HomeMy WebLinkAboutSDP 2018-0022; RESORT VIEW APARTMENTS; PRELIMINARY DRAINAGE STUDY; 2019-10-15IDB
ENGINEERING
Professional Civil Engineer and Land Surveyor
Preliminary Drainage Study
for
Resort View
Prepared for:
BNR INVESTMENT & DEVELOPMENT, LLC
23800 VIA DEL RIO
YORBA LINDA, CA 92887
(714) 692-9120
Proiect Site Address
Viejo Castilla Way, Carlsbad, CA
Prepared by:
Michael L. Benesh, R.C.E. 37893
Date:
October 15, 2019
404 South Live Oak Park Road Fallbrook, CA 92028
7 60 731-6603
-·~ City of Carlsbad
OCT 2 2 2019
Planning Division
Engineering Resort View Preliminary Drainage Study
Contents
Section 1. Certification ............................................................................................... 2
Section 2. Discussion ................................................................................................. 2
Section 2.0 l Purpose .......................................................................................... 2
Section 3. Project ........................................................................................................ 3
Section 3.01 Description ..................................................................................... 3
Section 3.02 Topography and Land Use .......................................................... 3
Section 3.03 Off-Site Drainage .......................................................................... 3
Section 4. Methodology .............................................................................................. 5
Section 4.01 Rational Method ........................................................................... 5
Section 4.02 Unit Hydograph ............................................................................. 6
Section 4.03 Hydraulics ...................................................................................... 6
C Section 5. Summary .................................................................................................... 8
Section 5.0 l Post Construction Storm Runoff Impacts .................................... 8
5.0 l . l Storm Runoff Entering the Site ..................................................... 8
5.01 .2 Storm Runoff .................................................................................. 9
Attachment A -Vicinity Map ............................................................................................. A-1
Attachment B -Hydrology Map .......................................................................................... B-1
Attachment C -San Diego County Soils Group Map ...................................................... C-1
Attachment D -San Diego County Hydrology Manual Excerpts ................................... D-1
Attachment E -San Diego County Point Rainfall Maps .................................................... E-1
Attachment F -TC Calculations .......................................................................................... F-1
Attachment G -Rational Method Calculations ................................................................ G-1
Attachment H -Post Development Ql 00 Calculations .................................................... H-1
Attachment I -Hydraulic Calculations ............................................................................... 1-1
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Section 1.
Certification
Declaration of Responsible Charge
Resort View Preliminary Drainage Study
I hereby declare that I a m the engineer of work for this project as defined in Section
6703 of the Business and Professions Code, and that the design is consistent with
current standards.
I understand that the check of prject drawing and specifications by the City of
Carlsbad is confined to a review only and does not relieve me, as engineer of work,
of my responsibilities for project design.
~--C~ L_C_ -10/15/19
Michael L Benesh, RCE 37893
Section 2.
Discussion
Section 2.01 Purpose
Date
RCE 37893
The purpose of this study is to determine the existing and anticipated 100-year storm
runoff and required size of hydraulic structures to protect the proposed and existing
slopes and structures on the site, and to identify existing drainage problems that may
be caused, or aggravated, by project development.
The project is required to meet County of San Diego Hydromodification Mitigation
that requirement that the Post-project runoff conditions (flow rates and durations)
must not exceed pre-development runoff conditions by more than 10 percent for
storms in the range of 0. 1 Q2 up to to the ten year storm event. The SWQMP for the
project contains the hydromodification management plan and supporting
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Engineering Resort View Preliminary Drainage Study
calculations. The detention tanks being proposed to satisfy the hydromodification
requirements will also act to reduce the peak storm runoff from a 100-year storm
event.
Section 3.
Project
Section 3.01 Description
The project is a 0.858 acre site located in the City of Carlsbad, California.
The site is bordered by Viejo Castilla Way to the east, a golf course to the south, and
multi-family residential developments to the north and west.
The site does not caontain any natural drainage channels or significant natural
vegetation. The project site is currently vacant.
The proposed project includes the construction of a 26 unit apartment complex in 4
buildings. The project parking will be inside covered garages and carports below
each building. The construction will include driveways, buildings and the extension of
utilities from Viejo Castilla Street into the site. The proposed activities will be typical
attached residential living.
A detailed vicinity map is included in Attachment A.
Section 3.02 Topography and Land Use
The site slopes generally down from the southwest corner to the northeast corner. The
runoff from the site drains overland to Viejo Castilla Way on the east side of the site.
The runoff travels north in Viejo Castilla Way to Navarra Drive and then east to an inlet
in the cul-de-sac. From there it conveyed to San Marcos Creek by means of a city
storm drain system, and a concrete lined watercourse through the golf course to the
north of the project site.
Section 3.03 Off-Site Drainage
There does not appear to be any significant runoff entering the project site from the
adjoining properties. The previously developed site to the west is generally lower than
the project site and does not drain onto the project site. The Golf Course to the south
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does have some drainage running onto the site that will be directed along the
property line retaining walls to the street after development. The property to the north
is much lower than the site and slopes away.
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Engineering Resort View Preliminary Drainage Study
Section 4.
Methodology
Section 4.01 Rational Method
The Rational Method as described in the San Diego County Hydrology Manual,
Section 3, (Revised June 2003) shall be used to determine storm runoff.
The Rational Method formula is expressed as follows:
Q=CIA
Where:
Q = peak discharge, in cubic feet per second (cfs)
C = runoff coefficient, proportion of the rainfall that runs off the surface.
The coefficient C has no units and is based on the soil group and the
development type for the drainage sub-area. Attachment F includes
calculations for the runoff coefficient for each drainage sub-area.
I= average rainfall intensity for a duration equal to the Tc for the area, (in/Hr.)
A = drainage area contributing to the design location, in acres
The following values are used in the calculations:
Soil Group D from San Diego County Soils Group Map. See Attachment C.
C (Coefficient of Runoff) from Table 3-1.
100 year 6 Hr. Rainfall= 2.7"
100 year 24 Hr. Rainfall =4.8"
See Attachment D.
See Attachment E.
" "
The site is first divided into drainage sub-areas. See the On-Site Hydrology Maps in
Attachment B. The time of concentration, Tc, for each sub-area along the drainage
path is computed based on the initial time of concentration for the initial area and
the travel time to reach each succeeding node. Based on the time of concentration,
the rainfall intensity is determined using Figure 3-2 (See Attachment D ) . Then applying
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Engineering Resort View Preliminary Drainage Study
the rational method equation, the peak runoff is determined at each node along the
drainage path. Q's are tabulated for each sub-area along the drainage path.
The rational method calculations are in Attachment G.
Section 4.02 Unit Hydograph
The Rational Method Unit Hydrograph procedure as described in the San Diego
County Hydrology Manual, Section 6, shall be used to determine time based storm
inflow into the detention tanks. Using this information, and the capacity of the tanls,
the effect of the storage tanks on the peak outflow can be determined.
For the creation of the Rational Method Hydrograph, a 100 year, 6-hour storm event
and a Time of Concentration, Tc, approxiimately equivalent to the Tc determined in
the rational method calculations is used. Peak flow is assumed to occur four hours
into the storm. The incremental flows for each time period are then arranged in
descending order, two thirds before and one third after, around the peak flow to
construct the hydrograph. The hydrograph calculations are in Attachment H.
Section 4.03 Hydraulics
Hydraulic Capacity is determined by use of the Mannings Equation.
The Mannings formula is expressed as follows:
V = 1.49(R 2/3 5112 )/n
Where:
V = velocity (ft./sec.)
R = hydraulic radius which h is determined by dividing the area of flow by the
wetted perimeter (ft.)
s = slope of conduit or channel (ft./ft.)
n= Mannings roughness factor for the conduit or channel
Autocad Hydraflow Express is used to determine the flow in the parkway culverts.
Inlet Capacity is determined using the weir equation.
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Q=3Lh312 or h=(Q/3L)213
Where:
Q = flow (cfs)
L = perimeter of the inlet (ft.)
h = depth of water at the grate (ft.)
The calculations are included in Attachment I.
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Section 5.
Summary
Section 5.01 Post Construction Storm Runoff Impacts
The proposed project will substantially alter the drainage patterns on the site, but will
not alter the off-site or the surrounding area drainage patterns. The Storm water
discharge points after development will not divert runoff from existing conditions. The
potential polutants generated by the additional impervious areas will be mitigated by
directing the flows through bio-filtration BMPs prior to draining to the street. These
infiltration BMPs will be sized to treat the storm runoff from the site. A sump pump
system and detention tank will provide flow control per the County of San Diego
Hydromodification Management Plan and therefore the project will not increase the
rate or amount of surface runoff in a manner which would result in flooding on-or off-
site. If fact, the calculations indicate that the post development 100-year peak runoff
will be considerably less than the storm runoff from the existing site in the same size
storm.
The proposed project will not alter the course of a stream or river, in a manner which
would result in erosion or siltation either on-site or off-site.
The proposed project will not create or contribute runoff water which would exceed
the capacity of existing or planned storm water drainage systems. The potential
increases in runoff flows flow from the site will be mitigated by the inclusion of
hydromodification BMPs in the site drainage system.
The project will not place housing within a 100-year flood hazard area as mapped on
a federal Flood Hazard Boundary or Flood Insurance Rate Map or County Floodplain
Maps as the site to be developed is not within a floodplain.
5.01. 1 Storm Runoff Entering the Site
There are approximately 0.062 acres of undeveloped (Golf Course)property to the
south of the project that drain onto the project site. After construction, a concrete
brow ditch along the south property line will direct the drainage from the south
directly to Viejo Castilla Way, avoidingthe on-site BMPs.
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5.01.2 Storm Runoff
The amount of driveway and parking exposed to storm runoff has been kept to a
minimum through the use of parking garages located under the proposed
residences, but there will still be an increase to the amount of impervious area
prredominantly due to the construction of the buildings and drive aisles. This increase
in impervious area will cause an increase the storm runoff from the project drainage
area.
Prior to development the project site has no impervious areas. After the site is
developed, the impervious area will increase to 0.730 acres (31,804 sf), or 85 percent
of the drainage area.
A comparison of pre-and post-construction runoff for the site drainage basin is
included in Table 5.2 below.
Area Pre-Post-Net
(Ac.) Const. Const. Change
%Imp %Imp
0.920D 0 85 +85%
A See rational method calculations.
8 See rational method calculations.
c See Attachment H.
Pre-Const.
Runoff,
QlO()A
(CFS)
1.4
0 0.858 acres on-site + .0062 acres off-site.
Un-mitigated Mitigated Net Post Const.
Runoff, Q1008 Post Const. Change
(CFS) Runoff, (CFS)
QlQQC
(CFS)
4.4 0.43 -0.97
The Detention Tank BMP has a storage capacity of 5,426 cf. per the SWQMP for the
project. The anticipated runoff from the site in a 100-year 6-hour storm event is 6,777
cf per the calculations in Attachment H. The storage capacity of the detention tanks
is 80% (5,426/6,777) of the storm runoff from the site. The peak flow will be attenuated
by the BMPs and the overall peak runoff from the project will be substantially reduced
after it is developed.
The hydraulic calculations in Attachment I indicate that the proposed storm drain
structures are adequate to protect the site during a 100-year storm event. The on-site
storm drain pipes will be sized with the final plans.
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Attachment A -Vicinity Map
SITE
Portion of U.S.G.S. Encinitas Quadrangle.
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Attachment B -Hydrology Map
Attachment 8-1: Existing Condition Hydrology Map
The full size map is included in folder at back of report.
Attachment 8-2: Proposed Condition Hydrology Map.
The full size map is included in folder at back of report.
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Engineering Resort View Preliminary Drainage Study
Attachment C -San Diego County Soils Group Map
Soils Group Map
Legend
SdlGroupe
r==) Gn>upA
--PB c=i Gn,upC
c:::::J Gn,up D
SOLANABEAC
c::::) U..d<a-1.onnlln,oct C=1 oe,,-u .............
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RI MWF COEFFICIE'.\TS FOR l RDA'.\ .\IU:.\S
Land Use Runoff Coefficient ··c·
Soil Type
NRCS Elements Coun ' Element:;; %IMPER. A B C D
Undisturbed Natwal Terrain (Natural} Permanent Open Space o• 020 0.25 0 30 0 35
Low Density Residential (LOR) Resu:lenlial. 1.0 DU/A or less 10 027 0.32 036 0.41
Low Density Residential (LOR) Residenttal. 2 0 DlJ/A or less 20 0 34 0.38 042 0.46
Low Density Residential (LOR) Res1den1Jal. 2 9 DUI A or less 25 0 38 0.41 045 0.49
Medium Density Residential (MOR) Residential, 4.3 DU/A or less 30 041 0.45 048 0.52
Medium Density Residentnd (MOR) Res1den1Jal. 7.3 DlJ!A or less 40 048 0.51 0 54 0.57
Medium Density Residential (MOR) Res1denllal, 10 9 DlJ/A or less 45 0 52 0.54 0 57 0.60
Medium Density Residential (l\-lDR) Res1den1tal, 14 5 DlJ/A or less 50 0 55 0.58 0.60 063
Hil,!h Density Residential (HOR) Residential, 24 0 DlJ/A or less 65 066 0.67 0.69 0.71
High Density Residential (HOR) Res1denttal, 43 o DU/A or less 80 0.76 077 0 78 079
C:ommercialilnduslflal IN Com) Neighborhood Commercial 80 076 0.77 0.78 0.79
CommercaaVlndustnal (G. Com) General Commercial 85 080 0.80 0.81 082
CommerciaL'lndustnal (0 P. Com) Office Profeiisional/Commercial 90 083 0.84 0.84 0.85
Commercial1Jndustnal (Lmtited I.) L11111ted lndustnal 90 083 0.84 0.84 085
Commercial!lndustr1al General I. General Industrial 95 087 0.87 0.87 087
"The ,-alues associated with 0"1;, impervious may be used for direct calculat1on of the runoff coeflic1ent as descnbed m Section 3.1.2 (repreiienlmg the perv1ous nmoff
coefficient, Cp, for the soil type). or for areas that will remam undisturbed in perpelmty Justaficatton must be given thal the area will remain natural fore\·er (e.g, the area
is located in Cleveland National Forest).
DlHA " dwelling WIiis per acre
NRCS ~ Na11onal Resources Conservation Service
n
)> gt ~ = CQ
Q s· -=-CD n CD ..,,
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Engineering Resort View Preliminary Drainage Study
Table 3-2
MAXIMUM OVERLAND FLOW LENGTH (LM)
& INITIAL TIME OF CONCENTRATION (T1)
Element* Dl l/ Sh, 1 o/1, 2% 3%, 501c,
Acre LJ\,1 Ti LM Ti LM Ti LM Ti LM Ti
"'.'Jatural 50 13.2 70 12.5 85 10.9 100 10.3 100 8.7
LDR 1 50 12.2 70 11.5 85 10.0 100 9.5 JOO 8.0
LDR 2 50 11.3 70 10.5 85 9.2 100 8.8 JOO 7.4
l,DR 2.9 50 10.7 70 10.0 85 8.8 95 8.1 100 7.0
MDR 4.3 50 10.2 70 9.6 80 8.1 95 7.8 100 6.7
l\..fDR 7.3 50 9.2 65 8.4 80 7.4 95 7.0 100 6.0
MDR 10.9 50 8.7 65 7.9 80 6.9 90 6.4 JOO 5.7
MDR 1-l.5 50 8.2 65 7.4 80 6.5 90 6.0 100 5.4
IIDR 24 50 6.7 65 6.1 75 5.1 90 4.9 95 4.3
HDR 43 50 5.3 65 4.7 75 4.0 85 3.8 95 3.4
'."I.Com 50 5.3 60 4.5 75 4.0 85 3.8 95 3.4
G.Com 50 4.7 60 4.1 75 3.6 85 3.4 90 2.9
O.P./Corn 50 4.2 60 3.7 70 3.1 80 2.9 90 2.6
Limited I. 50 4 ') 60 3.7 70 3.1 80 2.9 90 2.6
General I. 50 3.7 60 3.2 70 2.7 80 2.6 90 2.3
*Sec Tahk 3-1 for more tktailcd description
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LM Ti
l00 6.9
100 6.4
100 5.8
l00 5.6
l00 5.3
100 4.8
100 4.5
JOO 4.3
100 3.5
100 2.7
100 2.7
100 2.4
100 ') 1 -·-
100 2.2
JOO 1.9
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Engineering Resort View Preliminary Drainage Study
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J "· .......... I r--...... J ---......::.<,"·• .......... t--.1 , '-.....-....... I ·7-i'-.... -~ V I ~~ I/ r--.... I/ I"-~I .... I'-...
UAWL!
Cllll!o:0 •1G S•2.R.
Cbol1 u,,,• Depth= 0 4 Vt1oc•v = 4 4 lp.a.
I"--.. ....
' I 7 I t 10 n,llclu>,oa cc: ~ s > 20 JII ,IC) !,O
SOURCE San ()9gO COIJlllY 1>91)ilrtn'enl of Sp«:111 Di1hcl SenlicH ONign !Aanual
f I C. l It I'
Gullw, ■IIU ~UiKJw11y Obu:lt<Hgv • Vvlix:lly CIUIII I a-6 I
October 15, 2019
C:\MLB Projects\County or Son Diego\ 17-id<IOO Resoo View Ca\Droinoge S1udy\Resoo View Preimlnary Drainage S1udy.docx
Page D-4
Engineering Resort View Preliminary Drainage Study
Attachment E -San Diego County Point Rainfall Maps
t ~ -1--------+----
j_t ! to . 1 I ()) 1 () .,,,,,.. t ~ ..,. .,,,,,. .
(i) t
r ~ 0
()Ci) l t -+-
I
1()1
-::>_
t 11 ;!1
l
r-t+tl1 r j r
'
100 Year -6 Hour Rainfall
October 15, 2019 Page E-1
C:\MLB Projects\County of Son Diego\ I 7""1400 Resort View Co\Droinoge Study\Resort View Prelminory Drainage Study.docx
Engineering Resort Vfew Preliminary Drainage Study
(_
OCEAN
t t
t-f • I
I t
.. ..
+
+ l b
100 Year -24 Hour Rainfall
October 15, 2019 Page E-2
C:\MLB Projects\County of Son Diego\ 17-sd400 Resort View Ca\Dralnage Study\Resort View Preliminary Drainage Study.docx
Engineering
Attachment F -TC Calculations
Existing Condition
Tc, Initial Area OMA 1
Total Area= 0.920 Acres
% Imp = 0% Use Natural
L=310', h=23'
Initial Slope > 10%
Ti=6.9 Min., Lm=lO0'
L=210', h=13'
Tt=( l 1.9(L/5280)3/h)0-385 = 0.023 hrs= 1.4 min
Tc=6.9 + 1.4 = 8.3 min.
Proposed Condition
Tc, Initial Area DMA-P-10
Total Area = 0.290 Acres
% Imp= 81.8% Use HOR 43
L=180'
Initial Slope 1 %
Ti=4.7 Min., Lm=65'
Curb & Gutter @ 0.5%
V=l .6 fps
Tt=l 15'/(l.6 fps x 60 sec/min)= 1.2 min
Tc=4.7 + 1.2 = 5.9 min.
Tc, Initial Area DMA-P-20
Total Area= 0.439 Acres
% Imp= 88.9% Use OP-Com
L=135', h=l.3'
Initial Slope 1 %
Ti=3.9 Min., Lm=60'
Curb & Gutter @ 0.5%
V=l .7 fps
Tt=75'/(l .7 fps x 60 sec/min)= 0.7 min
Tc=3.9+0.7 = 4.6 min., Use 5 min.
October 15, 2019
Resort View Preliminary Drainage Study
Overland Flow
Page F-1
C:\MLB Projects\County of San Diego\ I 7-sd400 Resort View Ca\Drainage Study\Resort View Preliminary Drainage Sludy.docx
(
Engineering Resort View Preliminary Drainage Study
Attachment G -Rational Method Calculations
The Rational Method as described in the San Diego County Hydrology Manual,
Section 3, (Revised June 2003) shall be used to determine storm runoff.
The Rational Method formula is expressed as follows:
Q=CIA
Where:
Q = peak discharge, in cubic feet per second (cfs)
C = runoff coefficient, proportion of the rainfall that runs off the surface.
The coefficient C has no units and is based on the soil group and the
development type for the drainage sub-area. Attachment F includes
calculations for the runoff coefficient for each drainage sub-area.
I= average rainfall intensity for a duration equal to the Tc for the area, (in/Hr.)
A = drainage area contributing to the design location, in acres
The following values are used in the calculations:
Soil Groups from San Diego County Soils Group Maps. See Attachment C.
C (Coefficient of Runoff) from Table 3-1.
100 year 6 Hr. Rainfall = 2.7"
100 year 24 Hr. Rainfall =4.8"
See calculations on the folowing pages.
October 15, 2019
See Attachment D.
See Attachment E.
II II
C:\MLB Projects\County of San Diego\ 17-sd400 Resort View Ca\Drainage Study\Resort View Preliminary Drainage Study.dacx
Page G-1
Rational Method Calculation Form
Project: Resort View
Drainage Soil %Imp A
Area Type Area Acres
C CA I:CA I
Frequency 100 Year
Developed Condition
P6=2.7 in./hr
Q Slope
In./Hr. CFS
Delays caused by biofilters & pumping ignored.
DMA-P-10 D 81.8% 0.290 0.79 0.230 0.230 6.39 1.5
0.01 DMA-P-11 D 0.0% 0.009 0.30 0.000 0.230 6.19 1.4
To Pump 0.230 6.11 0.01 1.4
DMA-P-20 D 88.9% 0.439 0.83 0.360 0.360 7.11 2.6
DMA-P-21 D 0.0% 0.014 0.30 0.000 0.360 7.11 2.6
To Pump 0.360 7.02 2.5 0.01
Pump Confl 0.521 7.02 3.7
DMA-P-30 D 100.0% 0.033 0.90 0.030 0.030 7.11 0.2
DMA-P-31 D 0.0% 0.001 0.30 0.000 0.030 7.11 0.2
DMA-P-40 D 100.0% 0.038 0.90 0.030 0.030 7.11 0.2
DMA-P-41 D 0.0% 0.001 0.30 0.000 0.030 7.11 0.2
DMA-P-50 D 100.0% 0.032 0.90 0.030 0.030 7.11 0.2
DMA-P-51 D 0.0% 0.001 0.30 0.000 0.030 7.11 0.2
Tank Conf 0.611 7.02 4.3
DMA-P-60 D 0.0% 0.062 0.30 0.020 0.020 7.11 0.1
Section V L Tt
'/Sec. Ft. Min.
12" 4 74 0.3
12" 4 30 0.1
12" 4 25 0.1
Tc
Min.
5.9
6.2
6.3
5.0
5.0
5.1
5.1
5.0
5.0
5.0
5.0
5.0
5.0
5.1
5.0
Page G-2
Calculated by MB
Date: 8/15/2019
Remarks
Attachment F-L=180' h=2.1'
Pipe flow to BF-1
Pipe Flow to Pump
Attachment F-L=135' h=l.3'
BF-2 Add-in Area
Pipe Flow to Pump
Pump Conf
Small area, assumed.
Add in area
Small area, assumed.
Add in area
Small area, assumed.
Add in area
Tank Conf
Small area, assumed.
~
Rational Method Calculation Form
Project: Resort View
Drainage Soil %Imp A
Area Type Area Acres
DMA-1 D 0.0% 0.920
C CA l:CA
0.30 0.280 0.280
I
Frequency 100 Year
Existing Condition
P6=2. 7 in./hr.
Q Slope
In./Hr. CFS
5.13 1.4
Section V
'/Sec.
L Tt
Ft. Min.
Tc
Min.
8.3
Page G-3
Calculated by MB
Date: 8/15/2019
Remarks
Attachment F-L=310' h=23'
(
Engineering Resort View Preliminary Drainage Study
Attachment H -Post Development Q100 Calculations.
The Rational Method Unit Hydrograph procedure as described in the San Diego County Hydrology
Manual, Section 6, shall be used to determine time based storm inflow into the detention tanks. Using
this information, and the capacity of the tanls, the effect of the storage tanks on the peak outflow can
be determined.
For the creation of the Rational Method Hydrograph the following information is used:
l 00 year, 6-hour rainfall, P6= 2.7" from Attachment E.
Time of Concentration, Tc= 6 min. from Rational Method Calculations-developed site, Attachment G.
CA= 0.69 from Rational Method Calculations for developed site, Attachment G.
Rainfall intensity, I=7.44P6T-0.64s
The Unit Hydrograph calculations on on the following pages.
The storage capacity of the two detention pipes is 3, 135 cf each, or 6,270 cf when the water is at the
overflow riser height of 7.5 feet. The outflow of the 0.3" orifice flowing freely with 7.5 feet of head is less
than 0.01 cfs and wil lbe ignored for determining the peak outflow from the site.
From the calculations, it can be seen 6-hour, l 00-year storm runoff from the site is just 108% of the
detention pipe capacity of 6,270 cf.
The tanks drain to the dry-wells at an elevation lower than the outflow to the street. Assuming no
infiltration, the outflow of the orifice will be virtually zero as the water surface in the dry well will be well
above it. The outflow from the tanks, and the site, will be approximately equivalent to the inflow.
Therefore based on the hydrograph calculations, the tanks fill up at the 5 hour mark on the 6-hour
storm. The peak inflow into the tanks after this point in time is 0.17 cfs. The actual outflow will be further
reduce by the effects of infiltration and storage at the dry wells, but these calculations are more than
sufficicient to demonstrate that the peak runoff after development will be much less than the current
condition.
October 15, 2019 Page H-1
C:\MLB Projects\County of San Diego\ l 7-sd400 Resort View Ca\Drainage Study\Resorl View Preliminary Drainage Study.docx
Unit Oograph Calculation Form
.r-,, rOH-2 Frequent, /oo Year
Project: Resort View 6-Hour Storm Calculated by MB
P6=2.7 in./hr. Date: 8/15/2019
Tc= 6 min. Pipe Storage 5,426 cf
CA= 0.69
P6= 2.70 in
UH Elapsed Effective Tank Tank Tank Tank Tank Tank
Time Tc I p Time Time Rainfall Inflow Inflow Outflow Storage Depth Discharge
Period Min. in/hr. in Period Hrs. in. Rate cfs Volume cf Volume cf CF Ft cfs
1 6 6.32 0.63 1 0.10 0.02 0.112 40 40 0.03 0.000
2 12 4.04 0.18 2 0.20 0.02 0.114 41 82 0.06 0.001
3 18 3.11 0.13 3 0.30 0.02 0.116 42 0 123 0.09 0.001
4 24 2.59 0.10 4 0.40 0.02 0.119 43 0 165 0.12 0.001
5 30 2.24 0.09 5 0.50 0.02 0.120 43 0 208 0.16 0.002
6 36 1.99 0.07 6 0.60 0.02 0.123 44 1 252 0.19 0.002
7 42 1.80 0.07 7 0.70 0.02 0.124 45 1 296 0.22 0.002
8 48 1.65 0.06 8 0.80 0.02 0.128 46 1 341 0.26 0.002
9 54 1.53 0.06 9 0.90 0.02 0.129 47 1 387 0.29 0.002
10 60 1.43 0.05 10 1.00 0.02 0.133 48 1 434 0.33 0.002
11 66 1.35 0.05 11 1.10 0.02 0.135 49 1 482 0.36 0.002
12 72 1.27 0.05 12 1.20 0.02 0.139 50 1 531 0.40 0.003
13 78 1.21 0.04 13 1.30 0.02 0.141 51 1 581 0.44 0.003
14 84 1.15 0.04 14 1.40 0.02 0.146 53 1 632 0.48 0.003
15 90 1.10 0.04 15 1.50 0.02 0.148 53 1 685 0.51 0.003
16 96 1.06 0.04 16 1.60 0.02 0.153 55 1 739 0.56 0.003
17 102 1.02 0.04 17 1.70 0.02 0.156 56 1 794 0.60 0.003
18 108 0.98 0.04 18 1.80 0.02 0.162 58 1 851 0.64 0.003
19 114 0.95 0.03 19 1.90 0.02 0.165 60 1 909 0.68 0.004
20 120 0.92 0.03 20 2.00 0.02 0.172 62 1 970 0.73 0.004
21 126 0.89 0.03 21 2.10 0.03 0.176 63 1 1,032 0.78 0.004
22 132 0.86 0.03 22 2.20 0.03 0.184 66 1 1,097 0.83 0.004
23 138 0.84 0.03 23 2.30 0.03 0.189 68 1 1,164 0.88 0.004
24 144 0.81 0.03 24 2.40 0.03 0.198 71 1 1,234 0.93 0.004
25 150 0.79 0.03 25 2.50 0.03 0.204 73 1 1,306 0.98 0.004
26 156 0.77 0.03 26 2.60 0.03 0.216 78 2 1,382 1.04 0.004
27 162 0.75 0.03 27 2.70 0.03 0.223 80 2 1,461 1.10 0.005
Unit Oograph Calculation Form n Frequent.., 100 Year OH-3
Project: Resort View 6-Hour Storm Calculated by MB
P6=2.7 in./hr. Date: 8/15/2019 CA= 0.69
P6= 2.70 in
UH Elapsed Effective Tank Tank Tank Tank Tank Tank
Time Tc I p Time Time Rainfall Inflow Inflow Outflow Storage Depth Discharge
Period Min. in/hr. in Period Hrs. in. Rate cfs Volume cf Volume cf CF Ft cfs
28 168 0.74 0.03 28 2.80 0.03 0.238 86 2 1,545 1.16 0.005
29 174 0.72 0.03 29 2.90 0.04 0.247 89 2 1,632 1.23 0.005
30 180 0.71 0.03 30 3.00 0.04 0.267 96 2 1,726 1.30 0.005
31 186 0.69 0.02 31 3.10 0.04 0.278 100 2 1,824 1.37 0.005
32 192 0.68 0.02 32 3.20 0.04 0.306 110 2 1,933 1.45 0.005
33 198 0.66 0.02 33 3.30 0.05 0.323 116 2 2,047 1.54 0.005
34 204 0.65 0.02 34 3.40 0.05 0.366 132 2 2,177 1.64 0.006
35 210 0.64 0.02 35 3.50 0.06 0.393 142 2 2,317 1.74 0.006
36 216 0.63 0.02 36 3.60 0.07 0.468 168 2 2,483 1.87 0.006
37 222 0.62 0.02 37 3.70 0.07 0.521 188 2 2,669 2.01 0.006
38 228 0.61 0.02 38 3.80 0.10 0.699 252 2 2,918 2.19 0.006
39 234 0.60 0.02 39 3.90 0.13 0.871 314 2 3,229 2.43 0.007
40 240 0.59 0.02 40 4.00 0.63 4.400 1,584 2 4,811 3.62 0.112
41 246 0.58 0.02 41 4.10 0.18 1.228 442 40 5,212 3.92 0.252
42 252 0.57 0.02 42 4.20 0.09 0.593 214 91 5,335 4.01 0.303
43 258 0.56 0.02 43 4.30 0.06 0.426 153 109 5,380 4.04 0.329
44 264 0.55 0.02 44 4.40 0.05 0.343 123 118 5,385 4.05 0.329
45 270 0.54 0.02 45 4.50 0.04 0.292 105 118 5,371 4.04 0.329
46 276 0.54 0.02 46 4.60 0.04 0.256 92 118 5,345 4.02 0.329
47 282 0.53 0.02 47 4.70 0.03 0.230 83 118 5,310 3.99 0.303
48 288 0.52 0.02 48 4.80 0.03 0.210 75 109 5,276 3.97 0.303
49 294 0.51 0.02 49 4.90 0.03 0.193 70 109 5,237 3.94 0.277
50 300 0.51 0.02 50 5.00 0.03 0.180 65 100 5,202 3.91 0.252
51 306 0.50 0.02 51 5.10 0.02 0.169 61 91 5,172 3.89 0.252
52 312 0.49 0.02 52 5.20 0.02 0.159 57 91 5,138 3.86 0.227
53 318 0.49 0.02 53 5.30 0.02 0.151 54 82 5,111 3.84 0.227
54 324 0.48 0.02 54 5.40 0.02 0.144 52 82 5,081 3.82 0.203
55 330 0.48 0.02 55 5.50 0.02 0.137 49 73 5,057 3.80 0.203
56 336 0.47 0.02 56 5.60 0.02 0.131 47 73 5,032 3.78 0.203
~ 0
[)H-4 Unit Hy,../ograph Calculation Form Frequenc, /oo Year
Project: Resort View 6-Hour Storm Calculated by MB
P6=2.7 in./hr. Date: 8/15/2019
CA= 0.69
P6= 2.70 in
UH Elapsed Effective Tank Tank Tank Tank Tank Tank
Time Tc I p Time Time Rainfall Inflow Inflow Outflow Storage Depth Discharge
Period Min. in/hr. in Period Hrs. in. Rate cfs Volume cf Volume cf CF Ft cfs
57 342 0.47 0.02 57 5.70 0.02 0.126 45 73 5,004 3.76 0.179
58 348 0.46 0.02 58 5.80 0.02 0.121 44 64 4,984 3.75 0.179
59 354 0.46 0.02 59 5.90 0.02 0.117 42 64 4,961 3.73 0.156
60 360 0.45 0.02 60 6.00 0.02 0.113 41 56 4,946 3.72 0.156
total 16.5 0.59 total 2.00 6,777 1,831
Unit O graph Calculation Form
Project: Resort View
Frequency ,00 Year
6-Hour Storm
P6=2. 7 in./hr.
Pa::, H-5
Calculated by MB
Date: 8/15/2019
5.000
4.500
4.000
3.500
3.000
2.500
2.000
1.500
1.000
0.500
0.000
V'l LL u
-Inflow -Tank Outflow
000000000000000000000000000000000000000000000000000000000000 ~Nm¢~~~~mOMNm¢~~~oomo~Nmv~w~oomo~Nm~~~~oomorlNm¢~~~oomoMNm¢~~~oomo ciOOciciOciciO~~~~~~~~~~NNNNNNNNNNMmmmmmmmmMq¢~q¢qqq¢~~~~~~~~~~~~
Time (hours)
Unit Oograph Calculation Form
Project: Resort View
Pipe Lookup Table I Depth (ft) I Storage (A-F) I
0.00 0.000000
0.05 0.001442
0.09 0.002884
0.14 0.004325
0.19 0.005767
0.24 0.007209
0.28 0.008651
0.33 0.010093
0.38 0.011535
0.43 0.012976
0.47 0.014418
0.52 0.015860
0.57 0.017302
0.61 0.018744
0.66 0.020185
0.71 0.021627
0. 76 0.023069
0.80 0.024511
0.85 0.025953
0.90 0.027395
0.94 0.028836
0.99 0.030278
1.04 0.031720
1.09 0.033162
1.13 0.034604
1.18 0.036045
1.23 0.037487
1.28 0.038929
1.32 0.040371
1.37 0.041813
1.42 0.043255
1.46 0.044696
1.51 0.046138
1.56 0.047580
1.61 0.049022
1.65 0.050464
1.70 0.051905
1.75 0.053347
Storage (CF) I
0
63
126
188
251
314
377
440
502
565
628
691
754
816
879
942
1005
1068
1131
1193
1256
1319
1382
1445
1507
1570
1633
1696
1759
1821
1884
1947
2010
2073
2135
2198
2261
2324
"' . I Frequent., ,00 Year
Outflow (cfs)
0.0000
0.0009
0.0013
0.0016
0.0019
0.0021
0.0023
0.0025
0.0027
0.0028
0.0030
0.0031
0.0033
0.0034
0.0035
0.0037
0.0038
0.0039
0.0040
0.0041
0.0042
0.0043
0.0044
0.0045
0.0046
0.0047
0.0048
0.0049
0.0050
0.0051
0.0052
0.0053
0.0053
0.0054
0.0055
0.0056
0.0057
0.0057
6-Hour Storm
P6=2.7 in./hr.
0 iJ ... l:IJ H-6
Calculated by MB
Date: 8/15/2019
Unit 11Jograph Calculation Form
Project: Resort View
Pipe Lookup Table I Depth (ft) I Storage (A-F) I
1.79 0.054789
1.84 0.056231
1.89 0.057673
1.94 0.059115
1.98 0.060556
2.03 0.061998
2.08 0.063440
2.13 0.064882
2.17 0.066324
2.22 0.067765
2.27 0.069207
2.31 0.070649
2.36 0.072091
2.41 0.073533
2.46 0.074974
2.50 0.076416
2.55 0.077858
2.60 0.079300
2.64 0.080742
2.69 0.082184
2.74 0.083625
2.79 0.085067
2.83 0.086509
2.88 0.087951
2.93 0.089393
2.98 0.090834
3.02 0.092276
3.07 0.093718
3.12 0.095160
3.16 0.096602
3.21 0.098044
3.26 0.099485
3.31 0.100927
3.35 0.102369
3.40 0.103811
3.45 0.105253
3.49 0.106694
3.54 0.108136
Storage (CF) I
2387
2449
2512
2575
2638
2701
2763
2826
2889
2952
3015
3077
3140
3203
3266
3329
3391
3454
3517
3580
3643
3706
3768
3831
3894
3957
4020
4082
4145
4208
4271
4334
4396
4459
4522
4585
4648
4710
~
Frequency 1bO Year
6-Hour Storm
P6=2.7 in./hr.
Outflow (cfs) I
0.0058
0.0059
0.0060
0.0060
0.0061
0.0062
0.0063
0.0063
0.0064
0.0065
0.0065
0.0066
0.0067
0.0067
0.0068
0.0069
0.0069
0.0070
0.0071
0.0071
0.0072
0.0072
0.0073
0.0074
0.0074
0.0075
0.0075
0.0076
0.0077
0.0077
0.0078
0.0083
0.0152
0.0262
0.0399
0.0557
0.0732
0.0921
0
f1-0~d H-7
Calculated by MB
Date: 8/15/2019
Unit Oograph Calculation Form
Project: Resort View
Pipe Lookup Table I Depth (ft) I Storage (A-F) I
3.59 0.109578
3.64 0.111020
3.68 0.112462
3.73 0.113904
3.78 0.115345
3.83 0.116787
3.87 0.118229
3.92 0.119671
3.97 0.121113
4.01 0.122554
4.06 0.123996
4.11 0.125438
4.16 0.126880
4.20 0.128322
4.25 0.129764
Storage (CF) I
4773
4836
4899
4962
5024
5087
5150
5213
5276
5338
5401
5464
5527
5590
5653
0
Frequenc., i'oo Year
6-Hour Storm
P6=2. 7 in./hr.
0 utflow ( cfs) I
0.1123
0.1336
0.1558
0.1788
0.2026
0.2269
0.2518
0.2772
0.3029
0.3289
0.3552
0.4164
0.5856
0.8175
1.0895
l)H-8
Calculated by MB
Date: 8/15/2019
Engineering
Attachment I -Hydraulic Calculations.
Precast Concrete Drain Inlets:
Resort View Preliminary Drainage Study
There are two precast concrete drains on the project. Each one captures the runoff from the driveway
in which it is located. The runoff in the driveway is approximately half of the total runoff for each
drainage area. For preliminary sizing, the entire drainage area will be assumed to drain to the inlet.
Overflow at the inlet in BF-2 flows to the sump pump. The inlet has the largest Ql00 peak flow at 2.6 cfs
and must capture the flow and direct it to sump. The inlet is a 24" square grate and the grate is 0.50
feet below the top of the BMP.
The weir equation for determining the capacity of the inlet is:
Q=3Lh3l2 or h={Q/3L)2l3
Wher:
L = 8'
Q100 = 2.6 cfs
C h =(2.6/(3*8))213 = 0.23' ✓OK
Parkway Culvert:
Autocad Hydraflow Express is used to determine the flow in the parkway culverts. The culvert is the
outfall from the detention tank and will be sized to carry the un-mitigated peak flow in the event of a
failure at the detention tank outlet.
The culverts dimensions are:
Width= 4.0'
Height= 4"
Slope= 0.02
Peak Q 100 = 4.3 cfs
The results are on the following page.
October 15, 2019
C:\MLB Projects\County of San Diego\ 17-sd400 Resort View Ca\Drainage Study\Resort View Preliminary Drainage Study.docx
Page 1-1
Engineering
Channel Report
~ EJqllH& Elllensian fer Auladftll&CMI 3DC by Aulal_._, Ille.
T ANK-1 Outfall
Reclangular
Bottom Width (ft)
Total Depth (ft)
Invert Elev (ft)
Slope(%)
N-Value
calculatlona
Compute by:
Known Q (cfs)
Elev (ft)
68.00
67.50
87.00
86.50
86.00
0
October 15, 2019
.5
= 4.00
= 0.33
-66.70
-2.00 = 0.015
Known a
= 4.30
1.5 2
Section
-..~ --..
2.5
Resort View Preliminary Drainage Study
Highlighted
Depth (ft) a (els)
Area (sqft)
Velocity (ft/s)
Wetted Perim (ft)
Crit Deplh, Ye (ft)
Top Width (ft)
EGL (ft)
3 3.5 4
Thursday, .-Ug 15 2019
= 0.23
-4.300
= 0.92
-4.67
-4.46
-0.33
-4.00
-0.57
4.5
Depth
1.30
0.80
0.30
-0.20
-0.70
5
Page 1-2
C:\MLB Projects\County of San Diego\ 17-sd400 Resort View Ca\Drainage Study\Resort View Preliminary Drainage Study.docx
.:..6S.1!f!,-...
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QlOO = 1.4 cfs
Elev c 66.2
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Notes:
• Underlying Hydrologic Soils Group for the entire project is Soils Group D.
• Runoff Factor per Table B-1.1 = 0.30
• There are no existing impervious areas on the site.
Legend:
DMA Name
DMA Area
DMA Impervios Cover
DMA % Impervious
Drainage Area Boundary
DMA-0
100 SF
(10 SF IMP)
0.0% IMP
------
SHEET I
Engine¢ring
Professional f;ivil ifngineers and Land Surveyors
Attachment B1
Resort View
(Viejo Castilla Way) 1 404 South Live cj)ak Park Road, Fallbrook, CA 92028
"Phone 760 731-6603
E-Mail: MLBcnc,;h@pacbcll.net
Existing Condition Hydrology Map
OF 1
<l
'11
11-----M------M------x, ------M------M------M------M------M,,-----M------------M------M------M------M-~-----M------M------M------M---------w------w----
-----......... w -------w
QlOO = 0.3 cfs (mitigated)
Q100 = 4.3 cfs (unmititgated)
~ \ ,ii \ 64.5'\\ -~-1'2 ----,~
-----
,-, ,-, ~
' 66
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Scale: 1"=10'
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+-+-,,---. ,:;;D-_------··sD·
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\
DM1-P-20
0.439 AC
(170051SF IMP)
88.9r, IMP
'
QlOO = 1.4 cfs
I;; '
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DMA-P-10
0.290 AC
(10312 SF IMP)
81.8% IMP
\
Q100 = 1.5 cfs
. : ~-: .. ·...--:-·
~ ...
• -s --< ..
' '
DMA-P-50
0.032 AC
(1410 SF IMP)
100.0% IMP
.. / .. --:--..
Q100 = 1.5 cfs
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rl--7 ;j,
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----
Q100 = 0.1 cfs
=
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79.8 TG
74.5 INV 1
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,
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,
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12" Cone
I
I
I
Brow-Ditch
TANK-1
' 5313 cf
STORAGE TANK
DMA-P-60
0.062 AC
(0 SF IMP)
0.0% IMP
I
,
'
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I
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I
!
'i ,_I
Notes:
• Underlying Hydrologic Soils Group for the entire project is Soils Group D.
• Runoff Factor per Table B-1.1 = 0.30
• There are no existing impervious areas on the site.
Legend:
Impervious Surface
(Parking, building, sidewalk)
Storm Drain
Drain Inlet
Detention Tank
Bifi/ter BMP
Sump Pump
Storm Drain Pressure Main
DMA Name
DMA Area
DMA Impervios Cover
DMA % Impervious
Drainage Area Boundary
i--s--
+ + + + + + + + + + + + + + + + + + + +
+ + + + +
-----FM-----
DMA-0
100 SF
(10 SF IMP)
0.0% IMP
------
SHEET
Engineeting
Professional C{vil .Engineers and Land Surveyors
Attachment B2
Resort View
(Viejo Castilla Way) 1 404 Sol1th Live Oat{ Park Road, Fallbrook, CA 92028
Phone 760 731-6603 ' E-Mail: 1\1LBencsh@pacbcll.net
Proposed Condition Hydrology Map
OF 1