UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 SCHEDULE 13G/A Under the Securities Exchange Act of 1934 (Amendment No. 2) Northwest Pipe Company (Name of Issuer) Common Stock (Title of Class of Securities) 667746101 (CUSIP Number) December 31, 2010 (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). CUSIP No. 667746101 1. Names of Reporting Person Wentworth, Hauser & Violich, Inc. 2. Check the Appropriate Box if a Member Of a Group [ ] (a) [ ] (b) 3. SEC Use Only 4. Citizenship or Place of Organization Washington, United States 5. Sole Voting Power: 9,300 Number of Shares 6. Shared Voting Power: 0 Beneficially Owned by 7. Sole Dispositive Power: 9,300 Each Reporting Person With 8. Shared Dispositive Power: 0 9. Aggregate Amount Beneficially Owned by Each Reporting Person 9,300 10. Check if the Aggregate Amount in Row (9) Excludes Certain Shares 11. Percent of Class Represented by Amount in Row (9) 0.10% 12. Type of Reporting Person IA Item 1. (a) Issuer: Northwest Pipe Company Address: 5721 SE Columbia Way, Suite 200 Vancouver, Washington 98661 Item 2. (a) Name of Person Filing: Wentworth, Hauser & Violich, Inc. ("Wentworth") (b) Address of Principal Business Offices: 301 Battery Street, Suite 400 San Francisco, CA 94111-3203 United States (c) Citizenship: Please refer to Item 4 on each cover sheet for each filing person. (d) Title of Class of Securities Common Stock (e) CUSIP Number: 667746101 Item 3. Wentworth, Hauser & Violich, Inc. is an investment adviser in accordance with ss.240.13d-1(b)(1)(ii)(E); Item 4. Ownership Please see Items 5 - 9 and 11 on each cover sheet for each filing person. Under the definition of "beneficial ownership" in Rule 13d-3 under the Securities Exchange Act of 1934, it is also possible that the individual directors, executive officers, and/or shareholders of Wentworth might be deemed the "beneficial owners" of some or all of the securities to which this Schedule 13G/A relates in that they might be deemed to share the power to direct the voting or disposition of such securities. Neither the filing of this Schedule 13G/A nor any of its contents shall be deemed to constitute an admission that any of such individuals is, for any purpose, the beneficial owner of any of the securities to which this Schedule 13G/A relates, and such beneficial ownership is expressly disclaimed. Item 5. Ownership of Five Percent or Less of a Class X Item 6. Ownership of More than Five Percent on Behalf of Another Person Not Applicable 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 I certify that, to the best of my knowledge and belief, the securities referred to above were acquired and 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: February 14, 2011 Wentworth, Hauser & Violich, Inc. By: /s/ Pavita Fleischer -------------------------- Name: Pavita Fleischer Title: Chief Compliance Officer