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 under ground 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 com munities, on regions, and on the hydrologic regimen.
CONTENTS
Page Page Page Abstract ______A1 Effects-Continued Television examination of earth Introduction and ackno" ledg- Penstock, surge tank, and quake damage to underground rnents ______1 anchor block ______A13 communication and electrical Geologic setting ______4 Powerplant and associated systems in Anchorage, by Lynn R. Burton ______The first 24 hours ______5 structures ______15 A25 Introduction______25 Effects on indiYidual features Tailrace ______20 Underground systems ______25 of the Eklutna project ______6 Transmission lines ______23 Eqmprnent ______25 Eklutna Darn ______Substations ______6 23 Procedure ______27 Intake structure ______6 Other earthquake effects in the Damage to systems ______27 area ______Tunnel and gate shaft ____ _ 9 23 Interpretation of data ______30
ILLUSTRATIONS
FIGURES
Page 1. Index map of the Eklutna 14. Photograph of Eklutna power- 24. Photograph showing darnaged Hydroelectric Project ___ _ A2 plant before the earthquake_ A15 pump in project office_____ A20 2. Topography and surface ge 15. Photograph showing piling 25. Typical section of tailrace ology of the project area __ 3 in the powerplant founda- channeL ___ - ____ ------20 3. Schematic plan and profile of tion _____ --______15 26. Photograph showing cleaning- the Eklutna project ______4 16. Geologic section through up operation at outlet of 4. Map and section of darnsite surge tank, penstock, and tailrace conduit ____ - __ --- 21 area showing exploratory powerhouse______16 27. Plan, section, and chart giv- work ______7 17. Typical ground settlement ing summary of damage 5. Photograph of spillway gate resulting from the earth- to tailrace conduiL _ _ _ _ _ 21 structure ______7 quake______17 28. Aerial photograph showing 6. Aerial photograph of intake 18. Plan view of powerplant locations of cracks near area showing network of g1vmg measurements of the powerplant______22 cracks ______8 settlement and deflection_ 17 29. Aerial photograph showing 7. Geologic section showing lo 19. Photograph of machine-shop Eklutna Lake area______24 cation of earthquake darn- foundation, showing sep 30. Photograph of truck-mounted age to intake structure __ _ 9 aration of backfill mate- television equipment being 8. Geologic section along the rial from concrete footing_ 18 loaded at Denver for its line of the pressure tunneL 10 20. Photograph showing damaged flight to Anchorage______25 9. Photograph of debris depos 20,000-kva transformer con- 31. Details of television probes_ 26 ited in Eklutna tunneL __ 12 duit and terminal box____ 18 32. Arrangement of television 10. Geologic section through gate 21. Photograph showing damaged equipment during exami- shaft ______12 heating-system piping in nation______27 11. Geologic sect1on through the floor of the automotive 33. Topographv, surface geol surge tank ______13 repair shop______19 ogy, and location of frac 12. Section through surge tank, 22. Sketch map of major earth- tures in underground penstock, and anchor- quake cracks in power- communication and elec- block area ______14 plant area______19 trical systems______28 13. Photograph showing earth 23. Photcgraph ~howing cracks 34. Axial view of breaks in the settlement over penstock in pavement of Eklutna ducts, as seen on the tele- anchor block ______14 roadway______20 vision 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
ABSTRACT
The March 27, 1964, Alaslm ea:r!th ported from Eklutna Dake .to the power consolidated sediments and overburden quake and its a:ssoctalted aftershocks plant rut tidewa:ter on Knik Arm of Oook which densified and subsided during the caused damage requiring several milHon Inlet by an underwater intake con earthquake. Structures built on bed dolLars worth of repaiir to the Eklwtna nected to a 4.46-mile tunnel pel113tock. rock experienced little or no damage. Hydroelectric Project, 34 miles north The primary damage caused by the Underground communication and elec ea:st of Anchorage. Electric service earthquake was 1at the intake struc!ture trical .systems in Anchorage were exam 1lrom the Eklutna powerplant was inter in Eklutna Dake. No damage to the ined with a small-diameter television rupted during the early phase of the power tunnel wa•s observed. The pile camera to locate damaged areas requir Mal'ch 27 eal'thquake, bu:t was restored •suppor.ted powerplant •and appurtenant ing repair. Most of the damage wars (intermittently) until May 9,1964, when structures, Anchorage and Palmer sub concentrated at or near val'ley slopes. the plant was closed for inspection and stations, and the transmission lines suf Those parts of the sy·stems within the repair. fered minor da.mage. Most damage major rslide area's of the city were Wa:Der for Eklutna project is trans- occurred to facilities constructed on un- destroy·ed.
INTRODUCTION AND ACKNOWLEDGlVIENTS
The Eklutna Hydroelectric The lake is 7 mi1les long and is fed Although this report does not Project is a 30,000-kw (kilowatt) hy meil't walter from Eklutna Gla discuss earthquake-damage reha power development designed and 'Cier, 4 miles above the lake, and by bilitation, the repair of facilities constructed by the Bureau of Rec precipitation runoff from 'a 119- damaged by the great Alaska lamation, U.S. Department of the square-mile watershed. Wruter is earthquake of March 1964 was dif Interior, to bring urgently needed ·transported from the lake by an ficult, hazardous, and costly. electric power to the rapidly ex underwa'ter intake connected to a Transmission poles had to be set panding metropolitan area at An 4.46-mile tunnel and 'tunnel pen on steep icy mountain slopes; ~horage, Alaska. The project was ~stock through Goat Mountain to weakened precast-concrete con constructed during the 4-year pe the pawerplant (figs. 1, 2, 3) . The duits could be strengthened only riod 1951-55. The powerpl'ant project is for power production by working under 40 feet of near (fig. 1) is loca,ted 34 miles north only. Transmission lines, opel"at freezing water; and sand and erust of Anchorage on the Glenn ing a;t 115 kv (kilovolts) and ter gravel were mucked from 4.46 Highway and is supplied by water minruting at subst:ation facilities, miles of 9-foot tunnel requiring from Eklutna Lake, about 10 miles extend north to Prulmer and south access by means of a 220-foot by road from the Glenn Highway. to Anchorage from the plant. 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
EXPLANATION I I I - ./ FLOOD PLAIN 1$:::.:.
Glacial till
Graywacke containing argillite inclusions
Greenish-gray metagraywacke
Thin-bedded argillite and some thin beds of graywacke
Contact
-,-I--75 Fault, approximately located Showing dip of fault plane
73 _L Strike --and- dip of beds Shattered zone o33 Drill hole
10 Test pit
700u 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, Anchor- during 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 dur- terest 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 inter- Goat Mountain, a prominent local In places, glacial and more recent montane structural basin that feature of )the Chugnch Range, streams have reworked the 'till, so trends northeast-southwest be- rises abruptly from the southeast- it is sorted and somewhat bedded. tween the Chigmit and Talkeetna ern flank of the Knik Arm low- In some areas, nearly pure silt and Mountains on the north and the lands and forms a divide between clay are interstratified with coarser Kenai and Chugach Mountains on the Knik River and Eklutna River material. I11 the stream channels the south. Knik Arm, a north- drainages. and flood plain of the Ihik River, easterly extension of Cook Inlet, The Knik and Eklutna Rivers well-rounded gravel and clean occupies a lowland that is char- are in old glacial valleys, and hence sand predominate. acterized by glacial and al- the overburden consists of glacial Very little well-rounded gravel luvial sediments. braided streams, till containing material ranging in occurs along Eklutna River-the marshy areas, and broad tidal flats. size from large boulders to clay. stream which drains Eklutna Lake. EFFECTS ON EKLUTNA HYDROELECTRIC PROJECT, ANCHORAGE A5
The present stream channel is nar The mountain through which densification of unconsolidated row and the steep banks have been the tunnel is driven is composed sediments and overburden. Myr cut through a succession of sand, of a series of graywacke, argillite, iad cracks, ranging from a frac clay, silt, and "dirty" gravel beds. and slate, all metamorphosed to tion of an inch to several feet in All this material is partly re varying degrees (fig. 2) . The width, were formed in areas un worked glacial till. Where the rocks in the graywacke-slate derlain by the unconsolidated velocity of the present stream is argillite series on the north slope sediments. Near bedrock out slow, rounded gravel is found but have been extremely metamor crops, a linear pattern of cracks its extent is not great. Shingle phosed and crushed; bedding formed which, in general, paral gravel mantles the ground surface planes are indistinct, and the rocks leled the bedrock configuration. in the vicinity of the dam. are highly weathered along the in As distance from bedrock and Several terrace remnants, repre tricate fractures and are jointed, depth of overburden increased, the senting old glaci·al lakeshores, are in several places the rocks are ser linear pattern graded into a blocky present at higher altitudes along pentinized and slickensided. On pattern having the general ap the south slope the rocks are the Eklutna River valley. Drill pearance of magnified mud cracks. poorly exposed. The bedding holes through the glacial till on All cracking observed on the Ek planes are recognizable but vary this shore revealed varying depths in attitude within short distances. lutna project was caused by ten to bedrock. In the floor of the The higher peaks are composed of sional failure resulting from valley, bedrock is estimated to be dark-greenish-gray graywacke. densification of saturated alluvial several hundred feet below the The most obvious factor con sediments. No failures were ob surface; elsewhere it is closer to tributing to the destruction of the served where structures were built the surface. Eklutna project facilities was the on bedrock.
THE FIRST 24 HOURS
When the earthquake occurred, amination, was started and station gized through a bus tie switch at at 5:36 p.m. (Alaska standard service was restored at 5 :55 p.m. 10: 10 p.m. The 115-kv Palmer time) on March 27, 1964, the pow A wood-pole transmission line line, which had been damaged by erplant was operating at near structure on the 115-kv Palmer the slide, was isolated a't the power maximum capacity (31,000 kw), line had been carried away by snow plant. Service was first restored and the power system was inter slides. Two adjacent spans of to the Matanuska Electric Associa connected through the Anchorage, transmission line, totalling 7,500 tion at Reed substation at 10: 43 Reed, and Palmer substations. feet, were destroyed. p.m., March 27, after compl&ion Major damage was sustained by Radio communication was tem of system repairs. Service was re two 115-kv air circuit breakers porarily interrupted between the stored to the Pa.Imer substation and bushing-type circuit trans Anchorage substation 'and the about 10 :00 a.m. on March 28 after formers serving the Anchorage powerplant. Damage at the An completion of system repairs. and Palmer lines, but there was chorage substation consisted of At 12 : 12 a.m., March 28, both no visible indication of damage to fractured porcelain on all three generating units at Eklut.na went either generating unit. The 115-kv lightning arresters. All off the line when the normal pen two 20,000-kva (kilovolt-ampere) transformers shifted on their bases, stock pressure dropped apprecia power transformers had shifted but, although the 115-kv bus work bly. At 12: 40 a.m., penstock pres on their rails and had subsided was distorted and severe strain sure restored itself and Unit 2 was several inches, as had the Camp placed on several bushings, there put back on the line. An exami line transformer. All bushings were no failures. Indicating and ll'ation of the intake area showed and connecting busses were intact, alarm circuits had conduit damage, that the headgUJte was still in full although under abnormal me but all circuits remained operable. open position bu't was accepting chanical strain. The generator, A temporary bypass was installed, only a very small flow of water. which had been stopped for ex- and the Anchorage line was ener- There was no apparent damage A6 ALASKA EARTHQUAKE, MARCH 2 7, 1 9 6 4 although shattered and upturned energized and an aerial patrol of areal subsidence disrupted cooling ice on the lake indicated that there all lines and the lake WUJS made. water facilities. Structural dam had been considerable disturbance At 2: 40 p.m., March 28, a shear age also occurred to the power in the lakebed and shoreline. At pin was lost on the Unit 1 wicket plant building and boilers. The approxima;tely 1: 30 a.m., low pen gate drive, and thus began the first Chugach Electric Association Coo stock pressure aga.in caused a com of a long series of shutdowns to per Lake plant was isolated by ex plete plant outage. At 3 : 55 a.m., remove rock and other debris from tensive damage to its 115-kv pressure began to return to normal, the gates and scrollc~Uses. transmission line, and widespread so one unit was again started and During this period, other util damage in the Anchorage area pro station service and the camp load ities in the area were also having duced many distribution-system was picked up. At about 8:00 problems. In the city of Anchor faults which had to be located, then a.m., the penstock pressure started age, two 15,000-kv gas turbines either repaired or isolated. The dropping again, 't::hen suddenly were inoperable because of broken power-generating facilities at El surged to above normal before lev gas mains and ruptured oil tanks. mendorf Air Force Base and Fort eling off. A considerable amount The Chugach Electric Association Richardson were partly crippled of debris was noted in the tailrace. Knik Arm steamplant lost coal by the loss of cooling-water The Anchorage line was again and ash-handling facilities, and facilities.
EFFECTS ON INDIVIDUAL FEATURES OF THE EKLUTNA PROJECT
EKLUTNA DAM On the upstream slope of the dam, gate structure (fig. 5) began to sub the riprap is underlain by a sand side into the underlying void. The dam is an enlargement of a and gravel blanket 12 inches thick. This movement did not take place nrutural dam formed by a receding The dam has a height of 26 feet to any noticeable extent until early alpine glacier. As indicated in above the foundation, a length of in July 1964. At this time, two figure 4, the site was thoroughly 555 feet, and a volume of 5,000 cracks approximately 1 inch wide explored by means of drill holes, cubic yards. formed-one in the base of the test pits, and geologic mapping. An uncontrolled overflow spill spillway slab and one in the sill of The reservoir, which is an enl·arge way having a crest altitude of 867.5 the gate structure. In addition, a ment of Eklutna Lake, is about 10 feet and a length of 150 feet is lo large part of the spillway base slab miles southeast of the powerplant. cruted on the right abutment. Lake had been deprived of foundation The lake has a surface area of level at the time of the earthquake support by the densification that 3,24 7 acres, a length of 7 miles, was approximately 20 feet below caused the void. The gate struc and a capacity of 182,000 acre-feet the spillway gate sill. ture was then declared unsafe for at maximum water surface alti Early inspections of the dam impounding water. All gates tude of 867.5 feet. after the earthquake revealed no were locked open, pending recon Construction of Eklutna Dam apparent damage. Immediately struction of the dam. after the quake, no cracks or other was completed by private interests evidence of quake-induced move INTAKE STRUCTURE in 1929. In 1943 it was purchased ment were found in the vicinity of Diversion from Eklutna Lake is by the city of Anchorage from the dam and spillway. The frozen made through an inlet channel, 100 which the Federal Government ground near the surface probably feet wide and about 500 feet long, purchased it at the time the Bu moved as a mass during the quake. excavated in the lake bottom about reau's Eklutna project was built. L a t e r observations, however, 60 feet below lake-surface altitude The dam was raised to a crest alti showed that the alluvium beneath (fig. 3). The intake structure ex tude of 875 feet above sea level. the frozen layer had densified and tends from this inleJt channel for The upstream and downstream created a void. As thawing pro 133 feet 8 inches. slopes of the dam and other areas gressed, therefore, the upper layers The intake structure has anini have been covered with riprap. of alluvium under the spillway tial trashmck, 112 feet long, built EFFECTS ON EKLUTNA HYDROELECTRIC PROJECT, ANCHORAGE A7
g0 g0 g0 g0 g0 oo m o ~ N ~ ~ m ~ ~ EXPLANATION TYPE OF E4s,oooLz~------z-+------ztrr~~------z+------z~- e6 DEPOSITS U.S. Geological Survey Churn-drill hole (4 in.) [2] .3 Alluvium --~-N Test pit (6 ft >< 7 ft)
0 110 Drill hole (8-to 3-in. casing) Lacustrine
. 0 . Bulldozer pit LJ Till X
Bench mark -Ar Water table A,---,A Several perched tables Proposed dam axis noted during drilling
A' A' 950' z g.. 850' G:j 800' ...J w 750' ::_}~~-~. i~·· t4>.\!r~P~~ :~l~$ ,co_ ~- 6ies. bo~ld~r~. San(fy .ci"a_y ~nd ~- n&JJiar . · · ·· · ~~d · _1~seS1 · rOck -· tr.agrrlen-tS
25+00 26+00 27+00 28+00 29+00 32+00 33+00 34+00 35+00 0 100 200 '300 FEET I!!!!I!J!!! I I
4.-Map and Section of damsite area showing exploratory work.
5.-Spillway gate structure. 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 the structure and bo ()btain samples The trash rack, transition, bulk sections. E·aJCh sootion is 26 foot of the glacial flour and till on the head, and conduit sootions back of 8 inches wide and 37 feet long. lake bottom for st:Jability studies. station 19 + 06 in the bottom of Immediately downstream from the Two types of glacial materials, Eklutna Lake sustained the major trashrack structure is 'a precast designated A and B, were found damage from the earthquake. concrete transition s~tion, 14 feet in the intake structure area. (Station numbers start at the in 2 inches long. The inside of this take and increase in the direction These materials were classified pri transition section tapers from a of water flow.) marily by their compaction andre rectangular reinforced -concrete Earthquake-induced densifica section 9 feet by 22 foot 8 inches to lated construction charncteristics tion of materials in Eklutna Lake a circular section 9 feet in diam rather than by composition: (fig. 6) caused the intake structure eter. At the end of the square-t:JO Material A.-Owing to the in to move approximately 44 inches round transition section ·is a bulk sta:bili'ty of the material, the gla toward the lake. Principal move head section 7 feet 6 inches long. cial flour was excavated on a 20 to ment was in a horizontal direction, Slots •are provided in the bulkhead 1 slope, and the lower part ·of mate but was accompanied by a lesser section for either gtop planks or a rial A was excavated on a 10 to 1 amount of vertical displacement. fabricated bulkhead to be used in slope. A thin layer of sandy clay Tensional forces produced by the event of an emergency or for containing many boulders as much the horizontal shift caused separa inspection purposes. as 3 feet in diameter underlies the tion along joints in the precast From the end of the bulkhead glacial flour and overlies ·a loosely conduit, as shown in figure 7. section 'the water is conveyed to compaeted glacial till. Unconsolidated sediments, rang the entrance of Eklutna tunnel Material B.-From the top of ing in size from fine sand to cobbles •the size of a football, through a 9-foot (inside-diameter) the B gla;cial-till cont:Jactio the bot funneled through these ruptures. precast-concrete pipe 225 feet long. tom of the inlet channel, the mate An elliptical cone-shaped depres The wall of the pipe is 12 inches rial had to be blasted prior to sion, approximately 40 feet in thick. The pipe was cast in 16- dredging. Hs clay content and maximum dimension, formed at foot sections, each section weigh impermeability caused the mate the edge of Eklutna Lake over the ing about 40 tons. rial to be very compact in place conduit alinement near station Numerous holes were drilled in and even to settle back as a com 18 +55, and numerous cracks were the general area of 'the tunnel in pact mass on the lake bottom after present along the lakeshore on take to ·select the best location for blasting. either side of the conduit. EFFECTS ON EKLUTNA HYDROELECTRIC PROJECT, ANCHORAGE A9
Cobbles and boulders in sand and clay
830
820
17+00 18+00 19+00 20+00 PRECAST CONDUIT
JOINT SEPARATIONS, OFFSET, JOINT SEPARATIONS, OFFSET, IN INCHES IN INCHES IN INCHES IN INCHES A 10 20 30 FEET Joint A B c D Joint A B c D HORIZONTAL ANO VERTICAL 1 1% !V. ll 1\0 0 9 1!1 2 1!1 0 FLOW 2 1 y, 'II ¥. 0 10 3y, 3\1 2 2Y, 0 0-n--B 3 1\1 1 1JI 1Y, 0 11 3 3Y, 3!1 0 - v 4 1\1 1Y, 1!1 1Y, 0 12 1Y, 1!1 2 1Y, D c 5 2Y, 1¥. ll 1'1\ 0 13 2!1 2Y, 1Y, 1Y, 0 ALTITUDE AT JOINT SECTION A-A' 6 10 10 10 4 14 ll 1\1 1\1 1 7 6 Y, 6!1 8 4Y, 15 2!1 2\0 1Y, 0
PRECAST CONDUIT 8 3!1 3 3!1 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 bed cling 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 wheel gate that is used both for per minute. From station 25+32 A circular concrete-lined pres emergency closure of the tunnel in to station 198+00 the rock is most sure tunnel, D feet in inside diam case the penstocks below or the ly interbedded argillite and gray eter and 23,550 feet long ( 4.46 turbine in the powerplant are dam wacke. The bedding planes are miles), com·eys water from the in aged and for dewatering the pen closely spaced and are recognizable take structure to the penstocks stock for inspection and mainte but erratic. Much of the rock is leading to the pmYerplant. The nance. intensely fractured, and innumer capacity of the tunnel is 6±0 sec A tunnel adit is located at the able minor fault planes and slip ond-feet. at a nlocity of 10.06 feet outlet end of the tunnel near the page planes cut through the rock per second. The slope of the in surge tank. The adit, which is at various angles to the tunnel axis. Yert is 0.00:3±1. ~~ D-foot-diam Yirtually the same diameter as the From station 198+00 to station eter gate shaft, bet"·een im-ert main tunnel and is approximately 234+75 the rock is a metamor altitude 790.76 and 1,012 feet, is :300 feet long, provides one means phosed greenish-gray gray"·acke. located at station 27+25 so that of access to the tunnel for inspec From station 234+ 75 dmvnstream, the tunnel may be de"·atered. tion and maintenance. H also the rock is uniformly fractured The tunnel termin.ates at a surge acts as a free-flo,v conduit for graywacke containing irregular in tank installed directly oYer the draining the tunnel "·hen entrance clusions of argillite. During con tunnel 22,805 feet dom1stream into the tunnel is necessary. The struction, ground water flowed from the bulkhead gate shaft. access door from the adit to the from most of the open joints. The surge tank, of the restricted tunnel is watertight. \Vater also flowed through many orifice type, has an inside diameter From station 20 + 00 to station fault-gouge seams, which range in of 30 feet and a concrete-wall 25+32 (fig. 8) the material con thickness from a fraction of an thickness of 18 inches, it extends sists of B-type glacial till. The inch to several feet and dissect the 176 feet vertically above the tun sand layers coni:ain some ground rock at varying angles. nel. A 4¥2-foot rectangular sep water, which has a maximum total Approximately 2,000 cubic yards aration serves as a slot for the fixed flow of approximately 300 gallons of material was deposited along the AIO ALASKA EARTHQUAKE, MARCH 27, 1964
Zo Oo g i=+ g 600 ·N: i;• E. N. 5· E. N. 13" E. N. 33" E. N. 10" E. Q,g 1 84"1W. 68" W. I 78" E. 88" S.E. 87" E. 1 SEA s~ AXIS OF TUNNEL BEARING N. 10"52'45 " W. SLOPE=0.00341- No supports LEVEL None-roc~ section 1------lHHHIHHHHI H H 5-in. H-beams or lighter on centers more than 4ft ~r---lHH H~ Light support-- H I H IIHHI HIHI 1------i 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 0 ~t il tl i~ ~· ~ ~: i; • • 1 • f. ~~ H EH iH do H i C::;h:;;'e;";;;<,;t•c:..r--+ ;= +---~ i --+----~.: -+- •• -+-- • ~ • --f--1--. ~ • --+ :+-----:; 0 - ----.h.-+--- of rock ~ f-+- '\Fairly sound th in- "' :i - j t :; ~ : -: ~ : I :; :§ : ~ t----- J! •"' :.t: 1l •e Fairlybedded sound a re thinillit~ j- .o.. •c: bedded 111illite ~;S•~· ·.-~=-= -i_u ....,1 =.~.·.-- : ~ .q H anda:raywacke lnderaywacke 8 :io • 40" F. Rock 40" F.40" F. 41" F. 42" F. 43 .5" F. 44 " F. 44.5" F. 45" F. 46" F. 46.5" F. 47.5" F. 48" F. 50" F. temperature Steel reinforcement 0' EZJ ~ 0 Type 1 Type 2 + § EXPLANATION N. s· E. ~·E. Glacial till Steeply dipping inter Fault trace Strike and dip of bedded graywacke and Showing direction of bedding planes argillite movement (In plan view) EFFECTS ON EKLUTNA HYDROELECTRIC PROJECT. ANCHORAGE All 1500 zo g g 8 oo 8000-10,000 gallons\ ;::+ + + per 3000 gallons + 4200 ;:,:_·_. -:~>-><·: 0 ~ .::~ :· ... '_:_:_~·-: 0 3600 tV.~ . . -~-:::-::.. -·. + ~ "'c 0 3000 ~ ~ ~ ;;!; "' 2400..; 0 ....::> >= 1800 ;;i 1200 : ~>3~ £:. N:· 30; W\N: 65• E. ,. i ., ...... 600 180 1 "1~vert .~&;~~'!ion~~; ~nde rdrain · ': Bedrock f---Roofbolts -----j 1foofbolts n "f ···:·:< urface SEA --JI------11---1 f--1HHI----Ii----j HI------; H I! H HHH H Hf---iHH Sd;;:\l';o LEVEL 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 + HH H Hij-11---tt----t I H I I 60~~s~ a::~ CI)N 40 ~ ~ 20 ~~ Roof overbJeak ~ 0 35.5" F. so· F. 49" F. 48" F. 47 .5" F. 47" F. 46.5" F. 45 .5"·F. 44" F. 40" F. 39" F. 37" F. 36' F. 36" F. ~pe3 ?//t///,7/T~ ' g g' 8 + + + :iS ~ ~ "' 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 0 600 1200 1800 2400 FEET 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 8 (above and left) .-Geologic section along the line of the pressure tunnel. 224-630 0 - 67 - 3 A12 ALASKA EARTHQUAKE, MARCH 27, 1964 1060 1040 --- 6" H-rings 5' outside circumference Entire shaft lagged with 2" x 12" timbers 1020 Open cut excavation 1000 980 joints 960 9.-Debris in Eklutna tunnel, typical of 940 that deposited throughout the initial l;j UJ 3lh miles of tunnel as a result of the u. earthquake. ~ LL.f 92Q 0 ...::J i= ..J tunnel invert. The debris con < sisted predominantly of rock frag 900 ments 1 inch in diameter, bu't ranged in size from sand to an oc casional fragment 14 inches across. 880 The debris (fig. 9) was 12-18 All this water dried up inches deep and was uniformly dis when the same strata was penetrated in the 860 tributed from the gate shaft at sta tunnel from station tion 27-t-25 to near Station 103+ 24+97 to station 25+ 13 00. From station 103 + 00 to sta tion 235+00, debris was deposited 840 in gravel bars of varying depths. The last mile of tunnel was rela tively free of material. No struc 820 tural damage to the tunnel was found. BOO As part of the plan to design an earthquake-resistant structure, the gate shaft at station 27 + 25 was 26+65 founded in competent rock (figs. 8, STATIONS 10) ; it was reinforced to withstand internal bursting pressures. Hori zontal joints in the shaft, indi cated by dashed lines on figure 10, 20 40 FEET helped compensate for any possi HORIZONTAL AND VERTICAL ble vertical deflections during an 10 ~ -Geologic section through gate shaft. earthquake. No damage to this structure was discernible. EFFECTS ON EKLUTNA HYDROELECTRIC PROJECT, . ANCHORAGE Al3 PENSTOCK, SURGE TANK, 920 AND ANCHOR BLOCK The power penstock conveys wa 900 ter from the surge tank !lit the end 6 " H-steel 4' outside of the Eklutna twmel to the pow 880 erplant 'turbines. The penstock is rubout 1,088 feet long, is installed in 1 30-foot sections, and is a vari3Jble 860 75-in~h 6" H-steel 5' outside diameter (91-, 83-, and out circumference side diameter) welded and coupled Solid timber lagging 840 steel pipe encased in concrete. ::-Mostly grayish-black Plate 'thickness of the penstock argillite varies from %G inch at the initial t;j Very weathered iron-stained and broken graywacke section to 1% inches at the terminal ~ 820 containing scattered inclu sions of argillite ~ section. In profile, the penstock w 0 roughly parallels the mountain :J t:: 800 side, descending for approxi ~ <( mately 864 feet at an angle of 53°; it t'hen levels off and continues 780 through a horizontal section aibout ·501 feet in 'length. At the power plan't the penstock hifurcates into 760 two 51-inch-diameter 23-foot-}ong branches which are connected to the spiral cases of the tur vated in weathered rock, except at 720 Begin vertical the lower end where the tunnel sec- Very broken and weathered bend 6on emerges into overburden ma graywacke Station 255+30 terial (figs. 11, 12). In order to 7ooL-----~----_L ______L______L ____ ~L-----~----~ 254+70 254+90 255+10 255+50 255+70 255+90 traverse this overburden material, which l EXPLANATION 1000 Topsoil and pebbles, cobbles 10 Graywacke and argillite. Quartz and calcite-filled fractures. Weathered rock, greenish-gray Very broken, brecciated, some 3 Graywacke and argillite, dark-gray crushed core, slickensides, to black; distorted. Quartz- and small intrusions~ contorted calcite-filled joints and fractures. 900 11 Topsoil Slickensides. Iron-stained. Some open joints 12 Clay, sandy, Gravel and boulders 4 Moss, topsoil 13 Graywacke, argillite, and spilitic Sand, silt, gravel, boulders basalt. Broken, crushed and 800 brecciated. Contorted. Granite Siliceous graywacke, argillite and intrusions. Quartz and calcite metasiltstone. Badly broken, stringers shattered, brecciated. stained weathered fractures . 14 Organic material Quartz- and calcite-filled joints 15 Clay, silty, plastic 700 and fractures and open joints 16 Sand, boulders, rock fragments 7 Clay, sandy, silty 17 Rock, fragments 8 Weathered rock, granular, brown ish-gray 18 Graywacke and argillite. broken 9 Graywacke, fine-grained; contains and weathered 600 intrusions of brown felsitic ma- 19 Rock fragments, broken, crushed, terial brecciated, serpentinized f-w w u.. 500 z w 0 :::l f- i= 400 ...:-' 300 200 End of penstock, OH 84 Station 266+ 10 Alt81.4'± Alt 25.0' 100 0 100 200 300 FEET (HIGH LEVEL) Station 261 +00.38 On drift Alt 26.77' 100 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 di vided 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 automo tive repair shop, warehouse, and office building. The powerhouse is a reinforced concrete structure 71 feet long and 80 feet 8 inches wide. Because of the relatively unstable foundation conditions and the high earth quake potential, the design in cluded pile foundations for the powerhouse, machine shop, trans 14.-Eklutna pow.erplant before the earthquake. former structure, and penstock anchor block. The foundation included 289 vertical and 110 bat tered 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 sec ond per second. An average pile penetration of 5.0 feet into bed rock was achieved. Foundation material between the piles con sisted 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 su perstructure of the machine shop has structural-steel framing and reinforced-concrete walls 10 inches thick. The structure is pinned to 15.-Some of the piling in the powerplant foundation during construction. Piles in piles through concrete pile caps. lower foreground and along left side have been cut off to grade prior to capping. The main power transformers that step up the generator low protect the transformers from The switching equipment for voltage are located in the pile snow and rock slides. Firewalls the powerplant is located on three supported transformer structure separate the transformers and levels. The switchyard equip adjacent to and southwest of the serve as foundations for the take ment itself-consisting of the powerhouse at altitude 41.25 feet. off structures ·that carry the pow power circuit breakers, disconnect Protective walls were placed on erlines to the switchyard on the ing switches, and main busses-is the south side of the structure to powerhouse roof. on the roof of the powerplant at A 1.6 ALASKA EARTHQUAKE, MARCH 27, 1964 h + 2 '5 c a .P m 6i 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 thick- ness 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. Ap- proximate 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 - Graywacke and argillite - 700 IIIIII 0 0 L 8 8 0 k! 400 - 5, 7 Lo3 LD 8 f ui - CONTINUATION OF PROFILE n 3 FROM POINT H '- 300 - 3 - 200 - - 100 - - 0 - - Graywacke and loo 0 0 0 0 0 0 0 0 0 0 o+ 8 + 8 8 ? Y 7 0 ? 0+ 0 2 m 0 d Lo h 01 rn rn % w 2 w 0 w w 2 w F w N N N N N N N N N % 2 N r. N 16.-Generalized geologic section through surge tank,penstock, and powerhouse. altitude 92.50. The main power penetration resistance holes made conduit were excavated in water- transformers that step up the gen- to evaluate the bearing capaci,ty of bearing river sand and gravel, and erator low voltage are located in the overburden material under the the area had to be pumped during the transformer bay at altitude powerhouse foundation. A gener- excavation. Some sloughing of the 41.25. The high-voltage bushings alized geologic section is shown in backslope in the noritheast corner of these main power transformers figure 16. of the excavation occurred during are connected to the main switch- The upper 10-12 feet of the sec- the extreme high-water period of ing equipment locater? Dn the roof tion consists of organic, slightly the Lake Gwrge breakup. at altitude 92.50. The 115-kv bus plast,ic sil,t containing occasional Interstratified discontinuous lay- structure on the powerplant roof angular graywacke fragments. ers of stream gravel, sand, silt, and oonsists of two bays to supply the Below the silt a layer of talus 5-8 clay underlie the talus and overlie 115-kv lines to the cities of Palmer feet thick, containing angular the weathered bedrock surface. A and Anchorage. graywacke boulders in dark- flood plain extends north and w&t About 30 holes were drilled in brownish-gray organic sandy clay, from the powerplant site for sev- the powerplant area during the ex- lensed out downstream from the eral miles. The drainages from ploratory and early construction powerhouse foundation. The base both the Knik and Matanuska stages. Nineteen of these were of the powerhouse and the tailrace Rivers spasmodically aggrade, EFFECTS ON EKLUTNA HYDROELECTRIC PROJECT, ANCHORAGE A17 degrade, and change their chan nels throughout the spring, sum mer, and fall seasons. These erratic sedimentation phases ac count for the interstratified sedi ments 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 plas tic organic silt recently deposited during the annual flood stage of the Lake George breakup. The water table beneath the power plant 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 17.-Typical ground settlement resulting from th1:l earthquake. Settlement is near the northeast corner of the powerhouse at the location of the septic tank. cork-filled expansion joint. The two structures oscillated at differ r ')(Subsided areas ent intensities, and the intercon \ --.,_ L/"'" \ "- 1\ necting drainage and electrical '-.__) systems were sheared. The differ ential horizontal displacement be "-Area around transformer tween buildings was three-fourths structure has been graded. Extent of of an inch, but the vertical dis settlement could not placement was negligible. Back be measured 11/4" Horizontal movement fill around the entire periphery of (gravel surface and concrete) the plant and under the machine POWERHOUSE shop settled ermtically from a few inches to a few feet (figs. 17-19). The fill in which these failures occurred is composed of well Relative movement W~ ~ graded sand 'and gravel obtained from the Knik River. Most of the L><_ gvavel part'icles were subrounded 48 d's and were composed of a wide va 16 16 riety of unweathered igneous, met NOTE: Numbers indicate inches of relative 0 20 40 FEET amorphic, and sedimentary rocks. settlement as measured between earth The sand ranged in shape from surface (backfill) and concrete rounded ,to 'angular, a noticea-ble lB.-Measurements of settlement and deflection at the powerplant. percen'tage being elongated and flattened. The sand was composed bution in the gmvel fraction of the A dragline and two bulldozers backfill materi'al is as follows: were used for placing and sprerud predominantly of slate gvains. StandarcZ ing the 'backfill. The material was Silt-size particles were presen't in Bieve Percent Percent Bize retained cumulative wetted for proper compaction and small amounts, but tended to wash 6 in______0 0 oonsolidated by equipment travel. away during handling. The pit 3 in______2 2 Gasoline-powered immersion-type 1~ in ______22 run material consisted of 3'5.1 per 24 vibrators and mechanical tampers ~ in ______36 cent sand and 64.9 percent gravel. 60 ~ in ______27 87 were used in areas inaccessible to A weighted average of size distri- No. 4 ______13 100 the bulldozers. A18 ALASKA EARTHQUAKE, MARCH 27, 1964 / Postearthquake examination . ...-' showed that the drainage system y 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 Concrete footing the drains was quite prevalent. . ~ Ground wa'ter from the surround ing sediments and fuel oil from a ruptured, buried tank entered the drainage system through the sheared l'ine. Within the transformer struc ture, the two 20,000-kva transform ers moved from 3 to 5 inches when tack-welded rail stops hroke loose. Backfill material Both transformers settled a few inches but not enough to overstress any of the bushings or bus connec 19.-Machine-shop foundation showing the separation of backfill material from the tions. Alt:hough the bottom of the concrete footing. Approximately 1.5 feet of H-section pile is now exposed as a result of settlement caused by tht> earthquake. 120-volt terminal ca:binet (fig. 20) on one of 'the transformers broke open and the atlia.ched conduits were pulled loose, the circuits re mained 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 ten sively damaged. Two single phase air circuit breakers were damaged. Each phase consists of an air receiver, two hollow porce lain insulator columns, porcelain extinction chambers, arcing con tacts, and a bushing-type current transformer. The hollow insula tor columns are mounted at the ends of the air receiver and carry compressed air to, and provide sup port for, the extinction chambers and arcing contacts. The free standing hollow insulator columns broke at the base and thus caused complete collapse of the contact 20.-The 20,000-kva transformer conduit and terminal box damaged by movement of mechanism. Porcelain of the cur 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 rent transformer cracked and oil move on the :rails. was lost. EFFECTS ON EKLUTNA HYDROELECTRIC PROJECT, ANCHORAGE A19 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 fix tures were torn loose from the wall. 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 ex tended from the garage to the 21.-Damage to the heating-system piping in the floor of the automotive repair shop southwest corner of the warehouse. caused by the earthquake. Graywacke and argillite .d£1/.Ld _LLLU..Ld -.:4/~ dU/ .L0VL2Z: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 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 adjustment believed to have been caused by ground thaw along the cracks continued 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 wood frame 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 approxi 23.-Pavement damage caused by the earthquake. Cracks extend from the garage mately 5 inches above the floor (fig. east along the north wall of the warehouse (right of photograph) and thence across 24). Miscellaneous damage con the road to the project office (left of photograph). sisted of overturned files and storage cabinets, cracked floors, damaged light fixtures, and broken joints in the chimney. The north wall of the structural steel 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 ap proximately 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 as phalt roofing were caused by the flexing of the cold roofing paper. TAILRACE Water from the draft tubes of 24.-Pump in Eklutna project office showing the effect of the earthquake. Base of the turbines in the powerplant is pump is now approximately 5 inches above the floor. discharged through a 209-foot long pressure tailrace conduit un der the Glenn Highway to an open tailrace channel leading to the Knik River. The tailrace conduit is made up of rectangular reinforced-concrete 25.-Typical section of tailrace channel. 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 rip rap at the junction with the tail race conduit. The channel has a top width of about 75 feet, a bot 26.-Cleaning-up operation at the outlet of the tailrace conduit. Debris was de tom width of 25 feet, and a depth posited following the rupture of the tunnel intake at Eklutna Lake during the of about 12 feet 6 inches. earthquake. The upper 4-6 feet of material underlying the tailrace is silt and TAILRACE CONDUIT sandy silt, which in turn is under Joint Remarks lain by a 2-foot layer of sand and Joint open 2'/ in. on top, open % in. on bottom A 4 fine gravel. Beneath the sand and Waterstop torn for about 1 ft, gravel visible above tear fine gravel is sand and coarse Joint open % in. on top, open 11/2 in . on bottom with 3 in. gravel. During construction of B vertical offset, downstream side lower. Larger leak on left the tailrace, some sloughing oc side of left unit near floor Joint closed on top, open 1'/2 in. on bottom with 1'/4 in. curred in the sand and gravel c vertical offset, upstream side lower layers during extreme high tides Between Crack in ceiling, right unit and when water was added to the C and D channel by operation of the pow D Joint closed erplant. Also, during the period Joint open evenly 1'/• in. all around with 2V in. vertical offset, E 2 of extremely high water at the upstream side lower time of the Lake George breakup, F Joint closed Joint open 1 in. all around with in . vertical offset, up- there was some sloughing of the G % stream side lower. Leaking at top 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 depos B i 1~~==~==~======~ t--t=o=*=='~='----+- -+-+-- --- ited in t he conduit, presumably Approximate ground surface after the break in t he precast pipe Alt 40.0' section of the tunnel intake. The inspection also revealed consider G able shifting of the sections near est the powerplant (fig. 27). Regional subsidence raised the SECTION B-B high-tide water level approxi mately 3 feet. 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 Matanuska Electric Association's on their bases. Primary bushings cracked (fig. 28) in the area ad 34.5-kv line and the 12.47-kv were not damaged, but one second jacent to, and parallel with, the Palmer area distribution system. ary bushing had sufficient stress 2,000-foot-long open canal section In order to carry the Palmer load on it to bend the transformer of the tailrace. The cracks through the limited capacity of cover. Conduits for the indicat ranged in width from a few inches the Reed substation, auxiliary ing circuits on the phase C trans to 5 feet and had the effect of cooling had to be provided by former were broken at the ground squeezing in the sides of the chan truck-mounted fans. line, but the circuits remained nel. The invert was irregu}arly operative. Sections of the rigid mantled by gravelly debris rang SUBSTATIONS bus at 'the high-voltage bus were ing in depth from a few inches to The Anchorage substation is bent. The single-phase station several feet. situated on a terrace of glacial till service transformer shifted on its overlain by less than 1 foot of soil. base but was not damaged. The TRANSMISSION LINES Beneath this overburden and be battery rack and radio equipment yond a depth of 8 feet, or below inside the substation building The 115-kv Anchorage line was foundation grade, 'the material shifted but were not damaged. not damaged, but the earthquake consists of a fairly uniform clayey The Palmer substation is in a triggered a snow and ice slide near sand and gravel. The water table heavily wooded area immediately the Knik River bridge that swept is 25 feet below ground surface. south of the town of Palmer. a>vay a three-pole guyed structure, Lightning arresters on each of Foundation materials consisted of 7,500 feet of conductor cable, and the single-phase power transform 0.8 feet of dark humus and topsoil, an access road on the Palmer line. ers at the substation were dam 3.0 feet of dark-grayish-brown The transmission lines were re aged. The arresters broke at their slightly sandy silt, and about a 1- paired on April 8, 1964, and serv bases and dangled from the line. foot mixture of dark-gray silty ice was restored on April 16, 1964, All three "stacks" of each arrester sand and poorly graded gravels after the air circuit breaker was were broken. One lightning ar and cobbles. The depth to the repaired at the Eklutna switch rester on the Chugach Electric water table was not determined. yard. w·hile the Palmer line was Association 16-mva (millivolt-am The only evidence of damage at the out of service, pmver was deliv pere) transformer was also dam Palmer substation was an oil leak ered to the Palmer substation aged. All three transformers at at the base of a transformer from the Reed substation over the the Anchorage substation shifted bushing. OTHER EARTHQUAKE EFFECTS IN THE AREA The,re is evidence, though mea The slides were composed of talus summarized as follows : ger, indicating a general subsi fragments held in an ice matrix, 1. No major slides were observed dence of the Eklutna powerplant but water was freely flowing be along the Copper River main area, including Goat Mountain. neath them and no ponding was stem, although a slide was An exceptionally high tide was re taking place. Earthquake effects present across Klutina River, a tributary of the Copper ported during the >veek of May 12- were confined to alluvial deposits, River. No water was being 15, 1964, but settlement of the gen and conspicuous cracks were ob impounded. eral area probably contributed to served in nearly all alluvial fans 2. Numerous snowslides were seen the flooding. bordering Eklutna Lake. along the Matanuska River A helicopter reconnaissance of Aerial surveys were conducted valley. the Eklutna Lake drainage area to determine if major damage had 3. Some shifting of the Lake (fig. 29) disclosed that earthquake occurred at poten'ti'al project areas. George, Surprise, and Colum slides had blocked three valleys. The results of these surveys can be bia 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 Creek, Kashwitna River, Hongkong Bend. The only assessed the earthquake ef T a 1 k e e t n a River, Sheep new large-scale landsliding fects on potential damsites in Creek, Swan Lake near J u was on the Kashwitna River, the Anchorage-Seward area. neau Creek, Moose Horn but this slide did not affect These sites are on Nellie Juan Rapids, Kenai River, Juneau consideration of a damsite Lake, Surprise Creek, Lost Creek, Kasilof River, and upstream. EFFECTS ON EKLUTNA HYDROELECTRIC PROJECT, ANCHORAGE A25 TELEVISION EXAMINATION OF EARTHQUAKE DAMAGE TO UNDERGROUND COMMUNICATION AND ELECTRICAL SYSTEMS IN ANCHORAGE BY LYNN R. BURTON, U.S. BUREAU OF RECLAMATION INTRODUCTION asbestos-cement ducts, buried 4-6 and brush before the examination. feet beneath the streets and alleys That part of the communication As a result of the earthquake of the city. These ducts, contain system extending from A Street to of March 27, 1964, the city of ing telephone and power cables, are E Street along the alley between Anchorage experienced s e v e r e encased in concrete envelopes. Third and Fourth A venues was de damage ·to its underground utili Manholes, spaced 180-540 feet stroyed by the Fourth A venue ties systems in addition ·to the apart, provide access to the en slide, and a section of the system great damage sustained by surface velopes. Each bank of ducts along Eighth Avenue west of L structures. Temporary repairs to includes at least one empty duct Street was destroyed by the L these systems were made as that was used for the television ex Street slide. quickly as possible after the earth amination. Any damage observed quake to permit resumption of in this duct was assumed to ind:. necessary services within the city. EQUIPMENT cake damage to the entire envelope Permanent repairs were included at that location. In areas where The closed -circuit television in that phase of the Alaska Resto the two systems are closely paral equipment used was designed pri ration Program administered by lel, only one system was examined. marily for examination of explor the Corps of Engineers. The ducts were cleaned by mandrel rutory drill holes 3 inches or more In order to avoid costly excava tion of the buried communication and electrical systems to determine the specific locations requiring re pair, the Corps of Engineers re quested the use of a small-diameter \ closed-circuit television camera owned by the U.S. Bureau of Rec lamation. 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 Serv ice (fig. 30). During September and early October 1964, 23,594 linear feet of communication sys tem and 10,510 feet of electrical system were examined in the An chorage business distriot and vari ous residential areas by means of this equipment. UNDERGROUND SYSTEMS The underground communica tion and electrical systems consist generally of banks of four to 30.-Truck-mounted television equipment being loaded at Denver for its flight to twelve 31;2-inch-inside-diameter Anchorage, Alaska. ALASKA EARTHQUAKE, MARCH 27, 1964 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: Lateral Axial - viewing 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 geo- PROCEDURE systems, locations of cracks ob- logic data. It also has numerous The television probe was drawn served during the examination, nongeologic applications. The through the ducts by a small-gage and approximata positions of the equipment is mounted on a truck wire rope attached to a pulling grabens formed at the heads of the and includes a control console and bridle on the probe and wound on L Street, Fourth Avenue, and monitoring unit, approximately a winching drum. The winching First Avenue slides are shown in 1,000 feet of coaxial cable, and two drum was coupled to an electric figure 33 (p. A28, A29). For aim- types of probes in which the mini- motor through a variable-speed plicity, the alinements of the two aturized television camera is in- transmission to permit variation in systems are combined and shown serted (fig. 31). All operating logging speed. Direct communi- as a single system. The direction switches and an 8-inch monitor or cation between the television and of movement, where it could be de- viewing screen are located at the winch operators by sound-powered termined, is indicated by small control console. The instrument telephone provided coordination arrows. operates on 110-volt 60-cycle alter- of viewing and logging speed, Cracks in ithe ducts were clearly nating current. An attempt was which was normally 10-12 feet per visible on the monitor screen, and made to use a lateral-viewing minute in undamaged ducts. The the amount of separation and off- probe in this examination, but its general arrangement of the various set was accurately determined. length (55 inches) prevented pas- components of equipment during Approximately 90 percent of the sage through many of the bends in operation is shown in figure 32. cracks exhibited no measurable the duct lines. The axial-viewing displacement and were not con- probe, which is only 30 inches long, DAMAGE TO SYSTEMS sidered indicative of serious dam- could be passed through all but the Topography and surface geol- age to the concrete envelopes. sharpest of the bends and was used ogy of the northern half of the Lateral, vertical, and longitudinal throughout the examination. city, alinement of the underground displacements along fractures were ALASKA EARTHQUAKE, MARCH 27, 1964 P 33.-Topography, surface geology, 'mdlocation of fractures EFFECTS ON EKLUTNA HYDROELECTRIC PROJECT, ANCHORAGE EXPLANATION 0 500 1000 1500 FEET Qal Alluvium ...... Qs Swamp deposits Contact - Qaf A'1uvia1 fan deposits ---- Alinement of underground communication N QO' Outwash and electrical systems Qc Abandoned-channel -*+- deposits Location of cracks having discernible 1 Qpi Pitted outwash separation or offset. Arrow indicates apparent direction of movement Geology from Miller, R.D., and Dobrovolny, Qgi Glaciofluvial ice-con- YL-L- -. . . Ernest, 1959 (1960). Surf~cialgeology of , tact deposits Location of cracks having no discernible Anchorage and vicinity, Alaska: U.S.Geol. Qbc Bootlegger Cove Clay separation or offset 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. Photo vicinity of the Fourth A venue slide Movement was to the north or graphs of two such fractures, as and in areas near the slopes of south at 13 of these locations. In viewed on the monitor screen, are stream valleys and local drainage general, these data suggest that the shown in figure 34. The maximum channels. The concentrations of north-south component of ground displacement noted was 1 inch, al fractures north of Sixth Avenue motion was more severe than the though most were in the Yt 6- to 1,4- between Barrow and F Streets are east-west component and that the inch range. Soil and water had clearly the result of ground adjust direction in which the induced entered the ducts through many ments related to the Fourth Ave tensile forces acted was strongly such openings, and water was nue slide. Others, such as those influenced by the free faces repre found in some areas where only located on Thirteenth A venue and sented by Ship Creek valley to the hairline cracks were present. along C Street south of Thirteenth north, Chester Creek valley to the Avenue, probably reflect local sub south, and the Cook Inlet bluffs to INTERPRETATION sidence resulting from incipient the west. Lack of a comparable OF DATA failure of outwash and alluvial materials on valley slopes. free face to the east rna y explain Although their plotted locations The direction of movement was the absence of serious damage to exhibit no well-defined pattern, the determined at 18 of the 52 loca the underground systems in the cracks are concell'trated in the tions where displacement occurred. eastern part of the area. U. S. GOVERNMENT PRINTING OFFICE: 1967 0 - 22 4-630