Iraqi regulators are threatening to shut down Basra’s newly expanded Najibiya power plant after an oil spill contaminated residential and agricultural water supplies.Iraqi Prime Minister Haider al-Abadi formally opened the plant less than a month ago, citing its refurbishment as an example of the government’s efforts to improve public services in Basra. But the 500 megawatt power station ran into problems on Jan. 21, when a build-up of rain water caused a storage tank to overflow and spill f…