QUEEN STREET FLOODING

New Zealand Herald, Volume LXVIII, Issue 20991, 30 September 1931, Page 10

QUEEN STREET FLOODING

REMEDIAL SCHEME. TOTAL COST £44,346. CITY ENGINEER'S PROPOSALS. 1 m EARLY START ON PART URGED. An estimate of £44,346 is made by the city engineer, Mr. J. Tyler, as the cost of giving practically complete relief from flooding in and around lower Queen Street during heavy rainstorms. In a report prepared for the City Council, Mr. Tyler describes a proposed system of intercepting stormwater sewers, and gives preference to three sections of the scheme, costing £31,038. He considers it important that these at least should be undertaken as soon as possible, although the seriousness of the position fully warrants carrying out tho whole project immediately. Explaining the present position, Mr. Tyler states that the business area generally is built at the lower end of a sharplydefined watershed, bounded on the east by Symonds Street, on tho south by Karangahape Road, and on the west by Hobson Street, and containing 342 acres, in early times the rainfall run-off on this area was taken by a creek which flowed generally along tho lino now occupied by Queen Street. The Existing SJewers. Many years ago a brick sewer, joined by two branches at Wellesley Street, was constructed along the eastern side of Queen Street to take both stormwater and sewage from tho watershed, with an outfall near Queen's Wharf. In the early eighties it was diverted along Customs Street East, and eventually the outfall was extended from Breakwater Road to a point under the site of the present King's Wharf, with a relief pipe at a higher level in Lower Queen Street. Unfortunately, these two outlets together were of less capacity than tho Queen Street sewer.

At tho outfall, Mr. Tyler states, the top of tho sewer is 18in. under water at ordinary high spring tides and the sea water then extends as far up as a pointopposite Vulcan Lane. At such times there is no storage capacity in the sewer, and, as the rain water cannot get away, it backs up tlie branches and rises in the manholes, giving a. head, but, before this has time to clear, the run-off from the upper area has raced down, is checked, cannot get away, backs up and causes back flooding through the cesspits and manholes in the lower area. Effects of Street Paving. While records covering the past 21 years show rainfall of an intensity of over Gin. an hour, they were of only two to three minutes' duration. Storms with an intensity of 2in., which has been taken as » basis, and lasting over 10 minutes, occur on an average at intervals of 18 months. When the Customs Street diversion was made 50 years ago the permeability of the city was much greater than to-day. The area was by no means completely built upon, and there were no impervious streets causing a direct and immediate discharge of rainwater into the sewer. To remedy this state of affairs, Mr. Tyler proposes to reduce by 65 per cent, the quantity of stormwater required to be taken by the lower part of the present sewer system. This can be done by constructing reiief sewers running from the western branch at Wellesley Street West and from the Queen Street sewer opposite Durham Street West to a junction under Albert Street, and thence to an outfall at mean sea level beneath Prince's Wharf. The sewers would be carried for much of their length in deep tunnels like the Drainage Board's sewers. They would drain all the 212 acres lying above Durham Street. Even with this relief, it will be necessary to provide an additional outlet sewer from Customs Street East to a point of discharge near King's Wharf. New pipes draining the Fort Street cesspits and Emily Place will also be required. The following is a schedule of the estimated costs:—Durham Street-Albert Street, £28.978; Commerce Street-Fort Street, £1400; Emily Place. £660; Breakwater Road, £6792; Wellesley StreetAlbert Street, £6516; total, i.44,346. Mr. Tyler considers that at least the first three works should be carried/out as soon as possible.