The public airing of concerns about banks' ownership of physical commodities and assets from pipelines to warehouses will renew scrutiny on Wall Street.

But experts said it may have little impact on an industry that is already retrenching and after the Federal Reserve has already signaled its intent to move forward in some way with changes in regulation.

Still, Goldman and its metals storage unit Metro will come under particular pressure when executives appear at the two-day hearing by the Senate's Permanent Subcommittee On Investigations, because it has maintained commodity trading is core to its business.

JPMorgan Chase & Co. and Morgan Stanley, which will also address the panel, have both made major moves to get out of the physical commodity space.

"If you like what Wall Street did for the housing market, you'll love what Wall Street is doing for commodities," said committee Chair Carl Levin, a Michigan Democrat, in his opening remarks.

"Goldman's ability to influence any portion of the price for a key component of the industrial economy is simply unacceptable."

Ahead of the upcoming hearing, the committee released a detailed 403-page bi-partisan report that criticized how banks purchased and exploited huge commodity stockpiles.

It shed light on two areas: the Fed's concerns about weakness in banks' ability to withstand a major catastrophe and intricate details of Metro's multi-million dollar payments to maintain the long wait times and bolster income.

According to a previously unpublished 2012 analysis by the Federal Reserve Commodities Team, the report said four major financial holding companies, including the three highlighted in the Senate report, had allocated an inadequate amount of capital and insurance to cover "extreme loss scenarios."

Republican Senator John McCain of Arizona, a committee member, said Wall Street banks have taken excessive risk, raised suspicions of market manipulation and gained unfair trading advantages" through their expansion into physical commodities trading.

The session will also include testimony on Friday by top oversight officials with the Federal Energy Regulatory Commission and the Fed's banking supervision arm.

"There will be a lot of sound and fury, but it won't amount to much in the long term," said Craig Pirrong, a finance professor at the University of Houston.

PLAYING BY THE RULES

Aluminum warehousing is likely to be in the spotlight from the report, based on 90,000 pages of bank and regulatory documents as well as 78 interviews and briefings,

In prepared testimony, chief executive officer of Goldman's metals warehouse, which was accused by a Senate probe of manipulating aluminum prices, defended his company's actions, saying it plays by the rules and contributes jobs to the Detroit area.

Chris Wibbelman, president and CEO of Metro International Trade Services LLC, said only a small percentage of aluminum stockpiles are subject to the kind of metal backlogs that have come under scrutiny.

About 80 percent of metal stored in Metro warehouses in and out of the London Metal Exchange's vast network is not subject to any queue and may be purchased by a customer through negotiations with the metal owner, Wibbelman said in prepared remarks.

"There simply is no lack of availability for aluminum."

MillerCoors LLC, the U.S. operations of Molson Coors Brewing Co. and SABMiller, has accused warehouses and their owners of inflating the prices of aluminum, and costing consumers billions of extra dollars annually.

Jacques Gabillon, Goldman's head of global commodities principal investments group, and Gregory Agran, Goldman's co-head of commodities, will also testify on Thursday.

"The investment in Metro was never part of Goldman Sachs' core franchise and has not been integrated into our commodities market making activities," Gabillon said in prepared remarks, adding that queues do not drive the overall price of aluminum that consumers pay.

Goldman is in the process of selling Metro, though details of bidders and timing remain unclear.

LAST YEAR'S FIGHT

This week's hearing stems from a two-year investigation by the subcommittee into banks and their influence on commodities and comes as Levin prepares to retire at the end of this year.

He has served on the panel for about 15 years.

The question will draw fresh attention to a controversy over the possible risks posed by the involvement of the largest U.S. investment banks, but is unlikely to have much lasting affect as JPMorgan and Morgan Stanley have already pulled out or are shrinking their commodities businesses.

Earlier in the year, the Fed took a preliminary step toward potential new regulations to check banks' decade-long expansion into the raw materials supply chain.

Democrats Sherrod Brown and Elizabeth Warren have grilled regulators and banking experts twice on the issue since July 2013.

"In some ways, this is fighting last year's war," said Pirrong.