West Baldwin Reservoir
West Baldwin Reservoir is impounded by an earth embankment dam with a maximum height of about 22.5 metres. The maximum depth of water impounded is just over 20 metres. The top water area of the reservoir is about 16.8ha. The dam has a vertical puddle clay core supported by zoned earth fill shoulders. The upper part of the upstream face is faced in dry rubble pitching about 600mm thick. The crest and downstream face are grassed.
The vertical puddle clay core connects to a puddle clay filled cut-off trench with a width of about 3 metres running across the base of the embankment from abutment to abutment. An account provided by G H Hill & sons for the Reservoir Inauguration Ceremony Programme, held on 6th September 1905, suggests that the cut-off trench was on average about 50 feet deep.
The draw-off pipework is contained within a tunnel driven through the left abutment. There is a dry vertical valve shaft about 14 metres upstream of the point at which the tunnel meets the line of the cut-off. The tunnel between the base of the shaft and a point just downstream of the cut-off, was provided with a segmental cast iron lining surrounded with concrete, the remainder of the tunnel having a plain cast insitu concrete lining. Upstream of the draw-off shaft the tunnel continues to a screened forebay structure. The wet tunnel upstream of the shaft was sealed off from the dry tunnel downstream of the shaft, by means of a strong blue brickwork plug.
The plug has built into it the 18 inch diameter cast iron lower draw-off pipe, a 12 inch diameter cast iron scour pipe, and a third pipe also 12 inches in diameter apparently intended as a spare intake pipe. Each of the three draw-off pipes has an isolating valve immediately downstream of the plug, though there are no secondary guard valves. Within the draw-off tower, the 18 inch diameter draw-off pipe is connected to a vertical cast iron stand pipe with 18 inch diameter valved intakes at two upper levels. The three intake isolating valves have rising spindles raised and lowered by geared headstocks installed within an octagonal masonry valve house at the top of the shaft. The scour isolating valve is operated from the base of the shaft using a geared hand-wheel directly on the valve.
There are two principal raw water mains laid from the reservoir to the treatment works at Glencrutchery, the original 12 inch diameter cast iron main laid when the reservoir was originally constructed, and a 15 inch diameter cast iron main laid circa. 1926/27. In addition, there is a third main between the dam and Ballachrink some 3km downstream, laid in 1979 in 18 inch diameter UPVC pipes. All three mains are cross connected at regular intervals where they are laid close together. Raw water from Kerrowdhoo and West Baldwin Reservoirs is blended prior to pressure treatment in a single process stream, and because of the difference in elevation between the two sources, water drawn from Kerrowdhoo generally needs to be booster pumped into the works inlet. At times of high demand, and when the water level at West Baldwin is low, a further set of booster pumps also needs to be brought into use, to maintain the required flows from West Baldwin, and again these are installed within the Water Treatment Works building at Glencrutchery.
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