32891_~~~
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L-10
HYDROLOGY / HYDRAULIC REPORT
Tentative Parcel Map No. 32891'— Parcel 1
LOCATED IN THE CITY OF LA QUINTA,
COUNTY OF RIVERSIDE, CALIFORNIA
OCTOBER 17, 2005
�o PROFESS1 -
D. Nc 55 66
Exp.12/31/06
sTgTF
OF I CA.\
PREPARED FOR:
ESSE SHAHANDEH
45 -175 Panorama Drive, Suite E
Palm Desert, CA 92260
Phone: (760) 340 -5597
PREPARED BY:
HACKER ENGINEERING
68 -487 Highway 111, Ste. 43
Cathedral City, Ca 92234
Phone: (760) 202 -1800
W.O. 050810
I
' HYDROLOGY /HYDRAULIC REPORT
Tentative Tract No. 32891 - Parcel 1
SITE DESCRIPTION AND PURPOSE OF STUDY
7
The existing offsite slope drainage naturally drains west towards Peerless Place. First
approach was to determine the location of a concentration point to convey the storm
waters to the existing Golf Course Lake. This report accounts four tributary areas: (Please
refer to Hydrology Map)
1 — Area "A "; 2.17 acres in size, includes the slopes east of toe line to the ridge line of
the south half of Lot 27 and north half of Lot 28.
2 — Area "B "; 1.01 acres in size, includes the buildable areas west of toe line to Peerless
Place right -of -way, of the south half of Lot 27 and north half of Lot 28.
3 — Area "C "; 1.88 acres in size, includes the slopes east of toe line to the ridge line of the
Parcel 1 and the north half of Lot 27.
4 — Area "D "; 0.88 acre in size includes the buildable areas west of toe line to Peerless
Place right -of -way, of Parcel 1 and north half of Lot 27.
A grouted rip -rap lined trapezoidal channel placed at the toe of slopes will convey the
flow from the high points at nodes #30, #60 and #80 to catch basins located at low
points, nodes #20 and #50. A pipe placed between catch basins and from node #50 to
Golf Course Lake, will conduct the runoff produced by all tributary areas.
Summary of the Runoff analysis and results are:
Tributary Area "A" —
The property herein described is located in a portion of the South one half of Section 6,
Tributary Area "B" —
Township 6 South, Range 7 East, San Bernardino Meridian, in the City of La Quinta,
'
County of Riverside, California. The 0.30 acres site is currently vacant and is bordered
on the east, north and south by foothills and on the west by Peerless Place.
Tributary Area "C" —
'
The purpose of this study is to provide hydrology and hydraulic analysis for the
subject Parcel 1 for future improvements and to determine the appropriate
4.89 c.f.s.
mitigation measures.
DRAINAGE DESIGN
7
The existing offsite slope drainage naturally drains west towards Peerless Place. First
approach was to determine the location of a concentration point to convey the storm
waters to the existing Golf Course Lake. This report accounts four tributary areas: (Please
refer to Hydrology Map)
1 — Area "A "; 2.17 acres in size, includes the slopes east of toe line to the ridge line of
the south half of Lot 27 and north half of Lot 28.
2 — Area "B "; 1.01 acres in size, includes the buildable areas west of toe line to Peerless
Place right -of -way, of the south half of Lot 27 and north half of Lot 28.
3 — Area "C "; 1.88 acres in size, includes the slopes east of toe line to the ridge line of the
Parcel 1 and the north half of Lot 27.
4 — Area "D "; 0.88 acre in size includes the buildable areas west of toe line to Peerless
Place right -of -way, of Parcel 1 and north half of Lot 27.
A grouted rip -rap lined trapezoidal channel placed at the toe of slopes will convey the
flow from the high points at nodes #30, #60 and #80 to catch basins located at low
points, nodes #20 and #50. A pipe placed between catch basins and from node #50 to
Golf Course Lake, will conduct the runoff produced by all tributary areas.
Summary of the Runoff analysis and results are:
Tributary Area "A" —
12.64 c.f.s
Tributary Area "B" —
5.84 c.f.s.
Total runoff to node #20 —
18.49 c.f.s.
Tributary Area "C" —
10.52 c.f.s.
Tributary Area "D" —
4.89 c.f.s.
2
Total runoff to node # 50 — 15.40 c.f.s.
Total runoff combined at node #50 — 33.23 c.f.s (to Lake).
Pipe diameter from node #20 to node #50 : 24 -inch.
Pipe diameter from node #50 to Lake: 21 -inch
Grouted rip -rap lined trapezoidal channel from node #30 to node #20 and node #60
to node 920:
- 6 to 8 -inch rock size for proper gradation and splash control.
- Side slopes 2:1
- Depth: 12 -inch
- Bottom width: 2.5 feet
- Width: 6.5 feet
- Flowrate: 9.3 c.f.s.
Grouted rip -rap lined trapezoidal channel from node #60 to node #50 and node #80
to node #50:
- 6 to 8 -inch rock size for proper gradation and splash control.
- Side slopes 2:1
- Depth: 12 -inch
- Bottom width: 2.5 feet
- Width: 6.5 feet
- Flowrate: 7.7 c.f.s.
Please refer to calculation sheets. J
As per Hydrology/ Hydraulic Report for the Tradition Golf Course Project in the City of
La Quinta (Tentative Tract 27613), Prepared by Keith International Inc, the original
runoff from the drainage areas referenced in this report, was taken to the Basin 4, that is,
the Golf Course Lake located at the northeast corner of the property. This design now is
proposing to redirect the mentioned runoff to the Basin 5 (Golf Course Lake located at
' west of Peerless Place). According to the same report, the total capacity .of this Lake is
27.4 acre -ft and the inflow is 15.54 acre -ft. The proposed incremental increase .to the
Lake is 1.59 acre -ft for peak flow of 33.23 c.f.s, please see attached unit hydrograph from
the report. The increase in elevation on Lake Surface will be 0.102 feet, no significant .
' impact on Lake Capacity or freeboard reduction.
' 3
METHODOLOGY AND REFERENCES
Methods used to calculate runoff are as prescribed by the Riverside County Flood
Control District Hydrology Manual to determine peak flow rates for the 100 year event.
Manning's equation was used for hydraulic calculations on the pipe and channel sizing.
CONCLUSION
The drainage report contained herein has been designed in accordance with applicable
state and local ordinances. Therefore, if developed as planned, the drainage from this site
will not adversely affect persons or property onsite or downstream.
9
4
®: �'�l mil a` i "/d � Y ► I''! �` ` , »
Standard intensity- duration curves data (Plate D -4.1)
For the [ La Quinta ] area used.
10 year storm 10 minute intensity = 2.770(In /Hr)
10 year storm 60 minute intensity = 0.980(In /Hr)
100 year storm 10 minute intensity = 4.520(In /Hr)
100 year storm 60 minute intensity = 1.600(In /Hr)
Storm event year = 100.0
Calculated rainfall intensity data:
1 hour intensity = 1.600(In /Hr)
Slope of intensity duration curve = 0.5800
31
0
laATIONAL HYDROLOGY STUDY
Riverside County Rational Hydrology Program
CIVILCADD /CIVILDESIGN Engineering Software,(c) 1989 - 1999 Version 6.1
'
Rational- Hydro.l.ogy Study-- Date /17/05 File:tocbl.out
-10
- - - - -- - - - - --
TENTATIVE PARCEL MAP No. 32891 - PARCEL 1
Preliminary Hydrology and Hydraulic Calculations
'
------------------------------------------------------------------------
********* Hydrology Study Control Information * * * * * * * * **
'
English (in -lb) Units used in input data file
'
------------------------------------------------------------------------
Hacker Engineering, Cathedral City, California - SIN 794
------------------------------------------------------------------------
Rational Method Hydrology Program based on
Riverside County Flood Control & Water Conservation District
'
1978 hydrology manual
Storm event (year) = 100.00 Antecedent Moisture Condition = 2
Standard intensity- duration curves data (Plate D -4.1)
For the [ La Quinta ] area used.
10 year storm 10 minute intensity = 2.770(In /Hr)
10 year storm 60 minute intensity = 0.980(In /Hr)
100 year storm 10 minute intensity = 4.520(In /Hr)
100 year storm 60 minute intensity = 1.600(In /Hr)
Storm event year = 100.0
Calculated rainfall intensity data:
1 hour intensity = 1.600(In /Hr)
Slope of intensity duration curve = 0.5800
31
0
n
1
1
++++++......+++++++++++++++++++++++++++++ + + + + + + + + + + + + + + + + + + +...... + + + + ++
Process from Point /Station 10.000 to Point /Station 20.000
* * ** INITIAL OFFSITE AREA EVALUATION - AREA "A" * * **
Initial area flow distance = 257.700(Ft.)
Top (of initial area) elevation = 257.500(Ft.)
Bottom (of initial area) elevation = 62.780(Ft.)
Difference in elevation = 194.720(Ft.)
Slope = 0.75561 s(percent)= 75.56
TC = k(0.530) *[(length ^3) /(elevation change)) ^0.2
Initial area time of concentration = 5.165 min.
Rainfall intensity = 6.635(In /Hr) for a 100.0 year storm
UNDEVELOPED (poor cover) subarea
Runoff Coefficient = 0.878
Decimal fraction soil group A = 0.000
Decimal fraction soil group B = 0.000
Decimal fraction soil group C = 0.000
Decimal fraction soil group D = 1.000
RI index for soil(AMC 2) = 89.00
Pervious area fraction = 1.000; Impervious fraction = 0.000
Initial subarea runoff = 12.645(CFS)
Total initial stream area = 2.170(Ac.)
Pervious area fraction = 1.000
+++++++++++++++++++++++++++++++++++++++ + + + + + + + + + + + + + + + + + + + + + + + + + + + + + ++
Process from Point /Station 30.000 to Point /Station 60.000
* * ** SUBAREA FLOW ADDITION - BUILDABLE AREA - AREA "B" * * **
SINGLE FAMILY (1/4 Acre Lot)
Runoff Coefficient = 0.872
Decimal fraction soil group A = 0.000
Cecimal fraction soil group B = 0.000
Decimal fraction soil group C = 0.000
Decimal fraction soil group D = 1.000
R.I index for soil(AMC 2) = 75.00
Pervious area fraction = 0.500; Impervious fraction = 0.500
Time of concentration = 5.16 min.
Rainfall intensity = 6.635(In /Hr) for a 100.0 year storm
Subarea runoff = 5.842(CFS) for 1.010(Ac.)
Total runoff = 18.487(CFS) Total area = 3.180(Ac.)
+++++++++++++++++++++++++++++++++++++++++ + + + + + + + + + + + + + + + +- F + + + +.- + + + + + ++
Process from Point /Station 20.000 to Point /Station 50.000
* * ** PIPEFLOW TRAVEL TIME (Program estimated size) * * **
Upstream point /station elevation = 62.780(Ft.)
Downstream point /station elevation = 59.200(Ft.)
Pipe length = 395.00(Ft.) Manning's N = 0.012
No. of pipes = 1 Required pipe flow = 18.487(CFS)
Nearest computed pipe diameter = 24.00(In.)
Calculated individual pipe flow = 18.487(CFS)
Normal flow depth in pipe = 16.13(In.)
Flow top width inside pipe = 22.54(In.)
Critical Depth = 18.58(In.)
Pipe flow velocity = 8.24(Ft /s)
Travel time through pipe = 0.80 min.
Time of concentration (TC) = 5.96 min.
+++++++++++++++++++++++++++++++++++++++ + + + + + + + + + + + + + + + + + + + + + + + + + + + + + ++
Process from Point /Station 20.000 to Point /Station 50.000
* * ** CONFLUENCE OF MINOR STREAMS * * **
Along Main Stream number: 1 in normal stream number 1
Stream flow area = 3.180(Ac.)
Runoff from this stream = 18.487(CFS)
Time of concentration = 5.96 min.
Rainfall intensity = 6.104(In /Hr)
Summary of stream data:
Stream Flow rate TC Rainfall Intensity
No. (CFS) (min) (In /Hr)
1 18.487 5.96 6.104
' Largest stream flow has longer time of concentration
Qp = 18.487 + sum of
Qp = 18.487
' Total of 1 streams to confluence:
Flow rates before confluence point:
18.487
' Area of streams before confluence:
3.180
Results of confluence:
Total flow rate = 18.487(CFS)
' Time of concentration = 5.964 min.
Effective stream area after confluence = 3.180(Ac.)
� a
1
u
++++ ...... i. +.l-... } } -I-........ . + } } +... i.........}.......... + } } ++ }.. .....{_ ...r .
Process from Point /Station 40.000 to Point /Station 50.000
* * ** INITIAL AREA EVALUATION AREA "C" * * **
Initial area flow distance = 265.200(Ft.)
Top (of initial area) elevation = 210.000(Ft.)
Bottom (of initial area) elevation = 59.200(Ft.)
Difference in elevation = 150.800(Ft.)
Slope = 0.56863 s(percent)= 56.86
TC = k(0.530) *[(length ^3) /(elevation change)] ^0.2
Initial area time of concentration = 5.530 min.
Rainfall intensity = 6.378(In /Hr) for a 100.0 year storm
UNDEVELOPED (poor cover) subarea
Runoff Coefficient = 0.877
Decimal fraction soil group A = 0.000
Decimal fraction soil group B = 0.000
Decimal fraction soil group C = 0.000
Decimal fraction soil group D = 1.000
RI index for soil(AMC 2) = 89.00
Pervious area fraction = 1.000; Impervious fraction = 0.000
Initial subarea runoff = 10.519(CFS)
Total initial stream area = 1.880(Ac.)
Pervious area fraction = 1.000
+++++++++++++++++++++++++++++++++++++++ + + + + + + + + + + + + + + + + + + + + + + + + + + + + + ++
Process from Point /Station 60.000 to Point /Station 80.000
* * ** SUBAREA FLOW ADDITION - BUILDABLE AREA "D" * * **
SINGLE FAMILY (1/4 Acre Lot)
Runoff Coefficient = 0.871
Decimal fraction soil group A = 0.000
Decimal fraction soil group B = 0.000
Decimal fraction soil group C = 0.000
Decimal fraction soil group D = 1.000
RI index for soil(AMC 2) = 75.00
Pervious area fraction = 0.500; Impervious fraction = 0.500
Time of concentration = 5.53 min.
Rainfall intensity = 6.378(In /Hr) for a 100.0 year storm
Subarea runoff = 4.887(CFS) for 0.880(Ac.)
Total runoff = 15.406(CFS) Total area = 2.760(Ac.)
+++++++++++++++++++++++++++++++++++++++ + + + + + + + + + + + + + + + + + + + + + + + + + + + + + ++
Process from Point /Station 40.000 to Point /Station 50.000
* * ** CONFLUENCE OF MINOR STREAMS * * **
Along Main Stream number: 1 in normal stream number 2
Stream flow area = 2.760(Ac.)
Runoff from this stream = 15.406(CFS)
Time of concentration = 5.53 min.
' Rainfall intensity = 6.378(In /Hr)
Summary of stream data:
Stream Flow rate TC Rainfall Intensity
No. (CFS) (min) (In /Hr)
I
u
1
+++++++++++++++++++++++++++++++++++++++ + + + + + + + + + + + + + + + + + + + + + + + + + + + + + ++
Process from Point /Station 50.000 to Point /Station 100.000
* ** PIPEFLOW TRAVEL TIME - TO GOLF COURSE LAKE Program estimated
size) * **
Upstream point /station elevation = 46.500(Ft.)
Downstream point /station elevation = 30.350(Ft.)
Pipe length = 318.80(Ft.) Manning's N = 0.012
No. of pipes = 1 Required pipe flow = 33.233(CFS)
Nearest computed pipe diameter = 21.00(In.)
Calculated individual pipe flow = 33.233(CFS)
Normal flow depth in pipe = 15.00(In.)
Flow top width inside pipe = 18.97(In.)
Critical depth could not be calculated.
Pipe flow velocity = 18.06(Ft /s)
Travel time through pipe = 0.29 min.
Time of concentration (TC) = 6.26 min.
End of computations, total study area = 5.940 (Ac.)
10
1 18.487 5.96 6.104
2 15.406 5.53 6.378
Largest stream flow has longer time of concentration
Qp = 18.487 + sum of
'
Qb Ia /Ib
15.406 * 0.957 = 14.745
Qp = 33.233
Total of 2 streams to confluence:
Flow rates before confluence point:
18.487 15.406
Area of streams before confluence:
'
3.180 2.760
Results of confluence:
Total flow rate = 33.233(CFS)
'
Time of concentration = 5.964 min.
Effective stream area after confluence = 5.940(Ac.)
I
u
1
+++++++++++++++++++++++++++++++++++++++ + + + + + + + + + + + + + + + + + + + + + + + + + + + + + ++
Process from Point /Station 50.000 to Point /Station 100.000
* ** PIPEFLOW TRAVEL TIME - TO GOLF COURSE LAKE Program estimated
size) * **
Upstream point /station elevation = 46.500(Ft.)
Downstream point /station elevation = 30.350(Ft.)
Pipe length = 318.80(Ft.) Manning's N = 0.012
No. of pipes = 1 Required pipe flow = 33.233(CFS)
Nearest computed pipe diameter = 21.00(In.)
Calculated individual pipe flow = 33.233(CFS)
Normal flow depth in pipe = 15.00(In.)
Flow top width inside pipe = 18.97(In.)
Critical depth could not be calculated.
Pipe flow velocity = 18.06(Ft /s)
Travel time through pipe = 0.29 min.
Time of concentration (TC) = 6.26 min.
End of computations, total study area = 5.940 (Ac.)
10
t
HYDRAULIC A ULIC CALCULATIONS
GROUTED RIPRAP LINED TRAPEZOIDAL CHANNEL
CALCULATIONS
NODE #30 TO NODE #20 AND NODE #60 TO NODE #20
Given Input Data:
Shape ...........................
Trapezoidal
Solving for .....................
Depth of
Flow
'
Flowrate ........................
9.3000
cfs
Slope
0.0100
ft /ft
Manning's n .....................
0.0330
'
Height ......
Bottom width ....................
1.0000
2.5000
ft
ft
Left slope ......................
0.5000
ft /ft (V /H)
Right slope .....................
0.5000
ft /ft (V /H)
'
Computed Results:
Depth ...........................
0.7789
ft
'
Velocity ........................
Full Flowrate
2.9425
15.1338
fps
cfs
Flow area .......................
3.1606
ft2
Flow perimeter ..................
5.9833
ft
Hydraulic radius ................
0.5282
ft
Top width
5.6156
ft
Area ............................
4.5000
ft2
'
Perimeter
Percent full ...:::::;: ^::::::::::::
6.9721
77.8888
ft
%
Critical Information
'
Critical depth ..................
Critical slope
0.6327
0.0220
ft
ft /ft
Critical velocity ...............
3.9034
fps
Critical area ...................
Critical perimeter ..............
2.3825
5.3297
ft2
ft
Critical hydraulic radius
0.4470
ft
Critical top width ..............
5.0309
ft
Specific energy ..................
0.9134
ft
'
Minimum energy
0.9491
ft
Froude number ...................
0.6915
Flow condition ..................
Subcritical
n
1
11
91
GROUTED RIPRAP LINED TRAPEZOIDAL CHANNEL CALCULATIONS
NODE #60 TO NODE #50 AND NODE #80 TO NODE #50
Given Input Data:
Shape...........................
Solving for .....................
Flowrate ........................
Slope...........................
Manning's n .....................
Height..........................
Bottom width ....................
Left slope ......................
Right slope .....................
Computed Results:
Depth...........................
Velocity ........................
Full Flowrate ...................
Flow area ................. .......
Flow perimeter ..................
Hydraulic radius ................
"op width .......................
Area............................
Perimeter .......................
Percent full ....................
Critical Informati
Critical depth ..................
Critical slope ..................
Critical velocity ...............
Critical area ...................
Critical perimeter ..............
Critical hydraulic radius .......
Critical top width ..............
Specific energy .................
Minimum energy ..................
Froude number ...................
Flow condition ..................
Trapezoidal
Depth of Flow
7.7000 cfs
0.0100 ft /ft
0.0330
1.0000 ft
2.5000 ft
0.5000 ft /ft (V /H)
0.5000 ft /ft (V /H)
0.7055 ft
2.7908 fps
15.1338 cfs
2.7591 ft2
5.6550 ft
0.4879 ft
5.3219 ft
4.5000 ft2
6.9721 ft
70.5475 %
on
0.5677 ft
0.0226 ft /ft
3.7308 fps
2.0639 ft2
5.0389 ft
0.4096 ft
4.7709 ft
0.82'65 ft
0.8516 ft
0.6833
Subcritical
12