The Delhi Jal Board has taken up the Herculean task of making Yamuna a grade 'C' river at a meagre cost of Rs 3,150 crore by December 2008. Making this announcement on Wednesday Chief Executive Officer of the Delhi Jal Board Arun Mathur said the objective would be achieved by strengthening already laid interceptor drains and laying new lines of such drains. The Supreme Court has set the target of turning Yamuna into a 'C' category river.