Kajaki dam: The great white elephant of Afghanistan

In the approaching twilight of its war in Afghanistan, the US is forging ahead with a giant infrastructure project long criticised as too costly in both blood and money. The effort to refurbish the massive Kajaki dam and hydro-electric power system, which is supposed to bring electricity to 332,000 people and increase crop yields, has cost $500m.

But completion, originally envisaged for 2005, is now projected for some time in 2015, the year after most combat troops will have left the country. And there are some crucial ifs: if a convoy carrying 900 tons of concrete can make it up a dangerous road to the site without being attacked by the Taliban … if the Afghan army can hold out in an area that thousands of US Marines struggled to secure … and if the Afghan government can manage the dam.

The Kajaki dam on the Helmand River symbolises for both the Afghans and their American backers what they had hoped the infusion of US troops and cash would produce nationwide: an Afghan government that can provide for its people and which can, in turn, count on their support against the Taliban insurgency. The US has spent more than $22bn (£14bn) on governance and development in Afghanistan since 2001, much of that on projects to build roads, schools, power plants and irrigation systems.

Kajaki is also a symbol of the American presence in Afghanistan dating back to the 1950s and the Cold War. That was when the US built the original dam, with a powerhouse added in the 1970s. But before the three turbines could be installed, the Soviet Union invaded and construction stopped. The dam was still squeezing out a small bit of power in 2001 when the US attacked and bombed the dam's power transmission line.

In the latest phase of the Kajaki saga, fighting as well as a limited oversight of spending has led to huge delays and cost overruns. And now Helmand province is seeing the first and largest wave of US troop reductions, with 10,000 of 17,000 Marines already gone. This means that the Kajaki project is going forward with Afghan forces providing nearly all the security in an area that was a Taliban stronghold until a year ago.

Meanwhile, the number of workers on a US-funded construction project next to Kajaki has dwindled from 200 to 20 since last autumn, and those remaining say they feel the risk isn't worth the $6 daily pay. "They can't come here because all the routes to the district are controlled by the Taliban," said Abdul Razziq, a 28-year-old villager working on a new district government centre next to the dam.

One worker said security is deteriorating as the Marines leave, but US officials say that Afghan security forces have increased their presence around the dam and that Taliban attacks, while still regular, appear to be decreasing. The company building the dam has been able to send supplies via road – four convoys of trucks have made the trip without incident. Previously, equipment was being helicoptered in at enormous cost.

Even if the project overcomes the security and logistical barriers, there are questions about whether it is worth the cost. The dam can't provide enough power to sustain the main city in the region, Kandahar, and the price tag is steep for the extra irrigation it brings to the Helmand River valley.

From the air, the river is a narrow turquoise ribbon through the desert. The dam is a stacked concrete wall that bisects the river, creating a reservoir ringed with trees. As resources and Americans dwindle, the US Army Corps of Engineers and USAID say they expect oversight to depend increasingly on Afghan partners.

Everyone says they are committed to finishing the project. Sayed Rasoul is an Afghan engineer who has spent decades in the management of Kajaki, as well as the Kandahar and Helmand power grid. He says he's confident the dam will be completed and will deliver the riches promised.