Track ballast

Track ballast forms the trackbed upon which railroad ties (sleepers) are laid. It is packed between, below, and around the ties.[1] It is used to bear the load from the railroad ties, to facilitate drainage of water, and also to keep down vegetation that might interfere with the track structure.[1] This also serves to hold the track in place as the trains roll by. It is typically made of crushed stone, although ballast has sometimes consisted of other, less suitable materials, for example burnt clay.[2] The term "ballast" comes from a nautical term for the stones used to stabilize a ship.[1]
Good quality track ballast is made of crushed stone. The sharp edges help the particles interlock with each other.
Close-up of railway track
Track ballast (close up) between railway sleepers and under railway track


The appropriate thickness of a layer of track ballast depends on the size and spacing of the ties, the amount of traffic on the line, and various other factors.[1] Track ballast should never be laid down less than 150 mm (6 inches) thick;[3] and high-speed railway lines may require ballast up to 12 metre (20 inches) thick.[4] An insufficient depth of ballast causes overloading of the underlying soil, and in unfavourable conditions overloading the soil causes the track to sink, usually unevenly.[5] Ballast less than 300 mm (12 inches) thick can lead to vibrations that damage nearby structures. However, increasing the depth beyond 300 mm (12 inches) adds no extra benefit in reducing vibration.[6]

In turn, track ballast typically rests on a layer of small crushed stones: the sub-ballast. The sub-ballast layer gives a solid support for the top ballast, and reduces the seepage of water from the underlying ground.[1] Sometimes an elastic mat is placed on the layer of sub-ballast and beneath the ballast, thereby significantly reducing vibration.[6]

It is essential for ballast to be piled as high as the ties, and for a substantial "shoulder" to be placed at their ends;[3] the latter being especially important, since this ballast shoulder is the main restraint of lateral movement of the track.[7] The ballast shoulder always should be at least 150 mm (6 inches) wide, and may be as wide as 450 mm (18 inches).[8]

Chelvey MMB 05 Bristol to Exeter Line
Ballast must be irregularly shaped to work properly

The shape of the ballast is also important. Stones must be irregularly cut, with sharp edges, so that they properly interlock and grip the ties in order to fully secure them against movement; spherical stones cannot do this. In order to let the stones fully settle and interlock, speed limits are often lowered on sections of track for a period of time after new ballast has been laid.[9]


Track ballast Boxmeer sp1
New track ballast ready for laying at Boxmeer railway station in the Netherlands
A ballast regulator shaping newly placed ballast
Ballast Tamper
Ballast tamping machine as used in railroad track maintenance (Dade City, Florida)

If ballast is badly fouled, the clogging will reduce its ability to drain properly; this, in turn, causes more debris to be sucked up from the sub-ballast, causing more fouling.[4][10] Therefore, keeping the ballast clean is essential. Bioremediation can be used to clean ballast.[11]

It is not always necessary to replace the ballast if it is fouled, nor must all the ballast be removed if it is to be cleaned. Removing and cleaning the ballast from the shoulder is often sufficient, if shoulder ballast is removed to the correct depth.[12][13] While this job was historically done by manual labour,[13] this process is now, like many other railway maintenance tasks, a mechanised one,[14] with a chain of specially-designed railroad cars handling the task. One wagon cuts the ballast and passes it via a conveyor belt to a cleaning machine, then the cleaning wagon washes the ballast, and deposits the dirt and ballast into other wagons for disposal and re-use, respectively.[12] Such machines can clean up to two kilometres (1.2 mi) of ballast in an hour.[15]

Cleaning, however, can only be done a certain number of times before the ballast is damaged to the point that it cannot be re-used; furthermore, track ballast that is completely fouled can not be corrected by shoulder cleaning.[16] In such cases, it is necessary to replace the ballast altogether. One method of "replacing" ballast, if necessity demands, is to simply dump fresh ballast on the track, jack the whole track on top of it, and then tamp it down;[13] alternatively, the ballast underneath the track can be removed with an undercutter, which does not require removing or lifting the track.[16]

The dump and jack method cannot be used through tunnels, under overbridges, and where there are platforms. Where the track is laid over a swamp, such as the Hexham swamp in Australia, the ballast continuously sinks, and needs to be topped up to maintain its line and level. After 150 years of topping up, there appears to be 10 m (33 ft) of sunken ballast under the tracks.[17] Chat Moss in the United Kingdom is similar.

Regular inspection of the ballast shoulder is important;[3] as noted earlier, the lateral stability of the track depends upon the shoulder. The shoulder acquires some amount of stability over time, being compacted by traffic; maintenance tasks such as replacing ties, tamping, and ballast cleaning can upset this stability. After performing these tasks, it is necessary for either trains to run at reduced speed on the repaired routes, or to employ machinery to compact the shoulder again.[18][19]

If the trackbed becomes uneven, it is necessary to pack ballast underneath sunk ties to level the track out again. This is, in the mechanized age, usually done by a ballast tamping machine. A more recent, and probably better,[4] technique is to lift the rails and ties, and to force stones, smaller than the track ballast particles and all of the same size, into the gap. This has the advantage of not disturbing the well-compacted ballast on the trackbed, as tamping is likely to do.[20] This technique is called pneumatic ballast injection (PBI), or, less formally, "stoneblowing".[21] However, this technique is not as effective with fresh ballast, as the smaller stones tend to move down between the larger pieces of ballast.[15]


The quantity of ballast tends to vary with gauge, with the wider gauges tending to have wider formations. The depth of ballast also tends to vary with the density of traffic, as faster and heavier traffic requires greater stability. The quantity of ballast also tends to increase over the years as more and more ballast is piled on. Some figures from an 1897 report[22] are:

  • first class line – 60 lb/yd (29.8 kg/m) rail – 1,700 cu yd/mi (810 m3/km).
  • second class line – 41.5 lb/yd (20.6 kg/m) rail – 1,135 cu yd/mi (539 m3/km).
  • third class line – 30 lb/yd (14.9 kg/m) rail – 600 cu yd/mi (290 m3/km).

See also


  1. ^ a b c d e Solomon (2001), p. 18.
  2. ^ S. W. Beyer and I. A. Williams, The Geology of Clays, pages 534-537
  3. ^ a b c Bonnett (2005), p. 60.
  4. ^ a b c Bell 2004, p. 396.
  5. ^ Hay 1982, p. 399.
  6. ^ a b Bachmann 1997, p. 121.
  7. ^ Hay (1982), p. 407.
  8. ^ 150 mm (6 inches) is considered an absolute minimum, and 300 mm (12 inches) being recommended for use in heavy traffic, or with continuous welded rail or concrete ties. Most railways use between 300 and 400 mm (12 and 16 inches). A 450 mm (18 in) shoulder significantly increases lateral stability and reduces maintenance effort, though little or no resistance to buckling is gained with a shoulder above this size. See Hay (1982), pp. 407-408; Kutz (2004), Section 24.4.2
  9. ^ Bibel, George (2012). Train Wreck: The Forensics of Rail Disasters. Baltimore, MD: Johns Hopkins University Press. pp. 287–88. ISBN 9781421405902. Retrieved 2 April 2016.
  10. ^ Solomon (2001), p. 40.
  11. ^ "Railway Gazette: Bacteria to clean ballast". Retrieved 27 February 2011.
  12. ^ a b Selig & Waters 1994, p. 1430.
  13. ^ a b c Solomon (2001), p. 41.
  14. ^ Institution of Civil Engineers (1988), p. 231.
  15. ^ a b IFSC #37, ch. 9.
  16. ^ a b Solomon 2001, p. 43.
  17. ^ "Railway Materials Case Study". Retrieved 4 August 2016.
  18. ^ Hay 1982, p. 408.
  19. ^ Kutz 2004, Section 24.4.2.
  20. ^ Anderson & Key (1999).
  21. ^ Ellis (2006), p. 265, Pneumatic Ballast Injection
  22. ^ "LIGHT RAILWAYS". The Brisbane Courier. National Library of Australia. 29 September 1897. p. 5. Retrieved 21 May 2011.


  • Anderson, W. F.; Key, A. J. (1999). "Two layer ballast beds as railway track foundations". Twelfth European Conference on Soil Mechanics and Geotechnical Engineering (Proceedings). AA Balkema. ISBN 90-5809-047-7.
  • Bachmann, Hugo; et al. (1997). Vibration Problems in Structures: Practical Guidelines. Birkhäuser. ISBN 3-7643-5148-9.
  • Bell, F.G. (2004). Engineering Geology and Construction. Spon Press. ISBN 0-415-25939-8.
  • Bonnett, Clifford F. (2005). Practical Railway Engineering (2nd ed.). London, UK: Imperial College Press. ISBN 978-1-86094-515-1. OCLC 443641662.
  • Ellis, Iain (2006). Ellis' British Railway Engineering Encyclopaedia. ISBN 1-84728-643-7.
  • Hay, William Walter (1982). Railroad Engineering. John Wiley and Sons. ISBN 0-471-36400-2.
  • Institution of Civil Engineers (1988). Urban Railways and the Civil Engineer. Thomas Telford. ISBN 0-7277-1337-X.
  • International Federation for Structural Concrete (fédération internationale du béton) bulletin #37.
  • Kutz, Myer (2004). Handbook of Transportation Engineering. McGraw-Hill. ISBN 0-07-139122-3.
  • Selig, Ernest Theodore; Waters, John M. (1994). Track Geotechnology and Substructure Management. Thomas Telford. ISBN 0-7277-2013-9.
  • Solomon, Brian (2001). Railway Maintenance Equipment: The Men and Machines that Keep the Railroads Running. MBI Publishing Company. ISBN 0-7603-0975-2.

Further reading

External links

Aberedw railway station

Aberedw railway station served the village of Aberedw in Powys, Wales. Aberedw Castle was demolished to build the station and some of the stone from the castle was used as track ballast.

Arenig railway station

Arenig railway station stood beneath Arenig Fawr on the Great Western Railway's Bala Ffestiniog Line in Gwynedd, Wales. It served this thinly populated upland area, but its particular purposes were to serve Arenig Granite quarry which opened in 1908 next to the station and to act as a passing loop on the largely single-track route. The railway was the quarry's main carrier and also its main customer, crushed stone being used for track ballast.The station closed to passengers in January 1960 and freight a year later, with the last revenue earning train on 27 January 1961.

Ballast cleaner

A ballast cleaner (also known as an undercutter) is a machine that specialises in cleaning the railway track ballast (gravel, blue stone or other aggregate) of impurities.Over time, ballast becomes worn, and loses its angularity, becoming rounded. This hinders the tessellation of pieces of ballast with one another, and thus reduces its effectiveness. Fine pieces of granite, like sand, are also created by attrition, known simply as "fines". Combined with water in the ballast, these fines stick together, making the ballast like a lump of concrete. This hinders both track drainage and the flexibility of the ballast to constrain the track as it moves under traffic.

Ballast cleaning removes this worn ballast, screens it and replaces the "dirty" worn ballast with fresh ballast. The advantage of ballast cleaning is that it can be done by an on-track machine without removing the rail and sleepers, and it is therefore cheaper than a total excavation.

A cutter bar runs beneath sleeper level excavating all of the ballast under the sleepers to a specified, variable depth. A conveyor then moves the ballast into the cleaner, where it gets forced through a mesh by a shaking chamber. Pieces of ballast which are smaller than the mesh size fall through and are rejected, those that are bigger than the mesh are returned to the track along with fresh ballast. Some ballast cleaners have both ballast and spoil wagons attached to it, to which the materials are fed by a series of conveyor belts. Others simply undercut the ballast, and allow for a work train to come through to dump fresh ballast. This process can be done in short possessions, meaning that track life can be considerably extended with the minimum of disruption.

Ballast regulator

A ballast regulator (also known as a Sweeper) is a piece of rail transport maintenance of way equipment used to shape and distribute the gravel track ballast that supports the ties in rail tracks. They are often used in conjunction with ballast tampers when maintaining track.

Batts Combe quarry

Batts Combe quarry, grid reference ST460550 is a limestone quarry on the edge of Cheddar village on the Mendip Hills, Somerset, England.

It has been operating since the early 20th century and is currently owned and operated by Singleton Birch Ltd. The output in 2005 was around 4,000 tonnes of limestone per day, one third of which was supplied to an on-site lime kiln, the remainder being sold as coated or dusted aggregates. The limestone at this site is close to 99% carbonate of calcium and magnesium (dolomite). In former years it was a major supplier of limestone for railway track ballast purposes.

A lime-burning kiln at the site was closed for a while in 2006 after testing showed quicklime dust was escaping into the atmosphere. The kiln, which produced 200,000 tonnes of quicklime a year for use in the steel industry, required £300,000 of investment to resolve the problems. The closure followed an earlier warning from the Environment Agency when the company was notified that it should tighten up procedures at the site. Quicklime dust is a health hazard, which in large quantities can cause skin irritation and damage to the eyes and throat. In March 2009 however the lime kiln closed, supposedly indefinitely, following a drop in demand from the site's sole customer, Corus.; the quarry has since been taken over by Melton Ross, Lincolnshire-based Singleton Birch.

There is some evidence of a Bronze Age field system at the site. Boxes were placed in Hanson woodland adjoining the company's Batts Combe quarry to encourage dormice to breed, and monitored with the help of pupils from Wells Cathedral School.

Gare TGV Haute-Picardie

TGV Haute-Picardie is a railway station on the LGV Nord-Europe between Lille and Paris. Geographically, it is located about 10 km (6.2 mi) west of Péronne, between the towns of Saint Quentin and Amiens, in the heart of the Battle of the Somme territory. When built, it was criticised by the press for being too far from any of the neighbouring towns to be useful. It was located near a trunk road rather than a connecting railway line: it was often nicknamed la gare des betteraves, or 'sugar beet station', as it is surrounded by sugar beet fields, as it was the case for some rail stations in the countryside at the beginning of the twentieth century, when those vegetables were still transported by train towards the next sugar refinery.

Today, the station is connected with the two local main cities, namely Amiens to the west and Saint Quentin to the east, by the A29 motorway – it takes around 30 minutes to reach either city and a bus shuttle service operates.

The annual number of passengers varies from 360,000 to 400,000.

As a very small TGV station, from the point of view of watching the trains the platform is only a few metres from the main running lines, where trains pass by at 300 km/h (190 mph), and there is a good view of the lines in both directions. At most stations on high-speed lines there is some form of barrier preventing this close up viewing from the platform. Since 2013, passengers are not allowed onto the platforms until the arrival of the next stopping train, in order to avoid any risk of being hit by flying track ballast.

There is a business park close to the station.

Gondola (rail)

In US railroad terminology, a gondola is an open-topped rail vehicle used for transporting loose bulk materials. Because of their low side walls, gondolas are also suitable for the carriage of such high-density cargos as steel plates or coils, or of bulky items such as prefabricated sections of rail track.


Harappa (Punjabi pronunciation: [ɦəɽəppaː]; Urdu/Punjabi: ہڑپّہ) is an archaeological site in Punjab, Pakistan, about 24 km (15 mi) west of Sahiwal. The site takes its name from a modern village located near the former course of the Ravi River which now runs 8 km (5.0 mi) in north. The current village of Harappa is less than 1 km (0.62 mi) from the ancient site. Although modern Harappa has a legacy railway station from the period of the British Raj, it is a small crossroads town of 15,000 people today.

The site of the ancient city contains the ruins of a Bronze Age fortified city, which was part of the Indus Valley Civilization centered in Sindh and the Punjab, and then the Cemetery H culture. The city is believed to have had as many as 23,500 residents and occupied about 150 hectares (370 acres) with clay brick houses at its greatest extent during the Mature Harappan phase (2600–1900 BC), which is considered large for its time. Per archaeological convention of naming a previously unknown civilization by its first excavated site, the Indus Valley Civilization is also called the Harappan Civilization.

The ancient city of Harappa was heavily damaged under British rule, when bricks from the ruins were used as track ballast in the construction of the Lahore–Multan Railway. In 2005, a controversial amusement park scheme at the site was abandoned when builders unearthed many archaeological artifacts during the early stages of building work. A plea from the Pakistani archaeologist Mohit Prem Kumar to the Ministry of Culture resulted in a restoration of the site.

Hopper car

A hopper car (US) or hopper wagon (UIC) is a type of railroad freight car used to transport loose bulk commodities such as coal, ore, grain, and track ballast. Two main types of hopper car exist: covered hopper cars, which are equipped with a roof, and open hopper cars, which do not have a roof.

This type of car is distinguished from a gondola car in that it has opening doors on the underside or on the sides to discharge its cargo. The development of the hopper car went along with the development of automated handling of such commodities, with automated loading and unloading facilities.

Covered hopper cars are used for bulk cargo such as grain, sugar, and fertilizer that must be protected from exposure to the weather. Open hopper cars are used for commodities such as coal, which can suffer exposure with less detrimental effect. Hopper cars have been used by railways worldwide whenever automated cargo handling has been desired. "Ore jennies" is predominantly a term for shorter open hopper cars hauling taconite by the Duluth, Missabe and Iron Range Railway on Minnesota's Iron Range.

A rotary car dumper permits the use of simpler and more compact (because sloping ends are not required) gondola cars instead of hoppers. Covered hoppers, though, are still in widespread use.

Manor railway station

Manor is a closed station which was located about halfway between Werribee and Little River stations on the Geelong railway line in Victoria, Australia.

A signal box was opened at the site in February 1911, controlling a new crossing loop on the single line between Werribee and Little River. Passenger and goods facilities were provided in 1914. At the start of the 1920s the Victorian Railways opened a bluestone quarry 1.5 kilometres south of the station, to provide track ballast. The quarry was served by a long siding leading from station yard. The quarry probably ceased operating in the 1930s.

Manor was closed in November 1970 when the line between Werribee and Little River was duplicated, making the crossing loop redundant. The buildings and platform were demolished shortly afterwards.

A crossing loop with the same name, located slightly to the north of the station site, was provided on the parallel Western standard gauge line when it opened in 1995. Manor is also where the Regional Rail Link branches from the direct Geelong-Melbourne rail line.

Media/Elwyn Line

The Media/Elwyn Line is a SEPTA Regional Rail line that runs from Center City Philadelphia west to Elwyn in Delaware County.

The line, originally known as the Media/West Chester Branch, offered service to West Chester. On September 19, 1986, service was truncated to the current terminus at Elwyn. SEPTA still calls the infrastructure along the line, but not the train service itself, the West Chester Branch.As of November 2016, most inbound Media-Elwyn line trains continue onto the West Trenton and Manayunk/Norristown lines.At the end of 2021, service is to expand westward to a new station in Wawa. Planning officials, rail proponents and SEPTA have also discussed a resumption to the original terminus in West Chester without success.

Since 1997, the heritage railway West Chester Railroad has operated on the tracks between Glen Mills and West Chester, where SEPTA no longer runs trains; this is the only such operation on a SEPTA-owned line. Amtrak maintenance trains also collect track ballast from a quarry near Glen Mills station.

Meldon Quarry

Meldon Quarry is a limestone quarry in Devon, England. It is at the northern edge of Dartmoor, about 2 miles SW of Okehampton. It was developed from 1897 to supply track ballast and other stone products for the London and South Western Railway (LSWR). It was privatised in 1994.

Railroad tie

A railroad tie or crosstie (American English) or railway sleeper (British English) is a rectangular support for the rails in railroad tracks. Generally laid perpendicular to the rails, ties transfer loads to the track ballast and subgrade, hold the rails upright and keep them spaced to the correct gauge.

Railroad ties are traditionally made of wood, but pre-stressed concrete is now also widely used, especially in Europe and Asia. Steel ties are common on secondary lines in the UK; plastic composite ties are also employed, although far less than wood or concrete. As of January 2008, the approximate market share in North America for traditional and wood ties was 91.5%, the remainder being concrete, steel, azobé (red ironwood) and plastic composite.The crosstie spacing of mainline railroad is approximately 19 to 19.5 inches for wood ties or 24 inches for concrete ties. (The spacing means the distance of the center of one tie to the center of the next tie, and equals to the width of one tie plus the width of one crib.) The amount of ties is 3,250 wooden crossties per mile (2019 ties/km, or 40 ties per 65 feet) for wood ties or 2640 ties per mile for concrete ties. Rails in the US may be fastened to the tie by a railroad spike; iron/steel baseplates screwed to the tie and secured to the rail by a proprietary fastening system such as a Vossloh or Pandrol are commonly used in Europe.

South Chicago and Indiana Harbor Railway

The South Chicago and Indiana Harbor Railway (reporting mark SCIH), owned by Mittal Steel Company (originally the International Steel Group), is the former Chicago Short Line Railway which operates 27 miles (43 km) of track between Chicago, Illinois and East Chicago, Indiana.The Chicago Short Line was incorporated in 1900 and leased four miles (6 km) of yard and sidings from the adjacent Iroquois Iron Company. By 1919, C&CC&DC owned and operated a whopping 7.68 miles (12.36 km) of tracks. until 1906, the railroad interchanged traffic connections in the South Chicago District through trackage-rights agreements with the B & O.

In December 1905, C&CC&DC sold the Iroquois Iron Company a chunk of land for expansion along the lake front. Included was the railroad and its right-of-way. There were some problems at first. Iroquois was a manufacturer incorporated under the General Laws of the State of Illinois, which prohibited manufacturers from operating a railroad. As a result, Iroquois leased the railroad to a new entity, the Chicago Short Line.

In 2003 Chicago Short Line became the South Chicago and Indiana Harbor railroad.

One of SCIH's main sources of revenue from the South Chicago operation was the intra-plant movement of pig iron, loaded slag ladles (to and from the cinder dump), and empty ladles to and from the ladle preparation building. The SCIH also handled substantial tonnages of slag, used by some Midwestern railroads for track ballast.

The railroad owns 4 diesel engines. 2 EMD SW1001's numbered 28 and 29 and two EMD SW1500's numbered 30 and 31.


A stoneblower is a railway track maintenance machine that automatically lifts and packs the sleepers with small grade ballast, which is blown under the sleepers to level the track. An alternative to the use of a ballast tamper, the totally self-contained machine levels track without the use of a large gang of workmen.


Tamper may refer to:

Tamper, to use a tamp, a tool for material compaction

Tamper, a pipe tool component

Tamper, a neutron reflector used in nuclear weapons

Tamper, to interfere with, falsify, or sabotage

Ballast tamper, a machine that tamps railroad track ballast

Tamping machine

A tamping machine or ballast tamper is a machine used to pack (or tamp) the track ballast under railway tracks to make the tracks more durable. Prior to the introduction of mechanical tampers, this task was done by manual labour with the help of beaters. As well as being faster, more accurate, more efficient and less labour-intensive, tamping machines are essential for the use of concrete sleepers since they are too heavy (usually over 250 kg (551 lb)) to be lifted by hand. Whilst also available as a plain tamper with no lifting or lining function this article will focus on the multi function machines.

Early machines only lifted the track and packed the ballast. More modern machines, sometimes known as a tamper-liner or tamping and lining machine, also correct the alignment of the rails to make them parallel and level, in order to achieve a more comfortable ride for passengers and freight and to reduce the mechanical strain applied to the rails by passing trains. This is done by finding places where the sleepers have sunk from the weight of the passing trains or frost action, causing the track to sag. The tamper lifts each sleeper and the rails up, and packs ballast underneath. When the sleeper is laid down again, the sagged rails now sit at the proper level. In cases where frost action has caused adjacent rails to rise higher, ballast tampers can raise rails above their original level to make the line level again. "Lining" rails doesn't involve ballast tamping, it merely ensures the rails are perfectly parallel and straight as possible. Combining tamping and lining into a single machine saves time and money, as only one machine needs to be run over the track to perform both functions.

Unit train

A unit train, also called a block train or a trainload service, is a train in which all cars (wagons) carry the same commodity and are shipped from the same origin to the same destination, without being split up or stored en route.

They are distinct from wagonload trains, which comprise differing numbers of cars for various customers.Unit trains enable railways to compete more effectively with road and internal waterway transport systems. Time and money is saved by avoiding the complexities and delays that would otherwise be involved with assembling and disassembling trains at rail yards near the origin and destination. Unit trains are particularly efficient and economical for high-volume commodities. Since they often carry only one commodity, cars are of all the same type; often the cars are identical.

Watts Point volcanic centre

The Watts Point volcanic centre is a small outcrop of Pleistocene age volcanic rock at Watts Point in British Columbia, Canada, about 10 kilometres (6 mi) south of Squamish and 40 kilometres (25 mi) north of Vancouver, and just north of Britannia Beach. It is the southernmost volcanic zone in the Squamish volcanic field and of the Garibaldi segment of the Cascade Volcanic Arc. The latest research indicates that it is most likely a subglacial mound. It comprises a continuous mass of sparsely porphyritic highly jointed dacitic lava overlying the mid-Cretaceous Coast Plutonic Complex and overlain locally by clay and of glacial till.

The volcanic outcrop at Watts Point extends from below the present sea level up the side of a steep slope over 240 metres (800 ft). The outcrop is less than 1 kilometre (0.6 mi) long, with an area of about 0.4 square kilometres (0.2 sq mi) and an eruptive volume of roughly 0.02 cubic kilometres (0.0048 cu mi). The location is heavily forested, and the BC Rail mainline passes through the lower portion of the outcrop about 40 m (130 ft) above sea level. Two railroad track ballast quarries, one near the middle and the other near the upper edge, provide the best exposure of the interior of the lava mass. BC Highway 99 climbs over the eastern shoulder of the complex before descending to the area of the Stawamus Chief and Murrin Park, south southeast of Squamish.

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