Exhibit 10.69

                        AMENDMENT NO. 6 TO LOAN AGREEMENT
                             DATED OCTOBER 25, 1996
               BY AND BETWEEN TANKNOLOGY-NDE INTERNATIONAL, INC.,
                           TANKNOLOGY/NDE CORPORATION,
                   TANKNOLOGY-NDE CONSTRUCTION SERVICES, INC.,
                      PROECO, INC. AND 2368692 CANADA, INC.
                                       AND
                              BANK ONE, TEXAS, N.A.


     This  Amendment No. 6 ("Sixth  Amendment")  to the Loan  Agreement,  by and
among  TANKNOLOGY-NDE  INTERNATIONAL,  INC. (formerly known as NDE ENVIRONMENTAL
CORPORATION)  ("NDE"), a Delaware  corporation,  TANKNOLOGY/ NDE CORPORATION,  a
Delaware corporation, PROECO, INC., a Delaware corporation, 2368692 CANADA, INC.
(formerly  known  as  TANKNOLOGY   CANADA  (1988)  INC.),  a  Canadian   federal
corporation, TANKNOLOGY-NDE CONSTRUCTION SERVICES, INC., a Delaware corporation,
and OUTBOUND SERVICES, INC., a California corporation (collectively, "Borrower")
and BANK ONE,  TEXAS,  N.A.,  a national  banking  association  (the  "Bank") is
entered into this 30th day of March 1999.

                              W I T N E S S E T H:

     WHEREAS,  Borrower and Bank entered into the Loan  Agreement on October 25,
1996,  as  amended  by the First  Amendment  dated  April 10,  1997,  the Second
Amendment  dated May 20, 1997, the Third  Amendment dated December 23, 1997, the
Fourth  Amendment  dated June 26, 1998 and the Fifth Amendment dated November 5,
1998 (the "Loan Agreement");

     WHEREAS,  Borrower  desires to increase the Revolving  Commitment under the
Loan
Agreement;

     WHEREAS,  Borrower  has  requested  that Bank  release  and  terminate  its
security interest in and to certain Collateral;

     WHEREAS,  Bank is willing to agree to the foregoing in accordance with, and
subject to, the terms and conditions set forth herein.

     NOW, THEREFORE, in consideration of the promises herein contained, and each
intending to be legally bound hereby, the parties agree as follows:

     I.   Amendments to Loan Agreement.

     Article I, DEFINITIONS, is amended by adding the following definitions:



                                        1

<PAGE>



          "Intangible  Assets"  means  all  the  assets  of  Borrower  that,  in
          accordance with GAAP, are not classified as tangible assets.

          "Ryder System Note" means that certain  promissory  note dated May 12,
          1998 executed by NDE in the face amount of $757,775.00 made payable to
          the order of Ryder System.

          "Sixth  Amendment"  means  Amendment  No.  6 to this  Loan  Agreement,
          executed by Borrower and Bank on March 30, 1999.

     Article I, DEFINITIONS, is amended by revising the following definitions in
their entirety to read as follows:

          "Adjusted  Net Worth" means  Consolidated  Net Worth minus  Intangible
          Assets plus Subordinated Debt, and outstanding principal under (i) the
          OSI Unsecured Note and (ii) the Ryder System Note.

          "Maximum Commitment Amount" $9,000,000.00 as of the date of the Fourth
          Amendment;  and  $12,500,000.00  upon  the  satisfaction  of  all  the
          conditions  under Article IV of the Sixth Amendment as acknowledged by
          Bank's  written  notice  to  Borrower  as  specified  under  Article V
          thereof.

          "Revolving  Note" means that certain  promissory  note in the original
          face  amount  of  $12,500,000.00  dated of even  date  with the  Sixth
          Amendment  made by  Borrower  payable  to the order of the Bank in the
          form attached as Exhibit "A-1" to the Sixth  Amendment,  together with
          all deferrals,  renewals,  extensions,  amendments,  modifications  or
          rearrangements  thereof,  which promissory note shall evidence certain
          advances to the  Borrower by the Bank  pursuant to Section 2.01 of the
          Loan Agreement.

     Article V, AFFIRMATIVE  COVENANTS,  of the Loan Agreement is hereby amended
by revising the following section in its entirety to read as follows:

          5.20 Net Worth  Requirement.  Maintain  its  Adjusted  Net Worth as of
          March 31,  1999,  which shall not be less than  $4,000,000.00  at that
          time, and each calendar  quarter  thereafter,  increasing on an annual
          basis by 70% of positive  annual Net Income  beginning the year ending
          December 31, 1999.

     "Exhibit A-1," the form of Revolving  Note attached to the Loan  Agreement,
as amended and restated  pursuant to the Third,  Fourth and Fifth  Amendments is
hereby replaced with Exhibit "A-1" attached to this Sixth Amendment.

     "Exhibit  B," the  form of  Compliance  Certificate  attached  to the  Loan
Agreement,  as  amended by the Third,  Fourth  and Fifth  Amendments,  is hereby
replaced with Exhibit "B" attached to this Sixth Amendment.


                                        2

<PAGE>



     "Schedule 1.01(a),  Collateral" attached to the Loan Agreement,  as amended
by the  Second,  Third,  Fourth,  and Fifth  Amendments,  is hereby  amended  by
deleting the reference to Pledged  Certificates of Deposit in subpart (b) at the
end of the section entitled "Tanknology-NDE International, Inc."

     "Schedule 3.10,  Collateral  Documents" attached to the Loan Agreement,  as
amended by the Fourth and Fifth Amendments,  is hereby further amended by adding
the following information to the identified subpart:

         3. Financing Statements:
                  Tanknology/NDE Corporation
                  FLORIDA: Secretary of State"

     II.  Conditions to the Effectiveness of the Sixth Amendment (Other than the
Increase in the Maximum Commitment  Amount). As a condition to the effectiveness
of the Sixth  Amendment,  other than the  increase  in the  Maximum  Commitment,
Borrower has satisfied the following conditions:

          A. Receipt of Amended and Restated  Revolving  Note,  Sixth  Amendment
     Certificate of Compliance and other Security Documents. The Bank shall have
     received  the  Amended  and  Restated  Revolving  Note (the  form  which is
     attached  hereto as Exhibit  "A-1"),  multiple  counterparts  of this Sixth
     Amendment  as  requested  by the  Bank,  the  Compliance  Certificate  duly
     executed by an  authorized  officer for each Borrower (the form of which is
     attached  hereto as Exhibit "B") and any other Security  Documents Bank may
     reasonably request.

          B. Receipt of Certified Copy of Corporate  Proceedings and Certificate
     of Incumbency of Borrower.  The Bank shall have received from each Borrower
     copies of all  resolutions  of its board of  directors  with respect to the
     transactions  set forth in this Sixth  Amendment  and the execution of this
     Sixth Amendment, such copy or copies to be certified by the Secretary or an
     Assistant  Secretary as being true and correct and in full force and effect
     as of the date hereof. In addition,  the Bank shall have received from each
     Borrower  a  certificate  of  incumbency  signed  by  the  Secretary  or an
     Assistant  Secretary setting forth (a) the names of the officers  executing
     this Sixth  Amendment,  (b) the  office(s)  to which such Persons have been
     elected  and in which they  presently  serve and (c) an  original  specimen
     signature of each such person.

          C.  Facility  Fee. As partial  consideration  for its agreement to the
     terms of the Sixth Amendment,  Bank shall have received $35,000.00 prior to
     or contemporaneous with the execution of the Sixth Amendment.



                                        3

<PAGE>



          D.  Borrower's  Opinion of  Counsel.  Bank shall  have  received  from
     counsel for Borrower a written  opinion in form and substance  satisfactory
     to Bank covering the matters set forth on Exhibit "C" attached to the Sixth
     Amendment.

          E.  Payment  of   Indebtedness.   Bank  shall  have  received  written
     authorization  and wiring  instructions (or other form of disbursement) for
     the  application  of proceeds from the  liquidation  of the  Certificate of
     Deposit  for  the  repayment  of  $3,000,000.00  of  outstanding  principal
     indebtedness of Borrower  evidenced by the Revolving Note, the Term Note or
     outstanding principal due under the Subordinated Indebtedness.

     III.  Release of  Collateral.  Upon the  satisfaction  of all the foregoing
conditions  precedent,  Bank shall execute and deliver to Borrower a release and
termination of that certain Pledge of Certificate of Deposit dated May 20, 1997,
by and among NDE (then known as NDE Environmental Corporation) and Bank.

     IV.  Conditions  to the  Effectiveness  of  the  Increase  in  the  Maximum
Commitment  Amount.  As a condition to the  effectiveness of the increase of the
Maximum Commitment, Borrower has satisfied the following conditions:

          A.  Receipt  of  the  Certified  Copy  of  Corporate  Proceedings  and
     Certificate of Incumbency of DH Holdings.  Bank shall have received from DH
     Holdings  Corp.  ("DHH"),  copies  of all  resolutions  of their  boards of
     directors with respect to the  transactions  contemplated by the this Sixth
     Amendment and the Second Amendment to the  Intercreditor  and Subordination
     Agreement,  such copy or  copies to be  certified  by the  Secretary  or an
     Assistant  Secretary as being true and correct and in full force and effect
     as of the date hereof. In addition, the Bank shall have received from DHH a
     certificate of incumbency signed by the Secretary or an Assistant Secretary
     setting forth (a) the names of the officers  executing the Second Amendment
     to the  Intercreditor  and  Subordination  Agreement,  (b) the office(s) to
     which such Persons have been elected and in which they presently  serve and
     (c) an original specimen signature of each such person.

          B. Receipt of the Second Amendment to Intercreditor  and Subordination
     Agreement.  Borrower,  DHH  and  Bank  shall  have  entered  into a  Second
     Amendment  to  Intercreditor  and  Subordination  Agreement in the form and
     substance satisfactory to Bank.

          C.  Receipt of the Third  Amended and  Restated  Standby  Commitment.
     Bank, Borrower and Proactive Partners, L.P. shall have entered into a Third
     Amended  and  Restated  Standby   Commitment  in  the  form  and  substance
     satisfactory to Bank.

     V. Written Notice to Borrower of  Satisfaction of Conditions to Increase in
Maximum Commitment Amount.  Upon the satisfaction of the conditions as set forth
in Article  IV hereof and  provided  no  Unmatured  Event of Default or Event of
Default has occurred and is continuing,  Bank shall contemporaneously  provide a
letter of notice to Borrower stating "Bank One, Texas, N.A. is satisfied that


                                        4

<PAGE>



the  conditions  set forth in Article IV of the Sixth  Amendment to that certain
Loan  Agreement  dated  October  25,  1996,  among  the Bank and  Tanknology-NDE
International,   Inc.  et  al.  have  been  fulfilled,"  whereupon  the  Maximum
Commitment Amount shall equal $12,500,000.00.

     VI.  Reaffirmation  of  Representations  and Warranties.  To induce Bank to
enter into this  Sixth  Amendment,  Borrower  hereby  reaffirms,  as of the date
hereof, its representations  and warranties  contained in Article IV of the Loan
Agreement, as amended, and in all other documents executed pursuant thereto, and
additionally represents and warrants as follows:

          A.  The  execution  and  delivery  of  this  Sixth  Amendment  and the
     performance by Borrower of its  obligations  under this Sixth Amendment are
     within  the  Borrower's   corporate  power,  have  received  all  necessary
     governmental  approval (if any shall be required),  and do not and will not
     contravene  or  conflict  with  any  provision  of law or of any  agreement
     binding upon the Borrower.

          B. The Loan Agreement, as amended by this Sixth Amendment,  represents
     the legal, valid and binding  obligations of Borrower,  enforceable against
     Borrower in  accordance  with its terms subject as to  enforcement  only to
     bankruptcy,  insolvency,  reorganization,  moratorium or other similar laws
     affecting  the  enforcement  of  creditors'  rights  generally  and general
     principles of equity.

          C. No Event of Default or Unmatured  Event of Default has occurred and
     is continuing as of the date hereof.

     VII.  Defined Terms.  Except as amended hereby,  terms used herein that are
defined in the Loan Agreement shall have the same meanings herein.

     VIII. Reaffirmation of Loan Agreement. This Sixth Amendment shall be deemed
to be an amendment to the Loan  Agreement,  and the Loan  Agreement,  as amended
hereby,  is hereby  ratified,  approved and confirmed in each and every respect.
All  references  to  the  Loan  Agreement  herein  and in  any  other  document,
instrument,  agreement or writing shall hereafter be deemed to refer to the Loan
Agreement as amended hereby.

     IX. Entire Agreement.  The Loan Agreement, as hereby amended,  embodies the
entire agreement  between Borrower and Bank, and supersedes all prior proposals,
agreements and  understandings  relating to the subject matter hereof.  Borrower
certifies  that  it is  relying  on no  representation,  warranty,  covenant  or
agreement except for those set forth in the Loan Agreement as hereby amended and
the other documents previously executed or executed of even date herewith.

     X. Governing Law. THIS SIXTH  AMENDMENT  SHALL BE GOVERNED BY AND CONSTRUED
IN ACCORDANCE WITH THE LAWS OF THE STATE OF TEXAS AND THE APPLICABLE LAWS OF THE
UNITED STATES OF AMERICA.  This Sixth  Amendment has been entered into in Harris
County, Texas, and it shall be performable for all purposes in Harris County,


                                        5

<PAGE>



Texas. Courts within the State of Texas shall have jurisdiction over any and all
disputes between Borrower and Bank, whether in law or equity, including, but not
limited  to,  any and all  disputes  arising  out of or  relating  to this Sixth
Amendment or any other Loan Document;  and venue in any such dispute  whether in
federal or state court shall be laid in Harris County, Texas.

     XI. Severability.  Whenever possible each provision of this Sixth Amendment
shall  be  interpreted  in  such  manner  as to be  effective  and  valid  under
applicable law, but if any provision of this Sixth Amendment shall be prohibited
by or invalid under  applicable  law, such provision shall be ineffective to the
extent of such prohibition or invalidity,  without invalidating the remainder of
such provision or the remaining provisions of this Sixth Amendment.

     XII. Execution in Counterparts. This Sixth Amendment may be executed in any
number of counterparts  and by the different  parties on separate  counterparts,
and each  such  counterpart  shall be  deemed  to be an  original,  but all such
counterparts shall together constitute but one and the same agreement.

     XIII.  Section Captions.  Section captions used in this Sixth Amendment are
for convenience of reference only, and shall not affect the construction of this
Sixth Amendment.

     XIV. Successors and Assigns. This Sixth Amendment shall be binding upon the
Borrower and Bank and their respective  successors and assigns,  and shall inure
to the benefit of the  Borrower  and Bank,  and the  respective  successors  and
assigns of Bank.

     XV. Non-Application of Chapter 346 of Texas Finance Code. The provisions of
Chapter 346 of the Texas Finance Code are  specifically  declared by the parties
hereto not to be  applicable to the Loan  Agreement as hereby  amended or any of
the other Loan Documents or to the transactions contemplated hereby.

     XVI. Notice.  THIS SIXTH AMENDMENT TOGETHER WITH THE LOAN AGREEMENT AND THE
OTHER LOAN DOCUMENTS  REPRESENT THE FINAL AGREEMENT  BETWEEN THE PARTIES AND MAY
NOT BE  CONTRADICTED  BY EVIDENCE OF PRIOR,  CONTEMPORANEOUS  OR SUBSEQUENT ORAL
AGREEMENTS OF THE PARTIES.  THERE ARE NO UNWRITTEN ORAL  AGREEMENTS  BETWEEN THE
PARTIES.




                                        6

<PAGE>



     IN WITNESS WHEREOF,  the parties hereto have caused this Sixth Amendment to
be duly executed as of the day and year first above written.


                                         BORROWER:

                                         TANKNOLOGY-NDE INTERNATIONAL, INC.
                                         (formerly known as NDE ENVIRONMENTAL
                                         CORPORATION)


                                         By:
                                                  Jay Allen Chaffee
                                                  Chairman of the Board


                                         TANKNOLOGY/NDE CORPORATION


                                         By:
                                                  Jay Allen Chaffee
                                                  Chairman of the Board


                                         TANKNOLOGY-NDE CONSTRUCTION
                                         SERVICES, INC.


                                         By:
                                                  Jay Allen Chaffee
                                                  Chairman of the Board

                                         PROECO, INC.


                                         By:
                                                  Jay Allen Chaffee
                                                  Chairman of the Board





                                        7

<PAGE>



                                         2368692 CANADA, INC. (formerly known as
                                         TANKNOLOGY CANADA (1988) INC.)


                                         By:
                                                  Jay Allen Chaffee
                                                  President


                                         OUTBOUND SERVICES, INC.


                                         By:
                                                  Jay Allen Chaffee
                                                  Chairman of the Board


                                         BANK:

                                         BANK ONE, TEXAS, N.A.


                                         By:
                                                    Lisa Kasling
                                                    Senior Vice President


                                        8

<PAGE>



                                  EXHIBIT "A-1"

                       AMENDED AND RESTATED REVOLVING NOTE

$12,500,000.00                                                    March 30, 1999


     FOR VALUE RECEIVED,  TANKNOLOGY-NDE INTERNATIONAL,  INC. (formerly known as
NDE ENVIRONMENTAL  CORPORATION) ("NDE"), a Delaware corporation,  TANKNOLOGY/NDE
CORPORATION,  a Delaware  corporation,  PROECO,  INC.,  a Delaware  corporation,
2368692  CANADA,  INC.  (formerly  known as TANKNOLOGY  CANADA  (1988) INC.),  a
Canadian federal  corporation,  TANKNOLOGY- NDE CONSTRUCTION  SERVICES,  INC., a
Delaware corporation, and OUTBOUND SERVICES, INC., a California corporation, all
of the foregoing having an address at 8900 Shoal Creek, Bldg. 200, Austin, Texas
78757 (collectively,  "Borrower") unconditionally promise to pay to the order of
BANK ONE, TEXAS, NATIONAL ASSOCIATION, (herein called "Bank"), at its offices at
910 Travis,  Houston,  Texas 77001,  the  principal  sum of TWELVE  MILLION FIVE
HUNDRED  THOUSAND  DOLLARS  ($12,500,000.00)  or, if less, the aggregate  unpaid
principal  amount of all Revolving Loans (as defined in the Loan Agreement) made
by the Bank to the  Borrower  pursuant  to the Loan  Agreement,  as shown in the
records of the Bank, outstanding on such date.

     The undersigned also promise to pay interest on the unpaid principal amount
hereof  from  time to time  outstanding  from the  date  hereof  until  maturity
(whether by acceleration  or otherwise) and, after maturity,  until paid, at the
rates  per annum and on the dates  specified  in the Loan  Agreement;  provided,
however,  that in no event  shall  such  interest  exceed the  Maximum  Rate (as
hereinafter defined).

     "Maximum Rate" means the Maximum Rate of  non-usurious  interest  permitted
from day to day by Applicable Law.

     "Applicable  Law" means that law in effect from time to time and applicable
to this Revolving Note which lawfully permits the charging and collection of the
highest  permissible  lawful,  non-usurious  rate of interest on this  Revolving
Note. To the extent federal law permits Bank to contract for,  charge or receive
a greater amount of interest, Bank will rely on federal law instead of the Texas
Finance Code for the purpose of determining the Maximum Rate.  Additionally,  to
the maximum extent permitted by applicable law now or hereafter in effect,  Bank
may,  at its  option  and from  time to time,  implement  any  other  method  of
computing  the  Maximum  Rate  under  the  Texas  Finance  Code or  under  other
applicable law, by giving notice, if required, to Borrower as provided by



                                                                  --------------
                                                                     Initial for
                                                                  Identification
                                       A-1

<PAGE>



applicable  law now or  hereafter  in effect.  Notwithstanding  anything  to the
contrary  contained herein or in any of the other Loan Documents,  it is not the
intention  of Bank to  accelerate  the  maturity  of any  interest  that has not
accrued at the time of such  acceleration or to collect unearned interest at the
time of such acceleration.

     In no event shall  Chapter 346 of the Texas  Finance Code (which  regulates
certain revolving loan accounts and revolving  tri-party accounts) apply to this
Note.  To the extent that Chapter 303 of the Texas Finance Code is applicable to
this Note, the "weekly ceiling"  specified in such Chapter 303 is the applicable
ceiling;  provided that, if any applicable law permits greater interest, the law
permitting the greatest interest shall apply.

     In no event shall the  aggregate  of the  interest  on this Note,  plus any
other  amounts  paid in  connection  with the loan  evidenced by this Note which
would under Applicable Law be deemed  "interest," ever exceed the maximum amount
of interest which, under Applicable Law, could be lawfully charged on this Note.
The Bank and the Borrower  specifically  intend and agree to limit contractually
the interest  payable on this Note to not more than an amount  determined at the
Maximum Rate. Therefore, none of the terms of this Note or any other instruments
pertaining to or securing this Note shall ever be construed to create a contract
to pay  interest  at a rate in excess  of the  Maximum  Rate,  and  neither  the
Borrower nor any other party liable herefor shall ever be liable for interest in
excess of that  determined  at the  Maximum  Rate,  and the  provisions  of this
paragraph  shall  control  over  all  provisions  of this  Note or of any  other
instruments pertaining to or securing this Note. If any amount of interest taken
or  received  by the Bank shall be in excess of the  maximum  amount of interest
which,  under  Applicable  Law, could lawfully have been collected on this Note,
then the excess shall be deemed to have been the result of a mathematical  error
by the  parties  hereto and shall be  refunded  promptly  to the  Borrower.  All
amounts paid or agreed to be paid in connection with the indebtedness  evidenced
by this Note which would under Applicable Law be deemed "interest" shall, to the
extent permitted by Applicable Law, be amortized, prorated, allocated and spread
throughout the full term of this Note.

     This Note is the  Revolving  Note  referred  to in and is  entitled  to the
benefits of a certain Loan  Agreement,  dated as of October 25, 1996, as amended
by that First Amendment  dated April 10, 1997,  that Second  Amendment dated May
20, 1997,  that Third  Amendment  dated December 23, 1997, the Fourth  Amendment
dated June 26, 1998,  the Fifth  Amendment  dated November 5, 1998 and the Sixth
Amendment  dated of even  date  herewith  (as the same may be  further  amended,
modified, supplemented,  extended, rearranged and/or restated from time to time,
the "Loan Agreement"),  entered into by and among Tanknology-NDE  International,
Inc., (f/k/a NDE Environmental  Corporation) et al., as Borrower,  and Bank One,
Texas,  National  Association  and secured by the Collateral  Documents (as such
term is defined in the Loan  Agreement).  Reference  is hereby  made to the Loan
Agreement for a statement of the prepayment rights and penalties and obligations



                                                                  --------------
                                                                     Initial for
                                                                  Identification
                                       A-2

<PAGE>



of  the  Borrower,  a  description  of  the  properties  and  assets  mortgaged,
encumbered and assigned, the nature and extent of the security and the rights of
the parties to the Collateral  Documents in respect of such security,  and for a
statement of the terms and conditions  under which the due date of this Note may
be accelerated.  Upon the occurrence of any Event of Default as specified in the
Loan Agreement, the principal balance hereof and the interest accrued hereon may
be  declared  to be  forthwith  due and  payable  in  accordance  with  the Loan
Agreement,  and any  indebtedness  of the holder  hereof to the  Borrower may be
appropriated and applied hereon.

     In addition to and not in  limitation  of the  foregoing,  the  undersigned
further agrees, subject only to any limitation imposed by applicable law, to pay
all  reasonable  expenses,   including  reasonable  attorneys'  fees  and  legal
expenses,  incurred  by the holder of this Note in  endeavoring  to collect  any
amounts payable  hereunder which are not paid when due,  whether by acceleration
or otherwise.

     All parties hereto, whether as makers,  endorsees, or otherwise,  severally
waive presentment for payment,  demand, protest, notice of intent to accelerate,
notice of acceleration and notice of dishonor.

     This Note is issued in substitution for, and in replacement,  modification,
rearrangement,  renewal  and  extension  of, but not in  extinguishment  of, the
outstanding   principal   indebtedness   evidenced   by  that  certain  note  of
Tanknology-NDE  International,   Inc.  (f/k/a  NDE  Environmental  Corporation),
Tanknology/NDE   Corporation,   ProEco,   Inc.,  2368692  Canada,  Inc.  (f/k/a/
Tanknology Canada (1988) Inc.) and Tanknology-NDE  Construction Services,  Inc.,
dated  October 25, 1996,  payable to the order of Bank One,  Texas,  N.A. in the
original principal sum of $5,000,000.00,  as amended and restated by the Second,
Third, Fourth and Fifth Amendments (the "Prior Note"); it being acknowledged and
agreed by Borrower that the indebtedness  evidenced by this Note consti tutes an
extension and renewal of the outstanding principal indebtedness evidenced by the
Prior Note,  and that all  security  interests  and other liens which secure the
repayment of the Prior Note shall continue to secure the indebtedness  evidenced
by this Note.

     THIS NOTE SHALL BE DEEMED TO BE A CONTRACT MADE UNDER THE LAWS OF THE STATE
OF TEXAS  AND  CONSTRUED  IN  ACCORDANCE  WITH THE LAWS OF THE  STATE OF  TEXAS,
WITHOUT REGARD TO PRINCIPLES OF CONFLICTS OF LAW.



                                       A-3

<PAGE>



     EXECUTED this 30th day of March, 1999.

                                         MAKER:

                                         TANKNOLOGY-NDE INTERNATIONAL, INC.
                                         (formerly known as NDE ENVIRONMENTAL
                                         CORPORATION)


                                         By:
                                                  Jay Allen Chaffee
                                                  Chairman of the Board


                                         TANKNOLOGY/NDE CORPORATION


                                         By:
                                                  Jay Allen Chaffee
                                                  Chairman of the Board


                                         PROECO, INC.


                                         By:
                                                  Jay Allen Chaffee
                                                  Chairman of the Board


                                         2368692 CANADA, INC. (formerly known as
                                         TANKNOLOGY CANADA (1988) INC.)


                                         By:
                                                  Jay Allen Chaffee
                                                  President


                                       A-4

<PAGE>



                                         TANKNOLOGY-NDE CONSTRUCTION
                                         SERVICES, INC.


                                         By:
                                                  Jay Allen Chaffee
                                                  Chairman of the Board


                                         OUTBOUND SERVICES, INC.


                                         By:
                                                  Jay Allen Chaffee
                                                  Chairman of the Board



                                       A-5

<PAGE>



                                   EXHIBIT "B"

                             Compliance Certificate


     I,  ______________________,  the _______________________ of TANKNOLOGY- NDE
INTERNATIONAL,  INC.  (the  "Company"),  pursuant  to  Section  5.05 of the Loan
Agreement  dated as of October 25, 1996, as amended by the First Amendment dated
April 10, 1997, the Second  Amendment  dated May 20, 1997,  the Third  Amendment
dated  December 23, 1997,  the Fourth  Amendment  dated June 26, 1998, the Fifth
Amendment dated November 5, 1998 and the Sixth Amendment dated March 30, 1999 by
and  among  BANK  ONE,  TEXAS,  N.A.  ("Bank")  and  the  Company  et  al.  (the
"Agreement") do hereby certify, as of the date hereof, that to my knowledge:

         1.    No Event of Default (as defined in the  Agreement)  has  occurred
               and is continuing,  and no Unmatured Event of Default (as defined
               in the Agreement)  has occurred and is continuing  except for the
               following events (include actions taken to cure such situations);

         2.    No  material  adverse  change  has  occurred  in  the  condition,
               financial or otherwise, of the Company since ________________;

         3.    Except as  otherwise  stated in the  Schedule,  if any,  attached
               hereto, each of the representations and warranties of the Company
               contained  in Article IV of the  Agreement is true and correct in
               all respects; and

         4.    The Company's financial condition for the month ending __________
               is as follows:

<TABLE>
<CAPTION>

      Financial Covenant          Time Period    Required Ratio                                         Actual Ratio
<S>                               <C>            <C>                                                    <C>
================================  ============   =====================================================  ============================
(a)  Adjusted Net Worth           Term of Loan   Not less than the Adjusted Net Worth as of 3/31/99,
                                                 which shall not be less than $4,000,000.00, and each
                                                 calendar quarter thereafter, increasing on an annual
                                                 basis by 70% of Borrower's annual Net Income (if
                                                 positive) beginning the year ending 12/31/99.

(b)  Capital  Expenditures        Term  of Loan  Not more than $6,800,000 for fiscal 1998 and  
                                                 $2,000,000 for each year thereafter.

(c)  Debt Service Coverage Ratio  Term of Loan   Not less than 1.2 to 1.0

(d)  Adjusted  Liabilities  to    Term of Loan   9/30/98 - 3/31/99 not more than 2.25 to 1.0;  
     Adjusted Net Worth                          4/1/99 - 6/30/99 not more than 2.00 to 1.0; 
                                                 7/1/99 - 3/31/2000 not more than 1.75 to 1.0;  
                                                 4/1/2000 - 9/30/2000  not more  than  1.25  to  1.0; 
                                                 and after  9/30/2000  not more than 1.0 to 1.0.
================================  ============   =====================================================  ============================
</TABLE>

This certificate is executed this ___ day of ___________ 199__.


                                         TANKNOLOGY-NDE INTERNATIONAL, INC.




                                         By:
                                         Its:



                                       B-1

<PAGE>


                                   EXHIBIT "C"

                     Form of Opinion of Counsel for Borrower
                              Baker & Botts, L.L.P.


     (1) The Borrower and the  Subsidiaries  are  corporations  duly  organized,
existing,  and in good  standing  under the Laws of their  respective  states of
incorporation  [naming such states] and are  qualified to transact  business and
are in good  standing in those  states  where the nature of business or property
owned by them requires  qualification,  as set forth in Schedule 4.01,  attached
hereto and made a part hereof,  and, to the knowledge of such  counsel,  are not
required to be qualified as a foreign corporation in any other jurisdiction;

     (2) The Borrower has the power to execute and deliver this Sixth Amendment,
to borrow  money  hereunder,  to grant the  Collateral  required  hereunder,  to
execute and deliver the Amended and  Restated  Revolving  Note,  and  Collateral
Documents, and to perform its obligations hereunder and thereunder;

     (3) All corporate actions by the Borrower and all consents and approvals of
any Persons  necessary to the validity of this Sixth Amendment,  the Amended and
Restated Revolving Note, the Collateral Documents, and each other document to be
delivered hereunder have been duly taken or obtained,  and this Sixth Amendment,
Amended and Restated  Revolving  Note,  and the Collateral  Documents,  and such
other  documents do not conflict with any provision of the charter or by-laws of
the Borrower,  or of any  applicable  Laws, or any other  agreement  binding the
Borrower or its property of which,  after reasonable  inquiry,  such counsel has
knowledge; and

     (4) This Sixth  Amendment,  the Amended and Restated  Revolving  Note,  and
Collateral  Documents to be delivered  hereunder have been duly executed by, and
each is a valid and binding  obligation of, the Borrower;  each of the foregoing
documents is in all respects sufficient to achieve its purported function and is
enforceable  in  accordance  with its terms,  except as  limited by  bankruptcy,
insolvency,   reorganization,   moratorium,  or  other  similar  laws  affecting
creditors' rights generally or by general equitable principles.


                                       C-1