It was therefore decided to carry the sewer across in two parallel pipelines laid on the bed of the Harbour where it was sufficiently deep not to interfere with shipping .
It was therefore to operate it as an inverted syphon .
It was therefore decided to carry the sewer across in two parallel pipelines laid on the bed of the Harbour where it was sufficiently deep not to interfere with shipping , and to operate it as an inverted syphon .