inuvik utilidor history

Inuvik NWT Utilidor Replacement

One of the most significant Canadian community milestones in the decades following World War Two was the development of the community of Inuvik, along with its above ground piped water and sewer system. The development was initiated by the chronic flooding and limited capacity of the nearby community of Aklavik, which was the regional centre for the Mackenzie Delta. In 1957, John Diefenbaker’s famous “northern vision” policy inspired the nation, and advanced further initiatives in northern infrastructure, such as Inuvik. Diefenbaker’s northern vision was one where “traditional activities like hunting and fishing co-exist alongside cutting-edge scientific research.” Diefenbaker, in fact, made the North one of the central themes of the 1958 general election, and he would triumph with the largest majority of seats in Canadian history.

The Town of Inuvik is Canada’s largest community north of the Arctic Circle, (68° 22’ N latitude, and 133° 44’ W longitude), 2000 kilometres northwest of Edmonton, and has a unique history as the first completely “engineered” northern community. The weather is typically northern with July mean temperatures ranging from 8.2°C to 19.7°C; January mean temperatures ranging from -26.1°C to -35.7°C, and; an average yearly temperature of -9.6°C.

The Town celebrated its official fiftieth anniversary in 2008, and according to some, there has never been a Canadian town so “pondered, proposed, projected, planned, prepared and plotted” as East-3, which was its original site identification back in the 1950’s. Diefenbaker dedicated Inuvik as, “the first community north of the Arctic Circle built to provide the facilities of a southern Canadian town. It was designed not only as a base for development and administration, but as a centre to bring education, medical care and new opportunity to the people of the western Arctic.”



SelectionandBuildingofEast-3

In 1953, federal government survey teams fanned out across the Mackenzie Delta looking for a new spot on which to build the settlement that would replace Aklavik. In 1954 twelve sites were targeted as worthy of detailed study for the community of “New Aklavik”; six on the west side of the Mackenzie Delta and six on the east side of the Delta. By the time the field investigation season started in the summer, four sites with the most potential were selected for detailed field investigations. The study team completed their work in late August, and in consultation with local residents, recommended the East-3 site because it had the highest overall rating. The 110 hectare community development area was well above flood levels, within the treeline, on a navigable waterway, had access to wood and large gravel sources, and had space for a large airport runway. The townsite sits on a broad terrace between the East Channel of the Mackenzie River and the upland that forms the Mackenzie Delta’s eastern boundary. The long, very cold winters, permafrost, and great distance from sources of supply were a challenge to engineers starting to design buildings, water, sewer, roads and drainage and even landscaping for East-3. Each of the elements of the community required unique design and construction considerations, and the work was breaking “new ground” in the field of cold region engineering.

East-3 was developed with a compact and efficient downtown business core just east of the East Channel. Primary and secondary schools were located on large blocks of land between the downtown core and surrounding residential areas, and a large regional hospital was sited at the south end of the townsite. The residential areas radiated outward from the central core area.

Construction of East-3 began in 1955, and the official dedication of Inuvik occurred in July, 1961 with Prime Minister Diefenbaker presiding over the ceremony. It was the first time in Canada that a community would be built from scratch, giving new meaning to the term “government town.”

The construction of Inuvik even started out with an environmental element with instructions for all construction crews to minimize vegetation disruption when building the infrastructure. Of particular note was the preservation of spruce trees along the main road. These trees were protected from construction, but unfortunately the trees died by the early 1960’s after drainage rerouting altered the soil conditions.

Figure1.TerrainassessmentofEast-3area.


InuvikPermafrost

Building on permafrost proved to be a significant challenge to engineers and contractors. They expected to find a metre of permafrost, but discovered that Inuvik sits on 350 metres of ground that is frozen year round. To prevent heat from warm buildings thawing the permafrost, and causing them to sink, most structures were designed to sit on timber piles drilled five metres into the ground with about half to one metre of space between the ground and the bottom of the building.

The permafrost ground below Inuvik is “ice rich”, which means that when it melts, the ground may settle by 300 millimetres or more as the soil fills the voids left by the melting ice.

Inuvik’s ground is also thaw sensitive (warm) permafrost, which means that the temperature of the permafrost is only a few degrees below zero. Small variations in the ground temperature caused by the removal of the ground cover or by excavations will cause the permafrost to melt.

OriginalInuvikUtilidor

The original utilidor network contained water and sewage lines, plus a circulating high temperature hot water system to heat buildings. The utilidor structure was metal clad, heavily insulated, and supported on timber piles. Lost heat from the heating pipe kept the water and sewer line above freezing during the winter. Water and sewer systems are usually buried, but this was not done in Inuvik because it was unknown how the buried system would react to the freezing conditions, and it was anticipated that any buried system would be frozen by the cold ground temperatures.

An econo utilidor was later introduced, which only carried water and sewer lines because building heat for some neighbourhoods came from oil fired furnaces. Hot water was added to the water line as necessary to keep this system from freezing in the winter.

Figure2.IcelensInInuvikpermafrost

Figure3.SteamexcavationfortimberpileplacementinInuvik.

Figure4.OriginalInuvikutilidorsystem.


The utilidor system functioned reasonably well, providing the “normal” amenities of southern Canada of running water and sewer, but had high capital and operating costs. At the time, the standard utilidor cost $600/metre to construct. The high costs arose from the construction of the high temperature, high pressure heating line, the 8 inch water lines and the utilidor alignment, which could not pass under buildings. Although well insulated, there was a high radiation heat loss from the side of the utilidor, which contributed to the high operating cost. ModernInuvikUtilidor

The modern Inuvik utilidor runs along a dedicated right-of-way at the back of each lot, along with the power poles that service each building and the cost of installing these services is over $50,000 per lot. In most cases the utilidor is positioned in a dedicated right-of-way, but in some cases no right-of-way exists. The service connections exit above ground from each building and resemble a large “metal centipede” as they connect to the water and sewer mains. Road crossings of the utilidor create another challenge because the road must literally bridge the utilidor, at a cost of nearly $50,000 each.

The first generation of the utilidor was built with timber piles. It was expected that the timber piles would last indefinitely because of the cold air and ground conditions. However, timber will eventually decompose if exposed to warm temperatures and moisture, even for brief periods of time in the north during the active layer thaw. This deterioration has been progressing for the past several decades and in a few cases houses have experienced catastrophic foundation failures. Steel piles have been used for the past 20 years to replace the decomposing timber piles.

The utilidor creates unique development and planning challenges because it is above ground. The minimum floor level in a building must be high enough to drain by gravity to the sewer utilidor. Road crossings of the utilidor create unique humps in the streets. “Open” back yards are not very common because the utilidor service connections usually fill a significant portion of the backyard.

Figure5.OriginalconceptforutilidorplacementNOTE:Atgradecrossingnotusedbecauseofpotentialpermafrostdegradation.

Figure6.Originalcompletedutilidorwithoutmetalcladding

Figure7:ModernutilidorsysteminInuvik


UtilidorDesign

The utilidor is supported by steel piles, and thermal stability is maximized by placing the piles to a minimum of 6 metres into the ground. The piles are coated with heavy grease and wrapped with polyethylene to maintain a non-bonding surface between the ground and the pile for the inevitable shifting of the ground in the active layer. The piles are backfilled with a sand slurry which helps the bottom section of the pile freeze into the existing permafrost regime.

The pipe used for the sewer and water system of the utilidor is an insulated steel pipe with a metal jacket covering the 50 mm of urethane insulation. The water and sewer pipes themselves serve as structural beams, which carry the gravity loads of water, cement mortar lining, the steel pipes, insulation, jacket, fittings and snow and ice. A standard space of 7 metres has been chosen as a reasonable balance between pile capacity, beam capacity and pile frequency. The pipes are Schedule 80 (12 mm wall thickness) with a cement mortar lining for corrosion resistance.

In addition to the thermal concerns in the vertical direction due to permafrost action, thermal movement is also a concern in the horizontal direction. With outside operating temperatures ranging from minus 50°C to plus 30°C, expansion and contraction of the pipe is significant. The thermal considerations for horizontal pipe movement include an expansion joint every 25 to 30 metres along the pipe. Each pipe support at the piles is a roller system to accommodate the horizontal movements. The movement of the pipe is also controlled with line anchors every 60 to 80 metres.

The ultimate objective of the utilidor system is to provide water and sewer connections to individual buildings. To accomplish this, a service box is attached to the utilidor near each building, and water and sewer services run into the box and ultimately into the building through a common carrier pipe. The service box provides easy access to the service connection or “utilidette”, and also provides a common space where heat from the system may provide additional freeze protection. The common carrier pipe for the water and sewer services accomplishes the same freeze protection objective.

A similar configuration is used for hydrant servicing along the utilidor with hydrant boxes placed at intervals along the utilidor. The hydrant boxes are painted red for easy identification.

Figure 8. Pipe support for modern utilidor system in Inuvik

Figure10.Waterandsewerserviceconnectiontoutilidorsystem.

Figure9.LineanchorformodernutilidorsysteminInuvik


UtilidorConstruction

Initial site work for the utilidor projects for both extension of the system, or replacement of the system includes: clearing and brushing of the utilidor alignment, temporary removal and replacement of private installations, excavation to the subgrade of the utilidor, preparation work pad and drainage related work.

The width of clear working area needed for a utilidor project is generally about 5 to 6 metres. About 4 metres may be required along one side of the pipe centerline for vehicle movement, as well as the utilidor installation.

Where the existing ground is excavated 250 mm or more for grading, the standard practice is to sub-excavate by a further 200 mm, install 100 mm of rigid close cell insulation and bring the ground elevation back up to grade. The insulation provides a thermal barrier to additional permafrost degradation.

The utilidor system (water and sewer mains, pile system, service connections, hydrants, etc.) have historically cost about $50,000 per lot or about $5,000 per metre. These costs were based upon a local contractor in Inuvik with a long standing success of capturing utilidor work. This contractor retired several years ago and the most recent costs for the utilidor (2010 construction season) have risen to $8,000 per metre.

Some of the individual cost components are: piles at $3,000 each; water and sewer mains at $1,000 per metre each; hydrant boxes at $6,000 each and expansion joints at $7,000 each.

ContinuingUtilidorConstruction

There are approximately 18 kilometres of water and sewer utilidor services in Inuvik, including 10 kilometres of the original utilidor, and 5 kilometres of new utilidor replacing the original utilidor. The community continues to grow, and the utilidor has been extended by 2 kilometres to service the growth. A program to replace the utilidor has been ongoing for the past 20 years, as funds come available, and will continue for many years into the future. The design and construction of the utilidor system is far from being a routine activity because of land use issues, permafrost conditions, and contractor skill.

The utilidor replacement is a continuing project, which ultimately depends upon the available capital funding. It is a very specialized system to operate as well as construct, and a globally unique cold region engineering design. The complete replacement of the original utilidor system in Inuvik may take decades to complete, with an estimated price tag of over a hundred million dollars.

Figure11.Utilidorgroundinsulationin2010.

Figure12.Completedpileconstructionforutilidorandmarkingofsewerinvertin2010.

Figure13.Completedutilidorin2010.

inuvik utilidor history

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