HomeMy WebLinkAboutPUD 2024-0002; CHERRY BEACH HOMES; FINAL HYDROLOGY STUDY; 2025-06-01
FINAL HYDROLOGY STUDY
FOR
CARLSBAD TRACT (TENTATIVE MAP) / SITE DEVELOPMENT PERMIT /
COASTAL DEVELOPMENT PERMIT
180 CHERRY AVENUE
MS 2024-0003 / PUD 2024-0002 / CDP 2024-0016 / SDP 2024-0013
GR 2024-0024
DWG 550-1A
CITY OF CARLSBAD, CA
PREPARED FOR:
RINCON CAPITAL
5315 AVENIDA ENCINAS, SUITE 200
CARLSBAD, CA 92008
PH: (888) 357-3553
PREPARED BY:
PASCO LARET SUITER & ASSOCIATES, INC.
1911 SAN DIEGO AVE
SAN DIEGO, CA 92110
PH: (858) 259-8212
FINAL: JUNE 2025
___________________________________________
Bryan A. Knapp, RCE 86542 DATE
06/2025---------------------
PLSA 4099
TABLE OF CONTENTS
SECTION
Executive Summary 1.0
Introduction 1.1
Existing Conditions 1.2
Proposed Project 1.3
Conclusions 1.4
References 1.5
Methodology 2.0
Introduction 2.1
County of San Diego Criteria 2.2
City of Carlsbad Standards 2.3
Runoff Coefficient Determination 2.4
Hydrology & Hydraulic Model Output 3.0
Pre-Developed Hydrologic Model Output (100-Year Event) 3.1
Post-Developed Hydrologic Model Output (100-Year Event) 3.2
Appendix 4.0
Appendix A: Hydrology Support Material
Appendix B: 100-Year Storm Event Detention Analysis
PLSA 4099
Page 1 of 7
1.0 EXECUTIVE SUMMARY
1.1 Introduction
This Final Hydrology Study for the proposed development at 180 Cherry Ave. has been
prepared to analyze the hydrologic and hydraulic characteristics of the existing and
proposed project site. This report intends to present both the methodology and the
calculations used for determining the runoff from the project site in both the pre-developed
(existing) conditions and the post-developed (proposed) conditions produced by the 100-
year, 6-hour storm.
1.2 Existing Conditions
The subject property is located at the intersection of Cherry Ave and Garfield Street. The
site is adjacent to residential properties to the north and west, Cherry Ave to the south and
Garfield Street to the east. The existing site consists of two single-family residences,
driveways and related hardscape. Natural vegetation onsite is made up of several trees, low
shrubs, and grass. The project site is located within the Agua Hedionda Hydrologic Area,
and, more specifically, the Los Monos Hydrologic Sub-Area (904.31) of the Carlsbad
watershed.
The existing site is comprised of approximately 0.179 acres. Based on a study of the
existing topography, the western portion of the site generally flows south to Cherry Ave;
and the eastern portion of the site generally flows easterly toward Garfield Street. The
runoff of the eastern portion follows the curb return and continues onto Cherry Ave. There
does not appear to be any existing storm drain infrastructure located onsite to convey
drainage, and runoff sheet flows through the site. The point of confluence for the entire site
is the southwestern corner of the property. Once in the Cherry Ave right-of-way, drainage
flows westerly onto Carlsbad Blvd entering an existing public storm drain curb inlet where
it enters the buried pipe network. From here, drainage is routed south to ultimately outlet
in the Agua Hedionda Lagoon prior to entering the Pacific Ocean.
Drainage Basin EX-1 is approximately 0.179 acres in size and 62% impervious. Per the
Web Soil Survey application available through the United States Department of
Agriculture, the area is generally categorized to have group B soils. Based upon soil type
B and the amount of existing impervious area onsite, a runoff coefficient of 0.66 was
calculated for Basin EX-1 using the methodology described in section 3.1.2 of the San
Diego County Hydrology Manual and the formula provided therein. Using the Rational
Method Procedure outlined in the San Diego County Hydrology Manual, a peak flow rate
and time of concentration was calculated for the drainage basin for the 100-year, 6-hour
storm event. Table 1 below summarizes the results of the Rational Method calculations.
PLSA 4099
Page 2 of 7
EXISTING DRAINAGE FLOWS
DRAINAGE
AREA
DRAINAGE
AREA
(ACRES)
Q100
(CFS)
I100
(IN/HR)
EX-1 0.179 0.78 6.60
Table 1. Existing Condition Peak Drainage Flow Rates
The peak flow rate for the 100-year, 6-hour storm for Basin EX-1 was determined to be
0.78 cfs with a time of concentration of 5 minutes used to calculate rainfall intensity for
drainage basin of this size and amount of impervious area; discharging the eastern property
line. Refer to pre-development hydrology calculations included in section 3.1 of this report
for detailed analysis and the pre-development hydrology map in Appendix A of this
hydrology report for existing drainage basin delineation and discharge locations.
1.3 Proposed Project
The proposed project includes the demolition of existing homes, hardscape, and clearing
of all onsite vegetation and the construction of 3 new single-family residential units. Site
grading along with drainage and utility improvements typical of this type of residential
development will also be constructed.
Similar to the existing condition, runoff from the proposed development will be directed
from east to west through a storm drain system and collected into a storm drain catch basin
before releasing onto Cherry Ave via a sidewalk underdrain. Runoff generated from the
proposed roof areas and hardscape will be directed to landscaped areas prior to being
collected via storm drain inlets. Once discharged from the subject property, runoff will
continue downstream through the neighboring properties as it does in the existing
condition, ultimately draining to Carlsbad Blvd and entering the curb inlet and continue to
the Agua Hedionda Lagoon. The proposed impervious area and total runoff is less than the
existing condition. No biofiltration system is required, however a trash capture system will
be implemented in the storm drain catch basin prior to discharging onto the street.
Similar to the existing condition, the analyzed watershed can be categorized into one major
drainage basin with one eventual discharge location from the subject property sheet
flowing toward the western property line. As in the pre-developed condition, Basin PR-1
is 0.179 acres in size, and is approximately 57% impervious. Based upon soil type B and
the amount of proposed impervious area onsite, a runoff coefficient of 0.62 was calculated
for the entire site using the methodology described in section 3.1.2 of the San Diego County
Hydrology Manual and the formula provided therein. Using the Rational Method
Procedure outlined in the San Diego County Hydrology Manual, a peak flow rate and time
of concentration was calculated for the post-development 100-year, 6-hour storm event.
Table 2 below summarizes the results of the Rational Method calculations.
PLSA 4099
Page 3 of 7
PROPOSED DRAINAGE FLOWS
DRAINAGE
AREA
DRAINAGE
AREA
(ACRES)
Q100
(CFS)
I100
(IN/HR)
PR-1 0.179 0.73 6.6
Table 2. Proposed Condition Peak Drainage Flow Rates
The peak flow rate for the 100-year, 6-hour storm for the entire Basin PR-1 was determined
to be 0.73 cfs with a time of concentration of 5 minutes used to calculate rainfall intensity
for drainage basin of this size and amount of impervious area discharging from the site.
1.4 Conclusions
Based upon the analysis included in this report, the proposed condition outputs less runoff
than the existing condition; therefore, there is no basin proposed for this project. The site
drainage will be captured via a network of storm drain pipes that leads into a storm drain
catch basin. A trash capture device will be installed within the catch basin to prevent debris
from being discharged onto the street. There is no diversion of flows, and water leaving
any portion of the site eventually is conveyed through the neighboring land in the same
methods that exist currently. Once leaving the project site, drainage continues west further
downstream through the adjacent property to enter the City’s public storm drain system by
means of an existing curb inlet located on Carlsbad Blvd. From here, the buried pipe
network conveys storm water to the ultimate outlet location in the Agua Hedionda Lagoon.
PLSA 4099
Page 4 of 7
1.5 References
“San Diego County Hydrology Manual”, revised June 2003, County of San Diego,
Department of Public Works, Flood Control Section.
“San Diego County Hydraulic Design Manual”, revised September 2014, County of San
Diego, Department of Public Works, Flood Control Section
“Engineering Standards, Volume 5: Carlsbad BMP Design Manual”, revised February
2016, City of Carlsbad
Soil Survey Staff, Natural Resources Conservation Service, United States Department of
Agriculture. Web Soil Survey. Available online at http://websoilsurvey.nrcs.usda.gov.
PLSA 4099
Page 5 of 7
METHODOLOGY
2.1 Introduction
The hydrologic model used to perform the hydrologic analysis presented in this report
utilizes the Rational Method (RM) equation, Q = CIA. The RM formula estimates the peak
rate of runoff based on the variables of area, runoff coefficient, and rainfall intensity. The
rainfall intensity (I) is equal to:
I = 7.44 x P6 x D-0.645
Where:
I = Intensity (in/hr)
P6 = 6-hour precipitation (inches)
D = duration (minutes – use Tc)
Using the Time of Concentration (Tc), which is the time required for a given element of
water that originates at the most remote point of the basin being analyzed to reach the point
at which the runoff from the basin is being analyzed. The RM equation determines the
storm water runoff rate (Q) for a given basin in terms of flow (typically in cubic feet per
second (cfs) but sometimes as gallons per minute (gpm)). The RM equation is as follows:
Q = CIA
Where:
Q = flow (in cfs)
C = runoff coefficient, ratio of rainfall that produces storm water
runoff (runoff vs. infiltration/evaporation/absorption/etc)
I = average rainfall intensity for a duration equal to the Tc for the
area, in inches per hour.
A = drainage area contributing to the basin in acres.
The RM equation assumes that the storm event being analyzed delivers precipitation to the
entire basin uniformly, and therefore the peak discharge rate will occur when a raindrop
that falls at the most remote portion of the basin arrives at the point of analysis. The RM
also assumes that the fraction of rainfall that becomes runoff or the runoff coefficient C is
not affected by the storm intensity, I, or the precipitation zone number.
PLSA 4099
Page 6 of 7
2.2 County of San Diego Criteria
As defined by the County Hydrology Manual dated June 2003, the rational method is the
preferred equation for determining the hydrologic characteristics of basins up to
approximately one square mile in size. The County of San Diego has developed its own
tables, nomographs, and methodologies for analyzing storm water runoff for areas within
the county. The County has also developed precipitation isopluvial contour maps that show
even lines of rainfall anticipated from a given storm event (i.e. 100-year, 6-hour storm).
One of the variables of the RM equation is the runoff coefficient, C. The runoff coefficient
is dependent only upon land use and soil type and the County of San Diego has developed
a table of Runoff Coefficients for Urban Areas to be applied to basin located within the
County of San Diego. The table categorizes the land use, the associated development
density (dwelling units per acre) and the percentage of impervious area. Each of the
categories listed has an associated runoff coefficient, C, for each soil type class.
The County has also illustrated in detail the methodology for determining the time of
concentration, in particular the initial time of concentration. The County has adopted the
Federal Aviation Agency’s (FAA) overland time of flow equation. This equation
essentially limits the flow path length for the initial time of concentration to lengths under
100 feet, and is dependent on land use and slope.
2.3 City of Carlsbad Standards
The City of Carlsbad has additional requirements for hydrology reports and drainage plans
which are outlined in the Grading Ordinance. Please refer to this manual for further details.
2.4 Runoff Coefficient Determination
As stated in section 2.2, the runoff coefficient is dependent only upon land use and soil
type and the County of San Diego has developed a table of Runoff Coefficients for Urban
Areas to be applied to basin located within the County of San Diego. The table, included
at the end of this section, categorizes the land use, the associated development density
(dwelling units per acre) and the percentage of impervious area.
PLSA 4099
Page 7 of 7
3.0 HYDROLOGY MODEL OUTPUT
Rational Method Parameters
Runoff Coefficient C= 0.9 x (% Impervious) + Cp (1-% Impervious)*
Cp=0.25* for existing condition pervious type “B” soils
Cn=0.9 for impervious surface
100 Year 6 Hour Storm Precipitation (P6)=2.5 in (see rainfall isopluvial*)
I= Intensity in/hr, I=7.44xP6xD-0.645*
Duration (D)= Time of Concentration, Tc
Q=Peak Runoff, Q=C*I*A (cfs)
*From San Diego County Hydrology Manual, June 2003 Revision
For a conservative measure, Tc is taken as 5 min for residential developments.
Total Area = 7,795sf 0.179 Acres
3.1 Existing Conditions:
Existing Impervious Area= 4,871 sf
CPRE= (4,871* 0.9) + (2,924*0.25)/7,795
CPRE=0.66
Ti = 5 mins
I =7.44(2.5)(5) -0.645
I =6.60 in/hr
Q100= 0.66 * 6.60 in/hr * 0.179 acres
Q100=0.78 cfs
3.2 Proposed Conditions:
Proposed Impervious Area= 4,786 sf
CPost= (4,786* 0.9) + (3,009*0.25)/7,795
CPost=0.65
Ti = 5 mins
I =7.44(2.5)(5) -0.645
I =6.60 in/hr
Q100= 0.65 * 6.60 in/hr * 0.179 acres
Q100=0.77 cfs
TOTAL ∆Q =TOTAL Qpost-TOTAL Qpre
TOTAL ∆Q = 0.77 cfs- 0.78 cfs
TOTAL ∆Q = 0.01 cfs Decrease
Note: The project proposed a reduction of impervious area yielding no need for a
retention basin onsite.
PLSA 4099
Page 2 of 2
4.0 APPENDIX
PROJECT SITE
IL__·-----_--_I
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10.0
9.0
8.0
7.0
6.0
5.0
4.0
3.0
2.0
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0.1
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I =
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EQUATION
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Intensity (in/hr)
6-Hour Precipitation (in)
Duration (min)
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1.0
Intensity-Duration Design Chart -Template
Directions for Application:
(1) From precipitation maps determine 6 hr and 24 hr amounts
for the selected frequency. These maps are included in the
County Hydrology Manual (10, 50, and 100 yr maps included
in the Design and Procedure Manual).
(2) Adjust 6 hr precipitation (if necessary) so that it is within
the range of 45% to 65% of the 24 hr precipitation (not
applicaple to Desert).
(3) Plot 6 hr precipitation on the right side of the chart .
(4) Draw a line through the point parallel to the plotted lines.
(5) This line is the intensity-duration curve for the location
being analyzed .
Application Form:
(a) Selected frequency ___ year
p
(b) p6 = ---in., P24 = ---'P 6 = %(2J
24
(c) Adjusted p6<2l = ___ in.
(d) tx = __ min .
(e) I = __ in./hr .
Note: This chart replaces the Intensity-Duration-Frequency
curves used since 1965.
I
P6 1 1.5 2 2.5 3 3.5 4 4.5 5 5.5 6
Duration I I I I I I I I I I I
5 2.63 3.95 5.27 6.59 7.90 9.22 10.54 11.86 13.17 14.49 15.81
7 2.12 3.18 4.24 5.30 6.36 7.42 8.48 9.54 10.60 11.66 12.72
10 1.68 2.53 3.37 4.21 5.05 5.90 6.74 7.58 8.42 9.27 10.11
15 1.30 1.95 2.59 3.24 3.89 4.54 5.19 5.84 6.49 7.13 7.78
20 1.08 1.62 2.15 2.69 3.23 3.77 4.31 4.85 5.39 5.93 6.46 -25 0.93 1.40 1.87 2.33 2.80 3.27 3.73 4.20 4.67 5.13 5.60
30 0.83 1.24 1.66 2.07 2.49 2.90 3.32 3.73 4.15 4.56 4.98 ~ 0.69 1.03 1.38 1.72 2.0~ 2.41 2.76_ 3.10 3.45 3.79 c---4.13
50 0.60 0.90 1.19 1.49 1.79 2.09 2.39 2.69 2.98 3.28 3.58
60 0.53 0.80 ,_~ 1.33 1.59 1.86 2.12 2.39 2.65 2.92 3.18
90 0.41 0.61 0.82 1.02 TI3 1.43 1.63 1.84 2.04 2.25 2 .45
120 0.34 0.51 0.613_ 0.85 ~ 1.19 1.36 1.53 1.70 1.87 2.04 --f--150 0.29 0.44 0.59 0.73 0.88 1.03 1.18 1.32 1.47 1.62 1.76
180 0.26 0.39 0.52 0.65 0.78 0.91 1.04 1.18 1.31 1.44 1.57
240 0.22 0.33 0.43 0.54 0.65 0.76 0.87 0.98 1.08 1.19 1.30
300 0.19 0.28 0.38 0.47 0.56 0.66 0.75 0.85 0.94 1.03 1.13
360 0.17 0.25 0.33 0.42 0.50 0.58 0.67 0.75 0.84 0.92 1.00
FIGURE ~
San Diego County Hydrology Manual Section: 3 Date: June 2003 Page: 6 of 26
Table 3-1 RUNOFF COEFFICIENTS FOR URBAN AREAS
Land Use Runoff Coefficient “C”
Soil Type
NRCS Elements County Elements % IMPER. A B C D
Undisturbed Natural Terrain (Natural) Permanent Open Space 0* 0.20 0.25 0.30 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
Medium Density Residential (MDR) Residential, 14.5 DU/A or less 50 0.55 0.58 0.60 0.63
High Density Residential (HDR) Residential, 24.0 DU/A or less 65 0.66 0.67 0.69 0.71
High Density Residential (HDR) Residential, 43.0 DU/A or less 80 0.76 0.77 0.78 0.79
Commercial/Industrial (N. Com) Neighborhood Commercial 80 0.76 0.77 0.78 0.79
Commercial/Industrial (G. Com) General Commercial 85 0.80 0.80 0.81 0.82
Commercial/Industrial (O.P. Com) 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
Commercial/Industrial (General I.) 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
3-6
3-3
f-w w LL 0 ~
w
(_) z <( f-(/)
0
w (/) a:: ::::> 0 (_) a:: w i
EXAMPLE:
Given: Watercourse Distance (D) = 70 Feet
Slope (s) = 1.3%
Runoff Coefficient (C) = 0.41
Overland Flow Time (T) = 9.5 Minutes
SOURCE: Airport Drainage, Federal Aviation Administration, 1965
C.:: o.95
T= 1.8(1.1-C)VD
3\fs
(/) w f-::::> z
20 ~
~
w ~
i==
~ 0 _J
LL
Cl 10 z <( _J a:: w > 0
FIGURE
Rational Formula -Overland Time of Flow Nomograph
Hydrologic Soil Group—San Diego County Area, California
Natural Resources
Conservation Service
Web Soil Survey
National Cooperative Soil Survey
1/8/2024
Page 1 of 4
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33° 9' 4'' N
11
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Map projection: Web Mercator Corner coordinates: WGS84 Edge tics: UTM Zone 11N WGS84
0 15 30 60 90Feet
0 5 10 20 30Meters
Map Scale: 1:365 if printed on A landscape (11" x 8.5") sheet.
Soil Map may not be valid at this scale.
USDA =
MAP LEGEND MAP INFORMATION
Area of Interest (AOI)
Area of Interest (AOI)
Soils
Soil Rating Polygons
A
A/D
B
B/D
C
C/D
D
Not rated or not available
Soil Rating Lines
A
A/D
B
B/D
C
C/D
D
Not rated or not available
Soil Rating Points
A
A/D
B
B/D
C
C/D
D
Not rated or not available
Water Features
Streams and Canals
Transportation
Rails
Interstate Highways
US Routes
Major Roads
Local Roads
Background
Aerial Photography
The soil surveys that comprise your AOI were mapped at
1:24,000.
Warning: Soil Map may not be valid at this scale.
Enlargement of maps beyond the scale of mapping can cause
misunderstanding of the detail of mapping and accuracy of soil
line placement. The maps do not show the small areas of
contrasting soils that could have been shown at a more detailed
scale.
Please rely on the bar scale on each map sheet for map
measurements.
Source of Map: Natural Resources Conservation Service
Web Soil Survey URL:
Coordinate System: Web Mercator (EPSG:3857)
Maps from the Web Soil Survey are based on the Web Mercator
projection, which preserves direction and shape but distorts
distance and area. A projection that preserves area, such as the
Albers equal-area conic projection, should be used if more
accurate calculations of distance or area are required.
This product is generated from the USDA-NRCS certified data as
of the version date(s) listed below.
Soil Survey Area: San Diego County Area, California
Survey Area Data: Version 19, Aug 30, 2023
Soil map units are labeled (as space allows) for map scales
1:50,000 or larger.
Date(s) aerial images were photographed: Mar 14, 2022—Mar
17, 2022
The orthophoto or other base map on which the soil lines were
compiled and digitized probably differs from the background
imagery displayed on these maps. As a result, some minor
shifting of map unit boundaries may be evident.
Hydrologic Soil Group—San Diego County Area, California
Natural Resources
Conservation Service
Web Soil Survey
National Cooperative Soil Survey
1/8/2024
Page 2 of 4USDA =
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Hydrologic Soil Group
Map unit symbol Map unit name Rating Acres in AOI Percent of AOI
MlC Marina loamy coarse
sand, 2 to 9 percent
slopes
B 0.2 100.0%
Totals for Area of Interest 0.2 100.0%
Description
Hydrologic soil groups are based on estimates of runoff potential. Soils are
assigned to one of four groups according to the rate of water infiltration when the
soils are not protected by vegetation, are thoroughly wet, and receive
precipitation from long-duration storms.
The soils in the United States are assigned to four groups (A, B, C, and D) and
three dual classes (A/D, B/D, and C/D). The groups are defined as follows:
Group A. Soils having a high infiltration rate (low runoff potential) when
thoroughly wet. These consist mainly of deep, well drained to excessively
drained sands or gravelly sands. These soils have a high rate of water
transmission.
Group B. Soils having a moderate infiltration rate when thoroughly wet. These
consist chiefly of moderately deep or deep, moderately well drained or well
drained soils that have moderately fine texture to moderately coarse texture.
These soils have a moderate rate of water transmission.
Group C. Soils having a slow infiltration rate when thoroughly wet. These consist
chiefly of soils having a layer that impedes the downward movement of water or
soils of moderately fine texture or fine texture. These soils have a slow rate of
water transmission.
Group D. Soils having a very slow infiltration rate (high runoff potential) when
thoroughly wet. These consist chiefly of clays that have a high shrink-swell
potential, soils that have a high water table, soils that have a claypan or clay
layer at or near the surface, and soils that are shallow over nearly impervious
material. These soils have a very slow rate of water transmission.
If a soil is assigned to a dual hydrologic group (A/D, B/D, or C/D), the first letter is
for drained areas and the second is for undrained areas. Only the soils that in
their natural condition are in group D are assigned to dual classes.
Rating Options
Aggregation Method: Dominant Condition
Hydrologic Soil Group—San Diego County Area, California
Natural Resources
Conservation Service
Web Soil Survey
National Cooperative Soil Survey
1/8/2024
Page 3 of 4USDA =
Component Percent Cutoff: None Specified
Tie-break Rule: Higher
Hydrologic Soil Group—San Diego County Area, California
Natural Resources
Conservation Service
Web Soil Survey
National Cooperative Soil Survey
1/8/2024
Page 4 of 4~
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63.28 TW
63.22 TW57.70 TW
57.70 TW
63.11 TW
63.15 TW
63.87 TW
63.25 TW
63.11 TW
61.43 TW
61.34 TW
61.31 TW
63.25 TW
57.81 TW
63.20 TW
63.11 TW
60.55 TC
60.14 FL
60.52 TC
60.12 FL
60.51 TC60.10 FL
60.18 TC60.08 FL
60.21 TC
60.11 FL
60.53 TC60.14 FL
60.56 TC60.11 FL
60.41 TC
59.94 FL
60.42 TC
59.93 FL
60.34 TC59.91 FL
59.84 TC
59.79 FL
60.23 TC
59.76 FL
60.21 TC
59.67 FL
59.96 TC59.27 FL
59.25 TC
58.67 FL
58.67 TC
58.56 FL
57.91 TC57.84 FL
58.33 TC57.77 FL
57.48 TC
56.84 FL
57.04 TC
56.40 FL
56.69 TC
55.89 FL
59.80 FF
59.81 FF
62.11 FF
62.16 FF
85.0 RF
81.9 RF
81.9 RF85.0 RF
76.8 RF
70.9 RF 70.9 RF
73.7 RF
74.3 RF 69.8 RF
75.3 RF
75.4 RF
80.0 RF
80.1 RF
58.53 58.91
59.50
59.52
59.82 60.80
61.13
61.09
61.06
60.28
62.72
59.6258.71
57.92
58.91
58.72
54
.
7
6
58.57
54.80
54.98
57.85
58.76 58.66
59.71 59.66
59.62
59.84
59.82
59.2958.55
58.92
58.19
59.1258.62 59.5557.76
60.92
60.91
60.90
60.88
60.89
60.89
60.60
60.44
60.61
60.75
60.70
60.66
60.94
59.61
57.16
57
58
59
60
61
60
5958
5
8
59
61
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EXISTING
1 STORY
BUILDING
EXISTING
2 STORYBUILDING
EX
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EXISTING
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S55°58'50"W 129.91'
N3
4
°
0
2
'
0
1
"
W
6
0
.
0
1
'
N55°59'13"E 129.91'
S3
4
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0
1
'
5
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E
5
9
.
9
9
'
DMA - "EX-1"
7,795 SF (0.179 AC)
C = 0.66
IMPERVIOUS AREA - BUILDING
FLOW PATH
LEGEND
DMA BOUNDARY
SITE BOUNDARY
PLSA 4099
SCALE: 1" = '
0 604020
20IMPERVIOUS AREA - HARDSCAPE
TOTAL IMPERVIOUS AREA - 4,871 SF
CHERRY AVE
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PASCO LARET SUITER
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San Diego I Encinitas I Orange County
Phone 858.259.8212 I www.plsaengineering.com
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63.22 TW57.70 TW
57.70 TW
63.11 TW
63.15 TW
63.87 TW
63.25 TW
63.11 TW
61.43 TW
61.34 TW
61.31 TW
63.25 TW
57.81 TW
63.20 TW
63.11 TW
60.55 TC
60.14 FL
60.52 TC
60.12 FL
60.51 TC
60.10 FL
60.18 TC
60.08 FL
60.21 TC
60.11 FL
60.53 TC
60.14 FL
60.56 TC
60.11 FL
60.41 TC
59.94 FL
60.42 TC
59.93 FL
60.34 TC
59.91 FL
59.84 TC
59.79 FL
60.23 TC
59.76 FL
60.21 TC
59.67 FL
59.96 TC
59.27 FL
59.25 TC
58.67 FL
58.67 TC
58.56 FL
57.91 TC
57.84 FL
58.33 TC
57.77 FL
57.48 TC
56.84 FL
57.04 TC
56.40 FL
56.69 TC
55.89 FL
59.80 FF
59.81 FF
62.11 FF
62.16 FF
85.0 RF
81.9 RF
70.9 RF
70.9 RF
73.7 RF
74.3 RF 69.8 RF
75.3 RF
75.4 RF
80.0 RF
80.1 RF
58.53 58.91
59.50
59.52
59.82
60.80
61.13
61.09
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62.72
59.6258.71
57.92
58.91
58.72
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60.91
60.90
60.88
60.89
60.98
61.00
60.60
60.44
60.61
60.75
60.70
60.66
60.94
59.61
57.1655.93
55.90
56
57
58
59
60
61
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5
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N55°59'13"E 129.91'
S3
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9
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SUB AREA A.3
411 SF / 0.009 AC
Q=0.04 CFS
SUB AREA B.2
720 SF / 0.017 AC
Q=0.09 CFS
SUB AREA C.2
670 SF / 0.02 AC
Q=0.09 CFS
SUB AREA C.1
2,090 SF / 0.048 AC
Q=0.21 CFS
SUB AREA B.1
1,600 SF / 0.037 AC
Q=0.16 CFS
SUB AREA A.1
1,933 SF / 0.044 AC
Q=0.19 CFS
CHERRY AVENUE
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371 SF / 0.009 AC
Q=0.04 CFS
6" PVC SD;51.0 LF @1.2%
4" PVC SD;
40.0 LF @1.0%
4" PVC SD;
8.0 LF @1.3%
6" PVC SD;4.3 LF @2.3%
6" PVC SD;
45.0 LF @1.4%
6" PVC SD;
49.5 LF @0.7%
6" PVC SD;
49.4 LF @0.5%
6" PVC SD;
35.2 LF @1.0%
4" PVC SD;7.6 LF@1.3%
6" PVC SD;
3.0 LF
@1.7%
4" PVC SD;
34.0 LF @1.2%
4" PVC SD;
35.0 LF @1.0%
TG 60.7IE 59.2
TG 59.4IE 58.2
TG 58.7
IE 57.75
*2 - 3" PVC UNDER DRAINS
IE 57.15
Q100=0.77 CFS
TG 59.1IE 57.85
TG 60.9IE 58.6
TG 60.9
59.0 IE
TG 59.4IE 58.6
TG 60.5
IE 59.6
TG 58.7IE 57.9
TG 58.5
IE 57.5
TG 58.7
IE 58.1
FL 61.1/HPHP/FL 59.9
HP/FL 59.9
HP/FL 61.2
HP/FL 61.2
HP/FL 58.9
HP/ FL 58.9
HP/FL 61.2
HP/ FL 58.9
IMPERVIOUS AREA
FLOW PATH
LEGEND
DMA BOUNDARY
SITE BOUNDARY
TOTAL IMPERVIOUS AREA - 4,786 SF
J:\ACTIVE JOBS\4099 RINCON-CARLSBAD-CHERRY AVE\CIVIL\DRAWING\EXHIBITS\WORKING
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PLAN VIEW - HYDRAULIC CAPACITY EXHIBIT
SCALE: 1" = 10' HORIZONTAL
*SEE AES PIPE FLOW ANALYSIS
CALCULATION FOR PRESSURIZED
FLOW OUT OF D-27 UNDER DRAINS
PIPE FLOW CAPACITY
4" PVC @1.0% (MIN.) = 0.19 CFS
6" PVC @0.5% (MIN.) = 0.42 CFS
6" PVC @1.0% (MIN.) = 0.60 CFS
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Channel Report
Hydraflow Express Extension for Autodesk® Civil 3D® by Autodesk, Inc.Tuesday, Jan 7 2025
4-INCH PVC @1.0%
Circular
Diameter (ft)= 0.33
Invert Elev (ft) = 100.00
Slope (%)= 1.00
N-Value = 0.013
Calculations
Compute by:Known Depth
Known Depth (ft) = 0.30
Highlighted
Depth (ft)= 0.30
Q (cfs)= 0.198
Area (sqft)= 0.08
Velocity (ft/s)= 2.43
Wetted Perim (ft) = 0.83
Crit Depth, Yc (ft) = 0.26
Top Width (ft)= 0.19
EGL (ft)= 0.39
0 1
Elev (ft)Section
99.75
100.00
100.25
100.50
100.75
101.00
Reach (ft)
-...,
/ -' -' ' I
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Channel Report
Hydraflow Express Extension for Autodesk® Civil 3D® by Autodesk, Inc.Friday, Jan 31 2025
6-INCH PVC @0.5%
Circular
Diameter (ft)= 0.50
Invert Elev (ft) = 100.00
Slope (%)= 0.50
N-Value = 0.013
Calculations
Compute by:Known Depth
Known Depth (ft) = 0.45
Highlighted
Depth (ft)= 0.45
Q (cfs)= 0.423
Area (sqft)= 0.19
Velocity (ft/s)= 2.27
Wetted Perim (ft) = 1.25
Crit Depth, Yc (ft) = 0.34
Top Width (ft)= 0.30
EGL (ft)= 0.53
0 1
Elev (ft)Section
99.75
100.00
100.25
100.50
100.75
101.00
Reach (ft)
~ -v .............. --
-
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-
Channel Report
Hydraflow Express Extension for Autodesk® Civil 3D® by Autodesk, Inc.Tuesday, Jan 7 2025
6-INCH PVC @1.0%
Circular
Diameter (ft)= 0.50
Invert Elev (ft) = 100.00
Slope (%)= 1.00
N-Value = 0.013
Calculations
Compute by:Known Depth
Known Depth (ft) = 0.48
Highlighted
Depth (ft)= 0.48
Q (cfs)= 0.601
Area (sqft)= 0.19
Velocity (ft/s)= 3.10
Wetted Perim (ft) = 1.37
Crit Depth, Yc (ft) = 0.40
Top Width (ft)= 0.20
EGL (ft)= 0.63
0 1
Elev (ft)Section
99.75
100.00
100.25
100.50
100.75
101.00
Reach (ft)
""r"7" ----
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-
____________________________________________________________________________
****************************************************************************
PRESSURE PIPE-FLOW HYDRAULICS COMPUTER PROGRAM PACKAGE
(Reference: LACFD,LACRD,& OCEMA HYDRAULICS CRITERION)
(c) Copyright 1982-2016 Advanced Engineering Software (aes)
Ver. 23.0 Release Date: 07/01/2016 License ID 1452
Analysis prepared by:
************************** DESCRIPTION OF STUDY **************************
* CHERRY BEACH HOMES *
* FLOW THROUGH 1 OF 2 THREE INCH PVC D-27 UNDERDRAINS *
* PASCO LARET SUITER AND ASSOCIATES (4099) *
**************************************************************************
FILE NAME: 4099-D3.DAT
TIME/DATE OF STUDY: 11:43 01/20/2025
============================================================================
NOTE: STEADY FLOW HYDRAULIC HEAD-LOSS COMPUTATIONS BASED ON THE MOST
CONSERVATIVE FORMULAE FROM THE CURRENT LACRD,LACFCD, AND OCEMA
DESIGN MANUALS.
DOWNSTREAM PRESSURE PIPE FLOW CONTROL DATA:
NODE NUMBER = 100.00 FLOWLINE ELEVATION = 53.30
PIPE DIAMETER(INCH) = 3.00 PIPE FLOW(CFS) = 0.29
ASSUMED DOWNSTREAM CONTROL HGL = 53.550
L.A. THOMPSON'S EQUATION IS USED FOR JUNCTION ANALYSIS
============================================================================
NODE 100.00 : HGL= < 53.550>;EGL= < 54.092>;FLOWLINE= < 53.300>
============================================================================
PRESSURE FLOW PROCESS FROM NODE 100.00 TO NODE 101.00 IS CODE = 1
UPSTREAM NODE 101.00 ELEVATION = 57.15
----------------------------------------------------------------------------
CALCULATE PRESSURE FLOW FRICTION LOSSES(LACFCD):
PIPE FLOW = 0.39 CFS PIPE DIAMETER = 3.00 INCHES
PIPE LENGTH = 18.40 FEET MANNINGS N = 0.01300
SF=(Q/K)**2 = (( 0.39)/( 0.884))**2 = 0.1947749
HF=L*SF = ( 18.40)*( 0.1947749) = 3.584
NODE 101.00 : HGL= < 56.696>;EGL= < 57.676>;FLOWLINE= < 57.150>
----------------------------------------------------------------------------
PRESSURE FLOW ASSUMPTION USED TO ADJUST HGL AND EGL
LOST PRESSURE HEAD USING SOFFIT CONTROL = 0.70
NODE 101.00 : HGL= < 57.400>;EGL= < 58.380>;FLOWLINE= < 57.150>
============================================================================
PRESSURE FLOW PROCESS FROM NODE 101.00 TO NODE 102.00 IS CODE = 5
UPSTREAM NODE 102.00 ELEVATION = 57.50
----------------------------------------------------------------------------
CALCULATE PRESSURE FLOW JUNCTION LOSSES:
NO. DISCHARGE DIAMETER AREA VELOCITY DELTA HV
1 0.0 6.00 0.196 0.000 0.000 0.000
2 0.4 3.00 0.049 7.945 -- 0.980
3 0.0 0.00 0.000 0.000 0.000 -
4 0.0 0.00 0.000 0.000 0.000 -
5 0.4===Q5 EQUALS BASIN INPUT===
LACFCD AND OCEMA PRESSURE FLOW JUNCTION FORMULAE USED:
DY=(Q2*V2-Q1*V1*COS(DELTA1)-Q3*V3*COS(DELTA3)-
Q4*V4*COS(DELTA4))/((A1+A2)*16.1)
UPSTREAM MANNINGS N = 0.01300
DOWNSTREAM MANNINGS N = 0.01300
UPSTREAM FRICTION SLOPE = 0.00000
DOWNSTREAM FRICTION SLOPE = 0.19478
AVERAGED FRICTION SLOPE IN JUNCTION ASSUMED AS 0.09739
JUNCTION LENGTH(FEET) = 1.00 FRICTION LOSS = 0.097
ENTRANCE LOSSES = 0.196
JUNCTION LOSSES = DY+HV1-HV2+(FRICTION LOSS)+(ENTRANCE LOSSES)
JUNCTION LOSSES = 0.784+ 0.000- 0.980+( 0.097)+( 0.196) = 0.097
NODE 102.00 : HGL= < 58.478>;EGL= < 58.478>;FLOWLINE= < 57.500>
============================================================================
END OF PRESSURE FLOW HYDRAULICS PIPE SYSTEM
TG per plan = 58.5 = HGL ~58.5
6-in Area Drain in Sag (Assumed 50% Clogging)
Cw 3 Unitless D 0.5 ft
Pe 0.79 ft
C0 0.67 Unitless Ae 0.3925
*Pe assumes 50% clogging
Weir Orifice
Q (cfs) d (ft)Q (cfs) d (ft)
0.07 0.1 0.67 0.1
0.21 0.2 0.94 0.2
0.39 0.3 1.16 0.3
0.60 0.4 1.33 0.4
0.83 0.5 1.49 0.5
1.09 0.6 1.63 0.6
Step 1. Calculate the capacity of a grate inlet operating as a w eir, using the weir equation
(Equation 2-16) with a length equivalent to perimeter of the grate. When the grate is
located next to a curb, disregard the length of the grate against the curb.
O=C Pd312 ~ W e (2-16)
w he.re ...
Q =
Cw =
Pe
d
inlet ,capacity of the grated inlet (ft3/s);
weir coefficient (CF3 .. 0 for U .S. Traditional Units);
effective grate perimeter length (ft); and.
flow deptl1 approaching inlet (ft).
To account for the effects of clogging of a grated inlet operating as a w eir, a clogging factor of
fifty percent (CI=0.50) shall be applied to the actua l (uncfogged) perimeter of the grate (P ):
Step 2. Calculate the capacity of a grate inlet operating as an orifice. Use the orifice
equation (Equation 2-1 8), assuming the clear opening of the grate redu ced by a
clogging factor CA=0.50 (Equation 2-19). A San Diego Regional Standard No. D-15
1 1 1 • r JI A ,-, c-.2 "T""1 ·..-, 1 1 "l'""f'" 1
where ...
Q
Co
g
grate has an actual c lear opening ot A =4.'/ tt~. The .t<ecteral Highway
Administration's Urban Drainage Design Manual (HEC-22) provides guidance for
other grate types and configurations.
inlet capacity of the grated inlet (ft3/s);
orifice coefficient (C0 =0.67 for U.S. Traditional Units);
gravitational acceleration (ft/s2);
(2-18)
(2-19)
d =
Ae
flow depth above inlet (ft);
effective (clogged) grate area (ft2);
CA
A
area c logging factor (CA=0.50); and
actual opening area of the grate inlet (i.e., the total area less the area of bars or
vanes). The actual opening area for a San Diego Regional Standard No. D-15
grate is A=4.7 ft2. The Federal Highway Administration's Urban Drainage
Design Manual (HEC-22) provides guidance for other grate types and
configurations.
12-in Grated Inlet in Sag (Assumed 50% Clogging)
Cw 3 Unitless L 1 ft
Pe 2.00 ft W 1 ft
C0 0.67 Unitless Ae 0.5
*Pe assumes 50% clogging
Weir Orifice
Q (cfs) d (ft)Q (cfs) d (ft)
0.19 0.1 0.85 0.1
0.54 0.2 1.20 0.2
0.99 0.3 1.47 0.3
1.52 0.4 1.70 0.4
2.12 0.5 1.90 0.5
2.79 0.6 2.08 0.6
Step 1. Calculate the capacity of a grate inlet opet-ating as a w eir, using the w eir equation
(Equation 2-16) w ith a length equiYalent to perimeter of the grate. When the g1·ate is
located next to a curb , disrega rd the length of the grate against the curb.
0 = C Pd312 (2-161 ~ W e '/
where ...
Q = inlet capacity of the grated inlet (ft3/s);
Cw weir coefficient (Cw=3.0 for U .S. T raditional U nits);
effectiYe g1-ate perimeter length (ft); and Pe =
d = flow depth approaching inlet (ft).
To account for the effects of clogging of a grated inlet operating as a w eir, a clogging factor of
fifty percent (CL=0 .50) shaU be applied to the actual (unclogged) perimeter of the grate (P ):
Step 2. Calculate the capacity of a grate inlet operating as an orifice. Use the orifi ce
equation (Equation 2-1 8), assuming the clear opening of the grate reduced by a
clogging factor CA=0.50 (Equation 2-19). A San D iego Regiona l Standard No. D-15
___ ...__ 1___ __.._ __ 1 _1 ______________ .£" ,I A -r .0...2 "T'L _ T:"_..J ___ 1 ,-.:_1_ _____ _
grate nas an actual clear openmg ot A==4. I tr. l ne J:<e<1era1 tt1gnway
Administration's Urban Drainage Design Manual (HEC-22) provides guidance for
other grate types and configurations.
where ...
Q
Co
g
d =
Ae
CA =
A
inlet capacity of the grated inlet (ft3/s);
orifice coefficient (C0=0.67 for U.S. Traditional Units);
gravitational acceleration (ft/s2);
flow depth above inlet (ft);
effective (clogged) grate area (ft2);
area clogging factor (CA=0.50); and
(2-18)
(2-19)
actual opening area of the grate inlet (i.e., the total area less the area of bars or
vanes). The actual opening area for a San Diego Regional Standard No. D-15
grate is A=4.7 ft2. The Federal Highway Administration's Urban Drainage
Design Manual (HEC-22) provides guidance for other grate types and
configurations.