HomeMy WebLinkAboutTract Map 3883 Lot 312 Hydro ReportDRAINAGE STUDY FOR:
Parcel 235 of Tr 3883
APN 919-210-015
Okpala Residence
City of Temecula, CA
PERMIT NO. LD22-4150
November 8, 2024
Prepared for:
Peterchris and Sandra Okpala
40530 Calle Fiesta
Temecula, CA 92591
(714) 325-5215
Prepared by:
DSB Engineering
43460 Ridge Park Drive, Suite 200T
Temecula, California 92590
(951) 440-5703
Dino San Buenaventura RCE 77348 Prepared by: DSB
Registration Expires 06/30/25 Checked by: DSB
APPROVED BY
CITY OF TEMECULA
PUBLIC WORKS
david.pina 11/25/2024
11/25/2024 11/25/2024
11/25/20
TABLE OF CONTENTS
I. PROJECT DESCRIPTION ....................................................................................................................................... 3
II. EXISTING SITE CONDITION DRAINAGE .............................................................................................................. 4
III. DEVELOPED SITE CONDITION DRAINAGE ........................................................................................................ 5
IV. HYDROLOGIC METHODOLOGY ........................................................................................................................ 6
V. HYDRAULIC METHODOLOGY ............................................................................................................................ 7
VII. DISCUSSION AND RESULT ............................................................................................................................... 8
APPENDIX A: HYDROLOGIC CALCULATIONS ......................................................................................................... 9
o 100 Year Hydrology Analysis (Existing Area 1A and Proposed Area 1A) ...................................... 9
APPENDIX B: HYDRAULIC CALCULATIONS........................................................................................................... 10
o 8” Onsite Storm Drain Hydraulics ............................................................................................... 10
APPENDIX C: REFERENCE .................................................................................................................................... 11
o Riverside County Excerpt: Plate D-5.6 Impervious Cover for Developed Areas ......................... 11
o Riverside County Excerpt: Plate D-4.3 2-Year 1-Hour Precipitation ........................................... 11
o Riverside County Excerpt: Plate D-4.4 2-Year 1-Hour Precipitation ........................................... 11
o Riverside County Excerpt: Plate D-4.6 Slope of Intensity-Duration Curve ................................. 11
o Riverside County Excerpt: Plate D-5.5 Runoff Index for Pervious Areas .................................... 11
o Riverside County Excerpt: Plate C-1.52 Soil Group Map for Bachelor Mtn. ............................... 11
o Riverside County Excerpt: Plate D-3 Time of Concentration Nomograph .................................. 11
o Riverside County Excerpt: Plate D-4.7 Intensity-Duration Curves Sheet .................................... 11
o Riverside County Excerpt: Plate D-5.7 Runoff Coefficient Data .................................................. 11
o Grading Plan Reference .............................................................................................................. 11
o USGS Contour Map Reference .................................................................................................... 11
MAP POCKET: EXISTING CONDITIONS EXHIBITS ................................................................................................. 12
o Existing Condition Hydrology Exhibit for Rational Method Study .............................................. 12
MAP POCKET: PROPOSED CONDITIONS EXHIBITS .............................................................................................. 13
o Proposed Condition Hydrology Exhibit for Rational Method Study ........................................... 13
I. PROJECT DESCRIPTION
The project is a residential project that will develop the property to include a single-family
home. The project will include the creation of one pad and private driveway entrance that leads
to the residence. The project is located in the City of Temecula on the major intersection of Via
Norte and Calle Fiesta, east of Interstate Freeway 15. The parcel measures approximately 0.83
Ac and is designated as Parcel 235 of Tr 3883 (APN 919-210-015) , referred thereafter as the
Okpala Residence.
The enclosed hydrology report analyzes the 100-year storm event hydrology for the existing
and proposed condition. Project flow rates and time of concentration were determined and
compared. Drainage facilities, were applicable, were analyzed for their hydraulic capacity and
document in Appendix B. Please refer to Appendix E Proposed Condition Hydrology Map for an
overview of the project drainage pattern.
II. EXISTING SITE CONDITION DRAINAGE
Referring to Existing Condition Hydrology Map in the map book section of this report, the local
drainage generally flow is split, draining east at an average slope is 20% and draining southwest
towards Calle Fiesta, draining at an average slope of 5%. The drainage from these two areas
ultimately meets downstream. There is no existing infrastructure, other than a wooden corral
that is located on the project’s westerly boundary.
Review of the NRCS Soil Survey Report and excerpt Plate C-1.53, the project hydrologic soil
classification is identified as Soil Class D, which is characterized as high runoff potential and a
low infiltration capacity. The project area has little to no ground cover with brush along the
existing flow line the traverses the site. The land cover is classified as Grass per the Riverside
County Hydrology Manual.
III. DEVELOPED SITE CONDITION DRAINAGE
As mentioned in the introduction, the project will construct a single-family home with a private
driveway entrance leading up to the residence. The overall drainage pattern follows the existing
condition, with drainage being split and flowing both east and in the southwest direction.
The onsite improvements that consist of impervious areas accounts for 75% of the developed
pad area. For that reason, using Plate D-5.6, the land use is described as a Mobile Home Park,
which is equally described with an average impervious fraction of 75%. Furthermore, given the
pervious area runoff index for the developed site is described as Urban Cover - Residential
Landscaping, which has a value of 75 for soil group type D for AMC II.
Please refer to Appendix E Proposed Condition Hydrology Map, where the overall project
drainage pattern is delineated.
IV. HYDROLOGIC METHODOLOGY
The overall drainage basin of study covers nearly 0.36 acres. A survey was done for the project
area, where contours were generated and used for the design of the proposed project. The
Riverside County Hydrology Manual’s Rational Method Procedure was the basis for the
proposed condition 100-Year hydrologic analysis. The rational method input parameters used
included an AMC of 3 and Land Use, which was modeled as Mobile Home Park and
Undeveloped (Poor Cover) for undeveloped/grass areas. Physical characteristics such as the
flow path and elevation difference were also used in calculating the time of concentration.
Please refer to Appendix A for the full hydrology analysis.
V. HYDRAULIC METHODOLOGY
Due to the projects limited grading and the natural drainage of the site, there are no drainage
facilities required to convey the onsite and offsite flow. Drainage will flow though the site with
limited impacts on the site and downstream drainage course.
VII. DISCUSSION AND RESULT
Table 1: Rational Method Analysis Summary Table
Condition Drainage
Area ID Area (ac) Q100 (cfs)
Existing
Condition 1A 0.39 1.72
Proposed
Condition 1A 0.39 1.77
Upon review of the hydrologic calculations and above summary table, the 100-year flow shows
a decrease in peak flow rates. Although there is an increase in the impervious area of the site,
projects existing condition has a lower time of concentration due to the steep grade condition
and contributes to a higher peak flow rate for the existing condition. Please refer to the
enclosed hydrology report with supporting conclusions hereon.
APPENDIX A: HYDROLOGIC CALCULATIONS
Rational Method Hydrology Analysis
o 100 Year Hydrology Analysis (Existing Area 1A and Proposed Area 1A)
Project Name:
Project Location:
Drainage Area (Acres) - 10 Acres Maximum
Longest Watercourse (Ft) - 1,000' Maximum
Upstream Elevation Of Watercourse (Ft)
Downstream Elevation Of Watercourse (Ft)
Existing Impervious Percentage (%)
Grass Poor Cover
Total=0.39 Ac.Weighted Average RI = 76 89
100-year Flowrate = 1.72 cfs
Tc, Min=4.76 min
100yr Peak Intensity (for drainage area) = 4.96 in/hr
Runoff Coefficient (100-year) = 0.89
Total Drainage Area (Acres) - 10 Acre Max
Longest Watercourse (Ft) - 1,000' Max
Upstream Elevation Of Watercourse (Ft)
Downstream Elev. Of Watercourse (Ft)
Proposed Impervious Percentage (%)Low Loss Rate (%) calc'd: 30.00 Over-ride:
Urban Landscaping Good Cover
Total= 0.39 Ac. Weighted Average RI = 57 75
100-year Flowrate = 1.77 cfs Q100Post = 1.77 cfs Tc100Post = 4.34 min
Tc, Min=4.34 min Q100Pre = 1.72 cfs Tc100Pre = 4.76 min
100yr Peak Intensity (for drainage area) = 5.22 in/hr Delta = 0.05 cfs Delta = -0.42 min
Runoff Coefficient (100-year) = 0.87
Riverside County Rational Method Hydrology - 100-Year Design Storm
Calculation Based on Riverside County Hydrology Manual, April 1978
Pre-Development - Hydrology Information Hydrology Manual Reference Values
AMC 3
88.0
Sub Area A1 - Post Condition Summary 100-Year Project Comparison
0 0 0
0 0 0
Area ID Subarea Acreage Cover Type Vegetative Cover Soil A % Soil B % Soil C % Soil D %
0.75
0.1Q2
0.39
110
1271
Impervious Percentage
(%, Plate D-5.6)75% Mobile Home Park
Sub Area A1 - Post-Development - Soils Information
RI Index
AMC I
RI Index
AMC II
RI Index
AMC III
1A 0.39 Ac.100 57 75 88
Sub Area A1 - Post-Development - Hydrology Information
0 0 0
Soil B %
0.1Q2
2-Year, 1-Hour Intensity (In/Hr) - Plate D-4.3
96
Soil D %Cover TypeSubarea Acreage
RI Index
AMC I
RI Index
AMC III
RI Index
AMC II
Slope Of The Intensity Duration - Plate D-4.6
100-Year, 1-Hour Intensity (In/Hr) - Plate D-4.1
0
0.5
1.2
96.0
Pre-Development - Soils Information
0.39 Ac.A1
Calculated
Input
Vegetative Cover
89
Soil A % Soil C %Area ID
76
Okpala Residence
City of Temecula
0
100
0
0.56
0.39
115
1281
1255
0
0% Undeveloped - Poor Cover
Impervious Percentage
(%, Plate D-5.6)
Existing Condition Summary
1274.7
1 of 1
APPENDIX B: HYDRAULIC CALCULATIONS
o 8” Onsite Storm Drain Hydraulics
Onsite Storm Drain Capacity Calculations
Project:Okapala Residence Location: City of Temecula
By: DSB Date:
ID:Date:mdo version 12.8.00
Mannings Formula
Q=(1.486/n)ARh
2/3S1/2
R=A/P
A=cross sectional area
P=wetted perimeter V=(1.49/n)Rh
2/3S1/2
S=slope of channel Q=V x A
n=Manning's roughness coefficient
Storm Drain ID
Diameter, D
(in)
Depth, d
(In)
Mannings
n q Slope, S (ft/ft)Area,ft2
Wetted
Perimeter, ft
Hydraulic
Radius, ft velocity ft/s flow, cfs
Onsite SD 8 8 0.012 0 1%0.35 2.09 0.17 2.65 0.93
1/30/2024
1/30/2024
d
q
D
Clear Data Entry Cells
d
q
D
Clear Data Entry Cells
APPENDIX C: REFERENCE
o Riverside County Excerpt: Plate D-5.6 Impervious Cover for Developed
Areas
o Riverside County Excerpt: Plate D-4.3 2-Year 1-Hour Precipitation
o Riverside County Excerpt: Plate D-4.4 2-Year 1-Hour Precipitation
o Riverside County Excerpt: Plate D-4.6 Slope of Intensity-Duration Curve
o Riverside County Excerpt: Plate D-5.5 Runoff Index for Pervious Areas
o Riverside County Excerpt: Plate C-1.52 Soil Group Map for Bachelor
Mtn.
o Riverside County Excerpt: Plate D-3 Time of Concentration Nomograph
o Riverside County Excerpt: Plate D-4.7 Intensity-Duration Curves Sheet
o Riverside County Excerpt: Plate D-5.7 Runoff Coefficient Data
o Grading Plan Reference
o USGS Contour Map Reference
0.75 %
Project Location
i=0.50"
Project
Location
i=1.20"
Project Location
slope=.56
4,973'-1 1/2"
Project Location
Existing Area 1A
Prop Area 1A
~3.55 in
~4.96 in/hr
UP
364
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CITY OF TEMECULA
LOT 312 OF TM 3883
PRECISE GRADING PLANS
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CONSTRUCTION NOTES AND QUANTITIES
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364 SF SITTING AREA
142 SF BAR/ BBQ
29 SF WOMEN29 SF MEN
1001 SF TERRACE
SECTION B-B
SECTION A-A SECTION A-A
SECTION C-C
SECTION D-D
DETAIL "A" (LOWER LEVEL PAD)
CONSTRUCTION NOTES
LL PAD=1265.50
C
F
SILT FENCE DETAIL (SC-1)
TYPICAL GRAVEL BAG DETAIL
GRAVELBAG CHECKDAM (SC-6)
ENTRENCHMENT DETAIL
TYPICAL GRAVEL BAG DETAIL (SC-6)
STABILIZED CONSTRUCTION ENTRANCE (TC-1)
TYPICAL FIBER ROLL INSTALLATION (SC-5)EROSION CONTROL PLAN
CONSTRUCTION NOTES
MATERIAL DELIVERY & STORAGE
CONCRETE WASTE MANAGEMENT
SOLID WASTE MANAGEMENT
WM-8
WM-1
WM-5
SPILL PREVENTION AND CONTROLWM-4
ENERGY DISSIPATOR
SILT FENCE
FIBER ROLLS
GRAVEL BAGS
STABILIZED CONSTRUCTION ENTRANCE
SC-1
SC-5
SC-6
SS-10
TC-1
SC-10 STORM DRAIN INLET PROTECTION
PRESERVATION OF EXISTINGSS-2
VEGETATION
HYDROSEEDING (SUMMER)SS-4
SC-7 STREET SWEEPING AND VACUUMING
SC-7
SC-7
SS-4
SC-5
SE-1
TC-1
WM-4
WM-5
WM-1
CA
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SC-6
SC-5
SC-5
SC-5
SC-5
SC-5
SE-1
SC-6
SC-6
SC-6
SC-6
RIPRAP DETAIL (SS-10)
EARTHEN BERM DETAIL
FILL OVER NATURAL SLOPE DETAIL
SS-4
SC-6
SC-6
SC-6
SC-6
SC-6
SC-6
DOWNDRAIN/V-DITCH DETAIL
Project Location
MAP POCKET: EXISTING CONDITIONS EXHIBITS
o Existing Condition Hydrology Exhibit for Rational Method Study
INDEX
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MAP POCKET: PROPOSED CONDITIONS EXHIBITS
o Proposed Condition Hydrology Exhibit for Rational Method Study
INDEX
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