HomeMy WebLinkAboutDrainage Reports - 10/25/1995 (3)PROPORTY OF
AMENDED
FINAL DRAINAGE STUDY
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FOR
COUNTRY CLUB CORNER, A PLANNED UNIT DEVELOPMENT
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AMENDED
FINAL DRAINAGE STUDY
FOR
COUNTRY CLUB CORNER, A PLANNED UNIT DEVELOPMENT
Prepared For:
Denver Holdings, Inc.
10065 E. Harvard Avenue, Suite 803
Denver, CO 80231
August 8, 1995
Project No. DENHO-94099C-04-110AH
CONSULTING ENGINEER
Landmark Engineering Ltd.
3521 West Eisenhower Boulevard
Loveland, Colorado 80537
-CERTIFICATION
I hereby certify that this Amended Drainage Study for Country Club Corner, A Planned Unit
Development was prepared by me or under my direct supervision in accordance with the
provisions of the City of Fort Collins Storm Drainage Criteria for the Owners thereof.
o
�N.F •.pa
Patrick M. Mestas � �' ° ,ss, � :• �
Colo. P.E. 13886 %9��"° :::•
AMENDED FINAL DRAINAGE STUDY
for
COUNTRY CLUB CORNER, A PLANNED UNIT DEVELOPMENT
PURPOSE
The Final Drainage Study is herein amended for changes to the drainage improvements at the
request of Denver Holding, Inc.
GENERAL DESCRIPTION OF CHANGES
The changes are applicable to improvements that will be constructed under Phase I. The
improvements identified in the final drainage study which were to be constructed under Phase
I and herein amended include:
1. Detention pond
2. Detention pond concrete inlet structure
3. Six foot concrete pan through detention.pond
4. Detention pond concrete outlet structure with an orifice plate
5. Onsite dual 30" storm drain from the outlet structure to Junction Boxes (JB) 4 and 3
6. Offsite dual 30" storm drain in Bristlecone Drive from JB 3 to JB 1 and 2
7. Offsite 34"x53" HERCP storm drain in Bristlecone Drive from JB 1 to the new headwall
at the existing open channel to the regional Evergreen West Pond
8. Offsite existing 30" RCP storm drain in Bristlecone Drive from JB 1 to the new headwall
9. Relocation of an existing 24" storm drain and manhole in the intersection of Bristlecone
Drive and Blue Spruce Drive
The changes with this amendment are:
1. Detention pond accommodating a larger volume
2. Detention pond concrete inlet structure that has been modified and incorporates rip -rap
3. Six foot concrete pan through the detention pond
' 4. A 24" FES with an orifice plate and rip -rap at the detention pond outlet
5. Onsite 24" storm drain and open channel from the pond outlet to JB2. The open channel
will have a concrete pan. FESs and rip -rap will be used on the 24" storm drain.
6. Offsite dual 30" storm drain in Bristlecone Drive from JB 1 to 2.
7. Utilization of the offsite existing 30" storm drain in Bristlecone Drive from JB 1 to the
existing headwall at the existing open channel to the regional Evergreen West Pond.
It is intended that the onsite storm drainage improvements identified in the Final Drainage Study
' for Phase I will constructed under Phase I. The changes are shown on Exhibit B, Drainage Plan
Phase I Interim.
' The changes utilize the Bristlecone Drive existing street section and existing 30" storm drain to
convey the Phase I release rate from the site. The limiting parameter to the release rate is the
capacity of the existing 30" storm drain which results in additional volume in the Phase I interim
' detention pond.
RUNOFF SUMMARY
A summary of the developed Phase I
runoff for the changes is as follows:
Q in street
Q in pipe
Q 100
' Subbasins cfs
cfs
cfs
As 0.00
5.99*
62.35
Bs 7.90
18.40
26.30
Cs 10.15
0.00
10.15
' Totals 18.05
24.39
98.80
' *Restricted release from detention pond based on:
Release rate = 25.00 (Ex 30" SD capacity) - 0.61 (Burger King) - 18.40 = 5.99 cfs
The total Phase I release rate from the site is 45.25 cfs
Bristlecone direct runoff 18.05 cfs
Willox direct runoff 2.81 cfs
Bristlecone existing 30" SD 24.39 cfs
' Total 45.25
There is sufficient capacity in the Bristlecone Drive street section to accommodate the Phase I
release rate as shown below:
Bristlecone Drive street section capacity = 43.22 cfs
Less direct release to Bristlecone Drive = 18.05 cfs
Less offsite contributory area = 7.55 cfs
Unused capacity 17.62 cfs
The volume of the Phase I interim detention pond has increased from 1.68 of to 2.05 af, however,
the configuration has remained essentially the same.
The runoff computations shown in the Final Drainage Study have been used for this amendment.
Computations applicable to the changes are shown in the Appendix.
APPENDIX
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DRAINAGE CRITERIA MANUAL
RIPRAP
1- 4
n
O 4C
0
Q
-Z
TYPE
.2 A Y /D .6 .8 1.0
t
Use Do instead of D whenever flow is supercritical in the barrel
**Use Type L for a distance of 3D downstream.
FIGURE 5-7. RIPRAP EROSION PROTECTION AT CIRCULAR
CONDUIT OUTLET.
11-15-82
URBAN DRAINAGE 9 FLOOD CONTROL DISTRICT
DRAINAGE CRITERIA MANUAL
MAJOR DRAINAGE
Table 5-1
CLASSIFICATION AND GRADATION OF ORDINARY RIPRAP
Riprap
% Smaller Than
Intermediate Rock
*
d50
Designation
Given Size
Dimension
By Weight
(Inches)
(Inches)
Type VL
70-100
12
50-70
9
35-50
6
6**
2-10'
2
Type L
70-100
15
50-70
12
35-50
9
9**
2-10
3
Type M
70-100
21
50-70
18
35-50
12
12
2-10
4
Type H
100
30
50-70
24
35-50
18
18
2-10
6
Type VH
100
42
50-70
33
35=50
24
24
2-10
9
*d50 = Mean particle size
** Bury types VL and L with native top soil and revegetate to protect
from vandalism.
5.2 Wire Enclosed Rock
Wire enclosed rock refers to rocks that are bound together in a
wire basket so that they act as a single unit. One of the major
advantages of wire enclosed rock is that it provides an alternative in
situations where available rock sizes.are too small for ordinary
riprap. Another advantage is the versatility that results from the
regular geometric shapes of wire enclosed rock. The rectangular
blocks and mats can be fashioned into almost any shape that can be
11-15-82
Table 8-1 lists several gradations of riprap. The minimum average size designation for loose riprap
shall be 12 inches. Smaller sizes of riprap shall be either buried on slopes which can be easily
maintained (4 to 1 minimum side slopes) or grouted if slopes are steeper. Grouted riprap should meet
all the requirements for regular riprap except that the smallest rock fraction (smaller than the 10 per-
cent size) should be eliminated from the gradation. A reduction of riprap size by one size designation
(from 18 inches to 12 inches or from 24 inches to 18 inches) is permitted for grouted riprap.
Table 8-1
CLASSIFICATION AND GRADATION OF ORDINARY RIPRAP
% of Total Weight
Smallerthanthe Stone Size d5ot
Riprap Designation Given Size (in pounds) (inches)
70-100 85
' Class 6 tt 50-70 35
35-50 10 6
2-10 <1
' 70-100 440
Class 12 50-70 275
35-50 85 12
2-10 3
100 1275
Class 18 50-70 655
35-50 275 18
2-10 10
100 3500
Class 24 50-70 1700
35-50 655 24
' . 2-10 35
t dso = Mean Particle Size. At least 50 percent of the mass shall be stones equal to or larger than this dimension.
tt Bury on 4 to 1 side slopes or grout rock if slopes are steeper.
Table 8-2 summarizes riprap requirements for a stable channel lining based on the following
relationship:
VSo.n
—�--� = 5.8
(dso) ' (S5 1)
in which, V = Mean channel velocity in feet per second
' S = Longitudinal channel slope in feet per. foot
Ss = Specific gravity of rock (minimum S,=2.50)
dso = Rock size in feet for which 50 percent of the riprap by weight is smaller.
' The rock sizing requirements in Table 8-2 are based on the rock having a specific gravity of 2.5 or
more. Also, the rock size does not need to be increased for steeper channel side slopes, provided the
side slopes are no steeper than 2h:1v. Rock lined side slopes steeper than 2h:1v are not
recommended.
Table 8-2
RIPRAP REQUIREMENTS FOR CHANNEL LININGS tt
VSo.»f(S,_ 1)0."t RockTypett
0 to 1.4 No Riprap Required '
1.5 to 4.0 Class 6 Riprap
4.1 to 5.8 Class 12 Riprap
5.9 to 7.1 Class 18 Riprap
7.2 to 8.2 Class 24 Riprap
t Use S, = 2.5 unless the source of rock and its densities are known at the time of design.
tt Table valid only for Froude number of 0.8 or less and side slopes no steeper than 2h:1v.
Kj
' MAY 1984 8-18 DESIGN CRITERIA
' The thickness of the riprap layer should be at least 1.75 times dso (at least 2.0 times d5o in sandy soils)
and should extend up the side slopes at least one foot above the design water surface. At the upstream
and downstream termination of a riprap lining, the thickness should be increased 50 percent for at least
' 3 feet to prevent undercutting. Where only the channel sides are to be lined, the riprap blanket should
extend at least three feet below the existing channel bed and the thickness of the riprap layer
underneath the channel bed increased to at least three times dso to prevent under cutting.
Riprap should be placed on either filter material (gravel bedding), a plastic filter cloth, or a combination
of both to protect channel embankment materials from washing out through the riprap. Generalized
filter material specifications are listed in Tables 8-3 and 8-4. The Type I filter in Table 8-3 is designed to
be the lower layer in a two layer filter for protecting fine grained soils and has a gradation identical to
Colorado Division of Highways concrete sand specification AASHTO M 6 (Section 703.01). The Type
II filter, the upper layer in a two layer filter, is equivalent to Colorado. Division of Highways Class A filter
material (Section 703.09) except that it permits a slightly larger maximum rock fraction.
For fine grained soils either a two layer filter (Type I topped by Type 11), or a single 12-inch layer of Type
II filter is required. For coarse sand and gravel (50% or more by weight retained on the #40 sieve), only
the Type 11 filter is required. Filter cloth is not a complete substitute for filter material. Recommenda-
tions for its use are made in the Urban Storm Drainage Criterial Manual.
' Table 8-3
GRADATION FOR FILTER MATERIAL
' % by Weight passing square Mesh Sieves
Type Type 11
(CDOH concrete sand specification (CDOH Class A,
' Sieve Size (AASHTO M6) Section 703.01) Section 703.09)
3" 90-100'
1-1 /2"
...
' 3/4"
20-90
3/8"
100
#4
95-100 0.20
'
# 16
45-80
#50
10-30
# 100
2-10
#200
0-2 0-3 ,
1
Table 8-4
' THICKNESS REQUIREMENTS FOR FILTER MATERIAL
Minimum Thickness (Inches)
Fine Grained Soils t Course Grained Soils tt
' Riprap Designation
Type I Type II Type ll
Gablons, slope mattresses,
Class 6 and Class 12 riprap...................................
4 4 6
Class 18 and Class 24 riprap.................................
4 6 8
t May substitute one 12 inch layer of Type Il.bedding.
tt Fifty percent or more by weight retained on the #40 sieve.
MAY 1984
8-19
DESIGN CRITERIA
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