No direct evidence pins the blame for Chicago beach pollution on Milwaukee sewage dumping, according to a letter from U.S. Environmental Protection Agency Administrator Christie Whitman released Wednesday. 

But raw sewage dumping by the Milwaukee Metropolitan Sewerage District also can't be ruled out as a culprit in Chicago beach pollution, a top regional environmental official said Wednesday. 

Recent scientific research suggests E. coli bacteria can live for years in beaches or the sandy bottom of the lake, making it theoretically plausible that Milwaukee dumping is a factor in Chicago beach problems, said Joe Cisneros, regional chief of enforcement for the EPA. The best scientific evidence points to multiple potential causes of E. coli beach pollution, including sewage dumping -- sometimes called overflows -- runoff and bird feces, Cisneros said in an interview. But there's not enough evidence to absolutely affix blame, he said. 

"Hopefully, by not having any more overflows," old E. coli eventually will die off and not be replaced by additional bacteria from human waste, he said. 

His remarks followed the release of an Aug. 1 letter from Whitman, in which she said: "To date, the EPA has no direct evidence that supports the contention that there is a direct relationship between Milwaukee (raw sewage) discharges and closures of beaches in the Chicago area." 

The letter was replying to a request from Chicago-area U.S. Rep. Janice Schakowsky, a Democrat, and seven other Chicago congressmen for EPA enforcement action against MMSD. The officials blamed MMSD dumping for Chicago beach pollution. 

The MMSD has dumped more than 13 billion gallons of raw sewage into Lake Michigan and local streams that empty into the lake since 1994. 

MMSD released the letter, along with its own press release, declaring MMSD was "pleased the EPA has come to the same conclusion on this issue as others in the scientific community." 

MMSD has frequently pointed to runoff pollution as a probable culprit in beach pollution, but district officials have been careful not to claim that sewage dumping plays no role. 

Nadeam Elshami, a spokesman for Schakowsky, said Whitman did not directly respond to the Illinois delegation's claim that the EPA was failing to enforce the federal Clean Water Act. 

"It's no surprise the Bush administration with its reluctant attitude as the environmental enforcement agency would not be concerned about the millions of gallons of sewage being dumped by Milwaukee into Lake Michigan," Elshami said. 

MMSD's major dumping episode this week underscores the need for additional federal action to halt the practice, Elshami said. MMSD dumped raw sewage for 13 hours Monday night and for several hours Tuesday, but has not revealed the total volume spewed into the lake. 

The EPA's Cisneros said the agency is working with the state Department of Natural Resources to enforce an agreement the MMSD made with the DNR last year to add capacity to the local sewer system. 

The federal agency also is working with the DNR to craft new standards for MMSD's sewer plant discharge permit, he said. 

The DNR is proposing a host of new conditions for MMSD's permit, said Jim Fratrick, a DNR watershed expert who works on MMSD issues. He declined to name specific permit changes the DNR was seeking. 

Fratrick also said he could not say when the DNR will unveil its proposed MMSD permit. Until a new permit is approved, MMSD will operate under terms of its old permit, which expired March 31, he said.