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                                 EMPLOYMENT AGREEMENT

     This EMPLOYMENT AGREEMENT (this "Agreement") is made as of April 30, 
1998 between Hach Company, a Delaware corporation (the "Company"), and Mark 
Stephenson (the "Executive").

                                  R E C I T A L S

     A.   Company is a major manufacturer and distributor of laboratory 
instruments, process analyzers, test kits and chemical reagents primarily 
used to analyze the chemical content and other properties of water.

     B.   Company and Environmental Test Systems, Inc., an Indiana 
corporation), have entered into an Agreement and Plan of Merger ("Merger 
Agreement") dated January 21, 1998, as amended as of February 26, 1998, 
pursuant to which Environmental Test Systems, Inc. will merge into a 
wholly-owned subsidiary of the Company (the "Merger") with the surviving 
company being a wholly owned subsidiary of the Company with its name changed 
to "Environmental Test Systems, Inc."  As used herein "ETS" shall mean both 
Environmental Test Systems, Inc. prior to the Merger and the surviving 
corporation in the Merger. 

     C.   Executive has served as the President of ETS, and the Company 
wishes to employ Executive from and after the closing of the Merger as a 
Vice-President of the Company and to work for Company and ETS, upon the terms 
and conditions set forth in this Agreement.

     D.   In the course of his employment, Executive has or will have 
knowledge of or access to, important trade secrets and confidential 
information of the Company and ETS and their affiliates.

                            AGREEMENT

     The parties, intending to be legally bound, agree as follows:

1.   DEFINITIONS

     For the purposes of this Agreement, the following terms have the 
meanings specified or referred to in this Section 1.

     "AFFILIATE" means any Person which controls, is controlled by, or is 
under common control with, the Company, and shall include, without 
limitation, the parent or subsidiary of the Company, if any.

     "AGREEMENT" means this Employment Agreement, as amended from time to 
time.

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     "BENEFITS" shall have the meaning given it in Section 3.2.

     "BOARD OF DIRECTORS" means the board of directors of the Company.

     "CONFIDENTIAL INFORMATION" means any and all:

     (a)  trade secrets concerning the business and affairs of the Company 
and its Affiliates, product specifications, data, know-how, formulae, 
compositions, processes, designs, sketches, photographs, graphs, drawings, 
samples, inventions and ideas, past, current, and planned research and 
development, current and planned manufacturing or distribution methods and 
processes, customer lists, current and anticipated customer requirements, 
price lists, market studies, business plans, computer software and programs 
(including object code and source code), computer software and database 
technologies, systems, structures, and architectures (and related formulae, 
compositions, processes, improvements, devices, know-how, inventions, 
discoveries, concepts, ideas, designs, methods and information) and any other 
information, however documented, that is a trade secret within the meaning of 
applicable Colorado and Indiana trade secret law; and

     (b)  information concerning the business and affairs of the Company and 
its Affiliates (which includes historical financial statements, financial 
projections and budgets, historical and projected sales, capital spending 
budgets and plans, the names and backgrounds of key personnel, personnel 
training and techniques and materials), however documented; and

     (c)  notes, analysis, compilations, studies, summaries, and other 
material prepared by or for the Company and its Affiliates containing or 
based, in whole or in part, on any information included in the foregoing.

     "DISABILITY" shall have the meaning given it in Section 6.2.

     "EFFECTIVE DATE" means the date stated in the first paragraph of the 
Agreement.

     "EMPLOYEE INVENTION" means any idea, invention, technique, modification, 
process, or improvement (whether patentable or not), any industrial design 
(whether registrable or not), any mask work, however fixed or encoded, that 
is suitable to be fixed, embedded or programmed in a semiconductor product 
(whether recordable or not), and any work of authorship (whether or not 
copyright protection may be obtained for it) created, conceived, or developed 
by the Executive, either solely or in conjunction with others, during the 
Employment Period, or a period that includes a portion of the Employment 
Period, that relates in any way to, or is useful in any manner in, the 
business then being conducted or proposed to be conducted by the Company and 
its Affiliates, and any such item created by the Executive, either solely or 
in conjunction with others, following termination of the Executive's 
employment with the Company or its Affiliates, that is based upon or uses 
Confidential Information.

     "EMPLOYMENT PERIOD" means the term of the Executive's employment under 
this Agreement.

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     "FOR CAUSE" shall have the meaning given it in Section 6.3.

     "PERSON" means any individual, corporation (including any non-profit 
corporation), general or limited partnership, limited liability company, 
joint venture, estate, trust, association, organization, or governmental body.

     "POST-EMPLOYMENT PERIOD" shall have the meaning given it in Section 8.2.

     "PROPRIETARY ITEMS" shall have the meaning given it in Section 
7.2(a)(iv).

     "SALARY" shall have the meaning given it in Section 3.1.

2.   EMPLOYMENT TERMS AND DUTIES

     2.1  EMPLOYMENT

     The Company hereby employs the Executive, and the Executive hereby 
accepts employment by the Company, upon the terms and conditions set forth in 
this Agreement.

     2.2  TERM

     (a)  INITIAL TERM.  Subject to the provisions of Section 6, the term of 
the Executive's employment under this Agreement will be for the period from 
the Effective Date through April 30, 2001, unless renewed in accordance with 
the provisions of Section 2.2(b).

     (b)  RENEWAL.  Subject to the provisions of Section 6, in the event the 
term of this Agreement ends on April 30, 2001, and Executive continues in the 
employment of the Company to that date without any of the events set forth in 
Section 6.1 having previously occurred, the term of this Agreement shall 
automatically be extended for an additional one year period (and thereafter, 
annually for successive additional one year periods) commencing May 1, 2001 
(and each May 1 thereafter) unless either party gives the other written 
notice of his or its intent not to renew by December 1, 2000 (and annually, 
by any December 1 thereafter).

     2.3  DUTIES

     The Executive will have such duties as are assigned or delegated to the 
Executive by the Board of Directors or Chief Executive Officer of the 
Company, and will initially serve as a Vice-President of the Company and 
President of ETS.  At all times during the term hereof, Executive shall be 
employed in an executive position with the Company. The Executive 
acknowledges that he may be assigned to provide services to or on behalf of 
the Company's Affiliates as part of his duties under this Agreement. The 
Executive will devote his entire business time, attention, skill, and energy 
exclusively to the business of the Company and its 

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Affiliates, will use his best efforts to promote the success of the business 
of the Company and its Affiliates, and will cooperate fully with the Board of 
Directors in the advancement of the best interests of the Company and its 
Affiliates.  If the Executive is elected as a director of the Company or as a 
director or officer of any of its Affiliates, the Executive will fulfill his 
duties as such director or officer without additional compensation.

3.   COMPENSATION

     3.1  SALARY.  

     The Executive will be paid an annual salary (the "Salary") during the 
term of this Agreement of $155,000.00 which shall be prorated for the period 
between the date of this Agreement and April 30, 1998. The Company by action 
of its Board of Directors reserves the right to increase, but not decrease, 
the Executive's Salary during the Term of this Agreement. The Salary will be 
payable in equal periodic installments according to the Company's customary 
payroll practices.  In the event the term of the Agreement is renewed beyond 
April 30, 2001, the Company and Executive will negotiate in good faith with 
respect to an annual salary for the renewal terms.

     3.2  BENEFITS.  The Executive will, during the Employment Period, be 
permitted to participate in such stock option, pension, profit sharing, 
bonus, life insurance, hospitalization, major medical, and other employee 
benefit plans of the Company that may be in effect from time to time, to the 
extent the Executive is and remains eligible under the terms of those plans 
(collectively, the "Benefits").

4.   EXPENSES

     (a)  The Company will pay on behalf of the Executive (or reimburse the 
Executive for) reasonable expenses incurred by the Executive at the request 
of, or on behalf of, the Company or its Affiliates in the performance of the 
Executive's duties pursuant to this Agreement, and in accordance with the 
Company's employment policies, including reasonable expenses incurred by the 
Executive in attending conventions, seminars, and other business meetings, in 
appropriate business entertainment activities, and for promotional expenses. 
The Executive must file expense reports prior to reimbursement with respect 
to such expenses in accordance with the Company's policies.

     (b)  The Company will pay for or reimburse Executive for all reasonable 
costs of moving his residence from Elkhart, Indiana to Loveland, Colorado.

5.   VACATIONS AND HOLIDAYS

     The Executive will be entitled to a paid vacation each year in 
accordance with the vacation policies of the Company in effect for its 
executive officers from time to time with seniority credit being given toward 
vacation eligibility for all years of service with ETS but without credit for 
accumulated vacation days not taken while employed by ETS. Vacation must be 
taken by the Executive at such time or times as approved by the Chairman of 
the Board or Chief Executive 

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Officer.  The Executive will also be entitled to the paid holidays set forth 
in the Company's policies.

6.   TERMINATION

     6.1  EVENTS OF TERMINATION

     Notwithstanding anything in this Agreement to the contrary, the term of 
Executive's employment under this Agreement, and any and all other rights of 
the Executive under this Agreement or otherwise as an employee of the 
Company, will terminate (except as otherwise provided in this Section 6):

     (a)  upon the death of the Executive;

     (b)  upon the disability of the Executive (as defined in Section 6.2) on 
the tenth (10) day following notice from either party to the other; or

     (c)  for cause (as defined in Section 6.3).

     6.2  DEFINITION OF DISABILITY

     For purposes of Section 6.1, the Executive will be deemed to have a 
"disability" if, for physical or mental reasons, the Executive is unable to 
perform the essential functions of the Executive's duties under this 
Agreement for 90 consecutive days, or 120 days during any twelve month 
period, as determined in accordance with this Section 6.2.  Prior to the 
tenth (10th) day after he receives notice from the Company that it is 
terminating this Agreement due to the disability of the Executive, the 
Executive may notify the Company in writing that he disputes the Company's 
assertion of his disability.  In such event, the disability of the Executive 
will be determined by a licensed medical doctor selected by the Company and 
reasonably acceptable to the Executive.  If the Company and the Executive 
cannot agree on the selection of a medical doctor within ten (10) days of 
Executive's notice of dispute, each of them will promptly select a medical 
doctor and the two medical doctors will select a third medical doctor who 
will determine whether the Executive has a disability.  The determination of 
the medical doctor selected under this Section 6.2 will be binding on both 
parties.  The Executive must submit to a reasonable number of examinations by 
the medical doctor making the determination of disability under this Section 
6.2, and the Executive hereby authorizes the disclosure and release to the 
Company of such determination and all supporting medical records.  If the 
Executive is not legally competent, the Executive's legal guardian or duly 
authorized attorney-in-fact will act in the Executive's stead, under this 
Section 6.2, for the purposes of submitting the Executive to the 
examinations, and providing the authorization of disclosure, required under 
this Section 6.2.

     6.3  DEFINITION OF "FOR CAUSE"

     For purposes of Section 6.1, the phrase "for cause" means: (a) the 
breach of a material provision of this Agreement by the Executive which 
continues uncured for 10 days after receipt 

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by the Executive of written notice of such breach from the Company; (b) the 
Executive's failure to comply with or adhere to any written policy of the 
Company or its Affiliates which failure continues for 10 days after receipt 
by the Executive of written notice from the Company which specifically 
identifies such failure; (c) the appropriation (or attempted appropriation) 
of a business opportunity of the Company or its Affiliates, including 
attempting to secure or securing any personal profit in connection with any 
transaction entered into on behalf of the Company or its Affiliates; (d) the 
misappropriation (or attempted misappropriation) of any of the funds or 
property of the Company or its Affiliates; (e) the conviction of, or the 
entering of a guilty plea or plea of no contest with respect to, Executive's 
commission of any criminal offense which involves dishonesty or breach of 
trust; or (f) any willful conduct by the Executive which is demonstrably and 
materially injurious to the reputation of the Company or its Affiliates.  The 
termination of the Executive's employment hereunder shall not be deemed "for 
cause" unless and until there shall have been delivered to the Executive a 
copy of a resolution duly adopted by the affirmative vote of not less than a 
majority of the entire membership of the Board at a meeting of the Board 
called and held for that purpose (after reasonable notice to and an 
opportunity for the Executive to be heard before the Board with 
representation by counsel if Executive so desires), finding that in the good 
faith opinion of the Board, the Executive was guilty of the conduct set forth 
in any one or more of clauses (a) through (f) above.

     6.4  TERMINATION PAY

     Effective upon the termination of this Agreement, the Company will be 
obligated to pay the Executive (or, in the event of his death, his designated 
beneficiary as defined below) only such compensation as is provided in this 
Section 6.4, and in lieu of all other amounts and in settlement and complete 
release of all claims the Executive may have against the Company and its 
Affiliates. For purposes of this Section 6.4, the Executive's designated 
beneficiary will be such individual beneficiary or trust, located at such 
address, as the Executive may designate by notice to the Company from time to 
time or, if the Executive fails to give notice to the Company of such a 
beneficiary, the Executive's estate.  Notwithstanding the preceding sentence, 
the Company will have no duty, in any circumstances, to attempt to open an 
estate on behalf of the Executive, to determine whether any beneficiary 
designated by the Executive is alive or to ascertain the address of any such 
beneficiary, to determine the existence of any trust, to determine whether 
any person or entity purporting to act as the Executive's personal 
representative (or the trustee of a trust established by the Executive) is 
duly authorized to act in that capacity, or to locate or attempt to locate 
any beneficiary, personal representative, or trustee.

     (a)  TERMINATION BY THE COMPANY FOR CAUSE. If the Company terminates 
this Agreement for cause, the Executive will be entitled to receive his 
Salary only through the date such termination is effective without prejudice 
as to the Company's rights to pursue any other remedy available to it at law 
or in equity.

     (b)  TERMINATION UPON DISABILITY.  If this Agreement is terminated by 
either party as a result of the Executive's disability, as determined under 
Section 6.2, the Company will pay the Executive his Salary through the 
remainder of the calendar month during which such termination 


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is effective.  Any bonuses which the Executive would have become entitled to 
for the fiscal year in which termination occurs, shall when determined, be 
prorated and paid to the termination date.

     (c)  TERMINATION UPON DEATH.  If this Agreement is terminated because of 
the Executive's death, the Executive will be entitled to receive his Salary 
through the end of the calendar month in which his death occurs. Any bonuses 
which the Executive would have become entitled to had he lived throughout the 
full fiscal year under the Company's Officers Bonus Plan when determined for 
the year in which the Executive's death occurred shall be prorated and paid 
to the date of death.

     (d)  BENEFITS.  The Executive's accrual of, or participation in plans 
providing for, the Benefits will cease at the effective date of the 
termination or non-renewal of this Agreement, and the Executive will be 
entitled to accrued Benefits pursuant to such plans only as provided in such 
plans.

7.   NON-DISCLOSURE COVENANT; EMPLOYEE INVENTIONS

     7.1  ACKNOWLEDGMENTS BY THE EXECUTIVE

     The Executive acknowledges that (a) during the Employment Period and as 
a part of his employment, the Executive was afforded access to Confidential 
Information; (b) public disclosure of such Confidential Information could 
have an adverse effect on the Company and its business; (c) because the 
Executive possesses substantial technical expertise and skill with respect to 
the Business, the Company (or, as applicable, its Affiliates) desires to 
obtain exclusive ownership of each Employee Invention, and the Company (or, 
as applicable, its Affiliates) may be at a substantial competitive 
disadvantage if it fails to acquire exclusive ownership of each Employee 
Invention; and (d) the provisions of this Section 7 are reasonable and 
necessary to prevent the improper use or disclosure of Confidential 
Information and to provide the Company (or, as applicable, its Affiliates) 
with exclusive ownership of all Employee Inventions. 

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7.2  AGREEMENTS OF THE EXECUTIVE

     In consideration of the compensation and benefits to be paid or provided 
to the Executive by the Company or its Affiliates under this Agreement, the 
Executive covenants as follows:

     (a)  CONFIDENTIALITY.

          (i)    During and following the Employment Period, the Executive will
     hold in confidence the Confidential Information and will not disclose it to
     any person except with the specific prior written consent of the Company
     (or, as applicable, its Affiliates) or except as otherwise expressly
     permitted by the terms of this Agreement.

          (ii)   Any trade secrets of the Company or its Affiliates will be
     entitled to all of the protections and benefits under applicable Colorado
     trade secret law and any other applicable law.  If any information that the
     Company or its Affiliates deems to be a trade secret is found by a court of
     competent jurisdiction not to be a trade secret for purposes of this
     Agreement, such information will, nevertheless, be considered Confidential
     Information for purposes of this Agreement.  The Executive hereby waives
     any requirement that the Company or its Affiliates submit proof of the
     economic value of any trade secret or post a bond or other security.

          (iii)  None of the foregoing obligations and restrictions applies to
     any part of the Confidential Information that the Executive demonstrates
     was or became generally available to the public other than as a result of a
     disclosure by the Executive.

          (iv)   The Executive will not remove from the premises of the Company
     (or, as applicable, its Affiliates) (except to the extent such removal is
     for purposes of the performance of the Executive's duties at home or while
     traveling, or except as otherwise specifically authorized by the Company
     (or, as applicable, its Affiliates)) any document, record, notebook, plan,
     model, component, device, or computer software or code, whether embodied in
     a disk or in any other form (collectively, the "Proprietary Items").  The
     Executive recognizes that, as between the Company and its Affiliates and
     the Executive, all of the Proprietary Items, whether or not developed by
     the Executive, are the exclusive property of the Company (or, as
     applicable, its Affiliates).  Upon termination of this Agreement by either
     party, or upon the request of the Company (or, as applicable, its
     Affiliates) during the Employment Period, the Executive will return to the
     Company all of the Proprietary Items in the Executive's possession or
     subject to the Executive's control, and the Executive shall not retain any
     copies, abstracts, sketches, or other physical embodiment of any of the
     Proprietary Items.

     (b)  EMPLOYEE INVENTIONS.  Each Employee Invention will belong 
exclusively to the Company (or, as applicable, its Affiliates).  The 
Executive acknowledges that all of the Executive's writing, works of 
authorship, and other Employee Inventions are works made for hire and the 
property of the Company (or, as applicable, its Affiliates), including any 
copyrights, patents, or other intellectual property rights pertaining 
thereto.  If it is determined that any such 

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works are not works made for hire, the Executive hereby assigns to the 
Company (or, as applicable, its Affiliates) all of the Executive's right, 
title, and interest, including all rights of copyright, patent, and other 
intellectual property rights, to or in such Employee Inventions.  The 
Executive covenants that he will promptly:

          (i)    disclose to the Company (or, as applicable, its Affiliates) in
     writing any Employee Invention;

          (ii)   assign to the Company or to a party designated by the Company
     (or, as applicable, its Affiliates), at the request of the Company (or, as
     applicable, its Affiliates) and without additional compensation, all of the
     Executive's right to the Employee Invention for the United States and all
     foreign jurisdictions;

          (iii)  execute and deliver to the Company (or, as applicable, its
     Affiliates) such applications, assignments, and other documents as the
     Company (or, as applicable, its Affiliates) may request in order to apply
     for and obtain patents or other registrations with respect to any Employee
     Invention in the United States and any foreign jurisdictions;

          (iv)   sign all other papers necessary to carry out the above
     obligations; and

          (v)    give testimony and render any other assistance but without
     expense to the Executive in support of the rights of the Company (or, as
     applicable, its Affiliates) to any Employee Invention.

     7.3  DISPUTES OR CONTROVERSIES

     The Executive recognizes that should a dispute or controversy arising 
from or relating to this Agreement be submitted for adjudication to any 
court, arbitration panel, or other third party, the preservation of the 
secrecy of Confidential Information may be jeopardized.  All pleadings, 
documents, testimony, and records relating to any such adjudication will be 
maintained in secrecy and will be available for inspection by the Company 
(or, as applicable, its Affiliates), the Executive, and their respective 
attorneys and experts, who will agree, in advance and in writing, to receive 
and maintain all such information in secrecy, except as may be limited by 
them in writing.

8.   NON-COMPETITION AND NON-INTERFERENCE

     8.1  ACKNOWLEDGMENTS BY THE EXECUTIVE

     The Executive acknowledges that:  (a) the services to be performed by 
him under this Agreement are of a special, unique, unusual, extraordinary, 
and intellectual character; (b) the business of the Company and its 
Affiliates is national in scope and its products are marketed throughout the 
United States; (c) the Company and its Affiliates compete with other 
businesses that are or could be located in any part of the United States; and 
(d) the provisions of this Section 8 are reasonable and necessary to protect 
the business of the Company and its Affiliates.

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     8.2  COVENANTS OF THE EXECUTIVE

     In consideration of the acknowledgments by the Executive, and in 
consideration of the compensation and benefits to be paid or provided to the 
Executive by the Company and its Affiliates, the Executive covenants that he 
will not, directly or indirectly:

     (a)  during the Employment Period, except in the course of his 
employment hereunder, and during the Post-Employment Period, engage or invest 
in, own, manage, operate, finance, control, or participate in the ownership, 
management, operation, financing, or control of, be employed by, associated 
with, or in any manner connected with, lend the Executive's name or any 
similar name to, lend Executive's credit to or render services or advice to, 
any business whose products or activities compete in whole or in part with 
the products or activities of the Company or its Affiliates anywhere within 
the United States; provided, however, that the Executive may purchase or 
otherwise acquire up to (but not more than) one percent of any class of 
securities of any enterprise (but without otherwise participating in the 
activities of such enterprise) if such securities are listed on any national 
or regional securities exchange or have been registered under Section 12(g) 
of the Securities Exchange Act of 1934; and, provided further, that this 
covenant shall not preclude Executive from becoming employed full time in a 
position with a major public company in a capacity that does not involve 
participation in any competitive activities which may be carried on as a 
separate line of business by a division or affiliate of such company.

     (b)  whether for the Executive's own account or for the account of any 
other person, at any time during the Employment Period and the 
Post-Employment Period, solicit business of the same or similar type being 
carried on by the Company or its Affiliates, from any person known by the 
Executive to be a customer of the Company or its Affiliates, whether or not 
the Executive had personal contact with such person during and by reason of 
the Executive's employment with the Company or its Affiliates;

     (c)  whether for the Executive's own account or the account of any other 
person (i) at any time during the Employment Period and the Post-Employment 
Period, solicit, employ, or otherwise engage as an employee, independent 
contractor, or otherwise, any person who is or was an employee of the Company 
or its Affiliates at any time during the Employment Period or in any manner 
induce or attempt to induce any employee of the Company or its Affiliates to 
terminate his employment with the Company; or (ii) at any time during the 
Employment Period and the Post-Employment Period, interfere with the 
relationship of the Company or its Affiliates with any person, including any 
person who at any time during the Employment Period was an employee, 
contractor, supplier, or customer of the Company or its Affiliates; or

     (d)  at any time during or after the Employment Period, disparage the 
Company or its Affiliates or any of their shareholders, directors, officers, 
employees, or agents.

     For purposes of this Section 8.2, the term "Post-Employment Period" 
means the twelve month period beginning on the date of termination of the 
Executive's employment with the Company or its Affiliates.


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     The period of time applicable to any covenant in this Section 8.2 will 
be extended by the duration of any violation by the Executive of such 
covenant. The Executive will, while the covenant under this Section 8.2 is in 
effect, give notice to the Company, within ten days after accepting any other 
employment, of the identity of the Executive's employer.  The Company or its 
Affiliates may notify such employer that the Executive is bound by this 
Agreement and, at its election, may furnish such employer with a copy of this 
Agreement or relevant portions thereof.

     Notwithstanding the other provisions of this Section 8.2, Executive may, 
during the Employment Period and during the Post-Employment Period, continue 
to own a minority ownership interest in Serim Research Corporation.

9.   GENERAL PROVISIONS

     9.1  INJUNCTIVE RELIEF AND ADDITIONAL REMEDY

     The Executive acknowledges that the injury that would be suffered by the 
Company or its Affiliates as a result of a breach of the provisions of this 
Agreement (including any provision of Sections 7 and 8) would be irreparable 
and that an  award of monetary damages to the Company or its Affiliates for 
such a breach would be an inadequate remedy. Consequently, the Company and 
its Affiliates will have the right, in addition to any other rights it may 
have, to obtain injunctive relief to restrain any breach or threatened breach 
or otherwise to specifically enforce any provision of this Agreement, and 
none of the Company or its Affiliates will be obligated to post bond or other 
security in seeking such relief. Without limiting the rights of the Company 
or its Affiliates under this Section 9 or any other remedies of the Company, 
if the Executive breaches any of the provisions of Section 7 or 8, the 
Company (and its Affiliates, as applicable) will have the right to cease 
making any payments otherwise due to the Executive under this Agreement.

     9.2  COVENANTS OF SECTIONS 7 AND 8 ARE ESSENTIAL AND INDEPENDENT 
          COVENANTS

     The covenants by the Executive in Sections 7 and 8 are essential 
elements of this Agreement, and without the Executive's agreement to comply 
with such covenants, the Company would not have entered into this Agreement 
or employed or continued the employment of the Executive.

     The Executive's covenants in Sections 7 and 8 are independent covenants 
and the existence of any claim by the Executive against the Company under 
this Agreement or otherwise, will not excuse the Executive's breach of any 
covenant in Section 7 or 8.

     If the Executive's employment hereunder expires or is terminated, this 
Agreement will continue in full force and effect as is necessary or 
appropriate to enforce the covenants and agreements of the Executive in 
Sections 7 and 8.

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     9.3  OBLIGATIONS CONTINGENT ON PERFORMANCE

     The obligations of the Company hereunder, including its obligation to 
pay the compensation provided for herein, are contingent upon the Executive's 
performance of the Executive's obligations hereunder.

     9.4  WAIVER

     The rights and remedies of the parties to this Agreement are cumulative 
and not alternative. Neither the failure nor any delay by either party in 
exercising any right, power, or privilege under this Agreement will operate 
as a waiver of such right, power, or privilege, and no single or partial 
exercise of any such right, power, or privilege will preclude any other or 
further exercise of such right, power, or privilege or the exercise of any 
other right, power, or privilege.  To the maximum extent permitted by 
applicable law, (a) no claim or right arising out of this Agreement can be 
discharged by one party, in whole or in part, by a waiver or renunciation of 
the claim or right unless in writing signed by the other party; (b) no waiver 
that may be given by a party will be applicable except in the specific 
instance for which it is given; and (c) no notice to or demand on one party 
will be deemed to be a waiver of any obligation of such party or of the right 
of the party giving such notice or demand to take further action without 
notice or demand as provided in this Agreement.
          
     9.5  BINDING EFFECT; DELEGATION OF DUTIES PROHIBITED

     The Company may assign this Agreement to an Affiliate only with the 
prior written consent of the Executive.  This Agreement shall inure to the 
benefit of, and shall be binding upon, the parties hereto and their 
respective successors, assigns, heirs, and legal representatives, including 
any entity with which the Company may merge or consolidate or to which all or 
substantially all of its assets may be transferred.  The duties and covenants 
of the Executive under this Agreement, being personal, may not be assigned or 
delegated.

     9.6  NOTICES

     All notices, consents, waivers, and other communications under this 
Agreement must be in writing and will be deemed to have been duly given when 
(a) delivered by hand (with written confirmation of receipt), (b) sent by 
facsimile (with written confirmation of receipt), provided that a copy is 
mailed by registered mail, return receipt requested, or (c) when received by 
the addressee, if sent by a nationally recognized overnight delivery service 
(receipt requested), in each case to the appropriate addresses and facsimile 
numbers set forth below (or to such other addresses and facsimile numbers as 
a party may designate by notice to the other parties):


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<TABLE>
<CAPTION>

<S>                           <C>
If to Company:                Hach Company
                              5600 Lindbergh Drive
                              Loveland, Colorado 80538
                              Attention: Gary R. Dreher
                              Facsimile No.: (970) 962-6709



     With a copy (which       McBride Baker & Coles
     shall not constitute     500 West Madison Street
     notice) to:              40th Floor
                              Chicago, Illinois  60661
                              Attention:     Robert O. Case
                              Facsimile No.: (312) 993-9350


If to the Executive:          Mark Stephenson
     Office:                  Environmental Test Systems, Inc.
                              23575 County Road 106
                              P. O. Box 4659
                              Elkhart, IN 46514-0659
                              Facsimile No.: (219) 262-2495


     with a copy (which       William R. Neale, Esq.
     shall not constitute     Krieg, DeVault, Alexander & Capehart
               notice) to:    One Indiana Square, Suite 2800
                              Indianapolis, IN  46204-2017
                              Facsimile No. (317) 636-1507
</TABLE>

     
     9.7  ENTIRE AGREEMENT; AMENDMENTS

     This Agreement contains the entire agreement between the parties with 
respect to the subject matter hereof and supersede all prior agreements and 
understandings, oral or written, between the parties hereto with respect to 
the subject matter hereof.  This Agreement may not be amended orally, but 
only by an agreement in writing signed by the parties hereto.

                                      13

<PAGE>

     9.8  GOVERNING LAW

     This Agreement will be governed by the laws of the State of Colorado 
without regard to conflicts of laws principles.

          9.9    JURISDICTION

     Any action or proceeding seeking to enforce any provision of, or based 
on any right arising out of, this Agreement shall be brought against either 
of the parties exclusively in the federal and state  courts located in the 
State of Colorado and each of the parties consents to the jurisdiction of 
such courts (and of the appropriate appellate courts) in any such action or 
proceeding and waives any objection to venue laid therein.  Process in any 
action or proceeding referred  to in the preceding sentence may be served on 
either party anywhere in the world.

     9.10  SECTION HEADINGS; CONSTRUCTION

     The headings of Sections in this Agreement are provided for convenience 
only and will not affect its construction or interpretation. All references 
to "Section" or "Sections" refer to the corresponding Section or Sections of 
this Agreement unless otherwise specified.  All words used in this Agreement 
will be construed to be of such gender or number as the circumstances 
require.  Unless otherwise expressly provided, the word "including" does not 
limit the preceding words or terms.

     9.11  SEVERABILITY

     If any provision of this Agreement is held invalid or unenforceable by 
any court of competent jurisdiction, the other provisions of this Agreement 
will remain in full force and effect.  Any provision of this Agreement held 
invalid or unenforceable only in part or degree will remain in full force and 
effect to the extent not held invalid or unenforceable.

     9.12  COUNTERPARTS

     This Agreement may be executed in one or more counterparts, each of 
which will be deemed to be an original copy of this Agreement and all of 
which, when taken together, will be deemed to constitute one and the same 
agreement.

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<PAGE>

     9.13  WAIVER OF JURY TRIAL

     THE PARTIES HERETO HEREBY WAIVE A JURY TRIAL IN ANY LITIGATION WITH 
RESPECT TO THIS AGREEMENT.

          9.14    EFFECTIVENESS

     This Agreement is binding upon the parties as of the date of its 
execution but it shall become effective only as of the Effective Time of the 
Merger (as defined in the Merger Agreement.)  If the Merger does not occur, 
this Agreement shall be treated as being null and void.

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

                              HACH COMPANY


                              By: /s/ Bruce J. Hach
                                  -----------------------
                              Its: President


                              /s/ Mark Stephenson
                             --------------------
                              Mark Stephenson


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