Exhibit 10.67

                               THIRD AMENDMENT TO
                            STOCK PURCHASE AGREEMENT

     This  Agreement  is the Third  Amendment to the Stock  Purchase  Agreement,
dated  October  7,  1996,  (the  "Stock  Purchase  Agreement")  by  and  between
Tanknology-NDE   International,   Inc.  (formerly  known  as  NDE  Environmental
Corporation  and hereinafter  referred to as "Buyer" ), a Delaware  corporation,
and TEI, Inc. (formerly known as Tanknology Environmental,  Inc. and hereinafter
referred  to as  "Seller" ), a Texas  corporation,  (jointly  referred to as the
"Parties");

     WHEREAS,  pursuant to the Stock Purchase Agreement, the Seller sold all the
capital  stock  of  (i)  Tanknology  Corporation  International,  including  its
cathodic protection division d/b/a Tanknology  Cathodic  Protection,  a Delaware
corporation,  (ii) USTMAN Industries,  Inc., a Delaware  corporation,  and (iii)
Tanknology  Canada  (1988),  Inc.  a  Canadian   corporation  (the  "Transferred
Companies"); and

     WHEREAS,  the Stock  Purchase  Agreement was closed on or about October 26,
1996 (the"Closing"); and

     WHEREAS,  the Parties have  negotiated  certain  matters  arising under the
Stock Purchase Agreement;

     NOW,  THEREFORE,  in  consideration  of the promises and of the  respective
agreements with conditions herein, the Parties hereto hereby agree as follows

     1. Release by Buyer. Buyer hereby unconditionally and irrevocably releases,
acquits and forever  discharges,  to the fullest  extent  permitted  by law, the
Seller from (i) all of Buyer's  claims  against  Seller  arising under the Stock
Purchase  Agreement Section 7.1(a) - (d) including,  but not limited to, (a) the
Seth Hunt Royalty Agreement and related management contract, (b) the PM Services
Agreement, (c) the MCI telephone services contact, and (d) the Mason termination
case, (ii) all of Buyer's claims against Seller arising under the Stock Purchase
Agreement  Section 2.3  including,  but not limited to, (a) accounts  receivable
adjustments,  (b) unaccrued  management bonus (c) uncollected prepaid insurance,
(d) the Royal Bank of Canada cash deposit, (e) various non-transferred deposits,
(f)  certain  miscellaneous   pre-closing  unpaid  taxes,  and  (g)  the  credit
adjustment for Petroleum  Products  Equipment,  and (iii) certain Buyer's claims
against  Seller  which arose after  Closing for  post-closing  health  insurance
payments in the amount of $25,517.14.

     2.  Release  by  Seller.  Seller  hereby  unconditionally  and  irrevocably
releases,  acquits and forever  discharges,  to the fullest extent  permitted by
law, the Buyer from (i) all of Seller's claims against Buyer arising under Stock
Purchase  Agreement  Section 2.3  including,  but not  limited to, (a)  interest
pursuant  to  Section  2.3(b),  and (b)  excess  cash in any of the  Transferred
Companies,  (ii) all of  Seller's  claims  against  Buyer  arising  under  Stock
Purchase Agreement Section 2.4 including, but not limited to, excess cash in any
of the  Transferred  Companies,  (iii)  all of  Seller's  claims  against  Buyer
pursuant to Stock Purchase Agreement Section 6.15(e) for payment of reimbursable


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taxes,  (iv) all of Seller's  claims  against Buyer arising under Stock Purchase
Agreement  Section  6.15(a) or otherwise for  non-federal  tax refund claims for
pre-closing  periods  collected  by Buyer  subsequent  to the  Closing,  and (v)
certain  Seller's  claims  against  Buyer for matters  arising after the Closing
relating to the Mitchell Hutchins replacement check for $3,158.00.

     3. Hold  Harmless,  Buyer  agrees to defend,  indemnify  and hold  harmless
Seller  from  and  against,  any and all  claims,  actions,  causes  of  action,
arbitrations,  proceedings, losses, damages, liabilities, judgments and expenses
(including,  without limitation,  reasonable attorneys' fees) incurred by Seller
arising out of claims made by Seth Hunt against Seller for post-closing  matters
relating to USTMAN Industries.

     4. Cash Payment.  Seller shall pay Buyer  $230,000 by check within two days
of the execution date of this agreement.

     5. Indemnification  Limitation.  The indemnification limitation provided by
Seller to Buyer  pursuant to Stock  Purchase  Agreement  Section 7.2(b) shall be
lowered from $1,250,000.00 to $600,000.00.


     6. No Other Amendment.  Only the matters  specifically  referenced shall be
amended;  otherwise,  the  original  Stock  Purchase  Agreement  and  the  prior
amendments shall remain in full force and effect.

     EXECUTED as of this _____ day of December, 1998.

                                             TANKNOLOGY-NDE INTERNATIONAL, INC.

                                             By:    //s// JAY ALLEN CHAFFEE
                                                  ----------------------------
                                                      Jay Allen Chaffee
                                                      Chairman of the Board

                                             TEI, INC.

                                             By:    //s// DONALD R. CAMPBELL
                                                  ----------------------------
                                                      Donald R. Campbell
                                                      President