The Northern Engineer, Vol. 05, No. 1 (Spring 1973)

Item Type Journal

Authors University of Alaska (College). Institute of Arctic Environmental Engineering

Publisher Institute of Arctic Environmental Engineering, University of Alaska

Download date 06/10/2021 20:18:43

Link to Item http://hdl.handle.net/11122/1407

THE NORTHERN ENGINEER

Volume 5, Number 1 WHITHER THE OIL OF NPR-4 Spring 1973 The well-publicized commercial oil leases on the Alaskan North Slope are expected to yield eventually at least 10 billion barrels. IN THIS ISSUE ... Immediately to the west, separated only by the Colville River, lies the U.S. Naval Petro­ leum Reserve Number 4, or NPR-4. It is sometimes called Pet-4, but this, strictly speak­ Editorial Dr. Tunis Wentink, Jr ...... 2 ing, applied to the 1944-1954 exploration program carried out by a Naval Construction Battalion. In view of the 1969 U.S. Geological articles and opinions Survey estimate· of recoverable reserves of 9 billion barrels under these federal lands, and probably a low figure due to incomplete ex­ 'Finding Faults' with EATS Imagery Larry Gedney ...... 3 ploratory drilling (the true test), this writer wonders about the future of these reserves. At least, in the fast approaching energy crisis, Alaska's Geothermal Resource Potential Robert Forbes and Norma Biggar ...... 6 how does NPR-4 enter? He finds it curious in particular to find little published mention of planning for tie-in with the projected trans­ Alaska pipeline, for a national emergency. The Northern Construction: Siting & Foundations Eb Rice ...... 11 1972 revised six-volume Environmental Impact Statement on the Alyeska pipeline relegates Ice Crossings Edwin M. Rhoads ...... 19 consideration of NPR-4 to a footnote, to a reference! There is no implication here that a Teapot Dome-type problem may arise; the able U.S. Transportation of Alaska's North Slope Coal Paul Clark ...... 25 Naval Petroleum and Oil Shale Reserves Office administering NPR-4 has too many constraints Design of Roofs for Northern Residential Construction Axel Carlson ...... 29 imposed on it under present law to permit such to happen. However, final responsibility rests in the law-making Congress. miscellaneous Rather, the opposite could occur; lack of planning may deny use of these fields when needed. Will planning be neglected until an Hickel Report Now Available ...... 5 emergency arises? Should plans for roads into NPR-4, gathering lines from the several Symposia & Conferences ...... · .. ··. ·· .. · · ·· ··· ... 35 probable major fields, and transit of the. Col­ ville be started now7 Of course, up to about the year 2000 commercial fields east of the Research Reports ...... 35 Colville can always be used while delivery systems from NPR-4 are being readied, should North Slope oil become a truly critical factor in national affairs. But time always moves THE NORTHERN ENGINEER on. Certainly, construction by commercial interests outside NPR-4 soon will provide much is a quarter,ly publication of the Institute of relating to Arctic Science and Engineering, or information allowing efficiencies in future Arctic Environmental Engineering, University fully developed research reports. While our NPR-4 exploration and exploitation. But, for of Alaska, Dr. Tunis Vllentink, Jr., Director focus is on technology, we view it broadly, thus example, will the planned bridge across the are interested in the social, natural and Yukon serve as a model for spanning the Col­ political aspects related to cold regions Editors: Dr. William R. Hunt (on leave) engineering. ville? Are barges in summer and temporary railroads on the ice as used during the siege of Mike Tauriainen All correspondence should be addressed to Stalingrad in winter usefu I alternatives? These THE NORTHERN ENGINEER, University of seem to be too crude. Are the soil problems in Managing Editor: Gina Brown Alaska, Fairbanks, Alaska 99701. Subscription rates are $6.00 per year, $10.00 for two years, NPR-4 pertinent to drilling pads and gatherir~g lines similar or different from the Prudhoe We will consider manuscripts of any length, $20.00 for five years. Single and back issues whether short descriptions of current projects may be obtained for $2.00 each. Bay area? A minimum effort now should be a problem definition program. COVER Tie-in of NPR-4 with the Alyeska line should be planned, but we do not advocate Photo by Dr. R. B. Forbes of the Geophysical exploitation of NPR-4 now. It should not be 1nstitute, University of Alaska, of a fumarole used as a short-term expedient, but should be field on the west flank of Griggs Volcano (Knife readied as an accessible and usable reserve. A Peak), Katmai National Monument, Alaska. peripheral but pertinent future problem is the question of where Alaskan oil will go, to the U.S. or elsewhere. Tunis Wentink, Jr. FINDING FAULTS' WITH ERTS-1 IMAGERY

by Larry Gedney

The following introduction is part of on a regional basis is laboring under analyses involving projects, twelve of the University of Alaska ERTS-B pro­ severe handicaps. Alaska is so vast, and which were eventually included in the posal submitted for the continuance of the Arctic so varied, that this environ­ ERTS-A contract with NASA. All of the investigations begun under ERTS-A. mental gap will not be bridged soon by these twelve projects are reaching the A portion is also taken from the Project conventional means. state of fruition, and some have already 12 section of the ERTS-B . proposal. In December 1969, the State of produced results of considerable import­ These are included here to give more Alaska and the U.S. Department of the ance and utility.... background to the ensuing article. Interior co-sponsored a symposium en­ Initial target objects for ERTS-A --Editor's Note titled "The Use of Remote Sensing in Project 12 were chosen largely on the Conservation, Development, and Manage­ basis of comparing current seismicity INTRODUCTION ment of Natural Resources of the State maps (Prepared at the Geophysical Insti­ of Alaska." In his introductory remarks tute) with the most rec(!nt information The Earth Resources Technology Sat­ to the symposium, the Honorable Walter on faults and fault systems which could ellite Program, with its demonstrateo J. Hickel, then Secretary of the Interior, be obtained from the U.S. Geological capability for economical large scale sur­ said: Survey and other sources. Linear zones veys, provides a unique opportunity to of epicenter concentrations where no " .... The conservation, development, narrow a great environmental knowledge faults were mapped were obvious objects ' and management of the natural re­ of interest. At least two of these linea­ gap which impedes planning at a critical sources of the State of Alaska are of juncture in the history of Alaska's eco­ concern to all the people of our coun­ ments have subsequently been identified nomic and social development. . . . try. Our nation's largest State is rich as major faults by independent workers. This problem has been recently and in resources vital to our continued However, the most significant findings well-being and economic growth. forcefully manifested in several ways, !rave come from areas in which the The sophisticated techniques of re­ investigators had not expected to find chief among which are: mote sensing offer advanced cost-effec­ 1) The controversy surrounding the pro­ tive means of locating, monitoring, anything of particular interest. They posed construction of the trans­ classifying and inventorying mineral de­ have identified in these areas such Alaska pipeline from the arctic coast posits, recreation areas, forest lands, previously unmapped features as faults, coastal zones, fisheries, water supplies to the southern port of Valdez, and joint systems, and other structures which and energy potential. The highly sensi­ aid in the interpretation of the nature the recent U.S. Appellate Court de­ tive instruments of this relatively new cision denying the permit for its con­ field can yield otherwise unobtainable of the tectonic deformation in central struction. information about the land and its Alaska. 2) The deterioration of fisheries resources effective use. Under the Department The interpretive methods used were of the Interior's Earth Resources Ob­ in the Alaska coastal zones and simple and straightforward. They in­ servation Satellite (EROS) Program, we cluded visual analysis of the ERTS ima­ continental shelf. This results partly are beginning to assess what these new from a poor environmental knowledge tools can do for us from aircraft and ges and projection of the 70mm positive of these regions. sate II ite platforms. In 1972 the N a­ transparencies so that group discussions 3) The establishment by Congress and tional Aeronautics and Space Adminis­ could be held, manipulation of the tration will launch the first Earth Re­ the Alaska State Legislature of the 70mm negatives using different exposure sources Technology Satellite(ERTS-A) times to best display the particular ob­ Joint State-Federal Land-Use Planning to provide small-scale synoptic and Commission. This Commission has repetitive views of the earth and its ject of interest, and the construction of the awesome task of recommending resources. false color scenes by reconstituting color by 1975 a comprehensive land-use Because of Interior's intimate parti­ images from the individual black and cipation in this experiment, we antici­ plan for Alaska's 375 million acres, white photographs. pate that the benefits. from these early thereby assisting the federal govern­ techniques will be greatest in developing ment, the State of Alaska, and the areas. I can, therefore, think of no Alaska Native Corporations with the better place to apply this technology Larry Gedney is an Associate Geophysicist selection of 220 million acres of pub­ than in Alaska .... " and is the principal investigator of Project lic domain lands. In recognizing this promising poten­ No. 12 of the University of Alaska's ERTS The basic data for informed land-use tial, and with the wholehearted support program. He is with the Silismology Depart­ ment of the Geophysical Institute, University research and planning in Alaska is very of government agencies in Alaska, the U­ of A Iaska, Fairbanks. sparse and often outdated. Therefore, niversity of Alaska proposed in 1971 an even the first task of planning in Alaska interdisciplinary program of ERTS-A

3 Vol. 5, No. 1 The Northern Engineer BACKGROUND

Along most of the highly seismically active Aleutian chain, earthquakes re­ sult as two crustal plates collide, with the southern plate underthrusting the northern plate along the line of the Aleutian Trench. Underthrusting of the type seen in the Aleutians has been thought to occur exclusively in oceanic trench-arc systems. However, as seismo­ graphic coverage in Alaska has improved in recent years, it is now being found that underthrusting is continuous from the Aleutian Trench, through Cook Inlet and along the eastern flank of the continental Alaska Range as far north as Mt. McKinley, with focal depths as great as 250 km. Contrasted with this, north of Mt. McKinley and the Alaska Range there is a broad zone of shallow seismicity at least as far north as the southern Brooks Range. Focal depths here seldom exceed 40 km, and there is no evidence of the type of underthrusting that is seen in the south, although the areas are laterally contiguous. Since 1904, eight earth­ quakes of between magnitude 6.0 and 7.8 have occurred in the Alaskan interior. Since shallow earthquakes are potentially -~--~--L-~~----~~--L-~1 KM more hazardous than deep ones because · o so roo they are closer, a matter of primary Dll SITY OF ALASKA _,.,.. IJWiWi!l~l.. ~ ..... ')g.~ ~ FIGURE 1. Mosaic of portions of six ERTS-1 images (Image ID Nos. E 1104-20554, concern to this investigation was to E-1104-20560, E-1104-20563, E-1105-21012, E-1105-21015, and combine seismic data with ERTS imagery E-1105-21021). in order to identify features with which to define the stress system responsible 150. 1° W. Prior to the 1968 earth­ large scale fracture system involving for the seismicity of the Alaskan interior. quake, this feature was not recognized many other linears. Parallel features can A logical outgrowth of the findings will as a fault. Since that time, aftershock be seen in the mountains across the Yu­ studies, source mechanism studies, and be a better understanding of seismic kon River, where they affect tributary geologic field mapping have revealed that risk across the area, with its obvious drainage, and two long lineaments are it is, indeed, a left-lateral fault. Had implications to land use planning and seen in the Kuskokwim Mountains to basic building codes. ERTS imagery been previously available, the southwest. Textural changes occur this conclusion would undoubtedly have across the latter two, although they are SOME PERTINENT FINDINGS FROM been reached long ago. The extreme lost in the alluvium of the Tanana River ERTS 1 IMAGERY sharpness of the stream incision, the at their northern ends. textural and tonal differences across the An almost equally impressive set of In October, 1968, an earthquake of valley, and the series of parallel fractures conjugate fractures intersects the Minook magnitude 6.5 occurred in the Minook in the surrounding mountains would have Creek complex at an angle of 55°, and Creek Valley northwest of Fairbanks. left little doubt. Although the left­ strikes southeast to the Alaska Range. Figure 1 is a mosaic composed of por­ lateral nature is not obvious on the This is roughly the dihedral angle at tions of six ERTS-1 images. Figure 2 Minook Creek fault, the third parallel which most brittle substances would be is a key to the ERTS mosaic; the solid feature to the east shows it quite well, expected to fail if compressive stress is lines indicate faults already mapped, with truncation of mountain lobes on applied in a direction bisecting the two while the broken lines represent faults both the north and south sides of the sets of fractures. In this case the direc­ not recognized prior to ERTS imagery. ridge line. tion is at an azimuth of about 345°, Minook Creek appears in the upper left On closer inspection, one sees that roughly perpendicular to the trend of center at approximately 65.4° N., the M inook Creek fault is only part of a the Alaska Range. The conjugate set of

Vol. 5, No. 1 4 The Northern Engineer CONCLUSIONS

While much of what has been said to this point has dealt with tectonic setting, the real point which should be made is this: It is possible, with ERTS imagery, to delineate seismically active faults which may dtherwise go unnoticed. Cer­ • tainly the Minook Creek fault (site of • the magnitude 6.5 earthquake in 1968) • would have been recognized long ago, • ..:· . •• .• had EATS imagery been available, and • •• • its freshness of appearance would have . • • labeled it as being recently active. In addition, the fact that the 1968 earth­ quake occurred within less than ten miles from the site of the proposed Ram part Dam would have been a factor in formu­ alting its design characteristics. Further, it bears pointing out that the site for the proposed Rampart bridge and trans­ Alaska oil pipeline crossing of the Yukon River is very near the Minook Creek • fault if it extends to the north, and that • • the proposed route also crosses the two • • • • strong lineaments in the upper top center • • • • of Figure 1. Particularly in Alaska, • • where these areas are remote and ac­ • • cessible only at great time and expense, • EATS imagery shows great promise as an 0 Ao aid in construction planning, zoning, and 6 seismic risk evaluation.

Key to ERTS mosaic: solid lines indicate faults already mapped, broken lines represent faults not recognized prior to ERTS imagery. * fractures is most apparent in the Ray presive stress was obtained, nearly per­ !\llountains, across the Yukon River from pendicular to the Alaska Range at this Minook Creek, but it is also visible in the point, as was true with the Minook Creek HICKEL REPORT NOW AVAILABLE mountains around Minook Creek, south event. The question which now arises is, of the Tanana River, and near the bottom "What causes the compression?" A Geothermal Energy: A Special Report center of Figure 1. The latter lineament possible explanation is that the forces by Walter J. Hickel, published by the appears to truncate the small mountain which caused the Alaska Range to University of Alaska and sponsored by near its center. "buckle," forming the great 90° bight the National Science Foundation in the range at Mt. McKinley, are still at (RANN), is now available for ordering. The implication is clearly that earth­ work. The primary cause may be axial Copies of the report can be ordered for quakes in this area are the product compression on the "ends" of the range, $4.85 apiece or microfishe can be ordered for 95 cents. The accessions number, of compressive stress radiating outward or it may be a result of deformation from around the great bend in the Alaska P.B. 216423, with the money should be resulting from collision with the north­ ~ sent to: Range, and that this stress system has westerly moving Pacific plate. Whatever United States Department resulted in the formation of a conjugate the basic energy source, it would seem of Commerce shear system with earthquakes occurring plausible that further buck I ing of the National Technical Infor­ along the individual fractures. A mech­ range would result in outwardly directed mation Service anism of this sort agrees well with the compressive stress around the outside of Springfield, Virginia 22151 fault plane solution obtained for the the bend, and would probably result in 1968 earthquake, and with one obtained the kind of conjugate fracture pattern for a magnitude 6.0 earthquake near that has been discussed. Fairbanks in 1967. For the latter event, a nearly north-south azimuth of com-

5 The Northern Engineer FIGURE 1. Map of Alaska showing lands EXPLANATION classified tor geothermal re­ sources effective December 24, 1970. Numbers corres· Geothermal• Resources Area pond to localities shown in inset. From U.S. Geological ·~ IL?I Survey Circular 647, Godwin CJ Areas Valuable Prospectively et al., 1971. ll 1. Pilgrim Springs 2. Geyser. Spring Basin and Okmok Caldera A LASKA

ALASKA'S GEOTHERMAL RESOURCE POTENTIAL By Robert B. Forbes and Norma Biggar

GEOTHERMAL ENERGY IN THE ·Geothermal Steam Act of 1970 (84 Stat NATIONAL INTEREST 1566). This report includes a map of the thermal gradient is not linear Until the last few years, the United Alaska showing lands classified for geo­ the crust to the core of the earth. States has not shown much concern or thermal resources, as of December 24, this discussion, however, we are not interest in the assessment or development 1970 (Figure 1). concerned about the deep structure of its geothermal resources. More recent· GEOTHERMAL GRADIENTS AND the earth, as the first 10 kilometers ly, however, possible world-wide energy HEAT FLOW the crust constitute the zone of econom shortages, growing pollution problems Sub-surface temperatures rise with in­ importance for geothermal energy and the awakening of a national environ­ creasing depth in the earth, but depth/ sources based on present techno! mental conscience have developed an temperature relations (thermal gradients) The average thermal gradient, as dete accelerated interest in geothermal energy. are not the same, as measured at world­ mined from drill holes, mine worki This new cognizance has been reinforced wide localities. Although the thermal etc., is about 30°C/kilometer. by the Congress, with the passage of the gradient is a rather good parameter for thermal gradient is believed to be gre "Geothermal Steam Act of 1970" ( 84 evaluating geothermal potential, heat in the oceanic rather than the conti Stat 1566), which authorizes and del ine· flow, a somewhat different value, may tal crust in areas of "normal" heat fl ates geothermal resource "provinces" and be more meaningful for inter-regional There is no significant difference in "areas," and defines leasing and regula­ comparisons. Heat flow is expressed as average heat flow as determined for 2 tive policies for federal lands. micro-calories/cm /second, and differs ocean floors and the continents. U.S. Geological Survey Circular 647, from measurements of the thermal gra­ "Classification of Public Lands Valuable dient as it considers the thermal conduc­ Dr. Robert Forbes is a Professor of ogy and has a joint appointment with for Geothermal Steam and Associated tivity of the rocks in which the measure­ University of Alaska's Geophysical 1nsti Geothermal Resources" (Godwin, et al., ments were obtained; and it also includes and Department of Geology, University 1971), presents the criteria for deter­ a time function, which expresses the rate Alaska, Fairbanks, Alaska. mining which Federal Lands are classi­ at which thermal energy or heat is being Norma Biggar is a graduate student work fiable as geothermal steam and associated conducted upward toward the surface of for her M.S. degree in Geology and holds part-time graduate assistantship with the U the earth. geothermal resources lands, under the versity of Alaska's Geophysical I Fairbanks, Alaska. Vol. 5, No. 1 6 The Northern Engine BERING ALASKA PENINSULA PACIFIC OCEAN BASIN SEA BASIN ~)) Katmai Kodiak Aleutian Seamounts t) Island Trench Sea level

Floor sediments Oceanic crust Mantle

FIGURE 2. oceanic crust and sediments, is erupted at the surface by Alaskan Peninsular volcanoes. is accompanied by the development of geothermal anomalies.

GEOTHERMAL ANOMALIES THERMAL GEOTHERMAL SPRING There are, however, "hot spots" in WELL both oceanic and continental settings, and these are critical targets in the search for geothermal energy resources. Such hot spots are usually characterized by anomalies where the heat flow is from one and a half to five times that of the world-wide average of 1.5 ( 1.5 micro­ calorieslcm2 /second). These areas, as _=-ff_-R~~~~:=-o~=ti=~=~=~~P presently recognized, are coincident with _L_9!i_ _P5~~!~~~L~!:!:_~~~~ ------belts of active or recent volcanism and orogeny. Such belts are usually located along the margins of crustal plates, where oceanic plates are being subducted under the continental margin (see Figure 2) or adjacent to spreading ridges (Muf­ fler and White, 1972). Geothermal fields that are presently being exploited or developed include those in three settings: ( 1) Along spreading ridges (i.e., Baja California), (2) Above subduction zones (Figure 2), and (3) In zones or belts that represent former or fossil subduction zones In all of these settings, it has been de­ duced that the thermal anomalies are related to molten rock that has moved up into the crust. Economically signifi­ cant concentrations of geothermal energy occur where elevated temperatures (40°C to 380°C) are found in permeable rocks at shallow depths or less than 3 km FIGURE 3. Diagram showing a hypothetical vapor-dominated, two-phase geothermal system (Muffler and White, 1972). as driven by convecting melt at depth. Meteoric (cold) water descends along fault line to hot Potentially useful thermal anomalies permeable reservoir rock where it is heated by the cooling melt. Due to lowbed density, the hot may occur in relatively dry rocks, but water ascends along another fault system to emerge at the surface as a thermal spring. A geo­ the most important resources are those thermal well has been driven into the reservoir rocks. In vapor-dominated systems,..tloiling will begin before the water reaches the surface.

Vol. 5, No. 1 7 The Northern Engineer TURBINE SEPARATOR GENERATOR STEAM, 320° F

MINERAL l ELECTRIC BRINE. POWER 320° F COOLING WATER !I \\ l MULTISTAGE FLASH EVAPORATOR CONDENSER

MIXTURE OF STEAM AND BRINE DESALTED WATER FROM GEOTHERMAL DRINKING SOURCE, l EVAPORATED WATER WATER 450°F CONCENTRATED BRINE, t t I I t I I 120° F MINERAL-SEPARATING EVAPORATORS

MINERALS EXTRACTED FROM BRINE

FIGURE 4. Multipurpose geothermal system, as designed by the UN and the Government of Chile. From "Geothermal Power" by Joseph Barnea. Copyright© January 1972 by Scie11tific American, Inc. All rights reserved. in which water occurs in the fracture and type, based on discoveries made up to (4) melting of snow on pore spaces in the host rocks. In a this time (White, 1970). runways, and geothermal system, heat is transferred 1n hot water systems, only a small (5) paper manufacturing by water from deeper sources to reser- part of the volume is steam, and the Proposed and possible applications also voirs which are shallow enough to be water and steam are separated mech- include: drilled. If rock porosity is low, the anically before the steam is routed to the ( 1) extraction of valuable movement of heated water may be con- turbine system. If heat exchange sys- metals and salts from hot strained, and heat may be stored in the terns utilizing low boiling point fluids (Figure 4), reservoir rocks beneath the less porous such as freon or isobutane are proved (2) desalinization of geothermal wa- layers (Figure 3). feasible, this will increase the number of ters (Figure 4), and Just a few years ago, most of the hot water systems which can be used for (3) refrigeration steam and/or water that was erupted by the generation of electricity. Producing WORLDWIDE GEOTHERMAL ENER- thermal springs and/or fumaroles was geothermal fields of this type include the GY POTENTIAL thought to be primary or magmatic New Zealand fields and more recent Muffler and White have estimated that water. More recently, however, based discoveries in Mexico and the Salton Sea. on oxygen and hydrogen isotope studies The vapor dominated systems produce geothermal energy is unlikely to supply and other evidence, we have learned that superheated steam with subordinate a­ more than about 10 percent of the world less than five percent of this water is of mounts of co and H s. Only three power demand, but that geothermal 2 2 magmatic origin and that about 95 per- commercial vapor dominated systems are power will be of great importance to cent is recirculated groundwater (Figure in production today, including those at underdeveloped countries, and to regions which have I imited sources of energy. 3). Lardello, Italy (since 1904); the Geysers, Although geothermal power is envi- GEOTHERMAL SYSTEMS California; and a field at Matsukawa, ronmentally attractive, because there are Geothermal systems, as discussed by Japan. fewer atmospheric pollutants as com­ White, Muffler and Truesdell (1971), DEVELOPMENT AND UTILIZATION pared to those generated by the fossil have been sub-divided into two types: Geothermal energy has been applied to fuels, effluent from geothermal power ( 1) Hot water systems, and various needs including: generation systems can pollute stream (2) Vapor dominated (dry steam ( 1) the generation of electricity, ground water systems; and federal regu­ systems) (2) space heating, lations require that such effluents must Hot water systems appear to be about 20 (3) gardening, farming and greenhouse be reinjected into a deep reservoir. If the times as common as the vapor dominated applications, dissolved components can be removed to Vol. 5, No. 1 The Northern Engineer 8 Prudhoe Bay areas, but analyses of these physical assessments of geothermal sys· produce potable water, the economics data are still in process ( Lachenbruch, are improved. Some of the dissolved tems. personal communication). Preliminary elements are economically important, and ALASKA'S GEOTHERMAL POTEN- data from a deep test hole near Eielson a system which could incorporate all of TIAL Air Force Base (Fairbanks district). how­ these processes would offer maximum Although an increasing amount of re- ever, indicates that the heat flow is utility (see Figure 4). search is being done on Alaskan vol· anomalously high at this locality( Lachen­ PROSPECTING FOR GEOTHERMAL canoes, very little is known about the bruch, personal communication). Al­ RESOURCES geothermal framework of Alaska. The though it is not known at this time Heat Flow present state of published knowledge on whether the anomaly is more than 1.5 thermal springs, for example, is not much times that of the world wide average of Although high heat flow and geother­ greater than that summarized in U.S. 1.5 microcalories/cm2/sec., the nearby lo­ mal gradient measurements are the most Geological Survey Paper No. 418, "Min­ cation of Chena and Circle Hot Springs, characteristic signatures of important eral Springs of Alaska" (Waring, 1917). and several thermal springs in the Salcha geothermal anomalies, subsurface thermal It is not surprising that there are many River drainage indicates that the Yukon data are often difficult to obtain if deep thermal springs in the Alaskan Peninsula­ Tanana Uplands deserve additional study. drill holes are not available. Localities Aleutian volcanic belt. The thermal producing heat flow values exceeding springs of northern and southeastern ALASKAN THERMAL SPRINGS 2 three microcalories/cm /sec., however, Alaska, however, are distributed through· Studies of the geochemistry, geophy­ would deserve additional study if de- out a wider range of geologic and tecton· sical characteristics and geologic (tecton­ tected. ic settings and the controls are as yet ic) setting of thermal springs appear to be There is a strong correlation between poorly understood. Based on present in­ a logical initial step in the assessment of the location\ of productive and poten­ formation, however, Alaskan thermal the geothermal energy potential of Alas­ tially productive geothermal systems and springs appear to occur in four geologic ka considering the present rarity of infor­ volcanic vents and calderas of late Ter­ settings: mation on heat flow and geothermal ( 1) On the margins of-or within­ tiary or Quaternary age. Presently active gradients. Figure 5 shows the location of granitic plutons of Cretaceous or volcanic provinces, such as the Alaska thermal springs that we have in our files, early Tertiary age (30-90 million Peninsula-Aleutian volcanic belt, are of and the relative temperature of waters particular interest. years). which issue from these springs (where (2) Along fault lines, Thermal Springs known). (3) Near Quaternary or Recent volcan­ The map indicates that the most ic fields or eruptive centers, and The temperature of thermal springs, significant concentrations of springs with (4) Areas of abnormally high heat fumaroles and mud volcanoes can pro­ the highest temperatures are located in vide valuable data on minimum subsur­ flow the Aleutian Archipelago and southeast­ face temperatures. The mere 'presence of ALASKAN GEOTHERMAL GRADI- ern Alaska. According to the sodium/ a thermal spring does not guarantee the ENTS AND HEAT FLOW potassium (Na/K) temperature curves de­ presence of an economically important We know very little about the thermal rived by Ellis (1970) and White (1970), subsurface geothermal system. However, gradient at Alaskan localities other than reservoir temperatures of some of the two geochemical parameters of thermal those located in the petroleum provinces, southeastern Alaska thermal springs spring waters appear to be related to and there are only a few reliable heat could be 300°C or higher, which suggests subsurface reservoir temperatures, inclu­ flow' measurements reported for Alaska that this province deserves further atten­ ding the silica content and the sodium/ ( Lachenbruch and Marshall, 1969; Lach- tion. potassium ratio (Fournier and Truesdell enbruch, personal communication). Even though exploitable Alaskan geo­ 1970). Thermal springs which have ~ According to Lachenbruch there are thermal systems will probably be dis­ at present only five reliable heat flow covered during the next decade, geother­ high dissolved Si02content, and/or those which deposit silicious sinter at the measurements from Alaskan localities, mally generated electricity will not be surface, are probably related to high although down and bottom hole tem­ competitive with that generated by mine­ temperature subsurface reservoirs. Gey­ perature data are available for many mouth, hydroelectric and natural gas sers are also 'a favorable indication of holes which have been drilled in Alaskan power plants for delivery to major popu­ high temperatures at depth. petroleum provinces. Heat flow values lation centers. calculated from data taken from drill If freon and isobutane generators at­ Geophysical Methods holes near Cape Thompson, Barrow and tain the desired efficiency, hot water Umiat ( Lachenbruch and Marshall, 1969) Several geophysical techniques have (rather than vapor-dominated) systems were not far from the world average, and produced encouraging results, including could be utilized for the generation of lo~ to average values ( 1.3 microcalories/ resistivity, gravity, magnetometer and electricity for villages in the more re­ em /sec.) have been reported by Sass and infrared surveys. Some geothermal reser­ mote areas. Munroe ( 1970) for the Amchitka deep voirs produce seismic noise in the form of Heat is a precious commodity in the drill holes. microearthquake swarms, and seismic arctic and sub-arctic, anq hot water from Heat flow data have been taken from surveys of thermal springs and other tar­ thermal springs or subsurface reservoirs other drill holes in the Cook Inlet and could also be applied to other needs such gets are now an essential part of the geo- RASMUSON LIBRARY The Northern Engineer Vol. 5, No.1 9 University of Alaska- Fairbanks ~- - ... 174•

~~-. - ~· 142• I r . ' c "\ /. I, ! THERMAL SPRINGS OF ALASKA ~·I \. Ga:lPHYSICAL INSTITUTE I AND GEOLOGY DEPARTMENT v UNIVERSITY OF ALASKA, 1971

Compiled by Norma 9iwr from 10UrC1S In U.S.G.S Wcrter SupPly Alper No.418, by G. A. Warinv; SIMcted U.S.G.S. ~ I oeoloaic and topooruphic maps ; ...cl ori9inal IOUfces. ~·I' • 0 I I I 50 50 100 lllll.ES i I

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C 1 F' I C ° C E

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FIGURE 5. Map of Alaskan thermal springs, as compiled by N. Biggar. This map is an updated version of the first map of as: Alaskan thermal springs which was produced by G. A. Waring in 1917. Hickel, Walter J., Geothermal Energy: A (1) The heating of residences and in the United States. If this proposed other buildings, program is approved and funded by the Special Report, (University of Alaska Press), University of Alaska, 1972. (2) Greenhouse heating systems, Congress of the United States, geother­ Lachenbruch, A. H. and B. V. Marshall, (3) Subsurface warming of agricul­ mal exploration and development will be "Heat Flow in the Arctic," Arctic,. tural land, and greatly accelerated, and Alaska will cer­ Vol. 22, 1969, pp. 300:311. (4) Snow removal from airstrips and tainly be among those states which will Muffler, L. J. P. and D. E. White, roads receive priority attention. "Geothermal Energy," The Science At present, Alaskan geothermal pros­ REFERENCES Teacher, Vol. 39, No. 3, 1972. pecting and development activities are Ellis, A. J., "Quantitative Interpretation Sass, J. H. and R. J. Munroe, "Heat Flow confined to the efforts of a few groups Of Chemical Characteristics of Hydro­ from Deep Boreholes on Two Island and individuals; as yet no vapor phase thermal Systems," Proceedings of the Arcs," Journal of Geophysical Re­ reservoirs are known to have been dis­ United Nations Symposium on Devel­ search, Vol. 75, 1970, pp. 4, 387-95. covered. We have too few data and opment and Utilization of Geothermal Waring, G. A., "Mineral Springs of Alas­ facts to make reliable estimates of Alas­ Resources, Pisa, Italy, 1970. ka," U.S.G.S. Water Supply Paper kan geothermal resources and reserves; Fournier, R. 0. and A. H. Truesdell, 418, 1917. but the discovery potential appears to "Chemical Indicators of Sub-Surface White, D. E., "Geochemistry Applied to be reasonably good. Temperature Applied to Hot Springs the Discovery, Evaluation and Exploi­ Quite recently, a group of distin­ Waters of Yellowstone National Park, tation of Geothermal Energy Re­ guished experts in various aspects of the Wyoming, USA," Proceedings of the sources (Rapporteurs Report)." "Pro­ geothermal energy field were convened United Nations Symposium on Devel­ ceedings of the United Nations Sym­ by the Honorable Walter J. Hickel under opment and Utilization of Geothermal posium on Geothermal Energy. Re­ the auspices of a grant to the University Resources, Pisa, Italy, 1970. sources, Pisa, Italy,, 1970. of Alaska from the National Science Godwin, L. H., et al., "Classification of L. J. P. Muffler and Foundation (RANN). This group pro­ Public Lands Valuable for Geothermal ---r;:~;;deli~'"Vapor Dominated Hydro- duced a proposed 10-year national pro­ S~eam and Associated Geothermal Re­ thermal Systems Compared with Hot gram (Hickel, 1972) for the exploration sources," Geological Survey Circular Water Systems," Economic Geoiogy, and development of geothermal resource~ 647, 1971. Vol. 66, 1971, pp. 75-97. Vol, 5, No. 1 10 The Northern Engineer NORTHERN CONSTRUCTION: SITING & FOUNDATIONS

By Eb Rice

SITING: SLEEP, SNOWDRIFTS & SUN This is the second in a series of articles affluent newcomer, and what he could Dr. Rice on building in the North. endure, all could endure for the sake of WORSHIPPERS status, style, and year-round occupance. The first, "Permafrost-Its Care and Choose the Site Wisely , " appeared in The Northern En· So people, native and newcomer, con­ gineer, Vol. 4, No. 2, Winter 1972) trived to exist in uncomfortable, costly, inadequate dwellings. Neither newcomer Special care is needed in siting the nor native seemed to be aware that the arctic dwelling for a number of reasons. temperate-zone dwelling was not always For example, in warmer regions the sun rises high overhead on every cloudless adapted to the Arctic. Indeed, as a A hundred years ago the inhabitants day; in the polar regions the sun is never fervent pioneer once said in an attempt of the North included mostly Eskimos, high, and in winter it rnay not even rise at to persuade me of the futility of striving Indians, Lapps and various Siberians. all. A site that fails to make maximum for comfort and economy, "When you Their dwellings were admirably adapted use of the horizontal southern sun is to their ways of life; and some of these hire out to come to Alaska, you hire out therefore one to be shunned. This is true to be a 'tough man' .... " It was unworthy, structures exhibited ingenuity and com­ in the sub-arctic as well. Even there, the mand of basic scientific fundamentals he figured, for a dweller in the last fron­ difference between south-facing slopes that deserve study and emulation even tier to be thinking of comfort. And as and other terrain is pronounced. The today. Now, however, as "southern for economy, one would be amazed at variety and health of vegetation on sun­ people" move into the northlands, and as how much fuel he could save if he never facing slopes attest to the favorable cli­ northern people seek to avail themselves removed his furs and mukluks .... Stefans­ mate to be found there. In the Fairbanks of the culture of the 70°F environment, son probably was giving much the same area-typical of the "zone of discontinu­ the design of dwellings will need to in­ message: if one lived in the old ways, ous permafrost"-slopes facing south are corporate special parameters. toughly, there would be plenty of drift­ usually without permafrost. Other slopes, wood for all. Stefansson, during the 1920's, be­ together with poorly-drained flat ground, moaned the fact that, in the American But frontier-toughness is in for a are often underlain by ice-rich ground. north, beaches once abundantly supplied change. The northern resident demands Such sites are "possible'' building sites, to with useful driftwood had become barren. and gets the comforts normal to the tem­ be sure. But for reasons of psychology Old-style houses, semi-buried and warm­ perate-zone: the flush toilet, the heated (one can see the sun in the south) as able by the heat of the occupants and bath, the centrally heated house, running well as for terrain, the south slope is much their cooking lamps, were being aban­ water, and even the attached garage. to be preferred and cheaper, too, in the doned for fuel-hungry frame dwellings This is thought to be merely our due. If long run. like those of the newly-come traders, people live like this "outside," the feeling missionaries, and government men. To is, we should live no less well in the Of course, a site is selected in the people experiencing a transition from North. North, as elsewhere, to be conveniently nomadic life to a settled existence near close to water, to transportation, or to a church, school and store, mining the Trouble is, these comforts and conven­ place of work. But once these con­ beaches for fuel was but a small price to iences were developed for temperate straints are satisfied, a dwelling should be pay for a house that could be lived in all places during many decades. To r~pro­ placed on ground that will not become a year round-one whose floor would not duce them in the northland without quagmire when thawed. Roads may be turn to mud with the coming of spring, knowledgeable modification sometimes needed, and so may waste water drainage and one which could have real windows. results in total failure, and always results areas and recreational space. A "view" in extra, unnecessarily high costs, now No matter that firewood was becoming is desirable. and forever.... I say "unnecessarily high scarce. No matter that the new houses costs" because careful attention to the There are a few other controls that cooled swiftly and bitterly when the fires particulars of the northern environment should be considered in the North, as died. No matter that drafts were frequent can and must reduce to a minimum the well. Wind in the treeless tundra is a and biting: this was the way of the inevitably high costs of building modern force to be reckoned with, and shelter dwellings in the North. And northerners from it is much to be desired. But con­ Dr. Rice is a Professor of Civil Engineering are properly becoming impatient with stant arctic winds can deposit an enor­ at the University of Alaska, Fairbanks, and, the inadequacy and costliness of the mous amount of snow, quite capable of does consulting work in both City and Regional! hasty and careless adaption of the tem­ filling completely a sheltered cove. Moral: Planning and in Arctic Engineering. perate-zone house to the frigid North. either move to the wooded taiga where

11 The Northern Engineer Vol. 5, No. 1 a dwelling for they prefer to sleep · turbed by the horizontal rays of the mer's midnight sun. My own nr<•f·,,r"n' is to place the side with the best toward the view (south), down (south), and capable of admitting noontime sun (south). But I like w dows facing all the other directions,

Shovel, Shovel, Toil & Trouble

Snow drifting can be important, snow drifts are not merely marvell sculptural elements: drifts can frustrating or even disastrous at an site. In the high arctic, winds blow tinuously over the treeless plains, winter lasts for many months. Sn drifts are not limited, therefore, by Fi~c..tre 1 availability of snow or by the wind of Beware 11 single storm: snow can accumulate +he '' c.o Z"j si +e ..•• virtually unlimited quantities; and if has to dig his roadway or outbuilding drifting is minor, or locate on exposed the arctic winter will discount the desir­ of a drift early in the autumn, the plains or ridge tops. Flood plains can be ability of having windows on the south, ject may continue every day, all used, if care is taken (proper arctic foun­ with perhaps a sheltered outdoor area as until late spring. It is therefore vital dations tend to be more or less flood­ well, to accommodate springtime sun locate roads, entryways and storage proof), but mountainous terrain may have worshippers. Conversely, newcomers tend away from the downwind side of a avalanche areas which are strictly to be to want few openings on the north side of building that obstructs the wind's avoided (Figure 1).

Which Way Should a Dwelling Face?

Woodsmen traditionally placed their tents so that the door faced east-the rising sun was expected not only to waken the occupants early, but also to I erase the night's chill. Religious struc­ / ______) I tures were also oriented with their altars l__ to the east (and thus their main entrances to the west). Mosques are supposed to face the Kaaba in Mecca. Most dwellings, if given ample land, are placed facing the "view," or at least facing downhill. What about the Arctic house? Does it /matter which way it should face?

This topic should perhaps remain a matter of personal preference, as well as a matter of semantics about what consti­ tutes the "face" of a building. There . are, however, some pertinent parameters. The first sun in the spring, for instance, appears briefly at the southern horizon. Figure 2 It is amazing with how much eagerness the daily lengthening of the sun's path is Snow Dri!ts M'lte a Dlf(er~n~--This 5He Ptan watched. No one who has lived through v/li J ~-lot f=uncfion

Vol. 5, No. 1 12 The Northern Engineer flow. And the building should, if possible, dwellers elevated their structures on piling reaching the ground, and to make certain be aligned with its narrowest face toward above the waters, partly for reasons of that the foundations are permanently the prevailing wind. Even vehicle parking defense, partly for convenience. Tropical immobilized in the frozen soil. This must be carefully arranged so as to dis- peoples in many areas elevated their means separation of the heat source (the courage drifting (Figure 2). houses on posts, too. Mostly this was for house) from the ground. Let us take this defense against rising flood-waters, but opportunity to dispel the idea that insula­ possibly also to quell somewhat the need tion alone will suffice: it will not. Insu­ to share the dwellings with livestock, lation, whatever its virtues in other con­ SO YOU'RE ACTUALLY PLANNING insects, or other casual tropic fauna. * * texts, can never stop thaw penetration; it TO BUILD IN THE ARCTIC? * can only delay the inevitable thaw. To However useful or aesthetic it may be repeat: total separation of ground from Foundations Unlimited to elevate structures above the ground in heat source is vital. Insulation alone can­ otller climates, in the Arctic where the not substitute for separation. Much as we There's a chance that your arctic gro~l)d is so often fat with i~e, it can be may abhor the idea of allowing winter to site is underlain by clean sand, gravel, or vitally necessary. To place a heated struc­ pass freely beneath our floors, there are bedrock. If so, you are lucky indeed: ture against the ground is to thaw that no inexpensive alternatives, nor are there even when frozen, such materials do not g~ound-and when ice-rich ground thaws, heave appreciably during freezing, nor likely to be. (True, any good arctic en­ no structure on it is likely to survive. settle when thawed. Cases are known gineer can devise a way to extract heat without elevating the structure, but he where massive ice occurs in gravels and The very essence of structural survival must be good indeed if his solution is to sands, of course, but they are rare enough is to prevent the buildings' heat from to qualify as exceptions-and the excep­ tions may be handled the same way as ice-rich ground is. ---- For it is the presence of high-ice­ - content ground that is the chief source of grief in the construction of structural footings. If the soil is free of massive ice, it can be thawed without settling, and you may use the same types of footings common at lower latitudes: piling, foun­ B. dation walls, slab-on-grade, or spread footings. No special arctic restraints will be needed. In fact, with such materials even the control of heat flow, which is so important for most arctic foundations, is unnecessary. And the "skirting" of buildings, which is anathema in ordinary arctic construction, actually has some advantages when the ground is free of massive ice. The Exposed Bottom C. D.

Corbusier has suggested that large buildings be elevated on massive columns (pilotis) so that the bottoms can be seen Fig. 3 by the passers-by. This, he claimed, gives a better feeling for their volume, so The. t\tZvate.d S+..-uc.iure that the structur,I!S can fulfill properly his dictum that a house is "a machine for (Drif+ins { ThowiV1.9 Co" 6'e living." The prehistoric Swiss lake- ~X'ci~ing)

*Or sub-Arctic. "Arctic" is where permafrost is continuous (See: "Permafrost, Its Care and Feeding," The Northern Engineer Vol. 4, No. 2, Winter, 1972). In the sub-Arctic you have a good chance to find a permafrost-free site, in **Elevated houses also are easy to keep cool. It is doubt­ which case, your problems are minor. ful that this virtue will have a strong appeal in the Arctic.

The Northern Engineer Vol. 5, No. 1 13 be competitive.) Why do we "expose the bottom?" Let me count the ways ....

First, a structure elevated high enough to allow the unimpeded intrusion of win­ ter between itself and the ground will remain stable, for its foundation can be easily contrived to remain frozen in place. Secon9,. an elevated structure can be installed with an absolute minimum of disturbance to a site: no alteration of drainage patterns, no massive excavation, no necessity for destruction of organic ground cover need occur (although I recommend a gravel pad over the area for fire and mud control). Third, the elevated structure is the only enclosure, other than a buried one, that will not promote severe snow drifting in the vicinity.

To these three main reasons for ele­ vating the structure, we may add the following: the elevated structure is, or can .be, flood proof. It is cheap. and easy. Sometimes "on-grade" construction can be disappointing. Its simplicities commend it for construc­ which ultimately may include the founda­ tion by inexperienced builders under Are There Alternatives? tion. Dramatic failures have occurred to difficult conditions. If, somehow, it foundations which were initially well should fail, the structure can be simply There are alternatives to the elevated designed and constructed, but which were structure but not, unfortunately, to cold and easily restored to rights. And piles, skirted by the occupants to improve bottoms. No warm surface can be juxta­ posts, and piers of a suitable type for comfort and utility. *** posed to icy ground without causing the foundations are comparatively easy to ice to melt, even if separated by generous transport-even by air-to most arctic To summarize: despite the cold hazard layers of insulation. Where loads are locations (Figure 3). to the exposed bottom of a building on a heavy and perhaps concentrated, as in foundation of piles, posts, piers or pilotis, Unluckily, an exposed bottom can aircraft hangars and heavy-equipment re­ there are many virtues that recommend it get cold. Maladroit designs have resulted pair shops, elevated floors are not so for arctic construction. Among these are in floors so uncomfortably cool as to practical. In such cases engineers have two salient ones: ( 1) the heat segregation encourage occupants to "skirt" structures devised ways of keeping a floor's under­ inherent in elevated construction protects with some kind of sheathing to protect side suitably cold while still carrying the against the leakage of heat from the struc­ the "crawl space" beneath the building heavy loads directly to the (frozen) ture into vulnerable, ice-rich ground, and from winter's cold. Such skirting can be subgrade. (2) pile foundations promote the unim­ used, carefully, for structures in the high In Thule, Greenland, for example, the peded flow of arctic winds, so that serious design engineers provided a heated hangar arctic, where the ground temperature is snow drifting is discouraged. Together quite low. But skirting can be disastrous for large aircraft. It is of more-or-less with simplicity, flood proofness, econ­ conventional slab-on-grade construction, in areas of marginally warm permafrost, omy, snowdrift control, and environ­ but the slab is special. The concrete floor as at Fort Yukon, Bethel, or Glennallen. mental suitablity, these two make the is underlain by strong foam-type insu­ In these areas, the frozen ground is only a thermal isolation of a dwelling by eleva­ lation. The insulation rests on another degree or so colder than the thaw point; tion a nearly unbeatable technique for concrete slab on a thick gravel pad. The and there is very little reserve to accom­ construction over icy terrain. **** (See key to structural security of the design modate heat inputs in addition to the Figure 4.) lies in this under-pad of gravel. It is filled summer flow. So a thaw bulb forms

***I regard this as an architectural or engineering failure: if the design leaves occupants so uncomfortable that they ****If you've wondered why there are so many foot~otes are impelled actually to do something, the failure is no less in this part, contemplate this: no engineer would be likely serious than if the foundation design had been inherently to recommend an exposed bottom (with piles) in the Arc­ faulty. tic, unless he had an extra *.

Vol. 5, No. 1 14 The Northern Engineer For marine construction they are .ubiqui­ tous: most piers are built on piling be­ Concr<2/e slab cause it is comparatively cheap and quick, and because pile construction minimally obstructs the passage of waves and cur­ rents. For arctic work, piling is popular because it is the simplest way of pro­ viding thermal isolation of a heated struc­ ture, and also because it is strong and permits easy passage of drifting snow or flood water.(Figure 6). Piling is placed in many ways: "pile­ driving" is popular for wood, steel, or concrete piles in soft ground. What is not commonly realized is that steel piling (both open-end pipe piles and H-piles) can be successfully driven into fine­ grained or peaty permafrost. Piles driven into ice-cemented gravel, however, oc­ casionally come to grief (Figure 7). Vibratory pile hammers are showing con­ siderable promise in this area, although double-acting steam, air, or diesel pow­ I ered hammers also work well, if extra \ large. \ __v__.••·- Commonly, piles of wood or concrete ' ---- have been placed in holes melted into the frozen ground by steam, hot water, or electricity. (They cannot be driven into frozen ground.) Ideally, the hole should Fig. 5 be thawed swiftly so that its width is but little more than the thickness of the pile. ' The pile may then be driver. into the hole Co)d- Botforr1ed Slab with conventional pile-driving equipment. A Possibly more piling has been placed in this way; than in any other fashion in the with large culvert pipes, laid side by side,. tropic and temperate-zone construction Arctic. And yet, it is not the best way: and so arranged that, in winter, cold air they are often used but rarely visible, depressing· failures have occurred because will flow through to cool and protect the located as they usually are beneath the structures were placed on such piles be- underlying ice from melting. In summer, lowest columns of a bridge or building. the pipes are kept closed to minimize the .,,EO of'lt.J heat flow into the subgrade during the fJ.." oo short summer. In several Alaskan instal· OI;,I{'JfJ ~rio r ,6 lations a similar technique is used: heat 13 which finds its way through the insulation under a floor is intercepted by a lacework of mechanically refrigerated tubes. The heat is dissipated harmlessly above ground. In a similar fashion, one-way heat tubes and their modifications show considerable promise in using "natural cold" to protect the underlying perma­ frost from thawing (Figure 5).

PILING

Placing the Piles Fig.6 Piles are posts or poles placed in the T~picol ?il~ Four'lc\otiol"\ ground to serve as structural supports. In The Northern Engineer Vol. 5, No. 1 15 fore they had time to freeze back. It is augers, if equipped with very sharp teeth, be different. The active layer may be obvious, upon reflection, that a column will penetrate frozen silts, sands, peat and thick-up to five meters-and the perma­ of hot muddy water, filled or not with a ice quite swiftly. (No cheap and easy way frost is warm, weak and willing to thaw. pile, is a heated pocket destined to of penetrating ice-cemented gravel or The task of designing a foundation in enlarge prior to finally freezing. If only bouldery ground is known to me, and in such locations is formidable. Decay may surface-freezing has taken place, as often such ground the driving of piles into be a problem, lateral loads may become happens in the ,Arctic, a sturdy looking, thawed holes will probably remain the significant, and, worst of all, "heaving" solid-feeling pile may be built upon, tn best way for some time to come.) may be so severe as to warrant elaborate

FIGURE 7. Avoid driving piles into ice-cemented gravel.

the belief that it is solid. Often it isn't, Some engineers recommend backfil­ and expensive countermeasures. and the results are disappointing. This ling piling with a slurry made of sand, In such places a pile foundation is the happened many times during the con­ silt, and water. Some argue that the pro­ preferred type: in fact it is difficult to struction of the DEW (Distant Early portions and quality of sand and silt are think of a reasonable alternative. In the Warning) Line in the north of Canada and important: they write elaborate specifica­ selection of a foundation, the designer Alaska in the early 1950's; and later, tiC>ns governing the mixing and placing of first assures himself that it will handle the during the construction of I nuvik, NWT, such backfill. Doubtless, where a builder's expected loads. Then, especially in the Canada, the hazard was considered so crew cannot be trusted to compact pro­ sub-Arctic, he must consider the other real, and the freeze-back time so uncer­ perly the annulus around the pile, the problems: tain, that it became customary to place slurry method may have merit. But I Will it Heave, Rot, Melt, Settle, or Lean? piling in the fall of the year, so that would favor, in that case, a backfill of freeze back would be surely complete in free-running sand or gravel. This is easier, One way to make certain that a foun­ time for spring construction. requires no special equipment, and is dation does not do any of these evil much cheaper. It is just as good, or bet­ A third way of installing piles is to things is to keep the piles frozen in ter, and what's more, dry fill rarely adds place them in drilled holes. This method, place, as they would be in the high Arctic. appreciable heat to the ground. where applicable, has nearly superseded This can be done through extraction of others. A hole, somewhat larger than the Immobilizing the Pile or Pole heat throughout the summer, or by so pile itself, and deep enough to extend thoroughly overcooling the ground in the well below the maximum expected thaw In the high Arctic, the piles can be winter that there is insufficient time in depth, is drilled into the permafrost. The short, and they act as end-bearing piles. the summer to complete the thawing of pile is then simply dropped in the hole, Their depth of burial must be sufficiently the foundation area. There are several braced in place, and backfilled with far below the depth of maximum thaw ways to accomplish this, all of which can material previously excavated from the that they will give adequate lateral sup­ be expensive. But sometimes a perma­ hole, or with gravel, or other selected port (for wind or earthquake) during the nently frozen condition of the foundation material. Since no appreciable heat is thawing season. No further precautions is the surest solution, and often it is inserted into the ground, the pile is ready need be taken, as a rule, for in such re­ cheapest among the alternatives. Methods for use as soon as its backfill is com­ gions the active layer is thin and the of achieving a permafrost-stabilized foun­ pacted. permafrost is cold and strong. Decay of dation range from mere snow removal and The holes are usually drilled by auger­ wood is slow and rarely critical in the shading, through provision for massive type drills mounted on vehicles for easy high Arctic. heat extraction in winter, to elaborate portability and convenient setup. Such In the sub-Arctic, though, things can refrigeration systems. In general, heat Vol. 5, No. 1 The Northern Engineer 16 extraction m winter through the use of automatic thermal valves (the Long "Thermo-valve," the Thermodynamics "Frost-Tube," or the MacDonnell-Douglas COLD \.IQUIO "Heat Pipe," for instance) is possible. SINKS A somewhat less sophisticated, but still effective, way of using winter's cold to maintain summer permafrost is ·'"Rice's f HEAT Ol.tT "Brute Force" system-a simple arrange­ i\ (PuMP z ment of pumps, pipes and heat exchang­ TO ~Uti ers which is operated in winter and shut O"'ii.V IN down in summer (Figure 8). ":a:~~ WIN Tilt) Where a permanently-frozen footing is impractical, other means of stabilizing ~ A. 8'. c. piles must be used. Permanently thawed LONG THERtiiO­ 6ALCU FrlOSI TU8£ RICE S'r'STEM footings involve no special problems in VALVE areas where there is no permafrost. But oftentimes foundations in the sub-Arctic can n~ither conveniently be kept frozen Fig. 8 nor thawed: there will be an active layer and this spells trouble. With the periodic O~E'-WAY HE.AT FLoW KEE'PS freezing of material near the foundation there can be serious yearly deformation (Figure 10). If some kind of mechanical freeze, or due to frost heave. This causes a pheno­ anchor is attached below the active layer, (2) Never let it thaw. Or, menon known as "frost-jacking" of piles, resistance to heaving can be enormously (3) Anchor the pile against uplift, and which is an insidious process which causes increased. Or if some method is employed (4) Break the bond in the active layer, piles to heave upward during the cold to make the pile too slippery for the fro­ or season, with' no countervailing tendency zen ground to hold, the heaving forces (5) Place piling only in non-frost­ to return to the original level when can be reduced. So there are really five susceptible soil thawed (Figure 9). things that can contribute to safety against pile jacking: If it's a wooden pile, of course it should The mechanism is simple enough, yet ( 1) Never let the surrounding soil be placed big end down. not widely understood. Figure 9a shows the freezing front beginning to penetrate the frost-susceptible ("heavable") ** *** soil. Ice lenses are forming, forcing the frozen layer upward. The pile, which is frozen solidly to the heaving layer, goes up with it. This process goes on, and the pile continues to rise so long as ice layers continue to form. In Figure 9b the heaving is complete, and in Figure 9c summer has come, thawing the upper layers. Excess water rises to the surface and is lost, and the thawed soil settles back as the thaw penetrates. By the time the thaw penetrates to the bottom of the active layer, the heaved soil has recon­ solidated, and it grips the pile anew D- (Figure 9d). But the pile is now elevated A. B. c somewhat, for until the last few inches of (;ARLY WINTER SPRIN~ 5ui"''MER .AUTUMN frost were melted, it was held in its raised positon by a frozen grip. This jacking process is the chief source Fig.9 of deformation of pile footings. For­ I-lOW rROST -JACKING I-I.APPE"N S tunately, something can· be ·done about it

*****Siltless soil is usually non-frost-susceptible, and non-troublesome. The Northern Engineer Vol. 5, No. 1 17 Boncl­ brcQ\r.,·,"~ pl a s-h'c. ""'nap IHE-

, r- or I .~· wecl~es Shi~'s r_J_ ~ tor --• I ' ~ adjustmcnf f I 'Po.ds ~a'j be t I or con tinlA.Oc.\ S I ~Anc"-ot" the soil. Posts are erected on the pads, DENOUEMENT 1b&low and the building is constructed on the posts as if they were piles embedded in The Site's Right .... ~ , ...ac.·hve laYer the world. Figure 11 shows how this When the problems of psychology, ~ t( ) might be accomplished. view, radiation, drainage, drifting, flood­ ...... - ing, convenience, and utility have been '---~ Are There Problems? reconciled, and the designer is ready to begin his plans, and such features as roads, Fi~, lO If post-and-pad footings are used over water supply, and waste disposal have "bad" ground, where heave or settlement been agreed upon, it is time to think of can be expected, then of course, the selecting a foundation type. How To supported structure will heave or settle. This will rarely be uniform, so the build­ How Firm a Foundation? .'' JAC.K-PROOF II ing will also wrack. The key to successful use of such a footing is therefore ( 1) to In the Arctic and sub-Arctic one can p,LcS select "good" ground-that is, bedrock or be certain that a solid foundation is pos­ iceless sand or gravel, or (2) to provide sible if underlying permafrost stays fro­ POST-AND-PAD: A "SOMETIMES" the means and personnel to monitor the zen. This usually means that the struc­ SOLUTION level of the building's floor and adjust it ture should be isolated from the ground as needed (which is to say, often). by piles, piers, posts, poles, or pilotis to Sometimes, piling is impractical. May­ This will require underfloor access for prevent heat input to the foundation soils. be there is no equipment available to drill jacking equipment, together with shims, Once this decision is made, subsequent holes. Possibly piling is too bulky to ship wedges, or turnbuckles to adjust the decisions must be made about how to with the transport available (for example, structure to its shifting foundation. I make sure a cold bottom does not cause to a remote hunting lodge served by small suggest that architects and engineers, in a cold floor, for a cold floor may be airplanes only). Or perhaps the ground is choosing such a foundation, do so with hazardous to your toes, and, ultimately, unsuited to a foundation of piling. In caution-one is entrusting the integrity of to your structures. such cases, where separation of structure his structure to the whims of a capricious Next Time and ground is needed, post-and-pad Nature, and still more to the. skill, construction can be used. In this kind of In the third installment of this series sobriety, or availability of some future on building in the North, we will attempt foundation, pads (usually of timber) are workman. placed on, or in the top few inches of, the inside story on insulation, and on windows, walls, doors and floors. * Vol. 5, No. 1 mation of ice. Therefore, accurate ice surveys are essential. Ice is a polycrystalline material which ICE CROSSINGS exists on earth very close to its melting point. It is visco-elastic in nature, and by Edwin M. Rhoads varies greatly in its mechanical proper­ ties, especially with relatively minor Historically, bodies of water have The equation was derived fro"" the changes in internal temperature as con­ trasted with other construction materials been at once important avenues of com­ physical principles of heat transfer and (Barnes, The behavior of ice munication and serious obstacles to over­ expresses the increase in thickness of 1928). has intrigued scientists for centuries, and land movement. It is not surprising that the ice in relation to the atmospheric the art of building bridges extends back temperature regime below the freezing while much study remains to be done, thousands of years. Even more ancient point (Jumikis, 1966). The latter is considerable practical knowledge has is the use of ice as a natural means of commonly expressed in degree-hours evolved. The tactical value of ice has crossing water obstacles. In today's or degree-days below freezing. been exploited by commanders from ancient times, and military engineers world of sophisticated modes of trans­ Stefan's equation: H = 0(..re­ portation, advantage is still being taken where have developed crude but adequate of nature's deep freeze to facilitate the h is the ice thickness in inches "rules of thumb" for weight and spacing movement of people and cargo. A e is the number of degree-days of loads on ice. Application of mechani­ number of techniques have been devel­ below freezing (°F) cal theory supported by field and labora­ oped through experience, and the ap­ 0( is a coefficient representing tory tests resulted in significant advances plication of science and technology, for the combined effects of local in the knowledge of ice as structural improving upon the natural freezing conditions such as snow material (Assur, 1956; Leggett, 1958; process to increase the capacity and cover, river conditions, and Kingery, 1962; Nevel, 1967; Weeks and duration of ice crossings. water properties. Average Assur, 1969; Gold, 1971; extensive bib­ values are shown in Table 1. liography contained in these references). ICE AS A BRIDGE MATERIAL The Russians developed considerable ex­ Table 1 (AFM 86-5) pertise during the years of World War The oldest and simplest method of Conditions· II (Lagutin, ed., 1946) as an outgrowth preparing ice crossings is to let nature 0.95--0.90 Practical maximum for ice of extensive use of ice as highways and take its course. Crossing sites are not covered with snow as foundations for railroad tracks. In selected with an eye to approaches and 0.80--0.75 Arctic sea ice (first ap­ the forest regions of Canada, Scandinavia reasonably quiet water. Often trans­ proximation) and Russia, lumbering is practiced in portation routes in northern countries Medium-sized lakes with winter specifically to exploit ice and for both man and wild life are pat­ 0.80--0.70 moderate snow cover frozen ground as a base for transport terned after the habitual ice crossing Bays with brackish water and stockpiling of heavy loads (Duff; sites used in winter. From experience, 0.70--0.65 0.65--0.58 Rivers with moderate flow 1958; Ager, 1961; Korunov, 1956). the beginning and end of the ice season When ice provides a principle means is pretty well known, and after pre­ Stefan's equation and others of a of supporting transportation, it is highly liminary testing for adequacy of the ice similar nature are approximations only desirable to use it for the longest pos­ strength, the crossings are used until the and do not take into consideration the sible time between freeze-up and break­ advent of spring. Animals are quite many factors influencing the complex up. This involves attaining the required wary about their footing, but man, being thermal processes involved in the for- ice strength as early as possible in the less sensitive to his surroundings, often plunges through. The physical and mechanical proper­ ties of ice and the influence of climatic factors on its formation and duration have been studied by scientists of north­ ern countries as a matter of practical Snow Ice SNOW necessity. When meteorological condi­ tions are known, prediction of the growth of the ice cover over bodies of water can be made with some degree of accuracy by mathematical expressions ...WATER such as that developed by Stefan in 1890.

Edwin M. Rhoads is a Research Assistant with the Mineral Industry Research Lab and is currently a graduate student working for his F I G U R E l. C R 0 S S-SE C T I 0 N of ICE C 0 V E R M.S. degree in Northern studies at the Uni­ versity of Alaska, Fairbanks.

The Northern Engineer Vol. 5, No.1 19 season, and frequently extending it as long as possible in the spring (Wolff,

1940). FIGURE 2 . ICE GROWTH The onset of freezing of rivers and "] lakes is generally accompanied by snow fall, and the newly formed ice cover is under a blanket of snow. The ice sags c: and frequently cracks under the ad­ ·- ditional weight and upwelling water ., 40'1 saturates the snow, which freezes into a c: v I porous ice, "snow ice," of lesser strength ·- ..c than the clear "black ice" formed from 1- water (Figure 1). Snow is an efficient ., insulation material and as it continues to 201 accumulate, extraction of heat from the water body to the atmosphere is re­ tarded . Consequently, the build-up of the ice cover is slowed, as indicated 2000 3000 4000 5000 6000 empirically by the coefficient 0(. for a Degree-Day,(°F) snow-covered lake in Table 1 above. Preparation of crossings by simply bla­ CLEARING SNOW FROM ICE CROS­ crossing at Pike's Landing, Fairbanks, to ding off the snow is economical. It is SINGS provide additional safety for the users frequently done on convenience or short­ (Figure 3) . term crossings such as the Chena River The simplest way of getting more heat transfer is to remove the snow. As soon as the ice will support a light weight tractor or oversnow vehicle equip­ ped with a blade or pulling drag (six inches or so). the snow is cleared off. As the ice becomes thicker, larger snow removing equipment may be used. A layer of compacted snow, two to three inches, is left on the ice surface to protect it from chipping. This is parti­ cularly necessary at extremely low temperatures, as ice becomes quite brit­ tle (Rose and Silversides, 1958). Except for the "snow ice" described above and that accumulated from freez­ ing rain, ice forms at the bottom of the ice layer. Therefore, as it increases in thickness, the rate of heat extraction is retarded and the ice accumulation grad­ ually slows down. Even with the snow removed, there is a limit to the increase in ice thickness, depending on the length and severity of the freezing period. To illustrate using Stefan's .equation (eq . 1) and Table 1, assume a lake where the annual freezing index is 3600 degree­ days (°F) and a moderate snow cover ( eX. = 0.75), h =0.75./3600 = 45 inches With snow removed,~ = 0.95, h = 0.95"3600 =57 inches. Theoretical rates of ice growth under the above conditions are shown in Figure 2. FIGURE 3.

Vol. 5, No. 1 The Northern Engineer BUILDING UP THICKNESS OF ICE CROSSINGS

Floodfng the initial surface with wa­ ter, and letting it freeze in layers permits a more rapid build-up and a greater ultimate thickness (Figure 4) . Well known in the lower states as a method of constructing skating rinks, it is a stan­ dard techni,que in the Canadian and Scandinavian logging industry (Ager, 1961; Rose and Silversides, 1958). In both areas logs are transported over snow or ice roads, and stacked on ice landings on a lake or river to await the spring thaw. The landings and necessary ice bridges are prepared in late fall or early winter to transport loads up to 50 tons and to stack cordwood at a loading den­ sity of 1100 tons per acre. Because of the short winter hauling season (60 to 75 days in eastern Canada), it is essential to have the ice landings available as soon as possible. The snow is compacted by men on snowshoes as soon as it will bear them, then the area is dragged using a horse or light oversnow vehicle. For bridges, a strip 150 to 200 feet wide is FIGURE 4. Flooding river ice for ice crossing, Tanana River south ot a1rbanKs. prepared. Pumps of 30,000 to 40,000 motors are very effective for spreading ture's engineering is by the use of rein­ gallons per hour capacity are used to water. A 10 horsepower outboard mo­ forcing and insulating materials. Freez­ flood the cleared areas. Generally lifts of tor mounted on a small sled splashing ing log stringers and cross members in two to three inches per day are built up water from a rectangular hole cut by a place, filling intervening spaces with in this manner, normally up to a total of chain saw can spread up to 130,000 brush and flooding the structure with 36 inches, considered adequate for the gph (Hughes, 1960). Two pumps and water is a common practice. Excellent above-mentioned load ings. Improved one power auger or chain saw can flood railroads have been constructed on ice pumps of higher capacity and less weight, a large sized bridge site daily with ease. this way. In many parts of Sweden, Rus­ based on the principle of the Archimedes sia and northern Canada, reinforced USE OF SUPPLEMENTAL MATERIALS screw, are being used now (Rose and bridges of this type are built routinely Silversides, 1958) and even outboard Yet another way to improve on na- (Wolff, 1940; Korunov, 1956; Rose and Silversides, 1958). Even south of the subarctic zone, safe ice crossings are possible with judicious assistance given ~------25 ft------1 to the available freezing index. A rein­ forced ice bridge was .successfully em­ 2 x 1 2 pIan k s placed over the tmjin River in South Korea in January, 1963 (Carnes, 1964). The bridge was 485 feet in length, with a 25 foot roadway. A four inch matting T1 of rice straw laid between two rows of 20" ..L. four to six inch logs formed the basis of the bridge beam. After flooding the rice straw, successive layers of brush ~~~==~-==-R=I-~~=- ~~R--_IC_E----~--~- - -~--~-~- :- ~__jl_ were frozen in, flooding about two in­ ches at a time until about nine inches of reinforced ice had been built up. The total ice thickness eventually reached FIGURE 5. IMJIN RIVER ICE BRIDGE 20 inches. A treadway of two by 12 inch timbers cleated together com­ pleted the structure (Figure 5). The

The Northern Engineer Vol. 5, No. 1 21 extra margin of safety when the river level drops. The drop in water level leaves air voids near the shores and causes cracking as the ice sags. When it is desired to use an ice bridge up to the last possible moment in the spring, the ice surface may be pro­ tected from atmospheric and solar heat­ ing by a layer of insulation. In Sweden, -~ -- -~-. - - it was common practice to use ice' bridges right up until ferries were able to operate, thereby minimizing the disrup­ tion in transportation usually associated with break-up (Wofff, 1940). A four to six inch layer of sawdust or wood shav­ ings makes this possible (Figure 8). Normally, the insulation is laid down in late winter, when the average daily tem­ perature begins to rise. COMPARISON OF TYPES OF ICE CROSSINGS To compare the several techniques discussed above for application to a FIGURE 6. Ice Bridge across Yukon River. specific situation in Alaska, the site of bridge remained in operation for about tank. Total gross weight was 200 tons, the proposed Trans-Alaska 48 inch pipe­ five weeks when operations were termi· but the crossing was made without diffi­ line crossing over the Yukon River 20 nated by a warm spell toward the end of culty. Each year less than 30 days of miles west of Stevens Village will be February. The maximum load- sustained construction time were required to com­ used as an example. The length of the by the bridge was a light tank M41 A 1 plete the bridges; however, the date of crossing is 1800 feet, and the maximum weighing 20 tons. According to ice completion is dependent on the extent gross load crossing the river is asStJmed strength tables published by the De­ of continuous cold weather. According to be 100 tons. A design ice thickness of partment of the Army, this tank requires to Bruce Robinson, Alaska Department 60 inches was selected for this load, 25% inches of unreinforced ice for safe of Highways, the reinforced design was derived from tables developed by the river crossings (Dept. of the Army, selected by the Department of Highways U.S . Cold Regions Research and Engin­ 1971 ). over straight flooding to provide an eering L,aboratory for ice airfields (Assur, During the winters of 1968-69 and 1956 and Dept. of the Air Force, 1969-70, the Alaska Department of Highways constructed a reinforced ice bridge across the Yukon River in the vicinity of Stevens Village to support the transport of heavy equipment and sup­ plies 11orth to the Prudhoe Bay oilfield . -40ft--l (Figure 6). These bridges (2000 feet 10-12 ' long with a 40 foot wide roadway) were 4-6"logs Packed snow I built using four longitudinal rows of I logs as stringers, with brush packed be­ tween them and flooded with water in successive layers. The roadway was corduroyed with smaller logs, and a layer of compacted snow maintained on RIVER ICE the surface (Figure 7). The design total thickness of river ice and the built-up section was five feet, calculated to sup­ port gross loads up to 1 00 tons. The maximum load to cross the bridge was a double trailer rig carrying two Cater­ FIGURE 7. Reinforced Ice Bridge , YukonRiver pillar D9 crawler-tractors, a Caterpillar (not to scale) Traxcavator loader, and a 10,000 gallon

The Northern Engineer Vol. 5, No. 1 22 (a) (b) Cross Section of~ Plank Bridge: Cross Section of~ Bridge: 1- Strong ice, 1-m thick at ferry 1- Strong ice . 2- Stringers 10-cm by 15-cm, 5 pieces, 60-cm center-to 2- Snow wall, 50-cm high, water soake~ to.bu1ld ice wall center 3- Ice layer, built by pouring water 1n l1fts 3- Floor planks, 7.5-cm by 10-cm, 4-m long, 2-cm between 4- 10-cm of sawdust insulation planks 5- Branches to mark edge 4- Sawdust insulation, 15-cm thick 6- Snow cover, built up during w~nter~ to be plowed away 5- Fir or birch poles as edge markers in later winter before the br1dge 1s used 6- Planks 7- Edge markers

FIGURE 8, a & b. Swedish Ice Crossings.

1958). The climatalogical regime for our model was derived from existing National a. Measured thicknesses: I Weather Service records of average daily A. --max temperatures in the vicinity of the site cleared section 60 0 -avg h=60" or at comparable locations on the Yukon C --min 5 March River for the winter of 1969-70. An )( --1 l/2 to 2 ft. snow cover 71~ ice crossing was established in February, I 1970, by clearing the snow. Figure 9 is I a graph of the degree-days of freezing on a square root scale and the recorded I I ice thickness build up. It was observed that the accumulation of naturally frozen I ice under cover of the seasonal snowfall I reached a maximum of 34 inches, there­ fore preparation of a crossing site by in­ I ~~ / creasing the ice thickness was necessary. / An assumed growth rate of the natural / "' ice cover was established by laying a (/ / / straight line from h = 0 at the beginning / D / of freeze-up. Note that the slope I 0(, = 0.49 correlates reasonably well to / 20 / "" 0 the value of 0(. in Table 1 for rivers I / I / with moderate flow ( o<:. = .58 to .65). / / I / The most economical approach is to I / remove the snow cover as early in the 10 jrf// season as possible beginning with light f/ tracked vehicles. In order to estimate the // 28 31 End of freezing probable rate of bare ice growth, a line Freeze-over ~0 31 31 Feb Mar~3 May 72 parallel to the straight line fitted to the ,...,17 Oct 71// Oct ~"' recorded average thicknesses along the 100 0 20 40 1970 ice crossing was laid out in Figure 9 from the point where the natural ice was six inches thick. We read then that Crossing the crossing would not reach the design FIGURE 9. Ice Thicknesses, TAPS

0 n Y u k o n R i v e r, 1 9 7 1 - 7 2

The Northern Engineer Vol. 5, No. 1 23 thickness until around the beginning of in northern countries. The simple snow­ Hughes, J. R., (1969), "The Outboard March, and would be usable for heavy cleared crossing has the advantage of low Motor -- The New Ice-Making Ma­ loads until near the end of the freezing cost, but is limited in capacity and dura­ chine," Pulp and Paper Magazine of season, a period of roughly eight weeks. tion of use. The flooded crossing is the Canada, Woodlands Section, Febru­ The total cost would be on the order of most efficient in terms of initial cost ary 1960. $1000. relative to traffic capacity. The rein­ Jumikis, Alfred R., (1966), Thermal Soil To make use of the crossing earlier, forced bridge is the most costly. but can Mechanics, Rutgers University Press, building up ice on the surface is re­ be used later in the spring if properly New Brunswick, N.J., 1966. quired. The easiest way of doing this, as insulated, and offers a possible margin of previously described, is by repeated safety over unreinforced ice. Kingery, W. D., ed., (1962), Ice and flooding. After clearing the surface and This brief discussion by no means Snow, Massachusetts, Institute of drilling holes about 200 feet apart along considers all possibilities for the prepara­ Technology Press, Cambridge, 1963. the centerline, a crew of three to four tion of ice crossings. For example, the Korunov, M. M., ( 1956). Load Carrying men with two 30,000 gph pumps could addition of fibrous materials within the Capacity of Ice for Timber Transport, flood the crossing site daily with three ice has demonstrated in the laboratory a NRC Technical Translation 863, Na­ inches of water for a width of 200 feet. considerable increase in ice stren~th tional Research Council of Canada, I Beginning with six inches of ice on 10 (Coble and Kingery, in Kingery, 1963). Ottawa, 1960. October and allowing 20 days for pre­ Fiberglass-resin mixing and spraying e­ paration, the crossing could be ready for quipment developed for preparing expe­ Lagutin, F. L., ed., (1946). Data on the traffic by 1 November at a cost of dient landing fields in South Vietnam Problem of Ice Crossings, TL 25, around $3000. A useful period of nearly might be adopted for spraying a mixture Arctic Construction and Frost Effects six months can be anticipated. of fiberglass and water. The choice of Laboratory, Office of the Chief of The third type of construction, a methods used, as the case with any Engineers, Boston, Mass., December reinforced bridge, is the most costly in other engineering decision, will depend 1954. terms of time, equipment, materials, and on the requirement, the economics, the labor. Although construction time conditions of the particular situation, Leggett, R. F., (1958), "Conference on , would not be much longer than that for and the resourcefulness of the project the Bearing Strength of Ice,'' Trans­ the flooded crossing, materials must be engineer. * actions, Engineering Institute of Cana­ assembled, and the use of construction References da, vol. 2, no. 3, September 1958. equipment must await an adequate initial Ager, B. Hison, (1961 ), "Snow Roads thickness of around 12 to 14 inches for and Ice Landings," Pulp Paper Maga­ Nevel, Donald E., (1967). Bearing Capa­ light truck-mounted equipment. By zine of Canada, Woodlands Section, city of Ice Sheets, Technical Note, clearing with light tracked vehicles ini­ July, 1961. U.S. Army Cold Regions Research tially as described above, the ,power Assur, Andrew, (1956), Airfields on and Engineering Laboratory, Hanover, equipment could begin operations by Floating Ice Sheets, SIPRE Report N. H., 29 November 1967. around 20 October. Based on the High­ 36, Snow Ice and Permafrost Research way Department experience, a crew of Establishment, Corps of Engineers, Robinson, Bruce, Maint. Division, North­ 20 men could complete the bridge in U.S. Army, Willamette, Mich., Janu­ ern District Alaska Department of about 25 days, at a cost in the neighbor­ ary 1956. Highways. hood of $25,000. Traffic could move Barnes, Howard T., (1928). Ice En- from mid November until around the gineering, Renouf, Montreal, 1928. Rose, L. B. and Silversides, C. R., (1958), beginning of May. If necessary, the "The Preparation of Ice Landings by traffic period could be extended by ap­ Carnes, Julian H., Capt., (1964). "Ice Pulp and Paper Companies in Eastern plying a layer of sawdust, wood chips Bridge in Korea," Military Engineer, Canada," Transactions, Engineering or other insulation before any thawing No. 370, March-April 1964. Institute of Canada, vol. 2, no. 3, occurs, as in the Swedish practice de­ Department of the Air Force, (1958), September 1958. scribed earlier. The reinforced bridge has Ice Airfields, AFM 86-5, Washington an added margin of safety in the event of D.C. 1958 Weeks, W. F. and Assur, A., (1969), unexpected cracking such as that en­ Fracture of Lake and Sea Ice, Re­ Department of the Army, (1971 ), North­ countered when the water level lowers. search Report 269, U.S. Army Cold ern Operations, FM 31-71, Washing­ The log stringers and fibrous material Regions Research and Engineering ton D. C., 21 June 1971. along the crack zone might make the dif­ Laboratory, Hanover, N. H., Septem­ ference between falling through or not. Duff, C. H., (1958). "Ice Landings," ber 1969. Certainly the overload factor was clearly Transactions, Engineering Institute of demonstrated on the State Highway Canada, vol. 2, no. 3, September bridge. 1958. Wolff, A., (1940), Winter Roads on Ice, In summary, the expedient procedures Gold, L. W., (1971). "Use of Ice Covers TL 23, Arctic Construction and Frost for Transportation," Canadian Geo­ for improving ice crossings described Effects Laboratory, Office of the herein are practical and used extensively technical Journal, vol. 8, no. 2, May Chief of Engineers, Boston, Mass., 1971, p. 170. April 1954. Vol. 5, No. 1 The Northern Engineer 24 significant coking qualities, as well as low TRANSPORTATION OF ALASKA'S moisture, ash and sulfur content. NORTH SLOPE COAL MARKET At the present time, Japan is the most by Paul R. Clark favorable market for coking coal from The following is a summary some of which is coking coal. This coal Alaska (Japanese Government regulations of the more detailed report, may be in an advantageous geographical restrict the importation of steam coal). "Transportation Economics position to one of the world's largest im­ Alaskan coal has a geographical advantage of Coal Resources of North­ porters of coking coal, Japan. This over many of Japan's other coking coal ern Slope Coal Fields, Alas­ study was undertaken to determine the suppliers;this advantage could result in a ka," M.S. ~hesis, 1973, sub­ economics of transporting coal from favorable competitive position through mitted to the Mining Engin­ these coal fields to Japan. lower shipping costs. eering Department of the Figure 1 shows the location of the University of Alaska. The northern coal fields. Barnes ( 1967) esti­ In 1971, 34.4 percent of U.S. coal thesis will soon be published mated the coal resources of the region to exports were shipped to Japan, all of in its entirety as Mineral In­ total120, 197 million tons under less than which originated from the east coast of 3000 feet of overburden, of which 19,292 dustry Research Laboratory the U.S., 9500 miles from Japan. In re- Report No. 30. million tons is bituminous coal in beds of

OCEAN

I I I BERING I \ I I ~ SEA I I ' \ .,I<;:::.)I (I)., I .,.I (I) I .I I<) I (I) I I I I I 0 200 I 0 200 I I

FIGURE 2 FIGURE --- COAL ~M COAL TRANSPORTATION SYSTEMS NORTH SLOPE COAL FIELDS - RR Sf, 82... lndlvidua I traftsportatlon systems

On the North Slope of Alaska, there • more than 14 inches thick and 100,905 c~nt years, coal from Australia and west­ is approximately 120 billion tons of million tons is subbituminous coal in ern Canada has captured an increasing subbituminous and bituminous coal, beds of more than two and one half feet portion of the Japanese market. The thick. average selling price per short ton of coal in Japan was $19.20 in 1971. Paul Clark is a graduate student with the Analysis of the bituminous coal from Department of Mineral Engineering at the the Kukpowruk River and Cape Beaufort The U.S.S.R. has proposed to Japan University of Alaska, Fairbanks. He will areas has revealed that these coals have the development of the South Yakutsk, receive his M.S. degree in Mineral Industry Management. 25 Vol. 5, No.1 The Northern Engineer Siberia coal field at a cost of 175-185 areas in the winter may require considera­ belt to short distances. New develop­ million dollars (International Coal Trade, tion of seasonal operation, a smaller ments such as the nylon belt, steel cord May 1972). Japan conveyed its intention water supply line from a large water belt and the cable belt have increased of importing up to 10 million tons per source, or recirculation of water. Nor­ belt tension ratings, which have permitted year from this field in the late 1980's mally pipelines are buried except over increases in the length of single flight provided the quality meets its- require­ river crossings or when traversing a moun­ belt conveyors. ments. tainous terrain. Burying a pipeline in Conveyors are widely accepted as Carbonization tests performed to date permafrost may cause complications. transportation vehicles for two main rea­ on the North Slope coal indicate that it Heat is generated from the abrasion of sons: ease of operation and low opera­ is a blending coal, not a premium coking the slurry along the pipe and pump walls. tion and maintenance costs. Similar to coal and would therefore sell at the Although this heat generation is not pipelines, long distance conveyor systems medium to low coking coal prices. great, it will have to be accounted for. are inflexible to increased tonnage since A year round pipeline system would they are designed for a specific tonnage, COAL TRANSPORTATION METHODS have to be insulated and/or heated. Facil­ source and destination. ities would be required to permit rapid The primary consideration in the con­ Railroads drainage of the pipeline if a breakdown struction of a belt conveyor system is occured in low temperatures. No long belt alignment. A misaligned belt will Railroads have been constructed and distance commercial slurry pipelines exist result in excessive belt wear and possible operated successfully in northern areas in areas where freezing of the line is a spillage. Alignment will be a more serious for many years. Recently a transporta­ problem. problem in northern areas because of tion study was performed to evaluate the land shifts caused by frost action. Belt cost of a railroad from Nenana, Alaska on Roads and Trucks conveyors have operated successfully be­ the existing Alaska Railroad, to Dead­ low -45 degrees F and belts can be horse on the North Slope of Alaska Compared to other modes of bulk designed to operate in temperatures as (Tudor, Kelly, Shannon, 1972). transport~ trucking is considered to be low as -67 degrees F. Conveyors which one of the most flexible since the trans­ are operated in cold climates are shut In the lower 48 states, most large coal portation system can be expanded simply down only for short periods of time. producers ship their coal to a port or by adding more trucks. This flexibility When material is not being transported, market by unit trains. The unit train advantage is offset somewhat by inher­ the conveyor continues to run but at a technique involves the dedication of a ently high operating and maintenance creep speed substantially lower than the train or number of trains exclusively to costs over other bulk transportation normal operating speed. the haulage of the bulk material, from methods. one source to one destination, and with a predetermined loading, unloading and There are two major classes of trucks travel time. The use of the unit train for the movement of bulk materials: on­ Shipping technique normally results in minimal the-highway trucks and off-the-highway transportation costs through maximum trucks. Off-the-highway trucks have ca­ The ice free season on the northwest­ utilization of equipment for haulage. pacities up to 250 tons and are normally ern coast of Alaska averages three months used for short hauls in open pit mining at Point Hope to about two months at Slurry Pipeline operations or on large construction pro­ Barrow. For the movement of large jects. On-the-highway trucks can be of amounts of coal from the North Slope of The movement of a fine, suspended two types: those operating on public Alaska, stockpiling and handling at both material through a pipeline is not a new roads and those operating on private Japanese ports and the northwestern concept, although its application over roads. Trucks operating on private roads coast of Alaska would be minimal if year long distances has only developed in re­ are not normally subject to restrictions round shipping could be achieved. How­ cent years. One of the most noted appli­ except those imposed by the condition ever, the problems involved with year cations to coal is the 273 mile long, 18 of the road on which they operate. round shipping in this area of Alaska may inch diameter, Black Mesa pipeline which Trucks operating on public roads are become paramount over the alternative transports approximately five million tons subject to length, width and weight re­ extra handling problems. To date, there of coal annually between Arizona and strictions. As a result of these restrictions, has been no successful navigation north Nevada. truck payloads usually range up to 25 of the Bering Strait in winter, even by A slurry pipeline has only one source or 30 tons. icebreakers. Alternatives to year round and one destination. Each application is shipping include shipment of all the coal a separate case and normally cannot be Belt Conveyors to Japan during the ice free season, ship­ used interchangeably with other materials. ment of the coal to an ice free trans­ The cold northern climate poses some Until recently, belt conveyors were shipment point during the ice free season unique problems to slurry pipeline con­ not considered for long distance trans­ for furtherance to Japan for the remain­ struction and operation: the scarcity of portation because the strength of the der of the year, and extension of the water in northern, particularly arctic, cotton carcass limited the length of the shipping season.

Vol. 5, No. 1 26 The Northern Engineer In the transportation systems analyses, the mouth of Ogortoruk Creek, south of movement of coal would benefit other 100,000 ton dwt. ships (draft of 50 feet) Cape Thompson. At this site, the shore­ resource developments, but no attempt were used for the computation of ship­ line is fairly flat and the sixty foot water was made in this study to evaluate the ping costs. This size of ship was selected depth is closer to shore (three miles) than magnitude of these benefits. as a trade-off between economy of scale at most points on the northwestern coast. System 'I consists of a railway which and the vessel draft. The draft of the A nuclear device was considered for the connects a mining area on the eastern ship is an important consideration due to excavation of an artificial harbor at this portion of the coal deposits to the port the shallow waters along the northwest­ location (Project Chariot). The ecological of Seward on the Pacific coast of Alaska. ern coast of Alaska. consequences of this detonation were l'he system requires the construction of a Ocean freight rates for coal to Japan determined to be long lasting, and the 492 mile railroad from the existing Alas­ are approximately $4.00 per ton from projected movement of materials through ka Railroad at Nenana to the coal de­ the U.S. east coast and $2.75 per ton this harbor was not sufficient to warrant posits, and the construction of coal from Vancouver, British Columbia. the expenditures required for its con­ handling facilities at Seward. Unit trains struction at that time. transport the coal directly from the Barging The information available on the sea­ northern coal fields to Seward without bottom of the northwestern coast near any handling or excess waiting time be­ Tug and barge combinations for the, Cape Thompson indicates that bedrock is tween the source and destination. Coal movement of bulk materials have tradi­ at or near the surface of the seafloor. The is unloaded at Seward, stockpiled, then tionally been confined to inland water­ cost of removi11g sediments from the loaded onto 100,000 ton deadweight ore ways and coastal areas. It has only been seafloor is up to $2.50 per cubic yard, carriers for year round conveyance to in the last few years that ocean barge while the cost of blasting and removing Japan. developments have become significant. rock from the seafloor can be as high as The use of a trans-ocean tug-barge $25.00 per cubic yard (Koisch, 1971). System II proposes the use of the system for the movement of coal from An excavation close to shore and a chan­ road that is to be constructed from northern Alaska has a number of advan­ nel to this excavation large enough for Fairbanks to Prudhoe Bay. The coal tages over self-propelled ships: tugs re­ large ore carriers would require the re­ deposits are reached by traveling on this quire a smaller crew than ships; a tug­ moval of approximately 10 million cubic road and a secondary spur road to the barge can operate in much shallower yards of material. It is doubtful that coal deposits. These two roads supply a waters than a ship; and further, there is the exploitation of the coal deposits linkage to the Alaska Railroad where the no tug port time except to change barges. alone could carry the economic burden coal is loaded into railway cars and However, tug-barge combinations have a of the construction of an artificial harbor shipped to Seward for furtherance to lower cruising speed than ships and are by conventional methods. Japan. The trucks used in this system restricted to very light ice conditions. This does not necessarily rule out ship­ have a capacity of 25 tons. loading in this area. Other methods System Ill involves the movement of Harbors which may be alternatives to an artificial coal by an overland system to a harbor harbor are structural steel, concrete or near Cape Thompson on the Chukchi Natural, deep water, ice free harbors earth filled piers to deep water; an arti­ Sea. exist in the southern areas of Alaska, but ficial island in deep water to act as base During the ice free season, the stock­ these harbors are at least 600 miles from for smaller, lighter craft from shore; a piled coal at this port is shipped simul­ the northern coal fields. On the tip of slurry pipeline from shore to a moored taneously to Japan and to an ice free Cape Darby . on Golovnin Bay, water vessel in deep water; and the use of transshipment port at Dutch Harbor in depths of 60 feet exist close to shore. lighter craft to a ship moored in deep the Aleutian Islands. The purpose of the This site is approximately 380 miles from water. The two most practical designs simultaneous shipment is to maintain a the northern coal fields. Also on the appear to be a rock and gravel filled pier, consistent delivery schedule to Japan. Seward Peninsula is the natural harbor of and slurry loading. These are the only The coal shipped to Dutch Harbor is Port Clarence, which is between 40 and two designs used in the cost analyses. stockpiled until the ice begins to form at 45 feet deep. Port Clarence has good the Chukchi Sea port. At this time, the potential for harbor development, but TRANSPORTATION SYSTEMS coal stockpiled at Dutch Harbor is will require dredging if large ships are to shipped to Japan. be used. Its usefulness to the northern Cost analyses were performed on five Three types of overland systems were coal deposits is again limited by the dis­ separate systems used for transporting considered in System Ill: railroad, slurry tance between the coal and the harbor. coal from the North Slope of Alaska to pipeline and belt conveyors. Two types The next natural harbor past Port Clar­ Japan (See Figure 2). These analyses of shiploading techniques were also con­ ence is at Herschel Island in the Canadian were confined to single use transporta­ sidered: dry loading and slurry loading. Arctic. tion. The establishment of a new over­ In the analysis performed for slurry pipe­ A potential site for the construction of land transportation system and harbor lines, the costs of a secondary smaller an artificial harbor close to the coal is at facility with the specific goal of the pipeline was added to the total cost.

27 Vol. 5, No. 1 The Northern Engineer Because of the scarcity of an inland sup­ During the ice free season, the coal is ply of water in this region, feed water transported to Japan and simultaneously would either have to be recirculated or to a transshipment point at Dutch Har- transported from a large lake or the bor. The coal stockpiled at Dutch Harbor ocean in order to operate a slurry pipe­ would then be transported to Japan by line year round. ocean barges when the Point Lay area is In order to use slurry loading for ship non-navigable due to ice conditions. (/) loading, two ponds would have to be ...a: System V is similar to System IV ex­ .J _j System Ill constructed on shore, one for the actual cept 100,000 ton dwt ships have re­ 0 loading of the coal to the 100,000 ton s CONVEYOR, LOADING placed the barges. A slurry loading z 20 SHIPPING dwt. ship and the second as a settling system loads the ships anchored eight to ...0 pond for the fine, suspended material 10 miles offshore. a: 15 decanted from the ship. "'CL 1- (/) CONCLUSIONS 0 u 10 z Syotom Ill 15,000,000 0 20 , , tons per The results derived from the analysis ;:: RAIL, LOADING, <( , ... "' year ... ___ slurry loodlno SHIPPING of System I indicate that it would not be a: 5 0 -- dry loading a. ' economically feasible to construct and (/) FIGURE 5 15 ' ' z <( COAL TRANSPORTATION COST operate a railroad from the North Slope a: - } 10,000,000 ... 0 "'a: , , , , , - :,.} 15,000,000 to Fairbanks if the coal deposit must 0 50 100 150 200 ~ 10 - ,, Q\lerland Miles from Cool SGur~ _j ,,' support the entire construction and oper­ 0 ation. The economics may be entirely e --.. - alurry loadinQ ...~ 5 --dry looding different if the additional benefits to a: FIGURE 3 other users were considered. COAL TRANSPORTATION COST "'CL 0 System II, the transportation of coal 0 50 100 150 200 ... Qyerlond Miles from Coal Source by truck from the coal fields to Fair­ "'0 0 banks, would be prohibitively expensive Syotom Ill ~ 20 even if the coal did not have to support ;::: SLURRY PIPELINE, LOADING (A complete bibliography can ... SHIPPING any of the main road construction and a: maintenance. be found in the M.S. thesis 0 15 CL The cost of moving the coal to the or M.I.R.L. Report No. 30). ..."'z !5,000,000 a: , ,"{10,000,000 northwestern coast of Alaska (Systems REFERENCES ... 10 ,- 15,000,000 Ill, IV, and V) appears to be competitive Barnes, Farrell, Coal Resources of the with the transportation costs of existing Cape Lisburne-Co/ville River Region, e coal suppliers to Japan, particularly if Alaska. U.S. Geological Survey, Bul­ these coal deposits are on or near the FIGURE 4 letin 1242-E, 1967a. COAL TRANSPORTATION COST coast. As the overland distance to the 0 Conwell, Cleland N., Alaskan Coals. 0 50 100 150 200 coal deposits increases, the costs become greater and the coal becomes less Fairbanks: Department of Natural Re­ sources, Division of Geological Survey, Figures 3, 4, and 5 are graphical competitive. State of Alaska, 1972. illustrations of the results of cost analysis on System II/. International Coal Trade. U.S. Bureau of Mines, May 1972. Koisch, Francis P., "Supercarriers vs. System IV consists of a railroad, pipe­ future Research line, or conveyor system to a port near U.S. Harbor Dimensions," Journal of the Waterways, Harbors and Coastal . Point Lay. At this port, the coal is There are many aspects of coal trans­ Engineering Division, Proceedings of loaded onto 60,000 ton capacity ocean portation in northern Alaska which re­ the American Society of Civil Engin­ barges by either dry loading or slurry quire further research. These include loading. The greatest advantage of a marine terminals and shiploading tech­ eers, Vol. 97, No. WWI (Feb. 1971); port at Point Lay over a port near Cape niques, arctic slurry pipeline operation, pp. 20-27. Thompson is its proximity to the major extension of the shipping season, and Tudor, Kelly, Shannon, Alaskan Trans­ portion of the coal reserves. A limitation probably most important, the delineation portation Consultants. Alaska Trans­ of the port is its shorter ice free season of favorable coal mining areas. portation Corridor Study, submitted of 75 days compared with a 90 day ice to the Federal Highway Administra­ free season at a port near Cape tion, U.S. Department of Transpor­ Thompson. * tation, 1972.

Vol. 5, No. 1 28 The Northern Engineer DESIGN OF ROOFS FO·R NORTHERN RESIDENTIAL CONSTRUCTION

by Axel R. Carlson

In spite of what is known about vapor barriers and roof ventilation, mois­ ture stains on the ceiling of a roof are still a common maintenance problem in the winter climates of Canada, Alaska, the Great Lakes and North Atlantic States. Water vapor produced in a building has a tendancy to I migrate from a warm to a cooler area. Water vapor will move through any air leaks in the floor, wall, and ceiling and will eventually travel to the roof cavity (Dickens, et al., 1966). During sub­ zero temperatures, the moisture may collect as ice in the roof cavity and does not present a problem until it melts in the spring or other warm periods. Leaks in the ceiling can be aggrevating as water can stain painted surfaces and soften and buckle wallboard. Sometimes the water unexpectedly dribbles out of a lighting fixture and may even ruin the finish on a piece of furniture. Lack of ventilation at the eaves resu Its in a "warm" roof cavity (Graee). This causes formation of ice dams and the backing of water over the flashing into the ceiling, which may be misinterpreted as a condensation prob­ lem (Figure 1). Methods of solving these problems are discussed in more detail below.

The complaints of individual home­ owners over condensation problems at the ceiling received very little seri­ ous attention on the part of the architect, the finance agency approving the plans, the building code officials, and the build­ ers until condensation problems began to occur in 600 electrically heated homes in a large tract housing development in Canada. Apparently the reactions of the tenants were concerted and vehement as the Canadian Central Mortgage and Hous­ ing Corporation issued a special Builders FIGURE 1. (Photo by Allan Curtis.) Bulletin suggesting more careful sealing bulletin was directed primarily to the the heating plant is located in the main of the vapor barrier in the roof (Builders builders of electrically heated homes, portion of the house, it draws air from Bulletin No. 220, 1972). Although this similar problems occur in Alaskan homes the house and exhausts it up the chim­ where a hot water boiler is installed in ney; this is an aid in the reduction of excess humidity levels within the home. Axel Carlson is an Extension Engineer with the garage and is isolated from the main the Cooperative Extension Service, University part of the house by a fire wall. When of Alaska, Fairbanks.

29 Vol. 5, No. 1 The Northern Engineer SCUTTLE OPENINGS ELECTRICAL WIRING The "chimney" action of air infiltra­ tion through windows, doors, and elec­ The inconspicuous scuttle opening lo­ A typical one-story three-bedroom trical outlets in the walls forces the cated on the ceiling of a closet or wall of house with a crawl space may have as moisture and heat into the attic through a split level house is one of the primary many as 64 electrical outlets consisting holes in the ceiling vapor barrier (Tamura, sources of vapor and air leaks into a cold of 14 outlets for ceiling lighting fixutres et al., 1963). This becomes apparent roof cavity. No scuttle openings or and ventilation fans, 18 switch outlets during prolonged periods of sub-zero stairways into a cold attic should be in the walls, and 14 convenience outlets temperatures by the appearance of cold permitted unless insulated and fitted with in the walls. Even though many of the drafts and frost at electrical outlets on vapor resistant gaskets and appropriate switch and convenience outlets are on the wall and the formation of frost in the latches. A scuttle opening should not be interior walls, the wiring extends on into roof cavity or attic. installed in the ceiling of an attached the roof cavity. At least 14 branch In the Scandinavian countries, the garage. Ideally, the access openings into circuits from · the electrical distribution electrical wiring is installed after the an uninsulated attic should be installed in panel spread through the framing like a insulation and vapor barrier have been the end wall of the gables as is done in spider web (Figure2). The holes drilled properly placed. In the United States the Scandinavian countries. in the studs, plate, and sole may result and Canada, the electrical wiring and in a tortuous path for migration of rough plumbing is placed first, followed VAPOR BARRIERS moisture, but it eventually leads to the by the placement of insulation and vapor roof cavity. Usually no attempt is made barrier as shown in Figures 3 and 4. In To minimize condensation problems, in Alaska to seal the openings in the Scandinavia either 2 x 3 or 2 x 4 nailers the entire ceiling should be sealed with a plate against the migration of water vapor are placed over the "warm" side of the continuous sheet of 4-mil polyethylene and air. vapor barrier, perpendicular to the roof (Visqueen) vapor barrier prior to instal­ lation of interior partitions. Interior load-bearing partitions, installed before the ceiling vapor barrier is placed, should have a 16-inch strip of polyethylene laid on the top of the plate prior to their placement. The plate of a double plumb­ ing wall or double sound-proofed parti­ tion should be fitted with a 16-inch strip of polyethylene. All lapped splices should be sealed against solid blocking placed between the framing members. If it separates a split-level home, the upper portion of a wall adjacent to a cold roof cavity should be vapor-proofed and insulated as if it were a fully exposed wall. Suitable blocking should be in­ stalled between the studs for sealing the vapor barrier and isolating the lower "warm" portion of the wall from the upper "cold" portion. The vapor barrier lap extending down from the ceiling should always be placed under the wall vapor barrier so that any condensation is diverted into the wall cavity rather than allowing it to stain ceiling or wall surfaces. All holes drilled in a wall plate at the ceiling for electrical wiring, and other minor openings, should be sealed with a non-hardening caulking compound to pre­ vent water vapor from migrating into the roof cavity. Openings around plumbing vent stacks and chimneys should be carefully sealed with suitable metal col­ lars and a non-hardening caulking com­ pound. Care must be taken to seal the FIGURE 2. plate of double plumbing walls.

Vol. 5, No. 1 30 The Northern Engineer Figure 3. REC01111ENOED CANTILEVER ROOF CONSTRUCTION v-,------.. ~ ---~ ~--- :;------~~ - >< >.< >< \ ""-.._ 2x4 Purlins, 16" O.C. ? 16"-24" Deep clear span Cold cavity roof joists, 48" D.C. T

II--IIII~- 2S:r~~-. ~~"__,., >< --. >< 1 ~lot intake f\11 Nailers serve /: ,.-r-r-- -1 f--- 1/\ as chases for 1; /;r-'-\...._ __ 1 I '="" '""'' 1111--"""-".' e~ectrical I( It I I Drop ceiling w1th r-----, . w1ring \~..... ;'' I I /recessed fixtures ( 6" f1_''_:'':__"_"_:_1 ___.... ~16" 111~- L,.---' •· I I _j__ 24" ( 9-l/2" fiberglass) t:::J /_·;::: ==-======~:;;_-;,_-;,_-::;,±__ === ==-====~ t=:1' : All electrical ~o~iring on ~LL warm side of vapor barrier All electrical wiring on .--:--' ~\ II warm side of vapor barrier or wall framing members. This provides as ice dams and icicles. Gas furnaces chases for the installation of the electrical interior partitions!. Prior to erection, the should be equipped with an approved outlets and the extension of electrical top of the plate should be covered with a all-fuel insulated metal chimney. The circuits without the need for puncturing 16-inch strip of polyethylene that can be chimney must be tightly vapor (air) the vapor barrier. After the insulation, sealed with the ceiling vapor barrier of sealed at the ceiling with a metal collar vapor barrier, electrical wiring and plumb­ rooms on each side of the wall. Any and non-hardening caulking compound. ing have been inspected and approved, openings cut in the plate for plumbing the sheet rock, paneling or other interior vent stacks should be neatly sealed with ROOF CONSTRUCTION finish may be applied. a metal collar and non-hardening caulking compound. The added cost of nailers may be off­ A double plumbing wall constructed The "cold" roof concept was origin· set by a four-foot spacing of roof trusses. on an outside wall should be carefully ally conceived in the effort to prevent Also allowing the "rough" carpenter to built to avoid condensation and freezing the formation of ice dams along the completely frame, insulate, and vapor problems. The exterior wall should be eaves and the backing-up of water proof the structure while on the job insulated and vapor proofed before set· through flashing on to the ceiling (Finne, without his having to return after the ting the interior wall. The vapor barrier 1963). Most everyone knows that a electrician and plumber have completed of the exterior wall should extend over one inch ventilation slot is installed in their work-except to patch holes in the the plate of the inner plumbing wall so the soffit along the eaves of the roof. Un· vapor barrier-cuts costs as well. Further, that no moisture or air can leak into the fortunately very few individuals realize the rough carpentry, insulation, vapor roof cavity. that the ventilation slot no longer per­ barrier, electrical wiring, and rough The plumber must be extremely care­ forms as intended because thicker appli­ plumbing can be inspected and approved ful when sweating copper water and cations of insulation restrict the flow of at one time before any sheet rock is waste fittings to avoid burning the vapor air from the slot intakes (Figure 5). To applied. Temporary heat can be used by barrier and the insulation. Perhaps the compound the problem, the heat flowing the electrician and plumber with no carpenter should install a sheet of fire through air leaks in the vapor barrier at hazard of damaging the siding due to resistant cement asbestos board between the scuttle openings, electrical outlets. condensation stains or ice formation. the insulated wall and the plumbing wall plumbing vent stacks, etc., often exceeds Nailers placed perpendicularly increase to protect the vapor barrier and insula· the thermal conduction through the in· the interior surface temperatures of the tion against fire and puncturing during sulation. As a consequence, the roof ceiling, which will minimize condensation the installation of the rough plumbing. cavity becomes sufficiently warm to melt stains of sheet rock nail heads. the snow over the insulation so that the CHIMNEYS melted snow migrates to the eaves and PLUMBING refreezes as ice dams over the colder Openings around the chimney can be portion of the eaves. If a roof is not Holes drilled in the plate and sole for a source of vapor and heat leaks into the flashed properly, the water may leak the plumbing are another source of vapor roof cavity. Light weight uninsulated under the asphalt shingles at the eaves or and air leaks into the roof cavity (Figure metal gas vents can result in excessive at the valley. In a flat roof, the water 2). A double plumbing wall with a split heat formation in a poorly vented roof may leak over the flashing at the parapet plate is a particular hazard as it has even cavity. This causes snow on the roof to walls, chimneys, etc. resulted in the freezing of plumbing on melt and flow to the eaves and to refreeze The Northern Engineer Vol. 5, No. 1 31 Although gable trusses constructed of 2 x 4 and 2 x 6 chords can be safely de­ signed to resist Alaskan snow loads, --~~~- \ special design considerations are neces­ ;-'------sary at the eaves to avoid restriction of the air flow at the eaves and a resultant "warm" roof (Carlson, July 1971). The ----- 2 x 4 and 2 x 6 chords only allow three and one half and five and one half inches of space, respectively, between the top of the plate and the bottom of the roof deck (Figure 5). A minimum of six inches of fiberglass insulation is re­ commended for Alaska; this does not leave sufficient ventilation space over the insulation even though a one inch slot is provided in the soffit. For electric­ ally heated homes, nine and one half Frost or mildew ·Electrical wiring inches of fiberglass insulation is suggested punctures vapor barrier creating and this aggrevates the problem even air and vapor leaks further. The author purchased a home in Fairbanks with roof trusses constructed of 2 x 4 chords and six inches of fiberglass insulation in the ceiling. The Figure 5. TYPICAL GABLE ROOF CONSTRUCTION icicles at the eaves by mid-November nearly hung to the ground. A carpenter annoying with low pitch trusses where ledger notched into the top of the joists was called on the project and he crawled one may be allergic to fiberglass. (Figure 6). The joist should extend over up into the attic and pressed insulation The Scandinavians have modified the the wall sufficiently to provide adequate down at the eaves with a long piece of gable truss designs by increasing the nailing surface to restrain horizontal 2 x 2 lumber. This allowed air to flow height over the bearing wall 15 to 18 thrusts of the rafter due to snow loads on over the insulation to form a "cool" inches to accommodate ten inch applica­ the rafter. roof as originally intended. After a tions of fiberglass. The upper chord has The cause of moisture problems in month or so, the icicles began to reform, two slopes to simplify stress analysis of single sloping "flat" roofs or double as the insulation apparently had begun to full triangles. A short rafter is scabbed sloping "cathedral" roofs is more diffi­ swell up and restrict the air flow. This over the lower portion of the truss to cult to determine as it is usually not resulted in a "warm" roof again. provide a uniform slope over the entire possible to look into the roof cavity Once the error in roof design has been roof surface. The author suggests a without cutting a hole in either the created on the drawing board and con­ simpler technique of cantilevering the ceiling or the roofing, which most people structed on the building site, a satisfac­ truss two feet over the wall, which will hesitate to do. People have even gone tory solution is nearly impossible to at­ provide 18 inches of space between the to the useless expense of installing new tain. Some builders have inserted fiber top of the plate and the bottom of the roofing, only to discover the "leak" still tubes over the insulation at the eaves roof deck (Figure 3). The cantilevered persists. As with a gable roof, air leaks which appear to be satisfactory in the truss involves more complex stress analy­ through the vapor barrier at such places warmer climates but are not recommend­ sis to account for internal redundant as outlets for electrical fixtures, holes ed for interior Alaska. Other builders forces, but these problems can be easily drilled in the wall plate and sole for have either tapered or pulled back the solved by the structural engineer. The electrical wiring and plumbing vent insulation at the eaves, which is heel of the truss must be supported by stacks, cracks of split plumbing walls, entirely unsatisfactory for prolonged per­ 2-foot long plywood gussets on both and chimneys are common sources of iods of sub-zero temperatures, particu­ sides and two inch blocking between the vapor and heat migration into the roof larly at higher humidity levels. In the upper and lower chords over the bearing cav.ity. Recessed beams between the latter situation, serious moisture and wall. living and dining areas often completely mildew stains have been observed at the Eave ventilation of a stick-built rafter restrict ventilation over the insulation. plate and under the lower chord, 10 to roof is often restricted by the conven­ This results in excessive accumulation of 15 inches from the outside wall. At­ tional method of notching the rafter into frost in the roof cavity, which later melts tempting to correct ventilation problems the plate, particularly when utilizing and leaks back onto the ceiling and stains at the eaves is difficult at best because of thicker applications of insulation (Figure painted surfaces. the laborious task of crawling between 5). To increase the height of the rafter at chords and diagonals. This is particularly All too often the rafters of a flat, shed the eaves, the rafter may be set on a or cathedral roof are selected on the Vol. 5, No.1 32 The Northern Engineer ventilation over the insulation and this results in a "warm" roof. To minimize costs, the Scandinavians place all roof Figure 6. RECOMMENOEO STICK-BUILT RAFTER ROOF CONSTRUCTION trusses for homes on four-foot spacing. The insulation is placed between the trusses, followed by the vapor barrier. Then 2 x 3 or 2 x 4 nailers, 16 inches on center, are secured perpendicular to the trusses. The nailers serve as a chase for the extension of electrical circuits with minimum rupturing of the vapor barrier. The ceiling finish is installed after the insulation, vapor barrier, and other con­ cealed work has been inspected and approved. The plank-and-beam has created con­ densation maintenance problems in Alas­ ka due to lack of insulation and the failure to seal the cracks between the (Slot intake insulation. If adequate foam plastic insulation is not provided, condensation may form between the deck and the insu­ I I I lation (Carlson, Summer 1972). Although =-= == =- == =-=i~ ~=t-=- .:S= == =-=- =--r rigid foam plastic insulation is an excel­ \_ Drop ceiling with recessed fixtures lent vapor barrier, the joints must be All electrical wiring on warm side of vapor barrier carefully sealed with a compatible adhe­ sive to avoid migration of water vapor. basis of local minimum code require­ maintain a "cold" roof, 16 to 24 inch Ice blisters may form under the roofing ments, hence sufficient space is not al­ deep span trussed joists or lumber­ and melt during warmer weather causing ways provided for adequate ventilation plywood "1-Beam" joists are used (Figure mildew stains on the roof deck. The over the insulation (Figure 7). The situ­ 4). In the United States and Canada, formation of condensation can be so ation is further aggravated by installing re­ 2" x 8" to 2" x 12"1umber joists span­ heavy at times that moisture has been cessed beams to support the roof between ning 12 to 16 feet are used which require known to stain walls and cause carpets to mildew. living and dining areas, as mentioned ear­ interior bearing walls. The shallower The "upside down" roof, developed lier. With three and one half inches of fi­ depth joists have a tendency to minimize berglass, this presents no particular prob­ lem; however, with the six inches mini­ mum thickness of insulation for Alaska, ~~ 7---- and the one and one half inches recom­ / - - _,___-----..Ice dam at eave""'-· caused------~'""' ''-....\.___ --- / ---- __ - ....:: mended for electrically heated homes, by warm roof cavity __ "" _ ____., _/ - - L-*------...... __7 '--_ _ ~ -- Insulation and recessea-- eave-to-eave or gable-to-gable ventilation ~-- ---~~ ~ ..._ __ beam :estricts ventilation ___ I y __ ~ '-...._ _ creat1ng a warm roof cavity may be totally cut off. As with the gable II'~~ ------· -- roof, the ventilation over insulation at the eaves may be restricted by the former (1 practice of placing blocking on the plate. ~...... ~..... li~r~-J;~u:·1:ti:; \,_J---L...,i)~ •• ~-: v~ ~~IV The blocking was sometimes used to 6" unr) l lA support the edge of the sheet rock on the ~ ~/~ Fib~gDs ~ ceiling. Fortunately this practice is ~\:_CA - >

Vol. 5, No.1 The Northern Engineer 33 by Dow Chemical Company, hopefully barrier would permit the inspection of should be installed on the "warm" side of will eliminate the problem of ice dams at the thickness of foamed-in-place plastic the vapor barrier by the use of nailers the eaves as well as prevent the freezing insulation or the R-value of fiberglass (furring strips) or surface-mounted race­ of roofs drains (Sturman, December insulation. After the vapor barrier has ways or cable. The vapor barrier should 1970). Foam plastic insulation is laid been approved, the sheet rock applicator be continuous and should be extended on the top of the roofing, as shown in and finish carpenter can move onto the over the top of all interior partitions. Figure 8, instead of the conventional job and need not be held up due to lack Air intakes, in addition to windows, method of laying it below the roofing. of vapor barrier, insulation, rough plumb­ should be provided for the control of In this situation the roofing also serves ing and electrical wiring. incoming fresh air and relief of excess as the vapor barrier. The snow melting If the building must be enclosed prior vapor during prolonged periods of sub­ on the roof deck can flow down between to the inspection and approval of the zero temperatures. Finally, no finish the planks of rigid foam insulation into a vapor barrier and other concealed work, ceiling or wall covering should be in­ warm temperature zone where it remains the contractor should be required to ex­ stalled until the vapor barrier, insulation, unfrozen and flows to the roof drains. tend the warranty or deposit sufficient and other concealed work has been in­ To prevent refreezing the roof drains funds in escrow with a bank to correct spected and approved by the prospective are also covered with rigid foam plastic any damage due to negligent workman­ owner or his authorized representative. insulation. The drain pipes are installed ship or faulty material for a period of * REFERENCES within the warm portion of the structure two years after final inspection. Such an so that they will not freeze as with agreement should be drawn up by the Anno., Measures to Control Condensa­ conventional down spouts. The insula­ buyer's attorney before any mortgage tion is weighted down with one and one tion, Canadian Central Mortgage and Housing Corporation, Builders' Bul­ letin No. 220; Ottowa, Canada, 1972. Carlson, A. R., Gable Roofs for Alaskan 1-1/2" Concrete----­ Homes, Cooperative Extension Service, patio blocks or coarse gravel Publication No. 552; University of Alaska, July 1971. ______, "Heat Loss and Conden­ sation in Northern Residential Con­ struction," The Northern Engineer, Vol. 2, No. 2, Institute of Arctic and Environmental Engineering; University Roofing membrane and vapor barrier of Alaska, Summer 1972. Dickens, H. B., et al., Moisture Accumf!· Insulated roof drain lation in Roof Spaces Under Extreme Winter Conditions, National Research Council, Division of Building Research, Technical Paper 228 (NRC 9132); Ottowa, Canada, 1966. Drain pipe Finne, Eirik, (Det Kalde Taks Funksjon) The Function of a Cold Roof, Nor­ wegian Building Research Institute, Publication 77; Oslo, Norway, 1963. Figure 8. "UPSIDE DOWN" FLAT ROOF CONSTRUCTION Graee, Trygve, (Luftlekkaisier Og Snos­ melting Pa Tak) Air Leaks and Snow half inch concrete patio blocks to prevent papers are signed with the finance agent. melting on Roofs, Institute of Agri­ the wind from carrying the insulation SUMMARY cultural Structures, Agricultural Col­ off. This type of construction is ideal Condensation problems on the ceiling lege of Norway, Reprint 132; As, for patios over garages or other heated as well as on other surfaces and ice dams Norway. areas at the eaves can virtually be eliminated Sturman, Gary G., A Discussion of the INSPECTION by the careful and diligent sealing of all "Upside Down" Roof System, Term The inspection of the vapor barrier, potential air, heat, and vapor leaks in the Paper for C. E. 603, Arctic Engin­ insulation, electrical wiring, and rough roof cavity and other exposed surfaces. eering I; University of Alaska, Decem­ plumbing should be a critical phase in No scuttle or other access openings ber 14, 1970. construction and no further work should should be permitted in a cold roof or Tamura, G. T., et al., Air Leakage and be permitted to proceed until inspected attic. All openings drilled in the wall Pressure Measurements of Two Occu­ and approved by the buyer or his author­ plate for electrical wiring and plumbing pied Houses, National Research Coun­ ized representative-either the architect, vent stacks should be properly sealed. Research Paper 207 (NRC 9648); the building inspector, finance agency, Recessed lighting fixtures cut into the Ottowa, Canada, 1963. and/or a disinterested builder. ceiling of a cold roof cavity should not The use of clear polyethylene vapor be prohibited. Ideally all electrical wiring

Vol. 5, No. 1 34 The Northern Engineer SYMPOSIA & CONFERENCES 24TH ALASKAN SCIENCE CONFERENCE University of Alaska, Fairbanks, Alaska, August 15-17, 1973 First Announcement RESEARCH CLIMATE * PHYSICAL CAUSES OF THE * BIOLOGICAL EFFECTS REPORTS ARCTIC * CONSEQUENCES TO MAN Conference Chairman-Or. Gunter E. Weller President, Alaska Division AAAS The following research reports are Geophysical Institute, University of Alaska now available to the public from the MAIN THEMES of the 1973 AAAS Conference will Include- University of Alaska's Institute of Water * The Climate Now * Climatic Hazards * Climate & Communications Resources, Dr. Robert F. Carlson, * Climates of the Past * Climate & Energy * Climate, Plants & Animals Director: * Future Climates * Climate & Transportation * Climate & Agriculture * International Climatology * Climate, Cities & Houses * Climate & Health Factors Affecting Water Management * Climate & Leisure on the North Slope of Alaska, Julian MANY DISCIPLINES can contribute to solving problems of the Arctic-Meteorology, K. Greenwood and R. Sage Murphy, physics, chemistry, oceanography, mathematics, geology, geography, glaciology, IWR-19. astronomy, history, anthropology, botany, zoology, physiology, economics, psych­ The Biodegradation of Organic Sub­ ology, sociology, art and architecture, engineering and agriculture. Authors wishing strates Under Arctic and Subarctic to contribute papers should write to - Conditions, Ann P. Murray and R. Sage CALL FOR PAPERS Murphy, IWR-20. Director Titles by June 1 A Computer Model of the Tidal Geophysical Institute Abstracts by July 1 University of Alaska Phenomena in Cook Inlet, Alaska, Ro­ Fairbanks, Alaska 99701 bert F. Carlson and Charles E. Behlke, Telephone (907) 479-7282 SYMPOSIUM ON WASTEWATER IWR-17. Application of the Finite-Element TREATMENT IN COLD CLIMATES Method for Simulation of Surface Water A Symposium on "Wastewater Treat­ Transport Problems, Gary L. Guymon, ment in Cold Climates" will be held on SECOND INTERNATIONAL IWR-21. the Saskatoon Campus of the University CONFERENCE ON PERMAFROST BioProcesses of the Oxidation Ditch of Saskatchewan on August 22-24, 1973 When Subjected to a Subarctic Climate, The program will include discussions The second "International Conference K.R. Ranganathan and R. Sage Murphy, covering the following topics: on Permafrost" will be held from July IWR-27. a) Problems and Solutions for Cold 16-28, 1973, in Yakutsk, USSR. For Development of a Conceptual Hy­ Climates information on this conference, residents drologic Model for a Subarctic Watershed, b) Operation of Stabilization Ponds in the United States should write: Robert F. Carlson, IWR-28. c) Aeration Under Low Temperature Dr. T. L. Pewe The Effects of Suspended Silts and Conditions Chairman, Department of Geology Clays on Self-Purification in Natural d) Biological Treatment for Organic Arizona State University Waters: Protein Absorption, Ann P. Mur­ and Nutrient Removal Tempe, Arizona 85281; ray, IWR-23. e) Physico-Chemical Treatment Canadians should write to: An Analysis of the Demands for f) Disinfection Mr. R. J. E. Brown Water From the Private Sector in a g) Disposal of Liquids and Sludges Northern Research, Geotechnical Sec- Subarctic Urban Area, Robert P. Haring, tion For further information on the Sympo­ IWR-22 National Research Council sium contact: Ottowa, Ontario K 1A OR 6; Dr. Eric Davis These reports are distributed without Information from the USSR can be Department of Civil Engineering charge. However, if a report is out-of­ obtained from: University of Saskatchewan print, the Institute of Water Resources Dr. P. I. Melnikov Saskatoon, Saskatchewan will Xerox a copy of the report at a fee Chairman, Organizing Committee Canada S79 OWO of 14 cents per page. International Permafrost Conference ALSO ..... Direct your inquiries to: c/o Institute of Permafrost Studies A session on "Cold Climate Waste­ Institute of Water Resources 11/4 Fersman Street water Treatment," a joint congress spon­ University of Alaska Moscow v 312, USSR sored by the American Institute of Fairbanks, Alaska 99701 Chemical Engineers and the Canadian Society for Chemical Engineering, will be The Northern Engineer Vol. 5, No. 1 held in Vancouver, British Columbia on September 9-12, 1973.