That pile of stuff making a figurative stink on an Eastern Shore chicken farm?  The one environmental groups said was polluting a Chesapeake Bay tributary?  It’s treated sewage sludge from Ocean City, not poultry manure.

That’s the latest from the Maryland Department of the Environment.  Department spokesman Jay Apperson emailed Tuesday that an inspection has confirmed what Perdue Farms and an Ocean City town official both have been saying – that the Assateague Coastkeeper and Waterkeeper Alliance misidentified the light-colored mound they saw from the air on the Hudson farm near Berlin.

The two groups threatened last week to sue Alan Hudson and Perdue Farms, accusing them of allowing polluted runoff from the farm to contaminate a drainage ditch that ultimately feeds into the Pocomoke River.  The keepers released an aerial photograph showing a large pile of something between a storage shed and a drainage ditch, with water draining from the pile to the ditch.  Perdue got dragged into it because Hudson raises birds under contract with the Salisbury-based company.

Farm runoff is clearly a major source of nutrient pollution fouling the Chesapeake Bay, according to government and independent scientists.  Some environmentalists have long argued that farms dealing in chicken manure need to be regulated more tightly to limit polluted runoff, that the loose, largely voluntary controls employed to date have not worked.  But the picture has grown a bit murky, at least with this particular farm.

Perdue, the owner of the chickens raised on the Hudson farm and the third largest poultry producer in the United States, is demanding an apology from the two environmental groups.

“We recommend the Waterkeepers check their facts before they make allegations that can damage reputations,” Perdue spokesman Luis Luna wrote in an email. “The right thing for them to do at this point is issue a retraction and an apology.”

Assateague Coastkeeper Kathy Phillips, though, is unapologetic.  “It’s not about the pile,” she said. “It’s about what’s coming off the farm. It’s about what’s polluting the water.”