EXHIBIT 4.11

[GRAPHIC OMITTED]        ENVIRONMENTAL SAFEGUARDS, INC.
--------------------------------------------------------------------------------




                                 March 11, 2003

Cahill, Warnock Strategic Partners Fund LP      Newpark Resources, Inc.
Strategic Associates LP                         3850 N. Causeway, Ste. 1770
One South Street, Ste. 2150                     Metairie, Louisiana 70002
Baltimore, Maryland 21202                       Attn:  Matt Hardey
Attn: David L. Warnock


James H. Stone
Stone Energy
909 Poydras Street, Ste. 2650
New Orleans, Louisiana 70112

     RE:  Certificate of Designation Preferences, Rights and Limitations of
          Series B Convertible Preferred Stock of Environmental Safeguards
          ("Series B Preferred Stock Certificate")

Gentlemen:

     Environmental Safeguards, Inc. (the "Company") along with National Fuel and
Energy, Inc. and OnSite Technology, LLC (collectively the "Borrower" or
"Borrowers") are intending  to enter into a Loan Agreement (the "Loan
Agreement") with Rineco Recycling, LLC, located in Haskell, Arkansas (the
"Lender").  The Loan Agreement will provide for (i) a 12% Secured Promissory
Note in the face amount of $1,500,000.00, with a final maturity date of May 31,
2008 ("Secured Note"), with twenty (20) quarterly installments of principal in
the amount of $75,000.00, plus accrued and unpaid interest on the unpaid
principal amount if the Secured Note, such equal quarterly installments of
principal plus accrued and unpaid interest, to be due and payable beginning
August 31, 2003, and on the last day of each November, February, May and August
thereafter until maturity, and (ii) warrants to purchase 1,500,000 shares of the
Company's common stock at an exercise price of $.01 per share (the "Warrants").
The Secured Note shall be secured by three (3) separate indirect thermal
desorption units.

     The issuance by the Company of the Warrants in connection with the Loan
Agreement would trigger a recalculation  of the Series B Preferred Stock
Certificate conversion price under the provisions of Section 2(g)(iii) of the
Series B Preferred Stock Certificate entitled "Conversion of Preferred Stock
into Common Stock - Issuances at Less than the Conversion Price."




           2600 SOUTH LOOP WEST * SUITE 845 * HOUSTON * TEXAS * 77054
                       (713)641-3836 * FAX: (713) 641-0750


<PAGE>
     In order for the Company to go forward with the Loan Agreement, the Company
is requesting that you waive your rights to trigger a recalculation of the
conversion price under the provisions of Section 2(g)(iii) of the Series B
Preferred Stock upon the issuance of the Warrants and any other subsequent
issuance of common stock upon exercise of the Warrants.

     Please sign this letter in the space indicated below and return to me by
facsimile.  If you have any questions, please feel free to contact me.

                                Very Truly Yours,

                                ENVIRONMENTAL SAFEGUARDS, INC.

                                /s/ James S. Percell

                                James S. Percell, President



By your signature below , the undersigned hereby agrees to waive any rights it
may have to trigger a recalculation of the Series B Preferred Stock Certificate
conversion price under the provisions of Section 2(g)(iii) of the Series B
Preferred Stock Certificate entitled "Conversion of Preferred Stock into Common
Stock - Issuances at less than the Conversion Price" upon the issuance of the
Warrants and any subsequent issuance of common stock upon exercise of the
Warrants in connection with the Loan Agreement.

CAHILL, WARNOCK STRATEGIC PARTNERS FUND L.P.
By:  CAHILL, WARNOCK STRATEGIC PARTNERS L.P.

/s/  David L. Warnock
-----------------------------------
David L. Warnock, A General Partner
Date:     3/13/03
      -----------------------------


STRATEGIC ASSOCIATES L.P.
By:  CAHILL, WARNOCK & COMPANY LLC

/s/  David L. Warnock
-----------------------------------
David L. Warnock, Managing Member
Date:     3/13/03
      -----------------------------


<PAGE>
NEWPARK RESOURCES, INC.


/s/  Matthew W. Hardey
-----------------------------------
By:    Matthew W. Hardey
       ----------------------------
Title: Vice President
       ----------------------------
Date:     3-14-2003
       ----------------------------


JAMES H. STONE


-----------------------------------
Date:
     ------------------------------


<PAGE>
[GRAPHIC OMITTED]        ENVIRONMENTAL SAFEGUARDS, INC.
--------------------------------------------------------------------------------




                                 March 11, 2003

Cahill, Warnock Strategic Partners Fund LP      Newpark Resources, Inc.
Strategic Associates LP                         3850 N. Causeway, Ste. 1770
One South Street, Ste. 2150                     Metairie, Louisiana 70002
Baltimore, Maryland 21202                       Attn:  Matt Hardey
Attn: David L. Warnock


James H. Stone
Stone Energy
909 Poydras Street, Ste. 2650
New Orleans, Louisiana 70112

     RE:  Certificate of Designation Preferences, Rights and Limitations of
          Series B Convertible Preferred Stock of Environmental Safeguards
          ("Series B Preferred Stock Certificate")

Gentlemen:

     Environmental Safeguards, Inc. (the "Company") along with National Fuel and
Energy, Inc. and OnSite Technology, LLC (collectively the "Borrower" or
"Borrowers") are intending  to enter into a Loan Agreement (the "Loan
Agreement") with Rineco Recycling, LLC, located in Haskell, Arkansas (the
"Lender").  The Loan Agreement will provide for (i) a 12% Secured Promissory
Note in the face amount of $1,500,000.00, with a final maturity date of May 31,
2008 ("Secured Note"), with twenty (20) quarterly installments of principal in
the amount of $75,000.00, plus accrued and unpaid interest on the unpaid
principal amount if the Secured Note, such equal quarterly installments of
principal plus accrued and unpaid interest, to be due and payable beginning
August 31, 2003, and on the last day of each November, February, May and August
thereafter until maturity, and (ii) warrants to purchase 1,500,000 shares of the
Company's common stock at an exercise price of $.01 per share (the "Warrants").
The Secured Note shall be secured by three (3) separate indirect thermal
desorption units.

     The issuance by the Company of the Warrants in connection with the Loan
Agreement would trigger a recalculation  of the Series B Preferred Stock
Certificate conversion price under the provisions of Section 2(g)(iii) of the
Series B Preferred Stock Certificate entitled "Conversion of Preferred Stock
into Common Stock - Issuances at Less than the Conversion Price."




           2600 SOUTH LOOP WEST * SUITE 845 * HOUSTON * TEXAS * 77054
                       (713)641-3836 * FAX: (713) 641-0750


<PAGE>
     In order for the Company to go forward with the Loan Agreement, the Company
is requesting that you waive your rights to trigger a recalculation of the
conversion price under the provisions of Section 2(g)(iii) of the Series B
Preferred Stock upon the issuance of the Warrants and any other subsequent
issuance of common stock upon exercise of the Warrants.

     Please sign this letter in the space indicated below and return to me by
facsimile.  If you have any questions, please feel free to contact me.

                                Very Truly Yours,

                                ENVIRONMENTAL SAFEGUARDS, INC.

                                /s/ James S. Percell

                                James S. Percell, President



By your signature below , the undersigned hereby agrees to waive any rights it
may have to trigger a recalculation of the Series B Preferred Stock Certificate
conversion price under the provisions of Section 2(g)(iii) of the Series B
Preferred Stock Certificate entitled "Conversion of Preferred Stock into Common
Stock - Issuances at less than the Conversion Price" upon the issuance of the
Warrants and any subsequent issuance of common stock upon exercise of the
Warrants in connection with the Loan Agreement.

CAHILL, WARNOCK STRATEGIC PARTNERS FUND L.P.
By:  CAHILL, WARNOCK STRATEGIC PARTNERS L.P.

/s/  David L. Warnock
-----------------------------------
David L. Warnock, A General Partner
Date:     3/13/03
      -----------------------------


STRATEGIC ASSOCIATES L.P.
By:  CAHILL, WARNOCK & COMPANY LLC

/s/  David L. Warnock
-----------------------------------
David L. Warnock, Managing Member
Date:     3/13/03
      -----------------------------


<PAGE>
NEWPARK RESOURCES, INC.


-----------------------------------
By:
       ----------------------------
Title:
       ----------------------------
Date:
       ----------------------------


JAMES H. STONE

/s/  James H. Stone
-----------------------------------
Date:     3/14/02
     ------------------------------


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