Reservoir, Kirnie Law

The Kirnie Law Reservoir, designed by Boving & Co, London, and constructed by Melville Dundas and Whitson for Henry Ballantyne and Sons, Limited, was started in 1919 and became operational in 1922. This free-standing reservoir has a square plan and features a subterranean 12-inch cast-iron pipe leading to a tall square-plan tower that contains a surge tank. It is made of ferro-concrete with cast-iron pipes, all steel riveted.

The reservoir itself has tapered side walls that are 8 inches thick at the top, tapering to 14 inches in the upper 10 feet 6 inches, and broadening to 21 inches at the base, supported by a reinforced concrete base. The southeast elevation previously displayed advanced concrete lettering that read "HENRY BALLANTYNE AND SONS, LTD KIRNIE LAW RESERVOIR," although a hole has now been blown through the center. To the left of the lettering is an overflow/sluice ramp, and on the far left, there is an iron ladder leading to a concrete viewing platform at the top of the angle, with another ladder on the opposite side leading down into the reservoir. The other elevations are plain, except for a projecting concrete lean-to at the south angle, which housed electrical recording appliances connected to the Barograph Recorder in the mill, showing the height of water in the reservoir, along with the outlet and inlet valve.

Inside, the reservoir measures 192 feet square and is 15 feet 6 inches deep. The concrete floor slab is 9 inches thick, with light reinforcement near the upper surface, increasing to 18 inches thick approximately 6 feet from the inner face of the walls. The floor slab continues to form a 2-foot thick toe to the exterior of the wall, with the slab being 21 inches thick under the wall and tapering to 9 inches thick at the outer point. The side walls are heavily reinforced and tied to the floor slab, finished with fine plaster.

The surge tank is housed in a tall square-plan ferro-concrete tower with projecting angle margins. A 9-inch steel riveted high-pressure pipeline is set within the ground at the front, featuring a pair of access manholes with cast-iron covers, although one is now missing, along with a lesser pipe adjacent to the left.