SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 SCHEDULE 13G Under the Securities Exchange Act of 1934 TETRA TECH INC ------------------------- (Name of Issuer) COMMON STOCK -------------------------------- (Title of Class of Securities) 88162G103 ---------------- (CUSIP Number) 02/22/2007 --------------------------------------------------------- (Date of Event Which Requires Filing of this Statement) Check appropriate box to designate the rule pursuant to which this Schedule is filed: | | Rule 13d-1(b) |X| Rule 13d-1(c) |_| Rule 13d-1(d) ----------------------- --------------------- CUSIP No. 88162G103 13G Page 1 of 1 Pages ----------------------- --------------------- -------------------------------------------------------------------------------- 1 Names of Reporting Persons/I.R.S. Identification Nos. of Above Persons (Entities Only) Pictet Asset Management SA("PAM SA") The reporting person disclaim beneficial ownership of the shares reported, which are owned of record and beneficially by three non-U.S. investment funds, both managed by PAM SA. -------------------------------------------------------------------------------- 2 Check the Appropriate Box if a Member of a Group (a) / / (b) / / -------------------------------------------------------------------------------- 3 SEC Use Only -------------------------------------------------------------------------------- 4 Citizenship or Place of Organization Pictet Asset Management SA - Switzerland -------------------------------------------------------------------------------- 5 Sole Voting Power: Number of Pictet Asset Management SA: 2,922,800 Shares ------------------------------------------------------- 6 Shared Voting Power: Beneficially Pictet Asset Management SA: None Owned by ------------------------------------------------------- 7 Sole Dispositive Power: Each Pictet Asset Management SA: 2,922,800 Reporting ------------------------------------------------------- 8 Shared Dispositive Power: Person With Pictet Asset Management SA: None -------------------------------------------------------------------------------- 9 Aggregate Amount Beneficially Owned by Each Reporting Person Pictet Asset Management SA: 2,922,800 -------------------------------------------------------------------------------- 10 Check if the Aggregate Amount in Row (9) Excludes Certain Shares / / -------------------------------------------------------------------------------- 11 Percent of Class Represented by Amount in Row (9) Pictet Asset Management SA: 5.04% -------------------------------------------------------------------------------- 12 Type of Reporting Person: Pictet Asset Management SA: IA -------------------------------------------------------------------------------- Item 1. (a) Name of Issuer: TETRA TECH INC (b) Address of Issuer's Principal Executive Offices: 3475 EAST FOOTHILL BOULEVARD PASADENA, CA 91107 UNITED STATES Item 2 (a) Names of Person Filing: Pictet Asset Management SA("PAM SA") (b) Address of Principal Business Office or, if none, Residence: Pictet Asset Management SA: 60 ROUTE DES ACACIAS GENEVA 73 SWITZERLAND CH-12 11 (c) Citizenship: Pictet Asset Management SA: United Kingdom (d) Title of Class Securities: COMMON STOCK (e) CUSIP Number: 88162G103 Item 3. If this statement is filed pursuant to Rule 13d-1 (b), or 13d-2 (b) or (c), check whether the person is A Not applicable. Item 4. Ownership The reporting persons disclaim beneficial ownership of the shares reported, which are owned of record and beneficially by three non-U.S. investment funds, both are managed by PAM SA. (a) Amount Beneficially Owned: Pictet Asset Management SA: 2,922,800 (b) Percent of Class: Pictet Asset Management SA: 5.04% (c) Number of shares as to which such person has: Pictet Asset Management SA: (i) sole power to vote or to direct the vote: 2,922,800 (ii) (iii) shared power to vote or to direct the vote: None (iv) sole power to dispose or to direct the disposition of: 2,922,800 (v) (vi) shared power to dispose or to direct the disposition of: None Item 5. Ownership of Five Percent or Less of a Class Not applicable. 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 See answer to Item 2 (a) Item 8. Identification and Classification of Members of the Group Not applicable. Item 9. Notice of Dissolution of the 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 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: 26TH FEBRUARY 2006 /s/ David Cawthrow ------------------------------ David Cawthrow Chief Compliance Officer AGREEMENT OF REPORTING PERSONS The undersigned herby agree that the foregoing Schedule 13G is filed on behalf of the undersigned. Pictet Asset Management SA By: /s/ David Cawthrow -------------------------------- David Cawthrow, Chief Compliance Officer