Phosphorus is a naturally occurring element but too much of it in the water can deprive fish of oxygen, according to the state Department of Ecology.
The company last year consistently exceeded state limits for the amount of phosphorus running off its property and eventually into the slough, according to the ecology department. The penalty for overstepping the limit is improving treatment of the runoff, ecology department spokesman Larry Altose said.
In 2011, the company also exceeded other state limits, such as discharges of copper.
Cedar Grove is asking for an exemption from the phosphorus requirement. The department will rule after the public comment period which ends July 18.
The company says there's no treatment that would stop the substance from running off the property and that its phosphorus discharge levels are not far above the limit.
Cedar Grove collects yard and food waste from trash haulers and restaurants in Snohomish and King counties and grinds, cures and sells it as compost for gardens. Cedar Grove has been the target of many odor complaints in recent years, especially from people in Marysville and north Everett. It twice has been fined by the Puget Sound Clean Air Agency.
Phosphorus is naturally found in green waste, such as grass clippings.
The ecology department allows Cedar Grove to release 2 parts per million of phosphorus in runoff from its property. In the first, second and fourth quarters of 2011, the company discharged between 2.7 and 2.9 parts per million into the stormwater, according to the ecology department. Samples are taken where the stormwater leaves the property.
If Cedar Grove's request is granted, there would be no restriction on the amount of phosphorus it could release into the slough, Altose said.
Cedar Grove's environmental consultant, Landau Associates of Edmonds, said in a letter to the company that none of the standard methods of treating runoff, which include ponds and sand filters, would stop the phosphorus from getting into the water. Cedar Grove sent the letter to the state as part of its application for the waiver.
The company uses a swale and three holding ponds to catch runoff, the letter said.
It also said state law gears phosphorus guidelines toward lakes but is silent about rivers and marine waters.
Steamboat Slough is a place where freshwater from the Snohomish River mixes with salt water from Puget Sound.
Landau Associates recommended to Cedar Grove that it apply for the waiver, Cedar Grove spokesman Laird Harris said in an email.
"One, they cannot find a treatment that would work; two, it is close to the 2.0 level; and three, it is being discharged in an area of the Sound that does not have a problem with phosphorus," he said.
Kurt Nelson, environmental division manager for the Tulalip Tribes, said juvenile salmon use Steamboat Slough to feed and grow. He said he hasn't had a chance to study the waiver application but that it raises concerns nonetheless.
"What this points out to me is that there are continuing issues with their stormwater system that really need to be investigated," he said.
The state guideline for copper is 14 parts per billion. Cedar Grove released 25.1 parts per billion of copper in its runoff the first quarter of 2011, according to the ecology department document. It met the guidelines for the second and fourth quarters.
Copper impairs the sense of smell in fish, reducing their ability to escape predators, Nelson said.
The company also exceeded limits for the level of turbidity, or cloudiness in the water, by up to six times the limit in 2011.
Harris said the company and its consultant are developing a plan to treat turbidity and will not request a waiver.
Two years ago, Cedar Grove paid more than $23,500 to the Puget Soundkeeper Alliance, a Seattle environmental group, after compost made its way into Steamboat Slough. The payment was to avoid a lawsuit.
An official with the environmental group in 2010 accused Cedar Grove of regularly exceeding discharge limits for pollutants from late 2005 through early 2009, based on quarterly reports filed with the Department of Ecology. Cedar Grove began operating on Smith Island in 2004.
The company agreed to the settlement after the Puget Soundkeeper Alliance said it was preparing to sue Cedar Grove in federal court.
"Litigation is very costly and the settlement was seen by both parties as a positive result," Harris said at the time.
Bill Sheets: 425-339-3439; email@example.com.
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