The intake of the project lies in the Melamchi valley in the gorge below Ghwakan, just upstream of the confluence of Melamchi River and Ribarma Khola. The main structure is the diversion weir, river-training structures, and sediment exclusion basin. A gravity concrete weir is 5 to 7 m high with the crest at an elevation of 1,425 m asl. The control system and the sediment exclusion basin have a design capacity of 6m3/s. The sediment exclusion basins are double-chambered with a length of 80 m each. The tunnel intake is at an elevation of about 1416m and the outlet is about 1,408 m asl. The length of the tunnel from the intake to the water purification facilities in Kathmandu Valley at Sundarijal is about 26 km. The tunnel is being excavated from adits at Ambathan, Gyalthum, Sindhu and Sundarijal waterfall. The diversion flow in 6m3/s. The tunnel has a cross-sectional area of 12.7 m2 and lined with shotcrete in most of the section; concrete lining is done only in the weak rock formation. The tunnel is excavated by drill and blast method. The geology of the areas consists mainly of gneiss with mica schist and laminated quartzite. The distribution work has nine service reservoirs at various locations in the Kathmandu. The water from Sundarijal to service reservoir is supplied by a Bulk Distribution System. The distribution to household is done by a network of pipes about 670 km long. About 540 km of sewerage network will also be upgraded in this project.
In 2007 August, the ministry of physical planning, Hislia Yami, cancelled the contract awarded to UK company Severn Trent clamining that Severn Trent did not have a sufficiently strong international track record.
In 2018, the deadline was extended to mid-February 2019 with CMC, the contractor.
In 2019, the contract with Cooperativa Muratori e Cementisti di Ravenna was terminated over payment dispute.
Accidents
2020-July 14: During testing of the tunnel, the breaking of bulkhead gate caused flooding in the tunnel resulting in the death of two staffs.
In 2006, Sweden withdraw from the funding of this project over corruption issues.
In 2019, the contractor Cooperativa Muratori e Cementisti di Ravenna alleged two senior Nepali bureaucrats Gajendra Kumar Thakur, a former secretary at the Water Supply Ministry, and Surya Raj Kadel, executive director of the Melamchi Water Supply Development Board for a cut of 3% of payment on NPR 300 million payment. This issue let CMC to break the contract with the government.
