Ballast is one of the least-understood elements of the railway infrastructure. Looking like a pile of stones on which the track rests, it is actually a carefully-engineered structure which the track rests, it is actually a carefully-engineered structure which supports and locates the track, aids drainage and keeps down vegetation.

It also wears out. The constant pounding from passing trains causes the individual stones to rub against each other, rounding off the sharp edges which are crucial to stabilising the structure, and creating dust.

After twenty years on the main line, it has to be renewed. However, the track itself is designed to last for 40 years so rail maintenance teams need a way to renew it without lifting the whole track.

Enter the high-output ballast cleaner – a long yellow train which cuts the ballast out from under the track while supporting the rails. The ballast is then screened and stones which are still to size are returned while worn ones are fed by conveyor into a rake of empty wagons. The ballast is then topped up from another set of wagons containing new material.

So, at the end of every night, one set of wagons of spent ballast need to be emptied while another has to be refilled with 1,100 tonnes of fresh stock.

Screening now at Willesden

One of the locations used for this work is at Willesden in north west London. A one-and-a-half acre site is operated by Lynch Plant, a plant-hire company with 30 years of experience in the highways, utilities, ground works, demolition, snow clearance and winter services fields as well as rail.

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Lynch currently has a nine-month contract for this work and is confident that Network Rail, which has three other high output ballast wagon trains dotted around the country, will come back to Willesden when it needs to operate in this region again.

Three trains a week bring 1,300 tonnes of new ballast from Barton Aggregates in box wagons. Lynch’s 13-strong rail team then load into the ballast wagons using clamshells.

Five nights a week, the train goes out and lays 800 – 1000 tonnes of new ballast and brings back the same amount of spent ballast for recycling. Once the train has returned to Willesden, the spent ballast is directly taken from the rail wagons and loaded into a large McCloskey International screening machine. This grades the spent spoil material and separates it into three different categories.

70-30mm ballast mix is used as a sub-base or as a soak away by the construction industry while 30mm-00mm dust mix comes off a different belt and is also used for construction. Both of these types of recycled material are delivered by road to local construction sites or batching plants as a sub base material for paths and foundations for building sites. Lynch has a large customer base who want raw aggregates so there is a steady but controlled flow of HGVs arriving at Willesden to collect the spent ballast brought back in by the trains.

Oversized waste products from the screener, which include all types of rubbish such as bolts, screws, pieces of concrete and random stones, are then hand-sorted before going off to a separate recycling process by lorry.

Containing the clay and mud

Being so close to the railway lines, Lynch had to make commitments that none of the clay, mud and ballast they process at this site would contaminate the tracks. Contract manager Ray Cripps commented: “When we took over the site, the biggest commitment was keeping 200 tipper wagons of clay and mud far enough away from the track whilst also maintaining operational safety of the yard. We had to separate lorries from diggers and plant loading the trains whilst keeping the moveable aggregates separate from the railway siding.”Page 30 please Matt RM 900-RT (1) [online]

To make sure that the various materials were contained, Lynch contracted A Jansen BV to build a modular wall divider using its Legio Block product. Following a full site survey, Jansen came up with a design that would withstand the pressures of plant rolling over it and working on top of it each day and then installed the design to drawings which they provided.

Keven Pope from A Jansen BV said: “Ray was looking to have his walls built really quickly. We surveyed the site, ran some tests to see the design would withstand the pressures and within 48 hours we had 25 lorries carrying in 340 blocks to build the retaining walls, safety walls and separating walls for each grade of ballast. Our engineer was able to construct
the walls using the Hiab cranes on the back of each lorry. Within 24 hours, we had finished construction and issued the certificate to say it was safe.”

“If, at a later date, Lynch wants to expand the site or move it around or put a roof on the walls, it is simple and easy to do. It provides a safe operating area and keeps staff, machines and trains separate from each other whilst storing, sorting and processing 1,300 tonnes of ballast.”

Fewer lorry movements

Lynch has been operating this new method of ballast disposal since April 2014. Previously, the old spent ballast was delivered to Colnbrook, near Terminal Five at Heathrow, irrespective of where the ballast was being replaced on the network. Now that Lynch is sending it direct to local contractors, that leg of the process is redundant. As a result, the operation is much more predictable as it removes a train path and, most importantly, it allows more time for maintenance of the equipment and reduces energy costs and pollution around London.

Director Rob Lynch commented: “We are very pleased to have been approached by Network Rail and to come up with the most efficient solution ever for dealing with the high output ballast train. It is a joy to watch our operation at work, as it is so simple. We expect to be operational at other locations soon.”

Lynch, which runs a fleet of 105 lorries in London, takes its environmental and safety responsibilities very seriously and has been able to halve the number of 90-mile round trips carried out by its 38 rigid tipper HGVs since opening the rail hub. It has thereby reduced its carbon footprint as rail produces 70% less carbon dioxide than the equivalent journey as well as reducing road congestion – an average freight train removes 60 HGVs from the roads.

Aiming to be a good neighbour, Lynch monitors and controls arrival and departure of HGVs for safety, accounting and congestion reasons. The site is kept clean and well below air quality limits by having a road sweeper vehicle working dawn to dusk to control dust and dirt while all HGV tyres are washed before leaving the site. The company recognises the safety benefits of using rail to remove HGV miles, especially with regard to cyclists in the capital; in the past five years 55% of cycling fatalities involved an HGV even though they represent less than 4% of London road miles driven.

By offering and running an integrated solution in which Lynch coordinates all the elements, including a full recycling service, Ray is able to offer an attractive package to a range of customers. The new process also highlights the crucial role that rail freight has in maintaining and developing the nation’s rail and road infrastructure.