HomeMy WebLinkAboutPD 2019-0037; CANHAM RESIDENCE; HYDROLOGY & HYDRAULIC REPORT; 2020-01-27HYDROLOGY & HYDRAULICS
REPORT
PROJECT:
Canham Residence
7164 Aviara Drive, Carlsbad
PD201 9-0037
GR2019-00042, DWG 52l6ATTl
APN: 215-610-20-00 MAR 16 ZOZJ
LAND DEv LOPMENT
ENGINLERING
PREPARED FOR:
Tom and Ellen Canham
285 Grande Way, Apt. 1804
Naples, FL 34110
PREPARED BY:
Kristin L. Greene, P.E.
dk GREENE CONSULTING, INC.
P.O. Box 143
Bonsall, CA 92003
J.N. 19-01
I hereby declare that Jam the engineer of work for this project, that I have exercised responsible
I
charge over the design of the project as defined in Section 6703 of the Business and Professions code,
and that the design is consistent with current standards.
cESSj
PSk
161 LD II
NO C57860 *
dkGreene
Consulting, Inc.
January 27, 2020
Kristin L. Greene, P.E. C57860 Date EXPIRES: JUNE 30, 2020
CONTENTS
1.0 PROJECT INFORMATION ..........................................................................................................1
1.1 SITE AND PROJECT DESCRIPTION .........................................................................................................1
1.2 ExISTING SITE TOPOGRAPHY AND DRAINAGE CONDITION........................................................................3
1.3 PROPOSED SITE TOPOGRAPHY AND DRAINAGE CONDITION .....................................................................5
2.0 HYDROLOGY AND HYDRAULIC CALCULATIONS.........................................................................5
2.1 METHOD OF CALCULATION ................................................................................................................5
2.2 SOIL TYPE, IMPERVIOUSNESS, SELECTION OF "C" ..................................................................................6
2.3 SUMMARY TABLE OFQ VALUES .......................................................................................................... 7
3.0 REPORT SUMMARY .................................................................................................................7
3.1 RECOMMENDATIONS ........................................................................................................................7
APPENDIXA.........................................................................................................................................9
EXISTINGHYDROLOGY MAP..........................................................................................................................10
PROPOSEDHYDROLOGY MAP........................................................................................................................11
APPENDIX B .......................................................................................................................................12
HYDROLOGY CALCULATION SPREADSHEET .......................................................................................................13
COUNTY OF SAN DIEGO HYDROLOGIC TABLES AND FIGURES 100 YEAR RAINFALL EVENT -6 HOURS ........................14
COUNTY OF SAN DIEGO HYDROLOGIC TABLES AND FIGURES 100 YEAR RAINFALL EVENT —24 HOURS ......................15
SOILS MAP FROM NRCS WEB SOIL SURVEY ....................................................................................................21
LIST OF FIGURES
FIGURE1-1. VICINITY MAP ..................................................................................................................................................1
FIGURE1-2. GOOGLE EARTH PLAN VIEW................................................................................................................................2
FIGURE 1-3. THE SITE LOOKING EASTERLY TOWARD AVIARA DRIVE..............................................................................................3
FIGURE 1-4. ExIsTING OUTLET POINT TO THE WEST..................................................................................................................4
dcGreene
Consulting, Inc.
HYDROLOGY & HYDRAULICS REPORT
I City of Carlsbad
I 1.0 Project Information
1.1 Site and Project Description
I This project provides for the development of a one-story single-family home with an
attached garage.
I A vicinity map is shown below.
VICINITY MAP
Figure 1-1. Vicinity Map
I
The lot is surrounded on the north, south and west by existing single-family residences
I of the same type. On the east, there is an existing golf course and an environmentally
sensitive area.
I This report will focus on the Drainage Study in response to the grading and
improvements associated with the development. In the pre-development condition, the
site has two basins that outlet to the east and to the west. In the post-development
I I ciGreene
Consulting, Inc.
condition, the site will drain toward the street in order to protect the environmental
sensitive area toward the west.
This report will evaluate the Qioo for the existing condition and compare it to the Qioo for
the proposed condition by using the Modified Rational Method and County of San
Diego's Hydrology Manual to evaluate peak flows.
7164AviaraDr ,
IV
I&i
: .
cc:
. 't.lp- ...,.- .. ....
jii s • 1 •
1 :
:7
if '.
:igure 1-2. Google Earth Plan View
2 .-.
Consuluny,
1.2 Existing Site Topography and Drainage Condition
Topography of the site was provided by Dale Greene, [S. The site has approximately
8 feet of elevation difference from the higher elevation at the north property line, to
lowest elevation at the east property line
Figure 1 3 The Site looking Westerly Toward Aviara Drive
The site is currently giaded per Cailsbad Tract Map 85-35. ihere is an existing fill slope
on the northerly property line and a fill slope along the southerly property line.
Generally, the existing 15,788 sq. ft. site drains partially westerly and partially easterly.
There is no "run-on" associated with this site.
2
-
I
1'
Figure 1-4. Existing Outlet Poini to the East
See Appendix A, Existing Hydrology Map.
Li ieer
Consulting, Inc.
I 1.3 Proposed Site Topography and Drainage Condition
The proposed grading and drainage pattern will mimic the existing drainage condition
and pattern, to the maximum extent practicable. The existing grading will be maintained.
I The site will be developed with a one-story single-family home.
All the runoff from the lot (0.36 ac.) will drain to the west (Basin A). Basin A (0.19 ac) is
divided into three drainage sub-basins, A-i, A-2, A-3 will drain westerly toward the
existing street and into public drainage system.
See Appendix A, Proposed Hydrology Map.
2.0 Hydrology and Hydraulic Calculations
2.1 Method of Calculation
This Hydraulics & Hydrology Report was prepared using the following Manual:
"San Diego County Hydrology Manual, June 2003."
The Rational Method was used to determine the 100-year Storm Q values. The Rational
Method uses the following formula to establish 100-year flow:
Q = C I A
where:
Q = The peak runoff in cubic feet per second.
C = Runoff coefficient representing the ration of runoff to rainfall.
= Time average intensity in inches per hour.
A = Area of sub-basin in acres.
5 dcGreene Consulting, Inc.
I
I
I
I
2.2 Soil Type, Imperviousness, Selection of "C"
I According to the soils report prepared for this project, by David Skelly of GeoSoils, Inc,
the soils Group should be classified as "D".
I According to the United States Department of Agriculture Natural Resources
Conservation Service Web Soil Survey online tool, the site soil is classified as "Soil
I
Group D". See Appendix B, Soils Map. The runoff coefficient "C" will be based on this
soils group for both the existing and proposed condition. The "C" for the existing
conditions will be based on 0% imperviousness (Cpre =0.35).
I The proposed condition "C" value will be based on the proposed condition of 54%
impervious (8,448 sq. ft./15,788 sq. ft.) which will result in Cpost = 0.65. See Appendix B,
I County of San Diego Hydrologic Tables and Figures, Table 3-1.
I
I
clGreene
Consulting, Inc. I
I
VICINITY MAP EXISTING HYDROLOGY MAP NTS
I4
APN 215-610-19
LOT 251
MAP 12412
S 82°S506
34.04
— —
L=215 GENERALU11L EASEMENT
PER MAP NO. 12412
-44' GENERAL UTL. & ACCESS
NT PE MAP NO 12412
N 87'31'28" E 170.91
APN2I5-611-01
LOT 253
MAP 12412
A
Ii
-- -- - — - --
dk Greene Consulting, Inc.
P.O. BOX 143
BONSALL, CA 92003
(760) 310-9408
BENCH MARK
DESCRIPTION: ELEVATIONS ARE BASED ON MONUMENT NO. CLSB 44
LOCATION:_____________________________________________
RECORDED: RECORD OF SURVEY 17271
ELEVATION: 240.26 DATUM:_NGVD 1929
7860
dREEME
/
"AS BUILT"
RCE _______ EXP._________ DATE
REVIEWED BY:
INSPECTOR . DATE
SHEET CITY OF CARL$BA SHEETS
1 ENGINEERING DEPARTMENT 1
EMOTWO HYDROLO(Y PLAN FOR:
CANHAM RESIDENCE
7164 AVIARA DRIVE
GR2019-0042
APPROVED: JASON S. GELDERT
CITY ENGINEER RCE 63912 EXPIRES 9/30/20 DATE
DWN BY: PROJEC NO. CHKDBY: To
DRAWING NO.
RVWD BY:
DATE INITIAL
REVISION DESCRIPTION I OTHER
DATE INITIAL DATE INITIAL
ENGINEER OF WORK APPROVAL CITY APPROVAL
.••.
.•
:..: •..... . ...
OS D HYDROLOGY MAP VICINITY MAP
NTS
EXISTING SINGLE FAMILY RESIDENCE BASIN "A-5"
0.10 ACRES (4,354 SF)
TOP-246.39/
RflTTflM=41
BASIN "A-2"
0.01 ACRES (561 SF)
TOP=
BOTTOM=
T _1 f?
APN 215-610-19
LOT 251
MAP 12412
- > - - -
-
L=215
EX. CONCRETE CURB,
GUTTER AND SIDEWALK
EX. FIRE HYDRANT—
BASIN "A-4"
0.10 ACRES (4,184 SF)
TOP=246.58
BOTTOM=242. 17
L= 1
44 GENERAL UTIL. EASEMENT
PER MAP NO. 12412
EX. WATER GATE VALVE
(247
EXISTJNG CONCRETE
DRIV WAY APRON
(TO REMAIN)
U,
U)......
U)
Uj
Uj
(I)>
ev
Wu
CIS
EX SEWERMHi
LL PRORI
DEVIC9
..........S.
..,....
S.
E
.5
11
i
0•
10
0
I
-
/N
/
LU /
10
iN
/ '0
V (I)
/
/
)UGHT IRON FENCE
(24100 1
I
A1241.04
SIDEWA
SIDEWALK DRAIN PIPE PE
QA(100)=1.02 cfs
JO F; INT TO JOINT
4' WIDE EASEMENT DEDICATED TO
PACIFICL BELL PER DOC. NO.
1990-0636009 DATED 11/29/1990
___ ThAC1T'KTt
I--j
2t LOT 253 tiP11N MAP 12412 0.05 ACRES (2,206 SF)
TOP=
BOTTOM=
L=30'
dk Greene Consulting, Inc.
P.O. BOX 143
BONSALL, CA 92003
(760) 310-9408
BENdH MARK
0 10 20 30
r 1.—
1
dGreene
consulting, Inc3
DESCRIPTION: ELEVATIONS ARE BASED ON MONUMENT NO. CLSB 44
LO CA TION:
RECORDED: RECORD OF SURVEY 17271
ELEVATION: 240.26 DATUM.-NGVD 1929
ry )
LIr0R'
"AS BUILT
RCE ____ ______ EXP.__________ DATE
REVIEWED BY :
INSPECTOR DATE
CITY OF CARL$BAD SHEETS
1 ENGINEERING DEPARTMENT 1
PR0POED HYDR0L0(Y PLAN FOR:
CANHAM RESIDENCE
7164 AVIARA DRIVE
GR2019-0042
APPROVED: JASON S. GELDERT
CITY ENGINEER RCE 63912 EXPIRES 9/30/20 DATE
DWN BY: PROJECT NO. DRAWING NO.
cI P02019-0037 521 -64
DATE INITIAL
REVISION DESCRIPTION
DATE INITIAL DATE INITIAL
ENGINEER OF WORK APPROVAL
CHK
OTHER CITY APPROVAL
-- ... -...-........---.-.....,. -- 1•........-. _._._....._.._._. . ........- ....-.-.. ..-..-......-...-... ....-... --...-..-.-.-.... ...-.......-
.-..... ..-...-..-..-,.,.......-.. __________________ - ...---.,-..-.-.----i.....,-.-..S..,.---- ..-. ..
.. ..._-.-..-...-i.-.....---....j---..... ., .
- _________________________-.. ......... .-_-...,
2.3 Summary Table of Q Values
Calculations were conducted for this project and are provided in the spreadsheet table
in the Appendices.
PRE VS. POST SUMMARY
Node
Pre Development
Discharge QIOO I Post Development I Difference
(cfs) Discharge QIOO (cfs) I (cfs)
Basin A 0.58 1.15 I
+0.57
I
The difference between the pre and post condition is shown above. The development
increases the impervious area. The existing storm drain system in Aviara Drive was
sized to accommodate this infill project and this increase in runoff for Basin A.
I
Calculations and maps of the existing and proposed hydrology are provided in
Appendices A and B.
I
3.0 Report Summary
3.1 Recommendations
This development project encompasses a single-family home, driveway and landscaped
areas on approximately 15,788 sq. ft. The proposed development does increase the
impervious surface and therefore generates an increase in runoff. However,
downstream facilities were sized and located to handle ultimate development and
therefore can accommodate the additional runoff created by this development.
In my professional opinion, the proposed project will not substantially alter the existing
drainage pattern of the area. The project has been designed to maintain the historical
drainage pattern. The small increase from the existing condition to the post-
development condition will not create downstream flooding or overwhelm the existing
drainage facilities due to the development of this project.
7 9 dGreene
Consulting, Inc.
APPENDICES
c Ic Greene
Consulting, Inc.
Appendix A
Existing Hydrology Map
Proposed Hydrology Map
9 dGreene - Consulting, Inc.
Appendix B
Hydrology Calculation Spreadsheet
County of San Diego Hydrologic Tables and Figures
Soils Map
12 ITicLGreene Consulting, Inc.
- - - - - - - - - - - - - - - - - - -
Hydrology Calculation Spreadsheet
PRE DEVELOPMENT CONDITION SUMMARY
SYSTEM AREA
(AC) C
U/S
ELEVATION
(Fr)
1)/S
(Fr)
ELEVATION LENGTH
(FT)
SLOPE
(%)
P 6
(IN)
Ti from
Figure 3-3
TC
(MIN) 3-4
SUM
OF T
(MIN)
I
(IN/HR)
Q
(CFS)
Basin A 100 yr 0.34 0.35 252.0 243.5 125.0 6.8 2.5 8.0 0.0 8.0 4.9 0.58
Total Area 0.34 j I Basin A Total Q 0.58
POST DEVELOPMENT CONDITION SUMMARY
SYSTEM AREA
(AC) C
U/S
ELEVATION
(Fr)
0/S
ELEVATION
(Fr)
LENGTH
(Fr)
SLOPE
(%)
P6
(IN)
Ti from
Figure 3-3
TC
(MIN) 3.4
SUM
OF T
(MIN)
I
(INIHR)
Q
(CFS)
BASIN A
Basin A-I 100 yr 0.12 0.65 247.1 246.9 16.0 1.2 2.5 3.0 0.0 5.0 6.6 0.51
Basin A-2 100 yr 0.10 0.65 246.6 243.0 146.0 2.5 2.5 7.3 0.0 7.3 5.2 0.34
Basin A-3looyr 0.10 0.65 246.4 241.0 209.0 2.6 2.5 8.5 0.0 8.5 4.7 0.30
Total Area 0.32 Basin A Total Q 1.15
- Difference in areas is due to theexisting east side slope and the pool, which are self mitigating.
Pre Post Difference
Basin 100 yr 0.58 1.15 0.57
13
County of San Diego Hydrologic Tables and Figures
100 Year Rainfall Event— 6 Hours
outy - j
Rede (
-
12
2.5
3)
SIE
Al
41
14
County of San Diego
I lydrology Manual
I?.
100 %*r RdnI&ll Event - 6 Hours
ISCO.ri, ,ec'
Lat. 33°06'
Long. 117°17'
P6 = 2.5
DPW --GIS SanGIS
County of San Diego Hydrologic Tables and Figures
100 Year Rainfall Event— 24 Hours
County I
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County of San Diego
Hydrology Manual
I?ain/al/ I.cop/u via/c
100 Near Rainfall Event 24 Hnurs
Lat. 33°06'
Long. 117°17'
P24 = 4.5
J; SGIS
Directions for Application:
From predpllatlon maps detem*e 61w end 24 1w amounts
for the aeleoted fre,ency. 11*se mws are included In the
CotrtyHoIogyManua1(10, 50, and 100 yr ms.,e included In the Design and Prowl Mont.is4)
Ad)ust 6 he precigitallon (d necessary) so that It is within,
the range of 45% to 65% of the 24 hr precipitation (not appliceple to Desert).
Not 81w preitalion on the right side of the chart.
Draw a line through the point parallel to the plotted lines.
ThIs line is the intensity-duration curve for the location
being -•
Appflcallon Form:
Selected frequenyj year
p P2 =56 %42)
(c)MJustadP6- .Z .in.
(d)Ie_ min.
t
See Appendix B,
(e) I Hydrology Calculation
Soreadsheet
Note: This cited replaces the Into zatlon-Frequency curves used since 1965.
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0.34
0.90 1.19
000 5.00
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1.45
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192
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591
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908
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2.6012.89 239T265
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320
292
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308
316
745
2.0'
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0.30 052
073
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099
079
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1.32 1,47 531
14.4 1.79
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16
- - - - - - - - - - - - - - - - - - -
San Diego County Hydrology Manual Section: 3 Date: June 2003 Page: 6 of 26
Table 3-1
RUNOFF COEFFICIENTS FOR URBAN AREAS
Land Use I Runoff Coefficient "C"
NRCS Elements County Elements % IMPER. A B C D I Existing
Undisturbed Natural Terrain (Natural) Permanent Open Space 0* 0.20 0.25 0.30 0.35 C=0.35
Low Density Residential (LDR) Residential, 1.0 DU/A or less 10 0.27 0.32 0.36 0.41
Low Density Residential (LDR) Residential 2.0 DU/A or less 20 0.34 0.38 0.42 0.46
Low Density Residential (LDR) Residential, 2.9 DU/A or less 25 0.38 0.41 0.45 0.49
Medium Density Residential (MDR) Residential. 4.3 DU/A or less 30 0.41 0.45 0.48 0.52
Medium Density Residential (MDR) Residential, 7.3 DU/A or less 40 0.48 0.51 0.54 0.57
Medium Density Residential (MDR) Residential 10.9 DU/A or less 45 0.52 0.54 0.57 0.60 Proposed
Medium Density Residential (MDR) Residential, 14.5 DU/A or less 50 0.55 0.58 0.60 0.63 C=0.65
65 0.66 0.67 0.69 0.71 High Density Residential (HDR) Residential, 24.0 DU/A or less
High Density Residential (HDR) Residential, 43.0 DU/A or less 80 0.76 0.77 0.78 0.79
Commercial/Industrial (N. Corn) Neighborhood Commercial 80 0.76 0.77 0.78 0.79
Commercial/Industrial (G. Corn) General Commercial 85 0.80 0.80 0.81 0.82
Commercial/Industrial (O.P. Corn) Office Professional/Commercial 90 0.83 0.84 0.84 0.85
Commercial/industrial (Limited I.) Limited industrial 90 0.83 0.84 0.84 0.85
Commercialflndustrial (General L) General Industrial 95 0.87 0.87 0.87 0.87
*The values associated with 0% impervious may be used for direct calculation of the runoff coefficient as described in Section 3.1.2 (representing the pervious runoff
coefficient, Cp, for the soil type), or for areas that will remain undisturbed in perpetuity. Justification must be given that the area will remain natural forever (e.g., the area
is located in Cleveland National Forest).
DU/A dwelling units per acre
NRCS = National Resources Conservation Service Existing Impervious Surface = 0% impervious - C = 0.35 I I Proposed Impervious Surface = 8,448 sq.ft. = 0.54 => C = 0.65 I 15,788 sq.ft.
17
Table 3-2
MAXIMUM OVERLAND FLOW LENGTH (L 1)
& INITIAL TIME OF CONCENTRATION (Ti)
Element* DU/
Acre
.5% 1% 2% 3% 5% 10%
LM T1 LM T1 LM T1 LM TiLM T1 LM T1
Natural 50 13.2 70 12.5 85 10.9 100 10.3 100 8.7 100 6.9
LDR 1 50 12.2 70 11.5 85 10.0 100 9.5 100 8.0 100 6.4
LDR 2 50 11.3 70 10.5 85 9.2 100 8.8 100 7.4 100 5.8
LDR 2.9 50 1 10.7 70110.0 851 8.8 95 8.1 100 7.0 100 5.6
MDR 4.3 50 10.2 70 9.6 80 8.1 95 7.8 100 6.7 100 5.3
MDR 7.3 501 9.2 65 8.4 80 7.4 95 7.0 100 6.0 100 4.8
MDR 10.9 50 8.7 65 7.9 80 6.9 90 6.4 100 5.7 100 4.5
MDR 14.5 50 8.2 65 7.4 80 6.5 90 6.0 100 5.4 100 4.3
HDR 24 50 6.7 65 6.1 75 5.1 90 4.9 95 4.3 100 3.5
HDR 43 50 5.3 65 4.7 75 4.0 1 85 3.8 1 95 3.4 1 100 2.7
N. Corn 50 5.3 60 4.5 75 4.0 85 3.8 95 3.4 100 2.7
G. Corn 50 4.7 60 4.1 75 3.6 85 3.4 90 2.9 100 2.4
O.P.ICom 50 4.2 60 3.7 70 3.1 80 2.9 90 2.6 100 2.2
Limited I. 50 4.2 60 3.7 70 3.1 1 80 1 2.9 90 2.6 100 2.2
General I. 1 501 3.7 60 3.2 70 1 2.7 801 2.61 90 2.3 100 1.9
See Table 3-1 for more detailed description
18
- - - - - - - - - - - - - - - - - - -
30
Cl)
W w D z 0 20
z
o 1 0 -J
:10
o
w
0
0
EXAMPLE:
Given: Watercourse Distance (D) = 70 Feet
Slope (s)1.3% 1.8 - Runoff Coefficient (C) = 0.41 T -
S Overland Flow Time (1) = 9.5 Minutes
SOURCE: Airport Drainage. Federal Aviation Administration, 1965
Rational Formula - Overland Time of Flow Nomograph
1
19
F I G U R E
3111113
2.0
100 FAA V Pr
VOO4- C)CC
- - - - - - - - - - - - - - - - - - -
EQUATION
AE /II.9L0°.3BS Feet T C
:-5000 Te = Tim. of conc.ntr.tion b0w,)
I Wat.rcou,se 005tinco fmls)
E Change ln elevation along effective slope line (See Figure 3-5)(1040 —3009 To
• Hours Minutes
—2005 ' -240
3— -100
- —1000
NO 2
1400
- -
-to.
.90
_500\ -so
—410 • \ -70
1- -60 —300 -50
—200 -40
I. \Mlles met -30
l.. —100
4z 4000 —20
-to -3000 -to
-50 14 0.5-- \
-40 2100 -12
ON 'S
-30 -1900 'S -10 -1400
.1200 -e 20 .I000 .900 -000 -0
709
-600 -5
-so .-500
400
-300
-200
I Ic
SOURCE: CWon4s Division of l0ghwse (1941) and Kpid, (1940)
FIGURE
Homograph for DeteeMnatlon of I Time of Concentralon (To) Cr Travel lime (11) for NattxatV.foteisheds
20
Soils Map from NRCS Web Soil Survey
This property was
determined to be
Hydrologic Soil Group D
per the United States
Department of Agriculture
Natural Resources
Conservation Service
(NRCS) Web Soil Survey
online tool.
Absence of an entre r'idicatec that the data were not estimated The dash indcates no to:imented presence
San Diego County Area, California
Map symbol and soil name Pct. of map unit Surface Runoff Hydrologic Soil Group
CfC—Chesterton fine sandy loam, 5 to 9 percent slopes
Chesterton 85 Very high D
LvF3—Loamy alluvial land- Huerhuero complex, 9 to 50 percent slopes,
severely eroded
Huerhuero 30 Very high D
Loamy alluvial land 30 High B
21
1/28/2020 Open Channel Flow Calculator
The open channel flow calculator
Select Channel Type:
T
D .r ____ Circle " b z2 Az2 8
Rectangle Trapezoid Triangle Circle
I Depth from Q VI unit system:
_slope: .01
Water depth(y): 0.38 Jft :] [R:ad—ius_(r) .25 Channel
ft ft
Flow _velocit312496
LeftS1ope (Zi): Ito 1 (H:V)
RightSlope (Z2): I
Flow_discharge ;51
Jft L9selectnI A3/S
Input n value . 013
F icuiateT Status:ICalculation finished ] I Reset
Wetted_perimeter 1.05 I
area 0.16 JftA2 Top width(T) 0.43
F
Flow
Specific energy 0.54
Froude numberO.94
Flow status
Subcritical flow -
Critical depthio.37
________ I
. . Critical slope 0.0104 Velocity headlo.16
Copyright 2000 Dr. Xing Fang, Department of Civil Engineering, Lamar University.
6' pipe okay for all Basin A
www.eng.auburn.edu/—xzf0001/HandbookiChannels.html 1/1