Document:

<PAGE>
                                                                   EXHIBIT 10.56

                             STOCK PLEDGE AGREEMENT

     THIS STOCK PLEDGE AGREEMENT (this "Agreement") is entered into on December
21, 2001, by and between IDS ENGINEERING MANAGEMENT, LC, a Texas company
("Pledgor"), and FLEET CAPITAL CORPORATION, a Rhode Island corporation, as Agent
for itself and the other financial institution(s) from time to time a party to
the Loan Agreement (as hereinafter defined) ("Pledgee").  All capitalized terms
used but not otherwise defined herein shall have the meanings ascribed to such
terms in the Loan Agreement.

          1.  For good and valuable consideration, the receipt and sufficiency
of which is hereby acknowledged, and as collateral security for and to secure
the prompt payment and performance in full of the Secured Obligations
(hereinafter defined), Pledgor hereby assigns to Pledgee and grants to Pledgee,
for the benefit of Lenders, a continuing security interest in all issued and
outstanding shares of capital stock (including, without limitation, all shares
of capital stock represented by the stock certificates identified on Schedule I
attached hereto) of Petrocon Engineering, Inc., a Texas corporation
("Borrower"), whether now or hereafter issued by Borrower, together with all
proceeds, products and increases thereof and substitutions and replacements
therefor (collectively, the "Collateral").

          As used in this Agreement, the term "Secured Obligations" shall mean
any and all (i) Obligations of Pledgor or Borrower to Pledgee and/or Lenders,
pursuant to that certain Second Amended and Restated Loan and Security
Agreement, dated as of the date hereof, by and among Pledgor, Borrower, IDS
Engineering, Inc., a Texas corporation, Thermaire, Inc., a Texas corporation,
Constant Power Manufacturing, Inc., a Texas corporation, Industrial Data
Systems, Inc., a Texas corporation, Triangle Engineers and Constructors, Inc., a
Texas corporation, Petrocon Systems, Inc., a Texas corporation, Petrocon
Technologies, Inc., a Texas corporation, Petrocon Engineering of Louisiana,
Inc., a Louisiana corporation, R.P.M. Engineering, Inc., a Louisiana
corporation, Alliance Engineering Associates, Inc., a Texas corporation,
Petrocon Construction Resources, Inc., a Texas corporation, Pledgee and Lenders
(as amended from time to time, the "Loan Agreement") and (ii) extensions,
renewals, modifications, increases and replacements of the foregoing.  The term
"Secured Obligations" shall include, without limitation, all unpaid accrued
interest thereon and all costs and expenses payable as hereinafter provided:
(i) whether now existing or hereafter incurred; (ii) whether direct, indirect,
primary, absolute, secondary, contingent, secured, unsecured, matured, or
unmatured; (iii) whether such indebtedness is from time to time reduced and
thereafter increased, or entirely extinguished and thereafter reincurred; (iv)
whether such indebtedness was originally contracted with Pledgee or with another
or others; (v) whether or not such indebtedness is evidenced by a negotiable or
nonnegotiable instrument or any other writing; and (vi) whether such
indebtedness is contracted by Pledgor or Borrower individually or jointly or
severally with another or others.

          2.  Pledgor represents and warrants that (i) Pledgor is the legal and
beneficial owner of the Collateral, free and clear of all liens and
encumbrances; (ii) there are no restrictions upon the transfer of any of the
Collateral, other than as may appear and may be referenced on the face of the
certificates, those arising under applicable state or federal securities laws
and those existing on the date hereof and disclosed to Pledgee in writing; (iii)
Pledgor owns 100% of the issued and

                                       1
<PAGE>

outstanding capital stock of Borrower; (iv) except as disclosed to Pledgee in
writing, there are no existing obligations to issue capital stock or securities
convertible into capital stock of Borrower.

          3.  In furtherance of Pledgee's security interest in the Collateral,
Pledgor agrees to deliver to Pledgee, on the date of this Agreement, the stock
certificates identified on Schedule I attached hereto, together with stock
powers duly executed in blank by Pledgor.

          4.  With respect to the Collateral, Pledgor hereby appoints Pledgee
its attorney-in-fact to arrange for the transfer of the Collateral on the books
of Borrower to the name of Pledgee during the continuance of any Event of
Default; provided, however, that Pledgee shall be under no obligation to do so.

          5.  During the term of this Agreement, provided no Event of Default
then exists, Pledgor shall have the right, where applicable, to vote the
Collateral on all corporate questions, and Pledgee shall, if necessary, execute
due and timely proxies in favor of Pledgor for this purpose.

          6.  While an Event of Default exists, Pledgee may exercise all of the
rights and privileges in connection with the Collateral to which a transferee
may be entitled as the record holder thereof, together with the rights and
privileges otherwise granted hereunder.  Pledgee shall be under no obligation to
exercise any of such rights or privileges.

          7.  If, with the consent of Pledgee, Pledgor shall substitute or
exchange other securities in place of those herein mentioned, all of the rights
and privileges of Pledgee and all of the obligations of Pledgor with respect to
the securities originally pledged or held as Collateral hereunder shall be
forthwith applicable to such substituted or exchanged securities.

          8.  While an Event of Default exists, Pledgee shall be authorized to
collect all dividends, interest payments, and other amounts (including amounts
received or receivable upon redemption or repurchase) that may be, or become,
due on any of the Collateral.  If Pledgor receives any such dividends, payments
or amounts after the occurrence and during the continuance of an Event of
Default, it shall immediately endorse and deliver the same to Pledgee in the
form received.  All such amounts which Pledgee receives and retains in
accordance with the terms of this paragraph 8 shall be applied to reduce the
principal amount outstanding on the Secured Obligations in the inverse order of
maturity.  Pledgee is, furthermore, authorized to give receipts in the name of
Pledgor for any amounts so received.  Pledgee shall be under no obligation to
collect any such amounts.

          9.  In the event that, during the term of this Agreement, subscription
warrants or any other rights or options shall be issued in connection with the
Collateral, such warrants, rights or options shall be immediately assigned, if
necessary, by Pledgor to Pledgee.  If any such warrants, rights or options are
exercised by Pledgor, all new  securities so acquired by Pledgor shall be
immediately assigned to Pledgee, shall become part of the Collateral and shall
be endorsed to, delivered to and held by Pledgee under the terms of this
Agreement in the same manner as the securities originally pledged.

                                       2
<PAGE>

          10.  In the event that, during the term of this Agreement, any share,
dividend, reclassification, readjustment or other change is declared or made in
the capital structure of Borrower, all new, substituted and additional shares,
or other securities, issued by reason of any such change shall become part of
the Collateral and shall be endorsed to, delivered to and held by Pledgee under
the terms of this Agreement in the same manner as the securities originally
pledged.

          11.  Pledgor authorizes Pledgee, without notice or demand, and without
affecting the liability of Pledgor hereunder, from time to time to:

          (A) hold security in addition to and other than the Collateral for the
payment of the Secured Obligations or any part thereof, and exchange, enforce,
waive and release any Collateral or any part thereof, or any other such
security, or part thereof;

          (B) release any of the endorsers or guarantors of the Secured
Obligations secured hereunder or any part thereof, or any other person
whomsoever liable for or on account of such Secured Obligations;

          (C) on the transfer of all or any part of the Secured Obligations
secured hereunder, Pledgee may assign all or any part of Pledgee's security
interest in the Collateral and shall be fully discharged thereafter from all
liability and responsibility with respect to the Collateral so transferred;
provided, however, that in no event shall Pledgee be liable for any act or
omission or negligent act or negligent omission with respect to the Collateral,
other than acts or omissions constituting gross negligence, willful misconduct,
tortious breach of contract or violation of law.  The transferee of the
Collateral shall be vested with the rights, powers and remedies of Pledgee
hereunder, and with respect to any Collateral not so transferred, Pledgee shall
retain all rights, powers and remedies hereby given; and

          (D) Pledgor hereby waives any right to require Pledgee to proceed
against Pledgor, Borrower  or any other person whomsoever, to proceed against or
exhaust any collateral or any other security held by Pledgee, or to pursue any
other remedy available to Pledgee.  Pledgor further waives any defense arising
by reason of any liability or other  defense of Pledgor or of any other person.
Pledgor shall have no right to require Pledgee to marshal collateral.

          12.  It shall not be necessary for Pledgee to inquire into the powers
of Pledgor or the officers, directors or agents acting or purporting to act on
behalf of Pledgor, and any obligations made or created in reliance on the
professed exercise of such powers shall be secured hereunder.

          13.  To the extent permitted by applicable law and in the Loan
Agreement, Pledgee shall be under no duty or obligation whatsoever to make or
give any presentments, demands for performance, notices of non-performance,
protests, notices of protest, or notices of dishonor in connection with the
Secured Obligations.

          14.  The occurrence of an "Event of Default" under the Loan Agreement
shall, at the option of Pledgee, constitute an "Event of Default" under this
Agreement.

                                       3
<PAGE>

          15.  While an Event of Default exists, Pledgee shall have the right to
exercise all rights and remedies afforded to it under the Loan Agreement and, in
this connection, the Pledgee may sell all or any part of the Collateral in such
manner as provided in the Loan Agreement.  Pledgee shall apply the proceeds of
any such sale or sales of the Collateral in the manner provided in the Loan
Agreement.

          16.  Upon the indefeasible repayment in full in cash of the Secured
Obligations, Pledgee will promptly, at Pledgor's expense, deliver all of the
Collateral to Pledgor along with all instruments of assignment executed in
connection therewith, and execute and deliver to Pledgor such documents as
Pledgor shall reasonably request to evidence Pledgee's release of Pledgee's
security interest hereunder.

          17.  THIS AGREEMENT SHALL BE INTERPRETED AND THE RIGHTS AND
LIABILITIES OF THE PARTIES HERETO DETERMINED IN ACCORDANCE WITH THE LOCAL LAW OF
THE STATE OF TEXAS EXCLUDING ANY CONFLICTS OF LAW RULE OR PRINCIPLE THAT MIGHT
OTHERWISE REFER CONSTRUCTION OR INTERPRETATION OF THIS AGREEMENT TO THE
SUBSTANTIVE LAW OF ANOTHER JURISDICTION.

                  [Remainder of Page Intentionally Left Blank]

                                       4
<PAGE>

          IN WITNESS WHEREOF, Pledgor and Pledgee have executed this Agreement
as of the date first above written.

                                 PLEDGOR:

                                 IDS ENGINEERING MANAGEMENT, LC

                                 By:
                                    -----------------------------
                                    Name:
                                    Title:

                                 PLEDGEE:

                                 FLEET CAPITAL CORPORATION, as Agent

                                 By:
                                    -----------------------------
                                    Dan A. Hughes
                                    Vice President
<PAGE>

                                   SCHEDULE I

            Capital Stock Pledged by IDS Engineering Management, LC

<TABLE>
<CAPTION>

    Name                    Certificate            Record Holder                 Number of
                               Number                                              Shares
<S>                         <C>             <C>                                  <C>
Petrocon Engineering, Inc.                  IDS Engineering Management, LC
 </TABLE>
<PAGE>

                                  SCHEDULE II
                                  -----------

                  Original Stock Certificates with Stock Power<PAGE>

                                                                   EXHIBIT 10.57

                  AMENDED AND RESTATED STOCK PLEDGE AGREEMENT

     THIS AMENDED AND RESTATED STOCK PLEDGE AGREEMENT (this "Agreement") is
                                                             ---------
entered into on December 21, 2001, by and between PETROCON ENGINEERING, INC., a
Texas corporation ("Pledgor"), and FLEET CAPITAL CORPORATION, a Rhode Island
                    -------
corporation, as Agent for itself and the other financial institution(s) from
time to time a party to the Loan Agreement (as hereinafter defined)
("Pledgee").  All capitalized terms used but not otherwise defined herein shall
  -------
have the meanings ascribed to such terms in the Loan Agreement.

     1.     For good and valuable consideration, the receipt and sufficiency of
which is hereby acknowledged, and as collateral security for and to secure the
prompt payment and performance in full of the Secured Obligations (hereinafter
defined), Pledgor hereby assigns to Pledgee and grants to Pledgee, for the
benefit of Lenders, a continuing security interest in all issued and
outstanding shares of capital stock (including, without limitation, all shares
of capital stock represented by the stock certificates identified on Schedule I
                                                                     ----------
attached hereto) of each of Triangle Engineers and Constructors, Inc., a Texas
corporation ("Triangle"), Petrocon Systems, Inc., a Texas corporation
              --------
("Petrocon Systems"), Petrocon Technologies, Inc., a Texas corporation
  ----------------
("Petrocon Technologies"), Petrocon Engineering of Louisiana, Inc., a Louisiana
  ---------------------
corporation ("Petrocon Louisiana"), R.P.M. Engineering, Inc., a Louisiana
              ------------------
corporation ("RPM"), Alliance Engineering Associates, Inc., a Texas corporation
              ---
("Alliance"), and Petrocon Construction Resources, Inc., a Texas corporation
  --------
("Petrocon Construction") (Triangle, Petrocon Systems, Petrocon Technologies,
  ---------------------
Petrocon Louisiana, RPM, Alliance and Petrocon Construction are sometimes
hereinafter referred to individually and collectively as "Borrower") whether
                                                          --------
now or hereafter issued by Borrower, together with all proceeds, products and
increases thereof and substitutions and replacements therefor (collectively,
the "Collateral").
     ----------

          As used in this Agreement, the term "Secured Obligations" shall mean
                                               -------------------
any and all (i) Obligations of Pledgor or Borrower to Pledgee and/or Lenders,
pursuant to that certain Second Amended and Restated Loan and Security
Agreement, dated as of the date hereof, by and among Pledgor, Borrower, IDS
Engineering, Inc., a Texas corporation, Thermaire, Inc., a Texas corporation,
Constant Power Manufacturing, Inc., a Texas corporation, ISD Engineering
Management, LC, a Texas limited liability company, Industrial Data Systems,
Inc., a Texas corporation, Pledgee and Lenders (as amended from time to time,
the "Loan Agreement") and (ii) extensions, renewals, modifications, increases
     --------------
and replacements of the foregoing.  The term "Secured Obligations" shall
                                              -------------------
include, without limitation, all unpaid accrued interest thereon and all costs
and expenses payable as hereinafter provided: (i) whether now existing or
hereafter incurred; (ii) whether direct, indirect, primary, absolute,
secondary, contingent, secured, unsecured, matured, or unmatured; (iii) whether
such indebtedness is from time to time reduced and thereafter increased, or
entirely extinguished and thereafter reincurred; (iv) whether such indebtedness
was originally contracted with Pledgee or with another or others; (v) whether
or not such indebtedness is evidenced by a negotiable or nonnegotiable
instrument or any other writing; and (vi) whether such indebtedness is
contracted by Pledgor or Borrower individually or jointly or severally with
another or others.

Stock Pledge Agreement (Petrocon) A&R

                                      1
<PAGE>

     2.     Pledgor represents and warrants that (i) Pledgor is the legal and
beneficial owner of the Collateral, free and clear of all liens and
encumbrances; (ii) there are no restrictions upon the transfer of any of the
Collateral, other than as may appear and may be referenced on the face of the
certificates, those arising under applicable state or federal securities laws
and those existing on the date hereof and disclosed to Pledgee in writing;
(iii) Pledgor owns 100% of the issued and outstanding capital stock of
Borrower; (iv) except as disclosed to Pledgee in writing, there are no existing
obligations to issue capital stock or securities convertible into capital stock
of Borrower.

     3.     In furtherance of Pledgee's security interest in the Collateral,
Pledgor agrees to deliver to Pledgee, on the date of this Agreement, the stock
certificates identified on Schedule I attached hereto, together with stock
                           ----------
powers duly executed in blank by Pledgor.

     4.     With respect to the Collateral, Pledgor hereby appoints Pledgee its
attorney-in-fact to arrange for the transfer of the Collateral on the books of
Borrower to the name of Pledgee during the continuance of any Event of Default;
provided, however, that Pledgee shall be under no obligation to do so.
--------  -------

     5.     During the term of this Agreement, provided no Event of Default
then exists, Pledgor shall have the right, where applicable, to vote the
Collateral on all corporate questions, and Pledgee shall, if necessary, execute
due and timely proxies in favor of Pledgor for this purpose.

     6.     While an Event of Default exists, Pledgee may exercise all of the
rights and privileges in connection with the Collateral to which a transferee
may be entitled as the record holder thereof, together with the rights and
privileges otherwise granted hereunder.  Pledgee shall be under no obligation
to exercise any of such rights or privileges.

     7.     If, with the consent of Pledgee, Pledgor shall substitute or
exchange other securities in place of those herein mentioned, all of the rights
and privileges of Pledgee and all of the obligations of Pledgor with respect to
the securities originally pledged or held as Collateral hereunder shall be
forthwith applicable to such substituted or exchanged securities.

     8.     While an Event of Default exists, Pledgee shall be authorized to
collect all dividends, interest payments, and other amounts (including amounts
received or receivable upon redemption or repurchase) that may be, or become,
due on any of the Collateral.  If Pledgor receives any such dividends, payments
or amounts after the occurrence and during the continuance of an Event of
Default, it shall immediately endorse and deliver the same to Pledgee in the
form received.  All such amounts which Pledgee receives and retains in
accordance with the terms of this paragraph 8 shall be applied to reduce the
                                  -----------
principal amount outstanding on the Secured Obligations in the inverse order of
maturity.  Pledgee is, furthermore, authorized to give receipts in the name of
Pledgor for any amounts so received.  Pledgee shall be under no obligation to
collect any such amounts.

     9.     In the event that, during the term of this Agreement, subscription
warrants or any other rights or options shall be issued in connection with the
Collateral, such warrants, rights or

Stock Pledge Agreement (Petrocon) A&R

                                      2
<PAGE>

options shall be immediately assigned, if necessary, by Pledgor to Pledgee.  If
any such warrants, rights or options are exercised by Pledgor, all new
securities so acquired by Pledgor shall be immediately assigned to Pledgee,
shall become part of the Collateral and shall be endorsed to, delivered to and
held by Pledgee under the terms of this Agreement in the same manner as the
securities originally pledged.

     10.    In the event that, during the term of this Agreement, any share,
dividend, reclassification, readjustment or other change is declared or made in
the capital structure of Borrower, all new, substituted and additional shares,
or other securities, issued by reason of any such change shall become part of
the Collateral and shall be endorsed to, delivered to and held by Pledgee under
the terms of this Agreement in the same manner as the securities originally
pledged.

     11.    Pledgor authorizes Pledgee, without notice or demand, and without
affecting the liability of Pledgor hereunder, from time to time to:

            (A)  hold security in addition to and other than the Collateral for
the payment of the Secured Obligations or any part thereof, and exchange,
enforce, waive and release any Collateral or any part thereof, or any other
such security, or part thereof;

            (B)  release any of the endorsers or guarantors of the Secured
Obligations secured hereunder or any part thereof, or any other person
whomsoever liable for or on account of such Secured Obligations;

            (C)  on the transfer of all or any part of the Secured Obligations
secured hereunder, Pledgee may assign all or any part of Pledgee's security
interest in the Collateral and shall be fully discharged thereafter from all
liability and responsibility with respect to the Collateral so transferred;
provided, however, that in no event shall Pledgee be liable for any act or
omission or negligent act or negligent omission with respect to the Collateral,
other than acts or omissions constituting gross negligence, willful misconduct,
tortious breach of contract or violation of law.  The transferee of the
Collateral shall be vested with the rights, powers and remedies of Pledgee
hereunder, and with respect to any Collateral not so transferred, Pledgee shall
retain all rights, powers and remedies hereby given; and

            (D)  Pledgor hereby waives any right to require Pledgee to proceed
against Pledgor, Borrower or any other person whomsoever, to proceed against or
exhaust any collateral or any other security held by Pledgee, or to pursue any
other remedy available to Pledgee.  Pledgor further waives any defense arising
by reason of any liability or other defense of Pledgor or of any other person.
Pledgor shall have no right to require Pledgee to marshal collateral.

     12.    It shall not be necessary for Pledgee to inquire into the powers of
Pledgor or the officers, directors or agents acting or purporting to act on
behalf of Pledgor, and any obligations made or created in reliance on the
professed exercise of such powers shall be secured hereunder.

     13.    To the extent permitted by applicable law and in the Loan
Agreement, Pledgee shall be under no duty or obligation whatsoever to make or
give any presentments, demands for

Stock Pledge Agreement (Petrocon) A&R

                                      3
<PAGE>

performance, notices of non-performance, protests, notices of protest, or
notices of dishonor in connection with the Secured Obligations.

     14.    The occurrence of an "Event of Default" under the Loan Agreement
shall, at the option of Pledgee, constitute an "Event of Default" under this
                                                ----------------
Agreement.

     15.    While an Event of Default exists, Pledgee shall have the right to
exercise all rights and remedies afforded to it under the Loan Agreement and,
in this connection, the Pledgee may sell all or any part of the Collateral in
such manner as provided in the Loan Agreement.  Pledgee shall apply the
proceeds of any such sale or sales of the Collateral in the manner provided in
the Loan Agreement.

     16.    Upon the indefeasible repayment in full in cash of the Secured
Obligations, Pledgee will promptly, at Pledgor's expense, deliver all of the
Collateral to Pledgor along with all instruments of assignment executed in
connection therewith, and execute and deliver to Pledgor such documents as
Pledgor shall reasonably request to evidence Pledgee's release of Pledgee's
security interest hereunder.

     17.    THIS AGREEMENT SHALL BE INTERPRETED AND THE RIGHTS AND LIABILITIES
OF THE PARTIES HERETO DETERMINED IN ACCORDANCE WITH THE LOCAL LAW OF THE STATE
OF TEXAS EXCLUDING ANY CONFLICTS OF LAW RULE OR PRINCIPLE THAT MIGHT OTHERWISE
REFER CONSTRUCTION OR INTERPRETATION OF THIS AGREEMENT TO THE SUBSTANTIVE LAW
OF ANOTHER JURISDICTION.

     18.    This Agreement is given in renewal, extension, modification and
amendment (and not in extinguishment or novation) of that certain Stock Pledge
Agreement (the "Original Agreement"), dated June 15, 1999, by and between
                ------------------
Pledgor and Pledgee.

     19.    The security interests and liens in the Collateral granted to
Pledgee by Pledgor hereunder are given in renewal, extension and modification
of the security interests and liens previously granted to Pledgee by Pledgor in
the Original Agreement.  Such prior security interests and liens are not
extinguished hereby, and the making, perfection and priority of such prior
security interests shall continue in full force and effect.

                  [Remainder of Page Intentionally Left Blank]

Stock Pledge Agreement (Petrocon) A&R

                                      4
<PAGE>

     IN WITNESS WHEREOF, Pledgor and Pledgee have executed this Agreement as of
the date first above written.

                                          PLEDGOR:
                                          -------

                                          PETROCON ENGINEERING, INC.

                                          By: _________________________________
                                          Name: _______________________________
                                          Title: ______________________________

                                          PLEDGEE:
                                          -------

                                          FLEET CAPITAL CORPORATION, as Agent

                                          By: _________________________________
                                               Dan A. Hughes
                                               Vice President

Stock Pledge Agreement (Petrocon) A&R
<PAGE>

                                   SCHEDULE I
                                   ----------

              Capital Stock Pledged by Petrocon Engineering, Inc.

             Name             Certificate        Record Holder           Number
                                 Number                                    of
                                                                         Shares

Triangle Engineers and
   Constructors, Inc.             A8        Petrocon Engineering, Inc.   50,100

Petrocon Systems, Inc.             1        Petrocon Engineering, Inc.    1,000

Petrocon Engineering of
   Louisiana, Inc./1/              1        Petrocon Engineering, Inc.      100

R.P.M. Engineering, Inc.          10        Petrocon Engineering, Inc.    3,000

Petrocon Construction
   Resources, Inc.                 1        Petrocon Engineering, Inc.    1,000

Petrocon Technologies, Inc.        1        Petrocon Engineering, Inc.    1,000

Alliance Engineering Associates,
   Inc.                            1        Petrocon Engineering, Inc.    1,000

----------------------------
/1/   Stock certificate in the name of Petrocon of Sulphur, Inc. which changed
its name to Petrocon Engineering of Louisiana, Inc.

Schedule I
<PAGE>

                                  SCHEDULE II
                                  -----------

                  Original Stock Certificates with Stock Power

Schedule II
<PAGE>

                             STOCK PLEDGE AGREEMENT

     THIS STOCK PLEDGE AGREEMENT (this "Agreement") is entered into on December
                                        ---------
21, 2001, by and between IDS ENGINEERING MANAGEMENT, LC, a Texas company
("Pledgor"), and FLEET CAPITAL CORPORATION, a Rhode Island corporation, as
  -------
Agent for itself and the other financial institution(s) from time to time a
party to the Loan Agreement (as hereinafter defined) ("Pledgee").  All
                                                       -------
capitalized terms used but not otherwise defined herein shall have the meanings
ascribed to such terms in the Loan Agreement.

     1.     For good and valuable consideration, the receipt and sufficiency of
which is hereby acknowledged, and as collateral security for and to secure the
prompt payment and performance in full of the Secured Obligations (hereinafter
defined), Pledgor hereby assigns to Pledgee and grants to Pledgee, for the
benefit of Lenders, a continuing security interest in all issued and
outstanding shares of capital stock (including, without limitation, all shares
of capital stock represented by the stock certificates identified on Schedule I
                                                                     ----------
attached hereto) of Petrocon Engineering, Inc., a Texas corporation
("Borrower"), whether now or hereafter issued by Borrower, together with all
  --------
proceeds, products and increases thereof and substitutions and replacements
therefor (collectively, the "Collateral").
                             ----------

          As used in this Agreement, the term "Secured Obligations" shall mean
                                               -------------------
any and all (i) Obligations of Pledgor or Borrower to Pledgee and/or Lenders,
pursuant to that certain Second Amended and Restated Loan and Security
Agreement, dated as of the date hereof, by and among Pledgor, Borrower, IDS
Engineering, Inc., a Texas corporation, Thermaire, Inc., a Texas corporation,
Constant Power Manufacturing, Inc., a Texas corporation, Industrial Data
Systems, Inc., a Texas corporation, Triangle Engineers and Constructors, Inc.,
a Texas corporation, Petrocon Systems, Inc., a Texas corporation, Petrocon
Technologies, Inc., a Texas corporation, Petrocon Engineering of Louisiana,
Inc., a Louisiana corporation, R.P.M. Engineering, Inc., a Louisiana
corporation, Alliance Engineering Associates, Inc., a Texas corporation,
Petrocon Construction Resources, Inc., a Texas corporation, Pledgee and Lenders
(as amended from time to time, the "Loan Agreement") and (ii) extensions,
                                    --------------
renewals, modifications, increases and replacements of the foregoing.  The term
"Secured Obligations" shall include, without limitation, all unpaid accrued
 -------------------
interest thereon and all costs and expenses payable as hereinafter provided:
(i) whether now existing or hereafter incurred; (ii) whether direct, indirect,
primary, absolute, secondary, contingent, secured, unsecured, matured, or
unmatured; (iii) whether such indebtedness is from time to time reduced and
thereafter increased, or entirely extinguished and thereafter reincurred; (iv)
whether such indebtedness was originally contracted with Pledgee or with
another or others; (v) whether or not such indebtedness is evidenced by a
negotiable or nonnegotiable instrument or any other writing; and (vi) whether
such indebtedness is contracted by Pledgor or Borrower individually or jointly
or severally with another or others.

     2.     Pledgor represents and warrants that (i) Pledgor is the legal and
beneficial owner of the Collateral, free and clear of all liens and
encumbrances; (ii) there are no restrictions upon the transfer of any of the
Collateral, other than as may appear and may be referenced on the face of the
certificates, those arising under applicable state or federal securities laws
and those existing on the date hereof and disclosed to Pledgee in writing;
(iii) Pledgor owns 100% of the issued and

Stock Pledge Agreement (IDSEM)

                                      1
<PAGE>

outstanding capital stock of Borrower; (iv) except as disclosed to Pledgee in
writing, there are no existing obligations to issue capital stock or securities
convertible into capital stock of Borrower.

     3.     In furtherance of Pledgee's security interest in the Collateral,
Pledgor agrees to deliver to Pledgee, on the date of this Agreement, the stock
certificates identified on Schedule I attached hereto, together with stock
                           ----------
powers duly executed in blank by Pledgor.

     4.     With respect to the Collateral, Pledgor hereby appoints Pledgee its
attorney-in-fact to arrange for the transfer of the Collateral on the books of
Borrower to the name of Pledgee during the continuance of any Event of Default;
provided, however, that Pledgee shall be under no obligation to do so.
--------  -------

     5.     During the term of this Agreement, provided no Event of Default
then exists, Pledgor shall have the right, where applicable, to vote the
Collateral on all corporate questions, and Pledgee shall, if necessary, execute
due and timely proxies in favor of Pledgor for this purpose.

     6.     While an Event of Default exists, Pledgee may exercise all of the
rights and privileges in connection with the Collateral to which a transferee
may be entitled as the record holder thereof, together with the rights and
privileges otherwise granted hereunder.  Pledgee shall be under no obligation
to exercise any of such rights or privileges.

     7.     If, with the consent of Pledgee, Pledgor shall substitute or
exchange other securities in place of those herein mentioned, all of the rights
and privileges of Pledgee and all of the obligations of Pledgor with respect to
the securities originally pledged or held as Collateral hereunder shall be
forthwith applicable to such substituted or exchanged securities.

     8.     While an Event of Default exists, Pledgee shall be authorized to
collect all dividends, interest payments, and other amounts (including amounts
received or receivable upon redemption or repurchase) that may be, or become,
due on any of the Collateral.  If Pledgor receives any such dividends, payments
or amounts after the occurrence and during the continuance of an Event of
Default, it shall immediately endorse and deliver the same to Pledgee in the
form received.  All such amounts which Pledgee receives and retains in
accordance with the terms of this paragraph 8 shall be applied to reduce the
                                  -----------
principal amount outstanding on the Secured Obligations in the inverse order of
maturity.  Pledgee is, furthermore, authorized to give receipts in the name of
Pledgor for any amounts so received.  Pledgee shall be under no obligation to
collect any such amounts.

     9.     In the event that, during the term of this Agreement, subscription
warrants or any other rights or options shall be issued in connection with the
Collateral, such warrants, rights or options shall be immediately assigned, if
necessary, by Pledgor to Pledgee.  If any such warrants, rights or options are
exercised by Pledgor, all new securities so acquired by Pledgor shall be
immediately assigned to Pledgee, shall become part of the Collateral and shall
be endorsed to, delivered to and held by Pledgee under the terms of this
Agreement in the same manner as the securities originally pledged.

Stock Pledge Agreement (IDSEM)

                                      2
<PAGE>

     10.    In the event that, during the term of this Agreement, any share,
dividend, reclassification, readjustment or other change is declared or made in
the capital structure of Borrower, all new, substituted and additional shares,
or other securities, issued by reason of any such change shall become part of
the Collateral and shall be endorsed to, delivered to and held by Pledgee under
the terms of this Agreement in the same manner as the securities originally
pledged.

     11.    Pledgor authorizes Pledgee, without notice or demand, and without
affecting the liability of Pledgor hereunder, from time to time to:

            (A)  hold security in addition to and other than the Collateral for
the payment of the Secured Obligations or any part thereof, and exchange,
enforce, waive and release any Collateral or any part thereof, or any other
such security, or part thereof;

            (B)  release any of the endorsers or guarantors of the Secured
Obligations secured hereunder or any part thereof, or any other person
whomsoever liable for or on account of such Secured Obligations;

            (C)  on the transfer of all or any part of the Secured Obligations
secured hereunder, Pledgee may assign all or any part of Pledgee's security
interest in the Collateral and shall be fully discharged thereafter from all
liability and responsibility with respect to the Collateral so transferred;
provided, however, that in no event shall Pledgee be liable for any act or
--------  -------
omission or negligent act or negligent omission with respect to the Collateral,
other than acts or omissions constituting gross negligence, willful misconduct,
tortious breach of contract or violation of law.  The transferee of the
Collateral shall be vested with the rights, powers and remedies of Pledgee
hereunder, and with respect to any Collateral not so transferred, Pledgee shall
retain all rights, powers and remedies hereby given; and

            (D)  Pledgor hereby waives any right to require Pledgee to proceed
against Pledgor, Borrower or any other person whomsoever, to proceed against or
exhaust any collateral or any other security held by Pledgee, or to pursue any
other remedy available to Pledgee.  Pledgor further waives any defense arising
by reason of any liability or other defense of Pledgor or of any other person.
Pledgor shall have no right to require Pledgee to marshal collateral.

     12.    It shall not be necessary for Pledgee to inquire into the powers of
Pledgor or the officers, directors or agents acting or purporting to act on
behalf of Pledgor, and any obligations made or created in reliance on the
professed exercise of such powers shall be secured hereunder.

     13.    To the extent permitted by applicable law and in the Loan
Agreement, Pledgee shall be under no duty or obligation whatsoever to make or
give any presentments, demands for performance, notices of non-performance,
protests, notices of protest, or notices of dishonor in connection with the
Secured Obligations.

     14.    The occurrence of an "Event of Default" under the Loan Agreement
shall, at the option of Pledgee, constitute an "Event of Default" under this
                                                ----------------
Agreement.

Stock Pledge Agreement (IDSEM)

                                      3
<PAGE>

     15.    While an Event of Default exists, Pledgee shall have the right to
exercise all rights and remedies afforded to it under the Loan Agreement and,
in this connection, the Pledgee may sell all or any part of the Collateral in
such manner as provided in the Loan Agreement.  Pledgee shall apply the
proceeds of any such sale or sales of the Collateral in the manner provided in
the Loan Agreement.

     16.    Upon the indefeasible repayment in full in cash of the Secured
Obligations, Pledgee will promptly, at Pledgor's expense, deliver all of the
Collateral to Pledgor along with all instruments of assignment executed in
connection therewith, and execute and deliver to Pledgor such documents as
Pledgor shall reasonably request to evidence Pledgee's release of Pledgee's
security interest hereunder.

     17.    THIS AGREEMENT SHALL BE INTERPRETED AND THE RIGHTS AND LIABILITIES
OF THE PARTIES HERETO DETERMINED IN ACCORDANCE WITH THE LOCAL LAW OF THE STATE
OF TEXAS EXCLUDING ANY CONFLICTS OF LAW RULE OR PRINCIPLE THAT MIGHT OTHERWISE
REFER CONSTRUCTION OR INTERPRETATION OF THIS AGREEMENT TO THE SUBSTANTIVE LAW
OF ANOTHER JURISDICTION.

                  [Remainder of Page Intentionally Left Blank]

Stock Pledge Agreement (IDSEM)

                                      4
<PAGE>

     IN WITNESS WHEREOF, Pledgor and Pledgee have executed this Agreement as of
the date first above written.

                                          PLEDGOR:
                                          -------

                                          IDS ENGINEERING MANAGEMENT, LC

                                          By:__________________________________
                                          Name: _______________________________
                                          Title: ______________________________

                                          PLEDGEE:
                                          -------

                                          FLEET CAPITAL CORPORATION, as Agent

                                          By:__________________________________
                                              Dan A. Hughes
                                              Vice President

Stock Pledge Agreement (IDSEM)
<PAGE>

                                   SCHEDULE I
                                   ----------

            Capital Stock Pledged by IDS Engineering Management, LC

           Name               Certificate     Record Holder           Number of
                                 Number                                Shares

Petrocon Engineering, Inc.                  IDS Engineering
                                               Management, LC

Schedule I
<PAGE>

                                  SCHEDULE II
                                  -----------

                  Original Stock Certificates with Stock Power

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