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


                                  SCHEDULE 13G



                    Under the Securities Exchange Act of 1934

                               (Amendment No.  )*


                             NORTHWEST PIPE COMPANY
--------------------------------------------------------------------------------
                                (Name of Issuer)


                                  COMMON STOCK
--------------------------------------------------------------------------------
                         (Title of Class of Securities)


                                    667746101
                         ------------------------------
                                 (CUSIP Number)


                                December 31, 2001
--------------------------------------------------------------------------------
             (Date of Event Which Requires Filing of this Statement)

Check the appropriate box to designate the rule pursuant to which this Schedule
is filed:

     [X] Rule 13d-1(b)
     [_] Rule 13d-1(c)
     [_] Rule 13d-1(d)

*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 the
disclosures provided in a prior cover page.

The information required in 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 6 pages



CUSIP NO. 667746101                   13G                    Page 2 of 6 Pages

------------------------------------------------------------------------------
      NAMES OF REPORTING PERSONS
 1    I.R.S. IDENTIFICATION NOs. OF ABOVE PERSONS

      HEARTLAND ADVISORS, INC.
      #39-1078128
------------------------------------------------------------------------------
      CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP
 2                                                              (a) [_]
                                                                (b) [_]
------------------------------------------------------------------------------
      SEC USE ONLY
 3
------------------------------------------------------------------------------
      CITIZENSHIP OR PLACE OF ORGANIZATION
 4
      WISCONSIN, U.S.A.
------------------------------------------------------------------------------
                          SOLE VOTING POWER
                     5
     NUMBER OF            134,200
      SHARES       -----------------------------------------------------------
                          SHARED VOTING POWER
   BENEFICIALLY      6
     OWNED BY             None
                   -----------------------------------------------------------
       EACH               SOLE DISPOSITIVE POWER
                     7
    REPORTING             459,600
      PERSON       -----------------------------------------------------------
                          SHARED DISPOSITIVE POWER
       WITH          8
                          None
------------------------------------------------------------------------------
      AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON
 9
      459,300
------------------------------------------------------------------------------
      CHECK IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES CERTAIN SHARES
10
                                                                    [_]
------------------------------------------------------------------------------
      PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW 9
11
      7.1%
------------------------------------------------------------------------------
      TYPE OF REPORTING PERSON
12
      IA
------------------------------------------------------------------------------



CUSIP NO. 667746101                   13G                    Page 3 of 6 Pages

------------------------------------------------------------------------------
      NAMES OF REPORTING PERSONS
 1    I.R.S. IDENTIFICATION NOs. OF ABOVE PERSONS

      WILLIAM J. NASGOVITZ       395-42-0703
------------------------------------------------------------------------------
      CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP
 2                                                              (a) [_]
                                                                (b) [_]
------------------------------------------------------------------------------
      SEC USE ONLY
 3
------------------------------------------------------------------------------
      CITIZENSHIP OR PLACE OF ORGANIZATION
 4
      U.S.A.
------------------------------------------------------------------------------
                          SOLE VOTING POWER
                     5
     NUMBER OF            300,000
      SHARES       -----------------------------------------------------------
                          SHARED VOTING POWER
   BENEFICIALLY      6
     OWNED BY             None
                   -----------------------------------------------------------
       EACH               SOLE DISPOSITIVE POWER
                     7
    REPORTING             None
      PERSON       -----------------------------------------------------------
                          SHARED DISPOSITIVE POWER
       WITH          8
                          None
------------------------------------------------------------------------------
      AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON
 9
      300,000
------------------------------------------------------------------------------
      CHECK IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES CERTAIN SHARES
10
                                                                    [_]
------------------------------------------------------------------------------
      PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW 9
11
      4.6%
------------------------------------------------------------------------------
      TYPE OF REPORTING PERSON
12
      IN
------------------------------------------------------------------------------



CUSIP NUMBER  667746101                           Page 4 Of 6 Pages

Item 1.
         (a) Name of Issuer:    Northwest Pipe Company


         (b) Address of Issuer's Principal Executive Offices:
         200 S.W. Market Street, Suite 1800
         Portland,  OR   97201

Item 2.
       (a) Name of Person Filing:
           ---------------------
       (1) Heartland Advisors, Inc.

       (2) William J. Nasgovitz


       (b) Address of Principal Business Office:
           ------------------------------------
            (1) 789 North Water Street
                Milwaukee, WI  53202

            (2) 789 North Water Street
                Milwaukee, WI  53202


       (c) Citizenship:  Heartland Advisors is a Wisconsin corporation.
           -----------
           William J. Nasgovitz - U.S.A

       (d) Title of Class of Securities:  Common Stock
           ----------------------------

       (e) CUSIP Number: 667746101
           ------------

Item 3. The persons filing this Schedule 13G are Heartland Advisors, Inc., an
investment adviser registered with the SEC, and William J. Nasgovitz, President
and principal shareholder of Heartland Advisors, Inc. Mr. Nasgovitz joins in
this filing pursuant to SEC staff positions authorizing certain individuals in
similar situations to join in a filing with a controlled entity eligible to file
on Schedule 13G. The reporting persons do not admit that they constitute a
group.

Item 4. Ownership.
        ---------

       (a) Amount beneficially owned:
           -------------------------
       459,600 shares may be deemed beneficially owned within the meaning of
Rule 13d-3 of the Securities Exchange Act of 1934 by (1) Heartland Advisors,
Inc. by virtue of its investment discretion and in some cases voting power over
client securities, which may be revoked; and (2) William J. Nasgovitz, as a
result of his position with and stock ownership of Heartland which could be
deemed to confer upon him voting and/or investment power over the shares
Heartland beneficially owns. Of these 459,600 shares, 300,000 shares also may be
deemed beneficially owned within the meaning of Rule 13d-3 of the Securities
Exchange Act of 1934 by Mr. Nasgovitz as a result of his position as an officer
and director of Heartland Group, Inc. which could be deemed to confer upon him
voting power over the shares Heartland Group beneficially owns.

       (b) Percent of Class:
           ----------------
       7.1%

       (c) For information on voting and dispositive power with respect to the
above listed shares, see Items 5-8 of the Cover Page.


Item 5. Ownership of Five Percent or Less of a Class.
        --------------------------------------------

       If this statement is being filed to report the fact that as
of the date hereof the reporting person has ceased to be the
beneficial owner of more than five percent of the class of



securities, check the following:[_]


Item 6.  Ownership of more than Five Percent on Behalf of Another
         --------------------------------------------------------
         Person.
         ------

         The shares of common stock to which this Schedule relates are held in
investment advisory accounts of Heartland Advisors, Inc. As a result, various
persons have the right to receive or the power to direct the receipt of
dividends from, or the proceeds from the sale of, the securities. No such
account is known to have such an interest relating to more than 5% of the class.


Item 7.  Identification and Classification of the Subsidiary Which Acquired the
         ----------------------------------------------------------------------
Security Being Reported on By the Parent Holding Company.
--------------------------------------------------------

         Not Applicable.


Item 8.  Identification and Classification of Members of the Group.
         ---------------------------------------------------------

         Not Applicable.


Item 9.  Notice of Dissolution of Group.
         ------------------------------

         Not Applicable.


Item 10. Certification.
         -------------

         By signing below, the undersigned certify that, to the best of their
knowledge and belief, the securities referred to above were acquired and are
held in the ordinary course of business and were not acquired and are not held
for the purpose of or with the effect of changing or influencing the control of
the issuer of the securities and were not acquired and are not held in
connection with or as a participant in any transaction having that purpose or
effect.

                                    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.

DATE: January 8, 2002



WILLIAM J. NASGOVITZ                        HEARTLAND ADVISORS, INC.

By: /s/ PAUL T. BESTE                       By: /s/ PAUL T. BESTE
    -----------------                           -----------------
    Paul T. Beste                                    Paul T. Beste
    As Attorney in Fact for                          Chief Operating Officer
    William J. Nasgovitz



EXHIBIT INDEX

      Exhibit 1     Joint Filing Agreement



EXHIBIT 1


                             Joint Filing Agreement

The undersigned persons agree and consent to the joint filing on their behalf of
this Schedule 13G in connection with their beneficial ownership of Northwest
Pipe Company at December 31, 2001.



ILLIAM J. NASGOVITZ

By: /s/ PAUL T. BESTE
    ----------------
         Paul T. Beste
As Attorney in Fact for William J. Nasgovitz



HEARTLAND ADVISORS, INC.


By:  /s/ PAUL T. BESTE
     -----------------
          Paul T. Beste
          Chief Operating Officer