WASHINGTON VALLEY

Nelson Evening Mail, 23 September 1916, Page 5

WASHINGTON VALLEY

STORMWATER DRAINAGE

The following report on stormwater. drainage in Washington Valley was pre-. sented "to the Cifcv Council last evening by tlip. City Engineer, Mr J. G. Littlejolin.: — Considerable comment having, been made as to the placing- and efficiency . of the culverts in Washington Valley I would suggest that there is ample evidence that the culverts were built.in the line of the original watercourse wMoh drained the Valley. They are, therefore, correctly placed, and they are adequate for "all 'but the most extraordinary circumstances against which provision is not usually made. The, formation of St. Vincent-street practically made a dam across the mudflat, but hero again adequate provision was made for the escape of the stormwater in tlie shape of a five foot culvert through the road. A portion of the mudflat was subsequently reclaimed along-St. Vincent ■street, and an open ditch ' was _ left through, the reclaimed ground leading to j the five foot culvert mentioned. Corirri cillor Watson has stated from his own knowledge of the locality that while this ditch remained open no trouble aross. The owner of the property through which the ditch passed • evidently persuaded the Council to fill it. up. Twelve-inch pipes wero used . to extend the culvert through this land* and the efficiency of the culvert as an. outlet was thereby destroyed-, causing in time of heavy rain the protracted flooding of the whole of the ground originally comprised in the mudflat on the upperside,of St. Vincent-street. There are, however, other causes contributory to the inundation of this land. The. overflow of the St. Vincent-street ditch and the backing- up of this ditch through, the-culvert from Washingtonroad and discharging near the Railway Station are largely responsible. The culvert extending from near the Gldbe Hotel to Saltwater Bridge has practically no fall, and the culvert is much obstructed with gas, water and drainage mains,.: which collect and hold all the debris ■: which comes down. The mudflat below this is higher than the invert of this culvert and necessarily" backs up the water. All these things contribute to obstruct the escape of the stormwater and cause trouble higher up. ■ The culverts as originally designed were adequate, and the proper remedy is to restore them and the levels'of the invert of the St. Vincent-street ditch to their original position. The Council, I <un aware, is not favourable to re-open-ing the ditch through Haase's property, and has instructed that.a new culvert be put in through its own land adjoining at a cost of £2OO. As far as Washington Vallev proper is concerned I am of opinion that no alteration should be made in the line of the existing ditches and culverts. lam also of opinion that the water from the south side of the valley cannot be better disposed of than at present except by straightening the ditch below Quebecroad, which has 'been deprived of fall 'by diverting it on to the road. An open 1 invert aloner Wasihngton-road and v a I culvert through St. Vincent-street near the Railwav Station, as an independent means of disposing, of the water from i 'he south side of the Valley is not feasi- | ble by reason of the levels, and would t be inexpedient in that it would create an I onen ditch on Washingfcon-road r where there is no difym. at present. The Kgfoemf; would simply be an -invitation to the ' St. Vincent-street ditch to inundate the low lying land a good deal worse . and I much sooner than at present. There is j exactly the same objection to the openinvert and culvert through St. Vincent-, - street proposed in Cr. Piper's scheme for the independent disposal of the water from the north, side of the Valley. It will 'be noted from the plan herewith that ,the bottom of the invert . would be above or below the ground I level for a considerable distance and apart from the water backing up from St. Vincent-street ditch an em'bankmenfc at least four feet high woiild be "required all along the south side of tHe* invert to prevent the water escaping on to the mudflat. I do not include this in my estimate of the cost of the work as it properly forms >part pf the scheme for filling up tlie land. Tfc is clear, however that without the embankment, and the full completion of the work the orooosal would be no improvement art" present conditions, and further it; leaves" the water from the south side of the valley to be "dealt with at additional expense. A scheme which deals with only one side of the Valley is inadequate, and a; scheme which deals with each side' separately is extravagant. The whole' 'of the water is already ' collected to onepoint by the culvert at the foot of Que-, bee-road, and it should 'be dealt with as a single proposition frori that point. The crux of the whole question is outlet through St. Vincent-street and get away on the mudflat. The through Haase's land should be removed or the new culvert tlrrough St. Vincentstreet constructed. The obstructions should be removed from the St. Vincentstreet culvert-. The waterway." should bo cleaned out and graded to the greatest fall obtainable from the' Railway Station right out on to the mudflat near Auckland Point. The cost Would be as follows: Five-foot culvert through St. Vincentstreet, £200; cutting 'ditch through Council's land, £3O; alteration of main* St. Vincent-street culvert, £80; grading waterway, £6O; total £370. The' cost of Cr. Piper's proposal would be : The 3-ft culvert through 396 ft, at 255, £495; invert, 968 ft at 16s, £775; 3ft culvert through'St.'Vincent- 1 street, 60ft at 255, £75; total,' £1246. The foregoing estimate "is probably", on the low side for culverts' 3ft in diameter, and for the invert is based on the assumption that a good foundation could 'be got within six inches of the invert levels, which is a matter of considerable doubt. It must also be borne in mind that the water from the south side " remains to be provided for, at about the same cost, if a similar scheme is adopted for it.

la -view'of the'correspondence" from Mr Haase, consideration of ..Cr'Piper's motion regarding .Washingt'oh'' Vallfey culvert waspostponed. for a - fortnight.