HomeMy WebLinkAboutAttachment 09 Preliminary Drainaige AnalysisPreliminary Drainage Study
For:
Project Name: Orange Corp Yard Workforce Housing
637 West Struck Avenue
Orange, CA 92867
APN(s): 375-291-14
Prepared for:
C & C Development Co., LLC
14211 Yorba St., S-200
Tustin, CA 92780
(714) 288-7600
Prepared by:
So Cal Civil Solutions, Inc.
Mike J-S Ma RCE No. C68130
26131 Via Oceano
Mission Viejo, CA 92691
(949) 322-3657
Prepared on: Mar 29, 2020
Preliminary Drainage Study for Orange Corp Yard Workforce Housing
Table of Contents
1.0 INTRODUCTION.......................................................................................................................2
1.1 Study Background..............................................................................................................................2
1.2 Project Overview................................................................................................................................2
2.0 SETTING.....................................................................................................................................5
2.1 Land Cover and Topography.............................................................................................................5
2.2 Soil Type..............................................................................................................................................5
2.3 FEMA's FIRM....................................................................................................................................5
2.4 Groundwater......................................................................................................................................5
2.5 Existing Drainage Facility.................................................................................................................6
2.6 Proposed Drainage Plan....................................................................................................................6
3.0 HYDROLOGY ANALYSES.......................................................................................................7
3.1 Introduction........................................................................................................................................7
3.2 Rational Method Analysis..................................................................................................................7
3.3 Results & Discussion..........................................................................................................................7
4.0 CONCLUSION............................................................................................................................9
5.0 APPENDICES...........................................................................................................................10
LIST OF APPENDICES
Appendix A Soil Group Map (A.1), Soil Report (A.2), FIRM (A.3) & As-built Plans for Orange
Corp. Yard (A.4)
Appendix B Rational Method Modeling: Hydrology Maps (B.1), Existing Condition Results (B.2)
& Proposed Condition Results (B.3)
Appendix C Preliminary Grading and Drainage Plan
1
Preliminary Drainage Study for Orange Corp Yard Workforce Housing
1.0 INTRODUCTION
1.1 Study Background
The purpose of this drainage study report is to provide necessary hydrology and hydraulics analyses
in association with the proposed project – “Orange Corp Yard Workforce Housing” (herein referred
to as the “Project”). As a technical support, this report accompanies the proposed drainage plan for
the Project to be reviewed by the City of Orange (herein referred to as the “City”) and other agencies
if appropriate. Therefore, approval of this report will serve as a basis for approving the
corresponding engineering plan. Yet this is a preliminary report thus subject to revisions as needed
over the course to the project’s final design.
1.2 Project Overview
C & C Development Co., LLC is proposing a multi-family residential apartments application along
with lot lines adjustment to be located at 637 West Struck Avenue in the City of Orange. The subject
site is vacant land, comprising approximately 2.7 acres of an irregular-shaped land which is situated
in the far east end of the 17.23-acre parcel (APN 375-291-14) that is located at the northeast corner
of the intersection at North Batavia Street and West Struck Avenue (See Figures 1-1 & 1-2). The site
is bound on the north by commercial buildings, on the east by two sets of railroad tracks with multi-
family residential beyond, on the south by West Struck Avenue, a fully improved roadway, followed
by commercial buildings, and on the west by the remainder of the City of Orange Corporate Yard.
Access to the site comes from the eastern most end of West Struck via the existing cul de sac to the
North and past Mary’s Kitchen.
The development proposes 62 affordable apartment homes in two – three story “walk up” style
buildings of similar size. There are 42 three-bedroom units and 20 one- bedroom units along with a
Leasing Office, Community Laundry Facility, 2 Community Rooms with a common Kitchen, a
computer lab and an onsite community service office. There are a total of 133 parking stalls. The
new community is walled & gated for added security.
2
Preliminary Drainage Study for Orange Corp Yard Workforce Housing
Figure 1.1 Vicinity Map
3
Project Site
Alton ParkwayVon Karman Ave McGaw AveBarranca Channel
Preliminary Drainage Study for Orange Corp Yard Workforce Housing
Figure 1.2 Site Map w/ Lot Lines
4
Preliminary Drainage Study for Orange Corp Yard Workforce Housing
2.0 SETTING
2.1 Land Cover and Topography
As aforementioned the subject site is vacant land. Under existing conditions, it is largely absent of
vegetation, with the exception of dense bushes and trees along the north boundary and landscaping
improvements and grass near the south side along West Struck Avenue. The ground surface of most
of the site is dirt covered in gravel and/or asphalt grindings and asphalt, with some bare dirt present.
Numerous items, trucks, tractors, trailers, plant trimmings, light standards, k-rails, and other items
associated with the site’s current use as a city yard. In topography, the site area is relatively planar
with a gentle fall towards the west-southwest.
The following table compares the land cover imperviousness between the pre- and post-development
conditions in the project area.
Land Imperviousness Comparison
Condion Pervious Impervious
Acres Percentage Acres Percentage
Pre-project1 2.48 81%0.19 19%
Post-project2 0.44 17%2.23 83%
Notes:
1) Pre-project condion was esmated per the site’s survey and aerial photograph.
2) Post-project condion was esmated per the Project’s landscape plan.
2.2 Soil Type
Per the Hydrologic Soil Groups Map from the Orange County Hydrology Manual (1986), the subject
site has soil type of “D”. Per the Project’s Soil Report, the site contains a depth of 3-feet of fill
materials, which consist of asphalt grindings underlain by silty sand and lean clay with sand.
Underlying the fill materials are the older alluvial materials which consist of lean clay with sand and
clayey sand with gravel, and lesser amounts unit of sandy silt. The excerption of the project’s Soil
Report and the site’ Soil Group Map are included in Appendix A.
2.3 FEMA's FIRM
The project area is not denoted in any flood hazard area on the FEMA Flood Insurance Rate Map.
For details please refer to the FIRM Panel 06059C0161J, which is included in Appendix A.
2.4 Groundwater
Per the Project’s Soil Report, groundwater was not encountered on site within the conducted
exploratory borings advanced to a maximum depth of approximately 41 feet below the existing
ground surface. In their conclusion, groundwater is anticipated to lie at a depth greater than 100 feet
in the general site area.
5
Preliminary Drainage Study for Orange Corp Yard Workforce Housing
2.5 Existing Drainage Facility
Per the as-built plan for the Orange Corporate Yard (included in Appendix A), the project area was
programed to sheet flow westward to its nearby warehouse (part of the “Orange Corporate Yard”
area) and then drain southerly in pipes to a 36” RCP on West Struck Avenue. This 36” RCP
originates from the east under the AT&SF Rail Road. It crosses the railroad approximately at the
midpoint of the east edge of the site and then it immediately turns to the south and traverses the west
edge of the railroad right-of-way. Then it turns eastward to West Struck Avenue and continues to
traverse the West Struck Avenue. There is no other existing storm drain facility located within the
project area.
2.6 Proposed Drainage Plan
In general the existing drainage pattern will be maintained after the site is developed and the project
will continue to drain its runoff to the 36” RCP on West Struck Avenue. In the proposed drainage
plan, runoffs from development areas will be conveyed via surface gutters and underground pipes to
a storm water quality treatment device first before discharge into the 36” RCP. The storm water
quality management and proposed BMPs will be described in details in the Project’s WQMP report.
For the project’s drainage plan details please see the Preliminary Grading and Drainage Plan
included in Appendix C.
6
Preliminary Drainage Study for Orange Corp Yard Workforce Housing
3.0 HYDROLOGY ANALYSES
3.1 Introduction
The purpose of the hydrologic analyses conducted in this report is mainly to provide a basis for
identifying any potential flood hazard concern arising from the Project’s development. The potential
flood concerns typically refer to adverse influence in flood protection in the project and its
downstream areas. In order to address the above concerns, the 10-year and 100-year storm events
will be analyzed using the “Rational Method” hydrology with respect to the pre- and post-project
conditions. The employed hydrology method conforms to the Orange County Hydrology Manual
(1986). Furthermore, it shall be noted that the post-project condition models conducted in Rational
Method” hydrology all assume a free-draining condition without considering any flood detention
and/or retention effect if existed.
3.2 Rational Method Analysis
The Rational Method hydrology calculations performed in this section were prepared using the Civil
Design Software. This computer program conforms to the standards of the Hydrology Manual of
Orange County Hydrology Manual (1986). Important modeling details are described and discussed
below:
As aforementioned current surface runoff cross the site is generally as sheet flow to the west and
southwest. Two outlets were established in the existing condition model. Both of them are located
on the west edge of the site with one approximately at the midpoint of the edge and the other at more
to the north side. In addition, it shall be noted that some tiny area at the south side of the site near
the cul de sac would in fact sheet flow to West Struck Avenue but it was hypothetically included with
the site’s westard drainage in the model. This was done to simplify the model and this approach was
not believed to affect the overall hydrologic results in flood impact assessment.
In the proposed condition, the drainage boundary established in the existing condition model and its
modeling parameters were generally followed except new SCS curve numbers and roughness
coefficients to be applied in the sub-areas and flow paths as to reflect the change in land use cover
and improved flow conveyance from the development. Provided that the project will convey all its
runoffs to the 36” RCP, there was only one outlet established in the proposed condition model,
representing the new storm drain connection from the site. In addition, the tiny area near the
entrance at the south side remained to be hypothetically included with the rest of the site’s drainage
not sheet flowing to West Struck Avenue.
3.3 Results & Discussion
The 10-year and 100-year events hydrology results from the existing and proposed conditions
models are summarized in the following tables. It shall be noted that the site’s peak discharge from
the existing condition model was calculated as the sum from two outlets. The complete modeling
outputs and hydrology maps are included in Appendix B.
7
Preliminary Drainage Study for Orange Corp Yard Workforce Housing
Comparison of Site's Peak Discharges – Ra onal Method
Design Storm Exisng Condion (cfs)Proposed
Condion (cfs)Change (cfs)
Outlet #1 Outlet #2 Total
Q10 1.42 4.70 6.12 7.37 1.25
Q100 2.25 7.43 9.68 11.40 1.72
Notes:
1) Please see Raonal Method Hydrology Map in Appendix B: Outlet #1 refers to Node 20; Outlet #2 refers to Node 30
2) Total = Outlet #1 + Outlet #2
As shown in the above tables, from the existing to proposed conditions, the peak discharges from the
site will be increased by one to two cfs for all analyzed events of 10-year and 100-year. To interpret
the results, the runoff potential from the existing site is considered to have been relatively high due
to the soil type “D” that corresponds to high SCS curve number within the site. On the other hand,
the project with proposed gutters, pipes, etc will allow its runoff to be routed along a longer and mild
slopped path of travel through the site; therefore, the time of concentration will be mitigated thereby
being able to reduce the corresponding rainfall intensity and peak flow at the site’s outlet.
In conclusion, the one to two cfs runoff increase from the project will not overload the 36” RCP
thereby to cause flood protection issues to the subject public storm drain system.
8
Preliminary Drainage Study for Orange Corp Yard Workforce Housing
4.0 CONCLUSION
This preliminary report has demonstrate that the proposed project has incorporated sufficient
measures to design its drainage system and has carefully selected the outlet to the downstream
system with ensured storm water quality. The such proposed development will not have an adverse
effect on adjacent properties, structures, or areas downstream.
Yet this is a preliminary study, no detailed design information for proposed storm drain facilities is
available at this stage. In the subsequent final report, hydraulic analyses will be provided to support
the facility sizing for the project.
9
Preliminary Drainage Study for Orange Corp Yard Workforce Housing
5.0 APPENDICES
10
Appendix A
Appendix A.1
"Proj Site
JSoil Group Map
Appendix A.2
PRELIMINARY GEOTECHNICAL INVESTIGATION
PROPOSED RESIDENTIAL DEVELOPMENT
EASTERN 2.54 ACRES OF APN 375-291-14
ORANGE, CALIFORNIA
PROJECT NO. 33616.1
FEBRUARY 25, 2020
Prepared For:
C & C Development
14211 Yorba Street, Suite 200
Tustin, California 92780
Attention: Mr. Scott Bering
February 25, 2020
C & C Development Project No. 33616.1
14211 Yorba Street, Suite 200
Tustin, California 92780
Attention: Mr. Scott Bering
Subject: Preliminary Geotechnical Investigation, Proposed Residential Development,
Eastern 2.54 Acres of APN 375-291-14, Orange, California.
LOR Geotechnical Group, Inc., is pleased to present this report summarizing our
geotechnical investigation for the above referenced project. In summary, it is our opinion
that the proposed development is feasible from a geotechnical perspective, provided the
recommendations presented in the attached report are incorporated into design and
construction.
To provide adequate support for the proposed residential structures, we recommend that
a compacted fill mat be constructed beneath footings and slabs. The compacted fill mat
will provide a dense, high-strength soil layer to uniformly distribute the anticipated
foundation loads over the underlying soils. All undocumented fill material and any loose
alluvial materials should be removed from structural areas and areas to receive engineered
compacted fill. The data developed during this investigation indicates that removals on the
order of approximately 5 feet will be required within the currently planned development
areas. The given removal depths are preliminary. The actual depths of the removals should
be determined during the grading operation by observation and/or in-place density testing.
Medium expansive soils and poor R-value quality soils were encountered on the site. A
negligible sulfate content was found for the soils tested. Near completion and/or at the
completion of site grading, additional foundation and subgrade soils should be tested to
verify their expansion potential, soluble sulf ate content, and R-value quality.
LOR Geotechnical Group, Inc.
Table of Contents Page No.
INTRODUCTION......................................................1
PROJECT CONSIDERATIONS. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2
EXISTING SITE CONDITIONS. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2
AERIAL PHOTOGRAPH ANALYSIS.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2
FIELD EXPLORATION PROGRAM.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
LABORATORY TESTING PROGRAM.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
GEOLOGIC CONDITIONS.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
Regional Geologic Setting. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
Site Geologic Conditions. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
Fill. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
Older Alluvium.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
Groundwater Hydrology.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
Surface Runoff.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
Mass Movement.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
Faulting. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
Historical Seismicity.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
Secondary Seismic Hazards. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
Liquefaction.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
Seiches/Tsunamis.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
Flooding (Water Storage Facility Failure). . . . . . . . . . . . . . . . . . . . . . . . . 9
Seismically-Induced Landsliding.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
Rockfalls. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
Seismically-Induced Settlement. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
SOILS AND SEISMIC DESIGN CRITERIA (California Building Code 2019). . . . . . 10
Site Classification.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
CBC Earthquake Design Summary. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
LOR GEOTECHNICAL GROUP, INC.
Table of Contents Page No.
CONCLUSIONS.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
General. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
Foundation Support. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
Soil Expansiveness. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
Sulfate Protection. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
Geologic Mitigations.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
Seismicity.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
RECOMMENDATIONS. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
Geologic Recommendations. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
General Site Grading.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
Initial Site Preparation. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
Preparation of Fill Areas. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
Preparation of Foundation Areas.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
Engineered Compacted Fill. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
Short-Term Excavations. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
Slope Construction.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
Slope Protection. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
Foundation Design.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
Settlement. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
Building Area Slab-On-Grade. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
Exterior Flatwork. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
Wall Pressures.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
Sulfate Protection. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
Preliminary Pavement Design. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
LOR GEOTECHNICAL GROUP, INC.
&RQVWUXFWLRQ 0RQLWRULQJ
Table of Contents Page No.
LIMITATIONS.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
TIME LIMITATIONS. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24
CLOSURE...........................................................25
REFERENCES........................................................26
APPENDICES
Appendix A
Index Map.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . A-1
Architectural Site Plan. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . A-2
Regional Geologic Map. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . A-3
Historical Seismicity Maps. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . A-4 and A-5
Appendix B
Field Investigation Program. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . B
Boring Logs. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . B-1 through B-6
Boring Log Legend. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . B-L
Soil Classification Chart. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . B-ii
Appendix C
Laboratory Testing Program.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . C
Gradation Curves. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . C-1
Atterberg Limits. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . C-2
Appendix D
Seismic Design Spectra. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . D
LOR GEOTECHNICAL GROUP, INC.
C & C Development Project No. 33616.1
February 25, 2020
INTRODUCTION
During February of 2020, a Preliminary Geotechnical Investigation was performed by LOR
Geotechnical Group, Inc., for proposed residential development of the eastern 2.54 acres
of APN 375-291-14 in the City of Orange, California. The purpose of this investigation was
to conduct a technical evaluation of the geologic setting of the site and to provide
geotechnical design recommendations for the proposed improvements. The scope of our
services included:
•Review of available pertinent geotechnical literature, reports, maps, and agency
information pertinent to the study area;
•Interpretation of aerial photographs of the site and surrounding regions dated 1946
through 2018;
•Geologic field reconnaissance mapping to verify the areal distribution of earth units
and significance of surficial features as compiled from documents, literature, and
reports reviewed;
•A subsurface field investigation to determine the physical soil conditions pertinent
to the proposed dev elopment;
•Laboratory testing of selected soil samples obtained during the field investigation;
•Development of geotechnical recommendations for site grading and foundation
design; and
•Preparation of this report summarizing our findings, and providing conclusions and
recommendations f or site development.
The approximate location of the site is shown on the attached Index Map, Enclosure A-1,
within Appendix A.
To orient our investigation at the site, you provided us with an Architectural Site Plan,
prepared by IDE Arc Architecture & Planning, dated Septem ber 12, 2019, that showed the
proposed development. As noted on that map, the site will be developed with a total of 62
apartment units within two, three-story structures and the associated improvements. The
Architectural Site Plan was utilized as a base map for our field investigation and is
presented as Enclosure A-2, w ithin Appendix A.
1
LOR GEOTECHNICAL GROUP, INC.
C & C Development Project No. 33616.1
February 25, 2020
PROJECT CONSIDERATIONS
The proposed two structures will be three stories in height and are anticipated to be of
wood frame construction with an exterior plaster veneer. Light to moderate foundation
loads are anticipated with such structures. Cuts and fills on the order of a few feet are
anticipated to create the planar building pads.
EXISTING SITE CONDITIONS
The subject site is vacant land, comprising approximately 2.5 acres of an irregular-shaped
portion of a larger 17.23-acre parcel of land which comprises the City of Orange Corporate
Yard and Police Department building, located at the northeast corner of the intersection
at North Batavia Street and W est Struck Avenue. The subject site is situated in the far east
end of the 17.23-acre parcel. The subject site is largely absent of vegetation, with the
exception of dense bushes and trees along the north boundary and landscaping
improvements consisting of pine trees, ornamental plants, and grass near and/or within the
south side of the subject site along the north side of W est Struck Avenue. The ground
surface of most of the subject site is dirt covered in gravel and/or asphal t grindings and
asphalt, with some bare dirt present. The site is relatively planar with a very gentle fall
towards the south-southwest to W . Struck Avenue. A concrete v-ditch traverses the eastern
site boundary from offsite to the northwest.
Numerous items, trucks, tractors, trailers, plant trimmings, light standards, k-rails, and other
items associated with the site’s current use as a city yard.
The site is bound on the north by commercial buildings, on the east by two sets of railroad
tracks with multi-family residential beyond, on the south by W . Struck Avenue, a fully
improved roadway, followed by commercial buildings, and on the west by the remainder
of the city yard for various departm ents.
AERIAL PHOTOGRAPH ANALYSIS
The aerial photographs reviewed consisted of vertical aerial stereoscopic photographs of
varying scales. W e reviewed imagery available from Google Earth (2020) and from Historic
Aerials (2020).
2
LOR GEOTECHNICAL GROUP, INC.
C & C Development Project No. 33616.1
February 25, 2020
The site consisted of groves with surrounding properties from 1946, the earliest photograph
available, to 1963 when the groves were removed. The site remained vacant until the 1980
photograph when it was a part of the city yard to present day. The southern approximately
half of the site contained asphalt concrete paving in 2002. Photographs from 1980 to 2018
showed the site was used for storage, similar to that seen today .
Our review of the aerial photographs did not reveal any adverse geologic conditions, such
as possible faults or landslides, as being present at or within close proximity to the site.
FIELD EXPLORATION PROGRAM
Our subsurface field exploration program was conducted on February 4, 2020 and
consisted of drilling 6 exploratory borings with a truck-mounted Mobile B-61 drill rig
equipped with 8-inch diameter hollow stem augers. The borings were drilled to depths of
approximately 15 to a refusal depth of 41 feet below the existing ground surface. The
approximate locations of our exploratory borings are presented on the attached
Architectural Site Plan, Enclosure A-2 w ithin Appendix A.
The subsurface conditions encountered in the exploratory borings were logged by a
geologist from this firm. Relatively undisturbed and bulk samples were obtained at a
maximum depth interval of 5 feet and returned to our geotechnical laboratory in sealed
containers for further testing and evaluation. A detailed description of the field exploration
program and the boring logs are presented in Appendix B.
LABORATORY TESTING PROGRAM
Selected soil samples obtained during the field investigation were subjected to laboratory
testing to evaluate their physical and engineering properties. Laboratory testing included
in-place moisture content and dry density, laboratory compaction characteristics, direct
shear, sieve analysis, sand equivalent, R-value, expansion index, Atterberg limits, and
soluble sulfate content. A detailed description of the laboratory testing program and the test
results are presented in Appendix C.
3
LOR GEOTECHNICAL GROUP, INC.
C & C Development Project No. 33616.1
February 25, 2020
GEOLOGIC CONDITIONS
Regional Geologic Setting
The subject site is located within northeastern Orange County between the Santa Ana
River to the west and the Peralta Hills to the east. These small hills form a series of low
hills that extend as a northwest trending flank of the larger Santa Ana Mountains to the
east and southeast. The Santa Ana Mountains are in turn one of the several mountain
ranges that form the interior portion of southern California known as the Peninsular Ranges
geomorphic province. This province consists of a series of northwest trending mountains
that extend from the Los Angeles Basin south, to the Mexican border and beyond. The
Santa Ana Mountains themselves form the eastern boundary of Orange County and
contain some of the oldest rocks within the County, the Triassic to Jurassic aged
metasedimentary rocks of the Bedf ord Canyon formation that formed around 225 million
years ago. Underlying the Bedford Canyon formation are units of relatively younger
igneous rocks of Cretaceous age that f orm the core of the mountains from intrusion of
magma into this area around 65 million years ago. Especially along the western flanks of
the Santa Ana mountains, these older metamorphic and igneous rocks are overlain by
younger rocks of sedimentary and volcanic origin that documents the fluctuating history of
this region from shallow continental sea to near shore continental environments, with
periodic volcanic eruptions.
Erosion of the Santa Ana Mountains to the east and southeast, as well as the hills to the
east, by the Santa Ana Rivera and its tributaries, such as the Santiago Creek to the
east-southeast, has deposited a relatively thick sequence of relatively unconsolidated
alluvium of varies ages and levels in a series of terraces along this broad valley. In their
regional geologic map of the area, the USGS indicated that the site is situated upon older
alluvial materials (Morton and Miller, 2006). This unit was described as composed of
indurated, reddish brown, silty sand alluvial fan deposits. This deposit is considered to
have been deposited in the late to middle Pleistocene age, or on the order of about 11,000
years or slightly older. This older unit has been slightly incised, and replaced with similar,
unconsolidated, m aterials along the active creek beds.
The region, like much of southern California, has numerous faults. These are all associated
with the San Andreas fault zone, located approximately 63 kilometers (39 miles) to the
northeast, that results from the area's location and history as a major plate boundary with
various types of relative motion. Many of these faults have been inactive for millions of
years and are noted only by abrupt changes of rock types. Other faults show evidence that
4
LOR GEOTECHNICAL GROUP, INC.
C & C Development Project No. 33616.1
February 25, 2020
they have been active in geologically recent times, since the Pleistocene Epoch within the
last 11,000 years, but not within the recorded history of Orange County, while other faults
have docum ented historical activity.
The San Andreas fault, noted above, is the largest known active fault in the region in terms
of anticipated events. The closest known fault, as seen on the Regional Geologic Map,
Enclosure A-3, is the Peralta Hills-El Modeno fault location, approximately 5.5 kilometers
(3.5 miles) to the east. The Peralta Fault may tie into the El Modeno Fault, located
approximately 2.8 kilometers (1.8 miles) northeast of the site. W hile little data is available
on the activity and potential of these faults, these reportedly break late Pleistocene (11,000
to 700,000 y ears old ) materials and may fault Holocene (from 0 to 11,000 years in age)
alluvial materials which would indicate these f aults are active.
The closest known active fault in relation to the site which data is readily available, is the
W hittier-Elsinore fault, which lies approximately 12.7 kilometers (7.8 miles) to the
northeast. The W hittier fault zone extends along the southwestern base of the Puente Hills.
The W hittier fault joins the Chino fault near Prado Dam, and they merge into the Elsinore
fault zone which trends along the eastern base of the Santa Ana Mountains. The 5.9
magnitude W hittier Narrows earthquake of October 1, of 1987, occurred on a previously
unknown concealed thrust fault approximately 20 kilometers east of downtown Los Angeles
that is now associated as part of the W hittier fault system.
Another well known active fault zone is Newport-Inglewood fault zone, located
approximately 16 kilometers (10 miles) to the west-southwest of the site, extends northwest
from offshore Newport Beach to Inglewood (distance of 40 miles) and, like the W hittier fault
and Elsinore faults, has had documented historical activity. The very destructive 1933 Long
Beach earthquake resulted f rom movement along this fault.
Located approximately 37 kilometers (23 miles) to the north is the Cucamonga-Sierra
Madre fault zone, which marks the southern boundary of the San Gabriel Mountains. This
system is comprised of steeply, north-dipping, thrust, range-front faults along which most
of the uplift of the San Gabriel Mountains, has occurred. The Cucamonga fault marks the
eastern portion of the Sierra Madre fault system, which the San Fernando fault marks the
western portion. It is believed that the Cucamonga fault is capable of producing an
earthquake on the order of 7.0 or greater.
5
LOR GEOTECHNICAL GROUP, INC.
C & C Development Project No. 33616.1
February 25, 2020
Associated with the San Andreas fault zone, the San Jacinto fault zone lies approximately
55 kilometers (34 miles) to the northeast. The San Jacinto fault zone is a sub-parallel
branch of the San Andreas fault zone, extending from the northwestern San Bernardino
area, southward to the El Centro region. This fault has been active in recent times, with
several large magnitude events. It is believed that the San Jacinto fault is capable of
producing an earthquake magnitude on the order of 6.5 or greater.
Site Geologic Conditions
Fill: As encountered within our exploratory boring placed at the site, fill materials to a depth
of 3 feet are present. These materials mainly consisted of asphalt grindings underlain by
silty sand and lean clay with sand.
Older Alluvium: Underlying the fill materials at the site, older alluvial materials were
encountered within all of our exploratory borings to the maximum depths explored. These
units were noted to consist of lean clay with sand and clayey sand with gravel, and lesser
amounts unit of sandy silt. The older alluvial materials were in a relatively stiff to very stiff
and dense state upon first encounter, becoming very dense/very stiff with depth based on
our equivalent Standard Penetration Test (SPT) data and in-place density testing. Refusal
was experienced at depth of approximately 41 f eet due to gravel and possible cobbles.
A detailed description of the subsurface soil conditions as encountered within our
exploratory borings is presented on the Boring Logs within Appendix B.
Groundwater Hydrology
Groundwater was not encountered within our exploratory borings advanced to a maximum
depth of approximately 41 feet below the existing ground surface.
Records for nearby wells which were readily available from the State of California
Department of W ater Resources online database (CDW R, 2020) were reviewed as a part
of this investigation.
This database indicates that the nearest water well is state well number 04S09W 19G001S
which is located approximately 0.7 kilometers (0.4 miles) to the north. This well lies at an
elevation of approximately 179 feet above mean sea level (m.s.l.). Recorded groundwater
measurements were available from 1991 to 2010. The records indicate that groundwater
in this well has fluctuated in depth between approximately 170 feet in November of 1992
6
LOR GEOTECHNICAL GROUP, INC.
C & C Development Project No. 33616.1
February 25, 2020
to a high of approximately 91 feet in July of 2006. This results in an approximate elevation
range of 9 feet below m.s.l. to 87 feet above m.s.l. The latest groundwater measurement
of approximately 128 feet was in October of 2010.
As illustrated on Enclosure A-1, the elevation of the site is approximately 180 feet above
mean sea level. Based on the information above, groundwater is anticipated to lie at a
depth greater than 100 f eet in the general site area.
Surface Runoff
Current surface runoff of precipitation waters across the site is generally as sheet flow to
the south-southwest.
Mass Movement
Mass movement features such as landslides, rockfalls, or debris flows within the site
vicinity are not known to exist and no evidence of mass movement was observed on the
site or in the vicinity during our review of aerial photographs or our site reconnaissance.
Faulting
No active or potentially active faults are known to exist at the subject site. In addition, the
subject site does not lie within a current State of California Earthquake Fault Zone (Hart
and Bryant, 2003).
As previously noted, the nearest known fault is the Peralta/El Moden o faults located
approximately 5.5 kilometers (3.5 miles) to the northeast. However, the activity rating of
these faults is not known. The nearest known active fault in relation to the site is the
W hittier fault. The W hittier fault runs along the base of the Puente Hills to the north. At the
closest approach, this fault lies approximately 12.7 kilometers (7.8 miles) to the
north-northeast. According to a study conducted by Cao et al. (2003), the W hittier fault
within the Elsinore fault system has a slip rate of 2.5 mm per year and is anticipated to be
capable of generating an earthquake with a moment magnitude on the order of 6.8. Other
known active faults in the region include the Newport-Inglewood fault located approximately
16 kilometers (10 miles) to the west-southwest. According to the study conducted by Cao
et al. (2003) the Newport-Inglewood fault has a slip rate of 1 mm per year and an
anticipated magnitude of 7.1.
7
LOR GEOTECHNICAL GROUP, INC.
C & C Development Project No. 33616.1
February 25, 2020
The Department of Conservation, California Geological Survey, formerly known as the
Department of Conservation, Division of Mines and Geology, has prepared seismic hazard
zone maps, in accordance with Seismic Hazards Mapping Act for various areas of northern
and southern California. The site and immediate surrounding region are shown on Seismic
Hazard Zone Map of the Orange 7.5 Quadrangle, released April 15, 1998. According to this
map, the site does not lie within an area where historic occurrence of liquefaction, or local
geological, geotechnical, and groundwater conditions indicate a potential for permanent
ground displacements, including earthquake induced landslides, such that mitigation as
defined in Public Resources Code Section 2693(c) w ould be required. Public Resources
Code Section 2693(c) states that "mitigation" means those measures that are consistent
with established practice and that will reduce seismic risk to acceptable levels. An
"acceptable level" is that level that provides reasonable protection of public safety, though
it does not necessarily ensure continued structural integrity and functionality of the project.
Current standards of practice often include a discussion of all potential earthquake sources
within a 100 kilometer (62 mile) radius. However, while there are other large earthquake
faults within a 100 kilometer (62 mile) radius of the site, none of these are considered as
relevant to the site due to the ir greater distance and/or sm aller anticipated m agnitudes.
Historical Seismicity
In order to obtain a general perspective of the historical seismicity of the site and
surrounding region a search was conducted for seismic events at and around the area
within various radii. This search was conducted utilizing the historical seismic search
website of the USGS. This website conducts a search of a user selected cataloged seismic
events database, within a specified radius and selected magnitudes, and then plots the
events onto a map. At the time of our search, the database contained data from January
1, 1932 through February 16, 2020.
In our first search, the general seismicity of the region was analyzed by selecting an
epicenter map listing all events of magnitude 4.0 and greater, recorded since 1932, within
a 100 kilometer (62 mile)radius of the site, in accordance with guidelines of the California
Division of Mines and Geology. This map illustrates the regional seismic history of
moderate to large events. As depicted on Enclosure A-4, w ithin Appendix A, the site lies
within a relatively quiet region lying east of the more active region to the west associated
with the Newport-Inglewood f ault zone to the west.
8
LOR GEOTECHNICAL GROUP, INC.
C & C Development Project No. 33616.1
February 25, 2020
In the second search, the micro seismicity of the area lying within a 15 kilometer (9.3 mile)
radius of the site was examined by selecting an epicenter map listing events on the order
of 2.0 and greater since 1978. In addition, only the “A” events, or most accurate events
were selected. Caltech indicates the accuracy of the “A” events to be approximately 1 km.
The results of this search is a map that presents the seismic history around the area of the
site with much greater detail, not permitted on the larger map. The reason for limiting the
events to the last 40± years on the detail map is to enhance the accuracy of the map.
Events recorded prior the mid 1970's are generally considered to be less accurate due to
advancements in technology. As depicted on this map, Enclosure A-5, w hile not distinct,
the Newport-Inglewood fault is conspicuous as a northwest trending lineation of small
seismic events located southwest of the site. In addition to these events there is a distinct
band of seismic events north of the site, roughly trending with the W hittier fault zone.
In summary, the historical seismicity of the site entails numerous small to medium
magnitude earthquake events occurring around the subject site, predominately associated
with the presence of the San Jacinto fault zone. Any future developments at the subject
site should anticipate that moderate to large seismic events could occur very near the site.
Secondary Seismic Hazards
Other secondary seismic hazards generally associated with severe ground shaking during
an earthquake include liquefaction, seiches and tsunamis, earthquake induced flooding,
landsliding and rockf alls, and seismic-induced settlem ent.
Liquefaction: The potential for liquefaction generally occurs during strong ground shaking
within granular loose sediments where the groundwater is usually less than 50 feet. As the
site is underlain by relatively dense/stiff to dense/very stiff deposits of older alluvium and
the depth to groundwater is considered to be greater than 50 feet, the possibility of
liquefaction within these units is considered nil.
Seiches/T sunamis: The potential for the site to be affected by a seiche or tsunami
(earthquake generated wave) is considered nil due to the absence of any large bodies of
water near the site.
Flooding (W ater Storage Facility Failure): There are no large water storage facilities
located on or upstream near the site which could possibly rupture during an earthquake
and af fect the site by flooding.
9
LOR GEOTECHNICAL GROUP, INC.
C & C Development Project No. 33616.1
February 25, 2020
Seismically-Induced Landsliding: Since the site is situated on a relatively flat plain, the
potential f or seismically induced mass movement is considered nil.
Rockfalls: No large, exposed, loose or unrooted boulders that could affect the integrity of
the site are present abov e the site.
Seismically-Induced Settlement: Settlement generally occurs within areas of loose,
granular soils with relatively low density. Since the site is underlain by dense/stif f to
dense/very stiff older alluvial materials, the potential for settlement is considered low. In
addition, the earthwork operations recommended to be conducted during the development
of the site will mitigate any near surf ace loose soil conditions.
SOILS AND SEISMIC DESIGN CRITERIA (California Building Code 2019)
Design requirements for structures can be found within Chapter 16 of the 2019 California
Building Code (CBC) based on building type, use and/or occupancy. The classification of
use and occupancy of all proposed structures at the site, and thus the design
requirements, shall be the responsibility of the structural engineer and the building official.
For structures at the site to be designed in accordance with the provisions of Chapter 16,
the subject site specif ic criteria is provided below:
Site Classification
Chapter 20 of the ASCE 7-16 defines six possible site classes for earth materials that
underlie any given site. Bedrock is assigned one of three of these six site classes and
these are: A, B, or C. Per ASCE 7-16, Site Class A and Site Class B shall be measured
on-site or estimated by a geotechnical engineer, engineering geologist or seismologist for
competent rock with moderate fracturing and weathering. Site Class A and Site Class B
shall not be used if more than 10 feet of soil is between the rock surface and bottom of the
spread footing or mat foundation. Site Class C can be used for very dense soil and soft
rock with values greater than 50 blows per foot. Site Class D can be used for stiff soil with
values ranging from 15 to 50 blows per foot. Site Class E is for soft clay soils with values
less than 15 blows per foot. Our Standard Penetration Test (SPT) data indicate that the
materials beneath the site are considered Site Class D soils.
10
LOR GEOTECHNICAL GROUP, INC.
C & C Development Project No. 33616.1
February 25, 2020
CBC Earthquake Design Summary
As determined in the previous section, earthquake design criteria have been formulated
for the site. However, these values should be reviewed and the final design should be
performed by a qualified structural engineer familiar with the region. Our design values are
provided in Appendix E.
CONCLUSIONS
General
This investigation provides a broad overview of the geotechnical and geologic factors which
are expected to influence future site planning and development. On the basis of our field
investigation and testing program, it is the opinion of LOR Geotechnical Group, Inc., that
the proposed development is feasible from a geotechnical standpoint, provided the
recommendations presented in this report are incorporated into design and implemented
during grading and construction.
The subsurface conditions encountered in our exploratory borings are indicative of the
locations explored. The subsurface conditions presented here are not to be construed as
being present the same everywhere on the site. If conditions are encountered during the
construction of the project which differ significantly from those presented in this report, this
firm should be notified immediately so we may assess the impact to the recommendations
provided.
Foundation Support
Based upon the field investigation and test data, it is our opinion that the existing fill/topsoil
and fill soils will not, in their present condition, provide uniform and/or adequate support
for the proposed improvements. Left as is, this condition could cause unacceptable
differential and/or overall settlements upon application of the anticipated foundation loads.
To provide adequate support for the proposed structural improvements, we recommend
that a com pacted fill mat be constructed beneath f ootings and slabs. T his compacted f ill
mat will provide a dense, high-strength soil layer to uniformly distribute the anticipated
foundation loads over the underlying soils. In addition, the construction of this compacted
fill mat will allow for the removal of the undocumented fill soils that are present within the
proposed building areas. Conventional foundation systems, using either individual spread
11
LOR GEOTECHNICAL GROUP, INC.
C & C Development Project No. 33616.1
February 25, 2020
footings and/or continuous wall footings, will provide adequate support for the anticipated
downward and lateral loads when utilized in conjunction with the recom mended fill mat.
Soil Expansiveness
Our laborato ry testing found the soils tested to have a medium expansion potential.
Therefore, recommendations for low expansive soils are given in the Foundation Design,
Building Area Slab-on-Grade, and Ex terior Flatwork sections of this report.
Careful evaluation of on-site soils and any import fill for their expansion potential should
be conducted during the grading operation.
Sulfate Protection
The results of the soluble sulfate tests conducted on selected subgrade soils expected to
be encountered at foundation levels indicate that there is a negligible sulfate exposure to
concrete elements in contact with the on site soils per the 2019 CBC. Therefore, no
specific recommendations are given for concrete elements to be in contact with the onsite
soils.
Geologic Mitigations
No special geologic recommendation methods are deemed necessary at this time, other
than the g eotechnical recom mendations provided in the f ollowing sections.
Seismicity
Seismic ground rupture is generally considered most likely to occur along pre-existing
active faults. Since no known faults are known to exist at, or project into the site, the
probability of ground surf ace rupture occurring at the site is considered nil.
Due to the site’s close proximity to the faults described above, it is reasonable to expect
a strong ground motion seismic event to occur during the lifetime of the proposed
development on the site. Large earthquakes could occur on other faults in the general
area, but because of their lesser anticipated magnitude and/or greater distance, they are
considered less significant than the faults described above from a ground motion
standpoint.
12
LOR GEOTECHNICAL GROUP, INC.
C & C Development Project No. 33616.1
February 25, 2020
The effects of ground shaking anticipated at the subject site should be mitigated by the
seismic design requirements and procedures outlined in Chapter 16 of the California
Building Code. However, it should be noted that the current building code requires the
minimum design to allow a structure to remain standing after a seismic event, in order to
allow for safe evacuation. A structure built to code m ay still sustain damage which might
ultimately result in the dem olishing of the structure (Larson and Slosson, 1992).
RECOMMENDATIONS
Geologic Recommendations
No special geologic recommendation methods are deemed necessary at this time, other
than the g eotechnical recom mendations provided in the f ollowing sections.
General Site Grading
It is imperative that no clearing and/or grading operations be performed without the
presence of a qualified geotechnical engineer. An on-site, pre-job meeting with the owner,
the developer, the contractor, and geotechnical engineer should occur prior to all grading
related operations. Operations undertaken at the site without the geotechnical engineer
present may result in exclusions of affected areas from the final compaction report for the
project.
Grading of the subject site should be performed in accordance with the following
recommendations as well as applicable portions of the California Building Code, and/or
applicable local ordinances.
All areas to be graded should be stripped of significant vegetation and other deleterious
materials.
It is our recommendation that any existing fills under any proposed flatwork and/or paved
areas be removed and replaced with engineered compacted fill. If this is not done,
premature structural distress (settlement) of the flatwork and pavement may occur. Any
undocum ented fills encountered during grading should be completely removed and
cleaned of significant deleterious materials. These may then be reused as compacted fill.
Cavities created by removal of undocumented fill soils and/or subsurface obstructions
should be thoroughly cleaned of loose soil, organic matter and other deleterious materials,
13
LOR GEOTECHNICAL GROUP, INC.
C & C Development Project No. 33616.1
February 25, 2020
shaped to provide access for construction equipment, and backfilled as recommended in
the following Engineered Compacted Fill section of this report.
Initial Site Preparation
Any and all existing uncontrolled fills and any loose/soft native alluvial soils should be
removed from structural areas and areas to receive structural fills. The data developed
during this investigation indicates that removals on the order of 5 feet from existing grades
will be required to encounter competent older alluvium. However, deeper removals may be
required locally. Removals should extend horizontally at a distance equal to the depth of
the removals plus proposed fill and at least a minimum of 5 feet. The actual depths of
removals should be determined during the grading operation by observation and/or by in-
place density testing.
Preparation of Fill Areas
After completion of the removals described above and prior to placing fill, the surfaces of
all areas to receive fill should be scarified to a depth of at least 6 inches. The scarified soil
should be brought to near optimum moisture content and compacted to a relative
compaction of at least 90 percent (AST M D 1557).
Preparation of Foundation Areas
All footings should rest upon a minimum of 24 inches of properly compacted fill material
placed over competent natural alluvial soils. In areas where the required fill thickness is not
accomplished by the removal of unsuitable soils, the footing areas should be further
subexcavated to a depth of at least 24 inches below the proposed footing base grade, with
the subexcavation extending at least 5 feet beyond the footing lines. The bottom of this
excavation should then be scarified to a depth of at least 6 inches, broug ht to between 2
to 4 percent optimum moisture content, and recompacted to at least 90 percent relative
compaction (ASTM D 1557) prior to refilling the excavation to grade as properly compacted
fill. Fill areas should not be constructed so as to place structures across any area where
the maximum depth of fill to minimum depth of fill is greater than a 3:1 ratio.
To provide adequate support, concrete slabs-on-grade should bear on a minimum of 24
inches of compacted soil. The remedial grading recommended above is anticipated to
accomplish the minimum 24 inches of compacted fill. The final pad surfaces should be
rolled to provide smooth, dense surf aces upon which to place the concrete.
14
LOR GEOTECHNICAL GROUP, INC.
C & C Development Project No. 33616.1
February 25, 2020
Engineered Com pacted Fill
Based upon our preliminary observations and laboratory results, most of the upper site
soils consist of lean clays which have a medium expansion potential. In general, these soils
can be used as structural fills, below foundations, provided that reinforcement measures
are incorporated in the desig n to counteract expansive soil behavior.
Unless approved by the geotechnical engineer, rock or similar irreducible material with a
maximum dimension greater than 6 inches should not be buried or placed in f ills.
Import fill, if required, should be inorganic, non-expansive granular soils free from rocks or
lumps greater than 6 inches in maximum dimension. Sources for import fill should be
approved by the geotechnical engineer prior to their use.
Fill should be spread in maximum 8-inch uniform, loose lifts, with each lift brought to 2 to
4 percent above optimum moisture content prior to, during and/or after placement, and
compacted to a relative compaction of at least 90 percent in accordance with ASTM D
1557.
Based upon the relative compaction of the near surface soils determined during this
investigation and the relative compaction anticipated for compacted fill soil, we estimate
a compaction shrinkage factor of approximately 10 to 15 percent. Therefore, 1.10 to 1.15
cubic yards of in-place materials would be necessary to yield one cubic yard of properly
compacted fill material. Subsidence is anticipated to be 0.10 feet. These values are for
estimating purposes only, and are exclusive of losses due to stripping or the removal of
subsurface obstructions.
These values may vary due to differing conditions within the project boundaries and the
limitations of this investigation. Shrinkage should be monitored during construction. If
percentages vary, provisions should be made to revise final grades or adjust quantities of
borrow or export.
As previously noted, the on-site clayey soils have potential for expansion. Therefore, a
careful evaluation of on-site and any imported soils for their expansion potential should be
conducted during the grading operation.
15
LOR GEOTECHNICAL GROUP, INC.
C & C Development Project No. 33616.1
February 25, 2020
Short-Term Excavations
Following the California Occupational and Safety Health Act (CAL-OSHA) requirements,
excavations 5 feet deep and greater should be sloped or shored. All excavations and
shoring should conform to CAL-OSHA requirements.
Short-term excavations 5-feet deep and greater shall conform to Title 8 of the California
Code of Regulations, Construction Safety Orders, Section 1504 and 1539 through 1547.
Based on our exploratory borings, it appears that Type C soil is the predominant type of
soil on the project and all short-term excavations should be based on this type of soil.
Deviation from the standard short-term slopes are permitted using Option 4, Design by a
Registered Prof essional Engineer (Section 1541.1).
Short-term slope construction and maintenance are the responsibility of the contractor, and
should be a consideration of his methods of operation and the actual soil conditions
encountered.
Slope Construction
Preliminary data indicates that cut and fill slopes should be constructed no steeper than
two horizontal to one vertical. Fill slopes should be overfilled during construction and then
cut back to expose fully compacted soil. A suitable alternative would be to compact the
slopes during construction, then roll the final slopes to provide dense, erosion-resistant
surfaces.
Slope Protection
Since the site soils are susceptible to erosion by running water, measures should be
provided to prevent surface water from flowing over slope faces. Slopes at the project
should be planted with a deep rooted ground cover as soon as possible after completion.
The use of succulent ground covers such as iceplant or sedum is not recommended. If
watering is necessary to sustain plant growth on slopes, the watering system should be
monitored to assure proper operation and to prev ent over watering.
Foundation Desig n
Since the site is underlain by medium expansive soils, we recommend that the planned
buildings be supported on reinforced, stiffened slab foundations resting over 24 inches of
16
LOR GEOTECHNICAL GROUP, INC.
C & C Development Project No. 33616.1
February 25, 2020
engineered compacted fill placed over competent older alluvium. The design of the slab
foundation could be performed in conformance to the Wire Reinforcement Institute (WRI)
method or the Post-Tensioning Institute (PTI) method.
For the application of the WRI method, an average, effective plasticity index of 18 is
recommended for foundation design. The slab thickness should be a minimum of 4 inches
and should have a reinforcement of at least Asfy equal to 2,900 pounds. This could consist
of #3 reinforcing bars of 60-grade steel placed at a maximum spacing of 18 inches on
center, each way or equivalent. Interior stiffening concrete beams should be placed at a
spacing not to exceed 17 feet. External concrete beams should be provided around the
perimeter of the slab. The minimum beam dimensions should be 24 inches high and 12
inches wide, and embedded approximately 18 inches below the lowest adjacent grade. The
beams should be properly reinforced to resist the moment and shears caused by the
differential heave of the expansive soil. Minimum beam reinforcement should be two #5
rebars at top of beam and two #5 rebars at bottom. Stirrups may be added, particularly in
the perimeter beams, to account for concentrated and exterior wall loads. These
reinforcement, depth, and spacing recommendations should be considered minimum. The
actual requirements for slab-on-grade foundations design and construction should be
provided by a structural engineer experienced in these matters.
The above recommendations were developed for medium expansive soils with an average,
effective plasticity index of 18. These conditions should be verified during the site grading
by additional evaluation of on-site and any imported soils for their expansion potential and
plasticity characteristics.
If slab-on-grade foundations per the PTI method are proposed, the following geotechnical
parameters should be used for design:
• Edge Moisture Variation Distance, em:
Center Lift Loading Conditions:9.0 ft
Edge Lift Loading Conditions:7.5 ft
• Differential Swell, ym:
Center Lift 0.3 in
Edge Lift 0.65 in
• Subgrade Soil Friction Coefficient, µ: 0.30
17
LOR GEOTECHNICAL GROUP, INC.
C & C Development Project No. 33616.1
February 25, 2020
The above design parameters are based upon the data collected during our site
investigation and are in accordance with Design of Post-Tensioned Slabs-on-Ground, third
edition, published by the Post-Tensioning Institute.
For preliminary sizing of foundations, we recommend an allowable bearing pressure of
1,500 pounds per square foot (psf) to be utilized for foundations with a minimum width of
12 inches and a m inimum depth of 18 inches below lowest adjacent grade. This bearing
pressure may be increased by 200 psf for each additional foot of width, and by 400 psf for
each additional f oot of depth, up to a m aximum of 4,000 psf.
The above values are net pressures; therefore, the weight of the foundations and the
backfill over the foundations may be neglected when computing dead loads. The values
apply to the maximum edge pressure for foundations subjected to eccentric loads or
overturning. The recommended pressures apply for the total of dead plus frequently
applied live loads, and incorporate a factor of safety of at least 3.0. The allowable bearing
pressures may be increased by one-third for temporary wind or seismic loading. The
resultant of the combined vertical and lateral seismic loads should act within the middle
one-third of the footing width. The maximum calculated edge pressure under the toe of
foundations subjected to eccentric loads or overturning should not exceed the increased
allowable pressure.
Resistance to lateral loads will be provided by passive earth pressure and base friction. For
foundations bearing against compacted fill, passive earth pressure may be considered to
be developed at a rate of 300 pounds per square foot per foot of depth. Base friction may
be computed at 0.30 times the normal load. Base friction and passive earth pressure may
be combined without reduction. These values are for dead load plus live load and may be
increased by one-third for wind or seismic loading.
Settlement
Total settlement of individual foundations will vary depending on the width of the foundation
and the actual load supported. Maximum settlement of shallow foundations designed and
constructed in accordance with the preceding recommendations are estimated to be on the
order of 0.5 inch. Differential settlements between adjacent footings should be about one-
half of the total settlement. Settlement of all foundations is expected to occur rapidly,
primarily as a result of elastic compression of supporting soils as the loads are applied, and
should be essentially completed shortly after initial application of the loads.
18
LOR GEOTECHNICAL GROUP, INC.
C & C Development Project No. 33616.1
February 25, 2020
Building Area Slab-On-Grade
To provide adequate support, concrete slabs-on-grade should bear on a minimum of 24
inches of compacted soil placed and maintained at 2 to 4 percent above optimum moisture
content. The final pad surfaces should be rolled to provide smooth, dense surfaces.
Concrete slabs-on-grade should be a minimum of 5 inches in thickness with No. 4 bars
spaced 12 inches on center each way. A 4-inch rock base should also be installed beneath
the slab.
Slabs to receive moisture-sensitive coverings should be provided with a moisture vapor
retarder/barrier. W e recommend that a vapor retarder/barrier be designed and constructed
according to the American Concrete Institute 302.1R, Concrete Floor and Slab
Construction, which addresses moisture vapor retarder/barrier construction. At a minimum,
the vapor retarder/barrier should comply with ASTM E1745 and have a nominal thickness
of at least 10 mils. The vapor retarder/barrier should be properly sealed, per the
manufacturer's recommendations, and protected from punctures and other damage. Per
the Portland Cement Association (www.cement.org/tech/cct_con_vapor_retarders.asp),
for slabs with vapor-sensitive coverings, a layer of dry, granular material (sand) should be
placed under the vapor retarder/barrier. For slabs in humidity-controlled areas, a layer of
dry, granular material (sand) should be placed abov e the vapor retarder/barrier.
The slabs should be protected from rapid and excessive moisture loss which could result
in slab curling. Careful attention should be given to slab curing procedures, as the site area
is subject to large temperature extremes, hum idity, and strong winds.
Exterior Flatwork
To provide adequate support, exterior flatwork improvements should rest on a minimum
of 12 inches of soil compacted to at least 90 percent (AST M D 1557).
If medium expansive soils are found underlying flatwork areas, these areas should be
pre-soaked to approximately 4 percent above the optimum moisture content to a minimum
depth of 18 inches.
General flatwork such as sidewalk, patios, curbs, etc., should have a thickness of at least
4 inches, with saw cuts every 10 feet or less. Driveways should be at least 6-inch thick,
with saw cuts every 15 feet or less.
19
LOR GEOTECHNICAL GROUP, INC.
C & C Development Project No. 33616.1
February 25, 2020
Reinforcement should be provided for all sidewalks, patio slabs, and driveways with a
minimum dimension greater than 5 feet. This should consist of #3 rebars of 60-grade steel
placed at a maximum spacing of 18 inches on center, each way Reinforcement for curbing
should be one continuous #4 rebars at top and bottom .
Flatwork surface should be sloped a minimum of 1 percent away from buildings and
slopes, to approved drainage structures.
W all Pressures
The design of footings for retaining structures should be performed in accordance with the
recommendations described earlier under Preparation of Foundation Areas and
Foundation Design. For design of retaining wall footings, the resultant of the applied loads
should act in the middle one-third of the footing, and the maximum edge pressure should
not exceed the basic allowable value without increase.
For design of retaining walls unrestrained against movement at the top, we recommend an
equivalent fluid density of 37 pounds per cubic foot (pcf) be used. This assumes level
backfill consisting of recompacted, non-expansive, soils placed against the structures and
with the backcut slope extending upward from the base of the stem at 35 degrees from the
vertical or flatter.
To avoid overstressing or excessive tilting during placement of backfill behind walls, heavy
compaction equipment should not be allowed within the zone delineated by a 45 degree
line extending from the base of the wall to the f ill surface.
The backfill directly behind the walls should be compacted using light equipment such as
hand operated vibrating plates and rollers. No material larger than 3-inches in diameter
should be placed in direct contact w ith the wall.
W all pressures should be verified prior to construction, when the actual backfill materials
and conditions have been determined. Recommended pressures are applicable only to
level, non-expansive, properly drained backf ill (with no additional surcharg e loadings).
If inclined backfills are proposed, this firm should be contacted to develop appropriate
active earth pressure parameters. Toe bearing pressure for non-structural walls on soils,
not prepared as described earlier under Preparation of Foundation Areas, should not
exceed California Building Code values.
20
LOR GEOTECHNICAL GROUP, INC.
C & C Development Project No. 33616.1
February 25, 2020
The parameters given above are based on the assumption that granular, non-expansive,
compacted sandy soils will be used as wall backfills. The preceding parameters were
developed assuming that the sandy backfill material may have a friction angle of
approximately 32 degrees and a compacted moist unit weight of approximately 120 pcf.
These materials may likely will require importation to the site. Much of the surficial site soils
are expansive clayey materials which normally have low permeability, uncertain behavior,
and exert higher lateral earth pressures on retaining structures. Therefore, we recommend
that these soils do not be used w ithin wall backfill areas.
Sulfate Protection
The results of the soluble sulfate tests conducted on selected subgrade soils expected to
be encountered at f oundation levels are presented on Enclosure C.
Based on the test results it appears that there is a negligible sulfate exposure to concrete
elements in contact with on site soils. T he CBC, therefore, does not recommend special
design criteria for concrete elements in conduct with such materials.
Preliminary Pavement Design
Testing and design for preliminary on-site pavement was conducted in accordance with the
California Highway Design Manual. Based upon our preliminary sampling and testing, and
upon a Traffic Index typical for such projects, it appears that the structural section
tabulated below should provide satisfactory pavement for the subject pavement
improvements:
AREA T.I.DESIGN
R-VALUE PRELIMINARY SECTION
Parking and Drive Areas (light
vehicular traffic and occasional
truck traffic)
6.0 5 0.25’ AC/1.15' AB
AC - Asphalt Concrete
AB - Class 2 Aggregate Base
21
LOR GEOTECHNICAL GROUP, INC.
C & C Development Project No. 33616.1
February 25, 2020
The above structural section is predicated upon 90 percent relative compaction (ASTM D
1557) of all utility trench backfills and 95 percent relative compaction (ASTM D 1557) of
the upper 12 inches of pavement subgrade soils and of any aggregate base utilized. In
addition, the aggregate base should meet Caltrans specifications for Class 2 Aggregate
Base.
In areas of the pavement which will receive high abrasion loads due to start-ups and stops,
or where trucks will move on a tight turning radius, consideration should be given to
installing concrete pads. Such pads should be a minimum of 0.5-foot thick concrete, with
a 0.35-foot thick aggregate base. Concrete pads are also recommended in areas adjacent
to trash storage areas where heavier loads will occur due to operation of trucks lifting trash
dumpsters. The recommended 0.5 feet thick portland cem ent concrete (PCC) pav ement
section should have a minimum modulus of rupture (MR) of 550 pounds per square inch
(psi).
It should be noted that all of the above pavement design was based upon the results of
preliminary sampling and testing, and should be verified by additional sampling and testing
during construction when the actual subg rade soils are exposed.
Construction Monitoring
Post investigative services are an important and necessary continuation of this
investigation. Project plans and specifications should be reviewed by the project
geotechnical consultant prior to construction to confirm that the intent of the
recommendations presented herein have been incorporated into the design. Additiona l
expansion index, R-value, and soluble sulfate testing may be required during site rough
grading.
During construction, sufficient and timely geotechnical observation and testing should be
provided to correlate the findings of this investigation with the actual subsurf ace conditions
exposed during construction. Items requiring observation and testing include, but are not
necessarily limited to, the f ollowing:
1.Site preparation-stripping and rem ovals.
2.Excavations, including approval of the bottom of excavation prior to f illing.
3.Scarifying and recompacting prior to fill placement.
22
LOR GEOTECHNICAL GROUP, INC.
C & C Development Project No. 33616.1
February 25, 2020
4.Subgrade preparation f or pavements and slabs-on-grade.
5.Placement of engineered compacted fill and backfill, including approval of fill
materials and the performance of sufficient density tests to evaluate the degree of
compaction being achieved.
6.Foundation excavations.
LIMITATIONS
This report contains geotechnical conclusions and recommendations developed solely for
use by C & C Development, and their design consultants, for the purposes described
earlier. It may not contain suff icient information for other uses or the purposes of other
parties. The contents should not be extrapolated to other areas or used for other facilities
without consulting LOR Geotechnical Group, Inc.
The recommendations are based on interpretations of the subsurface conditions concluded
from information gained from subsurface explorations and a surficial site reconnaissance.
The interpretations may differ from actual subsurface conditions, which can vary
horizontally and vertically across the site. If conditions are encou ntered during the
construction of the project which differ significantly from those presented in this report, this
firm should be notified immediately in order that we may assess the impact to the
recommendations provided.
Due to possible subsurface variations, all aspects of field construction addressed in this
report should be observ ed and tested by the project geotechnical consultant.
If parties other than LOR Geotechnical Group, Inc., provide construction monitoring
services, they must be notified that they will be required to assume responsibility for the
geotechnical phase of the project being completed by concurring with the
recommendations provided in this report or by providing alternative recommendations.
The report was prepared using generally accepted geotechnical engineering practices
under the direction of a state licensed geotechnical eng ineer. No warranty, expressed or
implied, is made as to conclusions and prof essional advice included in this report.
23
LOR GEOTECHNICAL GROUP, INC.
C & C Development Project No. 33616.1
February 25, 2020
Any persons using this report for bidding or construction purposes should perform such
independent investigations as deemed necessary to satisfy themselves as to the surface
and subsurface conditions to be encountered and the procedures to be used in the
performance of work on this project.
TIME LIMITATIONS
The findings of this report are valid as of this date. Changes in the condition of a property
can, however, occur with the passage of time, whether they be due to natural processes
or the work of man on this or adjacent properties. In addition, changes in the Standards-of-
Practice and/or Governmental Codes may occur. Due to such changes, the findings of this
report may be invalidated wholly or in part by changes beyond our control. Therefore, this
report should not be relied upon after a significant amount of time without a review by LOR
Geotechnical Group, Inc., verifying the suitability of the conclusions and recommendations.
24
LOR GEOTECHNICAL GROUP, INC.
Appendix A.3
Appendix A.4
Appendix B
Appendix B.1
!!!!!!!22
12
20
11
25
21
30
Ele = 184.5
Ele = 184.0
Ele = 182.3
Q10 = 1,42 cfs (Tc = 10.75 min)
Q100 = 2.25 cfs (Tc = 10.46 min)
(Outlet #1)
Ele = 188.0
Ele = 182.0
Ele = 188.0
Ele = 181.0
Q10 = 4.70 cfs (Tc = 9.96 min)
Q100 = 7.43 cfs (Tc = 9.69 min)
(Outlet #2)=D
1.05
=E
0.7=A
0.33
=B
0.32 =C
0.27
L
=
1
4
6'L = 174'L = 159'L = 75'Preliminary Drainage Study
Rational Method Hydrology Map
Existing Condition (100-Year Storm)Date: 03/30/2020 Sheet 1 of 2
Project:
Orange Corp Yard Workforce Housing
City of Orange o0 20 4010
Feet
1 inch = 20 feet
LEGEND
Drainage Boundary
Flow Path
=1A
0.40
Sub-area Designation
Acres
Hydrologic Node Designation11
Ele Ground Elevation
Inv Invert Elevation
L Flow Path Length
Tc Time of Concentration
Q100 Peak Flow for 100-Yr Frequency
Q10 Peak Flow for 10-Yr Frequency
Notes:
Flood Zone Designation: N/A
FIRM No: 06059C0161J
Effective Date: 12-03-2009
Soil Type = "D"
Land Use = "undeveloped"
Drainage Area = 2.67 ac
Ap = 0.81
!!!!!!!!!!!!!!!MWS
15
45
48
35
32
33
11
31
52
40
34
12
18
30
50
Ele = 183.8
Ele = 182.2
Ele = 185.4
Ele = 186.5
Inv = 181.0
Inv = 177.5
Inv = 178.9
Inv = 179.6
Inv = 175.0
Q10 = 7.37 cfs
(Tc = 7.87 min)
Q100 = 11.40 cfs
(Tc = 7.58 min)
Inv = 179.2
Inv = 180.3
Inv = 178.0
Inv = 177.0
Ele = 181.7
Inv = 180.0
Ele = 184.2
Inv = 181.2
L = 178'L = 172'
L = 153'
L = 143'L = 138'L = 103'
L = 76'L = 72'L = 61'L = 50'L = 44'L = 34'L = 2 5 'L = 72'=I
0.58
=L
0.28=A
0.22
=F
0.22
=K
0.21=G
0.2 =D
0.2=B
0.19=E
0.17
=C
0.14
=H
0.13 =J
0.13
Preliminary Drainage Study
Rational Method Hydrology Map
Proposed Condition (100-Year Storm)Date: 03/30/2020 Sheet 2 of 2
Project:
Orange Corp Yard Workforce Housing
City of Orange o0 20 4010
Feet
1 inch = 20 feet
LEGEND
Drainage Boundary
Flow Path
=1A
0.40
Sub-area Designation
Acres
Hydrologic Node Designation11
Ele Ground Elevation
Inv Invert Elevation
L Flow Path Length
Tc Time of Concentration
Q100 Peak Flow for 100-Yr Frequency
Q10 Peak Flow for 10-Yr Frequency
Notes:
Flood Zone Designation: N/A
FIRM No: 06059C0161J
Effective Date: 12-03-2009
Soil Type = "D"
Land Use = "apartments"
Drainage Area = 2.67 ac
Ap = 0.83
Appendix B.2
Page 1 of 3
Existing Condtion 10-Yr Event 3/29/20, 2:46 PM
Orange County Rational Hydrology Program
(Hydrology Manual Date(s) October 1986 & November 1996)
CIVILCADD/CIVILDESIGN Engineering Software, (c) 1989-2004 Version 8.0
Rational Hydrology Study, Date: 03/29/20 File Name: cydex10.roc
------------------------------------------------------------------------
------------------------------------------------------------------------
********* Hydrology Study Control Information **********
------------------------------------------------------------------------
Rational hydrology study storm event year is 10.0
Decimal fraction of study above 2000 ft., 600M = 0.0000
English Units Used for input data
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Process from Point/Station 11.000 to Point/Station 12.000
**** INITIAL AREA EVALUATION ****
______________________________________________________________________
UNDEVELOPED (poor cover) subarea
Decimal fraction soil group A = 0.000
Decimal fraction soil group B = 0.000
Decimal fraction soil group C = 0.000
Decimal fraction soil group D = 1.000
SCS curve number for soil(AMC 2) = 89.00
Pervious ratio(Ap) = 1.0000 Max loss rate(Fp)= 0.200(In/Hr)
Max Catchment Loss (Fm) = 0.200(In/Hr)
Initial subarea data:
Initial area flow distance = 174.000(Ft.)
Top (of initial area) elevation = 188.000(Ft.)
Bottom (of initial area) elevation = 184.000(Ft.)
Difference in elevation = 4.000(Ft.)
Slope = 0.02299 s(%)= 2.30
TC = k(0.525)*[(length^3)/(elevation change)]^0.2
Initial area time of concentration = 8.792 min.
Rainfall intensity = 2.938(In/Hr) for a 10.0 year storm
Effective runoff coefficient used for area (Q=KCIA) is C = 0.839
Subarea runoff = 0.813(CFS)
Total initial stream area = 0.330(Ac.)
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Process from Point/Station 12.000 to Point/Station 20.000
**** IMPROVED CHANNEL TRAVEL TIME ****
______________________________________________________________________
Upstream point elevation = 184.000(Ft.)
Downstream point elevation = 182.300(Ft.)
Channel length thru subarea = 159.000(Ft.)
Channel base width = 10.000(Ft.)
Slope or 'Z' of left channel bank = 10.000
Slope or 'Z' of right channel bank = 10.000
Estimated mean flow rate at midpoint of channel = 1.161(CFS)
Manning's 'N' = 0.020
Maximum depth of channel = 0.500(Ft.)
Flow(q) thru subarea = 1.161(CFS)
Depth of flow = 0.079(Ft.), Average velocity = 1.354(Ft/s)
Channel flow top width = 11.589(Ft.)
Flow Velocity = 1.35(Ft/s)
Travel time = 1.96 min.
Time of concentration = 10.75 min.
Critical depth = 0.073(Ft.)
Adding area flow to channel
UNDEVELOPED (poor cover) subarea
Decimal fraction soil group A = 0.000
Page 2 of 3
Existing Condtion 10-Yr Event 3/29/20, 2:46 PM
Decimal fraction soil group B = 0.000
Decimal fraction soil group C = 0.000
Decimal fraction soil group D = 1.000
SCS curve number for soil(AMC 2) = 89.00
Pervious ratio(Ap) = 1.0000 Max loss rate(Fp)= 0.200(In/Hr)
Max Catchment Loss (Fm) = 0.200(In/Hr)
Rainfall intensity = 2.618(In/Hr) for a 10.0 year storm
Effective runoff coefficient used for area,(total area with modified
rational method)(Q=KCIA) is C = 0.831
Subarea runoff = 0.602(CFS) for 0.320(Ac.)
Total runoff = 1.415(CFS) Total area = 0.65(Ac.)
Area averaged Fm value = 0.200(In/Hr)
Depth of flow = 0.089(Ft.), Average velocity = 1.455(Ft/s)
Critical depth = 0.083(Ft.)
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Process from Point/Station 21.000 to Point/Station 22.000
**** INITIAL AREA EVALUATION ****
______________________________________________________________________
UNDEVELOPED (poor cover) subarea
Decimal fraction soil group A = 0.000
Decimal fraction soil group B = 0.000
Decimal fraction soil group C = 0.000
Decimal fraction soil group D = 1.000
SCS curve number for soil(AMC 2) = 89.00
Pervious ratio(Ap) = 1.0000 Max loss rate(Fp)= 0.200(In/Hr)
Max Catchment Loss (Fm) = 0.200(In/Hr)
Initial subarea data:
Initial area flow distance = 146.000(Ft.)
Top (of initial area) elevation = 188.000(Ft.)
Bottom (of initial area) elevation = 184.500(Ft.)
Difference in elevation = 3.500(Ft.)
Slope = 0.02397 s(%)= 2.40
TC = k(0.525)*[(length^3)/(elevation change)]^0.2
Initial area time of concentration = 8.128 min.
Rainfall intensity = 3.073(In/Hr) for a 10.0 year storm
Effective runoff coefficient used for area (Q=KCIA) is C = 0.841
Subarea runoff = 0.698(CFS)
Total initial stream area = 0.270(Ac.)
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Process from Point/Station 22.000 to Point/Station 25.000
**** IMPROVED CHANNEL TRAVEL TIME ****
______________________________________________________________________
Upstream point elevation = 184.500(Ft.)
Downstream point elevation = 182.000(Ft.)
Channel length thru subarea = 146.000(Ft.)
Channel base width = 10.000(Ft.)
Slope or 'Z' of left channel bank = 10.000
Slope or 'Z' of right channel bank = 10.000
Estimated mean flow rate at midpoint of channel = 1.955(CFS)
Manning's 'N' = 0.020
Maximum depth of channel = 0.500(Ft.)
Flow(q) thru subarea = 1.955(CFS)
Depth of flow = 0.094(Ft.), Average velocity = 1.901(Ft/s)
Channel flow top width = 11.880(Ft.)
Flow Velocity = 1.90(Ft/s)
Travel time = 1.28 min.
Time of concentration = 9.41 min.
Critical depth = 0.102(Ft.)
Adding area flow to channel
Soil group(s) classification and AP values input by user
USER INPUT of soil data for subarea
Decimal fraction soil group A = 0.000
Decimal fraction soil group B = 0.000
Decimal fraction soil group C = 0.000
Page 3 of 3
Existing Condtion 10-Yr Event 3/29/20, 2:46 PM
Decimal fraction soil group D = 1.000
SCS curve number for soil(AMC 2) = 89.59
Pervious ratio(Ap) = 0.8800 Max loss rate(Fp)= 0.200(In/Hr)
Max Catchment Loss (Fm) = 0.176(In/Hr)
Rainfall intensity = 2.826(In/Hr) for a 10.0 year storm
Effective runoff coefficient used for area,(total area with modified
rational method)(Q=KCIA) is C = 0.842
Subarea runoff = 2.444(CFS) for 1.050(Ac.)
Total runoff = 3.142(CFS) Total area = 1.32(Ac.)
Area averaged Fm value = 0.181(In/Hr)
Depth of flow = 0.124(Ft.), Average velocity = 2.254(Ft/s)
Critical depth = 0.139(Ft.)
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Process from Point/Station 25.000 to Point/Station 30.000
**** IMPROVED CHANNEL TRAVEL TIME ****
______________________________________________________________________
Upstream point elevation = 182.000(Ft.)
Downstream point elevation = 181.000(Ft.)
Channel length thru subarea = 75.000(Ft.)
Channel base width = 10.000(Ft.)
Slope or 'Z' of left channel bank = 10.000
Slope or 'Z' of right channel bank = 10.000
Estimated mean flow rate at midpoint of channel = 3.949(CFS)
Manning's 'N' = 0.020
Maximum depth of channel = 0.500(Ft.)
Flow(q) thru subarea = 3.949(CFS)
Depth of flow = 0.152(Ft.), Average velocity = 2.250(Ft/s)
Channel flow top width = 13.046(Ft.)
Flow Velocity = 2.25(Ft/s)
Travel time = 0.56 min.
Time of concentration = 9.96 min.
Critical depth = 0.160(Ft.)
Adding area flow to channel
Soil group(s) classification and AP values input by user
USER INPUT of soil data for subarea
Decimal fraction soil group A = 0.000
Decimal fraction soil group B = 0.000
Decimal fraction soil group C = 0.000
Decimal fraction soil group D = 1.000
SCS curve number for soil(AMC 2) = 89.59
Pervious ratio(Ap) = 0.4400 Max loss rate(Fp)= 0.200(In/Hr)
Max Catchment Loss (Fm) = 0.088(In/Hr)
Rainfall intensity = 2.735(In/Hr) for a 10.0 year storm
Effective runoff coefficient used for area,(total area with modified
rational method)(Q=KCIA) is C = 0.851
Subarea runoff = 1.559(CFS) for 0.700(Ac.)
Total runoff = 4.701(CFS) Total area = 2.02(Ac.)
Area averaged Fm value = 0.149(In/Hr)
Depth of flow = 0.168(Ft.), Average velocity = 2.390(Ft/s)
Critical depth = 0.178(Ft.)
End of computations, total study area = 2.67 (Ac.)
The following figures may
be used for a unit hydrograph study of the same area.
Note: These figures do not consider reduced effective area
effects caused by confluences in the rational equation.
Area averaged pervious area fraction(Ap) = 0.806
Area averaged SCS curve number (AMC 2) = 89.4
Page 1 of 3
Existing Condtion 100-Yr Event 3/29/20, 2:47 PM
Orange County Rational Hydrology Program
(Hydrology Manual Date(s) October 1986 & November 1996)
CIVILCADD/CIVILDESIGN Engineering Software, (c) 1989-2004 Version 8.0
Rational Hydrology Study, Date: 03/29/20 File Name: cydex100.roc
------------------------------------------------------------------------
------------------------------------------------------------------------
********* Hydrology Study Control Information **********
------------------------------------------------------------------------
Rational hydrology study storm event year is 100.0
Decimal fraction of study above 2000 ft., 600M = 0.0000
English Units Used for input data
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Process from Point/Station 11.000 to Point/Station 12.000
**** INITIAL AREA EVALUATION ****
______________________________________________________________________
UNDEVELOPED (poor cover) subarea
Decimal fraction soil group A = 0.000
Decimal fraction soil group B = 0.000
Decimal fraction soil group C = 0.000
Decimal fraction soil group D = 1.000
SCS curve number for soil(AMC 2) = 89.00
Pervious ratio(Ap) = 1.0000 Max loss rate(Fp)= 0.200(In/Hr)
Max Catchment Loss (Fm) = 0.200(In/Hr)
Initial subarea data:
Initial area flow distance = 174.000(Ft.)
Top (of initial area) elevation = 188.000(Ft.)
Bottom (of initial area) elevation = 184.000(Ft.)
Difference in elevation = 4.000(Ft.)
Slope = 0.02299 s(%)= 2.30
TC = k(0.525)*[(length^3)/(elevation change)]^0.2
Initial area time of concentration = 8.792 min.
Rainfall intensity = 4.478(In/Hr) for a 100.0 year storm
Effective runoff coefficient used for area (Q=KCIA) is C = 0.860
Subarea runoff = 1.270(CFS)
Total initial stream area = 0.330(Ac.)
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Process from Point/Station 12.000 to Point/Station 20.000
**** IMPROVED CHANNEL TRAVEL TIME ****
______________________________________________________________________
Upstream point elevation = 184.000(Ft.)
Downstream point elevation = 182.300(Ft.)
Channel length thru subarea = 159.000(Ft.)
Channel base width = 10.000(Ft.)
Slope or 'Z' of left channel bank = 10.000
Slope or 'Z' of right channel bank = 10.000
Estimated mean flow rate at midpoint of channel = 1.794(CFS)
Manning's 'N' = 0.020
Maximum depth of channel = 0.500(Ft.)
Flow(q) thru subarea = 1.794(CFS)
Depth of flow = 0.103(Ft.), Average velocity = 1.586(Ft/s)
Channel flow top width = 12.052(Ft.)
Flow Velocity = 1.59(Ft/s)
Travel time = 1.67 min.
Time of concentration = 10.46 min.
Critical depth = 0.097(Ft.)
Adding area flow to channel
UNDEVELOPED (poor cover) subarea
Decimal fraction soil group A = 0.000
Page 2 of 3
Existing Condtion 100-Yr Event 3/29/20, 2:47 PM
Decimal fraction soil group B = 0.000
Decimal fraction soil group C = 0.000
Decimal fraction soil group D = 1.000
SCS curve number for soil(AMC 2) = 89.00
Pervious ratio(Ap) = 1.0000 Max loss rate(Fp)= 0.200(In/Hr)
Max Catchment Loss (Fm) = 0.200(In/Hr)
Rainfall intensity = 4.053(In/Hr) for a 100.0 year storm
Effective runoff coefficient used for area,(total area with modified
rational method)(Q=KCIA) is C = 0.856
Subarea runoff = 0.983(CFS) for 0.320(Ac.)
Total runoff = 2.254(CFS) Total area = 0.65(Ac.)
Area averaged Fm value = 0.200(In/Hr)
Depth of flow = 0.117(Ft.), Average velocity = 1.721(Ft/s)
Critical depth = 0.111(Ft.)
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Process from Point/Station 21.000 to Point/Station 22.000
**** INITIAL AREA EVALUATION ****
______________________________________________________________________
UNDEVELOPED (poor cover) subarea
Decimal fraction soil group A = 0.000
Decimal fraction soil group B = 0.000
Decimal fraction soil group C = 0.000
Decimal fraction soil group D = 1.000
SCS curve number for soil(AMC 2) = 89.00
Pervious ratio(Ap) = 1.0000 Max loss rate(Fp)= 0.200(In/Hr)
Max Catchment Loss (Fm) = 0.200(In/Hr)
Initial subarea data:
Initial area flow distance = 146.000(Ft.)
Top (of initial area) elevation = 188.000(Ft.)
Bottom (of initial area) elevation = 184.500(Ft.)
Difference in elevation = 3.500(Ft.)
Slope = 0.02397 s(%)= 2.40
TC = k(0.525)*[(length^3)/(elevation change)]^0.2
Initial area time of concentration = 8.128 min.
Rainfall intensity = 4.684(In/Hr) for a 100.0 year storm
Effective runoff coefficient used for area (Q=KCIA) is C = 0.862
Subarea runoff = 1.090(CFS)
Total initial stream area = 0.270(Ac.)
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Process from Point/Station 22.000 to Point/Station 25.000
**** IMPROVED CHANNEL TRAVEL TIME ****
______________________________________________________________________
Upstream point elevation = 184.500(Ft.)
Downstream point elevation = 182.000(Ft.)
Channel length thru subarea = 146.000(Ft.)
Channel base width = 10.000(Ft.)
Slope or 'Z' of left channel bank = 10.000
Slope or 'Z' of right channel bank = 10.000
Estimated mean flow rate at midpoint of channel = 3.073(CFS)
Manning's 'N' = 0.020
Maximum depth of channel = 0.500(Ft.)
Flow(q) thru subarea = 3.073(CFS)
Depth of flow = 0.122(Ft.), Average velocity = 2.236(Ft/s)
Channel flow top width = 12.449(Ft.)
Flow Velocity = 2.24(Ft/s)
Travel time = 1.09 min.
Time of concentration = 9.22 min.
Critical depth = 0.137(Ft.)
Adding area flow to channel
Soil group(s) classification and AP values input by user
USER INPUT of soil data for subarea
Decimal fraction soil group A = 0.000
Decimal fraction soil group B = 0.000
Decimal fraction soil group C = 0.000
Page 3 of 3
Existing Condtion 100-Yr Event 3/29/20, 2:47 PM
Decimal fraction soil group D = 1.000
SCS curve number for soil(AMC 2) = 89.59
Pervious ratio(Ap) = 0.8800 Max loss rate(Fp)= 0.200(In/Hr)
Max Catchment Loss (Fm) = 0.176(In/Hr)
Rainfall intensity = 4.358(In/Hr) for a 100.0 year storm
Effective runoff coefficient used for area,(total area with modified
rational method)(Q=KCIA) is C = 0.863
Subarea runoff = 3.873(CFS) for 1.050(Ac.)
Total runoff = 4.963(CFS) Total area = 1.32(Ac.)
Area averaged Fm value = 0.181(In/Hr)
Depth of flow = 0.162(Ft.), Average velocity = 2.643(Ft/s)
Critical depth = 0.184(Ft.)
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Process from Point/Station 25.000 to Point/Station 30.000
**** IMPROVED CHANNEL TRAVEL TIME ****
______________________________________________________________________
Upstream point elevation = 182.000(Ft.)
Downstream point elevation = 181.000(Ft.)
Channel length thru subarea = 75.000(Ft.)
Channel base width = 10.000(Ft.)
Slope or 'Z' of left channel bank = 10.000
Slope or 'Z' of right channel bank = 10.000
Estimated mean flow rate at midpoint of channel = 6.237(CFS)
Manning's 'N' = 0.020
Maximum depth of channel = 0.500(Ft.)
Flow(q) thru subarea = 6.237(CFS)
Depth of flow = 0.198(Ft.), Average velocity = 2.629(Ft/s)
Channel flow top width = 13.960(Ft.)
Flow Velocity = 2.63(Ft/s)
Travel time = 0.48 min.
Time of concentration = 9.69 min.
Critical depth = 0.213(Ft.)
Adding area flow to channel
Soil group(s) classification and AP values input by user
USER INPUT of soil data for subarea
Decimal fraction soil group A = 0.000
Decimal fraction soil group B = 0.000
Decimal fraction soil group C = 0.000
Decimal fraction soil group D = 1.000
SCS curve number for soil(AMC 2) = 89.59
Pervious ratio(Ap) = 0.4400 Max loss rate(Fp)= 0.200(In/Hr)
Max Catchment Loss (Fm) = 0.088(In/Hr)
Rainfall intensity = 4.235(In/Hr) for a 100.0 year storm
Effective runoff coefficient used for area,(total area with modified
rational method)(Q=KCIA) is C = 0.868
Subarea runoff = 2.465(CFS) for 0.700(Ac.)
Total runoff = 7.428(CFS) Total area = 2.02(Ac.)
Area averaged Fm value = 0.149(In/Hr)
Depth of flow = 0.219(Ft.), Average velocity = 2.787(Ft/s)
Critical depth = 0.238(Ft.)
End of computations, total study area = 2.67 (Ac.)
The following figures may
be used for a unit hydrograph study of the same area.
Note: These figures do not consider reduced effective area
effects caused by confluences in the rational equation.
Area averaged pervious area fraction(Ap) = 0.806
Area averaged SCS curve number (AMC 2) = 89.4
Appendix B.3
Page 1 of 9
Proposed Condtion 10-Yr Event 3/29/20, 2:48 PM
Orange County Rational Hydrology Program
(Hydrology Manual Date(s) October 1986 & November 1996)
CIVILCADD/CIVILDESIGN Engineering Software, (c) 1989-2004 Version 8.0
Rational Hydrology Study, Date: 03/27/20 File Name: cydpm10.roc
------------------------------------------------------------------------
------------------------------------------------------------------------
********* Hydrology Study Control Information **********
------------------------------------------------------------------------
Rational hydrology study storm event year is 10.0
Decimal fraction of study above 2000 ft., 600M = 0.0000
English Units Used for input data
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Process from Point/Station 11.000 to Point/Station 12.000
**** INITIAL AREA EVALUATION ****
______________________________________________________________________
APARTMENT subarea type
Decimal fraction soil group A = 0.000
Decimal fraction soil group B = 0.000
Decimal fraction soil group C = 0.000
Decimal fraction soil group D = 1.000
SCS curve number for soil(AMC 2) = 75.00
Pervious ratio(Ap) = 0.2000 Max loss rate(Fp)= 0.200(In/Hr)
Max Catchment Loss (Fm) = 0.040(In/Hr)
Initial subarea data:
Initial area flow distance = 172.000(Ft.)
Top (of initial area) elevation = 185.400(Ft.)
Bottom (of initial area) elevation = 184.200(Ft.)
Difference in elevation = 1.200(Ft.)
Slope = 0.00698 s(%)= 0.70
TC = k(0.324)*[(length^3)/(elevation change)]^0.2
Initial area time of concentration = 6.855 min.
Rainfall intensity = 3.388(In/Hr) for a 10.0 year storm
Effective runoff coefficient used for area (Q=KCIA) is C = 0.889
Subarea runoff = 0.663(CFS)
Total initial stream area = 0.220(Ac.)
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Process from Point/Station 12.000 to Point/Station 12.000
**** SUBAREA FLOW ADDITION ****
______________________________________________________________________
APARTMENT subarea type
Decimal fraction soil group A = 0.000
Decimal fraction soil group B = 0.000
Decimal fraction soil group C = 0.000
Decimal fraction soil group D = 1.000
SCS curve number for soil(AMC 2) = 75.00
Pervious ratio(Ap) = 0.2000 Max loss rate(Fp)= 0.200(In/Hr)
Max Catchment Loss (Fm) = 0.040(In/Hr)
Time of concentration = 6.86 min.
Rainfall intensity = 3.388(In/Hr) for a 10.0 year storm
Effective runoff coefficient used for area,(total area with modified
rational method)(Q=KCIA) is C = 0.889
Subarea runoff = 0.573(CFS) for 0.190(Ac.)
Total runoff = 1.235(CFS) Total area = 0.41(Ac.)
Area averaged Fm value = 0.040(In/Hr)
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Process from Point/Station 12.000 to Point/Station 15.000
Page 2 of 9
Proposed Condtion 10-Yr Event 3/29/20, 2:48 PM
**** PIPEFLOW TRAVEL TIME (Program estimated size) ****
______________________________________________________________________
Upstream point/station elevation = 181.200(Ft.)
Downstream point/station elevation = 181.000(Ft.)
Pipe length = 25.00(Ft.) Manning's N = 0.013
No. of pipes = 1 Required pipe flow = 1.235(CFS)
Nearest computed pipe diameter = 9.00(In.)
Calculated individual pipe flow = 1.235(CFS)
Normal flow depth in pipe = 6.29(In.)
Flow top width inside pipe = 8.26(In.)
Critical Depth = 6.14(In.)
Pipe flow velocity = 3.75(Ft/s)
Travel time through pipe = 0.11 min.
Time of concentration (TC) = 6.97 min.
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Process from Point/Station 15.000 to Point/Station 18.000
**** PIPEFLOW TRAVEL TIME (Program estimated size) ****
______________________________________________________________________
Upstream point/station elevation = 181.000(Ft.)
Downstream point/station elevation = 180.300(Ft.)
Pipe length = 143.00(Ft.) Manning's N = 0.013
No. of pipes = 1 Required pipe flow = 1.235(CFS)
Nearest computed pipe diameter = 12.00(In.)
Calculated individual pipe flow = 1.235(CFS)
Normal flow depth in pipe = 5.97(In.)
Flow top width inside pipe = 12.00(In.)
Critical Depth = 5.63(In.)
Pipe flow velocity = 3.17(Ft/s)
Travel time through pipe = 0.75 min.
Time of concentration (TC) = 7.72 min.
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Process from Point/Station 18.000 to Point/Station 18.000
**** SUBAREA FLOW ADDITION ****
______________________________________________________________________
APARTMENT subarea type
Decimal fraction soil group A = 0.000
Decimal fraction soil group B = 0.000
Decimal fraction soil group C = 0.000
Decimal fraction soil group D = 1.000
SCS curve number for soil(AMC 2) = 75.00
Pervious ratio(Ap) = 0.2000 Max loss rate(Fp)= 0.200(In/Hr)
Max Catchment Loss (Fm) = 0.040(In/Hr)
Time of concentration = 7.72 min.
Rainfall intensity = 3.165(In/Hr) for a 10.0 year storm
Effective runoff coefficient used for area,(total area with modified
rational method)(Q=KCIA) is C = 0.889
Subarea runoff = 0.312(CFS) for 0.140(Ac.)
Total runoff = 1.547(CFS) Total area = 0.55(Ac.)
Area averaged Fm value = 0.040(In/Hr)
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Process from Point/Station 18.000 to Point/Station 30.000
**** PIPEFLOW TRAVEL TIME (Program estimated size) ****
______________________________________________________________________
Upstream point/station elevation = 180.300(Ft.)
Downstream point/station elevation = 178.000(Ft.)
Pipe length = 72.00(Ft.) Manning's N = 0.013
No. of pipes = 1 Required pipe flow = 1.547(CFS)
Nearest computed pipe diameter = 9.00(In.)
Calculated individual pipe flow = 1.547(CFS)
Normal flow depth in pipe = 4.62(In.)
Flow top width inside pipe = 9.00(In.)
Critical Depth = 6.87(In.)
Page 3 of 9
Proposed Condtion 10-Yr Event 3/29/20, 2:48 PM
Pipe flow velocity = 6.77(Ft/s)
Travel time through pipe = 0.18 min.
Time of concentration (TC) = 7.90 min.
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Process from Point/Station 30.000 to Point/Station 30.000
**** SUBAREA FLOW ADDITION ****
______________________________________________________________________
APARTMENT subarea type
Decimal fraction soil group A = 0.000
Decimal fraction soil group B = 0.000
Decimal fraction soil group C = 0.000
Decimal fraction soil group D = 1.000
SCS curve number for soil(AMC 2) = 75.00
Pervious ratio(Ap) = 0.2000 Max loss rate(Fp)= 0.200(In/Hr)
Max Catchment Loss (Fm) = 0.040(In/Hr)
Time of concentration = 7.90 min.
Rainfall intensity = 3.124(In/Hr) for a 10.0 year storm
Effective runoff coefficient used for area,(total area with modified
rational method)(Q=KCIA) is C = 0.888
Subarea runoff = 1.590(CFS) for 0.580(Ac.)
Total runoff = 3.137(CFS) Total area = 1.13(Ac.)
Area averaged Fm value = 0.040(In/Hr)
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Process from Point/Station 30.000 to Point/Station 45.000
**** PIPEFLOW TRAVEL TIME (Program estimated size) ****
______________________________________________________________________
Upstream point/station elevation = 178.000(Ft.)
Downstream point/station elevation = 177.500(Ft.)
Pipe length = 44.00(Ft.) Manning's N = 0.013
No. of pipes = 1 Required pipe flow = 3.137(CFS)
Nearest computed pipe diameter = 12.00(In.)
Calculated individual pipe flow = 3.137(CFS)
Normal flow depth in pipe = 8.31(In.)
Flow top width inside pipe = 11.07(In.)
Critical Depth = 9.10(In.)
Pipe flow velocity = 5.40(Ft/s)
Travel time through pipe = 0.14 min.
Time of concentration (TC) = 8.03 min.
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Process from Point/Station 45.000 to Point/Station 45.000
**** SUBAREA FLOW ADDITION ****
______________________________________________________________________
APARTMENT subarea type
Decimal fraction soil group A = 0.000
Decimal fraction soil group B = 0.000
Decimal fraction soil group C = 0.000
Decimal fraction soil group D = 1.000
SCS curve number for soil(AMC 2) = 75.00
Pervious ratio(Ap) = 0.2000 Max loss rate(Fp)= 0.200(In/Hr)
Max Catchment Loss (Fm) = 0.040(In/Hr)
Time of concentration = 8.03 min.
Rainfall intensity = 3.094(In/Hr) for a 10.0 year storm
Effective runoff coefficient used for area,(total area with modified
rational method)(Q=KCIA) is C = 0.888
Subarea runoff = 0.519(CFS) for 0.200(Ac.)
Total runoff = 3.656(CFS) Total area = 1.33(Ac.)
Area averaged Fm value = 0.040(In/Hr)
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Process from Point/Station 45.000 to Point/Station 50.000
**** PIPEFLOW TRAVEL TIME (Program estimated size) ****
Page 4 of 9
Proposed Condtion 10-Yr Event 3/29/20, 2:48 PM
______________________________________________________________________
Upstream point/station elevation = 177.500(Ft.)
Downstream point/station elevation = 177.000(Ft.)
Pipe length = 34.00(Ft.) Manning's N = 0.013
No. of pipes = 1 Required pipe flow = 3.656(CFS)
Nearest computed pipe diameter = 12.00(In.)
Calculated individual pipe flow = 3.656(CFS)
Normal flow depth in pipe = 8.47(In.)
Flow top width inside pipe = 10.94(In.)
Critical Depth = 9.78(In.)
Pipe flow velocity = 6.17(Ft/s)
Travel time through pipe = 0.09 min.
Time of concentration (TC) = 8.12 min.
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Process from Point/Station 11.000 to Point/Station 50.000
**** CONFLUENCE OF MINOR STREAMS ****
______________________________________________________________________
Along Main Stream number: 1 in normal stream number 1
Stream flow area = 1.330(Ac.)
Runoff from this stream = 3.656(CFS)
Time of concentration = 8.12 min.
Rainfall intensity = 3.074(In/Hr)
Area averaged loss rate (Fm) = 0.0400(In/Hr)
Area averaged Pervious ratio (Ap) = 0.2000
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Process from Point/Station 31.000 to Point/Station 32.000
**** INITIAL AREA EVALUATION ****
______________________________________________________________________
APARTMENT subarea type
Decimal fraction soil group A = 0.000
Decimal fraction soil group B = 0.000
Decimal fraction soil group C = 0.000
Decimal fraction soil group D = 1.000
SCS curve number for soil(AMC 2) = 75.00
Pervious ratio(Ap) = 0.2000 Max loss rate(Fp)= 0.200(In/Hr)
Max Catchment Loss (Fm) = 0.040(In/Hr)
Initial subarea data:
Initial area flow distance = 138.000(Ft.)
Top (of initial area) elevation = 186.500(Ft.)
Bottom (of initial area) elevation = 183.800(Ft.)
Difference in elevation = 2.700(Ft.)
Slope = 0.01957 s(%)= 1.96
TC = k(0.324)*[(length^3)/(elevation change)]^0.2
Initial area time of concentration = 5.107 min.
Rainfall intensity = 4.010(In/Hr) for a 10.0 year storm
Effective runoff coefficient used for area (Q=KCIA) is C = 0.891
Subarea runoff = 0.607(CFS)
Total initial stream area = 0.170(Ac.)
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Process from Point/Station 32.000 to Point/Station 33.000
**** IMPROVED CHANNEL TRAVEL TIME ****
______________________________________________________________________
Upstream point elevation = 183.800(Ft.)
Downstream point elevation = 182.200(Ft.)
Channel length thru subarea = 178.000(Ft.)
Channel base width = 1.000(Ft.)
Slope or 'Z' of left channel bank = 0.100
Slope or 'Z' of right channel bank = 10.000
Estimated mean flow rate at midpoint of channel = 0.959(CFS)
Manning's 'N' = 0.015
Maximum depth of channel = 0.500(Ft.)
Flow(q) thru subarea = 0.959(CFS)
Page 5 of 9
Proposed Condtion 10-Yr Event 3/29/20, 2:48 PM
Depth of flow = 0.201(Ft.), Average velocity = 2.360(Ft/s)
Channel flow top width = 3.035(Ft.)
Flow Velocity = 2.36(Ft/s)
Travel time = 1.26 min.
Time of concentration = 6.36 min.
Critical depth = 0.215(Ft.)
Adding area flow to channel
APARTMENT subarea type
Decimal fraction soil group A = 0.000
Decimal fraction soil group B = 0.000
Decimal fraction soil group C = 0.000
Decimal fraction soil group D = 1.000
SCS curve number for soil(AMC 2) = 75.00
Pervious ratio(Ap) = 0.2000 Max loss rate(Fp)= 0.200(In/Hr)
Max Catchment Loss (Fm) = 0.040(In/Hr)
Rainfall intensity = 3.535(In/Hr) for a 10.0 year storm
Effective runoff coefficient used for area,(total area with modified
rational method)(Q=KCIA) is C = 0.890
Subarea runoff = 0.619(CFS) for 0.220(Ac.)
Total runoff = 1.227(CFS) Total area = 0.39(Ac.)
Area averaged Fm value = 0.040(In/Hr)
Depth of flow = 0.227(Ft.), Average velocity = 2.518(Ft/s)
Critical depth = 0.244(Ft.)
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Process from Point/Station 33.000 to Point/Station 34.000
**** IMPROVED CHANNEL TRAVEL TIME ****
______________________________________________________________________
Upstream point elevation = 182.200(Ft.)
Downstream point elevation = 0.000(Ft.)
Channel length thru subarea = 103.000(Ft.)
Channel base width = 1.000(Ft.)
Slope or 'Z' of left channel bank = 0.100
Slope or 'Z' of right channel bank = 10.000
Estimated mean flow rate at midpoint of channel = 1.541(CFS)
Manning's 'N' = 0.015
Maximum depth of channel = 0.500(Ft.)
Flow(q) thru subarea = 1.541(CFS)
Depth of flow = 0.065(Ft.), Average velocity = 17.913(Ft/s)
Channel flow top width = 1.655(Ft.)
Flow Velocity = 17.91(Ft/s)
Travel time = 0.10 min.
Time of concentration = 6.46 min.
Critical depth = 0.273(Ft.)
Adding area flow to channel
APARTMENT subarea type
Decimal fraction soil group A = 0.000
Decimal fraction soil group B = 0.000
Decimal fraction soil group C = 0.000
Decimal fraction soil group D = 1.000
SCS curve number for soil(AMC 2) = 75.00
Pervious ratio(Ap) = 0.2000 Max loss rate(Fp)= 0.200(In/Hr)
Max Catchment Loss (Fm) = 0.040(In/Hr)
Rainfall intensity = 3.505(In/Hr) for a 10.0 year storm
Effective runoff coefficient used for area,(total area with modified
rational method)(Q=KCIA) is C = 0.890
Subarea runoff = 0.613(CFS) for 0.200(Ac.)
Total runoff = 1.840(CFS) Total area = 0.59(Ac.)
Area averaged Fm value = 0.040(In/Hr)
Depth of flow = 0.072(Ft.), Average velocity = 18.906(Ft/s)
Critical depth = 0.299(Ft.)
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Process from Point/Station 34.000 to Point/Station 35.000
**** PIPEFLOW TRAVEL TIME (Program estimated size) ****
______________________________________________________________________
Page 6 of 9
Proposed Condtion 10-Yr Event 3/29/20, 2:48 PM
Upstream point/station elevation = 180.000(Ft.)
Downstream point/station elevation = 179.600(Ft.)
Pipe length = 72.00(Ft.) Manning's N = 0.013
No. of pipes = 1 Required pipe flow = 1.840(CFS)
Nearest computed pipe diameter = 12.00(In.)
Calculated individual pipe flow = 1.840(CFS)
Normal flow depth in pipe = 7.35(In.)
Flow top width inside pipe = 11.69(In.)
Critical Depth = 6.93(In.)
Pipe flow velocity = 3.65(Ft/s)
Travel time through pipe = 0.33 min.
Time of concentration (TC) = 6.79 min.
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Process from Point/Station 35.000 to Point/Station 35.000
**** SUBAREA FLOW ADDITION ****
______________________________________________________________________
APARTMENT subarea type
Decimal fraction soil group A = 0.000
Decimal fraction soil group B = 0.000
Decimal fraction soil group C = 0.000
Decimal fraction soil group D = 1.000
SCS curve number for soil(AMC 2) = 75.00
Pervious ratio(Ap) = 0.2000 Max loss rate(Fp)= 0.200(In/Hr)
Max Catchment Loss (Fm) = 0.040(In/Hr)
Time of concentration = 6.79 min.
Rainfall intensity = 3.407(In/Hr) for a 10.0 year storm
Effective runoff coefficient used for area,(total area with modified
rational method)(Q=KCIA) is C = 0.889
Subarea runoff = 0.342(CFS) for 0.130(Ac.)
Total runoff = 2.182(CFS) Total area = 0.72(Ac.)
Area averaged Fm value = 0.040(In/Hr)
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Process from Point/Station 35.000 to Point/Station 40.000
**** PIPEFLOW TRAVEL TIME (Program estimated size) ****
______________________________________________________________________
Upstream point/station elevation = 179.600(Ft.)
Downstream point/station elevation = 179.200(Ft.)
Pipe length = 76.00(Ft.) Manning's N = 0.013
No. of pipes = 1 Required pipe flow = 2.182(CFS)
Nearest computed pipe diameter = 12.00(In.)
Calculated individual pipe flow = 2.182(CFS)
Normal flow depth in pipe = 8.45(In.)
Flow top width inside pipe = 10.95(In.)
Critical Depth = 7.58(In.)
Pipe flow velocity = 3.69(Ft/s)
Travel time through pipe = 0.34 min.
Time of concentration (TC) = 7.13 min.
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Process from Point/Station 40.000 to Point/Station 40.000
**** SUBAREA FLOW ADDITION ****
______________________________________________________________________
APARTMENT subarea type
Decimal fraction soil group A = 0.000
Decimal fraction soil group B = 0.000
Decimal fraction soil group C = 0.000
Decimal fraction soil group D = 1.000
SCS curve number for soil(AMC 2) = 75.00
Pervious ratio(Ap) = 0.2000 Max loss rate(Fp)= 0.200(In/Hr)
Max Catchment Loss (Fm) = 0.040(In/Hr)
Time of concentration = 7.13 min.
Rainfall intensity = 3.312(In/Hr) for a 10.0 year storm
Effective runoff coefficient used for area,(total area with modified
Page 7 of 9
Proposed Condtion 10-Yr Event 3/29/20, 2:48 PM
rational method)(Q=KCIA) is C = 0.889
Subarea runoff = 0.557(CFS) for 0.210(Ac.)
Total runoff = 2.739(CFS) Total area = 0.93(Ac.)
Area averaged Fm value = 0.040(In/Hr)
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Process from Point/Station 40.000 to Point/Station 48.000
**** PIPEFLOW TRAVEL TIME (Program estimated size) ****
______________________________________________________________________
Upstream point/station elevation = 179.200(Ft.)
Downstream point/station elevation = 178.900(Ft.)
Pipe length = 61.00(Ft.) Manning's N = 0.013
No. of pipes = 1 Required pipe flow = 2.739(CFS)
Nearest computed pipe diameter = 15.00(In.)
Calculated individual pipe flow = 2.739(CFS)
Normal flow depth in pipe = 8.41(In.)
Flow top width inside pipe = 14.89(In.)
Critical Depth = 7.97(In.)
Pipe flow velocity = 3.87(Ft/s)
Travel time through pipe = 0.26 min.
Time of concentration (TC) = 7.40 min.
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Process from Point/Station 48.000 to Point/Station 48.000
**** SUBAREA FLOW ADDITION ****
______________________________________________________________________
APARTMENT subarea type
Decimal fraction soil group A = 0.000
Decimal fraction soil group B = 0.000
Decimal fraction soil group C = 0.000
Decimal fraction soil group D = 1.000
SCS curve number for soil(AMC 2) = 75.00
Pervious ratio(Ap) = 0.2000 Max loss rate(Fp)= 0.200(In/Hr)
Max Catchment Loss (Fm) = 0.040(In/Hr)
Time of concentration = 7.40 min.
Rainfall intensity = 3.244(In/Hr) for a 10.0 year storm
Effective runoff coefficient used for area,(total area with modified
rational method)(Q=KCIA) is C = 0.889
Subarea runoff = 0.318(CFS) for 0.130(Ac.)
Total runoff = 3.057(CFS) Total area = 1.06(Ac.)
Area averaged Fm value = 0.040(In/Hr)
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Process from Point/Station 48.000 to Point/Station 50.000
**** PIPEFLOW TRAVEL TIME (Program estimated size) ****
______________________________________________________________________
Upstream point/station elevation = 178.900(Ft.)
Downstream point/station elevation = 177.000(Ft.)
Pipe length = 50.00(Ft.) Manning's N = 0.013
No. of pipes = 1 Required pipe flow = 3.057(CFS)
Nearest computed pipe diameter = 9.00(In.)
Calculated individual pipe flow = 3.057(CFS)
Normal flow depth in pipe = 6.99(In.)
Flow top width inside pipe = 7.50(In.)
Critical depth could not be calculated.
Pipe flow velocity = 8.31(Ft/s)
Travel time through pipe = 0.10 min.
Time of concentration (TC) = 7.50 min.
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Process from Point/Station 50.000 to Point/Station 50.000
**** SUBAREA FLOW ADDITION ****
______________________________________________________________________
APARTMENT subarea type
Page 8 of 9
Proposed Condtion 10-Yr Event 3/29/20, 2:48 PM
Decimal fraction soil group A = 0.000
Decimal fraction soil group B = 0.000
Decimal fraction soil group C = 0.000
Decimal fraction soil group D = 1.000
SCS curve number for soil(AMC 2) = 75.00
Pervious ratio(Ap) = 0.2000 Max loss rate(Fp)= 0.200(In/Hr)
Max Catchment Loss (Fm) = 0.040(In/Hr)
Time of concentration = 7.50 min.
Rainfall intensity = 3.219(In/Hr) for a 10.0 year storm
Effective runoff coefficient used for area,(total area with modified
rational method)(Q=KCIA) is C = 0.889
Subarea runoff = 0.777(CFS) for 0.280(Ac.)
Total runoff = 3.834(CFS) Total area = 1.34(Ac.)
Area averaged Fm value = 0.040(In/Hr)
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Process from Point/Station 31.000 to Point/Station 50.000
**** CONFLUENCE OF MINOR STREAMS ****
______________________________________________________________________
Along Main Stream number: 1 in normal stream number 2
Stream flow area = 1.340(Ac.)
Runoff from this stream = 3.834(CFS)
Time of concentration = 7.50 min.
Rainfall intensity = 3.219(In/Hr)
Area averaged loss rate (Fm) = 0.0400(In/Hr)
Area averaged Pervious ratio (Ap) = 0.2000
Summary of stream data:
Stream Area Flow rate TC Fm Rainfall Intensity
No. (Ac.) (CFS) (min) (In/Hr) (In/Hr)
1 1.33 3.656 8.12 0.040 3.074
2 1.34 3.834 7.50 0.040 3.219
Qmax(1) =
1.000 * 1.000 * 3.656) +
0.954 * 1.000 * 3.834) + = 7.314
Qmax(2) =
1.048 * 0.923 * 3.656) +
1.000 * 1.000 * 3.834) + = 7.368
Total of 2 streams to confluence:
Flow rates before confluence point:
3.656 3.834
Maximum flow rates at confluence using above data:
7.314 7.368
Area of streams before confluence:
1.330 1.340
Effective area values after confluence:
2.670 2.567
Results of confluence:
Total flow rate = 7.368(CFS)
Time of concentration = 7.496 min.
Effective stream area after confluence = 2.567(Ac.)
Study area average Pervious fraction(Ap) = 0.200
Study area average soil loss rate(Fm) = 0.040(In/Hr)
Study area total (this main stream) = 2.67(Ac.)
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Process from Point/Station 50.000 to Point/Station 52.000
**** PIPEFLOW TRAVEL TIME (Program estimated size) ****
______________________________________________________________________
Upstream point/station elevation = 177.000(Ft.)
Downstream point/station elevation = 175.000(Ft.)
Pipe length = 153.00(Ft.) Manning's N = 0.013
No. of pipes = 1 Required pipe flow = 7.368(CFS)
Page 9 of 9
Proposed Condtion 10-Yr Event 3/29/20, 2:48 PM
Nearest computed pipe diameter = 15.00(In.)
Calculated individual pipe flow = 7.368(CFS)
Normal flow depth in pipe = 12.26(In.)
Flow top width inside pipe = 11.59(In.)
Critical Depth = 12.98(In.)
Pipe flow velocity = 6.86(Ft/s)
Travel time through pipe = 0.37 min.
Time of concentration (TC) = 7.87 min.
End of computations, total study area = 2.67 (Ac.)
The following figures may
be used for a unit hydrograph study of the same area.
Note: These figures do not consider reduced effective area
effects caused by confluences in the rational equation.
Area averaged pervious area fraction(Ap) = 0.200
Area averaged SCS curve number (AMC 2) = 75.0
Page 1 of 9
Proposed Condtion 100-Yr Event 3/29/20, 2:48 PM
Orange County Rational Hydrology Program
(Hydrology Manual Date(s) October 1986 & November 1996)
CIVILCADD/CIVILDESIGN Engineering Software, (c) 1989-2004 Version 8.0
Rational Hydrology Study, Date: 03/27/20 File Name: cydpm100.roc
------------------------------------------------------------------------
------------------------------------------------------------------------
********* Hydrology Study Control Information **********
------------------------------------------------------------------------
Rational hydrology study storm event year is 100.0
Decimal fraction of study above 2000 ft., 600M = 0.0000
English Units Used for input data
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Process from Point/Station 11.000 to Point/Station 12.000
**** INITIAL AREA EVALUATION ****
______________________________________________________________________
APARTMENT subarea type
Decimal fraction soil group A = 0.000
Decimal fraction soil group B = 0.000
Decimal fraction soil group C = 0.000
Decimal fraction soil group D = 1.000
SCS curve number for soil(AMC 2) = 75.00
Pervious ratio(Ap) = 0.2000 Max loss rate(Fp)= 0.200(In/Hr)
Max Catchment Loss (Fm) = 0.040(In/Hr)
Initial subarea data:
Initial area flow distance = 172.000(Ft.)
Top (of initial area) elevation = 185.400(Ft.)
Bottom (of initial area) elevation = 184.200(Ft.)
Difference in elevation = 1.200(Ft.)
Slope = 0.00698 s(%)= 0.70
TC = k(0.324)*[(length^3)/(elevation change)]^0.2
Initial area time of concentration = 6.855 min.
Rainfall intensity = 5.164(In/Hr) for a 100.0 year storm
Effective runoff coefficient used for area (Q=KCIA) is C = 0.893
Subarea runoff = 1.015(CFS)
Total initial stream area = 0.220(Ac.)
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Process from Point/Station 12.000 to Point/Station 12.000
**** SUBAREA FLOW ADDITION ****
______________________________________________________________________
APARTMENT subarea type
Decimal fraction soil group A = 0.000
Decimal fraction soil group B = 0.000
Decimal fraction soil group C = 0.000
Decimal fraction soil group D = 1.000
SCS curve number for soil(AMC 2) = 75.00
Pervious ratio(Ap) = 0.2000 Max loss rate(Fp)= 0.200(In/Hr)
Max Catchment Loss (Fm) = 0.040(In/Hr)
Time of concentration = 6.86 min.
Rainfall intensity = 5.164(In/Hr) for a 100.0 year storm
Effective runoff coefficient used for area,(total area with modified
rational method)(Q=KCIA) is C = 0.893
Subarea runoff = 0.876(CFS) for 0.190(Ac.)
Total runoff = 1.891(CFS) Total area = 0.41(Ac.)
Area averaged Fm value = 0.040(In/Hr)
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Process from Point/Station 12.000 to Point/Station 15.000
Page 2 of 9
Proposed Condtion 100-Yr Event 3/29/20, 2:48 PM
**** PIPEFLOW TRAVEL TIME (Program estimated size) ****
______________________________________________________________________
Upstream point/station elevation = 181.200(Ft.)
Downstream point/station elevation = 181.000(Ft.)
Pipe length = 25.00(Ft.) Manning's N = 0.013
No. of pipes = 1 Required pipe flow = 1.891(CFS)
Nearest computed pipe diameter = 12.00(In.)
Calculated individual pipe flow = 1.891(CFS)
Normal flow depth in pipe = 6.65(In.)
Flow top width inside pipe = 11.93(In.)
Critical Depth = 7.03(In.)
Pipe flow velocity = 4.23(Ft/s)
Travel time through pipe = 0.10 min.
Time of concentration (TC) = 6.95 min.
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Process from Point/Station 15.000 to Point/Station 18.000
**** PIPEFLOW TRAVEL TIME (Program estimated size) ****
______________________________________________________________________
Upstream point/station elevation = 181.000(Ft.)
Downstream point/station elevation = 180.300(Ft.)
Pipe length = 143.00(Ft.) Manning's N = 0.013
No. of pipes = 1 Required pipe flow = 1.891(CFS)
Nearest computed pipe diameter = 12.00(In.)
Calculated individual pipe flow = 1.891(CFS)
Normal flow depth in pipe = 7.81(In.)
Flow top width inside pipe = 11.44(In.)
Critical Depth = 7.03(In.)
Pipe flow velocity = 3.49(Ft/s)
Travel time through pipe = 0.68 min.
Time of concentration (TC) = 7.64 min.
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Process from Point/Station 18.000 to Point/Station 18.000
**** SUBAREA FLOW ADDITION ****
______________________________________________________________________
APARTMENT subarea type
Decimal fraction soil group A = 0.000
Decimal fraction soil group B = 0.000
Decimal fraction soil group C = 0.000
Decimal fraction soil group D = 1.000
SCS curve number for soil(AMC 2) = 75.00
Pervious ratio(Ap) = 0.2000 Max loss rate(Fp)= 0.200(In/Hr)
Max Catchment Loss (Fm) = 0.040(In/Hr)
Time of concentration = 7.64 min.
Rainfall intensity = 4.854(In/Hr) for a 100.0 year storm
Effective runoff coefficient used for area,(total area with modified
rational method)(Q=KCIA) is C = 0.893
Subarea runoff = 0.492(CFS) for 0.140(Ac.)
Total runoff = 2.383(CFS) Total area = 0.55(Ac.)
Area averaged Fm value = 0.040(In/Hr)
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Process from Point/Station 18.000 to Point/Station 30.000
**** PIPEFLOW TRAVEL TIME (Program estimated size) ****
______________________________________________________________________
Upstream point/station elevation = 180.300(Ft.)
Downstream point/station elevation = 178.000(Ft.)
Pipe length = 72.00(Ft.) Manning's N = 0.013
No. of pipes = 1 Required pipe flow = 2.383(CFS)
Nearest computed pipe diameter = 9.00(In.)
Calculated individual pipe flow = 2.383(CFS)
Normal flow depth in pipe = 6.12(In.)
Flow top width inside pipe = 8.39(In.)
Critical Depth = 8.20(In.)
Page 3 of 9
Proposed Condtion 100-Yr Event 3/29/20, 2:48 PM
Pipe flow velocity = 7.45(Ft/s)
Travel time through pipe = 0.16 min.
Time of concentration (TC) = 7.80 min.
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Process from Point/Station 30.000 to Point/Station 30.000
**** SUBAREA FLOW ADDITION ****
______________________________________________________________________
APARTMENT subarea type
Decimal fraction soil group A = 0.000
Decimal fraction soil group B = 0.000
Decimal fraction soil group C = 0.000
Decimal fraction soil group D = 1.000
SCS curve number for soil(AMC 2) = 75.00
Pervious ratio(Ap) = 0.2000 Max loss rate(Fp)= 0.200(In/Hr)
Max Catchment Loss (Fm) = 0.040(In/Hr)
Time of concentration = 7.80 min.
Rainfall intensity = 4.796(In/Hr) for a 100.0 year storm
Effective runoff coefficient used for area,(total area with modified
rational method)(Q=KCIA) is C = 0.892
Subarea runoff = 2.454(CFS) for 0.580(Ac.)
Total runoff = 4.837(CFS) Total area = 1.13(Ac.)
Area averaged Fm value = 0.040(In/Hr)
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Process from Point/Station 30.000 to Point/Station 45.000
**** PIPEFLOW TRAVEL TIME (Program estimated size) ****
______________________________________________________________________
Upstream point/station elevation = 178.000(Ft.)
Downstream point/station elevation = 177.500(Ft.)
Pipe length = 44.00(Ft.) Manning's N = 0.013
No. of pipes = 1 Required pipe flow = 4.837(CFS)
Nearest computed pipe diameter = 15.00(In.)
Calculated individual pipe flow = 4.837(CFS)
Normal flow depth in pipe = 9.27(In.)
Flow top width inside pipe = 14.58(In.)
Critical Depth = 10.70(In.)
Pipe flow velocity = 6.08(Ft/s)
Travel time through pipe = 0.12 min.
Time of concentration (TC) = 7.92 min.
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Process from Point/Station 45.000 to Point/Station 45.000
**** SUBAREA FLOW ADDITION ****
______________________________________________________________________
APARTMENT subarea type
Decimal fraction soil group A = 0.000
Decimal fraction soil group B = 0.000
Decimal fraction soil group C = 0.000
Decimal fraction soil group D = 1.000
SCS curve number for soil(AMC 2) = 75.00
Pervious ratio(Ap) = 0.2000 Max loss rate(Fp)= 0.200(In/Hr)
Max Catchment Loss (Fm) = 0.040(In/Hr)
Time of concentration = 7.92 min.
Rainfall intensity = 4.754(In/Hr) for a 100.0 year storm
Effective runoff coefficient used for area,(total area with modified
rational method)(Q=KCIA) is C = 0.892
Subarea runoff = 0.806(CFS) for 0.200(Ac.)
Total runoff = 5.643(CFS) Total area = 1.33(Ac.)
Area averaged Fm value = 0.040(In/Hr)
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Process from Point/Station 45.000 to Point/Station 50.000
**** PIPEFLOW TRAVEL TIME (Program estimated size) ****
Page 4 of 9
Proposed Condtion 100-Yr Event 3/29/20, 2:48 PM
______________________________________________________________________
Upstream point/station elevation = 177.500(Ft.)
Downstream point/station elevation = 177.000(Ft.)
Pipe length = 34.00(Ft.) Manning's N = 0.013
No. of pipes = 1 Required pipe flow = 5.643(CFS)
Nearest computed pipe diameter = 15.00(In.)
Calculated individual pipe flow = 5.643(CFS)
Normal flow depth in pipe = 9.43(In.)
Flow top width inside pipe = 14.50(In.)
Critical Depth = 11.54(In.)
Pipe flow velocity = 6.95(Ft/s)
Travel time through pipe = 0.08 min.
Time of concentration (TC) = 8.00 min.
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Process from Point/Station 11.000 to Point/Station 50.000
**** CONFLUENCE OF MINOR STREAMS ****
______________________________________________________________________
Along Main Stream number: 1 in normal stream number 1
Stream flow area = 1.330(Ac.)
Runoff from this stream = 5.643(CFS)
Time of concentration = 8.00 min.
Rainfall intensity = 4.727(In/Hr)
Area averaged loss rate (Fm) = 0.0400(In/Hr)
Area averaged Pervious ratio (Ap) = 0.2000
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Process from Point/Station 31.000 to Point/Station 32.000
**** INITIAL AREA EVALUATION ****
______________________________________________________________________
APARTMENT subarea type
Decimal fraction soil group A = 0.000
Decimal fraction soil group B = 0.000
Decimal fraction soil group C = 0.000
Decimal fraction soil group D = 1.000
SCS curve number for soil(AMC 2) = 75.00
Pervious ratio(Ap) = 0.2000 Max loss rate(Fp)= 0.200(In/Hr)
Max Catchment Loss (Fm) = 0.040(In/Hr)
Initial subarea data:
Initial area flow distance = 138.000(Ft.)
Top (of initial area) elevation = 186.500(Ft.)
Bottom (of initial area) elevation = 183.800(Ft.)
Difference in elevation = 2.700(Ft.)
Slope = 0.01957 s(%)= 1.96
TC = k(0.324)*[(length^3)/(elevation change)]^0.2
Initial area time of concentration = 5.107 min.
Rainfall intensity = 6.112(In/Hr) for a 100.0 year storm
Effective runoff coefficient used for area (Q=KCIA) is C = 0.894
Subarea runoff = 0.929(CFS)
Total initial stream area = 0.170(Ac.)
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Process from Point/Station 32.000 to Point/Station 33.000
**** IMPROVED CHANNEL TRAVEL TIME ****
______________________________________________________________________
Upstream point elevation = 183.800(Ft.)
Downstream point elevation = 182.200(Ft.)
Channel length thru subarea = 178.000(Ft.)
Channel base width = 1.000(Ft.)
Slope or 'Z' of left channel bank = 0.100
Slope or 'Z' of right channel bank = 10.000
Estimated mean flow rate at midpoint of channel = 1.444(CFS)
Manning's 'N' = 0.015
Maximum depth of channel = 0.500(Ft.)
Flow(q) thru subarea = 1.444(CFS)
Page 5 of 9
Proposed Condtion 100-Yr Event 3/29/20, 2:48 PM
Depth of flow = 0.245(Ft.), Average velocity = 2.628(Ft/s)
Channel flow top width = 3.478(Ft.)
Flow Velocity = 2.63(Ft/s)
Travel time = 1.13 min.
Time of concentration = 6.24 min.
Critical depth = 0.266(Ft.)
Adding area flow to channel
APARTMENT subarea type
Decimal fraction soil group A = 0.000
Decimal fraction soil group B = 0.000
Decimal fraction soil group C = 0.000
Decimal fraction soil group D = 1.000
SCS curve number for soil(AMC 2) = 75.00
Pervious ratio(Ap) = 0.2000 Max loss rate(Fp)= 0.200(In/Hr)
Max Catchment Loss (Fm) = 0.040(In/Hr)
Rainfall intensity = 5.451(In/Hr) for a 100.0 year storm
Effective runoff coefficient used for area,(total area with modified
rational method)(Q=KCIA) is C = 0.893
Subarea runoff = 0.970(CFS) for 0.220(Ac.)
Total runoff = 1.899(CFS) Total area = 0.39(Ac.)
Area averaged Fm value = 0.040(In/Hr)
Depth of flow = 0.279(Ft.), Average velocity = 2.822(Ft/s)
Critical depth = 0.305(Ft.)
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Process from Point/Station 33.000 to Point/Station 34.000
**** IMPROVED CHANNEL TRAVEL TIME ****
______________________________________________________________________
Upstream point elevation = 182.200(Ft.)
Downstream point elevation = 0.000(Ft.)
Channel length thru subarea = 103.000(Ft.)
Channel base width = 1.000(Ft.)
Slope or 'Z' of left channel bank = 0.100
Slope or 'Z' of right channel bank = 10.000
Estimated mean flow rate at midpoint of channel = 2.386(CFS)
Manning's 'N' = 0.015
Maximum depth of channel = 0.500(Ft.)
Flow(q) thru subarea = 2.386(CFS)
Depth of flow = 0.082(Ft.), Average velocity = 20.437(Ft/s)
Channel flow top width = 1.833(Ft.)
Flow Velocity = 20.44(Ft/s)
Travel time = 0.08 min.
Time of concentration = 6.32 min.
Critical depth = 0.340(Ft.)
Adding area flow to channel
APARTMENT subarea type
Decimal fraction soil group A = 0.000
Decimal fraction soil group B = 0.000
Decimal fraction soil group C = 0.000
Decimal fraction soil group D = 1.000
SCS curve number for soil(AMC 2) = 75.00
Pervious ratio(Ap) = 0.2000 Max loss rate(Fp)= 0.200(In/Hr)
Max Catchment Loss (Fm) = 0.040(In/Hr)
Rainfall intensity = 5.410(In/Hr) for a 100.0 year storm
Effective runoff coefficient used for area,(total area with modified
rational method)(Q=KCIA) is C = 0.893
Subarea runoff = 0.952(CFS) for 0.200(Ac.)
Total runoff = 2.851(CFS) Total area = 0.59(Ac.)
Area averaged Fm value = 0.040(In/Hr)
Depth of flow = 0.091(Ft.), Average velocity = 21.536(Ft/s)
Critical depth = 0.371(Ft.)
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Process from Point/Station 34.000 to Point/Station 35.000
**** PIPEFLOW TRAVEL TIME (Program estimated size) ****
______________________________________________________________________
Page 6 of 9
Proposed Condtion 100-Yr Event 3/29/20, 2:48 PM
Upstream point/station elevation = 180.000(Ft.)
Downstream point/station elevation = 179.600(Ft.)
Pipe length = 72.00(Ft.) Manning's N = 0.013
No. of pipes = 1 Required pipe flow = 2.851(CFS)
Nearest computed pipe diameter = 15.00(In.)
Calculated individual pipe flow = 2.851(CFS)
Normal flow depth in pipe = 8.31(In.)
Flow top width inside pipe = 14.91(In.)
Critical Depth = 8.14(In.)
Pipe flow velocity = 4.09(Ft/s)
Travel time through pipe = 0.29 min.
Time of concentration (TC) = 6.61 min.
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Process from Point/Station 35.000 to Point/Station 35.000
**** SUBAREA FLOW ADDITION ****
______________________________________________________________________
APARTMENT subarea type
Decimal fraction soil group A = 0.000
Decimal fraction soil group B = 0.000
Decimal fraction soil group C = 0.000
Decimal fraction soil group D = 1.000
SCS curve number for soil(AMC 2) = 75.00
Pervious ratio(Ap) = 0.2000 Max loss rate(Fp)= 0.200(In/Hr)
Max Catchment Loss (Fm) = 0.040(In/Hr)
Time of concentration = 6.61 min.
Rainfall intensity = 5.271(In/Hr) for a 100.0 year storm
Effective runoff coefficient used for area,(total area with modified
rational method)(Q=KCIA) is C = 0.893
Subarea runoff = 0.538(CFS) for 0.130(Ac.)
Total runoff = 3.390(CFS) Total area = 0.72(Ac.)
Area averaged Fm value = 0.040(In/Hr)
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Process from Point/Station 35.000 to Point/Station 40.000
**** PIPEFLOW TRAVEL TIME (Program estimated size) ****
______________________________________________________________________
Upstream point/station elevation = 179.600(Ft.)
Downstream point/station elevation = 179.200(Ft.)
Pipe length = 76.00(Ft.) Manning's N = 0.013
No. of pipes = 1 Required pipe flow = 3.390(CFS)
Nearest computed pipe diameter = 15.00(In.)
Calculated individual pipe flow = 3.390(CFS)
Normal flow depth in pipe = 9.45(In.)
Flow top width inside pipe = 14.48(In.)
Critical Depth = 8.92(In.)
Pipe flow velocity = 4.16(Ft/s)
Travel time through pipe = 0.30 min.
Time of concentration (TC) = 6.92 min.
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Process from Point/Station 40.000 to Point/Station 40.000
**** SUBAREA FLOW ADDITION ****
______________________________________________________________________
APARTMENT subarea type
Decimal fraction soil group A = 0.000
Decimal fraction soil group B = 0.000
Decimal fraction soil group C = 0.000
Decimal fraction soil group D = 1.000
SCS curve number for soil(AMC 2) = 75.00
Pervious ratio(Ap) = 0.2000 Max loss rate(Fp)= 0.200(In/Hr)
Max Catchment Loss (Fm) = 0.040(In/Hr)
Time of concentration = 6.92 min.
Rainfall intensity = 5.137(In/Hr) for a 100.0 year storm
Effective runoff coefficient used for area,(total area with modified
Page 7 of 9
Proposed Condtion 100-Yr Event 3/29/20, 2:48 PM
rational method)(Q=KCIA) is C = 0.893
Subarea runoff = 0.876(CFS) for 0.210(Ac.)
Total runoff = 4.266(CFS) Total area = 0.93(Ac.)
Area averaged Fm value = 0.040(In/Hr)
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Process from Point/Station 40.000 to Point/Station 48.000
**** PIPEFLOW TRAVEL TIME (Program estimated size) ****
______________________________________________________________________
Upstream point/station elevation = 179.200(Ft.)
Downstream point/station elevation = 178.900(Ft.)
Pipe length = 61.00(Ft.) Manning's N = 0.013
No. of pipes = 1 Required pipe flow = 4.266(CFS)
Nearest computed pipe diameter = 15.00(In.)
Calculated individual pipe flow = 4.266(CFS)
Normal flow depth in pipe = 11.58(In.)
Flow top width inside pipe = 12.59(In.)
Critical Depth = 10.04(In.)
Pipe flow velocity = 4.20(Ft/s)
Travel time through pipe = 0.24 min.
Time of concentration (TC) = 7.16 min.
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Process from Point/Station 48.000 to Point/Station 48.000
**** SUBAREA FLOW ADDITION ****
______________________________________________________________________
APARTMENT subarea type
Decimal fraction soil group A = 0.000
Decimal fraction soil group B = 0.000
Decimal fraction soil group C = 0.000
Decimal fraction soil group D = 1.000
SCS curve number for soil(AMC 2) = 75.00
Pervious ratio(Ap) = 0.2000 Max loss rate(Fp)= 0.200(In/Hr)
Max Catchment Loss (Fm) = 0.040(In/Hr)
Time of concentration = 7.16 min.
Rainfall intensity = 5.036(In/Hr) for a 100.0 year storm
Effective runoff coefficient used for area,(total area with modified
rational method)(Q=KCIA) is C = 0.893
Subarea runoff = 0.501(CFS) for 0.130(Ac.)
Total runoff = 4.767(CFS) Total area = 1.06(Ac.)
Area averaged Fm value = 0.040(In/Hr)
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Process from Point/Station 48.000 to Point/Station 50.000
**** PIPEFLOW TRAVEL TIME (Program estimated size) ****
______________________________________________________________________
Upstream point/station elevation = 178.900(Ft.)
Downstream point/station elevation = 177.000(Ft.)
Pipe length = 50.00(Ft.) Manning's N = 0.013
No. of pipes = 1 Required pipe flow = 4.767(CFS)
Nearest computed pipe diameter = 12.00(In.)
Calculated individual pipe flow = 4.767(CFS)
Normal flow depth in pipe = 7.30(In.)
Flow top width inside pipe = 11.71(In.)
Critical Depth = 10.85(In.)
Pipe flow velocity = 9.53(Ft/s)
Travel time through pipe = 0.09 min.
Time of concentration (TC) = 7.25 min.
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Process from Point/Station 50.000 to Point/Station 50.000
**** SUBAREA FLOW ADDITION ****
______________________________________________________________________
APARTMENT subarea type
Page 8 of 9
Proposed Condtion 100-Yr Event 3/29/20, 2:48 PM
Decimal fraction soil group A = 0.000
Decimal fraction soil group B = 0.000
Decimal fraction soil group C = 0.000
Decimal fraction soil group D = 1.000
SCS curve number for soil(AMC 2) = 75.00
Pervious ratio(Ap) = 0.2000 Max loss rate(Fp)= 0.200(In/Hr)
Max Catchment Loss (Fm) = 0.040(In/Hr)
Time of concentration = 7.25 min.
Rainfall intensity = 5.002(In/Hr) for a 100.0 year storm
Effective runoff coefficient used for area,(total area with modified
rational method)(Q=KCIA) is C = 0.893
Subarea runoff = 1.217(CFS) for 0.280(Ac.)
Total runoff = 5.984(CFS) Total area = 1.34(Ac.)
Area averaged Fm value = 0.040(In/Hr)
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Process from Point/Station 31.000 to Point/Station 50.000
**** CONFLUENCE OF MINOR STREAMS ****
______________________________________________________________________
Along Main Stream number: 1 in normal stream number 2
Stream flow area = 1.340(Ac.)
Runoff from this stream = 5.984(CFS)
Time of concentration = 7.25 min.
Rainfall intensity = 5.002(In/Hr)
Area averaged loss rate (Fm) = 0.0400(In/Hr)
Area averaged Pervious ratio (Ap) = 0.2000
Summary of stream data:
Stream Area Flow rate TC Fm Rainfall Intensity
No. (Ac.) (CFS) (min) (In/Hr) (In/Hr)
1 1.33 5.643 8.00 0.040 4.727
2 1.34 5.984 7.25 0.040 5.002
Qmax(1) =
1.000 * 1.000 * 5.643) +
0.945 * 1.000 * 5.984) + = 11.295
Qmax(2) =
1.059 * 0.906 * 5.643) +
1.000 * 1.000 * 5.984) + = 11.396
Total of 2 streams to confluence:
Flow rates before confluence point:
5.643 5.984
Maximum flow rates at confluence using above data:
11.295 11.396
Area of streams before confluence:
1.330 1.340
Effective area values after confluence:
2.670 2.545
Results of confluence:
Total flow rate = 11.396(CFS)
Time of concentration = 7.248 min.
Effective stream area after confluence = 2.545(Ac.)
Study area average Pervious fraction(Ap) = 0.200
Study area average soil loss rate(Fm) = 0.040(In/Hr)
Study area total (this main stream) = 2.67(Ac.)
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Process from Point/Station 50.000 to Point/Station 52.000
**** PIPEFLOW TRAVEL TIME (Program estimated size) ****
______________________________________________________________________
Upstream point/station elevation = 177.000(Ft.)
Downstream point/station elevation = 175.000(Ft.)
Pipe length = 153.00(Ft.) Manning's N = 0.013
No. of pipes = 1 Required pipe flow = 11.396(CFS)
Page 9 of 9
Proposed Condtion 100-Yr Event 3/29/20, 2:48 PM
Nearest computed pipe diameter = 18.00(In.)
Calculated individual pipe flow = 11.396(CFS)
Normal flow depth in pipe = 13.99(In.)
Flow top width inside pipe = 14.98(In.)
Critical Depth = 15.45(In.)
Pipe flow velocity = 7.73(Ft/s)
Travel time through pipe = 0.33 min.
Time of concentration (TC) = 7.58 min.
End of computations, total study area = 2.67 (Ac.)
The following figures may
be used for a unit hydrograph study of the same area.
Note: These figures do not consider reduced effective area
effects caused by confluences in the rational equation.
Area averaged pervious area fraction(Ap) = 0.200
Area averaged SCS curve number (AMC 2) = 75.0
Appendix C
V V ssssDENSE TREES ◊◊◊◊◊◊◊◊◊◊◊◊◊◊◊◊◊◊◊◊◊◊◊◊◊◊◊◊◊◊◊◊◊◊◊◊◊◊◊◊◊◊◊◊◊◊◊◊◊◊◊◊◊◊◊◊◊◊◊◊◊◊◊◊◊◊◊◊◊◊◊◊◊◊◊◊◊◊◊◊◊◊◊◊◊◊◊◊◊◊◊◊◊◊◊◊◊◊◊◊◊◊◊◊◊◊◊◊◊◊◊◊◊◊◊◊◊◊◊◊◊◊◊◊◊◊◊◊◊◊◊◊◊◊◊◊◊◊◊◊◊◊◊◊◊◊◊◊◊◊◊◊◊◊◊◊◊◊◊◊◊◊◊◊◊◊◊◊◊◊◊◊◊◊◊◊◊◊◊◊◊◊◊◊◊◊◊◊◊◊◊◊◊◊◊◊◊◊◊◊◊◊◊◊◊◊◊◊◊◊◊◊◊◊◊◊◊◊◊◊◊◊◊◊◊◊◊◊◊◊◊◊◊◊◊◊◊◊◊◊185185190190190190185190190185
184.1 184.7 185.5 186.7182.1181.4
181.9
184.9
181.7
182.4
181.5
180.8
182.9
183.6
191.7
190.4
191.7
191.1
188.8TRANSFERSTATIONTRANSFERSTATION36"42"48"TRANSFERSTATIONTRANSFERSTATION36"42"48"ORANGE CORP YARD WORKFORCE HOUSINGCivilSolutionsInc.26131 Via OceanoMission Viejo, CA 92691P: 949.322.3657F: 949.581.5531www.socalcivilsolutions.comPRELIMINARY GRADING AND DRAINAGE PLANC-1N