<PAGE>
 
                                                                   Exhibit 10.12

THE SECURITIES REPRESENTED BY THIS CERTIFICATE MAY NOT BE OFFERED FOR SALE, SOLD
OR OTHERWISE DISPOSED OF EXCEPT PURSUANT TO AN EFFECTIVE REGISTRATION STATEMENT
FILED UNDER THE SECURITIES ACT OF 1933, AS AMENDED, OR PURSUANT TO AN EXEMPTION
FROM REGISTRATION UNDER SUCH ACT.


                                                                   50,000 Shares



                       NATIONAL ENVIRONMENTAL SERVICE CO.

                         COMMON STOCK PURCHASE WARRANT



                       Transfer Restricted -- Section 5.2


     This certifies that, for and in consideration of $.001 per Warrant Share,
Peacock, Hislop, Staley & Given, Inc., or registered, permitted assigns, is
entitled to purchase from National Environmental Service Co., a corporation
incorporated under the laws of the State of Oklahoma (the "Company"), subject to
the terms and conditions hereof, at any time after the Effective Date and on or
prior to the Expiration Date, the number of Shares stated above at the Exercise
Price (as defined herein). The Exercise Price and the number and type of Shares
and component securities thereof (as defined below) purchasable hereunder are
subject to adjustment from time to time as provided in Article 3 hereof.


                                   ARTICLE 1

                                  DEFINITIONS

     Section 1.1 Definition of Terms. As used in this Warrant, the following
capitalized terms shall have the following respective meanings:

             (a) Business Day. A day other than a Saturday, Sunday or other day
     on which federal banks or banks chartered by the state of the principal
     place of business of the Company are authorized by law to remain closed.

             (b) Common Stock.  Common Stock of the Company.
<PAGE>
 
             (c) Common Stock Equivalents.  Securities that are convertible
     into or exercisable for shares of Common Stock.

             (d) Company.  National Environmental Service Co., an Oklahoma
     corporation.

             (e) Effective Date. January ___, 1998, the date of issuance of this
     Warrant by the Company.

             (f) Exchange Act.  The Securities Exchange Act of 1934, as amended.

             (g) Exercise Price. $2.00 per Share, as such price may be adjusted
     from time to time pursuant to Article 3 hereof.

             (h) Expiration Date. 5:00 p.m., local time on January ___, 2003 or,
     if such day is not a Business Day, the next succeeding day which is a
     Business Day.

             (i) Holder. A Holder of Registrable Securities.

             (j) NASD. National Association of Securities Dealers, Inc.

             (k) Person. An individual, partnership, joint venture, limited
     liability company, corporation, trust, unincorporated organization of
     government or department or agency thereof.

             (l) Piggyback Registration. A registration of securities under the
     terms of Section 6.1.

             (m) Piggyback Registration Rights. The rights of the Warrantholders
     to have securities received from the exercise of Warrants to be registered
     under the Securities Act in conjunction with a registration of securities
     by the Company as set forth in Section 6.1.

             (n) Placement Agent.  Peacock, Hislop, Staley & Given, Inc.
 
             (o) Prospectus.  Any prospectus included in any Registration
     Statement, as amended or supplemented by any prospectus supplement, with
     respect to the terms of the offering of any portion of the Registrable
     Securities covered by such Registration Statement and all other amendments
     and supplements to the Prospectus, including posteffective amendments and
     all material incorporated by reference in such Prospectus.

             (p) Public Offering. A public offering of any of the Company's
     equity or debt securities pursuant to a Registration Statement.
<PAGE>
 
             (q) Registration Expenses. Any and all expenses incurred in
     connection with any registration or action incident to performance of or
     compliance by the Company with Article 6, including, without limitation (i)
     all SEC, national securities exchange and NASD registration and filing
     fees; all listing fees and all transfer agent fees; (ii) all fees and
     expenses of complying with state securities or blue sky laws (including the
     fees and disbursements of counsel of the underwriters in connection with
     blue sky qualifications of the Registrable Securities); (iii) all printing,
     mailing, messenger and delivery expenses; (iv) all reasonable fees and
     disbursements of counsel for the Company and of its accountants, including
     the expenses of any special audits and/or "cold comfort" letters required
     by or incident to such performance and compliance; and (v) any
     disbursements of underwriters customarily paid by issuers or sellers of
     securities including the reasonable fees and expenses of any special
     experts retained in connection with the requested registration, but
     excluding underwriting discounts or concessions and commissions, brokerage
     fees and transfer taxes, if any, and fees of counsel or accountants
     retained by the Holders of Registrable Securities to advise them in their
     capacity as Holders of Registrable Securities.

             (r) Registrable Securities. Any shares of Common Stock issued to
     Placement Agent and/or its designees or transferees as permitted under
     Section 5.2 and/or other securities that may be or are issued by the
     Company upon exercise of this Warrant including those which may thereafter
     be issued by the Company in respect of any such securities by means of any
     stock splits, stock dividends, recapitalizations, reclassifications or the
     like, and as adjusted pursuant to Article 3 hereof; provided, however, that
     as to any particular security contained in Registrable Securities, such
     securities shall cease to be Registrable Securities when (i) a Registration
     Statement with respect to the sale of such securities shall have been
     declared effective under the Securities Act and such securities shall have
     been disposed of in accordance with such Registration Statement; (ii) such
     securities shall have been sold to the public pursuant to Rule 144 (or any
     successor provisions) under the Securities Act; or (iii) such securities
     shall have been sold, assigned or otherwise transferred to any person other
     than to any spouse, lineal descendants or adopted children of such Persons
     to whom such securities are transferred by operation of law or by bequest.

             (s) Registration Statement. Any registration statement of the
     Company filed or to be filed with the SEC which covers any of the
     Registrable Securities pursuant to the provisions of this Agreement,
     including all amendments (including post-effective amendments) and
     supplements thereto, all exhibits thereto and all material incorporated
     therein by reference.

             (t) SEC. The Securities and Exchange Commission or any other
     federal agency at the time administering the Securities Act or the Exchange
     Act.
<PAGE>
 
             (u) Securities Act. The Securities Act of 1933, as amended.

             (v) Share.  A share of Common Stock.

             (w) Transfers. The disposition or encumbering of a Warrant or
     Shares as set forth in Section 5.2.

             (x) Warrants. This Warrant and all other warrants that may be
     issued in its place (together initially evidencing the right to purchase an
     aggregate of one share of Common Stock, as adjusted), originally issued as
     set forth in the definition of Registrable Securities.

             (y) Warrantholder. The person(s) or entity(ies) to whom this
     Warrant is originally issued, or any successor in interest thereto, or any
     registered, permitted assignee or transferee thereof, in whose name this
     Warrant is registered upon the books to be maintained by the Company for
     that purpose.


                                   ARTICLE 2

                        DURATION AND EXERCISE OF WARRANT

     Section 2.1 Duration of Warrant. The Warrantholder may exercise this
Warrant at any time and from time to time after execution and delivery hereof
and before 5:00 p.m., local time, on the Expiration Date. If this Warrant is not
exercised on or before the Expiration Date, it shall become void, and all rights
hereunder shall thereupon cease.

     Section 2.2 Exercise of Warrant.

             (a) The Warrantholder may exercise this Warrant, in whole or in
     part, by presentation and surrender of this Warrant to the Company at its
     corporate office at 12331 East 60th Street, Tulsa, Oklahoma 74146 with the
     Subscription Form annexed hereto duly executed and accompanied by payment
     of the full Exercise Price for each Share to be purchased.

             (b) Upon receipt of this Warrant with the Subscription Form fully
     executed and accompanied by payment of the aggregate Exercise Price for the
     shares for which this Warrant is then being exercised, the Company shall
     cause to be issued certificates for the total number of whole shares of
     Common Stock for which this Warrant is being exercised (adjusted to reflect
     the effect of the anti-dilution provisions contained in Article 3 hereof,
     if any, and as provided in Section 2.4 hereof) in such denominations as are
     requested for delivery to the Warrantholder, and the Company shall
     thereupon deliver such certificates to the Warrantholder. The Warrantholder
     shall be deemed to be the Holder of record of the shares of Common Stock
     issuable
<PAGE>
 
     upon such exercise, notwithstanding that the stock transfer books of the
     Company shall then be closed or that certificates representing such shares
     of Common Stock shall not then be actually delivered to the Warrantholder.
     If at the time this Warrant is exercised, a Registration Statement is not
     in effect to register under the Securities Act the Shares issuable upon
     exercise of this Warrant, the Company may require the Warrantholder to make
     such representations, and may place such legends on certificates
     representing the Shares, as may be reasonably required in the opinion of
     counsel to the Company to permit the Shares to be issued without such
     registration.

             (c) In case the Warrantholder shall exercise this Warrant with
     respect to less than all of the Shares that may be purchased under this
     Warrant, the Company shall execute a new warrant in the form of this
     Warrant for the balance of such Shares and deliver such new warrant to the
     Warrantholder.

             (d) The Company shall pay any and all stock transfer and similar
     taxes which may be payable in respect of the issue of any Shares.

     Section 2.3 Reservation of Shares. The Company hereby agrees that at all
times there shall be reserved for issuance and delivery upon exercise of this
Warrant such number of shares of Common Stock or other shares of capital stock
of the Company from time to time issuable upon exercise of this Warrant and the
components thereof. All such shares shall be duly authorized, and when issued
upon such exercise, shall be validly issued, fully paid and non-assessable, free
and clear of all liens, security interests, charges and other encumbrances or
restrictions on sale (except as provided in Section 5.2 hereof) and free and
clear of all preemptive rights.

     Section 2.4 Fractional Shares. The Company shall not be required to issue
any fraction of a share of its capital stock in connection with the exercise of
this Warrant, and in any case where the Warrantholder would, except for the
provisions of this Section 2.4, be entitled under the terms of this Warrant to
receive a fraction of a share upon the exercise of this Warrant, the Company
shall, upon the exercise of this Warrant and receipt of the Exercise Price,
issue only the number of whole shares purchasable upon exercise of this Warrant.
The Company shall not be required to make any cash or other adjustment in
respect of such fraction of a share to which the Warrantholder would otherwise
be entitled.

     Section 2.5 Listing. Upon the issuance of any shares of Common Stock upon
exercise of this Warrant, the Company shall secure the listing of such shares of
Common Stock upon each national securities exchange or automated quotation
system, if any, upon which shares of Common Stock are then listed (subject to
official notice of issuance upon exercise of this Warrant) and shall maintain,
so long as any other shares of Common Stock shall be so listed, such listing of
all shares of Common Stock from time to time issuable upon the exercise of this
Warrant; and the Company shall so list on each national securities exchange or
automated quotation system, and shall maintain such listing of, any other shares
of capital stock of the Company issuable upon the exercise of this Warrant if
and so long as
<PAGE>
 
any shares of the same class shall be listed on such national securities
exchange or automated quotation system.


                                   ARTICLE 3

                              ADJUSTMENT OF SHARES
                       PURCHASABLE AND OF EXERCISE PRICE

     The Exercise Price and the number and kind of Shares shall be subject to
adjustment from time to time upon the happening of certain events as provided in
this Article 3.

     Section 3.1 Mechanical Adjustments.

             (a) In the event the Company at any time or from time to time prior
     to the exercise of this Warrant in full shall declare or pay any dividend
     on the Common Stock payable in Common Stock or Common Stock Equivalents, or
     effect a subdivision or combination of the outstanding shares of Common
     Stock (by reclassification or otherwise than by payment of a dividend in
     Common Stock or Common Stock Equivalents), then and in any such event, the
     Exercise Price shall be adjusted by multiplying the Exercise Price prior to
     the adjustment by the number of shares of Common Stock (assuming the
     issuance of all Common Stock in exchange for Common Stock Equivalents, if
     applicable, have been issued) outstanding immediately prior to the
     effective time of such event and dividing the result by the number of
     shares of Common Stock outstanding immediately after the effective time of
     such event, effective in the case of such dividend, immediately after the
     close of business on the record date for the determination of holders of
     Common Stock entitled to receive such dividend, or in the case of a
     subdivision or combination, at the close of business immediately prior to
     the date upon which such corporate action becomes effective.

             (b) In the event the Company at any time or from time to time prior
     to the exercise of this Warrant in full makes, or fixes a record date for
     the determination of holders of Common Stock entitled to receive a dividend
     or other distribution payable in capital stock of the Company other than
     shares of Common Stock or Common Stock Equivalents, then and in each such
     event provision shall be made so that the Holders receive upon exercise of
     this Warrant, in addition to the number of shares of Common Stock
     receivable thereupon, the amount of securities which such Holders would
     have received had they exercised the Warrant prior to such effective record
     date.

             (c) Whenever the Exercise Price payable upon exercise of each
     Warrant is adjusted pursuant to paragraph (a) of this Section 3.1, the
     number of Shares shall simultaneously be adjusted by multiplying the number
     of Shares initially issuable upon
<PAGE>
 
     exercise of each Warrant by the Exercise Price in effect on the date
     thereof and dividing the product so obtained by the Exercise Price, as
     adjusted.

             (d) All calculations under this Section 3.1 shall be made to the
     nearest cent or, subject to Section 2.4, to the nearest one-hundredth of a
     share, as the case may be. Notwithstanding anything in this Section 3.1 to
     the contrary, the Exercise Price shall not be reduced to less than the then
     existing par value of the Common Stock as a result of any adjustment made
     hereunder.

     Section 3.2 Notices of Adjustment. Whenever the number of Shares or the
Exercise Price is adjusted as herein provided, the Company shall prepare and
deliver forthwith to the Warrantholder a certificate signed by (i) its Chief
Executive Officer and President; and (ii) any Vice President, Treasurer or
Secretary. Such certificate shall set forth the adjusted number of shares
purchasable upon the exercise of this Warrant and the Exercise Price of such
shares after such adjustment, setting forth a brief statement of the facts
requiring such adjustment and setting forth the computation by which such
adjustment was made.

     Section 3.3 No Adjustment for Cash Dividends. Except as provided in Section
3.1 of this Agreement, no adjustment in respect of any cash dividends shall be
made during the term of this Warrant or upon the exercise of this Warrant.

     Section 3.4 Preservation of Purchase Rights in Certain Transactions. In
case of any reclassification, capital reorganization or other change of
outstanding shares of Common Stock (other than a subdivision or combination of
the outstanding Common Stock and other than a change in the par value of the
Common Stock) or in case of any consolidation or merger of the Company with or
into another corporation (other than merger with a subsidiary in which the
Company is the continuing corporation and that does not result in any
reclassification, capital reorganization or other change of outstanding shares
of Common Stock of the class issuable upon exercise of this Warrant) or in the
case of any sale, lease, transfer or conveyance to another corporation of the
property and assets of the Company as an entirety or substantially as an
entirety, the Company shall, as a condition precedent to such transaction, cause
such successor or purchasing corporation, as the case may be, to execute with
the Warrantholder an agreement granting the Warrantholder the right thereafter,
upon payment of the Exercise Price in effect immediately prior to such action,
to receive upon exercise of this Warrant the kind and amount of shares, and
other securities and property which the Warrantholder would have owned or have
been entitled to receive after the happening of such reclassification, change,
consolidation, merger, sale or conveyance had this Warrant been exercised
immediately prior to such action. Such agreement shall provide for adjustments
in respect of such shares of stock, and other securities and property, which
shall be as nearly equivalent as may be practicable to the adjustments provided
for in this Article 3. In the event that in connection with any such
reclassification, capital reorganization, change, consolidation, merger, sale or
conveyance, additional shares of Common Stock shall be issued in exchange,
conversion, substitution or payment, in whole or in part, for, or of, a security
of the Company other than Common Stock, any such issue shall be treated as an
issue of
<PAGE>
 
Common Stock covered by the provisions of Article 3. The provisions of this
Section 3.4 shall similarly apply to successive reclassifications, capital
reorganizations, consolidations, mergers, sales or conveyances.

     Section 3.5 Form of Warrant After Adjustments. The form of this Warrant
need not be changed because of any adjustments in the Exercise Price of the
number or kind of the shares, and Warrants theretofore or thereafter issued may
continue to express the same price and number and kind of shares as are stated
in this Warrant, as initially issued.

     Section 3.6 Treatment of Warrantholder. Prior to due presentment for
registration of transfer of this Warrant, the Company may deem and treat the
Warrantholder as the absolute owner of this Warrant (notwithstanding any
notation of ownership or other writing hereon) for all purposes and shall not be
affected by any notice to the contrary.


                                   ARTICLE 4

              OTHER PROVISIONS RELATING TO RIGHTS OF WARRANTHOLDER

     Section 4.1 No Rights as Shareholders; Notice to Warrantholders. Nothing
contained in this Warrant shall be construed as conferring upon the
Warrantholder, or such Warrantholder's transferees, the right to vote or to
receive dividends or to consent or to receive notice as a shareholder in respect
of any meeting of shareholders for the election of directors of the Company or
of any other matter, or any rights whatsoever as shareholders of the Company.
The Company shall give notice to the Warrantholder by registered mail if at any
time prior to the expiration or exercise in full of the Warrants, any of the
following events shall occur:

             (a) the Company shall authorize the payment of any dividend payable
     in any securities upon shares of Common Stock or authorize the making of
     any distribution to all holders of Common Stock;

             (b) the Company shall authorize the issuance to all Holders of
     Common Stock of any additional shares of Common Stock or Common Stock
     Equivalents or of any other subscription rights, options or warrants;

             (c) a dissolution, liquidation or winding up of the Company shall
     be proposed; or

             (d) a capital reorganization or reclassification of the Common
     Stock (other than a subdivision or combination of the outstanding Common
     Stock and other than a change in the par value of the Common Stock) or any
     consolidation or merger of the Company with or into another corporation
     (other than a consolidation or merger in which the Company is the
     continuing corporation and that does not result in any
<PAGE>
 
     reclassification or change of Common Stock outstanding) or any sale or
     conveyance to another corporation of the property of the Company as an
     entirety or substantially as an entirety.

Such giving of notice shall be initiated at least 10 Business Days prior to the
date fixed as a record date or effective date or the date of closing of the
Company's stock transfer books for the determination of the shareholders
entitled to such dividend, distribution or subscription rights, or for the
determination of the shareholders entitled to vote on such proposed merger,
consolidation, sale, conveyance, dissolution, liquidation or winding up. Such
notice shall specify such record date or the date of closing the stock transfer
books, as the case may be. Failure to provide such notice shall not affect the
validity of any action taken in connection with such dividend, distribution or
subscription rights, or proposed merger, consolidation, sale, conveyance,
dissolution, liquidation or winding up.

     Section 4.2 Lost, Stolen, Mutilated or Destroyed Warrants. If this Warrant
is lost, stolen, mutilated or destroyed, the Company may, on such terms as to
indemnity or otherwise as it may in its discretion impose (which shall, in the
case of a mutilated Warrant, include the surrender thereof), issue a new Warrant
of like denomination and tenor as, and in substitution for, this Warrant.


                                   ARTICLE 5

                        SPLIT-UP, COMBINATION, EXCHANGE
                            AND TRANSFER OF WARRANTS

     Section 5.1 Split-Up, Combination, Exchange and Transfer of Warrants.
Subject to the provisions of Section 5.2 hereof, this Warrant may be split-up,
combined or exchanged for another Warrant or Warrants containing the same terms
to purchase a like aggregate number of shares of Common Stock. If the
Warrantholder desires to split-up, combine or exchange this Warrant, the
Warrantholder shall make such request in writing delivered to the Company and
shall surrender to the Company this Warrant and any other Warrants to be so
split-up, combined or exchanged. Upon any such surrender for a split-up,
combination or exchange, the Company shall execute and deliver to the person
entitled thereto a Warrant or Warrants, as the case may be, as so requested. The
Company shall not be required to effect any split-up, combination or exchange
which will result in the issuance of a Warrant entitling the Warrantholder to
purchase upon exercise a fraction of a share of Common Stock or a fractional
Warrant. The Company may require such Warrantholder to pay a sum sufficient to
cover any tax or governmental charge that may be imposed in connection with any
split-up, combination or exchange of Warrants.

     Section 5.2 Restrictions on Transfer. This Warrant is registered on the
books of the Company and is transferable only by surrender thereof at the
principal office of the Company duly endorsed or accompanied by a written
instrument of transfer duly executed by the Warrantholder or its attorney duly
authorized in writing. This Warrant or the subject
<PAGE>
 
Shares may not be resold, transferred or disposed of in any manner unless
registered under applicable federal and state securities laws or an exemption
from registration is available and the holder obtains an opinion of counsel
satisfactory to the Company that such exemption is available and that transfer
will not jeopardize the Company's reliance on the exemption from registration in
connection with the issuance hereof. If at the time of a Transfer, a
Registration Statement is not in effect to register this Warrant or the subject
Shares, the Company may require the Warrantholder to make such representations,
and may place such legends on certificates representing this Warrant or the
subject Shares, as may be reasonably required in the opinion of counsel to the
Company to permit a Transfer without such registration.

     Section 5.3 Redemption. The Warrants are not redeemable by the Company.


                                   ARTICLE 6

                 REGISTRATION UNDER THE SECURITIES ACT OF 1933

     Section 6.1 Piggyback Registration of Common Stock.

             (a) If the Company proposes to register any of its Common Stock
     under the Securities Act, on any Registration Statement, whether or not for
     its own account (other than by a registration statement on Form S-8 or
     other form which does not include substantially the same information as
     would be required in a form for the general registration of securities,
     would not be available for the Common Stock or relates to any employee
     benefit plan or reorganization of the Company), it shall as expeditiously
     as possible give written notice to all Holders of such Holders' Piggyback
     Registration Rights as set forth in this Section 6.1. Upon the written
     request (which request shall, if applicable, specify that Holder shall be
     required to convert the shares and the number of shares of Registrable
     Securities intended to be sold by such Holder after conversion) of any
     Holder made within 20 days after receipt of any such notice, the Company
     shall (subject to the additional terms of these Articles) include in the
     Registration Statement the Registrable Securities which the Company has
     been so requested to register by the Holder thereof and the Company shall
     keep such registration statement in effect and maintain compliance with
     each federal and state law or regulation for the period necessary for such
     Holder to effect the proposed sale or other disposition (but in no event
     for a period greater than 120 days).

             (b) If, at any time after giving written notice of its intention to
     register Registrable Securities in a Piggyback Registration but prior to
     the effective date of the related Registration Statement, the Company shall
     determine for any reason not to register any Common Stock, the Company
     shall give notice of such determination to each Holder and, thereupon,
     shall be relieved of its obligation to register any Registrable Securities
     in connection with such Piggyback Registration (and shall not convert any
     of the shares into shares of Common Stock pursuant to Section 4, if
     applicable). All best efforts obligations of the Company shall cease if the
     Company
<PAGE>
 
     determines to terminate prior to such effective date any registration
     pursuant to this Section 6.1.

             (c) If a Piggyback Registration involves an offering by or through
     underwriters, all Holders requesting to have their Registrable Securities
     included in the Company's Registration Statement must sell their
     Registrable Securities to the underwriters selected by the Company on the
     same terms and conditions as apply to other selling shareholders, and any
     Holder requesting to have its Registrable Securities included in such
     Registration Statement may elect in writing, not later than three business
     days prior to the effectiveness of the Registration Statement filed in
     connection with such registration, not to have its Registrable Securities
     so included in connection with such registration.

             (d) If a Piggyback Registration involves an offering by or through
     underwriters, the Company, except as otherwise provided herein, shall not
     be required to include Registrable Securities therein if and to the extent
     the underwriter managing the offering reasonably believes in good faith and
     advises each Holder requesting to have Registrable Securities included in
     the Company's Registration Statement that such inclusion would materially
     adversely affect such offering, provided that if other selling shareholders
     who are employees, officers, directors or other affiliates of the Company
     have requested registration of securities in the proposed offering, the
     Company will reduce or eliminate such other selling shareholders'
     securities before any reduction or elimination of Registrable Securities
     held by Holders, and any such reduction or elimination (after taking into
     account the effect of preceding clause) shall be pro rata to all other
     holders of the securities of the Company exercising "Piggyback Registration
     Rights" similar to those set forth herein in proportion to the respective
     number of shares of Registrable Securities they have requested to be
     registered.

     Section 6.2 Payment of Registration Expenses. The Company shall pay all
expenses in connection with the registration of Registrable Securities other
than underwriters' fees, discounts, concessions or expenses, or attorneys fees
of any attorney representing the selling Holders. All fees and expenses (other
than registration expenses otherwise required to be paid) of any managing
underwriter, any co-manager or any independent underwriter or other independent
price required under the rules of NASD shall be paid for by such underwriters.

     Section 6.3 Indemnification.

             (a) In connection with each Registration Statement relating to
     disposition of Registrable Securities, the Company shall indemnify and hold
     harmless each Holder and each underwriter of Registrable Securities and
     each Person, if any, who controls such Holder or underwriter (within the
     meaning of Section 15 of the Securities Act or Section 20 of the Exchange
     Act) against any and all losses, claims, damages and
<PAGE>
 
     liabilities, joint or several (including any reasonable investigation,
     legal and other expenses incurred in connection with, and any amount paid
     in settlement of any action, suit or proceeding or any claim asserted), to
     which they, or any of them, may become subject under the Securities Act,
     the Exchange Act or other federal or state law or regulation, at common law
     or otherwise, insofar as such losses, claims, damages or liabilities arise
     out of or are based upon any untrue statement or alleged untrue statement
     of a material fact contained in any Registration Statement, prospectus or
     preliminary prospectus or any amendment thereof or supplement thereto, or
     arise out of or are based upon any omission or alleged omission to state
     therein a material fact required to be stated therein or necessary to make
     the statements therein not misleading; provided, however, that such
     indemnity shall not inure to the benefit of any Holder or underwriter (or
     any Person controlling such Holder or underwriter within the meaning of
     Section 15 of the Securities Act or Section 20 of the Exchange Act) on
     account of any losses, claims, damages or liabilities arising from the sale
     of the Registrable Securities if such untrue statement or omission or
     alleged untrue statement or omission was made in such Registration
     Statement, prospectus or preliminary prospectus, or such amendment or
     supplement, in reliance upon and in conformity with information furnished
     in writing to the Company by the Holder or underwriter specifically for use
     therein. The Company shall also indemnify selling brokers, dealer managers
     and similar securities industry professionals participating in the
     distribution, their officers and directors and each Person who controls
     such Persons (within the meaning of Section 15 of the Securities Act or
     Section 20 of the Exchange Act) to the same extent as provided above with
     respect to the indemnification of the Holders if requested. This indemnity
     agreement shall be in addition to any liability which the Company may
     otherwise have.

             (b) In connection with each Registration Statement, each Holder
     shall indemnify, to the same extent as the indemnification provided by the
     Company in Section 6.3(a), the Company, its directors and each officer who
     signs the Registration Statement and each Person who controls the Company
     (within the meaning of Section 15 of the Securities Act or Section 20 of
     the Exchange Act) but only insofar as such losses, claims, damages and
     liabilities arise out of or are based upon any untrue statement or omission
     or alleged untrue statement or omission which was made in the Registration
     Statement, the prospectus or preliminary prospectus or any amendment
     thereof or supplement thereto, in reliance upon and in conformity with
     information furnished in writing by such Holder to the Company specifically
     for use therein. The Company shall be entitled to receive indemnities from
     underwriters, selling brokers, dealer managers and similar securities
     industry professionals participating in the distribution, to the same
     extent as provided above, with respect to information so furnished in
     writing by such Persons specifically for inclusion in any prospectus,
     Registration Statement or preliminary prospectus or any amendment thereof
     or supplement thereto.
<PAGE>
 
             (c) Any party that proposes to assert the right to be indemnified
     hereunder will, promptly after receipt of notice of commencement of any
     action, suit or proceeding against such party in respect of which a claim
     is to be made against an indemnifying party or parties under this Section
     6.3, notify each such indemnifying party of the commencement of such
     action, suit or proceeding, enclosing a copy of all papers served.  No
     indemnification provided for in Section 6.3(a) or 6.3(b) shall be available
     to any party who shall fail to give notice as provided in this Section
     6.3(c) if the party to whom notice was not given was unaware of the
     proceeding to which such notice would have related and was prejudiced by
     the failure to give such notice, but the omission so to notify such
     indemnifying party of any such action, suit or proceeding shall not relieve
     it from any liability that it may have to any indemnified party for
     contribution or otherwise than under this Section 6.3.  In case any such
     action, suit or proceeding shall be brought against any indemnified party
     and it shall notify the indemnifying party of the commencement thereof, the
     indemnifying party shall be entitled to participate in, and, to the extent
     that it shall wish, jointly with any other indemnifying party similarly
     notified, to assume the defense thereof, with counsel satisfactory to such
     indemnified party, and after notice from the indemnifying party to such
     indemnified party of its election so to assume the defense thereof and the
     approval by the indemnifying party to such indemnified party of its
     election so to assume the defense thereof and the approval by the
     indemnified party of such counsel, the indemnifying party shall not be
     liable to such indemnified party for any legal or other expenses, except as
     provided below and except for the reasonable costs of investigation
     subsequently incurred by such indemnified party in connection with the
     defense thereof. The indemnified party shall have the right to employ its
     counsel in any such action, but the fees and expenses of such counsel shall
     be at the expense of such indemnified party, unless the employment of
     counsel by such indemnified party has been authorized in writing by the
     indemnifying parties, the indemnified party shall have reasonably concluded
     that there may be a conflict of interest between the indemnifying parties
     and the indemnified party in the conduct of the defense of such action (in
     which case the indemnifying parties shall not have the right to direct the
     defense of such action on behalf of the indemnified party), or the
     indemnifying parties shall not have employed counsel to assume the defense
     of such action within a reasonable time after notice of the commencement
     thereof, in each of which case the fees and expenses of counsel shall be at
     the expense of the indemnifying parties.  An indemnifying party shall not
     be liable for any settlement of any action, suit, proceeding or claim
     effected without its written consent.

             (d) In connection with each Registration Statement relating to the
     disposition of Registrable Securities if the indemnification provided for
     in subsection (a) hereof is unavailable to an indemnified party thereunder
     in respect to any losses, claims, damages or liabilities referred to
     therein, then the Company shall in lieu of indemnifying such indemnified
     party, contribute to the amount paid or payable by such indemnified party
     as a result of such losses, claims, damages or liabilities.  The amount to
     be contributed by the Company hereunder shall be an amount which is in the
     same
<PAGE>
 
     proportionate relationship to the total amount of such losses, claims,
     damages or liabilities as the total net proceeds from the offering (before
     deducting expenses) of the Registrable Securities bears to the total price
     to the public (including underwriters' discounts) for the offering of the
     Common Stock covered by such registration.

 
                                   ARTICLE 7

                                 OTHER MATTERS

     Section 7.1 Successors and Assigns. All covenants and provisions of this
Warrant by or for the benefit of the Company shall bind and inure to the benefit
of its successors and assigns hereunder.

     Section 7.2 No Inconsistent Agreements. The Company will not on or after
the date of this Warrant enter into any agreement with respect to its securities
which is inconsistent with the rights granted to the Holders in this Warrant or
otherwise conflicts with the provisions hereof. The rights granted to the
Holders hereunder do not in any way conflict with and are not inconsistent with
the rights granted to Holders of the Company's securities under any other
agreements.

     Section 7.3 Adjustments Affecting Registrable Securities. The Company will
not take any action outside the ordinary course of business, or permit any
change within its control to occur outside the ordinary course of business, with
respect to the Registrable Securities which is without a bona fide business
purpose, and which is intended to interfere with the ability of the Holders of
Registrable Securities to include such Registrable Securities in a registration
undertaken pursuant to this Warrant.

     Section 7.4 Integration/Entire Agreement. This Warrant is intended by the
parties as a final expression of their agreement and intended to be a complete
and exclusive statement of the agreement and understanding of the parties hereto
in respect of the subject matter contained herein. There are no restrictions,
promises, warranties or undertakings, other than those set forth or referred to
herein with respect to the registration rights granted by the Company with
respect to the Warrants. This Warrant supersedes all prior agreements and
understandings between the parties with respect to such subject matter (other
than warrants previously issued by the Company to the Warrantholder).

     Section 7.5 Amendments and Waivers. The provisions of this Warrant,
including the provisions of this sentence, may not be amended, modified or
supplemented. and waiver or consents to departures from the provisions hereof
may not be given unless the Company has obtained the written consent of Holders
of at least a majority of the outstanding Registrable Securities. Holders shall
be bound by any consent authorized by this Section whether or not certificates
representing such Registrable Securities have been marked to indicate such
consent.
<PAGE>
 
     Section 7.6 Governing Law. This Warrant shall be governed by and construed
in accordance with the internal laws of the State of Arizona without regard to
choice of law principles.

     Section 7.7 Severability. In the event that any one or more of the
provisions contained herein, or the application thereof in any circumstances, is
held invalid, illegal or unenforceable, the validity, legality and
enforceability of any such provisions in every other respect and of the
remaining provisions contained herein shall not be affected or impaired thereby.

     Section 7.8 Attorneys' Fees. In any action or proceeding brought to enforce
any provisions of this Warrant, or where any provisions hereof or thereof is
validly asserted as a defense, the successful party shall be entitled to recover
reasonable attorneys' fees and disbursements in addition to its costs and
expenses and any other available remedy.

     Section 7.9 Computations of Consent. Whenever the consent or approval of
Holders of a specified percentage of Registrable Securities is required
hereunder, Registrable Securities held by the Company or its affiliates (other
than the Warrantholder or subsequent Holders if they are deemed to be such
affiliates solely by reason of their holdings of such Registrable Securities)
shall not be counted in determining whether such consent or approval was given
by the Holders of such required percentage.

     Section 7.10 Notice. Any notices or certificates by the Company to the
Warrantholder and by the Warrantholder to the Company shall be deemed delivered
if in writing and delivered in person or by registered mail (return receipt
requested) to the Warrantholder at the address as set forth on the books and
records of the Company and to the Company at the address set forth in Section
2.2(a) hereof.

     In Witness Whereof, this Warrant has been duly executed by the Company
under its corporate seal as of this 21st day of January, 1998.
                                    ----                      

                                     National Environmental Service Co.


                                     By: /s/ Eddy L. Patterson
                                         ------------------------------
                                         Eddy L. Patterson, President
Attest:


  /s/ Larry G. Johnson
-----------------------------
Larry G. Johnson, Secretary
<PAGE>
 
                                   ASSIGNMENT

(To be executed only upon assignment of Warrant)


     For value received, ____________________ hereby sells, assigns and
transfers unto _________________________ the within Common Stock Purchase
Warrant, together with all right, title and interest therein, and does hereby
irrevocably constitute and appoint ________________ attorney, to transfer the
same on the books of the within-named Company with respect to the number of
Warrants set forth below, with full power of substitution in the premises:

          Name of Assignee and Address    No. of Warrants
          ----------------------------    ---------------



And if such number of Warrants shall not be all the Warrants represented by the
Common Stock Purchase Warrant, a new Common Stock Purchase Warrant is to be
issued in the name of the undersigned for the balance remaining of the Warrants
registered on the books of the Company.


Dated:
_____________________________         _____________________________
                                      Signature

                                      _____________________________
                                      Print Name

Note: The above signature should correspond exactly with the name on the face of
this Common Stock Purchase Warrant.
<PAGE>
 
                               SUBSCRIPTION FORM

                   (To be executed upon exercise of Warrant)

                                                    :
----------------------------------------------------

     The undersigned hereby irrevocably elects to exercise the right of
purchaser represented by the within Common Stock Purchase Warrant for, and to
purchase thereunder _____ shares of Common Stock as provided for therein, and
tenders herewith payment of the purchase price in full in the form of cash or a
certified or official bank check in the amount of $______________.

     The undersigned confirms and represents that the shares of Common Stock
being acquired pursuant hereto are being acquired for the undersigned's own
account and for investment and not with a view to, or for resale in connection
with, any distribution of such shares.  The undersigned is aware that the shares
subscribed for hereby are being sold pursuant to an exemption from registration
under the Securities Act of 1933, as amended (the "Securities Act"), and
pursuant to an exemption from registration under state securities laws. The
undersigned is aware that the shares may not be sold, assigned or transferred
unless (i) such sale, assignment or transfer is registered under the Securities
Act and other applicable state securities laws, and (ii) such sale, assignment
or transfer is exempt from registration under the Securities Act and such other
state securities laws and the Company is provided with an opinion of counsel
reasonably satisfactory to the Company that the shares may be sold pursuant to
such exemption.

     Please issue a certificate or certificates for such Common Stock in the
name of, and pay any cash for any fractional share to:
 
 
               -------------------------------------------------------------

               -------------------------------------------------------------
               (Please print Name, Address and Social Security No.)

 
               -------------------------------------------------------------
               Signature

               Note: The above signature should correspond exactly with the name
               on the first page of the within Common Stock Purchase Warrant or
               with the name of the assignee appearing in the assignment form
               below.

     If such number of shares shall not be all the shares purchasable under the
within Common Stock Purchase Warrant, a new Common Stock Purchase Warrant is to
be issued in the name of the undersigned for the balance remaining of the shares
purchasable thereunder rounded up to the next higher number of shares.