MANAWATU BRIDGE AT SHANNON.

Shannon News, 16 June 1925, Page 2

MANAWATU BRIDGE AT SHANNON.

INDEPENDENT ENGINEER'S REPORT.

Recently the directors of the Shannon Dairy Co., in co-operation with MH' ; .iani\on Borough Council, decidtu I*, obtain an independent report by j siUia.rieu engineer on the question of- to the bridge over the Mana\\l\u river at Shannon. The Dairy Company have now received the following "leport from Messrs R. W. Holmes and Sou, consulting, civil and mechanic d engineers, Wellington:— "In considering the question of repairs to the bridge over the Manawatu rivt v at Shannon, it is desirable ,to bear-in mind the importance of the bridge to the town of Shannon. A glance yi the map shows that the existing bridge affords ready means of access to a large area of very fertile country, which is known as the Moutoa, and it is b.n the shortest possible tine of road to Foxton, a seaport. The land referred to is served by the two towns, Shannon and Foxton. It is therefore necessary for Shannon to provide the very host inlucemems for trade to gravitate to■.vards fciiannon, and it is in the interests ol Foxton that as much trade and trai-ic should pass through that town fiv.ni and to Shannon in connection with sea-borne freight. Consider tl: - position if the bridge be placed further up the river than the present ;ite. The most important point is that i:ie distance from Shannon to Moutoa will be increased. Further, those v.:iq selected the present site were no doubt actuated by this fact. The Drainage Board appears to have carried out works which tend to indicate that the Board has adopted the presmt channel of the river as its main d'uin; whether, the ..River Board is in acvord with this idea we are not aware, out whatever, scheme may eventually be adopted, the flood waters of the river- will have to be confined to a well defined channel hy stop banks placed sufficiently far apart, and remote from the banks of the low water channel. The area between the stop banks will require to be free from large obstructions. Consequently any bridges which may be erected will have to be long enough to extend from stop batik to stop bank and must therefore be much longer than the present bridge was. The damage which has occurred to the bridge and the enlargement of the low river channel by the scour of'the left bank may at some future time prove 1 to be of use, providing, that the present channel of. the river be not. departed from. It .may be assumed definitely that j the present low river .channel is-large enough; that it will not require enlarging; that it canno't be maintained' any larger and therefore the present banks should be protected from further erosion.

- "The foregoing arguments tend to show conclusively that:— "First.—The- present .bridge should be restored. N "Second.—The river bank should be protected from scour. With regards to the bridge, there' is only one course to pursue,, viz., erect one span similar to the present ones, strengthen the present end pier, which is in the water .way, provide tor raising the level: of the bridge a few feet, and construct a new graded approach to the left of the Shannon-end. The new pier on the left bank, which will be the abutment pier, should .be similar to those in the water way as. regards the number of piles and general strength, so that witho.ut, any further cost, it will be suitable to carry another span and also be a permanent pier should further erosion of the river accidentally occur. "The floor of the bridge does not appear to be high enough in regard to the water level and also with, regard to the stop banks, which have been constructed. Investigations will require to be made to determine a suitable level for the bridge. In time the whole bridge will require raising, but not at present. We recommend that the new span be erected at the permanent level., a*d that the joining end only of the next span be raised/ The span being placed on a slope in the •meantime. This will keep the immediate expenditure down toj a, minimum.

"The following is an approximate estimate for carrying out the work recommended. It is not possible to prepare an exact 'estimate from the information available. We understand that it is desired at present to avoid incurring the expense' of preparing detail plan, etc., therefore we have done the best we* can by simple inspection. In any case the estimate will not be exceeded if present conditions continue.

/flie following is the . estimate of repairs-to the bridge:— 1 £ Strengthening present end pier 230 New end pier 400 Additional'span 1800 Raising end of present span ... 120 Forming and gravelling new approach 250 River bank protection 250 Engineering and legal ..,..-:...... 240 Total , £3300 j !