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GEOTECHNICAL EVALUATIONW.R. GRACE DAMRAINY CREEK, MONTANA

HLA Job No. 5891,053.03

Harding Lawson Associates

A Report Prepared for

W. R. Grace & CompanyConstruction Products DivisionP.O. Box 609Libby, Montana 59923

GEOTECHNICAL EVALUATIONW.R. GRACE DAMRAINY CREEK, MONTANA

HLA Job No. 5891,053.03

by

Shahriar Vahdani, Ph.D.Civil Engineer

Hugo/HansonGeotechnical Engineer

Robert T. LawsonCivil Engineer

Harding Lawson Associates303 Second Street, 630 NorthSan Francisco, California 94107415/543-8422

February 3, 1992

.~V ROBERT T.

\ LAWSON-


-J

TABLE OF CONTENTS

LIST OF ILLUSTRATIONS

I INTRODUCTION

II PROJECT DESCRIPTION

Ill FIELD INVESTIGATION AND LABORATORY TESTING

IV

V

VI

VII

DISCUSSIONA. Material Characterization

I. Tailings2. Embankment Soils3. Natural Foundation Soils

B. Seismic Design Criteria1. Regional and Site Geologv2. Seismicitv3. Design Ground Motion

C. Ground\vater ConsiderationsD. Static and Dynamic Design Considerations

1 . Consolidation Settlement2. Liquefaction Potential3. Stabi l i ty of Slopes-4. Deformation Analys is

CONCLUSION'S AND RECOMMENDATIONS

REFERENCES

ILLUSTRATIONS

iii

1

3

5

7777888

1 112131414141518

19

21

22

DISTRIBUTION

B12703-R71February 5, 1992


LIST OF ILLUSTRATIONS

Plate 1

Plates 2through J 1

Plate 12

Plate 13

Plate 14

Plates 15through 25

Plate 26

Plates 27through 30

Plate 31

Plate 32

Plate 33

Plate 34

Plate 35

Plate 36

Site Plan

Logs of Borings A-l t h rough A-10

Soil Classif icat ion Chart

Physical Properties Cr i t e r i a for Soil Classifications

Physical Propert ies Cr i te r ia for Rock Classif icat ion

Par t ic le Size Ana lys i s Data

P la s t i c i t y Chart

Unconsolidated-Undrained Triaxial CompressionTest Reports

Consol ida t ion Test Data

Compact ion Test Data

Geologic Map of Si te and V i c i n i t y

S t a b i l i t y A n a l y s i s for Wate r A p p r o x i m a t e l y 500 feetfrom E m b a n k m e n t

S t a b i l i t y A n a l y s i s for Water at Face of E m b a n k m e n t

Schemat ic Section of Proposed Dra inage /Moni to r ing Schemes

B12703-R71February 5, 1992


1 INTRODUCTION

This report presents the results of a geotechnical investigation and assessment

performed by Harding Lawson Associates ( H L A ) of the long-term s tab i l i ty of the W. R.

Grace Zonolite tailings retention dam in Libby, Montana. Our s tudy was conducted for

W. R. Grace Company, Construction Products Division, as part of the closure plans for

the mining facil i ty.

In the early 1970s, we performed a p r e l i m i n a r y explora t ion and a detai led

foundat ion inves t iga t ion for the cons t ruc t ion of the t a i l i n g s re tent ion dam. The resul ts

were presented in reports dated J a n u a r y ' 8 , 1971 and A u g u s t 18, 1971, respectively. We

subsequently performed const ruct ion observat ion sen ices for the project. In 1974, we

conducted waste disposal studies for the mine ta i l ings and presented the results in

reports dated Ju ly 19, 1974 and September 30, 1974. Final ly , we presented the results of

a processing s t udy in a report dated Februa ry 29, 1980.

The purpose of the c u r r e n t inves t iga t ion was to determine whe ther the

long-term s t a b i l i t y of the dam conforms to the State of Montana requi rements for

closure. Primary concerns regarding performance of the dam included'. 1) strength of

the tailings and the potential for a s i g n i f i c a n t downstream flow of t a i l ings in a

postulated dam f a i l u r e , 2) p o t e n t i a l for l i q u e f a c t i o n of the t a i l ings du r ing the max imum

credible ea r thquake (MCE)* and its p o t e n t i a l effects on the s t a b i l i t y of the dam, and

3) re l iabi l i ty and adequacy of the e x i s t i n g surface and in te rna l drainage systems for a

permanent embankment .

* The m a x i m u m credible ea r thquake is the m a x i m u m event which , consistent wi thcurrent knowledge, may ever be expected at the b u i l d i n g site w i t h i n the knowngeological f r amework .

B12703-R71 1 of 22


The scope of work for this phase of the study, as outlined in our revised

proposal dated April 10, 1991, was to review pertinent literature and reports, explore

subsurface conditions of the tailings, embankment, and foundation materials, and

perform engineering analyses to develop conclusions and, as appropriate,

recommendations regarding the following:

1. Seismic design criteria

2. Geotechnical characteristics of the tailings material.

3. Liquefaction potential of the tailings and foundation soil based on currentstandards of practice.

4. Long-term stat ic and dynamic stabil i ty of the dam.

5. Adequacy of the exist ing internal drainage system of the dam.

B12703-R71 2 of 22

1


11 PROJECT DESCRIPTION

W.R. Grace dam is located on R a i n y Creek, approximate ly 3 miles northeast of

the Kootenai River and nor thwest of V e r m i c u l i t e Moun ta in on which the mine and m i l l

were formerly situated. Construct ion of the ta i l ings retention dam began with a

50-foot-high starter e m b a n k m e n t , wh ich was completed in November 1971. Since tha t

time, the storage has been inc remen ta l l y increased us ing a downstream, staged method of

construction to raise the embankment as the t a i l i n g s accumulated. The embankment is

now J27 feet high wi th the crest at approximate E leva t ion +2927 feet.* The tai l ings

surface elevation adjacent to the dam var ies between +2913 and +2908 feet and slopes

down to about E l e v a t i o n +2903 feet where it in te rsec ts the surface of a pond upst ream

of the dam, as shown on the Site P lan , Plate I . At the t ime of our f ie ld i nves t iga t ion

(June 1991), the pond was about 750 feet f rom the dam. The m a x i m u m depth, surface

elevation, and distance of the pond from the dam vary seasonally; however, it is

important to note t h a t p resen t ly water is not impounded d i r ec t l y behind the dam and

tha t the excess water f rom the d r a i n a g e basin and R a i n y Creek is d i v e r t e d a round the

reservoir t h r o u g h a -18-inch d i a m e t e r c o r r u g a t e d meta l pipe c u l v e r t and an i n t a k e

s t ruc ture near the t a i l i n g s - w a t e r in te r face upst ream of the dam.

To restore R a i n y Creek to its n a t u r a l state, two a l t e rna t ives are being considered

by the design team: 1) to m a i n t a i n the water upst ream of the dam at approximate ly

Elevation +2510 feet by construct ing a shal low d ivers ion levee about 500 feet upstream

of the dam and by replacing the e x i s t i n g c u l v e r t w i t h a channe l s t a r t ing at the proposed

levee location to discharge excess water t h rough a new spillway to be constructed in the

left abutment , and 2) to allow water to flood the exis t ing ta i l ings reservoir and be

National Geodetic Ver t ica l Datum. NGVD.

B12703-R71 3 of 22


impounded direct ly behind the dam. The impounded water would be discharged

through a new spi l lway to be constructed in the lef t abu tmen t .

J

B12703-R71 4 of 22


| III FIELD INVESTIGATION AND LABORATORY TESTING

~1 We explored the subsurface condi t ions at the dam site by d r i l l i n g 10 test borings

at the locations shown on Plate 1. Borings A-l t h rough A-5 were dri l led in the ta i l ings

I to obtain soil samples for classification and laboratory testing. To augment available

subsurface informat ion and to obtain data needed for determining l iquefac t ion potent ial

and evaluating the natural foundat ion mater ia l (based on today's standards), Borings A-6

"1 through A-10 were drilled on the downstream side, near the left abu tmen t . The borings

were drilled to depths between 2 1 - 1 / 2 and 77 feet us ing a t ruck-mounted rotary

: ) d r i l l ing rig. An open well piezometer was i n s t a l l e d in Boring A-8. Boulders

encountered d u r i n g d r i l l i n g of Borings A-6 t h r o u g h A - 1 0 were cored us ing NX coring

I equ ipment . Our f i e ld eng inee r logged the bor ings and ob ta ined samples for visual

classif icat ion and l abora to ry t e s t i n g . The soil types encountered were classified in

. J accordance w i t h ASTM D2487-85 based on v i s u a l - m a n u a l procedures as o u t l i n e d in

i ASTM D2488-84. The bor ing logs are presented on Plates 2 through 11. The soil

classification system tha t was used is presented on Plate 12. Physical properties cr i ter ia

'. for soil and rock c lass i f ica t ions are presented on Pla tes 13 and 14, respect ively.

Soil samples were ob t a ined u s i n g a Sprague and Henwood (S&H) sp l i t -ba r re lIj sampler (3 .0 - inch-ou ts ide d i a m e t e r , 2 . 45 - inch - in s ide d i a m e t e r ) , a s tandard

, penetrat ion test (SPT) sampler, and t h i n - w a l l e d Shelby tubes (3.0-inch outside• J diameter, 2.87-inch inside diameter) . Both S&H and SPT samplers were dr iven by a

| 140-pound, automat ic- t r ip hammer f a l l i n g 30 inches. The number of blows required

B12703-R71 5 of 22

I


1

]

j

to drive the sampler the f i n a l 12 inches of an 18-inch drive were recorded. The S&H

blows were converted to pseudo SPT N-values* to aid in comparison wi th publ ished

data. This conversion is only approximate and its re l i ab i l i ty varies wi th soil type and

sampling procedures. The pseudo SPT N-va lues obtained with the S&H sampler and

N-values obtained w i t h the SPT sampler are shown on the boring logs. Shelby tubes

were used to obtain r e l a t i ve ly und is tu rbed samples of silty mater ia l .

The soil samples were ree.xamined in our laboratory to confirm field

classifications and to select representat ive samples for testing. Laboratory tests

determined mois ture content , dry dens i t y , At terberg l imi t s , gradat ion, percent passing

the No. 200 sieve, u n c o n s o l i d a t e d - u n d r a l n e d t r i a x i a l shear s t r eng th , consol idat ion

characteris t ics , and compact ion cha rac te r i s t i c s . The laboratory test r esu l t s are

summarized on the bor ing logs in the m a n n e r described in the Key to Test Data shown

on Plate 12.

Particle size ( g r a d a t i o n ) data are presented on Plates 15 t h r o u g h 25. At terberg

l imi t s test data are presented on Plate 26. Shear s t rength test data are presented on

Plates 27 t h rough 30. Conso l ida t ion test da ta are presented on Plate 31, and compact ion

test data are presented on Plate 32.

* The SPT N - v a l u e is defined as the number of blows of a 140-pound hammer,fall ing freely through the he igh t of 30 inches, required to drive a standard

] penetration test sampler (2-inch outs ide diameter . 1-3/8-inch shoe inside--' diameter , and 1 -1 /2 - inch tube ins ide d i a m e t e r ) the last 12 inches of an 18-inch

drive. For SPT procedures, see ASTM D1586-84.

1

B12703-R71 6 of 22

I

:l


] IV DISCUSSION

A. Material Character izat ion

1 1. Tailings

Borings A-l th rough A-5 were d r i l l ed in the ta i l ings mater ial . The• ' 1

I tailings consist of interbedded layers of soft to s t i f f elastic silt (60%) and loose to

medium dense poorly graded sands and s i l t y sands (40%) with mica and pyr i te flakes.

/ Silt and sand layers generally slope down and away from the embankment, reflecting the

;] fact that t a i l i n g s were discharged at the f ive d ischarge locations shown on Plate I.

On the basis of laboratory tests performed on elastic silt samples, we assigned a

I static undra ined shear s t r eng th to th i s ma te r i a l w h i c h varies l i n e a r l y from 50 pounds per

square foot (psf) at the surface to 1900 psf at the f o u n d a t i o n level (E leva t ion +2800

feet). Based on our exper ience w i t h s i m i l a r m a t e r i a l (San Francisco Bay Mud and other

plastic s i l ts) , we judge t h a t d u r i n g the design e a r t h q u a k e the shear s t rength of s i l ts

encountered w i l l be t emporar i ly reduced by about 30 percent due to pore water pressure

bu i ld -up caused by e a r t h q u a k e - i n d u c e d cycl ic loading condi t ions. \Ve assigned an

average f r ic t ion angle of 30 degrees to the sands and s i l t y sands for static load ing

conditions. Based on an emp i r i c a l method suggested by Seed and Harder (1990). we

assigned a pos t - l iquefact ion r e s idua l undra ined shear s t rength of 100 psf to th i s mate r ia l

(see Section IV.D.2 for discussion on l i que fac t i on po ten t i a l ) .

2. Embankment Soils

Embankmen t soils were encountered near the bottoms of borings A - l , A-

2 and A-4. These soils consist of dense to very dense, well graded s i l t y sands. On the

basis of 1) data obtained d u r i n g t h i s i nves t iga t ion . 2) laboratory tests performed on

representat ive samples d u r i n g the 1971 s tudy , and 3) correlat ion wi th published data, we

B12703-R71 7 of 22


assigned the embankment soils an ef fect ive friction angle of 37 degrees and cohesion

values ranging between 50 and 500 psf. The upper bound effective cohesion value of

500 psf was obtained from unconsolidated undrained triaxial tests. Due to strain

rate/creep effects, however, the field cohesion value could be somewhat lower.

Therefore, consideration of a range in the cohesion value (as stated above) was deemed

appropriate.

3. Natural Foundation Soils

Natural foundation soils encountered during both the 1971 and present

explorations, consist mainly of dense to very dense poorly graded gravels, dense to very

dense poorly graded sands and moderately hard, friable pyroxenite bedrock, with

abundant magnetite and pyriie.

B. Seismic Design Criteria

1. Regional And Site Geology*

The project site on Rainy Creek is in a region exposing pre-Cambrian

age bedrock. The rocks, chiefly argillite and qunrtz i te of the Belt Series, are folded in a

series of broad open northwest- t rending folds. In Rainy Creek, the rocks are intruded

by basic plutonic igneous rocks consisting of pyroxeni te and syenite. A geologic map of

the site and vicinity is shown on Plate 33.

The terrain within the region is relatively flat, and is the result of long continued

erosion until mid-Tertiary geologic time. During the Pliocene through mid-Pleistocene

epochs, the area was subjected to faulting and uplift which resulted in renewed stream

Harding, Miller. Lawson & Associates. 1971. "Foundation Investigation andEngineering Analyses, Tailings Dam, \V. R. Grace & Company, ConstructionProducts Division, near Libby, Montana," dated August 18, 1971.

B12703-R71 8 of 22


downcutt ing. This formed the basic e x i s t i n g d r a inage pattern. Dur ing the Pleistocene

epoch, glacial action widened and deepened the va l leys , i nc lud ing Ra iny Creek va l ley .

The valley of the Kootenai R ive r was dammed by a glacier and a lake was formed

which reached a surface elevation of about 2500 feet.

Intermittent active displacement of the faul ts developed during the Pliocene and

early Pleistocene epochs. These displacements c o n t i n u e at a few locations in western

Montana. However, there is no indication of active faulting at or near the site either in

the geologic l i t e r a t u r e or f rom v i s i b l e t e r r a in features .

Bedrock u n d e r l y i n g the dam and t a i l i n g s pond areas consists of p redominan t ly

dark green to black pyroxenite which is generally f ine grained and highly friable. The

upper few feet of p y r o x e n i t e bedrock has physica l charac te r i s t ics not u n l i k e those of a

dense sand. In uench exposures on the canyon slopes, the pyroxenite contains th in ,

discont inuous, crushed zones. These c rushed zones are p l ana r and oriented

approximate ly pa ra l l e l to the canyon slope su r f ace , suggesting t h a t t h e y are the resul t of

glacial movement and /o r g r a v i t y creep.

Syenite dikes, genera l ly 6 inches or less in t h i ckness , local ly i n t r u d e into the

pyroxenite. The syenite is general ly q u i t e hard and coarse-grained. Quartz- tremoli te

veins also cut the py roxen i t e . The t r e m o l i t e a l t e r a t i o n is also accompanied by va ry ing

amounts of i ron su lph ides and oxides.

Dur ing the Pleistocene g l a c i a t i o n , the R a i n y Creek va l l ey was occupied by a

glacier that produced a somesvhat f l a t t ened va l ley bottom wi th rounded sides, in contrast

to the typical V-shaped canyon tha t would result from stream erosion alone. As the

glacier retreated ups t ream (possibly more t h a n once), outwash a l l u v i u m was deposited in

the valley bottom. The a l l u v i u m consisted of mixed s i l t s , sands, and gravels, w i t h i n

which are zones w i t h n inny large boulders of hard q u a r t z i t e . Occasionally, the boulders

B12703-R71 9 of 22


reach a diameter of 4 to 5 feet. Where viewed in t r ench walls, the glacial outwash

consists p r e d o m i n a n t l y of f ine- to coarse-grained grave l s wi th about 10 percent or less

of fine sands and silts. The gravels con ta in zones of very high porosity and

permeability.

Zones of f iner-grained a l l u v i u m consist ing of clayey gravels to t h i n l y laminated

silts are found in the valley bottom near the r igh t abu tment . These sediments appear to

be largely rock f lour deposited in a lake formed d u r i n g glaciat ion.

The r igh t a b u t m e n t slope is u n d e r l a i n by a t h i c k b l anke t of g lac ia l outwash and

t i l l , probably a l a te ra l mora ine , to a p p r o x i m a t e l y E l e v a t i o n +2890 feet. The th ickness of

this zone varies from a few feet to about 40 feet. Near the top of the a b u t m e n t slope,

the a l luv ium consists of near ly h o r i z o n t a l l y bedded s i l t y and sandy gravels over la in by

approx imate ly 6 feet of t h i n l v l a m i n a t e d f i n e s i l t , possibly of l acus t r i ne o r i g i n .

The l e f t a b u t m e n t slope, in con t ras t , is b l a n k e t e d by a r e l a t i ve ly t h i n (10 feet and

less) mant le of slope debr is and r e m n a n t s of a l a t e r a l mora ine near the base of the

canyon slope. At about E l e v a t i o n +2830 feet, the re is a r emnan t of an ou twash terrace

capped by a hor izon ta l , 4 - foo t - th ick bed of h i g h l y permeable, r e l a t i v e l y clean sand and

gravel.

A 1- to 2 - i n c h - t h i c k bed of n e a r l y w h i t e s i l t overl ies the top of the g lac ia l

outwash g rave l s in the v a l l e y bo t tom, s u g g e s t i n g t h a i the re was a t emporary lake in

Rainy Creek at the close of the Pleistocene g l ac i a t ion .

Recent unconsolidated a l l u v i u m in the va l l ey bottom consists of a blanket of soft

silt up to about 6 feet th ick. This flood p l a i n deposit locally contains f ine sand and

gravel streaks wi th occasional large boulders near the present stream course. These

materials are reworked g lac ia l outwash.

B12703-R71 10 of 22

J


2. Seismicitv

The project s i te is w i t h i n a s e i smica l l y ac t ive zone tha t forms an arc

through western Montana, no r thwes te rn Wyoming , southeastern Idaho, and Utah.

Earthquakes of both large and small in tensi t ies have an epicentral concentration w i t h i n

this seismic zone. In Montana , six ea r thquakes wi th intensities of VI I I (Modified

Mercalli Scale) or greater have occurred w i t h i n th i s zone since 1868. Most of the strong

historic earthquakes in Montana , i n c l u d i n g the Hebgen Lake ear thquake which occurred

in 1959, have occurred between Yellowstone N a t i o n a l Park and Helena. The 1959

Hebgen Lake e a r t h q u a k e had no s i g n i f i c a n t effect on the L ibby area. There is no

record of moderate to large e a r t h q u a k e s local ly . However , smal ler "random" events

(events t ha t are not related to k n o w n a c t i v e or p o t e n t i a l l y active f a u l t s ) w i t h a m a x i m u m

magni tude of 5 have occurred in the region.

There are severa l p o t e n t i a l l y ac t ive f a u l t s in the region t h a t may affect the

project site. These are the Lenia . B u l l Lake. Savage Lake, O'Brien Creek, Snowshoe,

Rock Lake, and Hope f a u l t s . The closest, the O'Brien Creek f a u l t , is about 13 km west

of the site (see Plate 33).

The Lenia f a u l t has been traced c o n t i n u o u s l y for 16 km w i t h i n the Libby

quadrangle. I t almost c e r t a i n l y con t inues s o u t h w a r d , e i t h e r under the Bu l l Lake, or less

probably, th rough the Trio prospect. Ev idence suggests tha t movement along the f a u l t is

vertical.

The B u l l Lake f a u l t is a normal f a u l t w i t h younger beds exposed in the r e l a t i v e l y

downthrown block on the west. It has been traced for 21 km along a c u r v i n g course,

concave to the east. The f a u l t is not observed n o r t h of Madge Creek, and is joined by

the Savage Lake f a u l t south of Crowell Creek. From th i s junc t ion , the Bul l Lake faul t

trends southward and then curves to the southeast .

B12703-R71 11 of 22


j

The Savage Lake f a u l t is largely inferred from physiographic and s t r u c t u r a l

evidence. The f a u l t , seen at the Carter prospect about 2 km east of Savage Lake, trends

first, southwestward, then southward along the east side of the Libby Formation.

The O'Brien Creek f a u l t is a normal f a u l t t hough t to pass through the "island" of

Wallace Formation just north of Savage Lake in a nor th-nor thwester ly fashion and cross

beneath the Great Northern tracks. The f a u l t is concealed under a l l u v i u m north of the

Kootenai River. It then passes very close to the mountain front on the east side of

O'Brien Creek.

The Snowshoe f a u l t s t r ikes n o r t h and is n e a r l y ver t ica l for most of its trace of

26 km. It cuts the crest of the n o r t h w a r d - p l u n g i n g Snowshoe an t i c l i ne and is cut off at

the north by a sma l l f a u l t a long Horse Creek. The f a u l t te rminates at the Snowshoe

anticl ine east of E l e p h a n t Peak.

The Rock Lake f a u l t , a p p r o x i m a t e l y 19 km long, extends from Dad Peak

southeastward past NVan le s s Lake . Disp lacement a long t h i s f a u l t has been i r r egu l a r in

magn i tude and d i r ec t i on , but movement has been es sen t i a l ly ver t i ca l . The Hope f a u l t , a

normal f au l t w i t h the d o w n t h r o w on the sou thwes t , was traced from Hope, Idaho, to

Heron, Montana.

On the basis of f a u l t l e n g t h and pub l i shed r e l a t i onsh ips correla t ing f a u l t r u p t u r e

length and e a r t h q u a k e m a g n i t u d e , we have conse rva t i ve ly assigned a m a x i m u m credib le

magnitude of 7 to these faults.

3. Design Ground Mot ion

Based on a postulated magn i tude 7 ea r t hquake on the nearby O'Brien

Creek fau l t (about 13 km from the s i te ) and us ing publ i shed a t t enua t ion relat ionships

(Idriss, 1987), we estimate the peak bedrock acceleration (PBA) at the site to be about

0.30 grav i ty (g). The est imated PBA corresponding to a "random" m a g n i t u d e 5 event at

B12703-R71 12 of 22


a close distance (less than 1 km) is less t h a n 0.30g. The Uni form B u i l d i n g Code (UBC,

1991) maps the project site in the Seismic Zone 2B w i t h the expected PBA of 0.20g. We

believe that a 0.30g acceleration conserva t ive ly envelopes expected long-term seismic

activities in the region.

C. Groundwafe r Considerations

Because we used a rotary wash d r i l l i n g system, the groundwater level could not

be measured du r ing our field i nves t i ga t i on . However , stabilized groundwater table was

measured about 10 feet below ground su r face from the piezometer ins ta l led in

Boring A-8. In a d d i t i o n , g r o u n d w a t e r leve l data are a v a i l a b l e from f ive piezometers

installed fol lowing the cons t ruc t ion of the s tar ter dam in 1971 (see Plate 1 for

piezometer locations). Since t hen , g r o u n d w a t e r level has been monitored by NV. R. Grace

staff on a m o n t h l y basis. Wate r levels obse rved in piezometers i nd ica t e t ha t water f lows

m a i n l y i n t h e h i g h l v p r ev ious n a t u r a l g r a \ e l l y f o u n d a t i o n m a t e r i a l a n d t ha t t h e ph rea t i c

surface rises o n l y occas iona l ly above the f o u n d a t i o n leve l (one of the six piezometers

indicates temporary water leve ls t h a t were abou t 3 feet above the dam f o u n d a t i o n ) .

Dur ing the cons t ruc t ion of the s t a r t e r e m b a n k m e n t , a series of 20-foot-wide.

2-foot-high dra inage b l anke t s cons i s t ing of n a t i v e g r a v e l m a t e r i a l was placed at the

embankment foundat ion level . E i g h t - i n c h - d i a m e i e r perforated pipes were embedded

w i t h i n the d ra inage b l a n k e t s to collect the w a t e r and t ranspor t i t to the downstream side.

These pipes were connected to a s ing le M - i n c h - d i a m e t e r pipe which was extended at

each subsequent stages of cons t ruc t ion and p resen t ly emerges from the downstream face

near Boring A-8. The volume of discharged water was roughly est imated to be 300

gallons per m i n u t e (gpm) at the t ime of t h i s i n v e s t i g a t i o n .

B12703-R71 13 of 22


D. Static and D y n a m i c Design Cons idera t ions

1. Consolidation Set t lements

As described above, two scenarios are being considered for the restoration

of Rainy Creek. If water is kept near the proposed levee, consolidat ion se t t lements w i l l

continue to occur in the t a i l i n g s as water dra ins f rom the ta i l ings mater ia l . The

magnitude of sett lement w i l l vary w i t h the th ickness of the ta i l ings . Where the ta i l ings

are 100 feet thick, we ant ic ipa te a total se t t l ement of approximately 5 feet would occur

over a 30-year period based on the consolidation characteristics of the tailings. We

estimate that half of t h i s s e t t l e m e n t w i l l occur d u r i n g the next few years. On the other

hand, if water is a l lowed to rise and pond aga ins t the e m b a n k m e n t , the pore pressure

would be unchanged , and the re fo re no a d d i t i o n a l s e t t l e m e n t of the surface of t a i l i n g s

would occur.

2. L ique fac t ion P o t e n t i a l

Using f ie ld and labora tory test data to evalua te the po ten t ia l for

l iquefact ion of the t a i l i n g s m a t e r i a l , we d e t e r m i n e d t h a t i f the t a i l i ngs remain sa tura ted ,

the d i scon t inuous loose sand and s i l t y sand layers encoun te red in the t a i l i n g s ma te r i a l

wi l l l i k e l y l i q u e f y d u r i n g the design e a r t h q u a k e ( M C E ) . We f u r t h e r de te rmined t h a t

set t lements of up to several inches could r e s u l t f rom l i q u e f a c t i o n and/or dens i f ica t ion of

loose sands in the t a i l i n g s . These se t t l emen t s would l i k e l y be n o n u n i f o r m because of the

variable thicknesses and depths of the sand layers.

Due to thei r h i g h p l a s t i c i t y indices , s a tu ra ted s i l t s encountered in the t a i l i n g s are

not susceptible to l i q u e f a c t i o n . However, we be l i eve t h a t a b u i l d - u p of pore water

pressure ( i f the t a i l i n g s reservoir r ema in s a t u r a t e d ) d u r i n g the design e a r t h q u a k e could

result in a decrease of up to 30 percent in the s t a t i c und ra ined shear s t rength of these

soils. If the sil ts are dra ined , there would be no reduct ion in undra ined shear s trength

due to cyclic loading condi t ions .

B12703-R71 14 of 22


3. S t ab i l i t y of Slopes

Stab i l i ty analyses of the e m b a n k m e n t and tai l ings were performed for

four dif ferent cases, using the Bishop's Modif ied Method of Slices. The method

analyzes circular slip surfaces using conventional l imi t equil ibrium theory to compute

factors of safety for the slope geometry and soil parameters being considered.

The cases analyzed were:

Case I - Static analysis with the water about 500 feet upstream of the dam(Plate 34).'

Case II - Dynamic (pseudo-static) analysis wi th the water about 500 feetupst ream of the dam and w i t h se ismic coef f ic ien ts k s , of O . l O g , O . I 5 gand 0.20g. For t h i s case a y ie ld seismic coef f ic ien t ky was alsode te rmined . (This coe f f i c i en t y ie lds a factor of safety, F.S., of 1.0)(P l a t e 34).

Case III - Stat ic ana ly s i s w i t h the water at the upstream face of the dam, at thet a i l i ngs e l e v a t i o n (Pla te 35).

Case IV - Dynamic (pseudo-s ta t i c ) a n a l y s i s w i t h the water at the ups t ream faceof the dam, at the t a i l i n g s e l eva t ion . Seismic coeff ic ients of O . l O g ,0.15g and 0.20g were used and a \ i e l d coeff ic ient ky was alsod e t e r m i n e d (P l a t e 35).

On the basis of e n g i n e e r i n g a n a l y s i s and measured g r o u n d w a t e r levels in

the piezometers, we b e l i e v e t h a t the g r o u n d w a t e r level i m m e d i a t e l y upstream of the

embankment does not rise above the f o u n d a t i o n level . Therefore, for our s t a b i l i t y

analyses, we have assumed t h a t the water level is at the base of the e m b a n k m e n t

(Plates 34a and 34b). If water is allowed to come in contact w i th the e m b a n k m e n t , it

could become pa r t i a l l y sa tura ted, as shown by the phreat ic surface on Plates 35a and

35b, with water emerg ing f rom the downs t ream face of the e m b a n k m e n t . As a worst-

case condit ion, we assumed t h a t the perv ious n a t u r a l gravel layer w i l l be clogged at some

time in the f u t u r e and would no longer be e f f e c t i v e in provid ing dra inage as present ly

observed. In reality, the re la t ively high permeabili ty of the foundation material l ikely

B12703-R71 15 of 22


wil l cause the phrea t i c surface to drop, and w a t e r may never emerge from the

downstream face of the e m b a n k m e n t .

Without a permanent monitoring system in place, however, it would be

inadvisable to assume a long- te rm phrea t i c surface lower than tha t shown on Plate 35a

and 35b. As indicated in our 1971 reports, the m a t e r i a l used in cons t ruc t ion of the dam

is highly susceptible to erosion. Therefore, water emerging from the downst ream face of

the embankment and r u n n i n g para l le l to surface would be unacceptable for both s t ab i l i t y

and erosion considerations. The problem could be mi t iga t ed e i the r by I) p rov id ing a

permanent moni tor ing program, such as i n s t a l l i n g piezometers in the downstream face to

monitor the actual location of the p h r e a t i c surface w i t h i n the e m b a n k m e n t , or 2)

p r o v i d i n g a new i n t e r n a l d r a i n a g e system, such as a c h i m n e y d r a i n cons t ruc ted near the

downstream toe to col lect w a t e r w h i c h o t h e r w i s e could cause erosion of the downstream

face. Assuming one of these a l t e r n a t i v e s w i l l be put in place to mi t iga t e the po ten t ia l

for a "localized" i n s t a b i l i t y and/or erosion, we e \ a l u a t e d the overa l l global s ta t i c and

dynamic s t a b i l i t y of the two a l t e r n a t i v e s shown on Plates 34 and 35.

The analyses were pe r fo rmed c o n s i d e r i n g a range of shear s t r eng th va lues

appropriate for s t a t i c and d y n a m i c l o a d i n g c o n d i t i o n s . The shear s t r eng th va lues are

summarized below:

I ) E m b a n k m e n t Ma te r i a l

c1 = 50 psf, <£'= 37 degrees (see Plates 34b and 35b)c' = 500 psf, 0'= 37 degrees (see Plates 34a and 35a)

ii) Tailings

a) Elastic Si l ts

Su (s ta t ic ) = 50 psf at 0 feet depth1900 psf at 100 feet depth

B12703-R71 16 of 22


Su (dynamic) = 35 psf at 0 feet depth1330 psf at 100 feet depth

b) Sands and Silty Sands

#' (static) = 30 degreesSu (dynamic) = 100 psf

i i i ) Foundation Ma te r i a l

<F = 45 degrees

The results of the analyses are presented in the fol lowing table.

Case

1 and 11

111 and IV

SeismicCoefficient. ks

00.100.150.20

00.100.150.20

Minimum Factor Yield Seismicof Safety F.S Coefficient. ky

1.83 - 2.281.44 - 1.791.29 - 1.61 0.28 - 0.421.17 - 1.46

1.741.301.16 0.221.05

It shou ld be noted t h a t the s l i p surface shown on Plate 35b was not

considered c r i t i ca l in our ana lyses because of the f u t u r e i n s t a l l a t i o n of a new c h i m n e y or

b l a n k e t d ra in . E i t h e r d r a in system would reduce the seepage and rave l l ing forces tha t

would, produce localized i n s t a b i l i t y associated w i t h the s l ip surface on Plate 35b.

The results of our s t a b i l i t y ana ly s i s ind ica te tha t the dam is stable d u r i n g

both static and dynamic loading condi t ions . According to recommendat ions by Seed

(1979), earth dams of s i m i l a r c o n s t r u c t i o n are expected to experience l imi t ed

deformations and remain stable d u r i n g and a f t e r a magn i tude 7 ea r thquake provided tha t

1) the bu i ld -up of pore water pressure does not s i g n i f i c a n t l y reduce the static strength

B12703-R71 17 of 22


of embankment ma t e r i a l and 2) n m i n i m u m factor of safety of 1 . 1 5 is computed from a

i pseudo-static analysis using a seismic coef f ic ien t of O. lOg. The pseudo-static factors of

safety computed for various phrea t ic surface locations and soil properties are well above

| the minimum required value. In add i t ion , the e m b a n k m e n t material is dense to very

dense and is not susceptible to an appreciable loss of shear s t rength. Therefore, the dam

is expected to remain stable d u r i n g and fol lowing the design earthquake.

4. Deformat ion Ana lys i s

To es t imate the m a g n i t u d e of pe rmanen t displacement of the e m b a n k m e n t

dur ing the design e a r t h q u a k e , we performed s tud ie s u s i n g a s i m p l i f i e d response and

deformat ion analys is based on methods developed by Makd i s i and Seed (1978, 1979).

First , the i n t e n s i t y o f s h a k i n g w i t h i n the e m b a n k m e n t was est imated

I based on the estimated n a t u r a l f r e q u e n c y of ihe e m b a n k m e n t , an t ic ipa ted f requency

content of the i n p u t base m o t i o n , and d y n a m i c soi l proper t ies of s i m i l a r dam

1 e m b a n k m e n t ma te r i a l . The response spectra for rock sites by Idriss (1987) scaled to a

i PBA of 0.3g was used in our a n a l y s i s . A m a x i m u m crest accelerat ion of about 0.8g was

computed.

Nex t , based on the geometry and loca t ion of the c r i t i ca l s l ip surface, and

a yield coeff icient of 0.22 to 0.-42g (see Plates 34 and 35), we calculated permanent

deformations to be i n s i g n i f i c a n t , which conf i rms conc lus ions by Seed (1979).

B12703-R71 18 of 22


V CONCLUSIONS AND RECOMMENDATIONS

The results of field investigation and laboratory testing performed on the tailings

material indicate that during a hypothetical embankment failure, the potential for a

tailings material flow and contamination of the downstream area is very low because of

the strength of the tailings as they now exist . We judge that the consistency of the

tailings material is such that if a section of the embankment were removed, the tailings

would fail but would maintain approximately a 4:1 (horizontal to vertical) slope.

On the basis of 1) the results of our 1971 studies, 2) geotechnical data obtained

during our construction observation services, 3) piezometric data collected during about

20 years of operation, and 4) results of our present studies, we conclude that the

embankment, in its present condition, is adequately safe during both static and

maximum credible seismic lending condit ions. \Ve also judge that if the water were

allowed to come in contact wi th the embankment, the dam would be safe under stat ic

and seismic loading conditions. However, due to potential problems discused below, we

strongly recommend that the long-term performance of the dam be carefully monitored

and mitigation measures be immediately implemented should the monitoring program

indicate potential instabi l i ty.

If, as part of restoration of the Rainy Creek, water is allowed to flood the

tailings reservoir area and is maintained at the present tailings level, it could potentially

emerge from the downstream face of the embankment causing erosion of soil and

eventually, localized slope instability problems.

For the past 20 years, the drain pipe beneath embankment has successfully

collected water at the dam foundation le\el and discharged it into the creek at the

downstream side. This system is expected to operate effectively in the future.

However, it is possible that the pipe may corrode or clog during long-term operation. If

B12703-R71 19 of 22


so, water could be released from the pipe w i t h i n the embankmen t , and, if not absorbed

{ by previous na tura l drainage mater ia l upon e x i t , erode the downstream face, e v e n t u a l l y

causing localized instability of the embankment. Although unlikely, the same problems

) could arise from clogging of the n a t u r a l gravel d ra inage system.

~i An acceptable moni to r ing program would consist of the i n s t a l l a t i on of new

piezometers at locations shown on Plate 36 to detect the presence of water and the

location of the phreat ic surface inside the e m b a n k m e n t . The piezomeuic data should be

regularly reviewed and condi t ions of the dam be per iod ica l ly inspected. M i t i g a t i n g

measures such as i n s t a l l a t i o n of a b l a n k e t d r a i n , c h i m n e y d r a i n , or other acceptable

. . drainage system (see Plate 36) near the d o w n s t r e a m toe should be adopted if and when

' water approaches the downstream face of the e m b a n k m e n t .

If water is kept at E l e v a t i o n +2910 feet a b o u t 500 feet ups t ream of the dam and

a channel is cons t ruc ted to col lect R a i n y Creek and flood water , n o n u n i f o r m se t t lement

of the t a i l ings shou ld be a n t i c i p a t e d . Since a to ta l long- te rm se t t l ement of about 5 feet

is ant ic ipated as water d r a i n s out of the t a i l i n g s m a t e r i a l , the c h a n n e l and i ts l i n i n g

system should be f l ex ib l e e n o u g h to to le ra te the p o t e n t i a l l y large d i f f e r e n t i a l se t t l ement .

To min imize ant ic ipated d i f f e r e n t i a l s e t t l e m e n t , we recommend tha t the channe l be

constructed as close as possible to the l e f t a b u t m e n t cu a s t a r t i ng e levat ion of about

I +2910 feet.

B12703-R71 20 of 22


VI REFERENCES

Idriss, I. M., 1987. Earthquake Ground Motions, Lecture Notes, Course on StrongGround Motions, Earthquake Engineering Research Institute, Pasadena,California, April 10-11, 1987.

Pardee, J.T., 1950, Late Cenozoic Block Faulting in Western Montana, GSA Volume 61,pages 359-406.

Pardee, J.T. and Larsen, E.S., 1928, Deposits of Vermiculite and other Minerals in theRainy Creek District near Libby, Montana. Economic Geology Part 1, pages 17-29.

Ross, Clyde P. and Nelson, Willis H.. 1959, Regional Seismicity and Brief History ofMontana Earthquakes, U.S. Geological Survey Professional paper No. 435-E.pages 25-30.

Seed, H. B., 1979. Considerations in the Earthquake Resistant Design of Earth andRockfill Dams, Geotechnique 29, No. 3, p. 215-263.

Seed, H.B. and Harder, L.F., Jr., 1990, SPT-Based Analysis of Cyclic Pore PressureGeneration and Undrained Residual Strength, H.B. Seed Memorial Symposium,v.Il. pages 351 -376.

B12703-R7: 21 of 22


V I I I L L U S T R A T I O N S

B12703-R71 22 of 22

NTAKE STRUCTURE

ses^r.-^x, ;r'^'—^r \^ ^

APPROXIMATE LOCATION OFDISCHARGE POINTS PRESENT LOCATION OF WATER

PROPOSED LEVEEN Crest at elevation 2910)

A-9

EXPLANATION

Boring Number and Location

• Piezometer Number and Location

200

Approximate Scale in Feet

Reference: Topographic Map prepared by Walter and Associates, Inc.untitled, undated.

Harding Lawson AssociatesEngineering andEnvironmental Services

Site PlanW.R. Grace DamRainy Creek, Montana

PLATE

1DRAWN

AMJOB NUMBER

5891.053.03APPROVED DATE

11/91REVISED DATE

-3 C

•»- 01(/)•*-

Laboratory Tests

oa3)-I-

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Equipment 4" dia. Rotary

Elevation 2912.9 ft** Date 06/27/91

5 -

14* 10

-200=7.7%MA, See Plate 15TxUU 312(450)LL=60, PI=8-200=75.9%

71.1 56Push

-200=45.7MA, See Plate 16

'Blow counts converted topseudo-standard pentrationblow counts using aconversion factor of 0.6.

"Elevation referenced toNational Geodetic VerticalDatum.

25 -

30

59.7 67

GRAY-BROWN SILTY GRAVEL WITHSAND (GM)moist

ACCESSFILL

OLIVE GREEN ELASTIC SILT (MH)soft to medium st iff , saturated,abundant fine grained platey minerals(diesel odor)

color changes to blue-green with interbeddedsandy silt and silty sand stringers(diesel odor)

GREEN POORLY GRADED SAND (SP)loose, saturated, fine grained(diesel odor)

OLIVE GREEN SILTY SAND (SM)loose, saturated(diesel odor)

OLIVE GREEN ELASTIC SILT (MH)medium stiff, saturated, abundant finepyrite flakes (diesel odor)

OLIVE-GREEN SILTY SAND (SM)loose, saturated, fine-grained, abundant mica

OLIVE GREEN ELASTIC SILT (MH)medium stiff , saturated, moderately plastic

Harding Lawson AssociatesEngineering and

™ Environmental Services

Log of Boring A- 1W. R. Grace DamRainy Creek, Montana

(Sheet 1 of 2)PLATE

2aDRAWN JOB NUMBER

5891,053.03APPROVED . FILE

11529G19DATE REVISED DATE

:i;)

Laboratory Tests

.V

v

Is8

M-U0.

UlC

oo«fI/I

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Elevation 2912.9 ft** Date 06/27/91

13*

38

30/5.5"

-200=8.4%MA, See Plate 17

12.9 132 30/5"* 55 -U-T

60 -

65 -

70 -

75 -

80 J

OLIVE GREEN POORLY GRADED SAND (SP)loose, saturated, fine-grained, angular to platey,trace silt and gravel (diesel odor)

becoming medium dense

MOTTLED GRAY-GREEN WELL GRADED SANDWITH SILT AND GRAVEL (SW-SM)

very dense, saturated, fine to coarse grained sandangular to subrounded gravel, with abundantplatey minerals

(Embankment Material)

Boring was terminated at 56.0 feet.No free groundwater was encountered.



(Sheet 2 of 2)PLATE

2bDRAWN JOB NUMBER

5891.053.03APPROVED FILE


:i

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01L+-

Laboratory Tests O O L 01EU OO

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Elevation 2911.4 ft" Date 06/26/91

5 -

10

15

20

TxUU 382(500),See Plate 28LL=51, PI=10,See PLate 26-200=71.3%

63.2 62 25

Push

30

-200=75.3% 67.8 64 5*35

40 J

GRAY-BROWN SILTY GRAVEL WITH SAND4(GVmoist (auger cutt ings)

ACCESS

FELL

DARK GRAY-GREEN SILTY SAND (SM)very loose, saturated, fine-grained,platey grains, with abundant pyrite

_L

GRAY-GREEN ELASTIC SILT (MH)soft, saturated, trace fine-grained sand,moderate to high plasticity

DARK GREEN SILTY SAND (SM)very loose, saturated, fine-grained,platey grains

OLIVE GREEN ELASTIC SILT (MH)soft, saturated, trace fine pyrite flakes,with occasional thin stringers of silty sand

becoming medium st i f f , with interbeddedbrown silty sand stringers

BROWN AND OLIVE GREEN SILTY SAND (SM)loose, saturated, fine platey grained

OLIVE GREEN ELASTIC SILT (MH)stiff, saturated, high plasticity,trace platey pyrite



(Sheet 1 of 2)PLATE

3aDRAWN JOB NUMBER

5891,053.03APPROVED FILE


:i

:i

Laboratory Tests

~ o.v a»—• x^01L+- 3)3 C -H

•I- 01«>•»- m— c ji cO O (.01nu aa

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Equipment 4" dia. Rotary.c —Q. e Elevationo (/>

40

2911.4 ft" Date 06/26/91

TxUU 946(800),See Plate 29LL=71, PI=27,See Plate 26-200=84.5%CC=0.75

-200=33.5%MA, See Plate 18

60.4 64 45Push

47.4 7712*

50

14 55

60

13

2365

70

21

75 -

80 J

OLIVE GREEN SANDY ELASTIC SILT (MH)stiff, saturated, with abundant fineplatey minerals, fine-grained sand withinterbedded silty sand seams

DARK GREEN SILTY SAND (SM)medium dense, saturatedabundant platey minerals

DARK GREEN POORLY GRADED SAND WITHSILT (SP-SM)

medium dense, saturated, fine to mediumgrained, angular to platey grains, withoccasional sandy silt stringers

OLIVE GREEN ELASTIC SILT (MH)stiff, saturated, abundant platey minerals,moderately plastic

GREEN SILTY SAND (SM)medium dense, saturated, pockets of sandy silt

DARK GREEN POORLY GRADED SAND WITHSILT (SP-SM)

medium dense, saturated, fine grained sand,platey grains

(Embankment Material)

Boring was terminated at 77.0 feet .No free groundwater was encountered.



(Sheet 2 of 2)PLATE

3bDRAWN JOB NUMBER



;i

Laboratory Tests

.v

•t- 01tn-t-o o

oQ.

inc

-200=9.7%MA, See Plate 19

-200=76%

TxUU 1006(750),See Plate 30LL=69, PI=25,See Plate 26-200=82.5%

64.0 62

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0

15 -

20

25 -

30

35

Push

40

GREEN WELL GRADED SANDWITH GRAVEL (SW)

moist (auger cuttings)

4ACCESS

FILL

GREEN WELL GRADED SAND WITH SILTAND GRAVEL (SW-SM)

loose, saturated, coarse grained sand,angular to platey grains, angular gravel

OLIVE GREEN ELASTIC SILT WITH SAND (MH)very soft, saturated, moderate to high plasticity

SILTY SAND (SMJloose, saturated, fine to medium grained

OLIVE GREEN ELASTIC SILT (MH)very soft, saturated, trace f i ne grained sand

OLIVE GREEN SILTY SAND (SM)very loose, saturated, fine grained, platey

BLUE-GREEN ELASTIC SILT (MH)soft to stiff , saturated,trace pyrite, occasional thin stringers ofsandy silt



(Sheet 1 of 2)PLATE

4aDRAWN JOB NUMBER



M-/-, O.V Q. +- ~~ ~ 0 -t-

01 O '*-

a"c •? \" ~+- 01 — l/> £IA 4- (A 3 +•— c 3> c o a

T , _ O O L O l — 0 )Laboratory Tests ru on to a40 -

-200=6.0% ^MA, See Plate 20 14.0 128 18»

50 -

55 -

60 -

65 -

70 -

75 -

80 -1

v Equipment 4" dia. Rotary

I E10

1"^"''"J* '

levation 2913.5 ft** Date 06/28/91

GREEN WELL GRADED SAND WITH GRAVEL(SW)dense, saturated, fine to coarsegrained sand, gravel to 1 inch diameter




(Sheet 2 of 2)PLATE

4bDRAWN JOB NUMBER


I I529G19DATE REVISED DATE

Laboratory Tests

«n+- in— c 3» cO O L 01

QQ

OO

«*-

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~ u Equipment 4" dia. Rotaryf~ ^^

a I Elevation 2913.6 ft" Date 06/27/910) fl>a (o0 TT-r

-200=1.7MA, See Plate 21-200=6.1MA, See Plate 22

31.7 84 5*

7*

16

25 -

30 -

35 -

40 J

BROWN GRAY POORLY GRADED GRAVEL jWITH SAND (GP) T

moist IACCESS

FILL

1

OLIVE BLUE-GREEN ELASTIC SILT (MH)soft to medium s t i f f , saturated, interbedded with

silty sand stringers

OLIVE GREEN ELASTIC SILT (MH)soft, saturated, abundant f ineplatey minerals, with interbedded sand stringers(diesel odor)

GREEN POORLY GRADED SAND WITH GRAVEL(SP) loose, saturated, fine to coarse grained

aubangular to platey sand, trace subroundedgravel (diesel odor)

GREEN WELL GRADED SAND (SW)medium dense, moist, fine to coarse grained

sand,syenite and pyroxinite up to 1" diameter

(Embankment Material)Boring terminated at 21.5 feet.No free groundwater was encountered



(Sheet 1 of 1)PLATE

5DRAWN JOB NUMBER



.vN^

01L-t-3 C+. ojUI+-

Laboratory Tests

oo.

(fl

?£QD

-200=55.3MA, See Plate 23

-200=76.6% 67.6 61

OO«*-\Ifl

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Equipment 4" dia. Rotary.c —a01O

e Elevation 2910.1 ft" Date 06/28/91o>

1*

5 -

10

15

20

,. 25

30

35

40

BROWN SILTY GRAVEL WITH SAND (GM)moist

ACCESSFILL

LDARK GREEN POORLY GRADED SANDWITH SILT (SP-SM)

loose, saturated, fine to medium grained,platey minerals (diesel odor)

OLIVE BLUE-GREEN ELASTIC SILT (MH)very soft, saturated, abundant pyrite minerals,with pockets of silty sand

BROWN AND OLIVE-GREEN SILTY SAND (SM)very loose, saturated,occasional stringers of sandy silt

GREEN SANDY ELASTIC SILT (MH)medium st i f f , saturated, f ine grained sand,stringers of silty sand

BROWN-GREEN POORLY GRADED SAND (SP)very loose, saturated, f ine grained

BLUE-GREEN ELASTIC SILT (MH)medium s t i f f , saturated, trace pyrite flakes



(Sheet 1 of 2)PLATE

6aDRAWN JOB NUMBER



-200=69.2%MA, See Plate 24

^ 0.V 0. *• ~v^ <•/ O •»-

01 O «*•

ii'c •? \ ~+- QJ — in jim-»- in 3 •»-

— c 3> c o a_ O O C. 01 — 0)Tests no ao ca a

' " 124 Push

50 -

55 -

60 -

65 -

70 -

75 -

80 -"

a. E

1 E(0

en

1

auioment 4" dia. Rotary

levation 2910.1 ft" Date 06/28/91

BROWN AND GREEN SILTY SAND (SM)loose, saturated, wi th interbedded layersof medium stiff elastic silt

Boring was terminated at 50.0 feet.No groundwater was encountered.



(Sheet 2 of 2)PLATE

6bDRAWN JOB NUMBER

5891,053.03APPROVED F I L E


Laboratory Tests

Oa

3c 2•4-0)Ul-t- U)

O O C. 01EU QQ

in

CD

JU

•i- aa £ai aa v>



0

5 -

10 -

15 -

20 -

25 -

30 -

35 -

40 J ^ -

GRAY AND BROWN POORLY GRADED GRAVELWITH SAND (GP)

dense, moist, cobbles up to 2' dia.with trace silt, subrounded to subangular

occasional seams of syenite, tremolite, andquartz in boulders



(Sheet 1 of 2)PLATE

7aDRAWN JOB NUMBER


11529GI9DATE REVISED DATE

Laboratory Tests

~ o.v aat£-•*- 313 C -K

4-01 —U1+- I/I

— C Jl Co o L atEU aa

oo««-ut

CO

Equipment 4" dia. Rotary•i- aa. £ai n)a c/)


40

50/3"

Core45 -

50/2" 50 -*

50/2" 55

60 -

65 -

70 -

75 -

80 J

GRAY-BROWN SANDY SILT (ML)very s t i f f , saturated, fine tomedium-grained sand, with stringers of silty sand

GRAY-GREEN POORLY GRADED SAND (SP)very dense, saturated, medium to coarse grained,abundant gravel, magnetite

GRAY POORLY GRADED GRAVELWITH SAND (SP)

very dense, saturated,coarse sand with boulders up to 2' dia.

GRAY-GREEN POORLY GRADED SAND (SP)very dense, saturated, with abundant magnetite(weathered pyroxenite)

GRAY-GREEN PYROXENITEmoderately hard, f r iable , wi th abundant magnetite


Harding Lav/son AssociatesEngineering andEnvironmental Services


(Sheet 2 of 2)PLATE

7bDRAWN JOB NUMBER



Laboratory Tests

oa

3 C +••I- 01in*- w>— C 3> CO O (.01no aa

oo

8CD

HI

•»- 0.a. E01 ID

O V)

Equipment _4" dia. Rotary


0

5 -

10 -

15 -

43

20 -

25 -

50/5"30 -

50/1" 35

40 J

iACCESS

FILL

GRAY POORLY GRADED GRAVELWITH SAND (GP)

moist

GRAY-BROWN POORLY GRADED GRAVELWITH SAND (GP)

dense, saturated, coarse grained aand,subrounded to angular gravel

GRAY-GREEN POORLY GRADED SAND (SP)very dense, saturated, medium grained,with abundant magnetite crystals and pyrite flakeswith seams of syenite and tremolite

\GREEN PYROXENITE

moderately hard, fr iable, wi th abundant magnetiteand pyrite




(Sheet 1 of 1)PLATE

8DRAWN JOB NUMBER

5891,053.03APPROVED F I L E

I529G19DATE REVISED DATE

:iLaboratory Tests

at£.-•-3 C

-t- 01

*to ono

ua.

inL. 01QQ

OOH-

10

O


0.01Q

0

a

CO


5 -

10 -

15 -

50/5" ^O

50/4"

so/r 2550/5.5"

30 -

35 -

I

40 J

GRAY POORLY GRADED SANDWITH GRAVEL (SP)

moist (auger cuttings)ACCESS

FILLGRAY-BROWN POORLY GRADED GRAVELWITH SILT (GP)

dense, saturated, cobbles up to 1' dia.(auger cuttings)

becoming very dense

GRAY-GREEN POORLY GRADED SAND WITHGRAVEL (SP)

very dense, saturated, f ine to medium grainedsand

GRAY POORLY GRADED GRAVELWITH SILT (GP)

very dense, saturated


Harding Lawsoo AssociatesEngineering andEnvironmental Services


(Sheet 1 of 1)PLATE

9DRAWN JOB NUMBER



Laboratory Tests

3 C +•-HO)lfi+- (fl

— C J>C0 0 C O )HU QO

-200=26.2%MA, See Plate 25

12.5 133

OO4-

tfiO

CD

3

18

25

10

Equipment 4" dia. Rotary£ —

a I Elevation 2828.1 ft" Date 06/30/9101 *QO U)

0

5 -

10

15

so/i" 20

25 -

30 -

35 -

40 J

BROWN SILTY SAND WITH GRAVEL (SM)loose, moist, with cobbles to 6" dia.

becoming very loose

becoming medium dense

wood pieces up to 1" at 15.2 feet

GRAY POORLY GRADED GRAVEL WITH SAND(GP)

dense, saturated, f ine to medium grained sand

Boring was terminated at 25.5 feetafter h i t t ing obstruction.No free groundwater was encountered.


~ Environmental Services


(Sheet I of 1)PLATE

10DRAWN JOB NUMBER



oa.<u

Laboratory Tests

_

3 c•f- 01tn-t-o o

oo»*- Equipment 4" dia. Rotary

?£00

a.10

Elevation 2828.5 ft" Date 06/30/91a co

5 -

10 -

15 -

20 -

25 -

30 -

35 -

40 J

BROWN SANDY SILT WITH GRAVEL (ML)soft to s t i f f , saturated, cobbles up to 6",occasional thin stringers of siltysand up to 1/2" thick (auger cutt ings)

BROWN-GRAY POORLY GRADED GRAVELWITH SILT (GP)

dense, saturated


Log of Boring A-10W. R. Grace DamRainy Creek, Montana

(Sheet 1 of 2)PLATE

DRAWN JOB NUMBER



Laboratory Tests

ua

L-t- 3»3 C •*-

-»- 41Ut-t- I/I

— C 31 CO O t- 01

QQ

OO

«+-\ino

03


Elevation

40 i r--m

aaia2828.5 ft" Date 06/30/91

45 -

50 -

55 -

60 -

65

70 -

75 -

80 J

GRAY-BROWN WELL GRADED GRAVELWITH SAND AND SILT (GW-GM)

GREEN PYROXENITE^ moderately hard, friable



Log of Boring A-10W. R. Grace DamRainy Creek, Montana

(Sheet 2 of 2)PLATE

DRAWN JOB NUMBER



135230

UNIFIED SOIL CLASSIFICATION SYSTEM - ASTM D2487-85

MAJOR DIVISIONS

CO

AR

SE

-GR

AIN

ED

SO

ILS

Mor

e th

an 5

0% r

etai

ned

on t

he N

o. 2

00 s

ieve

ED

SO

ILS

e pa

sses

0 si

eve

i SS

i!*!$"

GRAVELS

More than 50% ofcoarse fraction

retained onNo. 4 sieve

SANDS

50% or more ofcoarse fraction

passes No. 4 sieve

Clean gravelsless than5% fines

Gravels withmore than12% fines

Clean sandless than5% fines

Sands withmore than12% fines

SILTS AND CLAYSLiquid limit less than 50%

SILTS AND CLAYSLiquid limit 50% or more

HIGHLY ORGANIC SOILS

GW

GP

GM

GC

SW

SP

SM

SC

ML

CL

OL

MH

CH

OH

Pt

X• "%

iTV*"T;'*i

^

V,\ \

1 1

1 I

|]%S %s &,

^jj^^

U£t » Jf

GROUP NAMES

WELL-GRADED GRAVEL,WELL-GRADED GRAVEL WITH SAND

POORLY-GRADED GRAVEL,POORLY-GRADED GRAVEL WITH SAND

SILTY GRAVEL, SILTY GRAVELWITH SAND

CLAYEY GRAVEL, CLAYEY GRAVELWITH SAND

WELL-GRADED SAND, WELL-GRADEDSAND WITH GRAVEL

POORLY-GRADED SAND,POORLY-GRADED SAND WITH GRAVEL

SILTY SAND, SILTY SANDWITH GRAVEL

CLAYEY SAND, CLAYEY SANDWITH GRAVEL

SILT, SILT WITH SAND OR GRAVEL,SANDY OR GRAVELLY SILT

LEAN CLAY, LEAN CLAY WITH SAND ORGRAVEL, SANDY OR GRAVELLYLEAN CLAYORGANIC SILT OR CLAY, ORGANIC SILTOR CLAY WITH SAND OR GRAVEL, SANDYOR GRAVELLY ORGANIC SILT OR CLAYELASTIC SILT, ELASTIC SILT WITH SANDOR GRAVEL, SANDY OR GRAVELLYELASTIC SILTFAT CLAY, FAT CLAY WITH SAND ORGRAVEL. SANDY OR GRAVELLY FATCLAYORGANIC SILT OR CLAY, ORGANIC SILTOR CLAY WITH SAND OR GRAVEL, SANDYOR GRAVELLY ORGANIC SILT OR CLAY

PEAT

For definit ion of dual and borderline symbols, see ASTM D2487-8S.

KEY TO TEST DATA

Perm - PermeabilityConsol - ConsolidationLL - Liquid Limit (%)PI - Plasticity Index (%)Gs - Specific GravityMA - Particle Size Analysis

• - " Undisturbed" Sample

[2 - Bulk or Classification Sample

OH - Lost Sample

Shear Strength (psf)-^ p Confining Pressure

A fTxUU 3200(2600) - Unconsolidated-Undrained Tri.ixi.il Slicnr

(FM) or (S) (field moisture or saturated)TxCU 3200 (2600) - Consolidated-Undrained Tri.-ixinl Shear

(P) (with or without pore pressure measurement)TxCD 3200 (2600) - Consolidated Drained Triaxial ShearSSCU 3200 (2600) - Simple Shear Consolidated Undrruned

(P) (with or without pore pressure measurement)SSCD 3200 (2600) - Simple Shear Consolidated DrainedDSCD 2700 (2000) - Consolidated Drained Direct ShearUC 470 - Unconfined CompressionLVS 700 - Laboratory Vane ShearTV 800 - Torvane ShearPP 400 - Pocket Penetrometer

(actual reading divided by 2)


B Environmental Services

Soil Classification Chartand Key to Test DataW.R. Grace DamRainy Creek, Montana

PLATE

12DRAWN

AMJOB NUMBER


12/91REVISED DATE

135230

Relative Density of Coarse-Grained Soils

RelativeDeniity

Standard Penetration Test Blow Count(blows per foot)

very looseloose

medium densedense

very dense

<44 - 1010- 3030 - 50

>50

Consistency of Fine-Grained Soils

ConsistencyIdentification

Procedure

ApproximateShear Strength

(pif)

Very softSoftMedium stiff

Stiff

Very StiffHard

Easily penetrated several inches with fistEasily penetrated several inches with thumbPenetrated several inches by thumbwith moderate effortReadily indented by thumb, but penetratedonly with great effortReadily indented by thumb nailIndented with difficulty by thumb nail

Natural Moisture Content *

less than 250250-500

500 - 1000

1000 - 2000

2000 - 4000greater than 4000

Dry - Requires considerable moisture to obtain optimum moisture content* forcompaction

Moist - Near the optimum moisture content for compaction

Wet - Requires drying to obtain optimum moisture content for compaction

Saturated - Near or below the water table, from capillarity, or from perched orponded water

Optimum moisture content as determined in accordance with ASTM TestMethod D1567-78.

Where laboratory data are not available, the above field classifications provide a generalindication of material properties; the classifications may require modification if laboratory testsare subsequently conducted.

Harding Lawaon AaaociaUaEngineering andEnvironmental Services

Physical Properties Criteriafor Soil ClassificationsW.R. Grace DamRainy Creek, Montana

DRAWN

AMJOB NUMBER


11/91

PLATE

13REVISED DATE

135290

]

n

j

II

VI

CONSOLIDATION OF SEDIMENTARY ROCKS; usually determined from unweathered samples. Largely dependent oncementation.

U = unconsolidatedP = poorly consolidatedM = moderately consolidatedW = well consolidated

BEDDING OF SEDIMENTARY ROCKS

Splitting Property Thickness (feet)

MassiveBlockySlabbyFlaggyShaly or platyPapery

III FRACTURING

Intensity

Very little fracturedOccasionally fracturedModerately fracturedClosely fracturedIntensely fracturedCrushed

IV HARDNESS

Greater than 4.02.0 to 4.00.2 to 2.00.05 to 0.20.01 to 0.05Less than 0.01

Stratification

Very thick beddedThick beddedThin beddedVery thin beddedLaminatedThinly laminated

Site of Pieces (Feet)

Greater than 4.01.0 to 4.00.5 to 1.00.1 to 0.50.05 to 0.1Less than 0.05

1. Soft - Reserved for plastic material alone.2. Low hardness - Can be gouged deeply or carved easily with a knife blade.3. Moderately hard - Can be readily scratched by a knife blade; scratch leaves a heavy trace of dust and is readily visible

after the powder has been blown away.4. Hard - Can be scratched with difficulty; scratch produces little powder and is often faintly visible.5. Very hard - Cannot be scratched with knife blade; leaves a metallic streak.

STRENGTH

1. Plastic or very low strength.2. Friable - Crumbles easily by rubbing with fingers.3. Weak - An unfractured specimen of such material will crumble under light hammer blows.4. Moderately strong - Specimen will withstand a few heavy hammer blows before breaking.5. Strong - Specimen will withstand a few heavy ringing hammer blows and will yield with difficulty only dust and small

flying fragments.6. Very strong - Specimen will resist heavy ringing hammer blows and will yield with difficulty only dust and small f ly ing

fragments.

WEATHERING - The physical and chemical disintegration and decomposition of rocks and minerals by natural processes suchas oxidation, reduction, hydration, solution, carbonation, and freezing and thawing.

D.

M.

L.

F.

Deep - Moderate to complete mineral decomposition; extensive disintegration; deep and thorough discoloration; manyfractures, all extensively coated or filled with oxides, carbonates, and/or clay or silt.Moderate - Slight changes or partial decomposition of minerals; little disintegration; cementation little to unaffected;moderate to occasionally intense discoloration; moderately coated fractures.Little - No megascopic decomposition of mineral*; little or no effect on normal cementation; slight and intermittent, orlocaliied discoloration; few stains on fracture surfaces.Fresh - Unaffected by weathering agents; no disintegration or discoloration; fractures usually less numerous than joints.

ANDESITE,BASALT,RHYOL1TE

CHERT

CONGLOMERATE

• -i-L

II

1

GRAYWACKE

LIMESTONE,CORAL

SANDSTONE

SCHIST

SERPENTINE

SHALE

SILTSTONE, MUDSTONECLAYSTONE

TUFF

PYROXENTTE

Harding Law con AssociatesEngineering andEnvironmental Services

Physical Properties Criteriafor Rock ClassificationsW.R. Grace DamRainy Creek, Montana

PLATE

14DRAWN

AMJOB NUMBER


11/91REVISED DATE

U.S. Stan

100

QO

ftf)

?nX0

> 60-< DU

00

PF, RO, — jLLJ 3U2U_I-^ Anjfi 4U

ODCUJ0- or\_J

on£\J

m -

3 1!/2 3 /4 3 /a 4 81

;- -- -

- .- -~

id

6

-"\: • : : . - : \^•- \

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:-

3040 50 100 20

••••. -

VV-\ -

\\' \ • •

•\• \ "\

0

- - - ••

N\b

ter

Refeience: ASTM D 422

100 50 10 5 1 0.5 0.1 0.05 0.01 0.005 0.001

GRAIN SIZE IN MILLIMETERS

GOBBLEDCOARSE FINE

J GRAVEL

Symbol

0

COARSE) MEDIUM | FINE

Sample Source

A-l @ 15.0 FT

SANDSILT OR CLAY

Classification

GRAY SAND W/ SILT (SW-SM)

Harding Lawson AssociatesEngineers. Geologists& Geophysicists

Particle Size AnalysisW.R. Grace DamRainy Creek, Montana 15

DRAWN JOB NUMBER


07-15-1991REVISED

11/91

U.S. Stan

100

onOU

70/uIg> OU

CD

2LLI-

LUoDCLU

mIU

0 •

3 r/2 3/4 3/e

' '

'. : i

'•--•:• — -

. • i • :

i :

•. '

(

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! :

4 8 1

idard Siev

6 304

- : • • : ;'"••• «v

; • . ; • ; ;; i i : . ? ! ; ; ; ;; ! : ' • ' :: • • T 1 T • " " 'T ' " T

I! i : • i : . ; : ;1' ; : I ,' . : ' \

1 ; '

i. •

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: * '' ' ' _I ' '

. : i • ;

j( -

'! ' •' ' : '.

.- .

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:i •

100 50 10

COBBLE!COARSE | FINE

3 GRAVEL

i •

!

;

i

10 50 100 2C

s^N

: : ; : : ' • \

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ter

Reference: ASTM D 422

5 . 1 0.5 0.1 0.05 0.01 0.005 0.001


Symbol

D

COARSE| MEDIUM

SAND

FINE

Sample Source

A-l 9 25.0 FT

SILT OR CLAY

Classification

OLIVE-GREEN S1LTY SAND (SM)

Harding Lawson Associate*Engineers, Geologists& Geophysicists

Particle Size AnalysisW.R. Grace DamRainy Creek, Montana 16

DRAWN JOB NUMBER


07-15-1991REVISED DATE

11/91

U.S. Stan

100

QO

on

i-CD

^ fin> OU

CQocuj 502LL

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occUJ

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: • ' : : ' .. \i; ' '. ; ! ; • ; \:' . i . : ; • "

'•'. . '*• ' I- :

-'••' •• -

• . ""! ' ":'

i. ' • >

'• . \ .

'•:• • -• -. i ;j ,

; ; . ; '

• • . • ; • -

100 50 10

COBBLECOARSE FINE

GRAVEL

^,

3040 50 100 2C

•

\

... ..L...:.._. ... . . ._. ._ .

. - • • ' . "

\:\: :

V

A

• . .1.: \V

0

.i .

er

Reference: ASTMD 422

-•

5 1 0.5 0.1 0.05 0.01 0.005 0.001


Symbol

D


Sample Source

A-l @ 55.0 FT

SANDSILT OR CLAY

Classification

MOTTLED GRAY-GREEN SAND W/ SILT (SW-SM)

Harding Lawson A«*ociat«sEngineers. Geologists& Geophysicists

Particle Size AnalysisW.R. Grace DamRainy Creek, Montana

PLATE

17DRAWN JOB NUMBER



11/91

U.S. Stan

100

Qn

on _

7nIVIo

^ fin< ou

CO

zu.1-LUOocLLJ

°~ 30 H

in -

3 11/2 3/4 3/8

• : • • • -

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.;

' • • : I

; • •• - '.':

';

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4 8 1

id

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••••--• - - '

=, . *

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;'; . '

.,...;.

^ :

i : '• .

: L

• •• - - - - - •

- = ' ! i •- .

,; '

i

100 50 10

COBBLE,COARSE | FINE

GRAVEL

Symbol

e

3040 50 100 20

\-

l '\-; . \\r~.~:\; : : ; \.

' : \• ' ' \:: • i . V

\

,

'•/•••

0

:

\ '

\\i

ter

Reference. ASTMD 422

..:..

5 1 0.5 0.1 0.05 0.01 0.005 . 0.001



Sample Source

A-2 @ 50.5 FT

SANDSILT OR CLAY

Classification

DARK GREEN SILTY SAND (SM)

Harding Lawson AssociatesEngineers, Geologists& Geophysicists


PLATE

18DRAWN JOB NUMBER



11/91

U.S. Stan

100

onOU — '

7n« u

Io

^ fin> ou

CO

m 50zLL

Z 4noDCUJQ- onou

mIU

3 V /2 3 A 3 /a 4 81

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• •

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i ;

: ', ' \

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A

r: \ -' :: I . \

: ! : • • : ' i^

. . .

•

• - •

. . . . . .

; - • - . • ' •

Bl

ter

Reference: ASTMD 422

.. .

- •• •

100 50 10 5 1 0.5 0.1 0.05 0.01 0.005 0.001


COBBLE!COARSE I FINE COARSEl MEDIUM I FINE

3 GRAVEL

Symbol

Q

Sample Source

A-3 @ 5.0 FT

Harding Lawson Associates^^^fl Engineers. Geologists^ j y & Geophysicists

DRAWN JOB NUMBER

5891.053.03

SANDR CLAY

Classification

GREEN SAND W/ SILT AND GRAVEL (SW-SM)

Particle Size Analysis p ATE

W.R. Grace Dam ^ ARainy Creek, Montana | %J

APPROVED DATE REVISED DATE

^\ 07-15-1991 11/91

U.S. Stan

100

Qfl

OnOU

7O,1 U

ICDUJ on> OU

CQ

m 50zLLh-

LJJ

LUD_ JQ J

mIU

dard Sieve Size

3 V/2 3

(in.) • — »•

/4 3/8

L^~-.

1

:=

=

•

1 .; -

- '- - • •'

• • ' •• -\

• •

100 50

COBBLES

Symbol

D

COARSE

4 8 1

id

6

• • '. i i . • !

: ' • ; ! ,;

• ] ' • ' •. ' ••

» •

; ' '

\ i

._i_._.; -._... . ..* t? .-

. ' •

• . . ' - '->-•• --.

;. - •-•

': i i ; i :

; : : ; ; • ; ; :

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10

FINE

GRAVEL

3040 50 100 20

\!\

•••\: .' \

! : - \

\ .

I\\:-\

. ....• \

::- V\

0

•

\

ter

Reference- ASTMD -»22

5 1 0.5 0.1 0.05 0.01 0.005 0.001



Sample Source

A-4 e 10.5 FT

SANDSILT OR CLAY

Classification

BROWN SAND (SP)



SLATE

21DRAWN JOB NUMBER



11/91

U.S. Stan

100

onOU

yn/U

IO

£ finJ5 OU

m SOLU OUzUL

Z /intuOoc1110- on _,

OU

mIU

0 ~

3 1!/2 % 3/a 4 8 16 3040 50 100 200

•••

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\A

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•• ' • -: - • ••

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ter

Reference ASTMD<i22

•-

100 50 10 5 1 0.5 0.1 0.05 0.01 0.005 0.001


COBBLEvCOARSE FINE COARSEl MEDIUM I FINE

3 GRAVEL SAND OIL-' ^R CLAY

Symbol

B

Sample Source Classification

A-4 @ 11.0 FT GRAY SAND W/ SILT (SP-SM)

Harding Lawson Associates Particle Size Analysis PLATE

^^^ Engineers. Geologists W.R. Grace Dam *\f\&GeophySicists Rainy Creek, Montana 22

DRAWN JOB NUMBER APPROVED DATE REVISED DATE

5891.053.03 ^\\ 07-15-1991 11/91

U.S. Stan

100

on —

onou

7nr U

X0

£ fin-^ oU

CO

ffi ^nLLJ Owzu_I-^ /inUJ 4°ODCUJ°- inJU

on<iU

mIU

0 •

3 V/2 3/4 3/8

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.' '-• -

>..' • ••••-- ---

•:- '• --•••-•••••••• ••••

[ ; •• •

*' : .

100 50 10

COBBLE!COARSE FINE

3 GRAVEL

Symbol

D

...

^l

3040 50 100 2C

K

-rt\- • •V :;: • ; \\: : - . ;

- -- -

:

;

0

\\

- •

ter

Reference: ASTM D 422

••

5 1 0.5 0.1 0.05 0.01 0.005 0.001GRAIN SIZE IN MILLIMETERS

COARSE) MEDIUM | FINESAND

Sample Source

A-5 @ 30.5 FT

SILT OR CLAY

Classification

GRAY SANDY SILT (ML)



PLATE

23DRAWN JOB NUMBER

5891.053.APPRQV

03 WrID DATE


11/91

U.S. Stan

100

qn _

on _jou

70, — iIV

Ig

mm 50 -JzLL

Z 4ntuII 1

occLU

°- ^n

m

0 •

3 11/2 3/4 3/8

~

•' ' -:.-

i'i '

'• - :; ' :

; ' •:

1 . • .

1

- - -H ;;

: : !J . •;

' '; : : :: ;;: ' i

-1

* I I °

4 8

Stand

16

•i i : : . :

- , . • ' • : :

;i ! i ••'• ' • : •t! ' • ' \ ! :

;l ; ! ; ; : : ; , ;

1- '• ' '- • . ' '. J

i • :{ ' • ' . ' • :

I: ; ; : M . i ; i! ; ; :

, I ; • i I .. i

i • , ; \ •

! ; ; ! | ; ' ; :

' : • : ' . • , ' ' • • • • '

i •

•] ;• .

100 50 10

COBBLECOARSE | FINE

J GRAVEL

Symbol

D

3040 50 100 2C

"^\

\r m_

• • i

< . ; . . . - ;

i !

.: ' • ' '• ': . ;

i !

i . • •

• ! : . i

0

fc:• • •

I .

ter

Reference- ASTMD 422

-

5 1 0.5 0.1 0.05 0.01 0.005 0.001


COARSE MEDIUM | FINE

SAND

Sample Source

A-5 6 45.7 FT

SILT OR CLAY

Classification

GRAY SANDY ELASTIC SILT (MH)


AnalysisW.R. Grace DamRainy Creek, Montana

PLATE

DRAWN JOB NUMBER


07-17-1991REUSED DATE

11/91

U.S. Stan

100

onOU

I-I0

^ fin-i^ ou

m *50UJ 3UZ

O<rLitQ- -in-

mIVJ

0 ~

3 1Vz 3/4 3/8

: i . : . •• • K• ; l

• : 1 ; i!

\ \ ' ' • ' i

• ! • i!

': • i1 t. ii

i i ; ; | i i }

; ; ; • • ij^ - i

:;

• -^ • ' it

• a ; '; ' !'

i i M • :' l :i

: | . ; : ^ • j! ! ' : : • ! • iJ: •. ' ''

4 8 1

id

6

! : j ; ; ; ' ! ; :

\1 •;: ; N'j i ;

i! 1 |! '

l\ \ ,

( ; ; i

ii .L!_

Ui

V

.

i *'

\i ; ' i

!\: I

! ! H!M ' : X

\ ' ' l ^

h i 1

E1 !

;

ii; : , i i : :

- ' . ' . ' .

; i • • ; • '

I! i i i | ' ; ; ::; i 1

ii!

rr"i1 !

' i i

i|

[ • ' : •

I ' l ' '

j i : ! :

} ' M :

;

««—

.,r:...,_.) — -_, _ - ,..

, ' '. • ' • '• «

100 50 10

COBBLE!COARSE FINE

GRAVEL

3040 50 100 2C

; ; i

1 : : i :

: 1 I ; • ; ;

. E '• ; ' • '

' . ' ' • ' • \ ' '

' \ i ; i : !

\ ! i ! : <

:\; : ! : ;;i \ ;

\; \

- , ; < ; ; \. : • ' : : :

•• '• ' i i !: : , 1

.'! . i ; ; : i

, : ; i > ii • • i '• '• '•

, - • ' ! ' • • • :

0

•'-

\ ••": t . \

; _ ' : . - • :

• ' ' . ' • ' • : '• 1

i !*' ' ' • " •, 'i- : :

''• :l: 1 ; :

- : * : • ' •

\iiii ; ; • • ,- •; ,

•;; :

: ;= ' ' ' -

; - . ' : • :

ter

Reference: ASTM 0^22

-

•• -'

. •

'••

5 1 0.5 0.1 0.05 0.01 0.005 0.001


Symbol

D


Sample Source

A-9 @ 9.0 FT

SANDSILT OR CLAY

Classification

BROWN SILTY SAND W/ GRAVEL (SM)



PLATE

25DRAWN JOB NUMBER



11/91

/ u

60

^

XHIQZ 40

•r—O 30

PCO

_J 20CL

10

74

o

CL or OL

///

CL - ?v1L v /N /"t /s

ML or OL

CH or OH /

/s

//

///

// o;/ +

MH or OHn

Q

0 10 20 30 40 50 60 70 80 90 100

LIQUID LIMIT (%)

Reference: ASTM D-431B

SYMBOL

a

V

O

4-

BORINGNUMBER

A-l

A-l

A-2

A-2

A-3

DEPTH(feet)

16.7

35.5

25.2

46.0

36.5

CLASSIFICATION

GRAY ELASTIC SILT W/SAND (MH)

OLIVE-GREEN SILTYSAND (SM)

OLIVE-GREEN ELASTIC SILTW/ SAND (MH)

OLIVE-GREEN SANDYELASTIC SILT (MH)

BLUE-GREEN ELASTICSILT (MH)

* NON PLASTIC - NOT SHO\

LL

60

NP*

51

71

69

VN ON Cr

PL

52

NP

41

44

44

<ART

PI

8

NP

10

27

25

MOISTURECONTENT (%)

71.1

63.2

60.4

64.0

Dl .. .* f»Kar» =• AT-

BHarding Lawson Associates riasilCIIy Wnari

Engineering and W.R. GraCB Dam ** **Environment Serves Rajny Creek> Monlana y C

fm\JDRAWN .OB NUMBER APPROVED GATE RE'/iSEC 3«.TE

5B9 1.053. 03 RV\ 07-15-1991 11/91

1.0

0.8

a)

COCOLJJDCHCO

(TO

111O

0.6

AXIAL STRAIN (percent)

SPECIMEN TYPE UNDISTURBED SHEAR STRENGTH 312 psf

DIAMETER (In) 2.87 HEIGHT (in) 6.00 STRAIN AT FAILURE 7.0MOISTURE CONTENT 71.1 CONFINING PRESSURE 450 psf

DRY DENSITY 56 pel STRAIN RATE 0.60 %/mlnCLASSIFICATION GRAY ELASTIC SILT W/ SAND (MH) SOURCEA-1 3 16.7'


Engineers. Geologists& Geophysicists

Unconsolidated - UndrainedTriaxial Compression Test ReportW.R. Grace DamRainy Creek, Montana 27

DRAWN JOB NUMBER



11/91

CO

COCO111rrKco(TOf-

111O

1.0 r

0.8

0.0



DIAMETER (In) 2.87 HEIGHT (In) 6.00 STRAIN AT FAILURE 10.3MOISTURE CONTENT 63.2 CONFINING PRESSURE 500 paf

DRY DENSITY 62 pcf STRAIN RATE 0.60 %/mln

CLASSIFICATION OLIVE-GREEN ELASTIC SILT VW SAND (MH) SOURCEA-2 @ 25.2*


Engineers, Geologists& Geophysicists

Unconsolidated - UndrainedTriaxial Compression Test ReportW.R. Grace DamRainy Creek. Montana 28

DRAWN JOB NUMBER



11/91

2 . O r

OT

COCOLUDCr-CO

DCOr-

111Q

0.4

0.0



DIAMETER (In) 2.87 HEIGHT (In) 5.70 STRAIN AT FAILURE 8.8

MOISTURE CONTENT 60.4 CONFINING PRESSURE 800 paf

DRY DENSITY 64 pel STRAIN RATE 0.60 %/mlnCLASSIFICATION OLIVE-GREEN SANDY ELASTIC SILT (MH) SOURCEA-S 3 46.0'


Unconsolidated - Undrained

Triaxial Compression Test ReportW.R. Grace DamRainy Creek, Montana

PLATE

29DRAWN JOB NUMBER

5891.053.03APPROVED

^

DATE


11/91

S.Sr

tn

COCO01ccI-coccor-

111Q


SPECIMEN TYPE UNDISTURBED SHEAR STRENGTH 1006 petDIAMETER (In) 2.89 HEIGHT (In) 6.00 STRAIN AT FAILURE 7.3MOISTURE CONTENT 64.0 CONFINING PRESSURE 7BO psf

DRY DENSITY 62 pcf STRAIN RATE 0.60 %/mln

CLASSIFICATION BLUE-GREEN ELASTIC SILT (MH) SOURCEA-3 0 36.0'

Harding Lawson AssociatesEngineers, Geologists& Geophysicists

Unconsolidated - UndrainedTriaxial Compression Test ReportW.R. Grace DamRainy Creek. Montana

PLATE

30DRAWN JOB NUMBER

5891.053.03DATE REVISED

07-12-1991DATE

11/91

1.8

c

1.6

0 1.40h-

1

Q

O i 2

1.0

0.8

PRESSURE (ksf)

\

1

?o

> xO "«

a«*.

o

N

•

N

*>

»s

s,

xs

l _* V

X

\y

\

x

\\\

•N.

\

s

\

3.

L

y

\\\

'-^,

^1 10 100 1000

Rafwmca: A8TM D-84S(SPECIMEN TYPE TRIMMED

DIAMETER (In) 2.43

OVERBURDEN PRESSURE,

HEIGHT (In) 0.80

0"vo' p«fPRECONSOL PRESSURE. (Ovo')max 2800 paf

COMPRESSION INDEX, Cc

LIQUID LIMIT

0.78PLASTIC LIMIT

BEFORE TEST

MOISTURE CONTENT

VOID RATIO

SATURATION

DRY DENSITY

w0

eoSo

^d

67.1 %1.68

100 %69 pcf

PLASTICITY INDEX

CLASSIFICATION OLIVE GREEN SANDY ELASTIC SILT (MH)

AFTER TEST

wfef

Sf

"*d

43.0 %1.27

100 %81 pcf

SPECIFIC GRAVITY 2.96

SOURCE A-2 • 48.7 FT

HLAHarding Lawson Associates

Engineers. Geologists& Geophysicists

Consolidation Test ReportW.R. Grace DamRainy Creek, Montana

PLATE

31DRAWN JOB NUMBER

5891.063.03APPROVED

£#/DATE


11/91

105649

MAXIMUM DRY DENSITY (pcf) 144

CORRECTED MAXIMUM DRY DENSITY (pcf) i44

OPTIMUM WATER CONTENT (%) 7.9

146

145

144

143

1

> 14235z01

£ 141DCa

140

139

13B

137

i i !! iii ^^

• 'i^^^\I \

\

.

1 \\

\\i rij

i J

1 ! !i i ;

i - ' : !

; | : I i

2 3 4 5 6 7 8 9 10 11 12

MOISTURE CONTENT (percent)

Reference: ASTM D-1557

1 2 3

MOISTURE CONTENT (%) 4.1 6.2 7.9

DRY DENSITY (pcf) 143 143 144

% PASSING3//' 100.0 SPECIFIC GRAVITY (g/cc) 2.70 MOLD DIAMETER

4

9.8

139

6.00

CLASSIFICATION BRN SAND W/ SILT S 6RVL (SP-SM) SOURCE BULK § 0.0 FT

•••Hi Harding Law»on A*»oclut«i CuillpdLllUII Test Reportffff^^ Engineers and Geoscieniists W.R. Grace Dam

HBft RainV Creek- Montana

DRAWN JOB NUMBER APPROVED DATE REVISED

5891.053.03 n< 07-17-1991

PI ATE

32^^ Bl B

DATE

11/91

- - ~": -- —- : - : " - -

1 L

iri 1

^/> i

- • -i,f •=|tet-^-A^;jte^..^i i ' : \-f

f^fr\~ - AXJ.iisa

vl""L/w?%i- «^:^^ „-"^ -/' K ^

:' Qar^

*v MKl" >-c;-rr'.^S^. •''w^^^JM;•„ ^_^-x ;.-.-fir:-.•••.•'

mKtfe—kf. \ r

j\,-'

41> :, '££. •C^ -^ "^^ / md ^*&x&*

^&t s«=i

:

'?m^.?jmrs- . ----- -^S^ y 1& !.'P.)» r/ "~

32,Ca.^v, ^

^ Y

• •-^T\ i— i V- . - . \Kf, \\ Lr:,j ,Txi :PJL \^_ n.,i 1 : * ~ C( S_

EXPLANATION

Qal - Mainly valley fill consisting of silt, sandand gravel

Qg - Glacial drift; morainal and outwash plaindeposits of mountain glaciers (Quaternary)

pCm - Missoula Group, chiefly red, maroon or purpleargillite, sandy orquartzitic argillite, andgsnerally impure quartzite and limestone (Pre-Cambrian)

pCw - Wallace Formation; dark gray argillite, arenaceousand argillaceous limestone and gray limy quartzitewith shale and sandstone in large areas (Pre-Cambrian)

Geologic boundaryDashed where approximately located

• ~ Geologic boundary indicated by the compilers onthe basis of incomplete data

-— Fault, character not designatedDashed where approximately located

Concealed fault

Thrust faultT, ijpper plate

Fault indicated by the compilers on the basis ofincomplete data

10

Scale

20 Miles

(1:500,000)

ra10n

/ Jf =^ \. I#-\N •• ' . - , \ n~«! .// '_ *£t _ IT!Reference: Geologic Map of Montana prepared by Ross, Andrews and Witkind

(in cooperation with Montana Bureau of Mines and Geology), dated 1955.


Geologic Map of Site and VicinityW.R. Grace DamRainy Creek, Montana

PLATE

33DRAWN

AMJOB NUMBER

5891,053.03APPROVED DATE

2/92REVISED DATE

-500'±(NTS)

F.S. (Static) - 2.28

Ky=0.42

•PIEZOMETER

50

0'=37»c'= 500 psf£=125pcf

ELASTIC SILT W/SAND(Tailings Material)£-100pcf

OF NEW LEVEEcrest elevation 291Q)

UNDRAINEDSHEARSTRENGTH

1900VARIATION IN GROUNDWATER LEVEL

3.0-r

£u.35

2.0- •

§1.0-

o

0\-

70

Ky - 0.42Scale in Feet

I T0.2 0.4

SEISMIC COEFFICIENT, K

Case I, II: Stability Analysis - Water at 500 feetfrom Embankment (C1 = 500 psf)


DRAWN

AMJOB NUMBER

5891.053.03

Sheet 1 of 2Analytical UocM andSou PropMtiMW.R. Grace DamRainy Creek. Montana

PLATE

34aAPPROVED DATE

11/91REVISED DATE

Ky-0.28

/PIEZOMETER

F.S. (Static)-1.83

EMBANKMENT MATERIAL

0 = 37°c'= 50 psf>r=125pcf

VARIATION IN GROUNDWATER LEVEL'

- 500't (NTS)-

50

ELASTIC SILT W/SAND(Tailings Material)

Q. OF NEW LEVEE(crest elevation 2910)V

1900

UNDRAINEDSHEARSTRENGTH(psf)

2.0-r-cn

LLJLL

CO

&

rr

1.0-

Ky = 0.28

0.1 0.2SEISMIC COEFFICIENT, K

70

Scale in Feet

Case I, II: Stability Analysis - Water at 500 feetfrom Embankment (C1 = 50 psf)


DRAWN

AMJOB NUMBER

5891,053.03

Analytical Model andSoil PropertiesW.R. Grace DamRainy Creek, Montana

Sheet 2 of 2PLATE

34bAPPROVED

GuyDATE

11/91REVISED DATE

F.S. (Static) - 1.74

PHREATC SURFACE

Ky-0.22

VARIATION IN GROUNDWATER LEVElT

r 'IEZOMETER

EMBANKMENT MATERIAL0-37°c'- 500 psf7-125pcf

50ELASTIC SILT W/SAND(Talings Material)7-100pcf

RAINEDSHEARSTRENGTH(psf)

1900

2.0-rcoLL

U.

.occo

1.0

70

Scale in Feet

Ky = 0.22 Case III, IV: Stability Analysis - Water at Faceof Embankment (C1 = 500 psf)

i i0 0.1 0.20



DRAWN

AMJOB NUMBER

5891,053.03

Sheet 1 of 2

Analytical Model andSoil PropertiesW.R. Grace DamRainy Creek, Montana

PLATE

35aAPPROVED

6UVDATE

11/91REVISED DATE

PHREATIC SURFACE

PIEZOMETER

-F.S. (Static) = 1.14Ky= 0.05

50

0-37°c'= 50 psfVr=125pd

EMBANKMENT MATERIAL

ELASTIC SILT W/SAND(Tailings Material)X.-100pcf \ .UNDRAINED

V^ SHEAR/\ STRENGTH

\ (PS«)

\1900

VARIATION IN GROUNOWATER LEVEL

1.5-r-

70

Scale in Feet

0 0.1 0.2


Case III, IV: Stability Analysis - Water at Faceof Embankment (C1 = 50 psf)

Sheet 2 of 2


DRAWN

AMJOB NUMBER

5891,053.03

Analytical Model andSoil PropertiesVV.R. Grace DamRainy Creek, Montana

PLATE

35bAPPROVED DATE

11/91REVISED DATE

EXISTING PIEZOMETER

ELASTIC SILT WITH SAND

EMBANKMENT MATERIALALTERNATIVE 1-DRAIN ROCK BLANKETCAPPED WITH CLAYEYSOIL

ALTERNATIVE 2-ROCK •CHMNEY' DRAIN

PROPOSED PIEZOMETER LOCATIONS-TOTAL OF 5 STAGGERED ALONGLENGTH OF EMBANKMENT

40

Scale in Feet

Harding Lawson Associate*Engineering andEnvironmental Services

DRAWN

AMJOB NUMBER

5891,053.03

Schematic Section ofProposed Drainage/Monitoring SystemW.R. Grace DamRainy Creek, Montana

PLATE

36APPROVED

GUVDATE

11/91REVISED DATE


DISTRIBUTION

3 copies: W. R. Grace & CompanyConstruction Products Divis ionP.O. Box 609Libby Montana 59923Attention: Mr. Alan Str inger

G L W / m f b / B I 2 7 0 3 - R 7 1

QUALITY CONTROL R E V I E W E R

Keith H. BergmanGeotechnical Eng inee r

geotechnical evaluation w.r. grace dam · pdf fileembankment soils 3. ... ~1 we explored the...

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