FORM 4 Check this box if no longer subject to Section 16. Form 4 or Form 5 obligations may continue. See Instruction 1(b).

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 STATEMENT OF CHANGES IN BENEFICIAL OWNERSHIP OF SECURITIES Filed pursuant to Section 16(a) of the Securities Exchange Act of 1934, Section 17(a) of the Public Utility Holding Company Act of 1935 or Section 30(h) of the Investment Company Act of 1940

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(Print or Type Responses)

1. Name and Address of Reporting Person * LEMMON RICHARD A   2. Issuer Name and Ticker or Trading Symbol TETRA TECH INC [TTEK] 5. Relationship of Reporting Person(s) to Issuer (Check all applicable) _____ Director _____ 10% Owner __X__ Officer (give title below) _____ Other (specify below) SVP, CORPORATE ADMINISTRATION (Last) (First) (Middle) 3475 EAST FOOTHILL BOULEVARD 3. Date of Earliest Transaction (Month/Day/Year) 11/21/2017 (Street) PASADENA,, CA 91107 4. If Amendment, Date Original Filed(Month/Day/Year) 6. Individual or Joint/Group Filing(Check Applicable Line) _X_ Form filed by One Reporting Person ___ Form filed by More than One Reporting Person (City) (State) (Zip) Table I - Non-Derivative Securities Acquired, Disposed of, or Beneficially Owned

1.Title of Security (Instr. 3) 2. Transaction Date (Month/Day/Year) 2A. Deemed Execution Date, if any (Month/Day/Year) 3. Transaction Code (Instr. 8) 4. Securities Acquired (A) or Disposed of (D) (Instr. 3, 4 and 5) 5. Amount of Securities Beneficially Owned Following Reported Transaction(s) (Instr. 3 and 4) 6. Ownership Form: Direct (D) or Indirect (I) (Instr. 4) 7. Nature of Indirect Beneficial Ownership (Instr. 4) Code V Amount (A) or (D) Price COMMON STOCK 11/21/2017   A   6,156 (1) A $ 0 36,002 D   COMMON STOCK 11/21/2017   A   5,817 (2) A $ 0 41,819 D   COMMON STOCK 11/21/2017   F   4,533 (3) D $ 50 37,286 D   COMMON STOCK 11/21/2017   F   402 (4) D $ 50 36,884 D

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Table II - Derivative Securities Acquired, Disposed of, or Beneficially Owned
(e.g., puts, calls, warrants, options, convertible securities)

1. Title of Derivative Security (Instr. 3)

2. Conversion or Exercise Price of Derivative Security

3. Transaction Date (Month/Day/Year)

3A. Deemed Execution Date, if any (Month/Day/Year)

4. Transaction Code (Instr. 8)

5. Number of Derivative Securities Acquired (A) or Disposed of (D) (Instr. 3, 4, and 5)

6. Date Exercisable and Expiration Date (Month/Day/Year)

7. Title and Amount of Underlying Securities (Instr. 3 and 4)

8. Price of Derivative Security (Instr. 5)

9. Number of Derivative Securities Beneficially Owned Following Reported Transaction(s) (Instr. 4)

10. Ownership Form of Derivative Security: Direct (D) or Indirect (I) (Instr. 4)

11. Nature of Indirect Beneficial Ownership (Instr. 4)

Code

V

(A)

(D)

Date Exercisable

Expiration Date

Title

Amount or Number of Shares

Reporting Owners

Reporting Owner Name / Address	Relationships
	Director	10% Owner	Officer	Other
LEMMON RICHARD A 3475 EAST FOOTHILL BOULEVARD PASADENA,, CA 91107			SVP, CORPORATE ADMINISTRATION

Signatures

Janis B. Salin for Richard A. Lemmon		11/22/2017
**Signature of Reporting Person		Date

Explanation of Responses:

*	If the form is filed by more than one reporting person, see Instruction 4(b)(v).
**	Intentional misstatements or omissions of facts constitute Federal Criminal Violations. See 18 U.S.C. 1001 and 15 U.S.C. 78ff(a).
(1)	Each performance share unit ("PSU") represents the right to receive one share of Common Stock. The PSUs awarded cliff-vest after a 3-year performance period. The Performance Period was the Company's fiscal years 2015, 2016 and 2017. The number of PSUs earned by the Awardee was determined at the end of the Performance Period by measuring earnings per share ("EPS") growth, which was 35% year-over-year growth. Therefore, 200% of the 3,078 PSUs awarded on November 21, 2014 were earned and vested on November 21, 2017.
(2)	Each performance share unit ("PSU") represents the right to receive one share of Common Stock. The PSUs awarded cliff-vest after a 3-year performance period. The Performance Period was the Company's fiscal years 2015, 2016 and 2017. The number of PSUs earned by the Awardee for the Performance Period was determined at the end of the Performance Period by measuring relative total shareholder return ("TSR"), with equal weight given to the selected industry peer group and to the S&P 1000. The TSR peer group performance percentile was 89%, and the TSR S&P 1000 performance percentile was 82%. Straight line interpolation determined the vesting credit percentage. Therefore, 189% of the 3,078 PSUs awarded on November 21, 2014 were earned and vested on November 21, 2017.
(3)	4,533 of the shares underlying PSUs which vested on 11/21/2017 were withheld to pay the related tax liability.
(4)	402 of the shares underlying restricted stock which vested on 11/21/2017 were withheld to pay the related tax liability.

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