Chirk Aqueduct on the Llangollen CanalA Landmark of Canal Engineering

Chirk Aqueduct one of the most impressive and historically significant structures on the Llangollen Canal

Carrying the waterway high above the River Ceiriog on the England–Wales border. Built during the height of Britain’s canal age, the aqueduct is a striking example of early industrial engineering, combining elegance, strength, and practical design.

Today, it remains a vital part of the canal and a dramatic gateway into North Wales for boaters, walkers, and heritage enthusiasts.

Dates of Construction and Historical Background
Construction began: 1796 - Completed: 1801 - Opened to navigation: 1801

Chirk Aqueduct was built as part of the Ellesmere Canal project, an ambitious scheme intended to link the rivers Dee, Severn, and Mersey.

Although the full plan was never completed, the section that became the Llangollen Canal proved hugely successful and remains in use today.

The Engineers Behind Chirk Aqueduct

The aqueduct was designed by two of the most important engineers of the Industrial Revolution:

• William Jessop – Principal engineer of the Ellesmere Canal
• Thomas Telford – Assistant engineer, later becoming one of Britain’s greatest civil engineers

While Jessop provided the overall design leadership, Chirk Aqueduct was one of the projects where Telford’s talent became increasingly evident, particularly in structural design and construction methods.

Why Chirk Aqueduct Was Built

The purpose of Chirk Aqueduct was straightforward but challenging:

• To carry the canal across the deep valley of the River Ceiriog
• To maintain a level, lock-free waterway across difficult terrain
• To create a continuous navigation route towards Llangollen and the River Dee

Without an aqueduct at Chirk, the canal would have required steep descents, additional locks, or lengthy detours, all of which would have reduced its commercial value and efficiency.

Design and Construction

Chirk Aqueduct is built from local stone and consists of:

• 10 semi-circular arches
• A total length of approximately 720 feet
• A height of around 70 feet above the river
• A narrow cast-iron-lined trough to hold the canal water
• A towpath on one side, protected by a stone parapet

The structure runs parallel to the Chirk Viaduct, a railway bridge built later, creating a dramatic double crossing of the valley.

Obstacles Overcome During Construction

Building Chirk Aqueduct in the late 18th century presented numerous challenges:

• Remote Location
  Materials had to be transported to a rural valley with limited infrastructure
  Workforce accommodation and supply were logistical challenges
• Foundation Challenges
  Strong foundations were required on uneven valley sides
  The structure had to withstand water weight, frost, and weather exposure
• Water Retention
  Preventing leaks was critical
  The canal channel was lined with iron plates sealed with puddled clay to ensure watertight integrity
• Precision Engineering
  The aqueduct had to maintain an exact level to allow uninterrupted navigation
  Any settlement or misalignment could have caused structural failure

The successful completion of Chirk Aqueduct demonstrated the growing confidence and skill of British engineers at the turn of the 19th century.

Relationship to Pontcysyllte Aqueduct

Chirk Aqueduct is often overshadowed by the nearby Pontcysyllte Aqueduct, completed in 1805 and now a UNESCO World Heritage Site. However, Chirk played a crucial role as a proof of concept.

Lessons learned during its construction helped Telford refine his techniques, directly influencing the more daring iron-built design of Pontcysyllte.

Chirk Aqueduct Today
Today, Chirk Aqueduct:

Remains fully operational and carries regular canal traffic
Is a Grade I listed structure
Forms part of the Llangollen Canal World Heritage corridor
Is popular with walkers and photographers
Offers boaters a dramatic crossing high above the River Ceiriog
For many crews, crossing Chirk Aqueduct is a memorable highlight of a Llangollen Canal cruise.

Why Chirk Aqueduct Is So Important
Built between 1796 and 1801
Designed by William Jessop with Thomas Telford
Enabled the canal to cross a deep river valley without locks
Demonstrated advanced stone aqueduct construction
Helped pave the way for later engineering masterpieces
Chirk Aqueduct represents the moment when canal engineering moved confidently into large-scale landscape-spanning structures.

Conclusion
Chirk Aqueduct is a remarkable achievement of early canal engineering, blending strength, precision, and elegance. Built to overcome the formidable obstacle of the River Ceiriog valley, it played a vital role in the success of the Llangollen Canal and the wider Ellesmere Canal scheme. More than 200 years after its completion, the aqueduct continues to serve its original purpose, standing as a lasting tribute to the ingenuity of William Jessop and Thomas Telford.