Chapter 2 

Revised Project Description 

The chapter discusses the characteristics of the currently proposed project, 

particularly as related to Alternative 3 - the Preferred Alternative, and describes how 

and why certain characteristics of the currently proposed project differ from those 

presented in the Draft EIS/EIR. As described in greater detail below, the Partner 

Agencies have revised the project description in response to comments on the Draft 

EIR, paying particular attention to concerns expressed by the local community. 

Additionally, technical data recently developed by the Partner Agencies regarding 

hydrologic analyses for the Folsom Facility suggest that the need for, and extent of, a 

raise greater than 3.5 ft is no longer necessary to provide dam safety and flood 

damage reduction benefits. The raise element of the project will undergo detailed 

design during the Corps’ pre-construction, engineering and design phase and if 

needed, supplemental NEPA/CEQA documentation would be prepared. 

While the basic nature, purpose, and fundamental elements of the project remain the 

same as described in the Draft EIS/EIR, the Partner Agencies have refined certain 

aspects of the project in response to concerns raised during the public comment 

period and the development of recent data indicating a reduced need for certain flood 

control improvements (such as a raise of more than 3.5 ft). The following sections 1) 

summarize the four basic action elements associated with the project, 2) describe 

how the project description has changed since publication of the Draft EIS/EIR, with 

particular attention to Alternative 3 and a brief discussion of the other alternatives, 

and 3) describe the implementation sequence (i.e., phasing) of the currently proposed 

project. 

2.1 Description of the Folsom DS/FDR Preferred 

Alternative 

The Folsom DS/FDR Preferred Alternative incorporates four action elements to be 

implemented by Reclamation and the Corps. 

1. A new Auxiliary Spillway would be controlled by 6 submerged tainter 

gates (6STG). The Auxiliary Spillway, also referred to as the JFP, would 

be implemented jointly by Reclamation and the Corps to address 

hydrologic Dam Safety and Flood Damage Reduction concerns related to 

controlled release of water from Folsom Dam. Reclamation has also 

evaluated a Fuseplug Spillway alternative as a stand-alone dam safety 

alternative to be implemented only if the Corps is unable to receive 

timely construction funding or realize timely hydrologic risk reduction by 

Folsom DS/FDR Final EIS/EIR – March 2007 2-1 
Chapter 2 

Project Description 

construction of the 6STG spillway. Reclamation and the Corps will 

jointly identify the final environmental mitigation and commitments for 

the new Auxiliary Spillway project element, inclusive of the Fuseplug 

option, under a joint JFP ROD. 

2. Additional Dam Safety modifications will be undertaken by Reclamation 

to address seismic and static concerns related to the Main Concrete Dam 

and six of the eleven earthen structures. Seismic modifications would be 

made to MIAD by undertaking foundation jet grouting in conjunction 

with a downstream overlay and the reinforcement of Main Concrete Dam 

existing gates and piers. Static modifications would be undertaken to the 

Right and Left Wing Dams (RWD, LWD), Dikes 4, 5 and 6 and MIAD. 

Reclamation will independently identify the final environmental 

mitigations and commitments for this effort under a stand-alone ROD. 

3. Security improvements will be undertaken by Reclamation to key 

Folsom facilities to address national security concerns. Reclamation will 

independently identify the final environmental mitigations and 

commitments for this effort under the dam safety ROD. 

4. Flood Damage Reduction improvements in addition to the 6STG will be 

undertaken by the Corps including modification or replacement of 

existing emergency spillway gates and a 3.5-ft raise to all Folsom 

embankment facilities. The Corps will prepare a separate ROD for the 

3.5-ft raise, emergency gate modifications or replacement, and other 

flood damage reduction features. As described more in this section, 

detailed design for these flood damage reduction features at the Folsom 

Facility would occur during the Corps’ pre-construction, engineering and 

design phase. The issuance of a ROD by the Corps for such 

improvements at the Folsom Facility is not expected to occur in 

conjunction with the currently proposed DS/FDR actions, but rather 

would occur later as a separate action with supplemental environmental 

documentation if necessary. 

The following sections describe the basic nature and characteristics of each of these 

four actions. Section 2.2.4 of the Draft EIS/EIR provides detailed descriptions of the 

various engineering measures (i.e., improvements) associated with these actions, 

which were included to varying degrees in the six alternatives (i.e., No Action/No 

Project Alternative and Alternatives 1 through 5). 

2.1.1 Auxiliary Spillway - JFP (Reclamation and the Corps) 

The JFP involves the construction of a new Auxiliary Spillway (6STG or Fuseplug 

control structure) downstream of the toe of the LWD to provide the operational 

capability for improved hydrologic control (controlled sustained discharge earlier 

2-2 Folsom DS/FDR Final EIS/EIR – March 2007 
Chapter 2 

Project Description 

 

and for longer durations and/or prevention of overtopping) of storm induced floods 

in excess of reservoir storage capacity in advance of and during a major storm. The 

new Auxiliary Spillway Preferred Alternative (6STG) would be constructed jointly 

by Reclamation and the Corps. Reclamation would initiate excavation of the 

spillway channel and stilling basin and the Corps would complete excavation of the 

channel including the approach channel, and construct the control structure and 

concrete lining of the channel and stilling basin. The Draft EIS/EIR addressed the 

impacts of constructing either spillway option, including operating the new facility to 

existing operational parameters. The Corps has initiated further study, including the 

follow-up environmental documentation process, to address the future operational 

issues for the 6STG spillway. 

Common (soil) rock material excavated from the spillway channel would be hauled 

eastward on government property for temporary stockpiling and/or permanent 

disposal of excess material at or near the downstream toe of the LWD, Observation 

Point area, Dike 7, and the D1/D2 area near MIAD (see Figure 2-1 for locations of 

site features and stockpile areas under the Preferred Alternative). Although not part 

of the JFP, the temporarily stockpiled material would be used for the proposed dam 

safety improvements (Section 2.1.2 below) including construction of a downstream 

overlay at MIAD and various staging platforms. 

2.1.2 Dam Safety Improvements (Reclamation) 

To address seismic and static concerns for structures comprising the Folsom Facility, 

Reclamation has planned modifications for the Main Concrete Dam, the RWD and 

LWD, Dikes 4, 5, and 6, and MIAD. All of these modifications would be 

constructed independently by Reclamation. 

To address seismic concerns for the Main Concrete Dam, three types of 

improvements are planned to provide reinforcement to the existing spillway gates 

and piers to withstand a major earthquake. Deformation of the gate piers and during 

earthquake loading could result in failure of several spillway gates. This failure could 

release significant quantities of water that could cause flooding and possible failure 

of the downstream levees. The three types of improvements proposed to enhance 

dam safety include: 

a) Bracing between existing piers - The project design is intended to inhibit pier 

bending during an earthquake. The braces consist of steel trusses that span 

the distance between piers. The braces (seven per spillway bay) are designed 

to carry the cross-canyon force during a seismic event. The braces would 

reduce bending stresses in the pier reinforcing steel and minimize deflections 

of the piers and potential loading of the spillway gates. 

b) Pier wrap - This improvement involves placement of a steel plate wrapped 

around the downstream portion of the pier and anchored with bolts on both 

Folsom DS/FDR Final EIS/EIR – March 2007 2-3 
Chapter 2 

Project Description 

sides that extend completely through the pier, upstream of the area of 

concern. The steel plate would carry the load placed on it if the pier tends to 

shear and displace; the pier would hold in place. 

c) Spillway gate bracing - Spillway gates would be overstressed during large 

seismic events and could fail from buckling of the gate arms. Failure of 

several spillway gates could release significant quantities of water that could 

cause flooding and failure of the downstream levees. Designs for reinforcing 

and/or replacing the existing gate arm members were developed as part of the 

project to address this failure mode. These modifications would strengthen 

the gate arms and reduce the probability of gate failure. This strengthening 

could be performed with the gate in place. During construction, a bulkhead 

would be installed upstream of the gate to eliminate loading on the gate and 

the reinforcement installed. 

To address seismic concerns for MIAD, two types of improvements are planned. 

The first improvement involves stabilization of the foundation of MIAD using a 

subsurface jet grouting process. A cement-grout mixture would be formed on-site 

using a cement material hauled to the MIAD project site and mixed with water. The 

cement water mixture would be injected into the subsurface by a drilling method and 

would solidify in situ. Following jet grouting, material temporarily stockpiled from 

the new Auxiliary Spillway site at the D1/D2 area, along with processed sand and 

gravel material, would be placed as an overlay on the downstream face of MIAD. 

To address static concerns for LWD, RWD, Dikes 4, 5, and 6, and MIAD, 

Reclamation would install new seepage control filters within the downstream face of 

each earthen structure. The filter material would be processed sand and gravel 

material and would be delivered to each individual facility from offsite in highway 

legal haul trucks and/or processed from materials excavated from the Auxiliary 

Spillway on-site at or near the LWD. The construction improvements involve 

stripping a layer of shell material from the downstream face of the wing dams and 

dikes, placing the filter material, and replacing the shell. Additional material needed 

to rebuild the shell would either be excavated from the Auxiliary Spillway site or 

from supplemental borrow sites. 

2.1.3 Dam Security Improvements (Reclamation) 

Reclamation would install security cameras at access points to the Main Concrete 

Dam, Dikes 4 through 7, and at MIAD. The cameras would be placed on 30-ft steel 

poles with electrical and cable connections buried. To improve the night visibility of 

the Main Concrete Dam and control gates, Reclamation would install lighting to 

focus on the critical aspects of this structure. To the extent practicable, lighting 

would be installed in a manner that meets security mission requirements and 

2-4 Folsom DS/FDR Final EIS/EIR – March 2007 
Chapter 2 

Project Description 

 

minimizes glare or reflection impacts to homes and other private property 

surrounding the reservoir. 

2.1.4 Flood Damage Reduction Actions (Corps) 

To provide for improved flood damage reduction benefits in addition to the 6STG 

spillway, the Corps plans two separate actions as their Selected Plan. Construction 

of the JFP Auxiliary Spillway would increase project discharge capacity at lower 

pool elevations with no net increase in pool elevation. This allows lowering of the 

maximum pool and a decrease in the need for surcharge storage space in the 

reservoir. The additional modifications include the modification and/or replacement 

of existing emergency spillway gates and a 3.5-ft parapet wall or earthen raise to all 

embankment structures. The spillway gate replacement is to account for differing 

gate sizes and/or improve flow capacity; the raise is intended to provide additional 

freeboard. The 3.5-ft raise and emergency gate replacement portion of the Corps’ 

Selected Plan would undergo further design during the Corps’ pre-construction, 

engineering, and design phase. 

2.2 Changes to the Project Since the Release of the Draft 

EIS/EIR 

Based upon additional engineering analysis and responding to public comments on 

the Draft EIS/EIR, the following section introduces the changes to the project 

description as revised since the release of the Draft EIS/EIR. 

2.2.1 Sequencing and Length of the Folsom DS/FDR Actions 

The Partner Agencies have modified the proposed sequencing of construction at each 

of the Folsom facilities. The proposed completion date for certain dam safety 

actions have been extended several years and there is less overlap of construction 

work for the dikes and wing dams. The new Auxiliary Spillway would now be 

constructed as part of three phases. Table 2-1 provides the proposed sequencing of 

the Folsom DS/FDR actions. It is important to note that the schedule proposed in 

Table 2-1 is tentative and subject to change based on engineering design 

considerations and availability of funding for each activity. 

2.2.2 Inundation Due to Raises 

The Draft EIS/EIR introduced the possibility of constructing a Folsom Facility raise 

greater than 4 ft which could result in constructing new embankments to contain 

reservoir water resulting from an increased reservoir surface elevation beyond 

existing conditions. Since publishing the Draft EIS/EIR, Reclamation has 

determined that a Fuseplug Spillway alternative could pass the PMF without the 

need for embankment raises above the current crest elevation. As a result, 

Folsom DS/FDR Final EIS/EIR – March 2007 2-5 
Chapter 2 

Project Description 

Table 2-1 

 Folsom DS/FDR Project Phase Sequencing 

Activity 

ID 

Folsom Facility Construction Period 

1 Auxiliary Spillway Excavation Phase 1 September 2007 to March 2009 

2 Right and Left Wing Dam Static Modifications October 2007 to November 

2008 

3 MIAD Jet Grouting July 2008 to November 2009 

4 Auxiliary Spillway Excavation Phase 2 September 2010 to January 

2014 

5 Dike 5 Static Modifications September 2009 to May 2010 

6 MIAD Seismic Overlay June 2015 to April 2017 

7 Dikes 4 and 6 Static Modifications September 2017 to April 2018 

8a Pier Tendon Installation at Main Concrete Dam January 2014 to March 2015 

8b Spillway Pier Wraps & Braces August 2016 to April 2018 

8c Spillway Gate Repairs January 2018 to August 2020 

9 Auxiliary Spillway Approach Channel Excavation 

Phase 3 and Gate Structure Construction 

September 2011 to November 

2014 

10 Raise of all Folsom Facilities May 2010 to September 2014 

Reclamation has determined that no property takes, flowage easements, or additional 

small scale impoundment features such as dikes or berms are planned as part of its 

role in the Folsom DS/FDR actions. 

Based upon additional engineering analysis since the Draft EIS/EIR was published, 

the Corps has concluded that with optimization of all elements of the Selected Plan 

(6STG, emergency spillway gate modification and 3.5-ft raise) an increase to 

maximum reservoir water surface elevation beyond current dam crest elevation is not 

anticipated to provide for flood damage reduction benefits. 

Under the Selected Plan, the future maximum reservoir water surface elevation 

would not exceed the existing take line for a 200-year design event and there would 

be a lower maximum water surface elevation than the without-project condition for 

all flood events inclusive of a PMF event. This would eliminate the risk that 

surrounding properties would be flooded. Consequently, no property takes, flowage 

easements or additional small scale impoundment features such as dikes or berms 

beyond the existing take line are planned in the Final EIS/EIR. The 3.5-ft raise 

portion of the Selected Plan will undergo further design during the Corps’ preconstruction, engineering, and design phase and if needed, supplemental 

NEPA/CEQA documentation would be prepared. 

2-6 Folsom DS/FDR Final EIS/EIR – March 2007 
Chapter 2 

Project Description 

 

2.2.3 Folsom DS/FDR Optimized Project Area 

The project footprint evaluated in the Draft EIS/EIR included areas required to 

construct raises of all structures up to 17 ft in height (Alternative 5).1 Based upon 

further engineering analysis and considering public comments on the Draft EIS/EIR, 

the Partner Agencies have concluded that raises above 3.5 ft are not required and 

have eliminated them as project alternatives. As a result, the project footprint has 

been reduced to the minimum area necessary to support the new Auxiliary Spillway; 

work on the main concrete dam; the seismic and static modifications to Dikes 4, 5, 6, 

LWD and RWD and MIAD; and any 3.5-ft raise. Reducing the project footprint has 

reduced impacts to those presented in the Draft EIS/EIR, primarily pertaining to 

recreation, vegetation and wildlife, and other elements of vital concern to the 

surrounding communities. Upon completion of construction, project staging areas, 

haul roads, stockpiles, temporary access roads, detours, trails and paths or similar 

features would either be reclaimed/restored as close to practical to the pre-existing 

condition and/or similar to the surrounding terrain and/or be graded to provide 

unimproved platforms as elected by Reclamation. 

The following text summarizes specific individual changes to the project footprint as 

a result of eliminating raises above 3.5 ft, along with the commensurate reduction in 

impacts. Figures 2-1 and 2-2 illustrate the reduction in project footprints under the 

Draft EIS/EIR and the revised Preferred Alternative. These figures should be 

reviewed in relation to the text below. 

Dike Crest and Toe Construction Zones 

In the Draft EIS/EIR, the maximum area of impact for the dike construction zones 

was assumed to encompass a 150-ft vegetation clearing buffer from the downstream 

toe of all earthen embankments except at Dike 7, the LWD and MIAD and 

embankment crest widths to accommodate up to a 17-ft raise. In the revised project 

description, areas below Dikes 1, 2, and 8 have been removed from consideration. 

Areas at Dike 7, the RWD, LWD, and MIAD remain largely the same. Minor 

adjustments include extending areas to the federal property boundary limits below 

Dike 7 to accommodate material stockpiles; at the site of the new Auxiliary Spillway 

below the LWD to the newly granted easement limit provided for the Folsom Bridge 

Project; and at MIAD to the federal property boundary bordering Green Valley Road 

to accommodate jet grouting and the seismic overlay modifications. All other toe 

buffers have been eliminated from Dikes 1, 2, 3, and 8 and reduced to 80 ft or less at 

Dikes 4, 5, and 6. 

 

1

 While several of the alternatives considered in the Draft EIS/EIR propose a dam/facility raise less 

than the 17 ft anticipated under Alternative 5, a single most-conservative impact footprint was used 

in the programmatic-level analysis of all alternatives that proposed any raise (i.e., Alternatives 2 

through 5). 

Folsom DS/FDR Final EIS/EIR – March 2007 2-7 
Chapter 2 

Project Description 

Crest widths on all earthen embankments have been reduced to the limit of the 

existing crest width, typically 20 ft, to accommodate the 3.5-ft raise. No additional 

toe area is required to accomplish the raise element for Dikes 4, 5, 6, and 7. For 

Dikes 1 to 3 and Dike 8, a 50-ft temporary construction easement is assumed. 

Chapter 3 of this Final EIS/EIR discusses how these changes would reduce impacts 

to the natural, physical, and social environments. Figures 2-1 and 2-2 of this 

document provide a comparison of the reduced footprints for construction zones near 

the facilities proposed for modifications. 

Haul Routes 

In response to public comments on the Draft EIS/EIR, the Partner Agencies have 

further clarified the proposed haul routes identified in the Draft EIS/EIR. The haul 

routes are predominantly within the Federal property boundary and use existing 

service routes along the immediate toes of existing embankments and/or in-reservoir 

(i.e. at or below elevation 480.5 ft and typically above normal operational reservoir 

water surface elevation of 466.0 ft). The identified routes avoid surveyed cultural 

resources sites, incorporate public safety protection measures, such as fencing and 

with traffic control measures and/or grade separated crossings, and/or provide for 

temporary alternate public access detours at major recreation area access points. To 

the extent practicable, the Partner Agencies would use natural topography and 

stockpiled materials to reduce noise along haul routes and control fugitive dust 

emissions with combinations of water, dust control surfactants, and gravel. The use 

of haul routes, along with other impact reduction measures would reduce recreational 

impacts. A summary explanation is provided below and detailed explanation of this 

change to relevant specific impacts, such as recreation, is addressed in Chapters 3 

and 4. 

As outlined in Section 2.5 and Chapter 4 of this document, there would be nearly 

continuous public access to recreation areas throughout the construction period. 

Access would be facilitated through the use of traffic control measures and/or grade 

separated vehicular and/or pedestrian crossings and/or temporary alternate public 

access detours. Temporary closures could occur during construction of the grade 

separation or other access measures or to meet unforeseen project circumstances. In 

such cases, temporary closures would be accomplished during off-peak days or the 

off-season to minimize impacts on recreation activities. 

Reclamation’s Central California Area Office will notify local agencies and the 

general public and accept input in advance of any possible extended closure(s) that 

may be necessary due to unforeseen project circumstances. 

2-8 Folsom DS/FDR Final EIS/EIR – March 2007 
El D orado Co. 

El Dorado Co. P

al cer Co. 

P al cer Co.

El Dorado Co. El Dorado Co. Sacramento Co. 

Sacramento

Co.

Placer Co. Placer Co.

Sacramento Co. Sacramento Co.

400 

42

40

5 

425 400

400

4 25 465 

465 

500 

500 

500 

500 

500 

500 

500 

DIKE 1

DIKE 2

DIKE 3

DIKE 4 

DIKE 5 

CSAD5S

DIKE 6 RIGHT WING

DAM

DIKE 7

(CSAD7S)

DIKE 8

PROPOSED

AUXILIARY

SPILLWAY MIAD

MIAD

RIGHT

D2

D1 

CSAMIADN

CSAMIADS

Granite 

Bay 

Beals 

Point 

Folsom 

Point 

CSALWDE

CSAD7N CSAD8

LEFT WING

DAM

CSAD4NW

CSAD4NE

CSAD5N

CSAD4SE

CSAD6E

CSARWDN

CSARWDS

FOLSOM DAM

CSALWDS



Figure 2-1

The Preferred Alternative

Construction Zones

0 3000

FEET

1:36,000

NORTH

Potential Construction Zones

Potential Borrow Areas

Potential Contractor Use / Staging Areas

Seasonal Staging Area

Potential Borrow Areas and Potential

Contractor Use/ Staging Areas

Processing Only 

(Approximate Location) 

Concrete and Processing 

(Approximate Location) 

465ft

500ft

425ft

400ft

Haul Route

Contours

Folsom

Reservoir