HomeMy WebLinkAboutMS 2021-0004; ACACIA BEACH HOMES; HYDROLOGY STUDY; 2023-03-01PLSA 3580-02
FINAL HYDROLOGY STUDY
FOR
TENTATIVE PARCEL MAP / MINOR SITE DEVELOPMENT PLAN /
COASTAL DEVELOPMENT PERMIT
ACACIA BEACH HOMES - 245 ACACIA AVENUE
MS 2021-0004 / CDP 2021-0036 / PUD 2021-0006 / SDP 2021-0018
DWG 537-8A
245 ACACIA AVENUE,
CITY OF CARLSBAD, CA 92008
PREPARED FOR:
RREG INVESTMENTS SERIES, LLC SERIES I041
5315 AVENIDA ENCINAS, SUITE 200
CARLSBAD, CA 92008
PREPARED BY:
PASCO LARET SUITER & ASSOCIATES, INC.
535 N. HIGHWAY 101, SUITE A
SOLANA BEACH, CA 92075
PH: (858) 259-8212
Prepared: July 2022
__________________________________________________
Bryan A Knapp, PE #86542 DATE
PLSA 3580-02
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
Runoff Coefficient Determination 2.3
Hydrology & Hydraulic Model Output 3.0
Pre-Developed Hydrologic Calculations (100-Year Event) 3.1
Post-Developed Hydrologic Calculations (100-Year Event) 3.2
Pre-Developed vs. Post-Developed Peak Flows (100-Year Event) 3.3
Appendix 4.0
Isopluvial Maps
Intensity Duration Design Charts
Runoff Coefficients
Hydrologic Soil Group - USDA Web Soil Survey
Pre-Development Hydrology Node Map
Post-Development Hydrology Node Map
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1.0 EXECUTIVE SUMMARY
1.1 Introduction
This Preliminary Hydrology Study for the proposed development at 245 Acacia Avenue,
known as Acacia Homes, 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 along Acacia Avenue, northeast of the intersection of
Acacia Avenue and Garfield Street, in the City of Carlsbad. The site is bound by a
combination of existing single-family and multi-family developments to the west, south,
and east, as well as Acacia Avenue, a public road, to the north. The existing site consists
of two-family residences, a driveway, walkways, landscaping, open space consisting of
mostly dirt, and miscellaneous improvements typical of this type of development. The
project site is located in the Agua Hedionda Hydrologic Area, and, more specifically, the
Los Monos Hydrologic Sub-Area (904.31) of the Carlsbad watershed.
The subject property including the off-site public right-of-way has an approximate area of
0.258 acres and is approximately 49.8% impervious in the existing condition. The on-stie
portion of the site has an approximate area of 0.212 acres and is approximately 42.2%
impervious. The public right-of-way portion has an approximate area of 0.046 acres and
is approximately 84.7% impervious. Per the Web Soil Survey application available
through the United States Department of Agriculture, the basin is generally categorized to
have type B hydrologic soils. Based on the existing impervious area and land use type, a
pre-development weighted runoff coefficient for the on-site development and public right-
of-way were calculated to be 0.52 and 0.80 respectively using the methodology described
in section 3.1.2 of the San Diego County Hydrology Manual and the formula provided
therein.
After review of the site edge conditions, existing topography, and adjacent developments,
it was determined that there is no additional offsite runon entering the site from the
neighboring properties. The existing site can be categorized into two (2) major drainage
basin, with one (1) primary discharge location leaving the property. Drainage basin EX-1
consists of the entirety of the projects on-site development and primarily drains from west
to east through the property via sheet flow methods. Based on a study of the existing site
topography, there currently exists a cross-lot drainage scenario as runoff leaves the site
along the eastern property line before ultimately being conveyed out to Acacia Avenue
further downstream. Drainage basin EX-2 is the entirety of the off-site portion of the
project and runoff sheet flows to the existing gutter as it drains west to east. Once all runoff
reaches the Acacia Avenue right-of-way, runoff leaving on-site from basin EX-1
confluences with the off-site runoff from basin EX-2 then travels east approximately 100
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feet toward an existing storm drain inlet. The storm drain inlet is on the south side of
Acacia Avenue. Surface flow enters the storm drain inlet ultimately are conveyed south to
outlet in the Agua Hedionda Lagoon prior to entering the Pacific Ocean.
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 100-year, 6-hour
storm event for the onsite drainage basin. Table 1 below summarizes the results of the
Rational Method calculations.
EXISTING DRAINAGE FLOWS
DRAINAGE
AREA
DRAINAGE
AREA
(ACRES)
Q100
(CFS)
I100
(IN/HR)
EX-1 0.212 0.72 6.59
EX-2 0.046 0.24 6.59
Total 0.258 0.96 6.59
Table 1. Existing Condition Peak Drainage Flow Rates
Refer to pre-development hydrology calculations included in Section 3.1 of this report for
a detailed analysis of the existing drainage basin, as well as a pre-development hydrology
node map included in the appendix of this report for pre-development drainage basin
delineation and discharge locations.
1.3 Proposed Project
The proposed project includes the demolition of all existing onsite improvements and the
construction of three (3) new multi-family condominium units. The project proposes a
private driveway to provide vehicular access to the proposed garages. Three private onsite
parking stalls interior to the site are also shown for site residents. There are three different
proposed pad elevations for the three (3) proposed structures. The northern structure is to
be built on a graded 53.5 pad elevation, and the southern structures are to be built on a
graded 54.0 and 54.5 pad elevations, respectively. Site grading, drainage and utility
improvements typical of this type of multi-family residential development will also be
constructed as can be seen on the Preliminary Grading Plan prepared by Pasco, Laret,
Suiter & Associates under separate cover.
The on-site portion of the subject project is approximately 76.9% impervious in the
proposed condition. The off-site portion of the subject project within the public right-of-
way is approximately 84.4% impervious. Based on the proposed impervious area and land
use type, a post-development weighted runoff coefficient for the on-site portion of the
project and the public right-of-way were calculated to be 0.75 and 0.80 respectively using
the methodology described in section 3.1.2 of the San Diego County Hydrology Manual
and the formula provided therein. The proposed site consists of two (2) major drainage
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basin, with one (1) primary discharge location from the northeast corner of the property
similar to the existing condition. The site proposes to discharge water onto Acacia Avenue
from the proposed curb outlet pipe to the northeast. The onsite drainage basin was further
broken down into two sub-basins, for analysis based on the area that each storm drain
network will receive prior to confluence. Runoff from basin PR-2 will be the same as in
the existing condition; runoff will sheet flow to the gutter and them confluence with on-
site runoff before entering an existing curb inlet.
Drainage sub-basin PR-1.1 consists of the majority of the site and will continue to convey
runoff generally from a high point in the southeast corner of the site to the Acacia Avenue
right-of-way by means of curb outlet. A concrete ribbon gutter located at the center of the
driveway will also serve to capture and convey drainage to a proposed area drain. Runoff
is then routed east to confluence with the rest of the site runoff before leaving the site
through a curb outlet. Drainage sub-basin PR-1.2 consists of the eastern portion of the site
and will convey runoff from the project high point to the proposed storm drain conveyance
system and then to Acacia Avenue through the same curb outlet as sub-basin PR-1.1. When
runoff from each basin confluence the overall runoff leaving the site during the 100-year
storm will be less than combined runoff from each sub-basin during the 100-year storm.
Using the Rational Method Procedure outlined in the San Diego County Hydrology
Manual, a peak flow rate and time of concentration were calculated for the 100-year, 6-
hour storm event for the onsite drainage basins. Table 2 below summarizes the results of
the Rational Method calculations in the post-developed condition.
PROPOSED DRAINAGE FLOWS
DRAINAGE
AREA
DRAINAGE
AREA
(ACRES)
Q100
(CFS)
I100
(IN/HR)
PR-1.1 0.140 0.52 4.98
PR-1.2 0.072 0.33 6.17
PR-1(TOT) 0.212 0.79 6.17
PR-2 0.046 0.24 6.17
TOT 0.258 1.03 6.59
Table 2. Proposed Condition Peak Drainage Flow Rates
Additionally, drainage will be routed from the rear of the property out to Acacia Avenue
to alleviate an existing cross-lot drainage scenario discussed in the previous section.
Subsequently, the proposed project will increase the Tc and flow length through the
property, decreasing intensity to account for the increase in hardscape from the pre-
development to post-development condition. Refer to post-development hydrology
calculations included in Section 3.2 of this report for a detailed analysis of the proposed
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drainage basin, as well as a post-development hydrology node map included in the
appendix of this report for post-development drainage basin delineation and discharge
locations.
In an effort to comply with the City of Carlsbad storm water standards, the proposed site
has incorporated LID design techniques to optimize the site layout. Runoff from proposed
roofs and new or removed and replaced hardscape areas will be directed to landscaped
areas as applicable to disperse drainage to pervious surfaces. The landscaped areas will
assist to remove sediment and particulate-bound pollutants from storm water in addition to
helping mitigate peak runoff by providing some volume retention, evapotranspiration, as
well as slightly increasing the site’s overall time of concentration.
1.4 Conclusions
Based upon the analysis included in this report, there is no net change in peak runoff as a
result of the proposed development due to the 3,210 square feet of increased hardscape in
the proposed condition as compared the existing site. This can be considered negligible,
and peak runoff leaving the property in the post-developed condition is mitigated by
increasing the time of concentration through the site as well as promoting incidental
infiltration and evapotranspiration. Additionally, as mentioned above the site will alleviate
an existing cross-lot drainage scenario by routing runoff from the rear of the property out
to Acacia Avenue as opposed to the neighboring property to the east. As runoff ultimately
reaches an existing storm drain inlet in Acacia Avenue, water will not be diverted away
from existing drainage patterns. Additionally, runoff produced by the proposed
development will not have an adverse effect on the downstream watershed. The proposed
site conditions will function to mitigate peak runoff to pre-project conditions, and the slight
increase in runoff due to the proposed surface improvements can be considered negligible.
The proposed project will be exempt from hydromodification compliance requirements as
it does not qualify as a Priority Development Project as defined in the Regional Municipal
Separate Storm Sewer System (MS4) Permit and the San Diego County Model BMP
Design Manual.
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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
“City of Carlsbad Engineering Standards, Volume 5: Carlsbad BMP Design Manual
(Post Construction Treatment BMPs)”, revised February 2016
“Low Impact Development Handbook – Stormwater Management Strategies”, revised
July 2014, County of San Diego, Department of Public Works
Soil Survey Staff, Natural Resources Conservation Service, United States Department of
Agriculture. Web Soil Survey. Available online at http://websoilsurvey.nrcs.usda.gov.
Accessed September 2, 2020
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2.0 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.
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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. The time of concentration minimum is 5
minutes for purposes of calculating rainfall intensity per the County of San Diego
Hydrology Manual requirements.
2.3 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
in the Appendix of this report, categorizes the land use, the associated development density
(dwelling units per acre) and the percentage of impervious area.
For this study, a weighted runoff coefficient was used for both the pre-project and post-
developed site in accordance with the equation provided in Section 3.1.2 of the County of
San Diego Hydrology Manual. The weighted runoff coefficient is a function of the total
impervious and pervious surface areas in the existing and proposed conditions.
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3.0 HYDROLOGY MODEL OUTPUT
3.1 Pre-Developed Hydrologic Model Output (100-Year Event)
Pre-Development:
Q = CIA *Rational Method Equation
P100 = 2.5 *100-Year, 6-Hour Rainfall Precipitation
Basin EX-1
Total Area = 9,250 sf 0.212 Acres
Impervious Area = 3,905 sf 0.089 Acres
Pervious Area = 5,345 sf 0.123 Acres
Cn, Weighted Runoff Coefficient
- 0.25, Cn value for natural ground, Type B soils
* Per San Diego Hydrology Design Manual (SDHDM) Section 3.1.2
- 0.9, C value for developed / impervious surface
* Per SDHDM Section 3.1.2
Cn = 0.9 x 3,905 sf + 0.25 x 5,345 sf = 0.52
9,250 sf
Tc = 5.0 Min *Minimum Tc for Rainfall Intensity per SDHDM
I = 7.44 x P6 x D-0.645 *Rainfall Intensity Equation
I = 7.44 x 2.5 x 5.0-0.645 ≈ 6.59 in/hr
Q100 = 0.52 x 6.59 in/hr x 0.212 Ac = 0.72 cfs
Total Off-Site
Total Area = 2,000 sf 0.046 Acres
Impervious Area = 1,688 sf 0.039 Acres
Pervious Area = 312 sf 0.007 Acres
Cn, Weighted Runoff Coefficient
- 0.25, Cn value for natural ground, Type B soils
* Per San Diego Hydrology Design Manual (SDHDM) Section 3.1.2
- 0.9, C value for developed / impervious surface
* Per SDHDM Section 3.1.2
Cn = 0.9 x 1,694 sf + 0.25 x 306 sf = 0.80
2,000 sf
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Basin EX-2
Total Area = 2,000 sf 0.046 Acres
Tc = 5.0 Min *Minimum Tc for Rainfall Intensity per SDHDM
I = 7.44 x P6 x D-0.645 *Rainfall Intensity Equation
I = 7.44 x 2.5 x 5.0-0.645 ≈ 6.59 in/hr
Q100 = 0.80 x 6.59 in/hr x 0.046 Ac = 0.24 cfs
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3.2 Post-Developed Hydrologic Model Output (100-Year Event)
Post-Development (without considering HMP/BMP treatment):
Q = CIA *Rational Method Equation
P100 = 2.5 *100-Year, 6-Hour Rainfall Precipitation
Total On-Site
Total Area = 9,250 sf 0.212 Acres
Impervious Area = 7,115 sf 0.163 Acres
Pervious Area = 2,135 sf 0.049 Acres
Cn, Weighted Runoff Coefficient
- 0.25, Cn value for natural ground, Type B soils
* Per San Diego Hydrology Design Manual (SDHDM) Section 3.1.2
- 0.9, C value for developed / impervious surface
* Per SDHDM Section 3.1.2
Cn = 0.9 x 7,115 sf + 0.25 x 2,135 sf = 0.75
9,250 sf
Basin PR-1
Total Area = 9,250 sf 0.212 Acres
Ti = . ∗ . . ∗ √ . % *Per SDCHM Figure 3-3, Initial TC
Ti = 6.30 min
Tt = Tt1 *Overland flow to eastern PL
Tt1 = .
. ! .
*Per SDCHM Figure 3-4, in hours
Tt1 = 0.0235 hr * 60 min / 1 hr = 1.41 Min
Tc = Ti + Tt1 = 6.30 Min + 1.41 Min = 7.71 Min
I = 7.44 x P6 x D-0.645 *Rainfall Intensity Equation
I = 7.44 x 2.5 x 7.71-0.645 ≈ 4.98 in/hr
Q100 = 0.75 x 4.98 in/hr x 0.212 Ac = 0.79 cfs
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Sub-Basin PR-1.1
Total Area = 6,103 sf 0.140 Acres
Ti = . ∗ . . ∗ √ . % *Per SDCHM Figure 3-3, Initial TC
Ti = 6.30 min
Tt = Tt1 *Overland flow to eastern PL
Tt1 = .
". ! .
*Per SDCHM Figure 3-4, in hours
Tt1 = 0.0237 hr * 60 min / 1 hr = 1.42 Min
Tc = Ti + Tt1 = 6.30 Min + 1.42 Min = 7.72 Min
I = 7.44 x P6 x D-0.645 *Rainfall Intensity Equation
I = 7.44 x 2.5 x 7.72-0.645 ≈ 4.98 in/hr
Q100 = 0.75 x 4.98 in/hr x 0.140 Ac = 0.52 cfs
Sub-Basin PR-1.2
Total Area = 3,147 sf 0.072 Acres
Ti = . ∗ . . ∗ # √ . % *Per SDCHM Figure 3-3, Initial TC
Ti = 4.49 min
Tt = Tt1 *Overland flow to eastern PL
Tt1 = . $
".% ! .
*Per SDCHM Figure 3-4, in hours
Tt1 = 0.017 hr * 60 min / 1 hr = 1.04 Min
Tc = Ti + Tt1 = 4.49 Min + 1.04 Min = 5.53 Min
I = 7.44 x P6 x D-0.645 *Rainfall Intensity Equation
I = 7.44 x 2.5 x 5.53-0.645 ≈ 6.17 in/hr
Q100 = 0.75 x 6.17 in/hr x 0.072 Ac = 0.33 cfs
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Total Off-Site
Total Area = 2,000 sf 0.046 Acres
Impervious Area = 1,688 sf 0.039 Acres
Pervious Area = 312 sf 0.007 Acres
Cn, Weighted Runoff Coefficient
- 0.25, Cn value for natural ground, Type B soils
* Per San Diego Hydrology Design Manual (SDHDM) Section 3.1.2
- 0.9, C value for developed / impervious surface
* Per SDHDM Section 3.1.2
Cn = 0.9 x 1,688 sf + 0.25 x 312 sf = 0.80
2,000 sf
Basin PR-2
Total Area = 2,000 sf 0.046 Acres
Tc = 5.0 Min *Minimum Tc for Rainfall Intensity per SDHDM
I = 7.44 x P6 x D-0.645 *Rainfall Intensity Equation
I = 7.44 x 2.5 x 5.0-0.645 ≈ 6.59 in/hr
Q100 = 0.80 x 6.59 in/hr x 0.046 Ac = 0.24 cfs
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3.3 Pre-Developed vs. Post-Developed Peak Flows (100-Year Event)
Total Pre-Development (Discharge Leaving Site)
Basin EX-1 Q100 = 0.72 cfs
*Discharging from the site at the northeast corner to Acacia Avenue
Basin PR-2 Q100 = 0.24 cfs
*Off-site runoff from Right-of-Way that sheet flows in the existing gutter
Total Q100 = 0.96 cfs
Total Post-Development (Discharge Leaving Site)
Sub-Basin PR-1.1 Q100 = 0.52 cfs
*Discharging from the site to Acacia Avenue via proposed curb outlet
Sub-Basin PR-1.2 Q100 = 0.33 cfs
*Discharging from the site to Acacia Avenue via proposed curb outlet
Basin PR-1 Q100 = 0.79 cfs
*Discharging from the site to Acacia Avenue via proposed curb outlet
Basin PR-2 Q100 = 0.24 cfs
*Off-site runoff from Right-of-Way that confluences with on-site runoff at curb outlet
Total Q100 = 1.03 cfs
Pre-Development vs. Post-Development (Discharge Leaving Site):
Pre-Development Post-Development Delta
Q100 = 0.96 cfs Q100 = 1.03 cfs 0.07 cfs
*Changes in runoff less than 0.1 cfs can be considered negligible and will not
negatively affect the downstream watershed.
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4.0 APPENDIX
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
Hydrologic Soil Group—San Diego County Area, California
Natural Resources
Conservation Service
Web Soil Survey
National Cooperative Soil Survey
7/1/2021
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Map projection: Web Mercator Corner coordinates: WGS84 Edge tics: UTM Zone 11N WGS84
0 25 50 100 150
Feet
0 5 10 20 30
Meters
Map Scale: 1:553 if printed on A portrait (8.5" x 11") sheet.
Soil Map may not be valid at this scale.
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 15, May 27, 2020
Soil map units are labeled (as space allows) for map scales
1:50,000 or larger.
Date(s) aerial images were photographed: Jan 24, 2020—Feb
12, 2020
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
7/1/2021
Page 2 of 4
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 0.7 100.0%
Totals for Area of Interest 0.7 100.0%
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
7/1/2021
Page 3 of 4
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
7/1/2021
Page 4 of 4
32"TP
24"TC
E
G
S
W
12"TD
SHED
GARAGE
1FT CONCRETE BLOCK WALL
1.5 FT CONCRETE BLOCK RETAINING WALL
6FT WOOD FENCE ON WALL 6FT WOOD FENCE ON WALL 6FT WOOD FENCE
1FT CONCRETE BLOCK WALL
6F
T
W
O
O
D
F
E
N
C
E
6FT WOOD FENCE
6F
T
W
O
O
D
F
E
N
C
E
GRAVEL
CONCRETE
TW=53.8
BW=53.5
BW=53.4TW=53.5 TW=53.7BW=52.2
TW=54.1BW=53.7BW=54.1
TW=53.7BW=51.8
TW=54.1BW=53.4
BW=54.1 TW=54.1BW=53.5
BW=54.2
TW=53.6BW=51.8
BW=53.6
BW=52.9TW=53.7
BW=51.0TW=52.4
BW=50.9TW=51.3
BW=49.7
BW=50.9TW=51.9
BW=50.3
BW=49.9TW=51.3
BW=48.8
BRICK
1.5 FT CONCRETE BLOCK RETAINING
WALL
3FT CHAINLINK FENCE
56
55
55
55
54
54
5454
54
54
54
54
54
53
535353
53
53
52
52
52
52
52
51
51
51
5151
51
50
50
505050
49
49
AS
P
H
A
L
T
W
I
T
H
C
O
N
C
R
E
T
E
C
&
G
CONCRETE
TC=54.29FL=53.83
TC=53.18FL=52.72
TC=52.40FL=51.92
TC=51.73FL=51.67
TC=51.20FL=51.13
TC=50.76FL=50.68
TC=50.87FL=50.41
TC=50.27FL=49.78
TC=49.37FL=49.29
TC=49.10FL=49.01
TC=49.26FL=48.78
51.8
51.7
51.6
51.2
51.6
51.5
51.4
51.2
51.7
51.8
52.6
51.6
51.451.2
51.9 51.5
51.6
51.8
51.7
51.7
51.7
51.7 51.752.2
52.2
52.6
53.4
52.6
52.3
52.3
51.8
50.6 50.6 50.4 50.8 50.6 50.8
54.2
54.253.854.254.5
54.5
52.7
51.8
51.3
51.1
50.7
Z:49.4 Z:49.4 49.4 49.6 50.2 50.2
IE IN=37.1
SHED
SHED
1 STORY HOUSE
1 STORY HOUSE
3FT WOOD FENCE
CANOPY
N 34°03'15" W 150.00'
N
5
5
°
5
7
'
4
2
"
E
61
.
6
1
'
N 34°02'01" W 150.00'
N
5
5
°
5
7
'
4
2
"
E
61
.
6
4
'
AC
A
C
I
A
A
V
E
N
U
E
XX
X
X
XXXXXX X X X X X X
X
X
X X X X X X X X
X
X
X
X
X
X
SD SD SD SD SD SD SD SD SD
SD
SD
W
W
W
W
W
W
W
W
W
W
W
W
W
W
W
W
W
OE
OE
OE
OE
OE
OE
OE
OE
OE
OE
OE
OE
OE
OE
OE
OE
OE
OE
OE
OE
OEOEOEOEOEOE
S
S
S
S
S
S
S
S
S
S
S
S
S
S
S
GGGGGGG
G
G
G
G
G
G
G
G
G
G
G
G
G
G
G
S S S S S S S S S S S S S S
SSS
W
W
W
W
W
W W W W W W W W W W W W W
JT JT JT JT JT JT JT JT JT JT JT JT JTGGGG
E
E
E
E
E
E
E E E
E
E
E
E
E
E
SSS
S S SW
W
W
W
W
W
30' 30'
60'
12' 18'
NODE PR-102
53.1 TG
51.6 IE
Q100 = 0.52 CFS
NODE PR-101
53.55 FL
(51.0 FS)
ON-SITE
Q100=0.79 CFS
V100=3.76 FPS
54.3 TC53.8 FL
54.0 FL
NODE PR-100
54.4 HP / FL
53.1 FL
NODE PR-20253.1 TG
51.4 IE
Q100=0.33 CFS
53.5 FG
54.5 FG
L1 = 100'
L1 = 47'
54.0 FG53.5 FG
53.9 FL
L2 = 117'0.7%
LOT 10
MAP 1803
LOT 1MAP 1747
APN: 204-240-09-00 LOT 2MAP 1747
APN: 204-240-10-00 LOT 3MAP 1747
APN: 204-240-11-00
APN: 204-240-07-00
POR. LOT 10BLOCK QMAP 1803
APN: 204-240-12-00
LOT 4
MAP 1747
APN: 204-240-12-00
BASIN PR-2
AREA = 2,000 SF
(0.046 AC)
Cn = 0.80
NODE PR-201
54.0 TG
52.4 IE
0.7%
L1 = 95'
SUB-BASIN PR-1.1
AREA = 6,103 SF
(0.140 AC)
Cn = 0.75
SUB-BASIN PR-1.2
AREA = 3,147 SF
(0.072 AC)Cn = 0.75
L3 = 20'
OFF-SITE
Q100=0.24 CFS
TOTAL
Q100=1.03 CFS
LEGEND
PROPERTY BOUNDARY
CENTERLINE OF ROAD
ADJACENT PROPERTY LINE
PUBLIC RIGHT-OF-WAY
BASIN BOUNDARY
SUB BASIN BOUNDARY
FLOW LINE
PROPOSED IMPERVIOUS AREA
PROPOSED HYDROLOGY EXHIBIT
245 ACACIA AVE
CARLSBAD, CA 92008
ON-SITE - AREA CALCULATIONS
TOTAL SITE AREA 11,250 SF (0.258 AC)
ON-SITE TOTAL AREA 9,250 SF (0.212 AC)
ON-SITE IMPERVIOUS AREA 7,115 SF (0.163 AC)
ON-SITE PERVIOUS AREA 2,135 SF (0.049 AC)
ON-SITE % IMPERVIOUS 76.9%
Cn 0.75
10 20 30
GRAPHIC SCALE 1" = 10'
010
PLAN VIEW - POST-DEVELOPMENT NODE MAP
SCALE: 1" = 10' HORIZONTAL
SUB-BASIN PR-1.1 - AREA CALCULATIONS
BASIN PR-1.1 TOTAL AREA 6,103 SF (0.140 AC)
Cn 0.75
TIME OF CONCENTRATION 7.72 MINUTES (PER SDCHM)
SUB-BASIN PR-1.2 - AREA CALCULATIONS
BASIN PR-1.2 TOTAL AREA 3,147 SF (0.072 AC)
Cn 0.75
TIME OF CONCENTRATION 5.53 MINUTES (PER SDCHM)
J:\ACTIVE JOBS\3580 RINCON ACACIA\CIVIL\REPORTS\HYDROLOGY\GP\APPENDIX\3580-CV-HYDD.DWG PLSA 3580
BASIN PR-1 - AREA CALCULATIONS
BASIN PR-1 TOTAL AREA 9,250 SF (0.212 AC)
Cn 0.75
TIME OF CONCENTRATION 7.71 MINUTES (PER SDCHM)
BASIN PR-2 - AREA CALCULATIONS
BASIN PR-2 TOTAL AREA 2,000 SF (0.046 AC)
Cn 0.80
TIME OF CONCENTRATION 5.0 MINUTES (PER SDCHM)
OFF-SITE - AREA CALCULATIONS
TOTAL SITE AREA 11,250 SF (0.258AC)
ROW AREA 2,000 SF (0.046 AC)
ROW IMPERVIOUS AREA 1,688 SF (0.039 AC)
ROW PERVIOUS AREA 312 SF (0.007 AC)
ROW % IMPERVIOUS 84.4%
Cn 0.80
Channel Report
Hydraflow Express Extension for Autodesk® AutoCAD® Civil 3D® by Autodesk, Inc.Thursday, Mar 17 2022
<Name>
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) = 0.50
Highlighted
Depth (ft) = 0.50
Q (cfs) = 0.561
Area (sqft) = 0.20
Velocity (ft/s) = 2.86
Wetted Perim (ft) = 1.57
Crit Depth, Yc (ft) = 0.39
Top Width (ft) = 0.00
EGL (ft) = 0.63
0 1
Elev (ft)Section
99.75
100.00
100.25
100.50
100.75
101.00
Reach (ft)
6" PVC @ 1%
Channel Report
Hydraflow Express Extension for Autodesk® AutoCAD® Civil 3D® by Autodesk, Inc.Thursday, Mar 17 2022
<Name>
Rectangular
Bottom Width (ft) = 1.00
Total Depth (ft) = 0.25
Invert Elev (ft) = 100.00
Slope (%) = 2.00
N-Value = 0.015
Calculations
Compute by: Known Depth
Known Depth (ft) = 0.25
Highlighted
Depth (ft) = 0.25
Q (cfs) = 1.060
Area (sqft) = 0.25
Velocity (ft/s) = 4.24
Wetted Perim (ft) = 1.50
Crit Depth, Yc (ft) = 0.25
Top Width (ft) = 1.00
EGL (ft) = 0.53
0 .25 .5 .75 1 1.25 1.5
Elev (ft)Depth (ft)Section
99.75 -0.25
100.00 0.00
100.25 0.25
100.50 0.50
100.75 0.75
101.00 1.00
Reach (ft)
Modified D-25 capacity @ 2.0 %
Channel Report
Hydraflow Express Extension for Autodesk® Civil 3D® by Autodesk, Inc.Sunday, Aug 7 2022
<Name>
Rectangular
Bottom Width (ft) = 1.00
Total Depth (ft) = 0.25
Invert Elev (ft) = 100.00
Slope (%) = 2.00
N-Value = 0.015
Calculations
Compute by: Known Q
Known Q (cfs) = 0.79
Highlighted
Depth (ft) = 0.21
Q (cfs) = 0.790
Area (sqft) = 0.21
Velocity (ft/s) = 3.76
Wetted Perim (ft) = 1.42
Crit Depth, Yc (ft) = 0.25
Top Width (ft) = 1.00
EGL (ft) = 0.43
0 .25 .5 .75 1 1.25 1.5
Elev (ft)Depth (ft)Section
99.75 -0.25
100.00 0.00
100.25 0.25
100.50 0.50
100.75 0.75
101.00 1.00
Reach (ft)