§ Mr. Spearingasked the Secretary of State for the Environment what arrangements have been made for the permanent allocation of tugs to stand by the Thames Barrier when completed;what is the estimated annual cost at current prices; who will pay for them; and what other consultations he has made concerning their provision and operation.
§ Mr. Graham PageI have agreed in principle that tugs will be available as may be found necessary and that their cost will not fall upon the Thames shipping organisations. With at least six years to go before the barrier is complete, further consideration would be premature at this stage.
§ Mr. Spearingasked the Secretary of State for the Environment what communications he has received from Trinity House and the Port of London Authority concerning the design of the proposed Thames Barrier; what replies he has sent; and if he will place copies of any documents and correspondence in the Library.
§ Mr. Graham PageFollowing discussions last December, Trinity House and the Port of London Authority informed me that a rising sector gate barrier, while less attractive to them than a drop-gate, would nevertheless be practicably negotiable by shipping using Woolwich Reach and that they could accept it in principle. My reply stated that, having regard to an estimate of cost £12 million less than that of a drop-gate and a construction period shorter by a year, I had no doubt that the balance of advantage lay with the rising sector gate. I do not consider it necessary to place copies of this correspondence in the Library.
§ Mr. Spearingasked the Secretary of State for the Environment if, in order to ensure freedom of navigation in the River 323W Thames over the period of construction, operation, maintenance, or trial closure of a flood barrier, he will consider the advantages of immediate construction of a lock at Silvertown in Woolwich Reach that could be incorporated in any future works.
§ Mr. Graham PageConstruction, maintenance and trial closure are not expected to impede navigation unduly. For some time after completion of the barrier, closure upon flood warning will be relatively infrequent and the capital cost of a lock will be justified only if half-tide control is judged both practicable and desirable. Before deciding that, we need to know more about the effect of river siltation and on the ground-water table. Studies are proceeding, but meanwhile the barrier design will include provision for the later addition of a lock.