ML021080686

Attachment: Slides for the April 11, 2002 Meeting (S104718-A)

ML021080686
Person / Time
Site:	Diablo Canyon
Issue date:	04/11/2002
From:	Pacific Gas & Electric Co
To:	Office of Nuclear Material Safety and Safeguards, Office of Nuclear Reactor Regulation
References
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Download: ML021080686 (150)

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NRC/PG&E Open Meeting, San Francisco, CA Diablo Canyon Power Plant Independent Spent Fuel Storage Installation m 8:00 Introduction NRC Strickland/Grebel

• 8:10 Overview Cluff

• 8:40 Seismicity McLaren

• 9:10 Ground Motions Abrahamson

• 11:15 Break

- 11:30 Public Comments NRC

• 11:45 Lunch April 11, 2002

NRC/PG&E Open Meeting, San Francisco, CA Diablo Canyon Power Plant Independent Spent Fuel Storage Installation

• 12:30 Slope-Material Properties White

• 1:15 Slope Stability Sun

• 2:15 Transport Slope stability White

• 2:45 Break

• 3:00 Cutslope Stability Bachhuber

• 3:45 Slope Stability Summary Team

• 4:45 Public Comment NRC

• 5:00 Adjourn April 11, 2002

,I- * .,, ,', ' ""

NRC/PG&E Open Meeting, San Francisco, CA Diablo Canyon Independent Spent Fuel Storage Installation Geology, Ground Motions, and Geotechnical Studies Lloyd Cluff Director PG&E Geosciences Department April 11, 2002

Project Team

"*PG&E Lloyd S. Cluff, Project Management.

William D. Page, Engineering Geology Marcia McLaren, Seismology Norman A. Abrahamson, Ground Motions Robert K.White, Geotechnical Engineering Joseph I. Sun, Geotechnical Engineering William U. Savage, Seismology

"*Consultants William R. Lettis, Consultant, Geology Jeff Bachhuber, Consultant, Geology Faiz Makdisi, Consultant, Geotechnical Engineering

Technical Review Board mClarence Allen - Geology/Tectonics mRobert Kennedy - Structural Engineering m Bruce Bolt- Seismology/Ground Motions 0 I. M. Idriss - Geotechnical Engineering/

Ground Motions 1I Uili

Peer Reviewers and Technical Specialists "u Skip Hendron Geotechnical Engineering

"* Paul Somerville - Seismology

"* Dale Marcum Geotechnical Engineering

-t CD

Investigations

"*Site geology

"*Seismieity and seismic geology

"-Earthquake ground motions

"*Geotechnical engineering

!t I.

I;I I.1 IiI I'

Previous Seismicity and Seismic Geology Studies (LTSP)

"*Detailed geologic mapping, trenching, surveying of coastal terraces, and offshore geophysics to locate active-faults in region

"*Detailed analysis of regional seismicity

"*PG&E seismic network established in 1987 to supplement existing USGS regional network

"*Hosgri fault confirmed to be the controlling earthquake source for the DCPP

Ground Motions n Compare earthquake source and distance and ISFSI site conditions with those at DCPP to confirm applicability of DCPP ground motions n Use DCPP ground motions as basis for developing ISFSI design ground motions, in accordance with 10 CFR 72.102(f)

Ground Motions m For ISFSI components sensitive to longer-period motions need to develop appropriate response spectra and time histories u ISFSI long-period (ILP) spectra, taking into account the influence of near-fault effects recorded in recent large earthquakes, such as fault rupture directivity and fling

' I

NRC/PG&E Open Meeting, San Francisco, CA Diablo Canyon Independent Spent Fuel Storage Installation Seismicity Marcia McLaren Seismologist PG&E Geosciences Department 4 April 11, 2002

Outline mTectonic setting m Seismographic station coverage MSeismicity patterns and focal mechanisms m Conclusions

Tectonic setting Quatemary faults From LTSP (PG&E, 1988)

0

'S /fit 4

- A~~

op, '

z 7,

/1-17 O~d

'14)

CdL

Tectonic setting Los Osos domain SSalinian Terrane SStanley Mountain Terrane 1 SSSur-Obispo Composite

-' San Simeon Terrane (McCulloch, 1987)

S Patton Terrane _ 121" 30 120' From LTSP (PG&E, 1988)

Seismographic station coverage 1987-present 360 Seismographic stations A PG&E (Vertical)

)VPG&E (3-component)

A USGS I 1200 From LTSP (PG&E, 1988)

Magnitude 5 and greater earthquakes since 1830 19

% ~ 1955 19 -15 + - EXPLANATION 1966 W4 areadler 0 Event location that is

... ea-,.aqakes poorly constrained 19C) Event location that is within 20 km and generally within 10 km

35. 1 90 10OW27 MAGNITUDES 0 5.0-5.9 i.\

196* 1 t QO 6.0-6.9

19. 115 :07.0-7.9 From McLaren and Savage (2001), SAR Figure 2.6-39

Seismicity recorded by the PG&E network Oct. 1987 through Jan. 1997 30' 121 30 1200 From McLaren and Savage (2001), SAR Figure 2.6-40

Seism icity _,_4%

recorded by ' Z the PG&E ""

network Oct. 1987. _.

throug.h Jan. 1997 S.

• 0.0-0.9. o o' 30'- "1 1.9. **

aao -o.ao Data Umit_

S014.-.90 20 km 50' 30' 1210 30' 120" From McLaren and Savage (2001)

Focal mechanisms  : ,952 1076 9,.

19862 Magnitude 3 \$,\

and greater 8- \jc J1U earthquakes,U9 1927-1986 +

192 0 20 km I I 50 30 121*

30.

From McLarei ,nand Savage (2001)

Focal mechanisms Oct. 1987 through Jan. 1997 120*

From McLaren and Savage (2001), SAR Figure 2.6-42

Conclusions

• Seismicity patterns and focal mechanisms of the 1987-1997 earthquakes recorded by the PG&E and USGS networks are consistent with the data presented in the Final Report of the Long Term Seismic Program (PG&E, 1988).

" Focal mechanisms along the Hosgri fault zone show consistent strike-slip motion along northwest trending, nearly vertical fault planes.

NRC/PG&E Open Meeting, San Francisco CA Diablo Canyon Independent Spent'Fuel Storage Installation Ground Motions:

Lessons from Recent Earthqualces Norm Abrahamson Engineering Seismologist PG&E Geosciences Department l April 11, 2002

' I

Outline

"*Lessons from recent earthquakes

• Three large earthquakes in 1999

"*Application of those lessons to the ground motions for the ISFSI

Importance of Recent Earthquakes

"* LTSP Evaluation Earthquake

"*M=7.2, Dist = 4.5 km

"*Prior to 1999, few empirical recordings were available for this magnitude and distance range

"* Recent Earthquakes Have Greatly Increased the Empirical Data Base of Strong Motion Recordings Close to Large Crustal Earthquakes

• 1999 Kocaeli, Turkey (M=7.4)

• 1999 Chi-Chi, Taiwan (M=7.6)

• 1999 Duzce, Turkey (M=7.1)

"* Resulting in new models for long period ground motion

Strong Motion Recordings Close to Large Crustal Earthqualkes M">_7.0 Mý_7.0 M_'7.0 DZ 20km D:_ 10km D* 5 km Prior to 9 5 2 1999

.1999 6 3. 2 Kocaeli 1999 Chi- 63 32 14 Chi 1999 6 2 1 Duzce

Evaluation of Ground Motions from Recent Earthqualkes

"*Compare response spectra to predicted values from recent attenuation relations

"*Compute residuals (observed - calculated) from Sadigh et al (1997) attenuation relation

• Mean residual

• Standard deviation of the residuals a "

' a I I a I a

Mean Residuals for Short Distances (D< 20 km)

Chi-Chi (D<20 kin)

Under-p ediction-

_ - 0 Kocaeli (D<20)

- :. A Duzce (D<20) 0.5 "

I " -I

• - - "" .- I

.m-0.5.

IiI e-rdction

-1.5  ;  ;  ; , ,

0.01 0.1 10

• * . , , SPeriod (Sec) iII II' I HI

Ground Motion Variability (D< 20 km) 0.7 0.6 0.3 C

0

"* 0.2 E[ sigma (D<20 km) 010 Sadigh et al(1997)

S 0

0.01 0.1 1 10 Period (Sec)

Lessons for Low and Moderate Periods mCompared to current attenuation relations used in for California earthquakes:

• Medianground motion lower than expected (T< 2 sec)

• Variability (standard deviation) of the ground motion is larger than expected at short periods (T<0.2 sec)

Lessons for Long Periods (T>2 seconds)

"* Recordings close to the fault showed strong near fault effects

"*Large velocity pulse

"*Increased long period spectral values

"* Two Causes of large velocity pulses

+ Directivity

• Fling

Example of Near-Fault Effects 0.3_

(Kocaeli Earthquake) 0.20

%M0.

1 -0.1

-0.2 /P PT E

-0.3-. YPT NS 10 15 20 25 .30.35 200, 0.1.100 0 .*, *2,* 2. YP7TNS F YPT NEW

-100' ' , . . . , . ... . .. , ..

5 10. 15 20 25 30 35 300 S2001 1.31 n100'- _2.YTN

.=_0~ ~ YPT EW-0_

So.I

-100 -'?

5 10 15 20 25 30 35 Time (sec)

Causes of Velocity Pulses

"- Directivity

• Related to the direction of the rupture front

+ Forward directivity: rupture toward the site (site away from the epicenter)

+ Backward directivity: rupture away from the site (site near the epicenter)

"*Fling

• Related to the permanent tectonic deformation at the site I I

Velocity Pulses

"* Forward Directivity

• Two-sided velocity pulse due to constructive interference of SH waves from generated from parts of the rupture located between the site and epicenter

+ Constructive interference occurs if slip direction is aligned with the rupture direction

• Occurs at sites located close to the fault but away from the epicenter for strike-slip

"* Fling

"*One-sided velocity pulse due to tectonic deformation

"*Occurs at sites located near the fault rupture independent of the epicenter location

Observations of Directivity and Fling Sense of Slip Directivit Fling Strike-Slip Fault Normal Fault Parallel Dip-Slip Fault Normal Fault Normal

Directivity Effects (Somerville et al, 1997)

Two Effects on Ground Motion Amplitudes n Changes in the average horizontal component as compared to standard attenuation relations

"* Increase in the amplitude of long period ground motion for rupture toward the site

"*Decrease in the amplitude of long period ground motion for rupture away from the site

• Systematic differences in the ground motions on the two horizontal components

• Fault normal component is larger than the fault parallel component at long periods

Landers Earthquake 34.5 (1992)

PIepicenter Directivity SJoshuaTree 34" 0 Km 30 F- i 20 sec -116.5 -116 Figure 1. Map of the 1992 Landers earthquake showing the velocity time histories at Lucerene (forward directivity) and Joshua Tree (backward directivity).

I

Directivity II

Model for Directivity Effects Additional Parameters Required m Strike-Slip Fault X = fraction of fault rupture between the epicenter and the site o = angle between the fault strike and the epicentral direction from the site

Directivity Parameters for Strike-Slip Faults ate Epcenter Fault Rupture S

-L--,,

L X=sL.

Abrahamson (2000) Directivity Factors 5% damping, Ave Horiz, Strike-Slip 1.8 1.6 -- - -- - -

1.4 1.2- P I 0,0 0.8 - XCos(theta)=O /

X Cos(theta)= 0.1 2 06X cos(theta) = 0.2 3.

0.4 - Xcos(theta) = 0.3 q -

0.2 0.2

- X Cos(theta) >= 0.4 5 0.01 0.1 1 10 Period (sec)

Somerville et al (1997) Scale Factors for FN/Ave Horiz 1.5- -

1.4 1.3 "

1..1 1.2

_______i__3_ -

00 J40.8 _____

H 0.7- - theta= 30 i qtheta =45 0.6 0.5 0.1 10 Period (sec)

Kocaeli Rupture and Strong Motion Stations 41 Ir 40.75-ARCJ.

A YPT IZI" Ad SKR SKR A /"ý pf 4a1 rt;A- . . .

2 I5.

30 30I.

. 25I ' I II a.. 1. 0. 75. . 1.

29

-F-I

.2.25 29.5 *II 29.75 'gI7 30 30.25 I1 30.5 30.75 31

IZT (near epicenter) 0.25 0

-0.5 5 10 15 2(

0 5 10 15 20 3O 0 5 10 15 20 Time (sec)

Spectral Acceleration (g) CD 0

0 0 .4 0

0 if 0*

• a bI- -ii p p ip i i i i ? iiri -i ir - irri iiFi i ? ! if??i I- II 0.1 I' 1k -I

-D CD

.o C0 0.

cjA .14 Si*PF i I I I 0

ARC 0.25 (off end of fault, down strike from epicenter) 0 el 2..I ARC NS 05 10 15 20 25 30 35 50

• ARC EW S,,*-L - ARC NS

-50 ' i . . .. i .. .. i ..

5 10 15 20 25 30 35 60=

30-"*

.0" ARC EW S -- Z- ARC NS

-61 .'

15 10 15 20 25 30 35 Time (sec)

I I I I

ARC (off end of fault, downstrike from epicenter)

I-I - 1 111l I I 1 1 1 1"II 1 1 t I II aI l Vt.--

. I II L7 :_ .I III -- ARC-NS

-- ARC-EW F-I

• 1* * "* - - '" L I I IWWI 0 0.1 ba 0

U*

C) l)

0.01 0.001 .I 14I 0).Ol 0.1 i Period (sec)

YPT 0.3 (near fault, down strike from epicenter)

O30.1o u-0.1

-0.3. 2.YP1

- i4 . . . . .. , , , , .. .. aI, ,

"10 15 20 25 30 100

-100I I 5 10 15 20 25 30 300 2 0 0 -_ _ - - _ ____.

._a I - YPT E 5 0

-100 5 10 15 20 25 30 35 Time (sec)

HI

YPT (near fault, down strike from epicenter) 10 I l iNS (FN)

III EWW(FP)

M00 CO) 0..

0.01 Period (sec)

I

Strong Motion Stations from the Chi-Chi 24 Earthqualke 23.5 12

Chi-Chi Earthquake S " cuIW5 -TCU04 N ,

Deip - 2Jkm 3MI Mil D20

• I

0.4*

Fling Effects 0.3 0.2 o.- - TCU049E.2 TC0052 E2 * *

• 0.1

-0.2

-0.31 20 25 30 35 40 45 50 55 60 100 2-S-100 - - TCU 049 E TC 0052 E

-200 , . .1 . .Fi. . . 1..

. . I I..

. . a. . . . .

.I 6. 1'a'I 2-200 35 4 Time (sec)

Time Domain Fling Model 0.1 "le 0

-0.11.. . . . . .

0 2 4 6 8 10 12 Time (sec) 10 40

~0

-40 0 2 4 6 8 10 Time (sec) 150 "0

-150 * , ' ' ' ' ' ' '

0o2 4 6 8 10 12 Time (sec)

I II

Separation of Fling and Wave Propagation Effects 0.5 S 0.25 v -- TCU052E

-0 35 40 45 50 55 60 100 50

~-100oln

-150 TCU052E

-200 ' ' ' , i . . . . .. u ..

30 35 40 45 50 55 60 100 0" **fling 6-100.--

TCU052E m200

• oo300 Time (sec)

Parameters Required for Fling "i Amplitude of Fling

+ From fault slip and geodetic data "i Duration (period) of Fling

• From strong motion data m Arrival Time of Fling

+ From numerical modeling

+ Relative timing of fling and S-waves

Fault Displacement L I ..... 6thPemntle~e 6.57.

Magnitudel Iloilo& 84thPercentile rioI SIe I

Attenuation of Fling Amplitude Example from Kocaeli Geodetic Data

-- I 1000 100 U *UJ 4

• 1 E

0.

U -0 a o 1999 Kocaeli 0 10- -- model i Mta

- I t i i i i i v i-I 10 100 Distance (kin)

• 0 O S~l C

C*-

Duration of Fling Measured.from Strong Motion Recordings (SKR from Kocaeli) 200 150 S100 50

-50

• ~T1 25 30 35 40 45 50 55 60 Time (sec)

I ,

Fling Period 150--

r 100 4..

50.

--- Fling Model (Tfling=l sec)

Straight Line Fit 0.

0 0.2 0.4 0.6 0.8 Time (sec)

Model for Duration of Fling (slope fixed by assuming median slip-velocity is independent of magnitude)

I I(

IWT I -Aý

-V I-F MedianT'ling from strong motion Model (Constant Median Slip-velocity) 1 7 7.5 8 Magnitude

Lessons for Long Period Ground Motions

"* Near fault ground motions can have large velocity pulses caused by directivity and/or fling "i Forward Directivity Effects

"*Observed in Kocaeli earthquake

• Consistent with previously derived models

"*Not observed in Chi-Chi earthquake due to shallow depth of hypocenter

"*Fling

• Observed in both Kocaeli and Chi-Chi III

• II I;

Lessons for Long Period Ground Motions mDirectivity

• Current scaling relations for directivity effects are generally consistent with data from new earthquakes

• Directivity effects result in narrow band peak in the long period spectrum

Lessons for Long Period Ground Motions

"* Fling

• Commonly used attenuation relations do not include fling

+ Fling effects are not represented in the empirical data prior to 1999

"* A separate ground motion model is needed for the fling,

• Fling effects scale differently with magnitude and distance than ground motion due to wave propagation

"* Ground motion from fling effects needs to be combined with the ground motion due to wave propagation

NRC/PG&E Open Meeting, San Francisco CA Diablo Canyon Independent Spent Fuel Storage Installation Ground Motions Norm Abrahamson Engineering Seismologist PG&E Geosciences Department 1.0&1 April 11, 2002

DCPP Ground Motions

"* Design Basis Ground Motions

"*Design Earthquake (DE)

"*Double Design Earthquake (DDE)

"4 Hosgri Earthquake (HE)

+ Newmark Hosgri

+ Blume Hosgri

"* Margin Evaluations

• Long Term Seismic Program (LTSP)

Response Spectra (5% damping)

O.i  ! *ji2!

,-Pend~d(se)

Time Histories for Hosgri Eqk E Approach

" Develop spectrum compatible time histories

" Use recorded ground motions as the reference

• Lucerne recording from the 1992 Landers earthquake M = 7.3, Strike-slip, Dist-= 1 km

" Satisfy SRP 3.7.1 requirements for time histories

Cf)

C.)

Example Spectrum for HE Time History I T I

Accounting for Lessons from Recent Earthqual es

"*No change was made to account for smaller ground motions at short-periods from recent earthquakes

"*An ISFSI Long-Period (ILP) spectrum was developed to account for the new information on long period ground motions

• Envelope of HE'and LTSP for T<2 sec

• Extended to T= 10 seconds using attenuation relations developed by PG&E

• Increased at T> 0.5 sec for directivity effects

"* Fling effects were added to the time history

"*ILP ground motions were used for ISFSI Part 72 analyses

ILP Spectra w/o Directivity I

Directivity Parameters X = 70km/13Okm X = 0.64 0 = 3 degrees

Directivity Effects on the Average Horizontal Component

z 0

4-4 o0l 0l, o3

Combined Directivity Effects

.Total F ditiit fao f m Total FN directivity factor (from model)

Total FP directivity factor

-- Total FN directivity factor used

~.I Period (se) 7 7*

~1

ILP Spectra with Directivity ILP Spectra: Vertical ILP Spectra (5% damping)

II

ILP Time Histories

• 5 Sets of 3-component spectrum-compatible time histories were developed (SRP 3.7.1 criteria)

• Time histories are matched to the ILP spectra Set Earthquake Station 1 1992 Landers Lucerne 2a 1999 Kocaeli Yarimca 3 1989 Loma Prieta LGPC 5 1940 Imperial Valley El Centro 6 1989 Loma Prieta Saratoga

ectra of ILP (5 sets)

Example of Time Histories for ILP (Set 1 FN)

I

Fling m Use 84th Percentile

• Two parameters: Displacement at site and Fling period

• Use 84th percentile displacement

+ Use fling period to give 84th percentile acceleration Fling Displacement Median slip on fault = 233 cm Median disp at site = 59 cm 84th percentile disp at site = 115 cm Fling Period 3.2 sec (84th percentile acc = 0.072g)

Issues for Combining Fling and Vibratory Ground Motion m What is the timing between fling and S-waves?

• For sites close to the fault, fling arrives-near the S-wave m Polarity of fling and S-waves?

• For design ground motions, require constructive interference of velocity

Example Timing of Fling hf) 0 rMM4

Average FP Spectrum Including Fling

- i

,) ,

I

/-

• Average FP without fling SJ ]-Average FP with Fling -

0 "0.1

~~ I

Effects of Directivity and Fling Ground Motion Summary

"- Used DCPP design basis ground motions

+HE, DDE spectra

• HE time histories

"*Applied new research results for directivity and fling

" ILP spectra and time histories

• Increase in the long period ground motions

" Approaches are new and are not standard in earthquake engineering practice III

NRC/PG&E Open Meeting, San Francisco, CA Diablo Canyon Independent-Spent Fuel Storage Installation Geology William Page Engineering Geologist PG&E Geosciences Department April 11, 2002

Geology Team

"*Bill Page, PG&E Geosciences Dept.

"*Jeff Bachhuber, William Lettis & Assoc.

"*Charlie Brankman, William Lettis & Assoc.

"*Bill Lettis, William Lettis & Assoc.

Purpose of Geologic Investigations m Foundation conditions

+ Rock characteristics

• Surficial deposits m Slope stability

• Landslides, debris flows

• Rock characteristics

+Bedding, joints, faults

• Clay beds

11

Bedrock in ISFSI Area

Dolomite Outcrop Sandstone outcrop

' I

Surficial Deposits in ISFSI Area Marine Terraces 400 Feet, CIA.

ý:l ,

WI tzý CD 0n oc$

0 C/) CD W T1 ~0 P-A 0 fl+ CI)

CA II

Surficial

Deposits in ISFSI Area Cross

• Sections Figure 2.6.7),

600 500" 400

. 300 w

200 100 0

D West East 4

.U, I

(From SAR, Figure 2.6-16a) 1, 1

Friable Rock

Friable Rock J a

Clay beds Folds Rose Diagrams for Joints and Faults

!TNT ,E.

ý;__Wuo gn- 44 0 31i lkv.Pl Ise IF z

-I-ýQ_

4,73 '4w.

JF W If 974K lylý , kv.

P t.2W Apr _4 AU

P 4r qr,,

pre tF, A .

Co 4.)

'I E

A C C)

S74 C)

m4 H

01-N NI-429tImm 11 1 1 e

1/16- to 314-inch thick clay beds Clay Beds in Trench T- 14 1- to 4-inch thick clay beds

Optical televiewer image Core Thick Clay Bed in Boring OOBA-1 at 55 Feet I I I

A a a a -- A k . m - -

Clay bed 01-1 at 130 feet Clay bed 01-G at 19 feet Thin Clay Beds in Boring 01-I and 01-G

Elevation (feet)

CA) 0: -P, o:

o 0 0)

.00: 0 0 0 0 0

Z) 0 co 0

Cross Section B-B

(WG;~) U048UAGS Comparison of Bedrock at ISFSI and Power Block w Same stratigraphic unit

• Obispo Formation Tofb n Same lithology and density

+ Dolomite and sandstone m Similar shear wave velocity

Cross Section I-1

700 600 500 1971 re-borrow topgraphy ST-14A C-- 00A- R irRoad fail "400 a)a 1000 (From SAR, Fig re 2.6-18) 00 Facies Change I!

Geologic Constraints for Modeling Potential Large-scale Rock Mass Movements "i Geometry of clay beds.

"* Clay strength

"* Discontinuity of clay beds

"*Rock mass discontinuities

"*Groundwater I

II 700 600 500

"*, 400 0

300 200 100 0

Dip Direction

Geometry of Clay Beds

" Change in dip directions across the structural transitions from monocline to syncline Upper part of slope bedding dips out of slope

• 10 to 20 degrees

"*Lower part of slope bedding dips to the west; apparent dip is subhorizontal

"* These structural changes limit size of potential rock mass movements I

0 tIw '51 iL_ =**

o~ee cce) o 0 0 0 0 0 0 0

0', Ue)u

Discontinuity of Clay Beds m Clay beds have limited lateral extent

. Limited correlation between borings and outcrops

• Clay beds more common in dolomite, do not extend across facies contacts

• Analysis indicates beds extend a few tens to a few hundreds of feet

• Potential large rock mass movements would step between clay beds along joints and through rock in a "staircase" profile.

I 700 -- 0 100Feet* 18tol/4- =*50ft,.

<118 *25ft.

Scale V=H 600 1971 " " ,re-borrow T1 A -**

• 500 tOp: )graphy -

• " Resrve VrlRoa-T-14 0 o1.CTF-A o1-A Is00 "100 S(From SAR, Figre 2.6-18) T-1D_

OOBA- 01 4 Clay Bed Thickness 141

,T 100 17 (Fro Figre SAR 26-18

Clay Strength Clay bed thickness varies laterally from a few inches to less than 1/8-inch thick

"*Rock to rock contact through the clay bed is typical, increasing effective shear strength

"*Clay strength measured in laboratory used i the modeling analysis (presented later)

Joints and Faults Rock Mass Discontinuities m Joints and minor faults disrupt the continuity of the clay beds causing large-scale rock mass movement to break through rock.

m Faults and joint sets that are subparallel to the potential down slope motion would form the

.lateral margins of potential rock slides

Elevation CO(

(feet) 3M 0 00 o 0 0 0 0 CD

Groundwater in ISFSI Area i Main water table 200 feet below ISFSI

• (100 ft elevation)

• Hence, not an issue for slope stability m Temporary perched ground water

• Top of clay beds in slope above ISFSI

• Assume clay beds are saturated in large rock mass models

• Assume perched water in cutslope rock wedge models II 11

Elevation (feet) co 00 pot Il CD rn

Potential Large-scale Rock Mass Model -Intermediate Slope Ir Nomt Somth 800 MODEL 2 700 600 971 pr-o rrow O*,va~tl topogaphy lower *csae ISFSI /N CTF ~Pads T1 400 200 .

100 .

Potential Large-scale Rock Mass Model -Lower Slopeit I

I SOUth 800 North.

MODEL 3 700 600 o91IeIn tower access '"°"O"""

1971 pro .. "

500 toporaphy

" ~~tower access TI II FS, Pads t CTF jj - O 01.5 0 c---.

300 '20y.

MT W.- 1 100

II 700 " 0 p100 Feet 1/8t1:1/4 - - 50ft.

Scale <18*5 V=H 600 500 Pre-1971 topography ----- A 4000TF"FA-r. AY

• ,, * *"* T-18 40 f7-B 0B ResS" r rRoad T1 01-CTF-A 01-A 300 200 1004 (From SAR, Figtre 2.6-18) __-

0 Evidence of No Landslides at ISFSI

Evidence of No Landslides at ISFSI No evidence on pre-1970 air photos No evidence at the borrow site in studies thereof or during excavation

"*No evidence of any fissures or fissure fills in trenches for ISFSI

"*Topography of ridge 430,000 years old

"* Slope has been subjected to numerous large earthquakes in this time period I.I

"Back Calculation" mNever the less, assume 3 to 4 inches of movement for a "back calculation".

m Results indicate that undrained clay strengths are substantially greater than those from the laboratory tests.

Conclusions mThe ISFSI and CTF sites will be founded on bedrock

. Sandstone and dolomite

+ Contain zones of friable rock SThe ISFSI will be founded on bedrock that is the same as the DCPP power block.

Conclusions (cont' d)

"*The slope above the ISFSI site has stratigraphy and geometry that allows for potential large rock mass movements.

"*This is extremely unlikely because

"*no rock slides have occurred in the past 430,000 years

" modeling ignores several geologic factors that tend to resist down slope movements

Conclusions (cont' d) a The transport route has variable foundation conditions - rock, dense surficial deposits, and engineered fill.

0 Small debris flows could potentially close portions of the transport route during or immediately following intense rainstorms.

Ii II II

Conclusions (cont' d) m The several minor bedrock faults'at the ISFSI site are not capable. Therefore, there is no potential for surface faulting at the ISFSI or CTF .sites.

I Ir