Check dams constructed by the Delhi Development Authority on the hilly terrain next to the Nelson Mandela Marg a year ago have reportedly started leaking. Experts allege that DDA's faulty construction is the reason. The check dam project was a result of an initiative taken by Leo Environment, an NGO. Two dams were constructed in 1999, to trap the run off water from JNU, Mahipalpur, Vasant KunJ and Vasant Vihar.