i-580/meadowood complex improvements

GEOTECHNICAL INVESTIGATION VOLUME I

REPORT THROUGH APPENDIX C

I-580/MEADOWOOD COMPLEX IMPROVEMENTS

RENO, NEVADA

OCTOBER 2008

Prepared for:

CH2M HILL

Prepared by:

Black Eagle Consulting, Inc.

TABLE OF CONTENTS

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1.0 INTRODUCTION................................................................................................................... 1 1.1 General ............................................................................................................................. 1 1.2 Scope of Work.................................................................................................................. 1 1.3 Other Reports and Investigations ..................................................................................... 2

2.0 PROJECT DESCRIPTION ..................................................................................................... 3 2.1 Site Conditions ................................................................................................................. 3 2.2 Existing Structures ........................................................................................................... 4 2.3 Proposed Improvements ................................................................................................... 5 2.4 Bridge Structural Design Information.............................................................................. 8

3.0 GEOLOGIC CONDITIONS AND SEISMICITY ................................................................ 12 3.1 Local Geology ................................................................................................................ 12 3.2 Seismicity and Faulting.................................................................................................. 13

4.0 FIELD INVESTIGATIONS.................................................................................................. 13 4.1 Drilling ........................................................................................................................... 13 4.2 Material Classification ................................................................................................... 14 4.3 Drive Hammer Calibration............................................................................................. 15

5.0 LABORATORY ANALYSES.............................................................................................. 15 5.1 Index Tests ..................................................................................................................... 15 5.2 In Situ Moisture-Density Tests ...................................................................................... 16 5.3 Direct Shear Tests .......................................................................................................... 16 5.4 Consolidation Tests ........................................................................................................ 16 5.5 R-Value Tests ................................................................................................................. 16 5.6 Chemical Tests ............................................................................................................... 17

6.0 DISCUSSION......................................................................................................................... 17 6.1 Anticipated Subsurface Conditions ................................................................................ 17

6.1.1 Northbound Frontage Road from Neil Road to Meadowood Mall Way............. 18 6.1.2 Southbound Frontage Road from Meadowood Mall Way to Neil Road............. 18 6.1.3 Meadowood Mall Way Interchange Bridge ........................................................ 18 6.1.4 Meadowood Mall Way from South Virginia Street West to Kietzke Lane ........ 19 6.1.5 Northbound On-Ramp from Meadowood Mall Way to I-580 ............................ 19 6.1.6 Southbound Off-Ramp from I-580 to Meadowood Mall Way............................ 19 6.1.7 I-580/South McCarran Boulevard Structure Widening....................................... 20 6.1.8 I-580/South Virginia Street Structure Widening................................................. 20 6.1.9 Ground Water ...................................................................................................... 20

6.2 Geologic Hazards ........................................................................................................... 21 6.2.1 Faulting................................................................................................................ 21 6.2.2 Liquefaction......................................................................................................... 21 6.2.3 Expansive or Compressible Clay Soils................................................................ 22

7.0 SUMMARY OF ENGINEERING ANALYSES AND CALCULATIONS ......................... 23

TABLE OF CONTENTS (continued)

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8.0 RECOMMENDATIONS ...................................................................................................... 23 8.1 Site Grading and Earthwork........................................................................................... 24

8.1.1 Stripping .............................................................................................................. 24 8.1.2 Subgrade/Foundation Preparation ....................................................................... 24 8.1.3 Temporary Cut Slopes......................................................................................... 25 8.1.4 Embankment Stability ......................................................................................... 26

8.1.4.1 Global Stability ................................................................................. 26 8.1.4.2 Erosional Stability............................................................................. 29 8.1.4.3 Settlement.......................................................................................... 29 8.1.4.4 Construction Considerations ............................................................. 30

8.1.5 Use of Materials .................................................................................................. 31 8.1.6 Drainage .............................................................................................................. 31

8.2 Foundations .................................................................................................................... 32 8.2.1 Meadowood Mall Way Bridge Foundations ....................................................... 32

8.2.1.1 Foundation Type Selection .............................................................. 32 8.2.1.2 Abutment Drilled Shaft Compressive Capacity............................... 32 8.2.1.3 Abutment Drilled Shaft Lateral Load Analysis ............................... 33 8.2.1.4 Construction Considerations ............................................................ 34

8.2.2 Meadowood Mall Way Light Towers ................................................................. 34 8.2.2.1 Foundation Type Selection .............................................................. 34 8.2.2.2 Drilled Shaft Compressive Capacity................................................ 34 8.2.2.3 Drilled Shaft Lateral Load Analysis ................................................ 34 8.2.2.4 Construction Considerations ............................................................ 35

8.2.3 South McCarran Boulevard Bridge Foundations ................................................ 35 8.2.3.1 Foundation Type Selection .............................................................. 35 8.2.3.2 Abutment Foundation Design .......................................................... 35 8.2.3.3 Pier Drilled Shaft Compression and Uplift Capacity....................... 36 8.2.3.4 Pier Drilled Shaft Lateral Load Analysis ......................................... 37 8.2.3.5 Construction Considerations ............................................................ 37

8.2.4 South Virginia Street Bridge Foundations .......................................................... 38 8.2.4.1 Foundation Type Selection .............................................................. 38 8.2.4.2 Abutment Foundation Design .......................................................... 38 8.2.4.3 Pier Drilled Shaft Compression and Uplift Capacity....................... 38 8.2.4.4 Pier Drilled Shaft Lateral Load Analysis ......................................... 39 8.2.4.5 Construction Considerations ............................................................ 39

8.2.5 Conventional Cast-In-Place Concrete Cantilever Retaining Wall Foundations.. 39 8.2.5.1 Foundation Design ............................................................................ 39 8.2.5.2 Construction Considerations ............................................................. 40

8.2.6 Drilled Shaft with Concrete Soldier Beam and CIP Concrete Lagging Wall Foundations ......................................................................................................................... 40

8.2.6.1 Drilled Shaft Compressive Capacity................................................. 40 8.2.6.2 Drilled Shaft Lateral Load Analysis ................................................. 40 8.2.6.3 Construction Considerations ............................................................. 40

8.3 Retaining Walls .............................................................................................................. 41 8.3.1 Wall Type Selection ............................................................................................ 41 8.3.2 Concrete Cantilever, Drilled Shafts with Concrete Soldier Pile Extensions and CIP Lagging, and Secant Pile Walls.................................................................................... 41

8.3.2.1 Lateral Earth Pressures...................................................................... 41


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8.3.2.2 Construction Considerations ............................................................. 43 8.3.3 Soil Nail Walls .................................................................................................... 43

8.3.3.1 Soil Nail Wall Design ....................................................................... 43 8.3.3.2 Construction Considerations ............................................................. 46

8.3.4 Additional Retaining Wall Design Considerations ............................................. 46 8.4 Sign and Lighting Foundations ...................................................................................... 47 8.5 Private Driveway Pavement Sections ............................................................................ 47

9.0 CONSTRUCTION SPECIFICATIONS ............................................................................... 48

10.0 RECOMMENDED CONSTRUCTION OBSERVATIONS, TESTING AND INSTRUMENTATION................................................................................................................... 48

11.0 STANDARD LIMITATIONS CLAUSE............................................................................. 49

12.0 REFERENCES..................................................................................................................... 50

TABLES

Table 1 - Summary of Bridge Foundation Geometry Table 2 - Design Loads for Meadowood Mall Way Bridge Table 3 - Design Loads for South McCarran Boulevard and South Virginia Street Bridge Widenings Table 4 - Soil Properties Used in Slope Stability Analyses Table 5 - Slope Stability Analyses Results Table 6 - Allowable Stress Design Lateral Earth Pressures (Equivalent Fluid Density) Table 7 - Soil Properties and Assumptions Used In Soil Nail Wall Design Table 8 - Soil Nail Wall Design Sections

APPENDICES

APPENDIX A - PLATES A.1 Plot Plan A.2 Subsurface Fence Diagram, Meadowood Mall Way A.3 Liquefaction Potential versus Depth, Meadowood Mall Way Bridge A.4 Drilled Shaft Compressive Resistance, Meadowood Mall Way Bridge A.5 Lateral Load Versus Drilled Shaft Group Deflection, Meadowood Mall Way Bridge A.6 Maximum Drilled Shaft Moment Versus Drilled Shaft Group Deflection, Meadowood

Mall Way Bridge A.7 Drilled Shaft Displacement Versus Distance Below Abutment, Meadowood Mall Way

Bridge A.8 Drilled Shaft Moment Versus Distance Below Abutment, Meadowood Mall Way Bridge A.9 Allowable Pier Drilled Shaft Capacity, South McCarran Boulevard Bridge A.10 Lateral Load Versus Drilled Shaft Group Deflection, South McCarran Boulevard Bridge


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A.11 Maximum Drilled Shaft Moment Versus Drilled Shaft Group Deflection, South McCarran Boulevard Bridge

A.12 Drilled Shaft Displacement Versus Distance Below Cap, South McCarran Boulevard Bridge

A.13 Drilled Shaft Moment Versus Distance Below Cap, South McCarran Boulevard Bridge A.14 Allowable Pier Drilled Shaft Capacity, South Virginia Street Bridge A.15 Seismic Active Earth Pressure Values (Equivalent Fluid Pressure) Versus Wall Height and

Maximum Slope Height

APPENDIX B - SUBSURFACE EXPLORATION DATA

B.1 Boring Log Key B.2 Boring Logs

APPENDIX C - LABORATORY TESTING

C.1 Index Tests Results C.2 In Situ Moisture Density Tests Results

C.3 Direct Shear Tests Results C.4 Consolidation Tests Results C.5 R-Value Tests Results C.6 Chemical Tests Results

APPENDIX D - ENGINEERING ANALYSES AND CALCULATIONS

D.1 Liquefaction Analyses D.2 Embankment Stability Analyses D.3 Meadowood Mall Way Bridge Abutment Drilled Shaft Axial Loading Analyses D.4 Meadowood Mall Way Bridge Abutment Drilled Shaft Lateral Loading Analyses D.5 South McCarran Boulevard Bridge Abutment Analyses D.6 South McCarran Boulevard Bridge Pier Drilled Shaft Axial Loading Analyses D.7 South McCarran Boulevard Bridge Pier Drilled Shaft Lateral Loading Analyses D.8 South Virginia Street Bridge Pier Drilled Shaft Axial Loading Analyses D.9 Concrete Cantilever Retaining Wall Foundation Analyses D.10 Cantilever Retaining Wall Lateral Earth Pressure Analyses D.11 Wedge Analyses of Seismic Pressure D.12 Soil Nail Wall Design Analyses

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GEOTECHNICAL INVESTIGATION

I-580/MEDOWOOD COMPLEX IMPROVEMENTS RENO, NEVADA 1.0 INTRODUCTION 1.1 General Presented herein are the results of Black Eagle Consulting, Inc. geotechnical investigation, laboratory testing, and associated geotechnical design recommendations for the proposed infrastructure improvements for the I-580/Meadowood Complex improvements located in Reno, Nevada. This interchange will provide additional access to and from I-580 in the South Virginia Street, South McCarran Boulevard, and Meadowood Mall Way area. These recommendations are based on surface and subsurface conditions encountered in our explorations, and on details of the proposed project as described in this report. The services described above were conducted in accordance with CH2M HILL Purchase Order No. 21873 dated November 13, 1998, and subsequent Purchase Order No. 922762 dated June 26, 2007. 1.2 Scope of Work Black Eagle Consulting, Inc. was contracted by CH2M HILL to provide the following services: 1. Research existing geotechnical and design documents for the project alignment. 2. Explore the site to determine general soil and ground water conditions pertaining to design and

construction of the proposed improvements. 3. Perform geotechnical and chemical laboratory testing on representative material samples

obtained from the site exploration to determine the physical and mechanical properties of the various on-site materials.


4. Perform geotechnical analyses in support of the structural design of improvements on this project.

5. Prepare a report summarizing Items 1 through 4 above and containing geotechnical design

recommendations for the project. Results of our field exploration and testing programs form the basis for all conclusions and recommendations.

1.3 Other Reports and Investigations As a part of this project, the following design documents were reviewed to supplement information obtained in our site exploration: 1. Geotechnical Investigation, Interstate 580, South Virginia Street to Del Monte Lane, dated

August 1, 1984, and prepared by SEA Incorporated of Reno, Nevada; 2. Lateral Earth Pressures and Bearing Capacity for Hilton Inn Underpass, I-580 and South

McCarran Boulevard, dated February 24, 1986, and prepared by Summit Engineering of Reno, Nevada;

3. Geotechnical Investigation Report, Off-Ramp and Bridge Structure, I-580 and South Virginia,

Reno, Nevada, dated February 4, 1994, and prepared by Kleinfelder, Inc. of Reno, Nevada; and

4. NDOT As-Built Drawings for original and modified freeway construction of the project

alignment. In addition to this information, geologic maps of the area, earthquake hazard maps, and flood insurance maps were reviewed to evaluate the presence of any faults, flood zones, or geologic or other hazards in the project area.


2.0 PROJECT DESCRIPTION 2.1 Site Conditions The proposed interchange will connect the proposed extension of Meadowood Mall Way with I-580 approximately at milepost 21.3. The freeway runs approximately south to north in the project area. The project begins at the I-580/Neil Road interchange to the south and extends to the I-580/South Virginia Street interchange to the north, and is generally bounded to the east and west by commercial development. Existing Meadowood Mall Way extends approximately 450 feet west from South Virginia Street and terminates approximately 350 feet east of the existing freeway. The project improvements will be contained in Sections 25 and 36, Township 19 North, Range 19 East; and Sections 30 and 31, Township 19 North, Range 20 East, M.D.M. The overall project site location is shown on Plate A.1 (Plot Plan) in Appendix A (Plates). In the project area, I-580 presently has three through-lanes in each direction plus merging on and diverging off ramps from the Neil Road interchange. The centerline and eastern shoulder of the freeway each have a barrier rail divider throughout the length of the project area. The western side of the freeway has barrier rail along the shoulder from north of the project area to approximately 1,400 feet south of the South McCarran Boulevard overpass. There is an 8-foot-wide inside shoulder on both sides of the centerline barrier rail, and a 10-foot-wide outer shoulder. The freeway alignment within the project limits is elevated on embankment fill. The southern end of the project area is marked by the northern Neil Road interchange on- and off-ramps. Within the Neil Road interchange, the freeway embankment is 16 to 25 feet above adjacent grade. Embankment slopes exhibit slope ratios that vary from 2H:1V (Horizontal:Vertical) to 6H:1V and there is typically 10 to 80 feet of gently sloping native ground on either side of the embankment within the right-of-way. From the northern end of the Neil Road ramps to the planned Meadowood Mall Way extension, the freeway embankment is elevated 7 to 12 feet above adjacent grade with 3H:1V to 6H:1V side slopes and 20 to 40 feet of gently sloping ground within the right-of-way at the base of the slope. The freeway embankment starts to rise north of the proposed Meadowood Mall Way extension. Between the Hilton Inn underpass and the South Virginia Street bridge, the freeway embankment exhibits 2H:1V slopes and is between 20 and 25 feet high above original grade, with 0 to 50 feet of gently sloping original ground within the right-of-way at the toe of the embankment.


Original ground adjacent to the project generally slopes to the east at grades of 2 to 4 percent. Drainage on adjacent commercial parcels east of the freeway is generally away from the freeway, and these properties receive freeway embankment runoff at a number of locations. Drainage on the west side of the freeway is toward the base of the freeway embankment, and several drainage swales are present between Neil Road and the Hilton Inn underpass. North of the Hilton Inn underpass, drainage at the western edge of the embankment is by sheet flow toward the South McCarran Boulevard and South Virginia Street bridges. Nine storm drain culverts, varying from 18- to 42-inch-diameter reinforced concrete pipe, convey drainage under the freeway between Neil Road and the Hilton Inn underpass. Most connect to the drainage swales immediately west of the embankment, but at least two of the storm drains convey water from commercial developments further west. Municipal utilities (water, sanitary sewer, storm drain, electric, and communications) are generally present under the major streets crossing the freeway (Neil Road, South McCarran Boulevard, and South Virginia Street). Sanitary sewer, electric, and communication lines cross under the freeway along the line of Crummer Lane, 650 feet south of the planned Meadowood Mall Way bridge. Underground electrical wiring associated with freeway lighting is present along the elevated portion of the freeway. Underground Service Alert (U.S.A) calls made prior to drilling in the right-of-way did not result in identification of other buried utilities within the right-of-way. Within the unpaved portions of the right-of-way, vegetation consists mainly of low to medium density grasses, rabbit brush, sage brush, and weeds to 3 feet in height. 2.2 Existing Structures Three freeway bridge structures and the Hilton Inn underpass box culvert currently exist within the limits of the project. The freeway crosses over the Neil Road interchange on a single-span, closed-abutment bridge. This bridge is at the southern limits of the project and will not be modified. The Hilton Inn underpass is 3,100 feet north of the Neil Road interchange and 350 feet south of the South McCarran Boulevard grade separation bridge, and was originally built through the freeway embankment for storm water conveyance and to provide vehicular access to connect a parcel bisected by freeway construction. The underpass is a double 31-foot-wide by 16-foot-high by 140-foot-long box culvert. The freeway crosses over South McCarran Boulevard on a two-span, steel-I-beam bridge with open abutments. The freeway also crosses over South Virginia Street on a two-span, steel-I-beam bridge with open abutments. Both the South McCarran Boulevard and South Virginia Street structures have abutments supported on conventional spread footings bearing on embankment fill and the center piers supported on spread footings bearing on native granular soils under the median of each road. The Kietzke Lane off-ramp flyover over South


Virginia Street is a two-span, steel-I-beam-girder bridge on the northwest side of I-580 that is at the northern limit of the project and will not be modified. Numerous commercial buildings exist east and west of I-580 in this area outside of the right-of-way. 2.3 Proposed Improvements A plan of the project area and proposed improvements is shown on Plate 1. The project will involve extending the existing Meadowood Mall Way under the freeway connecting South Virginia Street and Kietzke Lane. The existing northern ramps of the Neil Road interchange will be removed and replaced with frontage roads on both sides of the freeway between Neil Road and Meadowood Mall Way. Two new northern ramps will also be constructed to connect Meadowood Mall Way and I-580 to the north. A new bridge will be constructed to allow for Meadowood Mall Way to cross under the freeway, and the I-580 bridges over South McCarran Boulevard and South Virginia Street will be widened to accommodate the northern ramps. The proposed improvements will generally be built within the existing freeway right-of-way, plus the acquisition and dedication of a new right-of-way for Meadowood Mall Way from 450 feet west of South Virginia Street to a new intersection with Kietzke Lane. The design of this interchange complex, from south to north, will include the following roadway geometry, embankment, bridge and retaining wall improvements. Retaining walls retain level ground at the tops of the walls except where noted: A northbound frontage road will be constructed on the east side of the freeway from Neil Road to the new Meadowood Mall Way extension. The existing northbound on-ramp from Neil Road to I-580 will be eliminated. The frontage road will require up to 5 feet of fill, as much as 12 feet of cut below original grade, and locally as much as 17 feet of cut into the toe of the existing I-580 embankment. A new retaining wall (Wall 21FN), approximately 375 feet long and up to 14 feet high, will be required to retain the existing freeway embankment (2H:1V) slopes where the on-ramp above the frontage road will be removed. The retaining wall will likely be a combination of a soil nail and conventional concrete cantilever walls. An intersection will be constructed where the frontage road crosses Crummer Lane. As the northbound frontage road nears the proposed depressed Meadowood Mall Way, retaining walls will be required along both sides of the northbound (eastern) frontage road within 600 feet south of the Meadowood Mall Way bridge. Wall 31FN will retain the existing freeway embankment (2H:1V slope) and native ground above the new frontage road, will be up to 17 feet


high, and will likely be built with a combination of soil nail wall and conventional concrete cantilever wall. Portions of the slope above Wall 31FN may be steepened to 1.5H:1V. Wall 32FN will be built between the commercial property (Macy’s Furniture) to the east and the depressed frontage road, and will retain up to 12 feet of native soil. Wall 32FN will be built with a combination of drilled shafts with concrete soldier pile extensions and cast-in-place (CIP) concrete lagging, and conventional concrete cantilever walls. A southbound frontage road will be constructed on the west side of the freeway from the new Meadowood Mall Way extension to Neil Road. The existing southbound off-ramp from I-580 to Neil Road will be eliminated. The frontage road will require up to 7 feet of fill, as much as 10 feet of cut below original grade, and locally as much as 14 feet of cut into the toe of the existing I-580 embankment. Retaining walls will be required along both sides of the southbound (western) frontage road within 400 feet south the Meadowood Mall Way bridge. Wall 30FS will retain the existing freeway embankment (2H:1V slope) and native ground above the new frontage road, will be up to 14 feet high, and will likely be built with a combination of soil nail wall and conventional concrete cantilever wall. Near the Meadowood Mall Way bridge, Wall 29FS will be built between the commercial properties to the west (the Nevada State Highway Patrol and a medical clinic) and the depressed frontage road. Wall 29FS will retain up to 10 feet of native soil, and will be built with a combination of drilled shafts with concrete soldier pile extensions and CIP concrete lagging, secant pile, and conventional concrete cantilever walls. The secant pile wall will be built where the Nevada Highway Patrol building is within 7 feet of the right-of-way and top of wall, and the building footing is estimated to be 3 to 9 feet above the bottom of wall elevation on the east side of the wall. A new single-span bridge will be built for I-580 over Meadowood Mall Way. Details of the Meadowood Mall Way bridge are provided under the bridge structure design section below. Existing Meadowood Mall Way will be extended from its existing terminus, approximately 450 feet west of South Virginia Street, to connect to Kietzke Lane at Sierra Rose Street on the west side of the existing freeway. Meadowood Mall Way will require cuts of 0 to 10 feet with respect to existing grade, and 22 feet of cut under the center of the freeway embankment. Three retaining walls will be required along the depressed section of Meadowood Mall Way on either side of the freeway. Wall 12MW will extend approximately 200 feet west along northern edge of the southwestern commercial property and the southern edge of Meadowood Mall Way. Wall 12MW will retain up to 12 feet of native soil, and will be built with a combination of drilled shafts with concrete soldier pile extensions and CIP concrete lagging, and conventional concrete cantilever


walls. Wall 18MW starts at the end of Wall 32 FN and extends approximately 350 feet east along the northern edge of the southeastern commercial property along the southern edge of Meadowood Mall Way. Wall 18MW will retain up to 12 feet of native soil, and will be built with a combination of drilled shafts with concrete soldier pile extensions and CIP concrete lagging, and conventional concrete cantilever walls. Wall 19MW will extend approximately 350 feet west along southern edge of the northeastern commercial property and the northern edge of Meadowood Mall Way. Wall 19MW will retain up to 12 feet of native soil, and will be built with a combination of drilled shafts with concrete soldier pile extensions and CIP concrete lagging, and conventional concrete cantilever walls. A new on-ramp will be constructed on the east side of the freeway from Meadowood Mall Way to I-580 northbound. The ramp will require up to 12 feet of cut and 20 feet of fill, and locally as much as 15 feet of cut into the toe of the existing I-580 embankment. Three retaining walls will be required along the northbound on-ramp within 450 feet north the Meadowood Mall Way bridge. Wall 13RD will retain the existing freeway embankment (2H:1V slope) above the new on-ramp, will be up to 15 feet high, and will likely be built with a combination of drilled shafts with concrete soldier pile extensions and CIP concrete lagging, and conventional concrete cantilever walls. Wall 12RD will be built between the commercial property (Best Buy) to the east and the depressed frontage road. Wall 12RD will retain up to 12 feet of native soil, and will be built with a combination of drilled shafts with concrete soldier pile extensions and CIP concrete lagging, and conventional concrete cantilever walls. Wall 12RD also extends approximately 350 feet east along the northern edge of the commercial property along the southern edge of Meadowood Mall Way. Wall 14RD will be built to retain the northbound on-ramp where it rises above adjacent native ground to the east, will retain up to 16 feet of soil, and will be built with conventional concrete cantilever walls. A new off-ramp will also be constructed on the west side of the freeway from I-580 southbound to Meadowood Mall Way. The ramp will require up to 20 feet of fill and 12 feet of cut, and locally as much as 18 feet of cut into the toe of the existing I-580 embankment. Two retaining walls will be required along the southbound off-ramp within 500 feet north the Meadowood Mall Way bridge. Wall 12RC will retain the existing freeway embankment (2H:1V slope) above the new frontage road, will be up to 18 feet high, and will likely be built with a combination of soil nail and conventional concrete cantilever walls. Wall 11RC will be built between the commercial property (PF Chang’s) to the west and the depressed frontage road. Wall 11RC will retain up to 12 feet of native soil and will be built with conventional concrete cantilever walls.


The existing Hilton Inn underpass will be abandoned by backfilling to provide support for the proposed mainline widening in this area. A smaller single reinforced concrete box culvert will be installed through the existing opening for drainage. Both sides of the South McCarran Boulevard bridge will be widened. Widening of the east side of the South Virginia Street interchange bridge will also be required. Additional details are provided under the bridge structure design section below. Two new retaining walls (Wall 30RD and Wall 283VA) will be required on the east side of I-580 north at the South Virginia Street bridge. The maximum wall heights will be 10 feet and the walls will be built with conventional concrete cantilever walls. The retaining walls will support the widened freeway mainline (as the northbound on-ramp ends) above the existing South Virginia Street on-ramp to I-580 northbound. 2.4 Bridge Structural Design Information As noted previously, a new bridge will be built at Meadowood Mall Way and widening of the existing South McCarran Boulevard and South Virginia Street bridges will be performed as a part of this project. Foundation geometry and elevations for the proposed bridge and bridge widenings are shown in Table 1 (Summary of Bridge Foundation Geometry).


TABLE 1 - SUMMARY OF BRIDGE FOUNDATION GEOMETRY

Bridge Location

Substructure

Existing Footings

Dimensions (ft)

Planned Foundation Dimensions

Existing/ Planned

Footing/Pier Cap

Elevation (ft)

Freeway Grade

Elevation (ft)

Burial of Footing/ Drilled Shaft Cap

Relative to Adjacent Highest

Grade

Lower Grade Elevation (ft)

Burial of Footing/Drilled

Shaft Cap Relative to Adjacent Lowest

Grade

Abutment 1 NA 16 drilled shafts, 145–

foot abutment Meadowood Mall Way (new) Abutment 2 NA Same

4,487.5 – 4,490.5

4,495.5 – 4,498.5

8 feet below grade

4,474.0 – 4,474.4

(Meadowood Mall Way)

14 feet above Meadowood Mall

Way

Abutment 1 10 x 128 4,482.1

2.5 and 20 – 23 feet burial at downhill and uphill sides of abutment footing

4 - 8 feet above South McCarran

Boulevard

Pier 2 footings

5 x 5 4 drilled shaft group

4,470.0 – 4,471.3

NA 5 feet below South

McCarran Boulevard

South McCarran Boulevard (H-1798)

Abutment 2 12 x 128 4,482.1

4,502.5 – 4,505.5

2.5 and 20 – 23 feet burial at downhill and uphill sides of abutment footing

4,474.3 – 4,478.2 (South

McCarran Boulevard)

4 - 8 feet above South McCarran

Boulevard

Abutment 1 10 x 164 4,476.4

8 and 16 feet burial at downhill and uphill sides of

abutment footing

11.5 feet above South Virginia

Street

Pier 2 footings

8 x 42 4 drilled shaft group

4,464.3 – 4,464.7

NA 5 feet below South

Virginia Street

South Virginia Street (I-1799)

Abutment 2 12 x 150 4,475.0

4,492.5 – 4,494.0

8 and 17.5 feet burial at downhill and uphill sides of abutment footing

4,465.0 (South Virginia Street)

10 feet above South Virginia Street

NA = Not Applicable


The I-580/Meadowood Mall Way interchange bridge will consist of a single-span, cast-in-place, post-tensioned concrete box girder supported on closed abutments. The bridge will be built in three separate adjoining segments across the width of the freeway to maintain freeway traffic while the bridge is constructed. Each adjoining section of the bridge will have its own wing walls, two of which would be permanently embedded in the middle of the freeway embankment when the bridge is complete. Drilled shaft foundations would be installed first, followed by abutment installation, bridge deck construction, and the simultaneous soil-nail wall installation and embankment excavation. The new Meadowood Mall Way will be 22 feet below existing freeway grade and will be depressed as much as 10 feet below adjacent existing grade. The base of the bridge abutments will be founded approximately 8 feet below existing elevations on the mainline. The abutments will be supported by drilled shafts. The drilled shafts will derive all of their axial support from native soils present below the base depth of the adjacent soil nail wall, and will be installed in a single row with fixed-head conditions to resist abutment rotation in the transverse direction. This bridge structure will be designed according to Load and Resistance Factor Design (LRFD) methods (American Association of State Highway and Transportation Officials [AASHTO], 2007). Soil nail walls around the abutment piers will be designed according to Allowable Stress Design (ASD) methods (AASHTO, 2002). The drilled shafts will provide vertical support for the abutments. Since the abutments will be approximately 14 feet above the adjacent roadway level, the soil nail wall facing will need to exhibit sufficient stiffness in order for the abutment drilled shafts to provide for lateral load resistance. A summary of design loads is provided in Table 2 (Design Loads for Meadowood Mall Way Bridge).


TABLE 2 - DESIGN LOADS FOR MEADOWOOD MALL WAY BRIDGE

Location Maximum Vertical

Load (kips) Longitudinal Shear

Load (kips) Transverse Shear

Load (kips) Longitudinal

Moment

Abutments – Strength Design

6,779 (455)(1) 976(3) (61(3,4)) 0

6,464 k-ft (404 k-ft

per pile)***

Abutments – Extreme Event 1

250(2) 816(3) (51(3,4)) 1,072(3) (67(3,4))

Load is per abutment, load in parenthesis is load divided among 16 drilled shafts. Loads are based on design iterations as of January 2008. Final loads may vary. NE= Not Evaluated (1) Approximate Strength I Load should be compared to the resistance-factored pier capacity. (2) Approximate Extreme Event I (earthquake) load with all load factors = 1. Should be compared with the nominal pier capacity (resistance factor = 1) (3) Unfactored load only are shown. (4) Load per pile after resistance from base sliding and wing walls, is taken into account.

The existing I-580/South McCarran Boulevard structure will be widened to both the east and west. The northbound widening will vary between 15.0 and 15.6 feet, while the southbound widening will vary between 15.0 and 16.6 feet. The widening structures will be two-span, steel-girder superstructures with spread footings at the abutments to match the existing bridge structures. The new piers for each widening will be a single column supported on a group of drilled shafts. This structure will be designed to match the existing structures using ASD methods (AASHTO, 2002). The existing I-580/South Virginia Street structure will be widened on the east side only. The northbound lanes will be widened by 15 feet. The widening structure will be a two-span, steel-girder superstructure with spread footings at the abutments to match the existing bridge structures. The new piers for each bridge will be a single column supported on a group of drilled shafts. This structure will be designed to match the existing structures using ASD methods (AASHTO, 2002). A summary of design loads for the South McCarran Boulevard and South Virginia Street bridge widenings is provided on Table 3 (Design Loads for South McCarran Boulevard and South Virginia Street Bridge Widenings).


TABLE 3 - DESIGN LOADS FOR SOUTH MCCARRAN BOULEVARD AND SOUTH VIRGINIA STREET BRIDGE WIDENINGS

Location Maximum Vertical

Load Longitudinal Shear

Load Transverse Shear

Load Moment

Abutments – Service(1)

38 kips/ft 12 kips/ft NE 92 k-ft/ft moment

longitudinally at top of footing

Piers – Service(1) 940 kips 0 0 360 k-ft transverse to

bridge

Piers – Earthquake(1)

8 kips 335 kips 248 kips

5,732 k-ft transverse to bridge at top of footing; 6,485 k-ft

longitudinal to bridge

Loads are based on design iterations as of January 2008. Final loads may vary. NE = Not Evaluated. (1) Unfactored loads per substructure without factoring.

3.0 GEOLOGIC CONDITIONS AND SEISMICITY 3.1 Local Geology The site has been mapped by the Nevada Bureau of Mines and Geology (NBMG) as being underlain by Donner Lake Outwash (Bonham and Rogers, 1983). These materials are described as consisting of Bouldery outwash [in] extensive mantle thickening eastward; unconsolidated small cobble gravel and interbedded coarse sand. Highly rounded clasts; unit locally contains very large, deeply weathered boulders of basalt and quartz monzonite more than 2 m (6 ft) in diameter. Strongly developed argillic B-horizon; weakly to strongly developed siliceous and calcic duripan 1-2 m (3-6 ft) thick; granitic clasts thoroughly disintegrated in weathered profile. The published earthquake hazards map (Szecsody, 1983) states that the site could be subjected to Moderate severity of shaking. Includes units from I (Greatest severity of shaking where ground water is less than 3 m [10 ft]) where depth to ground water is greater than 3 m (10 ft); also includes unconsolidated deposits with moderate rigidity where depth to ground water is less than 10 m (33 ft) May be subject to liquefaction.


3.2 Seismicity and Faulting The Reno area lies within an area with a high potential for strong earthquake shaking. Seismicity within the Reno-Sparks area is considered about average for the western Basin and Range Province (Ryall and Douglas, 1976). It is generally accepted that the maximum credible earthquake in this area would be in the range of magnitude 7 to 7.5 along the frontal fault system of the Eastern Sierra Nevada. The most-recently active segment of this fault system in the Reno area is located at the base of the mountains near Thomas Creek, Whites Creek, and Mt. Rose Highway, some 4-1/2 miles southwest of the project. The AASHTO design manual (AASHTO, 2002) shows horizontal bedrock acceleration to be about 0.39g for a 10 percent probability of exceedance in 50 years. Per NDOT Materials Division Policy, all bridges and other structures in this area should be designed for a horizontal bedrock acceleration of 0.40 g. All structures are founded on site soils that provide a Soil Profile Type II. The published earthquake hazards map published by the NBMG shows several early to mid-Pleistocene (approximately 100,000 to 1.8 million years old) faults no closer than 2,000 feet northwest of the northern limits of the project alignment (Szecsody, 1983). 4.0 FIELD INVESTIGATIONS Thirty-two borings were performed to explore the project alignment. Additional samples of existing embankment fill were obtained by surface sampling. Locations of the borings are shown on Plate 1 in Appendix A. Boring logs are included in Appendix B.2 (Boring Logs) of Appendix B (Subsurface Explorations Data). 4.1 Drilling The project site was initially explored in December 1998 by drilling twenty-seven test borings (B-06 through B-32) in the area of the proposed improvements. Twenty-two of these borings were drilled using 6-inch-outside-diameter, 3-1/4-inch-inside-diameter hollow-stem augers (HSA) and a truck-mounted CME 55 soils sampling drill rig. Four (4) borings were advanced using rotary-mud techniques and the referenced CME 55 drill rig, while one (1) hand auger was advanced in an area not accessible to the drill rig. The 1998 borings were drilled by Andresen Drilling of Reno, Nevada.


The initial phase of exploration was performed shortly before the project was put on hold in 1998; therefore, no as-built survey was performed for the boring locations. The boring stationing and elevations shown in Appendix B are approximate only. Five borings were advanced in August 2007 (B-01 through B-05) using a CME 75 soil sampling drill rig operated by Haz-Tech Drilling of Boise Idaho. Four of the borings were advanced using 8-inch-outside-diameter, 3-1/2-inch-inside-diameter, continuous-flight, hollow-stem augers. One boring (B-05) was advanced using 4-inch-nominal-diameter rotary-mud methods to allow for liquefaction evaluation. The maximum depth of exploration was 61.5 feet below the existing ground surface. These borings have not yet been located by survey in the field. Subsurface soils were sampled at 2.5- to 5-foot depth intervals. A standard, 2-inch outside-diameter, split-spoon “Standard Penetration Test” (SPT) sampler was driven by a 140-pound hammer with a 30-inch stroke (AASHTO T206; ASTM D 1586). A 2.95-inch outside-diameter, 2.42-inch inside-diameter “Modified California” (MC) split-spoon sampler (ASTM D 3550) was also used to sample soils where larger-diameter, intact samples of subsurface materials were required for testing. This sampler was driven using the same hammer and stroke as the SPT sampler. Because of the larger diameter of the sampler, blow counts are typically higher than those obtained with the standard penetration test (SPT) and should not be directly equated to SPT blow counts. Undisturbed samples of fine-grained soils were obtained by pushing a 3-inch-inside-diameter, thin-wall Shelby tube into the desired strata in accordance with AASHTO T207 and ASTM D 1587. The logs indicate the type of sampler used for each sample. Due to the relatively small diameter of the samplers, the maximum particle size that could be obtained was approximately 1-1/2 to 3 inches. The final logs may not, therefore, adequately represent the actual quantity or presence of cobbles or boulders. Ground water levels were measured where encountered. 4.2 Material Classification A geotechnical engineering technician and/or geologist examined and identified all soils in the field in general accordance with ASTM D 2488. Additional soil classification was subsequently performed on soil samples in accordance with ASTM 2487 (Unified Soil Classification System [USCS]) upon completion of laboratory testing. Where soil tests are not listed in the appropriate column of the boring log, or soil gradation in the material description column is listed as


“estimated,” the USCS symbols and terminology are based solely on manual identification (ASTM D 2488) rather than laboratory classification. Pocket penetrometer testing was performed on various samples of fine-grained soils in order to evaluate unconfined compressive strength. A classification and symbol key has been included in Appendix B.1 (Boring Log Key) in Appendix B. 4.3 Drive Hammer Calibration Standard Penetration Testing in the original 1998 exploration (B-06 through B-31) was performed using a 140-pound safety hammer raised and dropped 30 inches using standard rope-and-cathead equipment. No calibration was performed for this drill rig. Dynamic energy measurements were performed for the automatic hammer used for the 2007 borings (B-01 through B-05). An average efficiency of 73 percent is applicable to these latter borings (Foundation Tech, LLC, 2007). The field SPT values shown on the respective logs should therefore be multiplied by 1.21 to obtain an equivalent blow count at a standard 60 percent efficiency. The hammer efficiency is also listed in the “remarks” column on each boring log.

5.0 LABORATORY ANALYSES All soils testing performed in the Black Eagle Consulting, Inc. soils laboratory is conducted in general accordance with current standards and methodologies described in the NDOT Materials Division Testing Manual (NDOT, 2003), the AASHTO methods of sampling and testing standards (AASHTO, 1998), Volume 4.08 of the ASTM Standards (ASTM, 2007), as applicable. Copies of all laboratory test results are contained in Appendix C (Laboratory Test Results). 5.1 Index Tests A total of sixty-seven (67) samples of significant soil types were analyzed to determine their in situ moisture content (NDOT T112C), grain size distribution (NDOT T206F), and plasticity index (NDOT T210E, T211E, and T212E). Results of these tests were used to classify the soils according to ASTM D 2487 and to verify the field logs, which were then updated as appropriate. Copies of the index test results are contained in Appendix C.1 (Index Tests Results).


5.2 In Situ Moisture-Density Tests Five (5) in situ moisture-density tests (ASTM D 2937) were performed on representative samples of native soils at this site in order to determine in situ material properties. The materials’ moisture contents and in situ dry unit weights were determined. A summary of the test results are contained in Table C.2 (In Situ Moisture-Density Tests Summary) in Appendix C.2. 5.3 Direct Shear Tests Six (6) Consolidated-Drained (CD) direct shear tests (AASHTO 236-92) were performed on representative samples of site soils. Tests were run on both undisturbed and remolded samples under saturated conditions and a range of normal loads. For remolded samples, the material was screened past a No. 4 sieve prior to testing. Two direct shear tests were performed by Sierra Testing Laboratories, Inc of El Dorado Hills, California, while the remaining four were performed by Black Eagle Consulting, Inc. Copies of the direct shear tests results are contained in Appendix C.3 (Direct Shear Tests Results). 5.4 Consolidation Tests Four (4) one-dimensional consolidation tests (AASHTO T 216) were performed on representative samples of fine-grained foundation soils. Tests were run on intact and relatively undisturbed samples. The samples were inundated prior to loading. Copies of the consolidation test results are contained in Appendix C.4 (Consolidation Test Results). 5.5 R-Value Tests A total of nine (9) Resistance Value tests (NDOT T115C) were performed on representative samples of native subgrade soils and existing embankment materials. Where existing embankment was sampled in areas proposed to host mainline widening, the samples were obtained at approximate subgrade elevation. Testing of the native subgrade soils was performed by Earth Science Consultants Associated of Sparks, Nevada, in 1998 while testing of the existing embankment material was performed by Black Eagle Consulting, Inc. in 2007. R-Value testing is a measure of subgrade strength and expansion potential, and is used in design of flexible pavements. In summary, the native clay and fine grain site soils exhibit R-values that vary between 2 and 8. Surficial granular materials, which contain appreciable amounts of clay and fine particles, exhibit R-values that generally vary between 10 and 17. Cleaner granular soils present


at depth will exhibit higher R-values. Existing embankment materials exhibit R-values that vary between 71 and 75. Copies of the R-Value tests results are contained in Appendix C.5 (R-Value Tests Results). 5.6 Chemical Tests A total of three (3) series of chemical tests were performed on representative material samples to assess potential for corrosion of or attack on buried metal and concrete components. Chemical testing was performed by Acculabs Inc. and Western Environmental Testing Laboratory of Sparks, Nevada. Testing for pH was performed in accordance with AASHTO T 289. Testing for soil resistivity was performed in accordance with Test T 235B or 2510B. Testing for soluble sulfate was performed in accordance with AASHTO Test T 290 or Test 300.0, and testing for sulfides was performed in accordance with Test A21.5-99. Testing for redox potential was performed in accordance with Test SM 2580B. Copies of the chemical tests results are contained in Appendix C.6 (Chemical Tests Results).

6.0 DISCUSSION 6.1 Anticipated Subsurface Conditions The areas to host the Meadowood Mall Way extension, frontage roads, and ramps, are underlain by a variety of silty to clayey sand, clay, and silt soils lying in complex interbedded, gradational, and lensing relationships. No two adjacent borings exhibit the same soil profile. Soils encountered in the field were finer-grained than the NBMG geologic description, due to the project location near the downhill, rather than uphill or middle portions of the alluvial fan. No cobbles or boulders were encountered in the native materials, and only moderate amounts of gravel were observed. Native and embankment fill is present throughout the site due to adjacent development and the presence of the elevated freeway alignment. Where this material could be identified, it is labeled as fill in the borings logs. Occasional cobbles and possibly boulders were encountered in the embankment fill.


6.1.1 Northbound Frontage Road from Neil Road to Meadowood Mall Way Borings along the northbound frontage road from Neil Road to Meadowood Mall Way (B-18 to B-22) encountered native soils that consisted primarily of silty to clayey sand with minor gravel, interbedded with occasional sandy clay and poorly graded sand with silt layers. The majority of the silty to clayey sand exhibited 25 to 45 percent low to medium plasticity fines and no more than 15 percent gravel, and clays typically exhibited 60 to 75 percent low to medium plasticity fines. A poorly graded sand with silt and gravel was present in B-21 from 5 to 10 feet in depth. Soils in the southern portion of the alignment (B-18 and B-19) were classified as loose to 5 to 7 feet in depth and medium dense to dense at depth. Soils in the remainder of the borings were generally classified as medium dense to very dense, or very stiff to hard. The soils were also classified as moist to isolated areas that were wet. 6.1.2 Southbound Frontage Road from Meadowood Mall Way to Neil Road Borings along the southbound frontage road from Meadowood Mall Way to Neil Road (B-02, B-03, and B-28 to B-31) encountered complexly interbedded native granular and clay/fine grain soils. Clay soils are present at the existing ground surface in several areas. The majority of the silty to clayey sand exhibited 25 to 45 percent low to medium plasticity fines and no more than 15 percent gravel, and silts and clays typically exhibited 50 to 75 percent non-plastic to high plasticity fines. Soils at the southern end of the alignment (B-28) were classified as stiff. Soils in the remainder of the borings were classified as dense to very dense or stiff to hard. The soils were also classified as slightly moist to moist. 6.1.3 Meadowood Mall Way Interchange Bridge The site of the proposed Meadowood Mall Way bridge currently exhibits up to approximately 14 feet of embankment fill under the freeway mainline. The fill is classified as silty/clayey sand with 15 to 25 percent medium plasticity fines and 15 to 20 percent gravel. The fill was further classified as moist and loose to very dense. Native soils that underlie the embankment fill at this location are consistent with those encountered throughout the site. Exploration into native soils encountered alternating layers of clayey/silty sand and gravels, sandy lean clays, and sandy silty clays to a depth of 51-1/2 feet below original grade. These granular materials typically exhibited 10 to 45 percent non-plastic to medium plasticity fines, 45 to 85 percent sand, and 0 to 45 percent gravel, and were classified as moist to wet and medium dense to dense. The clay layers were generally classified as moist to wet below the ground water table, stiff to very stiff, and as exhibiting 60 to 90 percent low to medium plasticity fines.


6.1.4 Meadowood Mall Way from South Virginia Street West to Kietzke Lane A subsurface fence diagram along Meadowood Mall Way is shown on Plate A.2 (Subsurface Fence Diagram, Meadowood Mall Way) in Appendix A. Granular soils are generally present to 5 to 8 feet depth under the east end of Meadowood Mall Way (B-11 and B-12), but clay-rich soils were present at anticipated roadway subgrade elevations for all locations west of and including Boring B-13. At the Meadowood Mall Way bridge, the planned roadway will be depressed approximately 8 to 12 feet below original ground, so that the walls will retain largely clayey soils, but roadway subgrade for the depressed portion of Meadowood Mall Way, frontage road, and ramps, may be supported on deeper, slightly stronger, sands and silty sands with lower fines content. 6.1.5 Northbound On-Ramp from Meadowood Mall Way to I-580 The northbound on-ramp from Meadowood Mall Way to I-580 will start 9 feet below original ground at Meadowood Mall Way and climb to original grade approximately 250 feet to the north. Beyond this area, the ramp will be constructed on embankment fill on top of or adjacent to the existing freeway embankment. Borings along the northbound on-ramp from Meadowood Mall Way to I-580 encountered native materials alternating between silty to clayey sand and poorly graded sand or gravels with silt to depths of 20 feet below the original ground surface. Near-surface clayey sand and silty sand layers that exhibit 30 to 45 percent low plasticity fines are present near the Meadowood Mall Way alignment (B-23 and B-24), but cleaner sands (material that exhibits 5 to 25 percent fines) and some gravel layers are present within the surface layers to the north (B-25, B-10, and B-09). The granular soils were generally classified as moist, and medium dense to dense. Freeway widening for the northbound ramp will be on existing embankment fill between the South McCarran Boulevard structure and the South Virginia Street structure, and for 600 feet north of the Virginia Street structure. 6.1.6 Southbound Off-Ramp from I-580 to Meadowood Mall Way The southbound off-ramp from I-580 to Meadowood Mall Way will require widening starting on the existing embankment between South Virginia Street and South McCarran Boulevard, transitioning to new embankment fill adjacent to the existing freeway embankment. The ramp will drop below original grade within about 250 feet of Meadowood Mall Way, and will end approximately 8 feet below original grade at Meadowood Mall Way. Borings along the


southbound off-ramp encountered native soils alternating between silty to clayey sand, and poorly graded sand or gravel. Near-surface clayey sand and silty sand layers with 30 to 45 percent low to medium plasticity fines are present near the Meadowood Mall Way alignment (B-01 and B-27), but cleaner sands (material that exhibits 5 to 25 percent fines) and some gravel layers are present within the same depth interval to the north (B-07 and B-08). The soils were generally classified as dry to moist, and medium dense to very dense. 6.1.7 I-580/South McCarran Boulevard Structure Widening The existing pier columns associated with the South McCarran Boulevard structure are underlain (at the lower roadway level) by approximately 3 feet of clayey sand with approximately 25 percent low plasticity fines. Below this unit, soils generally consist of poorly graded sand and silty sand to depths of approximately 35 feet. These materials exhibit 5 to 25 percent non-plastic or low plasticity fines, 55 to 95 percent sand, and 0 to 20 percent gravel, and were classified as moist to very moist and medium dense to dense. From 35 to 50 feet depth, silts and clays with varying amounts of sand were encountered. These materials exhibited 55 to 65 percent low to medium plasticity fines and 35 to 45 percent sand, and were classified as moist and very stiff to hard. 6.1.8 I-580/South Virginia Street Structure Widening The existing South Virginia Street structure is underlain by silty and clayey sands, as well as poorly graded sands and gravels, which extend up to 30-1/2 feet below the existing ground surface. The materials were described as containing 5 to 35 percent non-plastic, low, or medium plasticity fines, 50 to 95 percent sand, and 0 to 35 percent gravel, and were classified as moist and medium dense to very dense. From 30.5 to 50 feet, silts and clays with varying amounts of sand were encountered. These materials exhibited 50 to 70 percent low to high plasticity fines and 35 to 50 percent sand, and were classified as moist to wet and stiff to hard. From 50 feet to the maximum depth explored (51.5 feet), a poorly graded sand was encountered that was classified as wet and dense. 6.1.9 Ground Water Ground water was encountered at depths ranging between 33.5 and 45 feet below existing grade at the time of exploration in December 1998. These depths correspond to variable elevations of 4,449 to 4,454 feet at the proposed Meadowood Mall Way bridge site, and 4,429 to 4,445 feet in the vicinity of South McCarran Boulevard and South Virginia Street. At the time of exploration in August 2007, ground water was encountered at depths ranging between 14 and 21 feet below


existing grade on the west side of the Meadowood Mall Way bridge site, and 27 feet on the east side. These depths correspond to elevations of 4,469 to 4,474 feet on the west side and 4,457 feet on the east side of the proposed bridge site. Based on the above information, ground water elevations at this site will vary depending on the time of year of construction, winter precipitation levels prior to construction, and irrigation practices of upslope areas. Due to the inter fingering of alluvial granular and clay/fine grain soils, ground water and snow melt will travel in granular layers that results in varying levels of ground water. Ground water levels are, however, generally present at depths that should not affect construction with the exception of the Meadowood Mall Way roadway and structure improvements, and retaining walls south of South McCarran Boulevard that will have drilled shaft foundations. At these locations, saturated subgrade soils and even lenses of free water may be encountered during mass grading, and drilled shafts will also most likely encounter ground water at depth. Drilled shafts associated with the South McCarran Boulevard and South Virginia Street column foundations could also encounter ground water at depth depending on winter precipitation levels and time of construction. 6.2 Geologic Hazards 6.2.1 Faulting Since no faults mapped in the area cross the project site or were identified during site investigation, no additional fault investigations or fault hazard mitigation are required. 6.2.2 Liquefaction Liquefaction analysis was performed using methods recommended by the Federal Highway Administration (FHA, 1998). Standard penetration test data was obtained from Boring B-05 which corresponds to the location of Meadowood Mall Way bridge. Previous borings were considered, but drill rig hammer calibration was not performed for the previous borings and results are less reliable. The other 2007 borings were performed using hollow-stem auger drilling techniques, which have the potential to disturb granular soils and result in reduced penetration resistance and increased (overly conservative) prediction of liquefaction potential. Ground water was assumed to be at an elevation of 4,474 feet during the design earthquake, the shallowest ground water level found in adjacent borings. A peak horizontal bedrock acceleration of 0.40g and an assumed earthquake magnitude of 7 were used in the liquefaction analysis.


The variations of soil consistency, penetration resistance, and liquefaction threshold with depth are shown on Plate A.3 (Liquefaction Potential versus Depth). The figure shows the corrected penetration resistance in blows per foot versus depth, with the predicted liquefaction thresholds for the design earthquake. Three thresholds (black, blue, and red) are shown for clean sands (less than 5 percent fines), slightly silty sands (less than or equal to 15 percent fines), and silty to clayey sands (15 to 35 percent fines, occasionally including soils to 50 percent fines), respectively. Different symbols are used to identify the varying soil consistency identified in the samples at each depth. Soil samples designated by an “X”, including silts and clays with greater than 50 percent fines, are not liquefiable regardless of the indicated blowcount. The threshold shown on the figure is the penetration resistance below which liquefaction will occur. Penetration values plotting to the left of the threshold line indicate liquefaction potential. The symbols of each color (black, red, or blue) should be related to the liquefaction threshold of the same color. The results of the analysis show that the liquefaction potential at the Meadowood Mall Way bridge site is negligible, as all penetration data on Plate A.3 plot to the right or above the corresponding liquefaction threshold for the appropriate range of soils fines content for the penetration sample. Supporting calculations are contained in Appendix D.1 (Liquefaction Analyses) of Appendix D (Engineering Analyses and Calculations). 6.2.3 Expansive or Compressible Clay Soils Native clay soils at this site will exhibit considerable shrink-swell potential with changes in moisture content. Such soils are present in random areas, at the existing ground surface outside areas of existing embankment, and at depth across the site. The clay soils were classified as slightly moist to wet at depth, soft to hard, and as exhibiting low to high plasticity. Laboratory testing performed on these materials indicates the clay soils exhibit plasticity indices between 12 and 38, indicative of low to high expansion potential (Nelson and Miller, 1992). In most of the explorations, clays were generally moist to wet, indicating that if overlying soils were removed the clay soils would tend to shrink if allowed to dry out. The layers of clay soils present at depth and below the ground water table also exhibit some consolidation potential when loaded.


7.0 SUMMARY OF ENGINEERING ANALYSES AND CALCULATIONS

All geotechnical design calculations were performed in accordance with NDOT and AASHTO methodologies. Results of all analyses are contained in Appendix D.

8.0 RECOMMENDATIONS The earthwork on this project will result in excess cut that will need to be disposed of off site. There should be sufficient quantities of embankment cut to satisfy fill requirements on this project such that the re-use of native cut should not be necessary. For the purposes of this report, clay soils are defined as native soil materials with a fines content of 35 percent or greater and a plasticity index of 15 or higher, while fine grain soils are defined as native soil materials with a fines content of 40 percent or greater and a plasticity index less than 15. Granular soils are those not defined by the above criteria. Design of the proposed pavement sections has been performed by the Nevada Department of Transportation (NDOT). Based on information supplied by CH2M HILL (2008), the mainline pavement section will match the existing pavement section that consists of 12 inches of Portland cement concrete, which overlies 3 inches of Type 2C asphalt pavement that is underlain by 6 inches of Type 1, Class B, aggregate base. The pavement section from FS 10+41.38 to FS 12+62.10 will consist of 8 inches of Portland cement concrete underlain by 3 inches of Type 2C asphalt pavement that is underlain by 6 inches of Type 1, Class B, aggregate base. For all other ramps and roadways, the pavement section will consist of ¾ inches of open-grade and 6 inches of Type 2C asphalt concrete overlying 12 inches of Type 1, Class B, aggregate base. This base layer will be underlain by a geogrid, which will in turn be underlain by an additional 12 inches of Type 1, Class B, aggregate base. A non-woven geotextile will be placed below the bottom aggregate base section. For the purposes of this report, these structural sections will be known as the pavement section. All construction shall be performed in accordance with NDOT Standard Specifications (2001), except where amended as noted below.


8.1 Site Grading and Earthwork 8.1.1 Stripping Where vegetation is present, a stripping depth of 3 to 4 inches should be anticipated. Large roots (greater than 6 inches in diameter) should be removed to the maximum depth possible. 8.1.2 Subgrade/Foundation Preparation Except beneath utilities, all clay and fine grain soils shall be separated from overlying structural improvements. Footings will require 3 feet of separation from underlying clay/fine grain soils, while concrete flatwork and pavement sections will require 18 inches of separation. This may require additional excavated depth for retaining walls in areas of cut where improvements extend to the wall face. The width of over-excavation should extend laterally from the edge of footings and asphalt pavement sections a minimum of 3 feet, while the width of over-excavation should extend laterally from the edge of concrete flatwork a minimum of 2 feet. The required separation may be achieved by any combination of site filling and/or over-excavation and replacement. Based on laboratory test results, over-excavation will be limited to areas where native clay and fine grain soils will be encountered such that over-excavation in areas of existing embankment is not anticipated. Based on preliminary roadway profiles, areas of over-excavation should be anticipated during subgrade preparation on the southbound (“FS”) and northbound (“FN”) frontage roads, Meadowood Mall Way (“MW”), the southern portions of the southbound (“RC”) and northbound (“RD”) ramps and beneath concrete cantilever retaining wall foundations. Based on the complex stratigraphy of the native soil materials and the varying finish grade profile of the roadway and retaining wall improvements, delineation of areas requiring over-excavation should be made during construction once subgrade elevations have been established, and potholing areas to host concrete cantilever retaining wall foundations should be performed to verify adequate separation from native clay and fine grain soils. This will greatly minimize the amount of over-excavation and associated construction costs, as oppose to specifying a blanket over-excavation along entire roadway and retaining wall profiles. This can be accounted for in the engineer’s estimate by assuming that 50 percent of the subgrade in this area will require over-excavation. Clays to be left in place and covered with fill should be moisture-conditioned to 2 to 4 percent over optimum for a minimum depth of 12 inches. This moisture level will significantly decrease the magnitude of shrink-swell movements in the upper foot of clay. The high moisture content


must be maintained by periodic surface wetting, or other methods, until the surface is covered by at least one lift of fill. If allowed to dry out, subsequent expansion of clay soils beneath structural improvements could significantly affect the performance of the improvement. The roadway profile along Meadowood Mall Way, the southbound exit ramp, and the southbound frontage road will extend well below original ground elevations. Ground water elevations in this area fluctuate depending on the level of winter precipitation and upslope irrigation practices as discussed previously. Test results indicate native soil samples present at depth near proposed Meadowood Mall Way finish grade elevations typically exhibit in situ moisture contents well above optimum moisture content. As a result, subgrade soils will typically exhibit over-optimum moisture content at depth that would preclude proper compaction unless substantial moisture conditioning is performed. In addition, isolated areas of seepage could be encountered depending on the finish subgrade elevations and time of year of construction. Therefore, a blanket drain should be constructed in this area in order to minimize impacts to the construction schedule, provide a stable subgrade on which to construct the pavement section, and to allow for hydraulic relief beneath the pavement section. Once in place, the pavement section can be constructed directly on this layer. Detailed design information for the blanket drain is provided in the Site Drainage section below. The blanket drain section referenced above can also be used in other areas as a subgrade stabilization layer where a stable construction platform cannot be achieved beneath the proposed improvements, in particular pavement sections. When constructed, the blanket drain section can be incorporated into the recommended separation requirement outlined previously. Laboratory testing has been performed on representative samples of existing embankment material in areas of proposed mainline widening in order to determine the suitability of these materials in supporting the proposed pavement section. The results of the laboratory testing indicate the existing embankment material in these areas exhibits an R-value well in excess of 45 such that the proposed mainline pavement section can be constructed directly on the existing embankment. 8.1.3 Temporary Cut Slopes Temporary trenches and excavations with near-vertical sidewalls should be stable to a depth of approximately 5 feet. Temporary trenches and excavations are defined as those that will be open for less than 24 hours. Excavations to greater depths will require shoring or laying back of sidewalls to maintain adequate stability.


All trenching and excavation shall be performed in accordance with OSHA standards. On the basis of our exploration, the native site soils are predominately Type B, while the existing embankment materials can be considered Type C (Federal Register, 1989). Any area in question should be examined by qualified personnel during construction. Regardless of excavation soil type or required trench slopes or shoring, payment quantities shall be determined per NDOT Standard Plans (2007). Some zones of clean granular backfill or drain rock associated with installation of utilities or other improvements may be encountered, and may need to be supported or the material could ravel into the excavations. The contractor should be prepared for local layers which may retain surface seepage or perched water levels from precipitation or adjacent landscaping irrigation. These areas may require opening up with a stable soil slope for a period of time until water has drained, before a steeper slope can be excavated. 8.1.4 Embankment Stability 8.1.4.1 Global Stability Slope stability analyses were performed to confirm stability of the freeway at critical cross sections including areas where 1.5H:1V slope ratios are being considered in and around the proposed light towers at the Meadowood Mall Way bridge (cut slopes). In addition, global stability checks were performed for several of the planned retaining walls. Based on laboratory testing performed on a representative sample of existing embankment material obtained from the proposed light tower area, an angle of internal friction of 30 degrees and 400 per square foot (psf) cohesion was assigned to the existing embankment material when analyzing 1.5H:1V slope ratios. This value is conservative as the material was screened on a No. 10 sieve prior to testing, which removes the effects of the larger particles from the test. In addition, only a portion of the measured cohesion was used in the analysis. For all other cases, an angle of internal friction of 34 degrees and no cohesion was assigned to the embankment fill as this value is conservative in relation to the test results. Laboratory testing performed on native granular soils indicate these materials generally exhibit an angle of internal friction of 34 degrees and 0 to 700 psf cohesion; however, native soils were conservatively assigned an angle of internal friction of 28 degrees and 200 psf cohesion for the purpose of slope stability analyses as these values reflect the lowest values measured for native clay and/or fine grain soils. The assumed soil properties used in the slope stability analyses are summarized in Table 4 (Soil Properties Used in Slope Stability Analyses).


TABLE 4 - SOIL PROPERTIES USED IN SLOPE STABILITY ANALYSES

Condition Analyzed Angle of Internal Friction (degrees)

Cohesion (psf)

Embankment, 2H:1V or flatter slope ratio

34 0

Embankment, 1.5H:1V slope ratio 30 400 Native ground 28 200

Static and seismic slope stability analyses were performed based on the procedures described in FHA (2002) using the SLIDE (Rocscience, 2006) program. The results of the analyses are summarized below in Table 5 (Slope Stability Analyses Results), and contained in Appendix D.2 (Embankment Stability Analyses) for embankment slopes and Appendix D.12 (Soil Nail Wall Design Analyses) for soil nail wall areas. Where the 1.5H:1V slopes will be constructed above soil nail walls, the steepened slope was accounted for in the design of the soil nail wall as discussed in the Soil Nail Wall Design section below.


TABLE 5 - SLOPE STABILITY ANALYSES RESULTS

Case Factor of Safety

(Static) Factor of Safety (Pseudo-Static)

Meadowood soil nail walls at bridge abutment, 45-foot-long nails at 4 feet vertical and 9 feet-4 inch horizontal spacing

1.66 1.24 (0.25g)

7-foot-high soil nail wall with 2H:1V embankment slope above the walls (23 feet), 15-foot-long soil nails spaced at 5 feet horizontally and vertically

1.96 1.94 (0.25g)


1.65 1.37 (0.25g)


1.49 1.20 (0.25g)

Wall 13RD 10+83, 6 feet high soil nail wall. Composite 24-ft-high 2H:1and 1.5H:1V slope above wall.

2.49 (circular) 2.45 (block)

1.75 (circular, 0.20g) 1.72 (block, 0.20g)

kyield = 0.63g Wall 30RD, maximum concrete cantilever wall at top of slope above 2H:1V slope (“X” 314+20) embankment

1.56 (circular) 1.59 (block)

1.04 (circular, 0.2g) 1.08 (block, 0.2g)

kyield = 0.23g A higher seismic acceleration was used for soil nail walls due to the soil nail wall design methodology.

The results indicate that the required minimum static factor of safety of 1.50 (1.53 for LRFD design) will be satisfied. In addition, the subject slopes will also typically exhibit a pseudo-static factor of safety greater than 1.1, which satisfies FHA (2002) design criteria. As noted below, expanded polystyrene (EPS) geofoam will be used to construct select embankments on this project. Seismic external stability of geofoam embankments is governed by global failure of typically weak (soft clay) foundation soil. As the foundation materials on this project exhibit adequate strength to maintain sufficient factors of safety with respect to slope stability for 2H:1V embankment slope ratios as noted above in Table 5, geofoam embankments constructed at a maximum 2H:1V slope ratio will exhibit adequate static and pseudo-static factors of safety with respect to external embankment stability (TRB, 2004). Internal static and pseudo-static stability of the geofoam embankment is controlled by the shear resistance between the pavement system and the geofoam interface. In order to provide sufficient shear resistance to maintain internal stability, the embankment fill/geofoam interface strength needs to be a minimum of 15 degrees. This value is easily obtained when soil cover is placed directly over the top of the


geofoam, but care must be taken when specifying any geomembrane protective barrier to ensure such interface strength will be maintained. 8.1.4.2 Erosional Stability In addition to global stability of the embankment slopes, erosional stability must also be maintained. For the proposed 1.5H:1V cut slopes around the proposed light towers and the South McCarran Boulevard and South Virginia Street widened corners, the architectural design calls for Class 150 rip rap (Section 706.03.05, NDOT 2001) that could also provide erosional stability. Prior to rip rap placement, a non-woven geotextile (Section 731, NDOT, 2001) should be placed on the prepared embankment face. A minimum 18-inch-thick rip rap layer should then be placed. 8.1.4.3 Settlement Embankment fills up to approximately 20 feet in height will be constructed immediately adjacent to the existing Hilton Inn underpass structure, and the underpass structure itself will be backfilled as a part of this project. As settlement of this structure would also induce differential settlement across the existing mainline, settlement analyses were performed to estimate the amount of potential settlement associated with a 20-foot-tall embankment section and backfilling the structure. The results of the analyses indicate that a total settlement in excess of 2 inches would be experienced beneath the fill assuming that only native granular materials are present beneath the embankment section. As layers of clay soils are known to be present in the area, the actual total settlement would likely be much greater. Results of the settlement analyses are contained in Appendix D.2. Based on the above discussion, EPS geofoam should be used to backfill the existing culvert structure and construct the embankment is this area as well. Design of the geofoam followed the procedures recommended by the Transportation Research Board (TRB, 2004). Loading information was provided by CH2M HILL. In summary, live load due to vehicular traffic varies between 352 psf and 195 psf at the top of the existing box culvert based on an overlying soil cover of 4 and 5.8 feet, respectively. Taking into account the weight of the existing pavement section, the underlying soil, the weight of the concrete box culvert lid, and up to 18 inches of pneumatically placed concrete mortar on top of the underlying geofoam, a total dead load between 1,100 psf and 1,316 psf will need to be supported by the geofoam. Based on this input information and a factor of safety of 1.2 (TRB, 2004), the geofoam needs to exhibit a minimum elastic limit stress of 1,813 psf (12.6 psi). Therefore, an EPS 100 geofoam with an elastic limit stress of 14.5 psi is suitable for use in this application. Outside the limits of the Hilton Inn


underpass structure, the height of overlying embankment fill should not exceed 8 feet in order to minimize settlement beneath the fill and stress on the geofoam blocks to acceptable levels. Supporting calculations are contained in Appendix D.2. 8.1.4.4 Construction Considerations In order to minimize potential differential settlement of the overlying mainline, backfilling of the Hilton Inn underpass shall involve placement of EPS geofoam from the base of the underpass structure up to a height that allows for practical placement by construction workers, while at the same time minimizes the void between the top of the EPS geofoam and the top of the culvert. The remaining void between the top of the underpass structure and the geofoam shall be filled by pumping pneumatically placed concrete mortar (Section 660, NDOT, 2001) from the low end out using tremie methods to completely fill the void. The geofoam should extend out past the limits of the box culvert in both the longitudinal and transverse direction. In the transverse direction, the geofoam should underlie the embankment section so that no more than 8 feet of embankment fill will be placed over the geofoam. In the longitudinal direction, the geofoam should extend a minimum of 40 and 50 feet beyond the limits of the existing box culvert on the east and west sides of the mainline, respectively. No more than 8 feet of embankment fill shall be placed over the geofoam within these limits. The initial lifts of geofoam block shall be placed on a relatively planar surface that exhibits a vertical deviation of no more than 0.4 inches over any 9.8-foot horizontal distance (TRB, 2004). The blocks shall be placed so that all vertical and horizontal joints are tight. Care shall be taken so that the block surfaces are not subjected to any direct vehicular or construction equipment traffic during or after block placement. Blocks shall not be placed above blocks on which ice has developed on the surface. At no time shall heat or open flame be used near the blocks. Overlying soil or aggregate base shall be pushed onto the geofoam blocks using appropriate construction equipment such as a bulldozer or a front-end loader. A minimum of 12 inches of soil cover over the blocks must be in place prior to compaction of the overlying soil. In order to prevent degradation of the geofoam blocks due to fuel spills, a geomembrane shall be placed directly below the pavement section outside the limits of the existing box culvert. The geomembrane shall consist of an 8130 XR-5 geomembrane.


8.1.5 Use of Materials Testing was performed on representative samples of existing embankment in and around the proposed Meadowood Mall Way structure and areas of proposed mainline widening. The test results indicate the existing embankment materials exhibit an R-value in excess of 45 such that these materials are considered suitable for re-use as borrow. There could be, however, areas within the existing embankment material where the materials may not exhibit an R-value of 45 such that testing during construction should be performed to verify acceptability. Based on the results of laboratory testing, surficial native soils with an appreciable fines content (i.e. 30 percent or more) generally exhibit R-values between 2 and 17, which does not satisfy NDOT requirements for borrow. In addition, the identification and segregation of native granular soils from native clay/fine grain soils would be difficult. Since there should be sufficient embankment cut to satisfy fill requirements on this project, native soils should not be used for borrow but can be used as fill in nonstructural (i.e. landscaping) areas. 8.1.6 Drainage As noted above in the Subgrade/Foundation Preparation section, a blanket drain will be constructed in and around Meadowood Mall Way and its intersection with the southbound exit ramp (“RC”) and the southbound frontage road (“FS”). The drain shall consist of placing a geotextile (Section 731, NDOT, 2001) at the base of over-excavation limits (i.e. 18 inches beneath the pavement section) that will be covered by 18 inches of compacted Type 1 drain backfill (Section 704.03.01, NDOT, 2001). The blanket drain shall extend from “MW” 13+50 to 15+00; from “FS” 33+50 to “MW”; and from “MW” to “RC” 10+90. The blanket drain in Meadowood Mall Way shall be hydraulically connected the proposed storm drain manhole at “MW” Station 15+95. This can be accomplished by bedding and backfilling the storm drain line with Type 2 drain backfill from “MW” 13+50 (the beginning of the blanket drain) to the manhole at “MW” Station 15+95. Within the limits of the blanket drain, the Type 2 drain backfill for the storm drain line should be extended up to the base of the blanket drain. The ponding of water on finish grade or at the edge of pavements should be prevented by proper grading.


8.2 Foundations The Meadowood Mall Way bridge foundations and piers for the South McCarran Boulevard and South Virginia Street bridges are proposed to be built on drilled shafts, due to the complexity of the Meadowood Mall Way bridge and to reduce settlement potential for the other bridges. Retaining wall types have been selected for the project and will include conventional concrete cantilever walls, soil nail walls, drilled shafts with concrete soldier pile extensions and CIP concrete lagging walls, and a secant pile wall. 8.2.1 Meadowood Mall Way Bridge Foundations 8.2.1.1 Foundation Type Selection The base of the Meadowood Mall Way bridge abutments will be approximately 8 feet below mainline finish grade, immediately adjacent to a planned soil nail wall that will be approximately 14 feet tall. As the surcharge load on the soil nail wall from conventional spread footings would be significant, drilled shafts are preferred to support the abutment loads. The drilled shafts will be installed in a single row with fixed-head conditions to resist abutment rotation. The exterior of the drilled shafts will be less than 6 inches from the back of the underpass wall facing. The drilled shafts will transmit vertical loads from the abutments to below the roadway level, and then start developing compressive capacity in native ground. This structure will be designed according to LRFD methods (AASHTO, 2007). 8.2.1.2 Abutment Drilled Shaft Compressive Capacity Nominal and factored compressive resistances are provided on Plate A.4 (Drilled Shaft Compressive Resistance, Meadowood Mall Way Bridge) for 3-foot-diameter drilled shafts. Drilled shaft design was performed using the O’Neill and Reese methods (AASHTO, 2002). The factored compressive resistances shown on the plate include a resistance factor of 0.45 to 0.65 for side friction, and 0.45 to 0.55 for tip bearing, depending on the soil characteristic of each layer. Results of the analyses are contained in Appendix D.3 (Meadowood Mall Way Bridge Abutment Drilled Shaft Axial Loading Analyses). Settlement compatibility was estimated for 50-foot-deep drilled shafts using the displacement/compatibility method in AASHTO (2002). Based on design axial loads, overall


displacement of the top of drilled shaft would be approximately 0.1 inch based on service loads, with approximately 90 percent of the load supported by side friction and 10 percent supported by end bearing. 8.2.1.3 Abutment Drilled Shaft Lateral Load Analysis Based on discussions with CH2M HILL, lateral loading in the transverse direction will be the critical condition for the drilled shafts. As the outermost drilled shaft will be near sloping embankment that would reduce the lateral load carrying capacity of this foundation element, it was assumed that the leading drilled shaft in the direction of loading for each abutment would not provide any lateral load capacity. This allowed the analysis to be simplified such that level ground conditions were assumed. The ability of the drilled shafts to resist lateral loads, including seismic and wind loading, was analyzed using the Strain Wedge Model (SWM) computer program (Ashour, Norris and Pilling, 1998). The SWM program uses p-y characterization of soil/drilled-shaft interaction to analyze the pier as a “beam on elastic foundation.” The p-y curve is developed from soil strength parameters, shaft diameter, shaft bending stiffness, and shaft-head conditions. Drilled shaft group effects were considered for a single row of 3-foot-diameter drilled shafts spaced at 9 feet, 4 inches on center in the transverse direction. Drilled shaft heads were analyzed as fixed, where fully fixed conditions are present in the transverse direction, and a specified moment is applied to drilled shafts in the longitudinal direction. In order to determine drilled shaft stiffness, axial reinforcement was assumed to be 1 percent of the drilled shaft area and the concrete was assumed to exhibit a compressive strength of 4,000 pounds per square inch (psi). The reinforcing steel was assumed to exhibit a yield strength of 60 kips per square inch (ksi). The results of the lateral loading analyses are summarized on Plate A.5 (Lateral Load Versus Drilled Shaft Group Deflection, Meadowood Mall Way Bridge), Plate A.6 (Maximum Drilled Shaft Moment Versus Drilled Shaft Group Deflection, Meadowood Mall Way Bridge), Plate A.7 (Drilled Shaft Displacement Versus Distance Below Abutment, Meadowood Mall Way Bridge), and Plate A.8 (Drilled Shaft Moment Versus Distance Below Abutment, Meadowood Mall Way Bridge). Supporting calculations are contained in Appendix D.4 (Meadowood Mall Way Bridge Abutment Drilled Shaft Lateral Loading Analyses).


8.2.1.4 Construction Considerations The drilled shafts at the Meadowood Mall Way bridge location will extend through existing embankment fill and into native soils. Cobbles were encountered within the embankment fill during site exploration and should be anticipated during shaft excavation. Depending on the time of year of construction, fluctuation of ground water levels in the drilled shaft excavations should be expected. During installation of the drilled shafts, static ground water and/or ground water flowing in lenses of native granular soils may be encountered. Exposing the native soils will tend to cause caving of the sides of the drilled shaft excavations. Therefore, drilled shaft installation should anticipate lenses of caving sands and gravels, and temporary steel casing or the use of drilling slurry should be anticipated. The use of a water-head drilling technique is not considered appropriate on this project. Cleaning of shaft bottoms should include the use of a clean-out bucket in order to provide a shaft base free of loose material. 8.2.2 Meadowood Mall Way Light Towers 8.2.2.1 Foundation Type Selection Due to space limitations and significant loading conditions, the Meadowood Mall Way light towers will be supported by drilled shaft foundations. The pile head elevation will be at an elevation of 4,481.60 feet, but the drilled shaft foundation will be located behind a soil nail wall with a sidewalk elevation of 4,473.60 feet. The light tower foundation will be designed according to LRFD methods (AASHTO, 2007). 8.2.2.2 Drilled Shaft Compressive Capacity As these foundations are in the same location as the proposed shaft foundations for the Meadowood Mall Way bridge abutment foundations, the design information presented on Plate A.4 is applicable for the light tower foundations drilled shafts. 8.2.2.3 Drilled Shaft Lateral Load Analysis As these foundations are in the same location and extend above finish grade as the proposed drilled shaft foundations for the Meadowood Mall Way bridge abutment foundations, the design information presented on Plates A.5, A.6, A.7, and A.8 is applicable for the light tower foundations drilled shafts.


8.2.2.4 Construction Considerations The drilled shafts at the Meadowood Mall Way light tower locations will extend through existing embankment fill and into native soils. Cobbles were encountered within the embankment fill during site exploration and should be anticipated during shaft excavation. Depending on the time of year of construction, fluctuation of ground water levels in the drilled shaft excavations should be expected. During installation of the drilled shafts, static ground water and/or ground water flowing in lenses of native granular soils may be encountered. Exposing the native soils will tend to cause caving of the sides of the drilled shaft excavations. Therefore, drilled shaft installation should anticipate lenses of caving sands and gravels, and temporary steel casing or the use of drilling slurry should be anticipated. The use of a water-head drilling technique is not considered appropriate on this project. Cleaning of shaft bottoms should include the use of a clean-out bucket in order to provide a shaft base free of loose material. 8.2.3 South McCarran Boulevard Bridge Foundations 8.2.3.1 Foundation Type Selection Shallow spread footings and drilled shafts were considered for the design of the South McCarran Boulevard bridge widenings. Extension of the existing spread footing abutments to support the widening structures is feasible. For the pier foundations, however, the settlement associated with spread footings could potentially cause excessive differential settlement between the new and widened bridges. Pier footings would also typically be founded at greater depth than drilled shaft caps, and therefore would require wider excavations that would have a greater impact on traffic on existing South McCarran Boulevard. As a result, 3, 7, and 8-foot-diameter drilled shaft foundations were considered. Due to clay layers present at depth, a single, large-diameter drilled shaft would have to extend to considerable depth in order to develop sufficient capacity. Therefore, a 2 by 2 group of 3-foot-diameter drilled shafts was selected as the foundation system for the piers. The South McCarran Boulevard Bridge widenings will be designed using ASD methods (AASHTO, 2002) to match the design methodology of the existing bridge. 8.2.3.2 Abutment Foundation Design Abutments will be supported on new and existing embankment fill that slopes down away from the abutment foundations. Assuming an angle of internal friction of 34 degrees and no cohesion


for the new and existing embankment fill, an allowable bearing capacity of 3.5 kips per square foot (ksf) is appropriate for use in design of the abutment foundations. This value takes into account reduced bearing capacity factors for footings near the crest of a slope (AASHTO, 2002), an ultimate bearing capacity of 11.5 ksf, and a factor of safety of 3.0. Settlement of ¾ inch or less is expected to occur during construction as the fill and loads are placed, including any settlement associated with the wedge of new embankment fill. Results of the analyses are contained in Appendix D.5 (South McCarran Boulevard Bridge Abutment Analyses). Differential settlement of the abutment foundation is not expected to exceed ½ inch. Based on conversations with CH2M Hill design engineers, lateral seismic design of abutment foundations will follow seismic design criteria recommended by the California Department of Transportation (CalTrans) in Section 7.8.1 of the Seismic Design Criteria (CalTrans, 2006). Black Eagle Consulting, Inc. has reviewed these design criteria, and considers them appropriate for use. 8.2.3.3 Pier Drilled Shaft Compression and Uplift Capacity Allowable axial compression and tension capacities for 3-foot-diameter drilled shafts are provided on Plate A.9 (Allowable Pier Drilled Shaft Capacity, South McCarran Boulevard Bridge) and contained in Appendix D.6 (South McCarran Boulevard Bridge Pier Drilled Shaft Axial Loading Analyses). Drilled shaft design was performed using the O’Neill and Reese methods (AASHTO, 2002). Due to decreasing tip resistance and the potential for adverse settlement of shafts overlying clay layers present at depth, the drilled shafts should be a maximum of 23.5 feet in length, assuming the pile head elevation will be approximately 7 feet below finish grade. The compression capacities shown on the plate should be reduced by a factor of safety of 2.5 for static conditions, while the tension capacities can be reduced by a factor of safety of 1.25 for seismic conditions to account for some reduction in the effective overburden pressure during seismic events. Settlement compatibility was estimated for 23.5-foot-deep drilled shafts using the displacement/compatibility method in AASHTO (2002). Based on design axial loads, overall displacement of the top of pier would be approximately 0.1 inch based on service loads, with approximately 91 percent of the load supported by side friction and 9 percent supported by end bearing.


8.2.3.4 Pier Drilled Shaft Lateral Load Analysis The ability of the drilled shafts to resist lateral loads, including seismic and wind loading, was analyzed using the SWM computer program (Ashour, Norris and Pilling, 1998). A 2 by 2 group of 3-foot-diameter drilled shafts spaced at 3 pile diameters on center was analyzed. In order to determine drilled shaft stiffness, axial reinforcement was assumed to be 1 percent of the drilled shaft area and the concrete was assumed to exhibit a compressive strength of 4,000 psi. The reinforcing steel was assumed to exhibit a yield strength of 60 ksi. Both fixed and free-head conditions were analyzed for use in the structural design. The results of the lateral loading analyses are summarized on Plate A.10 (Lateral Load Versus Drilled Shaft Group Deflection, South McCarran Boulevard Bridge), Plate A.11 (Maximum Drilled Shaft Moment Versus Drilled Shaft Group Deflection, South McCarran Boulevard Bridge), Plate A.12 (Drilled Shaft Displacement Versus Distance Below Cap, South McCarran Boulevard Bridge), and Plate A.13 (Drilled Shaft Moment Versus Distance Below Cap, South McCarran Boulevard Bridge). Supporting calculations are contained in Appendix D.7 (South McCarran Boulevard Bridge Pier Drilled Shaft Lateral Loading Analyses). 8.2.3.5 Construction Considerations The drilled shafts at the South McCarran Boulevard bridge widening location will extend through native granular soils. Cobbles were encountered during site exploration and should be anticipated during shaft excavation. Depending on the time of year of construction, fluctuation of ground water levels in the drilled shaft excavations should be expected. During installation of the drilled shafts, static ground water and/or ground water flowing in lenses of native granular soils may be encountered. Exposing the native soils will tend to cause caving of the sides of the drilled shaft excavations. Therefore, drilled shaft installation should anticipate lenses of caving sands and gravels, and temporary steel casing or the use of drilling slurry should be anticipated. The use of a water-head drilling technique is not considered appropriate on this project. Cleaning of shaft bottoms should include the use of a clean-out bucket in order to provide a shaft base free of loose material.


8.2.4 South Virginia Street Bridge Foundations 8.2.4.1 Foundation Type Selection Shallow spread footings and drilled shafts were considered for the design of the South Virginia Street bridge widening. Extension of the existing spread footing abutment to support the widening structure is feasible. For the pier foundations, however, the settlement associated with spread footings could potentially cause excessive differential settlement between the new and widened bridges. Pier footings would also typically be founded at greater depth than drilled shaft caps, and therefore would require wider excavations that would have a greater impact on traffic on existing South Virginia Street. As a result, 3, 7, and 8-foot-diameter drilled shaft foundations were considered. Due to clay layers present at depth, a single, large-diameter drilled shaft would have to extend to considerable depth in order to develop sufficient capacity. Therefore, a 2 by 2 group of 3-foot-diameter drilled shafts was selected as the foundation system for the piers. The South Virginia Street Bridge widening will be designed using ASD methods (AASHTO, 2002) to match the design methodology of the existing bridges. 8.2.4.2 Abutment Foundation Design The results of the analyses performed for the South McCarran Boulevard bridge abutments and the associated recommendations are applicable to this structure, and are contained in Appendix D.5. 8.2.4.3 Pier Drilled Shaft Compression and Uplift Capacity Allowable axial compression and uplift capacities for 3-foot-diameter drilled shafts are provided on Plate A.14 (Allowable Pier Drilled Shaft Capacity, South Virginia Street Bridge) and contained in Appendix D.8 (South Virginia Street Bridge Pier Drilled Shaft Axial Loading Analyses). Drilled shaft design was performed using the O’Neill and Reese methods (AASHTO, 2002). Due to decreasing tip resistance and potential for adverse settlement of shafts overlying clay layers present at depth, the drilled shafts should be a maximum of 22 feet in length, assuming the pile head elevation will be approximately 7 feet below finish grade. The compression capacities shown on the plate should be reduced by a factor of safety of 2.5 for static conditions, while the tension capacities can be reduced by a factor of safety of 1.25 for seismic conditions to account for some reduction in the effective overburden pressure during seismic events.


Settlement compatibility was estimated for 22-foot-deep drilled shafts using the displacement/compatibility method in AASHTO (2002). Based on design axial loads, overall displacement of the top of pier would be approximately 0.1 inch based on service loads, with approximately 92 percent of the load supported by side friction and 8 percent supported by end bearing. 8.2.4.4 Pier Drilled Shaft Lateral Load Analysis Lateral drilled shaft capacity for the South Virginia Street bridge can be based on the soil profile at the South McCarran Boulevard Bridge. Lateral drilled shaft analyses and results in the preceding section are therefore applicable to the bridge pier at South Virginia Street. 8.2.4.5 Construction Considerations The drilled shafts at the South Virginia Street bridge widening location will extend through native granular soils. Cobbles were encountered during site exploration and should be anticipated during shaft excavation. Depending on the time of year of construction, fluctuation of ground water levels in the drilled shaft excavations should be expected. During installation of the drilled shafts, static ground water and/or ground water flowing in lenses of native granular soils may be encountered. Exposing the native soils will tend to cause caving of the sides of the drilled shaft excavations. Therefore, drilled shaft installation should anticipate lenses of caving sands and gravels, and temporary steel casing or the use of drilling slurry should be anticipated. The use of a water-head drilling technique is not considered appropriate on this project. Cleaning of shaft bottoms should include the use of a clean-out bucket in order to provide a shaft base free of loose material. 8.2.5 Conventional Cast-In-Place Concrete Cantilever Retaining Wall Foundations 8.2.5.1 Foundation Design Concrete cantilever retaining walls with associated conventional shallow foundations will be constructed as a part of this project, and will conform to NDOT Standard Plans (NDOT, 2007). The walls will bear in both embankment and native ground. For the analyses, an angle of internal friction of 32 degrees and no cohesion was assumed for both embankment and native ground since clay and fine grain soils, where present at foundation grade, will be over-excavated and replaced with structural fill. The results of the analyses indicate the allowable and ultimate bearing capacity of the foundation materials will satisfy the design assumptions shown on Drawing B-


30.1.1 and Drawing B-30.1.3 (NDOT, 2007). Supporting calculations are presented in Appendix D.9 (Concrete Cantilever Retaining Wall Foundation Analyses). 8.2.5.2 Construction Considerations The base of concrete cantilever retaining walls will require inspection by a qualified geotechnical professional to identify the presence of any clay/fine grain soils that will require over-excavation and replacement with suitable structural fill. Potholing should also be performed to verify proper separation requirements. 8.2.6 Drilled Shaft with Concrete Soldier Beam and CIP Concrete Lagging Wall

Foundations 8.2.6.1 Drilled Shaft Compressive Capacity As these foundations are in the same general vicinity as the proposed drilled shaft foundations for the Meadowood Mall Way bridge abutment foundations, the design information presented on Plate A.4 is applicable for the retaining wall drilled shafts. 8.2.6.2 Drilled Shaft Lateral Load Analysis Lateral load analysis of these foundations will be performed by CH2M Hill using the LPILE computer program (Ensoft, Inc., 1989). For such an analysis, the designer can assume dry sand, a moist soil unit weight of 125 pounds per cubic foot (pcf), an angle of internal friction of 31 degrees, and a soil modulus of 90 pounds per cubic inch (pci). 8.2.6.3 Construction Considerations The drilled shafts for these walls will typically extend through and into native soils, although one wall (Wall 13RD) will retain existing freeway embankment. at the South Virginia Street bridge widening location will extend through native granular soils. Drilling in existing embankment may encounter cobbles. Depending on the time of year of construction, fluctuation of ground water levels in the drilled shaft excavations should be expected. During installation of the drilled shafts, static ground water and/or ground water flowing in lenses of native granular soils may be encountered. Exposing the native soils will tend to cause caving of the sides of the drilled shaft excavations. Therefore, drilled shaft installation should anticipate lenses of caving sands and gravels, and temporary steel casing or the use of drilling slurry should be anticipated. The use of a


water-head drilling technique is not considered appropriate on this project. Cleaning of shaft bottoms should include the use of a clean-out bucket in order to provide a shaft base free of loose material. 8.3 Retaining Walls Based on information provided by CH2M HILL, all retaining wall design will be performed using ASD methods (AASHTO, 2002). 8.3.1 Wall Type Selection Based on information provided by CH2M HILL, the project will include conventional cast-in-place, semi-gravity concrete cantilever walls; drilled shafts with concrete soldier pile extensions and CIP lagging walls; a secant pile wall; and soil nail walls. Concrete cantilever walls will be used for short retained heights in areas where there is sufficient room to temporarily slope excavations to allow construction of the walls, and for return walls at the end of other wall types. Drilled shafts with concrete soldier pile extensions and CIP lagging walls will be used where the frontage road and ramps will be in cut with respect to adjacent property lines to limit the need to over-excavate at the edge of right-of-way. A secant pile wall will be constructed for Wall 29FS, adjacent to the Nevada Highway Patrol building on the southeast side of the interchange, due to the proximity of building footings to the proposed wall and the vibration/settlement-sensitive nature of the existing building. Secant pile walls, consisting of a continuous row of adjacent reinforced concrete drilled shafts, provide considerably greater stiffness than drilled shafts with concrete soldier pile extensions and CIP lagging walls, and avoid construction issues with excavation and exposure of the in situ soil behind the wall during placement of lagging. Soil nail walls will be used where the frontage road and ramps will be in cut with respect to the freeway embankment, to avoid the need to over-excavate behind these walls and under the freeway. Wall type selection was performed by CH2M HILL. 8.3.2 Concrete Cantilever, Drilled Shafts with Concrete Soldier Pile Extensions and CIP

Lagging, and Secant Pile Walls 8.3.2.1 Lateral Earth Pressures The following recommendations are applicable for the ASD design of walls with vertical back faces and level or sloping backfill. Although test results indicate the existing embankment


material exhibits an angle of internal friction of 30 degrees and approximately 870 psf cohesion, oversize material (i.e. that larger than a No. 10 sieve) was removed from the sample prior to testing. Therefore, embankment fill was conservatively assumed to exhibit an angle of internal friction of 34 degrees, no cohesion, and a moist unit weight of 125 pounds (pcf) when developing lateral earth pressures. Laboratory testing on native soils indicate these materials generally exhibit an angle of internal friction of 34 degrees and 0 to 700 psf cohesion; however, native soils were conservatively assumed to exhibit an angle of internal friction of 32 degrees and no cohesion for the purpose of lateral earth pressure analyses. The recommended lateral earth pressures are summarized in Table 6 (Allowable Stress Design Lateral Earth Pressures Equivalent Fluid Density). Supporting calculations are presented in Appendix D.10 (Cantilever Retaining Wall Lateral Earth Pressure Analyses). Surcharge loads, including construction and traffic loads, should be added to the values presented in Table 6.

TABLE 6 - ALLOWABLE STRESS DESIGN LATERAL EARTH PRESSURES (EQUIVALENT FLUID DENSITY)

Static Earthquake Retained Slope

Active1, 3 Passive2 At-Rest3 Active1, 3,4 Passive

Level, Imported Fill 32 307 55 50 N/A

2H:1V, Imported Fill 50 807 55 Varies5 N/A

Level, Native 35 269 59 53 N/A

All values shown are in units of pounds per square foot per foot depth. 1 For walls that are free to yield at least 0.1 to 0.2 percent of the wall height. 2 The value presented has been reduced from the ultimate passive resistance using a factor of safety of 3 to limit

deflection under static conditions. 3 The value presented is an unfactored value. 4 For design of a structure under dynamic at-rest conditions, use active earthquake pressure unless walls are rigidly

restrained by soil anchors. 5 See Plate A.15 for dynamic active earth pressure coefficients for 2H:1V slopes of finite height.

In order to develop appropriate active lateral earth pressure values under seismic conditions, Wedge Analysis of Seismic Pressure (WASP) was used where Mononabe-Okabe analyses are not applicable. Plate A.15 (Seismic Active Earth Pressure Values [Equivalent Fluid Pressure] Versus Wall Height and Maximum Slope) provides active earthquake coefficients, Kae, for 2H:1V slopes for varying wall and embankment heights using WASP. While short walls (at the base of high embankment) have very high active earthquake coefficients, the seismic forces for shorter walls are still much lower than for taller walls supporting the same embankment height since the overall


wall pressure is a function of the square of the wall height (H2). Supporting calculations are present in Appendix D.11 (Wedge Analyses of Seismic Pressure). Lateral loads will be resisted by friction along the base of retaining wall footings and by passive resistance against buried foundation walls or wall keys. As described in the Subgrade/Foundation Preparation section above, clay/fine grain soils shall be over-excavated from beneath concrete cantilever retaining walls when encountered at foundation subgrade elevation. Therefore, foundation wall footings cast directly on properly prepared native granular soils, borrow, selected borrow, and/or granular backfill may be designed using a coefficient of base friction of 0.45. 8.3.2.2 Construction Considerations A pre- and post-construction survey of the existing NHP building, as well as deformation monitoring of the secant pile wall, will also be necessary. 8.3.3 Soil Nail Walls 8.3.3.1 Soil Nail Wall Design Soil nail walls have been designed in accordance with FHA (2003) and AASHTO (2002). Analysis was performed using SNAILWin 3.10 (CalTrans, 2007). Assumptions and design parameters are summarized on Table 7 (Soil Properties and Assumptions Used in Soil Nail Wall Design), and included analyzing the proposed walls for both long-term (static) and short-term (dynamic) loading conditions. For existing embankment, values were assumed using the same rationale as described above in the previous section. For native soils, the direct shear test with the lowest angle of internal friction was used (28 degrees), and the cohesion was greatly reduced from the measured value (approximately 20 percent of measured value).


TABLE 7 - SOIL PROPERTIES AND ASSUMPTIONS USED IN SOIL NAIL WALL DESIGN Property Embankment Fill Native Soils

Unit Weight (pcf) 125 125 Long-Term Design Strength c = 0 phi = 34 degrees C = 200 psf, phi = 28 degrees Short-Term Design Strength (earthquake)

c = 0 phi = 34 degrees C = 1,500 psf, phi = 0 degrees

Ultimate bond stress (psi) 15 7 Assumptions: 1. A 250 psf traffic surcharge load was applied, where applicable. 2. The horizontal seismic acceleration should be 0.5 and 0.67 Amax; a kh = 0.25g was used in the analysis (FHA, 2003). 3. Based on discussions with CH2M HILL, an additional load of 6 kips per lineal foot additional horizontal load was applied under both static and seismic conditions for the soil nail wall beneath the Meadowood Mall Way bridge to reflect lateral load from superstructure during a seismic event.

Based on the material properties and assumptions noted in Table 7, soil nail wall design sections were developed as shown in Table 8 (Soil Nail Wall Design Sections). The design assumed a soil nail hole diameter of 8 inches and a hole inclination of 15 degrees. In addition, soil nail walls that will retain embankment fill that slopes up away from the wall at both a 1.5:1V and 2H:1V slope ratio were analyzed. Supporting calculations are presented in Appendix D.12 (Soil Nail Wall Design Analyses).


TABLE 8 - SOIL NAIL WALL DESIGN SECTIONS

Maximum Spacing (ft) Design Soil Nail Force (kips)

Wall Station Slope Above Wall Height

(ft) Horizontal Vertical

Minimum Soil Nail

Length (ft) Static Loading

Seismic Loading

Meadowood Bridge

Abutment “X” 294+95 and 296+06

Surcharge due to abutment lateral

loads ≤15 9.33

4 (4 rows minimum)

45 28.8 52.2

“RC” 10+67 to 12+87 RT 2H:1V ≤18 5 5 32 15.1 31.1 12 RC

“RC” 12+87 to 13+12 RT 2H:1V ≤14 5 5 26 9.9 20.9

13 RD “RD” 10+83 to 12+74 LT 2H: 1V ≤10 5 5 26 9.9 20.9

“FN” 20+43 to 22+23 LT 2H:1V ≤12 5 5 26 9.9 20.9 21 FN

“FN” 22+23 to 22+83 LT 2H:1V ≤7 5 5 15 3.7 17.0

“FS” 30+88 to 31+25 RT 2H:1V ≤7 5 5 15 3.7 17.0 30 FS

“FS” 31+25 to 33+49 RT 2H:1V ≤14 5 5 26 9.9 20.9

“FN” 30+50 to32+55 LT 2H:1V ≤14 5 5 26 9.9 209

“FN”32+55 to 33+25 LT 2H:1V ≤15 5 5 32 15.1 31.1 31 FN

“FN” 33+25 to 34+20 LT approx 1.5H:1V and 2H:1V 11-15 5 4 35 10.1 25.7

Notes: 1. The maximum vertical distance from the top of the soil nail wall to the first soil nail should not exceed 2 feet. 2. Soil nails should be corrosion protected for permanent ground contact. 3. Soil nails should be #10 bars (1.27-inch-diameter, A722 steel).


8.3.3.2 Construction Considerations Construction of the soil nail walls beneath the Meadowood Mall Way bridge will be performed after the bridge deck has been constructed and in conjunction with the mass excavation of the existing embankment fill. As a result, limited head room will be available for the initial rows of soil nails such that limited access drilling equipment will be necessary. In addition, installation of the soil nails will most likely require mechanical coupling of shorter nail sections. Soil nails on this project will extend into existing embankment fill and native soils. Cobbles were observed within the embankment fill and should be anticipated during drilling. Depending on the time of year of construction and the corresponding ground water levels, installation of the soil nails into native soils may encounter ground water flowing in lenses of native granular soils. These materials will tend to cave under such conditions. Soil nails shall be designed with corrosion protection sufficient to achieve their structural design life. 8.3.4 Additional Retaining Wall Design Considerations Excavated wall types, particularly soil-nail, secant pile, and drilled shafts with concrete soldier pile extensions and CIP lagging walls, should be designed to allow for temporary over-excavation at the toe of the wall to allow for over-excavation of clay and fine grain soils and placement of borrow or structural fill under improvements (pavement sections and concrete flatwork). This additional depth of over-excavation is relatively minor relative to wall height, and typically can be accommodated by a temporary reduction in factor of safety for construction conditions. For soil nail walls, the depth of cast-in-place concrete facing should extend to the base of the adjacent pavement section. For drilled shafts with concrete soldier pile extensions and CIP lagging walls, the depth of lagging should also extend to the base of the pavement section. To ensure adequate performance, all walls should be designed to provide drainage behind the face of the wall so that hydrostatic pressure does not build up behind the wall. The conventional NDOT weep-hole detail is appropriate for concrete cantilever walls and drilled shafts with concrete soldier pile extensions and CIP lagging walls that will be backfilled with granular backfill. Soil nail walls should have strips of geocomposite drain layers installed between the soil nails on the soil face immediately behind the initial shotcrete. These strip drains, which should provide at least 30 percent coverage of the wall face, would be extended continuously to the bottom of the wall. For most locations, seepage would be directed through the temporary shotcrete and permanent wall facing with a weep hole drain fixture at each strip drain location.


Under the Meadowood Mall Way bridge, it may be more desirable to connect the strip drains to the blanket drain in this area to avoid possible seepage on the sidewalks in the underpass. 8.4 Sign and Lighting Foundations Lighting pole locations can be designed using the foundation recommendations in the standard plans (NDOT, 2007 Sheet T-30.1.11). Lighting standards located on existing or proposed embankment, or on native ground from 200 feet north of Meadowood Mall Way to the northern project limits, can be designed for sand conditions. Lighting standards from 200 feet north of Meadowood Mall Way to the southern project limits can be assumed to be supported on stiff clay. Overhead signs can be constructed according to the standard plans using spread footings (NDOT, 2007, Sheet T-36.1.1) for those located on existing or proposed embankment, or on native ground from 200 feet north of Meadowood Mall Way to the northern project limits. For those located in native ground from 200 feet north or Meadowood Mall Way to the southern project limits, drilled shaft foundations (NDOT, 2007, Sheet T-36.1.12) should be used. Drilled shafts for several of the sign and lighting foundations will extend through both existing embankment and native soils. Drilling in existing embankment may encounter cobbles. Depending on the time of year of construction, fluctuation of ground water levels in the drilled shaft excavations should be expected. During installation of the drilled shafts, static ground water and/or ground water flowing in lenses of native granular soils may be encountered. Exposing the native soils will tend to cause caving of the sides of the drilled shaft excavations. Therefore, drilled shaft installation should anticipate lenses of caving sands and gravels, and temporary steel casing or the use of drilling slurry should be anticipated. The use of a water-head drilling technique is not considered appropriate on this project. Cleaning of shaft bottoms should include the use of a clean-out bucket in order to provide a shaft base free of loose material. 8.5 Private Driveway Pavement Sections Several new private driveways will be constructed as a part of this project. As these driveways will often be subjected to delivery truck traffic, the pavement section should satisfy City of Reno minimum standards for a collector street (City of Reno, 2006). The City of Reno specifies that this section shall consist of a minimum of 5 inches of asphalt concrete over a minimum of 8 inches of Type 2, Class B, aggregate base (Standard Specifications for Public Works Construction, 2006). A minimum of 18 inches of borrow shall underlie the pavement section at driveway locations. Depending on the subgrade soil and in situ moisture conditions present at the time of construction, a non-woven geotextile (Section 731, NDOT, 2001) may be required directly beneath the borrow


section to allow for proper compaction of the borrow layer if the construction schedule precludes moisture conditioning by scarifying and air drying.

9.0 CONSTRUCTION SPECIFICATIONS All construction shall conform to the Standard Specifications for Road and Bridge Construction (NDOT, 2001). Special provisions should include material and construction specifications for EPS geofoam, and shall satisfy the requirements of the TRB (2004). The EPS geofoam material shall exhibit a minimum block density of 1.80 pcf and an elastic limit stress of 14.5 psi. Special provisions should also include material specifications for an 8130 XR-5 geomembrane. The XR-5 geomembrane shall exhibit a minimum thickness of 30 mils, a minimum puncture resistance of 350 pounds, and a minimum breaking yield strength of 550 pounds. The special provisions shall include material specifications for geocomposite wall drains. The geocomposite wall drains shall consist of a manufactured core not less than ¼-inch thick nor more than 2 inches thick with one or both sides covered with a layer of filter fabric that will provide a drainage void. The drain shall produce a flow rate, through the drainage void, of at least 6.5 gallons per minute per foot of width at a hydraulic gradient of 1.0 and a minimum externally applied pressure of 24 psi.

10.0 RECOMMENDED CONSTRUCTION OBSERVATIONS, TESTING AND INSTRUMENTATION

The identification of native clay and fine grain soils at subgrade elevations in native soil materials shall be performed by a qualified geotechnical professional during construction in order to delineate areas requiring over-excavation. In particular, inspection shall be performed at the following locations: 1. The entire length of the southbound frontage road (“FS”); 2. The entire length of the northbound frontage road (“FN”);


3. The southbound off ramp (“RC”) between Station 10+41.00 and Station 13+60; 4. The northbound on ramp (“RD”) between Station 10+46.36 and Station 14+00; 5. The entire length of Meadowood Mall Way (“MW”); and 6. Footing excavations associated with all concrete cantilever retaining walls, except Wall

30RD. Potholing shall be included. Wall-deformation monitoring should be performed for both the secant pile wall and the adjacent NHP building. A preconstruction survey and photographs should be taken of the interior and exterior of the wall to document any existing cracks or wall movements. Crack displacement gauges should be placed on all existing wall cracks. These gauges typically consist of two clear plastic plates, which are attached on opposing sides of the crack and have a cross-hair and grid marking to allow easy reading of crack displacement. During construction, the building wall face and the top of the secant pile wall (once constructed) should have temporary benchmarks established every 20 feet and measured to determine vertical and horizontal position. Measurements should be taken initially, at least three times during secant pile installation, six times during wall excavation, and an additional three times during wall face construction. Exact measurement intervals should be determined once the contractor provides his schedule, and measurements should be at even intervals during each construction operation. Qualified geotechnical personnel shall be on site during drilled shaft installation at the Meadowood Mall Way bridge abutments and light tower foundations, South McCarran Boulevard bridge widening, and South Virginia Street bridge widening to verify the shafts encounter and are founded in materials anticipated at these locations.

11.0 STANDARD LIMITATIONS CLAUSE This report has been prepared in accordance with generally accepted geotechnical practices. The analyses and recommendations submitted are based on field exploration performed at the locations shown on Plate A.1 of Appendix A. This report does not reflect soils variations that may become evident during the construction period, at which time re-evaluation of the recommendations may be necessary. Equilibrium water level readings were made on the dates shown on Boring Logs in Appendix B of this report. Fluctuations in the water table or shallow perched ground water tables may occur due


to rainfall, temperature, seasonal runoff or adjacent irrigation practices. Construction planning should be based on assumptions of possible variations. This report has been prepared to provide information to allow the engineer to design the project. In the event of changes in the design and location of the project later than this report, recommendations should be reviewed and possibly modified by the geotechnical engineer. If the geotechnical engineer is not accorded the privilege of making this recommended review, he can assume no responsibility for misinterpretation or misapplication of his recommendations or their validity in the event changes have been made in the original design concept without his prior review. The geotechnical engineer makes no other warranties, either expressed or implied, as to the professional advice provided under the terms of this agreement and included in this report.

12.0 REFERENCES American Association of State Highway and Transportation Officials (AASHTO), 2007, LRFD

Bridge Design Specifications, Customary U.S. Units, 4th Edition. AASHTO, 2002, Standard Specifications for Highway Bridges, 17th Edition. AASHTO, 1998, Standard Specifications for Transportation Materials and Method of Sampling

and Testing, Part II. American Society for Testing and Materials (ASTM), 2005, Soil and Rock; Dimension Stone;

Geosynthetics, Volume 4.08. ASTM, 2008, Soil and Rock; Geosynthetics, Volumes 4.08, 4.09, and 4.13. Ashour, M., G. Norris, and P. Pilling, 1998, “Lateral Loading of a Pile in Layered Soil using the

Strain Wedge Model,” Journal of Geotechnical and Geoenvironmental Engineering, ASCE, Vol. 124, No. 4, pp. 303-315.

Bonham, H. F. and D. K. Rogers, 1983, Geologic Map, Mt. Rose NE Quadrangle: Nevada Bureau

of Mines and Geology, Map 4Bg. California Department of Transportation (CalTrans), 2006, Seismic Design Criteria, Version 1.4. CalTrans, 2007, Soil Reinforcement Program, Version SNAILWin 3.1D.


CH2M HILL, 2008, Preliminary Construction Plans, I-580/Meadowood Complex. Ensoft, Inc., 1989, Documentation of Computer Program LPILE, Version 3.0 Ensoft, Inc., Austin

Texas. Federal Highway Administration (FHA), 1988, Drilled Shafts, Construction Procedures and

Design Methods: Publication No. FHA-HI-88-042. FHA, 2003, Geotechnical Engineering Circular No. 7 Soil Nail Walls, FHWA-IF-03-017, March

2003. FHA, 2002, Reference Manual, Soil Slope and Embankment Design, FHWA NH1-01-026, January

2002. Federal Register, 1989, Construction Standards for Excavations, 29 CFR No. 209, Volume 54. Foundation Tech, LLC, 2007, SPT Hammer Energy Measurements Highway 395, Reno, Nevada,

Letter to Black Eagle Consulting, Inc., Reno Nevada, Dated September 14, 2007, Foundation Tech, LLC, Walnut Creek California.

Nelson, John D. and Debora J. Miller, 1992, Expansive Soils: Problems and Practice in

Foundation and Pavement Engineering, John Wiley and Sons, Inc., New York. Nevada Department of Transportation (NDOT), 2007, Standard Plans for Road and Bridge

Construction. NDOT, 2001, Standard Specifications for Road and Bridge Construction. Reno, City of, Public Works Department, Public Works Design Manual, 2006. Rocscience, Inc., 2006, Slide, v. 5.006, computer program, Toronto, Ontario. Ryall, A. and B. M. Douglas, 1976, Regional Seismicity, Reno Folio: Nevada Bureau of Mines

and Geology. Standard Specifications for Public Works Construction (SSPWC), 2006.


Szecsody, G. C., 1983, Earthquake Hazards Map, Reno NW Quadrangle: Nevada Bureau of Mines and Geology, Map 4Di.

Transportation Research Board of the National Academies (TRB), 2004, National Cooperative

Highway Research Program (NCHRP), Report 529, Guideline and Recommended Standard for Geofoam Applications in Highway Embankments.

i-580/meadowood complex improvements

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