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Natural Phosphorus Makes TMDL Goals Unrealistic

by Pat McCoy
Capital Press - March 22, 2002

Much comes from irrigation runoff, treatment plants and other industry

Phosphorus levels are frequently a point of contention when total maximum daily load implementation plans become controversial within the agricultural industry.

A lot of phosphorous occurs naturally in Western soils and waters. More comes from irrigation runoff, city waste treamtent plants, food processing plants and other industry. As a nutrient, it contibutes to algae blooms. TMDLs often include goals to reduce phosphorus levels, and that's where the debate begins.

Many people question whether the targeted reductions are realistic, said Clint Shock, superintendent of the Malheur Experiment Station, Oregon State University.

For instance, the propsed TMDL for the portion of the Snake River bordering Idaho and Oregon through Hells Canyon proposes a maximum phosphorus level of 0.07 milligrams per liter.

The proposed limit also applies to Snake River tributaries such as the Malheur River, which leaves the high mountains at the Beulah Reservoir and flows toward the Treasure Valley. The Malheur River above Beulah Reservoir contains 0.085 mg/L phosphorus. That raises a real question about whether 0.07 mg/L is achievable, given current technology and the presence of high levels of naturally occuring phosphorus in the area, said Shock.

Another question is whether that standard would improve anything. The exact level of phosphorus required to trigger an algae bloom varies in relationship to other conditions, but it is well below 0.07 mg/L, he said.

Idaho's Water Quality Standard sets no statewide numeric criteria for phosphorus. Instead, it says, "surface waters of the state shall be free from excess nutrients that can cause visible slime growth or other nuisance aquatic growth impairing beneficial uses."

Marine Deposit

A marine deposit stretching from Southwest Wyoming into Southeast Idaho left one of the world's largest phosphorus reserves lying for someone to develop and harvest it. If it were closer to a coast where it could be more easily hauled to market, it probably would be mined, Shock said.

To say that phosphorus levels are extremely high in all soils across Southwest Idaho and Eastern Oregon is not correct. The region has isolated pockets of very rich deposits, he said.

The Malhuer Watershed Coucil has five years' worth of data from an extensive sampling program. It proves the phosphorous levels are higher than the proposed maximum in forest soils well above the points at which streams reach the valley where human influence begins, said Ron Jones, district manager, Malheur County Soil and Water Conservation District.

"DEQ in Idaho and Oregon have excellent employees who understand water chemistry very well, but they're removed from on-the-land reality. Too often they fail to consider the economic effect of trying to remove that much phosphorus," Jones said.

Seasonal Standard

One proposal in the Snake River-Hells Canyon TMDL would make the phosphorus limit seasonal, in effect from May through September.

"That helps the cities temporarily, especially those who land-apply treated wases during those months and discharge them into the river the rest of the year," said Jones. "It means city residents won't see their sewer bills double in the next year or so, but it won't fix the problem," he said.

Phosphorus stays in the water as long as sediment stays, and that doesn't go away from May through September, said Jones.

"To set a standard for only certain months is kind of voodoo science. We'll make improvements and move forward. Things will get better. But we'll never attain test-tube pure water out of the Malheur River," he said.

50-Year TMDL

The Snake River-Hells Canyon TMDL proposes allowing 50 years for full implementation, said Steve West, regional administrator for Idaho DEQ.

"We're pretty comfortable with the science that's gotten us this far. It's been a very difficult, complex process, but we've used common sense as well as good science. The important thing to remember is that the TMDL process is ongoing. New information is used to adjust it as necessary, and to recognize progress as it occurs," West said.

DEQ has some pretty compelling proof that phosphorus from human-caused sources can be reduced, with resulting benefits in water quality, he said.

by Pat McCoy Capital Press Staff Writer
Water Temperatures a Bone of Contention for TMDLs
Capital Press - March 22, 2002

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