Drainage And Sewage Disposal Key Factors In Growing City

Press, Volume XCVII, Issue 28529, 7 March 1958, Page 18

Drainage And Sewage Disposal Key Factors In Growing City

Christchurch is not • on the best of sites for a city. From its earliest years it has been plagued by drainage problems, and the history of the struggle to drain the land and install sewers is a sad record of frustrations for those who tried to tackle the problems. The light to make up the present backlog of sewerage work and the prospects for the immediate future expansion of the sewered area are two of the most important items which have guided town planning in Christchurch. Most of the city’s development has been on the formerly swampy plain, and more recently on the sandy country along the coast. But the hillslopes lying to the sun which are desirable for residential building, but difficult to sewer, have been barely touched. After many of the natural drains had been filled in on the flat there were for many years lamentably few artificial drains in early Christchurch. Up to 1876, the land drainage system was very crude indeed. And it was several years after that before a beginning was made on the installation of sewers. Lack of funds in the 1880’s, followed by the depression in the ’nineties, caused the Christchurch Drainage Board to suspend its operations almost entirely, and for 17 years no sewers at all were laid. With the turn of the century, the board received support from the Christchurch City Council and the board embarked on a programme which by , 1914 had sewered the city within the four belts and parts of St. Albans, Linwood and Sydenham. Another delay, chiefly over finance, followed World War I, but in the 1920’s efforts were made to extend the system outwards from the original area. The depression of the 1930’s again curtailed activities and new sewerage work proceeded only slowly from 1935, through World War II and the post-war years of labour and material shortages. There has been an all-out effort since 1950. The following paragraphs summarise the present position and the work necessary to carry out the sewerage of the unserviced areas in the district. Since contractors are already working to capacity and there seems ho hope that the present rate of work can be increased, the huge works programme will take many years. This summary is taken from the sewerage and drainage report by the Christchurch Regional Planning Authority at the end of last year. Hornby-Islington Here there are further large areas of residential and industrial development without sewers. When the main extensions along Blenheim road have been completed collecting sewers can be laid along Main South road,

Waterloo roads and Buchanans road to serve these districts. The large Government housing block between Waterloo road and Buchanans road is provided with a sewerage system draining into two large septic tanks. Soakage in the area is reasonably good. Papanui The newly developed areas out to Bishops road have recently been connected to the sewers but the existing Grants road main, into which they drain, is heavily overloaded, and further connexions cannot be permitted until new mains mentioned above are completed and extended along Sawyers Arms road. Large-scale Government and private housing development is proposed for the near future. Soakage is generally poor in the area, and in some Darts heavy clay subsoil conditions cause a tendency. towards bad land drainage. Bryndwr The developed areas are connected to the sewers, but further extension is dependent on the laying of the new collecting sewers in Wairakei road, Ham road, and Burnside road. These in turn would be connected to the Leinster road branch of the northern relief sewer. Considerable areas of land in the vicinity are scheduled for State housing development. Much of the land is shingle country and disposal of sullage is easily accomplished. Avonhead-W'aimairi In order to sewer this area a collecting sewer must be laid from the southern relief branch at Wainui street by way of Kirkwood avenue to Waimairi road and from there north along that road. Soakage is good in the area, apart from odd patches. Upper Riccarton Sockburn, Upper Riccarton, and Yaldhurst road comprise a large area of existing development without sewerage, although development generally is not dense. Before reticulation of the area can be effected the Southern relief sewer must be extended along Blenheim road from Division street to Curletts road and collecting sewers laid from there. Soakage is good in this area. Northcote The sewering of the Northcote area is dependent on the completion of the northern relief branch main to Mays road, and its extension by way of Grassmere street to the Main North road. Soakage in the area is poor' and the disposal of sullage is not very satisfactory. W'igram-Lincoln In order that this area may be sewered a new collecting sewer will need to be laid for the whole length of Lincoln road, discharging into the Southern relief sewereither at Hagley avenue or Fitzgerald avenue. Soakage in Annex road is bad but in the remainder of the area it is good.

HoonHay The provision of a sewer outfall for this area necessitates a formidable amount of major work to be done throughout the south-

ern part of the city. This involves new pumping machinery, the duplication of sewers and mains and new pumping stations. The subsoil is clay and the sullage disposal is extremely difficult. Because of poor land drainage the area becomes waterlogged during the winter months. The Valleys Hillsborough and St. Martins Valley are being sewered. An extention of the Hillsborough sewers can be effected to serve the Avoca Valley as and when develooment warrants it. Horotane Valley must await completion of the Woolston trade waste sewerage system after which a collecting sewer can be laid along Chapmans road. Soakage in the valley itself is good. At the present time a new septic tank and pumping station for Heathcote are being built in Truscotts road. In the immediate future this will discharge into the Heathcote river, but ultimately it will pump into the Woolston trade waste system by way of the proposed Chapmans road sewer. Port Hills Of the main hillside suburbs all are served by sewers except the upner areas of Mount Pleasant, Moncks spur, Scarborough, and Clifton. The smaller areas of development are without the service. The disposal of sullage on the hills offers no easy solution. In certain isolated areas—parts of Moncks spur are an example—good soakage is found and septic tanks function satisfactorily. In other isolated cases, underground runnels provide an easy method of disposal. Apart from these isolated . areas it is generally found ‘that soakage below the topsoil level is impossible.

For new houses on unsewered, parts of the hills the Health De-

partment requires that the overflow from septic tanks shall be discharged parallel to the contours at shallow depth to permit seepage between topsoil and subsoil, and that there is no building or terracing below such a line of discharge. In view of this difficulty it is desirable that large scale development op the hills should be confined to those areas where new roads and sewers can easily be linked with the existing system. The laying of sewers is complicated not only by the steep slopes but also the presence of rock. New Brighton

North, Central and South Brighton will be completely sewered in the very near future, leaving only the Rocking Horse road area to be dealt with. This will need a new pumping station. Aranui will be served in the near future and Bexley can be reticulated after the construction of a pumping station and rising main. This area is low-lying, soakage is poor and the water table is high. Many parts of the area need building up. Eastern W'ainoni

This area also requires a pumping station and rising main. There is very little existing development but it may expand when the large Government housing block is built up. This is expected to follow the advent of adequate electric power to the area in about two years' time. Soakage is good in the area except near the river where the river water table is high. . Avondale, Horseshoe Lake and Burwood can be sewered after the reticulation of the Dallington area which is scheduled for early attention. A siphon under the Avon river will have to be constructed before the Avondale district can be served. Much* of the land is low-lying and the winter water table is high.