PHOENIX - In a decision yesterday, the Arizona Corporation Commission allowed Duke Energy to expand the Arlington Valley Energy Facility as a water-cooled power project. In January, Duke Energy received conditional approval to construct a 600-megawatt expansion of the Arlington Valley Energy Facility currently under construction in western Maricopa County. The project will be a water-cooled power plant, using a maximum of 3,900 acre-feet of groundwater per year. During Tuesday's meeting, the Commission imposed two additional environmental restrictions on the project.

Summary of Spitzer Amendment 1: Duke Energy can use groundwater to cool the turbines at the expanded Arlington plant. However, the company must purchase a minimum of 3,900 acre-feet of surface water from the Central Arizona Project - representing the plant's maximum water usage - and recharge that water in the critical Agua Fria aquifer.

Recharge programs such as the Central Arizona Water District's Agua Fria Recharge Project involve returning water to an endangered underground aquifer. The area around the Sun Cities and also near Luke Air Force Base are experiencing subsidence - cracks, fissures or dips in the surface of the earth - because the water deep underground that provided physical support is no longer there.

Summary of Mundell Amendment 1: The Commission also added an amendment that requires Duke Energy to install the absolute, most effective emission control equipment, regardless of cost. The plant will have to adhere to the tightest pollution control standards even though such stringent controls are not required by county, state or federal environmental agencies.

Background

As an offset to the plant's groundwater impact and since no aquifer recharge project exists in the area, the Spitzer amendment also required Duke to participate in the Central Arizona Water District's Agua Fria Recharge Project, in cooperation with the Arizona Water Banking Authority. The Agua Fria Aquifer is within the Phoenix Active Management Area and is in critical need of recharge.

In January, the Commission approved an amendment offered by Commissioner Marc Spitzer that required Duke to use dry cooling technology. Under the prior decision, Duke Energy would have recharged only 1,000 acre-feet of water per year throughout the life of the power plant.