HomeMy WebLinkAboutParcel Map 28530-1 Lot 22 Hydrology StudyAPPROVED BY
CITY OF TEMECULA
PUBLIC WORKS
david.pina 04/11/2023
04/11/2023 04/11/2023
04/11/20
Table of Contents
Discussion……………………………………………………………………………………………………………………………………………1‐2
Appendix A
Vicinity Map
Hydrologic Soils Group Map
Isohyetal Maps
Appendix B
Rational Method Output (Pre‐developed)
Appendix C
Rational Method Output (Developed)
Appendix D
Hydraulic Design
1
Discussion
The project proposes to re‐develop a 1.08‐acres of a 1.23‐acre site located within an existing
retail development at 26478 Ynez Rd. in the city of Temecula. The site is bounded to the south and west
by an existing paved drive aisle, to the north by an existing retail development, and to the east by the
right‐of‐way of Rind Rd.
Site soils have been identified as Hydrologic Soil Group “B.” The Hydrologic Soils Group Map of
the RCFCD Hydrology Manual indicates a soil group of B and C at the project site. However, the soils
investigation of the project site prepared by Soil Pacific Inc. dated May 25, 2021 describes site soils as
gravel, sand, and thin sandy silt layers. Furthermore, infiltration testing performed by Soil Pacific Inc.
determined a good infiltration rate 4‐in/hr of native soils. This information led to the classification of site
soils as being soil group B.
The project site is currently developed for retail use. Impervious surfaces consist of roofs, AC
pavement, concrete hardscape, and concrete gutters. Existing landscape areas are throughout the site.
The imperviousness of the existing development is 87%. The project site is one drainage area. Storm
water sheets across existing landscape areas, AC pavement, and concrete hardscape in a southwesterly
direction. An existing concrete gutter conveys flows westerly through the project site, discharging at the
site’s westerly boundary into the drive aisle of the retail center. Storm water also sheets across the
southerly boundary of the project site into said drive aisle. At the northwesterly corner of the project
site an existing concrete gutter conveys storm water from the adjacent property westerly through the
corner of the site. These flows from the adjacent property bypass the project site and do not comingle
with site runoff. See the Pre‐Developed Hydrology Map in Appendix B.
The project proposes to re‐develop the site for use as a car wash facility. Proposed
improvements consist of proposed a building structure, awnings, AC pavement, concrete hardscape,
concrete curb, concrete gutter, landscaping, fencing, a trash enclosure structure, two catch basin inlets,
an underground infiltration system, an underwalk drain, and a rip‐rap pad. The imperviousness of the
proposed development will be 84%. The proposed development will mimic the existing drainage
patterns of the property, directing storm flows to the existing drive aisle along the westerly and
southerly boundary of the project site. There is one drainage area within the project limits, further
subdivided into two subareas. Drainage Area A1 consists of the majority of the project site. Storm water
sheets across proposed landscape and AC pavement to be intercepted by a proposed concrete gutter.
This conveys flows southerly and storm water is intercepted by a proposed inlet located at the
southwesterly corner of the site. The inlet discharges flows into the proposed underground infiltration
2
system located in the southerly area of the project site. Drainage Area A2 consists of the northwesterly
corner of the project site. Storm water sheets across proposed landscape and AC pavement to be
intercepted by a proposed inlet located along the westerly boundary of the site. This inlet discharges
flows into the same proposed underground infiltration system as Drainage Area A1. Overflows of the
system pond up in the inlet and sheet across a proposed rip‐rap pad into a proposed underwalk drain
located at the southwesterly corner of the project site. This drain discharges flows into the existing drive
aisle as in the existing condition.
A Rational Study has been prepared for both the pre‐developed and post‐developed conditions
of the project site for a 100‐year storm. See Appendix B and C. The results are as follows:
QPRE TC,PRE QPOST TC,POST ΔV VSTORAGE
(CFS) (MIN) (CFS) (MIN) (CF) (CF)
100‐YR 4.27 6.5 3.42 9.8 ‐750 3,075
The change in run‐off volume due to the proposed development has been calculated as follows:
ΔV = 1.5 (ΔQ) (TC,POST*60)
This formula models an estimation of the change in storm water volume, hence it is multiplied by a
factor of 1.5. The proposed development decreases the impervious footprint as well as increases the
time of concentration, and, thus, the volume of storm water runoff (ΔV) generated decreases from the
volume of the pre‐developed condition of the site. The proposed underground infiltration system will
provide retention of storm water runoff that further reduces the volume of storm water discharge from
the project site.. Therefore, the project will not increase the discharge of stormwater runoff from the
site.
The proposed drainage structures have been designed to 100‐year storm flow rate. See
Appendix D.
Appendix A
PROJECT SITE
PROJECT SITE
PROJECT SITE
Appendix B
6373RU100
Riverside County Rational Hydrology Program
CIVILCADD/CIVILDESIGN Engineering Software,(c) 1989 ‐ 2005 Version 7.1
Rational Hydrology Study Date: 10/28/21 File:6373RU100.out
‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐
JN6373 RATIONAL STUDY
PRE‐DEVELOPED CONDITION
100YR STORM
‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐
********* Hydrology Study Control Information **********
English (in‐lb) Units used in input data file
‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐
Program License Serial Number 5016
‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐
Rational Method Hydrology Program based on
Riverside County Flood Control & Water Conservation District
1978 hydrology manual
Storm event (year) = 100.00 Antecedent Moisture Condition = 3
Standard intensity‐duration curves data (Plate D‐4.1)
For the [ Murrieta,Tmc,Rnch CaNorco ] area used.
10 year storm 10 minute intensity = 2.360(In/Hr)
10 year storm 60 minute intensity = 0.880(In/Hr)
100 year storm 10 minute intensity = 3.480(In/Hr)
100 year storm 60 minute intensity = 1.300(In/Hr)
Storm event year = 100.0
Calculated rainfall intensity data:
1 hour intensity = 1.300(In/Hr)
Slope of intensity duration curve = 0.5500
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Process from Point/Station 1.000 to Point/Station 2.000
**** INITIAL AREA EVALUATION ****
______________________________________________________________________
Initial area flow distance = 241.000(Ft.)
Top (of initial area) elevation = 1062.180(Ft.)
Bottom (of initial area) elevation = 1059.140(Ft.)
Difference in elevation = 3.040(Ft.)
Slope = 0.01261 s(percent)= 1.26
TC = k(0.300)*[(length^3)/(elevation change)]^0.2
Initial area time of concentration = 6.453 min.
Rainfall intensity = 4.432(In/Hr) for a 100.0 year storm
COMMERCIAL subarea type
Runoff Coefficient = 0.892
Decimal fraction soil group A = 0.000
Decimal fraction soil group B = 1.000
Decimal fraction soil group C = 0.000
Decimal fraction soil group D = 0.000
RI index for soil(AMC 3) = 74.80
Pervious area fraction = 0.100; Impervious fraction = 0.900
Initial subarea runoff = 4.268(CFS)
Total initial stream area = 1.080(Ac.)
Pervious area fraction = 0.100
Page 1
6373RU100
End of computations, total study area = 1.08 (Ac.)
The following figures may
be used for a unit hydrograph study of the same area.
Area averaged pervious area fraction(Ap) = 0.100
Area averaged RI index number = 56.0
Page 2
Appendix C
6373RD100
Riverside County Rational Hydrology Program
CIVILCADD/CIVILDESIGN Engineering Software,(c) 1989 ‐ 2005 Version 7.1
Rational Hydrology Study Date: 10/28/21 File:6373RD100.out
‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐
JN6373 RATIONAL STUDY
POST‐DEVELOPED CONDITION
100YR STORM
‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐
********* Hydrology Study Control Information **********
English (in‐lb) Units used in input data file
‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐
Program License Serial Number 5016
‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐
Rational Method Hydrology Program based on
Riverside County Flood Control & Water Conservation District
1978 hydrology manual
Storm event (year) = 100.00 Antecedent Moisture Condition = 3
Standard intensity‐duration curves data (Plate D‐4.1)
For the [ Murrieta,Tmc,Rnch CaNorco ] area used.
10 year storm 10 minute intensity = 2.360(In/Hr)
10 year storm 60 minute intensity = 0.880(In/Hr)
100 year storm 10 minute intensity = 3.480(In/Hr)
100 year storm 60 minute intensity = 1.300(In/Hr)
Storm event year = 100.0
Calculated rainfall intensity data:
1 hour intensity = 1.300(In/Hr)
Slope of intensity duration curve = 0.5500
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Process from Point/Station 1.000 to Point/Station 2.000
**** INITIAL AREA EVALUATION ****
______________________________________________________________________
Initial area flow distance = 395.000(Ft.)
Top (of initial area) elevation = 1061.600(Ft.)
Bottom (of initial area) elevation = 1059.800(Ft.)
Difference in elevation = 1.800(Ft.)
Slope = 0.00456 s(percent)= 0.46
TC = k(0.300)*[(length^3)/(elevation change)]^0.2
Initial area time of concentration = 9.639 min.
Rainfall intensity = 3.554(In/Hr) for a 100.0 year storm
COMMERCIAL subarea type
Runoff Coefficient = 0.890
Decimal fraction soil group A = 0.000
Decimal fraction soil group B = 1.000
Decimal fraction soil group C = 0.000
Decimal fraction soil group D = 0.000
RI index for soil(AMC 3) = 74.80
Pervious area fraction = 0.100; Impervious fraction = 0.900
Initial subarea runoff = 3.226(CFS)
Total initial stream area = 1.020(Ac.)
Pervious area fraction = 0.100
Page 1
6373RD100
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Process from Point/Station 2.000 to Point/Station 3.000
**** PIPEFLOW TRAVEL TIME (User specified size) ****
______________________________________________________________________
Upstream point/station elevation = 1055.300(Ft.)
Downstream point/station elevation = 1055.150(Ft.)
Pipe length = 31.00(Ft.) Manning's N = 0.012
No. of pipes = 1 Required pipe flow = 3.226(CFS)
Given pipe size = 18.00(In.)
Calculated individual pipe flow = 3.226(CFS)
Normal flow depth in pipe = 8.00(In.)
Flow top width inside pipe = 17.89(In.)
Critical Depth = 8.20(In.)
Pipe flow velocity = 4.25(Ft/s)
Travel time through pipe = 0.12 min.
Time of concentration (TC) = 9.76 min.
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Process from Point/Station 1.000 to Point/Station 3.000
**** CONFLUENCE OF MAIN STREAMS ****
______________________________________________________________________
The following data inside Main Stream is listed:
In Main Stream number: 1
Stream flow area = 1.020(Ac.)
Runoff from this stream = 3.226(CFS)
Time of concentration = 9.76 min.
Rainfall intensity = 3.530(In/Hr)
Program is now starting with Main Stream No. 2
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Process from Point/Station 21.000 to Point/Station 3.000
**** INITIAL AREA EVALUATION ****
______________________________________________________________________
Initial area flow distance = 306.000(Ft.)
Top (of initial area) elevation = 1056.680(Ft.)
Bottom (of initial area) elevation = 1055.150(Ft.)
Difference in elevation = 1.530(Ft.)
Slope = 0.00500 s(percent)= 0.50
TC = k(0.300)*[(length^3)/(elevation change)]^0.2
Initial area time of concentration = 8.543 min.
Rainfall intensity = 3.798(In/Hr) for a 100.0 year storm
COMMERCIAL subarea type
Runoff Coefficient = 0.890
Decimal fraction soil group A = 0.000
Decimal fraction soil group B = 1.000
Decimal fraction soil group C = 0.000
Decimal fraction soil group D = 0.000
RI index for soil(AMC 3) = 74.80
Pervious area fraction = 0.100; Impervious fraction = 0.900
Initial subarea runoff = 0.203(CFS)
Total initial stream area = 0.060(Ac.)
Pervious area fraction = 0.100
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Process from Point/Station 21.000 to Point/Station 3.000
**** CONFLUENCE OF MAIN STREAMS ****
______________________________________________________________________
The following data inside Main Stream is listed:
In Main Stream number: 2
Stream flow area = 0.060(Ac.)
Runoff from this stream = 0.203(CFS)
Page 2
6373RD100
Time of concentration = 8.54 min.
Rainfall intensity = 3.798(In/Hr)
Summary of stream data:
Stream Flow rate TC Rainfall Intensity
No. (CFS) (min) (In/Hr)
1 3.226 9.76 3.530
2 0.203 8.54 3.798
Largest stream flow has longer time of concentration
Qp = 3.226 + sum of
Qb Ia/Ib
0.203 * 0.929 = 0.189
Qp = 3.415
Total of 2 main streams to confluence:
Flow rates before confluence point:
3.226 0.203
Area of streams before confluence:
1.020 0.060
Results of confluence:
Total flow rate = 3.415(CFS)
Time of concentration = 9.760 min.
Effective stream area after confluence = 1.080(Ac.)
End of computations, total study area = 1.08 (Ac.)
The following figures may
be used for a unit hydrograph study of the same area.
Area averaged pervious area fraction(Ap) = 0.100
Area averaged RI index number = 56.0
Page 3
Appendix D