D Geotechnical Investigation Report NFU2 Project 2_6_24.pdf

Geotechnical Investigation Report NERSC Facility Upgrade II (NFU2) Project Lawrence Berkeley National Laboratory Berkeley, California

SUBMITTED TO:

David Topete, PE, SE Lawrence Berkeley National Laboratory One Cyclotron Road, MS 76R0225 Berkeley, CA 94720 DTopete@lbl.gov

February 6, 2024

North Site (looking north)

East Site (looking west)

A3GEO, Inc. 821 Bancroft Way, Berkeley CA 94710

February 6, 2024

David Topete, PE, SE Project Manager/Projects & Infrastructure Modernization Division Lawrence Berkeley National Laboratory One Cyclotron Road, MS 76R0225 Berkeley, CA 94720 DTopete@lbl.gov

RE: Geotechnical Investigation Report NERSC Facility Upgrade II (NFU2) Project Lawrence Berkeley National Laboratory Berkeley, California

Dear Mr. Topete:

This report presents the results of A3GEO’s geotechnical investigation for the NFU2 project at the Lawrence Berkeley National Laboratory (LBNL; Berkeley Lab). The design-level geotechnical investigation described herein was authorized in December 2021 under LBNL Subcontract No.

7623192. LBNL’s NERSC1 Facility is located in Building 59 (B59), which is sited in sloping terrain along the west side of the Berkeley Hills. The NFU2 Project involves the design and construction of improvements inside and outside of B59. This geotechnical report pertains to planned improvements at two non-contiguous sites located north and east of B59.

This report and the attached materials present geotechnical data, interpretations, evaluations, and recommendations for the envisioned NFU2 project. Our investigative scope included a review of existing information, onsite observations, five new borings, and geotechnical laboratory testing.

The opinions presented in this report were developed in accordance with generally accepted geotechnical principles and practices at the time that the report was prepared. This report completes our authorized scope under Subcontract No. 7623192. A3GEO’s future geotechnical scope for the project will include reviewing contractor submittals, providing as-needed geotechnical consultation, and observing/testing the geotechnical aspects of construction.

Should you have questions or comments concerning this report or the attached materials, please do not hesitate to contact us.

Yours very truly, A3GEO, Inc.

Attachments: Report (text)

Plates Figures Appendices

1 National Energy Research Scientific Computing Center

Wayne Magnusen, P.E., G.E.

Principal Engineer Cell: (510) 325-5724 wayne@a3geo.com

A3GEO, Inc. • 821 Bancroft Way, Berkeley CA 94710

1. INTRODUCTION

This report presents the results of A3GEO’s geotechnical investigation for the NERSC Facility Upgrade II Project (NFU2 Project) at the Lawrence Berkeley National Laboratory (LBNL; Berkeley Lab). Attached to this report are a series of illustrative plates, technical figures, and appendices. A list of references is presented in Section 8.

1.01 Project Description

We obtained information about the NFU2 Project from LBNL and members of the Design Team, which includes ENERCON (A/E Team Lead), Gensler (Architecture), IDA (Structural Engineering), and JMA (Civil Engineering). LBNL’s NERSC1 Facility is located in Building 59 (B59), which is sited in sloping terrain along the west side of the Berkeley Hills (Plate 1). The NFU2 Project involves the design and construction of improvements inside and outside of B59. Outside improvements include new structures that will support air-cooled heat exchanger (ACHE) units and electrical switchgear.

This geotechnical report pertains to planned improvements at two non-contiguous sites located north and east of B59 (Plate 2) as described below.

North Site – The North Site lies within a narrow strip of land roughly bounded by Chu Road (on the west and north), Perlmutter Road (on the east), and B59 (on the south). The ground surface within the North Site slopes steeply down towards the west towards Chu Road. Planned North Site improvements include an elevated steel platform supported on drilled pier foundations connected by grade beams, underground utility installations between the North Site and B59, and relatively minor earthwork and paving on the west side of Perlmutter Road.

East Site – The East Site lies within a south-facing slope roughly bounded by B70A (on the north), the B59 cooling tower facility (on the south), and B59 (on the west). Planned East Site improvements include a two level concrete structure oriented parallel to the contours of the slope. The structure will be notched into the slope and will connect to existing B59 construction at an oblique angle. The north (upslope) side of the structure will include tied-back retaining walls at both levels.

B59 is less than 10 years old and various drawings and photographs are available detailing its construction. The 2013 aerial photograph on Plate 3 shows B59 sitework in progress. As shown on Plate 3, much of the North Site and East Site appear relatively unaffected by B59 construction. However, due to the sloping nature of the B59 site, the upslope sides of B59, the B59 cooling towers, and the B59 loading dock road are retained by walls and tiebacks, soil nails, and fill from B59 construction are present in some areas where NFU2 site improvements are planned.

1.02 Purpose and Scope

The primary purpose our geotechnical investigation was to: 1) characterize geotechnical/geologic conditions in areas where exterior site improvements are planned; and 2) provide geotechnical data, conclusions and recommendations for the design and construction of the envisioned NFU2 Project. This geotechnical investigation was conducted under LBNL Subcontract (No. 7623192), which is dated December 23, 2021. The scope of our geotechnical investigation consisted of:

Reviewing geologic, seismic, and historical information;

Compiling and reviewing relevant data from previous LBNL projects;

Drilling and logging five new borings;

Sampling subsurface materials and performing laboratory tests on selected samples;

1 National Energy Research Scientific Computing Center

Characterizing geotechnical conditions in areas where new site improvements are planned;

Evaluating potential geologic and seismic hazards;

Developing conclusions and recommendations for the geotechnical aspects of the Project; and Preparing this geotechnical investigation report.

The scope of our geotechnical investigation did not include environmental investigations or consultation relating to non-natural (e.g., chemical) constituents in soil, construction materials, groundwater, or air. Other limitations in the scope of our study are noted in Section 7 of this report.

1.03 Elevation Conversions

The figures attached to this this report include elevation contours relative to NAVD88 Datum, whereas older drawings and reports for the lab (including materials attached in appendices to this report) utilize UC Datum.

LBNL recently transitioned from UC Datum to NAVD88 Datum and we understand that the difference in elevation between the two reference datums is in the range of about 6.45 to 6.92 feet. For the purposes of this geotechnical study, we converted UC elevations to approximate NAVD88 elevations using by adding +7.0 feet.

2. METHODS OF INVESTIGATION

2.01 Borings

Between March 28 and 31, 2022, our drilling subcontractor (Taber Drilling of West Sacramento, California) advanced one boring at the North Site (B1N) and four test borings in the vicinity of the East Site2 (B1S through B4S) using track-mounted solid-stem-auger drilling equipment. The approximate locations of our five test borings are shown on Figures 1 and 2. Approximate ground surface elevations at the borehole locations and total drill depths are summarized in the following table.

As-Drilled Borehole Data

Boring ID Approximate Ground

Surface Elevation Total Depth

B1N +689 feet 16.4 feet

B1S +725 feet 31.5 feet

B2S +722 feet 51.2 feet

B3S +702 feet 11.0 feet

B4S +707 feet 37.7 feet

Boring B1N was accessed from the parking area on the west side of Perlmutter Drive near its intersection with Chu Road. Due to physical access constraints, Boring B1N was advanced using a small Simco 2400 crawler drill rig. Borings B1S through B4S were accessed from the south end of Perlmutter via an existing road leading to the southwest corner of B70A. From there, an LBNL contractor graded a temporary access road across steeply sloping terrain to facilitate access by a larger and more powerful CME 55 heavy-duty crawler drill rig.

During drilling, an A3GEO engineer supervised the drilling operations, obtained samples, and prepared field boring logs of the subsurface materials and conditions encountered. Due to nearby sloping ground conditions, the borings were samples on a near-continuous basis to check for indications of shearing related to landsliding (e.g., slide planes). Finalized versions of the boring logs are presented in Appendix A along with two explanatory figures (Key to Exploratory Boring Logs and Physical Properties Criteria for Rock Descriptions).

Soil samples were obtained using a 2-inch outside-diameter (O.D.) Standard Penetration Test (SPT) sampler, a 2.5-inch O.D. California Sampler, and a 3-inch O.D. Modified California sampler. Samplers were driven with a 140-pound automated trip hammer with an approximately 30-inch fall. The number of hammer blows required to drive the sampler the final 12 inches of each 18-inch drive are presented on the boring logs. Where a full 12-inch drive could not be achieved, the number of blows and amount of penetration achieved is shown. The blow counts presented on the logs can be considered approximate SPT N-values; field blow counts obtained using the 2.5-inch O.D. and 3.0-inch O.D. samplers have been adjusted for sampler type (end area), only.

Soils were visually/manually classified in general accordance with ASTM D2488 classifications, which are based on the Unified Soil Classification System (USCS). Field classifications were subsequently checked and revised, where appropriate, based on laboratory test data. The boring logs in Appendix A reflect our current interpretation of the subsurface conditions encountered at the locations shown on Figures 1 and 2 at the time that the borings were drilled. At the completion of drilling, each hole was checked for the presence of free groundwater before backfilling the borehole with grout.

2 The location of the East Site shifted towards the southwest after our 2022 field investigation was complete.

2.02 Laboratory Tests

The following geotechnical laboratory tests were performed on samples from borings drilled for this investigation:

Atterberg Limits per ASTM D4318;

Sieve analysis by ASTM D422;

Moisture content by ASTM D2216; and Dry density by ASTM D2937.

Geotechnical laboratory testing was performed by B. Hillebrandt Soils Testing, Inc. of Alamo, California.

We also screened for naturally occurring corrosive materials by conducting a suite of geochemical laboratory tests on one sample of near-surface soil obtained from each of the subject sites. The geochemical laboratory tests were performed by Cooper Testing Labs, Inc. and included measurements of:

Resistivity (100% saturated) per Caltrans 643;

Chloride ion concentration per Caltrans 422 (modified);

Sulfate ion concentration per Caltrans 417 (modified);

pH per Caltrans 643; and Moisture per ASTM D2216.

Laboratory test data sheets from this study are presented in Appendix B.

2.03 Existing Information and Data

We reviewed a variety of published and unpublished materials in preparing this report. A list of references is presented in Section 8. Selected reference materials are attached in appendices, as noted below.

Approximate locations of previous test borings and exploratory trenches proximate to the subject sites are indicated on Figures 1 and 2. Logs from the explorations shown on Figures 1 and 2 are attached in Appendix C.

Figures 1 and 2 show the approximate locations of tiebacks and soil nails installed in association with B59 construction. Record drawings for the tiebacks and soil nails shown on Figures 1 and 2 are attached in Appendix D. Appendix D also includes B59 foundation drawings showing grade beam tiebacks (designated GB-2 tiebacks), record drawings for which have not been located.

The topographic contours and shadings on Figures 1 and 2 were derived from LBNL-provided aerial LiDAR data. Recent topographic survey drawings for the two sites are attached in Appendix E.

Historical aerial and ground-based photographs were used to evaluate geotechnical conditions and the nature of B59 improvements proximate to the subject sites. Selected photographs from LBNL’s online photo archive (https://photos.lbl.gov/bp/#/) are presented on the Plates that accompany this report.

3. GEOLOGIC, SEISMIC AND HISTORICAL SETTING

3.01 Geologic Overview

LBNL is located on the west side of the Berkeley Hills, which generally trend southeast-northwest. Bedrock geology in this part of the Berkeley Hills is complex and includes a variety of moderately to highly deformed sedimentary, volcanic, and metamorphic rock units that have been subjected to a long history of regional uplift, faulting and folding. The approximate ages of the bedrock units that underlie most of the LBNL campus are tabulated below (Ma =millions of years ago):

Ages of Geologic Units (Jones and Curtis 1991)

Unit Period/Epoch Age

Great Valley Sequence Upper Jurassic- Lower Cretaceous 159-99 Ma

Orinda Formation Tertiary/Middle to Late Miocene 13.5- 10.5 Ma

Moraga Formation Tertiary/Late Miocene 10.2-8.4 Ma

During the late Miocene and early Pliocene (11.2 to 3.6 Ma) an extended period of tectonic compression resulted in the folding and uplifting of these rock units creating the Berkeley Hills. The natural topography of LBNL includes ridgelines and intervening valleys. In general, the ridgelines at LBNL are mostly underlain by shallow rock, whereas the intervening valleys include deeper deposits of soil and rock materials shed from areas upslope.

3.02 Geologic Mapping

The 1982 geologic map by HLA (Plate 4) illustrates near-surface geologic conditions within the Project Study Area. Uncolored portions of the map show areas where HLA interpreted Cretaceous-age rocks (map symbol K) to be present at or near the ground surface. The colors on Plate 4 highlight the areas where HLA interpreted that fill (map symbol f) and colluvium3 (map symbol Qc) to overlie rock.

In general, HLA’s 1982 map shows the North Site and the East Site both underlain at relatively shallow depth by rock. HLA maps “small landslides”, which are indicated using asterisks, near the western corner of the North Site and east of the East Site near B54. HLA (1982) maps colluvium within the lower portions of the valley south of the East Site, noting that colluvium on this map “includes landslide deposits (ls) of incoherent soil and rock”.

On Plate 4, the bold lines west of Building 88 represent various interpreted traces of the Hayward fault. The dashed line that passes through Building 50B and the southeast corner of B70A represents an interpreted fault trace that is not considered active. HLA (1982) does not map any fault traces (active or inactive) passing through either of the subject sites, which is generally consistent with other geologic maps that we reviewed.

3.03 Geologic Hazard/Risk Mapping

The California Geological Survey (CGS) prepares seismic hazard zone maps delineating zones of required investigation for surface fault rupture, liquefaction and earthquake-induced landsliding. Within such zones, additional requirements apply relating to the evaluation and mitigation of hazards for defined “Projects” involving structures intended for human occupancy (e.g., buildings).

The CGS Fault Zone Map on Plate 5 shows the North Site entirely within the Alquist-Priolo Earthquake Fault Zone (AP Zone) that surrounds the active Hayward fault, whereas the East Site is mostly outside the AP Zone.

3 Colluvium is a geologic term referring to soil that has moved downslope by gravity.

The potential for earthquake fault rupture in the general area of the North Site was previously investigated and dismissed in previous fault investigation reports prepared in association with the development of B59 (Fugro, 2002a; Kleinfelder, 2006). The North Site and East Site are approximately 360 feet and 560 feet, respectively, from the nearest CGS-mapped Hayward fault traces. The CGS Seismic Hazard Map on Plate 6 shows the East Site within a Zone of Required Investigation for Earthquake-Induced Landsliding and the North Site mostly outside the CGS-mapped zones. The potential for earthquake-induced landsliding at the East Site has not previously been evaluated.

The Slope Instability Map on Plate 7 shows the locations of unstable and repaired slopes identified by LBNL’s Facilities Division. The North Site includes a feature qualitatively mapped as “medium risk”. No slope instability features are mapped in the vicinity of the East Site.

3.04 Previous Geologic Evaluations

3.04.1 North Site

Plate 7 shows a slope instability feature within the North Site that is identified with the reference number 019.

The numbers on this map reference reports in LBNL’s geotechnical database and the reports in LBNL File # 019 (HLA, 1975) include tabular summaries titled “Summary of Conditions - Known Area of Unstable Slopes, Lawrence Berkeley Laboratory”. In all, 41 slope features were qualitatively evaluated by HLA during the 1970s.

The slope at the North Site is located near UC Grid Coordinates 7+00N, 13+00E, and is described by HLA (1975) as a “slough or slump” with subsurface conditions consisting of “slope debris.” No borings were drilled during HLA’s evaluation and this mapped feature is not known to have exhibited significant movement since HLA’s 1975 report was prepared.

3.04.2 East Site

To our knowledge, no slope instability features have previously been mapped in the direct vicinity of the East Site. The foundation investigation report for B70A (D&M, 1959) includes a geologic summary attributed to their field geologist concluding that the rocks encountered at the site are “highly contorted and sheared” due to “the proximity of the Hayward fault.” D&M’s notes “analyses have indicated that the slopes which will exist west and south of the building could be unstable, if loads due to shallow footings were imposed upon them” and concludes the “west and south building lines of the structure should be supported on drilled piles”. The “as-built” foundation plan for B70A shows drilled piers below the south and west walls upslope of the East Site. D&M (1959) notes that rock strata at the B70A site “generally strike northerly and dip to the east at an inclination of approximately 50 degrees”, which suggests the absence of adversely-oriented bedding within west and south-facing slopes.

GRC’s 1990 geotechnical investigation report for air handler units adjacent to the south wall of B70A also notes that “crushed, sheared shale” was encountered adjacent to the south wall of B70A and concludes ”this fracturing and shearing was caused by tectonic deformation” (i.e. not by landsliding). A detailed geologic map prepared by Fugro (2002b) interprets the East Site to be underlain by shallow rock, with no mapped slope instability features present within the site.

3.04.3 B59 Site

Cross sections contained in the final geotechnical investigation report for B59 (Kleinfelder, 2011) note that “colluvium may vary from 5 to 20 feet in thickness across the site.” Previous geologic investigations identified the presence of shallow landslide deposits on west-facing slopes within the footprint of B59, which were entirely removed during the excavation of the B59 site. Logs of exploratory fault trenches oriented upslope-downslope across the B59 site (Kleinfelder, 2006) identify a “dormant landslide slip surface” characterized as a “shear zone” with the descriptions: “thin gray clay seam with abundant roots and clay pressure faces” and “gray clay seam, ½” thick, abundant rootlets”. Below the shear zone, apparently in-place siltstone rock is described as

“moderately weathered, weak and intensely fractured”. The landslide shear zone was observed in trenches at depths of about 7 to 10 feet below the ground surface. To our knowledge, there is no evidence of deeper landslide slip surfaces within Great Valley Complex rock beneath the B59 site.

3.05 Seismicity

LBNL is within the seismically-active San Francisco Bay region, which includes a series of major northwest-trending active faults. Approximate distances and directions to major active Bay Area faults are shown in the following table.

Approximate Distances and Directions to Major Active Faults (Jennings and Bryant, 2010; CDMG, 1982).

Active Fault Approximate Distance from Site (miles) Approximate Direction from Site

Hayward ≈ 0.1 Southwest

Calaveras 13.8 East

Rodgers Creek 22.5 Northwest

Concord-Green Valley 13.4 Northeast

San Andreas 18.7 Southwest

Greenville 18.1 Northeast

West Napa 19.6 North

San Gregorio 23.8 Southwest

Since 1836, six earthquakes of magnitude 6.5 or greater have occurred in the region; the dates, magnitudes (M) and epicentral locations of these earthquakes are summarized in the following table.

Magnitude 6.5 or Greater Historical Earthquakes; 1836-1998

(Bakun, 1999; Tuttle and Sykes, 1992)

Date Magnitude Epicenter Location

June 10, 1836 6.5 East of Monterey Bay

June 1838 6.8 – 7.2 Peninsula section of the San Andreas fault

October 8, 1865 6.5 Southwest of San Jose

October 21, 1868 6.8 Southern Hayward fault (Hayward Earthquake)

April 18, 1906 7.8 San Andreas fault (San Francisco Earthquake)

October 18, 1989 6.9 Santa Cruz Mountains (Loma Prieta Earthquake)

The closest active fault is the Hayward fault, which runs along the base of the Berkeley Hills near the southwest corner of B88 (Plate 5). Relative to other Bay Area active faults, the Hayward fault is estimated to have the highest likelihood of producing one or more major (M6.7 or greater) earthquake events in the near future.

Estimated 30-year likelihoods of M6.7 or greater earthquakes on Bay Area active faults are shown in the following table.

Magnitude 6.7 or Greater Earthquake Forecast; 2016-2046

(Aagaard et al., 2016)

Earthquake Fault 30-year Likelihood of one or more

Earthquake Events with M≥6.7

Hayward - Rodgers Creek 33%

Calaveras - Paicines 26%

San Andreas 22%

Hunting Creek, Berryessa, Green Valley, Concord, Greenville

16%

Maacama 8%

San Gregorio 6%

3.06 Local Development History

The east-facing 1935 Aerial Photograph on Plate 8 shows the Project vicinity prior to the start of LBNL development. As shown on Plate 8, at that time the North Site was on a relatively smooth west-facing slope and the East Site was on a south-facing slope partially obscured by trees. The 1946 Aerial Photograph on Plate 9 shows similar conditions within the Study Area.

In the late 1940s, Berkeley Lab expanded to the north and west following the annexation of an adjacent parcel known as the Wilson Tract. Building 50 was built on the crest of the ridge upslope of the North Site in about 1950 (Plate 10). B70 and B54 were completed prior to 1956 (Plate 11) and B70A was completed around 1960.

By 1966, B50A, B50B, and the road now known as Perlmutter Road had all been built (Plate 12). The aerial photograph on Plate 13 shows the Study Area in 1968. The 1988 Aerial Photograph on Plate 14 shows B50E and B50F in place. The 2012 Aerial Photograph on Plate 15 shows the initial grading of the B59 site. Between 1988 and 2012, relatively minor grading appears to have been performed near the south side of B70A to construct the improvements discussed in GRC’s 1990 report.

As previously noted, construction related to B59 included excavation cuts retained by walls that can be seen on the 2013 Aerial Photograph presented on Plate 3. Plate 16 shows the retaining wall on the upslope (east) side of the B59 loading dock access road, which has tiebacks that extend below portions of the North Site. Plates 17 through 20 show various stages of B59 construction adjacent to the East Site. The Line 1 grade beam indicated on Plate 17 underlies the south exterior wall of B59. Plate 18 shows shotcrete walls on the north side of the cooling tower pad and the east side of the B59 excavation that have soil nails that extend below portions of the East Site. At the base of the B59 east wall, the grade beam tiebacks indicated on Plate 19 also extend below a portion of the East Site. Plate 20 shows grade beams perpendicular to the east wall that underlie the B359 exterior slab-on-grade adjacent to the East Site.

The photograph at the top of Plate 21 shows conditions at the East Site in November 2021 prior to the start of our investigation. The photograph at the bottom of Plate 18 shows the grading performed to facilitate drill rig access following the placement of wattles and jute netting for erosion control.

4. SITE CONDITIONS

4.01 North Site

4.01.1 Surface Conditions

The North Site is located between Chu Road and Perlmutter Road west of B50A, B50B and B50E (Figure 1;

oriented with north to the left). As shown on Figure 1, Chu Road slopes up towards the north and east and Perlmutter Road slopes up towards the south. The sweeping turn and parking area west of B50E is in an area that was cut to grade during the construction of Perlmutter road in the 1960s. Relatively steep excavation cuts exist along the south side of the bend on Chu Road and east of Perlmutter Road adjacent to B50A and B50E.

Within the North Site, the ground surface generally slopes down towards the north and west. In the southern portion of the site (closest to B59) the ground surface is relatively smooth and free of trees; this portion of the site was regraded as part of recent B59 construction. Southwest of Boring B1N is an area where the ground surface is more irregular and there are trees present; this portion of the site is where an area of shallow slope instability has been mapped (Plate 7). The trees in this area were not present in 1956 (Plate 11) but appear to have been present in 1966 (Plate 12) following the construction of Perlmutter Road. We did not observe any indications of active slope instability within the North Site during our reconnaissance.

4.01.2 Subsurface Conditions

The cross sections presented of Figures 3, 4 and 5 (Cross Sections A-A’, B-B’ and C’-C’, respectively) present our interpretation of subsurface conditions within the North Site. The locations of North Site Cross Sections A- A’, B-B’, and C-C’ are indicated on Figure 1.

Existing Tiebacks - Cross Section B-B’ (Figure 4) shows the loading dock retaining wall built during the B59 Project. Record drawings for the loading dock retaining wall are included in Appendix D. The loading dock retaining wall includes tiebacks; the approximate zone into which record drawings show that the tiebacks extend is indicated on Figure 1.

Soil Conditions - Boring B1N, drilled west of the parking area off Perlmutter Road, extended to a total depth of 16.4 feet where practical drilling refusal was met. The log of Boring B1N is presented in Appendix A. Boring B1N encountered less than 6 feet of natural soil classified as stiff sandy lean clay.

The results of Atterberg Limits determinations performed on a sample of soil from a depth of 2 to 3 feet produced a Plasticity Index of 16, which is generally indicative of soil that is only slightly expansive4.

The results of geochemical tests performed on a sample from a depth of 4 to 5 feet are generally indicative of soil that classifies as non-corrosive to mildly corrosive (see notes and test results at the end of Appendix C). The upper 5 feet of Boring B1N was excavated using a hand auger due to the presence of nearby utilities. Consequently, no reportable sampler blow counts were obtained in soil in Boring B1N.

Rock Conditions - Boring B1N encountered shale rock at a depth of about 5.8 feet, which we interpret as “in-place” (i.e., bedrock). Six Standard Penetration Test (SPT) blow counts greater than 50 blows per foot were obtained between depths of 5.0 feet and 16.4 feet, with five of the six producing blow counts of 50 for 5 inches. Very hard drilling was noted at a depth of 13 feet and no obvious evidence of highly sheared or crushed rock was noted in Boring B1N. Generally similar rock is exposed at the ground surface in road cuts along the upslope sides of Chu Road and Perlmutter Road. The log of an exploratory trench excavated across the southern half of the North Site (Fugro, 2002a; Appendix C) shows generally similar shallow rock with no evidence of active faulting.

Groundwater Conditions - Boring B1N, which was drilled at the North Site in March of 2022, did not

4 Expansive soils shrink and swell with changes in moisture. Soils with a PI of 15 or less are commonly considered “non-expansive”.

encounter free groundwater. Logs of previous borings drilled east of Perlmutter Road (Appendix C) do not show stabilized groundwater levels but “seepage” is noted at various depths. We anticipate that seepage zones may also be present in rock below the North Site. We did not attempt to interpret a groundwater surface below the site due to the presence of shallow rock and the absence of long-term groundwater monitoring data from wells installed for that purpose.

4.02 East Site

4.02.1 Surface Conditions

The East Site is roughly bounded on the west by B59, on the south by the B59 cooling towers, and on the north and east by ground that slopes down towards the south (Figure 2). The topographic contours and shadings on Figure 2 reflect site conditions prior to the start of our investigation. Plate 21 presents photographs taken before and after the temporary road for drill rig access was created. An updated post-investigation survey drawing is attached in Appendix E.

Borings B1S and B2S were drilled proximate to a pre-existing unpaved access road that slopes down from west to east (Figure 2). An LBNL utility corridor containing a gas line and electrical conduits underlies the road alignment depicted on Figure 2. Boring B1S and B2S were drilled to the south and to the north of the utility corridor (respectively). Buried water lines also exist beneath the western end of the access road and near the south wall of B70A.

Within the East Site, the ground surface is relatively smooth and free of trees; this area was cleared of trees prior to the start of B59 construction. Figure 2 shows Boring B3S (the closest boring to the East Site) on a subtle north-south trending topographic rise. We did not observe any indications of active slope instability within or directly adjacent to the East Site during our reconnaissance.

4.02.2 Subsurface Conditions

The cross sections presented of Figures 6 and 7 (Cross Sections A-A’ and B-B’, respectively) present our interpretation of subsurface conditions in the vicinity of the East Site. The locations of East Site Cross Sections A-A’ and B-B’ are indicated on Figure 2.

Existing Soil Nails - Cross Section A-A’ (Figure 6) shows the cooling tower retaining wall built during the B59 Project. The cooling tower retaining wall includes soil nails; as does the portion of the B59 rear wall closest to the East Site. Record drawings for both retaining walls are included in Appendix D. The approximate zones into which record drawings show that the soil nails extend are indicated on Figure 2.

Existing Grade Beam Tiebacks - The record drawings in Appendix D show 12-inch PVC blockouts near the base of the B59 retaining wall to facilitate future tieback installations (GB-2 tiebacks). The GB- 2 tieback locations are shown in plan and profile on the retaining wall record drawings; however, tieback lengths are not indicated. The GB-2 tiebacks are also shown on the foundation drawings with a notation indicating 240-kip capacity, but without a specified length. The zone into which GB-2 tiebacks extend are not shown on the version of Figure 2 attached to this report.

Soil Conditions - Boring B1S, drilled uplsope of the East Site, encountered about 11 feet of fill classified as stiff sandy lean clay overlying rock. Adjusted sampler blow counts (approximate N-Values) of 6 and 18 blows per foot were obtained in the fill layer. The other three borings (B2S, B3S, and B4S) encountered natural clayey soils overlying rock. The results of Atterberg Limits determinations performed on a sample of soil from a depth of 2 to 2.5 feet in Boring B3S produced a Plasticity Index of 25, which is generally indicative of soil that is moderately expansive. The results of geochemical tests performed on a sample from a depth of 2 to 2.5 feet in Boring B4S are generally indicative of soil that classifies as non-corrosive to mildly corrosive (see notes and test results in Appendix C).

Bedrock Depths/Elevations - The approximate elevation of the bedrock surface at each of our boring locations is indicated in the following table.

Approximate Bedrock Depths/Elevations

Boring ID Approximate Rock Depth

Approximate Ground Surface Elevation

Approximate Rock Elevation

B1S 11 feet +725 feet +714 feet

B2S 5 feet +722 feet +717 feet

B3S 3 feet +702 feet +699 feet

B4S 3 feet +707 feet +704 feet

An exploratory trench excavated near the northwest corner of the East Site (Trench KT-1; Kleinfelder, 2006a) encountered shallow rock interpreted as in-place. Review of available construction photographs (including a high resolution version of the images presented on Plates 17 and 18) generally suggest shallow rock is also likely to present near the western and southern edges of the East Site.

Rock Conditions - As shown on the cross sections on Figures 6 and 7, all of the rock encountered in our borings drilled in the vicinity of the East Site is interpreted as “in-place” bedrock. The data from Boring B1S is generally consistent with that logged in a previous boring drilled near the southwest corner of B70A (D&M, 1959). Boring B3S, drilled downslope of B1S, extended to a total depth of 11 feet where practical drilling refusal was met. Boring B2S was drilled farther east than planned to avoid conflicts with buried utilities. Boring B4S was also drilled farther east than planned as it was our objective to develop an upslope-downslope cross section using the data from Borings B2S and B4S.

The lower of the two borings (B4S) encountered shale that included zones of sheared and/or crushed material. Boring B4S was terminated at a depth of 37.7 feet in shale below a thin layer of conglomerate that the field log identified as a “possible shear zone”. The upper boring (B2S), drilled in an area that was recently cut to grade, encountered 5 feet of soil overlying shale that also included zones of sheared and/or crushed material. Boring B2S was terminated in shale at a depth of 51.2 feet. The deepest shear zone noted on the log of Boring B2S is at a depth of 26 feet.

Geologic Stability - We considered the possibility that the sheared and crushed zones of rock in Borings B2S and B4S could be related to landsliding; however, this hypothesis was ultimately discounted. First, we plotted the depths at which shears were noted on Cross Section B-B’ (Figure 7) and were unable to construct any plausible landslide slip surfaces between the shears in the two borings. Second, we reviewed several LiDAR-generated earth shadings and found no compelling evidence of obvious landsliding in the area directly east of the East Site where B2S and B4S were drilled. Third, we checked previous consultant-prepared reports and maps for evidence of nearby landsliding and found no analogues that would support a hypothesis of deep-seated landsliding in Great Valley Complex rocks. And fourth, we noted that “clay seams” such as those identified as the basal surface of landsliding in Kleinfelder’s trenches at the B59 site were not seen any of our East Site borings. Based on these analyses, we presently interpret that: 1) all of the rock in Borings B2S and B4S is essentially in-place and the sheared and crushed materials observed in samples are likely tectonic in origin; and 2) any past or future landsliding in this area is likely to be relatively shallow and generally similar to the type of surficial sliding noted in previous reports by Kleinfelder and HLA.

Groundwater Conditions - Free groundwater was not encountered in any of the borings drilled in March 2022. The final geotechnical investigation report for B59 (Kleinfelder, 2011) notes “groundwater levels were found to be variable” with the shallowest groundwater recorded at a depth of 27 feet near Building 70A. We anticipate that seepage zones may be present in rock below the East Site; however, we did not attempt to interpret a groundwater surface below the site due to the presence of shallow rock and the absence of long-term groundwater data in the geotechnical and geologic reports that we reviewed.

5. CONCLUSIONS AND EVALUATIONS

5.01 Geologic Hazard Potential

5.01.1 Earthquake Groundshaking

LBNL is located in the highly seismic San Francisco Bay Area and it is likely that subject sites will be subjected to one or more episodes of strong earthquake groundshaking over the anticipated life of the Project. Strong earthquake groundshaking is a hazard shared throughout the region and its effects on structures are mitigated through the seismic design provisions of the California Building Code. Geotechnical criteria for seismic design per the 2019 California Building Code and ASCE 7-16 are presented in Section 6.01 of this report.

5.01.2 Surface Fault Rupture

The Project is located close to a major regional fault (the Hayward fault) and one of the sites (the North Site) is within a State-defined hazard zone for surface fault rupture. The potential for earthquake fault rupture was recently investigated and evaluated in association with the siting of B59 by excavating exploratory trenches roughly perpendicular to the northwest-trending Hayward fault. The northernmost fault trench excavated by Fugro in 2002 (location shown on Figure 1) passes through the North Site. The B59 site was cleared of surface fault rupture hazards through detailed engineering geologic evaluations of conditions exposed in the exploratory trench walls (Fugro, 2002a; Kleinfelder, 2006). In our opinion, the overall potential for surface fault rupture at the North Site is low based on previous fault hazard investigations conducted for B59.

The East Site is mostly outside the State-defined hazard zone for surface fault rupture and the one trench excavated in this area during the evaluation of B59 does not extend all the way across the site (Trench KT-1;

Kleinfelder, 2006; Figure 2). Previous geologic maps that we reviewed do not show any known or inferred faults crossing the East Site and we did not observe any obvious tonal lineaments suggestive of faulting in the vicinity of the East Site on any of the aerial photographs or LiDAR-derived topographic earth shade imagery that we reviewed. In our opinion, the overall potential for surface fault rupture at the East Site can also be considered low.

The geotechnical evaluations in this section are based on our understanding that the Project does not include structures intended for human occupancy (i.e., buildings that may be occupied more than 2,000 person-hours per year). This evaluation is not intended to comply with published CGS Note 49 guidelines5, which assist geologists who evaluate faults relative to the hazard of surface fault rupture.

5.01.3 Landsliding

The subject sites include areas of sloping ground and one of the sites (the East Site) is within a State-defined hazard zone for earthquake-induced landsliding. Borings drilled for this investigation generally encountered Great Valley Complex rock interpreted as in-place (bedrock) at relatively shallow depths. Previous consultant prepared reports identify landslides in the project vicinity that have been active under wet-weather conditions, most notably the relatively shallow “slough or slump” documented by HLA at the North Site in 1975. This feature appears to have remained inactive for 45+ years and we consider the potential for significant landslide-type movement at the North Site under wet-weather conditions to be generally low. No recent slope failures have been documented in the vicinity of the East Site; although downslope creep of clayey soils has been noted in other parts of the valley, particularly in the area downslope of B54 (HLA,1981). Geologic mapping by Fugro (2002b) interprets landslide scars in the upper portion of slopes between B54 and B70A; however, these features are neither proximate to the East Site nor historically active. Overall, we consider the potential for significant landslide-type movement at the East Site under wet-weather conditions to also be low.

5 https://www.conservation.ca.gov/cgs/Documents/Publications/CGS-Notes/CGS-Note-49.pdf

The potential for earthquake-induced landsliding at LBNL is difficult to assess in that there have been no large earthquakes along the adjacent segment of the Hayward fault in recorded history. Investigations conducted in other parts of Berkeley Lab have identified potential earthquake-induced landslide hazards; however, the earthquake-induced landslide hazards that have been identified are in areas where younger Orinda Formation rocks are present and there are known landslide deposits with well-defined basal slip surfaces. These conditions generally do not exist at either of the subject sites, both of which are underlain by relatively shallow Great Valley Complex rock. Based on the foregoing, we judge the overall potential for earthquake-induced landsliding to affect either of the subject sites to be generally low. However, the potential for earthquake-induced landsliding may be slightly higher in areas where Great Valley Complex rocks are extensively crushed and sheared, such as they are east of the East Site in the vicinity of Borings B2S and B4S.

Please note that the geotechnical evaluations in this section are based on our understanding that the Project does not include structures intended for human occupancy (i.e., buildings that may be occupied more than 2,000 person-hours per year). This evaluation is not intended to comply with published CGS Special Publication 117A guidelines6, which assist geotechnical engineers and geologists who evaluate the hazard of earthquake-induced landsliding.

5.01.4 Other Geologic Hazards Not Present

The onsite soils are relatively thin, predominantly cohesive (contain appreciable fractions of plastic silt and/or clay) and are not susceptible to earthquake-induced liquefaction or densification. There are no significant bodies of water upslope and the site is roughly 800 feet above sea level, so inundation is not a concern.

5.02 Geotechnical Site Considerations

5.02.1 Undocumented Fill

In this context, the term “undocumented” refers to fill for which there are no records documenting that the fill was placed and compacted under engineering controls. Undocumented fill is poorly-suited for the support of new foundations, new fill, and new exterior flatwork. Where undocumented fill is present, typical geotechnical mitigation alternatives include: 1) excavation and replacement with new engineered fill; and 2) deep foundations that gain their support below the undocumented fill layer.

Any/all existing fills in the vicinity of the North Site and the East Site are presently considered undocumented. At the North Site, undocumented fill is interpreted to be present in primarily areas that were graded during the construction of B59 (Plate 3) and where fill was placed to construct Perlmutter Road (Plate 4). At the East Site, undocumented fill is interpreted to be mostly absent; although some undocumented fill may exist near the walls of B59 and the B59 cooling towers. In addition, all of the fill placed in March 2022 to facilitate drill rig access to the East Site is undocumented.

5.02.2 Expansive Soil and Rock

Expansive materials have the potential to shrink and swell with changes in moisture and can cause significant damage to improvements with which they are in contact unless appropriately mitigated. Adverse shrink-swell effects are commonly related to expansive soils within several feet of the ground surface where seasonal changes in moisture are the greatest.

For engineering purposes, materials having a Plasticity Index (PI) no greater than 15 and a Liquid Limit (LL) no greater than 40 are commonly considered “non-expansive”. Where expansive materials are present, typical geotechnical mitigation alternatives include; 1) excavation and replacement of near-surface soils with non-expansive fill; and 2) deepened footings or deep foundations (e.g., drilled piers) that gain their support below

6 https://www.conservation.ca.gov/cgs/Documents/Program-SHP/SP_117a.pdf the depth of significant seasonal moisture change. Under some circumstances, treating soils with lime or cement is an acceptable means to reduce expansion potential. Additionally, non-vertical structural elements that overlie soils prone to seasonal shrinking and swelling are often either:1) designed to structurally resist expansive soil uplift pressures; or 2) elevated or otherwise isolated from the ground by a void to avoid contact with expansive soils. Atterberg limits determinations conducted for this study generally indicate moderately expansive soil and rock materials are present at both the North Site and the East Site.

5.02.3 Slope Stability

Based on the available information and data, we consider the potential for deep-seated landslide-type movement at either the North Site or the East Site to be low. Both sites are underlain at relatively shallow depth by rock that is interpreted as geologically stable. However, expansive soils on steep slopes are generally susceptible to downslope creep and it is possible that sloughing/sliding of near-surface soils may occur under wet-weather conditions or during an earthquake.

5.03 Geotechnical Design Considerations

5.03.1 Subsurface Drainage and Moisture Control

The available data suggests that groundwater at both sites is relatively deep and the NFU2 project does not include any deep basements, sumps, or pits that would extend below the water table. Consequently, hydrostatic forces on structures are not a significant consideration for the NFU2 Project.

As currently planned, tieback retaining walls at the East Site will be drained to prevent the buildup of hydrostatic pressure in a manner consistent with available technical design guidance and local design practice. However, retaining wall backdrains cannot be relied upon to prevent groundwater from intermittently coming in contact with the back side of the wall. Consequently, retaining walls are typically waterproofed in cases where moisture transmission through the wall would be considered undesirable. Similarly, it should be anticipated that groundwater may intermittently be present at the bottom of the lower level mat slab planned at the East Site unless a robust underdrainage system that includes perforated plastic pipes and a granular drainage layer is installed below the mat. With a robust underdrainage system, a heavy-duty moisture retarder (e.g., Stego 15-mil) installed on top of the underdrainage layer would provide a normal level of protection against water vapor transmission through the mat. Without a robust underdrainage system, the bottom of the mat would best be waterproofed if moisture transmission through the mat would be considered undesirable.

There are many variables involved in the design of effective moisture control and waterproofing systems. We recommend that a waterproofing expert be consulted to provide appropriate Project-specific recommendations if moisture transmission through retaining walls or slabs-on-grade is a concern.

5.03.2 Retaining Walls

As currently planned, retaining walls at the East Site will be installed using top-down excavation methods in order to avoid destabilizing areas upslope. Shotcrete shoring walls with tiebacks are currently planned due to access constraints that would make the installation of more conventional soldier pile and lagging walls difficult.

The planned construction sequence includes: 1) excavating vertical cuts of limited height; 2) installing drainage panels, shotcrete, and tiebacks; and 3) tensioning the tiebacks before beginning to excavate down to the next level. After the shoring wall is in place, reinforced concrete walls for the planned two-story structure would built using the shoring (and any waterproofing installed) as a back form. Because the tiebacks will be tensioned, the shoring wall will need a footing capable of resisting the downward component of the tieback loads. Because the tiebacks are permanent, they need to be protected against corrosion.

Recommendations for the design and construction of tieback retaining walls at the East Site are included in Section 6.04 of this report. The “apparent” lateral earth pressure diagram for tieback walls is trapezoidal in shape. Additional guidance pertaining to anchored wall system can be found in FHWA Publication No. FHWA- IF-99-015 (https://www.fhwa.dot.gov/engineering/geotech/pubs/if99015.pdf). Section 6.04 also includes recommended lateral earth pressure increases under surcharges and seismic loads and triangular earth pressure distributions for “free-to-rotate” cantilever walls and “fixed” basement walls.

5.03.3 Foundation Support

As currently planned, the new equipment platform at the North Site will be supported on drilled pier foundations that extend into rock. As shown on Figure 2, tiebacks for the existing loading dock retaining wall downslope extend below a portion of the North Site. Record drawings for the loading dock retaining wall tiebacks are included in Appendix E. The tieback locations shown on the as-built drawings are presumed to be reasonably accurate at/near the loading dock retaining wall but are likely to be less accurate as the distance from the wall increases due to the propensity for tieback holes to drift. It is essential that the existing tiebacks, which are under tension, are not encountered during pier drilling.