This morning the 55,000-gallon tank was still smoldering as black plumes of smoke filled the air above the silver tanks next to the railroad tracks on Tie Plant Road east of The Dalles Marina. The tank contained copper naphthenate, which is a copper-based, oil-borne wood preservative. It is a replacement for creosote in railroad ties and as a replacement for pentachlorophenol in utility poles, according to Nisus Corp.