Tennessee Valley Authority. Construction of Douglas Dam. Caisson construction on TVA&#x27;s new Douglas Dam on the French Broad River. This dam will be 161 feet high and 1,682 feet long, with a 31,600 acre reservoir area extending forty-three miles upstream. With a useful storage capacity of approximately 1,330,000 acre-feet this reservoir will make possible the addition of nearly 100,000 kilowatts of continuous power to the TVA system in dry years and almost 170,000 kilowatts in the average year