TETRA TECHNOLOGIES INC (Form: SC 13G, Received: 07/10/1998 20:17:06)

SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549

SCHEDULE 13G

(Rule 13d-102)

INFORMATION STATEMENT PURSUANT TO RULES 13d-1 AND 13d-2

Under the Securities Exchange Act of 1934
(Amendment No. 1 )

Tetra Technologies Inc.
(Name of Issuer)

Common Stock
(Title of Class of Securities)

88162F105
(CUSIP Number)

Check the following box if a fee is being paid with this statement [ ].

*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.88162F105                    13G                    Page 2  of 8  Pages



--------------------------------------------------------------------------------
   1.  NAME OF REPORTING PERSON(S)
       S.S. OR I.R.S. IDENTIFICATION NO. OF ABOVE PERSON(S)

          Morgan  Stanley Dean  Witter &  Co.
          IRS  #  39-314-5972



--------------------------------------------------------------------------------
   2.  CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP*
                                                             (a)  [  ]
                                                             (b)  [  ]


--------------------------------------------------------------------------------
   3.  SEC USE ONLY




--------------------------------------------------------------------------------
   4.  CITIZENSHIP OR PLACE OF ORGANIZATION

          The state of organization is Delaware.


--------------------------------------------------------------------------------
   NUMBER OF      5.   SOLE VOTING POWER
     SHARES            0
  BENEFICIALLY    --------------------------------------------------------------
    OWNED BY      6.   SHARED VOTING POWER
      EACH             1,470,700
   REPORTING      --------------------------------------------------------------
     PERSON       7.   SOLE DISPOSITIVE POWER
      WITH             0
                  --------------------------------------------------------------
                  8.   SHARED DISPOSITIVE POWER
                       1,470,700
--------------------------------------------------------------------------------
   9.  AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON

          1,470,700

--------------------------------------------------------------------------------
  10.  CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES CERTAIN SHARES*



--------------------------------------------------------------------------------
  11.  PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (9)

          10.83%

--------------------------------------------------------------------------------
  12.  TYPE OF REPORTING PERSON*

          IA, CO

--------------------------------------------------------------------------------
                     *SEE INSTRUCTIONS BEFORE FILLING OUT!

CUSIP No. 88162F105                   13G                    Page 3  of 8  Pages



--------------------------------------------------------------------------------
   1.  NAME OF REPORTING PERSON(S)
       S.S. OR I.R.S. IDENTIFICATION NO. OF ABOVE PERSON(S)

          Dean Witter InterCapital Inc.
          IRS # 13-3680016

--------------------------------------------------------------------------------
   2.  CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP*
                                                             (a)  [  ]
                                                             (b)  [  ]


--------------------------------------------------------------------------------
   3.  SEC USE ONLY




--------------------------------------------------------------------------------
   4.  CITIZENSHIP OR PLACE OF ORGANIZATION

          The state of organization is Delaware.


--------------------------------------------------------------------------------
   NUMBER OF      5.   SOLE VOTING POWER
     SHARES            0
  BENEFICIALLY    --------------------------------------------------------------
    OWNED BY      6.   SHARED VOTING POWER
      EACH             1,111,200
   REPORTING      --------------------------------------------------------------
     PERSON       7.   SOLE DISPOSITIVE POWER
      WITH             0
                  --------------------------------------------------------------
                  8.   SHARED DISPOSITIVE POWER
                       1,111,200
--------------------------------------------------------------------------------
   9.  AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON

          1,111,200

--------------------------------------------------------------------------------
  10.  CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES CERTAIN SHARES*



--------------------------------------------------------------------------------
  11.  PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (9)

          8.18%

--------------------------------------------------------------------------------
  12.  TYPE OF REPORTING PERSON*

          IA, CO

--------------------------------------------------------------------------------
                     *SEE INSTRUCTIONS BEFORE FILLING OUT!

CUSIP No. 88162F105                   13G                   Page 4  of  8  Pages





Item 1.     (a)   Name of Issuer:
                  Tetra Technologies Inc.
                  --------------------------------------------------------------
            (b)   Address of Issuer's Principal Executive Offices:
                  25025 I-45 North
                  Woodlands, TX 77380
                  --------------------------------------------------------------
Item 2.     (a)   Name of Person Filing:
                  (a)  Morgan Stanley Dean Witter & Co.
                  (b)  Dean Witter InterCapital Inc.
                  --------------------------------------------------------------
            (b)   Address of Principal Business Office, or if None, Residence:
                  (a)  1585 Broadway
                       New  York, New  York  10036

                  (b)  Two World Trade Center
                       New  York, New  York  10048
                  --------------------------------------------------------------
            (c)   Citizenship:
                           Incorporated  by  reference  to  Item  4  of  the
                           cover page  pertaining  to  each  reporting  person.

                               -------------------------------------------------
            (d)   Title of Class of Securities:
                           Common Stock
                  --------------------------------------------------------------
            (e)   CUSIP Number:
                           88162F105
                               -------------------------------------------------

Item 3.           (a)  Morgan  Stanley  Dean  Witter &  Co. is (e) an Investment
                       Adviser  registered  under Section 203 of  the Investment
                       Advisers Act of 1940.

                  (b)  Dean Witter InterCapital Inc.is (e) an Investment Adviser
                       registered under Section 203 of  the Investment  Advisers
                       Act of 1940.

CUSIP No.88162F105                   13-G                   Page 5  of  8  Pages



Item 4.     Ownership.

               Incorporated  by  reference  to  Items  (5) - (9) and (11) of the
               cover page.

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

Item 6.     Ownership of More Than Five Percent on Behalf of Another Person.

               Accounts  managed  on  a  discretionary   basis  by  Dean  Witter
               InterCapital  Inc., a wholly owned  subsidiary of Morgan  Stanley
               Dean Witter & Co.,  are known to have the right to receive or the
               power to direct the receipt of  dividends  from,  or the proceeds
               from,  the sale of such  securities.  No such account  holds more
               than 5 percent of the class.

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


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


Item 9.     Notice of Dissolution of Group.


Item 10.    Certification.

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

CUSIP No.88162F105                    13-G                   Page 6  of  8 Pages


                                  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:       July 10, 1998


Signature:  /s/ Bruce Bromberg
            -----------------------------------------------------------------

Name/Title  Bruce Bromberg / Vice President Morgan Stanley & Co. Incorporated
            -----------------------------------------------------------------
            MORGAN STANLEY DEAN WITTER & CO.

Date:       July 10, 1998


Signature:  /s/ Barry Fink
            -----------------------------------------------------------------

Name/Title  Barry Fink / Senior Vice President Dean Witter InterCapital Inc.
            -----------------------------------------------------------------
            DEAN WITTER INTERCAPITAL INC.


                       INDEX TO EXHIBITS                           PAGE
                       -----------------                           ----

EXHIBIT 1       Agreement to Make a Joint Filing                      7

EXHIBIT 2       Secretary's Certificate Authorizing Bruce Bromberg    8
                to Sign on behalf of Morgan Stanley Dean Witter & Co.


* Attention. Intentional misstatements or omissions of fact constitute federal
  criminal violations (see 18 U.S.C. 1001).

(022597DTI)

Cusip No. 88162F105 13G Page 7 of 8 Pages

EXHIBIT 1 TO SCHEDULE 13G

JULY 10, 1998

MORGAN STANLEY DEAN WITTER & CO. AND DEAN WITTER INTERCAPITAL

INC. hereby agree that, unless differentiated, this Schedule 13G

is filed on behalf of each of the parties.

MORGAN STANLEY DEAN WITTER & CO.

BY:       /s/ Bruce Bromberg
           ---------------------------------------------------------------------
          Bruce Bromberg  /  Vice President Morgan Stanley &  Co., Incorporated

DEAN WITTER INTERCAPITAL INC.

BY:       /s/ Barry Fink
           --------------------------------------------------------------------
          Barry Fink  /  Senior Vice President Dean Witter InterCapital Inc.

Page 8 of 8 Pages
EXHIBIT 1 ------------------

MORGAN STANLEY, DEAN WITTER, DISCOVER & CO.

SECRETARY'S CERTIFICATE

I, Charlene R. Herzer, a duly elected and acting Assistant Secretary of Morgan Stanley, Dean Witter, Discover & Co., a corporation organized and existing under the laws of the State of Delaware (the "Corporation"), certify that as approved by a Unanimous Consent of Directors in Lieu of a Meeting dated as of May 31, 1997, the following persons are each authorized to sign reports to be filed under Sections 13 and 16 of the Securities Exchange Act of 1934 on behalf of the Corporation, and such authorizations are in full force and effect as of this date:

Stuart J.M. Breslow Robert G. Koppenol Bruce Bromberg Robin Sherak

IN WITNESS WHEREOF, I have hereunto set my name and affixed the seal of the Corporation as of the 3rd day of June, 1997.

 /s/ Charlene R. Herzer
------------------------
    Charlene R. Herzer
    Assistant Secretaty

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