There is a controversy brewing for about 10 years that hydroelectric power plants are not a clean, renewable source of electricity. The current review indicates that the source of methane is not in the mechanics or mechanical design of the equipment used. The source of the methane is from nature, and man's failure to do the right thing. This methane may be reduced or completely eliminated. If this cannot be accomplished or if it is too expensive to retrofit the hydroelectric plant, then the deep water may be preprocessed (and the methane collected) before being used in the water turbine. Several methods have been introduced and discussed. Details have been omitted so that practicing engineers and other professionals can obtain funds to research and develop or invent the practical solutions suited to conditions local to the problem.