Built Heritage

The Mourne Wall was built between 1904 and 1922 (with a brief interruption due to World War I). It was constructed to enclose the water catchment area for the Silent Valley Reservoir, under the guidance of the Belfast Water Commissioners.

Stretching 22 miles, the wall crosses 15 mountain peaks and is made of roughly trimmed stone topped with broad coping stones. On average the wall is about 1.5 metres (4 ft 11 in) high and 0.8 to 0.9 metres (2 ft 7 in to 2 ft 11 in) thick. It features 3 stone towers, each marked with the year of its completion: Slieve Donard (1910), Slieve Commedagh (1913) and Slieve Meelmore (1921). Construction took place during the warmer months (March to October), with workers often camping overnight in the mountains to avoid the daily commute.

Background

By the end of the 19th century, Belfast was a blossoming city. It had become a hub for shipbuilding and was also known as the linen capital of the world. The city’s population grew rapidly as people moved from rural areas for job opportunities. After investigating five sites, the Mournes were chosen to supply enough water for Belfast’s current and future needs. Consequently, in 1893, the Belfast & District Water Commissioners bought 9,000 acres from Lord Kilmorey to create a water catchment area.

In 1901, they built an underground pipeline to transport water 35 miles to Knockbracken Reservoir, on the outskirts of Belfast. This pipeline met the city’s immediate water needs while the Silent Valley reservoir was under construction.

A Challenging Landscape

The Silent Valley’s topography was ideal for water storage. It had deep valleys (widened by ice), nearby rivers, and many high springs. However, this landscape posed significant challenges, causing delays. Pearson & Sons of London began constructing the reservoir in 1923. However, two years into the project, they encountered a major issue. Initial borehole tests indicated bedrock at depths of 28 to 65 feet. However, when it came to construction, they discovered that it was significantly deeper. Consequently, the contractors could no longer honour the original contract and a legal battle ensued. A new contract was eventually agreed and work recommenced.

Unfortunately, a new problem led to further delays. Water and silt kept flowing back into the trench, preventing the construction of the cut-off wall. Attempts to use a pump and sump method failed. They then sunk drainage shafts, 11-12 feet in diameter, under compressed air to extract large quantities of water. This untested method required only the fittest men to work in the shafts. Workers wore heavy woollen Donkey jackets to stay warm during the two-hour decompression period. This was necessary to avoid the bends (air bubbles forming in the blood). Subsequently, filling the trench took nearly a year.

The project, initially expected to take six years, was completed in ten years. The final cost was £1.38 million, equivalent to approximately £126 million today.

Lord Carson cut the first sod for the Silent Valley construction on October 10, 1923. Within weeks, “Watertown” was built on the western side of the valley along the “Back Road,” near the construction site.

They started by building wooden houses for the workers. At its peak, around 2,000 workers were on site. About 600-700 people lived in Watertown, so nearly a third of the workers lived there. The rest lived locally and many walked long distances to work each day.

As the town grew, it added amenities like a cinema showing early silent films. There was also a recreation hall with weekly entertainment and dances, and a hospital with a doctor and nurse. Health and safety were minimal, so these services were crucial. The town also had a working men’s club for billiards, darts and boxing. It even had its own police barracks with a policeman named Constable Lawless ! A large coal-fired power station provided electricity for the construction site and the town.

Watertown quickly became self-sufficient. A blue van (the “Tin Lizzie”) took people to nearby Kilkeel on Fridays and Saturdays for items not available on-site. Job opportunities were scarce in 1923. Many men travelled 6 or 7 miles from areas like Greencastle, Hilltown, Cabra, and Slievenamann to work. They often carried lamps to light their way.

Tollymore Forest Park is a place where history and architecture come together. Established as a private deer park in the 18th century, it was later transformed into a picturesque landscape. Today, much of its rich built heritage remains, offering a glimpse into the past.

Throughout the park, ornamental structures add character and charm. Stone bridges, Gothic-style gates, and decorative follies line the paths, many following the course of the Shimna River. These features were carefully designed to enhance the park’s natural beauty, blending seamlessly with the rolling hills and woodlands.

Beyond its built heritage, Tollymore has long been a place of recreation and inspiration. Visitors continue to explore its scenic trails, cross its historic bridges, and admire the craftsmanship of its ornamental buildings. This unique blend of nature and history makes Tollymore a treasured part of the Mourne landscape. For more information on the history of the park and its various structures, see below.

The Binnian Tunnel, completed in 1952, was a ground-breaking project. It diverted water from Annalong Valley to the Silent Valley. Originally, a reservoir was planned for Annalong Valley, but engineers chose a tunnel instead due to challenges experienced with the Silent Valley project.

The tunnel stretches 2¼ miles, measuring 7 feet 6 inches high and 8 feet wide. It runs half a mile beneath the mountain, dropping 18 feet along its length.

Work began in 1949, with two teams tunnelling from opposite ends. Despite limited technology, they met in the middle with just a 1.5-inch margin of error—an incredible achievement! However, the project faced a setback. Workers hit flowing sand and cracked rock, requiring cement grout and delaying progress by six months.

Conditions were brutal. Over 150 men blasted through rock using dynamite, working by candlelight. During explosions, they stayed inside with little protection. Poor ventilation left dust hanging in the air, and newcomers quickly learned to stand aside—the force of the blasts could knock them off their feet!

The Binnian Tunnel remains a testament to skill, perseverance, and determination.