4 t4 125 art -
INLET /6
8 I.
�6 I11 Qy491 ISI
1 IEASENEN T� 1 L NM.. I
24- Aps/ri a �-
le•-OVERFLOW SWALEi� /
STORM 10 LePPC1TY
SEWER SYSTEM 8 3.pi
r_ 1 )
Q-a6L / eeee
RPRAP ae e f
BLANKET
'` ,0i �t
I I ED m: CAPACITYl jjIPY STRAW INSSWALE
TALL
j
s 6ma
` 1A 1 _ %IJS ell CAPACITY 1
TRACT _
4, I I
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-� \y
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/ � I
I I DETENTION POND
INSTALL STRAW OIRE
TABLE 41 BASIN DISCHARGES - RATIONAL
A
41
TARI F A 1 1ITTFO T-APAITITV
Street
Manning. a N
Z
Y
2
Slope
Thearsical
Capacity
Hoduclian
Factor
PI CKUPb0
I capacity
Ilelq
(felt)
(feet)
Y
(eis)
(cis)
Dunne Dr.
O.OW
IB
0.36
50
133
14
0.9
11.2
Derry Dr.
O.dB
Ifi
ED 36
50
4.00
23
0.6
13.8
ITTI TEMPORARY ACCESS ROAD
cf$
fit \
Huntington Hills P.U.D
Future Filings
TALL STRAW MULCH
2 i0NA/AC
Coca -215 CIS \
Y
EASEM ENT r EASEMENT
LINE l LINE
4 1
B
1 SWALE CROSS SECTION G-G
�-
/0 Be OF 6• PIPRAP EACH GUTTER.
.SHAPE TO FIT BORROW DITCHES,
PLACE ON FILTER CLOTH, MIRAFI
PLACE 6" TOP SOIL OVER RIPRAP AND SEED.
SWALE AND OMd26.OScb
0� \ SWALE CROSS SECTION A -A
STRAWMULCH
2 TOxSI I Y20 .59' CIS \\\
EASEMENT 1 EASEMENT LIN
LIN44 I
V
q ... - aeo III e' 2
// d' SWALE CROSS SECTION B-6
•ye
cents
`E/ J90� EASEMENT �4 EASEMENT
LINE LINE
lllA/ ,� 5
Even
Nso
I YE BxfEi Ba L _. 40'
SWALE CROSS SECTION C-C
44
Wy
' 0ao-914c1s
1 a 0 AN in In » Y•0.75'
1 EASEMENT I EASEMENT
I LINE N
I (arm) I
] IrcL a SO S. 5
0 1. 54cfs
Y°6 sz /{�����r��
EASEMENT 1 E4"ta•
-f
EASEMENT e"ill
LINE L LINE W OVERFLOW SWALE CROSS SECTION D-D
a /
Is Pt Y-Creo,
EASEMENT EASEMENT
r- 'arts L heceep. IN
SWALE CROSS SECTION F-F
PROPOSED SPILLWAY EC o I 10'
OVERFLOW SWALE CROSS SECTION E-E
BASIN
A
CUMULATIVE
AR A
RUNOFF
CF
CF
OVERLAND
FLOW
AVERAGE
OVERLAND
OUTTEP
FLOW
AVERAGE
GUTTER
GUTTER
FLOW
OVERLAND TIME OF
CONCENTRATION
GUTTER
TRAVEL
TOTAL NET TIME
To To
RAINFALL INTENSITY
I 1
PEAK DI CHARGE
0 0
'Y
-
-
-
-
(cc)
(as)
C
2-YR
100-YR
(It)
(1)
(it)
1Y)
(fps)
(min.)
(min.)
(min.)
(min.)
(min.I
0a/hrl
(in./hr)
Icls)
left)
A
1.0t
101
025
1CO
1.25
GO
2.60
383
2.00
2.1
BID
8.3
30
12.0
11.3
233
Sol
0.59
2.15
B
0.53
0.53
0.59
1.00
1,25
58
2.60
345
1ISS
L33
83
62
2.7
11.0
SW
2.73
8.34
0'"
3.26
C
0.26
0.26
051
1.00
1.25
60
3.30
165
1.40
1.40
5.7
4.5
13
7.0
5,8
2.as
8.64
03e
1.43
➢1
0.51
051
0.59
1.00
1.25
57
3,N
244
4.00
4.0
4.6
33
1.0
5.6
4.3
312
9.60
0.94
3.61
E
0.27
22T
0A9
1.00
1.25
TB
3.30
165
1.40
A2.I
6.8
5.4
1.3
0.1
6.7
2.71
8.22
0.36
1.36
D2
On
059
0,29
1.00
1.25
59
4.20
445
2DO
21
22
6.6
3,5
107
10.1
243
7.IB
042
1.54
PROJECT: HUNTINGTON HILLS- FILING 3 STANDARD FORM C
SEQUENCE FOR 1994 ONLY
COMPLETED BY Chris Careen DATE: 3/8/94
Indicate by use at a bar line of Symbols when erosion
Control measures v II be t II a. Major moo rc01 ors
too approved Schedule may reaure submitting anew schedule for approval by In Coy Engineer.
JULY
OVERLOT GRADING
WIND EROSION CONTROL
Sell Roughing
Perimeter Barrier
Additional Barriers
Vegetative Methods
Soil Sealant
Other
RAINFALL EROSION CONTROL
STRUCTURAL:
Sediment Trap / Basin
Inlet Friers
Straw Barriers
Silt Fence Seniors
Sand 8091
Bare Sol Preparation
Contour Furrows
Terracing
Asphalt / Concrete Paving
VEGETATIVE
Permanent Seed Planting
Mulching / Sealant
Temporary Seed Planting
See Installation
Nett ngs /.Malt / Blankets
HOME CONSTRUCTION: I
ENRON
Convocer MAINTAPE]br 11 'o..
Contractor
STRUCTURES: INSTALLED BY
VEGETATION / MULCHING CiryTRACTOR'
DATE SUBMITTED: 5/11/94
APPROVED BY CITY OF FOE1O _ .S
wwwAN
ey.aeO�
01
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Notes:
I. Each lot owner Will be responsible for grOdmg end Ondin3ping
as (squired by the covenantsn h e 1Storm
rurrolf to the front and roar lot Jinov All foundations ore to be
designed such that the finished floor oevatiormsn th e
plans '• met to Mlowpolitso drainage y from the t 1 rs On
II bu and driveways f 1 e to provide positive
drainage Stay from the godge,
2. Topsod AA to be removed and replaced to a depth of 6" In all
Arabs Inat will be disturbed by graierg.
3. Topsail stockpiled are not to exceed 6'In height. are to be
aInarowed or roughened on Ibp.. and are to have A 2' berm bum
round the toe Wmdrove to be HE to SW),
4. All disturbed I twing p d are to be reseeded and
mulched win a mixture1 q 30 percent blue grame And 50
percent iftermedad whoolgrato dr,f d at a role of 1140 PLS/AC.
and the mulch anchored
s. Straw Sale dikes Are to doinstalled as Shan as the Swale has
been fi l graded.
6. All little h II keep their gravel Intel tiller, which rare
eadled for Filing 2, until Filing is bltol.
L The details to all ovs,to utilitiesfound on The plans for
Huntington Hills, Filing 2 prepared by TST. INC. July 1992.
B. All storm drainage facilitiesthe public 'ght 1 aY 'llhe
mbl l dby Ih City fFort Cll otherwise they are to be
maintained by the pruper fy owner.
�9. The developer will be reepanable 'or 31, dancer, a ro ic
loen the north button per the Tremble oreegoofed by t
alto construction is mplrean. T ere camr Term She' be
responsible during Constructions
LEGEND
ODesign Point
D2 Subbaaln Identification
59a Are
Basin Boundary
Existing Contour
Proposed Contest
Swale
IF 72,5 First Floor Elevation
� WiU
US eyw
US ENO C
2x0Wt
IN Aron.
0
M
/
STRAW BAIL /
/ DIKE
A.
RIPRAP
24" ADS PIPE —\
24' ADS PIPE
I
Y /
MATCH EXISTING
{•sAs
GROUTED flIP
F,lt*r Cloth
SECTION A -A
�_.
UNEO CHANNEL
IB• OF Q 1 I DWl RIPRAP
I
SWAIF �
iT Filler Cloth
I Mine 00�
E
m n H CIRRI
WHI TOOK ..
yie
3s
w00
u
UJ
J
Q
r
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a
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