SAN ANTONIO -- Three enormous cooling stacks rise from the center of Calaveras Lake. On any given day, at least one of the three stacks can be seen pumping a mix of smoke and steam into the air.

Coal continues to be one of the most abundant and cheapest forms of energy in the United States. However, concerns over the toxins emitted by the burning of coal have virtually brought the construction of coal-fired power plants to a halt in theUnited States,the notable exception: CPS's new Spruce 2 plant.

Named after former CPS General Manager Jack Spruce, Spruce 2 is the latest power plant to go on-line in San Antonio. Behind nuclear, coal is the cheapest energy to produce, and Spruce 2 will produce more than 750 megawatts of electricity, enough electricity to power 185,000 homes.

Ground was broken for Spruce 2 in 2006 when virtually no coal fired power plants were being built in the state, a trend that has continued to this day.

Coal-fired power plants continue to generate as much controversy as electricity in the state, with the permitting process through the Texas Commission on Environmental Quality issuing fewer and fewer permits to build the plants due to the levels of carbon released into the atmosphere. CPS says if it were to try and build this plant today the process would be very difficult .

Citing concerns of pollution, CPS spent almost $1 billion to construct Spruce 2 calling it the cleanest and most energy efficient plant in the company's history.

The plant, which was completed weeks ago, will not begin full operation until a number of final tests are run.