In 1832 engineer James Green advised on extending the system, and suggested a line with three inclined planes to reach Cwmmawr, further up the Gwendraeth Valley.

Thomas Kymer began mining at Pwll y Llygod and Great Forest (near Carway) in 1760, and sought parliamentary approval to construct a canal at his own expense in early 1766.

The act included powers to divert the course of the Gwendraeth Fawr from Pwll y Llygod to Pont Spwdwr, where the Kidwelly to Llanelli turnpike road crossed the river.

Two engineers, Edward Martin and David Davies, proposed an extension of the canal to the top of the Gwendraeth valley, and another which would cross Pinged marsh and would terminate at Llanelli.

The act envisaged an upper terminus beyond Cwmmawr at Cwm y Glo, and a series of feeder canals or tramroads to connect to the pits and levels where extraction of coal was taking place.

[4] The newly formed company was required to complete the extension from Pwll y Llygod to Pontyates and the first section of the Llanelly branch to the point where it crossed the Ashburnham Canal within six years.

3. c. lxxv), was obtained on 28 May 1818, which extended the time limit for building the canal and removed the requirement to clear the river channels to the harbour.

Pinkerton and Allen pressed on with construction, completing the routes to Pontyates and the Ashburnham Canal crossing in 1824, while the company directors asked the engineers John Rennie and Edward Bankes to examine the issue of a suitable harbour.

Rennie suggested extending the canal towards what is now Burry Port, and the construction of a new harbour on the sands at Tywyn Bach.

Between late 1823 and April 1824 he built two miles (3.2 km) of canal, including a lock at Cross Lane cottage.

A second report, supplied three months later, recommended an extension along the Gwendraeth valley, and the construction of three inclined planes to reach a terminus just above Cwmmawr.

He had been the engineer for the Bude Canal, which included six planes, five powered by water wheels and one by a descending bucket mechanism.

He was at the time the engineer for the Grand Western Canal, which included seven vertical boat lifts and an inclined plane at Wellisford, again to be powered by a descending bucket mechanism.

The rise on the final section of the canal to Cwmmawr was 190 feet (58 m), and three inclined planes would be much quicker and use much less water than the alternative of 20 or more locks.

[11] At the southern end, access to Burry Port harbour required a deep cutting to be constructed, and this was completed by March 1835.

[12] The Grand Western Canal Company had taken a similar action three days earlier, when the Wellisford inclined plane had failed to work because of a design fault in the sizing of the descending bucket.

A local writer called Ap Huw[14] stated that "the inclined planes were manipulated by hydraulic pumps which were considered to be great discoveries".

The railway engineer W. Robinson described "balance caissons with hydraulic brakes apparatus to check the barges in their descent and to arrange that the full ones coming down pull the empty ones up".

These clearly show twin-track inclines at Capel Ifan and Pont Henry, and because most of the traffic was in the downhill direction, a simple counterbalanced system was probably employed, although it has also been suggested that the barge may have been balanced by a water tank on the second track to more easily control the speed of descent.

The new company built a railway from Burry Port to Pontyberem, along the towpath over Pinged marsh, and on the bed of the canal elsewhere.

[17] Although the main canal was replaced by the railway, Kymer's dock continued to be used for the transfer of coal to coastal ships for another 50 years.

Most of the traffic had transferred to the railway by 1914, but some coasters continued to transport coal; the last recorded sailing was in the early 1920s, and was bound for Llanstephan.