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November 30, 2009 California Energy Commission Docket Unit 1516 Ninth Street Sacramento, CA 95814-5512

Subject: BLYTHE SOLAR POWER PLANT PRE-DEVELOPMENT

DRAINAGE CONDITIONS REPORT DOCKET NO. (09-AFC-6)

Enclosed for filing with the California Energy Commission is the original copy of the BLYTHE SOLAR POWER PLANT PRE-DEVELOPMENT DRAINAGE CONDITIONS REPORT, for the Blythe Solar Power Project (09-AFC-6). Sincerely,

Marie Mills

DATE RECD.

DOCKET09-AFC-6

NOV 30 2009

NOV 30 2009

Blythe Solar Power Plant

Pre-Development Drainage Conditions November 25, 2009

This report has been prepared for:

Solar Millennium

1625 Shattuck Ave., Suite 270

Berkeley, CA 94709-1611

This report was prepared by:

AECOM Inc.

999 Town & Country Road

Orange, CA 92686

Project Manager: Bill Hagmaier, P.E.

Senior Drainage Engineer: Matthew Brown, P.E.

Drainage Engineer: Enrique Triana, Ph.D.

Blythe Solar Power Plant – Pre-Development Drainage Conditions i

TABLE OF CONTENTS

EXECUTIVE SUMMARY ................................................................................................................... ii GLOSSARY OF TERMS .................................................................................................................... iv 1. PROJECT DESCRIPTION .............................................................................................................. 1

1.1 Introduction.................................................................................................................... 1 1.2 Site Description .............................................................................................................. 1 1.3 Existing Condition Flow Patterns................................................................................... 2 1.3.1 Off-Site Flow Patterns ................................................................................................ 2 1.3.2 On-Site Flow Patterns ................................................................................................ 2

2. METHODOLOGY......................................................................................................................... 3 2.1 Spatial Configuration...................................................................................................... 3 2.2 Elevation ......................................................................................................................... 4 2.3 Manning’s N.................................................................................................................... 4 2.4 Rainfall-Runoff Modeling............................................................................................... 5 2.5 Inflow to the FLO-2D Model .......................................................................................... 5 2.6 Outflow from the FLO-2D Model ................................................................................... 7 2.7 Precipitation ................................................................................................................... 7

3. RESULTS AND CONCLUSIONS .................................................................................................... 9

Appendix A: 100-year Existing Hydrology Flow Depth, Velocity, and Water Surface Maps

Appendix B: 25-year Existing Hydrology Flow Depth, Velocity, and Water Surface Maps

Appendix C: 10-year Existing Hydrology Flow Depth, Velocity, and Water Surface Maps

List of Figures

Figure 1. Model Boundary and Drainage Basins outside the Model Boundary.......................... 4 Figure 2. Spatial distribution of overland flow roughness coefficients ...................................... 5 Figure 3. Inflow hydrographs for 100, 25 and 10 year hydrologic events................................... 6 Figure 4. Flow Cross Section Locations ......................................................................................... 8

Blythe Solar Power Plant – Pre-Development Drainage Conditions ii

EXECUTIVE SUMMARY

This report provides results of analysis of on-site, pre-development drainage conditions at the

Blythe Solar Power Plant site. This report is a supplement to the Blythe Solar Power Plant,

Drainage Report: August 7, 2009 (August 2009 report). This report utilizes refined topographic

site data (LIDAR) and a detailed two-dimensional, unconfined flow modeling approach (FLO-2D)

to document the pre-development flows.

Appendices A, B, and C include site maps of the Blythe site (associated with the 100-year, 25-

year and 10-year storm events, respectively) of FLO-2D simulated maximum flow depth (Sheet

1 of 3), maximum velocity (Sheet 2 of 3), and maximum water surface elevation (Sheet 3 of 3).

Tables 1, 2, and 3 below provide a summary of peak flow rate (cfs), total flow volume (acre-

feet), and maximum flow width (feet) at the four “Flow Analysis Cross Sections” defined in the

FLO-2D model and shown on Appendix maps (for the 10-, 25-, and 100-year storm events,

respectively). The four “Flow Analysis Cross Sections” represent the location at the

downstream side of the project boundary where water exits the site. The four Flow Analysis

Cross Section locations associated with existing flows are utilized in the proposed design to

align the post-development drainage discharges closely with the existing condition.

TABLE 1

PRE-DEVELOPMENT FLO2D RESULTS

10-Year Storm Event

Flow Analysis

Cross Section

Peak Flow

Rate (cfs)

Total Flow

Volume (ac-ft)

Max. Flow

Width (ft)

1 310 164 800

2 0 0 0

3 23 9 1200

4 0 0 0

TABLE 2


25-Year Storm Event

Flow Analysis

Cross Section

Peak Flow

Rate (cfs)

Total Flow

Volume (ac-ft)

Max. Flow

Width (ft)

1 726 348 1040

2 0 0 0

3 199 101 2480

4 0 0 0

Blythe Solar Power Plant – Pre-Development Drainage Conditions iii

TABLE 3


100-Year Storm Event

Flow Analysis

Cross Section

Peak Flow

Rate (cfs)

Total Flow

Volume (ac-ft)

Max. Flow

Width (ft)

1 1478 1508 1760

2 75 59 1600

3 823 594 2640

4 96 76 800

The FLO-2D model simulates volumetric mass balance of water inflows, losses, and outflows

consisting of five primary components listed below and tabulated in Table 4 by column:

A. Off-Site Surface Water Inflow (estimated with HEC-HMS model from August 2009 report).

B. On-Site Precipitation Inflow (estimated with FLO-2D model).

C. On-Site Initial Abstraction and Infiltration Losses (estimated with FLO-2D model).

D. On-Site Watershed Storage (estimated with FLO-2D model).

E. Surface Water Outflow (calculated with FLO-2D model as item A plus B minus C minus D).

TABLE 4

FLO-2D MODEL RESULTS (MASS BALANCE)

A B C D E

Storm

Event

Off-Site SW

Inflow (ac-ft)

On-Site Precip.

Inflow (ac-ft)

On-Site Initial Ab.

and Infil. Loss (ac-ft)

On-Site Watershed

Storage (ac-ft)

Surface Water

Outflow (ac-ft)

(ac-ft) (ac-ft) (ac-ft) (ac-ft) (ac-ft)

10-Yr 268 3228 2317 1171 8

25-Yr 396 4100 2619 1711 168

100-Yr 640 5552 2983 2053 1156

Blythe Solar Power Plant – Pre-Development Drainage Conditions iv

GLOSSARY OF TERMS

The following glossary provides brief definitions of technical terms used throughout this report.

Drainage Basin: Extent of land where water from rain or snow-melt drains by gravity into a

body of water (e.g., river, lake, reservoir, estuary, wetland, sea, or ocean).

Dynamic Wave: One solution method used (in FLO-2D) to solve the momentum equation.

FLO-2D Model: An integrated river/floodplain and flood routing hydrologic/hydraulic model.

Grid Element (also Grid Cell): Geographic space, as an array, of equally sized square grid points

arranged in rows and columns. Each grid point stores a numeric value that represents a

geographic attribute (such as elevation or surface slope) for that unit of space. Each grid cell is

referenced by its X and Y coordinate location.

Hydrograph: Graph showing changes in flow rate over time.

Hydrologic Model: Simplified, conceptual representation of portions of the hydrologic cycle.

Hydrology: Study of movement, distribution, and quality of water through a system.

Initial Abstraction (also Interception): The portion of rainfall that does not reach the ground

(initially) due to vegetated cover or other man-made obstructions.

Model Domain: Geographic area represented by the FLO-2D model.

Momentum Equation: Equation to represent open channel flow and flow over floodplains.

Model Stability: The ability of the model to solve governing equations given computational

time and error considerations.

Non-Uniform Flow: Flow characterized by varying velocity with respect to distance at a given

time.

Spatial/Model Domain: Geographic area represented by the FLO-2D model.

Spatial Resolution: The level of detail that can be included in the geographic representation of

the model. The smaller the model grid cell size, the higher the model resolution.

Time Step: A discrete length of time used in the model calculations.

Unsteady Flow: Flow characterized by varying velocity with respect to time at a given location.

Blythe Solar Power Plant – Pre-Development Drainage Conditions Page 1 of 12

1. PROJECT DESCRIPTION

1.1 Introduction

Solar Millennium and Chevron Energy Solutions (Chevron) propose to locate a solar power plant

near the City of Blythe, in Riverside County, California, on land administered by the Bureau of

Land Management (BLM).

A hydrologic study (Blythe Solar Power Plant, Drainage Report: August 7, 2009) was completed

to analyze surface water drainage characteristics at the proposed Blythe site. The August 2009

study included pre- and post-development hydrologic modeling (HEC-HMS) of drainage areas

off-site (upslope) and through the proposed site and post-development, one-dimensional

hydraulic modeling (HEC-RAS) of proposed drainage channel improvements adjacent to and

through the site to downstream discharge points. The August 2009 study utilized USGS 20-foot

contour-interval topography as a portion of the model input parameters.

Subsequent to completion of the August 2009 report, LIDAR one-foot contour-interval

topography over the site was collected to refine on-site, pre-development hydrology and

hydraulic analysis. For the purposes of the current report, a detailed, two-dimensional, physical

modeling approach (FLO-2D) was implemented, using the LIDAR topography data, to refine

results of the original hydrologic model (HEC-HMS).

The two-dimensional FLO-2D approach summarized herein allows a more detailed

characterization of unconventional, unconfined surface water flow over topography consisting

of “alluvial fans”, as identified on the Blythe site. Off-site (up-slope) HEC-HMS hydrology data

(taken from the August 2009 report) was used, in combination with the LIDAR topography and

on-site rainfall and physical land attributes, as input parameters for the FLO-2D model, to

analyze pre-development flow characteristics (flow rate, velocity, volume, depth, and width)

across the project site.

1.2 Site Description

The general area surrounding the proposed project site consists of approximately 9,400 acres

located 8 miles west of Blythe, California and 2.5 miles north of Highway I–10. Access to the

site is from the Mesa Drive exit on I–10. The total area of land currently proposed for

development is approximately 7,030 acres.


1.3 Existing Condition Flow Patterns

1.3.1 Off-Site Flow Patterns

The major watercourse in the project area is McCoy Wash (east of the project site) which

drains 210 square miles of the Palo Verde Mesa, McCoy Mountains, Little Maria

Mountains and Big Maria Mountains and exits the mesa to the southeast of the site.

The project site lies in the Palo Verde Mesa east of the McCoy Mountains. The general

stormwater flow pattern is from higher elevations in the McCoy Mountains, located

approximately 3 miles west of the project site, into shallow moderately defined channels

at the base of the mountains. Alluvial fans radiate out from the base of the McCoy

Mountains and mesa discharging to a broad flat expanse of desert terrain sloping in a

southeasterly direction, passing surface water flow through the project to lower

elevations in the Palo Verde Mesa to the east and into irrigation canals in the Palo Verde

Valley. Ephemeral washes that traverse the project site from the McCoy Mountains in a

west to east orientation abate into the landscape prior to any surface hydrological

connection with the McCoy Wash.

1.3.2 On-Site Flow Patterns

Flow Patterns onsite are generally in a southeasterly direction. A hill at the northeast

corner of the site diverts flow in a southerly direction away from McCoy Wash. As it flows

past the southern end of the hill at about the middle of the project site, flow turns east

again toward McCoy Wash. Berms located southeast of the project site were constructed

offsite by others to divert flow east and south around agricultural land. Storm flows

generated on the existing site generally sheet flow to the southeast as well.


2. METHODOLOGY

Pre-development drainage over the Blythe site was analyzed using FLO-2D Version 2007.06, a

physical process model that routes rainfall-runoff and flood hydrographs over unconfined flow

surfaces or in channels. FLO-2D, owned by FLO-2D Software, Inc., is on FEMA’s list of approved

hydraulic models for riverine and unconfined alluvial fan flood studies, and has been

extensively used by the US Army Corps of Engineers.

The FLO-2D model’s spatial domain is represented as a system of square grid elements (tiles),

called cells, each with an elevation derived from a digital terrain model of the LIDAR topography

and hydraulic characteristics. The model provides results of water surface elevation, flow rate

and velocity, and other hydraulic parameters for all grid elements in discrete time steps, using a

dynamic wave approximation to the momentum equation1. FLO-2D simulates infiltration and

runoff after rainfall initial abstraction2, using the Soil Conservation Service (SCS) Curve Number

method.

Drainage conditions were simulated for a 48-hour period for the 10-, 25-, and 100-year

hydrologic events using the same base model configuration and parameters for all three

hydrologic events. The remainder of this section describes key user-selected model parameters

used for this study.

2.1 Spatial Configuration

A modeled area is defined by the model computational boundary (the model boundary), a line

that encloses the terrain to be modeled. The model boundary was placed around the project

site to accurately define flood distribution along the upstream and downstream project site

boundaries. The model boundary for this study is a closed polygon defined by lines along the

McCoy Mountain foothills to the west of the site, along a drainage basin boundary to the north

of the site, along a southeast trending line to the east of the site (west of McCoy Wash), and

along an east-west trending line at least 1000 feet south of the site. This polygon includes all

drainage areas that contribute to the western and southern project site boundaries and most of

the drainage area contributing to the northern project site boundary. Figure 1 shows the model

boundary and drainage basins extending outside the model boundary as delineated in the

August 2009 report, all superimposed on an area map showing project site boundaries.

The grid element size was selected to coincide with FLO-2D efficiency (stability / computation)

guidelines, resulting in grid squares measuring 80 feet square. This cell size provides good

spatial resolution of the floodplain, without compromising model run time and stability.

1 The dynamic wave approximation represents the change of momentum in a body of water as a function of the change in local and convective accelerations, the pressure force, and the gravity force and friction losses. 2 Portion of rainfall that does not reach the ground (initially) due to vegetated cover or other man-made obstructions.


Site Boundary

Model Boundary

PrivateProperty

PrivateProperty

Model Boundary

N5b

N4b

N3a

N2a NW3

NW1

W1

SW5

Figure 1. Model Boundary and Drainage Basins outside the Model Boundary

2.2 Elevation

Grid elevations were interpolated from a contour map generated by merging high-resolution

(1.0-foot contour) LIDAR data inside the site with lower-resolution (20.0-foot contour) USGS

topography outside the site. The FLO-2D model package tools were utilized to perform the

interpolation, assigning representative elevation to each grid element.

2.3 Manning’s N

Overland flow velocities and depths vary with topography and the surface roughness. A

composite overland flow roughness value was assigned to each grid cell to account for

vegetation, surface irregularity, and non-uniform3 and unsteady flow

4. Sparse vegetation and

sandy soils are predominant across the site. Areas of slightly denser vegetation and farm lands

were also identified in the modeled area, based on field observations and aerial imagery.

Figure 2 shows areas of similar surface roughness characteristics (by color) and their assigned

values. These values were chosen based from documented FLO-2D tabular values, attributed to

the US Army Corps of Engineers’ HEC-1 Manual and Technical Engineering and Design Guide.

3 Flow characterized by a varying velocity with respect to distance at a given time. 4 Flow characterized by a varying velocity with respect to time at a given location.


Site Boundary

Model Boundary

PrivateProperty

PrivateProperty

0.15

0.3

0.2

Sparse Vegetation Sandy Soil

Farm land

Denser Vegetation

Figure 2. Spatial distribution of overland flow roughness coefficients

2.4 Rainfall-Runoff Modeling

The SCS Curve Number approach, including water loss through infiltration, was used to account

for rainfall-runoff processes inside the modeled area. Soil types and cover conditions of the

modeled area (from the August 2009 report) were used to assign a general curve number (80)

and an initial abstraction (0.59 inches) for this study, providing consistency with the August

2009 report / hydrologic analysis.

2.5 Inflow to the FLO-2D Model

The Blythe project site receives surface water flow from higher elevations in the mountains

located 3 miles west of the site. Flow contributions from drainage basins outside the model

boundary (defined in section 2.1 above) were input to the FLO-2D model from results of the

August 2009 report. Figure 1 shows these “exterior” drainage basin delineations and

corresponding identifiers (circled labels). Hydrographs (flow rate over time) from these

“exterior” drainage basins are distributed evenly across the FLO-2D model boundary, providing

inflows to the FLO-2D model. Figure 3 shows the off-site 24-hour storm hydrographs through

each of the “exterior” drainage basins, corresponding to 10-year, 25-year, and 100-year

precipitation events. The drainage basins are identified in Figure 1 and Figure 3 with the

original HEC-HMS name used in the August 2009 report.


100-yr Off-site Hydrology - Model Inflows

0

200

400

600

800

1000

1200

1400

1600

1800

0 5 10 15 20 25Hours

Flo

w [c

fs]

W1 N4b N3a SW5 NW3 NW1 N5b N2a


0

200

400

600

800

1000

1200

1400

0 5 10 15 20 25Hours

Flo

w [c

fs]



0

100

200

300

400

500

600

700

800

900

0 5 10 15 20 25Hours

Flo

w [c

fs]


Figure 3. Inflow hydrographs for 100, 25 and 10 year hydrologic events


2.6 Outflow from the FLO-2D Model

Movement of water inside the FLO-2D modeled area is based on topography and roughness

characteristics; therefore, an approximate and rather extensive portion of the south and east

model boundaries were designated as potential model outflow locations. Simulation of

drainage outflow through the model boundary was achieved by designating cells along this

boundary as “floodplain outflow cells”. The two-dimensional modeling process across and

through the site simulates exact outflow locations along the model boundary based on the

topographic direction of the overland flow at each model boundary cell.

Within the FLO-2D model boundary, “Flow Analysis Cross Sections” were established at the

downstream site boundary locations where existing drainage water exits the site. The drainage

outflow through these cross sections at the east and southeast project site boundaries,

provides the basis of surface water discharge over time for each of the 10, 25 and 100 year

events. Flow Analysis Cross Sections are defined by a set of cells aligned at a right angle with

the main direction of flow exiting the model boundary. Figure 4 shows the location of the

implemented Flow Analysis Cross Sections. The four Flow Analysis Cross Section locations

associated with existing flows are utilized in the proposed design to align the post-development

drainage discharges closely with the existing condition.

2.7 Precipitation

The 24-hour precipitation event that generates the modeled inflow from upstream drainage

basins is assumed to occur contemporaneously over the model domain. The 24-hour

precipitation depth was obtained from NOAA’s Precipitation Frequency Data Server (PFDS).

Rainfall depths used for 10-year, 25-year, and 100-year return periods were, respectively, 2.0

inches, 2.54 inches, and 3.44 inches.

Comparable with the August 2009 report, precipitation was distributed temporally as a Type II

storm, in accordance with the U.S. Soil Conservation Service (now NRCS) Technical Release 55

recommendation for extreme eastern California.


Site Boundary

Model Boundary

PrivateProperty

PrivateProperty

Flow Cross Section 1




Figure 4. Flow Cross Section Locations


3. RESULTS AND CONCLUSIONS

� This report provides results of analysis of on-site, pre-development drainage conditions at

the Blythe site, which are supplement to the August 2009 report through utilization of

refined topographic site data (LIDAR) and a detailed two-dimensional, unconfined flow

modeling approach (FLO-2D) described in more detail in the report introduction. This

refined model approach was utilized to generate a more detailed representation of water

movement across the Blythe site, including routing flow from mountainous terrain through

shallow moderately-defined channels at the base of the mountains that radiate outward in

a complex alluvial fan onto a broad, flat expanse of desert terrain.

� Appendices A, B, and C include site maps of the Blythe site (associated with the 100-year,

25-year and 10-year storm events, respectively) of FLO-2D simulated maximum flow depth

(Sheet 1 of 3), maximum velocity (Sheet 2 of 3), and maximum water surface elevation

(Sheet 3 of 3, which also provides an inset chart summarizing flow hydrographs at four

“Flow Analysis Cross Sections” identified on the maps).

Review of the maps described above provide several general flow characteristics. The

“Flow Areas” are noted on Sheet 1 of the respective Appendix maps:

• Flow Area 1 – Water contributions from north of the project site flow easterly within

relatively parallel small channels that converge near the northeastern corner of the

project site, cross the northern site boundary, and flow in a southern direction within

the site area.

• Flow Area 2 – The southerly flow mentioned above constitutes the largest

concentration of surface water flow within the model area, flowing south within the

eastern site boundary, between the proposed solar fields to the west and a

topographic high (hill) to the east. A “Flow Analysis Cross Section 1” (shown on all the

Appendix maps) has been identified in the FLO-2D model at a location where Flow

Area 2 crosses (exits) the southeastern site boundary. Tables 1, 2, and 3 below (for

the 10-, 25-, and 100-year storm events, respectively) provide a summary of peak flow

rate (cubic feet per second or cfs), total flow volume (acre-feet), and maximum flow

width (feet) at this Flow Analysis Cross Section.

• Flow Area 3 – Within the project site boundary, water is conveyed within two primary

“bands” of flow: one (Flow Area 3) originating from the western site boundary,

extending near and along the northern edge of the site boundary, eventually joining

the southerly flow routes originating from areas north of the site (described in the

previous bullet item). This band of flow increases in width as it extends easterly until

it joins the southerly flow route mentioned above.

• Flow Area 4 – A second “band” of on-site flow originates from the approximate middle

of the western site boundary, extending in a southeasterly direction. This band of

flow increases in width as it extends southeasterly until it exits at the southeast corner

of the project site. A “Flow Analysis Cross Section 2” and “Flow Analysis Cross Section


3” (shown on all the Appendix maps) have been identified in the FLO-2D model at a

location where Flow Area 4 crosses (exits) the southeastern site boundary. Tables 1,

2, and 3 below (for the 10-, 25-, and 100-year storm events, respectively) provide a

summary of peak flow rate (cfs), total flow volume (acre-feet), and maximum flow

width (feet) at this Flow Analysis Cross Section.

• Flow Area 5 – Minor southeasterly flows are apparent along the southern project site

boundary, concentrating on a small surface water course that exits at the southern

boundary of the project site. A “Flow Analysis Cross Section 4” (shown on all the

Appendix maps) has been identified in the FLO-2D model at a location where Flow

Area 5 crosses (exits) the southern site boundary. Tables 1, 2, and 3 below (for the 10-

, 25-, and 100-year storm events, respectively) provide a summary of peak flow rate

(cfs), total flow volume (acre-feet), and maximum flow width (feet) at this Flow

Analysis Cross Section.

• Flow Area 6 – Flows reaching the down-slope project site boundary (east side of the

site) are spread out several thousands of feet in complex (shallow multi-channel)

alluvial fans.

� Tables 1, 2, and 3 below provide a summary of peak flow rate (cfs), total flow volume (acre-

feet), and maximum flow width (feet) at the four “Flow Analysis Cross Sections” defined in

the FLO-2D model and shown on Appendix maps (for the 10-, 25-, and 100-year storm

events, respectively). The four “Flow Analysis Cross Sections” represent the location at the

downstream side of the project boundary where existing drainage water exits the site.

TABLE 1


10-Year Storm Event

Flow Analysis

Cross Section

Peak Flow

Rate (cfs)

Total Flow

Volume (ac-ft)

Max. Flow

Width (ft)

1 310 164 800

2 0 0 0

3 23 9 1200

4 0 0 0

TABLE 2


25-Year Storm Event

Flow Analysis

Cross Section

Peak Flow

Rate (cfs)

Total Flow

Volume (ac-ft)

Max. Flow

Width (ft)

1 726 348 1040

2 0 0 0

3 199 101 2480

4 0 0 0


TABLE 3


100-Year Storm Event

Flow Analysis

Cross Section

Peak Flow

Rate (cfs)

Total Flow

Volume (ac-ft)

Max. Flow

Width (ft)

1 1478 1508 1760

2 75 59 1600

3 823 594 2640

4 96 76 800

� The FLO-2D model simulates volumetric mass balance of water inflows, losses, and

outflows consisting of five primary components listed below and tabulated in Table 4 by

column:

A. Off-Site Surface Water Inflow (estimated with HEC-HMS model from August 2009 report).

B. On-Site Precipitation Inflow (estimated with FLO-2D model).

C. On-Site Initial Abstraction and Infiltration Losses (estimated with FLO-2D model).

D. On-Site Watershed Storage (estimated with FLO-2D model).

E. Surface Water Outflow (calculated with FLO-2D model as item A plus B minus C minus D).

TABLE 4

FLO-2D MODEL RESULTS (MASS BALANCE)

A B C D E

Storm

Event

Off-Site SW

Inflow (ac-ft)

On-Site Precip.

Inflow (ac-ft)

On-Site Initial Ab.

and Infil. Loss (ac-ft)

On-Site Watershed

Storage (ac-ft)

Surface Water

Outflow (ac-ft)

(ac-ft) (ac-ft) (ac-ft) (ac-ft) (ac-ft)

10-Yr 268 3228 2317 1171 8

25-Yr 396 4100 2619 1711 168

100-Yr 640 5552 2983 2053 1156

� In general, the results presented above portray peak flow rates and total flow volumes that

are less than those results presented in the August 2009 Drainage Report. Comparison of

results between this report and the August 2009 report must include qualification of model

assumptions utilized for each report, as summarized below.

1. The August 2009 Drainage Report was prepared to analyze the post-development

drainage flows on a full graded site with no localized depressions, no detention, and to

size drainage channels to convey the storm events around and through the site to avoid

damage to the project infrastructure. The HEC-RAS model is the appropriate tool for this

type of flow modeling. This predevelopment report was prepared to analyze existing

flows on a site that contains depressions, braided washes, and alluvial fan flows. FLO-2D is

the appropriate model for this type of flow. The comparison of canalized flow to overland

flow will naturally create differences.

2. The August 2009 analysis included HEC-HMS modeling based on 20-foot contour-interval

topography; the current report analysis includes FLO-2D modeling based on 1-foot


contour-interval topography. Contour interval resolution affects watershed slope and

boundary delineation, flow routing dynamics, flow concentration and flow diffusion.

3. The August 2009 analysis included HEC-HMS modeling based on Muskingum routing; the

current report analysis includes FLO-2D modeling based on dynamic wave approximation.

Each of these methods is appropriate for their respective modeling (channel flow versus

overland flow) but they are difficult to compare because they analyze different types of

flow.

4. The August 2009 Drainage Report utilized HEC-HMS modeling, a software package for

sizing the post development drainage channels. It does not have the modeling capability

for predicting watershed storage. The current report analysis utilizes FLO-2D modeling, a

software package that includes an on-site “Watershed Storage” factor that will hold water

in on-site storage when simulated hydraulic head is beneath a specific threshold. This

“storage factor” results in different flow rates at the site boundary.

Blythe Solar Power Plant – Pre-Development Drainage Conditions Appendix

APPENDIX A:

100-year Existing Hydrology Flow Depth, Velocity, and Water Surface Maps

PrivateProperty

PrivateProperty

Flow Area 1

Flow Area 2

Flow Area 3

Flow Area 4

Flow Area 5 Flow Area 6

1

2

3

4

2

1

1

1

1

2

11

2

1

2

1

1

1

450

450

450

450

450

425

425

475

475

475

500

525

550

550

600

600

600

575

575

400

625

625

875

675

850

900

900

900

900

900

900

700

825 825

825

925

725

650

650

650

950

800 800

8008

00

775

775

775

775

775

975

750

375

350

350

Flow Depth at Cell [ft]0.000 - 0.1700.171 - 0.3100.311 - 0.5200.521 - 0.7700.771 - 1.0001.001 - 1.2401.241 - 1.5101.511 - 1.8401.841 - 2.2302.231 - 2.6902.691 - 3.2403.241 - 4.0004.001 - 6.2006.201 - 11.32011.321 - 17.870

0 2,300 4,6001,150Feet


Riverside County, California

Exisiting Conditions100-Yr StormMax. Flow Depth

Designed:Checked:Drawn:Record Drawing by/date:

Revisions:# DATE DESCRIPTION

Prepared for:

SolarMillennium LLC

Date: 11/25/09Sheet: 1 of 3

LEGEND:

Flow Analysis Section1234

Flow Depth at Cell (Contour)Model BoundarySite BoundaryArea of Concentrated Flow*

* Area of maximum concentrated flow with water depthexceeding 0.3 feet

AECOM Inc.999 Town & Country RoadOrange, CA 92686

www.aecom.com

PrivateProperty

PrivateProperty

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Velocity at Cell [ft/s]0.000 - 0.1100.111 - 0.2300.231 - 0.3600.361 - 0.4900.491 - 0.6300.631 - 0.7900.791 - 0.9900.991 - 1.2201.221 - 1.4601.461 - 1.7201.721 - 2.0502.051 - 2.4502.451 - 3.0403.041 - 3.9403.941 - 5.270

0 2,500 5,0001,250Feet



Exisiting Conditions100-Yr StormMaximum Velocity



Prepared for:

SolarMillennium LLC


LEGEND:


Model BoundarySite BoundaryContours 5ftVelocity at Cell (Contour)


www.aecom.com

PrivateProperty

PrivateProperty

Q = 1052.6 cfsV = 223.6 AF

N5b Q = 425 cfsV = 98.2 AF

N4b

Q = 1654.4 cfsV = 106.7 AF

N3a

Q = 242.4 cfsV = 14.4 AF

N2a

Q = 1282.7 cfsV = 95.3 AF

Q = 280.8 cfsV = 16.7 AF

NW3

SW5

Q = 151.2 cfsV = 9.0 AF

NW1

W1Q = 1217.9 cfsV = 77.4 AF

Q = 822.6 cfsV = 594.5 AF

Q = 1478.1 cfsV = 1508.4 AF

13

4 Q = 96.4 cfsV = 75.7 AF

2 Q = 1478.1 cfsV = 1508.4 AF

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0 2,400 4,8001,200Feet



Exisiting Conditions100-Yr StormMax. Water Surface



Prepared for:

SolarMillennium LLC


LEGEND:


Model BoundarySite BoundaryMax Water ElevationSurface Contours Area of Concentrated Flow*

Q = Peak FlowV = Total 24-hour Volume


Property Line Outflow Hydrographs

-2000

200400600800

1000120014001600

0 5 10 15 20 25 30 35 40 45Hours

Disch

arge

[CFS

]

Section 1 Section 2 Section 3 Section 4


www.aecom.com


APPENDIX B


PrivateProperty

PrivatePropertyFlow Area 5

Flow Area 4

Flow Area 3

Flow Area 1

Flow Area 2

Flow Area 6

0.537

1.61

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0 2,300 4,6001,150Feet






Prepared for:

SolarMillennium LLC


LEGEND:





www.aecom.com

PrivateProperty

PrivateProperty

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0 1,900 3,800950Feet






Prepared for:

SolarMillennium LLC


LEGEND:




www.aecom.com

PrivateProperty

PrivateProperty

Q = 553.6 cfsV = 125.1 AF

N5b Q = 223.7 cfsV = 54.9 AF

N4b

Q = 1144.5 cfsV = 72.4 AF

N3a

Q = 167.9 cfsV = 9.8 AF

N2a

Q = 885.6 cfsV = 64.7 AF

Q = 194.5 cfsV = 11.3 AF

NW3

SW5

Q = 104.7 cfsV = 6.1 AF

NW1

W1Q = 843.5 cfsV = 52.5 AF

Q = 0.0 cfsV = 0.0 AF

Q = 0.0 cfsV = 0.0 AF

Q = 726.2 cfsV = 347.6 AF Q = 199.5 cfs

V = 101.2 AF

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0 2,200 4,4001,100Feet






Prepared for:

SolarMillennium LLC


LEGEND:


Model BoundarySite BoudaryMax Water ElevationSurface Contours Area of Concentrated Flow*




-1000

100200300400500600700800

0 5 10 15 20 25 30 35 40 45Hours

Disch

arge

[CFS

]



www.aecom.com


APPENDIX C


PrivateProperty

PrivatePropertyFlow Area 5

Flow Area 4

Flow Area 3

Flow Area 1

Flow Area 2

Flow Area 6

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0 2,000 4,0001,000Feet






Prepared for:

SolarMillennium LLC


LEGEND:





www.aecom.com

PrivateProperty

PrivateProperty

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0


0 2,000 4,0001,000Feet






Prepared for:

SolarMillennium LLC


LEGEND:




www.aecom.com

PrivateProperty

PrivateProperty

Q = 298.1 cfsV = 73.9 AF

N5b Q = 120.7 cfsV = 32.4 AF

N4b

Q = 838.1 cfsV = 52.4 AF

N3a

Q = 123.1 cfsV = 7.1 AF

N2a

Q = 648 cfsV = 46.8 AF

Q = 142.6 cfsV = 8.2 AF

NW3

SW5

Q = 76.8 cfsV = 4.4 AF

NW1

W1Q = 618.4 cfsV = 38.0 AF

Q = 0 cfsV = 0 AF

Q = 0 cfsV = 0 AF

Q = 310.4 cfsV = 164.1 AF Q = 22.6 cfs

V = 9.2 AF

2

4

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0 2,200 4,4001,100Feet






Prepared for:

SolarMillennium LLC


LEGEND:

Flow Analysis SectionMyGroups

1234Model BoundarySite BoudaryMax Water ElevationSurface Contours Area of Concentrated Flow*




www.aecom.com


050

100150200250300350

0 5 10 15 20 25 30 35 40 45Hours

Disch

arge

[CFS

]


*indicates change 1

BEFORE THE ENERGY RESOURCES CONSERVATION AND DEVELOPMENT

COMMISSION OF THE STATE OF CALIFORNIA 1516 NINTH STREET, SACRAMENTO, CA 95814

1-800-822-6228 – HUWWW.ENERGY.CA.GOVUH

1BAPPLICATION FOR CERTIFICATION Docket No. 09-AFC-6 FOR THE BLYTHE SOLAR POWER PLANT PROJECT PROOF OF SERVICE (Established 11/18/09) APPLICANT Gavin Berg Senior Project Manager 1625 Shattuck Avenue, Suite 270 Berkeley, CA 94709 [email protected] Carl Lindner AECOM Project Manager 1220 Avenida Acaso Camarillo, CA 93012 [email protected] Co-COUNSEL Scott Galati, Esq. Galati/Blek, LLP 455 Capitol Mall, Suite 350 Sacramento, CA 95814 [email protected] Co-COUNSEL Peter Weiner Matthew Sanders Paul, Hastings, Janofsky & Walker LLP 55 2nd Street, Suite 2400-3441 San Francisco, CA 94105 [email protected] [email protected]

INTERESTED AGENCIES California ISO [email protected] INTERVENORS ENERGY COMMISSION Karen Douglas Chair and Presiding Member [email protected] Jeffrey D. Byron Commissioner and Associate Member [email protected] Raoul Renaud Hearing Officer [email protected] Alan Solomon Siting Project Manager [email protected] Lisa DeCarlo Staff Counsel [email protected] Public Adviser’s Office [email protected]

2

DECLARATION OF SERVICE

I, Ashley Y. Garner, declare that on November 30, 2009, I served and filed copies of the attached BLYTHE SOLAR POWER PLANT PRE-DEVELOPMENT DRAINAGE CONDITIONS REPORT dated November 25, 2009. The original document, filed with the Docket Unit, is accompanied by a copy of the most recent Proof of Service list, located on the web page for this project at: [http://www.energy.ca.gov/sitingcases/solar_millennium_blythe] The document has been sent to both the other parties in this proceeding (as shown on the Proof of Service list) and to the Commission’s Docket Unit, in the following manner: (Check all that Apply)

FOR SERVICE TO ALL OTHER PARTIES:

__X__ sent electronically to all email addresses on the Proof of Service list; __X__ by personal delivery or by depositing in the United States mail at with first-class postage thereon fully prepaid and addressed as provided on the Proof of Service list above to those addresses NOT marked “email preferred.” AND

FOR FILING WITH THE ENERGY COMMISSION: __X__ sending an original paper copy and one electronic copy, mailed and emailed respectively, to the address

below (preferred method); OR ____ depositing in the mail an original and 12 paper copies, as follows:

CALIFORNIA ENERGY COMMISSION Attn: Docket No. 09-AFC-6

1516 Ninth Street, MS-4 Sacramento, CA 95814-5512 [email protected]

I declare under penalty of perjury that the foregoing is true and correct.

// Original Signed // Ashley Y. Garner

mailto:[email protected]�

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