Sacramento Solar Highways Initial Study and Mitigated Negative ...

Revised Final 

Sacramento Solar Highways 

Initial Study and 

Mitigated Negative Declaration 

SCH 2011032036 

Prepared for 

Sacramento Municipal Utility District 

P.O. Box 15830 MS B203 

Sacramento, CA 95852-1830 

July 2011 

Prepared by 

Burleson Consulting, Inc. 

950 Glenn Drive, Suite 135 

Folsom, CA 95630

Revised Final Mitigated Negative Declaration 


Sacramento Solar Highways 

Lead Agency: 


6201 S Street 


or 

P.O. Box 15830 MS B203 


Attn: Kim Crawford 

(916) 732-5063 or kcrawfo@smud.org 

Introduction 

This document has been prepared to evaluate Sacramento Municipal Utility District‟s 

(SMUD) proposed project for compliance under the California Environmental Quality Act 

(CEQA). SMUD is the lead agency responsible for complying with the provisions of CEQA. 

SMUD proposes the Sacramento Solar Highways Project (also referred to as “the project”) in 

order to develop photovoltaic (PV) generation facilities, an A123 lithium-ion energy storage 

system and electrical interconnection in the cut-slope and open space along the Highway 50 

corridor in Sacramento County, California. 

Proposed Project Description 

The project consists of installing PV generation facilities, an A123 lithium-ion energy storage 

system and electrical interconnection in two project sections along Highway 50 within the 

California Department of Transportation (Caltrans) right-of-way (ROW). The project 

sections include: the East Sacramento section, which is the north cut-slope from 59th Street 

to 43rd Street; and the Mather Field Interchange section, which includes the north cut-slope 

westbound on-ramp and the northwest open space portion of the Mather Field 

Road/Highway 50 interchange. Two distinct PV technologies are proposed for 

demonstration in this project: flat-plate PV arrays (flat plate), and a concentrating 

photovoltaic (CPV) array manufactured by SolFocus. Flat-plate arrays would be used at the 

East Sacramento section and both technologies may be used at the Mather Field Interchange 

section. Since the project is a demonstration of the application of solar PV technology along 

a highway system, a successful project could lead to significant, long-term solar resource 

development throughout the SMUD service area, the region, and ultimately the State of 

California. 

Project construction is planned to start in Fall 2011 and is expected to conclude by December 

2012. 

i 

SACRAMENTO SOLAR HIGHWAYS PROJECT 

REVISED FINAL INITIAL STUDY AND MITIGATED NEGATIVE DECLARATION

MITIGATED NEGATIVE DECLARATION 

Findings 

As lead agency for compliance with CEQA requirements, SMUD finds that the proposed 

project would be implemented without causing a significant adverse impact on the 

environment. Mitigation measures for potential impacts associated with aesthetics, air 

quality, biological resources, cultural resources, geology and soils, hazards and hazardous 

materials, hydrology and water quality, noise, and transportation/traffic would be 

implemented as part of SMUD‟s proposed project description (see Table A-1). 

Cumulative Impacts 

CEQA requires that SMUD assess whether its proposed project‟s incremental effects are 

significant when viewed in connection with the effects of other projects. Based on the 

analysis presented in this Initial Study (IS)/Mitigated Negative Declaration (MND), the 

proposed project would not contribute incrementally to considerable environmental 

changes when considered in combination with other projects in the area. This is because: 

(1) potential environmental effects of the proposed project were determined to be less than 

significant; and (2) all identified potentially significant impacts would be mitigated to a lessthan-significant 

level. 

Growth-Inducing Impacts 

SMUD exists as a public agency to supply electricity. The project is a demonstration project 

to determine the feasibility of installing PV electrical generation on publicly owned land 

along the State‟s highways and freeways. The PV system planned capacity is approximately 

1.4 megawatts (MW), and the electricity it will produce may be made available to the 

community via SMUD‟s SolarShares SM , a program for SMUD customers to purchase locally 

generated solar power to accommodate the electrical service needs of the existing as well as 

planned growth within SMUD‟s service territory. Therefore, SMUD projects are not 

considered to be “growth inducing,” as defined by CEQA. In addition, SMUD‟s proposed 

project would not cause increased demand on public infrastructure, public services, 

housing, circulation, or other resources. 

Determination 

On the basis of this evaluation, SMUD concludes: 

a) The proposed project does not have the potential to degrade the quality of the 

environment, substantially reduce the habitat of a fish or wildlife species, cause 

a fish or wildlife population to drop below self-sustaining levels, threaten to 

eliminate a plant or animal community, substantially reduce the number or 

restrict the range of a rare or endangered species, or eliminate important 

examples of the major periods of California history or prehistory. 

b) The proposed project would not achieve short-term environmental goals to the 

disadvantage of long-term environmental goals. 

c) The proposed project would not have impacts that are individually limited, but 

cumulatively considerable. 


REVISED FINAL INITIAL STUDY AND MITIGATED NEGATIVE DECLARATION 

ii


d) The proposed project would not have environmental effects that would cause 

substantial adverse effects on human beings, either directly or indirectly. 

e) No substantial evidence exists to demonstrate that the proposed project would 

have a substantive negative effect on the environment. 

This IS/MND has been prepared to provide the opportunity for interested agencies and the 

public to provide comment. Pending public review and SMUD Board approval, this MND 

will be filed pursuant to CEQA Guidelines. Written comments should be submitted to 

SMUD at the address previously identified by 5:00 p.m. on April 15, 2011. 

(Signature) 

Kimberly Crawford 

Environmental, Safety, & Health Specialist II July 7, 2011 

(Title) 

(Date) 

iii 



Table of Contents 

Introduction ....................................................................................................................................... i 

Proposed Project Description .......................................................................................................... i 

Findings ............................................................................................................................................. ii 

Cumulative Impacts ....................................................................................................................... ii 

Growth-Inducing Impacts ............................................................................................................. ii 

Determination .................................................................................................................................. ii 

1.0 Introduction ..................................................................................................................................1 

Review of the Draft IS/MND ......................................................................................................... 2 

Preparation of the Final IS/MND ................................................................................................. 2 

2.0 Comments and Responses .......................................................................................................12 

Letter No. 1 – Scott Morgan, Director, Governor‟s Office of Planning and Research, State 

Clearinghouse and Planning Unit .............................................................................................. 15 

Letter No. 2 – Cyrus Abhar, Public Works Director, City of Rancho Cordova .................... 18 

Letter No. 3 – Eric Fredricks, Chief, Office of Transportation and Planning-South, Caltrans 

District 3 ......................................................................................................................................... 29 

Letter No. 4 – Sean Bechta, East Sacramento Resident ............................................................. 35 

Letter No. 5 - Kerry Freeman, East Sacramento Resident ........................................................ 37 

Letter No. 6 - Melissa Jones, California Energy Commission.................................................. 39 

3.0 Changes and Edits to the Draft IS/MND ..............................................................................41 

Project Overview............................................................................................................................ 41 

General Project Information ......................................................................................................... 41 

Project Schedule. ............................................................................................................................ 41 

Figure 2b (42nd Street to 48th Street) .......................................................................................... 41 

Figure 2c (48th Street to 51st Street) ............................................................................................ 42 

Project Features .............................................................................................................................. 42 

Project Construction ...................................................................................................................... 42 

Project Schedule ............................................................................................................................. 42 

Required Permits and Approvals ................................................................................................ 42 

Initial Study - Checklist I. Aesthetics .......................................................................................... 42 

Initial Study - Checklist III. Air Quality ..................................................................................... 46 

Initial Study - Checklist IV. Biological Resources ..................................................................... 46 

Initial Study - Checklist IX. Hazards and Hazardous Materials ............................................. 46 

Initial Study - Checklist XIII. Noise ............................................................................................. 50 

Initial Study - Checklist XIII. Public Services ............................................................................ 50 

References ....................................................................................................................................... 51 

Appendix G .................................................................................................................................... 51 

Appendix J ...................................................................................................................................... 51 

4.0 Final Mitigation Monitoring Plan ..........................................................................................52 

Introduction ................................................................................................................................ 5252 

Mitigation Implementation and Monitoring ......................................................................... 5252 

Mitigation Enforcement ................................................................................................................ 53 

Tables 

A-1 Final Mitigation Monitoring Plan ..................................................................................... …54 

v 




Figures 

1 Sacramento Solar Highways Project Vicinity Map ................................................................ 6 

2a 

2b 

2c 

2d 

Sacramento Solar Highways Project Overview of East Sacramento Section 

Location Map .............................................................................................................................. 7 

Sacramento Solar Highways Project East Sacramento Section 42nd Street to 

48th Street Location Map .......................................................................................................... 8 

Sacramento Solar Highways Project East Sacramento Section 48th Street to East 

of 59th Street Location Map ...................................................................................................... 9 

Sacramento Solar Highways Project East Sacramento Section East of 59th Street 

Location Map ............................................................................................................................ 10 

3 Sacramento Solar Highways Project Mather Field Interchange Location Map ............... 11 

Appendix 

G Residential Glint and Glare Study (addendum to Glare and Glint Studies) 

J Heat Transfer Equation 


REVISED FINAL INITIAL STUDY AND MITIGATED NEGATIVE DECLARATION 

vi

1.0 Introduction 

Sacramento Municipal Utility District (SMUD) proposes the Sacramento Solar Highways 

Project (also referred to as “the project”) to develop photovoltaic (PV) generation facilities, 

an A123 lithium-ion energy storage system and electrical interconnection in the cut-slope 

and open space along the Highway 50 corridor in Sacramento County, California. The 

installation of PV in highway corridors is becoming more common in Europe, particularly in 

Germany, which has outpaced the world in its rate of solar installations in recent years. The 

installation of a small PV project in the highway corridor outside of Portland, Oregon 

represents the first project of this nature in the United States (US). If completed on schedule, 

SMUD‟s Solar Highways project will be the first of its kind in California, the largest in the 

US, and will assist in the development of a blueprint for similar installations throughout the 

State. 

Sacramento Solar Highways is a demonstration project intended to determine the feasibility 

of installing PV electrical generation on publicly owned land along the State‟s highways and 

freeways. SMUD and California Department of Transportation (Caltrans) have a 

Memorandum of Understanding (MOU) in effect through December 31, 2011 to guide the 

cooperative work of both agencies. In January 2010, the project was awarded $1.5 million in 

U.S. Department of Energy (DOE) grant funding, and $100,000 from the California Energy 

Commission (CEC) as a part of SMUD‟s Community Renewable Energy Deployment 

program. SolFocus, which designs and manufactures advanced concentrating photovoltaic 

(CPV) systems, is also a partner in the project and is contributing $500,000 in match support 

to the Mather Field Interchange portion of the project. 

This project will assist SMUD in meeting a number of its environmental and operational 

objectives. The first of these is the SMUD Board-mandated Sustainable Power Supply goal, 

which requires SMUD to reduce its long-term greenhouse gas (GHG) emissions from 

electrical generation to 10% of its 1990 carbon dioxide (CO 2) emissions levels by 2050, while 

assuring reliability of the system, minimizing environmental impacts on land, habitat, water 

and air quality, and maintaining a competitive position relative to other California 

electricity providers. SMUD also has an aggressive Renewable Portfolio Standard (RPS) 

goal, which requires it to provide 33% of its energy supply from renewable sources by the 

year 2020. This project also supports SMUD Strategic Directive SD-9, which directs SMUD 

to develop more distributed sources of electrical generation, including solar power, within 

the service territory. 

Finally, by locating this project near Sacramento‟s load center where the power is demanded 

and by utilizing previously disturbed, engineered land areas within the transportation right 

of way, this project responds to the issues surrounding the installation of renewable 

generation projects in remote, environmentally sensitive areas of in which habitat disruption 

can occur. It also presents an opportunity to minimize costs associated with the 

transmission of renewable power from distant locations. 

1 SACRAMENTO SOLAR HIGHWAYS PROJECT 


INTRODUCTION 

The major objectives of the project are to: 

Promote public awareness and support of solar technology and local renewable energy; 

Create a highly visible, well-designed demonstration of the region‟s commitment to 

sustainability and the development of “green” technology; 

Assist SMUD in meeting carbon reduction and renewable energy goals; 

Establish the feasibility and methods of placing utility-scale solar power installations on 

Caltrans properties throughout California; 

Generate 1.4 megawatts (MW) of renewable solar power, enough to power 250 homes 

and avoid 800 metric tons of GHG emissions per year. 

The project consists of installing PV generation facilities, an A123 lithium-ion energy storage 

system, and electrical interconnection in two project sections along Highway 50 within the 

Caltrans right-of-way (ROW) (Figure 1). The project sections include: (1) the East 

Sacramento section, which is the north cut-slope from 59th Street to 43rd Street, and (2) the 

Mather Field Interchange section, which includes the north cut-slope westbound on-ramp 

and the northwest open space portion of the Mather Field Road/Highway 50 interchange 

(Figures 2a through 2d, and Figure 3). 

Review of the Draft IS/MND 

Copies of the Draft IS/MND were distributed to the Governor‟s Office of Planning and 

Research, State Clearinghouse, and other interested parties on March 15, 2011. The public 

review period began on March 16, 2011 and ended on April 15, 2011; although the public 

comment period was extended 12 days beyond the 30 day review period mandated by 

§15073 of the CEQA Guidelines to accommodate late comments. 

At the end of the public review period, six comment letters had been received; five letters 

were received during the extended comment period and one was received prior to the start 

of the comment period. These letters are presented in the Comments and Response section 

of this document. The comments did not change the conclusions presented in the attached 

Draft IS/MND. 

Preparation of the Final IS/MND 

The comment letters were reviewed, comments were identified, and the responses were 

prepared (see Comments and Responses section). Based on the comments and 

recommendations received, minor changes and edits have been made to the Draft IS/MND. 

In addition, a minor change to the project description was made to include an energy 

storage system. These changes are reflected in the Changes and Edits to the Draft IS/MND 

section of the document. As described below the minor project description modification, 

edits and associated substitution of mitigation measure do not contain changes and/or 

additional details that warrant the recirculation of the mitigated negative declaration. 

CEQA GUIDELINES 

The CEQA Guidelines §15073.5 provides for recirculation of a negative declaration prior to 

SACRAMENTO SOLAR HIGHWAYS PROJECT 2 



adoption. §15073.5(a) states: “A lead agency is required to recirculate a negative declaration 

when the document must be substantially revised after public notice of its availability has 

previously been given pursuant to §15072, but prior to adoption.” According to §15073.5(b) 

a substantial revision is defined as: 

“(1) A new, avoidable significant effect is identified and mitigation measures or project 

revisions must be added in order to reduce the effect to insignificance, or 

(2) The lead agency determines that the proposed mitigation measures or project revisions 

will not reduce potential effects to less than significance and new measures or revisions 

must be required.” 

Section 15073.5(c) defines circumstances that recirculation is not required including: 

“(1) Mitigation measures are replaced with equal or more effective measures pursuant to 

§15074.1. …. 

(4) New information is added to the negative declaration which merely clarifies, amplifies, 

or makes insignificant modifications to the negative declaration.” 

Guidance for substitution of a mitigation measure in a proposed mitigated negative 

declaration is provided in §15074.1. Section 15074.1(a) states: “as a result of the public 

review process for a proposed mitigated negative declaration, including any administrative 

decisions or public hearings conducted on the project prior to its approval, the lead agency 

may conclude that certain mitigation measures identified in the mitigated negative 

declaration are infeasible or otherwise undesirable. Prior to approving the project, the lead 

agency may, in accordance with this section, delete those mitigation measures and 

substitute them for other measures which the lead agency determines are equivalent or 

more effective. 

In addition according to §15074.1 (b) “prior to deleting and substituting for a mitigation 

measure, the lead agency shall do both of the following: 

(1) Hold a public hearing on the matter. Where a public hearing is to be held in order to 

consider the project, the public hearing required by this section may be combined with that 

hearing. Where no public hearing would otherwise be held to otherwise be held to consider 

the project, then a public hearing shall be required before a mitigation measure may be 

deleted and a new measure adopted in its place 

(2) Adopt a written finding that the new measure is equivalent or more effective in 

mitigating or avoiding potential significant effects and that it in itself will not cause any 

potentially significant effect on the environment. 

§15074.1 (c) states: “No recirculation of the proposed mitigated negative declaration 

pursuant to Section 15072 is required where new mitigation measures are made conditions 

of, or are otherwise incorporated into, project approval in accordance with this section.” 

§15074.1 (d) states: “‟Equivalent or more effective‟ means that the new measure will avoid or 

reduce the significant effect to at least the same degree as, or to a greater degree than, the 

original measure and will create no more adverse effect of its own than would have the 

original measures.” 

3 



INTRODUCTION 

If none of the aforementioned conditions have been met and Staff finds that none has been 

met, recirculation of the Draft IS/MND is not required. Rather the Lead Agency may 

approve the Final IS/MND with the incorporated revisions. 

CHANGES TO THE PROJECT 

Applicable changes to the Final IS/MND include: 

Integration of an Energy Storage System: SMUD proposes to install and integrate an A123 

lithium-ion energy storage system with the East Sacramento PV panels. The energy storage 

system, which is comprised of one or two enclosures, will include multiple batteries housed 

in a single enclosure and a second enclosure to house power electronics. The energy storage 

system would be located within the Caltrans ROW and on the western end of the East 

Sacramento project section. The energy storage system will be used to stabilize the 

intermittency of the PV production and integrate generated electricity into SMUD‟s grid. 

The energy storage system was included in a project funded by a CEC Public Interest 

Energy Research (PIER) grant. 

Substitution of Mitigation Measures: 

Bio-2: Mitigation measure for the removal of the East Sacramento trees. Revised mitigation 

measure includes additional potential locations for mitigation and vegetation types for 

mitigation. 

Haz-1: Mitigation measure for accidental spills, releases, and leaks of hazardous materials. 

Revised mitigation measure includes mitigation for the duration of project operation as well 

as the construction period. 

Haz-5: Mitigation measure for protection of the public, workers, and the environment. 

Revised mitigation measure includes clarification that excess soil should be analyzed prior 

to leaving the Caltrans ROWs. 

Project Schedule: The Final IS/MND includes a more accurate estimate of construction start 

dates. 

Residential Glint and Glare Study: An analysis was to study and identify potential glint 

and glare issues for two representative residential vantage points in the vincinity of the two 

project sections. 

Evaluation of PV Panels on Local Temperature: An analysis was conducted to examine the 

potential heat reflection from PV panels creating a change in the local ambient temperature. 

ANALYSIS 

The Final IS/MND includes minor changes to the project description that were not 

previously evaluated in the Draft IS/MND, but are not anticipated to generate new 

environmental impacts because: 

No new or increased effects to significant impacts would be triggered by project 

changes or project circumstances; 




No new information of substantial importance has changed the effects 

determination or the feasibility of mitigation measures; and 

No new feasible mitigation has been rejected by SMUD. 

In addition, SMUD staff has made the determination the minor changes to the project 

description do not constitute a substantial revision as defined by §15073.5(b). Specifically, 

the minor changes do not create a new, avoidable significant effect. In addition, SMUD staff 

has made the determination that the mitigation measure substitutions do not constitute 

recirculation as defined by §15073.5(c). Specifically, the three revised mitigation measures 

are equivalent or more effective than the mitigation measures included in the Draft 

IS/MND. 

None of the provisions of §15073.5 or 15074.1 apply to the proposed changes; therefore, 

recirculation of the Draft is not required. Specifically, the addition of the energy storage 

system is not considered a „substantial revision‟ because this change would not result in 

new, avoidable significant effects; and mitigation measures or project revisions are not 

required to reduce any effect to less than significant. In addition, mitigation measures will 

be replaced with equal or more effective measures. Therefore based on this analysis, none of 

the situations described in CEQA Sections 15073.5 and 15074.1 applies and the Draft 

IS/MND will not be recirculated. 

5 



Figure 2a 

SMUD 

Sacramento Solar Highways Project 

Overview of East Sacramento Section 

Location

59TH ST 

48th St 

Legend 

Photovoltaic System Locations 

Potential Location of Energy Storage System 

Inverter Transformer Pad 

Switch Location 

21-kV Interconnection Line 

Figure 2b 

SMUD 


42nd Street to 48th Street 

East Sacramento Section 

Location 

0 75 150 300 Feet 

± 

V ST 

48TH ST 

51ST ST 

J ST 

FOLSOM BLVD 

T ST 

Sacramento Municipal Utility District, Sacramento County, California 

Data Source: Aerial image provided by Bing Maps aerial imagery web mapping service & ESRI 2010 

1 inch = 165 feet 

BROADWAY

48th St 

Us Highway 50 

51st St 

Legend 

Photovoltaic System Locations 

Potential Location of Energy Storage System 

Inverter Transformer Pad 

Switch Location 

21-kV Interconnection Line 

Figure 2c 

SMUD 


48th Street to 51st Street 


Location 

0 125 250 375 Feet 

± 

V ST 

48TH ST 

51ST ST 

J ST 

FOLSOM BLVD 

T ST 

Sacramento Municipal Utility District, Sacramento County, California 

Data Source: Aerial image provided by Bing Maps aerial imagery web mapping service & ESRI 2010 

1 inch = 175 feet 

BROADWAY

Figure 2d 

SMUD 


East of 59th Street 


Location

2.0 Comments and Responses 

Five letters were received during the public review period in response to the distribution of 

the Draft IS/MND, and one letter was received prior to the release of the Draft IS/MND. 

Table 1 lists the source of the comment letter and the number of comments contained in the 

letter. 

Table 1 

List of Commenters 

Commenter 

Scott Morgan, Director, 

Governor’s Office of Planning and Research, 

State Clearinghouse 

Cyrus Abhar, Public Works Director, 

City of Rancho Cordova 

Eric Fredricks, Chief, Office of Transportation and Planning- 

South, Caltrans District 3 

Sean Bechta 

East Sacramento Resident 

Kerry Freeman 

East Sacramento Resident and Elmhurst Neighborhood 

Association Board member 

Malissa Jones, Executive Director 

California Energy Commission 

Letter Number 

Number of 

Comments 

1 1-1 

2 2-1 through 2-7 

3 3-1 through 3-13 

4 4-1 through 4-3 

5 5-1 

6 6-1 

12 SACRAMENTO SOLAR HIGHWAYS PROJECT 

FINAL INITIAL STUDY AND MITIGATED NEGATIVE DECLARATION

COMMENTS AND RESPONSES 

Letter 1 

Comment 1-1 

13 




Letter 1, Page 2 




Letter No. 1 – Scott Morgan, Director, Governor’s Office of 

Planning and Research, State Clearinghouse and Planning Unit 

Response to Comment 1-1 

This letter confirmed receipt of the IS/MND and confirmed the end of the public comment 

period. Please note that the Governor‟s Office of Planning and Research listed the end of 

the comment period as April 13, 2011; although, the end of the official comment period was 

April 15, 2011. Although the officially public comment period was extended 12 days beyond 

the 30 day review period mandated by §15073 of the CEQA Guidelines to accommodate late 

comments. Comment noted. 

15 




Letter 2 

Comment 2-1 

Comment 2-2 





Comment 2-2, 

continued 

Comment 2-3 

Comment 2-4 

Comment 2-5 

Comment 2-6 

Comment 2-7 

17 




Letter No. 2 – Cyrus Abhar, Public Works Director, City of 

Rancho Cordova 

Please note responses are primarily focused on the Mather Field Interchange project section. 


Site selection criteria for the project included proximity to SMUD electrical facilities in order 

to minimize the cost of interconnection. The Mather Field Interchange project site will 

interconnect to an existing overhead 12-kV line, which crosses Highway 50 and parallels the 

UPRR spur bridge. Additionally, the project would require adding to the existing 

infrastructure, which services the existing Caltrans pump house, including upgrading a 

pad-mounted transformer and installing an inverter. The additional electrical infrastructure 

would require concrete pads and would be similar in construction to the existing 

infrastructure. The scope of the project does not include undergrounding existing or 

proposed electrical facilities. 

The existing Caltrans pump house located adjacent to the Mather Field Interchange project 

site is not included in the project scope and will not be altered upon completion of the 

project. 


As summarized in the Sacramento Solar Highways Draft IS/MND, the potential effects of 

glint and glare were analyzed for motorists and pilots. The section below reviews the 

conclusions of the glint and glare studies. Because this particular comment came from the 

City of Rancho Cordova, the focus of this response is on the SolFocus system that is planned 

for installation at the Mather Field Road site. 

The SolFocus panels, which would be located within the Mather Field Interchange project 

section, would be pole-mounted on dual-axis trackers in order to track the sun throughout 

the day and optimize energy output. The dual-axis trackers will have moving parts 

although the movement will be very gradual throughout the day, and the main pivot point 

and the system‟s moving parts are located approximately 12 feet above ground and 

substantially out of reach. Additionally, as described below site access and opportunities for 

tampering will be discouraged to further mitigate safety and security concerns. 

This CEQA report utilizes site-specific analysis and a previous glare study which was 

performed on the SolFocus system. This previous study evaluated reflection of light from 

three sources: retro reflection, reflection from the primary mirror, and reflection from the 

front window of the panels. The study also reviewed three locations where these types of 

panels were installed near airports or freeways: Palo Alto Regional Water Quality Control 

Plant near Palo Alto General Aviation Airport in California; Natural Energy Laboratory 

near Kona International Airport in Hawaii; and Dumbarton Bridge along Route 84 in 

California. There were no reports of pilot complaints at the two locations near airports. 

Caltrans was satisfied with the low level of distraction on the Dumbarton Bridge, where the 

panels face morning commuter traffic and are placed at grade relative to the highway (a 

configuration very similar to that which will exist between the panels and morning traffic 

on the Mather Field Road overcrossing of Highway 50). The study concluded that the 




mechanism that causes glint and glare from the SolFocus system would not be a significant 

hazard to pilots, motorists, or pedestrians. Finally, in the range in which any potential glint 

or glare could be of concern, the SolFocus system at the Mather Field Interchange project 

section will be significantly elevated above Highway 50, therefore the exposure of motorists 

on Highway 50 will be further limited relative to an at-grade installation. There are more 

distant portions of Highway 50 in which motorists would be in line of sight of the arrays, 

and that distance provides further mitigation of potentially hazardous glint or glare. 

A site-specific Glint and Glare Study was conducted to analyze the possible glint and glare 

effects of the flat plate PV panels planned for the East Sacramento project location. At that 

location, the panels will be fixed and directly adjacent to the highway itself, therefore 

considered of much greater potential concern as a source of glare to passing motorists than 

the SolFocus panels which move throughout the day and will be elevated above the 

highway. The purpose of the study was to determine if glint and glare from the panels 

would potentially cause unsafe conditions for passing motorists or pilots. The analysis 

concluded that the potential for experiencing glint and glare would be for 15 to 30 minutes 

in the morning while traveling eastbound on Highway 50 from March 21st through 

September 21st, and in the afternoon while traveling westbound on Highway 50 from May 

28th through July 22nd. A vehicle traveling 55 MPH will be exposed to the glare for 

approximately 90 seconds. Additionally, the study included that the glare from the flat plate 

PV panels will be lower in intensity than the glare from car windows and office buildings 

along the highway. The findings from the study concluded that the flat plate PV panels 

along Highway 50 fall within acceptable limits for glint and glare visibility and duration 

and glint and glare intensity. Additionally, the study concluded that the project would not 

create a significant hazard to motorists and no additional mitigation measures are necessary 

at this time. 

The SolFocus panels, which would be located within the Mather Field Interchange project 

section, would be pole-mounted on dual-axis trackers in order to track the sun throughout 

the day and optimize energy output. The dual-axis trackers will have moving parts 

although the movement will be very gradual throughout the day, and the main pivot point 

and the system‟s moving parts are located approximately 12 feet above ground and 

substantially out of reach. Additionally, as described below site access and opportunities for 

tampering will be discouraged to further mitigate safety and security concerns. 

In addition, SMUD commissioned the engineering consulting firm IEC to conduct a 

Residential Glint and Glare Study to analyze the possible glint and glare effects to the 

residential neighborhoods on the south side of Highway 50 and to provide conclusions for 

residential-specific glint and glare analyses conducted as part of the Phase 2 Feasibility 

Study. The study utilized analytical models to evaluate potential glint and glare impacts, 

and the study referenced a number of scientific industry papers and field experiences to 

evaluate the potential environmental effects of glint and glare. The results of the study were 

used to determine the significance of the potential environmental effects; the potential glare 

produced by the project was evaluated based on the existing ambient glare conditions, 

proximity to light-sensitive land uses, and intensity of the potential glare. 

The key vantage point (KVP) analyzed for the Mather Field Interchange analysis was 

located southeast of the project section at the Ashgrove Place Apartments near Abington 

Way and Laurelhurst Drive. The study concluded that due to the mobile nature of the CPV 

19 




arrays it is anticipated that residents with a direct line of sight, which includes a small 

number of residents with a view of the proposed CPV installation site from their secondand 

third- story balconies, will see glare during morning and early afternoon hours at 

various intensities. Glare will be visible from as early as 5:45am to 2:30pm during the spring 

and summer months and from 6:45am to 1:00pm during the fall and winter months with a 

maximum intensity when the CPV arrays are close to the horizontal position around noon 

and residents have an acute viewing angle of the primary mirror components. 

The maximum glare intensity is approximately 90% of the sun‟s brightness. While this is a 

considerable intensity, it is important to note that the sun‟s image will occupy only 1% of 

the area of the primary mirror, and the brightness of these images can be compared to the 

brightness of reflections seen on a lake or the brightness of a common white aluminum roof. 

For residents of the Ashgrove Place Apartments, the perceived intensity from the primary 

mirror components is expected to be approximately 6% of the sun‟s brightness due to a 

number of factors including scatter and beam spreading. In addition, residents would see 

graduations in intensity but the distinct points of light from the CPV arrays will appear out 

of focus; thus the distinct points of the light will have been smoothed into gradual 

undulations across the face of the CPV unit and the glare would appear reduced. In the 

early morning, the CPV arrays will be in a position that is nearly perpendicular to the KVP 

and glare will be at a minimum because light leakage from the primary mirror components 

will not be visible to residents. During daylight hours, residents will experience intermittent 

glare from the CPV systems until mid-afternoon when the CPV arrays face west out of the 

view of the residents. 

The residences with views similar to those of the KVP currently outlook an urban landscape 

which includes multiple sources of daytime glare such as direct beam sunlight, a large white 

warehouse, highway pavement, concrete traffic barriers, other shiny reflective surfaces as 

well as vehicles with high reflective windshields on Highway 50 and Mather Field Road. 

Therefore the glare is anticipated to be similar to that from objects in the existing 

environment. 

SolFocus CPV systems have been installed in similar urban environments without reports of 

glint or glare problems. A 1 MW solar power facility consisting of 122 SolFocus CPV 

systems was completed at Victor Valley College in Victorville, California in May 2010. This 

facility has more than 3 times the amount of CPV systems than the proposed Mather Field 

Interchange site will have installed. The north and east boundaries of the facility site are 

directly adjacent to a residential area consisting of single family homes. To date, there have 

been no complaints about glare from the residents living near the CPV installations. The 

lack of complaints about glare from the Victor Valley College installations indicates that 

glare from the CPV systems is likely not disruptive to nearby residents. This field experience 

suggests that glare impacts from the Mather Field Interchange CPV installations site, with 

significantly fewer systems than the Victor Valley College site, will be minimal and 

nondisruptive for residents at the Ashgrove Place Apartments located a distance away from 

the installations. Overall, the glare impacts are expected to be minimal and would not 

impact the well-being of the residents or create significant negative impacts. 

Due to the subjective nature of aesthetic impacts, if disruptive glare is identified by residents 

(although not anticipated) then SMUD will meet with the affected residents and offer glare 

reducing measures for residents impacted by the project. 




The final project design will incorporate safety and security measures designed specifically 

for each project site (East Sacramento and Mather Field Interchange). The measures will be 

designed to integrate into the final project design and minimize aesthetic impacts while 

providing safety and security. At the Mather Field Interchange project site, safety and 

security measures may include taller, more secure fencing located adjacent to the UPRR 

spur and at the top of the cut-slope fencing along Mather Field Road, low-level, downward 

facing perimeter security lighting, and video monitoring. Additionally, safety and security 

features have been specified for each site as appropriate, such as anti-theft bolts, reinforcing 

the durability of the PV panels, installing the flat-plate panels close to the ground and 

implementing a horizontal „stow‟ night mode for the SolFocus panels in order to make 

access to the fasteners and wiring more difficult for potential thieves. In addition, 

landscaping will be integrated into the final project design to address aesthetic and security 

requirements (landscaping is further discussed in response to comment 2-3). 

The intent of the final project design, including the placement of the PV panels, their 

supporting structures, the surrounding landscape and security features, is to be aesthetically 

acceptable so that they are viewed as a public asset and do not degrade the visual character 

of the project sites or their surroundings. 


It is a major project goal for the Sacramento Solar Highways installations to be purposefully 

visible along Highway 50 to promote public awareness of innovative, clean, technologies 

and the region‟s commitment to sustainability. In order to achieve that goal, SMUD intends 

to develop a well-designed, well-maintained project that will be viewed as a community 

asset. 

As to the attractiveness and perceived industrial nature of the project, the degree of 

aesthetic impact of a project, either negative or beneficial, to the visual character of the area 

is largely subjective. Few objective or quantitative standards are available to analyze visual 

quality, and individual viewers respond differently to changes in the physical environment. 

Based on the CEQA Guidelines Appendix G, a project would have a significant impact on 

aesthetics if it would have a substantial adverse effect on a scenic vista; substantially 

damage scenic resources, including but not limited to trees, rock outcroppings, and historic 

buildings within a State scenic highway; substantially degrade the existing visual character 

or quality of the site and its surroundings; and/or create a new substantial source of light 

and glare, which would adversely affect day or nighttime views in the area. 

Reasonable people can disagree as to whether alteration of visual character would be 

adverse or beneficial, and individual viewers respond differently to changes in the physical 

environment. With that being said, the project area is located in a highly visible urban 

landscape, which is dominated primarily by the highway itself and the previously disturbed 

land within the highway right of way, drivers on Highway 50, a commercial/industrial 

corridor, and limited residents with direct view of the project. People driving on Highway 

50 and area roads are considered to have a low sensitivity. Drivers have only transitory 

views of the site as they pass by. Residents of homes, on the other hand, typically view the 

surrounding landscape as an integral part of their home environment, and are sensitive to 

changes in the environment. Based on the IS/MND, there are very few homes at all 

proximate to the site, and most will not have clear views of the project sites. 

21 




Landscaping will be incorporated into the final project design in order to integrate the PV 

panels with the existing urban environment, and address aesthetic and security 

requirements. Landscaping will be installed to accomplish many additional goals including 

discouraging site access, storm water and erosion control, provide environmental value, and 

achieve an aesthetically acceptable completed project. Landscaping and signage within the 

Caltrans ROW is subject to Caltrans landscaping policies and final approval. 

The conceptual „Rancho Cordova‟ signage presented during the April and June 2010 

meetings has not been formally incorporated into the project design, and it is not clear if 

incorporating signage in the project scope will be allowed by Caltrans. If allowed, 

development of signage options will be coordinated with Caltrans and City of Rancho 

Cordova staff. 


The project will not conflict with a future bike trail located along the UPRR spur bridge. 

Modification of the UPRR spur will not occur as a component of the project. 


The potential environmental effects of the flat-plate portion of the Mather Field Interchange 

project site (west of the UPPR spur bridge) were evaluated in the Draft IS/MND; however, 

this portion of the project is not planned for development at this time. 

The entire project will be designed to allow for construction and operation in a manner that 

will not impact Highway 50. Caltrans height and setback and other project requirements 

have been designed to ensure the safety of the traveling public and to preserve their ability 

to maintain highway operations. Finally, the high-profile nature of this project, and the 

national and potentially international attention it is likely to receive, is expected to provide 

beneficial exposure to adjacent businesses and the City of Rancho Cordova itself. 


In order to ensure that the project area remains safe, well maintained and attractive 

throughout the life of the project, several mechanisms will be enacted including a Caltrans 

air space lease agreement (lease) and a power purchase agreement (PPA). The 

aforementioned contracts between SMUD, Caltrans and the equipment owner/operator will 

cover all aspects of the operations and maintenance of the project, as described below. 

A lease agreement will be required by Caltrans. The agreement will be between SMUD and 

Caltrans, and SMUD will execute a sublease with the equipment owner/operator which will 

be part of the Master Agreement governing the project execution and operation. This lease 

will give SMUD the authority to construct the project within the Caltrans ROW and will 

dictate safety, maintenance and aesthetic requirements. SMUD will also enter into a PPA 

with the owner/operator to govern the purchase of the power generated by the project. 

This agreement will contain standard of care and safety provisions. In addition, if the final 

project design incorporates portions of the ROW beyond the legal lease area, then Caltrans, 

SMUD and the project owner/operator are likely to enter into a landscape maintenance 




agreement to govern the maintenance of those areas. This agreement would contain 

additional performance standards. 

SMUD has incorporated mitigation measures Aes-1 and Aes-2 in the Final IS/MND. These 

mitigation measures are requirements of the project owner/operator and will be 

incorporated into the Master Agreement which will govern the project execution and ensure 

aesthetic standards are maintained. 

Aes-1: SMUD will require the equipment owner/operator of the project to be responsible 

for correcting graffiti, vandalism, or other physical damage to the solar panels, and 

maintaining the landscaping within the boundaries of the solar project. 

Aes-2: SMUD will require implementation of security measures designed specifically for 

the project sites. These may include barbed wire or reinforced fencing at the top of the cutslopes, 

and along Mather Field Road, as well as anti-theft bolts, and perimeter security 

lighting and video monitoring. In addition, the flat-plate panels may be installed closer to 

the ground making access to the fasteners and wiring more difficult for thieves. 


We appreciate the City of Rancho Cordova‟s support of the project. Due to the novel nature 

of this project and the need for extensive interagency coordination, the process to complete 

CEQA, select an equipment owner/operator and complete final design has taken longer 

than originally anticipated. SMUD stands by our commitment to further engage the City of 

Rancho Cordova when design proposals are available for review and comment. 

23 




Letter 3 

Comment 3-1 

Comment 3-2 





Comment 3-3 

Comment 3-4 

Comment 3-5 

Comment 3-6 

25 





Comment 3-6, 

continued 

Comment 3-7 

Comment 3-8 

Comment 3-9 





Comment 3-10 

Comment 3-11 

Comment 3-12 

27 





Comment 3-12, 

continued 

Comment 3-13 




Letter No. 3 – Eric Fredricks, Chief Office of Transportation 

Planning- South, Caltrans District 3 


Comment noted. The corresponding letter and title of each appendix is listed on pages IX 

and 3 of the Draft IS/MND; therefore, an edit will not be made to the Draft IS/MND. The 

suggested edit would not change the proposed finding that the project will not have a 

significant effect on the environment, and the adequacy of the document is not 

compromised as a result of not editing the Draft IS/MND to incorporate this change. 


Comment noted. Detailed information evaluating and summarizing the environmental 

resources, the corresponding potential environmental effects and mitigation measures, 

which reduce the potential effects to a less-than-significant level, are included in each 

environmental resource discussion in the Environmental Checklist (Chapter 3) of the Draft 

IS/MND. Therefore to avoid redundancy, edits will not be made to the Draft IS/MND. In 

addition, the suggested edit would not change the proposed finding that the project will not 

have a significant effect on the environment, and the adequacy of the document is not 

compromised as a result of not editing the Draft IS/MND to incorporate this change. 


Comment noted. The potential environmental effects of the flat-plate portion of the Mather 

Field Interchange project site were evaluated in the Draft IS/MND; although, this portion of 

the project is not planned for development at this time. Due to the fact that this portion of 

the project was evaluated in the Draft IS/MND, the listed figures will not be modified. 


Comment noted. An analysis of a no-build alternative and a range of reasonable project 

alternatives are not required content of a Mitigated Negative Declaration; therefore, the 

effects of a no-build alternative will not be addressed in the Draft IS/MND. Furthermore, 

the Draft IS/MND adhered to Article 6: Negative Declaration Process included in the CEQA 

Guidelines. 

Response to Comments 3-5 and 3-8 

Comment noted. Per the Environmental Checklist contained in Appendix G of the CEQA 

Guidelines paleontological resources is addressed in the cultural resources checklist section. 

As a result, in the Draft IS/MND paleontological and cultural resources were analyzed 

collectively in the cultural resources section included in the Environmental Checklist 

(Chapter 3) of the Draft IS/MND. In addition, division of cultural and paleontology 

mitigation measures would not modify the proposed findings that with mitigation, 

environmental impacts to potentially sensitive cultural and paleontological resources are 

considered less than significant. 

29 




Please note that SMUD has included mitigation measure Cul-1 in its project description in 

the event that subsurface archaeological or paleontological resources are discovered during 

project construction. Although no significant impacts have been identified there is always 

the possibility that potentially significant unidentified prehistoric, historic, or paleontologic 

materials could be encountered below the surface during project construction. In such a 

situation, SMUD would implement the following mitigation measures. Therefore, this 

impact is considered to be less than significant with mitigation incorporated. 

Cul-1: If any paleontologic or cultural resources, such as buildings, structures, or objects 

over 50 years old (excluding buildings that have been previously evaluated as ineligible for 

the National or California Register), including human remains, are encountered during any 

project development activities, work shall be suspended, and SMUD, Caltrans, and other 

applicable agencies shall be immediately notified. At that time, the County, Caltrans, and 

SMUD will coordinate any necessary investigations of the site with appropriate specialists, 

as needed. 


Comment noted. Please note that the flat-plate PV panels at the Mather Filed Interchange 

portion of the project are not planned for development at this time; however, SMUD and/or 

its equipment owner/operator will coordinate construction activities with Caltrans. In 

addition, at this time start of construction isn‟t anticipated until fall 2011. 


The „Required Permits and Approvals‟ section included in the Draft IS/MND will be 

updated to include approval by the Federal Highway Administration (FHWA). Please refer 

to Chapter 3 (Changes and Edits to the Draft IS/MND) of this document to view the 

aforementioned edit. 


Comment appears to be duplicative. Please see response to Comment 3-5. 


Comment noted. SMUD believes these comments are directed to the Environmental 

Checklist (Chapter 3: page 23) rather than the „Mitigation Measures Incorporated into 

Project Design Features and Construction Plans‟ and will be responded to accordingly. 

The Draft IS/MND includes a discussion of applicable federal, state, and local (regulatory) 

framework with the Environmental Setting sections of selected environmental resource 

discussions, and edits will not be made to the Draft IS/MND. In addition, the suggested 

edits would not change the proposed finding that the project will not have a significant 

effect on the environment, and the adequacy of the document is not compromised as a result 

of not editing the Draft IS/MND to incorporate these changes. 




The first sentence of the Draft IS/MND „this document has been prepared to evaluate 

SMUD proposed project for compliance under the CEQA‟ as well as the section entitled 

„Purpose of this Document‟ located on page 2 plainly explain to the reader why the 

environmental document is being prepared. Edits will not be made to the Draft IS/MND. 

SMUD‟s standard format for an IS/MND includes a comprehensive discussion of all the 

environmental resource areas included in Appendix G of the CEQA Guidelines regardless 

of their potential effects. Edits will not be made to the Draft IS/MND. 


Mitigation Measure Bio-2 has been updated to reflect that mitigation for the trees removed 

in the East Sacramento project section could occur on the north side of the freeway and 

ground-cover was added to the definition of landscaping. In addition, the final sentence was 

updated to reflect Caltrans‟ suggested edit. Please refer to Chapter 3 (Changes and Edits to 

the Draft IS/MND) of this document to view the aforementioned edits. 

Please note that panel spacing is governed by shading impacts and physical features of the 

site, therefore, landscaping apart from low-lying vegetation may not be feasible directly 

adjacent to or between the panel locations. In addition, low-lying vegetation between the 

panel arrays and the roadway is currently incorporated into the project description and will 

be subject to a Caltrans landscape maintenance agreement. 


Comment noted. Per the Environmental Checklist contained in Appendix G of the CEQA 

Guidelines paleontological resources is addressed in the cultural resources checklist section. 

As a result, in the Draft IS/MND paleontological and cultural resources were analyzed 

collectively in the cultural resources section included in the Environmental Checklist 

(Chapter 3) of the Draft IS/MND. In addition, division of cultural and paleontology 

discussion would not modify the proposed findings that with mitigation, environmental 

impacts to potentially sensitive cultural and paleontology resources are considered less than 

significant. Edits will not be made to the Draft IS/MND. 

Burleson Consulting‟s standard cultural resources report format follows the State Historic 

Preservation Officer (SHPO) publication titled „Archaeological Resource Management 

Reports: Recommended Contents and Format‟ and is similar to Caltrans‟ Archaeological 

Survey Report (ASR) format. The cultural resources section of the Draft IS/MND provides 

details regarding the contents and results of the cultural resources survey prepared. 

Burleson Consulting, which prepared the Draft IS/MND, has an archaeologist and geologist 

on staff. These qualified staff members were involved in preparation of the Draft IS/MND 

as indicated in Chapter 4 (List of Preparers) of the Draft IS/MND. 

31 





As indicated in Mitigation measure Haz-5 soil will be sampled in accordance with 

Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA) and 

CCR Title 22 requirements, which includes lead analysis, prior to disposal. The clarification 

of „prior to leaving the Caltrans ROW‟ was used to amend Mitigation measure Haz-5. Please 

refer to Chapter 3 (Changes and Edits to the Draft IS/MND) of this document to view the 

aforementioned edits. 

The project will comply with all applicable Cal/OSHA health and safety standard during 

construction and operation of the project including protection of construction workers in a 

lead environment; although, a potential for exposure is not anticipated based on SMUD‟s 

sample results. 


Comment noted. SMUD acknowledges that the standard format used for the Draft IS/MND 

is not the format prefer by Caltrans; although, format edits will not be made to the Draft 

IS/MND. The suggested edits would not change the proposed finding that the project will 

not have a significant effect on the environment, and the adequacy of the document is not 

compromised as a result of not editing the Draft IS/MND to incorporate these changes. 




Letter 4 

Comment 4-1 

33 





Comment 4-1, 

continued 

Comment 4-2 

Comment 4-3 




Letter No. 4 – Sean Bechta, East Sacramento Resident 


An additional Glint and Glare study was completed to analyze the possible glint and glare 

effects to the residential neighborhoods on the south side of Highway 50 and to provide 

conclusions for residential-specific glint and glare analyses conducted as part of the Phase 2 

Feasibility Study. The conclusions for the East Sacramento project section are summarized 

below. 

The study concluded that the East Sacramento KVP, located at 49th Street near Discovery 

Way, will not experience glint at any time of the year. The results of the analytical model 

indicate that, in order to observe glint, a viewer would need to be hundreds of feet above 

the KVP. The study concluded that glare will be visible if the panels are viewed at acute 

angles in an eastward direction in the early morning (7:30-8:15am) from March to 

September. Glare will also be visible if the panels are viewed at acute angles in a westward 

direction in the early evening (7:30-8:00pm) from May to June. Based on a visual inspection 

of the residential area, the acute viewing angles necessary to receive glare from the project 

are difficult to achieve, due to a limited field of view in the neighborhood, which is a result 

of the fence, foliage, and embankment that separates the neighborhood from the highway. 

Even at acute viewing angles, the glare is not anticipated to be significant and the 

reflectivity would be comparable to other standard roadside surfaces such as worn asphalt, 

and highly reflective windshields and metallic surfaces of vehicles and other shiny reflective 

surfaces which are visible in the view shed of the KVP, and would be significantly less 

bright than the setting or rising sun. Therefore the glare from PV panels located at the East 

Sacramento project section would not generate a significant source of light or glare or create 

significant negative impacts. 

The potential glint and glare effects of the flat-plate panels to passing motorists on the south 

side of the highway was addressed in the Glint and Glare Study Expansion (Glint and Glare 

Study) dated February 8, 2010 and was summarized in the Draft IS/MND. The Glint and 

Glare Study evaluated glint and glare issues for two key vantage points (KVPs). KVP 1 was 

located on the south side of the Highway (eastbound Highway 50) while KVP 2 was located 

on the north side of the Highway (westbound Highway 50). The analysis concluded that the 

potential for experiencing glint and glare would be for 15 to 30 minutes in the morning 

while traveling eastbound on Highway 50 (south side of the Highway) from March 21st 

through September 21st, and in the afternoon while traveling westbound on Highway 50 

(north side of the Highway) from May 28th through July 22nd. A vehicle traveling 55 MPH 

will be exposed to the glare for approximately 90 seconds. 


Details of mitigation measure Bio-2, which addresses mitigation of tree removal in the East 

Sacramento project section, remain in discussion with Caltrans. As addressed in the 

mitigation measure, the number of plants and locations are to be determined with Caltrans. 

35 




As a result of Caltrans‟ comments to the Draft IS/MND, mitigation Measure Bio-2 has been 

updated to reflect that mitigation for the trees removed in the East Sacramento project 

section could occur on the north side of the freeway and ground-cover was added to the 

definition of landscaping. In addition, preliminary discussions with Caltrans have resulted 

in a proposed value-per-tree based mitigation approach, rather than commonly used treeby-tree 

or inch-by-inch mitigation approaches. Additionally, in discussions with Caltrans 

SMUD has recommended planting evergreen trees, to satisfy the requests received from 

residents during the project‟s scoping meetings. 


As stated by the Draft IS/MND, the intent of mitigation measure Bio-2 is to mitigate for the 

loss of landscaping including trees in the East Sacramento project section. The purposes of 

the existing landscaping along the highway are to provide aesthetic and environmental 

value, integrate transportation facilities with the physical, natural, and constructed 

environments, and prevent erosion of soil on cut-slopes. The intent of mitigation measure 

Bio-2 is to mirror Caltrans‟ objectives of existing landscaping. 




Letter 5 

Comment 5-1 

37 




Letter No. 5 – Kerry Freeman, East Sacramento Resident and 

Elmhurst Neighborhood Association Board member 


Potential noise impacts from construction and operation of the project including reflected 

noise were analyzed in the Draft IS/MND. Briefly, the Draft IS/MND concluded that the 

project will result in a temporary increase in ambient noise levels in the project vicinity 

above the existing conditions. The temporary noise increase will be caused by construction 

of the project and will be mitigated to a less-than-significant level with incorporation of 

mitigation measures to reduce the construction-related noise. 

Additionally, the Draft IS/MND concluded the permanent increase in noise at existing 

residences from the introduction and operation of the project would be zero (0.0 dB) above 

the existing conditions. Therefore, mitigation measures such as a sound wall are not 

necessary to reduce any potential project-caused temporary or permanent noise increases to 

a less-than-significant level. 

In addition the Draft IS/MND evaluated the noise baseline conditions, and concluded in the 

East Sacramento project section that noise in this urbanized area of Sacramento is 

dominated by traffic noise from Highway 50 and RT light rail, which was modeled as 

approximately 70 dBA Ldn exterior noise levels at existing residences. Per CEQA 

Guidelines, project proponents do not have an obligation to mitigate for existing conditions 

regardless of its current state. 




Letter 6 

Comment 6-1 

39 




Letter No. 6 – Melissa Jones, Executive Director California 

Energy Commission 

Letter of support noted. 




3.0 Changes and Edits to the Draft IS/MND 

Project Overview 

1. Page 1, Add the following text to the project description (additions are underlined 

below): 

SMUD proposes to install and integrate an A123 lithium-ion energy storage system with the 

East Sacramento PV panels. The energy storage system, which is comprised of one or two 

enclosures, will include multiple batteries housed in a single enclosure and a second 

enclosure to house power electronics. The energy storage system would be located within 

the Caltrans ROW and on the western end of the East Sacramento project section. The 

energy storage system will be used to stabilize the intermittency of the PV production and 

integrate generated electricity into SMUD‟s grid. The energy storage system was included in 

a project funded by a CEC Public Interest Energy Research (PIER) grant. 

General Project Information 

2. Page 4, Project Description, Revise the text as follows (additions are underlined 

below) to include the project description modification: 

SMUD proposes the Solar Highways Project (also referred to as “the project”) to develop PV 

generation facilities, and A123 lithium-ion energy storage system and electrical 

interconnection in the cut-slope and open space along the Highway 50 corridor in 

Sacramento County, California. 


A123 lithium-ion energy storage system consisting of one or two enclosures with a 

total footprint of approximately 23 feet long by 12 feet wide 

Project Schedule 

3. Page 5, Project Schedule, Revise the text as follows (additions are underlined and 

deletions are shown in strikeout below): 

Project construction is planned to start Fall occur approximately between Summer 2011 and 

Summer 2012. The general schedule for work begins at the Mather Field Interchange in 

Summer 2011 and at the East Sacramento section in Winter 2011/2012. Construction, 

interconnection and commissioning activities are expected to conclude by December 2012. 

Figure 2b (42 nd Street to 48 th Street) 

4. Page 10, Update Figure 2b to show the approximate locations of the energy storage 

system enclosures (see updated Figure in Final IS/MND; page 8). 

41 




Figure 2c (48 th Street to 51 st Street) 

5. Page 11, Update Figure 2c to show the approximate locations of the energy storage 

system enclosures (see updated Figure in Final IS/MND; page 9). 

Project Features 

6. Page 16, Include the energy storage system as a project feature. 

A123 lithium-ion energy storage system installed at the East Sacramento project 

section. 

Project Construction 

7. Page 17, Revise the text as follows (additions are underlined are shown in strikeout 

below) to include the project description modification: 

The system components were selected to be “off-the-shelf” industry standard for the solar 

panels, energy storage system, and electrical equipment, array and mounting systems, 

foundation systems, and utility electrical interconnection. 


A123 lithium-ion energy storage system consisting of one or two enclosures with a 

total footprint of approximately 23 feet long by 12 feet wide 

Project Schedule 

8. Page 19, Project Schedule, Revise the text as follows (additions are underlined and 


Project construction is planned to start Fall occur approximately between Summer 2011 and 

Summer 2012. The general schedule for work begins at the Mather Field Interchange in 

Summer 2011 and at the East Sacramento section in Winter 2011/2012. Construction, 

interconnection and commissioning activities are expected is expected to conclude by 

December 2012. 

Required Permits and Approvals 

9. Page 20, Add the following approval requirement. 

Federal Highway Administration (FHWA) Approval. FHWA final approval of the project 

will be required. SMUD is working in coordination with Caltrans to support this 

requirement. This approval process is being developed and is expected to conclude by June 

22, 2011. 




Initial Study – Checklist I. Aesthetics 

10. Page 25, Impacts, Answers to Checklist Question, Question b. Revise the mitigation 

measure Bio-2 for the East Sacramento tree mitigation (additions are underlined and 


Bio-2: SMUD shall mitigate for trees removed in the East Sacramento project section by 

planting landscaping, including trees, and shrubs, and ground-cover, within the Caltrans 

right-of-way on the north and south side of the freeway (across from the project area). The 

type, quantity and location of landscape vegetation will be determined with Caltrans. The 

number of trees planted and locations will be determined with Caltrans. 

11. Page 28, Impacts, Answers to Checklist Question d. Revise the text as follows to 

incorporate conclusions of the residential glint and glare study the evaluation of PV 

panels on local temperature (additions are underlined below): 

Glint and Glare for Residences. SMUD commissioned the engineering consulting firm IEC 

to conduct a Residential Glint and Glare Study to analyze the possible glint and glare effects 

to the residential neighborhoods on the south side of Highway 50 and to provide 


Feasibility Study. The study utilized analytical models to evaluate potential glint and glare 

impacts at two key vantage points (KVPs) located in the vicinity of the East Sacramento and 

Mather Field Interchange project sections. In addition, the study referenced a number of 

scientific industry papers and field experiences to evaluate the potential environmental 

effects of glint and glare. The results of the study were used to determine the significance of 

the potential environmental effects; the potential glare produced by the project was 

evaluated based on the existing ambient glare conditions, proximity to light-sensitive land 

uses, and intensity of the potential glare. 








of the residential area, the acute viewing angles necessary to receive glare from the project 

are difficult to achieve, due to a limited field of view in the neighborhood, which is a result 

of the fence, foliage, and embankment that separates the neighborhood from the highway. 










43 
































environment. 





















Evaluation of PV Panels on Local Temperature. An analysis was conducted to examine 

potential heat reflection from the PV panels creating a change in the local ambient 

temperature. The analysis considered two factors which could result in local temperature 

change: 1) material reflectivity and 2) dissipated heat. 

Reflectivity. Solar panels are designed to absorb light, not reflect it; however, some light 

reflection will occur, as noted in the glare studies. This is a function of the albedo of the PV 

panels as compared to the ground that was there before. The term albedo is a property of a 

material or surface which is defined as the total amount of energy reflected divided by the 

total amount of energy impacting the material or surface. Albedo is expressed as a fraction 

or a percentage, and ranges from 0 (very dark) to 1 (very bright). The solar panels will have 

an albedo between 6% to 10%, compared to the reflectivity of the current site surface 

materials such as bare soil at 17%, green grass at 25%, and deciduous trees at 18% 

(Markvart and Castalżer 2003, SunPower Corporation 2009). Solar panels have a lower 

albedo than the existing landscape, and thus can be expected to absorb and radiate more 

heat than the existing landscape. However, as demonstrated below, the creation of an 

impact on local temperature requires large areas of low albedo. The scale of this project is 

not large enough to cause an impact on local temperature. 

The amount of energy reflected from a given area is equal to the solar energy impacting that 

area multiplied by the albedo of the terrain. The remainder of the solar energy is absorbed 

and stored as heat, and then dissipated through the day. In the California Valley, the 

amount of solar energy impacting the ground is 21.0 Megawatt-hour/acre/day 

(MWh/acre/day) (Sunpower Corporation 2010). Using an estimated pre-project albedo of 

20%, the amount of energy converted to heat and dissipated is equal to 16.8 

MWh/acre/day. 

For traditional flat-plate PV panels, most of the solar energy will impact the panels. With the 

introduction of the PV panels, the albedo has decreased from 20% to 8%; this increases the 

amount of solar energy absorbed as heat from 16.8 MWh/acre/day to 19.3 MWh/acre/day. 

In a typical tracking PV array, at most 40% of the total solar energy will impact the ground 

while the remaining 60% will impact the panels (Sunpower Corporation 2010). To evaluate 

the amount of heat generated in a large PV array, the effective albedo was calculated, which 

is the average albedo over the entire site. Using the equation below, the effective albedo of a 

tracking PV array in the central valley is 12.8% (Sunpower Corporation 2010). With the 

introduction of the tracking PV system, the albedo has decreased from 20% to 12.8%. This 

increases the amount of solar energy absorbed as heat from 16.8 MWh/acre/day to 18.3 

MWh/acre/day. For both the flat-plate PV panels and the tracking PV arrays, the increased 

reflection from the PV panels will be negligible related to the ground it was covering. 

Effective Albedo = (fraction of solar energy on ground)*(natural albedo of the ground) + 

(fraction of solar energy on PV)*(albedo of panels) 

45 




Dissipated heat. In addition to the albedo, the other factor evaluated which could potentially 

result in a change in the local ambient temperature is dissipated or reflected heat from the 

PV panels. The analysis evaluated the relative increase between the PV panels and the 

ground surface the panels were covering by calculating the heat transfer (see Appendix J). 

The total potential heat transfer from radiative effects of the panels being slightly hotter 

operating temperature than the hillside resulted in about 6 Watt per square meter (W/m2) 

of radiation, using very conservative assumptions of theoretical vertical PV panels. Typical 

diffuse radiation that heats up the house is on the order of 150 W/m2, so this is only 4% of 

that, and is likely very small relative to the heat transfer from the roadway. 

In conclusion, the albedo change on the project sites does not have broader implications to 

the surrounding land uses, and the residents in the vicinity of the project will not experience 

a net heat impact from the project. 

Initial Study – Checklist III. Air Quality 

12. Page. 40, Impacts, Answers to Checklist Question, Question b. Revise project 

schedule (additions are underlined and deletions are shown in strikeout below): 

Construction Impacts. LESS-THAN-SIGNIFICANT IMPACT. Project construction is 

planned to occur approximately between Fall Summer 2011 and Summer 2012. The general 

schedule for work begins at the Mather Field Interchange in Summer 2011 and at the East 

Sacramento section in Winter 2011/2012. Construction, interconnection and commissioning 

activities are expected to conclude by December 2012. As the ROW north cut-slope areas 

have previously been graded and prepared, minimal grading is required. Construction 

would consist of tree removal, ground preparation, installing panel bases and support 

mounts, and some trenching for connecting electrical lines. 

Initial Study – Checklist IV. Biological Resources 

13. Page. 50, Impacts, Answers to Checklist Question, Question e. Revise mitigation 

measure Bio-2 for the East Sacramento tree mitigation (additions are underlined and 


Bio-2: SMUD shall mitigate for trees removed in the East Sacramento project section by 

planting landscaping, including trees, and shrubs, and ground-cover, within the Caltrans 

right-of-way on the north and south side of the freeway (across from the project area). The 

type, quantity and location of landscape vegetation will be determined with Caltrans. The 

number of trees planted and locations will be determined with Caltrans. 

Initial Study – Checklist IX. Hazards and Hazardous Materials 

14. Page 76, Impacts, Answers to Checklist Questions a and b. Revise project impact 

discussion and mitigation measure Haz-1 to mitigate for an accidental release during 

operation and incorporate conclusions of the residential glint and glare study and 




the evaluation of PV panels on local temperature text as follows (additions are 

underlined below): 

Hazardous Materials Used Onsite during Construction. During construction, construction 

equipment and vehicles containing petroleum products would be onsite. Refueling would 

occur offsite either at a SMUD facility or private gas station. During operation, the energy 

storage system would contain a battery electrolyte in a sealed enclosure. Hazardous 

materials, including paints, greases, epoxies, and oil, would be delivered to the site, and 

stored in covered containers in accordance with Federal Occupational Safety and Health 

Administration (OSHA) and the California Occupational Safety and Health Administration 

(Cal/OSHA) regulations. During construction and operation activities, minor spills of fuel 

or oils/lubricants from ruptured fuel and/or hydraulic lines on the construction equipment 

may occur. SMUD has included Mitigation Measures Haz-1 and Haz-2 to address 

accidental spills during construction; therefore, this is considered a less-than-significant 

impact with mitigation incorporated. 

Mitigation Measure 

Haz-1: If an accidental release or spill occurs during construction or operation of the project, 

the release shall be cleaned up immediately and reported in accordance with applicable 

federal, State, and local requirements. 

Glint and Glare for Residences. SMUD commissioned the engineering consulting firm IEC 

to conduct a Residential Glint and Glare Study to analyze the possible glint and glare effects 

to the residential neighborhoods on the south side of Highway 50 and to provide 


Feasibility Study. The study utilized analytical models to evaluate potential glint and glare 

impacts two key vantage points (KVPs) located in the vicinity of the East Sacramento and 

Mather Field Interchange project sections. In addition, the study referenced a number of 

scientific industry papers and field experiences to evaluate the potential environmental 

effects of glint and glare. The results of the study were used to determine the significance of 

the potential environmental effects; the potential glare produced by the project was 

evaluated based on the existing ambient glare conditions, proximity to light-sensitive land 

uses, and intensity of the potential glare. 








of the residential area, acute viewing angles necessary to receive glare from the project are 

difficult to achieve, due to a limited field of view in the neighborhood, which is a result of 

the fence, foliage, and embankment that separates the neighborhood from the highway. 





47 





































environment. 





















Evaluation of PV Panels on Local Temperature. An analysis was conducted to examine 

potential heat reflection from the PV panels creating a change in the local ambient 

temperature. The analysis considered two factors which could result in local temperature 

change: 1) material reflectivity and 2) dissipated heat. 

Reflectivity. Solar panels are designed to absorb light, not reflect it; however, some light 

reflection will occur, as noted in the glare studies. This is a function of the albedo of the PV 

panels as compared to the ground that was there before. The term albedo is a property of a 

material or surface which is defined as the total amount of energy reflected divided by the 

total amount of energy impacting the material or surface. Albedo is expressed as a fraction 

or a percentage, and ranges from 0 (very dark) to 1 (very bright). The solar panels will have 

an albedo between 6% to 10%, compared to the reflectivity of the current site surface 

materials such as bare soil at 17%, green grass at 25%, and deciduous trees at 18% 

(Markvart and Castalżer 2003, SunPower Corporation 2009). Solar panels have a lower 

albedo than the existing landscape, and thus can be expected to absorb and radiate more 

heat than the existing landscape. However, as demonstrated below, the creation of an 

impact on local temperature requires large areas of low albedo. The scale of this project is 

not large enough to cause an impact on local temperature. 

The amount of energy reflected from a given area is equal to the solar energy impacting that 

area multiplied by the albedo of the terrain. The remainder of the solar energy is absorbed 

and stored as heat, and then dissipated through the day. In the California Valley, the 

amount of solar energy impacting the ground is 21.0 Megawatt-hour/acre/day 

(MWh/acre/day) (Sunpower Corporation 2010). Using an estimated pre-project albedo of 

20%, the amount of energy converted to heat and dissipated is equal to 16.8 

MWh/acre/day. 

For traditional flat-plate PV panels, most of the solar energy will impact the panels. With the 

introduction of the PV panels, the albedo has decreased from 20% to 8%; this increases the 

amount of solar energy absorbed as heat from 16.8 MWh/acre/day to 19.3 MWh/acre/day. 

In a typical tracking PV array, at most 40% of the total solar energy will impact the ground 

while the remaining 60% will impact the panels (Sunpower Corporation 2010). To evaluate 

the amount of heat generated in a large PV array, the effective albedo was calculated, which 

is the average albedo over the entire site. Using the equation below, the effective albedo of a 

tracking PV array in the central valley is 12.8% (Sunpower Corporation 2010). With the 

introduction of the tracking PV system, the albedo has decreased from 20% to 12.8%. This 

increases the amount of solar energy absorbed as heat from 16.8 MWh/acre/day to 18.3 

MWh/acre/day. For both the flat-plate PV panels and the tracking PV arrays, the increased 

reflection from the PV panels will be negligible related to the ground it was covering. 

49 




Effective Albedo = (fraction of solar energy on ground)*(natural albedo of the ground) + 

(fraction of solar energy on PV)*(albedo of panels) 

Dissipated heat. In addition to the albedo, the other factor evaluated which could potentially 

result in a change in the local ambient temperature is dissipated or reflected heat from the 

PV panels. The analysis evaluated the relative increase between the PV panels and the 

ground surface the panels were covering by calculating the heat transfer (see Appendix J). 

The total potential heat transfer from radiative effects of the panels being slightly hotter 

operating temperature than the hillside resulted in about 6 Watt per square meter (W/m2) 

of radiation, using very conservative assumptions of theoretical vertical PV panels. Typical 

diffuse radiation that heats up the house is on the order of 150 W/m2, so this is only 4% of 

that, and is likely very small relative to the heat transfer from the roadway. 

In conclusion, the albedo change on the project sites does not have broader implications to 

the surrounding land uses, and the residents in the vicinity of the project will not experience 

a net heat impact from the project. 

15. Page 80, Impacts, Answers to Checklist Questions a and b. Revise mitigation 

measure Haz-5 to mitigate for the potential to encounter contaminated soil 

(additions are underlined below) text as follows: 

Haz-5: If evidence of contaminated material is encountered during construction, cease 

construction immediately and notify Caltrans. Collect and analyze soil samples prior to 

leaving the Caltrans ROW to ensure proper off-site disposal of excess soil in accordance 

with Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA) 

and CCR Title 22 requirements. Applicable requirements of CERCLA and CCR Title 22 

regarding disposal of waste shall be implemented, as required. 

16. Page 81, Impacts, Answers to Checklist Questions d. Revise mitigation measure Haz- 

5 to mitigate for the potential to encounter contaminated soil (additions are 

underlined below) text as follows: 

Haz-5: If evidence of contaminated material is encountered during construction, cease 

construction immediately and notify Caltrans. Collect and analyze soil samples prior to 

leaving the Caltrans ROW to ensure proper off-site disposal of excess soil in accordance 

with Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA) 

and CCR Title 22 requirements. Applicable requirements of CERCLA and CCR Title 22 

regarding disposal of waste shall be implemented, as required. 

Initial Study – Checklist XIII. Noise 

17. Page 111, Answers to Checklist Questions a. (additions are underlined and deletions 

are shown in strikeout below): 

Nighttime Construction 




The RT light rail Orange Gold Line runs from Sacramento‟s downtown to the City of 

Folsom. 

Initial Study – Checklist XV. Public Services 

18. Page 119, Public Services Environmental Setting (additions are underlined and 


Rancho Cordova Schools include Abraham Lincoln Elementary School at 3324 Glenmoor 

Drive, Reymouth Elementary School on 10460 Reymouth Avenue, Cordova Villa 

Elementary School on 10359 South White Rock Road, Mills Middle School on 10439 Coloma 

Road, Williamson Elementary on 2275 Benita Drive, Rancho Cordova Elementary on 2562 

Chassella Way, Navigator Elementary on 10679 Bear Hollow Drive, Mather Heights 

Elementary on 4370 School Road, Cordova Meadows on 2550 La Loma Drive, Cordova 

Gardens on 2400 Dawes Street, Peter J Shields Elementary on 10434 Georgetown Drive, 

Mitchell Middle School on 2100 Zinfandel Drive, Cordova High School on 2239 Chase 

Drive, and San Joaquin Valley College on 11050 Olson Drive. 

Parks near the project site in Rancho Cordova are under the jurisdiction of Cordova 

Recreation and Parks District. Parks nearby include the Lincoln Village Park,, Mills Park, 

Countryside Park, River Bend Park, William B. Pond Recreation Area, Sonoma Park, 

Waterbrook Park, Stone Creek Park, Tuscany Park, Taylor Park, the Village Green Park, 

Hagan Community Park, and White Rock Community Park (Cordova Recreation and Parks 

District, 2010). 

References 

Incropera, Frank, P. and Dewitt, David, P. 1996. Fundamentals of Heat and Mass Transfer, 

4 th Edition. Blackbody Radiation Exchange Equation. 

Markvart, Tom and Castalżer, Luis. 2003. Practical Handbook of Photovoltaics: 

Fundamentals and Applications. Elsevier. ISBN 1-85617-390-9. 

SunPower Corporation. 2009. SunPower Solar Module Glare and Reflectance, Technical 

Report- *T09014. September 29. 

Sunpower Corporation. 2010. Impact of PV Systems on Local Temperature, Memorandum. 

Appendix G 

A Residential Glint and Glare Study, prepared by IEC, has been included in Appendix G. 

Appendix J 

Appendix J contains a heat transfer equation. 

51 




4.0 Final Mitigation Monitoring Plan 

Introduction 

The Sacramento Municipal Utility District (SMUD) included a series of mitigation measures 

in its project description for the Sacramento Solar Highways Project (also referred to as the 

“proposed project”) to minimize potential environmental impacts during project 

construction and operation. Those measures are incorporated into this Final Mitigation 

Monitoring Plan and are listed in Table A-1. 

This mitigation monitoring plan will be used by SMUD to ensure that each mitigation 

measure, adopted as a condition of project approval, is implemented. This monitoring plan 

meets the requirements of the California Environmental Quality Act, Guidelines Section 

14074(d), as amended, which mandates preparation of monitoring provisions for the 

implementation of mitigation assigned as part of project approval or adoption. 

Mitigation Implementation and Monitoring 

SMUD will be responsible for monitoring the implementation of mitigation measures 

designed to minimize impacts associated with the proposed project. While SMUD has 

ultimate responsibility for ensuring implementation, in most cases other entities have been 

assigned the responsibility of actually implementing the mitigation. SMUD will retain the 

primary responsibility for ensuring that the proposed project meets the requirements of this 

mitigation plan and other permit conditions imposed by participating regulatory agencies. 

SMUD will designate specific personnel who will be responsible for monitoring 

implementation of the mitigation that will occur during project construction. The 

designated personnel will be responsible for submitting all documentation and reports to 

SMUD on a timely basis and in a manner necessary for demonstrating compliance with 

mitigation requirements. SMUD will ensure that the designated personnel have authority 

to require implementation of mitigation requirements and will be capable of terminating 

project construction activities found to be inconsistent with mitigation objectives or project 

approval conditions. 

SMUD will be responsible for demonstrating compliance with other agency permit 

conditions to the appropriate regulatory agency. SMUD will also be responsible for 

ensuring that its construction personnel understand their responsibilities for adhering to the 

performance requirements of the mitigation plan and other contractual requirements related 

to the implementation of mitigation as part of project construction. 

In addition to the prescribed mitigation measures, Table A-1 lists each identified potential 

impact, the corresponding monitoring and reporting requirement, and the party responsible 

for ensuring implementation of the mitigation measure and monitoring effort. 




Mitigation Enforcement 

SMUD will be responsible for enforcing all mitigation measures. If alternative measures are 

identified that would be equally effective in mitigating the identified impacts, 

implementation of these alternative measures will not occur until agreed upon by SMUD. 

53 



Table A-1 The Sacramento Solar Highways Project Mitigation and Monitoring Plan Summary 

APPENDIX A: MITIGATION MONITORING PLAN 

Implementation Monitoring Responsibility 

Impact 

Aesthetics 

Mitigation 

One-time Ongoing One-time Ongoing Implementation Monitoring 

Visual quality 

of site, scenic 

resources, 

tree 

preservation 

and security 

for 

unauthorized 

access. 

See also 

Mitigation 

Measures Bio- 

2 and Bio-3. 

Aes-1 

SMUD will require the equipment owner/ operator of the 

project to be responsible for correcting graffiti, vandalism, 

or other physical damage to the solar panels, and 

maintaining the landscaping within the boundaries of the 

solar project. 

Requirements 

will be included 

in the request 

for offer (RFO) 

and as a 

condition of the 

awarded 

contract(s). 

During project 

construction 

and 

throughout 

the life of the 

project. The 

equipment 

owner/ 

operator 

would be 

required to 

continuously 

maintain the 

visual quality 

of the project 

under the 

contract with 

SMUD. 

Long-term 

maintenance 


monitoring 

under the 

awarded 

contract(s) 

with SMUD 

Equipment 

owner/ 

operator 

Equipment 

owner/ 

operator, 

Caltrans and 

SMUD 

Aes-2 

SMUD will require implementation of security measures 

designed specifically for the project sites. These may 

include barbed wire or reinforced fencing at the top of the 

cut-slopes, and along Mather Field Road, as well as antitheft 

bolts, perimeter security lighting and video monitoring. 

In addition, the flat-plate panels may be installed closer to 

the ground making access to the fasteners and wiring 

more difficult for thieves. 

Requirements 


in the RFO and 

during the 

project design 


construction 

period. SMUD 

will require the 

equipment 

owner/ operator 

to submit asbuilt 

construction 

drawings for 

verification of 

requirement. 


construction 


throughout 


project. 


construction 


throughout 


project. The 

Equipment 

owner/ 

operator 

would be 

required to 

continuously 

maintain 

project 

security 

under the 

contract with 

SMUD. 

Equipment 

owner/ 

operator and 

SMUD 

Equipment 

owner/ 


SMUD 

A-1 SACRAMENTO SOLAR HIGHWAYS PROJECT 

FINAL INITIAL STUDY AND MITIGATED NEGATIVE DECLARATION




Impact 

Air Quality 

Mitigation 


Fugitive dust 

during 

construction 

Air-1a 

Air-1b 

Air-1c 

Apply water or suitable soil stabilizers to inactive areas or 

other areas that can give rise to airborne dust. 

Water exposed surfaces up to three times daily to prevent 

fugitive dust from migrating beyond the project’s 

boundaries. 

Cover all inactive stockpiles with tarps or water to prevent 

airborne dust. 

Requirements 



as conditions of 

the awarded 

contract(s). 


construction. 


construction. 

Failure to 

comply could 

result in 

enforcement 

by the local 

air resource 

district 

Equipment 

owner/ 

operator 

Equipment 

owner/ 


local air 

resource 

district 

Air-1d 

Water all haul roads, as needed, to prevent airborne dust. 

Air-1e 

Limit speeds on any unpaved roads to less than 15 miles 

per hour, as applicable, and at potential offsite stockpile or 

staging areas. 

Air-1f 

Replace ground cover in disturbed areas as soon as 

construction in these areas is completed. 

Air-1g 

Maintain 2 feet of freeboard space on haul trucks. 

Air-1h 

Water soil piles three times daily. 

Air-1i 

Minimize the amount of disturbed area, the amount of 

material actively worked, and the amount of material 

stockpiled. 

Air-1j 

Sweep or wash paved streets adjacent to the project 

construction site at least once a day to remove 

accumulated dust. 

SACRAMENTO SOLAR HIGHWAYS PROJECT A-2 





Impact 

Biology 

Mitigation 


Impact to 

special –status 

birds or 

nesting birds 

Bio-1 

If construction activities would occur during the nesting 

season (estimated to be January through August), preconstruction 

surveys for the presence of special-status bird 

species or any nesting bird species shall be conducted by 

a qualified biologist within 500 feet of proposed 

construction areas. This survey shall be conducted no 

more than 14 days prior to the initiation of construction 

activities during the breeding season (raptors – January 

through August). During this survey, the biologist shall 

inspect the project area and immediately adjacent to the 

impact area for nests. If any other nest sites of bird 

species protected under the Migratory Bird Treaty Act 

(MBTA) are observed within the vicinity of the project site, 

then the project will be modified and/or delayed as 

necessary to avoid direct take of identified nest, eggs, 

and/or young. 

14 days prior to 

the initiation of 

construction 

activities 

SMUD 

SMUD 

Scenic 

resources and 

tree 

preservation in 

East 

Sacramento 

section 

Bio-2 

SMUD shall mitigate for trees removed in the East 

Sacramento project section by planting landscaping, 

including trees, and shrubs, and ground-cover, within the 

Caltrans right-of-way on the north and south side of the 

freeway (across from the project area). The type, quantity 

and location of landscape vegetation will be determined 

with Caltrans. The number of trees planted and locations 

will be determined with Caltrans. 

Within 1-year of 

construction 

completion 

Weekly for 

the first 3 

months after 

initial planting 

SMUD and 

Caltrans 


Caltrans 

Scenic 

resources and 

oak tree 

preservation in 

Mather Field 

Interchange 

section 

Bio-3 

SMUD shall mitigate for the oak trees in the Mather Field 

Interchange section, regardless of size, which were 

formerly planted as mitigation for the Folsom RT extension. 

SMUD will mitigate for the loss of these trees by partnering 

with the Sacramento Tree Foundation’s NATURE program. 

The NATURE program is off-site mitigation, which the Tree 

Foundation assumes responsibility for planting and 3-years 

of monitoring and reporting. Alternatively, a sum equivalent 

to the replacement cost of the number of trees removed 

shall be paid to the City of Rancho Cordova’s Tree 

Preservation Fund. 

Within 1-year of 

construction 

completion 

Monitoring 

per 


Tree 

Foundation or 

City of 

Rancho 

Cordova 

requirements 


the City of 

Rancho 

Cordova 


Tree 

Foundation 

or City of 

Rancho 

Cordova 






Impact 

Cultural Resources 

Mitigation 


Potential 

impacts to 

paleontologic 

or cultural 

resources 

Cul-1 

If any paleontologic or cultural resources, such as 

buildings, structures, or objects over 50 years old 

(excluding buildings that have been previously evaluated 

as ineligible for the National or California Register), 

including human remains, are encountered during any 

project development activities, work shall be suspended, 

and SMUD, Caltrans, and other applicable agencies shall 

be immediately notified. At that time, the County, Caltrans, 

and SMUD will coordinate any necessary investigations of 

the site with appropriate specialists, as needed. 

Requirements 



as a condition 

of the awarded 

contract(s). 


construction 

per the 

awarded 

contract(s) 

with SMUD 


construction 

per the 

awarded 

contract(s) 

with SMUD 

Equipment 

owner/ 

operator 

Equipment 

owner/ 

operator 

Potential 

impacts to 

Native 

American 

resources 

Cul-2 

When Native American archaeological, ethnographic, or 

spiritual resources are involved, all identification and 

treatment shall be conducted by qualified archaeologists 

who meet the federal standards, as stated in the Code of 

Federal Regulations (CFR) (36 CFR 61) and appurtenant 

(i.e., pursuant to the National Historic Preservation Act 

[NHPA], Senate Bill [SB] 18), and Native American 

representatives who are approved by the local Native 

American community as keepers of their cultural traditions. 

In the event that no such Native American is available, 

persons who represent tribal governments and/or 

organizations in the locale in which resources could be 

affected shall be consulted. 

Requirements 





contract(s). 


construction 

per the 

awarded 

contract(s) 

with SMUD 


construction 

per the 

awarded 

contract(s) 

with SMUD 

Equipment 

owner/ 

operator 

Equipment 

owner/ 

operator 






Impact 

Mitigation 


Potential 

impacts to 

human 

remains 

discovered 

during 

construction 

Cul-3 

Pursuant to Section 5097.98 of the California Public 

Resources Code (PRC) and Section 7050.5 of the 

California Health and Safety Code, if human remains or 

bone of unknown origin is found during construction, all 

work shall stop in the vicinity of the find and the 

Sacramento County Coroner shall be contacted 

immediately. If the remains are determined to be Native 

American, within 24 hours the coroner shall notify the 

NAHC who shall notify the person it believes to be the 

most likely descendant (MLD). The MLD shall work with 

the equipment owner/ operator to develop a program for 

re-interment of the human remains and any associated 

artifacts. No additional work shall take place within the 

immediate vicinity of the find until the identified appropriate 

actions have been implemented. If the Coroner 

determines that the remains are not related to a crime 

scene, then a qualified archaeologist who meets the 

federal standards, as stated in 36 CFR 61, shall be 

retained to assess the find and make further 

recommendations. 

Requirements 





contract(s). 


construction 


construction 

Equipment 

owner/ 

operator 

Equipment 

owner/ 

operator 

Geology and Soils 

Potential 

Impacts from 

soil erosion 

and impacts to 

water quality 

during 

operation 

Geo-1 

Infiltration of runoff from the solar panels would be 

encouraged and storm water controlled by design features 

such as low growing plantings, rock swales, special 

fabrics, and installation of storage to temporarily contain 

peak flows for later use or metering into the storm drain 

system. 

Requirements 



during the 

project design. 


construction 


throughout 


project 

Long-term 

maintenance 


monitoring 

Equipment 

owner/ 


Caltrans 

Equipment 

owner/ 


Caltrans 

See also 

Mitigation 

Measures 

Haz-1 and 

Wa-1. 






Impact 

Hazards and Hazardous Materials 

Mitigation 


Potential 

impacts from 

hazardous 

materials 

Haz-1 

If an accidental release or spill occurs during construction 

or operation of the project, the release shall be cleaned up 

immediately and reported in accordance with applicable 

federal, State, and local requirements. 

Requirements 





contract(s). 


construction 


construction 

Equipment 

owner/ 

operator 

Equipment 

owner/ 

operator 

Potential 

impacts from 

hazardous 

materials 

Haz-2 

Inspect equipment containing hazardous materials 

periodically for signs of spills or leakage. 

Requirements 





contract(s). 


construction 


construction 

Equipment 

owner/ 

operator 

Equipment 

owner/ 

operator 

Safety 

hazards for 

workers and 

the public, and 

security for 

unauthorized 

access. 

Haz-3 

Shore excavations in accordance with OSHA standards to 

protect workers and the public. During non-work periods, 

cover trenches or excavations to prevent accidents 

Requirements 





contract(s). 


construction 


construction 

Equipment 

owner/ 

operator 

Equipment 

owner/ 

operator 

See also 

Mitigation 

Measures 

Aes-1 and 

Aes-2. 






Impact 

Mitigation 


Potential 

impacts from 

hazardous 

materials and 

hazards to 

workers, and 

impacts to 

emergency 

response or 

evacuation 

plans. 

See also 

Mitigation 

Measure 

Trans-1. 

Haz-4 

Prepare Site Safety and Health Plan and conduct tailgate 

safety meetings. 

Requirements 





contract(s). 

SMUD will 

require the 

equipment 

owner/ operator 

to submit the 

Site Safety and 

Health Plan for 

SMUD’s review 

and approval. 


construction 


design and 

the 

construction 

period 


construction 

Equipment 

owner/ 


SMUD 

Equipment 

owner/ 

operator 

Potential 

hazard to the 

public and 

workers, and 

environment 

from 

subsurface 

soil 

contamination 

Haz-5 

If evidence of contaminated material is encountered during 

construction, cease construction immediately and notify 

Caltrans. Collect and analyze soil samples prior to leaving 

the Caltrans ROW to ensure proper off-site disposal of 

excess soil in accordance with Comprehensive 

Environmental Response, Compensation, and Liability Act 

(CERCLA) and CCR Title 22 requirements. Applicable 

requirements of CERCLA and CCR Title 22 regarding 

disposal of waste shall be implemented, as required. 

Requirements 





contract(s). 


construction 


construction 

Equipment 

owner/ 

operator 

Equipment 

owner/ 

operator 

Hydrology and Water Quality 

Potential 

impacts to 

water quality, 

erosion, and 

storm drain 

system during 

construction. 

See also 

Mitigation 

Measures 

Geo-1 and 

Haz-1. 

Wa-1 

Prepare construction storm water pollution prevention plan 

(SWPPP) in accordance with Board Order No. 2009-009- 

DWQ. Best management practices (BMPs) will be followed 

to minimize erosion, and protect the storm drain system 

and receiving waters. 

Requirements 



during the 

project design 


construction 

period. 


construction 


construction 

Failure to 

comply could 

result in 

enforcement 

by the State 

Water 

Resources 

Control Board 

Equipment 

owner/ 


Caltrans 

Equipment 

owner/ 

operator, 

Caltrans and 

State Water 

Resources 

Control 

Board 






Noise 

Impact 

Mitigation 


Minimize the 

noise impact 

from 

construction 

Noi-1 

Construction equipment powered by an internal 

combustion engine shall be equipped with suitable exhaust 

and intake silencers, in accordance with manufacturers’ 

specifications, and shall be maintained in good working 

order. 

Requirements 



included as 

conditions of 

the awarded 

contract(s). 


construction 


construction 

Equipment 

owner/ 

operator 

Equipment 

owner/ 

operator 

Noi-2 

Stationary construction equipment (e.g., portable power 

generators and compressors) shall be located at the 

furthest distance possible from nearby sensitive noise 

location. 

Requirements 



included as 

conditions of 

the awarded 

contract(s). 


construction 


construction 

Equipment 

owner/ 

operator 

Equipment 

owner/ 

operator 

Noi-3 

Motor vehicles and other equipment shall be turned off 

when the equipment is parked or not in operation. 

Requirements 



included as 

conditions of 

the awarded 

contract(s). 


construction 


construction 

Equipment 

owner/ 

operator 

Equipment 

owner/ 

operator 

Noi-4 

Equipment used for project construction shall be 

hydraulically or electrically powered whenever possible to 

avoid noise associated with compressed air exhaust from 

pneumatically powered tools. Where use of pneumatically 

powered tools is unavoidable, an exhaust muffler on the 

compressed air exhaust shall be used. 

Requirements 



included as 

conditions of 

the awarded 

contract(s). 


construction 


construction 

Equipment 

owner/ 

operator 

Equipment 

owner/ 

operator 






Impact 

Mitigation 


Minimize the 

noise impact 

from 

construction 

Noi-5 

Temporary sound walls or sound curtains/blankets shall be 

placed to block the noise from ground floor line of site to 

sensitive noise receptors to reduce the noise levels. Noise 

blankets or other appropriate noise barriers shall be used 

to cover stationary equipment while located adjacent to 

sensitive receptors, as appropriate. 

Requirements 



included as 

conditions of 

the awarded 

contract(s). 


construction 


construction 

Equipment 

owner/ 

operator 

Equipment 

owner/ 

operator 

Minimize the 

noise impact 

from nighttime 

construction 

Noi-6 

Residences located adjacent to the work area will be 

notified prior to any planned nighttime project construction. 

Prior to 

nighttime 

construction 

Prior to 

nighttime 

construction 

SMUD 

Transportation/Traffic 

Minimize the 

impacts to 

traffic and 

emergency 

response 

services 

Trans-1 

Prepare a Traffic Control Plan. Prior to the start of 

construction, the Equipment owner/ operator shall submit 

a Traffic Control Plan (TCP) to Caltrans, the City of 

Sacramento, and Regional Transit (RT). The TCP shall 

define the locations of any lanes that will need to be 

temporarily closed due to construction activities, including 

hauling of oversized loads by trucks, and trenching 

activities. The TCP shall define the use of flag persons, 

warning signs, lights, barricades, and cones according to 

standard guidelines outlined in the Caltrans Construction 

Manual (2007), the Standard Specifications for Public 

Works Construction (Public Works Standards, 2006), and 

the Work Area Traffic Control Handbook (WATCH) 

(American Public Works Association, 2006). 

Requirements 



included as 

conditions of 

the awarded 

contract(s). The 

TCP will be 

reviewed and 

approved by 

the responsible 

agencies. 


construction 

Prior to 

construction 

equipment 

owner/ 

operator will 

provide TCP 

to SMUD and 

Caltrans 


construction 

Equipment 

owner/ 

operator, 

SMUD, RT, 

City of 

Sacramento, 

and Caltrans 

Equipment 

owner/ 

operator, 

SMUD, RT, 

City of 

Sacramento, 

and Caltrans 



APPENDIX G 

Residential Glint and Glare Study

Highway 50 Photovoltaic Study 

Phase 2 

Residential Glint and Glare Study 

Prepared for 

6201 S Street 

Sacramento, CA 95817 

May 25, 2011 

Prepared by 

Sacramento, CA

TABLE OF CONTENTS 

LIST OF TABLES .................................................................................................................................................. 2 

LIST OF FIGURES ................................................................................................................................................ 2 

EXECUTIVE SUMMARY ........................................................................................................................................ 3 

1. INTRODUCTION & BACKGROUND ...................................................................................................................... 4 

2. DEFINITIONS & DESCRIPTIONS ......................................................................................................................... 5 

3. METHODOLOGY ........................................................................................................................................... 10 

4. RESULTS ..................................................................................................................................................... 11 

5. CONCLUSIONS ............................................................................................................................................. 22 

6. SOURCES .................................................................................................................................................... 23 

APPENDIX A – GLINT / GLARE RESULTS FOR KVP 1 

APPENDIX B – GLINT / GLARE RESULTS FOR KVP 2 

APPENDIX C – HAZARD ANALYSIS OF GLINT AND GLARE 

LIST OF TABLES 

Table 1: ALBEDO CHART ‐ MATERIAL REFLECTIVITY OF COMMON REFLECTIVE SURFACES ........................................... 19 

LIST OF FIGURES 

Figure 1: PHOTOVOLTAIC SOLAR PANELS GLINT & GLARE ....................................................................................... 6 

Figure 2: KVP 1 AT 49 TH STREET NEAR DISCOVERY WAY ........................................................................................ 7 

Figure 3: KVP 2 AT ASHGROVE PLACE APARTMENTS NEAR LAURELHURST DRIVE ........................................................ 8 

Figure 4: SF‐1100S CPV POWER UNIT .............................................................................................................. 9 

Figure 5: KVP 1 VIEW TO LOOK ALONG THE PV PANELS LOCATED ON THE NORTH EMBANKMENT OF US‐50 ................. 12 

Figure 6: KVP 1 VIEW TO LOOK AT THE PV PANELS LOCATED ON THE NORTH EMBANKMENT OF US‐50 ....................... 12 

Figure 7: REFLECTED IMAGES OF THE SUN SEEN IN PRIMARY MIRRORS OF SOLFOCUS CPV POWER UNITS ...................... 14 

Figure 8: EXAMPLE OF GLARE FROM A SOLFOCUS CPV SYSTEM IN STOW POSITION ................................................... 14 

Figure 9: KVP 2 VIEW OF SOLFOCUS CPV SYSTEMS FROM ASHGROVE PLACE APARTMENTS AT 9:48AM ..................... 15 

Figure 10: KVP 2 VIEW OF PROPOSED CPV INSTALLATIONS SITE FROM ASHGROVE PLACE APARTMENTS ...................... 16 

Figure 11: KVP 2 VIEW LOOKING TOWARD CPV INSTALLATIONS SITE FROM ASHGROVE PLACE APARTMENTS ............... 16 

Figure 12: KVP 2 DISTANCE BETWEEN ASHGROVE PLACE APARTMENTS AND CPV INSTALLATIONS SITE ........................ 20 

Figure 13: GLARE FROM SOLFOCUS CPV INSTALLATIONS SITE NEAR DUMBARTON BRIDGE ........................................ 20 

Figure 14: VICTOR VALLEY COLLEGE SOLFOCUS CPV INSTALLATIONS ..................................................................... 21 

Page | 2

EXECUTIVE SUMMARY 

IEC Corporation conducted a Residential Glint and Glare Study for the Proposed SMUD Solar Highways 

Project, to be located at two project sites within the transportation right‐of‐way along Highway 50 in 

Sacramento County. This report provides conclusions for residential‐specific glint and glare analyses 

conducted as part of the Phase 2 Feasibility Study. 

Our approach for this analysis was to study and identify potential glint and glare issues for two (2) key 

vantage points (KVPs)—KVP 1 located in the residential neighborhood on the south side of Highway 50 

and KVP 2 near the proposed CPV installations at the Mather Field Interchange: 

• KVP 1 – 49 th Street near Discovery Way 

• KVP 2 – Ashgrove Place Apartments near Abington Way & Laurelhurst Drive 

In order to complete the analysis, IEC developed analytical models to determine when glint and glare 

would occur at KVP 1 and KVP 2. 

Based on the results for this residential glint and glare study and reference to a number of scientific 

industry papers 1, 2, it was concluded that the there will be no glint and minimal glare at KVP 1. Glare will 

be visible at KVP 1 if the panels are viewed at acute viewing angles, or angles in which the line of sight 

and the glare source are less than 90º, in an eastward direction between 7:30 to 8:15AM from March to 

September. Glare will also be visible at KVP 1 if the panels are viewed at acute angles in a westward 

direction between 7:30 to 8:00PM from May to June. The glare at KVP 1 is not expected to be significant 

for residents living in the area near the East Sacramento section of the Solar Highways project and, as a 

result, no mitigation measures are necessary at this time. The CPV units near KVP 2 will track the sun for 

optimal sun exposure throughout daylight hours. Due to the mobile nature of the CPV arrays, it is 

anticipated that residents with a direct line of sight of the CPV systems will see glare during morning and 

mid‐afternoon hours at various intensities with a maximum intensity that is expected to be less than 6% 

of the sun’s intensity 3 . Glare will be visible at KVP 2 from as early as 5:45AM to 2:30PM during the spring 

and summer months and from 6:45AM to 1:00PM during the fall and winter months. Based on a lack of 

complaints about glare from current CPV installations, this glare is not expected to be disruptive and, as 

a result, no mitigation measures are considered necessary. The following sections describe the project, 

related equipment, and methodology undertaken for the glint and glare analyses, and present the 

findings and conclusions of the study. 

1 SolFocus. 2009. SF‐1100S CPV System Glare and Glint Study. September 26. 

2 Ho, C., Ghanbari, C.M., and R. Diver. Hazard Analyses of Glint and Glare from Concentrating Solar Power Plants. Solar PACES. 

Berlin, Germany. 2009. 

3 Provided by SolFocus 

Page | 3

1. INTRODUCTION & BACKGROUND 

1.1 Introduction 

SMUD is in the process of planning California’s first “Solar Highways” project to be located at two 

project sites within the transportation right‐of‐way along Highway 50 in Sacramento County. IEC 

Corporation conducted the Phase 1 and 2 Feasibility Studies for the project as well as a Glint and Glare 

Analysis for highway motorists. A resident of the Elmhurst neighborhood (located south of the East 

Sacramento portion of the proposed Solar Highways project) has expressed concern about the potential 

effects of glint and glare from the Solar Highway photovoltaic (PV) panels on residents and motorists in 

the neighborhood area south of Highway 50. In response, SMUD has tasked IEC with performing a 

residential‐specific glint and glare study to evaluate the potential impacts to neighborhoods located 

near the East Sacramento PV installations as well as the Mather Field Interchange concentrated 

photovoltaic (CPV) section of the Solar Highways project. The results of the study can also be used to 

expand the Aesthetics analysis included in the Draft Initial Study/Mitigated Negative Declaration 

(IS/MND) for SMUD’s Solar Highways Project. 

1.2 Objectives 

The objective of the Residential Glint and Glare Study is the following: 

1. Provide detailed explanation of conclusions from glint and glare analyses. Provide documentation 

of the estimated angles and paths of the potential glare for the project site including any glare 

intersections (locations, time (of day, month, duration), intensity, fields of view) that impact the 

homes located south of the East Sacramento PV installations and the residential apartments 

located southeast of the CPV units at the Mather Field Interchange. 

1.3 Background 

IEC Corporation (“IEC”) was contracted by SMUD to evaluate the cost, performance, and risks to install 

PV systems along Highway 50 in Sacramento County. IEC divided the feasibility study into two phases. 

Phase 1, completed in September of 2009, was a preliminary project evaluation that included a survey of 

the sites, preliminary PV system designs based on three (3) different types of off‐the‐shelf flat‐plate PV 

modules, an economic assessment of these designs, and a preliminary identification of potential project 

barriers and challenges unique to deploying PV systems along the highway corridor. Phase 1 study 

results found that the design utilizing poly‐crystalline PV modules was the most cost effective PV system 

for installation along the highway. SMUD determined it to be attractive enough to initiate the Phase 2 

analysis. IEC was contracted for Phase 2 to further evaluate the project cost and performance, fully 

examine the design parameters, barriers, mitigations, and project economics, and collect the findings 

required to gain approval from stakeholders and proceed to the environmental study and project bid 

phase. 

Page | 4

2. DEFINITIONS & DESCRIPTIONS 

2.1 Definitions 

The following definitions are key to understanding the methodology and results of this study. 

Glint – Glint, also known as specular reflection, is defined as a momentary flash of light that is produced 

from direct reflection of the sun (Figure 1). Glint is a significant source of visual issues and can cause 

viewer distraction. 

Glare – Glare is defined as a continuous source of excessive brightness caused by diffused or scattered 

reflections. It is not the result of direct reflection of the sun but rather a reflection of the bright sky 

around the sun. Glare is significantly less intense than glint (Figure 1). 

Key View Point (KVP) – KVPs are viewpoints used in the glint and glare analysis that serve as the 

reference locations for determination of the visibility of glint and glare effects. The two (2) KVPs used for 

this analysis are: 



See Figures 2 and 3 for map locations of each KVP. 

Acute viewing angle – An acute viewing angle describes the condition in which the angle between the 

line of sight and the glare source is less than 90º. 

Page | 5

Figure 1 – Photovoltaic Solar Panels Glint & Glare (courtesy of Power Engineers) 

Page | 6

Page | 7 

Figure 2 – KVP 1 at 49 th Street near Discovery Way (courtesy of Google)

Figure 3 – KVP 2 at Ashgrove Place Apartments near Laurelhurst Drive (courtesy of Google) 

Page | 8

2.2 Descriptions 

The following are descriptions of the PV Panels and Layout: 

KVP 1 

PV Array Layout: The East Sacramento portion of the Solar Highways project will consist of framemounted 

flat‐plate PV installations with an estimated total installed power of 1,100 kW. The total flatplate 

PV array is divided into multiple sections to account for the different azimuths (degrees from due 

south) that result from the varying directions of the Highway 50 corridor. The layout will contain 

approximately 3,400 linear feet of panels with earth screw foundations. 

PV Solar Panels: The Kyocera poly‐crystalline KD210GX‐LP module (or equivalent from another supplier) 

has a nominal power output of 210 W and a module efficiency of 14%. PV modules use solar glass that, 

by design, has high transmittance and low reflectance. This type of glass enables PV modules to absorb 

as much light as possible which results in less glare effects than occur for standard window glass 4 . 

KVP 2 

CPV Systems Layout: The Solar Highways section near the Mather Field Interchange will consist of 

approximately 32 concentrated photovoltaic (CPV) units with dual‐axis tracking. The total installed 

power of these systems is estimated to be 282 kW. Each 26 ft by 18 ft CPV array will be pole‐mounted at 

the Mather Field site. At night, the CPV systems will be in stow mode (array in a horizontal position) and 

will be fixed at 12 ft off the ground. 

CPV Units: The SolFocus SF‐1100S CPV units are equipped to do dual‐axis tracking for optimal sun 

exposure. SolFocus has reported that the CPV systems are capable of 25% panel efficiencies 5 . An SF‐ 

1100S system is made up of 28 modules that contain 20 power units per module. A power unit contains 

optical elements (primary and secondary mirrors) for concentrating sunlight into a high efficiency solar 

cell (Figure 4). The primary mirror is of most concern when considering glint and glare effects. 

Figure 4 –SF‐1100S CPV Power Unit (courtesy of SolFocus) 

4 Power Engineers. 2010. SolarGen Energy Panoche Valley Solar Farm Project Glint and Glare Study. Power Engineers, Inc. 2010. 

5 SolFocus Announces Leading 25% Efficient Concentrator PV (CPV) Systems. November 2008. www.solfocus.com 

Page | 9

3. METHODOLOGY 

3.1 Analysis 

Our approach for this analysis was to study and identify potential glint and glare issues for the two (2) 

key vantage points (KVPs): 



To accomplish the glint and glare assessment, IEC used analytical models to document the potential glint 

and glare between four (4) to eight (8) feet off of the ground for KVP 1 and between zero (0) and fiftyfive 

(55) feet off of the ground for KVP 2. Glare intersections (locations, time of day, month, and 

duration), and intensity were considered in the analysis. At KVP 1, a 131 degrees field of view was 

assumed—55 degrees east of the perpendicular corresponding to the westerly end of the array between 

48 th and 57 th Streets and 76 degrees west of the perpendicular corresponding to the most westerly point 

on the north bank visible from KVP 1 (Figure 5). For KVP 2, the angle that encompasses the range of 

views from within the apartment complex to the CPV installations was estimated to be 63 degrees. Sun 

calculations and results were based on hours of operational daylight. The results of the models were 

used to evaluate and document when glint and glare would be visible to each KVP (see Section 4). 

3.2 Assumptions 

The following assumptions were used as part of the analysis: 

• Viewpoint was assumed to be between 4 and 8 feet off the ground for KVP 1. 

• Viewpoint was assumed to be between 0 and 55 feet off the ground for KVP 2. 

• Field of view was assumed to be 131 degrees for KVP 1. 

• Angle between CPV installations site and range of views from within the apartment complex was 

estimated to be 63 degrees for KVP 2. 

• KVP was assumed to be static. 

• Glint/glare calculations assumed KVP was out in the open. As a result, the protective effects of 

residential window glass were not considered. 

• Sun calculations and results were based on hours of operational daylight. 

• Analysis considered the anti‐reflective coatings and properties of PV modules. 

• Tree plantings associated with the Bio‐2 Mitigation Measure were not incorporated in analyses 

for the East PV installations. 

• The site characteristics of KVP 1 are similar to the characteristics of the rest of the neighborhood 

which faces the length of the East Sacramento project, and the installation will be reasonably 

consistent throughout its entire length, making the use of KVP 1 a reasonable proxy for multiple 

views of the project. 

Page | 10

4. RESULTS 

4.1 Summary 

This study focused on determining time periods of the year when there was a potential for glint and/or 

glare in the neighborhoods near the East Sacramento and Mather Field Interchange sections of the Solar 

Highways project. Analytical models were developed that examined the sun angles that could cause glint 

and glare for residences near the proposed PV installations in East Sacramento and residences near the 

CPV installations at the Mather Field Interchange. In addition to the analytical calculations, visual review 

of the KVPs was conducted to further evaluate the potential for glare impacts in the neighborhoods 

specified. The following are descriptions of each type of situation studied and the associated results. 

• KVP 1 – The residential area around 49 th Street near Discovery Way will not experience glint at any 

time of the year. The results of the analytical model indicate that, in order to observe glint, a viewer 

would need to be hundreds of feet above KVP 1. The multi‐story homes in the residential area are only a 

fraction of the height necessary to receive glint so it was concluded that glint will not be an issue for the 

residences located south of Highway 50. In the previous glint and glare study for motorists on highway 

50 6 , it was determined that acute (as opposed to direct) viewing angles would result in glare for 

motorists traveling westbound in the early evening and for motorists traveling eastbound in the early 

morning during the spring and summer months. A visual inspection of the residential area indicates that 

the acute viewing angles necessary to receive glare from the PV installations are difficult to achieve due 

to a limited field of view in the neighborhood; a result of the fence, foliage and embankment that 

separates the neighborhood from the highway. A resident that looks along the panels (sample view 

shown in Figure 5), as opposed to at them (sample view shown in Figure 6), may experience glare at the 

directions and times (of day, month) found to have glare effects for motorists on Highway 50. The time 

periods for potential glare at KVP 1 are 7:30 to 8:15AM from March to September when the panels are 

viewed at acute angles in an eastward direction and 7:30 to 8:00PM from May to June when the panels 

are viewed at acute angles in a westward direction (Appendix A). Even at acute viewing angles, the glare 

is not anticipated to be significant (see Section 4.2). 

6 IEC. 2010. Highway 50 Photovoltaic Study Phase 2 Glint and Glare Study Expansion. IEC Corporation, February 1, 2010. 

Page | 11

Figure 5 – KVP 1 View to look along the PV panels located on the north embankment of US‐50 

(courtesy of IEC Corporation) 

Figure 6 – KVP 1 View to look at the PV panels located on the north embankment of US‐50 

(courtesy of IEC Corporation) 

Page | 12

• KVP 2 – The primary mirror component of each CPV power unit (total of 560 per CPV system) is the 

greatest contributor of glare from the CPV systems (Figure 4). An observer may experience glare across 

a wide range of viewing angles from distorted images of the sun reflected from the curved shape of the 

primary mirrors (Figures 7) 7 . These reflected images of the sun are a result of light that has leaked out of 

the primary mirror and not been focused to the secondary mirror. By geometry, these reflected images 

are visible at acute viewing angles of the primary mirrors on the CPV arrays. For example, the worst case 

scenario for glare will be when the CPV arrays are close to the horizontal position, also known as the 

stow position, and residents have an acute viewing angle of the primary mirror components (Figure 8). 

The CPV arrays will be close to stow position at around noon when the sun is overhead. In the early 

morning, the CPV arrays will be in a position that is nearly perpendicular to the Ashgrove Place 

apartments and glare will be at a minimum because light leakage from the primary mirror components 

will not be visible to residents. The tilted position of the CPV systems at around 9:30AM (shown in 

Figure 9) is anticipated to result in some glare for residents. During daylight hours, residents will 

experience intermittent glare from the CPV systems until mid‐afternoon when the CPV arrays face west 

out of the view of the residents. 

A small portion of residents at Ashgrove Place apartments, located southeast of the Mather Field 

Interchange, have a view from their second‐ and third‐story balconies of the proposed CPV installations 

site (Figures 10 and 11). A second‐story view from the Ashgrove Place apartments shows the landscape 

around the Mather Field Interchange which currently contains bright, reflective objects such as a large 

mainly white warehouse, highway pavement, concrete traffic barriers as well as transient semi‐trucks 

with large trailers and passenger vehicles with highly reflective windshields driving down Highway 50 

(Figure 11). Based on the results of the analytical model for the CPV systems, residents with a direct line 

of sight of the CPV installations are expected to experience glare at various intensities during the 

morning and mid‐afternoon hours with a maximum glare occurring when the CPV arrays are in a near 

horizontal position. Glare is expected to be visible at KVP 2 from as early as 5:45AM to 2:30PM during 

the spring and summer months and from 6:45AM to 1:00PM during the fall and winter months 

(Appendix B). Based on a lack of complaints about glare from current CPV installations, this glare is not 

anticipated to be disruptive for residents (see Section 4.3 for a discussion of SolFocus CPV systems field 

experience). 


Page | 13

Figure 7 –Reflected images of the sun seen in primary mirrors of SolFocus CPV power units 

(courtesy of SolFocus) 

Figure 8 –Example of glare from a SolFocus CPV system in stow position (courtesy of SolFocus) 

Page | 14

Figure 9 –KVP 2 View of SolFocus CPV systems from Ashgrove Place apartments at 9:48AM (courtesy of SolFocus)

Figure 10 – KVP 2 View of proposed CPV installations site from Ashgrove Place apartments 

(courtesy of SMUD) 

Figure 11 – KVP 2 View looking toward CPV installations site from Ashgrove Place apartments 

(courtesy of SMUD)

4.2 Glint and Glare Intensity 

Glint is the brief flash of light that occurs when an observer moves through the specular reflection of the 

sun’s direct reflection 8 . Glare, on the other hand, describes a continuous source of brightness caused by 

diffuse or scattered (as opposed to direct) reflection of light. For example, glare can result from diffuse 

reflection of sunlight off the top layer of fog. Brightness relates to the visual perception of a source of 

light that could be radiating or reflecting light. To quantify the perceived brightness, it can be useful to 

study the albedo, or diffuse reflectivity of the material. Table 1 presents the albedos of common 

reflective surfaces at different angles. The following are descriptions of the glare and reflectance levels 

(in terms of albedos) for KVP 1 and KPV 2. 

• KVP 1 – A PV panel is designed to absorb solar energy and convert it directly to electricity. 

Comparisons of albedo values in Table 1 indicate solar glass and solar glass with anti‐reflective 

coating have some of the lowest incidents of reflectivity compared with other standard roadside 

surfaces such as standard glass and worn asphalt 9 . All materials and equipment planned for use 

in the project will have less reflectivity than other materials and surfaces already present in the 

project vicinity. 

• KVP 2 – According to a glint and glare study conducted by SolFocus 10 , an operating SF‐1100 can 

project multiple images of the sun to an off‐axis observer. These images are a result of the 

geometry of the primary mirror which can map the image of most of a hemisphere (centered 

around the optical axis) and project it to an observer. The close‐up intensity of this image in the 

primary mirror is governed by the reflectivity of the mirror and the transmissivity of the front 

glass and is approximately 90% of the sun’s brightness. While this is a large intensity, it is 

important to note that the sun’s image will occupy less than 1% of the area of the primary 

mirror 11 . The brightness of these images can be compared to the brightness of reflections seen 

on a lake. 

For observers at 0.20 miles (the residents of Ashgrove Place apartments fall within this range), 

the perceived intensity from the primary mirror components will be a lot less than 90% of the 

sun’s brightness due to a number of factors including scatter and beam spreading (Figure 12). At 

this distance, the eye’s minimum resolution of approximately 1 arc‐second will resolve to 95 

mm, which translates to 15% of the area of the primary mirror. Based on this resolution, the 

eye will integrate the sun’s image and the background to a single value of much less than 90% x 

1/15 = 6% of the sun’s intensity 12 . An observer at 0.20 miles away will still see graduations in 

intensity but the distinct points of light from the CPV arrays will be out of focus. Calculating the 


9 SunPower. 2009. SunPower Solar Module Glare and Reflectance, Technical Report ‐ *T09014. SunPower Corporation, 

September 29, 2009. 




Page | 17

etinal intensity resulting from this effect yields a result that is significantly below any flashblindness 

limit discussed by Ho, et al 13 (Appendix C). In stow position (array is close to a 

horizontal position), the CPV system can cause a reflection that approximates the brightness of a 

common white aluminum roof (Figure 8) 14 . This case represents the worst case scenario for 

brightness from the CPV system. From the viewing angle shown in Figure 13, the metal surface 

of the CPV array (approximate with steel albedo values) appears more reflective than the 

primary mirror components. Note that the new SF‐1100S CPV systems no longer have this 

exposed metal surface (Figure 14). 

13 Ho, C., Ghanbari, C.M., and R. Diver. Hazard Analyses of Glint and Glare from Concentrating Solar Power Plants. Solar PACES. 

Berlin, Germany. 2009. 


Page | 18

Material Reflectivity (% of sun’s brightness) 

Table 1. Albedo Chart ‐ Material Reflectivity of Common Reflective Surfaces 15 , 16 , 17 , 18 , 19 

Common Reflective Surfaces 

Incident Angle in Degrees 

0 15 30 45 60 75 90 

Steel 37% 39% 46% 57% 70% 83% 94% 

Fresh Snow 35% 37% 44% 54% 67% 79% 90% 

Ocean Ice 27% 29% 34% 42% 52% 62% 70% 

New concrete 21% 23% 27% 33% 41% 48% 55% 

Desert Sand 16% 17% 20% 24% 30% 35% 40% 

Green Grass 10% 10% 12% 15% 19% 22% 25% 

Standard glass 8% 9% 11% 13% 16% 19% 22% 

Plexiglass 8% 9% 10% 12% 15% 18% 21% 

Plastic 7% 7% 9% 11% 13% 16% 18% 

Deciduous Trees 7% 7% 9% 11% 13% 16% 18% 

Bare Soil 7% 7% 8% 10% 13% 15% 17% 

Conifer Forest 6% 6% 7% 9% 11% 13% 15% 

Worn Asphalt 5% 5% 6% 7% 9% 11% 12% 

Solar Glass 4% 4% 5% 6% 8% 9% 10% 

Solar Glass w/ AR* coating 2% 3% 3% 4% 5% 6% 6% 

Fresh Asphalt 2% 2% 2% 2% 3% 4% 4% 

*AR‐anti‐reflective 

15 Pon, Brian (1999‐06‐30). "Pavement Albedo". Heat Island Group. http://eetd.lbl.gov/HeatIsland/Pavements/Albedo/. 

Retrieved 2007‐08‐27. 

16 Alan K. Betts, John H. Ball (1997). "Albedo over the boreal forest". Journal of Geophysical 102 (D24): 28,901– 

28,910.doi:10.1029/96JD03876. http://www.agu.org/pubs/crossref/1997/96JD03876.shtml. Retrieved 2007‐08‐27. 

17 "The Climate System". Manchester Metropolitan University. http://www.ace.mmu.ac.uk/Resources/gcc/1‐3‐3.html. 

Retrieved 2007‐11‐11. 

18 Tom Markvart, Luis CastaŁżer (2003). Practical Handbook of Photovoltaics: Fundamentals and Applications. 

Elsevier. ISBN 1856173909. 

19 SunPower. 2009. SunPower Solar Module Glare and Reflectance, Technical Report ‐ *T09014. SunPower Corporation, 

September 29, 2009. 

Page | 19

Figure 12 – KVP 2 Distance between Ashgrove Place apartments and CPV installations site 

(courtesy of Google) 

Page | 20 

Figure 13 – Glare from SolFocus CPV installations near Dumbarton Bridge 

(courtesy of SMUD)

4.3 SolFocus CPV Systems Field Experience 

The glint and glare impacts from SolFocus CPV systems have been evaluated for airports and highways 

and have not been found to be a problem for pilots and drivers. An aeronautical study conducted by the 

Federal Aviation Administration (FAA) for Kona International Airport in Hawaii concluded that the 

SolFocus CPV systems installed near the airport posed no hazard to air navigation 20 . The SolFocus CPV 

systems installed near the Dumbarton Bridge in Fremont, California have had no reports of glint or glare 

problems from Caltrans or the 80,000 commuters that drive by them each day 21 . The lack of glint and 

glare problems at current CPV installations indicates that the CPV systems near the Mather Field 

Interchange are unlikely to create a significant hazard for Highway 50 drivers or local residents. 

A 1 MW solar power facility consisting of 122 SolFocus CPV systems was completed at Victor Valley 

College in Victorville, California in May 2010 (Figure 14). This facility has more than 3 times the number 

of CPV systems than the proposed Mather Field Interchange site will have. The north and east 

boundaries of the facility site are directly adjacent to a residential area consisting of single family homes. 

To date, there have been no complaints about glare from the residents living near the CPV installations. 

The lack of complaints about glare from the Victor Valley College installations indicates that glare from 

the CPV systems is not disruptive to nearby residents. This field experience suggests that glare impacts 

from the Mather Field Interchange CPV installations site, with significantly fewer systems than the Victor 

Valley College site, will be minimal and nondisruptive for residents at the Ashgrove Place Apartments 

located a distance away from the installations. 

Figure 14 – Victor Valley College SolFocus CPV installations (courtesy of SolFocus) 



Page | 21

5. CONCLUSIONS 

As demand for solar energy increases, so has the concern for glint and glare issues surrounding 

reflectivity of PV panels and other solar energy devices. In particular, concern has been expressed about 

the possibility of solar energy systems creating visual distractions for motorists and aircraft. The focus of 

this study was evaluation of the glint and glare impacts on residents living in areas near the East 

Sacramento and Mather Field Interchange sections of SMUD’s Solar Highways project. 

5.1 Summary 

The following summarizes the conclusions found for glint and glare effects at KVP 1 and KVP 2: 

• KVP 1 – No glint will be visible to residents in the area south of Highway 50. Glare will be visible 

if the panels are viewed at acute angles in an eastward direction in the early morning (7:30‐ 

8:15AM) from March to September. Glare will also be visible if the panels are viewed at acute 

angles in a westward direction in the early evening (7:30‐8:00PM) from May to June. The 

viewing angles necessary to see the glare are difficult to achieve due to the fence, foliage and 

embankment that separates the neighborhood from the highway. The glare from the PV 

modules was found to be lower in intensity than the glare from car windows and office buildings 

along the highway. 

• KVP 2 – For residents with a direct line of sight of the Mather Field Interchange CPV installations 

site, glare is anticipated to be visible during morning and mid‐afternoon hours as the CPV arrays 

reposition to track the sun with a maximum glare occurring when the CPV arrays are close to the 

horizontal position. The time periods for visible glare at KVP 2 are expected to be in the ranges 

6:45AM to 1:00PM during the fall and winter months and 5:45AM to 2:30PM during the spring 

and summer months. Residents of Ashgrove Place apartments are close enough to the CPV 

installations site (within 0.4 miles) to experience glare that is expected to be less than 6% of the 

sun’s brightness which can be compared to the brightness visible from multiple reflections on a 

lake. The glare from the CPV systems is anticipated to be similar to that from objects in the 

existing environment around the Mather Field Interchange such as concrete traffic barriers and 

passenger vehicles with highly reflective windshields. Additionally, there have not been 

complaints about glare from residents living near current CPV installations. 

Based on analytical model results, field experience, and industry reports, it is IEC’s assessment that the 

glare resulting from the East Sacramento PV site and the Mather Field Interchange CPV installations site 

will not create a significant negative impact to residents living in areas near the proposed sites and that 

no mitigation measures are necessary. Overall, the glare impacts are expected to be minimal and 

nondisruptive for the limited number of residents that have views of SMUD’s Solar Highways projects. 

Page | 22

6. SOURCES 

Betts, Allan K. and Ball, John H. (1997). Journal of Geophysical .102 (D24): 28,901–28,910. 

http://www.agu.org/pubs/crossref/1997/96JD03876.shtml. Retrieved 2007‐08‐27. 

Ho, Clifford K., Cheryl M. Ghanbari, and Richard B. Diver. 2009. Hazard Analysis of Glint and Glare from 

Concentrating Solar Power Plants, SolarPaces 2009, Berlin Germany. Ph.D., Sandia National 

Laboratories, Solar Technologies Department, P.O. Box 5800, Albuquerque, NM 87185‐1127, 

USA Phone: 1‐505‐844‐2384, E‐mail: ckho@sandia.gov Test Engineer, Sandia National 

Laboratories, Solar Technologies Department Ph.D., Sandia National Laboratories, Solar 

Technologies Department. September 15‐18, 2009. 

IEC. 2010. Highway 50 Photovoltaic Study Phase 2 Glint and Glare Study Expansion. IEC Corporation, 

February 1, 2010. 

Markvart, Tom and CastaŁżer, Luis (2003). Practical Handbook of Photovoltaics: Fundamentals and 

Applications. Elsevier. ISBN 1856173909. 

Pon, Brian (1999‐06‐30). "Pavement Albedo". Heat Island Group. 

http://eetd.lbl.gov/HeatIsland/Pavements/Albedo/. Retrieved 2007‐08‐27. 

Power Engineers. 2010. SolarGen Energy Panoche Valley Solar Farm Project Glint and Glare Study. Power 

Engineers, Inc., May 21, 2010. 

SunPower. 2009. SunPower Solar Module Glare and Reflectance, Technical Report ‐ *T09014. SunPower 

Corporation, September 29, 2009. 

SolFocus. 2009. SF‐1100S CPV System Glare and Glint Study. September 26. 

SolFocus Announces Leading 25% Efficient Concentrator PV (CPV) Systems. November 2008. 

www.solfocus.com. 

"The Climate System". Manchester Metropolitan 

University. http://www.ace.mmu.ac.uk/Resources/gcc/1‐3‐3.html. Retrieved 2007‐11‐11. 

Page | 23

APPENDIX A 

GLINT / GLARE RESULTS FOR KVP 1

APPENDIX A 

GLINT / GLARE RESULTS FOR KVP 1 

7:00PM 

(TIME OF DAY) 

5:15AM 

5:30AM 

5:45AM 

6:00AM 

6:15AM 

6:30AM 

6:45AM 

7:00AM 

7:15AM 

7:30AM 

7:45AM 

8:00AM 

8:15AM 

8:30AM 

8:45AM 

9:00AM 

9:15AM 

9:30AM 

9:45AM 

10:00AM 

10:15AM 

10:30AM 

10:45AM 

11:00AM 

11:15AM 

11:30AM 

11:45AM 

12:00PM 

12:15PM 

12:30PM 

12:45PM 

1:00PM 

1:15PM 

1:30PM 

1:45PM 

2:00PM 

2:15PM 

2:30PM 

2:45PM 

3:00PM 

3:15PM 

3:30PM 

3:45PM 

4:00PM 

4:15PM 

4:30PM 

4:45PM 

5:00PM 

5:15PM 

5:30PM 

5:45PM 

6:00PM 

6:15PM 

6:30PM 

6:45PM 

7:15PM 

7:30PM 

7:45PM 

8:00PM 

8:15PM 

8:30PM 

8:45PM 

(TIME OF YEAR) 

JANUARY 1‐7 

JANUARY 8‐14 



JAN 29‐ FEB 4 

FEBRUARY 5‐11 



FEB 26‐MAR 4 

MARCH 5‐11 

MARCH 12‐18 DAYLIGHT SAVINGS DAYLIGHT SAVINGS 

MARCH 19‐25 

MAR 26 ‐ APR 1 

APRIL 2‐8 

APRIL 9‐15 

APRIL 16‐22 

APRIL 23‐29 

APR 30‐MAY 6 

MAY 7‐13 

MAY 14‐20 

MAY 21‐27 

MAY 28 ‐ JUNE 3 

JUNE 4‐10 

JUNE 11‐17 

JUNE 18‐24 

JUNE 25‐JULY 1 

JULY 2‐8 

JULY 9‐15 

JULY 16‐22 

JULY 23‐29 

JULY 30‐ AUG 5 

AUGUST 6‐12 

AUGUST 13‐19 


AUG 27‐ SEP 2 

SEPTEMBER 3‐9 




OCTOBER 1‐7 

NO GLINT/GLARE OBSERVED 

OCTOBER 8‐14 



OCT 29 ‐ NOV 4 

NOVEMBER 5‐11 DAYLIGHT SAVINGS DAYLIGHT SAVINGS 

NOVEMBER 12‐18 


NOV 26‐DEC 2 

DECEMBER 3‐9 




POSSIBLE GLARE LOOKING EAST FOR ALL OR PART OF TIME PERIOD NO SUNLIGHT 

POSSIBLE GLARE LOOKING WEST FOR ALL OR PART OF TIME PERIOD NO GLINT OR GLARE OBSERVED 

DAWN OR DUSK

APPENDIX B 

GLINT / GLARE RESULTS FOR KVP 2

APPENDIX B 

GLINT / GLARE RESULTS FOR KVP 2 

(TIME OF DAY) 

5:15AM 

5:30AM 

5:45AM 

6:00AM 

6:15AM 

6:30AM 

6:45AM 

7:00AM 

7:15AM 

7:30AM 

7:45AM 

8:00AM 

8:15AM 

8:30AM 

8:45AM 

9:00AM 

9:15AM 

9:30AM 

9:45AM 

10:00AM 

10:15AM 

10:30AM 

10:45AM 

11:00AM 

11:15AM 

11:30AM 

11:45AM 

12:00PM 

12:15PM 

12:30PM 

12:45PM 

1:00PM 

1:15PM 

1:30PM 

1:45PM 

2:00PM 

2:15PM 

2:30PM 

2:45PM 

3:00PM 

3:15PM 

3:30PM 

3:45PM 

4:00PM 

4:15PM 

4:30PM 

4:45PM 

5:00PM 

5:15PM 

5:30PM 

5:45PM 

6:00PM 

6:15PM 

6:30PM 

6:45PM 

7:00PM 

7:15PM 

7:30PM 

7:45PM 

8:00PM 

8:15PM 

8:30PM 

8:45PM 

(TIME OF YEAR) 

JANUARY 1‐7 




JAN 29‐ FEB 4 




FEB 26‐MAR 4 

MARCH 5‐11 

MARCH 12‐18 DAYLIGHT SAVINGS DAYLIGHT SAVINGS 

MARCH 19‐25 

MAR 26 ‐ APR 1 

APRIL 2‐8 

APRIL 9‐15 

APRIL 16‐22 

APRIL 23‐29 

APR 30‐MAY 6 

MAY 7‐13 

MAY 14‐20 

MAY 21‐27 

MAY 28 ‐ JUNE 3 

JUNE 4‐10 

JUNE 11‐17 

JUNE 18‐24 

JUNE 25‐JULY 1 

JULY 2‐8 

JULY 9‐15 

JULY 16‐22 

JULY 23‐29 

JULY 30‐ AUG 5 

AUGUST 6‐12 



AUG 27‐ SEP 2 





OCTOBER 1‐7 




OCT 29 ‐ NOV 4 

NOVEMBER 5‐11 DAYLIGHT SAVINGS DAYLIGHT SAVINGS 



NOV 26‐DEC 2 





POSSIBLE GLARE FOR ALL OR PART OF TIME PERIOD NO SUNLIGHT 

DAWN OR DUSK NO GLINT OR GLARE OBSERVED

APPENDIX C 

HAZARD ANALYSIS OF GLINT AND GLARE

HAZARD ANALYSES OF GLINT AND GLARE FROM 

CONCENTRATING SOLAR POWER PLANTS 

Clifford K. Ho 1 , Cheryl M. Ghanbari 2 , and Richard B. Diver 2 

1 

Ph.D., Sandia National Laboratories, Solar Technologies Department, P.O. Box 5800, Albuquerque, NM 87185-1127, USA 

Phone: 1-505-844-2384, E-mail: ckho@sandia.gov 

2 

Test Engineer, Sandia National Laboratories, Solar Technologies Department 

3 

Ph.D., , Sandia National Laboratories, Solar Technologies Department 

Abstract 

Because of the increased interest in deploying concentrating solar power systems, glint and glare from 

concentrating solar collectors and receivers is receiving increased attention as a potential hazard or 

distraction for motorists, pilots, and pedestrians. This paper provides a summary of previous analyses to 

evaluate glint and glare from concentrating solar power plants. In addition, a review of the physiology, 

optics, and damage mechanisms associated with ocular radiation is provided. A summary of safety metrics 

and standards is also compiled from the literature to evaluate the potential hazards of calculated irradiances 

from glint and glare. Previous safety metrics have focused on prevention of permanent eye damage (e.g., 

retinal burn). New metrics are introduced in this paper for temporary flash blindness, which can occur at 

irradiance values several orders of magnitude lower than the irradiance values required for irreversible eye 

damage. 

Keywords: glint, glare, retinal irradiation, retinal burn, flash blindness 

1. Introduction 

Assessment of the potential hazards of glint and glare from concentrating solar power plants is an important 

requirement to ensure public safety. Glint is defined as a momentary flash of light, while glare is defined as 

a more continuous source of excessive brightness relative to the ambient lighting. Hazards from glint and 

glare from concentrating solar power plants include the potential for permanent eye injury (e.g., retinal burn) 

and temporary disability or distractions (e.g., flash blindness), which may impact people working nearby, 

pilots flying overhead, or motorists driving alongside the site. 

Applications and certifications for solar thermal power plants often require an assessment of “visual 

resources” at the site, but these requirements typically focus on aesthetic qualities and standards. 

Certifications also require an evaluation of general health and safety issues associated with the site, but 

rigorous and uniform treatment of glint and glare are lacking. The purpose of this paper is to summarize 

previous analyses and provide general assessment methods that can be used to evaluate potential hazards of 

glint and glare for all of the primary concentrating solar power (CSP) technologies: (1) power tower 

systems, (2) linear concentrator systems (e.g., parabolic troughs, linear Fresnel), and (3) dish/engine systems. 

2. Review of Previous Assessments 

The following sections summarize previous assessments that were conducted to evaluate potential glint and 

glare hazards from power towers, linear receivers, and dish collector systems. Figure 1, Figure 2, and Figure 

3 show photographs of observed specular and diffuse reflections from these different types of systems. 

2.1 Power Towers 

Brumleve [1],[2] provided some of the earliest analyses of eye hazards associated with central receiver 

technologies. Analytical models were developed to assess light intensities and hazardous ranges of single 

and multiple coincident heliostat beams at ground level and in the air space above a central receiver facility 

at Sandia National Laboratories in Albuquerque, New Mexico. Distances were calculated to ensure safe

etinal irradiance levels (based on work from Sliney and Freasier [3]), and results showed that retinal 

irradiance from single heliostat beams exceeded the safe limits only within a short range (up to 40 m) within 

the focal distance of the heliostat. For heliostats with focal distances greater than 270 m, the safe retinal 

limits were never exceeded. The safe number of multiple coincident beams was also calculated as a function 

of distance, focal length, and projected area density of the multiple collectors on the retina. Based on these 

analyses, exclusion zones (restricted areas) and beam control techniques were recommended to minimize the 

potential hazards from single and multiple heliostat beams during operation. 

Brumleve [2] also used video techniques during helicopter flyovers and at ground level to determine retinal 

irradiance, image size, and receiver brightness for the 10 MW e solar thermal central receiver pilot plant in 

Barstow, California. Safe limits were not exceeded in the airspace above an altitude of ~240 m, which is the 

lowest allowable altitude for aircraft near the 91-m tall receiver tower. It was also found that the receiver 

was not bright enough to constitute an eye hazard during momentary viewing. 

The probability of multiple heliostat beams randomly crossing in the airspace above the proposed Ivanpah 

Solar Electric Generating System in California was calculated in an application submitted to the California 

Energy Commission [4]. In the application, they showed that the probability of a sufficient number of 

heliostat beams (8) crossing at the same point to exceed safety limits at an altitude of 1000 m was 

infinitesimally small. 

Figure 1. Left: Specular reflections from heliostats at Solar One (10 MW e Power Tower, Daggett, CA). 

Right: Diffuse reflections from receiver panel (National Solar Thermal Test Facility, SNL, NM). 

2.2 Linear Concentrators 

Glint and glare analyses have been performed for the proposed Carrizo Energy Solar Farm in San Luis 

Obispo County, California, which consists of nearly 200 lines of compact linear Fresnel reflector systems 

[5]. Diffuse reflection from the receiver pipes and spillage intensity from the reflectors were evaluated. 

Results showed that unsafe beam intensities could be posed to pedestrians within ~18 m of the perimeter 

fence; therefore, privacy slats in the perimeter fence were proposed. Other scenarios associated with 

reflected light were not found to be likely hazards. 

An application for certification of the Victorville 2 Hybrid Power Project [6] included a letter from the 

California Department of Transportation, Division of Aeronautics, that conducted flyovers of existing 

parabolic trough plants at Kramer Junction and Harper Lake in Southern California. The glare and flash was 

found to be similar to the reflection over a smooth water surface. In addition, a letter from the chief 

operating officer of the Kramer Junction facility stated that the observed reflections originated primarily 

from the receiver tubes and that the glare has not been a distraction to pilots in nearly 20 years of operation. 

A recent application for certification of the San Joaquin Solar 1 & 2 project submitted to the California 

Energy commission included a glint and glare analysis for their proposed parabolic trough plant [7]. The

analysis evaluated the diffuse reflection from the receiver pipes (heat collection elements), and they 

concluded that the diffusely reflected sunlight from the receiver pipes would be 150 times less than the 

intensity of the sun and therefore not a hazard. The beam intensity caused by specular reflection from the 

mirrors was also considered to evaluate potential glare when the parabolic troughs were being rotated from 

stow position to tracking position. Results showed that the beam intensity could be unsafe for pedestrians 

within 60 feet from the plant perimeter (although details of the calculations and metrics were not provided), 

so privacy slats in the perimeter fence were recommended. 

Figure 2. Specular and diffuse reflections from linear receiver tube (left) and trough field (aerial view, 

right) at Kramer Junction (150 MW e Parabolic Trough, Mojave Desert, CA). 

2.3 Dish/Engines 

A qualitative glint and glare analysis of dish/engine systems for the SES Solar Two Project was conducted as 

part of the application for certification that claimed that distracting, blinding, or hazardous glint or glare 

effects should not be a problem [8]. However, detailed analyses of the potential for hazardous reflections 

during off-axis positions (e.g., during stowing, start-up, or abnormal operations) was not performed. 

Ghanbari and Diver [9] developed a mathematical model to investigate the maximum viewing time of diffuse 

reflections from a dish receiver aperture plate (see Appendix). The maximum viewing time was based on 

exposure limits for optical radiation published by the American Conference of Governmental Industrial 

Hygienists (ACGIH) [10]. Their results showed that diffusely reflected radiation from the receiver did not 

pose hazards for retinal thermal damage, retinal photochemical injury, and infrared radiation damage. 

In 1980, Sliney evaluated hazards of the reflected sunlight from the point-focus collectors at the 

JPL/Edwards test site [11]. He first analyzed the hazards from viewing the sun directly and concluded that 

the natural blink response of 0.1 – 0.2 seconds is adequate to protect viewers from thermal retinal and 

photochemical injury. However, prolonged staring at the sun when it is high in the sky or viewing it, 

unfiltered, through a magnifier such as binoculars or telescopes will result in thermal retinal damage. He 

then analyzed viewing of reflected sunlight from a point-focus collector. Sliney concluded that if an 

observer is less than one focal length away from a single facet on a point-focus collector, even for short 

exposures, injury could occur. However, when a dish is tracking the sun, it is virtually impossible for 

anyone, worker or observer, to be less than one focal length for any one facet. The situation that is of greater 

concern is when the dish is not tracking the sun but is in an off-axis position that could still reflect sunlight 

onto a worker or observer. In these cases, however, the reflected sunlight would not emanate from the entire 

dish, but rather from an individual facet, and observers would not be exposed to reflections that are more 

dangerous than the sun itself.

Figure 3. Left: Specular reflections from stowed parabolic dish collectors. Right: Diffuse light 

emanating from dish receiver aperture. (National Solar Thermal Test Facility, SNL, NM) 

2.4 Discussion of Previous Analyses 

In the previous analyses of glint and glare for concentrating solar thermal power plants, permanent eye 

damage was used as the metric to determine safe retinal irradiance values. The safe retinal irradiance 

thresholds were based on retinal burn tests performed on rabbits [3]. In the next section, additional metrics 

are discussed, including temporary flash blindness. Data from past research on flash blindness and recovery 

times from after-image disability are reviewed to provide additional quantitative metrics that may be used for 

glint and glare evaluations of concentrating solar thermal power plants. 

3. Ocular Irradiation and Safety Metrics 

3.1 Anatomy of the Eye 

Figure 4 shows an illustration of the human eye and how an image is projected onto the retina. Light rays 

enter through the cornea and pass through the pupil, which can vary in aperture size from 2 – 3 mm for a 

sunlight-adapted eye to 7 – 8 mm for a dark-adapted eye. The rays pass through the lens and converge at a 

nodal point behind the lens. The image is then inverted and projected onto the retina, a distance 

approximately 1.7 cm behind the nodal point in healthy eyes. 

conjunctiva 

cornea 

lens 

choroid 

retina 

d s 

ω 

ω 

d r 

pupil 

s 

iris 

nodal point 

f 

Figure 4. Image projected onto the retina of a human eye.

Potential damage to the eye depends on a number of factors including the source radiance, source angle (size 

and distance to eye), duration of exposure, and wavelength. The spectral distribution of sunlight is heavily 

weighted in the visible bandwidth (400 – 700 nm), but the eye can pass wavelengths between 400 and 1400 

nm to the retina. The lens of the eye is a strong absorber of wavelengths less than 400 nm [3]. At lower 

wavelengths, UV-B and UV-C radiation are absorbed in the cornea and conjunctiva, and sufficient doses can 

cause keratoconjunctivitis (welder’s flash) and photokeratitis (snow blindness) [3],[12]. Solar retinitis and 

eclipse blindness are caused primarily by photochemical damage (rather than thermal injury) in the visible 

spectrum between 380 and 580 nm. Between 580 and 1400 nm, photothermal damage predominates over 

photochemical damage. Because the blink response of the eye is rapid (0.15 – 0.2 s) [3], exposure to 

reflected sunlight is expected to be short in duration. 

3.2 Retinal Irradiance 

The retinal irradiance (power per unit area) can be calculated from the total power entering the pupil and the 

retinal image area. The area projected onto the retina (assuming circular images) can be determined from the 

source angle (ω), which can be calculated from the source size (d s ) and distance (s), and the focal length (f), 

as follows (refer to Figure 4): 

d r = f ω 

where ω = d s / s (1) 

Eq. (1) assumes that the arc and the chord of a circle are the same for small angles. At a source angle, ω, of 

60°, the error in d r is ~5%. If the irradiance at a plane in front of the cornea, E c (W/m 2 ), is known, the power 

entering the pupil can be calculated as the product of the irradiance and the pupil area (the diameter of the 

pupil, d p , adjusted to sunlight is ~2 mm). The power is then divided by the retinal image area and multiplied 

by a transmission coefficient, τ (∼0.5 [11]), for the ocular media (to account for absorption of radiation 

within the eye before it reaches the retina) to yield the following expression for the retinal irradiance: 

2 

d 

p 

Er 

= E ⎛ 

c⎜ 

⎞ τ d 

2 

⎟ 

⎝ r ⎠ 

(2) 

If the source radiance, L (W/m 2 /sr) is known, the corneal irradiance in Eq. (2) can be determined by 

multiplying the radiance by the subtended solid angle of the source, Ω (sr): 

A ⎛ π ⎞ 

E L L L ω 

s 4 

s 

2 

c 

= Ω= ≈ 

2 ⎜⎝ ⎟ 

(3) 

⎠ 

and the retinal irradiance can be calculated directly from the radiance as follows: 

πLτ 

⎛ d 

p ⎞ 

Er 

= 

4 

⎜ ⎟ 

⎝ f ⎠ 

2 

(4) 

It should be noted that Brumleve [1] includes an additional coefficient (ν) to account for the fraction of solar 

irradiance between 400 and 1400 nm, but this has been included in the transmission coefficient, τ, above. As 

an example, the retinal irradiance caused by viewing the sun directly can be calculated using Eqs. (1) and (2) 

with E c = 0.1 W/cm 2 , d p = 0.002 m, f = 0.017 m, ω = 0.0093 rad, and τ = 0.5, which yields a retinal 

irradiance, E r , of ~8 W/cm 2 . Note that the retinal irradiance is significantly higher than the irradiance at the 

entrance of the eye. For applications involving images of the sun, the retinal irradiance can be converted to 

corneal irradiance using Eqs. (1) and (2) with d p = 0.002 m, f = 0.017 m, ω = 0.0093 rad (sun shape), and τ = 

0.5, yielding the following approximate relation: E c = 0.0125E r . 

3.3 Safety Metrics 

Safety metrics relevant to optical radiation and the prevention of permanent eye damage are reviewed and 

presented in this section. In addition, previous studies pertaining to flash blindness are also presented since

temporary flash blindness is potentially hazardous to motorists or pilots. Other consequences from glint and 

glare such as discomfort and distraction have been evaluated in the literature [13],[14], but the subjective 

impacts of discomfort and distraction glare are not considered in this paper. 

3.3.1 Safe Retinal Irradiance Values from Retinal Burn Data 

Sliney and Freasier [3] presented maximum permissible retinal irradiance levels (W/cm 2 ) based on retinal 

burn data using rabbits. Brumleve [1] used this data to develop a convenient metric for safe retinal 

irradiance, E rs (W/cm 2 ) based on retinal image size, d r (m), assuming circular images and a 0.15 second 

exposure (typical blink response): 

0.002 

E rs = for d r < 0.002 m 

dr 

E rs = 1 for d r ≥ 0.002 m (5) 

Eq. (5) has been used by several analyses of glint and glare for concentrating solar thermal power plants 

[4],[5],[7]. However, the calculated safe retinal irradiance value that was used in these analyses is based on 

specific properties of a heliostat (e.g., reflectivity, beam divergence) reported by Brumleve [2] that may not 

be generally applicable to other collector systems. The safe retinal irradiance value for viewing the sun 

directly can be calculated using Eq. (5) and the subtended angle of the sun (~9.3 mrad) to calculate the retinal 

image diameter. The safe retinal irradiance value is 12.7 W/cm 2 , which is about 1.6 times greater than the 

retinal irradiance experienced from viewing the sun directly (~8 W/cm 2 ). Note that the retinal irradiance is 

greater than the corneal irradiance (or “irradiance at the eye”) because of the smaller image area projected 

onto the retina (relative to the pupil size). The equivalent safe corneal irradiance for a subtended angle of 9.3 

mrad is 0.16 W/cm 2 or 1600 W/m 2 . 

3.3.2 ANSI 2000 Standard 

More recently, Delori et al. [15] provide a concise formulation and summary of the American National 

Standards Institute (ANSI) Z136.1-2000 Standard for the protection of the human eye from laser exposure. 

They note that the recommended exposure limits for lasers and broadband sources (such as the sun) are not 

substantially different. Delori et al. [15] present maximum permissible power levels entering the pupil as a 

function of exposure duration, wavelength, and source angle. For brief exposures (0.15 – 0.2 s), Table 3 in 

Delori et al. [15] provides the following expression for the maximum permissible power level, MP (W): 

MP = 6.93x10 -4 C T C E P -1 t -0.25 (6) 

where C T is a function of wavelength (ranges between 1 and 40 at wavelengths between 400 and 1400 nm), 

C E is a function of the source angle (6.2 for an angle of 9.3 mrad subtended by the sun), P is a pupil factor 

that is a function of exposure time and wavelength (ranges between 1.8 and ~1 for wavelengths between 400 

and 1400 nm), and t is the exposure time (s). Using solar-radiance spectrally weighted values for the 

coefficients provided by Delori et al. [15] and an assumed exposure duration of 0.15 seconds yields a 

maximum permissible power at the pupil of ~0.008 W and maximum retinal irradiance of ~40 W/cm 2 for 

direct viewing of the sun (which corresponds to a safe corneal irradiance of ~0.5 W/cm 2 or 5000 W/m 2 ). 

This value is about three times greater than the safe retinal irradiance values proposed by Brumleve [1],[2] 

for direct viewing of the sun. The difference is probably due to several factors including the use of different 

factors of safety (up to an order of magnitude or more) in the calculations. 

3.3.3 ACGIH Threshold Limit Values 

Spectrally weighted exposure limits for optical radiation have also been published by the American 

Conference of Governmental Industrial Hygienist (ACGIH) [10]. These limits are called Threshold Limit 

Values (TLVs) and are calculated from spectrally weighted radiometric values of radiance or irradiance. 

TLVs are evaluated for (1) retinal thermal damage, (2) photochemical injury from chronic blue light

exposure, (3) and infrared radiation damage. 

3.3.4 Flash Blindness 

Flash blindness results from bleaching of retinal visual pigments caused by bright (high luminance) sources 

of light. Photometric units are used to characterize the levels of brightness (or luminance) (lumens/m 2 /sr) or 

illuminance (lumens/m 2 ) that cause flash blindness. Most people have experienced flash blindness after 

viewing a flash bulb from a camera or a bright light in a darkened room. A number of tests were performed 

by the U.S. Air Force to assess the visual recovery times for individuals exposed to bright flashes of light, 

primarily to determine how long it would take for pilots to read their instrument panels after being exposed 

to illumination from nuclear blasts [16],[17]. These studies found that visual recovery times ranged from 4 – 

12 seconds for illuminance values ranging from ~650 – 1,100 lumens/m 2 . For light emitted within the solar 

spectrum, this corresponds to approximately 7 – 11 W/m 2 of solar irradiance at the eye. 

Additional tests were performed by Saur and Dobrash [18] to determine visual recovery times of individuals 

after being exposed to simulated sun reflections. They found that recovery times ranged from 0.8 – 2.7 

seconds for illuminance values ranging from 120 – 280 lumens/m 2 . Based on the solar spectrum, this is 

equivalent to approximately 1 – 3 W/m 2 of solar irradiance at the eye. 

From these data, it appears that a solar irradiance on the order of 1 – 10 W/m 2 or 1x10 -4 – 1x10 -3 W/cm 2 at 

the eye is sufficient to cause temporary flash blindness. Assuming that this solar irradiance originates from 

an image that subtends a similar angle to the sun (9.3 mrad) with d p = 0.002 m, f = 0.017 m, and τ = 0.5, the 

minimal retinal irradiance values that can cause flash blindness is ~0.01 – 0.1 W/cm 2 . Comparing these solar 

irradiance values against the metrics used for calculating irreversible eye damage (e.g., Eqs. (5) or (6)) shows 

that flash blindness can occur at irradiances that are several orders of magnitude less than the irradiance 

metrics used for irreversible eye damage. 

3.3.5 Summary of Safety Metrics 

Figure 5 summarizes the safe irradiance values and flash blindness metrics discussed above for a 0.15 s 

exposure. As the subtended source angle increases, the safe retinal irradiance threshold decreases because of 

the increased size of the retinal image area, and, hence, increased energy applied to the retina. The metrics 

proposed by Brumleve [1] for safe retinal irradiances appear to be more conservative relative to the other 

standards plotted. The potential for flash blindness shown in the plot was based on corneal irradiance values 

of 1x10 -4 – 1x10 -3 W/cm 2 from the above studies, and the retinal irradiance was then determined using Eqs. 

(1) and (2) with d p = 0.002 m, f = 0.017 m, and τ = 0.5 (the average retinal irradiance was plotted and the 

error bars represent the maximum and minimum values). The plotted retinal irradiance values for potential 

flash blindness appear reasonable when compared to retinal irradiance values of several common sources of 

light reported by Sliney and Freasier [3]: incandescent bulb (~10 -4 W/cm 2 ), pyrotechnic flare (~10 -3 W/cm 2 ), 

tungsten filament (~10 -2 W/cm 2 ). Depending on the subtended source angle, the retinal irradiance that causes 

flash blindness can be 2 – 4 orders of magnitude less than the safe retinal irradiance metrics to prevent 

irreversible //eye damage.

Retinal Irradiance (W/cm^2) 

1.E+03 

1.E+02 

1.E+01 

1.E+00 

1.E-01 

1.E-02 

1.E-03 

1.E-04 

subtended sun angle 

direct viewing of sun 

1.E-05 

1 10 100 1000 

Subtended Source Angle (mrad) 

Sliney and Freasier (1973, 

Table III) [3] 

Brumleve (1977) [1] 

Delori et al. (2007) ANSI 

2000 [15] 

Potential for Flash 

Blindness [16,17,18] 

Figure 5. Retinal irradiance metrics as a function of subtended source angle for 0.15 s exposure 

(typical blink response time). Sliney and Freasier [3], Brumleve [1], and Delori et al. [15] provide safe 

retinal irradiance values to prevent irreversible eye damage. The range of retinal irradiances that can 

induce flash blindness is from several data sources [16], [17], [18]. 

4. Summary and Conclusions 

This paper has presented methods to evaluate potential glint and glare hazards from specularly and diffusely 

reflected sunlight from concentrating solar collectors. First, a review of previous data and standards was 

performed to summarize metrics used to determine safe retinal irradiances as a function of subtended source 

angle (or retinal image size). These metrics were all based on preventing permanent eye damage, so a new 

metric that represents the potential for temporary flash blindness was introduced. The potential for 

temporary flash blindness can occur at irradiances several orders of magnitude lower than irradiances 

required for irreversible eye damage. Analytical models were then derived to calculate irradiances from both 

specular and diffuse sources. In addition, an example of irradiance calculations using a ray-tracing 

computational model was presented. 

The methods and equations presented in this paper can be used to calculate irradiances from various 

concentrating solar collector systems (e.g., heliostats, dishes, troughs, receivers). These calculated 

irradiances can then be used to calculate the retinal irradiance using equations in Section 3.2. Finally, the 

calculated retinal irradiance can be compared against the safe retinal irradiance metrics provided in Section 

3.3 to evaluate potential glint and glare hazards. Based on the configurations and operation of the various 

concentrating solar technologies, potential glint and glare hazards that should be considered include the 

following: 

• Power Towers 

o Specular reflections from heliostats when they are moving from stowed to tracking 

positions, in standby mode, or are not focused on the receiver 

o Diffuse reflections from the receiver 

• Linear Collectors 

o Specular reflections from the mirrors when they are moving from stowed to tracking and 

from specular reflections off the ends of the trough or mirrors when the sun has a low

elevation angle (e.g., reflections from the north end of a north-south field when the sun is 

low in the southern horizon). 

o Diffuse and specular reflections from receiver tubes 

• Dish/Engine Systems 

o Specular reflections from mirror facets when the dish is off-axis (e.g., moving from stow to 

tracking) 

o Diffuse reflections from the receiver aperture 

The impact of multiple coincident beams (i.e., from adjacent collectors or receivers) was not considered in 

this study. Brumleve (pp. 27-32) [1] provides a discussion of the impact of multiple sources that can be used 

together with the results of this study. In general, multiple sources can increase the retinal image size. In 

addition, the retinal irradiance may or may not increase depending on whether the projected retinal images 

overlap, which depends on the positions of the sources relative to the observer. For example, if two beams 

enter the eye but do not overlap, the affected retinal image area is increased, but the irradiance (W/cm 2 ) is the 

same as that from a single beam. If the two beam are nearly coincident and form a coalesced image on the 

retina, the retinal image size is about the same but the irradiance increases. 

Acknowledgments 

The authors would like to thank Jim Adams from the California Energy Commission and Bill Kanemoto for 

pointing us to information relevant to glint and glare assessments in various applications for certification 

(AFCs) of concentrating solar power plants. We also thank Chuck Andraka and Brian Myer for their insights 

and discussions regarding glint, optics, and imaging. 

Sandia is a multiprogram laboratory operated by Sandia Corporation, a Lockheed Martin Company for the 

United States Department of Energy’s National Nuclear Security Administration under contract DE-AC04- 

94AL85000. The United States Government retains and the publisher, by accepting the article for 

publication, acknowledges that the United States Government retains a non-exclusive, paid-up, irrevocable, 

world-wide license to publish or reproduce the published form of this manuscript, or allow others to do so, 

for United States Government purposes. 

References 

[1] Brumleve, T.D. (1977). Eye Hazard and Glint Evaluation for the 5-MW t Solar Thermal Test Facility, 

SAND76-8022, Sandia National Laboratories, Livermore, CA. 

[2] Brumleve, T.D. (1984). 10 MWe Solar Thermal Central Receiver Pilot Plant: Beam Safety Tests and 

Analyses, SAND83-8035, Sandia National Laboratories, Livermore, CA. 

[3] Sliney, D.H, and Freasier, B.C. (1973). Evaluation of Optical Radiation Hazards, Applied Optics, 12(1), 

1-24. 

[4] Carrier, J. (2008). Beam Safety Design Parameters, Data Response Attachment DR89-1, Appendix A, 

Data Response Set 1A. Dated on 1/14/2008, CH2MHILL, Ivanpah Solar Electric Generating System, 

Application for Certification (07-AFC-5), Submitted to California Energy Commission, 

http://www.energy.ca.gov/sitingcases/ivanpah/documents/applicant/DR_1a/2008-01- 

14_ISEGS_DR_SET_1A.PDF. 

[5] Carrizo Energy, LLC (2008). Responses to CEC Data Requests (#1-78), Application for Certification 

(07-AFC-8), Carrizo Energy Solar Farm, Submitted to California Energy Commission, 

http://www.energy.ca.gov/sitingcases/carrizo/documents/applicant/2008-02- 

27_DATA_RESPONSES_1-78.PDF. 

[6] City of Victorville, (2008). Victorville 2 Hybrid Power Project, Application for Certification (07-AFC- 

1), submitted to California Energy Commission, 

www.energy.ca.gov/sitingcases/victorville2/documents/. 

[7] San Joaquin Solar 1 & 2 – Application for Certification Volume 2, Appendix L, “Glint and Glare 

Study,” http://www.energy.ca.gov/sitingcases/sjsolar/documents/applicant/afc/AFC_volume_02/.

[8] SES Solar Two, LLC (2008). SES Solar Two Project, Application for Certification (08-AFC-5), 

submitted to California Energy Commission. 

[9] Ghanbari, C.M. and Diver, R.B. (1994). Glint Hazard Assessment, Sandia National Laboratories 

Internal Memo, April 21, 1994. 

[10] American Conference of Governmental Industrial Hygienists (ACGIH) (1992-1993). Threshold Limit 

Values for Chemical Substances and Physical Agents. 

[11] Sliney, D.H., (1980). An Evaluation of the Potential Hazards of the Point Focusing Solar Concentrators 

at the JPL-Edwards Test Site, Report submitted to the Jet Propulsion Laboratory (JPL Consulting 

Agreement No. JF 714696), California Institute of Technology, Pasadena, CA. 

[12] Hoover, H.L., (1986). Solar ultraviolet irradiation of human cornea, lens, and retina: equations of ocular 

irradiation, Applied Optics, 25(3), 359-368. 

[13] Osterhaus, W.K.E., (2005). Discomfort glare assessment and prevention for daylight applications in 

office environments, Solar Energy, 79, 140-158. 

[14] Iwata, T. and K. Kimura, (1990/1991). Discomfort Caused by Wide-source Glare, Energy and 

Buildings, 15-16, 391-398. 

[15] Delori, F.C., R.H. Webb, and D.H. Sliney, (2007). Maximum permissible exposures for ocular safety 

(ANSI 2000), with emphasis on ophthalmic devices, J. Opt. Soc. Am. A, 24(5), 1250-1265. 

[16] Metcalf, R.D and R.E. Horn, (1958).Visual Recovery Times from High-Intensity Flashes of Light, Air 

Force Aerospace Medical Research Lab, Wright Air Development Center Technical Report 58232. 

[17] Severin, S.L. N.L. Newton, and J.F. Culver, (1962). An Experimental Approach to Flash Blindness, 

Aerospace Medicine, 1199-1205. 

[18] Saur, R.L. and S.M. Dobrash, (1969). Duration of Afterimage Disability after Viewing Simulated Sun 

Reflections, Applied Optics, 8(9), 1799-1801.

APPENDIX J 

Heat Transfer Equation

Heat Transfer Equation 

Variable Definition Value Unit Assumption 

Ai Solar Panels and house areas 100 m2 

30 ft by 30 ft based on area of solar 

panels that would radiate heat to house 

(conservative) 

Fij View Factor 

Incomprara & DeWitt 3rd Edition Fig. 

13.4 View Factor for Aligned Parallel 

View Factors, assuming panels are 260 

ft from house and house and panels are 

0.01 Dimensionlessin parallel planes (conservative) 1 

e Emissivity 1 DimensionlessAssuming black body (conservative) 

sigma Stephan-Boltzmann constant 5.67E-08 W/m2/K^4 

Based on typical Normal Operating Cell 

Ti panel Temperature of PV module 120 degF Temperature for PV modules 

Ti panel Temperature of PV module 322 degK 

Tj house Temperature of House 70 degF 

Estimated House Wall Temperature in 

Shade 

Tj house Temperature of House 294 degK 

Ti Cutslope Temperature of Cutslope before PV 80 degF 

Estimated Temperature of Cutslope in 

sun 

Ti Cutslope Temperature of Cutslope before PV 300 degK 

qij (diff) Heat Transfer difference between solar panel and cutslope 

qij (diff) = Ai*Fij*Sigma*((Ti panel)^4-(Tj house)^4) - Ai*Fij*Sigma*((Ti cutslope)^4-(Tj house)^4) 

qij (diff) = 

609.5460842 Watts 

6.095460842 w/m2

Sacramento Solar Highways Initial Study and Mitigated Negative ...

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