UNDERGROUND RIVERS.

New Zealand Herald, Volume LXVIII, Issue 20827, 20 March 1931, Page 11

UNDERGROUND RIVERS.

DISCOVERY AT ROTORUA.

DRAINAGE WORK

[from our own correspondent.] EOTORUA, Thursday. In draining the western suburbs of Rotorua many difficulties have been mat with owing to the existence of underground rivers and hot springs in the lowlying areas. The intention iyt the outset was to provide a pumping plant to lift the sewage matter ovor the ridge in Ranolf Street, so that it would gravitate to the sewage treatment depot near the Wairoa Road. Main drains have been laid much reticulation has been completed in this portion of the town gravitating toward the position chosen for the erection of the pumping plant. When the site was being excavated the first sign of trouble was detected. First cold sulphur water was discovered flowing freely toward the lake. Pumps were installed capable of discharging 40,000 gallons an hour, but it was found impossible to reduce the flow below a certain level. The services of a water diviner were obtained, who traced back to its sourco and here it was found that several streams flowed in different directions toward the lake. Upon further investigation it was found that under tho sito chosen was an underground river about 20ft-, wide and sft. deep, carrying 22,000 gallons of water an hour. When attempting to deal with tho body of water by pumping it was found that tho other streams there wero drawn to tho river. An effort to divert the flow by driving long piles close* together has been tried, lliis diverted tho flow, but the water forced its way through the bottom of ii section of a drain and flooded tho workings. A short dam has been built and a pump started and by keeping it going continuously until tho wall is complete, .it is hoped to construct tho tank itself. This morning tho water diviner was engaged in marking out the track of the various streams, when another river of far larger proportions was discovered, estimated to be about 45ft. across and flowing in a ' north-westerly direction. The first one flows about south to north. The engineers have met with many unexpected difficulties in tfce work. At one point when preparing the site for a manhole a spring broke through of a high temperature.