Effects on Transportation and Utilities 

Eklutna 

Power Project 

GEOLOGICAL SURVEY PROFESSIONAL PAPER 545-A 
This page intentionally left blank
THE ALASKA EARTHQUAKE, MARCH 27, 1964: 

EFFECTS ON TRANSPORTATION, COMMUNICATIONS, AND UTILITIES 

Effect of the Earthquake 

Of March 27, 1964, on 

The Eklutna Hydroelectric 

Project, Anchorage, Alaska 

By MALCOLM H. LOGAN 

With a Section on 

TELEVISION EXAMINATION OF EARTHQUAKE 

DAMAGE TO UNDERGROUND COMMUNICATION 

AND ELECTRICAL SYSTEMS IN ANCHORAGE 

ByLYNN R. BURTON 

GEOLOGICAL SURVEY PROFESSIONAL PAPER 545-A 

APR 11 1991 
UNITED STATES DEPARTMENT OF THE INTERIOR 

STEW ART L. UDALL, Secretary 

GEOLOGICAL SURVEY 

William T. Pecora, Director 

UNITED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON 1967 

For sale by the Superintendent of Documents, U.S. Government Printing Office 

Washington, D.C. 20402- Price 35 cents (paper cover) 
THE 

ALASKA EARTHQUAKE 

SERIES 

The U.S. Geological Survey is publishing the results of its 

investigations of the Alaska earthquake of March 27, 1964, 

in a series of six professional papers. Professional Paper 

545 describes the effects of the earthquake on transportation, 

communications, and utilities. Where needed to complete 

the record, reports by individuals from organizations other 

than the Geological Survey are included in the series. Thus, 

this description of the Eklutna Hydroelectric Project-a key 

part of south-central Alaska's power system-was requested 

from the U.S. Bureau of Reclamation; so, too, was the section 

on the use of television for investigating damaged underground utility lines. Additional chapters in Professional 

Paper 545 will describe the effects of the earthquake on The 

Alaska Railroad and on highways, airports, utilities, and 

communications. 

Other professional papers describe the field investigations 

and reconstruction and the effects of the earthquake on communities, on regions, and on the hydrologic regimen. 

Abstract ____________________ _ 

Introduction and ackno" ledgrnents _____________________ _ 

Geologic setting ______________ _ 

The first 24 hours ____________ _ 

Effects on indiYidual features 

of the Eklutna project ______ _ 

Eklutna Darn ____________ _ 

Intake structure __________ _ 

Tunnel and gate shaft ____ _ 

1. Index map of the Eklutna 

Hydroelectric Project ___ _ 

2. Topography and surface geology of the project area __ 

3. Schematic plan and profile of 

the Eklutna project _____ _ 

4. Map and section of darnsite 

area showing exploratory work __________________ _ 

5. Photograph of spillway gate 

structure _______________ _ 

6. Aerial photograph of intake 

area showing network of 

cracks _________________ _ 

7. Geologic section showing location of earthquake darnage to intake structure __ _ 

8. Geologic section along the 

line of the pressure tunneL 

9. Photograph of debris deposited in Eklutna tunneL __ 

10. Geologic section through gate shaft __________________ _ 

11. Geologic sect1on through 

surge tank _____________ _ 

12. Section through surge tank, 

penstock, and anchorblock area _____________ _ 

13. Photograph showing earth 

settlement over penstock anchor block ___________ _ 

Page 

A1 

1 

4 

5 

6 

6 

6 

9 

Page 

A2 

3 

4 

7 

7 

8 

9 

10 

12 

12 

13 

14 

14 

CONTENTS 

Effects-Continued 

Penstock, surge tank, and 

anchor block ___________ _ 

Powerplant and associated 

structures _____________ _ 

Tailrace _________________ _ 

Transmission lines ________ _ 

Substations ______________ _ 

Other earthquake effects in the area ______________________ _ 

ILLUSTRATIONS 

FIGURES 

14. Photograph of Eklutna powerPage 

A13 

15 

20 

23 

23 

23 

plant before the earthquake_ A15 

15. Photograph showing piling 

in the powerplant foundation _____ --_____________ 15 

16. Geologic section through 

surge tank, penstock, and 

powerhouse_____________ 16 

17. Typical ground settlement 

resulting from the earthquake__________________ 17 

18. Plan view of powerplant 

g1vmg measurements of 

settlement and deflection_ 17 

19. Photograph of machine-shop 

foundation, showing separation of backfill material from concrete footing_ 18 

20. Photograph showing damaged 

20,000-kva transformer conduit and terminal box____ 18 

21. Photograph showing damaged 

heating-system piping in 

the floor of the automotive 

repair shop______________ 19 

22. Sketch map of major earthquake cracks in powerplant area_ _ _ _ _ _ _ _ _ _ _ _ _ _ 19 

23. Photcgraph ~howing cracks 

in pavement of Eklutna 

roadway__ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 20 

Television examination of earthquake damage to underground 

communication and electrical 

systems in Anchorage, by 

Lynn R. Burton ____________ _ 

Introduction _____________ _ 

Underground systems _____ _ 

Eqmprnent ______________ _ 

Procedure _______________ _ 

Damage to systems _______ _ 

Interpretation of data _____ _ 

24. Photograph showing darnaged 

Page 

A25 

25 

25 

25 

27 

27 

30 

pump in project office_____ A20 

25. Typical section of tailrace 

channeL ___ - ____ -------- 20 

26. Photograph showing cleaningup operation at outlet of 

tailrace conduit ____ - __ --- 21 

27. Plan, section, and chart giving summary of damage 

to tailrace conduiL _ _ _ _ _ 21 

28. Aerial photograph showing 

locations of cracks near 

the powerplant_ _ _ _ _ _ _ _ _ _ 22 

29. Aerial photograph showing 

Eklutna Lake area_______ 24 

30. Photograph of truck-mounted 

television equipment being 

loaded at Denver for its 

flight to Anchorage______ 25 

31. Details of television probes_ 26 

32. Arrangement of television 

equipment during examination__________________ 27 

33. Topographv, surface geology, and location of fractures in underground 

communication and electrical systems___________ 28 

34. Axial view of breaks in the 

ducts, as seen on the television monitor screen_____ 30 

v 

THE ALASKA EARTHQUAKE, MARCH 27,1964: EFFECTS ON TRANSPORTATION, 

COMMUNICATIONS, AND UTILITIES 

EFFECT OF THE EARTHQUAKE OF MARCH 27, 1964, ON THE 

EKLUTNA HYDROELECTRIC PROJECT, ANCHORAGE, ALASKA 

By Malcolm H. Logan, U.S. Bureau of Reclamation 

The March 27, 1964, Alaslm ea:r!thquake and its a:ssoctalted aftershocks 

caused damage requiring several milHon 

dolLars worth of repaiir to the Eklwtna 

Hydroelectric Project, 34 miles northea:st of Anchorage. Electric service 

1lrom the Eklutna powerplant was interrupted during the early phase of the 

Mal'ch 27 eal'thquake, bu:t was restored 

(intermittently) until May 9,1964, when 

the plant was closed for inspection and 

repair. 

Wa:Der for Eklutna project is transABSTRACT 

ported from Eklutna Dake .to the powerplant rut tidewa:ter on Knik Arm of Oook 

Inlet by an underwater intake connected to a 4.46-mile tunnel pel113tock. 

The primary damage caused by the 

earthquake was 1at the intake struc!ture 

in Eklutna Dake. No damage to the 

power tunnel wa•s observed. The pile-

•suppor.ted powerplant •and appurtenant 

structures, Anchorage and Palmer substations, and the transmission lines suffered minor da.mage. Most damage 

occurred to facilities constructed on unconsolidated sediments and overburden 

which densified and subsided during the 

earthquake. Structures built on bedrock experienced little or no damage. 

Underground communication and electrical .systems in Anchorage were examined with a small-diameter television 

camera to locate damaged areas requiring repair. Most of the damage wars 

concentrated at or near val'ley slopes. 

Those parts of the sy·stems within the 

major rslide area's of the city were 

destroy·ed. 

INTRODUCTION AND ACKNOWLEDGlVIENTS 

The Eklutna Hydroelectric 

Project is a 30,000-kw (kilowatt) 

power development designed and 

constructed by the Bureau of Reclamation, U.S. Department of the 

Interior, to bring urgently needed 

electric power to the rapidly expanding metropolitan area at An-

~horage, Alaska. The project was 

constructed during the 4-year period 1951-55. The powerpl'ant 

(fig. 1) is loca,ted 34 miles northerust of Anchorage on the Glenn 

Highway and is supplied by water 

from Eklutna Lake, about 10 miles 

by road from the Glenn Highway. 

The lake is 7 mi1les long and is fed 

hy meil't walter from Eklutna Gla-

'Cier, 4 miles above the lake, and by 

precipitation runoff from 'a 119-

square-mile watershed. Wruter is 

·transported from the lake by an 

underwa'ter intake connected to a 

4.46-mile tunnel and 'tunnel pen-

~stock through Goat Mountain to 

the pawerplant (figs. 1, 2, 3) . The 

project is for power production 

only. Transmission lines, opel"ating a;t 115 kv (kilovolts) and terminruting at subst:ation facilities, 

extend north to Prulmer and south 

to Anchorage from the plant. 

Although this report does not 

discuss earthquake-damage rehabilitation, the repair of facilities 

damaged by the great Alaska 

earthquake of March 1964 was difficult, hazardous, and costly. 

Transmission poles had to be set 

on steep icy mountain slopes; 

weakened precast-concrete conduits could be strengthened only 

by working under 40 feet of nearfreezing water; and sand and 

gravel were mucked from 4.46 

miles of 9-foot tunnel requiring 

access by means of a 220-foot 

vertical ladder. 

A1 
A2 ALASKA EARTHQUAKE, MARCH 27, 1964 

CANADA 

1000 MILES 

1.-Index map of the Eklutna Hydroelectric Project. 
EFFECTS ON EKLUTNA HYDROELECTRIC PROJECT, ANCHORAGE 

I I I - ./ FLOOD PLAIN 1$:::.:.</i< 

EXPLANATION 

Glacial till 

Graywacke containing argillite 

inclusions 

Greenish-gray metagraywacke 

Thin-bedded argillite and some 

thin beds of graywacke 

Contact 

75 -,-I-- 

Fault, approximately located 

Showing dip of fault plane 

73 _L 

Strike and dip of beds 

-- - 

Shattered zone 

o33 

Drill hole 

10 

Test pit 

700 

u 

0 700 2100 FEET 

CONTOUR INTERVAL 500 FEET 

2.-Topography and ourfare geology of the project area. 
ALASKA EARTHQUAICE, MARCH 2 7, 19 64 

' diameter gate shaft 115-kv 

transmission 

H igh-water line 

PLAN 

3.-Schematic plan and profile of the Eklutna project. 

The decisions, actions, and im- of flow of electric energy. Juneau, Alaska, to W. Williams, 

provisions of Alaskan personnel This report was prepared in the project superintendent, Anchorduring the emergency and subse- Enginwring Geology Division of age, Alaska, and to their staffs 

quest repair operation have since the Chief Engineer's Office, U.S. ~vhose \vritten contributions, 

proven to have been in the best in- Bureau of Reclamation, Denver, photographs, and assistance durterest of communities in an area Colo. Acknowledgment is made ing the investigation formed the 

grown to depend on the continuity to G. N. Pierce, distriot manager, basis of this work. 

GEOLOGIC SETTING 

Cook Inlet is an elongated intermontane structural basin that 

trends northeast-southwest between the Chigmit and Talkeetna 

Mountains on the north and the 

Kenai and Chugach Mountains on 

the south. Knik Arm, a northeasterly extension of Cook Inlet, 

occupies a lowland that is characterized by glacial and alluvial sediments. braided streams, 

marshy areas, and broad tidal flats. 

Goat Mountain, a prominent local 

feature of )the Chugnch Range, 

rises abruptly from the southeastern flank of the Knik Arm lowlands and forms a divide between 

the Knik River and Eklutna River 

drainages. 

The Knik and Eklutna Rivers 

are in old glacial valleys, and hence 

the overburden consists of glacial 

till containing material ranging in 

size from large boulders to clay. 

In places, glacial and more recent 

streams have reworked the 'till, so 

it is sorted and somewhat bedded. 

In some areas, nearly pure silt and 

clay are interstratified with coarser 

material. I11 the stream channels 

and flood plain of the Ihik River, 

well-rounded gravel and clean 

sand predominate. 

Very little well-rounded gravel 

occurs along Eklutna River-the 

stream which drains Eklutna Lake. 
EFFECTS ON EKLUTNA HYDROELECTRIC PROJECT, ANCHORAGE A5 

The present stream channel is narrow and the steep banks have been 

cut through a succession of sand, 

clay, silt, and "dirty" gravel beds. 

All this material is partly reworked glacial till. Where the 

velocity of the present stream is 

slow, rounded gravel is found but 

its extent is not great. Shingle 

gravel mantles the ground surface 

in the vicinity of the dam. 

Several terrace remnants, representing old glaci·al lakeshores, are 

present at higher altitudes along 

the Eklutna River valley. Drill 

holes through the glacial till on 

this shore revealed varying depths 

to bedrock. In the floor of the 

valley, bedrock is estimated to be 

several hundred feet below the 

surface; elsewhere it is closer to 

the surface. 

When the earthquake occurred, 

at 5:36 p.m. (Alaska standard 

time) on March 27, 1964, the powerplant was operating at near 

maximum capacity (31,000 kw), 

and the power system was interconnected through the Anchorage, 

Reed, and Palmer substations. 

Major damage was sustained by 

two 115-kv air circuit breakers 

and bushing-type circuit transformers serving the Anchorage 

and Palmer lines, but there was 

no visible indication of damage to 

either generating unit. The 

two 20,000-kva (kilovolt-ampere) 

power transformers had shifted 

on their rails and had subsided 

several inches, as had the Camp 

line transformer. All bushings 

and connecting busses were intact, 

although under abnormal mechanical strain. The generator, 

which had been stopped for exThe mountain through which 

the tunnel is driven is composed 

of a series of graywacke, argillite, 

and slate, all metamorphosed to 

varying degrees (fig. 2) . The 

rocks in the graywacke-slateargillite series on the north slope 

have been extremely metamorphosed and crushed; bedding 

planes are indistinct, and the rocks 

are highly weathered along the intricate fractures and are jointed, 

in several places the rocks are serpentinized and slickensided. On 

the south slope the rocks are 

poorly exposed. The bedding 

planes are recognizable but vary 

in attitude within short distances. 

The higher peaks are composed of 

dark-greenish-gray graywacke. 

The most obvious factor contributing to the destruction of the 

Eklutna project facilities was the 

THE FIRST 24 HOURS 

amination, was started and station 

service was restored at 5 :55 p.m. 

A wood-pole transmission line 

structure on the 115-kv Palmer 

line had been carried away by snow 

slides. Two adjacent spans of 

transmission line, totalling 7,500 

feet, were destroyed. 

Radio communication was temporarily interrupted between the 

Anchorage substation 'and the 

powerplant. Damage at the Anchorage substation consisted of 

fractured porcelain on all three 

115-kv lightning arresters. All 

transformers shifted on their bases, 

but, although the 115-kv bus work 

was distorted and severe strain 

placed on several bushings, there 

were no failures. Indicating and 

alarm circuits had conduit damage, 

but all circuits remained operable. 

A temporary bypass was installed, 

and the Anchorage line was enerdensification of unconsolidated 

sediments and overburden. Myriad cracks, ranging from a fraction of an inch to several feet in 

width, were formed in areas underlain by the unconsolidated 

sediments. Near bedrock outcrops, a linear pattern of cracks 

formed which, in general, paralleled the bedrock configuration. 

As distance from bedrock and 

depth of overburden increased, the 

linear pattern graded into a blocky 

pattern having the general appearance of magnified mud cracks. 

All cracking observed on the Eklutna project was caused by tensional failure resulting from 

densification of saturated alluvial 

sediments. No failures were observed where structures were built 

on bedrock. 

gized through a bus tie switch at 

10: 10 p.m. The 115-kv Palmer 

line, which had been damaged by 

the slide, was isolated a't the powerplant. Service was first restored 

to the Matanuska Electric Association at Reed substation at 10: 43 

p.m., March 27, after compl&ion 

of system repairs. Service was restored to the Pa.Imer substation 

about 10 :00 a.m. on March 28 after 

completion of system repairs. 

At 12 : 12 a.m., March 28, both 

generating units at Eklut.na went 

off the line when the normal penstock pressure dropped appreciably. At 12: 40 a.m., penstock pressure restored itself and Unit 2 was 

put back on the line. An examill'ation of the intake area showed 

that the headgUJte was still in full 

open position bu't was accepting 

only a very small flow of water. 

There was no apparent damage 
A6 

although shattered and upturned 

ice on the lake indicated that there 

had been considerable disturbance 

in the lakebed and shoreline. At 

approxima;tely 1: 30 a.m., low penstock pressure aga.in caused a complete plant outage. At 3 : 55 a.m., 

pressure began to return to normal, 

so one unit was again started and 

station service and the camp load 

was picked up. At about 8:00 

a.m., the penstock pressure started 

dropping again, 't::hen suddenly 

surged to above normal before leveling off. A considerable amount 

of debris was noted in the tailrace. 

The Anchorage line was again 

ALASKA EARTHQUAKE, MARCH 2 7, 1 9 6 4 

energized and an aerial patrol of 

all lines and the lake WUJS made. 

At 2: 40 p.m., March 28, a shear 

pin was lost on the Unit 1 wicketgate drive, and thus began the first 

of a long series of shutdowns to 

remove rock and other debris from 

the gates and scrollc~Uses. 

During this period, other utilities in the area were also having 

problems. In the city of Anchorage, two 15,000-kv gas turbines 

were inoperable because of broken 

gas mains and ruptured oil tanks. 

The Chugach Electric Association 

Knik Arm steamplant lost coaland ash-handling facilities, and 

areal subsidence disrupted coolingwater facilities. Structural damage also occurred to the powerplant building and boilers. The 

Chugach Electric Association Cooper Lake plant was isolated by extensive damage to its 115-kv 

transmission line, and widespread 

damage in the Anchorage area produced many distribution-system 

faults which had to be located, then 

either repaired or isolated. The 

power-generating facilities at Elmendorf Air Force Base and Fort 

Richardson were partly crippled 

by the loss of cooling-water 

facilities. 

EFFECTS ON INDIVIDUAL FEATURES OF THE EKLUTNA PROJECT 

EKLUTNA DAM 

The dam is an enlargement of a 

nrutural dam formed by a receding 

alpine glacier. As indicated in 

figure 4, the site was thoroughly 

explored by means of drill holes, 

test pits, and geologic mapping. 

The reservoir, which is an enl·argement of Eklutna Lake, is about 10 

miles southeast of the powerplant. 

The lake has a surface area of 

3,24 7 acres, a length of 7 miles, 

and a capacity of 182,000 acre-feet 

at maximum water surface altitude of 867.5 feet. 

Construction of Eklutna Dam 

was completed by private interests 

in 1929. In 1943 it was purchased 

by the city of Anchorage from 

which the Federal Government 

purchased it at the time the Bureau's Eklutna project was built. 

The dam was raised to a crest altitude of 875 feet above sea level. 

The upstream and downstream 

slopes of the dam and other areas 

have been covered with riprap. 

On the upstream slope of the dam, 

the riprap is underlain by a sand 

and gravel blanket 12 inches thick. 

The dam has a height of 26 feet 

above the foundation, a length of 

555 feet, and a volume of 5,000 

cubic yards. 

An uncontrolled overflow spillway having a crest altitude of 867.5 

feet and a length of 150 feet is locruted on the right abutment. Lake 

level at the time of the earthquake 

was approximately 20 feet below 

the spillway gate sill. 

Early inspections of the dam 

after the earthquake revealed no 

apparent damage. Immediately 

after the quake, no cracks or other 

evidence of quake-induced movement were found in the vicinity of 

the dam and spillway. The frozen 

ground near the surface probably 

moved as a mass during the quake. 

L a t e r observations, however, 

showed that the alluvium beneath 

the frozen layer had densified and 

created a void. As thawing progressed, therefore, the upper layers 

of alluvium under the spillway 

gate structure (fig. 5) began to subside into the underlying void. 

This movement did not take place 

to any noticeable extent until early 

in July 1964. At this time, two 

cracks approximately 1 inch wide 

formed-one in the base of the 

spillway slab and one in the sill of 

the gate structure. In addition, a 

large part of the spillway base slab 

had been deprived of foundation 

support by the densification that 

caused the void. The gate structure was then declared unsafe for 

impounding water. All gates 

were locked open, pending reconstruction of the dam. 

INTAKE STRUCTURE 

Diversion from Eklutna Lake is 

made through an inlet channel, 100 

feet wide and about 500 feet long, 

excavated in the lake bottom about 

60 feet below lake-surface altitude 

(fig. 3). The intake structure extends from this inleJt channel for 

133 feet 8 inches. 

The intake structure has aninitial trashmck, 112 feet long, built 
EFFECTS ON EKLUTNA HYDROELECTRIC PROJECT, ANCHORAGE A7 

0 0 0 0 0 

g g g g g 

oo m o ~ N ~ ~ m ~ ~ 

E4s,oooLz~---------------z-+----------------ztrr~~-----------z+----------------z~- EXPLANATION 

e6 

TYPE OF 

DEPOSITS 

z 

A' 950' 

g 850' 

.. 

G:j 800' ...J 

w 

750' 

--~-N 

::_}~~ i~·· t4>\!r~P~~ ~l~$ ,co 6ies. bo~ld~r~. · · ·· · ~~d _1~seS1 · 

25+00 26+00 27+00 28+00 29 +00 

0 100 200 '300 FEET I!!!!I!J!!! I I 

U.S. Geological Survey 

Churn-drill hole (4 in.) [2] .3 Alluvium 

Test pit (6 ft >< 7 ft) 

0 110 

Drill hole (8-to 3-in. casing) Lacustrine 

0 

Bulldozer pit 

X 

Bench mark 

A,---, A 

Proposed dam axis 

San(fy .ci"a_y ~nd n&JJiar . rOck-· tr.agrrlen-tS 

LJ . . 

Till 

-Ar 

Water table 

Several perched tables 

noted during drilling 

32+00 33+00 34+00 35+00 

4.-Map and Section of damsite area showing exploratory work. 

5.-Spillway gate structure. 

A' 
A8 ALASKA EARTHQUAKE, MARCH 27, 1964 

of intake structure Eklutna Lake 

caused by earthquake 

6.-View of Eklutna intake area, showing intricate network of cracks caused by the 

earthquake along the shore of the lake. 

of rectangular precast-concrete 

sections. E·aJCh sootion is 26 foot 

8 inches wide and 37 feet long. 

Immediately downstream from the 

trashrack structure is 'a precastconcrete transition s~tion, 14 feet 

2 inches long. The inside of this 

transition section tapers from a 

rectangular reinforced -concrete 

section 9 feet by 22 foot 8 inches to 

a circular section 9 feet in diameter. At the end of the square-t:JOround transition section ·is a bulkhead section 7 feet 6 inches long. 

Slots •are provided in the bulkhead 

section for either gtop planks or a 

fabricated bulkhead to be used in 

the event of an emergency or for 

inspection purposes. 

From the end of the bulkhead 

section 'the water is conveyed to 

the entrance of Eklutna tunnel 

through a 9-foot (inside-diameter) 

precast-concrete pipe 225 feet long. 

The wall of the pipe is 12 inches 

thick. The pipe was cast in 16-

foot sections, each section weighing about 40 tons. 

Numerous holes were drilled in 

the general area of 'the tunnel intake to ·select the best location for 

the structure and bo ()btain samples 

of the glacial flour and till on the 

lake bottom for st:Jability studies. 

Two types of glacial materials, 

designated A and B, were found 

in the intake structure area. 

These materials were classified primarily by their compaction andrelated construction charncteristics 

rather than by composition: 

Material A.-Owing to the insta:bili'ty of the material, the glacial flour was excavated on a 20 to 

1 slope, and the lower part ·of material A was excavated on a 10 to 1 

slope. A thin layer of sandy clay 

containing many boulders as much 

as 3 feet in diameter underlies the 

glacial flour and overlies ·a loosely 

compaeted glacial till. 

Material B.-From the top of 

the B gla;cial-till cont:Jactio the bottom of the inlet channel, the material had to be blasted prior to 

dredging. Hs clay content and 

impermeability caused the material to be very compact in place 

and even to settle back as a compact mass on the lake bottom after 

blasting. 

The trash rack, transition, bulkhead, and conduit sootions back of 

station 19 + 06 in the bottom of 

Eklutna Lake sustained the major 

damage from the earthquake. 

(Station numbers start at the intake and increase in the direction 

of water flow.) 

Earthquake-induced densification of materials in Eklutna Lake 

(fig. 6) caused the intake structure 

to move approximately 44 inches 

toward the lake. Principal movement was in a horizontal direction, 

but was accompanied by a lesser 

amount of vertical displacement. 

Tensional forces produced by 

the horizontal shift caused separation along joints in the precast 

conduit, as shown in figure 7. 

Unconsolidated sediments, ranging in size from fine sand to 

cobbles •the size of a football, 

funneled through these ruptures. 

An elliptical cone-shaped depression, approximately 40 feet in 

maximum dimension, formed at 

the edge of Eklutna Lake over the 

conduit alinement near station 

18 +55, and numerous cracks were 

present along the lakeshore on 

either side of the conduit. 
830 

820 

EFFECTS ON EKLUTNA HYDROELECTRIC PROJECT, ANCHORAGE A9 

FLOW 

-

17+00 

A 

0-n--B v c 

ALTITUDE AT JOINT SECTION A-A' 

PRECAST CONDUIT 

18+00 

10 20 30 FEET 

HORIZONTAL ANO VERTICAL 

JOINT SEPARATIONS, 

IN INCHES 

Joint A B c D 

1 1% !V. ll 1\0 

2 1 y, 'II ¥. 

3 1\1 1 1JI 1Y, 

4 1\1 1Y, 1!1 1Y, 

5 2Y, 1¥. ll 1'1\ 

6 10 10 10 

7 6Y, 6!1 8 

8 3!1 3 3!1 

Cobbles and boulders 

in sand and clay 

19+00 

PRECAST CONDUIT 

OFFSET, JOINT SEPARATIONS, OFFSET, 

IN INCHES IN INCHES IN INCHES 

Joint A B c D 

0 9 1!1 2 1!1 0 

0 10 3y, 3\1 2 2Y, 0 

0 11 3 3Y, 3!1 0 

0 12 1Y, 1!1 2 1Y, D 

0 13 2!1 2Y, 1Y, 1Y, 0 

4 14 ll 1\1 1\1 1 

4Y, 15 2!1 2\0 1Y, 0 

D 

7.-Geologic section showing location of earthquake damage to intal'e structure. Rupturing of joints in the precast conduit 

occurred at the numbered locations. Amount and direction of movement is shown in the table. Failure on or within the bedcling material, induced by the earthqual,e, is believed to haYe caused the damage to the intake structure. No earthquake damage 

in the glacial till foundation was detected. 

TUNNEL AND GATE SHAFT 

A circular concrete-lined pressure tunnel, D feet in inside diameter and 23,550 feet long ( 4.46 

miles), com·eys water from the intake structure to the penstocks 

leading to the pmYerplant. The 

capacity of the tunnel is 6±0 second-feet. at a nlocity of 10.06 feet 

per second. The slope of the inYert is 0.00:3±1. ~~ D-foot-diameter gate shaft, bet"·een im-ert 

altitude 790.76 and 1,012 feet, is 

located at station 27+25 so that 

the tunnel may be de"·atered. 

The tunnel termin.ates at a surge 

tank installed directly oYer the 

tunnel 22,805 feet dom1stream 

from the bulkhead gate shaft. 

The surge tank, of the restri ctedorifice type, has an inside diameter 

of 30 feet and a concrete-wall 

thickness of 18 inches, it extends 

176 feet vertically above the tunnel. A 4¥2-foot rectangular separation serves as a slot for the fixed 

wheel gate that is used both for 

emergency closure of the tunnel in 

case the penstocks below or the 

turbine in the powerplant are damaged and for dewatering the penstock for inspection and maintenance. 

A tunnel adit is located at the 

outlet end of the tunnel near the 

surge tank. The adit, which is 

Yirtually the same diameter as the 

main tunnel and is approximately 

:300 feet long, provides one means 

of access to the tunnel for inspection and maintenance. H also 

acts as a free-flo,v conduit for 

draining the tunnel "·hen entrance 

into the tunnel is necessary. The 

access door from the adit to the 

tunnel is watertight. 

From station 20 + 00 to station 

25+32 (fig. 8) the material consists of B-type glacial till. The 

sand layers coni:ain some ground 

water, which has a maximum total 

flow of approximately 300 gallons 

per minute. From station 25+32 

to station 198+00 the rock is mostly interbedded argillite and graywacke. The bedding planes are 

closely spaced and are recognizable 

but erratic. Much of the rock is 

intensely fractured, and innumerable minor fault planes and slippage planes cut through the rock 

at various angles to the tunnel axis. 

From station 198+00 to station 

234+75 the rock is a metamorphosed greenish-gray gray"·acke. 

From station 234+ 75 dmvnstream, 

the rock is uniformly fractured 

graywacke containing irregular inclusions of argillite. During construction, ground water flowed 

from most of the open joints. 

\Vater also flowed through many 

fault-gouge seams, which range in 

thickness from a fraction of an 

inch to several feet and dissect the 

rock at varying angles. 

Approximately 2,000 cubic yards 

of material was deposited along the 

20+00 
AIO ALASKA EARTHQUAKE, MARCH 27 , 1964 

.... "" :::l 

z 

i 

~ 0.. 

(/) 

z 

j 

"" "' 8 

.... 

:IE "" 

;:: 

~ 

Zo Oo 

i=+ 

<o 

:;;-

1000 

900 

800 

700 

600 

500 

400 

300 

200 

100 

600 Q,g 

SEA s ~ 

g 

+ 

0 

"' 

Damp 

I 

I 

Dripping Damp Dripping 

~~\/\ WATER CONDITIONS AT TIME TUNNEL WAS DRIVEN 

·N: i;• E. N. 5· E. 

1 84"1W. 68" W. I 

g 

+ 

§ 

AXIS OF TUNNEL BEARING N. 10"52'45" W. SLOPE=0.00341-

N. 13" E. N. 33" E. 

78" E. 88" S.E. 

No supports 

N. 10" E. 

87" E. 1 

LEVEL None-roc~ section 1-------lHHHIHHHHI H H 

Light support-- H I H IIHHI HIHI 1------------i 5-in. H-beams or lighter on centers more than 4ft ~r---lHH H~ 

Heavy support- H H H H 5-in. H-beams or heavier on centers 4 ft or less 

TUNNEL 

SUPPORTS 

20 ft l Roof overbreak r r, Roof pf tunnel 

~t il tl 

i~ ~· C::;h:;;'e;";;;<,;t•c:..r of rock --+ ;= +---~ t i 

~ --+----~.: :; f-+- ~ ~: i; • • 1 • f. ~~ H EH iH do H -+- •• -+-- • ~ • --f--1--. ~ • --+ :+-----:; 0 - ----.h.-+--- ~ : -: ~ : I :; :§ : '\Fairly sound thin- "' :i ~ -

J! "' t: 1l e Fairly sound thin - .. c: ~;S• ·.~=-= -

8

• :. • bedded re illit~ j .o • bedded 111illite ~· - i_ u ...., = ·.--

Rock 

temperature 

Steel 

reinforcement 

EZJ 

Type 1 ~ Type 2 

.q H 

40" F. 

40" F.40" F. 

• 

41" F. 

Glacial till 

42" F. 

anda:raywacke lnderaywacke 

43.5" F. 44" F. 44.5" F. 45" F. 46" F. 

0 ' 

0 

+ 

§ 

EXPLANATION 

Steeply dipping interbedded graywacke and 

argillite 

Fault trace 

Showing direction of 

movement 

46.5" F. 

N. s· E. 

~·E. 

47.5" F. 

Strike and dip of 

bedding planes 

(In plan view) 

48" F. 

0 

i 

j t----- : ~ :io 

50" F. 
g 

+ 

~ 

EFFECTS ON EKLUTNA HYDROELECTRIC PROJECT. ANCHORAGE 

Station 208+16 to 208+90: Cave in roof to a maximum height 

of 100± It and width of 50± ft. 1200 cubic yards of 

material removed. 

Maximum of 8000-10,000 gallons per minute developed from a 

2-11 gouge seam (Station 208 + 75). 

In this location supports are shown as 6-in., 20-lb. "H" Beam 

horseshoes on 2-ft centers but closer under point of maximum cave height (Station 208+35). Here there are 10 sets 

between Station 208+30 and Station 208+40 

g 

+ 

~ 

Damp Drip 

J, I 

;:,:_·_. -:~>-><·: 

.:: :· ... '_:_:_~·-: tV.~ . . -~-:::-:: .. -·. 

8000-10,000 

~~~~=per _ 

1500 

gallons\ per 

minute 

3000 gallons 

per minute 

800 gallons 

per ll)inute 

/ 

WATER CONDITIONS AT TIME TUNNEL WAS DRIVEN 

(NONCUMULATIVE) 

0 

0 

+ 

~ 

"' c 

0 

~ 

"' 

8 

+ 

:iS 

"' 

zo 

oo 

;::+ 

<O 

.... ~ 

"'"' 

Damp 

~ ~ 

: 3~ £:. N: ·30; W\N: 65• E. ,. i ., ...... . 180"1~vert .~&;~~'!ion~~; ~nde rdrain · ': Bedrock 

f---Roofbolts -----j 1foofbolts n "f ···:·:< urface 

--JI------11---1 f--1HHI----Ii----j HI--------; H I! H HHH H Hf---iHH Sd;;:\l';o H H I H H I H H H H H f-----1 H1 H H H H IHHI-H----11--i H H HHI--- ~--; 2 + 

so· F. 

' g 

+ 

~ 

HH H Hij-11---tt----t I H I I 60~~s~ 

49" F. 48" F. 47.5" F. 47" F. 46.5" F. 

' g 

+ 

~ 

NOTE: Bedding symbols are averages of bedding planes in 

areas indicated. Bedding dip and strike symbols .are 

averages in areas indicated and are plotted in plan view 

with tunnel line bearing N. 10"52'45" W. 

All geology on this summary sheet is from tunnel logs 

rather than projections from the surface 

45.5"·F. 44" F. 40" F. 39" F. 

a::~ CI)N 

40 ~ ~ 

20 ~~ 

Roof overbJeak 0 ~ 

35.5" F. 

37" F. 36' F. 36" F. 

~pe3 

?//t///,7/T~ 

0 

8 

+ 

:iS 

"' 

600 1200 1800 2400 FEET 

8 (above and left) .-Geologic section along the line of the pressure tunnel. 

224-630 0 - 67 - 3 

All 

1000 

900 "' .... 

::> 

800 z 

i 700 "' "' 0.. 

600 "' z 500 0 

::j 

400 < 

"' 300 8 

.... 

< 200 :E 

>= 100 "' "' 

4800 

4200 

3600 

3000 ~ 

~ 

;;!; 

2400..; 0 

::> 

.... 

>= 1800 ;;i 

1200 

600 

SEA 

LEVEL 
A12 

9.-Debris in Eklutna tunnel, typical of 

that deposited throughout the initial 

3lh miles of tunnel as a result of the 

earthquake. 

tunnel invert. The debris consisted predominantly of rock fragments 1 inch in diameter, bu't 

ranged in size from sand to an occasional fragment 14 inches across. 

The debris (fig. 9) was 12-18 

inches deep and was uniformly distributed from the gate shaft at station 27-t-25 to near Station 103+ 

00. From station 103 + 00 to station 235+00, debris was deposited 

in gravel bars of varying depths. 

The last mile of tunnel was relatively free of material. No structural damage to the tunnel was 

found. 

As part of the plan to design an 

earthquake-resistant structure, the 

gate shaft at station 27 + 25 was 

founded in competent rock (figs. 8, 

10) ; it was reinforced to withstand 

internal bursting pressures. Horizontal joints in the shaft, indicated by dashed lines on figure 10, 

helped compensate for any possible vertical deflections during an 

earthquake. No damage to this 

structure was discernible. 

ALASKA EARTHQUAKE, MARCH 27, 1964 

1060 

1040 --- 6" H-rings 

l;j 

UJ 

u. 

~ 

1020 

1000 

980 

960 

940 

LL.f 92Q 0 

::J 

... 

i= 

..J 

< 

900 

880 

860 

840 

820 

BOO 

5' outside circumference 

Entire shaft lagged with 

2" x 12" timbers 

All this water dried up 

when the same strata 

was penetrated in the 

tunnel from station 

24+97 to station 25+ 13 

26+65 

STATIONS 

joints 

Open cut 

excavation 

20 40 FEET 

HORIZONTAL AND VERTICAL 

10 -Geologic section through gate shaft. 
EFFECTS ON EKLUTNA HYDROELECTRIC PROJECT, . ANCHORAGE Al3 

PENSTOCK, SURGE TANK, 

AND ANCHOR BLOCK 

The power penstock conveys water from the surge tank !lit the end 

of the Eklutna twmel to the powerplant 'turbines. The penstock is 

rubout 1,088 feet long, is installed in 

30-foot sections, and is a vari13Jblediameter (91-, 83-, and 75-in~h outside diameter) welded and coupled 

steel pipe encased in concrete. 

Plate 'thickness of the penstock 

varies from %G inch at the initial 

section to 1% inches at the terminal 

section. In profile, the penstock 

roughly parallels the mountainside, descending for approximately 864 feet at an angle of 53°; 

it t'hen levels off and continues 

through a horizontal section aibout 

·501 feet in 'length. At the powerplan't the penstock hifurcates into 

two 51-inch-diameter 23-foot-}ong 

branches which are connected to 

the spiral cases of the tur<bines. 

The penstock tunnel was excavated in weathered rock, except at 

the lower end where the tunnel sec6on emerges into overburden material (figs. 11, 12). In order to 

traverse this overburden material, 

which l<ay between the rock-twmel 

section and the pile-supported penstock anchor, a special tunnel section had to be designed and built. 

In effect, this reach of tunnel was 

designed as a length of conduit 

supported at one end by the tunnel 

rock and at the other end by a pilesupported bent. 

The penstock, surge tank, pilesupported anchor block, and powerhouse evidently oscillated as an 

in'teg:ml unit during the earthquake. Very little rela,tive movement occurred between these features although backfill in the anchor-block area subsided (fig. 13). 

920 

900 

880 

860 

840 

t;j 

~ 820 

~ 

w 

0 

:J 

t:: 800 

~ <( 

780 

760 

740 

720 

Very weathered iron-stained 

and broken graywacke 

containing scattered 

inclusions of argillite 

Very broken and weathered 

graywacke 

Station 255+30 

6 " H-steel 4' outside 

6" H-steel 5' outside 

circumference 

Solid timber lagging 

::-Mostly grayish-black 

argillite 

Begin vertical 

bend 

7ooL-----~----_L ______ L_ ____ _L ____ ~L-----~----~ 

254+70 254+90 255+10 255+50 255+70 255+90 

H.-Geologic sec.tion through surge tank. 

A maximum residual separation 

of one-sixteenth tJo one-eighth inch 

was measured in the penstock ports 

of the powerhouse wall. The entire penstock from the tunnel to 

the units appeared to have sustained no permanent deform,ation. 

Fine }ine cracks in the overlapped 

painted surfa,ces at the coupled 

sleeve joints did, however, indicate 

unusu·al pipe vibration. 

In order to examine the interior 

of the penstock, an unusual method 

of descending through this 6-footdi·ameter pipe was devised. The 

penstock was filled with tunnel 

leakage water. After the penstock 

was filled, the leakage was diverted 

out through the adit-tunnel door 

and a two-man liferaft was floated 

down the penstock. The desired 

rate of descent of the raft was controlle.d, by releasing the water from 

the.pens.tock through 'the butterfly 

valves, wicket gates, 1

and drain 

lines. Instru('Jtions to obtain the 

desired water discharge were re-

}ayed fram the raft to the plant by 

radio and telephone. 
A14 

1000 

900 

800 

700 

600 

fw 

w 

u.. 500 

z 

w 

0 

:::l 

f- 400 i= 

-' ...: 

300 

200 

100 

0 

100 

100 

ALASKA EARTHQUAKE, MARCH 27, 1964 

EXPLANATION 

200 300 FEET 

Topsoil and pebbles, cobbles 

Weathered rock, greenish-gray 

3 Graywacke and argillite, dark-gray 

to black; distorted. Quartz- and 

calcite-filled joints and fractures. 

Slickensides. Iron-stained. Some 

open joints 

4 Moss, topsoil 

Sand, silt, gravel, boulders 

Siliceous graywacke, argillite and 

metasiltstone. Badly broken, 

shattered, brecciated. 

stained weathered fractures . 

Quartz- and calcite-filled joints 

and fractures and open joints 

7 Clay, sandy, silty 

8 Weathered rock, granular, brownish-gray 

9 Graywacke, fine-grained; contains 

intrusions of brown felsitic material 

(HIGH LEVEL) 

Station 261 +00.38 

Alt 26.77' 

10 Graywacke and argillite. Quartzand calcite-filled fractures. 

Very broken, brecciated, some 

crushed core, slickensides, 

small intrusions~ contorted 

11 Topsoil 

12 Clay, sandy, Gravel and boulders 

13 Graywacke, argillite, and spilitic 

basalt. Broken, crushed and 

brecciated. Contorted. Granite 

intrusions. Quartz and calcite 

stringers 

14 Organic material 

15 Clay, silty, plastic 

16 Sand, boulders, 

17 Rock, fragments 

rock fragments 

18 Graywacke and argillite. broken 

and weathered 

19 Rock fragments, broken, crushed, 

brecciated, serpentinized 

OH 84 

Alt81.4'± 

On drift 

End of penstock, 

Station 266+ 10 

Alt 25.0' 

12 (above) .-Section through surge tank, penstock, and anchor-block area, showing drill-hole data. 

13 (left) .-Earth settlement over the 

penstock anchor block directly behind 

the powerhouse. This settlement did 

not appear until 2 weeks after the 

earthquake. Presumably, the bridging 

effect of the blacktop and ground frost 

concealed the settlement during this 

period. 
EFFECTS ON EKLUTNA HYDROELECTRIC PROJECT, ANCHORAGE A15 

POWERPLANT AND 

ASSOCIATED STRUCTURES 

The powerplant (fig. 14) is divided into four main structures: 

the powerhouse containing the 

generating units and accessories, 

the machine shop, the transformer 

structure, and the switchyard. 

Surrounding the powerplant is a 

yard area containing an automotive repair shop, warehouse, and 

office building. 

The powerhouse is a reinforcedconcrete structure 71 feet long and 

80 feet 8 inches wide. Because of 

the relatively unstable foundation 

conditions and the high earthquake potential, the design included pile foundations for the 

powerhouse, machine shop, transformer structure, and penstock 

anchor block. The foundation 

included 289 vertical and 110 battered 14-inch, 73-pound, H-section 

piles (fig. 15) and was designed to 

withstand an earthquake faetor of 

0.15 gravity and an acceleration of 

the foundation of 4.8 feet per second per second. An average pile 

penetration of 5.0 feet into bedrock was achieved. Foundation 

material between the piles consisted of in-place water-bearing 

river sand and gravel. 

Adjacent to the west wall of the 

powerhouse is a pile-supported 

machine shop 78 feet long, 27 feet 

wide, and 20 feet high. The superstructure of the machine shop 

has structural-steel framing and 

reinforced-concrete walls 10 inches 

thick. The structure is pinned to 

piles through concrete pile caps. 

The main power transformers 

that step up the generator low 

voltage are located in the pilesupported transformer structure 

adjacent to and southwest of the 

powerhouse at altitude 41.25 feet. 

Protective walls were placed on 

the south side of the structure to 

14.-Eklutna pow.erplant before the earthquake. 

15.-Some of the piling in the powerplant foundation during construction. Piles in 

lower foreground and along left side have been cut off to grade prior to capping. 

protect the transformers from 

snow and rock slides. Firewalls 

separate the transformers and 

serve as foundations for the takeoff structures ·that carry the powerlines to the switchyard on the 

powerhouse roof. 

The switching equipment for 

the powerplant is located on three 

levels. The switchyard equipment itself-consisting of the 

power circuit breakers, disconnecting switches, and main busses-is 

on the roof of the powerplant at 
ALASKA EARTHQUAKE, MARCH 27, 1964 

Graywacke and 

argillite 

IIIIII 

A 1.6 

16.-Generalized geologic section through surge tank, penstock, and powerhouse. 

2 

'5 

a 

altitude 92.50. The main power 

transformers that step up the generator low voltage are located in 

the transformer bay at altitude 

41.25. The high-voltage bushings 

of these main power transformers 

are connected to the main switching equipment locater? Dn the roof 

at altitude 92.50. The 115-kv bus 

structure on the powerplant roof 

oonsists of two bays to supply the 

115-kv lines to the cities of Palmer 

and Anchorage. 

About 30 holes were drilled in 

the powerplant area during the exploratory and early construction 

stages. Nineteen of these were 

h 

+ 

c 

.P 

m 

6i 

penetration resistance holes made 

to evaluate the bearing capaci,ty of 

the overburden material under the 

powerhouse foundation. A generalized geologic section is shown in 

figure 16. 

The upper 10-12 feet of the section consists of organic, slightly 

plast,ic sil,t containing occasional 

angular graywacke fragments. 

Below the silt a layer of talus 5-8 

feet thick, containing angular 

graywacke boulders in darkbrownish-gray organic sandy clay, 

lensed out downstream from the 

powerhouse foundation. The base 

of the powerhouse and the tailrace 

NOTE: In DH 92, 65.5 ft east of centerline. fault material 

from altitude -27.4 to bottom of hole at altitude 

-87.6, indicates that fault zone increases in thickness and altitude to the east. Gouge layers within 1000 

the fault zone vary in thickness from 1/2 to about 4 

in. Drill core extremely difficult to recover. Approximate dip and strike -N 87" E-16' N. Fault W 

material is consolidated material except in the lL 

narrow seams. The rock is recemented fault breccia f 900 

and is fairly sound in place. When excessive water 

pressure is used indrilling, rock breaks into small 0 

particles I/. to % in. It can be cored with diamond 

- 

500 - 

- 700 

L 8 8 0 0 

7 0 

k! 400 - 3 

Lo 5, 

LD 8 

f 

ui - CONTINUATION OF PROFILE 

n 

3 FROM POINT H 

'- 300 - 3 

- 

200 - 

- 

100 - 

- 

0 - 

- Graywacke and 

loo 0 0 

o 8 8 8 0 0 0 0 0 0 0 0 0 0 

2 + + m 0 2 ? Y 7 

Lo 2 h F ? + d 01 

0 rn rn % w w 0 w w w w N N N N N N N N N % 2 N r. N 

conduit were excavated in waterbearing river sand and gravel, and 

the area had to be pumped during 

excavation. Some sloughing of the 

backslope in the noritheast corner 

of the excavation occurred during 

the extreme high-water period of 

the Lake Gwrge breakup. 

Interstratified discontinuous layers of stream gravel, sand, silt, and 

clay underlie the talus and overlie 

the weathered bedrock surface. A 

flood plain extends north and w&t 

from the powerplant site for several miles. The drainages from 

both the Knik and Matanuska 

Rivers spasmodically aggrade, 
EFFECTS ON EKLUTNA HYDROELECTRIC PROJECT, ANCHORAGE A17 

degrade, and change their channels throughout the spring, summer, and fall seasons. These 

erratic sedimentation phases account for the interstratified sediments in the powerplant area. 

Talus from the adjacent hillside 

extends a short distance from the 

toe of the slope. The talus is 

generally overlain by slightly plastic organic silt recently deposited 

during the annual flood stage of 

the Lake George breakup. The 

water table beneath the powerplant fluctuates with the Knik 

River and has a mean depth of 

28 feet. 

The principal area of damage 

occurred between the powerhouse 

and machine shop along the 1-inch 

cork-filled expansion joint. The 

two structures oscillated at different intensities, and the interconnecting drainage and electrical 

systems were sheared. The differential horizontal displacement between buildings was three-fourths 

of an inch, but the vertical displacement was negligible. Backfill around the entire periphery of 

the plant and under the machine 

shop settled ermtically from a few 

inches to a few feet (figs. 17-19). 

The fill in which these failures 

occurred is composed of wellgraded sand 'and gravel obtained 

from the Knik River. Most of the 

gvavel part'icles were subrounded 

and were composed of a wide variety of unweathered igneous, metamorphic, and sedimentary rocks. 

The sand ranged in shape from 

rounded ,to 'angular, a noticea-ble 

percen'tage being elongated and 

flattened. The sand was composed 

predominantly of slate gvains. 

Silt-size particles were presen't in 

small amounts, but tended to wash 

away during handling. The pit 

run material consisted of 3'5.1 percent sand and 64.9 percent gravel. 

A weighted average of size distri17.-Typical ground settlement resulting from th1:l earthquake. Settlement is near 

the northeast corner of the powerhouse at the location of the septic tank. 

r ')(Subsided areas 

\ --.,_ 

L/ "'" \ 1 "- \ 

11/4" Horizontal movement 

(gravel surface and 

concrete) 

'-.__) 

POWERHOUSE 

Relative movement W~ ~ 

L><_ 

48 d's 

16 16 

NOTE: Numbers indicate inches of relative 

settlement as measured between earth 

surface (backfill) and concrete 

0 20 40 FEET 

"-Area around transformer 

structure has been 

graded. Extent of 

settlement could not 

be measured 

lB.-Measurements of settlement and deflection at the powerplant. 

bution in the gmvel fraction of the 

backfill materi'al is as follows: 

StandarcZ 

Bieve Percent 

Bize retained 

6 in_________ 0 

3 in_________ 2 

1~ in _______ 22 

~ in ________ 36 

~ in ________ 27 

No. 4 ________ 13 

Percent 

cumulative 

0 

2 

24 

60 

87 

100 

A dragline and two bulldozers 

were used for placing and spreruding the 'backfill. The material was 

wetted for proper compaction and 

oonsolidated by equipment travel. 

Gasoline-powered immersion-type 

vibrators and mechanical tampers 

were used in areas inaccessible to 

the bulldozers. 
A18 ALASKA EARTHQUAKE, MARCH 27, 1964 

. ...-' / 

y 

Concrete footing ~ 

Backfill material 

19.-Machine-shop foundation showing the separation of backfill material from the 

concrete footing. Approximately 1.5 feet of H-section pile is now exposed as a result 

of settlement caused by tht> earthquake. 

20.-The 20,000-kva transformer conduit and terminal box damaged by movement of 

the transformer during the earthquake. Rail stops consisted of a :14- by l-inch-wide 

bar tack-welded to the rail. The tack-welds broke and allowed the transformer to 

move on the :rails. 

Postearthquake examination 

showed that the drainage system 

leading into the floor sump was 

plugged with a mixture of finely 

ground concrete and cork and the 

draii-rage line from the fanroom 

area was sheared. In addition, an 

aroma of fuel oil from several of 

the drains was quite prevalent. 

Ground wa'ter from the surrounding sediments and fuel oil from a 

ruptured, buried tank entered the 

drainage system through the 

sheared l'ine. 

Within the transformer structure, the two 20,000-kva transformers moved from 3 to 5 inches when 

tack-welded rail stops hroke loose. 

Both transformers settled a few 

inches but not enough to overstress 

any of the bushings or bus connections. Alt:hough the bottom of the 

120-volt terminal ca:binet (fig. 20) 

on one of 'the transformers broke 

open and the atlia.ched conduits 

were pulled loose, the circuits remained operative. The 750-kva 

camp transformer settled nearly a 

foot, •and the primary leads had oo 

be lengthened to relieve the strain. 

The 115-kv switchyard on the 

roof of the powerplant was ex tensively damaged. Two singlephase air circuit breakers were 

damaged. Each phase consists of 

an air receiver, two hollow porcelain insulator columns, porcelain 

extinction chambers, arcing contacts, and a bushing-type current 

transformer. The hollow insulator columns are mounted at the 

ends of the air receiver and carry 

compressed air to, and provide support for, the extinction chambers 

and arcing contacts. The freestanding hollow insulator columns 

broke at the base and thus caused 

complete collapse of the contact 

mechanism. Porcelain of the current transformer cracked and oil 

was lost. 
EFFECTS ON EKLUTNA HYDROELECTRIC PROJECT, ANCHORAGE 

The ground beneath the north 

end of the wood-frame structure 

housing the automotive repair 

shop settled about 1 foot and 

moved approximately 10 inches 

horizontally along a tensional 

crack that destroyed the floor and 

the radiant heating system in the 

floor slab (fig. 21). Lighting fixtures were torn loose from the wall. 

A19 

From a point west of the garage, 

cracks as much as a foot wide and 

several feet deep (figs. 22, 23) 

extended eastward adjacent to the 

north wall of the warehouse and 

crossed the roadway to the project 

office building. Cracks also extended from the garage to the 

southwest corner of the warehouse. 

21.-Damage to the heating-system piping in the floor of the automotive repair shop 

caused by the earthquake. 

Graywacke and argillite 

.d£1/ .Ld _LLLU..Ld -.:4/ ~ dU/ .L0V L2Z:L ~ _p'LP..L2U~ ~ ~_Ld.(, 

Alluvial sediments Sketched contact 

Open 6"-1 ' 

0 50 100 FEET 

22.-Location or major earthquake cracks in the powerplant area. 
A20 ALASKA EARTHQUAKE, MARCH 27, 1964 

23.-Pavement damage caused by the earthquake. Cracks extend from the garage 

east along the north wall of the warehouse (right of photograph) and thence across 

the road to the project office (left of photograph). 

24.-Pump in Eklutna project office showing the effect of the earthquake. Base of 

pump is now approximately 5 inches above the floor. 

25.-Typical section of tailrace channel. 

A much larger crack occurred in 

State Highway 1 opposite the 

entrance to the project area. 

Backfilling the pavement cracks 

was a continuing operation for 

several weeks as adjustmentbelieved to have been caused by 

ground thaw along the crackscontinued to take place. 

Damage to the camp housing 

was not extensive. Chimneys 

were damaged, and two heating-oil 

tanks tipped over. 

The project office is a woodframe structure with concrete 

floors. The concrete founda;tion 

and curb separated from the floor 

slab as much as 2 inches. The 

floor settled around the well casing, 

leaving the pump base approximately 5 inches above the floor (fig. 

24). Miscellaneous damage consisted of overturned files and 

storage cabinets, cracked floors, 

damaged light fixtures, and broken 

joints in the chimney. 

The north wall of the structuralsteel warehouse separated from 

the floor blab from 1 to 3 inches. 

Storage bins were tipped, and 

spare insulators were damaged. 

Foundations supporting the main 

structural members settled approximately an inch along the 

north side and a slight cracking 

of the building resulted. The 

electrical service-drop attached to 

the roof pulled loose during the 

earthquake, and breaks in the asphalt roofing were caused by the 

flexing of the cold roofing paper. 

TAILRACE 

Water from the draft tubes of 

the turbines in the powerplant is 

discharged through a 209-footlong pressure tailrace conduit under the Glenn Highway to an open 

tailrace channel leading to the 

Knik River. 

The tailrace conduit is made up 

of rectangular reinforced-concrete 

transition sections of varying 
EFFECTS ON EKLUTNA HYDROELECTRIC PROJECT, ANCHORAGE A21 

widths and depths. The terminal 

section of the conduit is 50 feet 

long and flares outward in the 

downstream direction from a 

width of 14 feet 6 inches to 46 feet 

6 inches. This terminal section is 

also of varying depth and has five 

openings separated by 10-inch 

walls through which the water 

passes into the tailrace channel. 

Stoplog slots 31t the outlet of the 

conduit are used to dewater the 

conduit or to dewater both draft 

tubes at the same time. 

The banks of the open tailrace 

channel (fig. 25) are built on a 

2 to 1 slope and are lined with riprap at the junction with the tailrace conduit. The channel has a 

top width of about 75 feet, a bottom width of 25 feet, and a depth 

of about 12 feet 6 inches. 

The upper 4-6 feet of material 

underlying the tailrace is silt and 

sandy silt, which in turn is underlain by a 2-foot layer of sand and 

fine gravel. Beneath the sand and 

fine gravel is sand and coarse 

gravel. During construction of 

the tailrace, some sloughing occurred in the sand and gravel 

layers during extreme high tides 

and when water was added to the 

channel by operation of the powerplant. Also, during the period 

of extremely high water at the 

time of the Lake George breakup, 

there was some sloughing of the 

banks. 

When the powerplant was shut 

down for repair of the intake (fig. 

26) , the 209-foot-long pressure 

tailrace conduit was inspected and 

cleaned. About 110 cubic yards 

of rock and mud had been deposited in t he conduit, presumably 

after the break in t he precast pipe 

section of the tunnel intake. The 

inspection also revealed considerable shifting of the sections nearest the powerplant (fig. 27). 

Regional subsidence raised the 

high-tide water level approximately 3 feet. 

26.-Cleaning-up operation at the outlet of the tailrace conduit. Debris was deposited following the rupture of the tunnel intake at Eklutna Lake during the 

earthquake. 

TAILRACE CONDUIT 

Joint Remarks 

A Joint open 2'/4 in . on top, open % in. on bottom 

Waterstop torn for about 1 ft, gravel visible above tear 

Joint open % in. on top, open 11

/2 in. on bottom with 3 in. 

B vertical offset, downstream side lower. Larger leak on left 

side of left unit near floor 

c Joint closed on top, open 1'/2 in . on bottom with 1'/4 in . 

vertical offset, upstream side lower 

Between Crack in ceiling, right unit 

C and D 

D Joint closed 

E Joint open evenly 1'/• in. all around with 2V2 in. vertical offset, 

upstream side lower 

F Joint closed 

G Joint open 1 in . all around with % in . vertical offset, upstream side lower. Leaking at top 

~~==~==~=======~ t--t=o=*=='~='----+- -+-+-- ---

SECTION B-B 

Approximate ground surface 

Alt 40.0' 

G 

27.-Sum.mary of damage to tailrace conduit. 
A22 ALASKA EARTHQUAKE, MARCH 27 , 1964 

28.-Location of ground cracks in the vicinity of the powerplant. 
EFFECTS ON EKLUTNA HYDROELECTRIC PROJECT, ANCHORAGE A23 

The ground surface was severely 

cracked (fig. 28) in the area adjacent to, and parallel with, the 

2,000-foot-long open canal section 

of the tailrace. The cracks 

ranged in width from a few inches 

to 5 feet and had the effect of 

squeezing in the sides of the channel. The invert was irregu}arly 

mantled by gravelly debris ranging in depth from a few inches to 

several feet. 

TRANSMISSION LINES 

The 115-kv Anchorage line was 

not damaged, but the earthquake 

triggered a snow and ice slide near 

the Knik River bridge that swept 

a>vay a three-pole guyed structure, 

7,500 feet of conductor cable, and 

an access road on the Palmer line. 

The transmission lines were repaired on April 8, 1964, and service was restored on April 16, 1964, 

after the air circuit breaker was 

repaired at the Eklutna switchyard. w·hile the Palmer line was 

out of service, pmver was delivered to the Palmer substation 

from the Reed substation over the 

Matanuska Electric Association's 

34.5-kv line and the 12.47-kv 

Palmer area distribution system. 

In order to carry the Palmer load 

through the limited capacity of 

the Reed substation, auxiliary 

cooling had to be provided by 

truck-mounted fans. 

SUBSTATIONS 

The Anchorage substation is 

situated on a terrace of glacial till 

overlain by less than 1 foot of soil. 

Beneath this overburden and beyond a depth of 8 feet, or below 

foundation grade, 'the material 

consists of a fairly uniform clayey 

sand and gravel. The water table 

is 25 feet below ground surface. 

Lightning arresters on each of 

the single-phase power transformers at the substation were damaged. The arresters broke at their 

bases and dangled from the line. 

All three "stacks" of each arrester 

were broken. One lightning arrester on the Chugach Electric 

Association 16-mva (millivolt-ampere) transformer was also damaged. All three transformers at 

the Anchorage substation shifted 

on their bases. Primary bushings 

were not damaged, but one secondary bushing had sufficient stress 

on it to bend the transformer 

cover. Conduits for the indicating circuits on the phase C transformer were broken at the ground 

line, but the circuits remained 

operative. Sections of the rigid 

bus at 'the high-voltage bus were 

bent. The single-phase station 

service transformer shifted on its 

base but was not damaged. The 

battery rack and radio equipment 

inside the substation building 

shifted but were not damaged. 

The Palmer substation is in a 

heavily wooded area immediately 

south of the town of Palmer. 

Foundation materials consisted of 

0.8 feet of dark humus and topsoil, 

3.0 feet of dark-grayish-brown 

slightly sandy silt, and about a 1-

foot mixture of dark-gray silty 

sand and poorly graded gravels 

and cobbles. The depth to the 

water table was not determined. 

The only evidence of damage at the 

Palmer substation was an oil leak 

at the base of a transformer 

bushing. 

OTHER EARTHQUAKE EFFECTS IN THE AREA 

The,re is evidence, though meager, indicating a general subsidence of the Eklutna powerplant 

area, including Goat Mountain. 

An exceptionally high tide was reported during the >veek of May 12-

15, 1964, but settlement of the general area probably contributed to 

the flooding. 

A helicopter reconnaissance of 

the Eklutna Lake drainage area 

(fig. 29) disclosed that earthquake 

slides had blocked three valleys. 

The slides were composed of talus 

fragments held in an ice matrix, 

but water was freely flowing beneath them and no ponding was 

taking place. Earthquake effects 

were confined to alluvial deposits, 

and conspicuous cracks were observed in nearly all alluvial fans 

bordering Eklutna Lake. 

Aerial surveys were conducted 

to determine if major damage had 

occurred at poten'ti'al project areas. 

The results of these surveys can be 

summarized as follows : 

1. No major slides were observed 

along the Copper River main 

stem, although a slide was 

present across Klutina River, 

a tributary of the Copper 

River. No water was being 

impounded. 

2. Numerous snowslides were seen 

along the Matanuska River 

valley. 

3. Some shifting of the Lake 

George, Surprise, and Columbia glacier icefield was nored. 
A24 ALASKA EARTHQUAKE, MARCH 27 , 1964 

29. Aerial photograph showing general area surrounding Eklutna Lake. 

4. The U.S. Geological Survey 

assessed the earthquake effects on potential damsites in 

the Anchorage-Seward area. 

These sites are on Nellie Juan 

Lake, Surprise Creek, Lost 

Creek, Kashwitna River, 

T a 1 k e e t n a River, Sheep 

Creek, Swan Lake near J uneau Creek, Moose Horn 

Rapids, Kenai River, Juneau 

Creek, Kasilof River, and 

Hongkong Bend. The only 

new large-scale landsliding 

was on the Kashwitna River, 

but this slide did not affect 

consideration of a damsite 

upstream. 
EFFECTS ON EKLUTNA HYDROELECTRIC PROJECT, ANCHORAGE A25 

TELEVISION EXAMINATION OF EARTHQUAKE DAMAGE TO UNDERGROUND 

COMMUNICATION AND ELECTRICAL SYSTEMS IN ANCHORAGE 

INTRODUCTION 

As a result of the earthquake 

of March 27, 1964, the city of 

Anchorage experienced s e v e r e 

damage ·to its underground utilities systems in addition ·to the 

great damage sustained by surface 

structures. Temporary repairs to 

these systems were made as 

quickly as possible after the earthquake to permit resumption of 

necessary services within the city. 

Permanent repairs were included 

in that phase of the Alaska Restoration Program administered by 

the Corps of Engineers. 

In order to avoid costly excavation of the buried communication 

and electrical systems to determine 

the specific locations requiring repair, the Corps of Engineers requested the use of a small-diameter 

closed-circuit television camera 

owned by the U.S. Bureau of Reclamation. This instrument, 21;2 

inches in diameter, was the only 

television camera available which 

was small enough to pass through 

the cable ducts. The television 

equipment was flown from Denver, 

Colo., to Anchorage and back by 

the Military Air Transport Service (fig. 30). During September 

and early October 1964, 23,594 

linear feet of communication system and 10,510 feet of electrical 

system were examined in the Anchorage business distriot and various residential areas by means of 

this equipment. 

UNDERGROUND SYSTEMS 

The underground communication and electrical systems consist 

generally of banks of four to 

twelve 31;2-inch-inside-diameter 

BY LYNN R. BURTON, U.S. BUREAU OF RECLAMATION 

asbestos-cement ducts, buried 4-6 

feet beneath the streets and alleys 

of the city. These ducts, containing telephone and power cables, are 

encased in concrete envelopes. 

Manholes, spaced 180-540 feet 

apart, provide access to the envelopes. Each bank of ducts 

includes at least one empty duct 

that was used for the television examination. Any damage observed 

in this duct was assumed to ind:.-

cake damage to the entire envelope 

at that location. In areas where 

the two systems are closely parallel, only one system was examined. 

The ducts were cleaned by mandrel 

\ 

, 

and brush before the examination. 

That part of the communication 

system extending from A Street to 

E Street along the alley between 

Third and Fourth A venues was destroyed by the Fourth A venue 

slide, and a section of the system 

along Eighth Avenue west of L 

Street was destroyed by the L 

Street slide. 

EQUIPMENT 

The closed -circuit television 

equipment used was designed primarily for examination of explorrutory drill holes 3 inches or more 

30.-Truck-mounted television equipment being loaded at Denver for its flight to 

Anchorage, Alaska. 
ALASKA EARTHQUAKE, MARCH 27, 1964 

Lateral 

viewing 

Configuration for 

fishing tool 

Coaxial cable 

Upper terminal piece 

Ball bearings 

Expanding seal 

Lower end of 

terminal piece 

Vidicon camera 

Vidicon tube 

Focusing coils 

Focusing port 

Camera lens 

Illumination bulb 

Mirror 

Compass 

Viewing window 

Illumination bulb 

Resistance clinometer 

Slip ring 

Servomotor 

Moisture warning 

Silica gel 

PROBES FOR: 

Axial - 

viewing 

31.-Details of television probes. 
EFFECTS ON EKLUTNA HYDROELECTRIC PROJECT, ANCHORAGE 

- 

Ground surface 

3%-inch-diameter 

Concrete envelope 

32.-Amngement of television equipment during examination. 

in diameter to obtain various geologic data. It also has numerous 

nongeologic applications. The 

equipment is mounted on a truck 

and includes a control console and 

monitoring unit, approximately 

1,000 feet of coaxial cable, and two 

types of probes in which the miniaturized television camera is inserted (fig. 31). All operating 

switches and an 8-inch monitor or 

viewing screen are located at the 

control console. The instrument 

operates on 110-volt 60-cycle alternating current. An attempt was 

made to use a lateral-viewing 

probe in this examination, but its 

length (55 inches) prevented passage through many of the bends in 

the duct lines. The axial-viewing 

probe, which is only 30 inches long, 

could be passed through all but the 

sharpest of the bends and was used 

throughout the examination. 

PROCEDURE 

The television probe was drawn 

through the ducts by a small-gage 

wire rope attached to a pulling 

bridle on the probe and wound on 

a winching drum. The winching 

drum was coupled to an electric 

motor through a variable-speed 

transmission to permit variation in 

logging speed. Direct communication between the television and 

winch operators by sound-powered 

telephone provided coordination 

of viewing and logging speed, 

which was normally 10-12 feet per 

minute in undamaged ducts. The 

general arrangement of the various 

components of equipment during 

operation is shown in figure 32. 

DAMAGE TO SYSTEMS 

Topography and surface geology of the northern half of the 

city, alinement of the underground 

systems, locations of cracks observed during the examination, 

and approximata positions of the 

grabens formed at the heads of the 

L Street, Fourth Avenue, and 

First Avenue slides are shown in 

figure 33 (p. A28, A29). For aimplicity, the alinements of the two 

systems are combined and shown 

as a single system. The direction 

of movement, where it could be determined, is indicated by small 

arrows. 

Cracks in ithe ducts were clearly 

visible on the monitor screen, and 

the amount of separation and offset was accurately determined. 

Approximately 90 percent of the 

cracks exhibited no measurable 

displacement and were not considered indicative of serious damage to the concrete envelopes. 

Lateral, vertical, and longitudinal 

displacements along fractures were 
ALASKA EARTHQUAKE, MARCH 27, 1964 

P 

33.-Topography, surface geology, 'md location of fractures 
EFFECTS ON EKLUTNA HYDROELECTRIC PROJECT, ANCHORAGE 

EXPLANATION 0 500 1000 1500 FEET 

Qal 

Qs 

Qaf 

Swamp deposits 

A'1uvia1 

Alluvium 

fan deposits Alinement of underground communication 

. 

---- 

. . . 

Contact 

. . . . . . . . . . . . . . . - 

QO' Outwash and electrical systems N 

Qc Abandoned-channel -*+- 

deposits Location of cracks having discernible 1 

Qpi Pitted outwash separation or offset. Arrow indicates 

apparent direction of movement Qgi Glaciofluvial ice-con- YL-L- 

, tact deposits -. . . Location of cracks having no discernible 

Qbc Bootlegger Cove Clay separation or offset 

Geology from Miller, R.D., and Dobrovolny, 

Ernest, 1959 (1960). Surf~cial geology of 

Anchorage and vicinity, Alaska: U.S.Geol. 

Survey Bull. 1093, pl. 1 

in underground communication and electrical systems. 
A30 ALASKA EARTHQUAKE, MARCH 27, 1964 

34.-Axial views of ·breaks in the ducts, as seen on the television monitor screen. 

observed at 52 locations. Photographs of two such fractures, as 

viewed on the monitor screen, are 

shown in figure 34. The maximum 

displacement noted was 1 inch, although most were in the Yt 6- to 1,4-

inch range. Soil and water had 

entered the ducts through many 

such openings, and water was 

found in some areas where only 

hairline cracks were present. 

INTERPRETATION 

OF DATA 

Although their plotted locations 

exhibit no well-defined pattern, the 

cracks are concell'trated in the 

vicinity of the Fourth A venue slide 

and in areas near the slopes of 

stream valleys and local drainage 

channels. The concentrations of 

fractures north of Sixth Avenue 

between Barrow and F Streets are 

clearly the result of ground adjustments related to the Fourth Avenue slide. Others, such as those 

located on Thirteenth A venue and 

along C Street south of Thirteenth 

Avenue, probably reflect local subsidence resulting from incipient 

failure of outwash and alluvial 

materials on valley slopes. 

The direction of movement was 

determined at 18 of the 52 locations where displacement occurred. 

Movement was to the north or 

south at 13 of these locations. In 

general, these data suggest that the 

north-south component of ground 

motion was more severe than the 

east-west component and that the 

direction in which the induced 

tensile forces acted was strongly 

influenced by the free faces represented by Ship Creek valley to the 

north, Chester Creek valley to the 

south, and the Cook Inlet bluffs to 

the west. Lack of a comparable 

free face to the east rna y explain 

the absence of serious damage to 

the underground systems in the 

eastern part of the area. 

U. S. GOVERNMENT PRINTING OFFICE: 1967 0 - 22 4-630