Bureau of Reclamation, Mid-Pacific Region 

U.S. Army Corps of Engineers, Sacramento District 

Central Valley Flood Protection Board 

Sacramento Area Flood Control Agency February 2008 

Supplemental Environmental Assessment/Initial Study 

to the Folsom Dam Safety and Flood Damage Reduction 

Final Environmental Impact Statement/Environmental Impact 

Report

Folsom, California 

Mid-Pacific Region 
Mission Statements 

The mission of the Department of the Interior is to protect and provide access to 

our Nation’s natural and cultural heritage and honor our trust responsibilities to 

Indian Tribes and our commitment to island communities. 

The mission of the Bureau of Reclamation is to manage, develop, and protect 

water and related resources in an environmentally and economically sound 

manner in the interest of the American public. 
Bureau of Reclamation, Mid-Pacific Region 

U.S. Army Corps of Engineers, Sacramento District 

Central Valley Flood Protection Board 

Sacramento Area Flood Control Agency February 2008 

Supplemental Environmental Assessment/Initial Study 

to the Folsom Dam Safety and Flood Damage Reduction 

Final Environmental Impact Statement/Environmental Impact 

Report

Folsom, California 

Mid-Pacific Region 

Prepared by: 

A

Pacific Legacy 

Contents 

Page 

Chapter 1 Introduction............................................................................................1-1 

1.1 Purpose and Need for the Folsom DS/FDR Project.................................1-2 

1.1.1 Project Background.........................................................................1-2 

1.1.2 Statement of Purpose and Need for the Folsom DS/FDR Project ..1-4 

1.2 Purpose and Need for this Supplemental EA/IS ......................................1-4 

1.2.1 Project Background.........................................................................1-4 

1.2.2 Statement of Purpose and Need for this Supplemental EA/IS........1-5 

1.3 Location and Site Description..................................................................1-6 

1.4 Decisions to be Made ...............................................................................1-6 

1.5 Document Organization ...........................................................................1-6 

Chapter 2 Proposed Action .....................................................................................2-1 

2.1 No Action Alternative ..............................................................................2-1 

2.1.1 Dike 5 Construction Site Access and Trail Detour .........................2-1 

2.1.2 Cofferdam .......................................................................................2-1 

2.2 Proposed Action .......................................................................................2-1 

2.2.1 Dike 5 Construction Site Access and Trail Detour .........................2-2 

2.2.2 JFP Auxiliary Spillway Stilling Basin Cofferdam ..........................2-8 

2.2.3 Folsom DS/FDR Project Schedule................................................2-13 

Chapter 3 Affected Environment and Environmental Consequences ................3-1 

3.1 Changes to the Affected Environment .....................................................3-1 

3.1.1 Changes and Clarifications that Reduce Impacts............................3-1 

3.1.2 Changes and Clarifications with No Impacts..................................3-2 

3.2 Environmental Consequences Analysis ...................................................3-3 

3.3 Hydrology, Water Quality, and Groundwater..........................................3-5 

3.3.1 Affected Environment.....................................................................3-5 

3.3.2 Environemtal Consequences ...........................................................3-6 

3.3.3 Cumulative Effects..........................................................................3-7 

3.4 Air Quality................................................................................................3-8 

3.4.1 Affected Environment.....................................................................3-8 

3.4.2 Environmental Consequences .........................................................3-8 

3.4.3 Minimization Measures.................................................................3-12 

3.4.4 Cumulative Effects........................................................................3-12 

3.5 Aquatic Resources..................................................................................3-12 

3.5.1 Affected Environment...................................................................3-12 

3.5.2 Environmental Consequences .......................................................3-13 

3.5.3 Cumulative Effects........................................................................3-14 

3.6 Terrestrial Resources..............................................................................3-14 

3.6.1 Affected Environment...................................................................3-14 

3.6.2 Environmental Consequences .......................................................3-15 

i February 2008 
Folsom Dam Safety and Flood Damage Reduction 

Supplemental Environmental Assessment/Initial Study 

3.6.3 Cumulative Effects........................................................................3-16 

3.7 Soils, Minerals, and Geological Resources............................................3-17 

3.7.1 Affected Environment...................................................................3-17 

3.7.2 Environmental Consequences .......................................................3-17 

3.7.3 Cumulative Effects........................................................................3-18 

3.8 Visual Resources ....................................................................................3-18 

3.8.1 Affected Environment...................................................................3-18 

3.8.2 Environmental Consequences .......................................................3-18 

3.8.3 Cumulative Effects........................................................................3-20 

3.9 Transportation and Circulation...............................................................3-20 

3.9.1 Affected Environment...................................................................3-20 

3.9.2 Environmental Consequences .......................................................3-24 

3.9.3 Minimization Measures.................................................................3-36 

3.9.4 Cumulative Effects........................................................................3-37 

3.10 Noise.......................................................................................................3-37 

3.10.1 Affected Environment...................................................................3-37 

3.10.2 Environmental Consequences .......................................................3-38 

3.10.3 Cumulative Effects........................................................................3-40 

3.11 Cultural Resources .................................................................................3-41 

3.11.1 Affected Environment...................................................................3-41 

3.11.2 Environmental Consequences .......................................................3-42 

3.11.3 Cumulative Effects........................................................................3-44 

3.12 Land Use, Planning, and Zoning............................................................3-44 

3.12.1 Affected Environment...................................................................3-44 

3.12.2 Environmental Consequences .......................................................3-44 

3.12.3 Cumulative Effects........................................................................3-45 

3.13 Recreation Resources .............................................................................3-45 

3.13.1 Affected Environment...................................................................3-45 

3.13.2 Environmental Consequences .......................................................3-46 

3.13.3 Cumulative Effects........................................................................3-47 

3.14 Public Services and Utilities ..................................................................3-47 

3.14.1 Affected Environment...................................................................3-48 

3.14.2 Environmental Consequences .......................................................3-48 

3.14.3 Cumulative Effects........................................................................3-48 

3.15 Public Health and Safety ........................................................................3-49 

3.15.1 Affected Environment...................................................................3-49 

3.15.2 Environmental Consequences .......................................................3-49 

3.15.3 Cumulative Effects........................................................................3-50 

3.16 Minimization Measures Incorporated into the Project...........................3-51 

3.17 References ..............................................................................................3-52 

Chapter 4 CEQA Evaluation ..................................................................................4-1 

4.1 Introduction ..............................................................................................4-1 

4.2 Environmental Checklist Form ................................................................4-2 

ii February 2008 
Contents 

4.3 Environmental Factors Potentially Affected ............................................4-5 

4.4 Determination...........................................................................................4-6 

4.5 Evaluation of Environmental Impacts......................................................4-7

Chapter 5 Consultation and Coordination ............................................................5-1 

5.1 Consultation and Coordination.................................................................5-1 

5.2 Federal, State, and Local Requirements...................................................5-1 

5.3 Distribution List .......................................................................................5-2 

5.3.1 Elected Officials and Representatives.............................................5-2 

5.3.2 Government Departments and Agencies.........................................5-3 

5.3.3 Regional, County, and City.............................................................5-3 

5.3.4 Private Organizations and Businesses.............................................5-4 

5.3.5 Members of the Public ....................................................................5-4 

Chapter 6 List of Preparers.....................................................................................6-1 

Tables 

Table 1-1 Related Documents......................................................................... 1-5 

Table 2-1 Folsom Dam Safety and Flood Damage Reduction Schedule...... 2-14 

Table 3-1 Cumulative Projects........................................................................ 3-5 

Table 3-2 Summary of Emissions from Dike 5............................................... 3-8 

Table 3-3 Summary of Total Emissions for 2008 and 2009 ........................... 3-9 

Table 3-4 Heavy-Duty Diesel Truck Emission Factors for Sacramento 

Valley.............................................................................................. 3-9 

Table 3-5 Paved Road Re-entrained Dust PM10 Emission Factors............... 3-10 

Table 3-6 Uncontrolled Construction Emission Inventories......................... 3-10 

Table 3-7 Local and Regional LOS Standards and Thresholds .................... 3-20 

Table 3-8 Existing Traffic Data .................................................................... 3-22 

Table 3-9 Cofferdam Traffic Impacts ........................................................... 3-36 

Table 5-1 Federal, State, and Local Requirements ......................................... 5-1 

Table 6-1 List of Preparers.............................................................................. 6-1 

Table 6-2 List of Contributors......................................................................... 6-3 

iii February 2008 
Folsom Dam Safety and Flood Damage Reduction 

Supplemental Environmental Assessment/Initial Study 

Figures 

Figure 1-1 The Folsom Facility ......................................................................... 1-2 

Figure 1-2 Folsom Reservoir ............................................................................. 1-6 

Figure 2-1 Dike 5 Construction Site Access...................................................... 2-5 

Figure 2-2 Proposed Location of Trail Detour................................................... 2-9 

Figure 2-3 Cofferdam for Stilling Basin .......................................................... 2-11 

Figure 3-1 Peak Hour Turning Movement Volumes (4 Legged Intersection). 3-27 

Figure 3-2 Peak Hour Levels of Service (4 Legged Intersection) ................... 3-29 

Figure 3-3 Peak Hour Turning Movement Volumes (3 Legged Intersection). 3-31 

Figure 3-4 Peak Hour Levels of Service (3 Legged Intersection) ................... 3-33 

Appendices 

Appendix A Traffic Analysis 

iv February 2008 
Contents 

Acronyms and Abbreviations 

ADT average daily trips 

APE Area of Potential Effects 

BMP Best Management Practice 

Bridge EIS/EIR Folsom Bridge Draft Supplemental EIS/EIR 

CARB California Air Resources Board 

CDFG California Department of Fish and Game 

CEQA California Environmental Quality Act 

CFR Code of Federal Regulations 

cfs cubic feet per second 

CO carbon dioxide 

Cofferdam JFP Auxiliary Spillway Stilling Basin Cofferdam 

Corps U.S. Army Corps of Engineers 

CRHR California Record of Historical Resources 

CVFPB Central Valley Flood Protection Board 

CVP Central Valley Project 

CVRWQCB Central Valley Regional Water Quality Control Board 

CWA Clean Water Act 

cy cubic yards 

dB decibel 

dBA A-weighted decibel scale 

DPR California Department of Parks and Recreation 

DS/FDR Dam Safety and Flood Damage Reduction 

EA/IS Environmental Assessment/Initial Study 

EIS/EIR Environmental Impact Statement/Environmental Impact Report 

FLSRA Folsom Lake State Recreation Area 

Folsom Facility Folsom Dam and Appurtenant Facilities 

FONSI Finding of No Significant Impact 

ft foot/feet 

FWCAR Fish and Wildlife Coordination Act Report 

GIS Geographic Information System 

GPS Global Positioning System 

g/VMT gallons per vehicle miles traveled 

HCP Habitat Conservation Plan 

ITA Indian Trust Asset 

JFP Joint Federal Project 

kV kilo volt 

lbs pounds 

lbs/day pounds per day 

LOS level of service 

LWD Left Wing Dam 

M&I Municipal and Industrial 

v February 2008 
Folsom Dam Safety and Flood Damage Reduction 

Supplemental Environmental Assessment/Initial Study 

MIAD Mormon Island Auxiliary Dam 

mph miles per hour 

NCCP Natural Community Conservation Plan 

ND Negative Declaration 

NEPA National Environmental Policy Act 

NHPA National Historic Preservation Act 

NPDES National Pollutant Discharge Elimination System 

NOD Notice of Determination 

NOx nitrogen oxides 

NRHP National Record of Historic Places 

O3 ozone 

PCAPCD Placer County Air Pollution Control District 

PM2.5 particles less than 2.5 micrometers 

PM10 particles of 10 micrometers or less 

Reclamation United States Department of the Interior, Bureau of Reclamation 

ROD Record of Decision 

ROG Reactive organic gases 

RWD Right Wing Dam 

SAFCA Sacramento Area Flood Control Agency 

SHPO State Historic Preservation Officer 

SMAQMD Sacramento Metropolitan Air Quality Management District 

SMUD Sacramento Municipal Utility District 

SO2 sulfur dioxide 

SOD Safety of Dams 

SSLE Safety, Security, and Law Enforcement Program 

SWPPP Storm Water Pollution Prevention Plan 

tpy tons per year 

USGS United States Geological Survey 

USFWS United States Fish and Wildlife Service 

V/C volume to capacity 

VOC volatile organic carbon 

vi February 2008 
Chapter 1 

Introduction 

This document is a joint Supplemental Environmental Assessment/Initial Study 

(EA/IS) to the Folsom Dam Safety and Flood Damage Reduction (DS/FDR) Final 

Environmental Impact Statement/Environmental Impact Report (EIS/EIR) (March 

2007), and satisfies the requirements of the National Environmental Policy Act 

(NEPA) and the California Environmental Quality Act (CEQA). This Supplemental 

EA/IS has been prepared by the U.S. Department of the Interior, Bureau of 

Reclamation (Reclamation), the U.S. Army Corps of Engineers (Corps), and the 

Corps non-Federal sponsors, the Central Valley Flood Protection Board (CVFPB)1

and the Sacramento Area Flood Control Agency (SAFCA). Reclamation is the 

NEPA lead agency for this document; CVFPB is the CEQA lead agency. 

Agency NEPA/CEQA Role 

Bureau of Reclamation NEPA Lead Agency 

U.S. Army Corps of 

Engineers Cooperating Agency under NEPA 

Central Valley Flood 

Protection Board CEQA Lead Agency 

Sacramento Area Flood 

Control Agency Responsible Agency under CEQA 

The purpose of this Supplemental EA/IS is to describe and analyze the effects of 

construction actions and refinements to the project since the completion of the 

Folsom DS/FDR Final EIS/EIR. The Folsom DS/FDR Project, as approved and 

authorized, is currently under construction. The actions proposed in this EA/IS are 

existing components of the authorized project currently underway and have been 

defined to a greater level of detail than was available at the time of the Folsom 

DS/FDR EIS/EIR. This document does not change the project originally described in 

the Joint Federal Project (JFP) Record of Decision (ROD) and Safety of Dams 

(SOD) ROD, but proposes refinements and clarifications to certain project actions 

that require further environmental analysis. The Supplemental EA/IS identifies and 

evaluates certain site specific actions. The results of this Supplemental EA/IS will 

provide the basis for determining whether a Finding of No Significant Impact 

(FONSI)/Negative Declaration (ND) can be issued or if additional environmental 

review such as an EIS/EIR is required. 

The document describes the affected environment and the potential direct, indirect, 

and cumulative effects related to construction of refined components of the Folsom 

DS/FDR Project. This document also identifies measures that have been incorporated 

into the design of the project to minimize or avoid project-related impacts. 

 

1

 Formerly known as the Reclamation Board of the State of California. 

1-1 February 2008 
Folsom Dam Safety and Flood Damage Reduction 

Supplemental Environmental Assessment/Initial Study 

1.1 Purpose and Need for the Folsom DS/FDR Project 

1.1.1 Project Background 

The Folsom Dam and Appurtenant Facilities (Folsom Facility) consists of 4 dams 

(Main Concrete Dam, Mormon Island Auxiliary Dam [MIAD], Right Wing Dam 

8), which impound flows 

on the American Rive

forming Folsom Reser

(See Figure 1-1). The 

Folsom Facility was 

constructed between 194

and 1956 by the Corps as 

multi-purpose facility. 

Upon completion of dam 

and dike construction

ownership of the Folsom

Facility was transferred 

Reclamation for op

and maintenance as an 

integrated feature of the 

Central Valley Project 

(CVP). In addition to CV

water supply, the Folsom

Facility is operated for 

flood control, municipal 

and industrial (M&I) 

water supply, power, fis

and wildlife, recreation, 

and water quality bene

The Folsom Powerplant 

construction, begun in 

1952 and completed in 

1956, was supervised by 

Reclamation. 

Both Reclamation and the

Corps share in 

[RWD], Left Wing Dam [LWD]) and 8 dikes (Dikes 1 to 

r 

voir 

8 

a 

, 

to 

eration 

P 

h 

fits. 

the 

responsibility of 

 under 

pective 

he Corps 

maintaining and operating 

the Folsom Facility

each agency’s res

dam safety regulations and guidelines, as defined by Congress. Reclamation is 

responsible for dam safety, operations, and maintenance at Folsom Dam. T

is responsible for flood damage reduction capital improvements and establishing 

Figure 1-1 

The Folsom Facility 

1-2 February 2008 
Chapter 1 

Introduction 

flood operation requirements at Folsom Reservoir, including regulations governin

flood management by setting flood storage and release criteria during specified 

annual seasons. 

g 

As a part of their responsibilities, Reclamation and the Corps have determined that 

sues. 

and 

Reclamation has identified the need for expedited action to reduce hydrologic, static, 

ighest 

The Corps, in partnership with the non-Federal sponsors, has determined that Folsom 

al 

st at 

Both Reclamation and the Corps have conducted engineering studies to identify 

nd 

uction 

s 

the Folsom Facility requires structural improvements to increase overall public 

safety above existing conditions including addressing dam safety and security is

The improvements will enhance the facility’s ability to reduce flood damages posed 

by hydrologic (flood), seismic (earthquake), and static (seepage) events. These 

events have a low probability of occurrence in a given year; however, due to the

large population downstream of Folsom Dam, modifying the facilities is prudent 

necessary to improve public safety above current baseline conditions. 

and seismic risks under its SOD Program and security issues under its Security 

Program. These identified risks are among the highest risks for all dams in 

Reclamation’s inventory and the Folsom Facility is among Reclamation’s h

priorities within its SOD Program. Additionally, there is a need to upgrade security

infrastructure at the Folsom Facility under Reclamation’s Safety, Security and Law 

Enforcement (SSLE) Program. Reclamation’s primary interest for participating in 

the Folsom DS/FDR is to achieve an expedited improvement in overall public 

protection and the cost sharing benefits of a combined project. 

Reservoir does not have sufficient release capacity to adequately manage severe 

flood flows, nor do the downstream levees have sustained capacity to exceed base

flood event flows of 145,000 cubic feet (ft) per second (cfs). The Corps’ non-Feder

sponsors have identified the need to reduce the risk of flooding in the Sacramento 

area. Due to the number and value of the exposed structures and the size of the 

potentially affected population, Sacramento has been identified as one of the mo

risk communities in the nation. Consequently, there is a need to expeditiously reduce 

this risk through interim and permanent flood damage reduction measures. The goal 

of the non-Federal sponsors is to safely pass the 200-year computed design flood 

event, as a minimum objective for Folsom Dam Modifications and Folsom Dam 

Raise projects. Pursuit of this goal constitutes the non-Federal sponsors’ primary 

interest for participating in the Folsom DS/FDR actions. 

potential corrective measures for the Folsom Facility to alleviate seismic, static, a

hydrologic dam safety issues, and flood management concerns. These two Federal 

Agencies have combined their efforts resulting in (1) a JFP for addressing 

Reclamation’s dam safety hydrologic risk and the Corps’ flood damage red

objectives and (2) other stand-alone flood damage reduction and dam safety action

to be completed by the respective agencies in a coordinated manner. Among the 

1-3 February 2008 
Folsom Dam Safety and Flood Damage Reduction 

Supplemental Environmental Assessment/Initial Study 

latter are separate, but related, downstream levee projects that are underway to 

increase flood damage reduction along the lower American River. 

1.1.2 Statement of Purpose and Need for the Folsom DS/FDR Project 

ty. 

lity. 

1.2 Purpose and Need for this Supplemental EA/IS 

s, CVFPB, and SAFCA released the 

The Final EIS/EIR was released to the public in March 2007 and identified 

des the 

, 5, 

all 

. 

A ROD addressing Reclamation’s Dam Safety and Security actions was signed in 

s 

or 

. 

There is a need to expeditiously implement engineering measures for the Folsom 

Facility in order to reduce potential failure due to seismic, static, and hydrologic 

conditions. There is also a need to incrementally increase minimum flood damage

reduction via flood storage capacity and/or reservoir pool release mechanisms. 

Furthermore, there is a need to implement security improvements at the Folsom

Facility consistent with its designation as a National Critical Infrastructure Facili

The purpose of the Folsom DS/FDR is to increase overall public safety, ensure the 

reliability of local power and water supply, and maintain an important recreational 

resource by: (1) expediting corrective action to address risks identified with the 

structural integrity of Folsom Dam and appurtenant structures in accordance with

Reclamation’s Public Protection Guidelines; (2) incrementally improving the flood

management capacity of the Folsom Facility to meet or exceed the 200-year 

recurrence level; and (3) upgrading security infrastructure at the Folsom Faci

1.2.1 Project Background 

On December 1, 2006, Reclamation, the Corp

Folsom DS/FDR Draft EIS/EIR for public review and comment. The Draft EIS/EIR

(State Clearinghouse # 2006022091) identified five alternatives to address dam 

safety, security, and flood damage reduction objectives for the Folsom Facility. 

Alternative 3 as the preferred alternative/proposed action. Alternative 3 inclu

JFP Auxiliary Spillway, seismic improvements to the Main Concrete Dam and 

MIAD, static improvements to specific earthen structures (RWD, LWD, Dikes 4

and 6), security upgrades, reinforcement of the five Main Concrete Dam spillway 

gates and replacement of the three emergency spillway gates, and a 3.5 -ft raise to 

Folsom Facility structures. Section 2.2 of the Draft EIS/EIR discusses concerns 

regarding the Folsom Facility and measures considered to address those concerns

Table 1-1 in the Final EIS/EIR lists the components of Alternative 3, the agency 

responsible for each component, and the issue that each component addresses. 

May 2007 by Reclamation. A joint ROD addressing the JFP Auxiliary Spillway wa

signed in May 2007 by Reclamation and the Corps. A Notice of Determination 

(NOD) and Statement of Findings were issued by the CVFPB on July 20, 2007 f

the JFP Auxiliary Spillway. Table 1-1 provides a list of all project-related 

documents, the agencies associated with them, and the date of their release

1-4 February 2008 
Chapter 1 

Introduction 

Table 1-1 

Related Documents 

Document Title Agency Date 

Folsom DS/FDR Draft EIS/EIR (Vol. I) 

Folsom DS/FDR Draft EIS/EIR (Vol. II 

Appendices) 

Reclamation, Corps, 

SAFCA, CVFPB December 2006 

Folsom DS/FDR Final EIS/EIR (Vol. III) Reclamation, Corps, 

SAFCA, CVFPB March 2007 

Folsom Dam SOD and Security Upgrades 

Projects ROD Reclamation May 2007 

Folsom DS/FDR JFP ROD Reclamation & Corps May 2007 

Folsom DS/FDR JFP NOD, Statement of 

Findings, and Findings of Overriding 

Consideration 

CVFPB July 2007 

Construction of the Folsom DS/FDR Project was initiated in December 2007 and the 

overall project is expected to be completed in phases by 2020. The actions described 

in this Supplemental EA/IS are part of the overall authorized projects being 

implemented jointly by Reclamation and the Corps and individually by Reclamation. 

1.2.2 Statement of Purpose and Need for this Supplemental EA/IS 

The following activities are addressed in this Supplemental EA/IS: 

• Dike 5 Construction Site Access and Trail Detour; and 

• JFP Auxiliary Spillway Stilling Basin Cofferdam. 

The purpose and need for the Dike 5 Construction Site Access is to provide a more 

direct route to the Dike 4, 5, and 6 reconstruction zones to reduce conflicts with 

recreation traffic at Beal’s Point. The purpose and need for the Trail Detour is to 

maintain trail connectivity between Beal’s Point and Mooney Ridge during dike 

construction. 

The purpose and need for the Cofferdam is to provide safety for construction 

workers during construction of the JFP Auxiliary Spillway and to allow Stilling 

Basin construction during water releases from Folsom Dam that would increase 

flows in the American River channel. Large releases from Folsom Dam may occur as 

part of normal operations. 

1-5 February 2008 
Folsom Dam Safety and Flood Damage Reduction 

Supplemental Environmental Assessment/Initial Study 

1.3 Location and 

Site Description 

Figure 1-2 

Folsom Reservoir 

The location for this 

Supplemental EA/IS 

includes the area 

surrounding Folsom 

Reservoir that falls within 

Placer and Sacramento 

Counties. No actions 

addressed in this 

Supplemental EA/IS would 

occur in El Dorado County. 

The study area mainly 

consists of Federally-owned 

lands that are currently 

leased to and managed by 

the California Department of 

Parks and Recreation (DPR). 

Figure 1-2 shows the 

location of the Folsom 

Reservoir in central 

California. 

1.4 Decisions to be 

Made 

The results of this 

Supplemental EA/IS will 

determine whether an 

EIS/EIR is required or a 

FONSI/ND will be issued 

for the actions addressed. 

1.5 Document Organization 

The remainder of this document is organized as follows: 

• Chapter 2 – presents the Proposed Action analyzed in this Supplemental 

EA/IS; 

• Chapter 3 – describes changes to the project and affected environment, and 

analyses the effects of the Proposed Action under NEPA; 

• Chapter 4 – contains the CEQA Initial Study Checklist; 

1-6 February 2008 
Chapter 1 

Introduction 

• Chapter 5 – describes the consultation and coordination that occurred during 

the development of this document; 

• Chapter 6 – presents the list of preparers; and 

• Appendix A – contains the Traffic analysis. 

1-7 February 2008 
Folsom Dam Safety and Flood Damage Reduction 

Supplemental Environmental Assessment/Initial Study 

This page left intentionally blank. 

1-8 February 2008 
Chapter 2 

Proposed Action 

This chapter describes the No Action Alternative and the Proposed Action for this 

Supplemental EA/IS. 

2.1 No Action Alternative 

For the purposes of impact analyses, environmental documents typically compare a 

No Action Alternative with that of the Proposed Action. The No Action Alternative 

examines the future without project conditions, that is, the future if the Proposed 

Action is not implemented or constructed. 

The RODs for the Folsom DS/FDR Project were signed in May 2007 and several of 

the actions defined in the RODs are well underway. Therefore, the affected 

environment and No Action Alternative in this EA/IS incorporate the Folsom 

DS/FDR Project actions described in the RODs. 

2.1.1 Dike 5 Construction Site Access and Trail Detour 

Under the No Action Alternative, the access to the Dike 5 construction site directly 

from Auburn-Folsom Road would not be constructed. Access to the dike work zones 

would occur from Beal’s Point as described in the EIS/EIR. This would increase the 

interference between recreation traffic and construction traffic. Under the No Action 

Alternative, the trail across the top of Dikes 4, 5, and 6 would be closed for 

construction safety purposes. Pedestrians, equestrians, and bikers would have 

difficulty moving between Beal’s Point and Mooney Ridge because of trail closures 

in the dike construction zones. 

2.1.2 Cofferdam 

Under the No Action Alternative, a cofferdam would not be built. Excavation of the 

Stilling Basin would be severely hampered by releases from Folsom Dam and 

significant pumping and water management would be necessary to complete the 

work. For safety reasons, construction workers may be unable to work on the Stilling 

Basin during periods of high releases and this would affect the construction schedule. 

Chapter 3 provides additional discussion on the No Action Alternative relative to 

specific resource areas. 

2-1 February 2008 
Folsom Dam Safety and Flood Damage Reduction 

Supplemental Environmental Assessment/Initial Study 

2.2 Proposed Action 

There is only one Proposed Action Alternative, which consists of two components: 

• Dike 5 Construction Site Access and Trail Detour; and 

• JFP Auxiliary Spillway Stilling Basin Cofferdam. 

2.2.1 Dike 5 Construction Site Access and Trail Detour 

The Dike 5 Construction Site Access and Trail Detour are associated with SOD work 

and will be completed by Reclamation. 

2.2.1.1 Dike 5 Construction Site Access 

In the Folsom DS/FDR Final EIS/EIR, work at Dike 5 was scheduled to start in 

September 2009. Due to SOD schedule priorities, Reclamation has elected to initiate 

the Dike 5 work by spring 2008. The proposed schedule is to complete the Dike 5 

work by March 2009. In addition, the Folsom DS/FDR Final EIS/EIR (see Section 

2.4.5 on page 2-26 of the Final EIS/EIR) stated that primary access to Dike 5 would 

be via the Beal’s Point access road. Access to Dike 5 for staging and reconstruction 

of the Dike 5 filters is now proposed to occur from Auburn-Folsom Road 

immediately west of Dike 5, thereby reducing conflicts with recreational traffic at 

Beal’s Point. 

Reclamation proposes to construct a new access road to accommodate construction 

equipment and trucks transporting materials to the Dike 5 work site. This would 

require trucks to turn into the Dike 5 construction staging area from Auburn-Folsom 

Road and would introduce trucks merging into traffic on the roadway. Figure 2-1 

shows the Dike 5 Construction Site Access location. For the duration of the Dike 5 

construction there would be approximately 27 daily morning and early afternoon 

construction worker trips from northbound and southbound on Auburn-Folsom Road 

to Beal’s Point, and 27 afternoon and nighttime trips out of Beal’s Point (assuming 

two work shifts). During peak construction activities, a period of no more than 30 

days, 40 haul trucks would enter and exit Beal’s Point throughout the day between 7 

am and 3 pm to deliver materials. To accommodate construction traffic with local 

traffic, Reclamation proposes to control traffic flow using either flagmen or 

installation of a temporary intersection with a traffic light. Trucks entering the 

staging area would only approach from the south (northbound on Auburn-Folsom 

Road) and would turn right into the staging area. Traffic leaving the site would be 

controlled by a temporary traffic light or flagmen, to allow trucks to safely turn right 

or left onto Auburn-Folsom Road. Turn outs and merge lanes along the shoulders 

and median of Auburn-Folsom Road could be included in the installation to further 

minimize traffic congestion. Use of Auburn-Folsom Road and construction of turn 

outs and merge lanes would be coordinated with Placer County and would require 

Placer County approval. 

2-2 February 2008 
Chapter 2 

Proposed Action 

During the time that Reclamation proposes to construct and use the Dike 5 

Construction Site Access, Placer County is proposing to initiate construction of the 

Auburn-Folsom Road Widening Project from County Line to Woodchase Drive, 

approximately 0.7 miles south of the Dike 5 area. Reclamation would coordinate 

closely with County traffic engineers in implementing the Dike 5 traffic control 

measures. 

2-3 February 2008 
Folsom Dam Safety and Flood Damage Reduction 

Supplemental Environmental Assessment/Initial Study 

 This page left intentionally blank.

2-4 February 2008 
DIKE 4 

DIKE 5 

DIKE 6 

Beal’s

Point

Auburn-Folsom Rd Auburn-Folsom Rd

Eureka Rd Eureka Rd

County Ct County Ct

Lou Pl 

Oak Hill Dr

Bell Dr Bell Dr

Ann Pl 

Approximate Location

of Temporary Intersection

Approximate Location

of Temporary Intersection

Figure 2-1

Dike 5 Construction Site Access

NORTH

NO SCALE
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2-6 February 2008 
Chapter 2 

Proposed Action 

Temporary Traffic Light (Signal) 

Installation of the temporary intersection with traffic control lights (signals) is 

scheduled to occur during the spring or summer of 2008 prior to the construction on 

Dike 5. The proposed traffic light would be programmed to operate only when trucks 

and other construction vehicles need to cross oncoming traffic. The traffic light 

would only be in use during construction periods and would be taken out of service 

between work on Dike 5 and work on Dikes 4 and 6. Oncoming traffic would be 

alerted to the temporary signal by signs or warning lights as required by Placer 

County. The County may require the temporary signal to be synchronized with 

adjacent signals to minimize impacts to existing traffic flow. 

The Dike 5 staging area would also be used for work at Dikes 4 and 6 (currently 

scheduled for 2013 to 2014). However, depending on Reclamation Dam Safety 

priorities and funding, work on these dikes may occur earlier. The traffic control 

light would be placed in an inactive (or stand- by) mode or removed after completion 

of the work on Dike 5, and would be reactivated or reinstalled for the Dike 4 and 6 

work. The traffic control light would be permanently removed after work is 

completed on Dikes 4 and 6. 

Flagmen 

An alternative to the installation of the traffic control light would be the use of 

flagmen to control traffic. Construction signs and warning lights would be posted 

along Auburn-Folsom Road warning of trucks turning onto the highway. 

Construction and local traffic would be required to follow the instructions of the 

flagmen to allow safe movement of the construction traffic. 

2.2.1.2 Trail Detour 

Although the Folsom JFP and SOD RODs provided commitments for installation of 

trail detours where possible to minimize recreation impacts, details for required 

detours were not available at the time the RODs were signed. Currently, recreational 

trails traverse the tops of Dikes 4, 5, and 6. The crests of the dikes would need to be 

closed during dike reconstruction with trail detours routed along the downstream side 

of the dikes. Placement of trails on the reservoir (water) side was eliminated as an 

alternative because the trails would become flooded as the reservoir fills, leaving the 

trails inaccessible during part of the year. 

To address ROD commitments, a trail detour would need to be established around 

the staging areas and dike construction zones to allow for continual public use of the 

trails during construction. Placement of the trail around the Dike 5 staging area could 

route the recreation trail through wetlands and oak woodland. Efforts will be made to 

avoid impacts to wetlands and oak trees. 

To provide a trail detour in response to the aforementioned ROD commitment, 

Reclamation proposes to construct a single trail to accommodate pedestrian, bicycle, 

2-7 February 2008 
Folsom Dam Safety and Flood Damage Reduction 

Supplemental Environmental Assessment/Initial Study 

and equestrian use. The trail would be approximately 5 to 6 ft wide with a maximum 

grade of 8 percent, and constructed of native earth material. Figure 2-2 presents the 

proposed Trail Detour location1. Because it is temporarily replacing an existing trail 

along the tops of the dikes, the Trail Detour would be managed by Reclamation’s 

Recreation Management Partner until the close of construction. Only the portion of 

the detour that crosses through the Dike 5 area would be the responsibility of 

Reclamation and the Construction Contractor. This portion of the trail would 

intersect truck traffic entering the staging area at Dike 5. Appropriate signs and 

flagmen would be established where the Trail Detour crosses construction traffic to 

ensure public safety. After construction is complete, Reclamation would either 

remove the Trail Detour and re-establish the original trail or turn it over to its 

Recreation Management Partner for management and use. 

2.2.2 JFP Auxiliary Spillway Stilling Basin Cofferdam (Cofferdam) 

Although the construction of a new Stilling Basin at the toe of the JFP Auxiliary 

Spillway was disclosed in the Folsom DS/FDR Final EIS/EIR, the construction 

details of the facility were not fully known at that time. One of the required details 

for the Stilling Basin excavation would be a cofferdam that would allow construction 

of the Stilling Basin to occur “in the dry” during times when releases are being made 

from Folsom Dam. The construction and use of a cofferdam were not addressed in 

the previous EIS/EIR and therefore will be addressed in this EA/IS. The Stilling 

Basin and Cofferdam are part of the JFP and would be completed by Reclamation. 

A cofferdam is a temporary dam or barrier used to divert water flow or to enclose an 

area during construction. The Cofferdam would be constructed during excavation 

work on the Stilling Basin. The Cofferdam would ensure that construction of the 

Stilling Basin could be completed in the dry and would also prevent water quality 

impacts from construction to the American River downstream of the Auxiliary 

Spillway. The Cofferdam would consist of either a wall made of reinforced concrete 

or a combination of a cellular Cofferdam and concrete wall. The maximum height of 

the Cofferdam would be approximately 55 ft. Approximately 6,700 cubic yards (cy) 

to 8,500 cy of concrete and 1,350,000 pounds (lbs) to 1,700,000 lbs of reinforcing 

bars would be required. The reinforced concrete wall would extend across the 

Stilling Basin excavation to high ground on each side. The wall would be designed to 

protect the Stilling Basin area from releases of up to 115,000 cfs from Folsom Dam. 

The Cofferdam would be fully or partially removed (leaving portions above and 

below the Stilling Basin channel) after construction of the Stilling Basin using 

standard demolition techniques. Measures would be implemented to prevent concrete 

material from entering the Stilling Basin or the river during removal of the wall. 

Figure 2-3 shows the proposed location of the Cofferdam for the Stilling Basin. 

 

1

 Figure 2-2 shows the approximately location for the Trail Detour; the actual location may change in 

order to reduce/avoid environmental impacts. 

2-8 February 2008 
DIKE 4

DIKE 5

DIKE 6

Beal’s

Point

Beal’s

Point

Auburn-Folsom Rd Auburn-Folsom Rd

Eureka Rd ureka Rd

County Ct County Ct

Lou Pl

Oak Hill DrOak Hill Dr

Bell Dr Bell Dr

Ann Pl

Figure 2-2

Proposed Location of Trail Detour

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Trail Detour

Existing Trails

LEGEND

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Reservoir
Folsom Dam Safety and Flood Damage Reduction 

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2-10 February 2008 
JFP Auxilia

SpillwayJFP AuxiliaSpillway

Cofferdam offerdam

Haul Route aul Route



0 500

FEET

1:6,000

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2-12 February 2008 
Chapter 2 

Proposed Action 

Increased discharges for any reason from the existing dam’s outlet works or spillway 

could flood the construction site. Releases from the dam can occur during any time 

of the year to address flood control, water supply, and lower American River 

temperature requirements. Therefore, protection of site workers and equipment by 

the Cofferdam would be necessary until completion of the new Stilling Basin and 

Auxiliary Spillway. 

As indicated above, the purpose of the Cofferdam would be to prevent flooding of 

the haul road and excavation area during release events requiring discharge from the 

existing dam outlet works or existing spillway. The invert of the JFP Stilling Basin 

excavation would be about elevation 113 to 116 ft. The lowest elevation of the haul 

road would be about elevation 123 ft. The normal water surface elevation in the main 

river channel downstream of the existing dam outlet works and spillway during 

releases is about 131 ft in the vicinity of the proposed Stilling Basin. Thus, releases 

would put the haul road and Stilling Basin work site under water. The Cofferdam 

would be constructed just above the normal water line during releases from Folsom 

Dam. Because of ridges between the Folsom Powerplant channel and the spillway 

channel, normal Powerplant flows would not flood the construction site but flows 

from the existing spillway channel would. 

The Stilling Basin and Cofferdam would be situated in a side channel separate from 

the deeper main channel of the American River, which receives releases from the 

Folsom Powerplant and existing spillway. The lowest elevation of the Cofferdam 

wall would be 133 ft. (Note the terrain along the axis of the proposed Cofferdam 

varies and not all of the Cofferdam would be in contact with river water during 

releases.) Typical discharges from Folsom Dam will place river water elevation at 

131 ft. However, it is expected that the river elevation would contact the lower 

portion of the Cofferdam during 50% of the releases from Folsom Dam. For higher 

discharge events, tailwater is controlled by the downstream channel configuration. 

Therefore, the Cofferdam may slightly raise the tailwater level immediately adjacent 

to the Cofferdam but this effect would not be carried downstream of the project site. 

Placement and design of the Cofferdam would not constrain downstream flows nor 

cause a measurable change in river water elevation at any flows. The Cofferdam 

would not change the downstream water surface elevation. 

2.2.3 Folsom DS/FDR Project Schedule 

As described in the EIS/EIR, the Folsom DS/FDR Project will be implemented 

through a series of phases and activities to address the hydrologic, static, and seismic 

issues. Refinements to the schedule have been made since issuance of the Final 

EIS/EIR. Table 2-1 presents the project schedule as of January 2008. Those portions 

of the project which are analyzed in this Supplemental EA/IS are highlighted in the 

2-13 February 2008 
Folsom Dam Safety and Flood Damage Reduction 

Supplemental Environmental Assessment/Initial Study 

table. Refinements to the schedule with the potential to affect air quality and traffic 

and are analyzed in Chapter 3 and 4. 

Table 2-1 

Folsom Dam Safety and Flood Damage Reduction Schedule

Activity 

ID Folsom DS/FDR Action Schedule 

1 Phase 1 JFP Auxiliary Spillway Excavation December 2007 to March 2009 

2 Right and Left Wing Dam Static Modifications December 2007 to March 2009 

3 Dike 5 Construction Site Access and Trail Detour April 2008 to September 2008 

4 Dike 5 Static Modifications September 2008 to March 2009 

5 Phase 2 JFP Auxiliary Spillway Construction September 2009 to January 2011 

6 Cofferdam Construction September 2009 to March 2010 

7 Stilling Basin Construction March 2010 to January 2011 

8 Dikes 4 and 6 Static Modifications September 2013 to April 2014 

9 Phase 3 JFP Auxiliary Spillway Construction September 2011 to November 2014 

10a Pier Tendon Installation at Main Concrete Dam January 2014 to March 2017 

10b Spillway Pier Wraps and Braces August 2014 to April 2016 

10c Spillway Gate Repairs January 2017 to August 2018 

11 MIAD Seismic and Static Improvements To be scheduled 

2-14 February 2008 
Chapter 3 

Affected Environment and 

Environmental Consequences 

This chapter presents the NEPA analysis for the Proposed Action. The CEQA 

analysis, provided in the form of a CEQA Initial Study Checklist, is presented in 

Chapter 4. 

3.1 Changes to the Affected Environment 

Since the release of the Folsom DS/FDR EIS/EIR, several changes have occurred to 

project features that would not result in any new or greater impacts beyond those 

previously analyzed in the EIS/EIR. Under NEPA, changes to a proposed action with 

no new impacts beyond those previously disclosed, or changes that diminish impacts 

from a previous analysis, do not require additional analysis prior to implementation. 

Therefore, the changes described in Section 3.11 and 3.12 are not included as part of 

the Proposed Action as they do not require additional analysis. 

For most resource sections, the affected environment remains similar to that 

described in the Folsom DS/FDR Draft EIS/EIR, with the addition of the Folsom 

DS/FDR Project. The Folsom DS/FDR Project, as approved and authorized in the 

RODs, is currently under construction and is therefore included as part of this 

affected environment. Changes and updates to the affected environment from that 

described in the previous EIS/EIR are described for each resource area, as necessary. 

Please refer back to the Folsom DS/FDR Draft and Final EIS/EIR and RODs for a 

detailed description of the authorized project’s affected environment, impacts, and 

mitigation measures. 

3.1.1 Changes and Clarifications that Reduce Impacts 

Several refinements to the project description, which are described below, will result 

in a reduction in the overall impacts that were described in the EIS/EIR. 

3.1.1.1 Borrow Area Near Mooney Ridge 

The borrow area near Mooney Ridge has been reduced in size from that described in 

the EIS/EIR. The borrow area proposed in the EIS/EIR included an area of 

approximately 85 acres that would be used to supply shell material as part of the 

static improvements to Dikes 4, 5, and 6. Reclamation has refined the project and 

substantially reduced borrow needs. Reclamation now proposes to borrow materials 

from an area of approximately 5 acres. An additional 5 acres will be needed for 

equipment and vehicle staging and hauling. The impacted area has been reduced by 

approximately 75 acres. 

3-1 February 2008 
Folsom Dam Safety and Flood Damage Reduction 

Supplemental Environmental Assessment/Initial Study 

3.1.2 Changes and Clarifications with No Impacts 

Several changes and clarifications to the project description will not result in any 

new impacts beyond those already analyzed in the EIS/EIR. 

3.1.2.1 JFP Auxiliary Spillway Width 

The width of the JFP Auxiliary Spillway has been increased to account for a stepped 

spillway design that requires sloped walls. The original width of the Auxiliary 

Spillway was approximately 170 ft, but has been expanded to 240 ft. The increase in 

width would not result in any new impacts as it would still fall within the project 

footprint described in the EIS/EIR. 

3.1.2.2 Stilling Basin Details 

Although the Folsom DS/FDR EIS/EIR explained that a Stilling Basin would be 

necessary for the JFP Auxiliary Spillway, no design or construction details were 

available at the time. This section provides new information on the Stilling Basin 

design and construction that would not result in any additional impacts beyond those 

previously analyzed. The purpose of the Stilling Basin is to reduce the energy in the 

flow during releases from the JFP Auxiliary Spillway, in order to prevent erosion of 

the American River channel. The JFP Auxiliary Spillway consists of a control 

structure (with an invert elevation of 368 ft) that discharges flow from Folsom 

Reservoir into a rectangular inclined chute. The chute then transitions into a stepped 

parabolic drop section approximately 2,000 ft downstream of the control structure, at 

an elevation of approximately 325 ft. This stepped drop section is designated as the 

beginning of the Stilling Basin structure and its purpose is to dissipate energy, 

allowing for the size of the Stilling Basin to be reduced. The steps would be formed 

in concrete; excavation for the structure would not be stepped. Approximately 400 ft 

downstream, the stepped parabolic section would transition to a constant slope of 

about 2.5:1 (at about elevation of 236.0 ft), and would continue to the Stilling Basin, 

at an elevation of 113 ft. The Stilling Basin would be approximately 169 ft wide and 

250 ft long. There would be an exit channel from the end sill of the Stilling Basin to 

the confluence with the American River. The invert of the exit channel would slope 

upward (at about 30:1 slope) until it meets the American River, about 370 ft 

downstream. The bottom width of the exit channel widens 10 ft on each side over a 

10 ft distance downstream of the end sill. 

Excavation for the Stilling Basin (from 2,000 ft below the Auxiliary Spillway 

channel to the American River) would be mostly rock excavation. The total 

excavation quantity for Stilling Basin excavation would be approximately 880,000 

cubic yards (cy), including approximately 630,000 cy of rock excavation. The rock 

excavation would be supported with rock reinforcement that consists of rock bolts, 

fabric mesh, and shotcrete. The excavated slope would only be supported where 

required. The Stilling Basin structure would be constructed of reinforced concrete. A 

haul road would be constructed to provide access to the Stilling Basin. The footprint 

3-2 February 2008 
Chapter 3 

Affected Environment and Environmental Consequences 

of the Stilling Basin and haul road were analyzed in the EIS/EIR as they were 

included in the overall footprint of the JFP Auxiliary Spillway. 

3.1.2.3 Jet Grouting at MIAD 

The Folsom DS/FDR EIS/EIR indicated that jet grouting at MIAD would start in 

July 2008 following completion of test sections using this technology. Reclamation 

is in the process of reviewing the data collected from the test sections and has not 

made a decision on when jet grouting or an alternative measure will be implemented 

to address the stability issue with the foundation of MIAD. Additional environmental 

documentation will be completed for MIAD, as necessary. 

3.1.2.4 RWD Access Road 

Since release of the Folsom DS/FDR EIS/EIR, Reclamation has determined that the 

preferred access for haul trucks and construction equipment to the eastern side of the 

RWD would be from Folsom Dam Road. The proposed RWD access road would 

likely follow an existing dirt road, but would require widening to accommodate large 

trucks. In addition, the staging area below the RWD would be extended to 

accommodate more stockpiling of filter material during work on RWD. All other 

stockpiled material will be placed at Beal’s Point in staging area referred to as 

CSARWDN. 

Reclamation proposes to use this access point as a two-way route along the toe and 

crest of the RWD. As discussed in the EIS/EIR, approximately 40 haul trucks per 

day would use the RWD entry from Folsom Dam Road for the reconstruction of 

RWD. The haul trucks that would use the new RWD access road for RWD 

reconstruction any other effects of this action were previously addressed in the 

EIS/EIR. The RWD access road was not specifically identified in the Folsom 

DS/FDR EIS/EIR. No impacts would occur from the widening of this road as the 

area has already been cleared/graded for the JFP Auxiliary Spillway and construction 

of the New Folsom Bridge by the Corps. As part of mitigation for the Folsom 

DS/FDR Project, all transplantable elderberry shrubs have been removed from the 

area. There are no existing wetlands. The RWD access road would not introduce any 

new truck traffic and would have no additional impacts beyond those addressed in 

the EIS/EIR. 

3.2 Environmental Consequences Analysis

The resource areas listed below have the potential to be affected by the Proposed 

Action and are discussed in Sections 3.3 through 3.15 of this NEPA analysis. 

Resource areas and the reasons that they are not addressed in this Chapter are 

discussed following the listing. 

• Hydrology, Water Quality, and Groundwater 

• Air Quality 

3-3 February 2008 
Folsom Dam Safety and Flood Damage Reduction 

Supplemental Environmental Assessment/Initial Study 

• Aquatic Resources 

• Terrestrial Resources 

• Soils, Minerals, and Geological Resources 

• Visual Resources 

• Transportation and Circulation 

• Noise 

• Cultural Resources 

• Land Use, Planning, and Zoning 

• Recreation 

• Public Services and Utilities 

• Public Health and Safety 

Based on review of the above changes and clarifications in Section 3.1.1 and 3.1.2, 

and the Proposed Action, the following environmental resources were determined to 

have no impacts and are not analyzed in this NEPA analysis. These resources are: 

• Water Supply - No changes to reservoir operations would occur and the 

Proposed Action would not affect water supply. 

• Agricultural Resources - No lands are designated as agricultural within the 

project area; therefore no agricultural resources would be affected by the 

Proposed Action. 

• Population and Housing - The Proposed Action would not result in any 

impacts that would result in population or housing changes. 

• Hydropower - No changes to the releases made from Folsom Reservoir 

would occur as part of the Proposed Action and therefore there would be no 

impact to hydropower. 

• Indian Trust Assets (ITAs) - No ITAs exist within or near the project site 

and no impacts to ITAs would occur. 

• Environmental Justice - No minority or low income populations are present 

within the project area; therefore no environmental justice impacts would 

occur. 

3-4 February 2008 
Chapter 3 

Affected Environment and Environmental Consequences 

A cumulative analysis is presented for each resource area. The analysis considers 

reasonable past, present, and future projects that could occur in the area of Folsom 

Dam and Reservoir and could contribute to cumulative impacts. The cumulative 

projects considered for the analysis are listed in Table 3-1. Only the projects 

highlighted in Table 3-1 are analyzed in the cumulative analysis for this EA/IS. The 

remaining projects would not result in any cumulative impacts when considered with 

the Proposed Action. 

Table 3-1 

Cumulative Projects 

No. Project Name Description Status Relationship to 

Proposed Action 

1 New Folsom Bridge New bridge downstream of Main 

Concrete Dam 

In Construction Water Quality, Air Quality, 

Aquatic Resources, 

Geology and Soils, Traffic, 

Noise, Visual Resources, 

Public Health and Safety 

2 Folsom Dam Road Closure Closure of Dam Road for public 

safety and security reasons 

Remains Closed Traffic 

3 Lower American River 

Common Features Project 

Levee stabilization and raising in 

Lower American River, Natomas 

Cross Canal, and elsewhere in 

Sacramento region 

Ongoing Downstream of Folsom 

Reservoir and does not 

affect any resources within 

the project area 

4 Sacramento Municipal Utility 

District (SMUD) 230kV 

Transmission Line Relocation 

Relocation of transmission lines 

and towers because of 

construction of New Folsom Bridge 

Ongoing Within the project footprint 

but does not affect any 

resources 

5 Auburn-Folsom Road Widening Widening of Auburn-Folsom Road 

near Dike 5 and 6 

Anticipated Start 

Date: May 2008 

Air Quality, Visual 

Resources, Traffic, Noise, 

Public Health and Safety 

6 L.L. Anderson Dam 

Improvements 

Widen the spillway of French 

Meadows Reservoir 

Unknown Would occur upstream of 

Folsom Reservoir and 

does not affect any 

resources 

7 Long-Term Reoperation of 

Folsom Dam and Reservoir 

Interim operation agreement with 

SAFCA expires 

2018 Operational change 

analyses; no construction 

impacts 

8 Future Redundant Water 

Supply Intake and Pipeline for 

Roseville, Folsom, and San 

Juan Water District 

A new 84-inch-diameter inlet water 

pipe connected to the proposed 

Auxiliary Spillway side approach 

channel. 

Proponents have 

decided not to 

pursue this 

project 

None 

3.3 Hydrology, Water Quality, and Groundwater 

This section presents the affected environment and environmental consequences for 

hydrology, water quality, and groundwater. 

3.3.1 Affected Environment 

Snowmelt and precipitation from the upper American River Watershed discharges 

water into Folsom Reservoir. In general, runoff from the relatively undeveloped 

watershed is of high quality and rarely exceeds the State of California’s water quality 

objectives (Wallace, Roberts, and Todd et al. 2003). The following beneficial uses 

3-5 February 2008 
Folsom Dam Safety and Flood Damage Reduction 

Supplemental Environmental Assessment/Initial Study 

have been defined by the Central Valley Regional Water Quality Control Board 

(CVRWQCB) for Folsom Reservoir and Lake Natoma: municipal and domestic 

water supply; irrigation; industrial power; water contact and non-contact recreation; 

warm and cold freshwater habitat, warm freshwater spawning habitat; and wildlife 

habitat, along with potential beneficial uses for industrial service supply. Water 

quality within Folsom Reservoir and Lake Natoma is generally acceptable to meet 

the beneficial uses currently designated for these waterbodies. 

Folsom Reservoir is located at the eastern edge of the Sacramento Valley 

Groundwater Basin, in the North American and South American subbasins. The area 

surrounding Folsom Reservoir primarily consists of bedrock formations of the Sierra 

Nevada foothill complex. Although groundwater is not a major resource in the 

vicinity of Folsom Reservoir, small amounts of groundwater are typically found in 

granitic fissures and cracks. Because fractured aquifer systems are typically low 

yielding, surface water sources are primarily used for drinking water or irrigation 

water sources rather than wells. 

For the Phase 1 construction contract currently underway, Reclamation has obtained 

the Clean Water Act (CWA) Section 404 dredge and fill permit from the Corps for 

the wetlands and waters of the U.S. affected by the authorized Folsom DS/FDR 

Project. Reclamation has also obtained CWA Section 401 water quality certification 

from the CVRWQCB. Reclamation’s Construction Contractor has filed a Notice of 

Intent with the CVRWQCB as part of the National Pollutant Discharge Elimination 

System (NPDES) permit. The Construction Contractor has developed a Storm Water 

Pollution Prevention Plan (SWPPP) to prevent water quality impacts associated with 

storm water runoff from the construction site. Best management practices (BMPs) 

have been implemented at the construction site in accordance with the SWPPP. 

3.3.2 Environmental Consequences 

This section presents the environmental consequences of the Proposed Action and 

the No Action Alternative. 

3.3.2.1 No Action Alternative 

Dike 5 Construction Site Access and Trail Detour 

There would be no change to the affected environment. 

Cofferdam 

Without the use of a cofferdam, construction of the Stilling Basin could contribute to 

water quality impacts. During construction of the Stilling Basin, construction 

materials, storm water runoff, and groundwater encountered during excavation could 

be discharged directly into the American River channel. 

3-6 February 2008 
Chapter 3 

Affected Environment and Environmental Consequences 

3.3.2.2 Proposed Action 

Dike 5 Construction Site Access and Trail Detour 

Construction of the Dike 5 access could result in some minor storm water runoff 

impacts. The Construction Contractor would obtain an NPDES Permit and 

implement a SWPPP to prevent any water quality impacts associated with storm 

water runoff. A drainage ditch runs parallel to Auburn-Folsom Road where the turn 

in and turn out lanes and access road would be constructed. A culvert would be 

installed to maintain storm water drainage. 

No adverse impacts to hydrology, water quality, or groundwater would result from 

the Dike 5 Construction Site Access and Trail Detour. 

Cofferdam 

During excavation activities involving the Stilling Basin, groundwater could be 

encountered. This water may have elevated levels of certain constituents which 

would cause it to exceed applicable surface water quality objectives and regulations. 

Reclamation and the Construction Contractor would test the water and obtain 

appropriate dewatering permits from the CVRWQCB before discharging it to any 

surface waters. This would reduce the potential for water quality impacts from 

dewatering during construction. 

Construction of the Cofferdam would temporarily confine the existing floodway 

channel along the construction site. Hydrological modeling of the water flow and 

elevation changes has identified no substantial upstream or downstream hydrological 

effects. The lowest elevation of the Cofferdam wall would be 133 ft. (Note the 

terrain along the axis of the proposed Cofferdam varies and not all of the Cofferdam 

would be in contact with river water during releases.) Typical discharges from 

Folsom Dam would place river water elevation at 131 ft. However, it is expected 

river elevation during 50% of the releases from Folsom Dam would contact the 

lower portion of the Cofferdam. For higher discharge events, tailwater is controlled 

by the downstream channel configuration. Therefore, the Cofferdam may slightly 

raise the tailwater level immediately adjacent to the Cofferdam but this effect would 

not be carried downstream of the project site. 

Placement of a Cofferdam as either a concrete wall or cellular type would be 

designed as to not constrain downstream flows such as to cause a measurable change 

in river water elevation at any flow rate. The Cofferdam would not change the 

downstream water surface elevation. 

3.3.3 Cumulative Effects 

The Cofferdam and the New Folsom Bridge Project would be built in the same 

vicinity and have the potential for water quality impacts as a result of construction 

activities. Each project is required to obtain an NPDES permit and implement a 

3-7 February 2008 
Folsom Dam Safety and Flood Damage Reduction 

Supplemental Environmental Assessment/Initial Study 

SWPPP. With implementation of a SWPPP and appropriate BMPs, the Proposed 

Action would be unlikely to contribute to cumulative water quality impacts. 

3.4 Air Quality 

This section presents the affected environment and environmental consequences for 

air quality. 

3.4.1 Affected Environment 

The Sacramento area is classified as a non-attainment area for the ozone (O3) and 

particulate matter less than 10 microns in diameter (PM10) California Ambient Air 

Quality Standards. Other criteria pollutants addressed below include volatile organic 

compounds (VOC), nitrogen oxides (NOx), carbon monoxide (CO), sulfur dioxide 

(SO2), and particulate matter less than 2.5 microns in diameter (PM2.5) 

The affected environment for air quality remains similar to that described in the 

Folsom DS/FDR EIS/EIR with a few exceptions. The schedule for the Dike 5 

construction has been shifted ahead of that originally proposed so that all 

construction will occur during 2008 and 2009. Furthermore, jet grouting at MIAD is 

not expected to occur in the 2008 and 2009 timeframe because Reclamation is in the 

process of reviewing test data. Emissions from jet grouting at MIAD have therefore 

been removed from the environmental analysis. Construction at LWD, RWD, and 

the Auxiliary Spillway has commenced and Reclamation’s Construction Contractor, 

has paid the appropriate emission mitigation fees to the Sacramento Metropolitan Air 

Quality management District (SMAQMD). 

3.4.2 Environmental Consequences 

This section presents the environmental consequences of the Proposed Action and 

the No Action Alternative. The emissions values presented as part of this air quality 

analysis are only estimates. The actual values will not be known until the 

Construction Contractor is onsite and has determined the exact equipment to be used. 

3.4.2.1 No Action 

Dike 5 Construction Site Access and Trail Detour 

There would be no change to the affected environment. 

Cofferdam 

There would be no change to the affected environment. 

3.4.2.2 Proposed Action 

Dike 5 Construction Site Access and Trail Detour 

In the Folsom DS/FDR Final EIS/EIR, work at Dike 5 was scheduled to start in 

September 2009. Due to SOD schedule priorities, Reclamation has elected to initiate 

the Dike 5 work by September 2008, continuing into 2009. The air quality impacts 

3-8 February 2008 
Chapter 3 

Affected Environment and Environmental Consequences 

related to construction at Dike 5 were already addressed in the Final EIS/EIR; the 

only action related to the Supplemental EA/IS is the date adjustment. 

Emissions estimates for Dike 5 construction equipment and haul trucks are 

summarized in Table 3-2. Both daily and project-level emissions (i.e., tons per year) 

are less than the Placer County Air Pollution Control District (PCAPCD) and 

General Conformity thresholds in 2008 and 2009. 

Table 3-2 

Summary of Emissions at Dike 5 

Pollutant 

NOx ROG1 CO PM10 PM2.5

Year Pounds per Day 

2008 64.66 7.28 29.40 2.90 2.67 

2009 60.95 6.96 27.90 2.76 2.51 

Thresholds 82 82 550 82 n/a 

Tons per Year 

2008 1.46 0.16 0.66 0.065 0.060 

2009 1.38 0.16 0.63 0.062 0.057 

Thresholds 50 50 100 100 n/a 1

 Reactive organic gases 

As is shown in Table 3-2, emissions are less than the PCAPCD thresholds for Dike 5 

construction, and therefore no substantial air quality impacts would occur. 

Combined emissions from Dike 5 and other Folsom DS/FDR actions scheduled for 

2008 and 2009 were reviewed to evaluate compliance with General Conformity. 

Table 3-3 summarizes total emissions from the project. 

Table 3-3 

Summary of Total Emissions for 2008 and 2009

Emissions (tpy) 

Pollutant 2008 2009 

General Conformity 

Threshold (tpy) 

NOx 43.9 27.5 50 

CO 41.5 17.0 100 

PM10 54.8 55.1 100 

As is demonstrated in Table 3-3, emissions would be less than the applicable General 

Conformity thresholds and therefore no adverse air quality impacts are expected. 

Overall, the change in schedule for the Dike 5 work is not expected to result in any 

substantial air quality impacts. 

Construction for the Trail Detour would have minimal impacts to air quality given 

the limited types of construction equipment required and the short time-frame 

required to grade and surface the trail route. 

3-9 February 2008 
Folsom Dam Safety and Flood Damage Reduction 

Supplemental Environmental Assessment/Initial Study 

Cofferdam 

The construction of the Cofferdam would require more trucks than originally 

assessed in the Folsom DS/FDR EIS/EIR to bring required materials to the site. It is 

expected that 40 trucks per day would be hauling material from local sites over a 45-

day period in 2009. Of these trucks, 30 would be hauling concrete and the remaining 

10 would be hauling steel. 

Emission Calculation Methodology 

The haul truck engine emissions estimates were calculated using EMFAC2002 

emission factors for heavy-duty diesel trucks in the Sacramento Valley Air Basin and 

estimates of total vehicle miles traveled per day. The emission factors used in this 

analysis are presented in Table 3-4. The average speed for off-site hauling was 

assumed to be 30 miles per hour (mph). 

Table 3-4 

Heavy-Duty Diesel Truck Emission Factors for Sacramento Valley (30 mph)

Pollutant Emission Factor (g/VMT) 

VOC/ROG 0.676 

CO 2.506 

NOx 11.147 

PM10 Total(1) 0.343 

SO2 0.021 

PM2.5 Total(1) 0.285 

(1)PM10 and PM2.5 totals include engine exhaust, tire wear, and brake wear. 

g/VMT = gallons per vehicle miles traveled

Re-entrained road dust from haul truck travel was estimated for paved and unpaved 

roads. Paved road dust was estimated using emission factors developed by the 

Midwest Research Institute (MRI 1996), presented in Table 3-5. The emission factor 

of 0.81 gallons per vehicle mile traveled (g/VMT) for average conditions was used in 

the analysis. 

Table 3-5 

Paved Road Re-entrained Dust PM10 Emission Factors (g/VMT) 

Average Daily Trips (ADT) 

Road Condition High Low Average 

Average conditions 0.37 1.3 0.81 

Worst-case conditions 0.64 3.9 2.1 

Source: (Midwest Research Institute 1996). 

Consistent with the original analysis, concrete and steel would be transported from 

local sites with a maximum roundtrip distance of 50 miles. Both exhaust emissions 

and re-entrained dust from paved roads were calculated for the hauling trucks above. 

3-10 February 2008 
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Affected Environment and Environmental Consequences 

Emission Inventories 

Construction impacts were estimated following the methodology described above. 

Table 3-6 provides a summary of peak daily and annual emission rates for VOC, 

NOx, CO, SO2, PM10, and PM2.5. In cases where emission factors were only provided 

for PM10, appropriate California Air Resources Board (CARB) PM size profiles were 

used to estimate PM2.5 emissions. Emissions are provided from the Cofferdam’s 

contribution only, as well as for the overall project. 

Table 3-6 

Uncontrolled Construction Emission Inventories 

Pollutant Cofferdam Emissions 

Peak Daily Emissions in lbs/day 

VOC 4.7 

NOx 76.9 

CO 17.5 

SO2 <1 

PM10 8.8 

PM2.5 3.1 

Peak Annual Emissions in tons/year 

VOC <1 

NOx 2 

CO <1 

SO2 <1 

PM10 <1 

PM2.5 <1 

NOx has a short-term (construction) significance threshold of 85 pounds per day. 

Under the General Conformity Rule, NOx and VOC each have a 50 tons per year 

(tpy) de minimis threshold, PM10 has a 100 tpy de minimis threshold, and CO has a 

100 tpy de minimis threshold. The emission estimates provided in Table 3-6 

indicates the uncontrolled NOx emissions would not exceed the SMAQMD’s daily 

emission rates, nor would uncontrolled NOx, PM10, and CO emissions exceed the 

General Conformity de minimis thresholds. 

Based on this analysis, construction of the Cofferdam itself would not cause an 

adverse impact that exceeds applicable thresholds. Since the peak annual emissions 

only represent a modest emissions increase, the General Conformity thresholds 

would not be exceeded when added to the other Folsom DS/FDR actions planned for 

2008 and 2009. Although emissions at the Cofferdam would not exceed 

SMAQMD’s daily thresholds, when combined with other Folsom DS/FDR actions 

happening concurrently, daily emissions would be considered substantial. The 

Cofferdam work would be operated in compliance with minimization measures 

described below and any necessary fees to the SMAQMD’s mitigation fund would 

be paid. The minimization measures described below would adequately address the 

air quality impacts associated with the Cofferdam. 

3-11 February 2008 
Folsom Dam Safety and Flood Damage Reduction 

Supplemental Environmental Assessment/Initial Study 

3.4.3 Minimization Measures 

Reclamation and the Construction Contractor will submit a plan for approval by 

SMAQMD, demonstrating that the heavy-duty off-road vehicles will achieve a 

project-wide fleet average 20 percent NOx reduction and 45 percent particulate 

reduction. The plan will also have to include an inventory of all off-road construction 

equipment equal to or greater than 50 horsepower that will be used an aggregate of 

40 or more hours during any portion of the project. Reclamation and the 

Construction Contractor will also have to demonstrate conformity with NOx 

thresholds, apply fugitive dust control on roadways, processing plants, and concrete 

batch plants and obtain power for construction facilities from the electric utility grid 

rather than diesel-driven generators and pumps. The Construction Contractor will be 

encouraged to seek additional control measures as part of emissions offsets. 

The above analysis estimates that project-wide emissions from the Cofferdam and 

ongoing operations related to the overall Folsom DS/FDR would exceed 85 pounds 

per day. Such operational impacts were previously addressed in the Folsom DS/FDR 

EIS/EIR and, as described therein, a mitigation fee will be paid to SMAQMD’s 

mitigation fund for any excess emissions. Emissions from the Cofferdam will be 

offset with the appropriate payment of this mitigation fee. 

3.4.4 Cumulative Effects 

Although construction of the Cofferdam would lead to air quality impacts, these 

impacts would be reduced by minimization measures discussed above. The New 

Folsom Bridge Project would also have the potential to impact air quality. Although 

the projects are occurring concurrently, both will employ minimization measures to 

reduce emissions to below the threshold levels. The Auburn-Folsom Road Widening 

Project has the potential to impact air quality and could occur concurrently with 

construction at Dike 5. Both projects will apply minimization measures as needed to 

reduce emissions below the appropriate threshold levels. Since all of the projects will 

minimize emissions as needed and required, the Proposed Action is not expected to 

contribute to cumulatively considerable air quality impacts. 

3.5 Aquatic Resources 

This section presents the affected environment and environmental consequences for 

aquatic resources. 

3.5.1 Affected Environment 

Native and introduced fishes are present in the Folsom Reservoir area. Native fishes 

occur primarily as a result of their continued existence in tributaries of Folsom 

Reservoir and Lake Natoma. Two native species are planted in Folsom Reservoir for 

fishing, rainbow trout and Chinook salmon. The populations of most other species 

are currently self-supporting. Introduced fishes are more commonly found in the 

3-12 February 2008 
Chapter 3 

Affected Environment and Environmental Consequences 

reservoirs than are native fishes. Most of these fishes were introduced into the State 

as game fish or as forage fish to support game fish populations. 

The lower American River has been designated as Critical Habitat for spring-run 

Chinook salmon, and steelhead. Anadromous fish, such as Chinook salmon and 

steelhead can access about 23 miles of the lower American River downstream of 

Nimbus Dam but do not ascend the river beyond Nimbus Dam. 

No vernal pools have been identified within the Dike 5 area, the Trail Detour area, or 

the Cofferdam area. 

3.5.2 Environmental Consequences 

This section presents the environmental consequences of the Proposed Action and 

the No Action Alternative. 

3.5.2.1 No Action Alternative 

Dike 5 Construction Site Access and Trail Detour 

There would be no changes to the affected environment. 

Cofferdam 

Aquatic habitat occurs downstream of the Stilling Basin. Without construction of the 

Cofferdam, water quality impacts on aquatic resources could occur during work on 

the Stilling Basin. Construction materials, storm water runoff, and groundwater 

encountered during excavation activities could be released into the American River 

channel and could adversely affect aquatic habitats. 

3.5.2.2 Proposed Action 

Dike 5 Construction Site Access and Trail Detour 

No aquatic resources are expected to be impacted by the construction of the Dike 5 

Construction Site Access or the Trail Detour. 

Cofferdam 

Aquatic habitat occurs downstream of the Stilling Basin and Cofferdam construction 

area. This habitat may be affected by construction activities including increased 

erosion and sedimentation or dewatering of the Stilling Basin. The current NPDES 

permit and SWPPP in place for the Folsom DS/FDR Project covers the area where 

the Stilling Basin would be constructed. This permit requires the implementation of 

BMPs to reduce or eliminate the potential for storm water runoff and erosion from 

the construction site. Any groundwater encountered during construction would be 

tested to ensure no adverse water quality impacts would occur before it is discharged 

to any surface water. The Cofferdam would be unlikely to create any substantial 

adverse effects to aquatic habitat with the proper implementation of BMPs described 

in the SWPPP and with testing of groundwater before it is discharged to surface 

water to ensure there are no contaminants. 

3-13 February 2008 
Folsom Dam Safety and Flood Damage Reduction 

Supplemental Environmental Assessment/Initial Study 

As described in Section 3.3 above, construction of the Cofferdam would temporarily 

confine the existing floodway channel along the construction site. Hydrological 

modeling of the water flow and elevation changes has identified no substantial 

upstream or downstream hydrological effects. The Cofferdam may slightly raise the 

tailwater level immediately adjacent to the Cofferdam but this effect would not be 

carried downstream of the project site. Placement of a Cofferdam would be designed 

as to not constrain downstream flows such as to cause a measurable change in river 

water elevation at any flow rate. The Cofferdam would not change the downstream 

water surface elevation. 

3.5.3 Cumulative Effects 

The implementation of the Proposed Action could lead to cumulative impacts when 

considered with projects in the same area. The Folsom Bridge Project could be under 

construction at the same time as the Cofferdam and could have some impacts to 

aquatic resources. However, these impacts have been disclosed in environmental 

documents and all impacts would be mitigated to the greatest extent possible. With 

proper implementation of BMPs as part of the SWPPP, the Cofferdam would not 

contribute to any cumulatively considerable impacts on aquatic resources. 

3.6 Terrestrial Resources 

This section presents the affected environment and environmental consequences for 

terrestrial resources. 

3.6.1 Affected Environment 

The project area is dominated by aquatic habitat within Folsom Reservoir, but stands 

of native vegetation occupy much of the area adjacent to the shoreline. This area 

supports seven major terrestrial vegetation types that are typical of the foothills of 

California’s Central Valley. These types include: interior live oak woodland, blue 

oak woodland and savanna, annual grassland, chaparral, cottonwood-willow riparian, 

freshwater marsh, and seasonal wetland. Examples of wildlife associated with these 

habitat types include woodpeckers (Picoides nuttallii), northern flickers (Colaptes 

auratus), whitebreasted nuthatches (Sitta carolinensis), oak titmice (Baeolophus 

inornatus), western gray squirrels (Sciurus griseus), raccoons (Procyon lotor), hoary 

bat (Lasiurus cinereus), pallid bat (Antrozous pallidus),California quail, (Callipepla 

californica), wild turkeys (Meleagris gallopavo), northern flickers, western scrubjays (Aphelocoma californica), ruby-crowned kinglets (Regulus calendula), bushtits 

(Psaltriparus minimus), warbling vireos (Vireo gilvus), Hutton’s vireos (Vireo 

huttoni), Wilson’s warblers (Wilsonia pusilla), American robins (Turdus 

migratorius), Bullock’s orioles (Icterus bullockii), house finches (Carpodacus 

mexicanus), spotted towhees, gopher snakes, common kingsnakes (Lampropeltis 

getula), bobcats, gray foxes, striped skunks (Mephitis mephitis), mule deer, and a 

variety of rodents. 

3-14 February 2008 
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Affected Environment and Environmental Consequences 

Based on known occurrences and quality of existing habitat, a total of 27 specialstatus terrestrial wildlife species have the potential to occur in the project area. These 

species include one invertebrate, three amphibians, three reptiles, sixteen birds and 

four mammals. Additionally, a total of five special-status plant species have potential 

to occur in the project area. Please see the Folsom DS/FDR Draft EIS/EIR for a 

complete description of terrestrial vegetation and wildlife within the project area. 

3.6.2 Environmental Consequences 

This section presents the environmental consequences of the Proposed Action and 

the No Action Alternative. 

3.6.2.1 No Action Alternative 

Dike 5 Construction Site Access and Trail Detour 

There would be no changes to the affected environment. 

Cofferdam 

There would be no changes to the affected environment. 

3.6.2.2 Proposed Action 

The majority of the Proposed Action would occur within the existing footprint of the 

Folsom DS/FDR Project currently under construction. Most terrestrial resources 

within this area would already be substantially disturbed or disrupted by construction 

of other aspects of the Folsom DS/FDR Project. For instance, the Cofferdam would 

be constructed within the footprint of the JFP Auxiliary Spillway. Impacts from 

construction of the Auxiliary Spillway are described and mitigated for in the Folsom 

DS/FDR EIS/EIR. The analysis below accounts for any impacts not described in the 

EIS/EIR. 

Section 7 consultation under the Endangered Species Act (ESA) was completed for 

Folsom DS/FDR Project effects to the federally listed valley elderberry longhorn 

beetle and vernal pool crustaceans on April 5, 2007 and amended on December 5, 

2007 and January 31, 2008. As required by the U.S. Fish and Wildlife Service 

(USFWS) Biological Opinion dated April 5, 2007, all elderberry shrubs from Dike 4 

down to the RWD have been removed within the Folsom DS/FDR Project area. 

Therefore the Proposed Action would have no effect on valley elderberry longhorn 

beetles. 

The USFWS Biological Opinion dated April 5, 2007, determined that the Folsom 

DS/FDR Project may adversely affect vernal pool fairy shrimp and vernal pool 

tadpole shrimp. No suitable habitat (i.e. vernal pools) occurs within the affected 

environment of this EA/IS, therefore the Proposed Action would have no effect on 

vernal pool fairy shrimp and vernal pool tadpole shrimp. 

3-15 February 2008 
Folsom Dam Safety and Flood Damage Reduction 

Supplemental Environmental Assessment/Initial Study 

The USFWS Biological Opinion dated April 5, 2007, had determined that though 

other federally listed species, such as the El Dorado bedstraw, Layne's Butterweed, 

California red-legged frog, and giant garter snake, may occur in Sacramento and/or 

Placer Counties, the project area is outside the known habitats for these species, and, 

therefore, the USFWS has determined that the project may affect but is not likely to 

adversely affect these species. Although the Proposed Action would affect an area 

outside the original DS/FDR footprint analyzed in the Biological Opinion, the 

Proposed Action would occur in similar habitat that is directly adjacent to the habitat 

of the original footprint and therefore it is assumed that no adverse effect on other 

federally listed species, including the El Dorado bedstraw, Layne's butterweed, 

California red-legged frog, and giant garter snake would occur. 

Dike 5 Construction Site Access and Trail Detour 

The Dike 5 staging area impacts were already disclosed in the EIS/EIR. The Dike 5 

Construction Site Access would not result in any changes to impacts from those 

already disclosed in the EIS/EIR because construction would occur within the same 

footprint. 

Oak woodlands and annual grasslands are present within the Dike 5 Construction 

Site Access and Trail Detour construction areas and may be affected by activities 

including vegetation trimming and cut and fill to widen the trail. Oak woodland and 

annual grassland provide resting, nesting, and forage habitat for a variety of wildlife. 

The Trail Detour would be rerouted to avoid the removal of trees and other 

vegetation but may require some trimming of vegetation to obtain the proper width. 

The Trail Detour would be constructed along existing dirt trails as much as possible 

to reduce vegetation and wildlife impacts. The Trail Detour would not be paved, but 

would be created mainly using native materials found onsite. Impacts to terrestrial 

resources are expected to be minimal. 

Although wetland habitats, such as seasonal wetlands and swales, are present within 

the Trail Detour construction area, the trail would be rerouted to avoid such areas or 

spans would be constructed to cross over them. Overall, the Trail Detour is not 

expected to require removal, filling, or hydrological disruption of seasonal wetlands 

and swales. 

Cofferdam 

Because the RWD, LWD, JFP Auxiliary Spillway, and haul road to MAID areas 

have already been cleared of vegetation, no terrestrial resources are expected to be 

impacted by the construction of the Cofferdam. 

3.6.3 Cumulative Effects 

The Proposed Action would lead to a minimal amount of impacts on terrestrial 

resources from construction of the Trail Detour. No other cumulative projects would 

3-16 February 2008 
Chapter 3 

Affected Environment and Environmental Consequences 

occur in the area of the Trail Detour; therefore, there would be no cumulative effects 

to terrestrial resources. 

3.7 Soils, Minerals, and Geological Resources 

This section presents the affected environment and environmental consequences for 

soils, minerals, and geological resources. 

3.7.1 Affected Environment 

Reclamation’s Construction Contractor is currently in the process of clearing the 

Phase 1 area to prepare for construction. As described above under Hydrology, 

Water Quality, and Groundwater, a SWPPP has been implemented to control erosion 

and prevent storm water runoff. 

No seismic issues or unstable soils occur in the area of the Proposed Action. The 

potential for landslides is low because of relatively thin soils. Although the Bear 

Mountain fault occurs north of the project area, this fault has not been designated as 

active by the U.S. Geological Survey and the ground shaking potential for the region 

is generally low. 

3.7.2 Environmental Consequences 

This section presents the environmental consequences of the Proposed Action and 

the No Action Alternative. 

3.7.2.1 No Action Alternative 

Dike 5 Construction Site Access and Trail Detour 

There would be no changes to the affected environment. 

Cofferdam 

There would be no changes to the affected environment. 

3.7.2.2 Proposed Action 

Dike 5 Construction Site Access and Trail Detour 

Construction of the new access road and turning lanes at Dike 5 would be unlikely to 

result in any soil erosion or loss of topsoil as the lanes and road would be paved. 

Construction vehicles and equipment entering and exiting the Dike 5 area could 

cause some soil erosion and dust if they move off the road. The proper 

implementation of the SWPPP would help to reduce the impacts from erosion. In 

addition, vehicles and equipment would be maintained in designated areas to reduce 

the erosion potential. 

The Trail Detour would require some cut and fill to provide appropriate slopes. A 

small quantity of topsoil would likely be removed and placed elsewhere onsite. The 

Trail Detour would be covered with native materials which would reduce the 

potential for soil erosion. In addition, the Trail Detour would improve the outslope 

3-17 February 2008 
Folsom Dam Safety and Flood Damage Reduction 

Supplemental Environmental Assessment/Initial Study 

and alignment of some existing trails and thereby reduce erosion. Also by providing 

one well defined well built trail that a variety of recreational users may use, erosion 

on adjacent rudimentary trails would be reduced. Geology and soils impacts from the 

Trail Detour construction are expected to be minimal. 

Cofferdam 

Construction of the Stilling Basin and Cofferdam would occur in an area that 

consists mainly of decomposed granite and would be unlikely to contribute to soil 

erosion with proper implementation of BMPs as outlined in the SWPPP. 

3.7.3 Cumulative Effects 

The Proposed Action would not be expected to lead to cumulative impacts. The only 

other project in the area, the New Folsom Bridge Project, has analyzed impacts to 

soils and geological resources in an environmental document and has developed 

measures to reduce these impacts. Both the Proposed Action and the New Folsom 

Bridge Project are required to implement SWPPPs which contain BMPs to reduce 

soil erosion and storm water runoff. Adherence to the SWPPP measures combined 

with diligent coordination between both projects would prevent cumulative impacts. 

3.8 Visual Resources 

This section presents the affected environment, and environmental consequences for 

visual resources. 

3.8.1 Affected Environment 

The proposed location for the Trail Detour is the downstream side of Dikes 4, 5, and 

6. The area contains views of grasslands, oak woodlands, and wetlands. Several 

unimproved recreation trails are visible in the area. The downstream side of Dike 5 

contains mostly grasslands that continue to Auburn-Folsom Road. Existing trails 

cross through the proposed staging area at Dike 5. Auburn-Folsom Road is visible 

from the trails on the downstream side of Dike 5. 

The area around the JFP Auxiliary Spillway and Stilling Basin is currently under 

construction. The area has been cleared and excavation activities are expected to 

commence in early 2008. The New Folsom Bridge is also under construction in this 

area and has cleared a large portion of land below RWD. Construction equipment 

and vehicles are visible throughout the week. 

3.8.2 Environmental Consequences 

This section presents the environmental consequences of the Proposed Action and 

the No Action Alternative. 

3-18 February 2008 
Chapter 3 

Affected Environment and Environmental Consequences 

3.8.2.1 No Action Alternative 

Dike 5 Construction Site Access and Trail Detour 

There would be no changes to the affected environment. 

Cofferdam 

There would be no changes to the affected environment. 

3.8.2.2 Proposed Action 

Dike 5 Construction Site Access and Trail Detour 

Construction of a traffic light and turning lanes on Auburn-Folsom Road would 

affect views of the area from several homes across the street and may be visible from 

recreation users on the trails. The traffic light and/or flagmen and turning lanes, as 

well as construction vehicles, would be visible at certain times of the day. There may 

also be flashing lights to the north and south of the new traffic light to warn drivers 

of stopped traffic. These impacts would only be temporary. The light would be 

constructed prior to work on Dike 5 and when Dike 5 work is complete, the light 

would be placed in an inactive (or stand- by) mode or removed until Dike 4 and 6 

work begins. When construction is complete at all of the dikes, the traffic light 

and/or flagmen would be removed. The turn lanes would also be removed and the 

road would be restored to pre-construction conditions. In the event that the Placer 

County commences construction of the Road Widening Project in the Dike 5 area, 

the agencies would coordinate to determine how the road would be restored. 

The Trail Detour could require the trimming of some trees and vegetation and would 

create a 5-to 6-ft wide trail composed of native materials. Portions of the trail would 

be constructed along an existing unimproved trail. Reclamation would avoid 

removing trees by re-routing the trail around them. Up to three construction vehicles 

would be required to construct the trail, which could take up to six months. The area 

cleared for the Trail Detour would be visible to users on the Pioneer Express Trail 

and other existing trails in the area. Construction of the Trail Detour and the 

trimming of vegetation would have a minimal affect to the visual quality of the area. 

The existing trail on top of Dikes 4, 5, and 6 has views of Folsom Reservoir and the 

shoreline. The Trail Detour would not have views of the reservoir because of its 

location on the downstream side of the dikes. The Trail Detour would instead 

provide views of wetlands, grasslands, and oak woodland. Because the Trail Detour 

would be temporary and would still provide views of natural landscapes, no 

substantial adverse effects are expected to visual resources. 

Cofferdam 

Construction of the Cofferdam is not expected to substantially degrade the existing 

visual character of the area. The area would already be substantially changed due to 

construction of the JFP Auxiliary Spillway and Stilling Basin. The Cofferdam would 

be constructed to ensure the Stilling Basin area remains dry during construction and 

3-19 February 2008 
Folsom Dam Safety and Flood Damage Reduction 

Supplemental Environmental Assessment/Initial Study 

would be partially or fully removed after construction is complete. The area of the 

JFP Auxiliary Spillway is not open to the public and would only be partially visible 

from traffic on the New Folsom Bridge being constructed by the Corps. The 

construction of the Cofferdam would not alter scenic vistas or views from scenic 

highways. Because it would be constructed in a disturbed area that is not open to the 

public, and it would be fully or partially removed after construction, this is not 

expected to adversely affect visual resources. 

3.8.3 Cumulative Effects 

It is unlikely that any substantial cumulative effects would occur to visual resources. 

The area of the Cofferdam is in close proximity to the New Folsom Bridge but is not 

open to the public and is generally not visible from any of the recreation areas or 

trails. The area would already be disturbed for construction of the JFP Auxiliary 

Spillway and the New Folsom Bridge and is not expected to contribute to a 

cumulative impact to visual resources. 

The Dike 5 area could be altered by construction of a temporary intersection and by 

construction traffic entering the site. At the same time, Placer County would be 

constructing the Auburn-Folsom Road Widening Project. This project is expected to 

be working south of the Dike 5 area but would have temporary visual impacts related 

to construction equipment and vehicles. The Proposed Action and the Placer County 

Road Widening Project would have construction-related visual impacts on AuburnFolsom Road but these would be temporary. Additionally, Phase 1 of the Road 

Widening Project would occur south of the Proposed Action. Overall, the Proposed 

Action would not contribute to any substantial cumulative visual impacts. 

3.9 Transportation and Circulation 

This section presents the affected environment and environmental consequences for 

transportation and circulation. 

3.9.1 Affected Environment 

3.9.1.1 Area of Analysis 

The roadways within the study area of the Supplemental EA/IS are within 

Sacramento County, Placer County, and the city of Folsom. Each of these 

jurisdictions has adopted standards regarding the desired performance level for 

traffic conditions on the circulation system within its jurisdiction. A measure called 

“Level of Service” (LOS) is used to characterize traffic conditions. Progressively 

worsening traffic conditions are given the letter grades “A” through “F”. While most 

motorists consider an “A”, “B”, “C” LOS as satisfactory, LOS “D” is considered 

marginally acceptable. Congestion and delay are considered unacceptable to most 

motorists and given the LOS “E” or “F” ratings. A more detailed explanation of LOS 

and how it is determined is provided in Section 3.9.3.1 of the DS/FDR EIS/EIR. 

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Affected Environment and Environmental Consequences 

These LOS thresholds, reflected at the local jurisdiction level through the County 

and City General Plans, define the minimum levels of acceptable traffic conditions 

within the respective jurisdictions, typically LOS C or, in more urbanized areas, LOS 

D. Related to those LOS thresholds are additional thresholds used to determine 

where a change in traffic conditions, such as that associated with additional traffic 

from a new development project, would result in a substantial impact to the local 

roadway system. Should a substantial impact be identified, the formulation of 

minimization measures for that impact is warranted. Table 3-7 presents the local and 

regional LOS standards and associated thresholds used in this impact analysis. 

Table 3-7 

Local and Regional LOS Standards and Significance Thresholds 

Regulatory 

Agency

Standards Significance Thresholds

Roadways/Signalized Intersections: A project is considered to have a 

significant effect if it would:

• result in a roadway or a signalized intersection operating at an acceptable 

LOS to deteriorate to an unacceptable LOS; or 

• increase the volume to capacity (V/C) ratio by more than 0.05 at a roadway 

or at a signalized intersection that is operating at an unacceptable LOS without 

the project. 

Unsignalized Intersections: A project is considered to have a significant effect 

if it would: 

• result in an unsignalized intersection movement/approach operating at an 

acceptable LOS to deteriorate to an unacceptable LOS, and also cause the 

intersection to meet a traffic signal warrant; or 

• for an unsignalized intersection that meets a signal warrant, increase the 

delay by more than 5 seconds at a movement/approach that is operating at an 

unacceptable LOS without the project. 

Freeway Ramps: A project is considered to have a significant effect if it would: 

• result in a facility operating at an acceptable LOS to deteriorate to an 

unacceptable LOS, according to the LOS threshold defined by Caltrans. 

Freeway Segments: A project is considered to have a significant effect if it 

would: 

• result in a facility operating at an acceptable LOS to deteriorate to an 

unacceptable LOS, according to the LOS threshold defined in the Caltrans 

Route Concept Report for that facility. 

Residential Streets: A project is considered to have a significant effect if it 

would: 

• result in a residential street operating at an acceptable LOS to deteriorate to 

an unacceptable LOS; or 

• increase the V/C ratio by more than 0.05 at a residential street that is 

operating at an unacceptable LOS without the project. 

Bicycle and Pedestrian Facilities: A project is considered to have a significant 

effect if it would:

• eliminate or adversely affect an existing bikeway or pedestrian facility in a 

way that would discourage its use; 

• interfere with the implementation of a planned bikeway as shown in the 

Bicycle Master Plan, or be in conflict with the Pedestrian Master Plan; or 

• result in unsafe conditions for bicyclists or pedestrians, including unsafe 

bicycle/pedestrian, bicycle/motor vehicle, or pedestrian/motor vehicle conflict. 

Safety: A project is considered to have a significant effect if it would: 

Sacramento 

County 

Rural collectors: 

LOS D 

Urban area 

roads: 

LOS E 

• substantially increase hazards due to a design feature (e.g., sharp curves or 

dangerous intersections) or incompatible uses (e.g., farm equipment). 

3-21 February 2008 
Folsom Dam Safety and Flood Damage Reduction 

Supplemental Environmental Assessment/Initial Study 

Table 3-7 

Local and Regional LOS Standards and Significance Thresholds 

Regulatory 

Agency

Standards Significance Thresholds

City of 

Folsom 

LOS C If the “no project” LOS is LOS C or better and the project-generated traffic 

causes the intersection level of service to degrade to worse than LOS C (i.e., 

LOS D, E or F) then the proposed project must implement mitigation measures 

to return the intersection to LOS C or better. If the “no project” LOS is worse 

than LOS C (i.e., LOS D, E or F) and the project-generated traffic causes the 

overall average delay value at the intersection to increase by five seconds or 

more, then the Folsom DS/FDR must implement mitigation measures to 

improve the intersection to the “no project” condition or better. It is not 

necessary to improve the intersection to LOS C. If the “no project” LOS is 

worse than LOS C (i.e., LOS D, E, or F) and the project-generated traffic 

causes the overall delay value at the intersection to increase by less than five 

seconds, then the traffic impact is considered less than significant and no 

mitigation is required. 

Placer 

County 

LOS C on rural 

roadways, except 

within one-half 

mile of state 

highways where 

the standard 

shall be LOS D. 

LOS C on 

urban/suburban 

roadways except 

within one-half 

mile of state 

highways where 

the standard 

shall be LOS D. 

Require mitigation to LOS C unless an intersection is within one-half mile of a 

State Highway, in which case the LOS standard is "D". This applies where the 

existing LOS is at these levels, or better. If the LOS is worse than these 

standards, seek to mitigate impacts back to the existing level (Brinkman 2006). 

The following describes the existing characteristics of the roadways and intersections 

located within the traffic analysis study area. Existing traffic volume data for the 

subject roadways were collected from a variety of sources. Recent EIS/EIR filings, 

City and County Transportation Divisions, and General Plan documents were 

researched to collect as much existing traffic volume data as possible. The primary 

source of traffic data information is the Folsom Bridge Draft Supplemental EIS/EIR 

(Bridge EIS/EIR) dated May 2006. 

Auburn-Folsom Road from Oak Leaf Way/Oak Hill Drive to Eureka Road: 

Auburn-Folsom Road is described in detail in Section 3.9 of the Folsom DS/FDR 

Draft EIS/EIR. This segment of Auburn-Folsom Road is 1 lane in each direction and 

the speed limit is 50 miles per hour. The terrain in this area is generally rolling, with 

several curves, both horizontal and vertical. At some locations, sight distance is very 

limited. It is surrounded by open space, recreational use, and residential use. The 

intersections at Oak Hill Drive and Eureka Road are both signalized. The proposed 

access road would be between these two signalized intersections. There are no other 

signalized intersections between these two intersections; however there are 

3-22 February 2008 
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Affected Environment and Environmental Consequences 

additional non-signalized intersections, primarily at minor residential streets and 

private driveways. 

Existing traffic volumes for this roadway segment and the corresponding LOS and 

volume to capacity ratio (V/C) are identified in Section 3.9 of the Folsom DS/FDR 

Draft EIS/EIR. Traffic counts performed in 2004 for the New Bridge EIS/EIR found 

the Average Daily Total of vehicles (ADT) on the segment to be 26,500, and the 

LOS to be F1. As described in the Folsom DS/EIR, a growth factor was applied to 

the 2004 data to determine the ADTs and LOS ratings in later years, as well as the 

V/C. A V/C value less than 1.0 indicates that the ADT is less than the capacity, 

where a V/C value greater than 1.0 indicates that the roadway volume is greater than 

the roadway capacity. For 2008, the ADT was projected to be 31,669 with an LOS F 

rating, and a V/C value of 1.692. In 2009 the projected ADT was 32,473, with LOS F 

and V/C 1.743. These projections include the traffic impacts of the Folsom DS/FDR 

as identified in the EIS/EIR, and are therefore considered the existing conditions on 

this roadway segment. 

Auburn-Folsom Road at Beal’s Point/Oak Hill Drive 

On Auburn-Folsom Road in the northbound direction, there is an exclusive left turn 

lane and one through lane. In the southbound approach there is an exclusive left turn 

lane, one through lane, and a right turn lane. Oak Leaf Way comes into the 

intersection with a shared/left through lane, and an exclusive right turn lane. Beal’s 

Point consists of a single general use lane. There are no bicycle lanes or sidewalks. 

The intersection was analyzed in the Folsom Bridge Draft Supplemental EIS/EIR 

and identified to have LOS B in the AM peak (7:00 AM-9:00 AM) and LOS C in the 

PM peak (4:00 PM-6:00 PM) (See Table 3-5 in the Folsom Bridge Draft 

Supplemental EIS/EIR). The turning count movements are also included in Figure 3-

5 of the Folsom Bridge EIS/EIR. 

Hauling Route from Tiechert Prairie City Borrow (White Rock/ Scott Road) to the 

LWD. 

As described in the Folsom DS/FDR EIS/EIR, aggregate materials for work in the 

vicinity of the JFP Auxiliary Spillway would come from the Tiechert Prairie City 

Borrow site on Scott Road, south of Highway 50/White Rock Road. This haul route 

would go north on Scott Road to White Rock Road, back to Scott Road, and then 

north on East Bidwell Street. It continues north on Oak Avenue Parkway, east on 

Blue Ravine Road, and then west on East Natoma Street until the beginning of 

Reclamation’s private haul road. The characteristics of these roads are described in 

 

1

 Traffic counts conducted in 2004 by Fehr and Peers and published in the Folsom Bridge 

Supplemental EIS/EIR May 2006 (Corps 2006). 2

 Modeled in the Folsom DS/FDR EIS/EIR. 

3

 Modeled in the Folsom DS/FDR EIS/EIR. 

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section 3.9 of the Folsom DS/FDR EIS/EIR. For this analysis, the without project 

ADT values on these roads is considered to be the ADTs determined in the EIS/EIR 

for the proposed DS/FDR project; these values are repeated in Table 3-9 below. 

3.9.2 Environmental Consequences 

This section presents the environmental consequences of the Proposed Action and 

the No Action Alternative. 

3.9.2.1 No Action Alternative 

Dike 5 Construction Access and Trail Detour 

Under the No Action Alternative, there would be no change from the affected 

environment. As described in the EIS/EIR, access to the Dike 5 construction site 

would occur through Beal’s Point. For the duration of the Dike 5 construction, this 

would add 27 daily morning and early afternoon construction worker trips from 

northbound and southbound on Auburn-Folsom Road to Beal’s Point, and 27 

afternoon and nighttime trips out of Beal’s Point (assuming two work shifts). During 

peak construction activities, a period of no more than 30 days, 40 haul trucks would 

enter and exit Beal’s Point throughout the day between 7 am and 3 pm to deliver 

materials. 

Under the No Action Alternative, construction traffic could adversely impact 

recreational traffic. The entrance to Beal’s Point can become heavily trafficked 

during peak recreation seasons, and adding slow moving trucks could cause back ups 

to the intersection with Auburn-Folsom Road. 

Cofferdam 

There would be no change to the affected environment. 

3.9.2.2 Proposed Action 

Dike 5 Construction Access and Trail Detour 

The access road to Dike 5 could either be implemented with the control of a 

temporary traffic signal or a flagman. Both of these options are analyzed below. 

There are two potential locations for the temporary intersection on Auburn-Folsom 

Road: a four-way intersection at existing Bell Drive or a three-way intersection 

slightly further south of Bell Drive. Reclamation and their Construction Contractor, 

in coordination with Placer County, would ensure the intersection is located in a way 

that does not result in a traffic hazard or pose a safety risk to the flagman or 

approaching vehicles. All safety precautions would be taken to alert drivers to the 

new temporary intersection when it is in use. 

Dike 5 Construction Site Access with Signalized Intersection 

The Proposed Action includes the addition of an access road to the Dike 5 

construction site from Auburn-Folsom Road. The access road could either be 

constructed off Auburn-Folsom Road across from Bell Drive, creating a four-way 

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Affected Environment and Environmental Consequences 

intersection, or it could be constructed further south of Bell Drive, creating a threeway signalized intersection. Either intersection could be controlled by a temporary 

traffic signal which would be installed prior to construction in September 2008 and 

would be blacked out or removed at the conclusion of construction in March 2009. 

The signal would be set back in operation for construction at Dikes 4 and 6, 

estimated to occur in 2013 to 2014, during which time the same access road to Dike 

5 would be used. This Proposed Action would allow access to Dike 5 for staging and 

construction to occur from Auburn-Folsom Road immediately west of Dike 5, 

thereby reducing conflicts with recreational traffic at Beal’s Point. 

To accommodate construction traffic under this alternative, the installation of a 

temporary intersection with a traffic signal was evaluated. The signal would provide 

red (stop) indications on Auburn-Folsom Road only for construction-related traffic 

leaving the construction site, or traffic exiting Bell Drive, in the case of the four-way 

intersection. Construction related heavy truck traffic entering the site would do so via 

a dedicated deceleration lane from the northbound lane only of Auburn-Folsom Road 

to further minimize traffic congestion. No heavy truck traffic would be allowed to 

enter the site via a left turn from the north. Traffic leaving the site would be 

controlled by the signal, and would be able to turn right or left onto Auburn-Folsom 

Road. Use of Auburn-Folsom Road and construction of turn outs and merge lanes 

would be coordinated with Placer County and would require an encroachment 

permit. Oncoming traffic would be alerted to the temporary signal by signs or 

warning lights as required by Placer County. Electronic variable message boards 

would be activated at least two weeks prior to installation of the temporary signal, 

notifying travelers of planned modifications to the traffic pattern. 

During peak construction at Dike 5, it is anticipated that up to 27 site workers and 40 

haul vehicles per day would enter and exit the Dike 5 staging location. Peak 

activities would be expected to last less than 30 days. As noted in the Folsom 

DS/FDR Draft EIS/EIR, two work shifts are assumed to be operated during 

construction of Dike 5; 5am to 2pm, and 2pm to 11pm, with material and equipment 

hauling activity occurring during the hours of 7am to 3pm. 

The proposed intersections were analyzed using Synchro 7 software and are based on 

the concepts and procedures in the Highway Capacity Manual (Transportation 

Research Board 2000). The analysis is based on AM and PM peak hour volumes 

obtained from 2004 counts provided by Fehr & Peers Transportation Consultants 

with a growth factor of 3% applied annually (calculations in Appendix A). With the 

hours noted above, the AM peak is only affected by material and equipment hauling, 

and the PM peak is unaffected by Dike 5 construction traffic. 

The results of the analysis of the four-way intersection at Bell Drive identify the 

intersection to operate at LOS A in the AM peak (7:00 AM-9:00 AM) and LOS A in 

the PM peak (4:00 PM-6:00 PM) (See analysis in Appendix A). Further, the analysis 

3-25 February 2008 
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Supplemental Environmental Assessment/Initial Study 

indicates queue lengths of 599 ft for northbound traffic and 700 ft for southbound 

traffic on Auburn-Folsom Road during the AM peak hour. Queue lengths during the 

PM peak hour are calculated to be 1,402 ft in the northbound direction and 550 ft for 

the southbound direction, assuming no outbound construction traffic from the Dike 5 

site occurs during that time. These delays reflect the minimal traffic flow exiting and 

entering Bell Drive which will still occur by local residents. There would be no 

substantial adverse construction-related impacts to transportation and circulation as a 

result of this added intersection. The turning count movements are included in Figure 

3-1 and 3-2 of this EA/IS. The capacity analysis reports are included in Appendix A. 

The results of the analysis of a three-way intersection south of Bell Drive identify the 

intersection to operate at LOS A in the AM peak (7:00 AM-9:00 AM) and LOS A in 

the PM peak (4:00 PM-6:00 PM) (See analysis in Appendix A). Further, the analysis 

indicates queue lengths of 618 ft for northbound traffic, and 724 ft for southbound 

traffic during the AM peak hour. Queue lengths during the PM peak hour are 

calculated to be 0 ft in the northbound and southbound directions, assuming no 

outbound traffic occurs during that time. There would be no substantial adverse 

construction-related impacts to transportation and circulation as a result of this added 

intersection. The turning movement counts are included in figure 3-3 and figure 3-4 

of this EA/IS. The capacity analysis reports are included in Appendix A. 

The two potential locations for a signalized intersection of the Dike 5 Construction 

Access Road and Auburn-Folsom Road would result in minimal impacts to the Level 

of Service rating; however, the locations of the proposed intersections might have 

different safety concerns for motorists. The location of the 3-way intersection south 

of Bell Drive might give approaching drivers somewhat more sight distance, which 

could potentially increase the safety of the new intersection. Reclamation and 

Reclamation’s Construction Contractor would be required to work with Placer 

County to address safety concerns of the proposed intersection. 

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Dike 5 Construction Access with Flagman 

The Proposed Action could include the addition of an access road to the Dike 5 

construction site, with a flagman at the intersection of the access road and AuburnFolsom Road. Construction signs would be posted along Auburn-Folsom Road 

warning that trucks would be turning onto the highway. Construction and local 

traffic would be required to follow the instructions of the flagman to allow safe 

movement of the construction traffic. 

Flagmen are generally posted at the intersection of such a proposed entrance, or in 

advance of the intersection, with one flagman per lane. As with use of a signal, 

flagmen would only stop traffic on the Auburn-Folsom Road to allow constructionrelated traffic to leave the construction site. Construction workers would be able to 

leave and enter the site without the presence of a flagman and utilize middle and 

right-hand turn out lanes as well as breaks in traffic created by coordinated traffic 

lights to the north. However, the 40 large haul trucks used during peak construction 

would require more time to accelerate and decelerate, therefore a flagman would be 

required from 7AM - 3PM to allow trucks to safely enter and exit the Dike 5 staging 

area using the access road. 

Flagmen would be equipped with high-visibility apparel, and employ Stop/Slow 

paddles to control traffic. In most situations where flagmen are used, work zone 

speed reductions are utilized to slow traffic for the safety of the flagmen and 

vehicular traffic. The speed limit on the Auburn-Folsom Road is currently posted for 

50 mph. Construction zone traffic speeds, with flagmen, would need to be lowered to 

approximately 35 mph. This could slow down traffic and would require the 

implementation of minimization measures in Section 3.9.3 to reduce impacts. 

The Trail Detour is not expected to have any traffic impacts because it would occur 

on Federal property and would not affect any existing roads. 

Cofferdam 

The construction of the Cofferdam would require additional material hauling truck 

trips. During a peak construction period of approximately 45 days, there would be 40 

haul trucks entering and exiting the site each day. Trucks would enter the site via the 

haul route described in the affected environment section above, and as described in 

the EIS/EIR for East Project Features. Existing traffic volumes for these roads are 

those calculated for 2009 for the Folsom Dam Project (in table 3.9-88 of the 

EIS/EIR). An analysis of the additional impact from Cofferdam construction 

materials is presented below in Table 3-8. The methodology used to determine the 

impact of the additional Cofferdam construction traffic is the same as that described 

in the EIS/EIR. 

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Table 3-8 

Cofferdam Traffic Impacts 

2009 Without Cofferdam* 2009 With Cofferdam 

Roadway ADT LOS V/C ADT LOS V/C 

% ADT 

Increase 

LOS F V/C 

Increase 

Scott Road South of 

White Rock 1,872 A/B 1,912 A/B 2.14 

White Rock Road 9,759 E 9,799 E 0.41 

Scott Road North of 

White Rock 6,718 D 6,758 D 0.6 

East Bidwell Street 42,071 F 1.12 42,111 F 1.13 0.1 0.01 

Oak Avenue Parkway 23,572 C 23,612 C 0.17 

Blue Ravine Road 20,834 D 20,874 D 0.19 

East Natoma Street 

(Folsom Dam Road to 

Green Valley Road) 

29,465 F 1.0195 29,505 F 1.02 0.14 0 

*These values include construction traffic from the Stilling Basin, which would not be constructed until 

after the completion of the Cofferdam and therefore would not contribute to impacts from construction 

on the identified roads. Therefore, overall impacts from construction haul trucks could be somewhat 

less than those calculated. 

The above analysis confirms that the Proposed Action would not deteriorate the LOS 

on any of the roads that would be used by haul trucks. In addition, increases to daily 

traffic volumes are all less than two percent (with the exception of Scott Road south 

of White Rock Road; however, this road is rural and lightly used, and would 

continue to operate at LOS A/B.) In those instances where the road is at LOS F, the 

volume to capacity (V/C) ratio would not increase more than 0.05%, which is below 

the threshold of significance. Based on the analysis, and the fact that traffic impacts 

from the Cofferdam would be temporary, impacts to transportation and circulation 

from construction of the Cofferdam would be minimal. 

3.9.3 Minimization Measures 

Minimization measures will include close coordination with Placer County to reduce 

potential cumulative impacts from the Auburn-Folsom Road Widening Project (see 

below). In addition, local emergency services will be notified of the temporary traffic 

light in order prevent unexpected delays in emergency services. The light will be 

designed to ensure it does not impede emergency vehicles. Appropriate signs will be 

installed to alert drivers to the new intersection. If flagmen are implemented, heavy 

truck deliveries to Dike 5 would be restricted to off-peak hours to reduce traffic 

impacts from slower speeds. If a temporary traffic signal is implemented, the lights 

at Eureka Road and Fuller Drive would be coordinated to allow appropriate gaps in 

Auburn-Folsom Road traffic such that construction trucks would have sufficient time 

to turn in and out of the access road. All measures will be coordinated with Placer 

County. 

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Affected Environment and Environmental Consequences 

3.9.4 Cumulative Effects 

The Placer County Road Widening Project on Auburn-Folsom Road would likely 

overlap with the Proposed Action. However, the portion of the road that Placer 

County is planning on upgrading in 2008 and 2009 is the South Phase, from County 

Line to Woodchase Drive, approximately 0.7 miles south of the proposed 

intersection. The Middle Phase of the project would occur in the area around Dike 5 

but the schedule for that construction is currently unknown. Any impacts from this 

project would not directly overlap with the Proposed Action, and minimization 

measures applied to each project would prevent cumulative impacts. Reclamation 

will coordinate with Placer County to reduce any cumulative traffic impacts and will 

design the intersection to maintain the flow of traffic. With coordination and proper 

design, the Dike 5 Construction Site Access would not contribute to a substantial 

cumulative impact on traffic. 

Both the Cofferdam and the New Folsom Bridge Project would be constructed in the 

same vicinity. Traffic required for construction of the Cofferdam would be 

temporary and would use designated truck routes. Because of the short duration, the 

Proposed Action is not expected to contribute to any substantial cumulative traffic 

impacts. If the New Folsom Bridge is completed before work on the Cofferdam 

begins, the New Folsom Bridge would help to alleviate traffic congestion in the area 

and further reduce the potential for cumulative impacts. 

3.10 Noise 

This section presents the affected environment and environmental consequences for 

noise. The Proposed Action would not result in a permanent source of noise. 

Therefore, no permanent noise impacts would occur. However, construction noise 

would be generated and related potential noise impacts have been evaluated in this 

section. 

3.10.1 Affected Environment 

The Folsom Reservoir area is a very unique land use and noise setting. The southern 

portion of the site is more of an urban locale with constant noise generated from the 

Folsom Prison shooting range and traffic along busy arterial roadways. The area of 

analysis transitions to a more rural character heading to the north and east of the site 

where there is less human activity. Therefore, background noise levels are higher at 

the southern portion of Folsom Reservoir and trend lower as one heads north and 

east. In addition, there are seasonal variations with the reservoir being an active site 

for recreational boating and jet and water skis activities during the summer, which 

tends to increase background noise levels. During the winter months, human and 

recreational activity is less; therefore, background noise levels tend to be lower. 

There are many factors that affect one’s perception of noise. These factors include 

pitch, loudness and the character of the noise. The standard unit of sound amplitude 

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measurement is the decibel (dB). Since the human ear cannot hear all frequencies, a 

special scale has been devised to relate noise to human sensitivity. The A-weighted 

decibel scale (dBA) de-emphasizes the low and high end frequencies and emphasizes 

those frequencies the human ear is able to hear. The following terms are typically 

used in analyzing noise: 

• Leq: Equivalent energy level. The A-weighted sound level corresponding to a 

steady state sound level containing the same total energy as a time varying 

signal over a given sample period. Leq is typically computed over 1, 8, and 24 

hour measurement periods. 

• Lmax: The maximum A-weighted sound level during the measurement period. 

• Ldn: Day-night average level. A 24-hour average Leq, with the addition of 10 

dBA to the sound level during the hours of 10:00 p.m. to 7:00 a.m. to account 

for greater noise sensitivity of people at night. 

• CNEL: Community Noise Equivalent Level. A 24-hour average Leq, with the 

addition of five dBA to sound levels from 7:00 p.m. to 10:00 p.m. and the 

addition of 10 dBA to sound levels from 10:00 p.m. to 7:00 a.m. 

It is widely accepted that most human sound perception can barely detect a change in 

sound level of 3 dBA (California Department of Transportation 1998). 

The existing noise conditions in the area, including the regulatory framework, were 

characterized in detail in the Folsom DS/FDR EIS/EIR. In general, the major source 

of noise in the project area is motor vehicle traffic on Auburn-Folsom Road. 

Additional noise sources include local construction activities and noise from boating 

and other recreation activities, primarily in the summer. 

Currently, with the initiation of the Folsom DS/FDR Project, Reclamation is 

implementing a Noise Control Plan with mitigation measures accepted in the RODs 

and NOD. 

3.10.2 Environmental Consequences 

This section presents the environmental consequences of the Proposed Action and 

the No Action Alternative. 

3.10.2.1 No Action Alternative 

Dike 5 Construction Site Access and Trail Detour 

Without the Dike 5 Construction Site Access, noise impacts from construction traffic 

would still occur, but they would occur at the Beal’s Point entrance rather than at 

Dike 5. Without the Trail Detour, the noise levels on the downstream side of the 

dikes would not change from the affected environment. 

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Affected Environment and Environmental Consequences 

Cofferdam 

There would be no change to the affected environment. 

3.10.2.2 Proposed Action 

None of the activities under the Proposed Action would have appreciable impacts to 

noise levels. Any minimal noise impacts are discussed below. 

Dike 5 Construction Site Access and Trail Detour 

Potential sources of noise impacts from the proposed Dike 5 Construction Site 

Access include both onsite construction noise sources and transportation-related 

noise sources from construction workers, visitors and deliveries. Onsite dike 

construction noise and area-wide construction traffic noise were evaluated in the 

Folsom DS/FDR EIS/EIR. This assessment evaluates only the transportation-related 

noise associated with use of the new proposed construction access road to Dike 5 

from Auburn-Folsom Road.

Transportation-related noise sources would consist of trucks hauling materials to 

Dike 5 via the new construction access road and construction worker, visitor and 

delivery vehicles. According to the traffic analysis, the volume of traffic generated 

by these sources would be very low in relation to existing traffic volumes on 

Auburn-Folsom Road. Because it takes a doubling of traffic to increase noise levels 

by 3 dBA4, the threshold of detectability, the noise generated by this short-term, 

relatively low volume of traffic would increase noise levels in the project area by 

considerably less than 3 dBA, and, therefore, would have imperceptible noise 

impacts. In future years, the Dike 5 construction staging area is proposed to be used 

for Dike 4 and 6 construction also. Noise impacts from this future constructionrelated use of the Dike 5 site access road are anticipated to be imperceptible, similar 

to that of the Dike 5 construction. 

If the onsite dike construction noise analyzed in the Folsom DS/FDR EIS/EIR is 

considered in conjunction with the increases from transportation related noise 

sources, the overall increase in noise levels would still be minimal. As described in 

the SOD and JFP RODs, the Folsom DS/FDR agencies would: 

• Incorporate the appropriate level of sound attenuation on equipment or near 

facilities that will attenuate sound at sensitive receptors to comply with local 

noise ordinances. Maintain equipment to comply with noise standards (e.g., 

exhaust mufflers, acoustically attenuating shields, shrouds, or enclosures). 

• Enclose above-ground conveyor systems in acoustically-treated enclosures, if 

necessary; 

 

4

 Source: (California Department of Transportation 1998). 

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• Line or cover hoppers, conveyor transfer points, storage bins and chutes with 

sound-deadening material; and 

• Schedule truck loading, unloading, and hauling operations so as to reduce 

nighttime noise impacts to comply with local noise ordinances. 

The Proposed Action would also incorporate the measures above, when appropriate. 

Overall, the Folsom DS/FDR construction activities and the traffic related noise from 

the Proposed Action would be unlikely to contribute to a substantial increase in 

noise. 

The Trail Detour alignment parallels Auburn-Folsom Road, a major thorough fare 

with heavy vehicular and truck traffic. Any noise produced during the brief 

construction period would be masked by the ambient noise levels and not apparent to 

residences across the road. No substantial adverse noise impacts are anticipated 

during construction of the Dike 5 Construction Site Access and Trail Detour.

Cofferdam 

Although construction and demolition of the Cofferdam would produce some noise, 

it would be in a location remote from sensitive receptors. Additionally, this noise 

would be masked by other noise from construction of the authorized project. The 

Auxiliary Spillway would likely be excavated at the same time the Cofferdam would 

be constructed. Because of the remote location and the other construction activities 

that would be producing noise, no substantial noise impact is predicted with 

construction of the Cofferdam. 

3.10.3 Cumulative Effects 

The Folsom DS/FDR EIS/EIR evaluated the potential cumulative noise impacts from 

nearby projects (such as the Folsom Bridge Project) anticipated to be occurring at the 

same time and found that, with the proposed inclusion of mitigation measures, the 

combined impact of concurrent projects is expected to be minimal. The AuburnFolsom Road Widening Project may be under construction in the area of Dike 5 at 

the same time as the Proposed Action. Construction noise from the Road Widening 

Project was evaluated in the Auburn-Folsom Road Widening EA/EIR and the 

anticipated noise impact was found to be minimal with the implementation of 

recommended mitigation measures. Since the proposed Dike 5 Construction Access 

Road does not add construction traffic to the cumulative noise impact evaluation but 

simply moves the location of one of the construction access roads that was 

previously evaluated, the cumulative noise impact of the Dike 5 construction access 

road and any concurrent construction on Auburn-Folsom Road is anticipated to be 

minimal. 

In addition, noise impacts from construction of the Trail Detour would be minor and 

temporary, and to some degree buffered by surrounding vegetation. For these reasons 

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Affected Environment and Environmental Consequences 

noise from the construction of the Trail Detour would not likely have a cumulative 

impact when considered with the noise that would be produced during the AuburnFolsom Road Widening Project. 

The construction of the Cofferdam would overlap with nearby construction for the 

Folsom Bridge Project. However, both the Cofferdam and Folsom Bridge Project are 

located away from sensitive noise receptors, and the minimal, temporary impacts 

from this noise, would not likely contribute to cumulative impacts. 

3.11 Cultural Resources 

This section presents the affected environment and environmental consequences for 

cultural resources. 

3.11.1 Affected Environment 

The affected environment for cultural resources is included herein by reference to the 

Folsom DS/FDR EIS/EIR. Portions of the Dike 5 Construction Site Access and Trail 

Detour were previously surveyed for cultural resources as part of the Folsom Dam 

DS/FDR EIS/EIR (Bartoy et al. 2007: 19-28).Two historic resources are recorded 

within current Dike 5 Trail Detour Area of Potential Effects (APE) (Bartoy et al. 

2007). The recorded portion of CA-SAC-945H is a concrete intake and aboveground pipe support for a “Siphon” connected to the Rose Springs Ditch (Welch 

2005a; Bartoy et al 2006a; Jones and Schrader 2007a). This portion of the resource 

was evaluated as part of the Folsom Dam DS/FDR EIS/EIR and found to be 

ineligible for listing on the National Register of Historic Places (NRHP). CA-SAC944H is an unidentified concrete feature and associated trash scatter (Welch 2005b; 

Bartoy et al. 2006b; Jones and Schrader 2007b) that was also found ineligible for 

listing on the NRHP as part of the Folsom Dam DS/FDR EIS/EIR (Bartoy et al. 

2007). The California State Historic Preservation Officer (SHPO) concurred with 

these determinations by letter dated November 2, 2007. 

The Cofferdam Area was previously surveyed as part of the Folsom Bridge Project 

(Corps 2004). Survey and archival research identified no resources in the Cofferdam 

or in the Dike 5 Construction Site Access APE (Bartoy et al. 2007: Table 2; Corps 

2006: 3-4). 

In February of 2008, an archaeological survey was conducted for unsurveyed 

portions of the Dike 5 Trail Detour (Jones 2008). Using a Geographic Information 

Systems (GIS) shapefile of the Dike 5 Trail Detour provided by the Bureau of 

Reclamation (Reclamation) and the on-the-ground flagging, Pacific Legacy 

archaeologists navigated the trail corridor and completed a full pedestrian survey of 

the Dike 5 Trail Detour APE and a 30 meter buffer on either side of the marked trail 

centerline. Eight historic cultural resources were noted. Two of these, CA-SAC944H and CA-SAC-945H, had been previously recorded, as mentioned above. The 

remaining six resources include four earthen trenches, one non-linear depression, and 

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an unnamed u-shaped ditch. The named Rose Springs Ditch and associated features 

were also noted and were recorded as a continuation of CA-SAC-945H. As a result 

of this survey, six newly discovered resources were recorded. 

3.11.2 Environmental Consequences 

This section presents the environmental consequences of the Proposed Action and 

the No Action Alternative. 

3.11.2.1 No Action Alternative 

Dike 5 Construction Site Access and Trail Detour 

There would be no change to the affected environment. 

Cofferdam 

There would be no change to the affected environment. 

3.11.2.2 Proposed Action 

Dike 5 Construction Site Access and Trail Detour 

No cultural resources are located within the Dike 5 Construction Site Access area. 

Within and adjacent to the Trail Detour, six previously undiscovered cultural 

resources were recorded during the survey and two known resources, CA-SAC-944H 

and CA-SAC-945H, were revisited and site records updated. The Trail Detour APE 

would be approximately 5 to 6 ft wide and constructed of Native Material. The 

archaeological survey width for the Trail Detour is substantially wider, 30 meters on 

either side of the trail centerline. 

CA-SAC-944H is a board-molded concrete feature and associated historic debris 

scatter within the Dike 5 Trail Detour APE. It was previously recorded as part of the 

Folsom Dam DS/FDR EIS/EIR and found ineligible for listing on the NRHP (Bartoy 

et al. 2007). No further management consideration is required. 

CA-SAC-945H (PL-1828-02) comprises a portion of the Rose Springs Ditch and 

associated siphon structure. The siphon portion of the resource was identified 

previously and was found to be ineligible for listing on the NRHP as part of the 

Folsom Dam DS/FDR EIS/EIR investigations (Bartoy et al. 2007). The current 

survey identified additional segments of the ditch, a concrete intake at the beginning 

of the ditch, an embankment to the west, and a small auxiliary ditch to the west of 

the main ditch channel. These structures were given the temporary field number PL1828-02. The Folsom CA 7.5’ United States Geological Survey (USGS) map 

indicates that PL-1828-02 and the previously recorded CA-SAC-945H are 

contiguous portions of the Rose Springs Ditch. Reclamation now believes that this 

entire segment of the Rose Springs Ditch is not eligible for inclusion in the NRHP. 

Reclamation will consult with SHPO to seek their concurrence in compliance with 

the 36 Code of Federal Regulations (CFR) Part 800 regulations that implement 

section 106 of the National Historic Preservation Act (NHPA). 

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Affected Environment and Environmental Consequences 

PL-1828-01 consists of two historic earth trenches spaced approximately 50 feet 

apart. The southwestern trench measures 16 feet long, 9 feet wide and 3 feet deep. 

The northeastern trench measures 9 feet long, 5 feet wide and 2.5 feet deep. Both 

trenches are located within the survey buffer approximately 3.5 meters (11 ft) east of 

the marked Trail 5 Detour APE centerline and can be avoided by the Proposed 

Action. 

PL-1828-03 is a historic earthen trench with rock and earth berms to either side. It 

measures approximately 55 feet long, 1-2 feet wide and 1 foot deep. Several small 

mounds of excavated dirt are also located around the trench. The resource is located 

within the survey buffer approximately 15 meters (49 ft) south of the Dike 5 Trail 

Detour APE centerline and can be avoided by the proposed project. 

PL-1828-04 is a historic earthen trench with a berm on its western edge. The trench 

is ephemeral and difficult to detect without noting the berm/push-pile. It is oriented 

generally north -south and is 31 feet long, 3 feet wide, and 1-1.5 feet deep. It is 

entirely of earthen construction and few rocks were noted in the vicinity. The trench 

is located within the survey buffer approximately 30 meters (98 ft) southeast of the 

Dike 5 Trail Detour APE centerline and can be avoided by the proposed project. 

PL-1828-05 is a historic earthen trench that is partially rock-lined with medium sized 

(2-12 inch) granitic boulders. There is a single berm on the south side of the trench. 

It is oriented generally east-west and measures approximately 20 feet long, 2 feet 

wide and 1 foot deep or less. Ground inspection of the ditch indicates that it is 

directly adjacent to (approximately 3 ft west of) the Dike 5 Trail Detour centerline. 

Data collected with the Trimble Geo XT, when compared to the shapefiles provided 

by Reclamation, indicate that the ditch crosses the Dike 5 Trail Detour centerline and 

extends less than half a meter (1.5 ft) to the east of the trail. It then continues 

approximately 5 meters (18 ft) west, according to Global Positioning System (GPS) 

data. Reclamation believes that this is not eligible for inclusion in the NRHP. 

Reclamation will consult with SHPO to seek their concurrence in compliance with 

the 36 CFR Part 800 regulations that implement section 106 of the NHPA. 

PL-1828-06 is a historic u-shaped ditch that is rock-lined in parts. It measures from 

2-4 feet wide and 1-2 feet deep. It meanders across a downhill slope on an 

approximate northwest-southeast orientation for approximately 360 feet. The ditch 

terminates at its southeast end at the base of slope. Upslope, its termination is 

difficult to detect as it becomes more ephemeral to the north and west. The ditch 

crosses the Dike 5 Trail Detour APE. The ditch would be affected by the current 

Trail Detour location. Reclamation believes that this is not eligible for inclusion in 

the NRHP. Reclamation will consult with SHPO to seek their concurrence in 

compliance with the 36 CFR Part 800 regulations that implement section 106 of the 

NHPA. 

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Folsom Dam Safety and Flood Damage Reduction 

Supplemental Environmental Assessment/Initial Study 

PL-1828-07 is an isolated historic earthen depression. It is bowl-shaped, 

approximately 6 feet in diameter at the top and 3-4 feet deep with a grassy bottom. 

Pushed earth is visible on its margins. The depression is located 8 meters (26 ft) west 

of the Dike 5 Trail Detour APE centerline and can be avoided by the proposed 

project. 

The project areas associated with the Dike 5 Construction Site Access and Trail 

Detour have been subject to cultural resources survey and inventory. The cultural 

resources identified would either be avoided by shifting the Trail Detour, or they 

have been considered ineligible for listing by Reclamation. Reclamation will consult 

with SHPO to seek their concurrence in compliance with the 36 CFR Part 800 

regulations that implement section 106 of the NHPA. No minimization measures 

would be required for the Dike 5 Construction Site Access and Trail Detour. 

Cofferdam 

The Cofferdam APE was previously surveyed as part of the Folsom Bridge Project 

(Corps 2004). Survey and archival research identified no historic properties in the 

Cofferdam APE (Corps 2006: 3-4). 

3.11.3 Cumulative Effects 

The proposed Dike 5 Construction Site Access, Trail Detour and Cofferdam would 

not result in cumulative effects as no historic properties were found to be within the 

APE. 

3.12 Land Use, Planning, and Zoning 

This section presents the affected environment and environmental consequences for 

land use, planning, and zoning. 

3.12.1 Affected Environment 

The entire area around Folsom Reservoir is owned by Reclamation and leased to 

DPR. Reclamation and DPR are currently developing the Folsom Lake State 

Recreation Area (FLSRA) General Plan and Resource Management Plan Update. 

The portion of Auburn-Folsom Road in the affected area is under the jurisdiction of 

Placer County. 

3.12.2 Environmental Consequences 

This section presents the environmental consequences of the Proposed Action and 

the No Action Alternative. 

3.12.2.1 No Action Alternative 

Dike 5 Construction Site Access and Trail Detour 

There would be no change from existing conditions. 

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Affected Environment and Environmental Consequences 

Cofferdam 

There would be no change from existing conditions. 

3.12.2.2 Proposed Action 

Dike 5 Construction Site Access and Trail Detour 

Auburn-Folsom Road along Dike 5 is owned and maintained by Placer County. 

Construction of a traffic light and turning lanes would require an encroachment 

permit from Placer County. Reclamation and their Construction Contractor would 

obtain the appropriate permit and would adhere to conditions stipulated in the permit. 

The traffic light and turning lanes would be constructed to meet Placer County 

design and safety standards. Auburn-Folsom Road would be restored to preconstruction conditions after work on the dikes is complete. This would not change 

any land use or zoning. 

Reclamation would coordinate with DPR to ensure the location of the Trail Detour 

would be consistent with the FLSRA General Plan and Resource Management Plan. 

Cofferdam 

The Cofferdam would not result in any impacts to land use, planning, and zoning. 

3.12.3 Cumulative Effects 

Placer County is planning on widening Auburn-Folsom Road beginning in 2008, 

around the same time as construction is scheduled to begin on Dike 5. The Dike 5 

work would take place north of Phase 1 of the Road Widening Project and is 

therefore not expected to lead to any cumulative impacts to land use, planning, or 

zoning. 

3.13 Recreation Resources 

This section presents the affected environment and environmental consequences for 

recreation resources. 

3.13.1 Affected Environment 

The FLSRA is one of the most popular recreation sites within California in the DPR 

system. The FLSRA area consists of Folsom Reservoir, including marinas, boat 

launching facilities, whitewater rafting facilities, and terrestrial facilities, including 

campgrounds, day use facilities, other facilities (i.e., Folsom Dam, the California 

State University Sacramento Aquatic Center at Nimbus Flat), and numerous multipurpose trails. Throughout the year, permitted special events are held at various 

locations in the FLSRA. Events include bass fishing tournaments, yacht races, 

mountain bike races, triathlons, mountain bike triathlons, adventure races, running 

races, and summer camps. 

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Supplemental Environmental Assessment/Initial Study 

Although FLSRA does not track the annual number of trail users, overall annual park 

usage has averaged approximately 2 million visitors over the past 10 years (Griffith 

2008). All trails in the FLSRA, including those on Dikes 4, 5, and 6, are used 

extensively throughout the seasons. Existing trails on Dikes 4, 5, and 6 accommodate 

pedestrian, bicycle, and equestrian users (Griffith 2007). Trails on the downstream 

side of the dikes include the Pioneer Express Trail and other unimproved multi-use 

trails. No recreation facilities exist in the area below Folsom Dam as this area is not 

open to the public. 

3.13.2 Environmental Consequences 

This section presents the environmental consequences of the Proposed Action and 

the No Action Alternative. 

3.13.2.1 No Action Alternative 

Dike 5 Construction Site Access and Trail Detour 

Under the No Action Alternative, a trail detour would not be constructed. The trails 

on the tops of the dikes would be closed to the public while construction occurs to 

upgrade the filter and shell material of the dikes. Some trail users would not be able 

to navigate around Dikes 4, 5, and 6 because the existing trails are unimproved and 

do not accommodate all types of trail users. Some trail users may decide to make 

their own trails or use trails not designated for their type of recreation. This could 

lead to environmental impacts and could cause conflicts on existing trails. 

Cofferdam 

There would be no change to the affected environment. 

3.13.2.2 Proposed Action 

Dike 5 Construction Site Access and Trail Detour 

The Dike 5 Construction Site Access could affect recreation because large 

construction vehicles and equipment would be operating and would make it difficult 

for trail users to move between Beal’s Point and Mooney Ridge. The Trail Detour 

described below and the associated safety measures that would be implemented 

would help maintain recreation when the Dike 5 Construction Site Access is in use. 

A Trail Detour would be established around the staging areas and construction zones 

of Dikes 4, 5, and 6 to keep a continuous stretch of trail available to recreation users 

throughout construction. Reclamation’s Recreation Management Partner would be 

responsible for managing the Trail Detour with the exception of the portion that 

crosses through the Dike 5 area. The proposed location for the Trail Detour is shown 

on Figure 2-2 in Chapter 2. The temporary Trail Detour would connect a series of 

existing unimproved trails, which would be cleared, and widened to serve combined 

pedestrian, bicycle, and equestrian use around Dikes 4, 5, and 6. Throughout 

construction, this Trail Detour would be the only access for travel between Beal’s 

Point and Mooney Ridge. During construction at each dike, which is planned in a 

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Affected Environment and Environmental Consequences 

phased manner, the crest-top trails and trails along the toes will be closed to 

accommodate construction work and vehicle access. The trails on top of the dikes 

would be re-opened to the public after construction is complete. Existing trails along 

the downstream sides of Dikes 4 and 6 outside the construction zones will remain 

open throughout construction, but they are unimproved and are not suitable for all 

types of recreation users. The Trail Detour would not impact any other existing 

recreation facilities. Because this would allow a continuous stretch of trail to remain 

open to all users during construction, the Trail Detour is expected to help maintain 

recreation throughout construction. 

The Trail Detour would intersect truck traffic entering the staging area at Dike 5. 

Trail users could be concerned about impacts to their recreational experience from 

potential safety issues. Reclamation and their Construction Contractor would: 

• Post signs to identify the Trail Detour and any trails closed during 

construction; 

• Erect fences and post signs in construction zones to keep the public out of 

any dangerous areas; and 

• Use flag men to help recreation users cross the Dike 5 area and avoid 

construction traffic. 

With implementation of the safety measures described above, recreation impacts 

from the Dike 5 Construction Site Access would be minimal. Trail Detour would 

help maintain recreation throughout construction and would provide a safe way to 

navigate between Beal’s Point and Mooney Ridge. 

Cofferdam 

There would be no recreation impacts from construction of the Cofferdam. 

3.13.3 Cumulative Effects 

Although a trail detour was required for construction of the New Folsom Bridge, it is 

not in the same vicinity as the Trail Detour for the Proposed Action. The AuburnFolsom Road Widening Project would not affect any trails. No cumulative effects 

would occur from the Proposed Action as no additional projects would affect 

recreation downstream of Dikes 4, 5, and 6. 

3.14 Public Services and Utilities 

This section presents the affected environment and environmental consequences for 

public services and utilities. 

3-47 February 2008 
Folsom Dam Safety and Flood Damage Reduction 

Supplemental Environmental Assessment/Initial Study 

3.14.1 Affected Environment 

Although Reclamation owns the land, the FLSRA is currently leased to and managed 

by DPR. All recreation within FLSRA, including the trails, are managed and 

maintained by DPR. 

3.14.2 Environmental Consequences 

This section presents the environmental consequences of the Proposed Action and 

the No Action Alternative. 

3.14.2.1 No Action Alternative 

Dike 5 Construction Site Access and Trail Detour 

There would be no change to the affected environment. 

Cofferdam 

There would be no change to the affected environment. 

3.14.2.2 Proposed Action 

Dike 5 Construction Site Access and Trail Detour 

A temporary traffic light at Dike 5 would require electricity to operate. This is not 

expected to have any impacts to existing electricity users and would require a 

minimal amount of electricity to operate. The traffic light would only be temporary 

and would be removed after construction of the dikes is complete. 

Operation of a temporary traffic light on Auburn-Folsom Road at Dike 5 would 

mean that fire, police, and other emergency vehicles would have a new light to 

circumnavigate during emergencies. Reclamation and the Construction Contractor 

would notify the appropriate authorities of the temporary traffic light and would 

design the light to ensure it does not impede any emergency vehicles. 

The Trail Detour would create an improved recreation trail at FLSRA. Reclamation’s 

Recreation Management Partner would manage and maintain the Trail Detour until 

the close of construction, with the exception of the portion that crosses over the Dike 

5 access road and staging area. The Trail Detour would temporarily replace an 

existing trail that would be closed during construction and is not expected to require 

any new public services or staff at FLSRA. The Trail Detour would not affect any 

existing public utilities. 

Cofferdam 

Construction of the Cofferdam would not affect any existing utilities or public 

services. 

3.14.3 Cumulative Effects 

The only cumulative project within the vicinity of the Dike 5 area that could have 

utility and public services impacts would be the Auburn-Folsom Road Widening 

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Affected Environment and Environmental Consequences 

Project. This project is not expected to impact FLSRA services or any existing 

utilities. The Proposed Action, in consideration with the Auburn-Folsom Road 

Widening Project, would be unlikely to contribute to any cumulative effects to public 

services and utilities. 

3.15 Public Health and Safety 

This section presents the affected environment and environmental consequences for 

public health and safety. 

3.15.1 Affected Environment 

Reclamation’s Construction Contractor has developed and implemented appropriate 

Worker Health and Safety Plans and Hazardous Materials Management Plans for 

Phase 1 activities of the Folsom DS/FDR Project. Reclamation has posted signs 

throughout the FLSRA to provide the public with information and updates on the 

project under construction. 

3.15.2 Environmental Consequences 

This section presents the environmental consequences of the Proposed Action and 

the No Action Alternative. 

3.15.2.1 No Action Alternative 

Dike 5 Construction Site Access and Trail Detour 

Under the No Action Alternative, the Trail Detour would not be constructed. 

Recreation users would be left to their own devices to navigate around Dikes 4, 5, 

and 6 during construction. Without a Trail Detour, it is expected that some recreation 

users would try to cross through construction zones. Large construction equipment 

and vehicles would be operating within these construction zones and could pose a 

threat to public health and safety. Trail users seeking to navigate around the Dike 5 

construction and staging area could also choose to use the shoulder of AuburnFolsom Road, which would increase the chance for vehicle-related injuries or 

accidents. 

Cofferdam 

There would be no change to the affected environment. 

3.15.2.2 Proposed Action 

Dike 5 Construction Site Access and Trail Detour 

Truck traffic turning off Auburn-Folsom Road into Dike 5 would cross over a 

portion of the proposed Trail Detour. As discussed in Section 3.13, this could pose a 

safety risk to trail users. The measures described above for recreation, including 

posting of signs, construction of fences, and the use of flagmen, would maintain 

public safety. 

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Supplemental Environmental Assessment/Initial Study 

The use of flagmen on Auburn-Folsom Road to direct traffic into the Dike 5 area 

could pose a safety risk to the flagmen and approaching vehicles. Traffic along 

Auburn-Folsom Road travels at high speeds and the proposed flagmen would be 

positioned on a potentially blind curve. Reclamation and the Construction Contractor 

would follow all safety standards and use flagmen with appropriate safety training. 

Signs would be posted to alert drivers and to construction traffic and flagmen up 

ahead. Lower speed limits would be enforced, as necessary, to slow down vehicles 

before they approach the flagmen. Flashing lights may be installed for additional 

visual warnings. Implementation of these measures and the use of trained flagmen 

would reduce the safety risks to the flagmen and vehicles using Auburn-Folsom 

Road. 

During construction for the Dike 5 access, materials for paving asphalt would be 

temporarily handled on-site. The small quantity required to pave the turning lanes 

and haul road is unlikely to require storage for more than several days. No permanent 

hazardous materials would be stored on-site. 

Work on the Trail Detour would occur in an area with grasslands and other 

vegetation with a fire threat is considered moderate to high. Private residences and 

other buildings are present across Auburn-Folsom Road and in the Mooney Ridge 

and Granite Bay area directly adjacent to Folsom Reservoir. The operation of 

construction vehicles in the dry vegetation could ignite fires and could pose a safety 

risk to existing residences. Appropriate fire suppression tools would be kept on-site 

during the dry months when the fire risk is high. The construction vehicles would be 

kept on existing dirt trails or in areas without vegetation to reduce the risk of fires. 

These measures would adequately address the fire hazard during construction. 

Cofferdam 

The purpose of the Cofferdam is to keep the Stilling Basin area dry from American 

River flows (ie releases from Folsom Reservoir) and to protect the workers during 

construction of the Stilling Basin. This would allow work to continue year-round and 

would ensure worker safety during releases from Folsom Dam. This would be 

beneficial for worker health and safety. 

Construction of the Cofferdam for the Stilling Basin could require the temporary use, 

storage, and transport of hazardous materials for vehicles and equipment. This is 

unlikely to pose a threat to the public because there are no residences in the vicinity 

and no recreation is allowed in the area. With the development and implementation 

of a Worker Health and Safety Plan and a Hazardous Materials Management Plan 

this is not expected to pose a health risk to construction workers. 

3.15.3 Cumulative Effects 

The New Folsom Bridge Project would also have the potential for health and safety 

impacts and would be constructed at the same time and in the same general areas as 

3-50 February 2008 
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Affected Environment and Environmental Consequences 

the Cofferdam. However, both projects require specific health and safety plans and 

measures to reduce the potential for health and safety impacts to workers and the 

public during construction. In addition, Reclamation and the Corps are working 

together to coordinate their ongoing projects near the Folsom Facility. Overall, with 

the implementation of a Worker Health and Safety Plan, and Hazardous Materials 

Management Plan, the Proposed Action is not expected to contribute to cumulative 

public health and safety impacts. 

Phase 1 of the Auburn-Folsom Road Widening Project is expected to overlap with 

work on Dike 5 but would occur south of the Dike 5 area. Reclamation would 

coordinate with Placer County throughout construction to help maintain safety. Both 

agencies would implement appropriate safety measures such as warning signs, 

reduced speed limits, and appropriate worker safety training. With adequate 

coordination and safety training, the Proposed Action is not expected to contribute to 

any health and safety impacts to workers, the public, or vehicles along AuburnFolsom Road. 

3.16 Minimization Measures Incorporated into the Project 

Based on the above NEPA analysis, the following minimization measures will be 

incorporated into the project to reduce or avoid all project-related environmental 

effects: 

Air Quality 

Reclamation and the Construction Contractor will submit a plan for approval by 

SMAQMD, demonstrating that the heavy-duty off-road vehicles will achieve a 

project-wide fleet average 20 percent NOx reduction and 45 percent particulate 

reduction. The plan will also have to include an inventory of all off-road construction 

equipment equal to or greater than 50 horsepower that will be used an aggregate of 

40 or more hours during any portion of the project. Reclamation and the 

Construction Contractor will also have to demonstrate conformity with NOx 

thresholds, apply fugitive dust control on roadways, processing plants, and concrete 

batch plants and obtain power for construction facilities from the electric utility grid 

rather than diesel-driven generators and pumps. The Construction Contractor will be 

encouraged to seek additional control measures as part of emissions offsets. 

The above analysis estimates that project-wide emissions from the Cofferdam and 

ongoing operations related to the overall Folsom DS/FDR would exceed 85 pounds 

per day. Such operational impacts were previously addressed in the Folsom DS/FDR 

EIS/EIR and, as described therein, a mitigation fee will be paid to SMAQMD’s 

mitigation fund for any excess emissions. Emissions from the Cofferdam will be 

offset with the appropriate payment of this mitigation fee. 

3-51 February 2008 
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Supplemental Environmental Assessment/Initial Study 

Transportation and Circulation 

Minimization measures will include close coordination with Placer County to reduce 

potential cumulative impacts from the Auburn-Folsom Road Widening Project (see 

below). In addition, local emergency services will be notified of the temporary traffic 

light in order prevent unexpected delays in emergency services. The light will be 

designed to ensure it does not impede emergency vehicles. Appropriate signs will be 

installed to alert drivers to the new intersection. If flagmen are implemented, heavy 

truck deliveries to Dike 5 would be restricted to off-peak hours to reduce traffic 

impacts from slower speeds. If a temporary traffic signal is implemented, the lights 

at Eureka Road and Fuller Drive would be coordinated to allow appropriate gaps in 

Auburn-Folsom Road traffic such that construction trucks would have sufficient time 

to turn in and out of the access road. All measures will be coordinated with Placer 

County. 

3.17 References 

Bartoy, K. 2006a. Archaeological Site Record for CA-SAC-944H (Dike 5-1). On file 

at the North Central Information Center, Sacramento State University, Sacramento, 

California. 

Bartoy K. 2006b. Archaeological Site Record for CA-SAC-945H (Dike 5-2). On file 

at the North Central Information Center, Sacramento State University, Sacramento, 

California. 

Bartoy, K., K. Jones, J. Holson, and E. Reese. 2007. Cultural Resources Literature 

Search, Inventory, and National Register Evaluations for the Folsom Dam Safety 

and Flood Damage Reduction EIS/EIR, El Dorado, Placer, and Sacramento 

Counties, California. On file at Pacific Legacy, Berkeley, California. 

California Department of Transportation. 1998. Technical Noise Supplement, 

October 1998. 

Griffith, Francine. January 9, 2007. (DPR) Personal communication with Andria 

Loutsch of CDM, Walnut Creek, California. 

Jones, K. 2008. Archaeological Survey for the Dike 5 Trail Detour for the 

Supplemental Environmental Assessment/Initial Study (EA/IS) to the Folsom Dam 

Safety and Flood Damage Reduction (DS/FDR) Final Environmental Impact 

Statement/Environmental Impact Report (EIS/EIR). Letter report on file at Pacific 

Legacy, Berkeley, California. 

Jones, K. and L. Schrader. 2007a. Archaeological Site Record Update for CA-SAC944H (Dike 5-1). On file at the North Central Information Center, Sacramento State 

University, Sacramento, California. 

3-52 February 2008 
Chapter 3 

Affected Environment and Environmental Consequences 

Jones, K. and L. Schrader. 2007b.Archaeological Site Record Update for CA-SAC945H (Dike 5-2). On file at the North Central Information Center, Sacramento State 

University, Sacramento, California. 

Midwest Research Institute. 1996. Improvement of Specific Emission Factors 

(BACM Project No. 1) – Final Report. Kansas City, MO (March 29). 

Transportation Research Board. 2000. Highway Capacity Manual. Washington, D.C. 

U.S. Army Corps of Engineers (Corps). 2004. Corps March 2004 Archaeological 

Survey: Appendix C of Cultural Resources Archaeological Survey and National 

Register Evaluation of Folsom Dam and Properties for the Folsom Bridge Project, 

Folsom, California. On file at Pacific Legacy, Berkeley. 

U.S. Army Corps of Engineers (Corps). 2006. American River Watershed Project, 

Folsom Dam Raise, Folsom Bridge Draft Supplemental Environmental Impact 

Statement/ Environmental Impact Report, May 2006. 

U.S. Army Corps of Engineers (Corps). 2006.Cultural Resources Archaeological 

Survey and National Register Evaluation of Folsom Dam and Properties for the 

Folsom Bridge Project, Folsom, California. On file at Pacific Legacy, Berkeley. 

U. S. Geological Survey. 1954.1954 Folsom 7.5’ Quadrangle. Archived at the USGS 

Library, Menlo Park, CA. 

Wallace, Roberts, and Todd, LLC; LSA Associates; Geotechnical Consultants, Inc; 

Psomas; Concept Marine Inc. 2003. Draft Resource Inventory for Folsom Lake State 

Recreation Area. Prepared for: CDPR and Reclamation. 

Welch, P. 2005a. Site Record for CA-SAC-944H (Dike 5-1). On file at Pacific 

Legacy, Berkeley, California. 

Welch, P. 2005b. Site Record for CA-SAC-945H (Dike 5-2). On file at Pacific 

Legacy, Berkeley, California. 

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3-54 February 2008 
Chapter 4 

CEQA Evaluation 

This Chapter presents the California Environmental Quality Act (CEQA) Initial 

Study evaluation of the Proposed Project. 

4.1 Introduction 

This document is a joint Supplemental Environmental Assessment/Initial Study 

(EA/IS) to the Folsom Dam Safety and Flood Damage Reduction (DS/FDR) Final 

Environmental Impact Statement/Environmental Impact Report (EIS/EIR) (March 

2007), and satisfies the requirements of the National Environmental Policy Act 

(NEPA) and the California Environmental Quality Act (CEQA). This Supplemental 

EA/IS has been prepared by the U.S. Department of the Interior, Bureau of 

Reclamation (Reclamation), the U.S. Army Corps of Engineers (Corps), and the 

Corps non-Federal sponsors, the Central Valley Flood Protection Board (CVFPB)1

and the Sacramento Area Flood Control Agency (SAFCA). Reclamation is the 

NEPA lead agency for this document; CVFPB is the CEQA lead agency. 

Agency NEPA/CEQA Role 

Bureau of Reclamation NEPA Lead Agency 

U.S. Army Corps of 

Engineers Cooperating Agency under NEPA 

Central Valley Flood 

Protection Board CEQA Lead Agency 

Sacramento Area Flood 

Control Agency Responsible Agency under CEQA 

The purpose of this Supplemental EA/IS is to describe and analyze the effects of 

construction actions and refinements to the project since the completion of the 

Folsom DS/FDR Final EIS/EIR. The Folsom DS/FDR Project, as approved and 

authorized, is currently under construction. The actions proposed in this EA/IS are 

existing components of the authorized project currently underway and have been 

defined to a greater level of detail than was available at the time of the Folsom 

DS/FDR EIS/EIR. This document does not change the project originally described in 

the Joint Federal Project (JFP) Record of Decision (ROD) and Safety of Dams 

(SOD) ROD, but proposes refinements and clarifications to certain project actions 

that require further environmental analysis. The Supplemental EA/IS identifies and 

evaluates certain site specific actions. The results of this Supplemental EA/IS will 

provide the basis for determining whether a Finding of No Significant Impact 

(FONSI)/Negative Declaration (ND) can be issued or if additional environmental 

review such as an EIS/EIR is required. 

 

1

 Formerly known as the Reclamation Board of the State of California. 

4-1 February 2008 
Folsom Dam Safety and Flood Damage Reduction 

Supplemental Environmental Assessment/Initial Study 

4.2 Environmental Checklist Form 

1. Project title: 

Supplemental Environmental Assessment/Initial Study to the Folsom Dam 

Safety and Flood Damage Reduction Final Environmental Impact 

Statement/Environmental Impact Report 

2. Lead agency name and address: 

CEQA: 

Central Valley Flood Protection Board 

Department of Water Resources 

Division of Flood Management 

3310 El Camino Ave. Room LL40 

Sacramento, CA 95821 

NEPA: 

Bureau of Reclamation 

Central California Area Office 

7794 Folsom Dam Road 

Folsom, CA 95630 

3. Contact person and phone number: 

CEQA: 

Annalena Bronson 

Staff Environmental Scientist 

Department of Water Resources 

Division of Flood Management 

3310 El Camino Ave. Room 140 

Sacramento, CA 95821 

NEPA: 

Elizabeth Ayres Vasquez 

Natural Resources Specialist 

Bureau of Reclamation 

Central California Area Office 

7794 Folsom Dam Road 

Folsom, CA 95630 

4. Project location: 

Folsom Reservoir in Sacramento and Placer Counties 

5. Project sponsor’s name and address: 

Central Valley Flood Protection Board 

Department of Water Resources 

Division of Flood Management 

4-2 February 2008 
Chapter 4 

CEQA Evaluation 

3310 El Camino Ave. Room LL40 

Sacramento, CA 95821 

6. General plan designation: 

Not Applicable 

7. Zoning: 

Not Applicable 

8. Description of project: (Describe the whole action involved, including but 

not limited to later phases of the project, and any secondary, support, or offsite features necessary for its implementation. Attach additional sheets if 

necessary.) 

There are three main aspects of the Proposed Project addressed within this 

EA/IS: 

• A Trail Detour that would provide safe passage for hikers, pedestrians, 

and bicyclists normally using the existing trail that occurs on the tops 

of Dikes 4, 5, and 6. 

• Dike 5 Construction Site Access with flagmen or a temporary traffic 

light, turn-in and turn-out lanes; and 

• Construction details on the Cofferdam for the JFP Auxiliary Spillway 

Stilling Basin. 

In conjunction with the above, a change in the schedule for work on Dike 5 is 

proposed. See Chapter 2 of this Supplemental EA/IS for additional details. 

9. Surrounding land uses and setting: Briefly describe the project’s 

surroundings: 

The location for Proposed Project addressed in this Supplemental EA/IS 

includes the area surrounding Folsom Reservoir that falls within Placer and 

Sacramento Counties. No actions addressed in this Supplemental EA/IS 

would occur in El Dorado County. The study area mainly consists of 

Federally-owned lands that are currently leased to and managed by the 

California Department of Parks and Recreation (DPR). 

4-3 February 2008 
Folsom Dam Safety and Flood Damage Reduction 

Supplemental Environmental Assessment/Initial Study 

10. Other public agencies whose approval is required (e.g., permits, financing 

approval, or participation agreement.) 

CVFPB – CEQA lead (Cofferdam) 

SAFCA – Corps local sponsor (Cofferdam) 

U.S. Environmental Protection Agency – Air Quality Conformity (Dike 5 

Change in Schedule) 

Sacramento Metropolitan Air Quality Management District (SMAQMD) – 

Air Quality (Cofferdam) 

Placer County Air Pollution Control District (PCAPCD) – Air Quality (Dike 

5 Change in Schedule) 

State Water Resources Control Board – National Pollutant Discharge 

Elimination System (NPDES) Permit (Dike 5 Construction Site) 

Placer County – Encroachment Permit (Dike 5 Construction Site Access) 

U.S. Fish and Wildlife Service (USFWS) – Section 7 Consultation, Fish and 

Wildlife Coordination Act Report 

4-4 February 2008 
Chapter 4 

CEQA Evaluation 

4.3 Environmental Factors Potentially Affected 

The environmental factors checked below would be potentially affected by this 

project, involving at least one impact that is a “Potentially Significant Impact” as 

indicated by the checklist on the following page. 

3 Aesthetics Agriculture Resources 3 Air Quality 

3 Biological Resources 3 Cultural Resources 3 Geology/Soils 

3 Hazards & Hazardous 

Materials 

3 Hydrology/Water Quality 3 Land Use/Planning 

3 Mineral Resources 3 Noise Population/Housing 

3 Public Services 3 Recreation 3 Transportation/Traffic 

3 Utilities/Service 

Systems 

3 Mandatory Findings of 

Significance 

4-5 February 2008 
Folsom Dam Safety and Flood Damage Reduction 

Supplemental Environmental Assessment/Initial Study 

4.4 Determination 

On the basis of this initial evaluation: 

I find that the proposed project COULD NOT have a significant effect on the 

environment, and a NEGATIVE DECLARATION will be prepared. 

3 I find that although the proposed project could have a significant effect on 

the environment, there will not be a significant effect in this case because 

revisions in the project have been made by or agreed to by the project 

proponent. A MITIGATED NEGATIVE DECLARATION will be prepared. 

I find that the proposed project MAY have a significant effect on the 

environment, and an ENVIRONMENTAL IMPACT REPORT is required. 

I find that the proposed project MAY have a “potentially significant impact” 

or “potentially significant unless mitigated” impact on the environment, but 

at least one effect 1) has been adequately analyzed in an earlier document 

pursuant to applicable legal standards, and 2) has been addressed by 

mitigation measures based on the earlier analysis as described on attached 

sheets. An ENVIRONMENTAL IMPACT REPORT is required, but it must 

analyze only the effects that remain to be addressed. 

I find that although the proposed project could have a significant effect on 

the environment, because all potentially significant effects (a) have been 

analyzed adequately in an earlier EIR or NEGATIVE DECLARATION 

pursuant to applicable standards, and (b) have been avoided or mitigated 

pursuant to that earlier EIR or NEGATIVE DECLARATION, including 

revisions or mitigation measures that are imposed upon the proposed project, 

nothing further is required. 

Signature Date 

Printed Name For 

4-6 February 2008 
Chapter 4 

CEQA Evaluation 

4.5 Evaluation of Environmental Impacts 

This section presents the evaluation of environmental impacts for the CEQA 

analysis. The following abbreviations are used: 

NI – No Impact 

LTS – Less Than Significant 

LTSWM – Less Than Significant With Mitigation 

B - Beneficial 

In the discussion that follows each portion of the checklist, the issue analysis 

particular to each of the three main components of the Project is delineated using an 

alphanumeric index based on Project component and environmental topic. For 

example, the discussion below of "1.c)" addresses the issue of whether the Trail 

Detour would substantially degrade the existing visual character or quality of the site 

and its surroundings. 

1 2 3 

AESTHETICS Trail 

Detour 

Dike 5 

Construction 

Site Access 

Cofferdam 

I. AESTHETICS -- Would the project: 

a) Have a substantial adverse effect on a scenic 

vista? NI NI NI 

b) Substantially damage scenic resources, 

including, but not limited to, trees, rock 

outcroppings, and historic buildings within a 

state scenic highway? 

NI NI NI 

c) Substantially degrade the existing visual 

character or quality of the site and its 

surroundings? 

LTS LTS LTS 

d) Create a new source of substantial light or 

glare which would adversely affect day or 

nighttime views in the area? 

NI LTS NI 

1-3.a,b) None of the activities would affect any existing scenic vistas. No scenic 

highways are designated in the area. 

1&3.d) The Trail Detour and Cofferdam would not create any new source of 

light. 

1.c) The Trail Detour would alter the visual character of the area, but only slightly. 

All trees would be avoided to eliminate the need for tree removal. The Trail 

Detour would be generally lined by native materials and is not expected to 

4-7 February 2008 
Folsom Dam Safety and Flood Damage Reduction 

Supplemental Environmental Assessment/Initial Study 

substantially degrade the visual character of the area. This would be less than 

significant. 

2.c) Construction of turning lanes and a temporary traffic light would alter the 

visual character around Dike 5 at Auburn-Folsom Road. The area may be 

visible from several homes across the street. This impact would be temporary 

and the area would be restored to pre-construction conditions after construction 

is complete. This impact would be less than significant. 

2.d) A temporary traffic light could be installed at the Dike 5 Construction Site 

Access. This is unlikely to create a new source of substantial light because it 

would only be in use during construction traffic and would be removed at the 

end of construction. Flashing lights may need to be installed to the north and 

south of the entrance to the access road in order to warn drivers about stopped 

traffic ahead, and this could potentially create light impacts to some homes. 

However, the use of these lights would be minimal and temporary as the lights 

would be used only when traffic enters or exits the access road. After 

completion of construction at Dikes 4, 5, and 6, the lights would be removed. 

These impacts would be less than significant. 

3.c) Construction of the Cofferdam is not expected to substantially degrade the 

existing visual character of the area. The Cofferdam consists of a wall that 

would be constructed to ensure the Stilling Basin area remains dry during 

construction. The area where the Cofferdam would be constructed is already 

undergoing construction and would be permanently altered by the JFP 

Auxiliary Spillway. This area is not open to the public and would only be 

partially visible from the New Folsom Bridge being constructed by the Corps. 

The construction of the Cofferdam would not alter scenic vistas or views from 

scenic highways. This impact would be considered less than significant. 

4-8 February 2008 
Chapter 4 

CEQA Evaluation 

1 2 3 

AGRICULTURAL RESOURCES Trail 

Detour 

Dike 5 

Construction 

Site Access 

Cofferdam

II. AGRICULTURE RESOURCES: In 

determining whether impacts to agricultural 

resources are significant environmental 

effects, lead agencies may refer to the 

California Agricultural Land Evaluation and 

Site Assessment Model (1997) prepared by 

the California Dept. of Conservation as an 

optional model to use in assessing impacts 

on agriculture and farmland. Would the 

project: 

a) Convert Prime Farmland, Unique 

Farmland, or Farmland of Statewide 

Importance (Farmland), as shown on the 

maps prepared pursuant to the Farmland 

Mapping and Monitoring Program of 

the California Resources Agency, to 

non-agricultural use? 

NI NI NI 

b) Conflict with existing zoning for 

agricultural use, or a Williamson Act 

contract? 

NI NI NI 

c) Involve other changes in the existing 

environment which, due to their location 

or nature, could result in conversion of 

Farmland, to non-agricultural use? 

NI NI NI 

1-3.a,b,c) No agricultural lands exist within the project area; therefore no 

agricultural impacts would occur as a result of the Proposed Project. 

4-9 February 2008 
Folsom Dam Safety and Flood Damage Reduction 

Supplemental Environmental Assessment/Initial Study 

1 2 3 

AIR QUALITY Trail 

Detour

Dike 5 

Construction 

Site Access 

Cofferdam

III. AIR QUALITY -- Where available, 

the significance criteria established by the 

applicable air quality management or air 

pollution control district may be relied 

upon to make the following determinations. 

Would the project: 

a) Conflict with or obstruct 

implementation of the applicable air 

quality plan? 

NI NI NI 

b) Violate any air quality standard or 

contribute substantially to an existing or 

projected air quality violation? 

LTS LTS LTSWM 

c) Result in a cumulatively considerable 

net increase of any criteria pollutant for 

which the project region is nonattainment under an applicable Federal 

or state ambient air quality standard 

(including releasing emissions which 

exceed quantitative thresholds for ozone 

precursors)? 

LTS LTS LTS 

d) Expose sensitive receptors to 

substantial pollutant concentrations? LTS LTS NI 

e) Create objectionable odors affecting a 

substantial number of people? NI NI NI 

1-3.a) The Trail Detour would not create any new permanent emissions and would 

have very little emissions during construction because of the limited types of 

equipment needed. All actions would comply with applicable air quality 

standards and air quality plans. 

1.b) Construction for the Trail Detour would have less than significant impacts to 

air quality given the limited types of construction equipment required and the 

short time-frame required to grade and surface the trail. 

1.c) Because construction of the Trail Detour would contribute only a minimal 

amount of emissions and would be of a short duration, this impact would be 

less than significant. 

4-10 February 2008 
Chapter 4 

CEQA Evaluation 

1-3.d) None of the actions would expose sensitive receptors to substantial pollutant 

concentrations. The Trail Detour would require a limited amount of 

equipment and construction would be of a short duration. The Cofferdam 

would not be constructed near any sensitive receptors. The Dike 5 

intersection would be constructed on Auburn-Folsom Road near several 

residences; however, all trucks would comply with existing air quality 

regulations and would use only designated truck routes. This impact would 

be less than significant. 

1-3.e) None of the actions would create odors that would affect a substantial 

number of people. 

2.b) In the Folsom DS/FDR Final EIS/EIR, work at Dike 5 was scheduled to start 

in September 2009. Due to SOD schedule priorities, Reclamation has elected 

to initiate the Dike 5 work by September 2008, continuing into 2009. The air 

quality impacts related to construction at Dike 5 were already addressed in 

the Final EIS/EIR; the only action related to the Supplemental EA/IS is the 

date adjustment. 

Emissions for Dike 5 construction equipment and haul trucks are summarized 

in Chapter 3, Table 3.4-1. Both daily and project-level emissions (i.e., tons 

per year) would be less than the PCAPCD and General Conformity 

thresholds in 2008 and 2009; therefore, emissions are expected to be less than 

significant. 

Combined emissions from Dike 5 and other Folsom DS/FDR actions 

scheduled for 2008 and 2009 were reviewed to evaluate compliance with 

General Conformity. As is demonstrated in Table 3.4-2 in Chapter 3, 

emissions are less than the applicable General Conformity thresholds and 

therefore air quality impacts are expected to be less than significant. 

2.c) Although the Dike 5 work would have some emissions, it would be 

temporary and would not result in any cumulatively considerable net increase 

of any pollutant for which the project region is non-attainment. 

3.b) Approximately 6,700 cubic yards (cy) to 8,500 cy of concrete and 1,350,000 

pounds (lbs) to 1,700,000 lbs of reinforcing bars would be required for 

construction of the Cofferdam. This would equate to 40 trucks per day for a 

total of 45 days. 

The emission estimates provided in Table 3.4-4 in Chapter 3 indicate the 

uncontrolled nitrogen oxides (NOx) emissions would not exceed the 

SMAQMD’s daily emission rates, nor would uncontrolled NOx, PM10, and 

CO emissions exceed the General Conformity de minimis thresholds. 

4-11 February 2008 
Folsom Dam Safety and Flood Damage Reduction 

Supplemental Environmental Assessment/Initial Study 

Based on this analysis, construction of the Cofferdam itself would not cause 

an adverse impact that exceeds applicable thresholds. Since the peak annual 

emissions only represent a modest emissions increase, the General 

Conformity thresholds will not be exceeded when added to the other Folsom 

DS/FDR actions planned for 2008 and 2009. Although emissions from the 

Cofferdam would not exceed SMAQMD’s daily thresholds, when combined 

with other Folsom DS/FDR actions happening concurrently, daily emissions 

could exceed 85 pounds per day and would be considered potentially 

significant. The mitigation measures described below would address the air 

quality impacts associated with the Cofferdam. With the appropriate 

mitigation described below, air quality impacts from Cofferdam construction 

would be considered less than significant. 

3.c) Although the Cofferdam work would have a limited amount of emissions, it 

would be temporary and would not result in any cumulatively considerable 

net increase of any pollutant for which the project region is non-attainment. 

Mitigation Measure: 

1. Reclamation and the Construction Contractor will submit a plan for approval by 

SMAQMD, demonstrating that the heavy-duty off-road vehicles will achieve a 

project-wide fleet average 20 percent NOx reduction and 45 percent particulate 

reduction. The plan will also be required to include an inventory of all off-road 

construction equipment greater than or equal to 50 horsepower that will be used 

an aggregate of 40 or more hours during any portion of the project. Reclamation 

and the Construction Contractor will also have to demonstrate conformity with 

NOx thresholds, apply fugitive dust control on roadways, processing plants, and 

concrete batch plants and obtain power for construction facilities from the 

electric utility grid rather than diesel-driven generators and pumps. The 

Construction Contractor will be encouraged to seek additional control measures 

as part of emissions offsets. 

2. Since project-wide emissions from the Cofferdam and ongoing operations related 

to the Folsom DS/FDR could exceed 85 lbs per day, the appropriate fee will be 

paid to SMAQMD’s mitigation fund for any excess emissions. Emissions from 

the Cofferdam will be offset with the appropriate payment of this mitigation fee. 

4-12 February 2008 
Chapter 4 

CEQA Evaluation 

1 2 3 

BIOLOGICAL RESOURCES Trail 

Detour 

Dike 5 

Construction 

Site Access 

Cofferdam

IV. BIOLOGICAL RESOURCES -- 

Would the project: 

a) Have a substantial adverse effect, either 

directly or through habitat modifications, 

on any species identified as a candidate, 

sensitive, or special status species in 

local or regional plans, policies, or 

regulations, or by the California 

Department of Fish and Game or U.S. 

Fish and Wildlife Service? 

LTS NI NI∗

b) Have a substantial adverse effect on any 

riparian habitat or other sensitive natural 

community identified in local or regional 

plans, policies, and regulations or by the 

California Department of Fish and Game 

or US Fish and Wildlife Service? 

LTS NI NI∗

c) Have a substantial adverse effect on 

federally protected wetlands as defined 

by Section 404 of the Clean Water Act 

(including, but not limited to, marsh, 

vernal pool, coastal, etc.) through direct 

removal, filling, hydrological 

interruption, or other means? 

NI NI NI∗

d) Interfere substantially with the 

movement of any native resident or 

migratory fish or wildlife species or with 

established native resident or migratory 

wildlife corridors, or impede the use of 

native wildlife nursery sites? 

LTS LTS NI 

e) Conflict with any local policies or 

ordinances protecting biological 

resources, such as a tree preservation 

policy or ordinance? 

NI NI NI 

 

∗ Although the Cofferdam could affect habitat and special status species, the Cofferdam 

would be constructed within the footprint of the JFP Auxiliary Spillway and therefore any 

impacts have already been addressed in the Folsom DS/FDR Draft and Final EIS/EIR.

4-13 February 2008 
Folsom Dam Safety and Flood Damage Reduction 

Supplemental Environmental Assessment/Initial Study 

 1 2 3 

BIOLOGICAL RESOURCES Trail 

Detour 

Dike 5 

Construction 

Site Access 

Cofferdam

f) Conflict with the provisions of an 

adopted Habitat Conservation Plan, 

Natural Community Conservation Plan, 

or other approved local, regional, or state 

habitat conservation plan? 

NI NI NI 

1.a) The Trail Detour would require the potential alteration of various habitats 

including oak woodlands and annual grasslands. The Trail Detour would be 

routed to avoid any existing wetlands or wet areas, or trees. Portions of the 

detour would follow existing trails to minimize impacts to vegetation. Some 

trimming of vegetation would likely be necessary to establish the proper width 

for the trail. The minimal vegetation alteration required for the Trail Detour is 

expected to have a less than significant impact to special status species and 

habitats. 

1.b) Oak woodlands and annual grassland habitats are present within the Trail 

Detour construction areas and may be affected by construction activities 

including vegetation trimming, as well as increased erosion and sedimentation. 

Oak woodland and annual grassland provide resting, nesting, and forage habitat 

for a variety of wildlife. Construction activities could result in the loss of this 

habitat. The Trail Detour would be rerouted to avoid the removal of trees and 

other vegetation but may require some trimming of vegetation to obtain the 

proper width. The Trail Detour would be constructed along existing dirt trails 

as much as possible to reduce vegetation and wildlife impacts. The Trail 

Detour would not be paved, but would be created using native materials found 

onsite and little soil erosion is expected. Impacts to sensitive habitats are 

expected to be less than significant. 

1.c) Construction of the Trail Detour would not require removal, filling or 

hydrological disruption of seasonal wetlands. The Trail Detour will be routed 

to avoid such areas. 

1.d) The Trail Detour would not substantially interfere with the movement of 

wildlife species or the use of nursery sites. The Trail Detour would be 

constructed using native materials and would follow along existing unimproved 

trails as much as possible to avoid or minimize vegetation and wildlife impacts. 

1.e) The Trail Detour would occur on Federal property and would not be subject to 

local policies or ordinances. 

4-14 February 2008 
Chapter 4 

CEQA Evaluation 

1.f) No Habitat Conservation Plans (HCPs) and Natural Community Conservation 

Plans (NCCPs) are in effect for the Trail Detour area. 

2.a) Impacts to special status species from the Dike 5 staging area (an area from 

Dike 5 to Auburn-Folsom Road) were already disclosed in the Folsom DS/FDR 

EIS/EIR. The only change to the Dike 5 area from that discussed in the 

EIS/EIR is the construction of a temporary intersection, turn-in and turn-out 

lanes, and truck traffic delivering materials to the site using these lanes. The 

lanes would be mainly constructed on Auburn-Folsom Road and would turninto the Dike 5 area, which would already be cleared of vegetation for staging, 

as described in the EIS/EIR. Pre-construction surveys completed for the 

Folsom DS/FDR Project identified no special-status species in the area around 

Dike 5. Because the area would already be cleared of vegetation for Dike 5 

staging, the Dike 5 Construction Site Access is not expected to affect specialstatus species, beyond what was disclosed in the EIS/EIR. In addition, the area 

would be restored to pre-construction conditions after work on the dikes is 

complete. 

2.b) The only habitats within the Dike 5 access area are annual grassland and 

ruderal habitats. Neither of these habitats are considered sensitive natural 

communities. 

2.c) Wetlands do not occur in the Dike 5 access and staging areas. 

2.d) Although no specific wildlife corridors have been identified in the Dike 5 area, 

it is reasonable to expect the construction traffic turning into the area could 

deter the movement of wildlife due to the increase in noise, dust, and heavy 

vehicles. This construction site access would only be used for work on Dikes 4, 

5, and 6 and would be restored to pre-construction conditions after work is 

complete. In addition, the area would already be disturbed for the Dike 5 

staging area, as described in the EIS/EIR. Because this impact would be 

temporary and would occur in an area already disturbed, it is expected to be 

less than significant. 

2.e) No additional trees would require removal for the Dike 5 Construction Site 

Access, beyond those already removed for the Dike 5 staging area and 

disclosed in the EIS/EIR. The Proposed Project would not conflict with local 

policies or ordinances as construction would occur on Federal property or on 

Auburn-Folsom Road 

2.f) No HCPS and NCCPs are in effect for the Dike 5 Construction Site Access area. 

3.a) The Cofferdam could require the potential alteration of various habitats 

including riparian and annual grassland. The alteration of these habitats could 

4-15 February 2008 
Folsom Dam Safety and Flood Damage Reduction 

Supplemental Environmental Assessment/Initial Study 

result in an adverse effect on special-status species such as the removal of 

resting, nesting, and foraging habitat. The EIS/EIR adequately addressed these 

impacts as the Cofferdam would be constructed within the JFP Auxiliary 

Spillway footprint. No new impacts beyond those discussed in the EIS/EIR for 

the JFP Auxiliary Spillway are anticipated. 

3.b) See 3.a) above. 

3.c) Construction of the Cofferdam would not result in additional removal, filling or 

hydrological disruption of wetland habitats along the American River. All 

wetlands in this area would be impacted by the JFP Auxiliary Spillway 

construction and were previously analyzed in the EIS/EIR. The current Clean 

Water Act Section 404 permit in place for the Folsom DS/FDR Project covers 

the entire JFP Auxiliary Spillway area including the Cofferdam. 

3.d) Construction of the Cofferdam would occur in an area already significantly 

disrupted by construction of the JFP Auxiliary Spillway and the New Folsom 

Bridge. Therefore, construction of the Cofferdam would not provide additional 

interference with the movement wildlife species or the use of nursery sites. 

3.e) Construction of the Cofferdam would occur on Federal property and would not 

conflict with local policies or ordinances. 

3.f) No HCPS and NCCPs are in effect for the Stilling Basin and Cofferdam area. 

4-16 February 2008 
Chapter 4 

CEQA Evaluation 

1 2 3 

CULTURAL RESOURCES Trail 

Detour 

Dike 5 

Construction Site 

Access 

Cofferdam

V. CULTURAL RESOURCES -- 

Would the project: 

a) Cause a substantial adverse change 

in the significance of a historical 

resource as defined in § 15064.5? 

LTS LTS LTS 

b) Cause a substantial adverse change 

in the significance of an 

archaeological resource pursuant 

to § 15064.5? 

LTS LTS LTS 

c) Directly or indirectly destroy a 

unique paleontological resource or 

site or unique geologic feature? 

LTS LTS LTS 

d) Disturb any human remains, 

including those interred outside of 

formal cemeteries? 

LTSWM LTSWM LTSWM 

1.a-c) Within and adjacent to the Trail Detour, six previously undiscovered 

cultural resources were recorded during the survey and two known 

resources, CA-SAC-944H and CA-SAC-945H, were revisited and site 

records updated. The Trail Detour area of potential effect (APE) would be 

approximately 5 to 6 ft wide. The archaeological survey width for the Trail 

Detour is substantially wider, 30 meters on either side of the trail centerline. 

CA-SAC-944H was previously recorded as part of the Folsom Dam 

DS/FDR EIS/EIR and found ineligible for listing on the National Register 

of Historic Places (Bartoy et al. 2007). The project areas associated with 

the Trail Detour have been subject to cultural resources survey and 

inventory. The cultural resources identified would either be avoided by 

shifting the Trail Detour, or they have been considered ineligible for listing 

by Reclamation. Reclamation will consult with SHPO to seek their 

concurrence in compliance with the 36 Code of Federal Regulations Part 

800 regulations that implement section 106 of the National Historic 

Preservation Act. This impact would be less than significant. 

1. d) Although construction could uncover unknown cultural or historic 

resources or human remains, measures described below would provide 

mitigation to reduce potential cultural resource impacts to less than 

significant. 

4-17 February 2008 
Folsom Dam Safety and Flood Damage Reduction 

Supplemental Environmental Assessment/Initial Study 

2-3. a-c) No cultural resources eligible for inclusion on the NRHP will be impacted 

by these actions. This impact would be less than significant. 

2-3. d) Although construction could uncover unknown cultural or historic 

resources or human remains, measures described below would provide 

mitigation to reduce potential cultural resource impacts to less than 

significant. 

Mitigation Measure: 

Include in the standard contract specifications directions to follow in the unlikely 

event of the discovery of human remains or other cultural resources during the 

construction phase of the Proposed Project.

4-18 February 2008 
Chapter 4 

CEQA Evaluation 

1 2 3 

GEOLOGY AND SOILS Trail 

Detour 

Dike 5 

Construction 

Site Access 

Cofferdam

VI. GEOLOGY AND SOILS -- Would 

the project: 

a) Expose people or structures to potential 

substantial adverse effects, including 

the risk of loss, injury, or death 

involving: 

i) Rupture of a known earthquake 

fault, as delineated on the most 

recent Alquist-Priolo Earthquake 

Fault Zoning Map issued by the 

State Geologist for the area or 

based on other substantial evidence 

of a known fault? Refer to Division 

of Mines and Geology Special 

Publication 42. 

NI NI NI 

ii) Strong seismic ground shaking? NI NI NI 

iii) Seismic-related ground failure, 

including liquefaction? NI NI NI 

iv) Landslides? NI NI NI 

b) Result in substantial soil erosion or the 

loss of topsoil? LTS LTS NI 

c) Be located on a geologic unit or soil 

that is unstable, or that would become 

unstable as a result of the project, and 

potentially result in on- or off-site 

landslide, lateral spreading, subsidence, 

liquefaction or collapse? 

NI NI NI 

d) Be located on expansive soil, as 

defined in Table 18-1-B of the Uniform 

Building Code (1994), creating 

substantial risks to life or property? 

NI NI NI 

e) Have soils incapable of adequately 

supporting the use of septic tanks or 

alternative waste water disposal 

systems where sewers are not available 

for the disposal of waste water? 

NI NI NI 

4-19 February 2008 
Folsom Dam Safety and Flood Damage Reduction 

Supplemental Environmental Assessment/Initial Study 

1-3.a) No new buildings would be constructed as part of the Proposed Project and 

therefore the project would not expose people or structures to any new risks 

associated with earthquakes. No seismic or unstable soil impacts are 

anticipated in the area of the Proposed Project. Although the Bear Mountain 

fault occurs north of the project, this fault has not been designated as active 

by the U.S. Geological Survey. Additionally, ground shaking potential is low 

in the area. The potential for landslides is low because of relatively thin soils. 

1.b) The Trail Detour would require a small amount of cut and fill to provide 

appropriate slopes. A minimal amount topsoil would likely be removed and 

placed elsewhere on site. The Trail Detour would be covered with native 

materials which would reduce the potential for soil erosion. This impact 

would be less than significant. 

1-3.c) As indicated above, the Project site is not located on an unstable geologic 

unit or soils. 

1-3.d) The Project site has been previously disturbed for construction of Folsom 

Dam and Reservoir and is unlikely to contain expansive soils. The Cofferdam 

area contains a shallow layer of soil over grantic rock. The Trail Detour and 

Dike 5 area are not expected to contain any expansive soils. 

1-3.e) No septic tanks or alternative waste disposal systems are proposed. 

2.b) The new turn-in and turn-out lanes would be unlikely to result in any soil 

erosion or loss of topsoil as the lanes would be paved. Construction vehicles 

and equipment entering and exiting the Dike 5 area could cause some soil 

erosion and dust. Prior to construction activity, a Notice of Intent will be filed 

with the Central Valley Regional Water Quality Control Board to indicate the 

intent to comply with the General Permit for Construction Activities greater 

than 1 acre. The General Permit establishes conditions to minimize sediment 

and pollutant loading and requires preparation and implementation of a 

Storm Water Pollution Prevention Plan (SWPPP) prior to construction. The 

purpose of the SWPPP is to prevent the movement of construction pollutants 

(in contact with stormwater) into receiving water. This is accomplished 

through the selection of Best Management Practices (BMPs) which are 

measures that are applied to control erosion and sediment transport. Proper 

implementation of the BMPs outlined in the SWPPP would help prevent 

erosion and reduce this impact to less than significant. 

3.b) The Cofferdam would be built in an area that mainly consists of decomposed 

granite and would be unlikely to contribute to any soil erosion. Any layer of 

topsoil would have already been removed for excavation of the JFP Auxiliary 

Spillway. 

4-20 February 2008 
Chapter 4 

CEQA Evaluation 

1 2 3 

HAZARDS AND HAZARDOUS 

MATERIALS 

Trail 

Detour 

Dike 5 

Construction 

Site Access 

Cofferdam

VII. HAZARDS AND HAZARDOUS 

MATERIALS -- Would the project: 

a) Create a significant hazard to the 

public or the environment through the 

routine transport, use, or disposal of 

hazardous materials? 

NI NI LTS 

b) Create a significant hazard to the 

public or the environment through 

reasonably foreseeable upset and 

accident conditions involving the 

release of hazardous materials into the 

environment? 

NI LTS LTS 

c) Emit hazardous emissions or handle 

hazardous or acutely hazardous 

materials, substances, or waste within 

one-quarter mile of an existing or 

proposed school? 

LTS NI NI 

d) Be located on a site which is included 

on a list of hazardous materials sites 

compiled pursuant to Government 

Code Section 65962.5 and, as a result, 

would it create a significant hazard to 

the public or the environment? 

NI NI NI 

e) For a project located within an airport 

land use plan or, where such a plan has 

not been adopted, within two miles of a 

public airport or public use airport, 

would the project result in a safety 

hazard for people residing or working 

in the project area? 

NI NI NI 

f) For a project within the vicinity of a 

private airstrip, would the project result 

in a safety hazard for people residing 

or working in the project area? 

NI NI NI 

g) Impair implementation of or physically 

interfere with an adopted emergency 

response plan or emergency evacuation 

plan? 

NI NI NI 

4-21 February 2008 
Folsom Dam Safety and Flood Damage Reduction 

Supplemental Environmental Assessment/Initial Study 

1 2 3 

HAZARDS AND HAZARDOUS 

MATERIALS 

Trail 

Detour 

Dike 5 

Construction 

Site Access 

Cofferdam

h) Expose people or structures to a 

significant risk of loss, injury or death 

involving wildland fires, including 

where wildlands are adjacent to 

urbanized areas or where residences 

are intermixed with wildlands? 

LTS NI NI 

1-2.a) The Proposed Project would not result in the permanent use, transport, or 

disposal of hazardous materials after construction is complete. 

1.b) Construction of the Trail Detour would not require the storage of hazardous 

materials. 

1-3.d) None of the actions would occur on a listed hazardous materials site. 

1-3.e,f) None of the proposed actions are located at, or within two miles of, a public 

airport. 

1-3.g) The actions would not interfere with any emergency plans. 

1-3.h) The Cofferdam and Dike 5 Construction Site Access would occur in an area 

cleared of existing vegetation. 

1.c) The final portion of the Trail Detour near Dike 4 would be constructed within 

a quarter mile of Cavitt Junior High School in the Granite Bay area. A small 

excavator and a BobcatTM would likely be the only construction equipment 

required to build the Trail Detour. These vehicles would have a small amount 

of air emissions when in operation. They would also require fuel, but no fuel 

is expected to be stored on-site. This action is unlikely to pose any hazard 

risk to Cavitt Junior High school and construction near the school would be 

completed within several weeks. This impact would be less than significant. 

1.h) Work on the Trail Detour would occur in an area with grasslands and other 

vegetation where the fire threat is designated as moderate to high. Private 

residences and other buildings are present across Auburn-Folsom Road and 

around the Mooney Ridge and Granite Bay area directly adjacent to the 

reservoir and Federal property. The operation of construction vehicles in the 

dry vegetation could start fires. Appropriate fire suppression tools will be 

kept on-site during the dry months when the fire risk is high. The 

4-22 February 2008 
Chapter 4 

CEQA Evaluation 

construction vehicles will be kept on existing dirt trails or in areas without 

vegetation to reduce the risk of fires. This impact would be less than 

significant. 

2.b) Materials for paving asphalt would be temporarily handled on-site. The small 

quantity required to pave the turn-in and turn-out lanes is unlikely to require 

storage for more than several days. The impact would be temporary and less 

than significant. 

2-3.c) The Dike 5 Construction Site Access and Cofferdam are not within a quarter 

mile of an existing school. 

3.a) Construction of the Cofferdam could require the temporary use and transport 

of hazardous materials associated with construction equipment maintenance 

and activities. There are no residences in the vicinity and no recreation is 

allowed in the area. Because this impact would be temporary and would not 

occur near any residences or recreation areas, this impact would be less than 

significant. 

3.b) Construction of the Cofferdam would require the use of hazardous materials 

such as concrete, and fuel within the area of the existing Folsom Dam 

Spillway. Reclamation and their Construction Contractor would develop and 

implement a Hazardous Materials Management Plan and Worker Health and 

Safety Plan that would provide proper procedures for storing and handling 

hazardous materials to prevent any environmental or health and safety 

impacts. This impact would be less than significant. 

4-23 February 2008 
Folsom Dam Safety and Flood Damage Reduction 

Supplemental Environmental Assessment/Initial Study 

1 2 3 

HYDROLOGY AND WATER 

QUALITY 

Trail 

Detour

Dike 5 

Construction 

Site Access 

Cofferdam

VIII. HYDROLOGY AND WATER 

QUALITY -- Would the project: 

a) Violate any water quality standards or 

waste discharge requirements? NI NI LTS 

b) Substantially deplete groundwater 

supplies or interfere substantially with 

groundwater recharge such that there 

would be a net deficit in aquifer volume 

or a lowering of the local groundwater 

table level (e.g., the production rate of 

pre-existing nearby wells would drop to 

a level which would not support 

existing land uses or planned uses for 

which permits have been granted)? 

NI NI LTS 

c) Substantially alter the existing drainage 

pattern of the site or area, including 

through the alteration of the course of a 

stream or river, in a manner which 

would result in substantial erosion or 

siltation on- or off-site? 

NI NI LTS 

d) Substantially alter the existing drainage 

pattern of the site or area, including 

through the alteration of the course of a 

stream or river, or substantially increase 

the rate or amount of surface runoff in a 

manner which would result in flooding 

on- or off-site? 

NI LTS LTS 

e) Create or contribute runoff water which 

would exceed the capacity of existing or 

planned stormwater drainage systems or 

provide substantial additional sources of 

polluted runoff? 

NI LTS NI 

f) Otherwise substantially degrade water 

quality? NI NI LTS 

g) Place housing within a 100-year flood 

hazard area as mapped on a federal 

Flood Hazard Boundary or Flood 

Insurance Rate Map or other flood 

NI NI NI 

4-24 February 2008 
Chapter 4 

CEQA Evaluation 

1 2 3 

HYDROLOGY AND WATER 

QUALITY 

Trail 

Detour

Dike 5 

Construction 

Site Access 

Cofferdam

hazard delineation map? 

h) Place within a 100-year flood hazard 

area structures which would impede or 

redirect flood flows? 

NI NI NI 

i) Expose people or structures to a 

significant risk of loss, injury or death 

involving flooding, including flooding 

as a result of the failure of a levee or 

dam? 

NI NI B 

j) Inundation by seiche, tsunami, or 

mudflow? NI NI NI 

1-3.g,h) The proposed Project would not place any structures in a flood plain. 

1-3.j) The proposed Project would not occur in an area with the potential for 

seiche, tsunami, or mudflows. 

1.a-f) The Trail Detour would avoid all wetlands and surface water and would 

not affect any existing hydrology, surface water runoff, or drainage. 

2.a,b,c,f) The Dike 5 Construction Site Access is temporary and would be restored 

to pre-construction conditions after construction of the dikes is complete. 

This action would not alter any existing streams or waterways and would 

not affect water quality. 

2.d) A drainage ditch runs parallel to Auburn-Folsom Road where the turn-in 

lanes would be constructed for the Dike 5 access. A culvert would be 

installed in the drainage ditch to maintain storm water drainage; therefore 

construction of the access road would not change the drainage of the area. 

2.e) Although paving of new turn-in and turn-out lanes for the Dike 5 

Construction Site Access could slightly increase the amount of surface 

area for runoff, it would be small area and is not expected to impact 

existing storm drainage systems. Additionally, the lanes would be 

temporary and the area would be restored to pre-construction conditions 

when work on the dikes is complete. This impact would be less than 

significant. 

3.a) During excavation activities involving the Stilling Basin and Cofferdam, 

groundwater could be encountered. This water may have elevated levels of 

4-25 February 2008 
Folsom Dam Safety and Flood Damage Reduction 

Supplemental Environmental Assessment/Initial Study 

certain constituents which would cause it to exceed applicable surface 

water quality objectives and regulations. Reclamation and the 

Construction Contractor would test the water and obtain appropriate 

permits before discharging it to any surface waters. This impact would be 

less than significant to water quality. 

3.b) Although groundwater may be encountered during work on the Stilling 

Basin, this is not expected to deplete any local wells as none exist in the 

area. The major water source for the surrounding communities is surface 

water from Folsom Reservoir. This impact would be less than significant. 

3.c) Construction of the Cofferdam would temporarily confine the existing 

floodway channel along the construction site. Hydrological modeling of 

the water flow and elevation changes has identified no significant 

upstream or downstream hydrological effects. This impact would be less 

than significant. 

3.d) Although the Cofferdam could slightly alter the drainage pattern of the 

site, this is not expected to result in any flooding and no residences exist in 

the area. This impact would be less than significant. 

3.f) The Cofferdam construction is not expected to substantially degrade water 

quality. The Hazardous Materials Management Plan, NPDES permit, and 

SWPPP would help to reduce any water quality impacts from construction 

of the Cofferdam. The Cofferdam could actually prevent groundwater and 

hazardous construction materials from being discharged into the American 

River. Measures proposed as part of the Project design would be 

implemented to prevent concrete material from entering the Stilling Basin 

or the river during removal of the wall. Overall, the potential impacts to 

water quality are considered less than significant. 

3.i) The purpose of the Cofferdam is to keep the Stilling Basin area dry from 

American River flows (i.e., releases from Folsom Dam) and to protect the 

workers during construction of the Stilling Basin. The Cofferdam would 

allow work to continue year-round and would ensure worker safety during 

releases from Folsom Dam. This structure would protect workers by 

eliminating the risk of flooding and is considered a beneficial impact. 

4-26 February 2008 
Chapter 4 

CEQA Evaluation 

1 2 3 

LAND USE AND PLANNING Trail 

Detour 

Dike 5 

Construction 

Site Access 

Cofferdam

IX. LAND USE AND PLANNING - 

Would the project: 

a) Physically divide an established 

community? NI NI NI 

b) Conflict with any applicable land use 

plan, policy, or regulation of an agency 

with jurisdiction over the project 

(including, but not limited to the 

general plan, specific plan, local coastal 

program, or zoning ordinance) adopted 

for the purpose of avoiding or 

mitigating an environmental effect? 

NI LTS NI 

c) Conflict with any applicable habitat 

conservation plan or natural community 

conservation plan? 

NI NI NI 

2.b) The Dike 5 Construction Site Access would require an encroachment permit 

for any work that would affect Auburn-Folsom Road because the road is under 

the jurisdiction of Placer County. Reclamation or the Construction Contractor 

would obtain all appropriate permits from Placer County prior to construction. 

Reclamation and the Construction Contractor would coordinate with Placer 

County to ensure the installation of the temporary traffic light and/or flagmen 

and turn-in and turn-out lanes would comply with the County’s traffic 

standards and regulations. This impact would be less than significant. 

The remainder of the activities under the Proposed Project would occur on Federal 

property, do not occur within or through an established community, do not involve or 

conflict with any conservation plans, and would not result in any other land use or 

planning impacts. 

4-27 February 2008 
Folsom Dam Safety and Flood Damage Reduction 

Supplemental Environmental Assessment/Initial Study 

1 2 3 

MINERAL RESOURCES Trail 

Detour 

Dike 5 

Construction 

Site Access 

Cofferdam

X. MINERAL RESOURCES -- Would 

the project: 

a) Result in the loss of availability of a 

known mineral resource that would 

be of value to the region and the 

residents of the state? 

LTS NI NI 

b) Result in the loss of availability of a 

locally-important mineral resource 

recovery site delineated on a local 

general plan, specific plan or other 

land use plan? 

NI NI NI 

2-3.a) and.b) The Dike 5 Construction Site Access would not result in the loss 

of availability of locally important mineral resource recovery 

site as none are designated within the project area. The 

Cofferdam would be constructed of concrete and reinforcing 

bars brought from off-site sources. This would not impact 

mineral resources at Folsom Reservoir. 

1.a) The Trail Detour would use native materials obtained from the surrounding 

Folsom Lake State Recreation Area (FLSRA) to surface the trail. The small 

quantity required would be considered less than significant. 

4-28 February 2008 
Chapter 4 

CEQA Evaluation 

1 2 3 

NOISE Trail 

Detour 

Dike 5 

Construction Site 

Access 

Cofferdam 

XI. NOISE -- Would the project result 

in: 

a) Exposure of persons to or 

generation of noise levels in excess 

of standards established in the local 

general plan or noise ordinance, or 

applicable standards of other 

agencies? 

NI NI LTS 

b) Exposure of persons to or 

generation of excessive 

groundborne vibration or 

groundborne noise levels? 

NI NI LTS 

c) A substantial permanent increase in 

ambient noise levels in the project 

vicinity above levels existing 

without the project? 

NI NI NI 

d) A substantial temporary or periodic 

increase in ambient noise levels in 

the project vicinity above levels 

existing without the project? 

LTS LTS LTS 

e) For a project located within an 

airport land use plan or, where such 

a plan has not been adopted, within 

two miles of a public airport or 

public use airport, would the project 

expose people residing or working 

in the project area to excessive 

noise levels? 

NI NI NI 

f) For a project within the vicinity of a 

private airstrip, would the project 

expose people residing or working 

in the project area to excessive 

noise levels? 

NI NI NI 

1-2.a) Development of the proposed Trail Detour and Dike 5 Construction Site 

Access would require minimal construction equipment that would not 

generate noise in excess of the standards, not would it be a permanent 

source of noise. 

4-29 February 2008 
Folsom Dam Safety and Flood Damage Reduction 

Supplemental Environmental Assessment/Initial Study 

1-2. b) Development of the proposed Trail Detour and Dike 5 Construction Site 

Access would not produce excessive groundborne vibration. As analyzed in the 

Folsom DS/FDR EIS/EIR, the potential construction vehicles used for these 

activities would not produce vibrations above a “barely perceptible” level from 

150 feet away. There are no sensitive receptors within 150 feet of the proposed 

work and any vibrations from construction would be imperceptible and 

temporary. 

1-3.c) The Proposed Project would not result in a permanent source of noise. 

Therefore, no permanent noise impacts would occur. 

1-3.e,f) None of the proposed actions are located at, or within two miles of, a 

public airport. 

1.d) The Trail Detour alignment parallels Auburn-Folsom Road, a major 

thorough fare with significant vehicular and truck traffic. Any temporary 

noise produced during the brief construction period would be masked by 

the ambient noise levels and not apparent to residences across the road. 

Noise impacts from the Trail Detour would be temporary and less than 

significant. 

2.d) Potential sources of noise impacts from the proposed Dike 5 Construction 

Site Access include both onsite construction noise and transportationrelated noise from construction workers, visitors and deliveries. Onsite 

dike construction noise and area-wide construction traffic noise were 

evaluated in the Folsom DS/FDR EIS/EIR. This assessment evaluates only 

the transportation-related noise associated with use of the new proposed 

construction access road to Dike 5 from Auburn-Folsom Road. 

 Transportation-related noise would consist of trucks hauling materials to 

Dike 5 via the new construction access road and construction worker, 

visitor and delivery vehicles. According to the traffic analysis, the volume 

of traffic generated by these sources would be very low in relation to 

existing traffic volumes on Auburn-Folsom Road. Because it takes a 

doubling of traffic to increase noise levels by 3 dBA, the threshold of 

detectability, the noise generated by this short-term, relatively low volume 

of traffic would increase noise levels in the project area by considerably 

less than 3 dBA, and, therefore, would have imperceptible noise impacts. 

In future years, the Dike 5 construction staging area is proposed to be used 

for Dike 4 and 6 construction. Noise impacts from this future constructionrelated use of the Dike 5 site access road are anticipated to be 

imperceptible, similar to that of the Dike 5 construction. 

4-30 February 2008 
Chapter 4 

CEQA Evaluation 

 If the onsite dike construction noise analyzed in the Folsom DS/FDR 

EIS/EIR is considered in conjunction with the increases from 

transportation-related noise sources, the overall increase in noise levels 

would still be minimal. Both projects would:

• Incorporate the appropriate level of sound attenuation on equipment 

that will attenuate sound at sensitive receptors to comply with local 

noise ordinances. Maintain equipment to comply with noise standards 

(e.g., exhaust mufflers, acoustically attenuating shields, shrouds, or 

enclosures). 

• Enclose above-ground conveyor systems in acoustically-treated 

enclosures, if necessary; 

• Line or cover hoppers, conveyor transfer points, storage bins and 

chutes with sound-deadening material; and 

• Schedule truck loading, unloading, and hauling operations so as to 

reduce nighttime noise impacts to comply with local noise ordinances. 

Noise impacts during construction of the Dike 5 Construction Site Access 

and Trail Detour are anticipated to be less than significant. 

3.a, b, d) Although construction and demolition of the Cofferdam would produce 

noise, it is in a location remote from sensitive receptors. Construction 

could produce some groundborne vibration from blasting and heavy 

equipment, however, the noise and vibration would be barely perceptible 

considering the distance of sensitive receptors (see analysis in Folsom 

DS/FDR EIS/EIR on page 3.10-26-27). With the construction noise 

control measures summarized above (that are part of the Project), noise 

impacts would be less than significant. 

4-31 February 2008 
Folsom Dam Safety and Flood Damage Reduction 

Supplemental Environmental Assessment/Initial Study 

1 2 3 

POPULATION AND HOUSING Trail 

Detour 

Dike 5 

Construction 

Site Access 

Cofferdam

XII. POPULATION AND HOUSING -- 

Would the project: 

a) Induce substantial population growth 

in an area, either directly (for example, 

by proposing new homes and 

businesses) or indirectly (for example, 

through extension of roads or other 

infrastructure)? 

NI NI NI 

b) Displace substantial numbers of 

existing housing, necessitating the 

construction of replacement housing 

elsewhere? 

NI NI NI 

c) Displace substantial numbers of 

people, necessitating the construction 

of replacement housing elsewhere? 

NI NI NI 

No new housing, public roads, or infrastructure would be constructed as part of the 

Proposed Project. No activities would require the displacement of existing housing 

or people. As such, the Proposed Project would not result in any population and 

housing impacts. 

4-32 February 2008 
Chapter 4 

CEQA Evaluation 

1 2 3 

PUBLIC SERVICES Trail 

Detour 

Dike 5 

Construction 

Site Access 

Cofferdam 

XIII. PUBLIC SERVICES 

a) Would the project result in substantial 

adverse physical impacts associated 

with the provision of new or physically 

altered governmental facilities, need for 

new or physically altered governmental 

facilities, the construction of which 

could cause significant environmental 

impacts, in order to maintain acceptable 

service ratios, response times or other 

performance objectives for any of the 

public services: 

Fire protection? NI LTS NI 

Police protection? NI LTS NI 

Schools? NI NI NI 

Parks? LTS NI NI 

Other public facilities? NI NI NI 

1.a) The Trail Detour would create an improved recreation trail at FLSRA that 

would temporarily replace an existing trail closed during construction. 

Reclamation’s Recreation Management Partner would manage and maintain 

the Trail Detour until the close of construction, with the exception of the 

portion that crosses the Dike 5 area. The Dike 5 portion would be managed by 

Reclamation and their Construction Contractor. Because this Trail Detour 

would temporarily replace an existing trail and would help maintain recreation 

throughout construction, it is not expected to affect public services at FLSRA. 

In summary, the only public service that may be affected by the Trail Detour is 

parks/recreation; however, the potential impacts would be less than significant. 

2.a) Operation of a temporary traffic light on Auburn-Folsom Road at Dike 5 would 

mean that fire and police vehicles have a new light to circumnavigate during 

emergencies. Reclamation and the Construction Contractor would notify the 

appropriate authorities of the temporary traffic light and would design the light 

to ensure it does not impede any emergency vehicles. This impact would be 

less than significant. 

 Construction traffic entering at the Dike 5 access would cross over a portion of 

Trail Detour below Dike 5. Reclamation and the Construction Contractor 

4-33 February 2008 
Folsom Dam Safety and Flood Damage Reduction 

Supplemental Environmental Assessment/Initial Study 

would be responsible for maintaining this portion of the Trail Detour and 

ensuring public safety; hence, potential impacts related to parks/recreation 

would be less than significant. There would be no impacts to schools or other 

public facilities. 

3.a) The Cofferdam is removed from any area requiring fire or police services, and 

is not near any schools, parks, or other public facilities. As such, construction 

of the Cofferdam would not affect any public services. 

4-34 February 2008 
Chapter 4 

CEQA Evaluation 

1 2 3 

RECREATION Trail 

Detour 

Dike 5 

Construction 

Site Access 

Cofferdam

XIV. RECREATION 

a) Would the project increase the use of 

existing neighborhood and regional 

parks or other recreational facilities 

such that substantial physical 

deterioration of the facility would 

occur or be accelerated? 

LTS LTS NI 

b) Does the project include recreational 

facilities or require the construction or 

expansion of recreational facilities 

which might have an adverse physical 

effect on the environment? 

LTS LTS NI 

1.a) The new Trail Detour is a mitigation measure described in the Folsom SOD 

ROD that would allow the continuous use of trails around Dikes 4, 5, and 6 

during construction. Because there will be no interruption in pedestrian, 

equestrian, or bicycle traffic between Beal’s Point and Mooney Ridge, it is 

expected that most recreation users will continue to visit the FLSRA and use 

the trails. The existing trails on the tops of the dikes would only be closed for 

the duration of construction, which is expected to be less than a year for each 

dike. Overall, the impact to recreation resulting from the Trail Detour would be 

less than significant. 

1.b) Work on the dikes would result in the closure of trails on the tops of Dikes 4, 5, 

and 6. In order to maintain a trail from Beal’s Point to Mooney Ridge, a trail 

detour would be constructed on the downstream side of the dikes. As described 

throughout this document, the Trail Detour would be constructed mainly of 

native materials and would have minimal effects to the physical environment, 

beyond some minor trimming of trees and other vegetation. Impacts of the 

Trail Detour on the physical environment are expected to be less than 

significant. 

2.a) Construction traffic using the Dike 5 Construction Site Access would cross 

over the Trail Detour. It is expected that this could deter some recreation trail 

users from using the Trail Detour during construction because of safety and 

noise issues. However, Reclamation and their Construction Contractor would 

make every attempt to maintain public safety during construction. Flagmen 

would be used, when necessary, to direct traffic. Signs would be posted to alert 

4-35 February 2008 
Folsom Dam Safety and Flood Damage Reduction 

Supplemental Environmental Assessment/Initial Study 

trail users of the truck crossings. In addition, construction traffic crossing the 

trail would be temporary. Once work is complete at each of the dikes, the truck 

traffic and construction would cease and the Trail Detour would no longer be 

the only option for moving between Beal’s Point and Mooney Ridge. Because 

this is temporary and all attempts would be made to maintain safety during 

construction, this is not expected to substantially increase the use of other parks 

in the area or deter large numbers of trail users. This impact would be less than 

significant. 

2.b) A portion of the Trail Detour would be required to cross the Dike 5 

Construction Site Access area. Impacts from the Trail Detour are described in 

2b above. The Trail Detour would result in less than significant impacts. No 

other recreation facilities would be required. 

3.a, b) No recreation facilities exist in the area of the Cofferdam; therefore, no 

impacts to recreation would occur. 

4-36 February 2008 
Chapter 4 

CEQA Evaluation 

1 2 3 

TRANSPORTATION/TRAFFIC Trail 

Detour

Dike 5 

Construction 

Site Access 

Cofferdam

XV. TRANSPORTATION/TRAFFIC -- 

Would the project: 

a) Cause an increase in traffic which is 

substantial in relation to the existing 

traffic load and capacity of the street 

system (i.e., result in a substantial 

increase in either the number of vehicle 

trips, the volume to capacity ratio on 

roads, or congestion at intersections)? 

NI LTSWM LTS 

b) Exceed, either individually or 

cumulatively, a level of service standard 

established by the county congestion 

management agency for designated roads 

or highways? 

NI LTSWM LTS 

c) Result in a change in air traffic patterns, 

including either an increase in traffic 

levels or a change in location that results 

in substantial safety risks? 

NI NI NI 

d) Substantially increase hazards due to a 

design feature (e.g., sharp curves or 

dangerous intersections) or incompatible 

uses (e.g., farm equipment)? 

NI LTSWM NI 

e) Result in inadequate emergency access? NI LTSWM NI 

f) Result in inadequate parking capacity? NI NI NI 

g) Conflict with adopted policies, plans, or 

programs supporting alternative 

transportation (e.g., bus turnouts, bicycle 

racks)? 

NI NI NI 

1.a-g) The Trail Detour would be constructed on Federal property and would not 

affect traffic on any roads, highways, or air travel routes. 

2.a) The Dike 5 Construction Site Access would shift the construction traffic on 

Auburn-Folsom Road from Beal’s Point to Dike 5. Although this increase in 

traffic would be temporary, this stretch of Auburn-Folsom Road currently 

experiences an “F” Level-of-Service during peak traffic periods, which 

exceeds the standard set by Placer County. Construction traffic during peak 

4-37 February 2008 
Folsom Dam Safety and Flood Damage Reduction 

Supplemental Environmental Assessment/Initial Study 

periods could exacerbate this problem. Mitigation measures below would 

reduce this impact to less than significant. 

2.b) The Dike 5 Construction Site Access would shift the temporary increase of 

construction traffic on Auburn-Folsom Road from Beal’s Point to Dike 5. 

This stretch of Auburn-Folsom Road experiences an “F” Level-of-Service 

during peak traffic periods, which exceeds the standard set by Placer County. 

Construction traffic during peak periods could exacerbate this problem. 

Mitigation measures below would reduce this impact to less than significant. 

2.c) There are no air travel routes/patterns in proximity to the Project site that 

would be affected by Dike 5 Construction Site Access. 

2.d) The temporary traffic light or flagmen would be positioned on a curve and 

could therefore result in a traffic hazard. Mitigation measures described 

below would reduce this impact to less than significant. 

2.e) The temporary intersection with a traffic light could impede emergency 

vehicles. Mitigation measures described below would reduce this impact to a 

less than significant level. 

2.f) The Dike 5 Construction Site Access project would not affect or require any 

parking, other than possibly that associated with worker parking, which 

would be accommodated as part of the overall Folsom DS/FDR Project. 

2.g) The basic nature of the Dike 5 Construction Site Access project does not 

involve alternative transportation. 

3.a) Although the Cofferdam construction would temporarily increase traffic, this 

increase is not expected to be significant (see Table 3-8 in Chapter 3 and the 

associated discussion). 

3.b) The Cofferdam construction traffic would not deteriorate the LOS on any of 

the roads that would be used by haul trucks. In addition, increases to daily 

traffic volumes are all less than two percent (with the exception of Scott Road 

south of White Rock Road; however, this road is rural and lightly used, and 

would continue to operate at LOS A/B.) In those instances where the road is 

at LOS F, the volume to capacity (V/C) ratio would not increase more than 

0.05%, which is below the threshold of significance (see Table 3-8 in Chapter 

3 and the associated discussion). Based on the analysis, and the fact that 

traffic impacts from the Cofferdam would be temporary, impacts to 

transportation and circulation from construction of the Cofferdam would be 

less than significant. 

4-38 February 2008 
Chapter 4 

CEQA Evaluation 

3.c) There are no air travel routes/patterns in proximity to the Project site that 

would be affected by the Cofferdam. 

3.d) The Cofferdam project does not involve any roadway design features or 

incompatible uses on roads. 

3.e) The Cofferdam project does not involve emergency access. 

3.f) The Cofferdam project would not affect or require any parking, other than 

possibly that associated with worker parking, which would be accommodated 

as part of the overall Folsom DS/FDR Project. 

Mitigation Measures: 

1. Reclamation and the Construction Contractor will coordinate with Placer County 

regarding installation of the temporary intersection and will install warning signs 

and other safety measures, as required. 

2. Deliveries will be scheduled during off-peak hours if flagmen are implemented at 

the Dike 5 Construction Site Access. 

3. If a temporary traffic signal is implemented, the lights at Eureka Road and Fuller 

Drive will be synchronized to allow appropriate gaps in Auburn-Folsom Road 

traffic such that construction trucks would have sufficient time to turn-in and out 

of the access road. 

4. Reclamation and the Construction Contractor will coordinate with appropriate 

local fire, police, and other emergency personnel to inform them of the new 

intersection and will design the traffic light in a way that does not impede 

emergency vehicles. 

4-39 February 2008 
Folsom Dam Safety and Flood Damage Reduction 

Supplemental Environmental Assessment/Initial Study 

1 2 3 

UTILITIES AND SERVICE SYSTEMS Trail 

Detour 

Dike 5 

Construction 

Site Access 

Cofferdam

XVI. UTILITIES AND SERVICE 

SYSTEMS -- Would the project: 

a) Exceed wastewater treatment 

requirements of the applicable 

Regional Water Quality Control 

Board? 

NI NI NI 

b) Require or result in the construction of 

new water or wastewater treatment 

facilities or expansion of existing 

facilities, the construction of which 

could cause significant environmental 

effects? 

NI NI NI 

c) Require or result in the construction of 

new storm water drainage facilities or 

expansion of existing facilities, the 

construction of which could cause 

significant environmental effects? 

NI LTS NI 

d) Have sufficient water supplies 

available to serve the project from 

existing entitlements and resources, or 

are new or expanded entitlements 

needed? 

NI NI NI 

e) Result in a determination by the 

wastewater treatment provider which 

serves or may serve the project that it 

has adequate capacity to serve the 

project’s projected demand in addition 

to the provider’s existing 

commitments? 

NI NI NI 

f) Be served by a landfill with sufficient 

permitted capacity to accommodate the 

project’s solid waste disposal needs? 

NI NI LTS 

g) Comply with federal, state, and local 

statutes and regulations related to solid 

waste? 

NI NI LTS 

1-3.a,b,d,e) The Proposed Project would not generate wastewater and would not 

require the construction of new wastewater or water treatment 

4-40 February 2008 
Chapter 4 

CEQA Evaluation 

facilities. The Proposed Project would not require a new water supply 

because no buildings would be constructed. 

1&3.c) No new storm water drainage facilities would be required for the Trail 

Detour or the Cofferdam. 

2.c) A drainage ditch runs parallel to Auburn-Folsom Road where the turn-in 

lanes would be constructed for the Dike 5 access. A culvert would be 

installed in the drainage ditch to maintain storm water drainage. Given the 

relatively minor nature of this improvement, the impact would be less than 

significant. 

1&2.f,g) The Trail Detour and Dike 5 Construction Site Access would not produce 

any notable amounts of solid waste requiring disposal. 

3.f) Solid waste would be generated during construction and demolition of the 

Cofferdam. The solid waste would be disposed at a landfill with adequate 

capacity. This impact would be less than significant. 

3.g) Reclamation and the Construction Contractor would comply with all 

applicable statues and regulations related to solid waste. This impact would 

be less than significant. 

4-41 February 2008 
Folsom Dam Safety and Flood Damage Reduction 

Supplemental Environmental Assessment/Initial Study 

1 2 3 

MANDATORY FINDINGS OF 

SIGNIFICANCE 

Trail 

Detour

Dike 5 

Construction 

Site Access 

Cofferdam

XVII. MANDATORY FINDINGS OF 

SIGNIFICANCE

a) Does the project 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 selfsustaining levels, threaten to eliminate a 

plant or animal community, reduce the 

number or restrict the range of a rare or 

endangered plant or animal or eliminate 

important examples of the major periods 

of California history or prehistory? 

LTS LTSWM LTSWM 

b) Does the project have impacts that are 

individually limited, but cumulatively 

considerable? (“Cumulatively 

considerable” means that the incremental 

effects of a project are considerable when 

viewed in connection with the effects of 

past projects, the effects of other current 

projects, and the effects of probable 

future projects)? 

NI LTS LTS 

c) Does the project have environmental 

effects which will cause substantial 

adverse effects on human beings, either 

directly or indirectly? 

LTS LTSWM LTSWM 

a) Although the Proposed Project has the potential for impacts to several of the 

environmental resources described above, including traffic, air quality, and 

cultural resources, the impacts would either be less than significant or would be 

reduced to a level that is less than significant with implementation of specified 

mitigation measures. All mitigation measures listed in this Supplemental EA/IS 

(and described below) will be incorporated into the Proposed Project. 

b) The Proposed Project would not result in cumulatively considerable impacts 

with the implementation of the suggested mitigation measures described above 

and close coordination with the Corps regarding the New Folsom Bridge 

4-42 February 2008 
Chapter 4 

CEQA Evaluation 

Project and Placer County regarding the Auburn-Folsom Road Widening 

Project. 

c) None of the actions would have substantial adverse effects on human beings 

following completion of the actions and implementation of the mitigation 

measures referenced in this Supplemental EA/IS. 

Mitigation Measures: 

The following mitigation measures will be incorporated into the Proposed Project to 

reduce all potentially significant impacts to a less than significant level. 

Air Quality 

1. Reclamation and the Construction Contractor will submit a plan for approval by 

SMAQMD, demonstrating that the heavy-duty off-road vehicles will achieve a 

project-wide fleet average 20 percent NOx reduction and 45 percent particulate 

reduction. The plan will also be required to include an inventory of all off-road 

construction equipment greater than or equal to 50 horsepower that will be used 

an aggregate of 40 or more hours during any portion of the project. Reclamation 

and the Construction Contractor will also have to demonstrate conformity with 

NOx thresholds, apply fugitive dust control on roadways, processing plants, and 

concrete batch plants and obtain power for construction facilities from the 

electric utility grid rather than diesel-driven generators and pumps. The 

Construction Contractor will be encouraged to seek additional control measures 

as part of emissions offsets. 

2. Since project-wide emissions from the Cofferdam and ongoing operations related 

to the Folsom DS/FDR could exceed 85 lbs per day, the appropriate fee will be 

paid to SMAQMD’s mitigation fund for any excess emissions. Emissions from 

the Cofferdam will be offset with the appropriate payment of this mitigation fee. 

Cultural Resources 

3. Include in the standard contract specifications directions to follow in the unlikely 

event of the discovery of human remains or other cultural resources during the 

construction phase of this project. 

Transportation/Traffic 

4. Reclamation and the Construction Contractor will coordinate with Placer County 

regarding installation of the temporary intersection and will install warning signs 

and other safety measures, as required. 

5. Deliveries will be scheduled during off-peak hours if flagmen are implemented at 

the Dike 5 Construction Site Access. 

4-43 February 2008 
Folsom Dam Safety and Flood Damage Reduction 

Supplemental Environmental Assessment/Initial Study 

6. If a temporary traffic signal is implemented, the lights at Eureka Road and Fuller 

Drive will be synchronized to allow appropriate gaps in Auburn-Folsom Road 

traffic such that construction trucks would have sufficient time to turn-in and out 

of the access road. 

7. Reclamation and the Construction Contractor will coordinate with appropriate 

local fire, police, and other emergency personnel to inform them of the new 

intersection and will design the traffic light in a way that does not impede 

emergency vehicles. 

4-44 February 2008 
Chapter 5 

Consultation and Coordination 

This section presents the agencies and parties that were consulted during 

development of the document, the applicable Federal, State, and local requirements 

the project will comply with, and the distribution list. 

5.1 Consultation and Coordination 

Several agencies and parties were consulted during the development of this 

document, including: 

• California Department of Parks and Recreation; 

• U.S. Fish and Wildlife Service; and 

• Placer County. 

5.2 Federal, State, and Local Requirements 

The Proposed Action analyzed in this Supplemental EA/IS must fulfill or comply 

with the Federal, State, regional, and local environmental requirements described in 

Table 5-1. 

Table 5-1 

Federal, State, and Local Requirements

Statute Relevant Permits/ 

Processes 

FEDERAL 

National Environmental Policy Act of 1969 (NEPA) EA, FONSI 

National Historic Preservation Act of 1966 (NHPA) Addressed in EA/IS 

Executive Order 12898, Environmental Justice Addressed in EA/IS 

Clean Air Act (Section 176) Conformity provisions 

Clean Water Act (CWA) NPDES permit 

Indian Trust Assets (ITA) Addressed in EA/IS 

Endangered Species Act (ESA) Not required as the Proposed Action will have no 

effect to listed species 

Fish and Wildlife Coordination Act (FWCA) Coordination with USFWS 

STATE 

California Environmental Quality Act (CEQA) IS, ND 

Porter-Cologne Water Quality Control Act NPDES permit 

Government Code Section 65040.12(e) 

Environmental Justice Addressed in EA/IS 

California Clean Air Act (CCAA) Ambient air quality standards 

LOCAL 

Placer County Traffic LOS thresholds, Encroachment Permit 

Sacramento Metropolitan Air Quality Management 

District (SMAQMD) Air Quality thresholds 

Placer County Air Pollution Control District 

(APCD) Air Quality thresholds 

5-1 February 2008 
Folsom Dam Safety and Flood Damage Reduction 

Supplemental Environmental Assessment/Initial Study 

5.3 Distribution List 

This section lists federal, state, regional, and local public and private agencies and 

organizations that have either received a copy of this Supplemental EA/IS or a 

notification of document availability. In addition to the regulatory agencies, agencies 

with special expertise or interest in evaluating environmental issues related to the 

project are included. Private agencies, organizations, and individuals who may be 

affected by the project or who have expressed an interest in the project through the 

public involvement process are also included. 

The Folsom DS/FDR Supplemental EA/IS is available on the internet at: 

http://www.usbr.gov/mp/nepa/nepa_projdetails.cfm?Project_ID=1808

Copies of the Supplemental EA/IS are available for public review at the following 

locations: 

• Bureau of Reclamation, Denver Office Library, Building 67, Room 167, 

Denver Federal Center, 6th and Kipling, Denver, CO 80225 

• Bureau of Reclamation, Mid-Pacific Regional Office Library, 2800 Cottage 

Way, W-1825, Sacramento, CA 95825-1898 

• El Dorado County Library, 345 Fair Lane, Placerville, CA 95667-5699 

• Folsom Public Library, 300 Persifer Street, Folsom, CA 95630 

• Natural Resources Library, U.S. Department of the Interior, 1849 C Street 

NW, Main Interior Building, Washington, DC 20240-0001 

• Roseville Public Library, 225 Taylor Street, Roseville, CA 95678 

• Sacramento Central Library, 828 I Street, Sacramento, CA 95814-2589 

5.3.1 Elected Officials and Representatives 

Governor of California 

Honorable Arnold Schwarzenegger 

United States Senate 

Honorable Barbara Boxer 

Honorable Dianne Feinstein 

House of Representatives 

Honorable John Doolittle 

Honorable Doris Matsui 

Honorable Daniel Lungren 

5-2 February 2008 
Chapter 5 

Consultation and Coordination 

California Senate 

Honorable Dave Cox 

California Assembly 

Honorable Roger Niello 

Honorable Ted Gaines 

Honorable Alan Nakanishi 

5.3.2 Government Departments and Agencies 

U.S. Government 

Advisory Council on Historic Preservation 

Army Corps of Engineers 

Bureau of Land Management 

Bureau of Reclamation 

Council on Environmental Quality 

Environmental Protection Agency 

Federal Emergency Management Agency 

Federal Highway Commission 

Fish and Wildlife Service 

National Marine Fisheries Service 

Natural Resources Conservation Service 

Office of Environmental Project Review 

Western Area Power Administration 

State of California 

Air Resources Board 

Central Valley Regional Water Quality Control Board 

Department of Conservation 

Department of Corrections 

Department of Transportation 

Department of Fish and Game 

Department of Parks and Recreation 

Department of Water Resources 

Reclamation Board 

State Clearinghouse 

5.3.3 Regional, County, and City 

City of Folsom 

Folsom Tourism Bureau 

Folsom Chamber of Commerce 

El Dorado County 

Granite Bay Advisory Council 

Placer County 

Sacramento Area Flood Control Agency 

5-3 February 2008 
Folsom Dam Safety and Flood Damage Reduction 

Supplemental Environmental Assessment/Initial Study 

Sacramento County 

Sacramento Metropolitan Air Quality Management District 

El Dorado County Air Quality Management District 

Sacramento Metropolitan Chamber of Commerce 

El Dorado County Water Agency 

San Juan Water District 

5.3.4 Private Organizations and Businesses 

SARA – Save The American River Association 

El Dorado Irrigation District 

Friends of the River 

LARTF – Lower American River Task Force 

Sacramento Valley Marine Association 

Northern California Marine Association 

5.3.5 Members of the Public 

Reclamation has created an extensive Folsom DS/FDR Project mailing list and 

continues to update this list regularly. All members of the general public who 

requested a copy of the Draft or Final Folsom DS/FDR EIS/EIR will be mailed a 

notice that provides the locations where this document may be viewed and the 

website address where the document is available online. 

5-4 February 2008 
Chapter 6 

List of Preparers 

Table 6-1 

List of Preparers 

Larry Hobbs 

Bureau of Reclamation 

Project Manager 

15 years of project development experience 

John Wondolleck 

CDM 

Associate 

30 years of experience in resource 

development with expertise in management of 

multidisciplinary environmental programs 

Elizabeth Vasquez 

Bureau of Reclamation 

Natural Resource Specialist 

8 years of natural resources experience

Hank Boucher 

CDM 

Associate 

30 years of experience as environmental 

engineer and planner with expertise in, impact 

assessment, planning, transportation, land 

use development 

Mike Nepstad 

Bureau of Reclamation 

Natural Resources Specialist 

14 years experience in Biological Sciences, 

Environmental Regulations and Compliance 

Gwen Pelletier 

CDM 

Environmental Scientist 

8 years of experience working on air quality 

projects 

Matt See 

Bureau of Reclamation 

Natural Resource Specialist 

2 year of natural resources experience

Charlie Liggett 

CDM 

Environmental Engineer 

28 years of experience as engineer and 

planner with expertise in design and 

construction of roadways, bridges, 

recreational facilities, and other civil projects 

Rosemary Stefani 

Bureau of Reclamation 

Environmental Specialist 

24 years of natural resources experience

Joe Solomon 

CDM 

Project Engineer 

9 years of experience with transportation 

projects and programs 

Rebecca Victorine 

Bureau of Reclamation 

Natural Resource Specialist 

8 years experience in Biological Sciences 

Gina Veronese 

CDM 

Environmental Planner/Resource Economist 

5 years of experience in planning and analysis 

of water resource projects and programs 

Stacy Porter 

CDM 

Environmental Planner 

3 years of experience in water resources 

planning 

Denise Ashley 

CDM 

Administrative Assistant 

10 years of word processing experience 

Patricia Reed 

CDM 

Environmental Scientist 

8 years of experience in environmental 

planning and biological sciences 

Auturo Smith 

CDM 

GIS Specialist 

13 years of experience specializing in 

cartographic design and GIS 

6-1 February 2008 
Folsom Dam Safety and Flood Damage Reduction 

Supplemental Environmental Assessment/Initial Study 

Table 6-1 

List of Preparers 

John Pehrson 

CDM 

Engineer 

20 years of experience and CDM’s lead 

technical engineer and dispersion modeler for 

air quality projects

Charlie Kincaid 

CDM 

Senior Civil Engineer 

25 years of experience in the construction and 

design of roads, bridges, and various civil 

works projects

Ilana Cohen 

CDM 

Environmental Scientist 

2 years of experience in environmental 

planning 

Andria Loutsch 

CDM 

Water Resources Planner 

11 years of experience in water resources and 

environmental planning

Marc Wallace 

CDM 

Senior Environmental Scientist 

17 years of experience specializing in ambient 

noise monitoring and noise impact 

assessments 

Carolyn Oliveira 

CDM 

Office Services Coordinator 

4 years of experience 

Jane Rinck 

U.S. Army Corps of Engineers 

Environmental Analysis Section 

20 years experience in Biological Sciences 

John Holson 

Pacific Legacy 

Senior Archaeologist 

30 years of experience in cultural resources 

management 

Robert Charney 

Department of Water Resources 

Sr. Water Resources Engineer 

16 years experience in Water Resources 

Engineering 

Annalena Bronson 

Central Valley Flood Protection Board 

Environmental Scientist 

25 years experience in CEQA 

6-2 February 2008 
Chapter 6 

List of Preparers 

Table 6-2 

List of Contributors

Douglas Weinrich 

U.S. Fish and Wildlife Service 

David Gore 

Bureau of Reclamation 

Stephanie Rickabaugh 

U.S. Fish and Wildlife Service 

Gary Egan 

Bureau of Reclamation 

Jim Michaels 

California Department of Parks and 

Recreation 

Michael Finnegan 

Bureau of Reclamation 

Michael Gross 

California Department of Parks and 

Recreation 

Richard Johnson 

Bureau of Reclamation 

Tom Heinzer 

Bureau of Reclamation 

Drew Lessard

Bureau of Reclamation 

Diane Williams 

Bureau of Reclamation 

Robert Schroeder 

Bureau of Reclamation 

Richard Welsh 

Bureau of Reclamation 

Donald Treasure 

Bureau of Reclamation 

Joel Sturm 

Bureau of Reclamation 

John Wilson

Bureau of Reclamation 

Bruce Muller 

Bureau of Reclamation 

John LaBoon 

Bureau of Reclamation 

Jonathan Harris 

Bureau of Reclamation 

Bill Fiedler 

Bureau of Reclamation 

Stuart Angerer 

Bureau of Reclamation 

Ernie Hall 

Bureau of Reclamation 

Terri Reaves 

Bureau of Reclamation 

Matt Sheskier 

Bureau of Reclamation 

Jonathan Harris 

Bureau of Reclamation 

Patrick Welch 

Bureau of Reclamation 

Nathan Snorteland 

Bureau of Reclamation 

Steven Sherer 

Bureau of Reclamation 

Stanley Parrott 

Bureau of Reclamation

Jared Vauk 

Bureau of Reclamation 

Stein Baur 

SAFCA 

Timothy Washburn 

SAFCA

Peter Buck 

SAFCA 

6-3 February 2008 
Folsom Dam Safety and Flood Damage Reduction 

Supplemental Environmental Assessment/Initial Study 

This page left intentionally blank. 

6-4 February 2008 
Appendix A 

Traffic Analysis 
Northbound Traffic 

A.M. Peak Hour 

 = Average of Auburn-Folsom / Eureka (NBL + NBT + NBR) and Auburn-Folsom 

 / Oak Hill (NBT + EBL + WBR) * Growth Factor 

 = [(48 + 1073 + 1081 + 1 + 19) / 2] * 1.034

 = 1250 

P.M. Peak Hour 

 = Average of Auburn-Folsom / Eureka (NBL + NBT + NBR) and Auburn-Folsom 

 / Oak Hill (NBT + EBL + WBR) * Growth Factor 

 = [(45 + 1178 + 1202 + 15 + 16) / 2] * 1.034

 = 1382 

Southbound Traffic 

A.M. Peak Hour 

 = Average of Auburn-Folsom / Eureka (SBT + EBR + WBL) and Auburn-Folsom 

 / Oak Hill (SBL + SBT + SBR) * Growth Factor 

 = [(1041 + 98 + 23 + 1117 + 4) / 2 ] * 1.034

 = 1285 

P.M. Peak Hour 

 = Average of Auburn-Folsom / Eureka (SBT + EBR + WBL) and Auburn-Folsom 

 / Oak Hill (SBL + SBT + SBR) * Growth Factor 

 = [(1049 + 101 + 20 + 1080 + 8) / 2] * 1.034

 = 1271 

Westbound Traffic 

Rates from ITE Trip Generation Manual, Seventh Edition; Institute of Transportation 

Engineers; Washington, DC; 2003. 

Land Use Code: 210 Single-Family Detached Housing 

Assume X=6 units using Bell Drive 

Assume 50% traffic turns left and 50% turns right 

A.M. Peak Hour Enter Exit 

T = 0.70(X) + 9.43 = 0.25(T) = 0.75(T) 

T = 0.70(6) + 9.43 = 0.25(14) = 0.75(14) 

T = 14 = 3 = 11 

P.M. Peak Hour Enter Exit 

Ln(T) = 0.90 Ln(6) + 0.53 = 0.63(T) = 0.37(T) 
Ln(T) = 0.90 Ln(6) + 0.53 = 0.63(9) = 0.37(9) 

Ln(T) = 2.14 = 6 = 3 

T = 9 

Eastbound Traffic 

A.M. Peak Hour 

 Assume 40 haul trips per day over a period of 7:00a.m. to 3:00p.m. Trips per 

 A.M. peak hour = 40/8 = 5 round trips during A.M. peak hour. 

 Assume trucks will enter and exit from the south. 

P.M. Peak Hour 

 Assume 40 haul trips per day over a period of 7:00a.m. to 3:00p.m. and will not 

 have any affect on the P.M. peak hour traffic. 
HCM Signalized Intersection Capacity Analysis A.M. Peak Hour

3: Bell Drive & Auburn - Folsom Road

2/20/2008 Synchro 7 - Report

MurphySP

Movement EBL EBT EBR WBL WBT WBR NBL NBT NBR SBL SBT SBR

Lane Configurations

Volume (vph) 5065001 1250 5 0 1285 2

Ideal Flow (vphpl) 1900 1900 1900 1900 1900 1900 1900 1900 1900 1900 1900 1900

Total Lost time (s) 4.0 4.0 4.0 4.0 4.0

Lane Util. Factor 1.00 1.00 1.00 1.00 1.00

Frt 0.92 1.00 1.00 0.85 1.00

Flt Protected 0.98 0.95 1.00 1.00 1.00

Satd. Flow (prot) 1681 902 1845 808 1844

Flt Permitted 0.98 1.00 1.00 1.00 1.00

Satd. Flow (perm) 1677 950 1844 808 1844

Peak-hour factor, PHF 0.92 0.92 0.92 0.92 0.92 0.92 0.92 0.92 0.92 0.92 0.92 0.92

Adj. Flow (vph) 5075001 1359 5 0 1397 2

RTOR Reduction (vph) 070000000000

Lane Group Flow (vph) 0500500 1360 5 0 1399 0

Heavy Vehicles (%) 2% 2% 2% 100% 2% 100% 2% 3% 100% 3% 3% 2%

Turn Type Perm Perm pm+pt Perm Perm

Protected Phases 2 2 3 1 1

Permitted Phases 2 2 1 1 1

Actuated Green, G (s) 2.9 2.9 112.9 112.9 112.9

Effective Green, g (s) 2.9 2.9 112.9 112.9 112.9

Actuated g/C Ratio 0.02 0.02 0.91 0.91 0.91

Clearance Time (s) 4.0 4.0 4.0 4.0 4.0

Vehicle Extension (s) 3.0 3.0 3.0 3.0 3.0

Lane Grp Cap (vph) 39 22 1682 737 1682

v/s Ratio Prot c0.76

v/s Ratio Perm 0.00 c0.01 0.74 0.01

v/c Ratio 0.13 0.23 0.81 0.01 0.83

Uniform Delay, d1 59.2 59.3 1.8 0.5 2.0

Progression Factor 1.00 1.00 1.00 1.00 1.00

Incremental Delay, d2 1.5 5.2 3.0 0.0 5.0

Delay (s) 60.8 64.6 4.8 0.5 7.0

Level of Service E E A A A

Approach Delay (s) 60.8 64.6 4.8 7.0

Approach LOS EEAA

Intersection Summary

HCM Average Control Delay 6.2 HCM Level of Service A

HCM Volume to Capacity ratio 0.82

Actuated Cycle Length (s) 123.8 Sum of lost time (s) 8.0

Intersection Capacity Utilization 84.4% ICU Level of Service E

Analysis Period (min) 15

c Critical Lane Group
Queues A.M. Peak Hour

3: Bell Drive & Auburn - Folsom Road

2/20/2008 Synchro 7 - Report

MurphySP

Lane Group EBT WBT NBT NBR SBT

Lane Group Flow (vph) 12 5 1360 5 1399

v/c Ratio 0.13 0.10 0.78 0.01 0.80

Control Delay 40.5 59.8 6.3 0.6 7.2

Queue Delay 0.0 0.0 0.0 0.0 0.0

Total Delay 40.5 59.8 6.3 0.6 7.2

Queue Length 50th (ft) 44000

Queue Length 95th (ft) 25 18 599 1 700

Internal Link Dist (ft) 282 336 598 555

Turn Bay Length (ft) 200

Base Capacity (vph) 202 111 1753 768 1753

Starvation Cap Reductn 00000

Spillback Cap Reductn 00000

Storage Cap Reductn 00000

Reduced v/c Ratio 0.06 0.05 0.78 0.01 0.80

Intersection Summary
Timings A.M. Peak Hour

3: Bell Drive & Auburn - Folsom Road

2/20/2008 Synchro 7 - Report

MurphySP

Lane Group EBL EBT WBL WBT NBL NBT NBR SBT

Lane Configurations

Volume (vph) 50501 1250 5 1285

Turn Type Perm Perm pm+pt Perm

Protected Phases 2 2 3 1 1

Permitted Phases 2211

Detector Phase 22223111

Switch Phase

Minimum Initial (s) 4.0 4.0 4.0 4.0 4.0 4.0 4.0 4.0

Minimum Split (s) 20.0 20.0 20.0 20.0 8.0 20.0 20.0 20.0

Total Split (s) 20.0 20.0 20.0 20.0 8.0 112.0 112.0 112.0

Total Split (%) 14.3% 14.3% 14.3% 14.3% 5.7% 80.0% 80.0% 80.0%

Yellow Time (s) 3.5 3.5 3.5 3.5 3.5 3.5 3.5 3.5

All-Red Time (s) 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5

Lost Time Adjust (s) 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0

Total Lost Time (s) 4.0 4.0 4.0 4.0 4.0 4.0 4.0 4.0

Lead/Lag Lag Lag Lag Lag Lead Lead Lead

Lead-Lag Optimize? Yes Yes Yes Yes Yes Yes Yes

Recall Mode None None None None None Max Max Max

Act Effct Green (s) 6.4 6.4 115.3 115.3 115.3

Actuated g/C Ratio 0.05 0.05 0.95 0.95 0.95

v/c Ratio 0.13 0.10 0.78 0.01 0.80

Control Delay 40.5 59.8 6.3 0.6 7.2

Queue Delay 0.0 0.0 0.0 0.0 0.0

Total Delay 40.5 59.8 6.3 0.6 7.2

LOS D E A A A

Approach Delay 40.5 59.8 6.3 7.2

Approach LOS D E A A

Intersection Summary

Cycle Length: 140

Actuated Cycle Length: 121.4

Natural Cycle: 140

Control Type: Actuated-Uncoordinated

Maximum v/c Ratio: 0.80

Intersection Signal Delay: 7.0 Intersection LOS: A

Intersection Capacity Utilization 84.4% ICU Level of Service E

Analysis Period (min) 15

Splits and Phases: 3: Bell Drive & Auburn - Folsom Road
HCM Signalized Intersection Capacity Analysis P.M. Peak Hour

3: Bell Drive & Auburn - Folsom Road

2/20/2008 Synchro 7 - Report

MurphySP

Movement EBL EBT EBR WBL WBT WBR NBL NBT NBR SBL SBT SBR

Lane Configurations

Volume (vph) 1020003 1382 0 0 1271 3

Ideal Flow (vphpl) 1900 1900 1900 1900 1900 1900 1900 1900 1900 1900 1900 1900

Total Lost time (s) 4.0 4.0 4.0

Lane Util. Factor 1.00 1.00 1.00

Frt 0.91 1.00 1.00

Flt Protected 0.98 1.00 1.00

Satd. Flow (prot) 1667 1845 1844

Flt Permitted 1.00 1.00 1.00

Satd. Flow (perm) 1695 1841 1844

Peak-hour factor, PHF 0.92 0.92 0.92 0.92 0.92 0.92 0.92 0.92 0.92 0.92 0.92 0.92

Adj. Flow (vph) 1020003 1502 0 0 1382 3

RTOR Reduction (vph) 020000000000

Lane Group Flow (vph) 0100000 1505 0 0 1385 0

Heavy Vehicles (%) 2% 2% 2% 100% 2% 100% 2% 3% 100% 3% 3% 2%

Turn Type Perm Perm pm+pt Perm Perm

Protected Phases 2 2 3 1 1

Permitted Phases 2 2 1 1 1

Actuated Green, G (s) 1.2 114.4 114.4

Effective Green, g (s) 1.2 114.4 114.4

Actuated g/C Ratio 0.01 0.93 0.93

Clearance Time (s) 4.0 4.0 4.0

Vehicle Extension (s) 3.0 3.0 3.0

Lane Grp Cap (vph) 16 1704 1707

v/s Ratio Prot 0.75

v/s Ratio Perm c0.00 c0.82

v/c Ratio 0.06 0.88 0.81

Uniform Delay, d1 60.6 1.9 1.4

Progression Factor 1.00 1.00 1.00

Incremental Delay, d2 1.7 5.8 4.3

Delay (s) 62.3 7.7 5.7

Level of Service E A A

Approach Delay (s) 62.3 0.0 7.7 5.7

Approach LOS EAAA

Intersection Summary

HCM Average Control Delay 6.8 HCM Level of Service A

HCM Volume to Capacity ratio 0.87

Actuated Cycle Length (s) 123.6 Sum of lost time (s) 8.0

Intersection Capacity Utilization 85.1% ICU Level of Service E

Analysis Period (min) 15

c Critical Lane Group
Queues P.M. Peak Hour

3: Bell Drive & Auburn - Folsom Road

2/20/2008 Synchro 7 - Report

MurphySP

Lane Group EBT NBT SBT

Lane Group Flow (vph) 3 1505 1385

v/c Ratio 0.04 0.84 0.77

Control Delay 43.3 7.6 5.0

Queue Delay 0.0 0.0 0.0

Total Delay 43.3 7.6 5.0

Queue Length 50th (ft) 1 0 0

Queue Length 95th (ft) 11 #1402 550

Internal Link Dist (ft) 282 598 555

Turn Bay Length (ft)

Base Capacity (vph) 197 1798 1802

Starvation Cap Reductn 0 0 0

Spillback Cap Reductn 0 0 0

Storage Cap Reductn 0 0 0

Reduced v/c Ratio 0.02 0.84 0.77

Intersection Summary

# 95th percentile volume exceeds capacity, queue may be longer.

 Queue shown is maximum after two cycles.
Timings P.M. Peak Hour

3: Bell Drive & Auburn - Folsom Road

2/20/2008 Synchro 7 - Report

MurphySP

Lane Group EBL EBT NBL NBT SBT

Lane Configurations

Volume (vph) 1 0 3 1382 1271

Turn Type Perm pm+pt

Protected Phases 2311

Permitted Phases 2 1

Detector Phase 22311

Switch Phase

Minimum Initial (s) 4.0 4.0 4.0 4.0 4.0

Minimum Split (s) 20.0 20.0 8.0 20.0 20.0

Total Split (s) 20.0 20.0 8.0 112.0 112.0

Total Split (%) 14.3% 14.3% 5.7% 80.0% 80.0%

Yellow Time (s) 3.5 3.5 3.5 3.5 3.5

All-Red Time (s) 0.5 0.5 0.5 0.5 0.5

Lost Time Adjust (s) 0.0 0.0 0.0 0.0 0.0

Total Lost Time (s) 4.0 4.0 4.0 4.0 4.0

Lead/Lag Lag Lag Lead Lead

Lead-Lag Optimize? Yes Yes Yes Yes

Recall Mode None None None Max Max

Act Effct Green (s) 5.7 117.7 117.7

Actuated g/C Ratio 0.04 0.98 0.98

v/c Ratio 0.04 0.84 0.77

Control Delay 43.3 7.6 5.0

Queue Delay 0.0 0.0 0.0

Total Delay 43.3 7.6 5.0

LOS D A A

Approach Delay 43.3 7.6 5.0

Approach LOS D A A

Intersection Summary

Cycle Length: 140

Actuated Cycle Length: 120.5

Natural Cycle: 150

Control Type: Actuated-Uncoordinated

Maximum v/c Ratio: 0.84

Intersection Signal Delay: 6.4 Intersection LOS: A

Intersection Capacity Utilization 85.1% ICU Level of Service E

Analysis Period (min) 15

Splits and Phases: 3: Bell Drive & Auburn - Folsom Road
HCM Signalized Intersection Capacity Analysis A.M. Peak Hour

3: Dike 5 Construction Access Road & Auburn - Folsom Road

2/20/2008 Synchro 7 - Report

MurphySP

Movement WBL WBR NBT NBR SBL SBT

Lane Configurations

Volume (vph) 5 0 1250 5 0 1285

Ideal Flow (vphpl) 1900 1900 1900 1900 1900 1900

Total Lost time (s) 4.0 4.0 4.0 4.0

Lane Util. Factor 1.00 1.00 1.00 1.00

Frt 1.00 1.00 0.85 1.00

Flt Protected 0.95 1.00 1.00 1.00

Satd. Flow (prot) 902 1845 808 1845

Flt Permitted 0.95 1.00 1.00 1.00

Satd. Flow (perm) 902 1845 808 1845

Peak-hour factor, PHF 0.92 0.92 0.92 0.92 0.92 0.92

Adj. Flow (vph) 5 0 1359 5 0 1397

RTOR Reduction (vph) 000000

Lane Group Flow (vph) 5 0 1359 5 0 1397

Heavy Vehicles (%) 100% 100% 3% 100% 3% 3%

Turn Type Perm

Protected Phases 8 2 6

Permitted Phases 2

Actuated Green, G (s) 1.6 113.6 113.6 113.6

Effective Green, g (s) 1.6 113.6 113.6 113.6

Actuated g/C Ratio 0.01 0.92 0.92 0.92

Clearance Time (s) 4.0 4.0 4.0 4.0

Vehicle Extension (s) 3.0 3.0 3.0 3.0

Lane Grp Cap (vph) 12 1701 745 1701

v/s Ratio Prot c0.01 0.74 c0.76

v/s Ratio Perm 0.01

v/c Ratio 0.42 0.80 0.01 0.82

Uniform Delay, d1 60.3 1.4 0.4 1.5

Progression Factor 1.00 1.00 1.00 1.00

Incremental Delay, d2 21.8 4.0 0.0 4.6

Delay (s) 82.1 5.4 0.4 6.1

Level of Service F A A A

Approach Delay (s) 82.1 5.4 6.1

Approach LOS F A A

Intersection Summary

HCM Average Control Delay 5.9 HCM Level of Service A

HCM Volume to Capacity ratio 0.82

Actuated Cycle Length (s) 123.2 Sum of lost time (s) 8.0

Intersection Capacity Utilization 77.6% ICU Level of Service D

Analysis Period (min) 15

c Critical Lane Group
Queues A.M. Peak Hour

3: Dike 5 Construction Access Road & Auburn - Folsom Road

2/20/2008 Synchro 7 - Report

MurphySP

Lane Group WBL NBT NBR SBT

Lane Group Flow (vph) 5 1359 5 1397

v/c Ratio 0.11 0.76 0.01 0.78

Control Delay 49.0 5.1 0.6 5.8

Queue Delay 0.0 0.0 0.0 0.0

Total Delay 49.0 5.1 0.6 5.8

Queue Length 50th (ft) 4000

Queue Length 95th (ft) 17 618 1 724

Internal Link Dist (ft) 336 598 555

Turn Bay Length (ft) 200

Base Capacity (vph) 105 1795 786 1795

Starvation Cap Reductn 0000

Spillback Cap Reductn 0000

Storage Cap Reductn 0000

Reduced v/c Ratio 0.05 0.76 0.01 0.78

Intersection Summary
Timings A.M. Peak Hour

3: Dike 5 Construction Access Road & Auburn - Folsom Road

2/20/2008 Synchro 7 - Report

MurphySP

Lane Group WBL NBT NBR SBT

Lane Configurations

Volume (vph) 5 1250 5 1285

Turn Type Perm

Protected Phases 8 2 6

Permitted Phases 2

Detector Phase 8226

Switch Phase

Minimum Initial (s) 4.0 4.0 4.0 4.0

Minimum Split (s) 20.0 20.0 20.0 20.0

Total Split (s) 20.0 90.0 90.0 90.0

Total Split (%) 18.2% 81.8% 81.8% 81.8%

Yellow Time (s) 3.5 3.5 3.5 3.5

All-Red Time (s) 0.5 0.5 0.5 0.5

Lost Time Adjust (s) 0.0 0.0 0.0 0.0

Total Lost Time (s) 4.0 4.0 4.0 4.0

Lead/Lag

Lead-Lag Optimize?

Recall Mode None Max Max Max

Act Effct Green (s) 6.5 116.8 116.8 116.8

Actuated g/C Ratio 0.05 0.97 0.97 0.97

v/c Ratio 0.11 0.76 0.01 0.78

Control Delay 49.0 5.1 0.6 5.8

Queue Delay 0.0 0.0 0.0 0.0

Total Delay 49.0 5.1 0.6 5.8

LOS D A A A

Approach Delay 49.0 5.1 5.8

Approach LOS D A A

Intersection Summary

Cycle Length: 110

Actuated Cycle Length: 120

Natural Cycle: 90

Control Type: Actuated-Uncoordinated

Maximum v/c Ratio: 0.78

Intersection Signal Delay: 5.5 Intersection LOS: A

Intersection Capacity Utilization 77.6% ICU Level of Service D

Analysis Period (min) 15

Splits and Phases: 3: Dike 5 Construction Access Road & Auburn - Folsom Road
HCM Signalized Intersection Capacity Analysis P.M. Peak Hour

7: Dike 5 Construction Access Road` & Auburn - Folsom Rd

2/20/2008 Synchro 7 - Report

MurphySP

Movement WBL WBR NBT NBR SBL SBT

Lane Configurations

Volume (vph) 0 0 1382 0 0 1271

Ideal Flow (vphpl) 1900 1900 1900 1900 1900 1900

Total Lost time (s) 4.0 4.0

Lane Util. Factor 1.00 1.00

Frt 1.00 1.00

Flt Protected 1.00 1.00

Satd. Flow (prot) 1845 1845

Flt Permitted 1.00 1.00

Satd. Flow (perm) 1845 1845

Peak-hour factor, PHF 0.92 0.92 0.92 0.92 0.92 0.92

Adj. Flow (vph) 0 0 1502 0 0 1382

RTOR Reduction (vph) 000000

Lane Group Flow (vph) 0 0 1502 0 0 1382

Heavy Vehicles (%) 16% 16% 3% 100% 3% 3%

Turn Type Perm Perm

Protected Phases 8 2 6

Permitted Phases 2 6

Actuated Green, G (s) 120.0 120.0

Effective Green, g (s) 120.0 120.0

Actuated g/C Ratio 1.00 1.00

Clearance Time (s) 4.0 4.0

Vehicle Extension (s) 3.0 3.0

Lane Grp Cap (vph) 1845 1845

v/s Ratio Prot c0.81 0.75

v/s Ratio Perm

v/c Ratio 0.81 0.75

Uniform Delay, d1 0.0 0.0

Progression Factor 1.00 1.00

Incremental Delay, d2 4.1 2.8

Delay (s) 4.1 2.8

Level of Service A A

Approach Delay (s) 0.0 4.1 2.8

Approach LOS A A A

Intersection Summary

HCM Average Control Delay 3.5 HCM Level of Service A

HCM Volume to Capacity ratio 0.81

Actuated Cycle Length (s) 120.0 Sum of lost time (s) 0.0

Intersection Capacity Utilization 76.1% ICU Level of Service D

Analysis Period (min) 15

c Critical Lane Group
Queues P.M. Peak Hour

7: Dike 5 Construction Access Road` & Auburn - Folsom Rd

2/20/2008 Synchro 7 - Report

MurphySP

Lane Group NBT SBT

Lane Group Flow (vph) 1502 1382

v/c Ratio 0.81 0.75

Control Delay 4.1 2.8

Queue Delay 0.0 0.0

Total Delay 4.1 2.8

Queue Length 50th (ft) 0 0

Queue Length 95th (ft) 0 0

Internal Link Dist (ft) 587 569

Turn Bay Length (ft)

Base Capacity (vph) 1845 1845

Starvation Cap Reductn 0 0

Spillback Cap Reductn 0 0

Storage Cap Reductn 0 0

Reduced v/c Ratio 0.81 0.75

Intersection Summary
Timings P.M. Peak Hour

7: Dike 5 Construction Access Road` & Auburn - Folsom Rd

2/20/2008 Synchro 7 - Report

MurphySP

Lane Group NBT SBT ø8

Lane Configurations

Volume (vph) 1382 1271

Turn Type

Protected Phases 2 6 8

Permitted Phases

Detector Phase 2 6

Switch Phase

Minimum Initial (s) 4.0 4.0 4.0

Minimum Split (s) 20.0 20.0 20.0

Total Split (s) 90.0 90.0 20.0

Total Split (%) 81.8% 81.8% 18%

Yellow Time (s) 3.5 3.5 3.5

All-Red Time (s) 0.5 0.5 0.5

Lost Time Adjust (s) 0.0 0.0

Total Lost Time (s) 4.0 4.0

Lead/Lag

Lead-Lag Optimize?

Recall Mode Max Max None

Act Effct Green (s) 120.0 120.0

Actuated g/C Ratio 1.00 1.00

v/c Ratio 0.81 0.75

Control Delay 4.1 2.8

Queue Delay 0.0 0.0

Total Delay 4.1 2.8

LOS A A

Approach Delay 4.1 2.8

Approach LOS A A

Intersection Summary

Cycle Length: 110

Actuated Cycle Length: 120

Natural Cycle: 120

Control Type: Actuated-Uncoordinated

Maximum v/c Ratio: 0.81

Intersection Signal Delay: 3.5 Intersection LOS: A

Intersection Capacity Utilization 76.1% ICU Level of Service D

Analysis Period (min) 15

Splits and Phases: 7: Dike 5 Construction Access Road` & Auburn - Folsom Rd