Cleaning Yamuna on the pattern of the Thames requires constant investment for building and maintaining infrastructure, a committee appointed by the Supreme Court has said in its interim report. It also said that the cost of the operations should be recovered from those polluting the river. The apex court is scheduled to hear the case on the cleaning of the river on Tuesday. The committee, which was constituted to monitor the Yamuna cleaning up operation, has said that the existing sewage treatment plants (STP) have not been utilised. This is due to the absence of an effective sewage/drainage system, and where such a system does exist, it is often choked and needs refurbishments.