Menifee City Council
December 6, 2023

Section 4
SECTION 4 - Hydrology Maps

• Drainage Management Area Map
• Existing Condition Hydrology Map
• Proposed Condition Hydrology Map

HUNSAKERENWS

HUNSAKER & ASSOCIATESINLAND EMPIRE REGIONIRVINE, INC
RIVERSIDE COUNTY FLOOD CONTROL DISTRICTFINAL W.Q.M.P. EXHIBITDRAINAGE MANAGEMENT AREA MAPFOR 'GOLDEN MEADOWS' - PHASE 4TRACT 31194 - MAJOR MODIFICATION16

INDEX MAP

DMA 'B' DMA 'A'DMA 'A'

DMA 'C'DMA 'D'

DMA 'A'

DMA 'F'

DMA 'E'
D D
C
C
B
C D
DD
CD
B
B
B
DCC
DA
C
B
B
B B
D
B
B
DDD
BDDD
D
B
BBB
CD D
DB
DD
DD
D
C
C
C
CBB
B
BB
B
B
B
B
B
B
BB
BB
CCC
C
CC
CCCC

C CC C C
D
D
L=756'
L=660'
L=800'
L=1,213'L=1,843'
L=790'
L=897'
L=903'
L=783'
L=567'
L=791'
L=987'
L=1,598'
L=4,105'
L=753'
L=756'

HUNSAKERENWS
PRELIMINARY HYDROLOGY MAPTRACT 31194 ~ GOLDEN MEADOWSINDEX MAPMAJOR MODIFICATION

HUNSAKER & ASSOCIATESINLAND EMPIRE REGIONIRVINE, INC

EXISTING CONDITION
Lp=165'
Lp=1,360'
Lp=25'Lp=22'
Lp=107'
L=1,850'
L=1,420'Lp=70'
Lp=116'
L=806'L=994'Lp=47'
L=616'
L=701'
Lp=290'
Lp=10'Lp=40'
Lp=50'
L=945'
L=104'
Lp=965'
L=196'
L=57'Lp=114'
Lp=307'Lp=256'
L=580'L=440'
Lp=660'
Lp=1693'Lp=57'Lp=30'
L=863'
L=636'
D CB
DCC
D
B D
B
DB
DD
BDDD
D
B
BBB
CD D
DB
D
C
B
BB
D
DBB
B
Lp=40'Lp=38'Lp=32'Lp=54'
Lp=45'
Lp=800'
Lp=333'
Lp=23'Lp=567'
L=320'
Lp=36'
L=442'
Lp=65'Lp=72'
L=570'

HUNSAKERENWS
PRELIMINARY HYDROLOGY MAPTRACT 31194 ~ GOLDEN MEADOWS

INDEX MAP

MAJOR MODIFICATION

HUNSAKER & ASSOCIATESINLAND EMPIRE REGIONIRVINE, INC

AREA 'A' - PROPOSED DEVELOPMENT
L=448'
L=618'
L=245'
L=1000'
L=38'
L=220'L=190'
Lp=165'
L=185'L=330'
L=104'
Lp=273'
Lp=351'
Lp=671'
L=500'
L=933'
L=722'
L=863'
L=727'
Lp=123'
Lp=15'Lp=42'Lp=29'
L=684'
L=553'
L=530'
Lp=620'
L=965'
L=610'
L=193'Lp=496'
Lp=26'Lp=20'
L=960'L=1,000'
L=425'L=623'
L=518'

HUNSAKERENWS

HUNSAKER & ASSOCIATESINLAND EMPIRE REGIONIRVINE, INC
PRELIMINARY HYDROLOGY MAPTRACT 31194 ~ GOLDEN MEADOWSMAJOR MODIFICATIONAREA 'A' - PROPOSED DEVELOPMENT D
C
B
C D D
B
D
D
DD
D
CBB
B
BB
B
B
B
BCC
L=647'
Lp=532'
Lp=170'
Lp=84'
Lp=21'Lp=30'
Lp=271'Lp=20'L=215'
L=500'L=535'
L=742'
Lp=48'

HUNSAKERENWS

INDEX MAP

HUNSAKER & ASSOCIATESINLAND EMPIRE REGIONIRVINE, INC
PRELIMINARY HYDROLOGY MAPTRACT 31194 ~ GOLDEN MEADOWSMAJOR MODIFICATIONAREA 'C' - PROPOSED DEVELOPMENT D C
C
B
B
D
B D
B
B
DD
BDDD
D
B
BBB
CD D
DB
D
D
C
C
BB
C
D
D
L=332'
Lp=316'Lp=52'L=508'
L=708'
L=790'
Lp=388'
L=763'L=777'
L=343'
Lp=45'L=395'L=515'
Lp=235'
Lp=322'
L=597'
L=380'
Lp=26'Lp=24'
Lp=350'
Lp=35'Lp=36'
Lp=25'Lp=20'
L=311'
Lp=55'
Lp=63'
L=760'
Lp=52'
Lp=20'
H9
F9
G9
DCC B

HUNSAKERENWSINDEX MAP

HUNSAKER & ASSOCIATESINLAND EMPIRE REGIONIRVINE, INC
PRELIMINARY HYDROLOGY MAPTRACT 31194 ~ GOLDEN MEADOWSMAJOR MODIFICATIONAREA 'D' - PROPOSED DEVELOPMENT D
C
B
C D
DD
B
D
D
D
DD
D
CBB
B
BB
B
B
B
B
B
CC
L=332'
Lp=316'Lp=52'
L=530'L=490'
L=1000'
Lp=31'Lp=28'
L=640' Lp=35'Lp=40'
Lp=89'L=42'
Lp=48'Lp=38'
L=388'
Lp=1,011'
Lp=72'
Lp=54'
C9
B9
A9
D9
H9
I9
E9
J9
K9L9
M9
L=1,000'
Lp=353'L=96'
L=759'

HUNSAKERENWS

HUNSAKER & ASSOCIATESINLAND EMPIRE REGIONIRVINE, INC
PRELIMINARY HYDROLOGY MAPTRACT 31194 ~ GOLDEN MEADOWSMAJOR MODIFICATIONAREA 'D' - PROPOSED DEVELOPMENT

This page intentionally left blank.

Appendix F. Water Quality Management Plan
Preliminary
Water Quality Management Plan
Tract 31194 – ‘Golden Meadows’ – Phase 4
Major Modification (WQ-0243)
Prepared for
Richland Communities, Inc.

May 2021
Revised: November 2021
Hunsaker & Associates

Preliminary Water Quality Management Plan
Tract 31194 –‘Golden Meadows’ –Phase 4
Major Modification (WQ-0243)
May 2021
Rev: Nov. 2021
Hunsaker
&
Associates

- 1 -

Project Specific Water Quality Management Plan
A Template for Projects located within the Santa Ana Watershed Region of Riverside County

Project Title: Golden Meadows – Phase 4 – Major Modification Development No: Tract Map Number 31194 – Phase 4
Design Review/Case No: __WQ-0243_____________

Original Date Prepared: May 14, 2021
Revision Date(s):November 2, 2021
Prepared for Compliance with
Regional Board Order No. R8-2010-0033
Template revised June 30, 2016

Contact Information:

Prepared for:

Richland Communities, Inc.
3161 Michelson Drive Suite 245
Irvine, CA 92612

Prepared by:

Hunsaker & Associates, Irvine Inc.

Adams Street; Suite A-15
Riverside, CA 92504
By: Brian Lowell, PE
Phone: (951) 352-7200

Preliminary
Final
- 2 -

A Brief Introduction
This Project-Specific WQMP Template for the Santa Ana Region has been prepared to help guide you in documenting compliance for your project. Because this document has been designed to specifically document compliance, you will need to utilize the WQMP Guidance Document as your “how-to” manual to help guide you through this process. Both the Template and Guidance Document go hand -in-hand, and will help facilitate a well prepared Project-Specific WQMP. Below is a flowchart for the layout of this Template that will provide the steps required to document compliance.

Section A
Project and Site
Information
Section B
Optimize Site
Utilization
Section C
Delineate Drainage
Management Areas
(DMAs)
Section G
Source Control
BMPs
Section I
Operation,
Maintenance, and
Funding
Section F
Hydromodification
Section E
Alternative
Compliance
Section D
Implement LID
BMPs
Section H
Construction Plan
Checklist
- 3 -

OWNER’S CERTIFICATION

This Project-Specific Water Quality Management Plan (WQMP) has been prepared for Richland Communities, Inc. by Hunsaker & Associates, Irvine Inc. for the Golden Meadows, Phase 4 project.

This WQMP is intended to comply with the requirements of the County or Riverside a nd the City of Menifee for City Ordinance Number 457, which includes the requirement for the preparation and implementation of a Project - Specific WQMP.

The undersigned, while owning the property/project described in the preceding paragraph, shall be respo nsible for the implementation and funding of this WQMP and will ensure that this WQMP is amended as appropriate to reflect up -to-date conditions on the site. In addition, the property owner accepts responsibility for interim operation and maintenance of S tormwater BMPs until such time as this responsibility is formally transferred to a subsequent owner. This WQMP will be reviewed with the facility operator, facility supervisors, employees, tenants, maintenance and service contractors, or any other party (o r parties) having responsibility for implementing portions of this WQMP. At least one copy of this WQMP will be maintained at the project site or project office in perpetuity. The undersigned is authorized to certify and to approve implementation of this WQMP. The undersigned is aware that implementation of this WQMP is enforceable under the City of Menifee Water Quality Ordinance number 457.
"I, the undersigned, certify under penalty of law that the provisions of this WQMP have been reviewed and accepted and that the WQMP will be transferred to future successors in interest."

Owner’s Signature Date

Owner’s Printed Name Owner’s Title/Position

PREPARER’S CERTIFICATION

“The selection, sizing and design of stormwater treatment and other stormwater quality and quantity control measures in this plan meet the requirements of Regional Water Quality Control Board Order No. R8-2010-0033 and any subsequent amendments thereto.”

November 2, 20210
Preparer’s Signature Date

Brian Lowell, PE Engineer
Preparer’s Printed Name Preparer’s Title/Position

Preparer’s Licensure:

- 4 -

Table of Contents
Section A: Project and Site Information........................................................................................................ 6 A.1 Maps and Site Plans ............................................................................................................................ 7 A.2 Identify Receiving Waters ................................................................................................................... 8 A.3 Additional Permits/Approvals required for the Project: .................................................................... 8 Section B: Optimize Site Utilization (LID Principles) ..................................................................................... 9 Section C: Delineate Drainage Management Areas (DMAs) ....................................................................... 11 Section D: Implement LID BMPs ................................................................................................................. 14 D.1 Infiltration Applicability .................................................................................................................... 14 D.2 Harvest and Use Assessment ............................................................................................................ 15 D.3 Bioretention and Biotreatment Assessment .................................................................................... 17 D.4 Feasibility Assessment Summaries ................................................................................................... 18 D.5 LID BMP Sizing .................................................................................................................................. 19 Section E: Alternative Compliance (LID Waiver Program) .......................................................................... 22 E.1 Identify Pollutants of Concern .......................................................................................................... 18 E.2 Stormwater Credits ........................................................................................................................... 18 E.3 Sizing Criteria ........................................................................................ Error! Bookmark not defined.

E.4 Treatment Control BMP Selection .................................................................................................... 18 Section F: Hydromodification ..................................................................................................................... 23 F.1 Hydrologic Conditions of Concern (HCOC) Analysis .......................................................................... 23 F.2 HCOC Mitigation ................................................................................................................................ 25 Section G: Source Control BMPs ................................................................................................................. 26 Section H: Construction Plan Checklist ....................................................................................................... 28 Section I: Operation, Maintenance and Funding ........................................................................................ 29

- 5 -

List of Tables
Table A.1 Identification of Receiving Waters ................................................................................................ 8 Table A.2 Other Applicable Permits .............................................................................................................. 8 Table C.1 DMA Classifications ..................................................................................................................... 11 Table C.2 Type ‘A’, Self-Treating Areas ....................................................................................................... 12 Table C.3 Type ‘B’, Self-Retaining Areas ..................................................................................................... 12 Table C.4 Type ‘C’, Areas that Drain to Self-Retaining Areas ...................................................................... 12 Table C.5 Type ‘D’, Areas Draining to BMPs ............................................................................................... 13 Table D.1 Infiltration Feasibility .................................................................................................................. 14 Table D.2 LID Prioritization Summary Matrix ............................................................................................. 18 Table D.3 DCV Calculations for LID BMPs ................................................................................................... 19 Table E.1 Potential Pollutants by Land Use Type ........................................... Error! Bookmark not defined.

Table E.2 Water Quality Credits .................................................................................................................. 18 Table E.3 Treatment Control BMP Sizing .................................................................................................... 18 Table E.4 Treatment Control BMP Selection .............................................................................................. 18 Table F.1 Hydrologic Conditions of Concern Summary .............................................................................. 24 Table G.1 Permanent and Operational Source Control Measures ............................................................. 26 Table H.1 Construction Plan Cross-reference ............................................................................................. 28

List of Appendices
Appendix 1: Maps and Site Plans ................................................................................................................ 30 Appendix 2: Construction Plans .................................................................................................................. 31 Appendix 3: Soils Information ..................................................................................................................... 32 Appendix 4: Historical Site Conditions ........................................................................................................ 33 Appendix 5: LID Infeasibility ........................................................................................................................ 34 Appendix 6: BMP Design Details ................................................................................................................. 35 Appendix 7: Hydromodification .................................................................................................................. 36 Appendix 8: Source Control ........................................................................................................................ 37 Appendix 9: O&M ....................................................................................................................................... 38 Appendix 10: Educational Materials ......................................................................................................... - 6 -

- 6 -

Section A: Project and Site Information

PROJECT INFORMATION
Type of Project: Detached Single Family Residential
Planning Area: N/A
Community Name: Golden Meadows, Phase 4
Development Name: Tract Map 31194

PROJECT LOCATION
Latitude & Longitude (DMS): 33°39'8.59"N, 117°11'28.81"W Project Watershed and Sub-Watershed: Santa Ana River Watershed – San Jacinto Sub-Watershed Gross Acres: 86.06 acres
APN(s): portions of: 360-300-002; 360-300-003; 360-300-004; 360-300-005; 360-300-006; 360-300-009; 360-350-001 Map Book and Page No.: Thomas Brothers Map Page 868, Grid B-7, C-7 and D-7

PROJECT CHARACTERISTICS
Proposed or Potential Land Use(s) Detached Single Family Residential Proposed or Potential SIC Code(s) 1521 – Single Family Residential Existing Area of Impervious Project Footprint (SF) 0 sf Total Area of proposed Impervious Surfaces within the
Project Footprint (SF)/or Replacement
1,042,502 sf

Does the project consist of offsite road improvements? Y N Does the project propose to construct unpaved roads? Y N Is the project part of a larger common plan of development (phased project)? Y N

EXISTING SITE CHARACTERISTICS
Total area of existing Impervious Surfaces within the Project limits Footprint (SF) 0 sf Is the project located within any MSHCP Criteria Cell? Y N If so, identify the Cell number: n/a
Are there any natural hydrologic features on the project site? Y N Is a Geotechnical Report attached? Y N
If no Geotech. Report, list the NRCS soils type(s) present on the site (A, B, C and/or D) n/a What is the Water Quality Design Storm Depth for the project? 0.60 n.

- 7 -

Project Description
The proposed development associated with this PWQMP is intended to be a modification to the approved water quality management plan for tract 31194. The portion of tract 31194 that is being revised consists of modifying drainage management areas ‘A’, ‘C’ and ‘D’. The proposed modifications will increase the residential densit y and therefore change the hydraulic analysis and water quality objectives.

The underlying project known as Tract 31194 “Golden Meadows” consists of 206.8 acres, and proposes the construction of 474 single family homes (103.2 ac.), 7.3 acres of park, 50.0 acres of open space, 2.7 acres of basins and 43.6 acres of paved streets, un -paved trails, and general improvements related to a residential development. The proposed project site is located within the San Jacinto watershed portion Santa Ana River, w ithin the City of Menifee, in the County of Riverside, California. The project site is bounded by Wickerd Road to the north, Ascot Way to the east, vacant land to the south and Evans Road to the west (see included vicinity map).

Proposed Conditions

As required by the Riverside Regional Water Quality Control Board (Santa Ana Watershed), and the MS4 Permit (Municipal Separate Storm Sewer System), the proposed grading of this site has been designed to be consistent with the existing drainage patterns. The p ortion of the project that is being modified has three distinct on -site drainage areas, area ‘A’, ‘C’ and ‘D’. DMA ‘A’ drains approximately 9 5.9 acres into Water Quality / Detention Basin ‘A’, located at the northwestern most corner of the site. The second drainage area (drainage management area ‘C’) drains approximately 14.2 acres into Water Quality / Detention Basins ‘B’, located in the south eastern most corner of the project. The third drainage area (drainage management area “D”) drains approximately 54.5 acres into Water Quality / Detention Basin D.

The proposed on -site water quality and detention basins are being designed to meet water quality requirements and mitigate for any increase in run -off associated with the development of areas ‘A’, ‘C’ and ‘D’. Furthermore, basins A and C are being designed as ‘Extended Detention Basins’, each which will include a concrete lined forebay, low flow gravel diversion channels, and a sand filter with a metered outlet structure. Basin D is designed as an infiltration basin, which is sized to capture and infiltrate the water quality volume in its entirety.

A.1 Maps and Site Plans
When completing your Project-Specific WQMP, include a map o f the local vicinity and existing site. In addition, include all grading, drainage, landscape/plant palette and other pertinent construction plans in Appendix 2. At a minimum, your WQMP Site Plan should include the following:

• Drainage Management Areas
• Proposed Structural BMPs
• Drainage Path
• Drainage Infrastructure, Inlets, Overflows
• Source Control BMPs
• Buildings, Roof Lines, Downspouts
• Impervious Surfaces
• Standard Labeling
• BMP Locations (Lat/Long)
- 8 -

Use your discretion on whether or not you may need to create multiple sheets or can appropriately accommodate these features on one or two sheet s. Keep in mind that the Co-Permittee plan reviewer must be able to easily analyze your project utilizing this template and its associated site plans and maps.

A.2 Identify Receiving Waters
Using Table A.1 below, list in order of upstream to downstream, the receiving waters that the project site is tributary to. Continue to fill each row with the R eceiving Water’s 303 (d) listed impairments (if any), designated beneficial uses, and proximity, if any, to a RARE beneficial use. Include a map of the receiving waters in Appendix 1.

Table A.1 Identification of Receiving Waters
Receiving Waters EPA Approved 303(d)
List Impairments
Designated
Beneficial Uses
Proximity to RARE
Beneficial Use
Existing Paloma Valley High School
Channel None None No RARE designation
Salt Creek Channel None none No RARE designation
Canyon Lake (a.k.a. San Jacinto
River Reach 2)Hydrologic Unit
802.11
Pathogens, Nutrients

MUN, AGR, GWR,
REC1, REC2,

WARM, WILD
No RARE designation
San Jacinto River (Reach 1)
Hydrologic Unit 802.32 None

GWR, MUN, AGR,
REC1, REC2,

WARM, WILD
No RARE designation
Lake Elsinore Santa Ana River Basin
WQCP Hydrologic Unit 802.31
Nutrients, organic
enrichment/low
dissolved oxygen,
PCBs, sediment toxicity,
unknown toxicity
REC1, REC2,
WARM, WILD No RARE designation

A.3 Additional Permits/Approvals required for the Project:

Table A.2 Other Applicable Permits
Agency Permit Required
State Department of Fish and Game, 1602 Streambed Alteration Agreement Y N State Water Resources Control Board, Clean Water Act (CWA) Section 401 Water Quality Cert. Y N US Army Corps of Engineers, CWA Section 404 Permit Y N US Fish and Wildlife, Endangered Species Act Section 7 Biological Opinion Y N Statewide Construction General Permit Coverage Y N
Statewide Industrial General Permit Coverage Y N
Western Riverside MSHCP Consistency Approval (e.g., JPR, DBESP) Y N Other (please list in the space below as required)
State Department of Fish and Game, 1602 Streambed Alteration Agreement City of Menifee Grading Permit
Y N
If yes is answered to any of the questions above, the Co -Permittee may require proof of approval/coverage from those agencies as applicable including documentation of any associated requirements that may affect this Project-Specific WQMP. - 9 -

Section B: Optimize Site Utilization (LID Principles)
Review of the information collected in Section ‘A’ will aid in identifying the principal constraints on site design and selection of LID BMPs as well as opportunities to reduce imperviousness and incorporate LID Principles into the site and landscape design. For example, constraints might include impermeable soils, high groundw ater, groundwater pollution or contaminated soils, steep slopes, geotechnical instability, high -intensity land use, heavy pedestrian or vehicular traffic, utility locations or safety concerns. Opportunities might include existing natural areas, low areas, oddly configured or otherwise unbuildable parcels, easements and landscape amenities including open space and buffers (which can double as locations for bioretention BMPs), and differences in elevation (which can provide hydraulic head). Prepare a brief narrative for each of the site optimization strategies described below. This narrative will help you as you proceed with your LID design and explain your design decisions to others.

The 2010 Santa Ana MS4 Permit further requires that LID R etention BMPs ( Infiltration Only or Harvest and Use) be used unless it can be shown that those BMPs are infeasible. Therefore, it is important that your narrative identify and justify if there are any constraints that would prevent the use of those categories of LID BMP s. Similarly, you should also note opportunities that exist which will be utilized during project design. Upon completion of identifying Constraints and Opportunities, include these on your WQMP Site plan in Appendix 1.

Consideration of “highest and best use” of the discharge should also be considered. For example, Lake Elsinore is evaporating faster than runoff from natural precipitation can recharge it. Requiring infiltration of 85% of runoff events for projects tributary to Lake Elsinore would only exacerbate current water quality problems associated with Pollutant concentration due to lake water evaporation. In cases where rainfall events have low potential to recharge Lake Elsinore (i.e. no hydraulic connection between groundwater to Lake Elsinore, or other factors), requiring infiltration of Urban Runoff from projects is counterproductive to the overall watershed goals. Project proponents, in these cases, would be allowed to discharge Urban Runoff, provided they used equally effective filtration-based BMPs.

- 10 -

Site Optimization
The following questions are based upon Section 3.2 of the WQMP Guidance Document. Review of the WQMP Guidance Document will help you determine how best to optimize your site and subsequently identify opportunities and/or constraints, and document compliance.

Did you identify and preserve existing drainage patterns? If so, how? If not, why? • Yes, the development will mimic the sites existing drainage patterns, which flow typically north and east in both the existing and proposed conditions.

Did you identify and protect existing vegetation? If so, how? If not, why? • Where feasible, the existing vegetation will be preserved. This is anticipated to be accomplished on only a very small portion of the site, if at all. However, the development proposes open space, common open space and private landscaping within the residential lots.

Did you identify and minimize impervious area? If so, how? If not, why? • The projects streets were designed to meet the minim um width requirements per the City of Menifee design standards.

Did you identify and disperse runoff to adjacent pervious areas? If so, how? If not, why? • Where feasible, landscape lots are included into the site design to receive runoff prior to being conveyed to the site’s storm drain system.

- 11 -

Section C: Delineate Drainage Management Areas (DMAs)
Utilizing the procedure in Section 3.3 of the WQMP Guidance Document which discusses the methods of delineating and mapping your project site into individual DMAs, complete Table C.1 below to appropriately categorize the types of c lassification (e.g., Type A, Type B, etc.) per DMA for your project site. Upon completion of this table , this information will then be used to populate and tabulate the corresponding tables for their respective DMA classifications.

Table C.1 DMA Classifications
DMA Name or ID Surface Type(s)12 Area (Sq. Ft.) DMA Type DMA ‘A‘ Mixed A-1 Roof 412,000 sf
A-2 Driveways 65,920 sf
A-3 Pavement 658,876 sf
A-4 Sidewalk 140,733 sf
A-5 Parkway 161,310 sf
A-6 Slopes 423,953 sf
A-7 Turf 767,086 sf
A-8 Natural 1,428,998 sf
A-9 Basin Bottom 31,401 sf
A-10 DG Trail 32,689 sf
A-11 Open Space 139,981 sf

1,162,979 sf modification to
overall DMA ‘A’ (4,262,947 sf)
Type ‘D’, Areas Draining
to BMPs

DMA ‘C‘ Mixed C-1 Roof 100,000 sf
C-2 Driveways 16,000 sf
C-3 Pavement 53,588 sf
C-4 Sidewalk 16,156 sf
C-5 Parkway 10,601 sf
C-6 Slopes 69,626 sf
C-7 Turf 131,267 sf
C-8 Basin 15,559 sf
C-9 DG Road 6,452 sf
C-10 Natural 198,182 sf
617,431 sf modification to
overall DMA ‘C’ (617,431 sf)
Type ‘D’, Areas Draining
to BMPs

DMA ‘D‘ Mixed D-1 Roof 378,000 sf
D-2 Driveways 60,480 sf
D-3 Pavement 395,799 sf
D-4 Sidewalk 112,435 sf
D-5 Parkway 83,596 sf
D-6 Slopes 137,022 sf
D-7 Turf 1,098,384 sf
D-8 Open Space 107,591 sf
D-9 Basin Bottom 56,338 sf
D-10 DG Access Road 2,670 sf
413,191 sf modification to
overall DMA ‘D’ (2,432,315 sf)
Type ‘D’, Areas Draining
to BMPs

1Reference Table 2-1 in the WQMP Guidance Document to populate this column 2If multi-surface provide back-up
- 12 -

Table C.2 Type ‘A’, Self-Treating Areas
DMA Name or ID Area (Sq. Ft.) Stabilization Type Irrigation Type (if any) DMA ‘A’ A-5 Parkway 161,310 sf
A-6 Slopes 423,953 sf
A-7 Turf 767,086 sf
A-11 Open Space 139,981 sf
Landscape Efficient irrigation, and
drip irrigation where
feasible
DMA ‘C’ C-5 Parkway 10,601 sf
C-6 Slopes 69,626 sf
C-7 Turf 131,267 sf
Landscape Efficient irrigation, and
drip irrigation where
feasible
DMA ‘D’ D-5 Parkway 83,596 sf
D-6 Slopes 137,022 sf
D-7 Turf 1,098,384 sf
D-8 Open Space 107,591 sf
Landscape Efficient irrigation, and
drip irrigation where
feasible

Table C.3 Type ‘B’, Self-Retaining Areas
Self-Retaining Area
Type ‘C’ DMAs that are draining to the Self -Retaining
Area
DMA
Name/ ID
Post-project
surface type
Area
(square
feet)
Storm
Depth
(inches) DMA Name /
ID
[C] from T able C.4
=
Required Retention Depth
(inches)
[A] [B] [C] [D]
n/a

[𝐷𝐷] = [𝐵𝐵] +
[𝐵𝐵] ∙ [𝐶𝐶]
[𝐴𝐴]
Table C.4 Type ‘C’, Areas that Drain to Self-Retaining Areas DMA Receiving Self-Retaining DMA
DMA Name/ ID
Area
(square feet)
Post-project
surface type
Impervious
fraction
Product
DMA name /ID
Area (square
feet) Ratio
[A] [B] [C] = [A] x [B] [D] [C]/[D]
n/a

- 13 -

Table C.5 Type ‘D’, Areas Draining to BMPs
DMA Name or ID BMP Name or ID
DMA ‘A’ Extended Detention Basin DMA ‘A’

DMA ‘C’ Extended Detention Basin DMA ‘C’
DMA ‘D’ Infiltration Basin DMA ‘D’

Note: More than one drainage management ar ea can drain to a single LID BMP, however, one drainage management area may not drain to more than one BMP.

- 14 -

Section D: Implement LID BMPs
D.1 Infiltration Applicability
Is there an approved downstream ‘ Highest and Best Use ’ for stormwater runoff (see discussion in Chapter 2.4.4 of the WQMP Guidance Document for further details)? Y N If yes has been checked, Infiltration BMPs shall not be used for the site; proceed to section D.3 If no, continue working thr ough this section to implement your LID BMPs. It is recommended that you contact your Co-Permittee to verify whether or not your project discharges to an approved downstream ‘Highest and Best Use’ feature.

Geotechnical Report
A Geotechnical Report or Phase I Environmental Site Assessment may be required by the Copermittee to confirm present and past site characteristics that may affect the use of Infiltration BMPs. In addition, the Co-Permittee, at their discretion, may not require a geotechnical repo rt for small projects as described in Chapter 2 of the WQMP Guidance Document. If a geotechnical report has been prepared, include it in Appendix 3. In addition, if a Phase I Environmental Site Assessment has been prepared, include it in Appendix 4.

Is this project classified as a small project consistent with the requirements of Chapter 2 of the WQMP Guidance Document? Y N
Infiltration Feasibility
Table D.1 below is meant to provide a simple means of assessing which DMAs on your site support Infiltration BMPs and is discussed in the WQMP Guidance Document in Chapter 2.4.5. Check the appropriate box for each question and then list affected DMAs as applicable. If additional space is needed, add a row below the corresponding answer.

Table D.1 Infiltration Feasibility
Does the project site… YES NO
…have any DMAs with a seasonal high groundwater mark shallower than 10 feet? X If Yes, list affected DMAs:
…have any DMAs located within 100 feet of a water supply well? X If Yes, list affected DMAs:
…have any areas identified by the geotechnical report as posing a public safety risk where infiltration of stormwater could have a negative impact?
X
If Yes, list affected DMAs:
…have measured in-situ infiltration rates of less than 1.6 inches / hour? X If Yes, list affected DMAs: DMA ‘A’, DMA ‘B’, DMA ‘E’
…have significant cut and/or fill conditions that would preclude in -situ testing of infiltration rates at the final infiltration surface?
X
If Yes, list affected DMAs:
…geotechnical report identify other site-specific factors that would preclude effective and safe infiltration? X Describe here:

If you answered “Yes” to any of the questions above for any DMA, Infiltration BMPs should not be used for those DMAs and you should proceed to the assessment for Harvest and Use below.

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D.2 Harvest and Use Assessment
Please check what applies:
☐ Reclaimed water will be used for the non-potable water demands for the project. ☐Downstream water rights may be impacted by Harvest and Use as approved by the Regional Board (verify with the Copermittee).
☒The Design Capture Volume will be addressed using Infiltration Only BMPs . In such a case, Harvest and Use BMPs are still encourage d, but it would not be required if the Design Capture Volume will be infiltrated or evapotranspired. DMA ‘D’ will infiltrate only.

If any of the above boxes have been checked, Harvest and Use BMPs need not be assessed for the site. If none of the above criteria applies, follow the steps below to assess the feasibility of irrigation use, toilet use and other non-potable uses (e.g., industrial use).

Irrigation Use Feasibility
Complete the following steps to determine the feasibility of harvest ing stormwater runoff for Irrigation Use BMPs on your site:

Step 1: Identify the total area of irrigated landscape on the site, and the type of landscaping used.

Total Area of Irrigated Landscape (public landscape): DMA ‘A’ – 585,263 sf (13.44 ac) DMA ‘C’ – 80,227 sf (1.84 ac)
DMA ‘D’ – 220,618 sf (5.06 ac)
Type of Landscaping (Conservation Design or Active Turf): Conservative Design Step 2: Identify the planned total of all impervious areas on the proposed project from which runoff might be feasibly captured and stored for irrigation use. Depending on the configuration of buildings and other impervious areas on the site, you may consider the site as a whole, or parts of the site, to evaluate reasonable scenarios for capturing and storing runoff and directing the stored runoff to the potential use(s) identified in Step 1 above.

Total Area of Impervious Surfaces: DMA ‘A’ – 1,277,529 sf (29.33 ac) DMA ‘C’ – 185,744 sf (4.26 ac)
DMA ‘D’ – 946,714 sf (21.73 ac)
Step 3: Cross reference the Design Storm depth for the project site (see Exhibit A of the WQMP Guidance Document ) with the left column of Table 2-3 in Chapter 2 to determine the minimum area of Effective Irrigated Area per Tributary Impervious Area (EIATIA).

Enter your EIATIA factor: 0.79
Step 4: Multiply the unit value obtained from Step 3 by the total of impervious areas from Step 2 to develop the minimum irrigated area that would be required.

Minimum required irrigated area: DMA ‘A’ – 1,009,248 sf (23.17 ac) DMA ‘C’ – 146,738 sf (3.37 ac)
DMA ‘D’ – 747,904 sf (17.17 ac)
Step 5: Determine if harvesting stormwater runoff for irrigation use is feasible for the project by comparing the total area of irrigated landscape ( Step 1) to the minimum required irrigated area (Step 4).

Minimum required irrigated area (Step 4) Available Irrigated Landscape (Step 1) DMA ‘A’ – 1,009,248 sf (23.17 ac)
DMA ‘C’ – 146,738 sf (3.37 ac)
DMA ‘D’ – 747,904 sf (17.17 ac)
DMA ‘A’ – 585,263 sf (13.44 ac)
DMA ‘C’ – 80,227 sf (1.84 ac)
DMA ‘D’ – 220,618 sf (5.06 ac)
- 16 -

Toilet Use Feasibility
Complete the following steps to determine the feasibility of harvesting stormwater runoff for toilet flushing uses on your site:

Step 1: Identify the projected total number of daily toilet users durin g the wet season, and account for any periodic shut downs or other lapses in occupancy:

Projected Number of Daily Toilet Users:

DMA ‘A’ – 206 dwelling units * 3.5 toilet users per D.U = 721 toilet users DMA ‘C’ – 50 dwelling units * 3.5 toilet users per D.U = 175 toilet users DMA ‘D’ – 189 dwelling units * 3.5 toilet users per D.U = 661.5 toilet users Project Type: Residential
Step 2: Identify the planned total of all impervious areas on the proposed project from which runoff might be feasibly captured and stored for toilet use. Depending on the configuration of buildings and other impervious areas on the site, you may consider the sit e as a whole, or parts of the site, to evaluate reasonable scenarios for capturing and storing runoff and directing the stored runoff to the potential use(s) identified in Step 1 above.

Total Area of Impervious Surfaces: DMA ‘A’ – 1,277,529 sf (29.33 ac) DMA ‘C’ – 185,744 sf (4.26 ac)
DMA ‘D’ – 946,714 sf (21.73 ac)
Step 3: Enter the Design Storm depth for the project site (see Exhibit A) into the left column of Table 2-2 in Chapter 2 to determine the minimum number or toilet users per tributary impervious acre (TUTIA).

Enter your TUTIA factor: 101 TU/Ac
Step 4: Multiply the unit value obtained from Step 3 by the total of impervious areas from Step 2 to develop the minimum number of toilet users that would be required.

Minimum number of toilet users: DMA ‘A’ – 2,962 tu
DMA ‘C’ – 430 tu
DMA ‘D’ – 2,195 tu
Step 5: Determine if harvesting stormwater runoff for toilet flushing use is feasible for the project by comparing the Number of Daily Toilet Users ( Step 1) to the minimum required number of toilet users (Step 4).

Minimum required Toilet Users (Step 4) Projected number of toilet users (Step 1) DMA ‘A’ – 2,962 tu
DMA ‘C’ – 430 tu
DMA ‘D’ – 2,195 tu

DMA ‘A’ – 721 tu
DMA ‘C’ – 175 tu
DMA ‘D’ – 661 tu

- 17 -

Other Non-Potable Use Feasibility
Are there other non -potable uses for stormwater runoff on the site (e.g. industrial use)? See Chapter 2 of the Guidance for further information. If yes, describe below. If no, write N/A. none

If Irrigation, Toilet and Other Use feasibility anticipated demands are less than the applicable minimum values, Harvest and Use BMPs are not required and you should proceed to utilize LID Bioretention and Biotreatment per Section 3.4.2 of the WQMP Guidance Document.

D.3 Bioretention and Biotreatment Assessment
Other LID Bioretention and Biotreatment BMPs as described in Chapter 2 .4.7 of the WQMP Guidance Document are feasible on nearly all development sites with sufficient advance planning.

Select one of the following:
☒ LID Bioretention/Biotreatment BMPs will be used for some or all DMAs of the project as noted below in Section D.4 (note the requirements of Section 3.4.2 in the WQMP Guidance Document).
☐ A site -specific analysis demonstrating the technical infeasibility of all LID BMPs has been performed and is included in Appendix 5 . If you plan to submit an analysis demonstrating the technical infeasibility of LID BMPs, request a pre -submittal meeting with the Copermittee to discuss this option. Proceed to Section E to document your alternative compliance measures.

- 18 -

D.4 Feasibility Assessment Summaries
From the Infiltration, Harvest and Use , Bioretention and Biotreatment Sections above, complete Table D.2 below to summarize which LID BMP s are technically feasible, and which are not , based upon the established hierarchy.

Table D.2 LID Prioritization Summary Matrix
DMA
Name/ID
LID BMP Hierarchy No LID
(Alternative
Compliance) 1. Infiltration 2. Harvest and use 3. Bioretention 4. Biotreatment A

C
D

For those DMAs where LID BMPs are not feasible, provide a brief narrative below summarizing why they are not feasible , include your technical infeasibility criteria in Appendix 5 , and p roceed to Section E below to document A lternative Compliance measures for those DMAs. Recall that each proposed DMA must pass through the LID BMP hierarchy before alternative compliance measures may be considered. n/a

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D.5 LID BMP Sizing
Each LID BMP must be designed to ensure that the Design Capture Volume will be addressed by the selected BMPs. First, calculate the Design Capture Volume for each LID BMP using the VBMP worksheet in Appendix F of the LID BMP Design Handbook. Second, design the LID BMP to meet the required V BMP using a method approved by the Copermittee. Utilize the worksheets found in th e LID BMP Design Handbook or consult with your Copermittee to assist you in correctly sizing your LID BMPs . Complete Table D.3 below to document the Design Capture Volume and the Proposed Volume for each LID BMP .

Provide the completed design procedure sheets for each LID BMP in Appendix 6. You may add additional rows to the table below as needed.

Drainage Management Area ‘A’ Vbmp Analysis
Table D.3 DCV Calculations for LID BMPs
DMA
Type/ID
DMA
Area
(square
feet)
Post-
Project
Surface
Type
Effective
Impervious
Fraction, If
DMA
Runoff
Factor
DMA Areas
x Runoff
Factor
Enter BMP Name / Identifier Here
[A] [B] [C] [A] x [C]
A-1 Roof 412,000 Roofs 1 0.89 367,504
Design Storm Depth (in)
Design Capture Volume, VBMP (cubic feet)
Proposed Volume on Plans (cubic feet)
A-2
Driveways 65,920 Concrete or
Asphalt 1 0.89 58,800.6
A-3
Pavement 658,876 Concrete or
Asphalt 1 0.89 587,717.4
A-4
Sidewalk 140,733 Concrete or
Asphalt 1 0.89 125,533.8
A-5
Parkway 161,310 Ornamental
Landscaping 0.1 0.11 17,818
A-6 Slopes 423,953 Ornamental
Landscaping 0.1 0.11 46,829
A-7 Turf 767,086 Ornamental
Landscaping 0.1 0.11 84,730.8
A-8
Natural 1,428,998 Natural (A
Soil) 0.03 0.06 89,371.2
A-9
Basin
Bottom
31,401 Natural (A
Soil) 0.03 0.06 1,963.9
A-10
DG Trail 32,689 Decomposed
Granite 0.4 0.28 9,143.5
A-11
Open
Space
139,981 Ornamental
Landscaping 0.1 0.11 15,462

AT =
Σ[A] Σ= [D] [E] [F] = [D]x[E]
12 [G]
4,262,947 1,404,874.2 0.60 70,243.7 70,500
[B], [C] is obtained as described in Section 2.3.1 of the WQMP Guidance Document [E] is obtained from Exhibit A in the WQMP Guidance Document [G] is obtained from a design procedure sheet, such as in LID BMP Design Handbook and placed in Appendix 6

- 20 -

Drainage Management Area ‘C’ Vbmp Analysis
Table D.4 DCV Calculations for LID BMPs
DMA
Type/ID
DMA
Area
(square
feet)
Post-Project
Surface
Type
Effective
Impervious
Fraction, If
DMA
Runoff
Factor
DMA
Areas x
Runoff
Factor
Enter BMP Name / Identifier Here
[A] [B] [C] [A] x [C]
C-1 Roof 100,000 Roofs 1 0.89 89,200
Design Storm Depth (in)
Design Capture Volume, VBMP (cubic feet)
Proposed Volume on Plans (cubic feet)
C-2
Driveways 16,000 Concrete or
Asphalt 1 0.89 14,272
C-3
Pavement 53,588 Concrete or
Asphalt 1 0.89 47,800.5
C-4
Sidewalk 16,156 Concrete or
Asphalt 1 0.89 14411.2
C-5
Parkway 10,601 Ornamental
Landscaping 0.1 0.11 1,171
C-6 Slopes 69,626 Ornamental
Landscaping 0.1 0.11 7,690.7
C-7 Res 131,267 Ornamental
Landscaping 0.1 0.11 14,499.5
C-8 Basin 15,559 Natural (A
Soil) 0.03 0.06 973.1
C-9
DG Road 6,452 Decomposed
Granite 0.4 0.28 1,804.7
C-10
Natural 198,182 Natural (A
Soil) 0.03 0.06 12,394.5

AT =
Σ[A] Σ= [D] [E] [F] = [D]x[E]
12 [G]
617,431 204,217.2 0.60 10,210.9 13,000
[B], [C] is obtained as described in Section 2.3.1 of the WQMP Guidance Document [E] is obtained from Exhibit A in the WQMP Guidance Document [G] is obtained from a design procedure sheet, such as in LID BMP Design Handbook and placed in Appendix 6

- 21 -

Drainage Management Area ‘D’ Vbmp Analysis
Table D.5 DCV Calculations for LID BMPs
DMA
Type/ID
DMA
Area
(square
feet)
Post-
Project
Surface
Type
Effective
Impervious
Fraction, If
DMA
Runoff
Factor
DMA Areas
x Runoff
Factor
Enter BMP Name / Identifier Here
[A] [B] [C] [A] x [C]
D-1 Roof 378,000 Roofs 1 0.89 337,173
Design Storm Depth (in)
Design Capture Volume, VBMP (cubic feet)
Proposed Volume on Plans (cubic feet)
D-2
Driveways 60,480 Concrete or
Asphalt 1 0.89 53,948.2
D-3
Pavement 395,799 Concrete or
Asphalt 1 0.89 353,052.7
D-4
Sidewalk 112,435 Concrete or
Asphalt 1 0.89 100,292
D-5
Parkway 83,596 Ornamental
Landscaping 0.1 0.11 9,233.8
D-6 Slopes 137,022 Ornamental
Landscaping 0.1 0.11 15,135.2
D-7
Turf 1,098,384 Ornamental
Landscaping 0.1 0.11 121,325.3
D-8
Open
Space
107,591 Ornamental
Landscaping 0.1 0.11 11,884.3
D-9
Basin
Bottom
56,338 Natural (A
Soil) 0.03 0.06 3.523.4
D-10
DG Access
Road
2,670 Decomposed
Granite 0.4 0.06 746.8

AT =
Σ[A] Σ= [D] [E] [F] = [D]x[E]
12 [G]
2,432,315 1,006,317.7 0.60 50,315.9 51,000
[B], [C] is obtained as described in Section 2.3.1 of the WQMP Guidance Document [E] is obtained from Exhibit A in the WQMP Guidance Document [G] is obtained from a design procedure sheet, such as in LID BMP Design Handbook and placed in Appendix 6

- 22 -

Section E: Alternative Compliance (LID Waiver Program)
LID BMPs are expected to be feasible on virtually all projects. Where LID BMPs have been demonstrated to be infeasible as documented in Section D , other Treatment Control BMPs must be used (subject to LID waiver approval by the Copermittee). Check one of the following Boxes:
☒ LID Principles and LID BMPs have been incorporated into the site design to fully address all Drainage Management Areas. No alternative compliance measure s are required for this project and thus this Section is not required to be completed.
- Or -
☐ The following Drainage Management Areas are unable to be addressed using LID BMPs. A site-specific analysis demonstrating technical infeasibility of LID BMPs has been approved by the Co-Permittee and included in Appendix 5 . Additionally, no downstream regional and/or sub - regional LID BMPs exist or are available for use by the project. The following alternative compliance measures on the following pages are being implemented to ensure that any pollutant loads expected to be discharged by not incorporating LID BMPs, are fully mitigated.

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Section F: Hydromodification
F.1 Hydrologic Conditions of Concern (HCOC) Analysis
Once you have determined that the LID design is ad equate to address water quality requirements, you will need to assess if the proposed LID Design may still create a HCOC. Review Chapters 2 and 3 (including Figure 3-7) of the WQMP Guidance Document to determine if your project must mitigate for Hydromodification impacts. If your project meets one of the following criteria which will be indicated by the check boxes below, you do not need to address Hydromodification at this time. However, if the project does not qualify for Exemptions 1, 2 or 3, then additional measures must be added to the design to comply with HCOC criteria. This is discussed in further detail below in Section F.2.

HCOC EXEMPTION 1: The Priority Development Project disturbs less than one acre. The Co - permittee has the discretion to require a Project-Specific WQMP to address HCOCs on projects less than one acre on a case by case basis. The disturbed area calculation should include all disturbances associated with larger common plans of development.

Does the project qualify for this HCOC Exemption? Y N If Yes, HCOC criteria do not apply.

HCOC EXEMPTION 2: The volume and time of concentration 1 of storm water runoff for the post - development condition is not significantly different from the pre-development condition for a 2-year return frequency storm (a difference of 5% or less is considered insignificant ) using one of the following methods to calculate:
• Riverside County Hydrology Manual
• Technical Release 55 (TR -55): Urban Hydrology for Small Watersheds (NRCS 1986), or derivatives thereof, such as the Santa Barbara Urban Hydrograph Method • Other methods acceptable to the Co-Permittee
Does the project qualify for this HCOC Exemption? Y N If Yes, report results in Table F.1 below and provide your substantiated hydrologic analysis in Appendix 7.

- 24 -

Table F.1 Hydrologic Conditions of Concern Summary
DMA ‘A’
2 year – 24 hour
Pre-condition Post-condition % Difference
Time of
Concentration 23.97 min. 14.85 min. -38.0 %
Volume (Cubic Feet) 125,888 cf 322,344 cf 256 %

DMA ‘C’
2 year – 24 hour
Pre-condition Post-condition % Difference
Time of
Concentration 12.54 min. 10.38 min. -17.2 %
Volume (Cubic Feet) 13,504 cf 46,609 cf 345 %

DMA ‘D’
2 year – 24 hour
Pre-condition Post-condition % Difference
Time of
Concentration 14.53 min. 19.12 min. 31.6 %
Volume (Cubic Feet) 43,560 cf 202,554 cf 465 %

1 Time of concentration is defined as the time after the beginning of the rainfall when all portions of the drainage basin are contributing to flow at the outlet.

The anticipated increase in both storm volume and time of concentration are being mitigated by the proposed water quality and detention basins. Full basin routing analysis will be provided during final engineering. In the preliminary hydrology design stage, the basins are being sized to accept the mitigation volume in its entirety. The mitigation volume is the difference between the existing and developed condition storm volumes.

HCOC EXEMPTION 3: All downstream conveyance channels to an adequate sump (for example, Prado Dam, Lake Elsinore, Canyon Lake, Santa Ana River, or other lake, reservoir or naturally erosion resistant feature) that will receive runoff from the project are engineered and regularly maintained to ensure design flow capacity; no sensitive stream habitat areas will be adversely affected; or are not identified on the Co -Permittees Hydromodification Susceptibility Maps.

Does the project qualify for this HCOC Exemption? Y N If Yes, HCOC criteria do not apply and note below which adequate sump applies to this HCOC qualifier:

- 25 -

F.3 HCOC Mitigation
If none of the above HCOC Exemption Criteria are applicable, HCOC criteria is considered mitigated if they meet one of the following conditions:
a. Additional LID BMPS are implemented onsite or offsite to mitigate potential erosion or habitat impacts as a result of HCOCs. This can be conducted by a n evaluation of site-specific conditions utilizing accepted professional methodologies published by en tities such as the California Stormwater Quality Association (CASQA), the Southern California Coastal Water Research Project (SCCRWP), or other Co -Permittee approved methodologies for site -specific HCOC analysis.

b. The project is developed consistent with an approved Watershed Action Plan that addresses HCOC in Receiving Waters.

c. Mimicking the pre -development hydrograph with the post -development hydrograph, for a 2 - year return frequency storm. Generally, the hydrologic conditions of concern are not significant, if the post -development hydrograph is no more than 10% greater than pre -development hydrograph. In cases where excess volume cannot be infiltrated or captured and reused, discharge from the site must be limited to a flow rate no greater than 110% of the pre- development 2-year peak flow.

Be sure to include all pertinent documentation used in your analysis of the items a, b or c in Appendix 7.

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Section G: Source Control BMPs
Source control BMPs include permanent , structural features that may be required in your project plans — such as roofs over and berms around trash and recycling areas — and Operational BMPs, such as regular sweeping and “housekeeping” , that must be implemented by the site’s occupant or user. Th e MEP standard typically requires both types of BMPs. In general, Operational BMPs cannot be substituted for a feasible and effective permanent BMP. Using the Pollutant Sources/Source Control Checklist in Appendix 8, review the following procedure to specify Source Control BMPs for your site:

1. Identify Pollutant Sources : Review Column 1 in the Pollutant Sources/Source Control Checklist .

Check off the potential sources of Pollutants that apply to your site.

2. Note Locations on Project -Specific WQMP Exhibit : Note the corresponding requirements listed in Column 2 of the Pollutant Sources/Source Control Chec klist. Show the location of each Pollutant source and each permanent Source Control BMP in your Project -Specific WQMP Exhibit located in Appendix 1.

3. Prepare a Table and Narrative: Check off the corresponding requirements listed in Column 3 in the Pollutant Sources/Source Control Checklist. In the left column of Table G.1 below, list each potential source of runoff Pollutants on your site (from those that you c hecked in the Pollutant Sources/Source Control Checklist ). In the middle column, list the corresponding permanent, Structural Source Control BMPs (from Columns 2 and 3 of the Pollutant Sources/Source Control Checklist) used to prevent Pollutants from enter ing runoff. Add additional narrative in this column that explains any special features, materials or methods of construction that will be used to implement these permanent, Structural Source Control BMPs.

4. Identify Operational Source Control BMPs: To complete your table, refer once again to the Pollutant Sources/Source Control Checklist . List in the right column of your table the Operational BMPs that should be implemented as long as the anticipated activities con tinue at the site. Copermittee stormwater ordinances require that applicable Source Control BMPs be implemented; the same BMPs may also be required as a condition of a use permit or other revocable Discretionary Approval for use of the site.

Table G.1 Permanent and Operational Source Control Measures Potential Sources of
Runoff Pollutants Structural Source Control BMPs
Operational Source Control BMPs
On-site storm drain
inlets
Mark all inlets with the words
“Only Rain Down the Storm
Drain” or similar. Catch Basin
Makers may be available from
the Riverside County Flood
Control and Water Conservation
District, call 951.955.1200 to
verify
Maintain and periodically repaint or replace inlet
markings.

Provide stormwater pollution prevention
information to new site owners, lessees, or
operators.

See applicable operational BMPs in Fact Sheet SC-
44, “Drainage System Maintenance,” in the CASQA
Stormwater Quality Handbooks at
www.cabmphandbooks.com
Include the following in lease agreements: “Tenant
shall not allow anyone to discharge anything to
storm drains or to store or deposit materials so as
- 27 -

to create a potential discharge to storm drains.”
Landscape/Outdoor
Pesticide Use
Preserve, existing native trees,
shrubs, and ground cover to the
maximum extent possible.

Design landscaping to minimize
irrigation and runoff, to promote
surface infiltration where
appropriate, and to minimize the
use of fertilizers and pesticides
that can contribute to
stormwater pollution.

Where landscaping areas are
used to retain or detain
stormwater, specify plants that
are tolerant of saturated soil
conditions.

Consider using pest-resistant
plants, especially to hardscape.

To insure successful
establishment, select plants
appropriate to site soils, slopes,
climate, sun, wind, rain, land use,
air movement, ecological
consistency, and plant
interactions.

Maintain landscaping using minimum or no
pesticides.

See applicable operation BMPs in “What you show
know for…..Landscaping and Gardening”.

Provide IPM information to new owners, lessees
and operators.

Pools, spas, ponds,
decorative fountains,
and other water
features.

If the Co-Permittee requires
pools to be plumbed to the
sanitary sewer, place a note on
the plans and state in the
narrative that this connection will
be made according to local
requirements.

See applicable operational BMPs in “Guidelines for
Maintaining Your Swimming Pool, Jacuzzi and
Garden Fountain”
Vehicle/Equipment
Repair and
Maintenance
Vehicle repairs shall be kept to
those that can be considered
“self-contained”. Clean-up
methods shall be done by dry
methods. Fluids drained from a
vehicle should be contained in a
recyclable container and turned
into a local facility for recycling.

No person shall dispose of, nor permit the disposal,
directly or indirectly of vehicle fluids, hazardous
materials, or rinse water from parts cleaning into
storm drains.

Fire Sprinkler Test
Water
Fire sprinkler test water shall be
drained to the sanitary sewer.

See the note in Fact Sheet SC – 41, “Building and
Grounds Maintenance,’ in the CASQA Stormwater
Quality Handbooks at ww.cabmphandbooks.com
Miscellaneous Drain or
Wash Water or Other
Sources
Roofing, gutters, and
trim
Avoid roofing, gutters, and trim
made of copper or other
unprotected metals

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Section H: Construction Plan Checklist
Populate Table H.1 below to assist the plan checker in an expeditious review of your project. The first two columns will contain information that was prepared in previous steps, while the last column will be populated with the corresponding plan sheets. This table is to be completed with the submittal of your final Project-Specific WQMP.

Table H.1 Construction Plan Cross-reference
BMP No. or
ID
BMP Identifier and
Description
Corresponding Plan Sheet(s) BMP Location (Lat/Long)
DMA ‘A’ Extended Detention
Basin DMA ‘A’
Rough Grading Plan LAT: 33°39’17.97”N
LON:117°11’41.01”W

DMA ‘C’ Infiltration Basin DMA
‘C’
Rough Grading Plan LAT: 33°38’57.24”N
LON:117°11’05.02”W
DMA ‘D’ Infiltration Basin DMA
‘D’
Rough Grading Plan LAT: 33°39’08.30”N
LON:117°11’32.55”W

Note that the updated table — or Construction Plan WQMP Checklist — is only a reference tool to facilitate an easy comparison of the construction plans to your Project -Specific WQMP. Co -Permittee staff can advise you regarding the process required to propose changes to the approved Project -Specific WQMP.

- 29 -

Section I: Operation, Maintenance and Funding
The Copermittee will periodically verify that Stormwater BMPs on your site are maintained and continue to operate as designed. To make this possible, your Copermittee will require that you include in Appendix 9 of this Project-Specific WQMP:

1. A means to finance and implement facility mainte nance in perpetuity , including replacement cost.

2. Acceptance of responsibility for maintenance from the time the BMPs are constructed until responsibility for operation and maintenance is legally transferred. A warranty covering a period following construction may also be required.

3. An outline of general maintenance requirements for the Stormwater BMPs you have selected.

4. Figures delineating and designating pervious and impervious areas, location, and type of Stormwater BMP, and tables of pervious and impervi ous areas served by each facility. Geo - locating the BMPs using a coordinate system of latitude and longitude is recommended to help facilitate a future statewide database system.

5. A separate list and location of self- retaining areas or areas addressed by LID Principles that do not require specialized O&M or inspections but will require typical landscape maintenance as noted in Chapter 5, pages 85-86, in the WQMP Guidance. Include a brief description of typical landscape maintenance for these areas.

Your loca l Co -Permittee will also require that you prepare and submit a detailed Stormwater BMP Operation and Maintenance Plan that sets forth a maintenance schedule for each of the Stormwater BMPs built on your site. An agreement assigning responsibility for maint enance and providing for inspections and certification may also be required.

Details of these requirements and instructions for preparing a Stormwater BMP Operation and Maintenance Plan are in Chapter 5 of the WQMP Guidance Document.

Maintenance Mechanism: Home Owners Association (HOA)
Will the proposed BMPs be maintained by a Home Owners’ Association (HOA) or Property Owners Association (POA)?
Y N

Include your Operation and Maintenance Plan and Maintenance Mechanism in Appendix 9. Additionally, include all pertine nt forms of educational materials for those personnel that will be maintaining the proposed BMPs within this Project-Specific WQMP in Appendix 10. - 30 -

Appendix 1: Maps and Site Plans
Location Map, WQMP Site Plan and Receiving Waters Map

NOT TO SCALE
HUNSAKER & ASSOCIATESINLAND EMPIRE REGIONIRVINE, INCFIGURE 1: VICINITY MAPHUNSAKERENWS THOMAS BROTHERS MAPS:PAGE 868, GRID B-6, B-7, C-6, C-7, D-6 & D-7

INDEX MAP
HUNSAKERENWSHUNSAKER & ASSOCIATESINLAND EMPIRE REGIONIRVINE, INCFIGURE 2: AERIAL PHOTOGRAPH

PROJECTSITE

HUNSAKERENWS

HUNSAKER & ASSOCIATESINLAND EMPIRE REGIONIRVINE, INC
RIVERSIDE COUNTY FLOOD COLTROL DISTRICTFINAL W.Q.M.P. EXHIBITDRAINAGE MANAGEMENT AREA MAPFOR 'GOLDEN MEADOWS' - PHASE 4TRACT 31194 - MAJOR MODIFICATION16

INDEX MAP

DMA 'B' DMA 'A'DMA 'A'

DMA 'C'DMA 'D'

DMA 'A'

DMA 'F'

DMA 'E'

HUNSAKERENWS HUNSAKER & ASSOCIATESINLAND EMPIRE REGIONIRVINE, INC RIVERSIDE COUNTY FLOOD COLTROL DISTRICTW.Q.M.P. EXHIBITDRAINAGE MANAGEMENT AREA MAPFOR 'GOLDEN MEADOWS' - PHASE 4TRACT 31194 - MAJOR MODIFICATION26

INDEX MAP
···············
ADDITIONAL STRUCTURAL ANDNONSTRUCTURAL SOURCE CONTROLBMP'S (SEE PROJECT WQMPOPERATIONS AND MAINTENANCEPLAN FOR DETAILS):
·······
SITE DESIGN AND SOURCECONTROL BMP'S INCLUDE:
···
LID PRACTICES TO BE IMPLEMENTEDFOR THIS PROJECT INCLUDE:

DRAINAGE MANAGEMENT AREA 'A'
C9B9A9
D9
H9
E9
F9
G9
J9
K9
L9
M9

HUNSAKERENWS HUNSAKER & ASSOCIATESINLAND EMPIRE REGIONIRVINE, INC RIVERSIDE COUNTY FLOOD COLTROL DISTRICTW.Q.M.P. EXHIBITDRAINAGE MANAGEMENT AREA MAPFOR 'GOLDEN MEADOWS' - PHASE 4TRACT 31194 - MAJOR MODIFICATION36

INDEX MAP
···············
ADDITIONAL STRUCTURAL ANDNONSTRUCTURAL SOURCE CONTROLBMP'S (SEE PROJECT WQMPOPERATIONS AND MAINTENANCEPLAN FOR DETAILS):
·······
SITE DESIGN AND SOURCECONTROL BMP'S INCLUDE:
···LID PRACTICES TO BE IMPLEMENTEDFOR THIS PROJECT INCLUDE:

DRAINAGE MANAGEMENT AREA 'A' - OVERALL

HUNSAKERENWSHUNSAKER & ASSOCIATESINLAND EMPIRE REGIONIRVINE, INC RIVERSIDE COUNTY FLOOD COLTROL DISTRICTW.Q.M.P. EXHIBITDRAINAGE MANAGEMENT AREA MAPFOR 'GOLDEN MEADOWS' - PHASE 4TRACT 31194 - MAJOR MODIFICATION46

INDEX MAP
···············
ADDITIONAL STRUCTURAL ANDNONSTRUCTURAL SOURCE CONTROLBMP'S (SEE PROJECT WQMPOPERATIONS AND MAINTENANCEPLAN FOR DETAILS):
·······
SITE DESIGN AND SOURCECONTROL BMP'S INCLUDE:
···
LID PRACTICES TO BE IMPLEMENTEDFOR THIS PROJECT INCLUDE:

DRAINAGE MANAGEMENT AREA 'C'

HUNSAKERENWSHUNSAKER & ASSOCIATESINLAND EMPIRE REGIONIRVINE, INC RIVERSIDE COUNTY FLOOD COLTROL DISTRICTW.Q.M.P. EXHIBITDRAINAGE MANAGEMENT AREA MAPFOR 'GOLDEN MEADOWS' - PHASE 4TRACT 31194 - MAJOR MODIFICATION56

INDEX MAP
···············
ADDITIONAL STRUCTURAL ANDNONSTRUCTURAL SOURCE CONTROLBMP'S (SEE PROJECT WQMPOPERATIONS AND MAINTENANCEPLAN FOR DETAILS):
·······
SITE DESIGN AND SOURCECONTROL BMP'S INCLUDE:
···
LID PRACTICES TO BE IMPLEMENTEDFOR THIS PROJECT INCLUDE:

DRAINAGE MANAGEMENT AREA 'D'

HUNSAKERENWSHUNSAKER & ASSOCIATESINLAND EMPIRE REGIONIRVINE, INC RIVERSIDE COUNTY FLOOD COLTROL DISTRICTW.Q.M.P. EXHIBITDRAINAGE MANAGEMENT AREA MAPFOR 'GOLDEN MEADOWS' - PHASE 4TRACT 31194 - MAJOR MODIFICATION66

INDEX MAP
···············
ADDITIONAL STRUCTURAL ANDNONSTRUCTURAL SOURCE CONTROLBMP'S (SEE PROJECT WQMPOPERATIONS AND MAINTENANCEPLAN FOR DETAILS):
·······
SITE DESIGN AND SOURCECONTROL BMP'S INCLUDE:
···
LID PRACTICES TO BE IMPLEMENTEDFOR THIS PROJECT INCLUDE:

DRAINAGE MANAGEMENT AREA 'D' - OVERALL
- 31 -

Appendix 2: Construction Plans
Grading and Drainage Plans

215SITE
OWNER

CIVIL ENGINEERGRADING QUANTITIES

LEGAL DESCRIPTIONASSESSORS PARCEL NUMBER

TOPOGRAPHY SOURCE
MAJOR MODIFICATION FORNov 10, 2021GOLDEN MEADOWSPLANNING APPLICATION NO. PLN21-0199REVISION DATEDESCRIPTIONTRACT 31194-4

SEE BELOW

SEE ABOVE
APPLICANTGOLDEN MEADOWSMAJOR MODIFICATION FORTRACT NO. 31194 PHASE 4 - 32 -

Appendix 3: Soils Information
Geotechnical Study and Other Infiltration Testing Data

Hydrologic Soil Group—Western Riverside Area, California Natural Resources
Conservation Service
Web Soil Survey
National Cooperative Soil Survey
10/10/2018

3723100 3723300 3723500 3723700 3723900 3724100
3723100 3723300 3723500 3723700 3723900 3724100
481300 481500 481700 481900 482100 482300 482500 482700 482900 481300 481500 481700 481900 482100 482300 482500 482700 482900 33° 39' 28'' N
117° 12' 9'' W
33° 39' 28'' N
117° 10' 57'' W
33° 38' 49'' N
117° 12' 9'' W
33° 38' 49'' N
117° 10' 57'' W
N
Map projection: Web Mercator Corner coordinates: WGS84 Edge tics: UTM Zone 11N WGS84 0 400 800 1600 2400
Feet
0 100 200 400 600
Meters
Map Scale: 1:8,490 if printed on A landscape (11" x 8.5") sheet.

Soil Map may not be valid at this scale.

MAP LEGEND MAP INFORMATION
Area of Interest (AOI)
Area of Interest (AOI)
Soils
Soil Rating Polygons
A
A/D
B
B/D
C
C/D
D
Not rated or not available
Soil Rating Lines
A
A/D
B
B/D
C
C/D
D
Not rated or not available
Soil Rating Points
A
A/D
B
B/D
C
C/D
D
Not rated or not available
Water Features
Streams and Canals
Transportation
Rails
Interstate Highways
US Routes
Major Roads
Local Roads
Background
Aerial Photography
The soil surveys that comprise your AOI were mapped at
1:15,800.

Warning: Soil Map may not be valid at this scale.

Enlargement of maps beyond the scale of mapping can cause misunderstanding of the detail of mapping and accuracy of soil line placement. The maps do not show the small areas of contrasting soils that could have been shown at a more detailed scale.

Please rely on the bar scale on each map sheet for map
measurements.

Source of Map: Natural Resources Conservation Service
Web Soil Survey URL:

Coordinate System: Web Mercator (EPSG:3857)
Maps from the Web Soil Survey are based on the Web Mercator projection, which preserves direction and shape but distorts distance and area. A projection that preserves area, such as the Albers equal-area conic projection, should be used if more accurate calculations of distance or area are required.

This product is generated from the USDA-NRCS certified data as of the version date(s) listed below.

Soil Survey Area: Western Riverside Area, California
Survey Area Data: Version 11, Sep 12, 2018
Soil map units are labeled (as space allows) for map scales 1:50,000 or larger.

Date(s) aerial images were photographed: Feb 24, 2015—Feb 26, 2015
The orthophoto or other base map on which the soil lines were compiled and digitized probably differs from the background imagery displayed on these maps. As a result, some minor shifting of map unit boundaries may be evident.

Hydrologic Soil Group—Western Riverside Area, California Natural Resources
Conservation Service
Web Soil Survey
National Cooperative Soil Survey
10/10/2018

Hydrologic Soil Group
Map unit symbol Map unit name Rating Acres in AOI Percent of AOI CaC2 Cajalco fine sandy loam,
2 to 8 percent slopes,
eroded
C 7.5 3.3%
CaD2 Cajalco fine sandy loam,
8 to 15 percent
slopes, eroded
C 7.3 3.3%
CbD2 Cajalco rocky fine sandy
loam, 5 to 15 percent
slopes, eroded
D 0.6 0.3%
CbF2 Cajalco rocky fine sandy
loam, 15 to 50 percent
slopes, eroded
D 13.6 6.1%
CkD2 Cieneba rocky sandy
loam, 8 to 15 percent
slopes, eroded
D 2.5 1.1%
GtA Grangeville fine sandy
loam, drained, 0 to 2
percent sl opes
A/D 0.2 0.1%
HcD2 Hanford coarse sandy
loam, 8 to 15 percent
slopes, eroded
A 2.8 1.2%
HnC Honcut sandy loam, 2 to
8 percent slopes
A 13.6 6.1%
HnD2 Honcut sandy loam, 8 to
15 percent slopes,
eroded
A 7.6 3.4%
LaC Las Posas loam, 2 to 8
percent slopes
D 0.2 0.1%
LaD2 Las Posas loam, 8 to 15
percent slopes,
eroded
D 6.7 3.0%
LkD2 Las Posas rocky loam, 8
to 15 percent slopes,
eroded
D 3.8 1.7%
LkF3 Las Posas rocky loam,
15 to 50 percent
slopes, severely
eroded
D 0.4 0.2%
PsC Porterville clay,
moderately deep, 2 to
8 percent slopes
D 4.8 2.2%
VeC2 Vallecitos loam, thick
solum variant, 2 to 8
percent slopes,
eroded
C 9.1 4.1%
Hydrologic Soil Group—Western Riverside Area, California Natural Resources
Conservation Service
Web Soil Survey
National Cooperative Soil Survey
10/10/2018

Map unit symbol Map unit name Rating Acres in AOI Percent of AOI WyC2 Wyman loam, 2 to 8
percent slopes,
eroded
C 79.8 35.7%
YbC Yokohl loam, 2 to 8
percent slopes
D 57.0 25.5%
YbE3 Yokohl loam, 8 to 25
percent slopes,
severely eroded
D 5.9 2.6%
Totals for Area of Interest 223.4 100.0%
Description
Hydrologic soil groups are based on estimates of runoff potential. Soils are assigned to one of four groups according to the rate of water infiltration when the soils are not protected by vegetation, are thoroughly wet, and receive precipitation from long-duration storms.

The soils in the United States are assigned to four groups (A, B, C, and D) and three dual classes (A/D, B/D, and C/D). The groups are defined as follows:

Group A. Soils having a high infiltration rate (low runoff potential) when thoroughly wet. These consist mainly of deep, well drained to excessively drained sands or gravelly sands. These soils have a high rate of water transmission.

Group B. Soils having a moderate infiltration rate when thoroughly wet. These consist chiefly of moderately deep or deep, moderately well drained or well drained soils that have moderately fine texture to moderately coarse texture.

These soils have a moderate rate of water transmission.

Group C. Soils having a slow infiltration rate when thoroughly wet. These consist chiefly of soils having a layer that impedes the downward movement of water or soils of moderately fine texture or fine texture. These soils have a slow rate of water transmission.

Group D. Soils having a very slow infiltration rate (high runoff potential) when thoroughly wet. These consist chiefly of clays that have a high shrink-swell potential, soils that have a high water table, soils that have a claypan or clay layer at or near the surface, and soils that are shallow over nearly impervious material. These soils have a very slow rate of water transmission.

If a soil is assigned to a dual hydrologic group (A/D, B/D, or C/D), the first letter is for drained areas and the second is for undrained areas. Only the soils that in their natural condition are in group D are assigned to dual classes.

Rating Options
Aggregation Method: Dominant Condition
Hydrologic Soil Group—Western Riverside Area, California Natural Resources
Conservation Service
Web Soil Survey
National Cooperative Soil Survey
10/10/2018

Component Percent Cutoff: None Specified
Tie-break Rule: Higher
Hydrologic Soil Group—Western Riverside Area, California Natural Resources
Conservation Service
Web Soil Survey
National Cooperative Soil Survey
10/10/2018

PROJECTSITE

PROJECTSITE
DRAFT

GEOTECHNICAL EXPLORATION
PROPOSED WATER TANK, GOLDEN MEADOWS –
TRACT 31194, MENIFEE AREA, RIVERSIDE

COUNTY, CALIFORNIA
Prepared for
RICHLAND COMMUNITIES, INC.
4100 Newport Place Drive
Newport Beach, California 92672
Project No. 11813.002
April 2, 2021
DRAFT
April 2, 2021
Project No. 11813.002
Richland Communities, Inc.
4100 Newport Place Drive
Newport Beach, California 92672
Attention: Mr. Brian Hardy, Vice President – Land Entitlement Subject: Geotechnical Exploration
Proposed Water Tank, Golden Meadows – Tract 31194
Menifee Area, Riverside County, California
In accordance with our February 11, 2021 , Leighton and Associates, Inc. (Leighton) is pleased to present this geotechnical exploration report for the proposed welded steel water tank to be constructed on the north side of the proposed Golden Meadows residential development, Tract 31194, located in the Menifee Area of Riverside County, California. This report presents our findings and conclusions , and geotechnical recommendations for design and construction of this proposed water tank.

Based on the results of this geotechnical exploration, the site of th e proposed tank is generally a ridge top with moderate to steep surrounding slopes underlain by Cretaceous- Aged granitic rock (Gabbro). The site is not located within a currently designated Alquist- Priolo Special Studies Zone or a Riverside County fault zone.

We appreciate the opportunity to be of additional service. If you have any questions or if we can be of further assistance, please contact us at your convenience.

Respectfully Submitted,
LEIGHTON AND ASSOCIATES, INC.

Simon I. Saiid, GE 2641
Principal Engineer
Robert F. Riha, CEG 1921
Senior Principal Geologist
Distribution: (1) addressee (PDF via email)
DRAFT
Geotechnical Exploration April 2, 2021
Proposed Water Tank, Golden Meadows – Tract 31194 Project No. 11813.002 - i -

T A B L E O F C O N T E N T S
Section Page

1.0 INTRODUCTION ......................................................................................................... 1

1.1 Site Location and Description ............................................................................. 1

1.2 Proposed Water Tank ......................................................................................... 1

1.3 Purpose and Scope of Work ............................................................................... 1

2.0 FINDINGS.................................................................................................................... 3

2.1 Regional Geology/Settings.................................................................................. 3

2.2 Site Geology ........................................................................................................ 3

2.2.1 Surficial Soils: ........................................................................................................................ 3

2.2.2 Cretaceous-Aged Gabbroic Bedrock: ................................................................................... 3

2.3 Rippability and Excavation Characteristics.........................................................4

2.4 Surface and Groundwater ................................................................................... 4

2.5 Faulting and Seismicity ....................................................................................... 4

2.6 Secondary Seismic Hazards...............................................................................5

2.6.1 Seismically Induced Settlement: ........................................................................................... 5

2.6.2 Seismically Induced Landslides: ........................................................................................... 5

2.7 Slope Stability ...................................................................................................... 5

3.0 CONCLUSIONS AND RECOMMENDATIONS .......................................................... 7

3.1 Tank Foundation Location ................................................................................... 7

3.2 Earthwork ............................................................................................................ 7

3.2.1 Site Preparation:....................................................................................................................7

3.2.2 Fill Placement and Compaction: ........................................................................................... 7

3.2.3 Utility Trench Backfill: ............................................................................................................ 8

3.3 Seismic Design Parameters ................................................................................ 8

3.4 Tank Spread/Ring Footing Foundations.............................................................9

3.4.1 Minimum Embedment and Width: ......................................................................................... 9

3.4.2 Allowable Bearing Pressure: ................................................................................................. 9

3.4.3 Lateral Load Resistance: ..................................................................................................... 10

3.4.4 Settlement Estimates:.......................................................................................................... 10

3.5 Lateral Pressures for Retaining Structures ....................................................... 10

3.6 Asphalt Paving for Driveway / Access Road ..................................................... 11

3.7 Soil Corrosivity .................................................................................................. 12

3.7.1 Sulfate Attack: ...................................................................................................................... 12

3.7.2 Ferrous Corrosivity: ............................................................................................................. 12

3.7.3 Soil Corrosivity Test Results Summary: ............................................................................. 13

4.0 CONSTRUCTION CONSIDERATIONS .................................................................... 14

4.1 Trench Excavations ........................................................................................... 14 DRAFT
Geotechnical Exploration April 2, 2021
Proposed Water Tank, Golden Meadows – Tract 31194 Project No. 11813.002 - ii -

4.2 Temporary Trench Shoring ............................................................................... 14

4.3 Geotechnical Services during Construction ...................................................... 15

5.0 LIMITATIONS ............................................................................................................ 16 References ......................................................................................................................... 17 List of Accompanying Tables, Figures and Appendices
Tables
Table 1. 2019 CBC Site-Specific Seismic Parameters ................................................ 9 Table 2. Static Lateral Earth Pressures ..................................................................... 10 Table 3. Preliminary Asphalt Pavement Section ...................................................... 12 Table 4. Sulfate Concentration and Sulfate Exposure ............................................. 12 Table 5. Relationship between Soil Resistivity and Soil Corrosivity ...................... 13 Table 6. Soil Corrosivity Test Results Summary ...................................................... 13 Figures
Figure 1 – Site Location Map
Figure 2 – Regional Geology Map
Figure 3 – Geotechnical Map
Appendices
Appendix A – Laboratory Test Results
Appendix B – Results of Seismic Refraction Survey
Appendix C – Site-Specific Seismic Coefficients
Appendix D - General Earthwork Grading Guidelines
Appendix E – GBA - Important Information About This Geotechnical-Engineering Report DRAFT
Geotechnical Exploration April 2, 2021
Proposed Water Tank, Golden Meadows – Tract 31194 Project No. 11813.002

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1 . 0 I N T R O D U C T I O N

1.1 Site Location and Description
The proposed water tank is located on a ridge top along t he northern portion of Tract 31194 , east of the intersection of Garbani Road and Evans Road in the Menifee Area of Riverside County, California (see Site Location Map, Figure 1).

This site is currently a vacant/undeveloped hilltop/ridgeline that slopes moderately to steeply in southerly and westerly directions. Site access is by a steep dirt road located to the south side of the site.

1.2 Proposed Water Tank
We understand that an approximately 103-foot diameter by 40 -foot high welded steel water tank is proposed to be constructed at the Site as depicted on the provided conceptual grading plan (see Figure 3) with expansion pad for a potential future tank. Based on this plan, a desired pad elevation of 1,660 feet and cut slopes of up to approximately 60 feet in height may be constructed to create the required pad (future tank). Site access is expected to extend from an extension of Grabani Road and will also require cut slopes up to approximately 20 feet in height and fill slopes of up to approximately 40 feet in height. For the purpose of bearing capacity evaluation and slope stability analyses, a static pressure of 2,500 pound- per-square-foot (PSF) is assumed to be exerted by the proposed tank.

1.3 Purpose and Scope of Work
The purpose of our geotechnical study is to explore subsurface conditions at this proposed tank site and provide geotechnical recommendations for design and construction. In accordance with our proposal, the scope of this exploration has included the following tasks:

 Desktop Review: We reviewed relevant geotechnical literature, reports and aerial photographs for this tank site. These documents are referenced at the end of this report.
 Geologic Mapping: On February 17, 2021 , we performed a site reconnaissance to observe site conditions and map any pertinent geologic features (i.e. bedding, joints, foliation, etc.) in existing/exposed cut slopes or DRAFT
Geotechnical Exploration April 2, 2021
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- 2 -
natural bedrock exposures. We also collected surface samples for the purpose of laboratory testing and evaluation.
 Geophysical Survey: Four (4) seismic refraction lines were performed by our sub-consultant Atlas Technical Consultants, LLC. The purpose of this survey is to obtain readings/points for both vertical and lateral velocities so “tomography models” can be provided. Tomography is an enhanced seismic refraction method that allows changes in layer velocity to be revealed as gradients rather than discrete contacts. The seismic refraction survey report is presented in whole in Appendix B. The approximate locations of the survey transects are shown on Figure 3, Geotechnical Map. Three survey lines were conducted at the tank site and one survey line was conducted along the cut area for the planned access road.
 Geotechnical Laboratory Testing : Geotechnical laboratory tests were performed on surficial earth material collected during our site reconnaissance.

Tests performed are included in Appendix A.
 Geotechnical Analyses: Data obtained from our background review, field exploration and geotechnical laboratory testing was evaluated to develop geotechnical conclusions and recommendations presented in this report.  Report Preparation : Results of our geotechnical exploration ha ve been summarized in this report to address geotechnic al conditions encountered at the site, including our geotechnical findings, conclusions and recommendations for tank design and construction.

Important information about limitations of geotechnical rep orts is presented in Appendix E, GBA Important Information About This Geotechnical Engineering Report.

DRAFT
Geotechnical Exploration April 2, 2021
Proposed Water Tank, Golden Meadows – Tract 31194 Project No. 11813.002

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2 . 0 F I N D I N G S

2.1 Regional Geology/Settings
The subject property is located within a prominent natural geomorphic province in southwestern California known as the Peninsular Ranges. This province is characterized by steep, elongated ranges and valleys that generally trend northwestward. Tectonic a ctivity along the numerous faults in the region has created the geomorphology present today. Specifically, the property is situated in the southern portion of the Perris Block, a stable, eroded mass of Cretaceous and older crystalline and metamorphic rock . Thin sedimentary, metamorphic and volcanic units locally mantle the bedrock with alluvial deposits filling in the lower valley and drainage areas. The Perris Block is bounded by the San Jacinto Fault Zone to the northeast, the Elsinore Fault Zone to the southwest, the Cucamonga Fault Zone to the northwest and the poorly -defined northern boundary of the Temecula Basin to the southeast. The Temecula segment of the active Lake Elsinore Fault Zone is located approximately 6.4 miles to the southwest.

2.2 Site Geology
As regionally mapped on Figure 2, the site is underlain by gabbroic bedrock. Our field exploration indicates that this bedrock is generally covered with a relatively thin layer of surficial soils as further described below.

2.2.1 Surficial Soils: Surficial soils including topsoil and localized artificial fill should be expected within the site. These soils are expected to be relatively shallow (<3 feet), but they may be deeper in localized areas such as current access road. Expansion Index (EI) t esting was performed on a representative soil sample indicate that these materials (silty sand) possess a very low expansion potential (EI=0). Test results are included in Appendix A.

2.2.2 Cretaceous-Aged Gabbroic Bedrock: Bedrock is exposed on outcrops and on steeper hillsides throughout the site. This granular granitic -type bedrock is generally dark gray in color , massive and jointed . Where exposed on the surface, the bedrock is moderately weathered and creates boulders along the hillsides up to 10 feet in diameter. The elevated portion of t he site (north of future tank) has been cut into a relatively flat pad with bedrock exposed at the surface. The bedrock breaks down into granular silty to well-graded sand with gravel.

DRAFT
Geotechnical Exploration April 2, 2021
Proposed Water Tank, Golden Meadows – Tract 31194 Project No. 11813.002

- 4 -
Jointing is common within this bedrock unit, limited exposures of undisturbed in-place bedrock were encountered throughout the site. Jointing typically dips to the south or southwest . B edrock cut slopes will need to be geologically mapped as they are excavated to confirm the anticipated structural pattern and long-term stability.

2.3 Rippability and Excavation Characteristics
Review of provided conceptual site design indicates cuts (excavation below existing ground surface) up to 60 feet may be required to create the proposed pad for future tank and up to 20 feet for the proposed access road.

Based on our seismic refraction survey data performed by Atlas Technical Consultants, LLC. (Appendix B), rippable bedrock using Caterpillar D-9 dozer with a single shank should be anticipated to a depth of 10 to 20 feet BGS or may vary depending on location. However, very difficult ripping or blasting (or other rock reducing techniques) should be anticipated for deeper excavations or where measured shear wave velocities exceed 4,000 foot-per-second (fps) as shown on the “Tomograpgy Models” included in Appendix B. The relatively shallow and hard rock zones (green to red color) are likely due to buried corestones/remnant boulders, dikes, and/or less weathered rock.

A summary of the seismic refraction survey including rippability criteria based a Caterpillar D-9 dozer with a single shank is further provided in Appendix B. Trench excavation characteristics using conventional excavators may vary based on the specific equipment used. It is important that a contractor with excavation experience in similar conditions be consulted for the proper excavation methodology, equipment, and production rate based on the findings of this report.

2.4 Surface and Groundwater
Surface water was not encountered on this site during our field exploration.

Groundwater is not expected to be encountered within the depth of excavation .

However, localized seeps may occur at Formation contacts or in fractured zones immediately after rain events.

2.5 Faulting and Seismicity
Seismic hazards in Southern California could include strong ground shaking and fault rupture. No currently-known active surface faults cross or trend towards this DRAFT
Geotechnical Exploration April 2, 2021
Proposed Water Tank, Golden Meadows – Tract 31194 Project No. 11813.002

- 5 -
project site. The subject site is not included within an Earthquake Fault Zone as created by the Alquist-Priolo Earthquake Fault Zoning Act (Bryant and Hart, 2007).

The nearest zoned active faults are the Temecula Segment of the Elsinore Fault Zone, approximately 6.4 miles southwest of the site and the Glen Ivy Segment of the Elsinore Fault Zone is located approximately 15.6 miles northwest of the site

A detailed review of vertical, sequential, stereo aerial photograph pairs was conducted to identify possible geomorph ic evidence of faulting and landsliding .

Various photos taken between 1949 and 1999 were reviewed (see references).

Our review of aerial photographs and subsequent field observations do not provide geomorphic evidence supporting the existence of faulting or reveal any photo - lineaments that are typically associated with faulting in this region. The recent (<11,000 years) geologic history of this area reflects that th is site is undergoing a regressive, erosional sequence. As observed in the aerial photographs, there are several deeply cut active , drainage channels that do not show any horizontal displacement that may be associated with active faulting.

2.6 Secondary Seismic Hazards
In general, secondary seismic hazards for sites in the region could include soil liquefaction, earthquake-induced settlement, lateral displacement and landsliding.

The potential for secondary seismic hazards at the site is discussed below.

2.6.1 Seismically Induced Settlement: Seismically induced settlement consists of dry dynamic settlement (above groundwater) and liquefaction -induced settlement (below groundwater). During a strong seismic event, seismically induced settlement can occur within loose to moderately dense sandy soil due to reduction in volume during and shortly after a lar ge, long -duration local earthquake. Settlement caused by ground shaking is often non -uniformly distributed, which can result in differential settlement. Based on the results of our exploration, seismic settlement is not considered a geotechnical constraint for this tank.

2.6.2 Seismically Induced Landslides : Based on the underlying bedrock formation and our review of aerial photographs and field observations, the site is not susceptible to seismically induced landslides.

2.7 Slope Stability
Proposed cut slopes up to 60 feet in height at 2:1 (horizontal:vertical) gradients are considered grossly stable for static and pseudo -static conditions. Compacted fill DRAFT
Geotechnical Exploration April 2, 2021
Proposed Water Tank, Golden Meadows – Tract 31194 Project No. 11813.002

- 6 -
slopes up to 20 feet in height at 2:1 gradients are also considered grossly stable for static and pseudo -static conditions. Cut slopes, should be observed by an engineering geologist during grading to verify jointing or fracture patterns and recommend remedial measures, if needed.

DRAFT
Geotechnical Exploration April 2, 2021
Proposed Water Tank, Golden Meadows – Tract 31194 Project No. 11813.002

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3 . 0 C O N C L U S I O N S A N D R E C O M M E N D A T I O N S Based on results of this geotechnical exploration, the proposed tank site pad is underlain by granitic rock/Gabbro. The site is not located within a currently designated Alquist - Priolo Special Studies Zone or a Riverside County fault zone. However, as is the case for most of Southern California, strong ground shaking has and will occur at this site. Our geotechnical recommendations for design and construction of this proposed water tank are presented in the following sections.

3.1 Tank Foundation Location
Based on proposed pad elevations, the tank pad will be entirely cut into the granitic rock. Due to potentially weathered bedrock material along the shallow cut (daylight) areas we recommend a setback of 15 feet horizontally from daylight to ring foundation.

3.2 Earthwork
Earthwork is expected to generally consist of cut pad and access road excavation, pad surface preparation, and footing and pipeline construction. In addition, minor filling (~15 feet) may be required on the downhill side for access road. Specific earthwork recommendations are provided in the following subsections:

3.2.1 Site Preparation: Based on proposed grading concept, the tank pad is expected to expose dense gabbroic rock. If highly weathered bedrock/ loose rocks or any undesirable geologic features are exposed within portions of the tank pad and/or subgrade for the access road, then such conditions should be addressed by the project geotechnical engineer or geologist prior to foundation construction.

3.2.2 Fill Placement and Compaction: Onsite very low expansive (EI<21) soils free of organics, debris, and oversized material less than (≤) 3 -inches in largest dimension are suitable for use as structural fill on this site. Soils to be placed as fill, whether onsite or import material, should be reviewed by Leighton and tested if and as necessary.

To provide uniform subgrade and fill any potential voids created from removal of loose rock/materials, we recommend that a minimum of 6-inch layer consisting of granular base (Caltrans Class 2 or equivalent) be placed prior to construction of concrete floor slab . However, if re moval of rock or loose material creates voids larger than 2 feet in depth, such areas should be subject to further evaluation as potentially needing additional filling procedures.

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Where fill is being placed at slopes steeper -than (>) 5:1 (horizontal:vertical), proper surface preparations and benching should be implemented in accordance with latest edition of the “Greenbook”, and approved by Leighton during construction. A 15 -foot wide minimum fill slope keyway should be prepared to support the tank pad slope and access road fill slope (see Figure 5). As such, all areas to receive fill, including processed areas, fill slope, and benches, should be observed, mapped, and approved or tested by Leighton prior to proceeding with placement of fill.

3.2.3 Utility Trench Backfill: Utility trenches should be backfilled with compacted fill in accordance with Sections 306 -1.2 and 306 -1.3 of the “Greenbook”. Utility trenches can be backfilled with on -site soils free of debris, organic and oversized material up to (≤) 3-inches in largest dimension. Prior to backfilling trenches, pipes should be bedded in and covered with either:

 Sand: A uniform, granular material that has a Sand Equivalent (SE) of (≥) 30 or greater and a maximum particle size of ¾-inches (or as specified by the pipe manufacturer), water densified in place, or
 CLSM: One sack cement slurry/Controlled Low Strength Material (CLSM) conforming to Section 201-6 of the “Greenbook”.

Pipe bedding should extend at least 4 -inches below any pipeline invert and at least 12 inches over the top of the pipeline. Native soils can be used as backfill over the pipe bedding zone, and should be placed in thin lifts, moisture conditioned above optimum, and mechanically compacted to at least 90 percent relative compaction, relative to the ASTM D 1557 laboratory maximum density.

3.3 Seismic Design Parameters
It is our understanding that the proposed water tank will be constructed of steel and the structural design of the tank will follow ANSI/AWWA D100-11. Therefore, the purpose of the seismic hazard evaluation is to identify and assess potential seismic haza rds at the site in general accordance with the requirements of ANSI/AWWA D100, which generally follows the requirements of ASCE 7-16. Our seismic hazard evaluation includes development of peak ground acceleration (PGA) and design response spectra by using a seismic source model based on proximity of the site to active faults, major historical earthquakes, regional seismicity, and subsurface soil conditions at the site. Specifically, our scope includes estimation of peak horizontal ground acceleration and the response spectra at the site for the Maximum Considered Earthquake (MCE) and the Design DRAFT
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Earthquake (DE) Site-specific ground motion parameters derived based on the requirements of ASCE 7-16, Chapters 11 and 21. These seismic coefficients were calculated utilizing an interactive program on current United States Geological Survey (USGS) website (referred to as USGS General Procedure). Based on our site-specific seismic refraction survey, this site is classified as a Class B site:

Table 1. 2019 CBC Site-Specific Seismic Parameters
2013 CBC Site-Specific Seismic Design Parameters Value
Site Longitude (decimal degrees) -117.18905
Site Latitude (decimal degrees) 33.6555
Site Class Definition B
Mapped Spectral Response Acceleration at 0.2s Period, Ss 1.41 Mapped Spectral Response Acceleration at 1s Period, S1 0.52 Short Period Site Coefficient at 0.2s Period, Fa 0.9
Long Period Site Coefficient at 1s Period, Fv 0.8
Adjusted Spectral Response Acceleration at 0.2s Period, SMS 1.26 Adjusted Spectral Response Acceleration at 1s Period, SM1 0.42 Design Spectral Response Acceleration at 0.2s Period, SDS 0.84 Design Spectral Response Acceleration at 1s Period, SD1 0.28 Long-Period Transitions, TL 8 sec

The results of this analysis also indicate that the adjusted Peak Ground Acceleration (PGAm) for the MCEG is 0.54g.

3.4 Tank Spread/Ring Footing Foundations
The proposed foundations and slabs should be designed in accordance with the structural consultants’ design, the minimum geotechnical recommendations presented herein, and applicable ANSI/AWWA D100-11 requirements.

3.4.1 Minimum Embedment and Widt h: Conventional shallow spread /ring footings may be used to support the proposed tank, bearing solely on an undisturbed granitic rock approved by the geotechnical consultant . Tank footings should be embedded at least 12-inch below lowest adjacent grade, with a minimum width of 12-inch. These footings should have a minimum of 15 feet setback from adjacent descending slope/daylight.

3.4.2 Allowable Bearing Pressure: An allowable bearing pressure of 5,000 pounds- per-square-foot (psf) may be used for static and sustained live loads, based on minimum embedment depth and widths recommended above. The bearing pressure value may be increased by 250 psf for each additional foot of DRAFT
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embedment or each additional foot of width to a max imum vertical bearing value of 6,000 psf. These allowable bearing pressures are for total dead loads and frequently applied live loads, and can be increased by one -third for short duration wind and seismic loads. Where applicable, a modulus of subgrade reaction of 450 pci may be used for design of footings/pads or any structures founded on this Formation.

All continuous footings should be reinforced with top and bottom reinforcing steel to provide structural continuity and to permit spanning of local irregularities. It is essential that we observe tank pad and footing excavations before reinforcing steel is placed.

3.4.3 Lateral Load Resistance: Lateral (horizontal) loads on foundations may be resisted by both frictional resistance along the base of the footing and passive resistance in properly compacted fill adjacent to the sides of footings. Frictional resistance between the base of footings poured (cast) directly on native rock or aggregate base may be computed using a coefficient of friction of 0. 35, or 35- percent of sustained dead loads. Passive resistance may be computed using an equivalent fluid pressure of 300 pounds-per-cubic-foot (pcf) for undisturbed Pauba and/or new properly compacted fill . Passive pressure should not exceed 3,000 psf. The se values may be increased by one -third when considering wind and seismic forces. Both friction and passive values have already been reduced by a factor -of-safety of 1.5, and can be used in combination.

3.4.4 Settlement Estimates: Based on the tank hydrostatic pressures presented in Section 1.2 (< 2,500 psf) and bearing on native rock, the settlement is expected to be less-than (<) ½-inch at the center of the tank and on the order of ¼-inch to negligible at the edge/perimeter.

3.5 Lateral Pressures for Retaining Structures
The lateral earth pressures below are provided for the design permanent retaining structures/walls. Earth pressures provided are ultimate values and a safety factor should be applied as appropriate.

Table 2. Static Lateral Earth Pressures
Conditions
Equivalent Fluid Weight (pcf)
Level
Backfill2
2:1 Slope
Backfill

1.5:1 Slope
Backfill
Active (cantilever) 35 55 70
At-Rest (braced) 50 75 95
Passive3 250 - -
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Notes:
(1) Assumes drained condition
(2) Assumes a level condition behind and in front of wall foundation of project. (3) Maximum passive pressure = 3,500 psf, level conditions.

Determination of appropriate design conditions (active or at-rest) depends on wall flexibility. If a rotation of more than 0.001 radian (0.06 degrees) is allowed, active pressure conditions apply; otherwise, at-rest condition governs.

Surcharge due to above grade loads on the wall backfill, such as traffic, should be considered in d esign of retaining walls. Vertical surcharge loads behind the retaining wall on or in the backfill within a 1:1 (horizontal:vertical) plane projection up and out from the retaining wall toe, should be considered as lateral and vertical surcharge. Unrestrained (cantilever) retaining walls should be designed to resist one-third of these surcharge loads applied as a uniform horizontal pressure on the wall. Braced walls should also be designed to resist an additional uniform horizontal-pressure equivalent to one-half of uniform vertical surcharge-loads.

Additional lateral earth pressures due to seismic shaking should also be considered in the design . In accordance with current engineering practices and research, a n increment of lateral earth pressure equal to 14H2 where H is the height of the wall, may be applied at a distance of 0.5H above the toe of the wall.

If the wall is restrained, the above increment of lateral earth pressure should be doubled. Under the combined effects of static and earthquake loads on the wall, a factor of safety between 1.1 and 1.2 is acceptable when evaluating the stability (sliding, overturning) of the wall (NAVFAC DM 7.2).

Where applicable, a coefficient of friction of 0.35 may be considered between the concrete/shotcrete walls and the backfill surrounding the tank to estimate downward drag forces.

3.6 Asphalt Paving for Driveway / Access Road
Pavement construction associated with the proposed access road should conform to latest version of Caltrans Standard Specifications or the Standard Specifications for Public Works Construction (Greenbook), and applicable County Standards.

Based on design procedures outlined in the current Caltrans Highway Design Manual, recommended flexible (asphalt) pavement section is tabulated below for an assumed Traffic Index (TI) of 4.0 and R-value of 40.

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Table 3. Preliminary Asphalt Pavement Section
Traffic Index
Thickness (inches)
Asphalt Concrete Class 2 Aggregate Base

4.0 3.0 4.0

Representative samples of the actual subgrade materials for R -value testing , during subgrade preparation or prior to pavement construction, can be performed to refine this pavement design. An a ppropriate Traffic Index (TI) should be selected or verified b y the project Civil Engineer prior to finalizing th is pavement section design, based on anticipated truck traffic . This TI is based on only light auto and pickup-truck traffic.

Pavement subgrade soils should be prepared in accordance with Section 3.1 above. The Aggregate Base (AB) should be compacted to a minimum of 95 percent relative compaction (modified Proctor, ASTM D 1557) . Aggregate base may be waived is asphalt concrete is placed directly on granitic rock.

3.7 Soil Corrosivity

3.7.1 Sulfate Attack: Sulfate ions in the soil can lower soil resistivity and can be highly aggressive to Portland cement concrete by combining chemically with certain constituents of the concrete, principally tricalcium aluminate. This reaction is accompanied by expansion and eventual disruption of the concrete matrix. Potentially high sulfate content could also cause corrosion of the reinforcing steel in concrete. T he table below summarizes current standards for concrete exposed to sulfate-containing solutions:

Table 4. Sulfate Concentration and Sulfate Exposure
Sulfate In Water
(parts-per-million)
Water-Soluble Sulfate (SO4)
in soil (percentage by weight) Sulfate Exposure
0-150 0.00 - 0.10 Negligible
150-1,500 0.10 - 0.20 Moderate (Seawater)
1,500-10,000 0.20 - 2.00 Severe
>10,000 Over 2.00 Very Severe

3.7.2 Ferrous Corrosivity: Many factors can affect corrosion potential of soil including soil moisture content, resistivity, permeability and pH, as well as chloride and sulfate concentration. In general, soil res istivity, which is a measure of how easily electrical current flows through soils, is the most influential factor. Based on the findings of studies presented in ASTM STP 1013 titled “Effects of Soil DRAFT
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Characteristics on Corrosion” (February, 1989), the rela tionship between soil resistivity and soil corrosiveness was developed as tabulated below:

Table 5. Relationship between Soil Resistivity and Soil Corrosivity Soil Resistivity
(ohm-cm)
Classification of
Soil Corrosiveness
0 to 900 Very Severely Corrosive
900 to 2,300 Severely Corrosive
2,300 to 5,000 Moderately Corrosive
5,000 to 10,000 Mildly Corrosive
10,000 to >100,000 Very Mildly Corrosive

Acidity is an important factor of soil corrosivity . The lower the pH (the more acidic the environment), the higher the soil corrosivity will be with respect to buried metallic structures and utilities. As soil pH increases above 7 (the neutral value), the soil is increasingly more alkaline and less corrosive to buried steel structures, due to protective surface films, which form on steel in high pH environments. Chloride and sulfate ion concentrations, and pH appear to play secondary roles in affecting corrosion potential. High chloride levels tend to reduce soil resistivity and break down otherwise protective surface deposits, which can result in corrosion of buried steel or reinforced concrete structures.

3.7.3 Soil Corrosivity Test Results Summary: As a preliminary screening process for sulfates in soils , we have performed laboratory tests on a representative surface soil-sample. As summarized in Table 6 (below), our laboratory test results indicated negligible concentration of soluble sulfates. No special measures to mitigate sulfate exposure are recom mended based on the test results. Import soils (if any) should also be tested for sulfate content.

Based on minimum-resistivity laboratory test results, the onsite soil is generally considered very mildly -corrosive to ferrous metals. Ferrous pipe can be protected by polyethylene bags, tape or coatings, di -electric fittings, concrete encasement or other means to separate the pipe from wet onsite clayey soils.

Further testing of import and possibly site soil corrosivity could be performed and specific rec ommendations for corrosion protection may need to be provided by a qualified corrosion engineer.

Table 6. Soil Corrosivity Test Results Summary
Boring
Number
Sample
Depth (feet)
Sulfate Content
(ppm)
Chloride Content
(ppm) pH Resistivity
(ohm-cm)
S-1 0 to 1 111 20 6.7 13,000

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4 . 0 C O N S T R U C T I O N C O N S I D ER A T I O N S

4.1 Trench Excavations
Based on our field observations, caving of cohesionless and sandy soils will likely be encountered in unshored trench excavations. To protect workers entering excavations, excavations should be performed in accordance with OSHA and Cal- OSHA requirements, and the current edition of the California Construction Safety Orders, see:
http://www.dir.ca.gov/title8/sb4a6.html
Contractors should be advised that fill and cohesionless alluvial /colluvial soils should be considered Type C soils as defined in the California Construction Safety Orders. As such, excavations less-than (<) 20 feet deep within Type C soils should be sloped back no steeper than 1½:1 (horizontal:vertical), where workers are to enter the excavation. Weathered rock within upper 10 feet BGS may be classified as OSHA soil Type A. Therefore, unshored temporary cut slopes should be no steeper than ¾:1 (horizontal:vertical), for a height no -greater-than ( ) 10 feet.

These recommended temporary cut slopes assume a level ground surface for a distance equal to one -and-a-half (x1.5) the depth of excavation . However, unshored excavations may be impractical near adjacent existing utilities and structures; so shoring may still be required depending on trench locations.

During construction, soil conditions should be regularly evaluated to verify that conditions are as anticipated. The contractor is responsible for providing the "competent person" required by OSHA standards to evaluate soil conditions.

Close coordination between the competent person and Leighton. should be maintained to facilitate construction while providing safe excavations.

4.2 Temporary Trench Shoring
Typical cantilever shoring can be designed based on the active equivalent fluid pressure of 33 pounds-per-cubic-foot (pcf) where there is no adverse bedding. If excavations are braced at the top and at specific depth intervals, then braced earth pressure may be approximated by a uniform rectangular soil pressure distribution.

This uniform pressure expressed in pounds -per-square-foot (psf), may be assumed to be 20 multiplied by H for design, where H is equal to the depth of the DRAFT
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excavation being shored, in feet. These recommendations are valid only for trenches not exceeding 10-feet in depth at this site.

4.3 Geotechnical Services during Construction
Our geotechnical recommendations presented in this report are based on subsurface conditions as interpreted from limited subsurface explorations and limited geotechnical laboratory testing. Our geotechnical recommendations provided in this report are based o n information available at the time the report was prepared and may change as plans are developed. Additional geotechnical exploration, testing and/or analysis may be required based on final plans. Leighton and Associates, Inc. should review site grading, foundation and shoring (if any) plans when available, to comment further on geotechnical aspects of th is project and check to see general conformance of final project plans to recommendations presented in this report.

Leighton and Associates , Inc. should be retained to provide g eotechnical observation and testing during excavation and all phases of earthwork. Our conclusions and recommendations should be reviewed and verified by us during construction and revised accordingly if geotechnical conditions encountered vary from our findings and interpretations. Geotechnical observation and testing should be provided:

 During all cut excavation,
 During compaction of all fill materials,
 After excavation of all footings and prior to placement of concrete,  During utility trench backfilling and compaction,
 During pavement subgrade and base preparation (if any), and/or  If and when any unusual geotechnical/geologic conditions are encountered.

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5 . 0 L I M I T A T I O N S
This report was necessarily based i n part upon data obtained from a limited number of observances, site visits, soil samples, tests, analyses, histories of occurrences, spaced subsurface explorations and limited information on historical events and observations.

Such information is necessarily incomplete. The nature of many sites is such that differing characteristics can be experienced within small distances and under various climatic conditions. Changes in subsurface conditions can and do occur over time. This exploration was performed with the understanding that th is subject site is proposed for development as described in Section 1. 2 of this report. Please refer to Appendix E, ASFE’s Important Information About Your Geotechnical Report , prepared by the Associated Soil and Foundation Engineers (ASFE) presenting additional information and limitations regarding geotechnical engineering studies and reports.

This report was prepared for Richland Communities, Inc. based on their needs, directions and requirements at the time of our exploration. This report is not authorized for use by, and is not to be relied upon by any party except Richland Communities, Inc. , and their successors and assigns, with whom Leighton has contracted for the work. Use of or reliance on this report by any other party is at that party 's risk. Unauthorized use of or reliance on this report constitutes an agreement to defend and indemnify Leighton from and against any liability which may arise as a result of such use or reliance, regardless of any fault, negligence, or strict liability of Leighton.

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R E F E R E N C E S

Army Corps of Engineers, Evaluation of Settlement for Dynamic and Transient Loads, Technical Engineering and Design Guides as Adapted from the US Army Corps of Engineers, No. 9, American Society of Civil Engineers Press.

American Society of Civil Engineers, 201 6, Minimum Design Loads for Buildings and Other Structures, ASCE/SEI 7-16 Publication.

Blake, T. F., 2000a, EQSEARCH, A Computer Program for the Estimation of Peak Horizontal Acceleration from California Historical Earthquake Catalogs, IBM-PC Compatible Version, User’s Manual, January 1996.

Blake T.F., 2000b, EQFAULT, Version 3, A Computer Program for the Deterministic Prediction of Peak Horizontal Acceleration from Digitized California Faults, User's Manual, 77pp.

Bryant, W.A., and Hart, E.W., 2007, Fault -Rupture Hazard Zones in California, Alquist - Priolo Earthquake Fault Zoning Act with Index to Earthquake Zones Maps, Department of Conservation, California Geological Survey, Special Publication 42. 2007 Interim Revision.

California Building Code, 2019, California Code of Regulations Title 24, Part 2, Volume 2 of 2.

California Department of Water Resources, 2021, Water Data Library, viewed March, 2021, www.water.ca.gov/waterdatalibrary.

Morton, D.M., Geologic Map of the Romoland 7.5 Minute Quadrangle, Riverside County, California, USGS Open-File Report 03-102.

Kennedy, Michael P., 1977, Regency and Character of Faulting along the Elsinore Fault Zone in Southern Riverside County, California, CDMG Special Report 131.

OSHPD, 2021, Seismic Design Maps, an interactive computer program on OSHPD website to calculate Seismic Response and Design Parameters based on ASCE 7 -16 seismic procedures, https://seismicmaps.org/
Public Works Standard, Inc., 2018, Greenbook, Standard Specifications for Public Works Construction: BNI Building News, Anaheim, California.

Tokimatsu, K., Seed, H. B., 1987, “Evaluation of Settlements in Sands Due to Earthquake Shaking,” Journal of the Geotechnical Engineering, American Society of Civil Engineers, Vol. 113, No. 8, pp. 861-878.

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Aerial Photos Reviewed:

3-12-99 C135 – 39 – 135-136
9-11-97 C116 – 39 – 46-47
10-4-95 CAP – 125-127
1-30-95 C104 – 39 – 10
2-2-93 C86 – 39 – 13
10-12-90 90205 – 125-126
7-30-86 86084
6-14-83 83045 – 101
12-14-79 79274 – 161A
5-15-67 2HH – 191-192
5-15-67 3HH – 20
5-23-49 9F – 124-125
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A P P E N D I X A
C u r r e n t S t u d y L a b o r a t o r y T e s t R e s u l t s Project Name: Golden Meadows TR31194 Tank Geo Tested By : M. Vinet Date: 02/22/21 Project No. : 11813.002 Data Input By: M. Vinet Date: 02/23/21 Boring No. S-1
Sample No. S-1
Sample Depth (ft) 0 - 1.0
100.00
100.00

0.00 0.00
100.00
1 1
850
Timer
45 25.1122

25.1095

0.0027
111.11
111
ml of Extract For Titration (B) 30
ml of AgNO3 Soln. Used in Titration (C) 0.4
PPM of Chloride (C -0.2) * 100 * 30 / B 20
PPM of Chloride, Dry Wt. Basis 20

6.70 21.0
PPM of Sulfate (A) x 41150
Wet Weight of Soil + Container (g)
Wt. of Residue (g) (A)
Beaker No.

Crucible No.

Furnace Temperature (°C)
PPM of Sulfate, Dry Weight Basis
Wt. of Crucible (g)
Poorly Graded
Sand with Silt
(SP-SM)
Wt. of Crucible + Residue (g)
CHLORIDE CONTENT, DOT California Test 422
Time In / Time Out
Weight of Soaked Soil (g)
Dry Weight of Soil + Container (g)
Weight of Container (g)
Duration of Combustion (min)
Temperature °C
pH Value
pH TEST, DOT California Test 643
TESTS for SULFATE CONTENT
CHLORIDE CONTENT and pH of SOILS
SULFATE CONTENT, DOT California Test 417, Part II
Soil Identification:

Moisture Content (%)

Project Name: Tested By : M. Vinet Date:

Project No. : Data Input By: M. Vinet Date:

Boring No.: Depth (ft.) :

Sample No. : S-1
Container No.

Initial Soil Wt. (g) (Wt)
Box Constant15000 15000
Poorly Graded Sand with Silt (SP-SM)
Resistance
Reading
(ohm)

16.60 Soil
Resistivity
(ohm-cm)
Golden Meadows TR31194 Tank Geo 02/22/21
02/23/21
0 - 1.0
11813.002
S-1

SOIL RESISTIVITY TEST
DOT CA TEST 643
Temp. (°C)pH
Soil pH
15000
13000
100.00

0.00 MC =(((1+Mci/100)x(Wa/Wt+1))-1)x100
13000 23.2 111 20 6.70 21.0
4 83
116
149
A
500.003 1300023.20
15000
Min. Resistivity
DOT CA Test 643DOT CA Test 417 Part II DOT CA Test 422
(%) (ppm) (ppm)
DOT CA Test 643

1.000
Chloride Content
(ohm-cm)

29.80 Moisture Content Sulfate Content
5 1
2 Water
Added (ml)
(Wa)
50 Adjusted
Moisture
Content
(MC) Dry Wt. of Soil + Cont. (g)
24000
Soil Identification:*
*California Test 643 requires soil specimens to consist only of portions of samples passing through the No. 8 US Standard Sieve before resistivity testing.  Therefore, this test method may not be representative for coarser materials.

Wt. of Container (g)10.00 24000

0.00 100.00
Moisture Content (%) (MCi)
Wet Wt. of Soil + Cont. (g)
Specimen
No.
0 5000
10000
15000
20000
25000
30000

0.0 5.0 10.0 15.0 20.0 25.0 30.0 35.0
Soil Resistivity (ohm-cm)
Moisture Content (%)
Minimum resistivity
read here
Project Name: Tested By: M. Vinet Date: 2/18/21
Project No. : Checked By: M. Vinet Date: 2/19/21
Boring No.: Depth: 0 - 1.0
Sample No. : Location:

Sample Description:

Dry Wt. of Soil + Cont. (gm.)
Wt. of Container No. (gm.)
Dry Wt. of Soil (gm.)
Weight Soil Retained on #4 Sieve
Percent Passing # 4
in distilled water for the period of 24 h or expansion rate < 0.0002 in./h.

Rev. 03-08

SPECIMEN INUNDATION

76.3 Dry Wt. of Soil + Cont. (gm.)

10.5 627.8
599.3

0.584
327.8
200.0
619.8
127.5
Elapsed Time
(min.)
Dial Readings
(in.)

89.248.6
Pressure
(psi)

0.368Total Porosity

2.70 352.9
200.0

18.9 0.364

74.9 EXPANSION INDEX of SOILS
Poorly Graded Sand with Silt (SP-SM), Olive Brown.

MOLDED SPECIMEN

4.01 1.0000
11Container No.

Specimen Diameter (in.)
Wt. Comp. Soil + Mold (gm.)
200.0
N/A
Golden Meadows TR31194 Tank Geo
11813.002
S-1
S-1
ASTM D 4829

96.3 4.01

2.70 3350.7

0.0 590.0
3350.7
124.3

0.9935
619.8
After TestBefore Test
Wet Wt. of Soil + Cont. (gm.)
11 0.573
Dry Density (pcf)
Wet Density (pcf)
Specific Gravity (Assumed)
Specimen Height (in.)
Wt. of Mold (gm.)
2/18/21
106.5
Moisture Content (%)
Date
11:30
Void Ratio
Pore Volume (cc)
Degree of Saturation (%) [ S meas]
117.6
Time
2/19/21 8:00

1.0 1.0
11:40 1.02/18/21

1.0 0 Expansion Index ( Report ) = Nearest Whole Number or Zero (0) if Initial Height is > than Final Height Add Distilled Water to the Specimen
Wt. of Container (gm.)
107.2

0.5000
10 0.5000

0.49352/19/21
0 1160
Expansion Index (EI meas) = ((Final Rdg - Initial Rdg) / Initial Thick.) x 1000 7:00
1220 0.4935
-6.5

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A P P E N D I X B
S e i s m i c R e f r a c t i o n S u r v e y

SEISMIC REFRACTION STUDY

GOLDEN MEADOWS TANK EXPLORATION
Menifee, California
PREPARED FOR:

Jeffery Deland
Leighton & Associates, Inc.
41715 Enterprise Circle North, Suite 103
Temecula, CA 92590
PREPARED BY:

Atlas Technical Consultants, LLC
6280 Riverdale Street
San Diego, CA 92120
March 9, 2021

6280 Riverdale Street
San Diego, CA 92120
(877) 215-4321 | oneatlas.com
March 9, 2021
Atlas No. 121058SWG
Report No. 1

MR. JEFFERY DELAND
LEIGHTON & ASSOCIATES, INC.
17781 COWAN
IRVINE, CA 92614

Subject: Seismic Refraction Study
Golden Meadows Tank Exploration
Menifee, California

Dear Mr. Deland:

In accordance with your authorization, Atlas Technical Consultants has performed a seismic refraction study pertaining to the Golden Meadows Tank Exploration project located in Menifee, California. Specifically, our evaluation consisted of performing four seismic P-wave refraction traverses at the project site. The purpose of our evaluation was to develop subsurface velocity profiles of the study areas in order to assess the depth to bedrock and apparent rippability of the subsurface materials. Our field services were conducted on February 17 th, 2021. This data report
presents our methodology, equipment used, analysis, and results.

If you have any questions, please call us at 619.280.4321.

Respectfully submitted,
Atlas Technical Consultants LLC

Evan C. Anderson Patrick F. Lehrmann, P.G., P.Gp.

Senior Staff Geophysicist Principal Geologist/Geophysicist ECA:PFL:ds
Distribution: Mr. Jeffery DeLand at @leightongroup.com

Atlas No. 121058SWG
Report No. 1
Page | i

CONTENTS

1. INTRODUCTION ............................................................................................................ ....... 1

2. SCOPE OF SERVICES ......................................................................................................... 1

3. SITE AND PROJECT DESCRIPTION ................................................................................... 1

4. STUDY METHODOLOGY ..................................................................................................... 1

5. DATA ANALYSIS .................................................................................................................. 3

6. RESULTS AND CONCLUSIONS .......................................................................................... 3

7. LIMITATIONS ........................................................................................................................ 3

8. SELECTED REFERENCES .................................................................................................. 4

TABLES
Table 1 – Rippability Classification ............................................................................................... 2

FIGURES
Figure 1 Site Location Map
Figure 2 Seismic Line Location Map
Figure 3 Site Photographs
Figure 4a P-Wave Profile (SL-1)
Figure 4b P-Wave Profile (SL-2)
Figure 4c P-Wave Profile (SL-3)
Figure 4d P-Wave Profile (SL-4)

Atlas No. 121058SWG
Report No. 1
Page | 1

1. INTRODUCTION
In accordance with your authorization, Atlas Technical Consultants has performed an additional seismic refraction study pertaining to the Golden Meadows Tank Exploration project located in Menifee, California (Figure 1). Specifically, our evaluation consisted of performing four seismic P-wave refraction traverses at the project site. The purpose of our evaluation was to develop subsurface velocity profiles of the study areas in order to assess the depth to bedrock and apparent rippability of the subsurface materials. Our field services were conducted on February 17 th, 2021. This data report presents our methodology, equipment used, analysis, and results.

2. SCOPE OF SERVICES
Our scope of services included:
 Performance of four seismic P-wave refraction traverses at the project site.  Compilation and analysis of the data collected.
 Preparation of this data report presenting our results and conclusions.

3. SITE AND PROJECT DESCRIPTION
The project site is generally located west of State Route 215 and east of State Route 15 in Menifee, California (Figure 1). Specifically, the seismic traverses are located at the termination of Garbani Road along the southern slope of the adjacent hill. The seismic traverses were performed over slight to moderately steep terrain. Granite outcrops were present throughout the study areas.

The study site was marked by dry, knee-high brush throughout. Figures 2 and 3 depict the general site conditions in the areas of the seismic traverses.

Based on our discussions with you, it is our understanding that new construction activities are proposed at the site and the results of our study may be used for the design and construction parameters pertaining to the project.

4. STUDY METHODOLOGY
A seismic P-wave (compression wave) refraction study was conducted at the project site to evaluate the rippability characteristics of the subsurface materials and to develop subsurface velocity profiles of the area studied. The seismic refraction method uses first-arrival times of refracted seismic waves to estimate the thicknesses and seismic velocities of subsurface layers.

Seismic P-waves generated at the surface, using a hammer and plate, are refracted at boundaries separating materials of contrasting velocities. These refracted seismic waves are then detected by a series of surface vertical component 14.5-Hz geophones and recorded with a 24-channel Geometrics Geode seismograph. The travel times of the seismic P-waves are used in conjunction with the shot-to-geophone distances to obtain thickness and velocity information on the subsurface materials.

Atlas No. 121058SWG
Report No. 1
Page | 2
Four seismic traverses (SL-1 and SL-4) were conducted in the study area. The general locations and lengths of the lines were determined by surface conditions, site access, and depth of investigation. Shot points (signal generation locations) were conducted along the lines at the ends, midpoint, and intermediate points between the ends and the midpoint.

The seismic refraction theory requires that subsurface velocities increase with depth. A layer having a velocity lower than that of the layer above will not generally be detectable by the seismic refraction method and, therefore, could lead to errors in the depth calculations of subsequent layers. In addition, lateral variations in velocity, such as those caused by core stones, intrusions, or boulders can also result in the misinterpretation of the subsurface conditions. In general, the effective depth of evaluation for a seismic refraction traverse is approximately one-third to one- fifth of the length of the spread.

In general, the seismic P-wave velocity of a material can be correlated to rippability (see Table 1 below), or to some degree “hardness.” Table 1 is based on published information from the Caterpillar Performance Handbook (Caterpillar, 2018) , as well as our experience with similar materials, and assumes that a Caterpillar D-9 dozer ripping with a single shank is used. We emphasize that the cutoffs in this classifi cation scheme are approximate and that rock characteristic, such as fracture spacing and orientation, play a significant role in determining rock quality or rippability. The rippability of a mass is also dependent on the excavation equipment used and the skill and experience of the equipment operator.

For trenching operations , the rippability values should be scaled downward. For example, velocities as low as 3,500 feet/second may indicate difficult ripping during trenching operations.

In addition, the presence of boulders, which can be troublesome in narrow trenching operations, should be anticipated.

Table 1 – Rippability Classification
Seismic P-wave Velocity Rippability
0 to 2,000 feet/second Eas y
2,000 to 4,000 feet/second Moderate
4,000 to 5,500 feet/second Difficult, Possible Blastin g 5,500 to 7,000 feet/second Ver y Difficult, Probable Blasting Greater than 7,000 feet/second Blastin g Generally Required

It should be noted that the rippability cutoffs presented in Table 1 are slightly more conservative than those published in the Caterpillar Performance Handbook. Accordingly, the above classification scheme should be used with discretion, and contractors should not be relieved of making their own independent evaluation of the rippability of the on-site materials prior to submitting their bids.

Atlas No. 121058SWG
Report No. 1
Page | 3

5. DATA ANALYSIS
The collected data was processed using SIPwin (Rimrock Geophysics, 2003), a seismic interpretation program, and analyzed using SeisOpt Pro (Optim, 2008). SeisOpt Pro uses first arrival picks and elevation data to produce subsurface velocity models through a nonlinear optimization technique called adaptive simulated annealing. The resulting velocity model provides a tomography image of the estimated geologic conditions. Both vertical and lateral velocity information is contained in the tomography m odel. Changes in layer velocity are revealed as gradients rather than discrete contacts, which typically are more representative of actual conditions.

6. RESULTS AND CONCLUSIONS
As previously indicated, four seismic traverses were conducted as part of our study. Figures 4a, 4b, 4c, and 4d present the velocity models generated from our analysis. Based on the results, it appears the project site is underlain by moderately low-velocity materials in the very near-surface and higher velocity materials in the shallow surface. Distinct vertical and lateral velocity variations are evident in the models. Moreover, the degree of weathering and the depth to possible bedrock varies across the study area.

Based on the refraction results, variability in the excavatability (including depth of rippability) of the subsurface materials should be expected across the project areas. In addition, oversized materials should be expected. A contractor with excavation experience in similarly difficult conditions should be consulted for expert advic e on excavation methodology, equipment, and production rate.

7. LIMITATIONS
The field evaluation and geophysical analyses presented in this report have been conducted in general accordance with current practice and the standard of care exercised by consultants performing similar tasks in the project area. No warranty, express or implied, is made regarding the conclusions, recommendations, and opinions presented in this report. There is no evaluation detailed enough to reveal every subsurface condition. Variations may exist and conditions not observed or described in this report may be present. Uncertainties relative to subsurface conditions can be reduced through additional subsurface exploration. Additional subsurface surveying will be performed upon request.

This document is intended to be used only in its entirety. No portion of the document, by itself, is designed to completely represent any aspect of the project described herein. Atlas should be contacted if the reader requires additional information or has questions regarding the content, interpretations presented, or completeness of this document. This report is intended exclusively for use by the client. Any use or reuse of the findings, conclusions, and/or recommendations of this report by parties other than the client is undertaken at said parties’ sole risk.

Atlas No. 121058SWG
Report No. 1
Page | 4

8. SELECTED REFERENCES
Caterpillar, Inc., 2018, Caterpillar Performance Handbook, Edition 48, Caterpillar, Inc., Peoria, Illinois.

Mooney, H.M., 1976, Handbook of Engineering Geophysics, dated February.

Optim, Inc., 2008, SeisOpt Pro, V-5.0.

Rimrock Geophysics, 2003, Seismic Refraction Interpretation Program (SIPwin), V-2.76.

Telford, W.M., Geldart, L.P., Sheriff, R.E., and Keys, D.A., 1976, Applied Geophysics, Cambridge University Pres.

Figure 2

SEISMIC LINE LOCATION
MAP
Golden Meadows Tank Exploration
Menifee, California
Project No.: 121058SWG Date: 03/21
approximate scale in feet
100 2000
0 240
SL-1
240
0 SL-2
0 200
SL-4
0 240
SL-3
Seismic Line
LEGEND
SL-4
2000

Geotechnical Exploration April 2, 2021
Proposed Water Tank, Golden Meadows – Tract 31194 Project No. 11813.002

A P P E N D I X C
Site-Specific Seismic Coefficients
October 9, 2017
Project No. 11813.001

RICHLAND PLANNED COMMUNITIES, INC
3161 Michelson Drive, Suite 425
Irvine, California 92612
Attention: Mr. Brian Hardy
Subject: Results of Onsite Percolation/Infiltration Testing Proposed Storm Water Infiltration Basins
Golden Meadows, Tract 31194-1, -2, &-3
City of Menifee, Riverside County, California
References: Design Handbook for Low Impact Development Best Management Practices, Riverside County Flood Control and Water Conservation District (District) , dated September 2011.

Rough Grading Plan for TR. No. 31194-1, TR. No. 31194-2, TR. No. 31194-3, TR. No. 31194, Golden Meadows, Sheet 16, by Hunsaker and Associates, (undated).

Geotechnical Review of Rough Grading Plans, Tract 31194, Menifee, County of Riverside, California, by Leighton and Associates, Inc., PN. 110712-002, dated January 30, 2004.

In accordance with your request and authorization, we are pleased to provide this report presenting the results of field percolation testing for the proposed storm water infiltration basins associated with the subject Tract. The location of field tests was primarily dictated by Hunsaker and Associates, Inc.

P U R P O S E A N D S C O P E O F W O R K
The purpose of our testing was to determine the infiltration rates of onsite soils with respect to the proposed storm water retention basins as depicted on the referenced rough grading plans. Services provided for this study consisted of the following:
 Drilling, sampling and logging of one exploratory boring within the proposed storm water basin area.

Results of Onsite Percolation/Infiltration Testing October 9, 2017 Proposed Storm Water Infiltration Basins Golden Meadows, Tract 31194-1, -2, &-3 Project No. 11813.001

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 Field percolation testing at 3 locations within the basin location in accordance with the procedures outlined in District’s Design Handbook, referenced above. One test was performed at approximately 12 inches bgs and one at approximately 5 feet bgs in the cut area of the basin. One additional percolation/infiltration test was performed at a depth of 9 feet to verify permeability of underlying bedrock.  Compilation of this report that presents the results of our field percolation/infiltration testing.

S I T E D E S C R I P T I O N
The proposed residential development (Tract 31194) is located southeast of Evans Road and Garbani Road in Menifee, California. The site is generally undeveloped and appeared to be used for agricultural purposes.

Topographically, the central and southeastern portions of the site are relatively flat lying while the northern region of the property is characterized by relatively steep hills . A small, northwest-trending drainage channel extends through the northwestern and central portion of the property. A rock knoll also exists near the southeast corner of the property. Site elevations range from approximately 1,720 feet above mean sea level (msl) in the northeastern corner of the site to approximately 1,500 feet (msl) at the northwestern portion of the site.

F I E L D E X P L O R A T I O N
Our field exploration consisted of excavating one deep geotechnical boring and three percolation tests
on October 4, 2017 utilizing a truck mounted CME 75 drill rig equipped with an 8-inch hollow-stem auger. The exploratory boring w as logged and sampled to a minimum depth of 12 feet below existing surface (encountered refusal). Representative samples were collected for further field and laboratory classification. A staff geologist from our office logged and observed all excavations. The locations of the exploratory borings
and percolation test holes are shown on Figure 1. The logs of the exploratory borings are included in Appendix A.

S O I L S A N D G R O U N D W A T E R C O N D I T I O N S Based on the results of this exploration and review of our previous geotechnical investigation reports, the site is underlain by granitic bedrock which is in turn mantled with a variable thickness of alluvial deposits . Within the proposed storm water basin area, Results of Onsite Percolation/Infiltration Testing October 9, 2017 Proposed Storm Water Infiltration Basins Golden Meadows, Tract 31194-1, -2, &-3 Project No. 11813.001 - 3 -
granitic bedrock was encountered in our Boring LB-1 at depth of approximately 7 feet below ground surface. Based on this exploration and previous investigations it is our opinion that historic groundwater does not exist within 10 feet below bottom of basin.

T E S T R E S U L T S
The percolation/infiltration tests were performed in accordance with the procedures of Section 2.3 of the Riverside County Flood Control and Water Conservation District Design Handbook (RCFC&WCD, 2011). Results reported below are the most conservative reading in minutes per inch drop. The infiltration rates were estimated using the “Porchet Method”.

Field test data are included in Appendix A.

Summary of Infiltration Test Results
Test
Hole #
Ex. Ground
Surface
Elev. (ft)
Depth
BGS
(ft)
Infiltration
Rate
(in/hr)
Soil Description
P-1 1535 9.0 1.35 Well-graded Sand (SW)/
Decomposed Granitic Rock
P-2 1534.5 4.0 0.24 Silty sand (SM) Alluvium
P-3 1531.5 1.0 0.10 Silty sand (SM) / Alluvium

C O N C L U S I O N S A N D R E C O M M E N D A T I O N S Based on the above, we recommend that the proposed basins be sized/designed using an average infiltration rate of 0.12 in/hr if bottom of basin is at elevation 1530 to 1531.

No factor of safety was applied to this recommended average infiltration rate.

L I M I T A T I O N S
This report was based in part on data obtained from a limited number of observations, soil excavations, samples and tests. Such information is, by necessity, incomplete.

The nature of many sites is such that differing soil or geologic conditions can be present within small distances and under varying climatic conditions. Changes in subsurface conditions can and do occur over time. Please notify the engineer if event conditions encountered during construction are different than those described or reflected in this report.

Results of Onsite Percolation/Infiltration Testing October 9, 2017 Proposed Storm Water Infiltration Basins Golden Meadows, Tract 31194-1, -2, &-3 Project No. 11813.001

- 4 -
This report was prepared for the sole use of Client and their design team, for application to design of the proposed infiltration basins, in accordance with generally accepted geotechnical engineering practices at this time in California. In addition, since this is subject to review by Riverside County, we recommend that data in this report be only used in the design of this project after review and approval by County , where applicable. Any premature (before County approval) or unauthorized use of or reliance on this report constitutes an agreement to defend and indemnify Leighton from and against any liability which may arise as a result of such use or reliance, regardless of any fault, negligence, or strict liability of Leighton.

If you have any question, please do not hesitate to contact this office. We appreciate this opportunity to be of service.

Respectfully submitted,
LEIGHTON AND ASSOCIATES, INC.

Simon I. Saiid, GE 2641
Principal Engineer
Robert F. Riha, CEG 1921
Sr. Vice President / Sr. Principal Geologist

Attachments: Figure 1 – Boring Location Plan
Appendix A – Perc Data Test Sheets & Log of Exploratory Borings

Distribution: (1) Addressee (one PDF copy via email)
(1) Hunsaker & Associates
&<
&(
&(
&(
LB-1
P-1
P-2
P-3
³
0 40 80
Feet
Figure 1
Scale:

Leighton
Base Map: Bing Maps 2017
Thematic Information: Leighton
1 " = 40 '
Project: 11813.001 Eng/Geol: SIS/RFR
Map Saved as V:\Drafting\11813\001\Maps\11813-001_F02_BLM_2017-10-06.mxd on 10/9/2017 7:51:11 AM Author: (mmurphy)
Date: October 2017

BORING LOCATION MAP
Golden Meadows - Tract 31194
Richland Planned Communities
Menifee, California
Legend
&< Approximate Boring Location
&( Approximate Percolation Test Location
LB-1
P-3
Results of Onsite Percolation/Infiltration Testing October 9, 2017 Proposed Storm Water Infiltration Basins Golden Meadows, Tract 31194-1, -2, &-3 Project No. 11813.001

APPENDIX A
Percolation Data Sheets
Log of Exploratory Borings
96 8°
8:18:00
8:48:00
8:48:00
9:18:00
9:18:00
9:48:00
9:48:00
10:18:00
10:18:00
10:48:00
10:48:00
11:18:00
11:18:00
11:48:00
11:48:00
12:18:00
* Based on Prochet Method
Percolation Project Number: 11813.001
Leighton
P-1
Date: Oct-17
Test Data
Project Name: Golden Meadows

10.00 74.50 77.00 2.50 1.348 4.000

10.00 74.00 76.50 2.50 1.319 4.000

10.00 75.50 77.75 2.25 1.263 4.444

10.00 74.25 77.25 3.00 1.618 3.333

10.00 74.00 77.25 3.25 1.743 3.077

10.00 74.00 77.75 3.75 2.034 2.667

25.00 69.50 77.25 7.75 1.511 3.226
inches/hour* minute/inch

25.00 69.50 87.50 18.00 4.431 1.389
USCS Soil Type: Grayish Brown SAND with Silt Diameter (in.) Sunny ~90 Time ∆t (min) Initial Water Depth
(inches)
Final Water Depth
(inches)
Change In Water Level
(inches)
Infiltration/Percolation
Rate
Tested by: BSS Date Tested 10/6/2017
Soil Unit: Granitic Bedrock (Kgr) Depth of Test Hole (in.) Test Hole Number: P-1 Project Golden Meadows
Date Excavated: 10/4/2017 Project Number 11813.001

0.000

1.000

2.000

3.000

4.000

5.000
0 20 40 60 80 100 120
Infiltration Rate
(in./hr)
Time (min)
48 8°
9:22:00
9:47:00
9:47:00
10:12:00
10:12:00
10:42:00
10:42:00
11:12:00
11:12:00
11:42:00
11:42:00
12:12:00
12:12:00
12:42:00
12:42:00
13:12:00
13:12:00
13:42:00
13:42:00
14:12:00
14:12:00
14:42:00
14:42:00
15:12:00
Date:

Oct-17
* Based on Prochet Method
Percolation Project Number: 11813.001
Leighton
Test Data
Project Name: Golden Meadows
P-2

30.00 12.00 13.50 1.50 0.161 20.000

30.00 12.00 13.50 1.50 0.161 20.000

30.00 12.00 13.75 1.75 0.189 17.143

30.00 12.00 13.50 1.50 0.161 20.000

30.00 12.00 14.00 2.00 0.216 15.000

30.00 12.00 13.75 1.75 0.189 17.143

30.00 12.00 14.00 2.00 0.216 15.000

30.00 12.00 13.75 1.75 0.189 17.143

30.00 12.00 15.00 3.00 0.329 10.000

30.00 12.00 15.25 3.25 0.357 9.231

25.00 12.00 14.75 2.75 0.360 9.091
inches/hour* minute/inch

25.00 18.00 20.50 2.50 0.390 10.000
USCS Soil Type: Brown Silty SAND Diameter (in.) Sunny ~90 Time ∆t (min) Initial Water Depth
(inches)
Final Water Depth
(inches)
Change In Water Level
(inches)
Infiltration/Percolation
Rate
Tested by: BSS Date Tested 10/6/2017
Soil Unit: Alluvium (Qal) Depth of Test Hole (in.)
Test Hole Number: P-2 Project Golden Meadows
Date Excavated: 10/4/2017 Project Number 11813.001

0.000

0.050

0.100

0.150

0.200

0.250

0.300

0.350

0.400

0.450
0 50 100 150 200 250 300 350 400
Infiltration Rate
(in./hr)
Time (min)
12 8°
9:24:00
9:49:00
9:49:00
10:14:00
10:14:00
10:44:00
10:44:00
11:14:00
11:14:00
11:44:00
11:44:00
12:14:00
12:14:00
12:44:00
12:44:00
13:14:00
13:14:00
13:44:00
13:44:00
14:14:00
14:14:00
14:44:00
14:44:00
15:14:00
Date:

Oct-17
* Based on Prochet Method
Percolation Project Number: 11813.001
Leighton
Test Data
Project Name: Golden Meadows
P-3

30.00 0.00 0.25 0.25 0.072 120.000

30.00 0.00 0.00 0.00 0.000 N/A

30.00 0.00 0.25 0.25 0.072 120.000

30.00 0.00 0.00 0.00 0.000 N/A

30.00 0.00 0.25 0.25 0.072 120.000

30.00 0.00 0.25 0.25 0.072 120.000

30.00 0.00 0.25 0.25 0.072 120.000

30.00 0.00 0.50 0.50 0.145 60.000

30.00 0.00 0.50 0.50 0.145 60.000

30.00 0.00 0.75 0.75 0.220 40.000

25.00 0.00 0.75 0.75 0.264 33.333
inches/hour* minute/inch

25.00 0.00 1.00 1.00 0.356 25.000
USCS Soil Type: Brown Silty SAND Diameter (in.) Sunny ~90 Time ∆t (min) Initial Water Depth
(inches)
Final Water Depth
(inches)
Change In Water Level
(inches)
Infiltration/Percolation
Rate
Tested by: BSS Date Tested 10/6/2017
Soil Unit: Alluvium (Qal) Depth of Test Hole (in.)
Test Hole Number: P-3 Project Golden Meadows
Date Excavated: 10/4/2017 Project Number 11813.001

0.000

0.050

0.100

0.150

0.200

0.250

0.300

0.350

0.400
0 50 100 150 200 250 300 350 400
Infiltration Rate
(in./hr)
Time (min)
1650-6''50-6''
50-0.5''
SMB-1R-1
R-2
R-3
QUATERNARY ALLUVIUM (Qal)SILTY SAND, medium dense, light brown, dry to moist, finesanddense, reddish brown, moist, fine sand, porousSILTY SAND, very dense, olive brown, moist, fine to coarsesand, highly weathered rockGRANITIC BEDROCK (Kgr)Difficult drillingWell-graded SAND with SILT, very dense, light olive brown, dryto moist, fine to coarse sand, (no recovery)Drilled to 12' Sampled to 12' Groundwater not encounteredBackfilled with soil cuttings (10/4/17) Hole Diameter
Moisture
Ground Elevation
Depth
Blows
Elevation
Per 6 Inches

1535'

BULK SAMPLECORE SAMPLEGRAB SAMPLERING SAMPLESPLIT SPOON SAMPLETUBE SAMPLEBCGRST BSSHollow Stem Auger - 140lb - Automatic - 30" Drop
Soil Class.
10-4-17
SOIL DESCRIPTIONSampled ByDrilling Co.Drilling Co.ProjectProject No.See Figure 1Golden Meadows11813.001Drilling Method8" Sample No.

FeetAttitudes
SAMPLE TYPES:

Martini Drilling
* * * This log is a part of a report by Leighton and should not be used as a stand-alone document. * * * Content, %
GEOTECHNICAL BORING LOG LB-1Logged ByDate DrilledBSS
FeetS
(U.S.C.S.)
Log
Type of Tests
Graphic
pcfLocation
Dry DensityN This Soil Description applies only to a location of the exploration at thetime of sampling. Subsurface conditions may differ at other locationsand may change with time. The description is a simplification of theactual conditions encountered. Transitions between soil types may begradual.

TYPE OF TESTS:-200ALCNCOCRCU% FINES PASSINGATTERBERG LIMITSCONSOLIDATIONCOLLAPSECORROSIONUNDRAINED TRIAXIALDSEIHMDPPRVDIRECT SHEAREXPANSION INDEXHYDROMETERMAXIMUM DENSITYPOCKET PENETROMETERR VALUESASESGUCSIEVE ANALYSISSAND EQUIVALENTSPECIFIC GRAVITYUNCONFINED COMPRESSIVE STRENGTH 1535
1530
1525
1520
1515
1510
1505
0 5
10 15
20 25
30 SM
SP-SM
QUATERNARY ALLUVIUM (Qal)SILTY SAND, medium dense, reddish brown, dry to moist, fineto coarse grained sand Poorly graded SAND with SILT, dense, light olive brown, dry tomoist, fine to medium sand, formationGRANITIC BEDROCK (Kgr)Hard drillingWell graded SAND, very dense, light brown, dry to moist, fine tocoarse sandDrilled to 9' Groundwater not encountered Backfilled with soilcuttings (10/4/17) Hole Diameter
Moisture
Ground Elevation
Depth
Blows
Elevation
Per 6 Inches

1535'

BULK SAMPLECORE SAMPLEGRAB SAMPLERING SAMPLESPLIT SPOON SAMPLETUBE SAMPLEBCGRST BSSHollow Stem Auger - 140lb - Autohammer - 30" Drop
Soil Class.
10-4-17
SOIL DESCRIPTIONSampled ByDrilling Co.Drilling Co.ProjectProject No.See Figure 1Golden Meadows11813.001Drilling Method8" Sample No.

FeetAttitudes
SAMPLE TYPES:

Martini Drilling
* * * This log is a part of a report by Leighton and should not be used as a stand-alone document. * * * Content, %
GEOTECHNICAL BORING LOG P-1Logged ByDate DrilledBSS
FeetS
(U.S.C.S.)
Log
Type of Tests
Graphic
pcfLocation
Dry DensityN This Soil Description applies only to a location of the exploration at thetime of sampling. Subsurface conditions may differ at other locationsand may change with time. The description is a simplification of theactual conditions encountered. Transitions between soil types may begradual.

TYPE OF TESTS:-200ALCNCOCRCU% FINES PASSINGATTERBERG LIMITSCONSOLIDATIONCOLLAPSECORROSIONUNDRAINED TRIAXIALDSEIHMDPPRVDIRECT SHEAREXPANSION INDEXHYDROMETERMAXIMUM DENSITYPOCKET PENETROMETERR VALUESASESGUCSIEVE ANALYSISSAND EQUIVALENTSPECIFIC GRAVITYUNCONFINED COMPRESSIVE STRENGTH 1535
1530
1525
1520
1515
1510
1505
0 5
10 15
20 25
30 SMQUATERNARY ALLUVIUM (Qal)SILTY SAND, dense, brown, moist, fine sand Drilled to 4' Groundwater not encountered Backfilled with soilcuttings (10/5/17) Hole Diameter
Moisture
Ground Elevation
Depth
Blows
Elevation
Per 6 Inches

1534'

BULK SAMPLECORE SAMPLEGRAB SAMPLERING SAMPLESPLIT SPOON SAMPLETUBE SAMPLEBCGRST BSSHollow Stem Auger - 140lb - Autohammer - 30" Drop
Soil Class.
10-4-17
SOIL DESCRIPTIONSampled ByDrilling Co.Drilling Co.ProjectProject No.See Figure 1Golden Meadows11813.001Drilling Method8" Sample No.

FeetAttitudes
SAMPLE TYPES:

Martini Drilling
* * * This log is a part of a report by Leighton and should not be used as a stand-alone document. * * * Content, %
GEOTECHNICAL BORING LOG P-2Logged ByDate DrilledBSS
FeetS
(U.S.C.S.)
Log
Type of Tests
Graphic
pcfLocation
Dry DensityN This Soil Description applies only to a location of the exploration at thetime of sampling. Subsurface conditions may differ at other locationsand may change with time. The description is a simplification of theactual conditions encountered. Transitions between soil types may begradual.

TYPE OF TESTS:-200ALCNCOCRCU% FINES PASSINGATTERBERG LIMITSCONSOLIDATIONCOLLAPSECORROSIONUNDRAINED TRIAXIALDSEIHMDPPRVDIRECT SHEAREXPANSION INDEXHYDROMETERMAXIMUM DENSITYPOCKET PENETROMETERR VALUESASESGUCSIEVE ANALYSISSAND EQUIVALENTSPECIFIC GRAVITYUNCONFINED COMPRESSIVE STRENGTH 1530
1525
1520
1515
1510
1505
0 5
10 15
20 25
30 SMQUATERNARY ALLUVIUM (Qal)SILTY SAND, loose, light brown, dry, fine sandTotal Depth 1' Groundwater not encountered Backfilled withsoil cuttings (10/5/17) Hole Diameter
Moisture
Ground Elevation
Depth
Blows
Elevation
Per 6 Inches

1531'

BULK SAMPLECORE SAMPLEGRAB SAMPLERING SAMPLESPLIT SPOON SAMPLETUBE SAMPLEBCGRST BSSHollow Stem Auger - 140lb - Autohammer - 30" Drop
Soil Class.
10-4-17
SOIL DESCRIPTIONSampled ByDrilling Co.Drilling Co.ProjectProject No.See Figure 1Golden Meadows11813.001Drilling Method8" Sample No.

FeetAttitudes
SAMPLE TYPES:

Martini Drilling
* * * This log is a part of a report by Leighton and should not be used as a stand-alone document. * * * Content, %
GEOTECHNICAL BORING LOG P-3Logged ByDate DrilledBSS
FeetS
(U.S.C.S.)
Log
Type of Tests
Graphic
pcfLocation
Dry DensityN This Soil Description applies only to a location of the exploration at thetime of sampling. Subsurface conditions may differ at other locationsand may change with time. The description is a simplification of theactual conditions encountered. Transitions between soil types may begradual.

TYPE OF TESTS:-200ALCNCOCRCU% FINES PASSINGATTERBERG LIMITSCONSOLIDATIONCOLLAPSECORROSIONUNDRAINED TRIAXIALDSEIHMDPPRVDIRECT SHEAREXPANSION INDEXHYDROMETERMAXIMUM DENSITYPOCKET PENETROMETERR VALUESASESGUCSIEVE ANALYSISSAND EQUIVALENTSPECIFIC GRAVITYUNCONFINED COMPRESSIVE STRENGTH 1530
1525
1520
1515
1510
1505
0 5
10 15
20 25
30 41715 Enterprise Circle N. Suite 103 ■ Temecula CA 92590-5626 (951) 296-0530 ■ Fax (951) 296-0534 ■ www.leightongroup.com

October 31, 2012

Project No. 110712-008

RICHLAND COMMUNITIES, INC
4100 NEWPORT PLACE DRIVE
Newport Beach, CA 92672

Attention: Mr. Mike Byer

Subject: Results of Onsite Percolation Testing
Proposed Storm Water Infiltration Basins
Golden Meadows, Tract 31194
City of Menifee, Riverside County, California

References: Design Handbook for Low Impact Development Best Management Practices, Riverside County Flood Control and Water Conservation District (District) , dated September 2011.

Various Site/Drainage Plans, Tentative Tract 31194 , by Hunsaker and Associates, (undated).

Geotechnical Review of Rough Grading Plans, Tract 31194, Menifee, County of Riverside, California, by Leighton and Associates, Inc., PN. 110712-002, dated January 30, 2004.

In accordance with your request and authorization, Leighton and Associates, Inc. (Leighton) is pleased to provide this report presenting the results of our percolation testing for the proposed storm water infiltration basins associated with the subject Tract.

The location of field tests was primarily dedicated by Hunsaker and Associates Tentative Tract map, site accessibility and/or prevailing subsurface conditions during field testing.

P U R P O S E A N D S C O P E O F W O R K
The purpose of our testing was to determine the infiltration rates of onsite soils with respect to the proposed storm water retention basins as depicted on the referenced rough grading plans. Services provided for this study consisted of the following:

Results of Onsite Percolation Testing October 31, 2012
Proposed Storm Water Infiltration Basins Golden Meadows, Tract 31194 Project No. 110712-008

- 2 -
 Drilling, sampling and logging of two exploratory borings within the proposed storm water basin areas.
 Field percolation testing at 4 locations within park site (Lot 488) and one location within park site/basin (Lot 487) in accordance with the procedures outlined in District’s Design Handbook, referenced above.
 Compilation of this report that presents the results of our percolation/infiltration testing and laboratory test results.

S I T E D E S C R I P T I O N
The proposed residential development (Tract 31194) is located southeast of Evans Road and Garbani Road in Menifee, California. The site is generally undeveloped and appeared to be used for agricultural purposes.

Topographically, the central and southeastern portions of the site are relatively flat lying while the northern region of the property is characterized by relatively steep hills . A small, northwest-trending drainage channel extends through the northwestern and central portion of the property. A knoll also exists near the southeast corner of the property. Site elevations range from approximately 1,720 feet above mean sea level (msl) in the northeastern corner of the site to approximately 1,500 feet (msl) at the northwestern portion of the site.

S U B S U R F A C E I N V E S T I G A T I O N
Our field investigation consisted of excavating two deep exploratory borings and five percolation tests
on October 23, 2012 utilizing a truck mounted CME 75 drill rig equipped with an 8-inch hollow-stem auger. The exploratory borings were continuously logged to a minimum depth of 10 feet below bottom of the proposed storm water basins unless encountering refusal . Representative samples were collected for further field and laboratory classification. A staff geologist from our office logged and observed all excavations. The locations of the exploratory borings and percolation test holes are shown on Figure 2. The logs of the exploratory borings are included in Appendix A.

S O I L S A N D G R O U N D W A T E R C O N D I T I O N S Based on the results of this study and review of our previous geotechnical investigation report referenced above, the site is underlain by granitic bedrock which is in turn mantled

Results of Onsite Percolation Testing October 31, 2012
Proposed Storm Water Infiltration Basins Golden Meadows, Tract 31194 Project No. 110712-008

- 3 -
with a variable thickness of alluvial deposits. Within Lot 488, alluvium was encountered in our Boring B-1 to a depth of approximately 8 feet below ground surface (BGS). The se alluvial soils are classified as silty sand (SM) with gravel. Within Lot 487, the alluvium extends to a depth of approximately 11 feet BGS. Groundwater was not encountered in any of our borings or within a depth of 10 feet below bottom of either basin.

P E R C O L A T I O N T E S T R E S U L T S
The percolation tests were performed in accordance with the procedures of Section 2.3 of the Riverside County Flood Control and Water Conservation District Design Handbook (RCFC&WCD, 2011). Results reported below are the most conservative reading in minutes per inch drop. The infiltration rates were estimated using the Prochet Method. Field test data are included in Appendix A.

Summary of Percolation/Infiltration Test Results
Location
Test
Hole
#
Ex. Ground
Surface
Elev. (ft)
Depth
BGS
(ft)
Percolation
Rate
(min/in)
Infiltration
Rate
(in/hr)
Soil Description
Lot 488
P-1 1523 9.0 42.9 0.12 Weathered Granitic Rock
P-2 1527 9.5 9.1 0.67 Silty sand (SM)
Alluvium/Rock
P-3 1520 2.5 8.1 1.15 Silty sand (SM) / Alluvium/
Granitic Rock
P-4 1518 2.5 4.2 2.14 Silty sand (SM) / Alluvium

Lot 487 P-5 1518 2.5 4.5 1.86 Clayey sand (SC) / Alluvium

C O N C L U S I O N S A N D R E C O M M E N D A T I O N S As summarized above , the locations tested appear suitable for onsite infiltration provided bottom of basins is within 3 feet of exiting ground surface (rates varying from

1.15 to 2.14 in/hr). The proposed “flow diversion” structur es are likely to be embedded in weathered granitic rock (~9 to 10 feet BGS) and the infiltration rates should be expected to range from 0.12 to 0.67 in/hr based on tests P-1 and P-2.

Based on the above, we recommend that the proposed basins be sized/desi gned to allow for at least 5 feet of permeable alluvial soils to remain below the bottom of basins.

As such, the bottom of basins at the locations tested should not extend more than 3 feet BGS.

Results of Onsite Percolation Testing October 31, 2012
Proposed Storm Water Infiltration Basins Golden Meadows, Tract 31194 Project No. 110712-008

- 4 -

L I M I T A T I O N S
This report was based in part on data obtained from a limited number of observations, soil excavations, samples and tests. Such information is, by necessity, incomplete.

The nature of many sites is such that differing soil or geologic conditions can be present within small distances and under varying climatic conditions. Changes in subsurface conditions can and do occur over time. Please notify the engineer if event conditions encountered during construction are different than those described or reflected in this report.

This report was prepared for the sole use of Client and their design team, for application to design of the proposed infiltration basins, in accordance with generally accepted geotechnical engineering practices at this time in California. In addition, since this is subject to review by Riverside County, we recommend that data in this report be only used in the design of this project after review and approval by County , where applicable. Any premature (before County approval) or unauthorized use of or reliance on this report constitutes an agreement to defend and indemnify Leighton from and against any liability which may arise as a result of such use or reliance, regardless of any fault, negligence, or strict liability of Leighton.

If you have any question, please do not hesitate to contact this office. We appreciate this opportunity to be of service.

Respectfully submitted,
LEIGHTON AND ASSOCIATES, INC.

Simon I. Saiid, PE, GE Robert F. Riha, PG, CEG
Principal Engineer Sr. Principal Geologist
Extension 8013, [email protected] Extension 8914, [email protected]

Attachments: Figure 1 – Percolation Test Location Plan
Appendix A – Perc Data Test Sheets, Log of Exploratory Borings & Laboratory Test Results

Distribution: (1) Addressee (one PDF copy via email)
(2) Hunsaker & Associates, Attention: Ben Etemadi
/X53/X69/X74/X65/X20/X50/X6C/X61/X6E/X20
/X47/X6F/X6C/X64/X65/X6E/X20/X4D/X65/X61/X64/X6F/X77/X73/X20/X20 /X54/X72/X61/X63/X74/X20/X33/X31/X31/X39/X34/X20
/X4D/X65/X6E/X69/X66/X65/X65/X2C/X20/X52/X69/X76/X65/X72/X73/X69/X64/X65/X20/X43/X6F/X75/X6E/X74/X79/X2C/X20/X43/X41 /X50/X2D/X31
/X50/X2D/X32
/X50/X2D/X33
/X50/X2D/X34
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/X42/X2D/X31/X42/X2D/X32
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/X50/X2D/X35

Results of Onsite Percolation Testing October 31, 2012
Proposed Storm Water Infiltration Basins Golden Meadows, Tract 31194 Project No. 110712-008

APPENDIX A

Percolation Data Sheets
Log of Exploratory Borings
Laboratory Test Results / Grain Size Analysis
108
9 °
10:32:00
11:02:00
11:03:00
11:33:00
11:33:00
12:03:00
12:04:00
12:34:00
12:35:00
1:05:00
1:05:00
1:36:00
1:36:00
2:06:00
2:06:00
2:36:00
2:37:00
3:07:00
3:07:00
3:37:00
10/23/2012 Project Number
Date Tested

0.126
Diameter (in.)

13.636

20.000
Sunny ~65
minute/inch

37.500

0.266

33.333

42.857

33.333
Tract 31194
110712-008
10/24/2012
Ex El ~1523' msl

0.165

42.8570.125

21.429
inches/hour*

0.118 46.154

0.147
Infiltration/Percolation
Rate

0.395

0.252

0.70 0.90

84.20 82.70

85.90 0.130

0.166
Final Water Depth
(inches)
Brown Silty Sand with Gravel
Change In Water Level
(inches)

85.20 P-1
BSS
Depth of Test Hole (in.)
Project
Granitic Bedrock

86.30 Time Δt (min)
Test Hole Number:

Date Excavated:

Soil Unit:

USCS Soil Type:

Tested by:

87.30 85.30

85.60 84.90

85.70 86.10

85.40 2.20

1.50 1.40

0.90 85.40

0.70 0.70

0.65 30.00

30.00 30.00

30.00 30.00
Initial Water Depth
(inches)

86.40 86.30

30.00 30.00

30.00 85.70

84.60 Project Number:
* Based on Prochet Method

42.857
Leighton
Oct-12
Basin 1
Percolation
Test Data
Golden Meadows
110712-008
Date:

Project Name:

P-1

86.20 84.10

0.80 85.05

30.00 30.00

0.000

0.050

0.100

0.150

0.200

0.250

0.300

0.350

0.400

0.450
30 60 90 120 150 180 210 240 270 300 330 360
Infiltration Rate
(in./hr)
Time (min)
114
9 °
10:20:00
10:50:00
10:50:00
11:20:00
11:22:00
11:52:00
11:53:00
12:23:00
12:24:00
12:54:00
12:54:00
1:24:00
1:25:00
1:55:00
1:56:00
2:26:00
2:27:00
2:57:00
2:57:00
3:27:00
Ex El ~1520' msl
Sunny ~75
Leighton

7.317

7.692

8.108

7.895

9.375
*Based on Prochet Method
Date:

30.00 Oct-12
Tract 30972
110712-008
10/24/2012

3.70 0.752 8.333

0.839
Basin 1 Project Name: Golden Meadows
P-2
Percolation Project Number: 110712-008
Test Data

3.60 3.25

0.674

9.091

9.2310.683

30.00 96.50 93.30 3.20

30.00 30.00

96.50 30.00 96.45 93.20

95.30 91.60

96.50 92.70 3.80 0.790

30.00 96.40 93.10 3.30 0.691

92.90 30.00 97.20 93.30 3.90 0.836

0.730

1.239

30.00 96.10 90.30 5.80

30.00 96.30 92.20 4.10

1.132

4.688

5.172

30.00 96.20 89.80 6.40
Change In Water Level
(inches)
Infiltration/Percolation
Rate
Inches/hour* minute/inch
Time Δt (min) Initial Water Depth
(inches)
Final Water Depth
(inches)
Diameter (in.)
Tested by: BSS Date Tested
Soil Unit: Alluvium (Qal)/Kgr
USCS Soil Type:

Test Hole Number: P-2 Project
Date Excavated: 10/23/2012 Project Number
Dark Brown Silty Sand (SM)
Depth of Test Hole (in.)

0.000

0.200

0.400

0.600

0.800

1.000

1.200

1.400
30 60 90 120 150 180 210 240 270 300 330 360
Infiltration Rate
(in./hr)
Time (min)

30 8 °
10:43:00
11:13:00
11:14:00
11:44:00
11:45:00
12:15:00
12:16:00
12:46:00
12:47:00
1:17:00
1:17:00
1:47:00
1:48:00
2:18:00
2:18:00
2:48:00
2:49:00
3:19:00
3:19:00
3:49:00
Leighton

1.156

21.00 1.179
Ex El ~1520.5' msl
Sunny ~75

1.178
Date: Oct-12 Leighton
110712-008
Basin 1

30.00 Tract 30972
110712-008
10/24/2012

8.108
Test Data

8.21930.00 21.20 17.55
Project Name: Golden Meadows
P-3

30.00 Percolation Project Number:

21.25 8.33317.65 3.60

17.20 3.80 7.895

1.147

21.20 17.10 4.10

3.65 30.00

30.00 21.30 17.60 3.70

30.00 21.00 16.80 4.20 1.282

1.276 7.317

1.266

7.143

1.360

7.317

6.97730.00 21.50 17.20 4.30

30.00 21.20 16.30 4.90

30.00 21.10 17.00 4.10

1.479

4.918

6.122

1.870
Time Δt (min) Initial Water Depth
(inches)
Final Water Depth
(inches)
Change In Water Level
(inches)
Infiltration/Percolation
Rate

30.00 22.00 15.90 6.10
Inches/hour* minute/inch
USCS Soil Type: Brown Silty Sand with Gravel Diameter (in.) Tested by: BSS Date Tested
Soil Unit: Alluvium (Qal) Depth of Test Hole (in.)
Test Hole Number: P-3 Project
Date Excavated: 10/23/2012 Project Number

0.000

0.500

1.000

1.500

2.000
30 60 90 120 150 180 210 240 270 300 330 360
Infiltration Rate
(in./hr)
Time (min)

30 8 °
10:45:00
11:15:00
11:16:00
11:46:00
11:47:00
12:17:00
12:18:00
12:48:00
12:49:00
1:19:00
1:20:00
1:50:00
1:51:00
2:21:00
2:22:00
2:52:00
2:53:00
3:23:00
3:23:00
3:53:00
*Based on Prochet Method

2.160

22.50 2.165
Ex El ~1517' msl
Sunny ~75

2.176
Date: Oct-12 Leighton
110712-008
Basin 1

30.00 Tract 31194
110712-008
10/24/2012

4.167
Test Data

4.22530.00 22.40 15.30
Project Name: Golden Meadows
P-4

30.00 Percolation Project Number:

22.30 4.22515.20 7.10

15.40 7.10 4.225

2.143

22.60 14.90 7.70

7.10 30.00

30.00 22.30 15.10 7.20

30.00 22.30 13.90 8.40 2.417

2.325 3.896

2.863

3.571

2.574

2.804

3.22630.00 22.20 12.90 9.30

30.00 22.30 10.90 11.40

30.00 22.40 11.70 10.70

2.961

2.542

2.632

3.168
Time Δt (min) Initial Water Depth
(inches)
Final Water Depth
(inches)
Change In Water Level
(inches)
Infiltration/Percolation
Rate

30.00 23.00 11.20 11.80
Inches/hour* minute/inch
USCS Soil Type: Brown Silty Sand (SM) Diameter (in.)
Tested by: BSS Date Tested
Soil Unit: Alluvium (Qal) Depth of Test Hole (in.)
Test Hole Number: P-4 Project
Date Excavated: 10/23/2012 Project Number

0.000

0.500

1.000

1.500

2.000

2.500

3.000

3.500
30 60 90 120 150 180 210 240 270 300 330 360
Infiltration Rate
(in./hr)
Time (min)

30 8 °
10:25:00
10:55:00
10:55:00
11:25:00
11:26:00
11:56:00
11:57:00
12:27:00
12:27:00
12:57:00
12:58:00
13:28:00
13:28:00
13:58:00
13:58:00
14:28:00
14:29:00
14:59:00
14:59:00
15:29:00
*Based on Prochet Method

1.872

22.00 1.868
Ex El ~1518' msl
Sunny ~74

1.939
Date: Oct-12 Leighton
110712-008
Basin 2

30.00 Tract 31194
110712-008
12/24/2012

4.478
Test Data

4.54530.00 21.20 14.60
Project Name: Golden Meadows
P-5

30.00 Percolation Project Number:

21.10 4.54514.50 6.60

15.60 6.40 4.688

1.859

21.50 14.80 6.70

6.60 30.00

30.00 21.00 14.30 6.70

30.00 22.00 14.40 7.60 2.203

1.935 4.478

2.464

3.947

2.074

3.371

3.89630.00 21.00 13.30 7.70

30.00 22.00 11.30 10.70

30.00 22.00 13.10 8.90

2.788

2.655

2.804

2.799
Time Δt (min) Initial Water Depth
(inches)
Final Water Depth
(inches)
Change In Water Level
(inches)
Infiltration/Percolation
Rate

30.00 21.50 10.20 11.30
Inches/hour* minute/inch
USCS Soil Type: Dark Brown Silty SAND Diameter (in.)
Tested by: JTD Date Tested
Soil Unit: Alluvium (Qal) Depth of Test Hole (in.)
Test Hole Number: P-5 Project
Date Excavated: 10/23/2012 Project Number

0.000

0.500

1.000

1.500

2.000

2.500

3.000
30 60 90 120 150 180 210 240 270 300 330 360
Infiltration Rate
(in./hr)
Time (min)

SM
(SM)g
GP
SAS-1
S-2
QUATERNARY ALLUVIUM (Qal)
SILTY SAND (SM), medium dense, light yellowish brown, dry, fine sand
dense, brown, dry to moist
GRANITIC BEDROCK (Kgr)
Completely to highly weathered Granitic Rock, breaks into:

SILTY SAND with gravel (SM), very dense, light brown, dry, fine to medium sand, weathered (13% fines, 17% gravel)
GRAVEL with silt and sand (GP), very dense, light brown, moist, coarse sand, weathered
Refusal @ 18' (Bedrock)
No Caving or Groundwater
Backfilled with Spoils
50-3"
50-1.5"
1515
1510
1505
1500
1495
1490
Hole Diameter
Moisture
Ground Elevation
Depth
0 5
10 15
20 25
30 Blows
Elevation
Per 6 Inches

1518'

BULK SAMPLE

CORE SAMPLE

GRAB SAMPLE

RING SAMPLE

SPLIT SPOON SAMPLE

TUBE SAMPLE
B
C
G
R
S
T
BSS
Hollow Stem Auger - 140lb - Auto Hammer - 30" Drop
Soil Class.
10-23-12

SOIL DESCRIPTION
Sampled By
Drilling Co.Drilling Co.

Project
Project No.

See Boring Location Map
Richland Tract 31194
110712008
Drilling Method
8"
Sample No.

Feet
Attitudes
SAMPLE TYPES:
2R Drilling, Inc.
* * * This log is a part of a report by Leighton and should not be used as a stand-alone document. * * * Content, %
GEOTECHNICAL BORING LOG B-1
Logged By
Date Drilled
BSS
Feet
S
(U.S.C.S.)
Log
Type of Tests
Graphic
pcf
Location
Dry Density
N
This Soil Description applies only to a location of the exploration at the time of sampling. Subsurface conditions may differ at other locations and may change with time. The description is a simplification of the actual conditions encountered. Transitions between soil types may be gradual.

TYPE OF TESTS:
-200
AL
CN
CO
CR
CU
% FINES PASSING

ATTERBERG LIMITS

CONSOLIDATION

COLLAPSE

CORROSION

UNDRAINED TRIAXIAL
DS
EI
H
MD
PP
RV

DIRECT SHEAR

EXPANSION INDEX

HYDROMETER

MAXIMUM DENSITY

POCKET PENETROMETER

R VALUE
SA
SE
SG
UC

SIEVE ANALYSIS

SAND EQUIVALENT

SPECIFIC GRAVITY

UNCONFINED COMPRESSIVE STRENGTH

SM
SC SAS-1
S-2
QUATERNARY ALLUVIUM (Qal)
SILTY SAND (SM), medium dense, dark brown, dry to moist, fine sand
QUATERNARY OLDER ALLUVIUM (Qaol)
CLAYEY SAND (SC), stiff, olive brown, moist, weathered (29% fines)
CLAYEY SAND (SC), very dense, olive gray to brown, moist, fine to medium sand
GRANITIC BEDROCK (Kgr)
Refusal @ 11.1' (Bedrock)
No Caving or Groundwater
Backfilled with Spoils
9 18
12 10
19 50-1"
1520
1515
1510
1505
1500
1495
1490
Hole Diameter
Moisture
Ground Elevation
Depth
0 5
10 15
20 25
30 Blows
Elevation
Per 6 Inches

1520'

BULK SAMPLE

CORE SAMPLE

GRAB SAMPLE

RING SAMPLE

SPLIT SPOON SAMPLE

TUBE SAMPLE
B
C
G
R
S
T
BSS
Hollow Stem Auger - 140lb - Auto Hammer - 30" Drop
Soil Class.
10-23-12

SOIL DESCRIPTION
Sampled By
Drilling Co.Drilling Co.

Project
Project No.

See Boring Location Map
Richland Tract 31194
110712008
Drilling Method
8"
Sample No.

Feet
Attitudes
SAMPLE TYPES:
2R Drilling, Inc.
* * * This log is a part of a report by Leighton and should not be used as a stand-alone document. * * * Content, %
GEOTECHNICAL BORING LOG B-2
Logged By
Date Drilled
BSS
Feet
S
(U.S.C.S.)
Log
Type of Tests
Graphic
pcf
Location
Dry Density
N
This Soil Description applies only to a location of the exploration at the time of sampling. Subsurface conditions may differ at other locations and may change with time. The description is a simplification of the actual conditions encountered. Transitions between soil types may be gradual.

TYPE OF TESTS:
-200
AL
CN
CO
CR
CU
% FINES PASSING

ATTERBERG LIMITS

CONSOLIDATION

COLLAPSE

CORROSION

UNDRAINED TRIAXIAL
DS
EI
H
MD
PP
RV

DIRECT SHEAR

EXPANSION INDEX

HYDROMETER

MAXIMUM DENSITY

POCKET PENETROMETER

R VALUE
SA
SE
SG
UC

SIEVE ANALYSIS

SAND EQUIVALENT

SPECIFIC GRAVITY

UNCONFINED COMPRESSIVE STRENGTH

Project Name: Tested By: JAP Date: 10/25/12
Project No.: 110712-008 Checked By: JMB Date: 10/26/12
Exploration No.: B-1 Depth (feet): 10.0
Sample No.: S-1
Soil Identification: SILTY SAND WITH LITTLE GRAVEL (SM)g, light brown.

X-35 545.2
545.2 535.5
144.2 144.2
391.3 2.5
X-35
485.4
144.2
341.2
(in.) (mm.)
3" 75.000
1" 25.000
3/4" 19.000
1/2" 12.500
3/8" 9.500
#4 4.750
#8 2.360
#16 1.180
#30 0.600
#50 0.300
#100 0.150
#200 0.075
GRAVEL: 17 %
SAND: 70 %
FINES: 13 %
GROUP SYMBOL: (SM)g N/A
N/A
Remarks:

PARTICLE-SIZE DISTRIBUTION (GRADATION)
ASTM D 6913
Container No.:

GOLDEN MEADOWS
of SOILS USING SIEVE ANALYSIS
Moisture Content of Total Air - Dry Soil
Wt. of Container No._____ (g)
Wt. of Air-Dried Soil + Cont.(g)
Moisture Content (%)
100.0
Dry Wt. of Soil (g)
Cumulative Weight
Dry Soil Retained (g)
100.0
Cu = D60/D10 =
Cc = (D30)²/(D60*D10) =

0.0 10.8

66.3 97.6
Percent Passing (%)
Wt. of Air-Dry Soil + Cont. (g)
After Wet Sieve Wt. of Dry Soil + Container (g)
Wt. of Container (g)
Dry Wt. of Soil Retained on # 200 Sieve (g)
Wt. of Dry Soil + Cont. (g)
Container No.

Wt. of Container (g)
U. S. Sieve Size
**
339.4

25.1 PAN
292.9

33.5260.3
213.8

13.3 317.9 18.8

97.2 83.1

45.4 61.9149.0

9.3 100.0

S-1
Oct-1217 : 70 : 13
Project Name:

PARTICLE - SIZE

DISTRIBUTION
ASTM D 6913
Soil Identification: SILTY SAND WITH LITTLE GRAVEL (SM)g, light brown. (SM)g
GR:SA:FI : (%)
Exploration No.:

Depth (feet): 10.0
SAND

SILT FINE

HYDROMETER

GOLDEN MEADOWS
Project No.:

B-1 Sample No.:

Soil Type :
110712-008

3.0" 1 1/2" 3/4" 3/8" #4 #8 #16 #30 #50 #100 #200 U.S. STANDARD SIEVE OPENING U.S. STANDARD SIEVE NUMBER

GRAVEL FINES

FINE CLAY COARSE COARSE MEDIUM
0 10
20 30
40 50
60 70
80 90
100

0.0010.0100.1001.00010.000100.000

PERCENT FINER BY WEIGHT
PARTICLE - SIZE (mm)
"

Sieve Landscape; B-1, S-1 ( 10-23-12 )
Project Name: Tested By: JAP Date: 10/25/12
Project No.: 110712-008 Checked By: JMB Date: 10/26/12
Exploration No.: B-2 Depth (feet): 5.0
Sample No.: S-1
Soil Identification: CLAYEY SAND WITH TRACE GRAVEL (SC), yellowish brown.

KR 684.8
684.8 613.0
158.9 158.9
454.1 15.8
KR
484.8
158.9
325.9
(in.) (mm.)
3" 75.000
1" 25.000
3/4" 19.000
1/2" 12.500
3/8" 9.500
#4 4.750
#8 2.360
#16 1.180
#30 0.600
#50 0.300
#100 0.150
#200 0.075
GRAVEL: 3 %
SAND: 68 %
FINES: 29 %
GROUP SYMBOL: SC N/A
N/A
Remarks:

PARTICLE-SIZE DISTRIBUTION (GRADATION)
ASTM D 6913
Container No.:

GOLDEN MEADOWS
of SOILS USING SIEVE ANALYSIS
Moisture Content of Total Air - Dry Soil
Wt. of Container No._____ (g)
Wt. of Air-Dried Soil + Cont.(g)
Moisture Content (%)
100.0
Dry Wt. of Soil (g)
Cumulative Weight
Dry Soil Retained (g)
100.0
Cu = D60/D10 =
Cc = (D30)²/(D60*D10) =

0.0 12.3
100.0
Percent Passing (%)
Wt. of Air-Dry Soil + Cont. (g)
After Wet Sieve Wt. of Dry Soil + Container (g)
Wt. of Container (g)
Dry Wt. of Soil Retained on # 200 Sieve (g)
Wt. of Dry Soil + Cont. (g)
Container No.

Wt. of Container (g)
U. S. Sieve Size
**
324.8

42.7 PAN
260.1

52.3216.4
158.4

28.5 296.5 34.7
100.0

97.3 65.1

81.683.6
100.0

S-1
Oct-123 : 68 : 29
Project Name:

PARTICLE - SIZE

DISTRIBUTION
ASTM D 6913
Soil Identification: CLAYEY SAND WITH TRACE GRAVEL (SC), yellowish brown.

SC
GR:SA:FI : (%)
Exploration No.:

Depth (feet): 5.0
SAND

SILT FINE

HYDROMETER

GOLDEN MEADOWS
Project No.:

B-2 Sample No.:

Soil Type :
110712-008

3.0" 1 1/2" 3/4" 3/8" #4 #8 #16 #30 #50 #100 #200 U.S. STANDARD SIEVE OPENING U.S. STANDARD SIEVE NUMBER

GRAVEL FINES

FINE CLAY COARSE COARSE MEDIUM
0 10
20 30
40 50
60 70
80 90
100

0.0010.0100.1001.00010.000100.000

PERCENT FINER BY WEIGHT
PARTICLE - SIZE (mm)
"

Sieve Landscape; B-2, S-1 ( 10-23-12 )
- 33 -

Appendix 4: Historical Site Conditions
Phase I Environmental Site Assessment or Other Information on Past Site Use

NOT APPLICABLE
- 34 -

Appendix 5: LID Infeasibility
LID Technical Infeasibility Analysis

NOT APPLICABLE
- 35 -

Appendix 6: BMP Design Details
BMP Sizing, Design Details and other Supporting Documentation

RIVERSIDE COUNTY FLOOD

CONTROL AND WATER

CONSERVATION DISTRICT
Isohyetal Map
for the 85th Percentile
24 hour Storm Event
July 2011
Rain Gage Locations
D85 = 0.60
Date
D85= 0.60 inches
DMA
Type/ID
DMA Area
(square feet)
Post-Project Surface
Type
Effective
Imperivous
Fraction, If
DMA
Runoff
Factor
DMA Areas x
Runoff Factor
Design
Storm
Depth (in)
Design Capture
Volume, VBMP
(cubic feet)
Proposed
Volume on
Plans (cubic
feet)
A-1 Roof 412,000 Roofs 1 0.89 367504
A-2
Driveways 65,920 Concrete or Asphalt 1 0.89 58800.6
A-3
Pavement 658,876 Concrete or Asphalt 1 0.89 587717.4
A-4
Sidewalk 140,733 Concrete or Asphalt 1 0.89 125533.8
A-5
Parkway 161,310 Ornamental
Landscaping 0.1 0.11 17818
A-6 Slopes 423,953 Ornamental
Landscaping 0.1 0.11 46829
A-7
Turf 767,086 Ornamental
Landscaping 0.1 0.11 84730.8
A-8
Natural 1,428,998 Natural (A Soil) 0.03 0.06 89371.2
A-9
Basin
Bottom
31,401 Natural (A Soil) 0.03 0.06 1963.9
A-10
DG Trail 32,689 Decomposed Granite 0.4 0.28 9143.5
A-11
Open
Space
139,981 Ornamental
Landscaping 0.1 0.11 15462
1 1
1 1
1 1
1 1
1 1
1 1
1 4262947 1404874.2 0.60 70243.7 70500
Notes:

Company Project Number/Name Golden Meadows - Phase 4 - Major Modification BMP Identification
Drainage Management Area Tabulation
Design Rainfall Depth

BMP NAME / ID DMA 'A'
Must match Name/ID used on BMP Design Calculation Sheet Santa Ana Watershed - BMP Design Volume, VBMP
(Rev. 10-2011)
Legend:

Required Entries
Calculated Cells
(Note this worksheet shall only be used in conjunction with BMP designs from the LID BMP Design Handbook ) Company Name Hunsaker & Associates Nov 2021
Total
85th Percentile, 24-hour Rainfall Depth,
from the Isohyetal Map in Handbook Appendix E
Insert additional rows if needed to accommodate all DMAs draining to the BMP Designed by Brian Lowell Case No

No. DMA A
Company Name: Date: Nov 2021
Designed by: County/City Case No.:

Tributary Area (BMP Subarea) AT = 97.8638 acres
Enter VBMP, determined from Section 2.1 of this Handbook VBMP= 70,244 ft3 240 ft
160 ft
z = 4 :1
DB = 6.00 ft
DFB = 2.00 ft
DREQ = 10.7 ft
DO = 6.0 ft
BMP Subarea
Design Volume

Depth of freeboard (if used)
Minimum Required Allowance for Total Depth (including proposed basin depth, freeboard, minimum depth of bottom stage (DBS=0.33') Legend:

Basin Footprint
Width =
Length =
Overall Geometry
Length at Basin Bottom Surface
Width at Basin Bottom Surface
Side Slopes per "Basin Guidelines", Sect. 1.2

Proposed Basin Depth (with no freeboard)
and minimum filter depth (DFD=2.33'))
Depth from design water surface elevation to lowest orifice Required Entries
Calculated Cells
Hunsaker & Associates
Brian Lowell
Extended Detention Basin Design Procedure
Meets 1.5 : 1 requirement?

DTOT = 8.00 ft
Slope = 1.00 %
Slope = 1 %
VBasin = 100116 ft3
VFB = 3326 ft3
Forebay Depth (height of berm) DFBY = 1.5 ft
Minimum Forebay Surface Area AFB = 2217 ft2
W = 4.00 in

Basin Invert Transverse Slope (1% min)
Rectangular weir (notch)
Basin Design
Basin Design
Proposed Total Basin Depth (proposed depth plus freeboard) Basin Volume
Bottom Stage
Forebay Design
Basin Invert Longitudinal Slope
Forebay Volume (3 - 5% VBMP)

Depth = 24 inches
Width = 48 inches
Trench Invert Longitudinal Slope Slope = 1 %
Depth = 24 inches
Width = 18 inches
Slope = 1 %
S = 25 feet
DBS = 4 in
ABS = 630 ft2
210 ft3
Depth of ASTM-C33 sand (18 inch minimum)
Ds = 18 inches
Diameter of Subdrains
φ = 6 in s = 10 ft. on center
Width (48 inches minimum)
Dry Weather and Low-Flow Management
Low-Flow Trench (see graphic below)

Is VBS no less than 0.5% VBMP? OK
Collector Trenches (see graphic below)
Width (18 inches minimum)
Trench Invert Longitudinal Slope
Surface Area of Bottom Stage
Spacing (25 feet on center maximum)
Dry Weather Ponded Volume (above sand layer) VBS =
Depth (24 inches minimum, gravel filled)
Depth (24 inches minimum)
Subdrain Spacing
Depth of the Bottom Stage (4" minimum ponding)
Bottom Stage (Sand Filter) Design

Transverse Slope
(1% min)
AASHTO No. 2
Coarse aggregate
24" (min)
48" (min)
18" (min)
24" (min)
Low-Flow Trench Collector Trench
DBS
Outlet Design

0.0000 0.0000
Discharge Coefficient, 0.1203 0.004 0.74

0.1703 0.018 1.20
Default, C = 0.66 0.2085 0.026 0.50

0.2407 0.047 1.15
Other, C = 0.66 0.2692 0.078 1.47

0.2948 0.148 3.00

0.3184 0.210 2.43

0.3404 0.292 3.04

0.3611 0.459 5.75

0.3806 0.639 5.87

0.3992 0.819 5.59
d = 1.9 inches 0.4169 0.999 5.34

0.4339 1.243 6.92
n = 2 per row 0.4503 1.486 6.66

0.4661 1.730 6.43
N = 1 rows 0.4814 2.024

0.4963 2.319
Aeff = 0.039 ft2 per row 0.5106 2.614
or
Aeff = 5.668 in2
per row

25.75 hrs

56.09 hrs
∑ = 56.09
Notes:

Discharge
(cfs)
Volume
(acre-ft)
OK
number of orifice rows, N (from the bottom up).

OK
has drained from the basin(within 72 hours):

Orifice Diameter, d; number of orifices per row, n; and Time (100 %) =
From outflow hydrograph, the time where 100% VBMP
has drained from the basin (24 hour minimum):

Time (50%) =
From outflow hydrograph, the time where 50% of VBMP

9.67 7.67

10.00 5.67

9.33 3.67

8.67 8.33
Orifice Area (ft2)

6.67 9.00

8.00 7.33

7.00 6.33

6.00 2.00

1.67 2.33

4.33 4.00

3.00 2.67

3.33 4.67

5.33 5.00
Flow Rate, Q (cfs)
0 Assume an orifice area. Based on the
information provided above, the spreadsheet
provides discharge vs. stage data. Enter the
volume vs. stage data for each interval. This
information is used to route the volume through
the basin. The size of the orifice is acceptable
when the data shows that less than 50% of
VBMP has drained in 24 hours, and that 100%
drawdown occurs within 72 hours.

Q=CA[2g(H-Ho)]0.5
Basin Outlet Design
∆t (hrs.)Headwater Elev.
/ Stage (ft)

1.00 1.33

0.67 0.33

Date
D85= 0.60 inches
DMA
Type/ID
DMA Area
(square feet)
Post-Project Surface
Type
Effective
Imperivous
Fraction, If
DMA
Runoff
Factor
DMA Areas x
Runoff Factor
Design
Storm
Depth (in)
Design Capture
Volume, VBMP
(cubic feet)
Proposed
Volume on
Plans (cubic
feet)
C-1 Roof 100,000 Roofs 1 0.89 89200
C-2
Driveways 16,000 Concrete or Asphalt 1 0.89 14272
C-3
Pavement 53,588 Concrete or Asphalt 1 0.89 47800.5
C-4
Sidewalk 16,156 Concrete or Asphalt 1 0.89 14411.2
C-5
Parkway 10,601 Ornamental
Landscaping 0.1 0.11 1171
C-6 Slopes 69,626 Ornamental
Landscaping 0.1 0.11 7690.7
C-7 Res 131,267 Ornamental
Landscaping 0.1 0.11 14499.5
C-8 Basin 15,559 Natural (A Soil) 0.03 0.06 973.1
C-9
DG Road 6,452 Decomposed Granite 0.4 0.28 1804.7
C-10
Natural 198,182 Natural (A Soil) 0.03 0.06 12394.5
1 1
1 1
1 1
1 1
1 1
1 1
1 1
617431 204217.2 0.60 10210.9 13000
Notes:

Company Name Hunsaker & Associates Nov 2021
Total
85th Percentile, 24-hour Rainfall Depth,
from the Isohyetal Map in Handbook Appendix E
Insert additional rows if needed to accommodate all DMAs draining to the BMP Designed by Brian Lowell Case No
Santa Ana Watershed - BMP Design Volume, VBMP
(Rev. 10-2011)
Legend:

Required Entries
Calculated Cells
(Note this worksheet shall only be used in conjunction with BMP designs from the LID BMP Design Handbook ) Company Project Number/Name Golden Meadows - Phase 4
BMP Identification
Drainage Management Area Tabulation
Design Rainfall Depth

BMP NAME / ID DMA 'C'
Must match Name/ID used on BMP Design Calculation Sheet

No. DMA C
Company Name: Date: Nov 2021
Designed by: County/City Case No.:

Tributary Area (BMP Subarea) AT = 14.17427 acres
Enter VBMP, determined from Section 2.1 of this Handbook VBMP= 10,211 ft3 206 ft
77 ft
z = 4 :1
DB = 6.00 ft
DFB = 2.00 ft
DREQ = 10.7 ft
DO = 6.0 ft
Meets 1.5 : 1 requirement?
Required Entries
Calculated Cells
Hunsaker & Associates
Brian Lowell
Extended Detention Basin Design Procedure
Basin Footprint
Width =
Length =
Overall Geometry
Length at Basin Bottom Surface
Width at Basin Bottom Surface
Side Slopes per "Basin Guidelines", Sect. 1.2

Proposed Basin Depth (with no freeboard)
and minimum filter depth (DFD=2.33'))
Depth from design water surface elevation to lowest orifice BMP Subarea
Design Volume

Depth of freeboard (if used)
Minimum Required Allowance for Total Depth (including proposed basin depth, freeboard, minimum depth of bottom stage (DBS=0.33') Legend:

DTOT = 8.00 ft
Slope = 1.00 %
Slope = 1 %
VBasin = 42547 ft3
VFB = 510.55 ft3
Forebay Depth (height of berm) DFBY = 1.5 ft
Minimum Forebay Surface Area AFB = 340 ft2
W = 4.00 in
Proposed Total Basin Depth (proposed depth plus freeboard) Basin Volume
Bottom Stage
Forebay Design
Basin Invert Longitudinal Slope
Forebay Volume (3 - 5% VBMP)
Basin Design
Basin Design
Basin Invert Transverse Slope (1% min)
Rectangular weir (notch)

Depth = 24 inches
Width = 48 inches
Trench Invert Longitudinal Slope Slope = 1 %
Depth = 24 inches
Width = 18 inches
Slope = 1 %
S = 25 feet
DBS = 4 in
ABS = 630 ft2
210 ft3
Depth of ASTM-C33 sand (18 inch minimum)
Ds = 18 inches
Diameter of Subdrains
φ = 6 in s = 10 ft. on center
Depth (24 inches minimum, gravel filled)
Depth (24 inches minimum)
Subdrain Spacing
Depth of the Bottom Stage (4" minimum ponding)
Bottom Stage (Sand Filter) Design

Width (48 inches minimum)
Dry Weather and Low-Flow Management
Low-Flow Trench (see graphic below)

Is VBS no less than 0.5% VBMP? OK
Collector Trenches (see graphic below)
Width (18 inches minimum)
Trench Invert Longitudinal Slope
Surface Area of Bottom Stage
Spacing (25 feet on center maximum)
Dry Weather Ponded Volume (above sand layer) VBS =
Transverse Slope
(1% min)
AASHTO No. 2
Coarse aggregate
24" (min)
48" (min)
18" (min)
24" (min)
Low-Flow Trench Collector Trench
DBS
Outlet Design

0.0000 0.0000
Discharge Coefficient, 0.0240 0.004 3.63

0.0340 0.007 1.50
Default, C = 0.66 0.0416 0.011 1.15

0.0480 0.040 7.92
Other, C = 0.66 0.0537 0.069 6.97

0.0588 0.099 6.30

0.0635 0.149 9.95

0.0679 0.199 9.24

0.0720 0.250 8.70

0.0759 0.326

0.0796 0.402
d = 1.2 inches 0.0832 0.478

0.0865 0.583
n = 1 per row 0.0898 0.689

0.0930 0.795
N = 1 rows 0.0960 0.855

0.0990 0.916
Aeff = 0.008 ft2 per row 0.1018 0.977
or
Aeff = 1.130 in2
per row

24.24 hrs

55.38 hrs
∑ = 55.38
Notes:

1.00 1.33

0.67 0.33
Flow Rate, Q (cfs)
0 Assume an orifice area. Based on the
information provided above, the spreadsheet
provides discharge vs. stage data. Enter the
volume vs. stage data for each interval. This
information is used to route the volume through
the basin. The size of the orifice is acceptable
when the data shows that less than 50% of
VBMP has drained in 24 hours, and that 100%
drawdown occurs within 72 hours.

Q=CA[2g(H-Ho)]0.5
Basin Outlet Design
∆t (hrs.)Headwater Elev.
/ Stage (ft)
Orifice Area (ft2)

6.67 9.00

8.00 7.33

7.00 6.33

6.00 2.00

1.67 2.33

4.33 4.00

3.00 2.67

3.33 4.67

5.33 5.00
OK
number of orifice rows, N (from the bottom up).

OK
has drained from the basin(within 72 hours):

Orifice Diameter, d; number of orifices per row, n; and Time (100 %) =
From outflow hydrograph, the time where 100% VBMP
has drained from the basin (24 hour minimum):

Time (50%) =
From outflow hydrograph, the time where 50% of VBMP

9.67 7.67

10.00 5.67

9.33 3.67

8.67 8.33
Discharge
(cfs)
Volume
(acre-ft)

Date
D85= 0.60 inches
DMA
Type/ID
DMA Area
(square feet)
Post-Project Surface
Type
Effective
Imperivous
Fraction, If
DMA
Runoff
Factor
DMA Areas x
Runoff Factor
Design
Storm
Depth (in)
Design Capture
Volume, VBMP
(cubic feet)
Proposed
Volume on
Plans (cubic
feet)
D-1 Roof 378,000 Roofs 1 0.89 337176
D-2
Driveways 60,480 Concrete or Asphalt 1 0.89 53948.2
D-3
Pavement 395,799 Concrete or Asphalt 1 0.89 353052.7
D-4
Sidewalk 112,435 Concrete or Asphalt 1 0.89 100292
D-5
Parkway 83,596 Ornamental
Landscaping 0.1 0.11 9233.8
D-6 Slopes 137,022 Ornamental
Landscaping 0.1 0.11 15135.2
D-7
Turf 1,098,384 Ornamental
Landscaping 0.1 0.11 121325.3
D-8
Open
Space
107,591 Ornamental
Landscaping 0.1 0.11 11884.3
D-9
Basin
Bottom
56,338 Natural (A Soil) 0.03 0.06 3523.4
D-10
DG Access
Road
2,670 Decomposed Granite 0.4 0.28 746.8
1 1
1 1
1 1
1 1
1 1
1 1
1 1
2432315 1006317.7 0.60 50315.9 51000
Notes:

Company Name Hunsaker & Associates Nov 2021
Total
85th Percentile, 24-hour Rainfall Depth,
from the Isohyetal Map in Handbook Appendix E
Insert additional rows if needed to accommodate all DMAs draining to the BMP Designed by Brian Lowell Case No
Santa Ana Watershed - BMP Design Volume, VBMP
(Rev. 10-2011)
Legend:

Required Entries
Calculated Cells
(Note this worksheet shall only be used in conjunction with BMP designs from the LID BMP Design Handbook ) Company Project Number/Name Golden Meadows - Phase 4
BMP Identification
Drainage Management Area Tabulation
Design Rainfall Depth

BMP NAME / ID DMA 'D'
Must match Name/ID used on BMP Design Calculation Sheet

Company Name: Date:

Designed by: County/City Case No.:

AT = acres
b) Enter VBMP determined from Section 2.1 of this Handbook VBMP= 50,316 ft3 I = 0.67 in/hr
FS = 3
D1 = D1 = 1.3 ft
1 ft
e) Enter depth to historic high ground water (measured from top of basin) 100 ft 20 ft
D2 = 14.0 ft
DMAX = 1.3 ft
z = 4 :1
dB = 1.3 ft
AS = 38705 ft2
AD = 56338 ft2
Volume = 252 ft3
Depth = 1.5 ft
Area = 168 ft2

4.0 in
Notes:
b) Proposed basin depth (excluding freeboard)
Forebay
c) Forebay surface area (minimum)
Width (W) =
b) Forebay depth (height of berm/splashwall. 1 foot min.) a) Forebay volume (minimum 0.5% VBMP)
d) Full height notch-type weir
d) Proposed Design Surface Area
c) Minimum bottom surface area of basin (AS= VBMP/dB)
Calculated Cells
Hunsaker & Associates Nov 2021
Casey Erickson
Infiltration Basin - Design Procedure
(Rev. 03-2012)
BMP ID Legend: Required Entries

DMA 'D'
h) DMAX is the smaller value of D1 and D2 but shall not exceed 5 feet Design Volume
a) Basin side slopes (no steeper than 4:1)
Maximum Depth
a) Infiltration rate
b) Factor of Safety (See Table 1, Appendix A: "Infiltration Testing" from this BMP Handbook)
c) Calculate D1
Basin Geometry
f) Enter depth to top of bedrock or impermeable layer (measured from top of basin) I (in/hr) x 72 hrs
12 (in/ft) x FS
Depth to groundwater - (10 ft + freeboard) and
Depth to impermeable layer - (5 ft + freeboard)
a) Tributary area (BMP subarea)
g) D2 is the smaller of:
d) Enter the depth of freeboard (at least 1 ft)
Riverside County - Low Impact Development BMP Design Handbook rev. 9/2011

3.6 Extended Detention Basin

Type of BMP LID - Biotreatment
Treatment Mechanisms Sedimentation, Infiltration, Biofiltration, Evapotranspiration, and Evaporation
Minimum Tributary Drainage Area 5 acres
Other Names Enhanced Water Quality Basin

Overview
The Extended Detention Basin (EDB) is designed to detain the design volume of stormwater, V BMP, and maximize opportunities for volume losses through infiltration, evaporation, evapotranspiration and surface wetting . Additional pollutant removal is provided through sedimentation, in which pollutants can attach to sediment accumulated in the basin through the process of settling. Stormwater enters the EDB through a forebay where any trash, debris, and sediment accumulate for easy removal. Flows from the forebay enter the basin which is vegetated with native grasses that enhance infiltration and evapotranspiration, and which is interspersed with gravel- filled trenches that help further enhance infiltration. Water that does not get infiltrated or evapotranspired is conveyed to the bottom stage of the basin. At the bottom stage of the basin, low or incidental dry weather flows will be treated through a sand filter and collected in a subdrain structure. Any a dditional flows will be detained in the basin for an extended period by incorporating an outlet structure that is more restrictive than a traditional detention basin outlet. The restrictive outlet structure extends the drawdown time of the basin which further allows particles and associated pollutants to settle out before exiting the basin, while maximizing opportunities for additional incidental volume losses.

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Riverside County - Low Impact Development BMP Design Handbook rev. 9/2011

Figure 1 – Extended Detention Basin

EXTENDED DETENTION BASIN BMP FACT SHEET
Riverside County - Low Impact Development BMP Design Handbook rev. 9/2011

Siting Considerations
Soils: EDBs can be used with almost all soils and geology. However, pollutant removal effectiveness is greatly improved when the underlying soil permits at least some infiltration.

Tributary Area: EDBs should only be used where the tributary drainage area is at leas t 5 acres, since meeting the draw -down requirements (discussed below) for smaller areas would result in very small outlet orifice diameters which would be prone to clogging.

Proximity to Receiving Waters: All site runoff must be treated to the MEP with appropriate BMPs before being discharged into Receiving Waters; as such the EDB cannot be constructed in-line within Receiving Waters.

Setbacks: Due to the infiltration characteristics incorporated into the EDB design, the lowest pervious point (beneath the filter drain) of the extended detention fac ility should be a minimum of 10' above the seasonal high groundwater table. All other setbacks shall be in accordance with applicable standards of the “Basin Guidelines” (Appendix C) or other guidelines issued by the Engineering Authority (EA).

Basin Guidelines: See Section 1 of the “Basin Guidelines” (Appendix C) for additional requirements (i.e., fencing, maintenance access, etc.) that may be required by the Engineering Authority (EA).

Landscaping Requirements
Basin vegetation provides erosion protection, enhances evapotranspiration and infiltration, and improves pollutant removal. The upper stage basin surface , berms and side slopes shall be planted with native grasses . Proper landscape management is also required to ensure that the vegetation does not contribute to water pollution through the use of pesticides, herbicides, or fertilizers. Landscaping shall be in accordance with applicable standards of the “ Basin Guidelines” (Appendix C) or other guidelines issued by the EA.

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Riverside County - Low Impact Development BMP Design Handbook rev. 9/2011

Maintenance Guidelines
Schedule Inspection and Maintenance Activity
During every scheduled
maintenance check (per below),
and as needed at other times
• Maintain vegetation as needed . Use of fertilizers, pesticides and herbicides should be strongly avoided to ensure they don’t contribute to water pollution. If appropriate native plant selections and other IPM methods are used, such products shouldn’t be needed. If such projects are used:
o Care should be taken to avoid contact with the low -
flow or other trenches, and the media filter in the
bottom stage.
o Products shall be applied in accordance with their
labeling, especially in relation to application to water, and in areas subjected to flooding.
o Fertilizers should not be applied within 15 days before, after, or during the rainy season.
• No ponded water should be present for more than 72 hours to avoid nuisance or vector problems. No algae formation should be visible.

Correct problems as needed.

Annually. If possible, schedule
these inspections before the
beginning of the rain season to
allow for any repairs to occur
before rains occur.
• Remove debris and litter from the entire basin
• Inspect hydraulic and structural facilities. Examine the outlet for clogging, the embankment and spillway integrity, as well as damage to any structural element.
• Check for erosion, slumping and overgrowth. Repair as needed. • Inspect sand media at the filter drain to verify it is allowing acceptable infiltration. Scarify top 3 inches by raking the filter drain’s sand surface annually.
• Check the media filter underdrains (via the cleanout) for damage or clogging. Repair as needed.
• Remove accumulated sediment and debris from the forebay , and ensure that the notch weir is clear and will allow proper drainage. • Check gravel filled low flow and collector trenches for sediment buildup and repair as needed.

Every 5 years or sooner
(depending on whether observed
drain times to empty the basin
are less than 72 hours).
• Remove the top 3 inches of sand from the filter drain and backfill with 3 inches of new sand to return the sand layer to its original depth .

When scarification or removal of the top 3 inches of sand is no longer effective, remove and replace sand filter layer.

Whenever substantial sediment
accumulation has occurred.
• Remove accumulated sediment from the bottom of the basin.

Removal should extend to original basin depth.

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Riverside County - Low Impact Development BMP Design Handbook rev. 9/2011

Design Summary

Note: The information contained in this BMP Factsheet is intended to be a summary of design considerations and requirements. Additional information which applies to all detention basins may be found in the “Basin Guidelines” (Appendix C). In addition, in formation herein may be superseded by other guidelines issued by the Engineering Authority.

Design Procedure
These steps correspond to and provide a description of the information required in the EDB Design Worksheet.

1. Find the Design Volume, VBMP.
a) Enter the tributary area, AT to the BMP. The minimum tributary area is 5 acres. b) Enter the Design Volume, VBMP, determined from Section 2.1 of this Handbook.

Design Parameter Extended Detention Basin
Drawdown time (total) 72 hours 2,3
Minimum drawdown time for 50% VBMP 24 hours 2
Minimum tributary area 5 acres 2
Outlet erosion control Energy dissipaters to reduce velocities1 Forebay volume 3 to 5 % of VBMP
3 Basin Invert Longitudinal Slope (min.) 1%
Basin Invert Transverse (cross) Slope (min) 1%
Low-flow trench width (min.) 48 inches
Low-flow trench depth (min.) 24 inches
Slope of low-flow trench along bottom
excavated Surface (max.) 1%
Slope of gravel collector trenches along
bottom excavated surface (max.) 1 %
Length to width ratio (min.) 1.5:1
Basin depth (min.) 1 foot 3
Bottom stage volume 0.5 % of VBMP 3
Bottom stage depth (min) 0.33 feet 3
Filter drain depth (min) 2.33 feet 3

1. Ventura County’s Technical Guidance Manual for Stormwater Quality Control Measures

2. CA Stormwater BMP Handbook for New Development and Significant Redevelopment

3. Denver, Colorado’s UDFCD Drainage Criteria Manual, Volume 3

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Riverside County - Low Impact Development BMP Design Handbook rev. 9/2011

2. Basin Footprint
a) Enter the length and width of the EDB. The length shall be measured between the inlet to the basin and the outlet structure ; and the width shall be measured at the widest point of the basin invert . The length to width ratio should be 1.5:1 or longer to prevent short-circuiting and increase the overall effectiveness of the BMP.

b) Enter the internal basin side slopes. See the “Basin Guidelines” (Appendix C) for side slope requirements. If variable internal side -slopes are used, enter the steepest slope that will be used.
c) Using Figure 1 as a guide, e nter the proposed basin depth, D B, and the freeboard depth, D FB. Based on the information provided, the spreadsheet will ca lculate the minimum total depth required, DREQ, for this BMP. D REQ is the depth from the bottom of the underdrain layer in the bottom stage (see step 5c) , to the top o f the freeboard. This calculated minimum required depth can be used to determine if enough elevation difference is available within the design topography to allow for use of this BMP.
d) Additionally, the basin depth D B is equal to DO, which is the depth from the design pond water surface elevation to the lowest orifice in the outlet structure. DO is confirmed by the spreadsheet and is used in the Basin Outlet Design described in step 6 below. It should be noted that this lowest orifice is a critical elevation in the design of this BMP. The Volume of the Basin V Basin described in step 3 d) is the volume of water above this lowest orifice. This lowest-orifice also represents the dry weather ponded water surface discussed in step 5c below. Below this elevation there must be a minimum of a 4 -inch drop down to the sur face of the Sand Filter in the bottom stage.

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Riverside County - Low Impact Development BMP Design Handbook rev. 9/2011

3. Basin Design
a) The Total Basin Depth , DTOT, is calculated automatically, and is the sum of the basin depth DB plus the freeboard depth DFB.
b) Enter the longitudinal slope of the basin invert. This slope must be at least 1% and is measured along the low flow trench between the forebay and the bottom s tage.

Note that the surface of the sand layer in the bottom stage must be level (see Figure 1).
c) Enter the transverse slope of the basin invert. This transverse (cross sectional) slope must be at least 1% sloped toward the low flow trench.
d) Enter the Volume of the Basin, V Basin. This volume must be the actual volume of water held within the basin as substantiated by modeling or appropriate volumetric calculations, and must be equal to or greater than V BMP. This volume must be held above the lowest orifice in the Basin Outlet Design described in step 6 below.

4. Forebay Design
All flows must enter the basin through the
forebay. The forebay provides a location for th e
settlement and collection of larger particles , and
any other trash or debris. A relatively smooth and
level concrete bottom surface should be provided
to facilitate mechanical removal of any
accumulated sediment, trash and debris.
a) Enter the Forebay Volu me VFB. This
volume must be from 3 to 5 percent of
V
BMP.
b) A rock or concrete berm must be constructed to d etain water before it drains into the basin. The top of the berm shall be set no higher than the invert of the inlet conveyance. Enter the Forebay Depth, D
FBY.
c) The spreadsheet will calculate the minimum surface area of the forebay, A FB, based on the pro vided Forebay Volume and Depth. Ensure that the plans provide for a forbay area at least this large.
d) Although the forebay will be well submerged in t he design event, a full height rectangular notch-type weir shall be constructed through the berm to prevent permanent ponding in the forebay, and allow water to slowly and fully drain to the main body of the basin. This notch should be offset from the inf low streamline to prevent low-flows from short circuiting. Enter the width, W, of this rectangular notch weir. The width shall not be less than 1.5 inches to prevent clogging . Additionally, Figure 2: Forebay filled with storm water

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Riverside County - Low Impact Development BMP Design Handbook rev. 9/2011

immediately outside the notch construct a minimum 1 -foot by 1 -foot gravel pad to prevent vegetative growth within the basin invert from blocking the notch.

5. Dry Weather and Low-Flow Management
The basin shall have both a low-flow gravel trench and a network of gravel collector trenches across the invert of the basin, as well as a bottom stage sand filter to treat low flows and dry weather flows (see Figure 1).
a) Low Flow Trench: The low-flow gravel trench conveys flow from the forebay to the bottom stage, while allowing fo r maximum
incidental infiltration and volume loss. The
trench shall be a minimum of 48 inches wide
by 24 inches deep. This trench shall be
unlined and backfilled with AASHTO No. 2
gravel (or similar) to the finished surface of
the basin invert , and shall n ot use
underdrains. The bottom excavated surface
of the low- flow trench shall be 1 percent or
flatter to promote infiltration.
b) Collector Trenches:

Gravel collector trenches beneath the top stage shall be arranged as illustrated in Figure 1 of Appendix C with minimal slope (1% maximum) along their bottom excavated surface to promote infiltration, and must extend from the low-flow trench to the toe of the basin side slopes. They shall be a minimum of 18-inches wide by 24 -inches deep, unlined and back filled with AASHTO No. 2 gravel (or similar) to the finished basin invert surface. The gravel collector trenches shall not use underdrains and shall be constructed with a maximum spacing of 25 feet, center to center. See Figure 1 of Appendix C.
c) Bottom Stage: A depressed sand filter drain area, referred to as the b ottom stage, must be constructed adjacent to the outlet structure to treat any dry weather flows.

To ensure that dry weather flows are treated through the sand filter and not discharged through the ori fice plate, the top surface of the sand filter must be depressed at least 4 inches below the lowest orifice in the outlet structure. This depressed area will create a micro pool of water that is then filtered down through the san d filter and out through under drains. Based on the minimum dimensions described below, the minimum depth of excavation below the lowest orifice in the outlet structure is 2.33 feet.
i. Enter the Depth of the b ottom stage, DBS. As mentioned above, this depth must be at least 4 inches, and extend down below the lowest orifice in the outlet structure.
ii. Enter the area of the bottom stage, A
BS.

Figure 3: Gravel filled low-flow trench

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Riverside County - Low Impact Development BMP Design Handbook rev. 9/2011

iii. Based on the D BS and A BS entered, the spreadsheet will calculate V BS. This volume is the volume of ponded water that will be held below the lowest orifice in the outlet structure, and above the surface of the sand filter. This volume must be at least 0.5% of VBMP.
iv. Enter the thickness of the ASTM C-33 sand layer that will b e provided, D S. A minimum thickness of 18 inches is required.
v. Below the sand layer, a minimum 10 -inch thick layer of gravel shall be installed with underdrains to drain the water that has been treated through the sand filter. The underdrains shall connect into the outlet structure. See Appendix B for standard underdrain construction. E nter the diameter of the underdrain pipe (minimum 6” dia.), and the spacing of the underdrains . The maximum spacing of the underdrains is 20 feet on center , however where the area of the bottom stage is particularly small (less than 500 square feet), the underdrain pipes shall be placed at no more than a 10-foot separation on center.

6. Basin Outlet Design

Figure 4: Basin Outlet Structure with Bottom Stage Shown Outlet structures for publicly maintained basins shall conform to District Standard Drawings WQ501 unless approved in advance by the local Engineering Authority (EA). This standardization is to provide for efficient maintenance. The basin outlet should be size d to release the design volume, VBMP, within a 72-hour period but 50 percent of VBMP within 24 hours. This is an iterative design process where an appropriate control orifice can be selected using the following steps:

a. Develop a Stage vs. Discharge Curve for the Outlet Structure

EXTENDED DETENTION BASIN BMP FACT SHEET
Riverside County - Low Impact Development BMP Design Handbook rev. 9/2011

Estimate the orifice size and outlet plate configuration (number per row, etc.). Based on DO provided in the Basin Footprint section, the spreadsheet will automatically generate the stage vs. discharge relationship for this outlet:

Q = C*A*[2*g*(H-Ho)]0.5
Where:

Q = discharge (ft3/s)
C = orifice coefficient
A = area of the orifice (ft)

g = gravitational constant (32.2 ft2/s)
H = water surface elevation (ft)
Ho = orifice elevation (ft)

The lowest orifice shall be located with its centerline at the top of the bottom stage; at least 4 inches above the surface of the sand filter drain. To help avoid clogging, the minimum orifice diameter is limited to 3/8 inch. Since the 1/4 inch thickness of the orifice plate will be less than the orifice diameter, a value for C of 0.66 may be used. If another value for C is used, justification may be required.
b. Develop a Discharge/Volume vs. Stage Table for the Basin Based on the shape and size of the basin, develop a relationship between the stage and the volume of water in the basin. Since the orifice spacing is 4 inches on center for the standard orifice plate, the stage intervals must also be 4 inches. Enter the basin volume at each interval starting at the centerline of the lowest orifice. c. Route the Design Volume through the Basin
The spreadsheet assumes that the Design Volume , V
BMP, enters the basin
instantaneously and as such, no inflow/outflow hydrograph is necessary. The drawdown time for each stage becomes:
∆t = Vi/Q
Where:
∆t = drawdown time for each stage
Vi = the volume at each stage
Q = the flow rate corresponding to the headwater elevation at each stage.

The spreadsheet automatically determines the drawdown time from the sum of the ∆ t values for each stage. If the orifice size and plate configuration estimate meets th e

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hydraulic retention time requirements (50% of the volume empties in not less than 24 hours, 100% of the volume empties in no more than 72 hours), the outlet is correctly sized. If these requirements are not met, select a new orifice size or configuration and repeat the process starting at Step 6a.

7. Outlet Protection
To prevent the orifices from clogging , trash racks are re quired where perforated vertical outlet control plates are used . This allows for easier access to outlet orifices for inspection and cleaning. Trash racks shall be sized to prevent clogging of the primary water quality outlet without restricting the hydraulic capacity of the outlet control orifices. The orifice plate shall be protected with a trash rack conforming to Standard Drawing WQ501 (at end of this section) with at least six square feet
of open surface area or 25 times the
total orifice area, whichever is greater.

The rack shall be adequ ately secured to
prevent it from being removed or
opened when maintenance is not
occurring.

Overflow Structure Similar to Standard Drawing
Number WQ 501
(Photo courtesy of Colorado Association of
Stormwater Floodplain Managers)

Trash rack with screen

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Riverside County - Low Impact Development BMP Design Handbook rev. 9/2011

8. Overflow Outlet
Overflow outlets for publicly maintained basins shall conform to Standard Drawing WQ501 (at end of this section) unless approved in advance by the Engineering Authority (EA).

9. Embankment
Embankments shall be designed in accordance with applicable standards of Riversid e County Flood Control District’s “Basin Guidelines” (Appendix C) or other guidelines issued by the Engineering Authority (EA) . Where applicable, embankment designs must additionally conform to the requirements of the State of California Division of Safety of Dams.

10. Spillway and Overflow Structures
Spillway and o verflow struct ures should be designed in accordance with applicable standards of the “Basin Guidelines” (Appendix C) or other guidelines issued by the Engineering Authority (EA).

EXTENDED DETENTION BASIN BMP FACT SHEET
Riverside County - Low Impact Development BMP Design Handbook rev. 9/2011

EXTENDED DETENTION BASIN BMP FACT SHEET
Riverside County - Low Impact Development BMP Design Handbook rev. 9/2011

EXTENDED DETENTION BASIN BMP FACT SHEET
Riverside County - Low Impact Development BMP Design Handbook rev. 9/2011

EXTENDED DETENTION BASIN BMP FACT SHEET
Riverside County - Low Impact Development BMP Design Handbook rev. 9/2011

EXTENDED DETENTION BASIN BMP FACT SHEET
Riverside County - Low Impact Development BMP Design Handbook rev. 9/2011

EXTENDED DETENTION BASIN BMP FACT SHEET
Riverside County - Low Impact Development BMP Design Handbook rev. 9/2011

EXTENDED DETENTION BASIN BMP FACT SHEET
Riverside County - Low Impact Development BMP Design Handbook rev. 9/2011

EXTENDED DETENTION BASIN BMP FACT SHEET
Riverside County - Low Impact Development BMP Design Handbook rev. 9/2011

Riverside County - Low Impact Development BMP Design Handbook rev. 2/2012

3.1  INFILTRATION BASIN

Description

An  Infiltration  Basin  is  a  flat  earthen  basin
designed  to  capture  the  design  capture  volume,
VBMP.  The  stormwater  infiltrates  through  the
bottom of the basin into the underlying soil over
a  72  hour  drawdown  period.  Flows  exceeding
VBMP  must  discharge  to  a  downstream
conveyance  system.  Trash  and  sediment
accumulate  within  the  forebay  as  stormwater
passes  into  the  basin.   Infiltration  basins  are
highly  effective  in  removing  all  targeted
pollutants from stormwater runoff.

See Appendix A, and Appendix C, Section 1 of Basin Guidelines, for additional requirements.

Siting Considerations
The use of infiltration basins may be restricted by concerns over ground water contamination, soil permeability, and clogging at the site. See the applicable WQMP for any specific feasibility considerations for using infiltration BMPs. Where this BMP is being used, the soil beneath the basin  must  be  thoroughly  evaluated  in  a  geotechnical  report  since  the  underlying  soils  are critical to the basin’s long term performance. To protect the basin from erosion, the sides and bottom of the basin must be vegetated, preferably with native or low water use plant species.

In addition, these basins may not be appropriate for the following site conditions:
 Industrial sites or locations where spills of toxic materials may occur  Sites with very low soil infiltration rates
 Sites with   high groundwater tables or excessively high soil infiltration rates, where pollutants can affect ground water quality
 Sites with unstabilized soil or construction activity upstream  On steeply sloping terrain
 Infiltration  basins  located  in  a  fill  condition  should  refer  to  Appendix  A  of  this Handbook for details on special requirements/restrictions Type of BMP  LID ‐ Infiltration
Treatment Mechanisms  Infiltration, Evapotranspiration (when vegetated), Evaporation, and Sedimentation
Maximum Treatment Area  50 acres
Other Names  Bioinfiltration Basin
Figure 1 – Infiltration Basin

INFILTRATION BASIN BMP FACT SHEET

Riverside County - Low Impact Development BMP Design Handbook rev. 2/2012

Setbacks

Always  consult  your  geotechnical  engineer  for  site  specific  recommendations  regarding setbacks  for  infiltration  trenches.   Recommended  setbacks  are  needed  to  protect  buildings, existing trees, walls, onsite or nearby wells, streams, and tanks.  Setbacks should be considered early in the design process since they can affect where infiltration facilities may be placed and how  deep  they  are  allowed  to  be.   For  instance,  depth  setbacks  can  dictate  fairly  shallow facilities  that  will  have  a  larger  footprint  and,  in  some  cases,  may  make  an  infiltration  basin infeasible.  In that instance, another BMP must be selected.

Infiltration basins typically must be set back:
 10 feet from the historic high groundwater (measured vertically from the bottom of the basin, as shown in Figure 2)
 5 feet from bedrock or impermeable surface layer (measured vertically from the bottom of the basin, as shown in Figure 2)
 From all existing mature tree drip lines as indicated in Figure 2 (to protect their root structure)
 100 feet horizontally from wells, tanks or springs
Setbacks  to  walls  and  foundations  must  be  included  as  part  of  the  Geotechnical  Report.  All other  setbacks  shall  be  in  accordance  with  applicable  standards  of  the  District’s  Basin Guidelines (Appendix C).

Figure 2 – Setback Requirements

INFILTRATION BASIN BMP FACT SHEET

Riverside County - Low Impact Development BMP Design Handbook rev. 2/2012

Forebay

A concrete forebay shall be provided to reduce sediment clogging and to reduce erosion.   The forebay shall have a design volume of at least 0.5% VBMP and a minimum 1 foot high concrete splashwall / berm.   Full height notch‐type weir(s), offset from the line of flow from the basin inlet  to  prevent  short  circuiting,  shall  be  used  to  outlet  the  forebay.   It  is  recommended  that two weirs be used and that they be located on opposite sides of the forebay (see Figure 2).

Overflow

Flows exceeding VBMP must discharge to an acceptable downstream conveyance system. Where an  adequate  outlet is  present,  an  overflow  structure  may  be  used.  Where  an embankment  is present, an emergency spillway may be used instead. Overflows must be placed just above the design water surface for VBMP and be near the outlet of the system. The overflow structure shall be  similar  to  the  District’s  Standard  Drawing  CB  110.  Additional  details  may  be  found  in  the District’s Basin Guidelines (Appendix C).

Figure 3 – Infiltration Basin

INFILTRATION BASIN BMP FACT SHEET

Riverside County - Low Impact Development BMP Design Handbook rev. 2/2012

Landscaping Requirements
Basin  vegetation  provides  erosion  protection,  improves  sediment  removal  and  assists  in allowing  infiltration  to  occur.   The  basin  surface  and  side  slopes  shall  be  planted  with  native grasses.  Proper landscape management is also required to ensure that the vegetation does not contribute to water pollution through pesticides, herbicides, or fertilizers.  Landscaping shall be in  accordance  with  County  of  Riverside  Ordinance  859  and  the  District’s  Basin  Guidelines (Appendix C), or other guidelines issued by the Engineering Authority.

Maintenance
Normal  maintenance  of  an  infiltration  basin  includes  the  maintenance  of  landscaping,  debris and  trash  removal  from  the  surface  of  the  basin,  and  tending  to  problems  associated  with standing water (vectors, odors, etc.). Significant ponding, especially more than 72 hours after an  event,  may  indicate that  the  basin  surface  is  no  longer  providing  sufficient  infiltration  and requires aeration. See the District’s Basin Guidelines (Appendix C) for additional requirements (i.e., fencing, maintenance access, etc.).

Table 1 ‐ Inspection and Maintenance

Schedule  Inspection and Maintenance Activity
Ongoing including just
before annual storm
seasons and following
rainfall events.
 Maintain vegetation as needed. Use of fertilizers, pesticides and herbicides should be strenuously avoided to ensure they don’t contribute to water pollution. If appropriate native plant selections and other IPM methods are used, such products shouldn’t be needed. If such projects are used,
o Products shall be applied in accordance with their labeling, especially in relation to application to water, and in areas subjected to flooding. o Fertilizers should not be applied within 15 days before, after, or during the rain season.
 Remove debris and litter from the entire basin to minimize clogging and improve aesthetics.
 Check for obvious problems and repair as needed. Address odor, insects, and overgrowth issues associated with stagnant or standing water in the basin bottom.

There should be no long‐term ponding water.
 Check for erosion and sediment laden areas in the basin. Repair as needed. Clean forebay if needed.
 Revegetate side slopes where needed.

Annually. If possible,
schedule these inspections
within 72 hours after a
significant rainfall.
 Inspection of hydraulic and structural facilities. Examine the inlet for blockage, the embankment and spillway integrity, as well as damage to any structural element.  Check for erosion, slumping and overgrowth. Repair as needed.  Check basin depth for sediment build up and reduced total capacity. Scrape bottom as needed and remove sediment. Restore to original cross‐section and infiltration rate. Replant basin vegetation.
 Verify the basin bottom is allowing acceptable infiltration. Use a disc or other method to aerate basin bottom only if there is actual significant loss of infiltrative capacity, rather than on a routine basis1.
 No water should be present 72 hours after an event. No long term standing water should be present at all. No algae formation should be visible.  Correct problem as needed.

1. CA Stormwater BMP Handbook for New Development and Significant Redevelopment

INFILTRATION BASIN BMP FACT SHEET

Riverside County - Low Impact Development BMP Design Handbook rev. 2/2012

Table 2 ‐ Design and Sizing Criteria for Infiltration Basins Note:  The  information  contained  in  this  BMP  Factsheet  is  intended  to  be  a  summary  of  design considerations and requirements.   Additional information which applies to all detention basins may be  found  in  the  District’s  Basin  Guidelines  (Appendix  C).   In  addition,  information  herein  may  be superseded by other guidelines issued by the co‐permittee.

INFILTRATION BASIN SIZING PROCEDURE

1. Find the Design Volume, VBMP.
a) Enter the Tributary Area, AT.
b) Enter the Design Volume, VBMP, determined from Section 2.1 of this Handbook.

2. Determine the Maximum Depth.
a) Enter  the  infiltration  rate.   The  infiltration  rate  shall  be  established  as  described  in Appendix A: “Infiltration Testing”.
b) Enter the design Factor of Safety from Table 1 in Appendix A: “Infiltration Testing”. c) The spreadsheet will determine D1, the maximum allowable depth of the basin based on the infiltration rate along with the maximum drawdown time (72 hours) and the Factor of Safety.

D1 =   [(t) x (I)] / 12s

Where    I = site infiltration rate (in/hr)
s = safety factor
t = drawdown time (maximum 72 hours)
Design Parameter  Infiltration Basin
Design Volume  VBMP
Forebay Volume  0.5% VBMP
Drawdown time (maximum)  72 hours
Maximum tributary area  50 acres 2
Minimum infiltration rate
Must be sufficient to drain the basin within the
required Drawdown time over the life of the BMP.

The WQMP may include specific requirements for
minimum tested infiltration rates.

Maximum Depth   5 feet
Spillway erosion control  Energy dissipators to reduce velocities1 Basin Slope  0%
Freeboard (minimum)  1 foot 1
Historic High Groundwater Setback (max)  10 feet
Bedrock/impermeable layer setback (max)  5 feet
Tree setbacks  Mature tree drip line must not overhang the basin Set back from wells, tanks or springs  100 feet
Set back from foundations  As recommended in Geotechnical Report

1.      Ventura County’s Technical Guidance Manual for Stormwater Quality Control Measures

2. CA Stormwater BMP Handbook for New Development and Significant Redevelopment

INFILTRATION BASIN BMP FACT SHEET

Riverside County - Low Impact Development BMP Design Handbook rev. 2/2012

d) Enter the depth of freeboard.
e) Enter  the  depth  to  the  historic  high  groundwater  level  measured  from  the  top  of  the basin.
f) Enter the depth to the top of bedrock or other impermeable layer measured from the finished grade.
g) The spreadsheet will determine D2, the total basin depth (including freeboard, if used) of  the  basin,  based  on  restrictions  to  the  depth  by  groundwater  and  an  impermeable layer.

D2 = Depth to groundwater – (10 + freeboard) (ft);
or
D2 = Depth to impermeable layer – (5 + freeboard) (ft)
Whichever is least.

h) The spreadsheet will determine the maximum allowable effective depth of basin, DMAX, based on the smallest value between D1 and D2. DMAX is the maximum depth of water only and does not include freeboard. DMAX shall not exceed 5 feet.

3. Basin Geometry

a) Enter the basin side slopes, z (no steeper than 4:1). b) Enter the proposed basin depth, d
B excluding freeboard.
c) The spreadsheet will determine the minimum required surface area of the basin:

A
s = VBMP / dB

Where    As    = minimum area required (ft2)
VBMP = volume of the infiltration basin (ft3)
dB= proposed depth not to exceed maximum allowable depth, DMAX (ft)

d) Enter the proposed bottom surface area. This area shall not be less than the minimum required surface area.

4. Forebay
A concrete forebay with a design volume of at least 0.5% V BMP and a minimum 1 foot high
concrete splashwall shall be provided.  Full‐height rectangular weir(s) shall be used to outlet the  forebay.   The  weir(s)  must  be  offset  from  the  line  of  flow  from  the  basin  inlet.  It  is recommended  that  two  weirs  be  used  and  that  they  be  located  on  opposite  sides  of  the forebay (see Figure 2).

a) The spreadsheet will determine the minimum required forebay volume based on 0.5% VBMP.
b) Enter the proposed depth of the forebay berm/splashwall (1foot minimum). c) The spreadsheet will determine the minimum required forebay surface area. d) Enter the width of rectangular weir to be used (minimum 1.5 inches). Weir width should be established based on a 5 minute drawdown time.
- 36 -

Appendix 7: Hydromodification
Supporting Detail Relating to Hydrologic Conditions of Concern

D
D
C
C
B
C D
DD
CD
B
B
B
DCC
DA
C
B
B
B B
D
B
B
DDD
BDDD
D
B
BBB
CD D
DB
DD
DD
D
C
C
C
CBB
B
BB
B
B
B
B
B
B
BB
BB
CCC
C
CC
CCCC

C CC C C
D
D
L=756'
L=660'
L=800'
L=1,213'L=1,843'
L=790'
L=897'
L=903'
L=783'
L=567'
L=791'
L=987'
L=1,598'
L=4,105'
L=753'
L=756'

HUNSAKERENWS
PRELIMINARY HYDROLOGY MAPTRACT 31194 ~ GOLDEN MEADOWSINDEX MAPMAJOR MODIFICATION

HUNSAKER & ASSOCIATESINLAND EMPIRE REGIONIRVINE, INC

EXISTING CONDITION
Lp=165'
Lp=1,360'
Lp=25'Lp=22'
Lp=107'
L=1,850'
L=1,420'Lp=70'
Lp=116'
L=806'L=994'Lp=47'
L=616'
L=701'
Lp=290'
Lp=10'Lp=40'
Lp=50'
L=945'
L=104'
Lp=965'
L=196'
L=57'Lp=114'
Lp=307'Lp=256'
L=580'L=440'
Lp=660'
Lp=1693'Lp=57'Lp=30'
L=863'
L=636'
D CB
DCC
D
B D
B
DB
DD
BDDD
D
B
BBB
CD D
DB
D
C
B
BB
D
DBB
B
Lp=40'Lp=38'Lp=32'Lp=54'
Lp=45'
Lp=800'
Lp=333'
Lp=23'Lp=567'
L=320'
Lp=36'
L=442'
Lp=65'Lp=72'
L=570'

HUNSAKERENWS
PRELIMINARY HYDROLOGY MAPTRACT 31194 ~ GOLDEN MEADOWS

INDEX MAP

MAJOR MODIFICATION

HUNSAKER & ASSOCIATESINLAND EMPIRE REGIONIRVINE, INC

AREA 'A' - PROPOSED DEVELOPMENT
L=448'
L=618'
L=245'
L=1000'
L=38'
L=220'L=190'
Lp=165'
L=185'L=330'
L=104'
Lp=273'
Lp=351'
Lp=671'
L=500'
L=933'
L=722'
L=863'
L=727'
Lp=123'
Lp=15'Lp=42'Lp=29'
L=684'
L=553'
L=530'
Lp=620'
L=965'
L=610'
L=193'Lp=496'
Lp=26'Lp=20'
L=960'L=1,000'
L=425'L=623'
L=518'

HUNSAKERENWS

HUNSAKER & ASSOCIATESINLAND EMPIRE REGIONIRVINE, INC
PRELIMINARY HYDROLOGY MAPTRACT 31194 ~ GOLDEN MEADOWSMAJOR MODIFICATIONAREA 'A' - PROPOSED DEVELOPMENT D
C
B
C D D
B
D
D
DD
D
CBB
B
BB
B
B
B
BCC
L=647'
Lp=532'
Lp=170'
Lp=84'
Lp=21'Lp=30'
Lp=271'Lp=20'L=215'
L=500'L=535'
L=742'
Lp=48'

HUNSAKERENWS

INDEX MAP

HUNSAKER & ASSOCIATESINLAND EMPIRE REGIONIRVINE, INC
PRELIMINARY HYDROLOGY MAPTRACT 31194 ~ GOLDEN MEADOWSMAJOR MODIFICATIONAREA 'C' - PROPOSED DEVELOPMENT D C
C
B
B
D
B D
B
B
DD
BDDD
D
B
BBB
CD D
DB
D
D
C
C
BB
C
D
D
L=332'
Lp=316'Lp=52'L=508'
L=708'
L=790'
Lp=388'
L=763'L=777'
L=343'
Lp=45'L=395'L=515'
Lp=235'
Lp=322'
L=597'
L=380'
Lp=26'Lp=24'
Lp=350'
Lp=35'Lp=36'
Lp=25'Lp=20'
L=311'
Lp=55'
Lp=63'
L=760'
Lp=52'
Lp=20'
H9
F9
G9
DCC B

HUNSAKERENWSINDEX MAP

HUNSAKER & ASSOCIATESINLAND EMPIRE REGIONIRVINE, INC
PRELIMINARY HYDROLOGY MAPTRACT 31194 ~ GOLDEN MEADOWSMAJOR MODIFICATIONAREA 'D' - PROPOSED DEVELOPMENT D
C
B
C D
DD
B
D
D
D
DD
D
CBB
B
BB
B
B
B
B
B
CC
L=332'
Lp=316'Lp=52'
L=530'L=490'
L=1000'
Lp=31'Lp=28'
L=640' Lp=35'Lp=40'
Lp=89'L=42'
Lp=48'Lp=38'
L=388'
Lp=1,011'
Lp=72'
Lp=54'
C9
B9
A9
D9
H9
I9
E9
J9
K9L9
M9
L=1,000'
Lp=353'L=96'
L=759'

HUNSAKERENWS

HUNSAKER & ASSOCIATESINLAND EMPIRE REGIONIRVINE, INC
PRELIMINARY HYDROLOGY MAPTRACT 31194 ~ GOLDEN MEADOWSMAJOR MODIFICATIONAREA 'D' - PROPOSED DEVELOPMENT

H:\00546\Planning\WQMP - Preliminary\Parts\Appendix 7 - Hydromodification\01 - EXA002.docx

Riverside County Rational Hydrology Program

CIVILCADD/CIVILDESIGN Engineering Software,(c) 1989 - 2014 Version 9.0 Rational Hydrology Study Date: 04/30/21 File:EXA002.out ------------------------------------------------------------------------ TRACT 31194 - 'GOLDEN MEADOWS' HYDROLOGY STUDY – AREA ‘A’ EXISTING CONDITION RATIONAL METHOD - 2 YEAR STORM

HUNSAKER & ASSOCIATES,
BY: BRIAN LOWELL, PE
------------------------------------------------------------------------ ********* Hydrology Study Control Information **********

English (in-lb) Units used in input data file

------------------------------------------------------------------------

Program License Serial Number 6406

------------------------------------------------------------------------ Rational Method Hydrology Program based on
Riverside County Flood Control & Water Conservation District 1978 hydrology manual

Storm event (year) = 2.00 Antecedent Moisture Condition = 1

2 year, 1 hour precipitation = 0.550(In.)
100 year, 1 hour precipitation = 1.300(In.)

Storm event year = 2.0
Calculated rainfall intensity data:
1 hour intensity = 0.550(In/Hr)
Slope of intensity duration curve = 0.5300

++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ Process from Point/Station 101.000 to Point/Station 102.000 **** INITIAL AREA EVALUATION ****
______________________________________________________________________ Initial area flow distance = 800.000(Ft.)
Top (of initial area) elevation = 1758.000(Ft.)
Bottom (of initial area) elevation = 1590.000(Ft.)
Difference in elevation = 168.000(Ft.)
Slope = 0.21000 s(percent)= 21.00
TC = k(0.530)*[(length^3)/(elevation change)]^0.2
Initial area time of concentration = 10.497 min.

Rainfall intensity = 1.386(In/Hr) for a 2.0 year storm UNDEVELOPED (poor cover) subarea
Runoff Coefficient = 0.554
Decimal fraction soil group A = 0.000
Decimal fraction soil group B = 1.000
Decimal fraction soil group C = 0.000
Decimal fraction soil group D = 0.000
RI index for soil(AMC 1) = 60.60
Pervious area fraction = 1.000; Impervious fraction = 0.000 Initial subarea runoff = 6.021(CFS)
Total initial stream area = 7.850(Ac.)
Pervious area fraction = 1.000

++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ Process from Point/Station 102.000 to Point/Station 103.000 **** NATURAL CHANNEL TIME + SUBAREA FLOW ADDITION ****
______________________________________________________________________ Top of natural channel elevation = 1590.000(Ft.)
End of natural channel elevation = 1533.000(Ft.)
Length of natural channel = 1213.000(Ft.)

H:\00546\Planning\WQMP - Preliminary\Parts\Appendix 7 - Hydromodification\01 - EXA002.docx Estimated mean flow rate at midpoint of channel = 22.099(CFS)

Natural valley channel type used
L.A. County flood control district formula for channel velocity:

Velocity(ft/s) = (7 + 8(q(English Units)^.352)(slope^0.5) Velocity using mean channel flow = 6.67(Ft/s)

Correction to map slope used on extremely rugged channels with drops and waterfalls (Plate D-6.2)
Normal channel slope = 0.0470
Corrected/adjusted channel slope = 0.0470
Travel time = 3.03 min. TC = 13.53 min.

Adding area flow to channel
UNDEVELOPED (poor cover) subarea
Runoff Coefficient = 0.554
Decimal fraction soil group A = 0.000
Decimal fraction soil group B = 0.750
Decimal fraction soil group C = 0.050
Decimal fraction soil group D = 0.200
RI index for soil(AMC 1) = 63.84
Pervious area fraction = 1.000; Impervious fraction = 0.000 Rainfall intensity = 1.211(In/Hr) for a 2.0 year storm Subarea runoff = 28.150(CFS) for 41.920(Ac.)
Total runoff = 34.171(CFS) Total area = 49.770(Ac.)

++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ Process from Point/Station 103.000 to Point/Station 104.000 **** NATURAL CHANNEL TIME + SUBAREA FLOW ADDITION ****
______________________________________________________________________ Top of natural channel elevation = 1533.000(Ft.)
End of natural channel elevation = 1514.000(Ft.)
Length of natural channel = 1843.000(Ft.)
Estimated mean flow rate at midpoint of channel = 59.437(CFS)

Natural valley channel type used
L.A. County flood control district formula for channel velocity:

Velocity(ft/s) = (7 + 8(q(English Units)^.352)(slope^0.5) Velocity using mean channel flow = 4.13(Ft/s)

Correction to map slope used on extremely rugged channels with drops and waterfalls (Plate D-6.2)
Normal channel slope = 0.0103
Corrected/adjusted channel slope = 0.0103
Travel time = 7.43 min. TC = 20.96 min.

Adding area flow to channel
UNDEVELOPED (poor cover) subarea
Runoff Coefficient = 0.580
Decimal fraction soil group A = 0.000
Decimal fraction soil group B = 0.250
Decimal fraction soil group C = 0.100
Decimal fraction soil group D = 0.650
RI index for soil(AMC 1) = 71.52
Pervious area fraction = 1.000; Impervious fraction = 0.000 Rainfall intensity = 0.960(In/Hr) for a 2.0 year storm Subarea runoff = 40.967(CFS) for 73.600(Ac.)
Total runoff = 75.138(CFS) Total area = 123.370(Ac.)

++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ Process from Point/Station 103.000 to Point/Station 104.000 **** CONFLUENCE OF MINOR STREAMS ****
______________________________________________________________________ Along Main Stream number: 1 in normal stream number 1
Stream flow area = 123.370(Ac.)
Runoff from this stream = 75.138(CFS)
Time of concentration = 20.96 min.

H:\00546\Planning\WQMP - Preliminary\Parts\Appendix 7 - Hydromodification\01 - EXA002.docx Rainfall intensity = 0.960(In/Hr)

++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ Process from Point/Station 105.000 to Point/Station 106.000 **** INITIAL AREA EVALUATION ****
______________________________________________________________________ Initial area flow distance = 790.000(Ft.)
Top (of initial area) elevation = 1543.000(Ft.)
Bottom (of initial area) elevation = 1522.000(Ft.)
Difference in elevation = 21.000(Ft.)
Slope = 0.02658 s(percent)= 2.66
TC = k(0.530)*[(length^3)/(elevation change)]^0.2
Initial area time of concentration = 15.791 min.

Rainfall intensity = 1.116(In/Hr) for a 2.0 year storm UNDEVELOPED (poor cover) subarea
Runoff Coefficient = 0.614
Decimal fraction soil group A = 0.000
Decimal fraction soil group B = 0.250
Decimal fraction soil group C = 0.000
Decimal fraction soil group D = 0.750
RI index for soil(AMC 1) = 72.00
Pervious area fraction = 1.000; Impervious fraction = 0.000 Initial subarea runoff = 4.457(CFS)
Total initial stream area = 6.500(Ac.)
Pervious area fraction = 1.000

++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ Process from Point/Station 106.000 to Point/Station 104.000 **** NATURAL CHANNEL TIME + SUBAREA FLOW ADDITION ****
______________________________________________________________________ Top of natural channel elevation = 1519.000(Ft.)
End of natural channel elevation = 1514.000(Ft.)
Length of natural channel = 634.000(Ft.)
Estimated mean flow rate at midpoint of channel = 10.738(CFS)

Natural valley channel type used
L.A. County flood control district formula for channel velocity:

Velocity(ft/s) = (7 + 8(q(English Units)^.352)(slope^0.5) Velocity using mean channel flow = 2.26(Ft/s)

Correction to map slope used on extremely rugged channels with drops and waterfalls (Plate D-6.2)
Normal channel slope = 0.0079
Corrected/adjusted channel slope = 0.0079
Travel time = 4.68 min. TC = 20.47 min.

Adding area flow to channel
UNDEVELOPED (poor cover) subarea
Runoff Coefficient = 0.546
Decimal fraction soil group A = 0.000
Decimal fraction soil group B = 0.500
Decimal fraction soil group C = 0.000
Decimal fraction soil group D = 0.500
RI index for soil(AMC 1) = 67.90
Pervious area fraction = 1.000; Impervious fraction = 0.000 Rainfall intensity = 0.973(In/Hr) for a 2.0 year storm Subarea runoff = 9.730(CFS) for 18.320(Ac.)
Total runoff = 14.187(CFS) Total area = 24.820(Ac.)

++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ Process from Point/Station 106.000 to Point/Station 104.000 **** CONFLUENCE OF MINOR STREAMS ****
______________________________________________________________________ Along Main Stream number: 1 in normal stream number 2
Stream flow area = 24.820(Ac.)
Runoff from this stream = 14.187(CFS)
Time of concentration = 20.47 min.

H:\00546\Planning\WQMP - Preliminary\Parts\Appendix 7 - Hydromodification\01 - EXA002.docx Rainfall intensity = 0.973(In/Hr)
Summary of stream data:

Stream Flow rate TC Rainfall Intensity No. (CFS) (min) (In/Hr)

1 75.138 20.96 0.960
2 14.187 20.47 0.973
Largest stream flow has longer time of concentration
Qp = 75.138 + sum of
Qb Ia/Ib

14.187 * 0.987 = 14.009
Qp = 89.146

Total of 2 streams to confluence:

Flow rates before confluence point:

75.138 14.187
Area of streams before confluence:
123.370 24.820
Results of confluence:

Total flow rate = 89.146(CFS)
Time of concentration = 20.961 min.

Effective stream area after confluence = 148.190(Ac.)

++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ Process from Point/Station 104.000 to Point/Station 107.000 **** NATURAL CHANNEL TIME + SUBAREA FLOW ADDITION ****
______________________________________________________________________ Top of natural channel elevation = 1514.000(Ft.)
End of natural channel elevation = 1504.000(Ft.)
Length of natural channel = 897.000(Ft.)
Estimated mean flow rate at midpoint of channel = 96.678(CFS)

Natural valley channel type used
L.A. County flood control district formula for channel velocity:

Velocity(ft/s) = (7 + 8(q(English Units)^.352)(slope^0.5) Velocity using mean channel flow = 4.96(Ft/s)

Correction to map slope used on extremely rugged channels with drops and waterfalls (Plate D-6.2)
Normal channel slope = 0.0111
Corrected/adjusted channel slope = 0.0111
Travel time = 3.01 min. TC = 23.97 min.

Adding area flow to channel
UNDEVELOPED (poor cover) subarea
Runoff Coefficient = 0.531
Decimal fraction soil group A = 0.000
Decimal fraction soil group B = 0.400
Decimal fraction soil group C = 0.300
Decimal fraction soil group D = 0.300
RI index for soil(AMC 1) = 68.18
Pervious area fraction = 1.000; Impervious fraction = 0.000 Rainfall intensity = 0.894(In/Hr) for a 2.0 year storm Subarea runoff = 11.886(CFS) for 25.040(Ac.)
Total runoff = 101.032(CFS) Total area = 173.230(Ac.) End of computations, total study area = 173.23 (Ac.) The following figures may
be used for a unit hydrograph study of the same area.

Area averaged pervious area fraction(Ap) = 1.000
Area averaged RI index number = 83.7

H:\00546\Planning\WQMP - Preliminary\Parts\Appendix 7 - Hydromodification\02 - pr002.docx

Riverside County Rational Hydrology Program

CIVILCADD/CIVILDESIGN Engineering Software,(c) 1989 - 2014 Version 9.0 Rational Hydrology Study Date: 11/08/21 File:PR002.out ------------------------------------------------------------------------ TRACT 31194 - 'GOLDEN MEADOWS' MAJOR MODIFICATION
PRELIMINARY HYDROLOGY STUDY – AREA ‘A’
DEVELOPED CONDITION RATIONAL METHOD - 2 YEAR STORM
HUNSAKER & ASSOCIATES, MAY 2021, BRIAN LOWELL, PE
------------------------------------------------------------------------ ********* Hydrology Study Control Information **********

English (in-lb) Units used in input data file

------------------------------------------------------------------------

Program License Serial Number 6406

------------------------------------------------------------------------ Rational Method Hydrology Program based on
Riverside County Flood Control & Water Conservation District 1978 hydrology manual

Storm event (year) = 2.00 Antecedent Moisture Condition = 1

2 year, 1 hour precipitation = 0.550(In.)
100 year, 1 hour precipitation = 1.300(In.)

Storm event year = 2.0
Calculated rainfall intensity data:
1 hour intensity = 0.550(In/Hr)
Slope of intensity duration curve = 0.5300

++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ Process from Point/Station 100.000 to Point/Station 101.000 **** INITIAL AREA EVALUATION ****
______________________________________________________________________ Initial area flow distance = 448.000(Ft.)
Top (of initial area) elevation = 1800.000(Ft.)
Bottom (of initial area) elevation = 1660.000(Ft.)
Difference in elevation = 140.000(Ft.)
Slope = 0.31250 s(percent)= 31.25
TC = k(0.530)*[(length^3)/(elevation change)]^0.2
Initial area time of concentration = 7.688 min.

Rainfall intensity = 1.634(In/Hr) for a 2.0 year storm UNDEVELOPED (poor cover) subarea
Runoff Coefficient = 0.588
Decimal fraction soil group A = 0.000
Decimal fraction soil group B = 1.000
Decimal fraction soil group C = 0.000
Decimal fraction soil group D = 0.000
RI index for soil(AMC 1) = 60.60
Pervious area fraction = 1.000; Impervious fraction = 0.000 Initial subarea runoff = 3.152(CFS)
Total initial stream area = 3.280(Ac.)
Pervious area fraction = 1.000

H:\00546\Planning\WQMP - Preliminary\Parts\Appendix 7 - Hydromodification\02 - pr002.docx

++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ Process from Point/Station 101.000 to Point/Station 102.000 **** NATURAL CHANNEL TIME + SUBAREA FLOW ADDITION ****
______________________________________________________________________ Top of natural channel elevation = 1660.000(Ft.)
End of natural channel elevation = 1565.300(Ft.)
Length of natural channel = 618.000(Ft.)
Estimated mean flow rate at midpoint of channel = 7.534(CFS)

Natural valley channel type used
L.A. County flood control district formula for channel velocity:

Velocity(ft/s) = (7 + 8(q(English Units)^.352)(slope^0.5) Velocity using mean channel flow = 8.61(Ft/s)

Correction to map slope used on extremely rugged channels with drops and waterfalls (Plate D-6.2)
Normal channel slope = 0.1532
Corrected/adjusted channel slope = 0.1366
Travel time = 1.20 min. TC = 8.88 min.

Adding area flow to channel
UNDEVELOPED (poor cover) subarea
Runoff Coefficient = 0.572
Decimal fraction soil group A = 0.000
Decimal fraction soil group B = 1.000
Decimal fraction soil group C = 0.000
Decimal fraction soil group D = 0.000
RI index for soil(AMC 1) = 60.60
Pervious area fraction = 1.000; Impervious fraction = 0.000 Rainfall intensity = 1.514(In/Hr) for a 2.0 year storm Subarea runoff = 7.899(CFS) for 9.120(Ac.)
Total runoff = 11.051(CFS) Total area = 12.400(Ac.)

++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ Process from Point/Station 102.000 to Point/Station 102.100 **** PIPEFLOW TRAVEL TIME (Program estimated size) **** ______________________________________________________________________ Upstream point/station elevation = 1565.300(Ft.)
Downstream point/station elevation = 1563.000(Ft.)
Pipe length = 123.00(Ft.) Manning's N = 0.013
No. of pipes = 1 Required pipe flow = 11.051(CFS)
Nearest computed pipe diameter = 18.00(In.)
Calculated individual pipe flow = 11.051(CFS)
Normal flow depth in pipe = 11.84(In.)
Flow top width inside pipe = 17.08(In.)
Critical Depth = 15.27(In.)
Pipe flow velocity = 8.96(Ft/s)
Travel time through pipe = 0.23 min.

Time of concentration (TC) = 9.11 min.

++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ Process from Point/Station 102.100 to Point/Station 102.100 **** SUBAREA FLOW ADDITION ****
______________________________________________________________________ SINGLE FAMILY (1/4 Acre Lot)
Runoff Coefficient = 0.624
Decimal fraction soil group A = 0.000
Decimal fraction soil group B = 1.000
Decimal fraction soil group C = 0.000

H:\00546\Planning\WQMP - Preliminary\Parts\Appendix 7 - Hydromodification\02 - pr002.docx Decimal fraction soil group D = 0.000
RI index for soil(AMC 1) = 36.00
Pervious area fraction = 0.500; Impervious fraction = 0.500 Time of concentration = 9.11 min.

Rainfall intensity = 1.493(In/Hr) for a 2.0 year storm Subarea runoff = 0.960(CFS) for 1.030(Ac.)
Total runoff = 12.011(CFS) Total area = 13.430(Ac.)

++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ Process from Point/Station 102.100 to Point/Station 103.000 **** PIPEFLOW TRAVEL TIME (Program estimated size) **** ______________________________________________________________________ Upstream point/station elevation = 1563.000(Ft.)
Downstream point/station elevation = 1549.000(Ft.)
Pipe length = 671.00(Ft.) Manning's N = 0.013
No. of pipes = 1 Required pipe flow = 12.011(CFS)
Nearest computed pipe diameter = 18.00(In.)
Calculated individual pipe flow = 12.011(CFS)
Normal flow depth in pipe = 12.09(In.)
Flow top width inside pipe = 16.90(In.)
Critical Depth = 15.76(In.)
Pipe flow velocity = 9.52(Ft/s)
Travel time through pipe = 1.17 min.

Time of concentration (TC) = 10.29 min.

++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ Process from Point/Station 102.100 to Point/Station 103.000 **** CONFLUENCE OF MINOR STREAMS ****
______________________________________________________________________ Along Main Stream number: 1 in normal stream number 1
Stream flow area = 13.430(Ac.)
Runoff from this stream = 12.011(CFS)
Time of concentration = 10.29 min.

Rainfall intensity = 1.400(In/Hr)
Summary of stream data:

Stream Flow rate TC Rainfall Intensity No. (CFS) (min) (In/Hr)

1 12.011 10.29 1.400
Largest stream flow has longer time of concentration
Qp = 12.011 + sum of
Qp = 12.011

Total of 1 streams to confluence:

Flow rates before confluence point:

12.011
Area of streams before confluence:

13.430
Results of confluence:

Total flow rate = 12.011(CFS)
Time of concentration = 10.288 min.

Effective stream area after confluence = 13.430(Ac.)

++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ Process from Point/Station 104.000 to Point/Station 105.000 **** INITIAL AREA EVALUATION ****
______________________________________________________________________ Initial area flow distance = 425.000(Ft.)

H:\00546\Planning\WQMP - Preliminary\Parts\Appendix 7 - Hydromodification\02 - pr002.docx Top (of initial area) elevation = 1572.000(Ft.)
Bottom (of initial area) elevation = 1556.200(Ft.)
Difference in elevation = 15.800(Ft.)
Slope = 0.03718 s(percent)= 3.72
TC = k(0.390)*[(length^3)/(elevation change)]^0.2
Initial area time of concentration = 8.479 min.

Rainfall intensity = 1.551(In/Hr) for a 2.0 year storm SINGLE FAMILY (1/4 Acre Lot)
Runoff Coefficient = 0.628
Decimal fraction soil group A = 0.000
Decimal fraction soil group B = 1.000
Decimal fraction soil group C = 0.000
Decimal fraction soil group D = 0.000
RI index for soil(AMC 1) = 36.00
Pervious area fraction = 0.500; Impervious fraction = 0.500 Initial subarea runoff = 0.926(CFS)
Total initial stream area = 0.950(Ac.)
Pervious area fraction = 0.500

++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ Process from Point/Station 105.000 to Point/Station 103.000 **** PIPEFLOW TRAVEL TIME (Program estimated size) **** ______________________________________________________________________ Upstream point/station elevation = 1549.200(Ft.)
Downstream point/station elevation = 1549.000(Ft.)
Pipe length = 15.00(Ft.) Manning's N = 0.013
No. of pipes = 1 Required pipe flow = 0.926(CFS)
Nearest computed pipe diameter = 9.00(In.)
Calculated individual pipe flow = 0.926(CFS)
Normal flow depth in pipe = 4.42(In.)
Flow top width inside pipe = 9.00(In.)
Critical Depth = 5.29(In.)
Pipe flow velocity = 4.29(Ft/s)
Travel time through pipe = 0.06 min.

Time of concentration (TC) = 8.54 min.

++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ Process from Point/Station 105.000 to Point/Station 103.000 **** CONFLUENCE OF MINOR STREAMS ****
______________________________________________________________________ Along Main Stream number: 1 in normal stream number 2
Stream flow area = 0.950(Ac.)
Runoff from this stream = 0.926(CFS)
Time of concentration = 8.54 min.

Rainfall intensity = 1.546(In/Hr)
Summary of stream data:

Stream Flow rate TC Rainfall Intensity No. (CFS) (min) (In/Hr)

1 12.011 10.29 1.400
2 0.926 8.54 1.546
Largest stream flow has longer time of concentration
Qp = 12.011 + sum of
Qb Ia/Ib

0.926 * 0.906 = 0.839
Qp = 12.849

Total of 2 streams to confluence:

Flow rates before confluence point:

H:\00546\Planning\WQMP - Preliminary\Parts\Appendix 7 - Hydromodification\02 - pr002.docx

12.011 0.926
Area of streams before confluence:

13.430 0.950
Results of confluence:

Total flow rate = 12.849(CFS)
Time of concentration = 10.288 min.

Effective stream area after confluence = 14.380(Ac.)

++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ Process from Point/Station 103.000 to Point/Station 106.000 **** PIPEFLOW TRAVEL TIME (Program estimated size) **** ______________________________________________________________________ Upstream point/station elevation = 1549.000(Ft.)
Downstream point/station elevation = 1548.700(Ft.)
Pipe length = 29.00(Ft.) Manning's N = 0.013
No. of pipes = 1 Required pipe flow = 12.849(CFS)
Nearest computed pipe diameter = 21.00(In.)
Calculated individual pipe flow = 12.849(CFS)
Normal flow depth in pipe = 14.18(In.)
Flow top width inside pipe = 19.67(In.)
Critical Depth = 16.03(In.)
Pipe flow velocity = 7.44(Ft/s)
Travel time through pipe = 0.06 min.

Time of concentration (TC) = 10.35 min.

++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ Process from Point/Station 103.000 to Point/Station 106.000 **** CONFLUENCE OF MINOR STREAMS ****
______________________________________________________________________ Along Main Stream number: 1 in normal stream number 1
Stream flow area = 14.380(Ac.)
Runoff from this stream = 12.849(CFS)
Time of concentration = 10.35 min.

Rainfall intensity = 1.396(In/Hr)

++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ Process from Point/Station 104.000 to Point/Station 107.000 **** INITIAL AREA EVALUATION ****
______________________________________________________________________ Initial area flow distance = 553.000(Ft.)
Top (of initial area) elevation = 1572.000(Ft.)
Bottom (of initial area) elevation = 1564.600(Ft.)
Difference in elevation = 7.400(Ft.)
Slope = 0.01338 s(percent)= 1.34
TC = k(0.390)*[(length^3)/(elevation change)]^0.2
Initial area time of concentration = 11.557 min.

Rainfall intensity = 1.317(In/Hr) for a 2.0 year storm SINGLE FAMILY (1/4 Acre Lot)
Runoff Coefficient = 0.611
Decimal fraction soil group A = 0.000
Decimal fraction soil group B = 1.000
Decimal fraction soil group C = 0.000
Decimal fraction soil group D = 0.000
RI index for soil(AMC 1) = 36.00
Pervious area fraction = 0.500; Impervious fraction = 0.500 Initial subarea runoff = 0.949(CFS)
Total initial stream area = 1.180(Ac.)
Pervious area fraction = 0.500

H:\00546\Planning\WQMP - Preliminary\Parts\Appendix 7 - Hydromodification\02 - pr002.docx ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ Process from Point/Station 107.000 to Point/Station 108.000 **** STREET FLOW TRAVEL TIME + SUBAREA FLOW ADDITION **** ______________________________________________________________________ Top of street segment elevation = 1564.600(Ft.)
End of street segment elevation = 1556.200(Ft.)
Length of street segment = 684.000(Ft.)
Height of curb above gutter flowline = 6.0(In.)
Width of half street (curb to crown) = 18.000(Ft.)
Distance from crown to crossfall grade break = 16.000(Ft.) Slope from gutter to grade break (v/hz) = 0.020
Slope from grade break to crown (v/hz) = 0.020
Street flow is on [1] side(s) of the street
Distance from curb to property line = 10.000(Ft.)
Slope from curb to property line (v/hz) = 0.020
Gutter width = 2.000(Ft.)
Gutter hike from flowline = 2.000(In.)
Manning's N in gutter = 0.0130
Manning's N from gutter to grade break = 0.0130
Manning's N from grade break to crown = 0.0130
Estimated mean flow rate at midpoint of street = 1.553(CFS) Depth of flow = 0.269(Ft.), Average velocity = 2.459(Ft/s) Streetflow hydraulics at midpoint of street travel:

Halfstreet flow width = 7.105(Ft.)
Flow velocity = 2.46(Ft/s)
Travel time = 4.64 min. TC = 16.19 min.

Adding area flow to street
SINGLE FAMILY (1/4 Acre Lot)
Runoff Coefficient = 0.612
Decimal fraction soil group A = 0.000
Decimal fraction soil group B = 0.750
Decimal fraction soil group C = 0.050
Decimal fraction soil group D = 0.200
RI index for soil(AMC 1) = 40.45
Pervious area fraction = 0.500; Impervious fraction = 0.500 Rainfall intensity = 1.101(In/Hr) for a 2.0 year storm Subarea runoff = 1.152(CFS) for 1.710(Ac.)
Total runoff = 2.101(CFS) Total area = 2.890(Ac.) Street flow at end of street = 2.101(CFS)
Half street flow at end of street = 2.101(CFS)
Depth of flow = 0.291(Ft.), Average velocity = 2.621(Ft/s) Flow width (from curb towards crown)= 8.214(Ft.)

++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ Process from Point/Station 108.000 to Point/Station 106.000 **** PIPEFLOW TRAVEL TIME (Program estimated size) **** ______________________________________________________________________ Upstream point/station elevation = 1549.200(Ft.)
Downstream point/station elevation = 1548.700(Ft.)
Pipe length = 42.00(Ft.) Manning's N = 0.013
No. of pipes = 1 Required pipe flow = 2.101(CFS)
Nearest computed pipe diameter = 12.00(In.)
Calculated individual pipe flow = 2.101(CFS)
Normal flow depth in pipe = 6.28(In.)
Flow top width inside pipe = 11.99(In.)
Critical Depth = 7.43(In.)
Pipe flow velocity = 5.04(Ft/s)
Travel time through pipe = 0.14 min.

Time of concentration (TC) = 16.33 min.

++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++

H:\00546\Planning\WQMP - Preliminary\Parts\Appendix 7 - Hydromodification\02 - pr002.docx Process from Point/Station 108.000 to Point/Station 106.000 **** CONFLUENCE OF MINOR STREAMS ****
______________________________________________________________________ Along Main Stream number: 1 in normal stream number 2
Stream flow area = 2.890(Ac.)
Runoff from this stream = 2.101(CFS)
Time of concentration = 16.33 min.

Rainfall intensity = 1.096(In/Hr)
Summary of stream data:

Stream Flow rate TC Rainfall Intensity No. (CFS) (min) (In/Hr)

1 12.849 10.35 1.396
2 2.101 16.33 1.096
Largest stream flow has longer or shorter time of concentration Qp = 12.849 + sum of
Qa Tb/Ta

2.101 * 0.634 = 1.332
Qp = 14.181

Total of 2 streams to confluence:

Flow rates before confluence point:

12.849 2.101
Area of streams before confluence:

14.380 2.890
Results of confluence:

Total flow rate = 14.181(CFS)
Time of concentration = 10.353 min.

Effective stream area after confluence = 17.270(Ac.)

++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ Process from Point/Station 106.000 to Point/Station 109.000 **** PIPEFLOW TRAVEL TIME (Program estimated size) **** ______________________________________________________________________ Upstream point/station elevation = 1548.700(Ft.)
Downstream point/station elevation = 1523.000(Ft.)
Pipe length = 620.00(Ft.) Manning's N = 0.013
No. of pipes = 1 Required pipe flow = 14.181(CFS)
Nearest computed pipe diameter = 18.00(In.)
Calculated individual pipe flow = 14.181(CFS)
Normal flow depth in pipe = 10.71(In.)
Flow top width inside pipe = 17.67(In.)
Critical Depth = 16.64(In.)
Pipe flow velocity = 12.94(Ft/s)
Travel time through pipe = 0.80 min.

Time of concentration (TC) = 11.15 min.

++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ Process from Point/Station 106.000 to Point/Station 109.000 **** CONFLUENCE OF MINOR STREAMS ****
______________________________________________________________________ Along Main Stream number: 1 in normal stream number 1
Stream flow area = 17.270(Ac.)
Runoff from this stream = 14.181(CFS)
Time of concentration = 11.15 min.

Rainfall intensity = 1.342(In/Hr)

++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++

H:\00546\Planning\WQMP - Preliminary\Parts\Appendix 7 - Hydromodification\02 - pr002.docx Process from Point/Station 110.000 to Point/Station 111.000 **** INITIAL AREA EVALUATION ****
______________________________________________________________________ Initial area flow distance = 530.000(Ft.)
Top (of initial area) elevation = 1540.000(Ft.)
Bottom (of initial area) elevation = 1530.000(Ft.)
Difference in elevation = 10.000(Ft.)
Slope = 0.01887 s(percent)= 1.89
TC = k(0.710)*[(length^3)/(elevation change)]^0.2
Initial area time of concentration = 19.312 min.

Rainfall intensity = 1.003(In/Hr) for a 2.0 year storm UNDEVELOPED (fair cover) subarea
Runoff Coefficient = 0.529
Decimal fraction soil group A = 0.000
Decimal fraction soil group B = 0.150
Decimal fraction soil group C = 0.000
Decimal fraction soil group D = 0.850
RI index for soil(AMC 1) = 65.45
Pervious area fraction = 1.000; Impervious fraction = 0.000 Initial subarea runoff = 1.560(CFS)
Total initial stream area = 2.940(Ac.)
Pervious area fraction = 1.000

++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ Process from Point/Station 111.000 to Point/Station 109.000 **** PIPEFLOW TRAVEL TIME (Program estimated size) **** ______________________________________________________________________ Upstream point/station elevation = 1523.400(Ft.)
Downstream point/station elevation = 1523.000(Ft.)
Pipe length = 40.00(Ft.) Manning's N = 0.013
No. of pipes = 1 Required pipe flow = 1.560(CFS)
Nearest computed pipe diameter = 9.00(In.)
Calculated individual pipe flow = 1.560(CFS)
Normal flow depth in pipe = 6.95(In.)
Flow top width inside pipe = 7.55(In.)
Critical Depth = 6.90(In.)
Pipe flow velocity = 4.26(Ft/s)
Travel time through pipe = 0.16 min.

Time of concentration (TC) = 19.47 min.

++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ Process from Point/Station 111.000 to Point/Station 109.000 **** CONFLUENCE OF MINOR STREAMS ****
______________________________________________________________________ Along Main Stream number: 1 in normal stream number 2
Stream flow area = 2.940(Ac.)
Runoff from this stream = 1.560(CFS)
Time of concentration = 19.47 min.

Rainfall intensity = 0.999(In/Hr)
Summary of stream data:

Stream Flow rate TC Rainfall Intensity No. (CFS) (min) (In/Hr)

1 14.181 11.15 1.342
2 1.560 19.47 0.999
Largest stream flow has longer or shorter time of concentration Qp = 14.181 + sum of
Qa Tb/Ta

1.560 * 0.573 = 0.893

H:\00546\Planning\WQMP - Preliminary\Parts\Appendix 7 - Hydromodification\02 - pr002.docx Qp = 15.074

Total of 2 streams to confluence:

Flow rates before confluence point:

14.181 1.560
Area of streams before confluence:

17.270 2.940
Results of confluence:

Total flow rate = 15.074(CFS)
Time of concentration = 11.151 min.

Effective stream area after confluence = 20.210(Ac.)

++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ Process from Point/Station 109.000 to Point/Station 112.000 **** PIPEFLOW TRAVEL TIME (Program estimated size) **** ______________________________________________________________________ Upstream point/station elevation = 1523.000(Ft.)
Downstream point/station elevation = 1520.800(Ft.)
Pipe length = 38.00(Ft.) Manning's N = 0.013
No. of pipes = 1 Required pipe flow = 15.074(CFS)
Nearest computed pipe diameter = 15.00(In.)
Calculated individual pipe flow = 15.074(CFS)
Normal flow depth in pipe = 11.91(In.)
Flow top width inside pipe = 12.14(In.)
Critical depth could not be calculated.

Pipe flow velocity = 14.43(Ft/s)
Travel time through pipe = 0.04 min.

Time of concentration (TC) = 11.20 min.

++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ Process from Point/Station 109.000 to Point/Station 112.000 **** CONFLUENCE OF MINOR STREAMS ****
______________________________________________________________________ Along Main Stream number: 1 in normal stream number 1
Stream flow area = 20.210(Ac.)
Runoff from this stream = 15.074(CFS)
Time of concentration = 11.20 min.

Rainfall intensity = 1.339(In/Hr)

++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ Process from Point/Station 113.000 to Point/Station 114.000 **** INITIAL AREA EVALUATION ****
______________________________________________________________________ Initial area flow distance = 965.000(Ft.)
Top (of initial area) elevation = 1567.900(Ft.)
Bottom (of initial area) elevation = 1556.000(Ft.)
Difference in elevation = 11.900(Ft.)
Slope = 0.01233 s(percent)= 1.23
TC = k(0.390)*[(length^3)/(elevation change)]^0.2
Initial area time of concentration = 14.678 min.

Rainfall intensity = 1.160(In/Hr) for a 2.0 year storm SINGLE FAMILY (1/4 Acre Lot)
Runoff Coefficient = 0.650
Decimal fraction soil group A = 0.000
Decimal fraction soil group B = 0.300
Decimal fraction soil group C = 0.300
Decimal fraction soil group D = 0.400
RI index for soil(AMC 1) = 48.00
Pervious area fraction = 0.500; Impervious fraction = 0.500 Initial subarea runoff = 2.135(CFS)

H:\00546\Planning\WQMP - Preliminary\Parts\Appendix 7 - Hydromodification\02 - pr002.docx Total initial stream area = 2.830(Ac.)
Pervious area fraction = 0.500

++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ Process from Point/Station 114.000 to Point/Station 115.000 **** STREET FLOW TRAVEL TIME + SUBAREA FLOW ADDITION **** ______________________________________________________________________ Top of street segment elevation = 1556.000(Ft.)
End of street segment elevation = 1529.800(Ft.)
Length of street segment = 610.000(Ft.)
Height of curb above gutter flowline = 6.0(In.)
Width of half street (curb to crown) = 18.000(Ft.)
Distance from crown to crossfall grade break = 16.000(Ft.) Slope from gutter to grade break (v/hz) = 0.020
Slope from grade break to crown (v/hz) = 0.020
Street flow is on [1] side(s) of the street
Distance from curb to property line = 10.000(Ft.)
Slope from curb to property line (v/hz) = 0.020
Gutter width = 2.000(Ft.)
Gutter hike from flowline = 2.000(In.)
Manning's N in gutter = 0.0130
Manning's N from gutter to grade break = 0.0130
Manning's N from grade break to crown = 0.0130
Estimated mean flow rate at midpoint of street = 2.847(CFS) Depth of flow = 0.267(Ft.), Average velocity = 4.581(Ft/s) Streetflow hydraulics at midpoint of street travel:

Halfstreet flow width = 7.035(Ft.)
Flow velocity = 4.58(Ft/s)
Travel time = 2.22 min. TC = 16.90 min.

Adding area flow to street
SINGLE FAMILY (1/4 Acre Lot)
Runoff Coefficient = 0.615
Decimal fraction soil group A = 0.000
Decimal fraction soil group B = 0.700
Decimal fraction soil group C = 0.000
Decimal fraction soil group D = 0.300
RI index for soil(AMC 1) = 41.70
Pervious area fraction = 0.500; Impervious fraction = 0.500 Rainfall intensity = 1.077(In/Hr) for a 2.0 year storm Subarea runoff = 1.330(CFS) for 2.010(Ac.)
Total runoff = 3.465(CFS) Total area = 4.840(Ac.) Street flow at end of street = 3.465(CFS)
Half street flow at end of street = 3.465(CFS)
Depth of flow = 0.282(Ft.), Average velocity = 4.772(Ft/s) Flow width (from curb towards crown)= 7.743(Ft.)

++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ Process from Point/Station 115.000 to Point/Station 112.000 **** PIPEFLOW TRAVEL TIME (Program estimated size) **** ______________________________________________________________________ Upstream point/station elevation = 1521.200(Ft.)
Downstream point/station elevation = 1520.800(Ft.)
Pipe length = 30.00(Ft.) Manning's N = 0.013
No. of pipes = 1 Required pipe flow = 3.465(CFS)
Nearest computed pipe diameter = 12.00(In.)
Calculated individual pipe flow = 3.465(CFS)
Normal flow depth in pipe = 8.44(In.)
Flow top width inside pipe = 10.97(In.)
Critical Depth = 9.55(In.)
Pipe flow velocity = 5.87(Ft/s)
Travel time through pipe = 0.09 min.

H:\00546\Planning\WQMP - Preliminary\Parts\Appendix 7 - Hydromodification\02 - pr002.docx Time of concentration (TC) = 16.98 min.

++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ Process from Point/Station 115.000 to Point/Station 112.000 **** CONFLUENCE OF MINOR STREAMS ****
______________________________________________________________________ Along Main Stream number: 1 in normal stream number 2
Stream flow area = 4.840(Ac.)
Runoff from this stream = 3.465(CFS)
Time of concentration = 16.98 min.

Rainfall intensity = 1.074(In/Hr)

++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ Process from Point/Station 104.000 to Point/Station 127.000 **** INITIAL AREA EVALUATION ****
______________________________________________________________________ Initial area flow distance = 623.000(Ft.)
Top (of initial area) elevation = 1572.000(Ft.)
Bottom (of initial area) elevation = 1552.000(Ft.)
Difference in elevation = 20.000(Ft.)
Slope = 0.03210 s(percent)= 3.21
TC = k(0.390)*[(length^3)/(elevation change)]^0.2
Initial area time of concentration = 10.175 min.

Rainfall intensity = 1.409(In/Hr) for a 2.0 year storm SINGLE FAMILY (1/4 Acre Lot)
Runoff Coefficient = 0.618
Decimal fraction soil group A = 0.000
Decimal fraction soil group B = 1.000
Decimal fraction soil group C = 0.000
Decimal fraction soil group D = 0.000
RI index for soil(AMC 1) = 36.00
Pervious area fraction = 0.500; Impervious fraction = 0.500 Initial subarea runoff = 1.549(CFS)
Total initial stream area = 1.780(Ac.)
Pervious area fraction = 0.500

++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ Process from Point/Station 127.000 to Point/Station 128.000 **** STREET FLOW TRAVEL TIME + SUBAREA FLOW ADDITION **** ______________________________________________________________________ Top of street segment elevation = 1552.000(Ft.)
End of street segment elevation = 1529.800(Ft.)
Length of street segment = 518.000(Ft.)
Height of curb above gutter flowline = 6.0(In.)
Width of half street (curb to crown) = 18.000(Ft.)
Distance from crown to crossfall grade break = 16.000(Ft.) Slope from gutter to grade break (v/hz) = 0.020
Slope from grade break to crown (v/hz) = 0.020
Street flow is on [1] side(s) of the street
Distance from curb to property line = 10.000(Ft.)
Slope from curb to property line (v/hz) = 0.020
Gutter width = 2.000(Ft.)
Gutter hike from flowline = 2.000(In.)
Manning's N in gutter = 0.0130
Manning's N from gutter to grade break = 0.0130
Manning's N from grade break to crown = 0.0130
Estimated mean flow rate at midpoint of street = 2.352(CFS) Depth of flow = 0.254(Ft.), Average velocity = 4.407(Ft/s) Streetflow hydraulics at midpoint of street travel:

Halfstreet flow width = 6.381(Ft.)

H:\00546\Planning\WQMP - Preliminary\Parts\Appendix 7 - Hydromodification\02 - pr002.docx Flow velocity = 4.41(Ft/s)
Travel time = 1.96 min. TC = 12.13 min.

Adding area flow to street
SINGLE FAMILY (1/4 Acre Lot)
Runoff Coefficient = 0.633
Decimal fraction soil group A = 0.000
Decimal fraction soil group B = 0.700
Decimal fraction soil group C = 0.000
Decimal fraction soil group D = 0.300
RI index for soil(AMC 1) = 41.70
Pervious area fraction = 0.500; Impervious fraction = 0.500 Rainfall intensity = 1.283(In/Hr) for a 2.0 year storm Subarea runoff = 1.552(CFS) for 1.910(Ac.)
Total runoff = 3.101(CFS) Total area = 3.690(Ac.) Street flow at end of street = 3.101(CFS)
Half street flow at end of street = 3.101(CFS)
Depth of flow = 0.274(Ft.), Average velocity = 4.658(Ft/s) Flow width (from curb towards crown)= 7.343(Ft.)

++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ Process from Point/Station 128.000 to Point/Station 112.000 **** PIPEFLOW TRAVEL TIME (Program estimated size) **** ______________________________________________________________________ Upstream point/station elevation = 1521.200(Ft.)
Downstream point/station elevation = 1520.800(Ft.)
Pipe length = 45.00(Ft.) Manning's N = 0.013
No. of pipes = 1 Required pipe flow = 3.101(CFS)
Nearest computed pipe diameter = 12.00(In.)
Calculated individual pipe flow = 3.101(CFS)
Normal flow depth in pipe = 9.09(In.)
Flow top width inside pipe = 10.28(In.)
Critical Depth = 9.06(In.)
Pipe flow velocity = 4.85(Ft/s)
Travel time through pipe = 0.15 min.

Time of concentration (TC) = 12.29 min.

++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ Process from Point/Station 128.000 to Point/Station 112.000 **** CONFLUENCE OF MINOR STREAMS ****
______________________________________________________________________ Along Main Stream number: 1 in normal stream number 3
Stream flow area = 3.690(Ac.)
Runoff from this stream = 3.101(CFS)
Time of concentration = 12.29 min.

Rainfall intensity = 1.274(In/Hr)
Summary of stream data:

Stream Flow rate TC Rainfall Intensity No. (CFS) (min) (In/Hr)

1 15.074 11.20 1.339
2 3.465 16.98 1.074
3 3.101 12.29 1.274
Largest stream flow has longer or shorter time of concentration Qp = 15.074 + sum of
Qa Tb/Ta

3.465 * 0.659 = 2.284
Qa Tb/Ta

3.101 * 0.911 = 2.825
Qp = 20.184

H:\00546\Planning\WQMP - Preliminary\Parts\Appendix 7 - Hydromodification\02 - pr002.docx

Total of 3 streams to confluence:

Flow rates before confluence point:

15.074 3.465 3.101
Area of streams before confluence:

20.210 4.840 3.690
Results of confluence:

Total flow rate = 20.184(CFS)
Time of concentration = 11.195 min.

Effective stream area after confluence = 28.740(Ac.)

++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ Process from Point/Station 112.000 to Point/Station 116.000 **** PIPEFLOW TRAVEL TIME (Program estimated size) **** ______________________________________________________________________ Upstream point/station elevation = 1520.800(Ft.)
Downstream point/station elevation = 1520.000(Ft.)
Pipe length = 32.00(Ft.) Manning's N = 0.013
No. of pipes = 1 Required pipe flow = 20.184(CFS)
Nearest computed pipe diameter = 21.00(In.)
Calculated individual pipe flow = 20.184(CFS)
Normal flow depth in pipe = 14.27(In.)
Flow top width inside pipe = 19.60(In.)
Critical Depth = 19.24(In.)
Pipe flow velocity = 11.59(Ft/s)
Travel time through pipe = 0.05 min.

Time of concentration (TC) = 11.24 min.

++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ Process from Point/Station 112.000 to Point/Station 116.000 **** CONFLUENCE OF MINOR STREAMS ****
______________________________________________________________________ Along Main Stream number: 1 in normal stream number 1
Stream flow area = 28.740(Ac.)
Runoff from this stream = 20.184(CFS)
Time of concentration = 11.24 min.

Rainfall intensity = 1.336(In/Hr)

++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ Process from Point/Station 117.000 to Point/Station 118.000 **** INITIAL AREA EVALUATION ****
______________________________________________________________________ Initial area flow distance = 500.000(Ft.)
Top (of initial area) elevation = 1543.800(Ft.)
Bottom (of initial area) elevation = 1539.300(Ft.)
Difference in elevation = 4.500(Ft.)
Slope = 0.00900 s(percent)= 0.90
TC = k(0.390)*[(length^3)/(elevation change)]^0.2
Initial area time of concentration = 12.017 min.

Rainfall intensity = 1.290(In/Hr) for a 2.0 year storm SINGLE FAMILY (1/4 Acre Lot)
Runoff Coefficient = 0.651
Decimal fraction soil group A = 0.000
Decimal fraction soil group B = 0.500
Decimal fraction soil group C = 0.000
Decimal fraction soil group D = 0.500
RI index for soil(AMC 1) = 45.60
Pervious area fraction = 0.500; Impervious fraction = 0.500 Initial subarea runoff = 0.748(CFS)
Total initial stream area = 0.890(Ac.)

H:\00546\Planning\WQMP - Preliminary\Parts\Appendix 7 - Hydromodification\02 - pr002.docx Pervious area fraction = 0.500

++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ Process from Point/Station 118.000 to Point/Station 119.000 **** STREET FLOW TRAVEL TIME + SUBAREA FLOW ADDITION **** ______________________________________________________________________ Top of street segment elevation = 1539.300(Ft.)
End of street segment elevation = 1529.800(Ft.)
Length of street segment = 933.000(Ft.)
Height of curb above gutter flowline = 8.0(In.)
Width of half street (curb to crown) = 38.000(Ft.)
Distance from crown to crossfall grade break = 20.000(Ft.) Slope from gutter to grade break (v/hz) = 0.020
Slope from grade break to crown (v/hz) = 0.020
Street flow is on [1] side(s) of the street
Distance from curb to property line = 40.000(Ft.)
Slope from curb to property line (v/hz) = 0.020
Gutter width = 2.000(Ft.)
Gutter hike from flowline = 2.000(In.)
Manning's N in gutter = 0.0130
Manning's N from gutter to grade break = 0.0130
Manning's N from grade break to crown = 0.0130
Estimated mean flow rate at midpoint of street = 1.339(CFS) Depth of flow = 0.265(Ft.), Average velocity = 2.215(Ft/s) Streetflow hydraulics at midpoint of street travel:

Halfstreet flow width = 6.914(Ft.)
Flow velocity = 2.21(Ft/s)
Travel time = 7.02 min. TC = 19.04 min.

Adding area flow to street
SINGLE FAMILY (1/4 Acre Lot)
Runoff Coefficient = 0.645
Decimal fraction soil group A = 0.000
Decimal fraction soil group B = 0.300
Decimal fraction soil group C = 0.000
Decimal fraction soil group D = 0.700
RI index for soil(AMC 1) = 50.16
Pervious area fraction = 0.500; Impervious fraction = 0.500 Rainfall intensity = 1.011(In/Hr) for a 2.0 year storm Subarea runoff = 1.101(CFS) for 1.690(Ac.)
Total runoff = 1.849(CFS) Total area = 2.580(Ac.) Street flow at end of street = 1.849(CFS)
Half street flow at end of street = 1.849(CFS)
Depth of flow = 0.288(Ft.), Average velocity = 2.369(Ft/s) Flow width (from curb towards crown)= 8.085(Ft.)

++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ Process from Point/Station 119.000 to Point/Station 116.000 **** PIPEFLOW TRAVEL TIME (Program estimated size) **** ______________________________________________________________________ Upstream point/station elevation = 1521.400(Ft.)
Downstream point/station elevation = 1520.000(Ft.)
Pipe length = 57.00(Ft.) Manning's N = 0.013
No. of pipes = 1 Required pipe flow = 1.849(CFS)
Nearest computed pipe diameter = 9.00(In.)
Calculated individual pipe flow = 1.849(CFS)
Normal flow depth in pipe = 5.62(In.)
Flow top width inside pipe = 8.72(In.)
Critical Depth = 7.46(In.)
Pipe flow velocity = 6.38(Ft/s)
Travel time through pipe = 0.15 min.

Time of concentration (TC) = 19.19 min.

H:\00546\Planning\WQMP - Preliminary\Parts\Appendix 7 - Hydromodification\02 - pr002.docx

++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ Process from Point/Station 119.000 to Point/Station 116.000 **** CONFLUENCE OF MINOR STREAMS ****
______________________________________________________________________ Along Main Stream number: 1 in normal stream number 2
Stream flow area = 2.580(Ac.)
Runoff from this stream = 1.849(CFS)
Time of concentration = 19.19 min.

Rainfall intensity = 1.006(In/Hr)
Summary of stream data:

Stream Flow rate TC Rainfall Intensity No. (CFS) (min) (In/Hr)

1 20.184 11.24 1.336
2 1.849 19.19 1.006
Largest stream flow has longer or shorter time of concentration Qp = 20.184 + sum of
Qa Tb/Ta

1.849 * 0.586 = 1.083
Qp = 21.267

Total of 2 streams to confluence:

Flow rates before confluence point:

20.184 1.849
Area of streams before confluence:

28.740 2.580
Results of confluence:

Total flow rate = 21.267(CFS)
Time of concentration = 11.241 min.

Effective stream area after confluence = 31.320(Ac.)

++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ Process from Point/Station 116.000 to Point/Station 120.000 **** PIPEFLOW TRAVEL TIME (Program estimated size) **** ______________________________________________________________________ Upstream point/station elevation = 1520.000(Ft.)
Downstream point/station elevation = 1519.500(Ft.)
Pipe length = 54.00(Ft.) Manning's N = 0.013
No. of pipes = 1 Required pipe flow = 21.267(CFS)
Nearest computed pipe diameter = 24.00(In.)
Calculated individual pipe flow = 21.267(CFS)
Normal flow depth in pipe = 19.17(In.)
Flow top width inside pipe = 19.24(In.)
Critical Depth = 19.82(In.)
Pipe flow velocity = 7.90(Ft/s)
Travel time through pipe = 0.11 min.

Time of concentration (TC) = 11.36 min.

++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ Process from Point/Station 116.000 to Point/Station 120.000 **** CONFLUENCE OF MAIN STREAMS ****
______________________________________________________________________ The following data inside Main Stream is listed:

In Main Stream number: 1
Stream flow area = 31.320(Ac.)
Runoff from this stream = 21.267(CFS)
Time of concentration = 11.36 min.