Sessional_Paper_1904 — Page 290

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which water entered the well from the layer of boulders precluded the possibility of pumping it dry in order to admit of an actual inspection of the bottom.

Work was then begun upon Well No. 3 and, after sinking it to a depth of 42 feet through clay silt and sand, the stratum of beach boulders above described was again encountered. Sinking operations were continued, and, after passing through about 10 feet of boulders, sand was again met with and it was not until the well had reached a depth of 582 feet that rock was finally found. Here also it was found impossible to dry the bottom by pumping and the extent and nature of the rock were ascertained by feeling it carefully all over. Pieces were also broken off and compared with the rock above water level at the sides of the bay, and, as the result of this comparison, there seems no room to doubt that rock in situ has been reached. Over a small portion of the area (6 feet diameter) covered by the well, the rock dipped away to greater depth. The sinking of this well was completed by the middle of October.

Whilst the operations above described were in progress, a large number of prickings with Nortou tubes (171 in all) were made all over the site of the dam, the result of which was to confirm the information obtained from No. 2 Well and borings formerly taken. They showed the presence of a hard layer, presumed to be rock, at an average depth of about 40 feet over the entire area.

As the information obtained from No. 3 Well cast some doubt upon the reliability of that derived from No. 2 and from the borings, &c., operations were undertaken with a view to sinking the latter to a greater depth, if possible. It was then found that what was formerly supposed to be rock was really a large boulder. The removal of such an obstacle was necessarily a work of some difficulty and it had not been accomplished by the close of the year.

In consequence of the results obtained from No. 3 Well, attention was turned to two sites further inland, where trial pits were made in the hillsides for the pur- pose of ascertaining whether a satisfactory foundation would be obtainable without excavating to great depths. Arrangements were also made for sinking a well on one of the sites with the same object. Work on the trial pits was completed by the close of the year, but on the well it was delayed until the plant could be released from No. 2.

As it appeared obvious from the results of the trial works that a lengthened period must elapse before a scheme for the low level dam could be definitely prepared, submitted and carried out, it became necessary to consider what could be done by way of a scheme which would enable this interval to be tided over and at the same time would not hamper or interfere in any way with the carrying out of the former,

After full investigation, it was decided that a dam on site No. 4 of Mr. COOPER'S 1896 Report, but of somewhat greater height than he recommended, would afford the most ready and economical means of doing this, and a scheme was accordingly prepared and submitted to Government.

It provided for the construction of the following works :----

(i.) A dam to impound 194 million gallons.

(ii.) A pumping station, with the necessary quarters, near the shore of Tytam Bay and below the site of any possible low-level dam, and the erection there of the pumping engines ordered from Eng- land (two sets, each capable of delivering 1 million gallons per day).

(iii.) A new road from the gap through which the Stanley Road passes, above Tytam Tuk, to near Tytam Bye-wash Reservoir (lengthi 1.40 miles).

(iv.) Access roads to the Pumping Station and to Tytam Gauge Basin

and a track for the temporary suction main.

(v.) A rising main, 18" diameter, from the Pumping Station to Tytam Gauge Basin by way of the new road (length 2.03 miles).

(vi.) A suction main, 18" diameter, from the small dam erected for the temporary pumping plant to the Pumping Station (length 1.25 miles). The pipes from this main are intended to be subse- quently used for duplicating the rising main.