STORM-WATER DRAINAGE

New Zealand Herald, Volume LXX, Issue 21492, 16 May 1933, Page 10

STORM-WATER DRAINAGE

NEW CITY SCHEME WORK NOW IN PROGRESS ALBERT STREET TUNNEL The first section of the storm-water drainage scheme, designed to prevent .the flooding of the lower end of the business portion of the city in times of heavy rainfall, is now under construction, and the whole scheme should bo completed early next winter. This work is part of the programme of constructive relief works adopted by the City Council. The scheme will comprise a large storm-water drain from the waterfront opposite the end of Albert Street, extending up that thoroughfare to Victoria Street, and along the line of Victoria Street to Queen Street, where it will intercept the storm-water drain carrying surface water from the higher ground to the south. From the Albert Street-Victoria Street junction there will be a smaller drain continuing along the line of Albert Street to Wellesley Street and following that thoroughfare to the vicinity of the Civic Theatre, where it will join with the existing storm-water drain at Ferguson Street. Draining Upper Valley

Tho new system will take the drainago of the whole of the Queen Street valley above Victoria Street and lying between Symonds Street, Karangahape Road and Hobson Street. The outlet will be at a point between the Queen's and Prince's Wharves. A start has now been made on the section close to the waterfront, where about two chains of roadway have been opened. Here, the trench has been dug to a depth of about 14ft., but owing to the wet nature of tho reclamation at this point, it has been possible to work only between tides. In making tho excavation, tho workmen encountered old piles which formed part of the former breastwork. They also encountered the largo concrete conduit which carried the Auckland Power Board's cables along the waterfront. Tho new sewer is to be semi-elliptical in form, with an inside measurement of 6ft. by sft., and will be constructed in reinforced concrete. It will be necessary to cut into the underside of the Power Board's conduit so that the sewer will project into tho conduit. As the work proceeds southward into solid ground, the open cut will be abandoned and the men will tunnel underground. Shafts will be sunk at suitable points to facilitate the removal of spoil from the tunnel. Maximum Depth of 60 Feet

This section of the sewer will have a total length of 2677 ft., of which 2300 ft. will be in the tunnel. Tho smaller sewer linking up with Ferguson Street will he circular, with a diameter of 4ft. Tho tunnelling will reach a maximum depth below tho street level of about 60ft. at tho junction of Albert and Victoria Streets. An unusual feature of tho new system will bo tho construction of a distributing or reduction chamber near the point of discharge. Tho main sewer will discharge into this chamber and tho water will be led through five pipes, spread in tho form of. a fan, and discharging into the harbour at intervals of 20ft. Thus t?AO storm-water will be delivered into tho harbour without any appreciable disturbance. At a later stage the existing stormwater sewers will be given further relief by tho construction of a sft. 9in. sewer laid beneath tho Gore Street extension, across tho old station site, and tapping the present system at Customs Street. Tho outfall for this sewer will be beneath the Central Wharf.