Sessional_Paper_1927 — Page 187

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Annexe A.

Extracts from a report of Mr. R. M. Henderson, Engineer-in-charge of Waterworks, on the Development of the Aberdeen

Valley Catchment Area.

The existing Paper Works Reservoir is situated on the main Aberdeen stream West of Bennet's Hill. The Dam which is of rubble concrete faced and backed with granite rubble was built in 1890, having a maximum depth of 40 ft. from stream bed to overflow, an overflow of 125 lin. ft., and con- tained 42 million gallons when full, top water level being + 243.85 O.D. Cost $24,000.

In 1899 the Dam was raised eighteen feet and strengthened by means of 10 concrete and rubble faced counterforts, the overflow being left the same length, top water level being raised 18 ft. to + 261.85 O.D. and the storage capacity raised to 92 million galls. Cost $48,000.

The Dam which has a total length of 465 ft. is shown on Drawing No. 3 and is constructed of a lime and cement concrete lining ( cement, 1. lime 2 red earth and 3 stone) backed by Rubble Concrete (1 lime, 2 red earth and 3 stone) and faced with granite rubble with 10 counterforts of rubble con- crete faced with granite rubble. There is one draw-off operated by a primi- tive headstock and sloping spindle, while there is a washout pipe at stream bed level.

The structure while apparently well built is constructed of poor materials and is a good exainple of what might be termed cheap construction.

The foundations in the stream bed and for some height on either side appear excellent, but further than that it is impossible to more than guess. As however leakage from the Dam is not excessive, the foundations generally would appear to be good.

The spur on which the West end of the Dam rests rises sharply, but the spur at the East end has a very flat slope, so that any possible raising of the Dam any considerable height would mean adding greatly to its length.

I have very carefully considered the possibility of raising this Dam and have had rough contours taken for thirty feet above the existing top water level to get capacities. Thirty feet added to the existing Dam would raise the capacity from 92 million gallons to 270 million gallons, but would make the Dam 700 feet long.

An entirely new Dam would require to be constructed immediately in front of the existing one, as the present structure would not stand the pressures and could therefore not be incorporated in the new structure and the foundations originally made for a 40 feet dam would not be safe for a 90 feet dam.

Annexe B.

For the foregoing reasons in the event of complete resumption of the Paper Co.'s rights, I would propose development of the valley on the following lines as shown generally on Drawing No. 4.

Build a concrete and masonry dam in the main stream about mile above the existing Dam, the reservoir to hold about 200 million gallons with a top water level of + 365 O.D.

Construct a West Catchwater 15,000 feet long draining 496 acres, and an East Catchwater 11,200 feet long draining 314 acres, both discharging into the reservoir, and raising the Drainage Area from 505 acres to 1,315 acres.

Paper Works Reservoir.

Drawing

No. 3.

Scheme A.

Drawing No. 4.