KATHMANDU, May 22: The electricity transmission line of the 900 megawatt Arun-III hydropower project under construction in Sankhuwasabha is going to be built in seven districts. The Arun-III project is going to build 597 towers for the transmission line in Sankhuwasabha, Bhojpur, Khotang, Udayapur, Siraha, Mahottari and Dhanusha districts.