1

UNITED STATES
SECURITIES AND EXCHANGE COMMISSION
WASHINGTON, D.C.  20549

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SCHEDULE 13D
(RULE 13d-101)

UNDER THE SECURITIES EXCHANGE ACT OF 1934
AMENDMENT NO. 2

NRG GENERATING (U.S.) INC.
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(Name of Issuer)

Common Stock, par value $.01 per share
- --------------------------------------------------------------------------------
(Title of Class of Securities)

628950 10 7
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(CUSIP Number)

Vice President and General Counsel
NRG Energy, Inc.
1221 Nicollet Mall, Suite 700
Minneapolis, MN 55403
(612) 373-5300
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(name, address and telephone number of person
authorized to receive notices and communications)

November 25, 1997
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(date of event which requires filing of this statement)

If the filing person has previously filed a statement on Schedule 13G
to report the acquisition which is the subject of this Schedule 13D, and is
filing this schedule because of Rule 13d-1(b)(3) or (4), check the following
box / /.

Note: Six copies of this statement, including all exhibits, should be
filed with the Commission.  See Rule 13d-1(a) for other parties to whom copies
are to be sent.

* The remainder of this cover page shall be filled out for a reporting
person's initial filing on this form with respect to the subject class of
securities, and for any subsequent amendment containing information which would
alter disclosures provided in a prior cover page.

The information required on the remainder of this cover page shall not
be deemed to be "filed" for the purpose of Section 18 of the Securities
Exchange Act of 1934 ("Act") or otherwise subject to the liabilities of that
section of the Act but shall be subject to all other provisions of the Act
(however, see the Notes).

(Page 1 of 5 Pages)

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13D
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CUSIP NO.   628950 10 7                          PAGE  2    OF  5     PAGES
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1      NAME OF REPORTING PERSONS
S.S. OR I.R.S. IDENTIFICATION NOS. OF ABOVE PERSONS

NRG ENERGY, INC.                  I.R.S. IDENTIFICATION NO. 41-1724239
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2      CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP*              (a)  / /
(b)  / /
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3      SEC USE ONLY

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4      SOURCE OF FUNDS*

00             

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5      CHECK BOX IF DISCLOSURE OF LEGAL PROCEEDINGS IS REQUIRED            / /
PURSUANT TO ITEM 2(d) OR 2(e)

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6      CITIZENSHIP OR PLACE OF ORGANIZATION

DELAWARE
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NUMBER OF       7      SOLE VOTING POWER
SHARES                
BENEFICIALLY            3,106,612
OWNED BY        ---------------------------------------------------------------
EACH          8      SHARED VOTING POWER
REPORTING
PERSON WITH             0               
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9      SOLE DISPOSITIVE POWER    

3,106,612        
---------------------------------------------------------------
10     SHARED DISPOSITIVE POWER

0                                  
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11     AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON

3,106,612        
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12     CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (11)                       / /
EXCLUDES CERTAIN SHARES*

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13     PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (11)

45.21%
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14     TYPE OF REPORTING PERSON* 

CO        
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ITEM 1.  SECURITY AND ISSUER

This statement relates to the common stock, par value $.01 per share
(the "Common Stock"), of NRG Generating (U.S.) Inc., a Delaware corporation
(the "Company"), formerly named O'Brien Environmental Energy, Inc. ("O'Brien"). 
The principal executive offices of the Company are located at 1221 Nicollet
Mall, Suite 600, Minneapolis, MN  55403.

ITEM 2.  IDENTITY AND BACKGROUND

This statement is being filed by NRG Energy, Inc., a Delaware
corporation, with its principal place of business at 1221 Nicollet Mall, Suite
700, Minneapolis, MN  55403 ("NRG").  NRG is an independent power company whose
principal business is the acquisition, development and operation of, and
ownership of interests in, independent power and cogeneration facilities
worldwide.  NRG is a wholly owned subsidiary of Northern States Power Company
("NSP").

The directors and executive officers of NRG include David H. Peterson,
Chairman, President and Chief Executive Officer, James J. Bender, Vice
President and General Counsel, Brian B. Bird, Treasurer, Leonard A. Bluhm,
Executive Vice President and Chief Financial Officer, Gary R. Johnson,
Director, Valorie A. Knudsen, Vice President--Finance, Cynthia L. Lesher,
Director, Craig A. Mataczynski, Vice President--U.S. Business Development,
Edward J. McIntyre, Director, John A. Noer, Director, David E. Ripka,
Controller, Louise T. Routhe, Vice President--Human Resources and
Administration, Ronald J. Will, Vice President--Operations and Engineering, and
Julie A. Jorgensen, Corporate Secretary.

The directors of NSP include H. Lyman Bretting, David A. Christensen,
W. John Driscoll, Dale L. Haakensted, James J. Howard, Chairman, Allen F.
Jacobson, Richard M. Kovacevich, Douglas W. Leatherdale, John E. Pearson, G.M.
Pieschel, Dr. Margaret R. Preska and A. Patricia Sampson.  The executive
officers of NSP include James J. Howard, President and Chief Executive Officer,
Paul H. Anders, Jr., Vice President and Chief Information Officer, Arland D.
Brusven, Vice President--Finance and Treasurer, Grady P. Butts, Vice
President--Human Resources, Gary R. Johnson, Vice President and General
Counsel, Cynthia L. Lesher, President--NSP Gas, Edward J. McIntyre, Vice
President and Chief Financial Officer, Thomas A. Micheletti,
Vice President--Public and Government Affairs, John P. Moore, Jr., Corporate
Secretary, Paul E. Pender, Vice President--Finance and Treasurer, Roger D.
Sandeen, Vice President and Controller, Loren L. Taylor, President--NSP
Electric, Michael D. Wadley, Vice President--Nuclear Generation, and Edward L.
Watzl, President--NSP Generation.

All the directors and executive officers of NRG and NSP are
collectively referred to as the "Related Persons."

Neither NRG nor any of the Related Persons has, during the past five
years, been convicted in a criminal proceeding (excluding traffic violations
or similar misdemeanors).  Neither NRG nor any of the Related Persons has,
during the last five years, been a party to any civil proceeding resulting in
its being subject to a judgment, decree or final order enjoining future
violations of, or prohibiting or mandating activities subject to, federal or
state securities laws or finding any violations with respect to such laws.

ITEM 3.  SOURCE AND AMOUNT OF FUNDS OR OTHER CONSIDERATION

In consideration for its acquisition of 396,255 shares of Common Stock
(the "Conversion Shares"), NRG has reduced by $3,000,000 the outstanding
principal amount of the note payable to NRG (the "Note") by O'Brien
(Schuylkill) Cogeneration, Inc. ("Schuylkill"), a wholly-owned subsidiary of
the Company.  The Note has been guaranteed by the Company.

(Page 3 of 5 Pages)

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ITEM 4.  PURPOSE OF TRANSACTION

NRG acquired a 41.86% interest in the Company pursuant to the
Composite Fourth Amended and Restated Plan of Reorganization for O'Brien (the
"Plan"), confirmed by order of the United States Bankruptcy Court for the
District of New Jersey under Chapter 11 of the United States Bankruptcy Code on
February 22, 1996 and pursuant to the Amended and Restated Stock Purchase and
Reorganization Agreement dated as of January 31, 1996 (the "Purchase
Agreement").  Copies of the Plan and the Purchase Agreement were filed as
exhibits to the Schedule 13D filed by NRG on May 10, 1996.

In connection with the negotiation and consummation of the Plan, on
March 8, 1996, NRG entered into a loan agreement (the "Loan Agreement") with
Schuylkill, pursuant to which NRG agreed to make a loan in the principal amount
of $10,000,000 available to Schuylkill upon Schuylkill's request.  As part of
the consideration for entering into the Loan Agreement, the Company entered
into an option agreement dated March 8, 1996 (the "Option Agreement") with NRG. 
Pursuant to the Option Agreement, the Company agreed that, on the date on which
NRG made a loan to Schuylkill pursuant to the Loan Agreement, NRG would have
the right, upon 15 business days' notice, to reduce the outstanding principal
amount of the Note by $3,000,000 in exchange for the Conversion Shares.

In June 1997, NRG agreed to allow Schuylkill to borrow funds under the
Loan Agreement on an "as needed" basis rather than requiring that Schuylkill
borrow the full $10,000,000 on the funding date.  On August 22, 1997, NRG made
a loan of $2,700,000 to Schuylkill pursuant to the Loan Agreement, bringing
the total outstanding principal amount under the Loan Agreement to $4,500,000
and thereby vesting in NRG an option, exercisable on 15 days' notice to the
Company, to acquire the Conversion Shares.  On August 28, 1997, NRG notified
the Company of its intention to exercise its option (the "Exercise Notice"). 
On November 25, 1997, NRG acquired the Conversion Shares and, as a result of
such acquisition, now owns an aggregate of 3,106,612 shares of Common Stock. 
Copies of the Option Agreement and the Exercise Notice were filed as exhibits
to the Amendment No. 1 to Schedule 13D filed by NRG on August 22, 1997.

NRG intends to review its investment in the Company on a continuing
basis and may, at any time, consistent with NRG's obligations under the federal
securities laws, determine to increase or decrease its ownership of shares of
Common Stock through purchases or sales of shares of Common Stock in the open
market or in privately-negotiated transactions.  NRG's review of its investment
in the Company will depend on various factors, including the Company's business
prospects, other developments concerning the Company, general economic
conditions, money and stock market conditions, and any other facts and
circumstances which may become known to NRG regarding its investment in the
Company.  At this time, NRG has no plans to purchase additional shares of
Common Stock in the open market or in privately negotiated transactions.

NRG has no present plans or proposals which relate to or would result
in (i) an extraordinary corporate transaction, such as a merger, reorganization
or liquidation, involving the Company or any of its subsidiaries, (ii) a sale
or transfer of a material amount of assets of the Company or any of its
subsidiaries, (iii) any change in the board of directors or management of the
Company or any of its subsidiaries, (iv) any material change in the present
capitalization or dividend policy of the Company, (iv) any other material
change in the Company's business or corporate structure, (vi) changes in the
Company's charter or bylaws or other actions which may impede the acquisition
of control of the Company by any person, (vii) causing a class of securities of
the Company to be delisted from a national securities exchange or cease to be
quoted in an inter-dealer quotation system of a registered national securities
association, (viii) a class of equity securities of the Company becoming
eligible for termination of registration pursuant to Section 12(g)(4) of the
Securities Exchange Act of 1934 or (ix) any action similar to any of those
described above.  However, NRG retains its rights to modify its plans with
respect to the transactions described in this Item 4, to acquire or dispose of
securities of the Company and to formulate plans and proposals which could
result in the occurrence of any such events, subject to applicable laws and
regulations.

(Page 4 of 5 Pages)

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ITEM 5.  INTEREST IN SECURITIES OF THE ISSUER

As of November 25, 1997, NRG directly beneficially owns and has the
sole power to vote 3,106,612 shares of Common Stock, which represent 45.21% of
the outstanding shares of Common Stock of the Company.

Except as disclosed in Item 4, NRG has not effected any transaction
involving shares of Common Stock of the Company during the past 60 days.

ITEM 6.  CONTRACTS, ARRANGEMENTS, UNDERSTANDINGS OR
RELATIONSHIPS WITH RESPECT TO SECURITIES OF THE ISSUER

To the best knowledge of NRG, there are at present no contracts,
arrangements, understandings or relationships (legal or otherwise) between NRG
and any person with respect to any securities of the Company, including, but
not limited to, transfer or voting of any of the securities of the Company,
finder's fees, joint ventures, loan or option arrangements, puts or calls,
guarantees of profits, division of profits or loss or the giving or withholding
of proxies, or a pledge or contingency the occurrence of which would give
another person voting power or investment power over the Common Stock of the
Company (other than standard default and similar provisions contained in loan
agreements).

ITEM 7.  MATERIAL TO BE FILED AS EXHIBITS

None

SIGNATURE

After reasonable inquiry and to the best of my knowledge and belief, I
certify that the information set forth in this statement is true, complete and
correct.

NRG ENERGY, INC.

Dated: December 2, 1997

/s/ James J. Bender
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Name: James J. Bender
Title: Vice President and General Counsel

(Page 5 of 5 Pages)