INDIANAPOLIS (AP) - An environmental group that helped push BP PLC to a multimillion-dollar settlement last year over air emissions at its northwestern Indiana oil refinery says the sprawling complex’s revised wastewater permit falls short of what’s needed to protect Lake Michigan’s waters.

BP’s Whiting refinery about 20 miles southeast of Chicago is nearing completion of a $3.8 billion expansion that will make it a top processor of heavy crude oil extracted from Canada’s tar sand deposits.

Environmental groups have raised concerns that the project, set for completion later this year, will result in worsened pollution in the area and warn that tar sands oil contains elevated levels of impurities.

The Natural Resources Defense Council outlines what it calls numerous shortcomings in BP’s draft wastewater permit in comments submitted to the Indiana Department of Environmental Management during a public comment period that ended Friday.

Chief among those is that the permit awaiting final approval by Indiana regulators fails to require BP to implement technologies it developed with two research partners that could help the refinery remove additional mercury from its wastewater discharges.

BP received permission from IDEM in late 2011 for the refinery to discharge an annual average of 23.1 parts per trillion of mercury - nearly 20 times the water quality standard for the Great Lakes. Such mercury variances are allowed under state law.

Ann Alexander, a senior attorney for the Natural Resources Defense Council, said the group is pleased that BP’s revised permit does commit it to more testing on technologies that could lower its mercury emissions to 1.3 parts per trillion, which is the Great Lakes standard.

But her group and others that signed on to its comments - including the Hoosier Environmental Council, Save the Dunes and the Alliance for the Great Lakes - are concerned the permit doesn’t set a schedule for installing those technologies at the refinery, nor require BP to ever do so.

“The permit should require a definite timetable that they implement the technology, unless there’s a good reason not to,” Alexander said. “What you really have is a system that’s set up where BP could potentially just study this problem to death” and never install new mercury-removal technologies.

She said IDEM should adjust the permit to include such a requirement because mercury, a potent neurotoxin, can accumulate in fish and could damage the developing brains of young children and fetuses if they or their mothers eat tainted fish.

Bruno Pigott, assistant commissioner for IDEM’s Office of Water Quality, said the state agency has reviewed the environmental groups’ comments and agrees that portions of the permit “could be stronger.”

He said Friday that IDEM is revising the permit to include a provision that BP implement mercury-removal technologies that have been proven to work at the refinery and to set a time frame for installing it.

BP spokesman Scott Dean said so far the new technologies have been tested on only “a very small volume” of wastewater over just a few weeks’ time. He said more testing is needed to make sure it can work in the long term and on a refinery scale.

“We’re still evaluating the technologies in terms of how scalable and how robust they are for 24/7, 365-type usage,” Dean said. “It’s just too soon to tell.”

Pigott said once that research by BP, Argonne National Laboratory and the Purdue-Calumet Water Institute is completed and shows “it really works, they’ll need to produce a schedule and get going on that as soon as possible.”

He said IDEM is also moving to address the environmental groups’ concerns that the permit doesn’t require BP to make its stormwater management plan for the 1,400-acre refinery public.

While the agency won’t require BP to release that plan, Pigott said IDEM is revising the permit to include a requirement that it prepare an annual report on its stormwater management efforts and submit it to the agency. He said those reports would be public documents.

Pigott said IDEM hopes to give final approval to BP’s permit in about a month.

After Indiana issued an air permit for the refinery expansion in 2008, the Natural Resources Defense Council joined the Sierra Club and other environmental groups in suing to block the project.

The U.S. Environmental Protection Agency later accused BP of Clean Air Act violations.

In May 2012, BP reached a settlement with the EPA and the environmental groups under which the company agreed to install $400 million in new air pollution controls at the refinery and pay an $8 million fine to settle alleged air quality permit violations.