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                                 UNITED STATES
                      SECURITIES AND EXCHANGE COMMISSION
                           WASHINGTON, D. C.  20549



                                 SCHEDULE 13 G


                   UNDER THE SECURITIES EXCHANGE ACT OF 1934
                              (AMENDMENT NO. 18)*

                            AMERICAN ECOLOGY CORP.

                               (NAME OF ISSUER)

                        Common Stock, without par value

                        (TITLE OF CLASS OF SECURITIES)


                                  02553310-0

                                (CUSIP NUMBER)


Check the following box if a fee is being paid with this statement / /. (A fee
is not required only if the filing person: (1) has a previous statement on file
reporting beneficial ownership of more than five percent of the class of
securities described in Item 1; and (2) has filed no amendment subsequent
thereto reporting beneficial ownership of five percent or less of such class.)
(See Rule 13d-7.)

*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).


                                  Page 1 of 5.

SEC 1745 (10-88)




-----------------------                                  ---------------------
  CUSIP NO. 02553310-0                  13G                PAGE 2 OF 5 PAGES
-----------------------                                  ---------------------

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

        FAYEZ SAROFIM
        451-54-0288
------------------------------------------------------------------------------
      CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP*
 2                                                              (a) [_]
                                                                (b) [x]

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


------------------------------------------------------------------------------
      CITIZENSHIP OR PLACE OF ORGANIZATION
 4
      U.S.A.

------------------------------------------------------------------------------
                          SOLE VOTING POWER
                     5
     NUMBER OF            826,656

      SHARES       -----------------------------------------------------------
                          SHARED VOTING POWER
   BENEFICIALLY      6
                          27,994
     OWNED BY
                   -----------------------------------------------------------
       EACH               SOLE DISPOSITIVE POWER
                     7
    REPORTING             826,656

      PERSON       -----------------------------------------------------------
                          SHARED DISPOSITIVE POWER
       WITH          8
                          32,620
------------------------------------------------------------------------------
      AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON
 9
      859,276

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


------------------------------------------------------------------------------
      PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW 9
11
      5.0%

------------------------------------------------------------------------------
      TYPE OF REPORTING PERSON*
12
      IN

------------------------------------------------------------------------------
                      *SEE INSTRUCTION BEFORE FILLING OUT!





                       SECURITIES AND EXCHANGE COMMISSION
                               Washington, D. C.

                       Amendment No. 18 to Schedule 13(G)
                   Under the Securities Exchange Act of 1934



Item 1(a)  Name of Issuer:

           American Ecology Corporation

Item 1(b)  Address of Issuer's Principal Executive Office:

           805 West Idaho, Suite 200
           Boise Idaho 83702

Item 2(a)  Name of Person Filing:

           Fayez Sarofim & Co. and Fayez Sarofim

Item 2(b)  Address of Principal Business Office, or if none, Residence:

           2907 Two Houston Center
           Houston, Texas  77010

Item 2(c)  Citizenship:

           U. S. A.

Item 2(d)  Title of Class of Securities:

           Common Stock, without par value

Item 2(e)  CUSIP Number:

           02553310-0

Item 3     Filing required pursuant to the Rules 13d-1(b), or 13d-2(b),:

           Fayez Sarofim & Co. is an Investment Adviser registered under Section
           203 of the Investment Advisers Act of 1940. Fayez Sarofim is Chairman
           of the Board and President, a director and owner of a majority of the
           outstanding capital stock of Fayez Sarofim & Co. and may be
           considered a parent holding company of Fayez Sarofim & Co. within the
           meaning of Rule 13d-1(b)(1)(ii)(G).

Item 4    Ownership as of December 31, 2004:

     (a)  Amount Beneficially Owned:

          (i)  20,419 shares are held in investment advisory accounts managed
               by Fayez Sarofim & Co. for numerous clients.  Pursuant to its
               investment advisory contract with its clients, Fayez Sarofim &
               Co. has full investment discretion with respect to such
               investment advisory accounts.  However, Fayez Sarofim & Co. is
               not the record owner of any of such shares as such shares are
               held of record by the respective clients or by trustees or
               custodians for such clients.  The clients are entitled to the
               economic benefits (dividend payments and sales proceeds) of
               ownership of such shares.  Each client also has the right to
               terminate its investment advisory relationship with Fayez Sarofim
               & Co. at any time.  Because Fayez Sarofim & Co. has power to
               dispose, or to direct the disposition of, such shares, it may be
               deemed to be the beneficial owner of these shares for the
               purposes of the Rule 13d-3 under the Securities Exchange Act of
               1934.  Because Fayez Sarofim is Chairman of the Board and
               President, a director and owner of a majority of the outstanding
               capital stock of Fayez Sarofim & Co., he may also be deemed to be
               an indirect beneficial owner of these shares for the purposes of
               Rule 13d-3.

          (ii) 396 shares are held in investment advisory accounts managed by
               Sarofim Trust Co., a wholly owned subsidiary of Fayez Sarofim &
               Co., which is also an Investment Adviser registered under Section
               203 of the Investment Advisers Act of 1940. Pursuant to its
               investment advisory contracts with its clients, Sarofim Trust Co.
               has full investment discretion with respect to such investment
               advisory accounts. However, Sarofim Trust Co. is not the record
               owner of any of such shares as such shares are held of record by
               the respective clients or by trustees or custodians for such
               clients. The clients are entitled to the economic benefits of
               ownership of such shares. Each client also has the right to
               terminate its investment advisory relationship with Sarofim Trust
               Co. at any time. Because Sarofim Trust Co. has power to dispose,


                                       3





               or to direct the disposition of, such shares, it may be deemed to
               be the beneficial owner of these shares for the purposes of Rule
               13d-3 under the Securities Exchange Act of 1934 and Fayez Sarofim
               & Co. and Mr. Sarofim as controlling persons of Sarofim Trust
               Co., may be deemed to be indirect beneficial owners of these
               shares for such purposes.

         (iii) 11,784 shares are owned directly by Sarofim International
               Management Company, a wholly owned subsidiary of Fayez Sarofim &
               Co. for its own account. Because Fayez Sarofim is a controlling
               person of Fayez Sarofim & Co., he may be deemed to be an indirect
               beneficial owner of these shares for the purposes of Rule 13d-3.

          (iv) 826,656 shares are owned of record and beneficially by Fayez
               Sarofim. Fayez Sarofim & Co. has no beneficial ownership of these
               shares.

          (v)  21 shares are held in trusts with respect to which Mr. Sarofim
               is a trustee. Fayez Sarofim & Co. has no beneficial ownership of
               these shares. Also, Mr. Sarofim has no beneficial interest in any
               of these trusts. Mr. Sarofim shares with the other trustees of
               such trusts the power to vote and to dispose of these shares.

     (b)  Percent of Class:

          (i)  0.1% -- as to shares held in accounts managed by Fayez Sarofim &
               Co. with power to dispose, or to direct the disposition of such
               shares.

          (ii) 0.0% -- as to shares held in accounts managed by Sarofim Trust
               Co. with power to dispose, or to direct the disposition of, such
               shares.

         (iii) 0.1% -- as to shares owned directly by Sarofim International
               Management Company for its own account.

          (iv) 4.8% -- as to shares owned of record and beneficially by Fayez
               Sarofim.

          (v)  0.0% -- as to shares held in trusts of which Mr. Sarofim is a
               trustee.

     (c) Number of shares as to which Fayez Sarofim has:

          (i)  sole power to vote or direct the vote:  826,656 shares.

          (ii) shared power to vote or direct the vote: 27,994 shares. The
               voting arrangements with respect to the shares held in the
               various investment advisory accounts managed by Fayez Sarofim &
               Co. or Sarofim Trust Co. vary. The contracts relating to certain
               of the investment advisory accounts do not grant any power to
               Fayez Sarofim & Co., Sarofim Trust Co. to vote securities held in
               such accounts. The contracts relating to other investment
               advisory accounts provide that the securities held in such
               investment advisory accounts will be voted in accordance with the
               directions given by the investment adviser. All securities held
               in investment advisory accounts are held of record by clients or
               by trustees or custodians for clients of Fayez Sarofim & Co.,
               Sarofim Trust Co. Proxies voting the shares are signed by the
               client, the trustee or the custodian. Accordingly, it is
               difficult to determine the extent of voting power possessed by
               Fayez Sarofim & Co., Sarofim Trust Co. Fayez Sarofim may be
               deemed to share the voting power possessed by Fayez Sarofim & Co.
               or Sarofim Trust Co. with respect to the securities held in such
               accounts by virtue of his control relationship to such investment
               advisers. Accordingly, it is believed that of the 32,620 shares
               which Mr. Sarofim may be deemed to own beneficially for purposes
               of Rule 13d-3 (excluding the 826,656 shares which he holds for
               his own account and has the sole power to vote but including the
               21 shares held by trusts of which he is a trustee), he may be
               deemed to share voting power with respect to not more than 27,994
               of such shares. Such voting power may be deemed to be shared with
               Fayez Sarofim & Co. with respect to securities held in investment
               advisory accounts managed by Fayez Sarofim & Co., with Fayez
               Sarofim & Co. and Sarofim Trust Co. with respect to securities
               held in investment advisory accounts managed by Sarofim Trust Co.
               and with Fayez Sarofim & Co. and Sarofim International Management
               Company with respect to securities held by Sarofim International
               Management Company for its own account. In many cases where
               securities are held in accounts managed by Fayez Sarofim & Co. or
               Sarofim Trust Co., voting power may also be deemed to be shared
               with trustees, other fiduciaries, clients of Fayez Sarofim & Co.
               or Sarofim Trust Co., or others.

                                       4






         (iii) sole power to dispose or direct the disposition of:  826,656
               shares.

          (iv) shared power to dispose or direct the disposition of: 32,620
               shares.  Such power may be deemed to be shared with Fayez Sarofim
               & Co. with respect to securities held in accounts managed by
               Fayez Sarofim & Co., with Fayez Sarofim & Co. and Sarofim Trust
               Co. with respect to the securities held in accounts managed by
               Sarofim Trust Co. and with Fayez Sarofim & Co. and Sarofim
               International Management Company with respect to securities held
               by Sarofim International Management Company for its own account
               and with other trustees of trusts of which Mr. Sarofim is a
               trustee with respect to the securities held in such trusts.

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.

          With respect to securities held in accounts managed by Fayez Sarofim &
          Co. or held in accounts managed by Sarofim Trust Co., clients 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 one client has
          such right with respect to more than five percent of the Class.

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

          As indicated in Item 3, Fayez Sarofim is Chairman of the Board and
          President, a director and owner of a majority of the outstanding
          capital stock of Fayez Sarofim & Co. and may be considered a parent
          holding company of Fayez Sarofim & Co.  Fayez Sarofim & Co. is an
          Investment Adviser registered under Section 203 of the Investment
          Advisers Act of 1940.

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 in the ordinary
          course of business and were not acquired for the purpose of e 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 purposes 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 11, 2005


/s/ Fayez Sarofim
_______________________________________
Signature   Fayez Sarofim


                                       5