f. beach leight environmental earth sciences `1e, cap s earth sciences s ... preliminary...

1F. Beach Leighton & Associates

•

I0

May 26, 1972

TO : Donald R. Warren CompanyAttention : Mr . Robert Cummins

FROM: F. Beach Leighton F Associates

`1e, cap sEnvironmental Earth Sciences

Project No . 1988

SUBJECT : Preliminary Geologic Investigation of Rocketdyne Tank Site(Coca Test Stand Area), Santa Susana Field Laboratory,Ventura County, Californi a

Introduction and Scope of Investigation

In accordance with your request, this report presents the results of our

preliminary investigation of the subject site to determine geologic factors

affecting grading feasibility and seismic design factors . The study included

(1) a site reconnaissance and geologic mapping of existing exposures, (2) exami-

nation, logging and analysis of core samples from three borings made at the site,

(3) measurement of seismic velocities of selected core samples to'determine rock

hardness, (4) a regional seismicity analysis to estimate probable ground accel-

erations at the site resulting from future earthquakes, (5) review of existing

pertinent maps and reports by others on the site area, and (6) examination of

stereoscopic pairs of aerial photographs taken in 1948 and 1957 .

Accompanying Illustrations

Index Map on Page 2 (1220-scale)

Geologic Map (80-scale) in pocket

Geologic Cross Section A-A' (20-scale)

D3 ;A`' 3 ' 1572

ONALD ~. V~Wr-.ii4,_N Co .

C . . . . . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

C✓ iP`i : . .. .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . .

. . . . . . . . . . . . . . . . . . . . .

LA HABRA • LOS ANGELES • SAN BERNARDINO • LAGUNA BEACH • SAN JOSE • SACRAMENTO

offices : 300 S . Beach Boulevard 357 West Second St. 15233 Ventura Boulevar dLa Habra, Calif. 90631 San Bernardino , Calif. 92401 Sherman Oaks, California 91403

(714) 526-1337 / (213) 694-1826 (714) 884-1988 (213) 990-107 0

I I I I LII I

BNA00222868HDMSeOO187159

EFFECTIVE DATE* i DEC 1964

SANTA SUSANA FIELD LABORATOR Y

BRAVO

WAREHOUSE .

RESEARCH

APPROXIMATE SCALE : 1 "=1220 F BEACH LEIGHTON & ASSOC.

INDEX MA P

7= Jzz:zd

GATE 503-STOP!!!(DD 250 - ROUTING)

D. -R . Marren Co . - Rocketdyne May 26, 1972

Site Conditions and Topography

The subject tank site, located in the south-central portion of the Rocketdyne

Field Laboratory facilities, is . approximately 3-1/2 miles west of Valley Circle

Boulevard in the Simi Hills . Access is via Woolsey Canyon Road and other pri-

vate roads within the property (see Index Map) .

The proposed high-pressure tank vault site, approximately 60 by 110 feet in

size, is to be excavated about 10 feet below the grade of the existing paved

drainage channel . Its location and details of the topography are shown on the

accompanying Geologic Map . Discrepancies between the base map contours and

the actual field conditions were adjusted on the profile of the Geologic Cross

Section A-A', based on our field measurements of the existing slope .

The site excavation would necessitate making a steep (1/4 :1 or somewhat flatter)

cut above the south side of the vault area . Maximum height of such a cut would

range between about 70 feet and 90 feet (including a 15-foot high vertical cut

at the toe of slope) .

- 3 -

F._Beach_Leiehton & Associates

I I I I I I IBNA00222870

HDMSe00187161

rn _ - Rocketdyne

rn Rocketdyne

rn _ - Rocketdyne

etdk ynern _ - Roc

rn Rocketdyne

rn _ - Rocketdyne

rn _ - Rocketdyne

rn Rocketdyne

rn _ - Rocketdyne

rn _ - Rocketdyne

rn Rocketdyne

rn _ - Rocketdyne

rn _ - Rocketdyne

rn _ - Rocketdyne

HDMSe00187162

D . R. Warren Co. - Rocketdyne May 26, 1972

Regionally, the nearest major faults are south and southwest of the site . The

closest is approximately 1700 feet southerly . None is considered potentially

active, however, judging from their relationship in the tectonic framework and

the apparent lack of seismic activity . Active faults are discussed belo w

under Seismicity Analysis .

Joints and Fractures

Rock discontinuities or defects include relatively planar joints along which

little or no movement has occurred, and fractures or open cracks which may be

curved, irregular and intersecting . Near weathered surfaces,exfoliation joints

or release fractures are subparallel to the ground surface . Combinations of

intersecting bedding planes, joints and fractures can facilitate rock falls,

ravelling and dislodgment of material from slopes . At depth, the amount of

fractures and joints generally diminishes . Some deeper existing cuts, however,

exhibited fracturing around shot holes made for blasting of the hard sandstone .

Effect of Geologic Structure on Slope Stabilit y

Bedding within the formation in the site area dips consistently north-northwest-

ward between about 25° and 30° . Although the sandstone is thick-bedded and not

particularly susceptible to bedding-plane sliding, all existing or proposed

cut-slopes facing northward should be carefully evaluated for potential insta-

bilities . Of particular importance is the detection of weak clay seams, beds,

or shale layers which could cause massive block failures . The extent of such

failures would depend on the continuity of the planes of weakness and the presence

of secondary features such as joints and fractures .

Careful examination of the 2" diameter cores obtained from Boring 1 did not

reveal the presence of clay or shale beds . Although the percentage of core

recovery was very good, a thin clay layer could have gone undetected . The

bedding where recognizable within the sandstone is shown on the Cross Section

at the various depths encountered . Since the cores could not be oriented, i t

is assumed that the dips measured were in the direction of the regional inclina-

tion, which is consistently north-northwestward .

- 5 -

F. Beach Leighton & Associates

I I I I I IBNA00222872

HDMSe00187163

R

D. R. Warren Co . - Rocketdyne May 26, 1972

The s andstone encountered in Borings 2 and 3 appeared similar to the interval

cored in Boring 1, except for a greater degree of weathering of the formation

in the lower area . No direct correlation of beds between the upper and lower

borings could be made, however . Nevertheless, the interval containing the

recognizable bedding (and possibly a southward continuation of the clay bed

in Boring 3) is expected to be intersected near the base of the proposed cut

along the south side of the tank vault . This would be the most likely zone

along which failures could occur (see Cross Section) .

- 6 -

F. Beach• Leighton & Associates .

11 11 11 lvi II III' I IBNA00222873

HDMSe00187164

D. R. Warren Co . - Rocketdyne

ROCK HARDNESS

Visual Observations

May 26, 1972

Past experience with excavations in the Chico Formation in the project area,

and elsewhere, indicates that grading difficulty is generally encountered at

relatively shallow depths wherever the massive, thick-bedded sandstone is

present . Normally, only the more weathered, less cemented sandstone along the

valley bottoms is rippable with conventional heavy-duty earthmoving equipment .

It is apparent from inspection of nearby cuts that drilling and blasting was

required for most of the deeper excavations .

Measured Seismic Velocitie s

To quantitatively analyze the rock hardness properties, the seismic velocities

(i .e ., the speed of elastic waves transmitted through the rock) were measured

for 6 typical core samples . A microseismic timer, DynaMetric Model 217B,

accurate to within one-millionth of a second, was used for these measurements .

The results are tabulated as follows :

Core Interval Measured VelocityBoring No. (feet) ( feet per second )

1 19 - 22 556041 - 44 6450 to 667064 - 68.4 845081 - 83 .6 8900 to 9440 (gravelly

sandstone )

2 11.5 - 13

3 19.5 - 20 . 8

7 -

F_ Reach Leighton Associates

4760 to 4890

4800 to 5560

I I I I I iBNA00222874

HDMSeOO187165


An average velocity for the upper limit of rippable rock is approximately

5500 feet per second, using a D-9 dozer (or equivalent size) and a single-

shank ripper . Rocks such as shales or other thinly laminated or jointe d

rock having somewhat higher velocities, however, can also be ripped . Massive,

thick-bedded sandstones (as are present under the subject site), on the other

hand, can cause extreme grading difficulties if the velocities are as low as

4000 feet per second .

Judging from the velocity measurements obtained, none of the core intervals

tested would be rippable . Based on visual observations, only the upper 5 to 10

feet of rock in the area of Borings 2 and 3 would be rippable . Blasting would

be necessary below these depths .

- 8 -


11 11 11 II III I IBNA00222875

HDMSe00187166

D . R . Warren Co. - Rocketdyne May 26, 1972

SEISMICITY ANALYSIS

Seismic hazards at the proposed tank site are expected to be confined to

ground shaking . No active or potentially active faults are known to transect

the site, and none were indicated by our field inspection or study of aerial

photographs of the area.

The following list of potential earthquakes for the area is based on the seismic

history and physical characteristics of the faults :

Causative Dist anceExpectedMagnitude

Expected MaximumGround Accelera-

Probability ofOccurrence

Fault Miles) (Richter) tion (Gravity) (50-Year Life )

Simi 4 .9 6 .0 - 7 .0 0 .3 - 0 .5 Very low

Santa Susana 7 .9 6 .0 - 7 .0 0 .3 - 0 .4 Low

San Fernando 16 6 .0 - 7 .0 0 .1 - 0 .2 -Intermediat e

San Andreas 35 7 .0 - 8 .0 0 .2 - 0 .3 Likely

8 .0 - 8 .5 0 .3 - 0 .5 'Intermediate

While data are not sufficient to statistically derive precise probabilities of

occurrence, the generalized ranges included above are estimated to have the

following numerical ranges : Very low, less than 5% ; Low, 5-15% ; Intermediate,

15-50% ; Likely, greater than 50% . From the above, maximum probable ground

acceleration is estimated at 0 .25g ., and maximum credible ground acceleration

at 0 .50g .

- 9 -


11 11 11 II II 11 I IBNA00222876

HDMSeOO187167

D . R. Warren Co . - Rocketdyne May 26, 1972

CONCLUSIONS AND RECOMMENDATIONS

General Statemen t

From a geologic standpoint, the proposed high cut and development of the

subject site appears feasible, based on the known site conditions . Because

of the steepness and height of the cut, however, and the possibility of

exposing undetected planes of weakness near the toe of the cut, a significant

degree of risk of slope failure either during construction or afterward (if

appropriate stabilization were not accomplished) must be assumed . The amount

of risk can be reduced if certain recommendations and considerations, discussed

below, are taken into account .

Summary of Chief Favorable Geologic Condition s

1 . The massive and thick-bedded nature of the underlying sandstone minimizes

the possibility of bedding plane sliding . No shale or clay beds were

evidenced in Core Borine 1 .

2 . Existing steep cuts nearby which expose similar sandstones with daylighted

bedding have been stable, so long as weak shale or clay beds have not been

undercut .

3 . The hardness and cementation of the sandstone, and the general lack of

jointing and fracturing (in the upper core boring), are favorable for

slope stability, even in steep cuts .

4 . No active or major faults are known to transect the site . Ground rupture

due to faulting, therefore, is not expected to occur on the site . The

nearest known potentially active fault is approximately 8 miles away .

S . No apparent seepage was encountered in the immediate site area .

6 . No evidence of landsliding or other significant existing slope stability

problems were found underlying the site .

- 10 -


11I 11 I II I IBNA00222877

HDMSeOO187168


Summary of Chief Unfavorable Geologic Condition s

1 . The bedding inclinations are unfavorably oriented for stability of the

proposed main cut-slope of the tank vault .

2 . A clay or shale bed (similar to that encountered in Boring 3 at 21 feet)

could be daylighted near the toe of the proposed cut, even though undetected

in Boring 1 .

3 . Blasting for excavation of the majority of the site is expected to be

•necessary .

Recommendation s

.1 . Serious consideration should be given to site relocation or modification

of design, because of significant costs which could be incurred in stabili-

zation work if adverse geologic conditions are exposed by the proposed

PY!`AII a'f i nn Tf+c ~orsrco n~ c l me •f . 4 l++rn v,i cL .+1.., +l,,S n.1 ,.+- . .- . .. . .,. .. ..- . . . . . .- ..Vbivv V.L . JiVj+V .~. v.ii , ..iV i .L•J1\ 111 uLLFt \illb Nl*V prvp\`~ia, .,+ \.u a ,

can be minimized by :

a . rock bolting or pinning prior to and during excavation (before the

zones of possible weakness are exposed) .

b . additional exploratory borings .

c . raising the grade or shifting the toe of the main cut-slope north-

ward to avoid the anticipated zones of possible weakness .

2 . We recommend that if site relocation or redesign is not elected, the

proposed main cut-slope be made no steeper than 1/2 :1, with a bench about

8 to 10 feet wide (at approximately elevation 1885 feet)-incorporated into

the design . The purpose of this bench would be twofold : to provide catch-

ment for rock dislodgment from the cut, and to provide a platform for

installation of any additional rock pins found necessary after completion

of the cut .

- 11 -


I I I I IBNA00222878

HDMSe00187169


3. Stability calculations should be made to, confirm the feasibility of such

steep cuts, from a soils engineering standpoint . Preliminary analyses

should also be made for the probable rock pinning requirements and the

feasibility of at least partial stabilization of the toe of the cut by

specially designing the southerly retaining wall of the vault structure .

4 . Seismic shaking equivalent to that shown on the table under Seismicity

Analysis should be taken into consideration during design and construction .

The maximum probable horizontal ground acceleration expected at the site

is estimated at 0 .25g .

5 . The site grading plans should be geologically reviewed once the details

of exact location and design are finalized . We recommend that the plans

be based on accurate topography .

Respectfully submitted ,

Richard LungEngineering Geologist (EG 111 )

Reviewed bye-'beach Lei EtonEngineering Geologist (EG 599 )

/mk

Distribution : 7

Donald R . Warren Company (7)Attention : Mr . Robert Cummins

- 12 -


I I I I I I

BNA00222879HDMSe00187170

f. beach leight environmental earth sciences `1e, cap s earth sciences s ... preliminary...

Documents