appendix 7 - san bernardino county, california

Appendix 7

Draft Alternatives Evaluation

DRAFT

ALTERNATIVES EVALUATION

REHABILITATION OF LAKE GREGORY DAM

DAM ID 1803-003 COUNTY OF SAN BERNARDINO, CALIFORNIA

Prepared for:

County of San Bernardino Special Districts Department

157 West Fifth Street, Second Floor San Bernardino, California 92415-0450

Prepared by:

Tetra Tech 1900 South Sunset Street, Suite 1-F

Longmont, Colorado 80501

Tetra Tech Project No. 133-01297-12006

June 2012

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TABLE OF CONTENTS Page

EXECUTIVE SUMMARY ............................................................................................................ 1

1.0 INTRODUCTION .............................................................................................................. 1 1.1 Scope ....................................................................................................................... 1 1.2 Limitations .............................................................................................................. 2

2.0 BACKGROUND INFORMATION ................................................................................... 2 2.1 General .................................................................................................................... 2 2.2 History of Modifications ......................................................................................... 2 2.3 Recognized Concerns .............................................................................................. 2

3.0 ALTERNATIVES .............................................................................................................. 3 3.1 General .................................................................................................................... 3 3.2 Alternative 1 – Downstream Stabilization Buttress ................................................ 4 3.3 Alternative 2 – Downstream Stabilization Buttress within Dam Footprint ............ 4 3.4 Alternative 3 – Horizontal Drains ........................................................................... 4 3.5 Alternative 4 – Cement Deep Soil Mixing ............................................................. 4 3.6 Alternative 5 – Stone Columns ............................................................................... 5 3.7 Alternative 6 and 7 –Cutoff Wall ............................................................................ 5 3.8 Alternative 8 – Upstream Stability Buttress ........................................................... 5 3.9 Alternative 9 – Upstream Concrete Face With Membrane ..................................... 6 3.10 Alternative 10 – Upstream Asphalt Face ................................................................ 6 3.11 Alternative 11 – New Embankment Dam ............................................................... 6

4.0 DESIGN CRITERIA .......................................................................................................... 7 4.1 Site Constraints ....................................................................................................... 7 4.2 DSOD ...................................................................................................................... 7 4.3 Use of Water ........................................................................................................... 7

5.0 ALTERNATIVES SELECTION PROCESS ..................................................................... 7 5.1 Alternative Selection ............................................................................................... 7

5.1.1 Alternatives Not Selected ........................................................................... 7 5.1.2 Selected Alternatives .................................................................................. 7

6.0 OPINION OF PROBABLE PROJECT COSTS ................................................................. 9

7.0 CONCLUSIONS AND RECOMMENDATIONS ........................................................... 10 7.1 Conclusions ........................................................................................................... 10 7.2 Recommendations ................................................................................................. 10

8.0 REFERENCES ................................................................................................................. 11

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List of Tables Table ES-1 Summary of Dam Features Table ES-2 Summary of Selected Remediation Alternatives Table 3-1 Summary of Remediation Alternatives Table 6-1 Opinion of Probable Project Cost List of Figures Figure 1 Existing Site Conditions Figure 2 Existing Conditions Typical Section Figure 3 Alternative 1 conceptual Downstream Stabilization Buttress Figure 4 Alternative 2 Downstream Buttress Within Embankment Figure 5 Alternative 3 Embankment Dewatering Figure 6 Alternative 4 CDSM Stabilization Figure 7 Alternative 5 Stone Column Stabilization Figure 8 Cutoff Walls: Alternative 6 Plastic Concrete; Alternative 7 Soil/Bentonite Figure 9 Alternative 8 Upstream Buttress Figure 10 Alternative 9 Upstream concrete Face and Geosynthetic Membrane Figure 11 Alternative 10 Upstream Asphalt Face Figure 12 Alternative 11 Dam Relocation List of Appendices Appendix A Figures Appendix B Stability Analyses Appendix C Detailed Cost Estimates

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EXECUTIVE SUMMARY This report presents an alternatives evaluation for the rehabilitation of Lake Gregory Dam. Lake Gregory Dam is a homogeneous earth fill dam with a downstream rock fill shell built between 1936 and 1938. The dam was constructed with silty sand and gravel borrowed from the weathered bedrock in the reservoir basin. Table ES-1 summarizes the existing and proposed dam features. The California Department of Water Resources, Division of Safety of Dams, (DSOD) has placed Lake Gregory under restricted use due to insufficient capacity of the outlet works and unresolved issues regarding dam stability during an earthquake. Tetra Tech previously evaluated the static and pseudo static stability of the dam as well as post-earthquake stability and deformation. The evaluation of the existing dam concluded that the dam is subject to unacceptable performance during a maximum credible earthquake. The results indicated that the dam does not meet minimum FOS requirements for pseudostatic seismic loading and post-earthquake stability.

Table ES-1 Summary Of Dam Features

Lake Gregory Dam

Dam Existing Proposed

Type: Earthfill Crest Elevation: 4530.0 ft Crest Width: 46’-57’ (Varies) Crest Length: 475 ft Streambed Elevation at Dam Axis: 4459 ft Lowest Foundation Elevation: 4420 ft Valley Floor Elevation at Downstream Toe: 4440 ft Embankment Height (spillway crest to streambed): 90 ft Structural Height (dam crest to lowest point in foundation): 97 ft

Spillway Type: Broad Crested Weir Crest Elevation: 4517 ft Crest Elevation with Flashboards: 4520 ft Width: 40 ft Maximum Capacity at elevation 4530: 8400 ft3/sec Freeboard above Spillway Crest Elevation: 13 ft Freeboard above Spillway Flashboards: 10 ft Reservoir Storage (at the spillway crest): 2,100 ac-ft

Low Level Outlet Works Type: 12” Steel 30” steel Invert Elevation at Intake Structure: 4459 ft Capacity with water surface at spillway crest elevation 16 ft3/sec 100 ft3/sec

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Eleven alternatives were developed to address the deficiencies of the dam. Tetra Tech developed the alternatives to provide mitigation of safety concerns resulting from damage to the dam from a large earthquake in the area. The alternatives range from low to high with respect to overall impact, cost, and public relations. The alternatives include:

1. Downstream stabilization buttress 2. Downstream stabilization buttress in

dam 3. Horizontal drains 4. Cement deep soil mixing 5. Stone column strengthening

6. Plastic concrete cutoff wall 7. Soil-bentonite cutoff wall 8. Upstream stability buttress 9. Upstream concrete face 10. Upstream asphalt membrane 11. New upstream dam

An alternatives selection discussion was conducted between San Bernardino County and Tetra Tech to narrow down the field of 11 alternatives to 4 potential stabilization alternatives. Alternatives 1, 4, 5, and 10 were determined to be the most cost effective and constructible alternatives and are shown in Table ES-2 below.

Alternative

- - -- -

- --

-- - -- - -

- -

--

- - -- - - Road closure during construction

- - Impact to utilities located in crest--

- - -- -- - -- - No road closure

- No utility impact - Potential damage during an earthqu

Lake Gregory Dam

Table ES-2Summary of Selected Remediation Alternatives

DescriptionDownstream stabilization buttress

1

Cons

Replace slope protection on new buttress

Construction of downstream stability buttressConstruction of chimney and blanket drains

Removal of downstream slope protectionRemoval of trees on and downstream of the dam Downstream property impact

Upstream stability not addressed

Location of borrow source


Approved and used in a different application (liquefiable foundation)

Installation accessInstallation spoils

Road closure during construction

4

Strengthen the low density zone with cement deep soil mixing (CDSM)

Minimal downstream disturbanceMinimal reservoir dewatering

ProsMinimal Reservoir Dewatering

Alternative Includes

Construction of installation platforms on Installation of CDSM columns

Method has been approved by DSOD and used within CA

10

Upstream asphalt face Complete dewatering of the reservoir or Removal of upstream rock protection

Installation of compacted gravel columns5

Strengthen the low density zone with stone columns

Large public relations issue due to dewatering reservoir

Construct a key 5-foot into bedrockConstruction of a asphalt face over the upstream

Complete dewatering of the

Installation access

Approved and used in a different

Construction of installation platforms on

Possible impact to outlet works


Minimal downstream disturbance


No downstream disturbance

No geosynthetic membrane required, less maintenance

Minimal reservoir dewatering

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1.0 INTRODUCTION

The California Department of Water Resources, Division of Safety of Dams, (DSOD) has placed Lake Gregory under restricted use due to insufficient capacity of the outlet works and unresolved issues regarding dam stability during an earthquake. Tetra Tech has evaluated the stability of the dam to develop alternatives to address the issues raised by DSOD. The work was performed in accordance with our January 26, 2012, proposal to the County of San Bernardino. The work performed for this study was based on the response of DSOD to the January 2012 Stability Investigation Report by Tetra Tech that presented evaluations of dam stability during a maximum credible earthquake (MCE) of 8.5 on the San Andreas Fault occurring near the dam. The January 2012 Stability Investigation Report involved evaluation of the material properties of the embankment and foundation, an analysis of liquefaction potential, and analyses of static and seismic stability and deformation of the dam under the MCE loading conditions. The embankment was analyzed, with steady-state seepage, for static stability, rapid drawdown and pseudostatic seismic loading of 0.65 g. Additionally, the embankment was modeled utilizing a coupled deformation and stability analysis using earthquake data to simulate a magnitude 8.5 earthquake occurring on the San Andreas Fault. The results indicated the dam meets minimum factor of safety (FOS) requirements for static and rapid drawdown stability. The results indicated that the dam does not meet minimum FOS requirements for pseudostatic seismic loading and post-earthquake stability. The evaluation of liquefaction potential indicated that a zone between approximately 20 and 55 feet below the dam crest could potentially liquefy during an earthquake on the San Andreas with a magnitude of 8.5 and under a horizontal acceleration of 0.65g. The Equivalent Linear Method estimated that under the MCE with a pga of 0.65, a maximum vertical deformation of 17.6 feet is anticipated. The results of the Stability Investigation Report indicated the dam meets minimum factor of safety (FOS) requirements for static and rapid drawdown stability. The results indicated that the dam does not meet minimum FOS requirements for pseudostatic seismic loading and post-earthquake stability.

1.1 Scope

The following scope of work was based on our understanding of the requirements for this phase of the project presented to Tetra Tech by San Bernardino County (SBC) on January 12, 2012. Task 1 – Develop Remediation Options Develop 11 options for the stabilization of Lake Gregory Dam. The options are based on the project team’s experience and on published literature from similar projects. Schematic level design drawings, and preliminary post construction stability analyses are included.


Task 2 – Quantify Remediation Options Selected remediation options developed in Task 1 are quantified on the basis of cost. The quantification includes discussions of the feasibility, cost, contingency, and the pros/cons of each stabilization option. Task 3 – Report Tetra Tech prepared this report describing options developed for the project. The report will rank the options on the basis of cost and feasibility. A matrix of the alternatives is included in the executive summary.

1.2 Limitations

This report was prepared to meet generally accepted engineering standards. The alternatives are conceptual and require additional design effort prior to construction.

2.0 BACKGROUND INFORMATION

2.1 General

The dam was constructed between 1936 and 1938 as a homogenous earth embankment. The dam is shown on Figure 1. An outlet works and diversion tunnel was excavated through the left abutment. The outlet works is presently being upgraded under a separate contract.

2.2 History of Modifications

A summary of the modifications that have occurred to the dam since the Certificate of Approval was issued by DSOD in 1941 is presented below.

• 1941 – Bridge constructed across spillway • 1945 – Outlet valve modification • 1945 – Flashboard installation in spillway (DSOD approval in 1949) • 1947 – 6-inch diameter steel pressure pipe installed in the roadway fill above the

downstream rock fill section • 1967 – 10-inch diameter concrete encased sewer line installed in the dam

embankment • 1970 – 8-inch diameter asbestos concrete pipe encased in a 16-inch diameter steel

pipe installed in the embankment • 1972 – Bridge replaced over the spillway • 1972 – 4-inch diameter gas line installed on the upstream side of the crest

2.3 Recognized Concerns

As discussed in the Stability Investigation report (February 2012), the Lake Gregory Dam does not perform with respect to good engineering practice under earthquake and post-earthquake conditions. Additionally, the dam does not meet DSOD requirements for stability under the


project design earthquake and post-earthquake conditions as well as DSOD requirements for earthquake-caused deformation.

3.0 ALTERNATIVES

3.1 General

Eleven stabilization alternatives have been developed for Lake Gregory Dam. The alternatives address the liquefaction of the embankment and the downstream embankment slope failures resulting from earthquake shaking. Upstream stabilization alternatives were developed. Several alternatives may not be ultimately viable due to complications arising from upstream slope instability. A summary of the alternatives is shown in Table 3-1 below.

Alternative- - -- -- --

-- - - Full reservoir dewatering required- - -- -- - ----- - -- - -- - DSOD may not approve

-- - -- - -

- -

--

- - -- - - Road closure during construction

- - Impact to utilities located in crest--

- - -- - -- - Impact to utilities located in crest

-- Potential damage during an earthquake

- - -- - - Road closure during construction - - Impact to utilities located in crest

-- Potential damage during an earthquake

- - -- - -- - No utility impact -- -- - -- - No road closure -- - No utility impact -- - Potential damage during an earthquake-- - -- - -- - No road closure -- - No utility impact - Potential damage during an earthquake- - -- - Outlet works realignment potential- - -- - Road closure during construction - - Road realignment

- Impact to utilities located in crest-

Possible impact to outlet works


Complete dewatering of the reservoir

Loss of storage volume

Construct a key 5-foot into bedrockConstruction of a asphalt face over the upstream




Construct a key 5-foot into bedrock

Installation of an upstream geosynthetic membrane

Removal of upstream rock protection

Construction of a concrete face over the upstream

New dam with modern construction techniques and

Replacement of upstream rock protection on new buttress

Removal of upstream rock protection

Upstream stability not addressedBackfill trench with mixture of excavated soils and bentonite


Installation platforms on downstream facesInstallation of CDSM columns


Approved and used in a different application (liquefiable foundation)

Installation of compacted gravel columnsMethod has been approved by DSOD and used within CA

Minimal downstream disturbance Installation accessMinimal reservoir dewateringExcavation of a 2.5 foot wide trench keyed into bedrock

Installation of platforms on downstream faces

Approved and used in a different



10

Upstream asphalt face Complete dewatering of the reservoirRemoval of upstream rock protection

New dam in an alternate location upstream

11


New dam from old dam material

Removal of upstream and downstream rock protection and

Realigning outlet works

9

Upstream concrete face with a geosynthetic membrane


8

Minimal downstream disturbance Installation accessMinimal reservoir dewatering Road closure during construction

Upstream stability not addressedPlacement of plastic concrete into trench

Complete dewatering of the reservoirPublic relations issue

Construction of buttress

No downstream disturbance Maintenance required

Complete dewatering of the reservoir Complete dewatering of the reservoir

Loss of storage volume

Possible impact to outlet worksUpstream buttress No downstream disturbance

No road closure

Soil/bentonite cut off wall Iinstallation of platform and containment berms on crest

6

Plastic concrete cut off wall

Installation of platform and containment berms on crestExcavation of a 2.5 foot wide trench keyed into bedrock

Downstream property impactUpstream stability not addressedLocation of borrow source

ProsMinimal Reservoir Dewatering


Public relations issuesBorrow from reservoir basin

Installation access

Mmultiple drains along the bottom of the low density layer3Horizontal or inclined drains to lower the pieziometric surface

Partial removal of downstream slope protection

1

Replacement of embankment material as buttress

Installation of a collection system to convey water to discharge area

Removal of downstream slope protectionRemoval of trees on and downstream of the dam

4

5

Strengthen low density zone with stone columns

Road closure during construction

Upstream stability not addressedStrengthen the low density zone with cement deep soil mixing (CDSM)

Reservoir lowered provides upstream access for stabilization

Installation accessInstallation spoils

Location required to stockpile removed embankment material


Rigorous analysesMay not be effective

Construction of chimney drain

Lake Gregory Dam

7

Foundation preparation (removal of existing dam)

No geosynthetic membrane

Public relations issue

Public relations issue

Public relations issues

Table 3-1Summary of Remediation Alternatives

DescriptionDownstream stabilization buttress

2

Downstream stabilization buttress within footprint of existing embankment

Minimal reservoir dewatering

Cons

Replace slope protection on new buttress

Partial removal of existing embankment Reservoir drawdownRemoval of downstream slope protectionRemoval of trees on and downstream of the dam Replace slope protection on new buttressConstruction of downstream stability buttressConstruction of chimney and blanket drains

Elements


3.2 Alternative 1 – Downstream Stabilization Buttress

Alternative 1, shown on Figure 3, consists of constructing a stabilization buttress on the downstream slope of the dam, extending beyond the current embankment toe. Additional borings and test pits at the valley bottom and investigations for a buttress borrow, drain material source, and slope protection makeup would be required prior to construction. Construction of the buttress would include removal of the downstream slope protection. A chimney and blanket drain would be part of the construction and will assist in lowering the phreatic surface within the dam embankment. Slope protection would be added at construction completion.

3.3 Alternative 2 – Downstream Stabilization Buttress within Dam Footprint

Alternative 2 consists of removing and stockpiling a portion of the downstream slope embankment as shown on Figure 4. The material would then be replaced in a controlled manner to ensure a stronger, more stable embankment that will not be susceptible to liquefaction. This alternative will not affect the overall dam footprint. The reservoir must be emptied to perform this alternative safely. Work includes removing the existing slope protection from the downstream slope of the dam, partial dam embankment removal, construction of a chimney drain, reconstruction of the embankment with the stockpiled and replacing the slope protection material. Drain material will likely have to be imported unless a suitable source can be identified nearby. Additional slope protection material for the downstream slope is anticipated to be required and a borrow location will need to be identified and the material analyzed.

3.4 Alternative 3 – Horizontal Drains

Alternative 3 consists of installing a row of vertical gravel drains connected to a horizontal or inclined drain system at the bottom of the low density soil layer in the dam to lower the phreatic surface within the dam embankment. Lowering the phreatic surface would lessen the liquefaction potential within the embankment. A typical drain configuration is presented on Figure 5. The drains will be installed on approximately 10-foot centers (pending detailed modeling) for the length of the dam. The seepage entering the drains would be diverted to a collection system located at the toe of the dam. The collection system would discharge into Huston Creek at the same location that the proposed outlet works realignment discharges. Prior to installing the drain system, multiple crest and downstream embankment borings must be drilled and a geophysical investigation should be performed to better identify the extents of the low density embankment layer. Partial removal of the downstream slope protection system and installation of a collection system are required as part of the construction of this alternative.

3.5 Alternative 4 – Cement Deep Soil Mixing (CDSM)

Alternative 4, shown on Figure 6, consists of using CDSM to strengthen the low density embankment zone. The CDSM would be on a grid pattern downstream of the embankment centerline. Preliminary analyses indicate that the CDSM zone will need to be 40 feet wide and constructed for the full length of the embankment. The CDSM zone will effectively stiffen the low density zone, reducing liquefaction potential.


Multiple crest and downstream borings must be drilled and a geophysical investigation must be performed prior to construction to better identify the extents of the dam’s low density zone. To install the CDSM columns, installation platforms must be constructed on the downstream embankment face.

3.6 Alternative 5 – Stone Columns

Alternative 5, shown on Figure 7, consists of using stone columns to strengthen the low density embankment zone. The stone columns would be constructed in rows downstream of the embankment centerline. Preliminary analyses indicate that three rows of stone columns are required and will be spaced 30-feet apart beginning 10 downstream of centerline. The stone columns would be installed for the full length of the embankment. The stone columns will effectively stiffen the low density zone, reducing liquefaction potential in addition to providing a conduit to relieve excess pore pressures that would develop in the event of liquefaction. Similar to Alternative 4, multiple crest and downstream borings must be drilled and a geophysical investigation must be performed prior to construction to better identify the extents of the dam’s low density zone. To install the stone columns, installation platforms must be constructed on the downstream embankment face.

3.7 Alternative 6 and 7 –Cutoff Wall

As shown on Figure 8, Alternatives 6 and 7 consist of excavating a 2.5-foot wide trench into bedrock along the alignment of the dam and backfilling it with plastic concrete (Alternative 7) or a soil bentonite slurry (Alternative 8). The cut off wall would be keyed 10 feet into the underlying bedrock. The purpose of the cutoff wall is to lower the phreatic surface within the dam embankment, thus increasing the strength of the low density soil zone. Multiple crest borings must be drilled prior to construction to adequately map the soils that will be encountered and the depth to bedrock along the dam alignment.

3.8 Alternative 8 – Upstream Stability Buttress

Alternative 8, shown on Figure 9, consists of building a stability buttress on the upstream dam slope. The upstream buttress would lower the phreatic surface within the dam by increasing the seepage path. Lowering the phreatic surface would lessen the liquefaction potential within the embankment increasing overall stability. Additionally, the buttress would stabilize the upstream slope. Complete reservoir dewatering is necessary to perform the work required for this alternative. After reservoir dewatering and prior to the buttress construction, valley bottom borings must be drilled and test pits must be dug to assess the buttress foundation conditions. Buttress material borrow and slope protection makeup investigations must be performed prior to construction, as well.


3.9 Alternative 9 – Upstream Concrete Face With Membrane

Alternative 9, shown on Figure 10, consists of the construction of an upstream dam slope concrete face with a geosynthetic membrane. The concrete face provides a firm semi-permeable face to the dam, with the geosynthetic membrane further decreasing the permeability by sealing any cracks that may develop as a result of embankment settling. This will increase the seepage paths and lower the phreatic surface thus increasing the strength of the low density soil zone. This alternative requires complete dewatering of the reservoir in order to be able to perform the work. Construction work for this alternative consists of removal of the upstream slope protection system, excavation of a 5-foot wide key at the toe of the upstream dam slope, construction of the concrete face, and installation of the geosynthetic membrane. Test pits must be dug at the key alignment to properly assess the soil strength prior to construction of the concrete face.

3.10 Alternative 10 – Upstream Asphalt Face

Alternative 10, shown on Figure 11, consists of the construction of an asphalt face on the upstream dam slope. The asphalt face provides a firm semi-permeable face to the dam. The asphalt is flexible enough to move with embankment settling, decreasing the possibility of crack formation and propagation. This alternative requires complete dewatering of the reservoir to construct. Removal of the existing upstream dam slope protection system and excavation of a 5-foot wide key at the toe of the slope is required prior to installation of the asphalt face on the dam slope. Test pits must be dug at the key alignment to properly assess the soil and bedrock strength prior to construction of the concrete key, as well.

3.11 Alternative 11 – New Embankment Dam

Alternative 11 consists of dewatering the reservoir, removing the embankment material from the existing dam, and constructing a new dam from the existing dam embankment material at an alternate location upstream of the existing dam location (see Figure 12). The new dam would utilize modern design methods and construction techniques. Foundation boring drilling and test pit excavation, geologic mapping, and soil in-situ testing will be required after dewatering of the reservoir and prior to construction of the new dam. Construction of the new dam will consist of foundation preparation, which includes removal of existing dam embankment from within the new dam footprint, soil grouting, and construction of a cutoff wall. The new dam will be constructed from material taken from the existing dam.


4.0 DESIGN CRITERIA

4.1 Site Constraints

Site constraints at Lake Gregory Dam include private property immediate downstream of the dam embankment. Once constructed, the remediation alternatives are not anticipated to impact the private property; however access easements are likely to be required during design and construction. An additional site constraint is the utility corridor located within the southbound lanes of Lake Drive within the crest of the dam. Alternatives 1, 4, and 5 will require the corridor to be relocated.

4.2 DSOD

DSOD has approved the results and recommendations from Tetra Tech’s 2012 Stability Investigation Report. This report presents the alternatives developed to address deficiencies in the dam.

4.3 Use of Water

There is no long term source of water into the reservoir. The initial filling of the reservoir occurred almost immediately after construction from local heavy precipitation events. Local precipitation has historically been the only method of reservoir recharge. Post construction reservoir filling can be accomplished via pumping raw water obtained from agricultural sources in the valley below or from Crestline Sanitation District as treated water. 5.0 ALTERNATIVES SELECTION PROCESS

5.1 Alternative Selection

An Alternatives Selection discussion was held on May 10, 2012. The elements and the alternatives were discussed and the reasons behind determining the selected alternative are discussed below.

5.1.1 Alternatives Not Selected

Alternatives 2, 3, 6, 7, 8, 9 and 11 were not selected for further consideration. Alternatives 2, 3, 6 and 7 were ruled out due to complex construction requirements or lower factors of safety when compared to the selected alternatives. The primary factor that contributed to ruling out alternatives 8, 9 and 11 is that the opinions of probable cost for these alternatives were greater than that for Alternative 1, 4, 5 and 10, as discussed in Section 7 of this report.

5.1.2 Selected Alternatives

All of the selected stabilization alternatives will require a complete and detailed site survey prior to engineering design. In addition, as part of all of the stabilization alternatives, removal of the trees on the embankment should be conducted and during construction traffic control will be required.


Alternatives 1, 4, and 5 will require the temporary relocation of Lake Dr. onto the upstream embankment. The road relocation will utilize the existing beach near the waterline and will be approximately 22-24 feet wide, requiring excavation into the upstream face above the high waterline with temporary vertical face stabilization. Alternative 1, downstream stability buttress, was judged to be preferred. This alternative includes the following elements:

• Element 1 – Geotechnical investigation, dam instrumentation installation, site survey • Element 2 – Removal of trees on downstream face and within the footprint of the

proposed buttress • Element 3 – Relocation of the utilities located within the crest of the dam • Element 4 – Temporary relocation of Lake Drive • Element 5 – Complete removal of the downstream rip rap and common fill • Element 6 – Preparation of the downstream embankment face and buttress foundation

including removal of excessively saturated and/or organic material • Element 7 – Construction of blanket and chimney drains • Element 8 – Construction of downstream buttress • Element 9 – Site Reclamation

This alternative satisfactorily addresses all of the county’s objectives and the estimated risk reduction required by DSOD. Alternative 4, strengthening with cement deep soil mixing (CDSM) of the downstream embankment, was judged to be acceptable, but at a higher cost than Alternative 1. This alternative includes the following elements:

• Element 1 – Removal of trees on downstream face • Element 2 – Relocation of the utilities located within the crest of the dam • Element 3 – Temporary relocation of Lake Drive • Element 4 – Removal of rockfill and common fill down to elevation 4495 • Element 5 – Installation of a CDSM construction platform (includes MSE wall and

temporary fill placement) • Element 6 – Installation of CDSM

Alternative 5, strengthening with stone columns of the downstream embankment, was judged to be acceptable, but at a higher cost than Alternative 1. This alternative includes the following elements:

• Element 1 – Removal of trees on downstream face • Element 2 - Relocation of the utilities located within the crest of the dam • Element 3 - Temporary relocation of Lake Dr. • Element 4 - Removal of rockfill and common fill down to elevation 4495 • Element 5 – Installation of a stone column construction platform (includes MSE wall

and temporary fill placement) • Element 6 – Installation of stone columns


Alternative 10, an upstream asphalt faced membrane, was judged to be acceptable, but at a higher cost than Alternative 1. This alternative includes the following elements:

• Element 1 – Removal of trees on downstream face • Element 2 – Complete removal of upstream riprap. • Element 3 – An open graded hydraulic asphalt to act as a leveling asphalt course and

also as a drainage layer. • Element 4 – Cleaning and preparation of the plinth excavation and placement of

plinth concrete to accept the new hydraulic asphalt. • Element 5 – Placement of a hydraulic asphalt layer as the primary water barrier. This

asphalt layer would have a very low air void content and consequently would have a very low permeability. This layer would be placed in a single lift from the upstream dam toe to the upstream dam crest.

• Element 6 – Hot mastic coating would be applied over the entire new AC facing to provide temporary UV and oxidation protection.

6.0 OPINION OF PROBABLE PROJECT COSTS

Tetra Tech prepared an opinion of probable project cost and a construction schedule estimated for each alternative discussed in Section 5. The opinion of probable project cost includes estimates for recognized items that are required for the construction of each element and alternative, design and construction engineering, and permitting. An Unlisted Items line item was also included to account for cost items that have not yet been identified at this limited level of project definition. Also included in the cost is allowance for mobilization/demobilization, and preparatory work. A 25 percent contingency was also included in the cost to account for: additional changes in conditions as a result of additional investigations and changes /additions to the project as the project develops further. The preliminary construction schedule for each element was estimated based on Tetra Tech’s experiences on other similar projects. The opinions of probable costs presented in this Section are based on information developed for the design and our knowledge of market conditions at the time of preparation of the opinions. Construction cost has been estimated with the use of a combination of historical unit pricing and detailed unit pricing, depending on the availability of information. The logic, methods and procedures for developing costs, is believed to be typical for the construction industry. Accuracy is not guaranteed and the use of unit pricing should not be deemed as an offering or proposal with respect to the outcome of the cost of an activity or project. Unit price opinions are subject to change with proper notice. Any estimate of unit prices is not intended to predict the outcome of hard dollar results from open and competitive bidding. The estimates shown, and any resulting conclusions on project financial or economic feasibility or funding requirements, have been prepared for guidance in project evaluation and implementation from the information available at the time of the estimate. The opinions of probable cost for each alternative are is presented in Table 6-1 below. A detailed breakdown of each opinion of probable cost is located in Appendix C.


Table 6-1 Opinion of Probable Project Cost

Alternative Cost

1 Downstream Stability Buttress $4,011,000 4 Cement Deep Soil Mixing $5,765,000 5 Stone Columns $4,945,000 10 Upstream Asphalt Membrane $7,113,000

7.0 CONCLUSIONS AND RECOMMENDATIONS

7.1 Conclusions

To be added after review.

7.2 Recommendations

To be added after review.


8.0 REFERENCES

The following references have been compiled for the project. Abrahamson, N.A. and Silva, W.J. Empirical Response Spectral Attenuation Relations for Shallow Crustal Earthquakes. Seismological Research Letters, Volume 68, Number 1, January/February 1997. Babbitt, Donald H. and Verigin, Stephen W. General Approach to Seismic Stability Analysis of Earth Embankment Dams. California Division of Safety of Dams. Boore, David M. et al. Equations for Estimating Horizontal Response Spectra and Peak Acceleration from Western North American Earthquakes: A Summary of Recent Work. Seismological Research Letters, Volume 68, Number 1, January/February 1997. California Division of Safety of Dams. LAKE GREGORY DAM 1803-3 SAFETY REVIEW REPORT. February 1986. COSMOS Virtual Data Center. Consortium of Organizations for Strong-Motion Observation Systems (COSMOS), http://db.cosmos-eq.org/scripts/default.plx Das, Braja M. 1999. Principles of Foundation Engineering. California State University, Sacramento. PWS Publishing. Hynes-Griffin, M. E., and Franklin, A. (1984). Rationalizing the Seismic Coefficient Method. Department of the Army Waterways Experiment Station, Corps of Engineers. Experiment Station Misc. Paper GL-84-13, Vicksburg, Mississippi. Idriss, I. M., Boulanger, R. W. (2008). Soil Liquefaction During Earthquakes. Magorien, Scott D. FAULT HAZARD EVALUATION REPORT, LAKE GREGORY DAM, San Bernardino County, California. April 2004. Naeini, S. A. and Moayed, R. Ziaie Evaluation of Undrained Shear Strength of Loose Silty Sands Using CPT Results. International Journal of Civil Engineering, Vol. 5, No. 2, June 2007. Ollier, C.D., 1975, Weathering, Addison-Wesley-Longman, Reading, MA. Pioneer Consultants. STABILITY EVALUATION – PHASE 1 – Lake Gregory Dam. December 1986. Sadigh, K., et al. Attenuation Relationships for Shallow Crustal Earthquakes Based on California Strong Motion Data. Seismological Research Letter, Volume 68, Number 1, January/February 1997.


Schnabel, B. and Seed, H. Bolton. Accelerations in Rock for Earthquakes in the Western United States. Bulletin of the Seismological Society of America. Vol. 63, No. 2, pp. 501-516. April 1973. Seed, H. Bolton; Idriss, M.; and Arango, Ignacio. Evaluation of Liquefaction Potential using Field Performance Data. ASCE Convention and Exposition. October 1981. Seed, H. Bolton; Idriss, M.; and Arango, Ignacio.Evaluation of Liquefaction Potential using Field Performance Data. ASCE Convention and Exposition. October 1981. Tetra Tech, “Stability Investigation Report, Lake Gregory Dam”, February 2012 USGS Earthquakes Hazard Program, United States Geological Survey, viewed 29 September 2006. <http://earthquake.usgs.gov/>. Woodward-Clyde Consultants. INTERIM REPORT PHASE II / TASK 1, GEOLOGICAL INVESTIGATION, LAKE GREGORY DAM, SAN BERNARDINO COUNTY, CALIFORNIA. May 1994. Woodward-Clyde Consultants. PHASE 1 INVESTIGATION – LAKE GREGORY REGIONAL PARK DAM STUDY, SAN BERNARDINO COUNTY, CALIFORNIA. June 1991. Youd, T. L. Liquefaction Resistance of Soils: Summary Report from the 1996 NCEER and 1998 NCEER/NSF Workshops on Evaluation of Liquefaction Resistance of Soils. Journal of Geotechnical and Geoenvironmental Engineering. October 2001.

APPENDIX A

FIGURES

C-1

TH-03

TH-01

BH-03

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SECTION INFORMATION IS FROM THE 1941 AS-BUILT DRAWINGS

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100E200E 100W

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APPROX.PIEZOMETRICLINE

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C-3

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4480

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4500

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APPENDIX B

STABILITY ANALYSES

Embankment Material

Name: Embankment Material Model: Saturated / Unsaturated K-Function: Embankment Material, Ksat = 3.28e-06 ft/s Ky'/Kx' Ratio: 1 Rotation: 0 °Name: Rock Fill Model: Saturated / Unsaturated K-Function: Rock Fill, Ksat = 0.0328 ft/s Ky'/Kx' Ratio: 0.25 Rotation: 0 °Name: Granite Model: Saturated / Unsaturated K-Function: Granite, Ksat = 3.28e-09 ft/s Ky'/Kx' Ratio: 0 Rotation: 0 °Name: Embankment Material Low Blow Count Model: Saturated / Unsaturated K-Function: Embankment Material-Low Blow Count, Ksat = 1.0e-06 ft/s (2) Ky'/Kx' Ratio: 1 Rotation: 0 °Name: Embankment Material_No Liquefaction Model: Saturated / Unsaturated K-Function: Embankment Material, Ksat = 3.28e-06 ft/s Ky'/Kx' Ratio: 1 Rotation: 0 °Name: Downstream Buttress Model: Saturated / Unsaturated K-Function: Embankment Material, Ksat = 3.28e-06 ft/s Ky'/Kx' Ratio: 1 Rotation: 0 °

Lake Gregory

P:\01297\133-01297-12006\SupportDocs\Calcs\Geostudio\Remediation Alternatives\Lake Gregory Downstream Buttress Test.gsz

SEEP/W

Embankment Material

Downstream Buttress

Granite

Embankment Material (Low Blow Count)

Distance (ft)0 20 40 60 80 100 120 140 160 180 200 220 240 260 280 300 320 340 360 380 400 420 440 460

Elev

atio

n (ft

)

4430

4450

4470

4490

4510

4530

4550

1.7

Embankment Material

Name: Embankment Material Model: Mohr-Coulomb Unit Weight: 135 pcf Cohesion': 0 psf Phi': 36 ° Phi-B: 0 °Name: Rock Fill Model: Mohr-Coulomb Unit Weight: 135 pcf Cohesion': 0 psf Phi': 42 ° Phi-B: 0 °Name: Granite Model: Mohr-Coulomb Unit Weight: 135 pcf Cohesion': 5,000 psf Phi': 40 ° Phi-B: 0 °Name: Embankment Material Low Blow Count Model: Mohr-Coulomb Unit Weight: 135 pcf Cohesion': 0 psf Phi': 32 ° Phi-B: 0 ° Steady State Strength (Css): 560 psf Collapse Surface Angle: 22 °Name: Embankment Material_No Liquefaction Model: Mohr-Coulomb Unit Weight: 135 pcf Cohesion': 0 psf Phi': 36 ° Phi-B: 0 °Name: Downstream Buttress Model: Mohr-Coulomb Unit Weight: 135 pcf Cohesion': 0 psf Phi': 36 ° Phi-B: 0 °

Lake Gregory


Stability Initial Upstream

Horz Seismic Load:

Embankment Material

Downstream Buttress

Granite


Distance (ft)0 20 40 60 80 100 120 140 160 180 200 220 240 260 280 300 320 340 360 380 400 420 440 460

Ele

vatio

n (ft

)

4430

4450

4470

4490

4510

4530

4550

2.0

Embankment Material


Lake Gregory


Stability Initial Upstream-Deep Failure

Horz Seismic Load:

Embankment Material

Downstream Buttress

Granite


Distance (ft)0 20 40 60 80 100 120 140 160 180 200 220 240 260 280 300 320 340 360 380 400 420 440 460

Elev

atio

n (ft

)

4430

4450

4470

4490

4510

4530

4550

1.9

Embankment Material


Lake Gregory


Stability Initial Downstream

Horz Seismic Load:

Embankment Material

Downstream Buttress

Granite


Distance (ft)0 20 40 60 80 100 120 140 160 180 200 220 240 260 280 300 320 340 360 380 400 420 440 460

Elev

atio

n (ft

)

4430

4450

4470

4490

4510

4530

4550

0.6

Embankment Material


Lake Gregory


Pseudostatic Upstream (0.325g)

Horz Seismic Load: 0.325

Embankment Material

Downstream Buttress

Granite


Distance (ft)0 20 40 60 80 100 120 140 160 180 200 220 240 260 280 300 320 340 360 380 400 420 440 460

Ele

vatio

n (ft

)

4430

4450

4470

4490

4510

4530

4550

1.0

Embankment Material


Lake Gregory


Pseudostatic Downstream (0.325g)


Embankment Material

Downstream Buttress

Granite


Distance (ft)0 20 40 60 80 100 120 140 160 180 200 220 240 260 280 300 320 340 360 380 400 420 440 460

Elev

atio

n (ft

)

4430

4450

4470

4490

4510

4530

4550

Embankment Material

Name: Rock Fill Effective Young's Modulus (E'): 30,000 psf Cohesion': 0 psf Phi': 42 ° Poisson's Ratio: 0.3 Unit Weight: 135 pcfName: Granite Effective Young's Modulus (E'): 15,000,000 psf Cohesion': 5,000 psf Phi': 40 ° Poisson's Ratio: 0.22 Unit Weight: 135 pcfName: Embankment Material Liquefaction Effective Young's Modulus (E'): 14,000 psf Cohesion': 0 psf Phi': 36 ° Poisson's Ratio: 0.334 Unit Weight: 135 pcfName: Embankment Material Low Blow liquefaction Effective Young's Modulus (E'): 8,000 psf Cohesion': 0 psf Phi': 32 ° Poisson's Ratio: 0.3 Unit Weight: 125 pcf Steady State Strength (Css): 560 psf Collapse Surface Angle: 0 °Name: Embankment Material_No Liquefaction Effective Young's Modulus (E'): 14,000 psf Cohesion': 0 psf Phi': 36 ° Poisson's Ratio: 0.3 Unit Weight: 135 pcfName: Downstream Buttress Effective Young's Modulus (E'): 14,000 psf Cohesion': 0 psf Phi': 36 ° Poisson's Ratio: 0.3 Unit Weight: 135 pcf

Lake Gregory


Stress Redistribution

Maximum Deformation ~ 10-feet

Embankment Material

Downstream Buttress

Granite


Distance (ft)0 20 40 60 80 100 120 140 160 180 200 220 240 260 280 300 320 340 360 380 400 420 440 460

Elev

atio

n (ft

)

4430

4450

4470

4490

4510

4530

4550

1.7

Embankment Material

Name: Rock Fill Model: Mohr-Coulomb Unit Weight: 135 pcf Cohesion': 0 psf Phi': 42 ° Phi-B: 0 °Name: Granite Model: Mohr-Coulomb Unit Weight: 135 pcf Cohesion': 5,000 psf Phi': 40 ° Phi-B: 0 °Name: Embankment Material Liquefaction Model: Mohr-Coulomb Unit Weight: 135 pcf Cohesion': 0 psf Phi': 36 ° Phi-B: 0 °Name: Embankment Material Low Blow liquefaction Model: Mohr-Coulomb Unit Weight: 125 pcf Cohesion': 0 psf Phi': 32 ° Phi-B: 0 ° Steady State Strength (Css): 560 psf Collapse Surface Angle: 0 °Name: Embankment Material_No Liquefaction Model: Mohr-Coulomb Unit Weight: 135 pcf Cohesion': 0 psf Phi': 36 ° Phi-B: 0 °Name: Downstream Buttress Model: Mohr-Coulomb Unit Weight: 135 pcf Cohesion': 0 psf Phi': 36 ° Phi-B: 0 °

Lake Gregory


Stability Upstream Post Earthquake

Embankment Material

Downstream Buttress

Granite


Distance (ft)0 20 40 60 80 100 120 140 160 180 200 220 240 260 280 300 320 340 360 380 400 420 440 460

Elev

atio

n (ft

)

4430

4450

4470

4490

4510

4530

4550

1.7

Embankment Material

Name: Rock Fill Model: Mohr-Coulomb Unit Weight: 135 pcf Cohesion': 0 psf Phi': 42 ° Phi-B: 0 °Name: Granite Model: Mohr-Coulomb Unit Weight: 135 pcf Cohesion': 5,000 psf Phi': 40 ° Phi-B: 0 °Name: Embankment Material Liquefaction Model: Mohr-Coulomb Unit Weight: 135 pcf Cohesion': 0 psf Phi': 36 ° Phi-B: 0 °Name: Embankment Material Low Blow liquefaction Model: Mohr-Coulomb Unit Weight: 125 pcf Cohesion': 0 psf Phi': 32 ° Phi-B: 0 ° Steady State Strength (Css): 560 psf Collapse Surface Angle: 0 °Name: Embankment Material_No Liquefaction Model: Mohr-Coulomb Unit Weight: 135 pcf Cohesion': 0 psf Phi': 36 ° Phi-B: 0 °Name: Downstream Buttress Model: Mohr-Coulomb Unit Weight: 135 pcf Cohesion': 0 psf Phi': 36 ° Phi-B: 0 °

Lake Gregory


Stability Downstream Post Earthquake

Embankment Material

Downstream Buttress

Granite


Distance (ft)0 20 40 60 80 100 120 140 160 180 200 220 240 260 280 300 320 340 360 380 400 420 440 460

Ele

vatio

n (ft

)

4430

4450

4470

4490

4510

4530

4550

Embankment Material

Name: Embankment Material Model: Saturated / Unsaturated K-Function: Embankment Material, Ksat = 3.28e-06 ft/s Ky'/Kx' Ratio: 1 Rotation: 0 °Name: Roadway Fill Model: Saturated / Unsaturated K-Function: Roadway Fill, Ksat = 3.28e-6 ft/s Ky'/Kx' Ratio: 1 Rotation: 0 °Name: Rock Fill Model: Saturated / Unsaturated K-Function: Rock Fill, Ksat = 0.0328 ft/s Ky'/Kx' Ratio: 0.25 Rotation: 0 °Name: Granite Model: Saturated / Unsaturated K-Function: Granite, Ksat = 3.28e-09 ft/s Ky'/Kx' Ratio: 0 Rotation: 0 °Name: Embankment Material Low Blow Count Model: Saturated / Unsaturated K-Function: Embankment Material-Low Blow Count, Ksat = 1.0e-06 ft/s (2) Ky'/Kx' Ratio: 1 Rotation: 0 °Name: Embankment Material_No Liquefaction Model: Saturated / Unsaturated K-Function: Embankment Material, Ksat = 3.28e-06 ft/s Ky'/Kx' Ratio: 1 Rotation: 0 °Name: CDSM Zone Model: Saturated / Unsaturated K-Function: Embankment Material, Ksat = 3.28e-06 ft/s Ky'/Kx' Ratio: 1 Rotation: 0 °

Lake Gregory

P:\01297\133-01297-12006\SupportDocs\Calcs\Geostudio\Remediation Alternatives\Lake Gregory CDSM.gsz

Roadway Fill

SEEP/W

Embankment Material

Rock Fill

Granite


CDSM Zone

Distance (ft)0 20 40 60 80 100 120 140 160 180 200 220 240 260 280 300 320 340 360 380 400 420 440 460

Ele

vatio

n (ft

)

4430

4450

4470

4490

4510

4530

4550

1.6

Embankment Material

Name: Embankment Material Model: Mohr-Coulomb Unit Weight: 135 pcf Cohesion': 0 psf Phi': 36 ° Phi-B: 0 °Name: Roadway Fill Model: Mohr-Coulomb Unit Weight: 135 pcf Cohesion': 1,244 psf Phi': 36 ° Phi-B: 0 °Name: Rock Fill Model: Mohr-Coulomb Unit Weight: 135 pcf Cohesion': 0 psf Phi': 42 ° Phi-B: 0 °Name: Granite Model: Mohr-Coulomb Unit Weight: 135 pcf Cohesion': 5,000 psf Phi': 40 ° Phi-B: 0 °Name: Embankment Material Low Blow Count Model: Mohr-Coulomb Unit Weight: 135 pcf Cohesion': 0 psf Phi': 32 ° Phi-B: 0 ° Steady State Strength (Css): 560 psf Collapse Surface Angle: 22 °Name: Embankment Material_No Liquefaction Model: Mohr-Coulomb Unit Weight: 135 pcf Cohesion': 0 psf Phi': 36 ° Phi-B: 0 °Name: CDSM Zone Model: Mohr-Coulomb Unit Weight: 135 pcf Cohesion': 42,000 psf Phi': 36 ° Phi-B: 0 °

Lake Gregory


Roadway Fill

Horz Seismic Load:


Embankment Material

Rock Fill

Granite


CDSM Zone

Distance (ft)0 20 40 60 80 100 120 140 160 180 200 220 240 260 280 300 320 340 360 380 400 420 440 460

Ele

vatio

n (ft

)

4430

4450

4470

4490

4510

4530

4550

2.0

Embankment Material


Lake Gregory


Roadway Fill

Horz Seismic Load:


Embankment Material

Rock Fill

Granite


CDSM Zone

Distance (ft)0 20 40 60 80 100 120 140 160 180 200 220 240 260 280 300 320 340 360 380 400 420 440 460

Ele

vatio

n (ft

)

4430

4450

4470

4490

4510

4530

4550

0.6

Embankment Material


Lake Gregory


Roadway Fill



Embankment Material

Rock Fill

Granite


CDSM Zone

Distance (ft)0 20 40 60 80 100 120 140 160 180 200 220 240 260 280 300 320 340 360 380 400 420 440 460

Ele

vatio

n (ft

)

4430

4450

4470

4490

4510

4530

4550

1.1

Embankment Material


Lake Gregory


Roadway Fill



Embankment Material

Rock Fill

Granite


CDSM Zone

Distance (ft)0 20 40 60 80 100 120 140 160 180 200 220 240 260 280 300 320 340 360 380 400 420 440 460

Ele

vatio

n (ft

)

4430

4450

4470

4490

4510

4530

4550

Embankment Material

Name: Roadway Fill Effective Young's Modulus (E'): 21,000 psf Cohesion': 1,244 psf Phi': 36 ° Poisson's Ratio: 0.334 Unit Weight: 135 pcfName: Rock Fill Effective Young's Modulus (E'): 30,000 psf Cohesion': 0 psf Phi': 42 ° Poisson's Ratio: 0.3 Unit Weight: 135 pcfName: Granite Effective Young's Modulus (E'): 15,000,000 psf Cohesion': 5,000 psf Phi': 40 ° Poisson's Ratio: 0.22 Unit Weight: 135 pcfName: Embankment Material Liquefaction Effective Young's Modulus (E'): 14,000 psf Cohesion': 0 psf Phi': 36 ° Poisson's Ratio: 0.334 Unit Weight: 135 pcfName: Embankment Material Low Blow liquefaction Effective Young's Modulus (E'): 8,000 psf Cohesion': 0 psf Phi': 32 ° Poisson's Ratio: 0.3 Unit Weight: 125 pcf Steady State Strength (Css): 560 psf Collapse Surface Angle: 0 °Name: Embankment Material_No Liquefaction Effective Young's Modulus (E'): 14,000 psf Cohesion': 0 psf Phi': 36 ° Poisson's Ratio: 0.3 Unit Weight: 135 pcfName: CDSM Zone Effective Young's Modulus (E'): 14,000 psf Cohesion': 42,000 psf Phi': 36 ° Poisson's Ratio: 0.3 Unit Weight: 135 pcf

Lake Gregory


Roadway Fill


Embankment Material

Rock Fill

Granite

Maximun Deformation ~ 6 feet


CDSM Zone

Distance (ft)0 20 40 60 80 100 120 140 160 180 200 220 240 260 280 300 320 340 360 380 400 420 440 460

Elev

atio

n (ft

)

4430

4450

4470

4490

4510

4530

4550

1.9

Embankment Material

Name: Roadway Fill Model: Mohr-Coulomb Unit Weight: 135 pcf Cohesion': 1,244 psf Phi': 36 ° Phi-B: 0 °Name: Rock Fill Model: Mohr-Coulomb Unit Weight: 135 pcf Cohesion': 0 psf Phi': 42 ° Phi-B: 0 °Name: Granite Model: Mohr-Coulomb Unit Weight: 135 pcf Cohesion': 5,000 psf Phi': 40 ° Phi-B: 0 °Name: Embankment Material Liquefaction Model: Mohr-Coulomb Unit Weight: 135 pcf Cohesion': 0 psf Phi': 36 ° Phi-B: 0 °Name: Embankment Material Low Blow liquefaction Model: Mohr-Coulomb Unit Weight: 125 pcf Cohesion': 0 psf Phi': 32 ° Phi-B: 0 ° Steady State Strength (Css): 560 psf Collapse Surface Angle: 0 °Name: Embankment Material_No Liquefaction Model: Mohr-Coulomb Unit Weight: 135 pcf Cohesion': 0 psf Phi': 36 ° Phi-B: 0 °Name: CDSM Zone Model: Mohr-Coulomb Unit Weight: 135 pcf Cohesion': 42,000 psf Phi': 36 ° Phi-B: 0 °

Lake Gregory


Roadway Fill


Embankment Material

Rock Fill

Granite


CDSM Zone

Distance (ft)0 20 40 60 80 100 120 140 160 180 200 220 240 260 280 300 320 340 360 380 400 420 440 460

Ele

vatio

n (ft

)

4430

4450

4470

4490

4510

4530

4550

1.6

Embankment Material

Name: Roadway Fill Model: Mohr-Coulomb Unit Weight: 135 pcf Cohesion': 1,244 psf Phi': 36 ° Phi-B: 0 °Name: Rock Fill Model: Mohr-Coulomb Unit Weight: 135 pcf Cohesion': 0 psf Phi': 42 ° Phi-B: 0 °Name: Granite Model: Mohr-Coulomb Unit Weight: 135 pcf Cohesion': 5,000 psf Phi': 40 ° Phi-B: 0 °Name: Embankment Material Liquefaction Model: Mohr-Coulomb Unit Weight: 135 pcf Cohesion': 0 psf Phi': 36 ° Phi-B: 0 °Name: Embankment Material Low Blow liquefaction Model: Mohr-Coulomb Unit Weight: 125 pcf Cohesion': 0 psf Phi': 32 ° Phi-B: 0 ° Steady State Strength (Css): 560 psf Collapse Surface Angle: 0 °Name: Embankment Material_No Liquefaction Model: Mohr-Coulomb Unit Weight: 135 pcf Cohesion': 0 psf Phi': 36 ° Phi-B: 0 °Name: CDSM Zone Model: Mohr-Coulomb Unit Weight: 135 pcf Cohesion': 42,000 psf Phi': 36 ° Phi-B: 0 °

Lake Gregory


Roadway Fill


Embankment Material

Rock Fill

Granite


CDSM Zone

Distance (ft)0 20 40 60 80 100 120 140 160 180 200 220 240 260 280 300 320 340 360 380 400 420 440 460

Ele

vatio

n (ft

)

4430

4450

4470

4490

4510

4530

4550

Embankment Material

Name: Embankment Material Model: Saturated / Unsaturated K-Function: Embankment Material, Ksat = 3.28e-06 ft/s Ky'/Kx' Ratio: 1 Rotation: 0 °Name: Roadway Fill Model: Saturated / Unsaturated K-Function: Roadway Fill, Ksat = 3.28e-6 ft/s Ky'/Kx' Ratio: 1 Rotation: 0 °Name: Rock Fill Model: Saturated / Unsaturated K-Function: Rock Fill, Ksat = 0.0328 ft/s Ky'/Kx' Ratio: 0.25 Rotation: 0 °Name: Granite Model: Saturated / Unsaturated K-Function: Granite, Ksat = 3.28e-09 ft/s Ky'/Kx' Ratio: 0 Rotation: 0 °Name: Embankment Material Low Blow Count Model: Saturated / Unsaturated K-Function: Embankment Material-Low Blow Count, Ksat = 1.0e-06 ft/s (2) Ky'/Kx' Ratio: 1 Rotation: 0 °Name: Embankment Material_No Liquefaction Model: Saturated / Unsaturated K-Function: Embankment Material, Ksat = 3.28e-06 ft/s Ky'/Kx' Ratio: 1 Rotation: 0 °Name: Upstrteam Cap Model: Saturated / Unsaturated K-Function: Upstream Cap, Ksat = 3.28e-08 ft/s Ky'/Kx' Ratio: 1 Rotation: 0 °

Lake Gregory

P:\01297\133-01297-12006\SupportDocs\Calcs\Geostudio\Remediation Alternatives\Lake Gregory Upstream Cap.gsz

Roadway Fill

Upstream Cap

Embankment Material

Rock Fill

Granite

SEEP/W


Distance (ft)0 20 40 60 80 100 120 140 160 180 200 220 240 260 280 300 320 340 360 380 400 420 440 460

Ele

vatio

n (ft

)

4430

4450

4470

4490

4510

4530

4550

3.3

Embankment Material

Name: Embankment Material Model: Mohr-Coulomb Unit Weight: 135 pcf Cohesion': 0 psf Phi': 36 ° Phi-B: 0 °Name: Roadway Fill Model: Mohr-Coulomb Unit Weight: 135 pcf Cohesion': 1,244 psf Phi': 36 ° Phi-B: 0 °Name: Rock Fill Model: Mohr-Coulomb Unit Weight: 135 pcf Cohesion': 0 psf Phi': 42 ° Phi-B: 0 °Name: Granite Model: Mohr-Coulomb Unit Weight: 135 pcf Cohesion': 5,000 psf Phi': 40 ° Phi-B: 0 °Name: Embankment Material Low Blow Count Model: Mohr-Coulomb Unit Weight: 135 pcf Cohesion': 0 psf Phi': 32 ° Phi-B: 0 ° Steady State Strength (Css): 560 psf Collapse Surface Angle: 22 °Name: Embankment Material_No Liquefaction Model: Mohr-Coulomb Unit Weight: 135 pcf Cohesion': 0 psf Phi': 36 ° Phi-B: 0 °Name: Upstrteam Cap Model: Mohr-Coulomb Unit Weight: 135 pcf Cohesion': 1,000 psf Phi': 45 ° Phi-B: 0 °

Lake Gregory


Roadway Fill

Horz Seismic Load:

Upstream Cap

Embankment Material

Rock Fill

Granite



Distance (ft)0 20 40 60 80 100 120 140 160 180 200 220 240 260 280 300 320 340 360 380 400 420 440 460

Ele

vatio

n (ft

)

4430

4450

4470

4490

4510

4530

4550

3.8

Embankment Material


Lake Gregory


Roadway Fill

Horz Seismic Load:

Upstream Cap

Embankment Material

Rock Fill

Granite



Distance (ft)0 20 40 60 80 100 120 140 160 180 200 220 240 260 280 300 320 340 360 380 400 420 440 460

Ele

vatio

n (ft

)

4430

4450

4470

4490

4510

4530

4550

1.5

Embankment Material


Lake Gregory


Roadway Fill

Horz Seismic Load:

Upstream Cap

Embankment Material

Rock Fill

Granite



Distance (ft)0 20 40 60 80 100 120 140 160 180 200 220 240 260 280 300 320 340 360 380 400 420 440 460

Ele

vatio

n (ft

)

4430

4450

4470

4490

4510

4530

4550

1.4

Embankment Material


Lake Gregory


Roadway Fill


Upstream Cap

Embankment Material

Rock Fill

Granite



Distance (ft)0 20 40 60 80 100 120 140 160 180 200 220 240 260 280 300 320 340 360 380 400 420 440 460

Ele

vatio

n (ft

)

4430

4450

4470

4490

4510

4530

4550

0.9

Embankment Material


Lake Gregory


Roadway Fill


Upstream Cap

Embankment Material

Rock Fill

Granite



Distance (ft)0 20 40 60 80 100 120 140 160 180 200 220 240 260 280 300 320 340 360 380 400 420 440 460

Ele

vatio

n (ft

)

4430

4450

4470

4490

4510

4530

4550

Embankment Material

Name: Roadway Fill Effective Young's Modulus (E'): 21,000 psf Cohesion': 1,244 psf Phi': 36 ° Poisson's Ratio: 0.334 Unit Weight: 135 pcfName: Rock Fill Effective Young's Modulus (E'): 30,000 psf Cohesion': 0 psf Phi': 42 ° Poisson's Ratio: 0.3 Unit Weight: 135 pcfName: Granite Effective Young's Modulus (E'): 15,000,000 psf Cohesion': 5,000 psf Phi': 40 ° Poisson's Ratio: 0.22 Unit Weight: 135 pcfName: Embankment Material Liquefaction Effective Young's Modulus (E'): 14,000 psf Cohesion': 0 psf Phi': 36 ° Poisson's Ratio: 0.334 Unit Weight: 135 pcfName: Embankment Material Low Blow liquefaction Effective Young's Modulus (E'): 8,000 psf Cohesion': 0 psf Phi': 32 ° Poisson's Ratio: 0.3 Unit Weight: 125 pcf Steady State Strength (Css): 560 psf Collapse Surface Angle: 0 °Name: Embankment Material_No Liquefaction Effective Young's Modulus (E'): 14,000 psf Cohesion': 0 psf Phi': 36 ° Poisson's Ratio: 0.3 Unit Weight: 135 pcfName: Upstrteam Cap Effective Young's Modulus (E'): 30,000 psf Cohesion': 1,000 psf Phi': 45 ° Poisson's Ratio: 0.3 Unit Weight: 135 pcf

Lake Gregory


Roadway Fill

Upstream Cap

Embankment Material

Rock Fill

Granite



Maximum Deformation ~ 8.5 feet

Distance (ft)0 20 40 60 80 100 120 140 160 180 200 220 240 260 280 300 320 340 360 380 400 420 440 460

Ele

vatio

n (ft

)

4430

4450

4470

4490

4510

4530

4550

2.4

Embankment Material

Name: Roadway Fill Model: Mohr-Coulomb Unit Weight: 135 pcf Cohesion': 1,244 psf Phi': 36 ° Phi-B: 0 °Name: Rock Fill Model: Mohr-Coulomb Unit Weight: 135 pcf Cohesion': 0 psf Phi': 42 ° Phi-B: 0 °Name: Granite Model: Mohr-Coulomb Unit Weight: 135 pcf Cohesion': 5,000 psf Phi': 40 ° Phi-B: 0 °Name: Embankment Material Liquefaction Model: Mohr-Coulomb Unit Weight: 135 pcf Cohesion': 0 psf Phi': 36 ° Phi-B: 0 °Name: Embankment Material Low Blow liquefaction Model: Mohr-Coulomb Unit Weight: 125 pcf Cohesion': 0 psf Phi': 32 ° Phi-B: 0 ° Steady State Strength (Css): 560 psf Collapse Surface Angle: 0 °Name: Embankment Material_No Liquefaction Model: Mohr-Coulomb Unit Weight: 135 pcf Cohesion': 0 psf Phi': 36 ° Phi-B: 0 °Name: Upstrteam Cap Model: Mohr-Coulomb Unit Weight: 135 pcf Cohesion': 1,000 psf Phi': 45 ° Phi-B: 0 °

Lake Gregory


Roadway Fill

Upstream Cap

Embankment Material

Rock Fill

Granite



Distance (ft)0 20 40 60 80 100 120 140 160 180 200 220 240 260 280 300 320 340 360 380 400 420 440 460

Ele

vatio

n (ft

)

4430

4450

4470

4490

4510

4530

4550

1.2

Embankment Material

Name: Roadway Fill Model: Mohr-Coulomb Unit Weight: 135 pcf Cohesion': 1,244 psf Phi': 36 ° Phi-B: 0 °Name: Rock Fill Model: Mohr-Coulomb Unit Weight: 135 pcf Cohesion': 0 psf Phi': 42 ° Phi-B: 0 °Name: Granite Model: Mohr-Coulomb Unit Weight: 135 pcf Cohesion': 5,000 psf Phi': 40 ° Phi-B: 0 °Name: Embankment Material Liquefaction Model: Mohr-Coulomb Unit Weight: 135 pcf Cohesion': 0 psf Phi': 36 ° Phi-B: 0 °Name: Embankment Material Low Blow liquefaction Model: Mohr-Coulomb Unit Weight: 125 pcf Cohesion': 0 psf Phi': 32 ° Phi-B: 0 ° Steady State Strength (Css): 560 psf Collapse Surface Angle: 0 °Name: Embankment Material_No Liquefaction Model: Mohr-Coulomb Unit Weight: 135 pcf Cohesion': 0 psf Phi': 36 ° Phi-B: 0 °Name: Upstrteam Cap Model: Mohr-Coulomb Unit Weight: 135 pcf Cohesion': 1,000 psf Phi': 45 ° Phi-B: 0 °

Lake Gregory


Roadway Fill

Upstream Cap

Embankment Material

Rock Fill

Granite



Distance (ft)0 20 40 60 80 100 120 140 160 180 200 220 240 260 280 300 320 340 360 380 400 420 440 460

Elev

atio

n (ft

)

4430

4450

4470

4490

4510

4530

4550

APPENDIX C

DETAILED COST ESTIMATES

P:\01297\133-01297-12006\SupportDocs\Calcs\Alternatives EOC\Appendix C

ITEM NO. ITEM DESCRIPTION QUANTITY UNIT UNIT COST

EXTENDED TOTAL COST

1 Geotechnical Investigation (Foundation, Buttress Borrow, Drain Borrow, Etc.) 1 LS $50,000 $50,000 2 Site Survey 1 LS $20,000 $20,000 3 Care and Diversion of Water 1 LS $30,000 $30,000 4 Erosion and Sediment Control 1 LS $20,000 $20,000 5 Temporary Lake Dr Relocation 1 LS $250,000 $250,000 6 Traffic Control 1 LS $50,000 $50,000 7 Security Fencing 450 LF $90 $40,500 8 Tree Removal Embankment 1 LS $25,000 $25,000 9 Tree Removal Foundaiton 1 LS $25,000 $25,000 10 Crest Utility Relocation 1 LS $300,000 $300,000 11 Rockfill Removal/Stockpile 4460 CY $20 $89,200 12 Embankment Preparation 1790 CY $10 $17,900 13 Foundation Preparation 4870 SY $15 $73,050 14 Chimney Drain 3400 CY $50 $170,000 15 Toe Drain 800 LF $55 $44,000 16 Buttress Fill 25000 CY $30 $750,000 17 Dam Instrumentation 1 LS $50,000 $50,000 18 Measuring Flume 1 EA $10,000 $10,000 19 Site Reclamation 3 AC $5,000 $15,000 20 Temporary Lake Drive Removal and Restoration 1 LS $75,000 $75,000 21 $0 22 $0 23 $0 24 $0 25 $0 26 $0 27 $0

$2,105,000 $210,500 $210,500

$2,526,000 $631,500

$3,158,000 $315,800 $379,000 $157,900

$4,011,000

Table C-1Opinion of Probable Project Cost

OPINION OF PROBABLE PROJECT COST

SUBTOTAL

Alternative 1 - Downstream Stability Buttress

SUBTOTAL

Unlisted Items-10%Mobilization, Demobilization, Preparatory Work-10%

Contingency - 25%CONSTRUCTION TOTALEngineering - 10%Construction Engineering-12%Permitting - 5%



EXTENDED TOTAL COST

1 Geotechnical Investigation (Construction Platform Foundation, Geophysics, Etc.) 1 LS $50,000 $50,000 2 Site Survey 1 LS $20,000 $20,000 3 Care and Diversion of Water 1 LS $30,000 $30,000 4 Erosion and Sediment Control 1 LS $20,000 $20,000 5 Temporary Lake Dr Relocation 1 LS $250,000 $250,000 6 Traffic Control 1 LS $50,000 $50,000 7 Security Fencing 450 LF $90 $40,500 8 Tree Removal Embankment 1 LS $25,000 $25,000 9 Rockfill Removal/Stockpile 500 CY $20 $10,000 10 Crest Utility Relocation 1 LS $300,000 $300,000 11 CDSM Construction Platform 1 LS $250,000 $250,000 12 CDSM Installation 400 LF $4,000 $1,600,000 13 Spoil Removal 7500 CY $30 $225,000 14 Slope Protection Replacement 500 CY $30 $15,000 15 Dam instrumentation 1 LS $50,000 $50,000 16 Site reclamation 3 AC $5,000 $15,000 17 Temporary Lake Drive Removal and Restoration 1 LS $75,000 $75,000 18 $0 19 $0 20 $0 21 $0 22 $0 23 $0 24 $0 25 $0 26 $0 27 $0 28 $0 29 $0

$3,026,000 $302,600 $302,600

$3,631,000 $907,800

$4,539,000 $453,900 $544,700 $227,000

$5,765,000

CONSTRUCTION TOTALEngineering - 10%Construction Engineering-12%Permitting - 5%OPINION OF PROBABLE PROJECT COST


Contingency -25%

Alternative 4 - Cement Deep Soil Mixing

SUBTOTALUnlisted Items-10%Mobilization, Demobilization, Preparatory Work-10%SUBTOTAL



EXTENDED TOTAL COST

1 Geotechnical Investigation (Construction Platform Foundation, Geophysics, Etc.) 1 LS $50,000 $50,000 2 Site Survey 1 LS $20,000 $20,000 3 Care and Diversion of Water 1 LS $30,000 $30,000 4 Erosion and Sediment Control 1 LS $20,000 $20,000 5 Temporary Lake Dr Relocation 1 LS $250,000 $250,000 6 Traffic Control 1 LS $50,000 $50,000 7 Security Fencing 450 LF $90 $40,500 8 Tree Removal Embankment 1 LS $25,000 $25,000 9 Rockfill Removal/Stockpile 500 CY $20 $10,000 10 Crest Utility Relocation 1 LS $300,000 $300,000 11 Stone Column Construction Platform 1 LS $250,000 $250,000 12 Stone Column Installation 255 EA $5,000 $1,275,000 13 Spoil Removal 4000 CY $30 $120,000 14 Slope Protection Replacement 500 CY $30 $15,000 15 Dam instrumentation 1 LS $50,000 $50,000 16 Site reclamation 3 AC $5,000 $15,000 17 Temporary Lake Drive Removal and Restoration 1 LS $75,000 $75,000 18 $0 19 $0 20 $0 21 $0 22 $0 23 $0 24 $0 25 $0 26 $0 27 $0

$2,596,000 $259,600 $259,600

$3,115,000 $778,800

$3,894,000 $389,400 $467,300 $194,700

$4,945,000 Permitting - 5%OPINION OF PROBABLE PROJECT COST

Contingency - 25%

Alternative 5 - Stone Columns



CONSTRUCTION TOTALEngineering - 10%Construction Engineering-12%



EXTENDED TOTAL COST

1 Reservoir Dewatering/Rewatering 2100 AF $550 $1,155,000 2 Site Survey 1 LS $20,000 $20,000 2 Care and Diversion of Water 1 LS $30,000 $30,000 3 Erosion and Sediment Control 1 LS $20,000 $20,000 4 Traffic Control 1 LS $50,000 $50,000 5 Security Fencing 450 LF $90 $40,500 6 Tree Removal Embankment 1 LS $25,000 $25,000 7 Rockfill Removal/Disposal 5710 CY $40 $228,400 8 Embankment Preparation 2290 CY $30 $68,700 9 Foundation Preparation 250 SY $30 $7,500 10 Keyway Excavation 420 CY $50 $21,000 11 Concrete Plinth 200 CY $700 $140,000 12 Grout Curtain 660 SY $300 $198,000 13 Base Course 1150 CY $40 $46,000 14 ACP Face 5800 TN $220 $1,276,000 15 Hot Mastic Coating 6850 SY $50 $342,500 16 Dam Instrumentaition 1 LS $50,000 $50,000 17 Site Reclamation 3 AC $5,000 $15,000 18 $0 19 $0 20 $0 21 $0 22 $0 23 $0 24 $0 25 $0

$3,734,000 $373,400 $373,400

$4,481,000 $1,120,300

$5,601,000 $560,100 $672,100 $280,100

$7,113,000

CONSTRUCTION TOTALEngineering - 10%Construction Engineering-12%Permitting - 5%OPINION OF PROBABLE PROJECT COST


Contingency - 25%

Alternative 10 - Upstream Asphalt Face


appendix 7 - san bernardino county, california

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