<SEC-DOCUMENT>0000831641-21-000105.txt : 20211122
<SEC-HEADER>0000831641-21-000105.hdr.sgml : 20211122
<ACCEPTANCE-DATETIME>20211122194425
ACCESSION NUMBER:		0000831641-21-000105
CONFORMED SUBMISSION TYPE:	4
PUBLIC DOCUMENT COUNT:		1
CONFORMED PERIOD OF REPORT:	20211118
FILED AS OF DATE:		20211122
DATE AS OF CHANGE:		20211122

REPORTING-OWNER:	

	OWNER DATA:	
		COMPANY CONFORMED NAME:			Teufele Bernard
		CENTRAL INDEX KEY:			0001722571

	FILING VALUES:
		FORM TYPE:		4
		SEC ACT:		1934 Act
		SEC FILE NUMBER:	000-19655
		FILM NUMBER:		211434267

	MAIL ADDRESS:	
		STREET 1:		14940 123 AVENUE
		CITY:			EDMONTON
		STATE:			A0
		ZIP:			T5V 1B4

ISSUER:		

	COMPANY DATA:	
		COMPANY CONFORMED NAME:			TETRA TECH INC
		CENTRAL INDEX KEY:			0000831641
		STANDARD INDUSTRIAL CLASSIFICATION:	SERVICES-ENGINEERING SERVICES [8711]
		IRS NUMBER:				954148514
		STATE OF INCORPORATION:			DE
		FISCAL YEAR END:			1003

	BUSINESS ADDRESS:	
		STREET 1:		3475 EAST FOOTHILL BOULEVARD
		CITY:			PASADENA
		STATE:			CA
		ZIP:			91107
		BUSINESS PHONE:		6263514664

	MAIL ADDRESS:	
		STREET 1:		3475 EAST FOOTHILL BOULEVARD
		CITY:			PASADENA
		STATE:			CA
		ZIP:			91107
</SEC-HEADER>
<DOCUMENT>
<TYPE>4
<SEQUENCE>1
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<DESCRIPTION>FORM 4
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        <issuerName>TETRA TECH INC</issuerName>
        <issuerTradingSymbol>TTEK</issuerTradingSymbol>
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            <rptOwnerName>Teufele Bernard</rptOwnerName>
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            <rptOwnerCity>EDMONTON</rptOwnerCity>
            <rptOwnerState>A0</rptOwnerState>
            <rptOwnerZipCode>T5V 1B4</rptOwnerZipCode>
            <rptOwnerStateDescription>ALBERTA, CANADA</rptOwnerStateDescription>
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            <isDirector>0</isDirector>
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            <isTenPercentOwner>0</isTenPercentOwner>
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            <officerTitle>SVP, Canada and South America</officerTitle>
            <otherText></otherText>
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    <derivativeTable>
        <derivativeTransaction>
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                <value>2019-11-18</value>
                <footnoteId id="F4"/>
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                <value>2022-11-18</value>
            </expirationDate>
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                <underlyingSecurityTitle>
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                </underlyingSecurityTitle>
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    <footnotes>
        <footnote id="F1">The award becomes vested as to 25% of the RSUs on the anniversary of the grant date.</footnote>
        <footnote id="F2">Represents the combined number of shares withheld to pay the related tax liability on a total of 1,845 restricted stock units (RSUs) which vested on 11/18/2021.</footnote>
        <footnote id="F3">Amount of securities beneficially owned have also been updated to reflect the acquisition of 45 shares of common stock pursuant to the Tetra Tech, Inc. Employee Stock Purchase Plan (ESPP) on December 15, 2020.</footnote>
        <footnote id="F4">The RSUs become vested as to 25% of the shares on November 18, 2019, and the anniversary of that date going forward until fully vested.</footnote>
        <footnote id="F5">The RSUs become vested as to 25% of the shares on November 18, 2020, and the anniversary of that date going forward until fully vested.</footnote>
        <footnote id="F6">The RSUs become vested as to 25% of the shares on November 18, 2021, and the anniversary of that date going forward until fully vested.</footnote>
    </footnotes>

    <remarks></remarks>

    <ownerSignature>
        <signatureName>/s/ Preston Hopson, Attorney-in-fact for Bernard Teufele</signatureName>
        <signatureDate>2021-11-23</signatureDate>
    </ownerSignature>
</ownershipDocument>
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</TEXT>
</DOCUMENT>
</SEC-DOCUMENT>
