|
Danger of Yellowstone sewage pond overflowing is over By MICHAEL MILSTEIN Gazette Cody Bureau YELLOWSTONE NATIONAL PARK, Wyo. - National Park Service maintenance crews on Tuesday stopped siphoning treated sewage from a sewage treatment pond into a meadow north of Fishing Bridge and said the danger of the pond overflowing and collapsing had ebbed. "The levels are down and things look much better," said Yellowstone Chief of Maintenance Tim Hudson. He said there has been no noticeable detrimental effects on either the marshy meadow that had been flooded with the treated sewage or the Yellowstone River, about a mile away. On June 8, crews began discharging more than a half-million gallons of treated sewage each day from a pond at the park's sewage treatment plant at Fishing Bridge to keep the pond from overflowing. Park officials feared that if the pond overflowed, it would wash out the earthen dike holding the pond. In such a scenario the surrounding wetlands would have been inundated with all of the pond's 4 million gallons of sewage, forcing the shutdown of the entire treatment plant. Without the treatment plant to handle sewage, officials would have had to close visitor facilities at Fishing Bridge, Lake and Bridge Bay. Over the course of about two weeks, crews siphoned more than 7 million gallons of sewage from one of the treatment plant's three ponds into the meadow. Wyoming Department of Environmental Quality officials have said they will probably cite the National Park Service for the discharge, even though it was essential to keep the pond from overflowing. The pond nearly overflowed because an extremely wet spring allowed thousands of gallons of ground water to infiltrate the area's sewage lines. Sewage arriving at the treatment plant flows through a series of tanks and settling ponds where bacteria break down solid matter and then enters one of two initial percolation ponds where it either seeps into the ground or evaporates. Remaining wastewater continues into a third and final pond, which has no outlet. Sewage does not percolate out of the ponds as quickly as it used to, so the extra influx of sewage filled the ponds so quickly that the third pond would have overflowed if park crews had not begun siphoning sewage out of it and into the adjacent meadow. Park officials began encouraging visitors to lodges, campgrounds and other visitor facilities in the area to conserve water to reduce the load on the treatment plant. A combination of such conservation, subsiding ground water and the siphoning has lowered the level of all three ponds at least a foot below overflow, Hudson said. Park officials also contracted with a Billings engineering company to study local sewage lines for ground-water infiltration in hopes of determining where most ground water is entering the lines so workers can seal any major inlets. So far the engineering company has found a major source of inflow between the rear of Lake Hotel and Lake Lodge, Hudson said. Park officials on Tuesday also released an environmental assessment of plans to rebuild the current aging sewage treatment plant at Old Faithful, which has leaked about a million gallons of sewage in the past few years. Congress has provided funding to rebuild the plant, but the park must first assess the environmental impacts of the work. Copies of the document can be obtained by writing to Superintendent, Attn: Planning and Compliance, Old Faithful Wastewater Treatment Plant, P.O. Box 168, Yellowstone NP, Wyo., 82190
|