EXHIBIT 2.4

                            STOCK PURCHASE AGREEMENT


         THIS STOCK  PURCHASE  AGREEMENT  ("Agreement")  dated  April 4, 1997,
1997,  among EMCON,  a California  corporation  ("Seller" or "EMCON"),  COLUMBIA
ANALYTICAL SERVICES,  INC., a Washington corporation ("CAS"), the members of the
senior  management  employee  group of CAS listed on the  signature  page hereto
("Management Purchasers") and NORTHWESTERN TRUST, as the trustee (the "Trustee")
of the COLUMBIA ANALYTICAL SERVICES, INC., EMPLOYEE STOCK OWNERSHIP TRUST ("ESOT
Purchaser").

                                R E C I T A L S:

         Pursuant  to a  Plan  of  Recapitalization  ("Recapitalization")  under
Section  368(a)(1)(E) of the Internal Revenue Code of 1986, as amended ("Code"),
a copy of which is attached  hereto as Exhibit A, the Seller owns the  following
shares  of stock in CAS:  1,250,000  shares  of  Class A Common  Stock  ("Common
Stock"),  4,000,000 shares of Class A Super Common Stock ("Super Common Stock"),
and 500,000 shares of Class A Preferred Stock  ("Preferred  Stock").  The Seller
desires to sell to ESOT  Purchaser and CAS certain of these shares in accordance
with the terms of this Agreement.

         NOW,  THEREFORE,  in consideration of the mutual covenants  hereinafter
contained, the parties hereby agree as follows:

                                   ARTICLE 1.
                           Purchase and Sale of Stock

     1.1 Purchase by ESOT Purchaser. Subject to the terms and conditions of this
Agreement, at the Closing, the Seller shall sell to the ESOT Purchaser,  and the
ESOT Purchaser shall purchase from the Seller,  4,000,000 shares of Super Common
Stock ("Super Common Shares") for a total purchase price of $5,000,000.

     1.2 Purchase by CAS. Subject to the terms and conditions of this Agreement,
at the Closing,  the Seller shall sell to CAS, and CAS shall  purchase  from the
Seller,  1,250,000 shares of Common Stock ("Common Shares") for a total purchase
price of $500,000.

     1.3 Stock  Retained by Seller.  Seller shall  retain the 500,000  shares of
Preferred Stock.

     1.4 Sale of Stock By CAS.  Subject  to the  terms  and  conditions  of this
Agreement,  within five (5) business days following  Closing,  CAS shall sell to
the Management Purchasers, and the Management Purchasers shall purchase from CAS
a total  of  461,538  shares  of  Common  Stock  for a total  purchase  price of
$300,000.  The shares of Common Stock shall be distributed  among the Management
Purchasers as shown on Schedule 1.4.

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     1.5 Options to Management  Purchasers.  At Closing, CAS shall grant options
to the  Management  Purchasers  to purchase the number of shares of Common Stock
shown on Schedule 1.5 hereof.  The Stock  Option  shall be in the form  attached
hereto as Exhibit 1.5.

                                   ARTICLE 2.
                            ESOT Purchaser Financing

         The  obligation of the ESOT  Purchaser to purchase the shares of Seller
as provided in Section 1.1 is  conditioned  upon ESOT  Purchaser  obtaining  the
necessary financing. ESOT Purchaser intends such financing to be as follows:

     2.1 Bank  Financing.  CAS will undertake to obtain a $3,500,000 loan from a
financial institution.  Upon receipt of the proceeds of that loan, CAS will then
loan $3,500,000 to ESOT Purchaser upon the same terms and conditions as the loan
from the financial  institution  and which shall be in the form of the ESOT Loan
and Pledge  Agreement  attached as Exhibit 2.1. The ESOT Purchaser shall use the
loan proceeds to pay part of the purchase price referred to in Section 1.1.

     2.2 Seller  Financing.  Seller  agrees to loan to CAS the sum of $1,500,000
upon the terms and  conditions  of the  Subordinated  Promissory  Note  attached
hereto as  Exhibit  2.2.  CAS  agrees to loan to the ESOT the sum of  $1,500,000
which  shall be in the form of the ESOT Loan and Pledge  Agreement  attached  as
Exhibit 2.1. The ESOT  Purchaser  shall use the loan proceeds to pay part of the
purchase price referred to in Section 1.1.

     2.3 Contributions.  CAS shall make cash contributions to the ESOT Purchaser
in such amounts and at such times which,  together with any cash  dividends that
may be declared by CAS with  respect to the Class A Super  Common  Shares,  will
enable  the  ESOT  Purchaser  to pay  when  due all  amounts  owing  by the ESOT
Purchaser  under the Notes to CAS described in Section 2.1 and 2.2,  whether for
principal  or  interest.  A  contribution  or  dividend  by the CAS to the  ESOT
Purchaser to enable the ESOT  Purchaser to make any given  payment shall be made
sufficiently  prior  to the date  such  payment  is due to  provide  for  timely
payment.

                                   ARTICLE 3.
                                    Closing

     3.1 Time and Place.  The  exchange of items  described in Section 3.2 below
("the Closing") shall be held at the offices of CAS,  located at 1317 South 13th
Avenue, Kelso, Washington,  at 10 a.m., local time, on April 4, 1997, or at such
other time and place as shall be mutually  agreed upon by the parties.  The date
of the Closing is sometimes referred to herein as the "Closing Date."

     3.2  Deliveries.  On the Closing Date (a) CAS and the ESOT Purchaser  shall
execute and exchange  counterparts of the ESOT Loan and Pledge  Agreement in the
form  attached  hereto as  Exhibit  2.1;  (b) the ESOT  Purchaser  and CAS shall
deliver to the Seller  payment by federal  wire  transfer  or  cashier's  checks
representing  the purchase  price in accordance  with Section 1.1 and 1.2 above;
(c) the  Seller  shall  deliver  to the  ESOT  Purchaser  and  CAS  certificates


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representing  the Super  Common  Shares and Common  Shares,  respectively,  duly
endorsed to the ESOT  Purchaser and CAS or  accompanied  by duly executed  stock
powers,  in transferable form with all requisite stock transfer stamps attached;
and (d) the parties shall deliver all other documents or agreements  required by
this Agreement.

                                   ARTICLE 4.
                          Other Transactions at Closing

     4.1  Subordinated  Promissory  Note.  CAS and Seller  acknowledge  that CAS
currently  owes  to  Seller  the sum of  $1,718,615.64.  As a  condition  to the
purchase of the shares by the ESOT  Purchaser,  Seller has agreed that this debt
shall be  represented  by a  Subordinated  Promissory  Note from CAS in the form
attached hereto as Exhibit 4.1.

     4.2 Terms of Subordination.  The two Subordinated Promissory Notes referred
to in Section  2.2 and 4.1 ("EMCON  Notes")  shall be  subordinated  to the bank
financing referred to in Section 2.1 and an operating line of credit for CAS not
to exceed  $1,200,000.  The  operating  line of credit  may  increase,  with the
approval of Seller, in its sole discretion, at the rate of $1.00 for every $2.00
in principal reduction under the EMCON Notes.

     4.3 Security for EMCON Notes.  The obligations of CAS under the EMCON Notes
shall be secured by an assignment by CAS of the Stock Pledge  Agreement  between
CAS and the ESOT. The form of assignment is attached hereto as Exhibit 4.3.

     4.4 Purchase of Seller's  Shares.  At Closing,  Seller will pay to CAS, via
wire  transfer,  a total of Two  Hundred Six  Thousand  Four  Hundred  Fifty-six
Dollars and Forty-three cents  ($206,456.43).  Four Hundred Eighty-seven Dollars
and Forty-three cents ($487.43) of such sum represents reimbursement of the cost
incurred by CAS pursuant to Section 4.6 below for the policy of title  insurance
on the property. CAS will promptly distribute the balance of such monies (net of
applicable  withholding)  to those persons and in the amounts listed on Schedule
4.4 in final  satisfaction  of  Seller's  agreements  to (a)  cancel  its Salary
Continuation  Agreements  with  Steve  Vincent;  (b) buy  back  shares  of EMCON
restricted  stock held by CAS  employees;  and (c) cash out  options to purchase
EMCON common stock held by CAS  employees.  Following the Closing,  CAS shall be
responsible  for  the  payment  of  all  income  tax,  withholding,   and  other
payroll-related taxes on all the payments described in this Section 4.4.

     4.5  State/Federal  Taxes.  The  following  amounts  shall  be  treated  as
additional  contributions  to  capital to CAS by  Seller:  (a) All  intercompany
payable amounts owed by Seller to Purchaser for past years accrued local, state,
and/or  federal  income taxes up through April 4, 1997; and (b) all debt owed by
CAS to  Seller  relating  to  Columbia  Aquatics.  Seller  agrees  to be  solely
responsible for the payment of these liabilities.

     4.6 Kelso Property.  The land and real property improvements for the Kelso,
Washington,  real estate legally  described on Schedule 4.6 hereof  ("Property")
shall be distributed to Seller by CAS as a dividend.  At the Closing,  CAS shall
convey to Seller by warranty deed  ("Deed") the fee title to the  Property.  The
form of the Deed shall be subject to the reasonable  approval of Seller and CAS.


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The Property  shall be conveyed to Seller  subject only to  non-delinquent  real
property taxes and assessments  and those certain  exceptions to title set forth
in that certain  preliminary report issued as order No. 111643 by Cowlitz County
Title Company (the "Title Company") and dated March 3, 1997  (collectively,  the
"Approved Exceptions to Title"). At the Closing, the Title Company shall issue a
standard  ALTA  Owner's  Policy  of Title  Insurance  to EMCON in the  amount of
$300,000,  subject only to the Approved Exceptions to Title. At the Closing, CAS
and Seller shall also execute a Lease  Agreement in the form attached  hereto as
Exhibit  4.6 (the  "Lease  Agreement"),  pursuant  to which CAS shall  lease the
Property from Seller for a period of ten (10) years. Subject to reimbursement by
Seller  pursuant  to Section  4.4  above,  CAS shall pay for the policy of title
insurance  issued  in  connection  with the  foregoing.  CAS  shall  pay for all
transfer taxes, escrow fees, and other closing charges in connection therewith.

     Prior to Closing,  CAS will deposit the duly  executed and  notarized  Deed
into escrow for  recordation at the Closing upon telephone  confirmation by both
parties that the Closing has occurred  with respect to the transfer of the Super
Common Shares and the Common  Shares.  Both parties shall deposit with the Title
Company  their  respective  portions  of the  closing  costs  hereunder,  escrow
instructions  sufficient to close escrow and cause  issuance of the Title Policy
at the Closing, and such other documents as may be reasonably necessary to close
the escrow.

                                   ARTICLE 5.
                     Seller's Representations and Warranties

     Subject to the limitations  set forth in Article 10, the Seller  represents
and warrants to the ESOT Purchaser,  as follows, and, subject to the limitations
set forth in  Article 10  hereof,  Seller  represents  and  warrants  to CAS the
statements  set forth in Sections  5.1,  5.2,  5.3, 5.5, 5.6, 5.7, 5.8, 5.9, and
5.10:

     5.1 Title to Stock.  The Seller is the record and beneficial  owners of the
Shares, which, as of closing,  shall be free and clear of any security interest,
claim, lien, pledge,  option,  encumbrance or restriction (on transferability or
otherwise)  whatsoever  in law or in equity.  The  delivery  to CAS and the ESOT
Purchaser on the Closing Date of  certificates  for the Common  Shares and Super
Common Shares will convey to CAS and the ESOT Purchaser  respectively lawful and
valid title  thereto,  free and clear of any  security  interest,  claim,  lien,
pledge, option,  encumbrance or restriction whatsoever,  except those created by
the ESOT Loan Agreement and the EMCON Notes.

     5.2  Necessary  Authority;   Enforceability.   The  Seller  has  the  legal
competence and full power to enter into,  deliver and perform this Agreement and
to consummate the transactions contemplated herein. This Agreement has been duly
executed  and  delivered by the Seller,  and  constitutes  the legal,  valid and
binding  obligations of the Seller enforceable  against the Seller in accordance
with its terms,  except as the same may be limited  by  bankruptcy,  insolvency,
reorganization  or other laws  affecting the  enforcement  of creditors'  rights
generally  now or  hereafter  in  effect,  and  subject to the  availability  of
equitable remedies.

     5.3 No  Conflicts.  Except for the consents  listed on Schedule 5.3, all of
which  consents  have been or are being  delivered  concurrently  herewith,  the
execution,  delivery  and  performance  of this  Agreement by the Seller and the
Seller's  consummation of the transactions  contemplated hereby, do not and will
not  (i)  require  the  consent,   approval,   authorization,   order,   filing,
registration or  qualification of or with any court,  governmental  authority or
third  person,  (ii)  conflict  with or result in any  material  violation of or


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<PAGE>

default  under any  provision of any mortgage,  indenture,  lease,  agreement or
other instrument,  permit, concession,  grant, franchise or license to which the
Seller is party or by which it may be bound,  (iii)  conflict  with or result in
any violation of or default under any provision of the Articles of Incorporation
or the By-Laws of the Seller, (iv) violate any law, ordinance, rule, regulation,
judgment,  order or  decree  applicable  to the  Seller,  or (v)  result  in the
creation of any security  interest,  claim, lien, charge or encumbrance upon any
of the Common  Shares and Super  Common  Shares  except as set forth in the ESOT
Loan Agreement and the EMCON Notes.

     5.4 Authorized and Outstanding Stock

        (a) Prior to  implementation  of the  Recapitalization,  the  authorized
stock of CAS consisted of 100,000 shares of common stock, of which 10,000 shares
were issued and outstanding in the name of Seller.  After the  Recapitalization,
the capitalization of CAS is as follows:  3,500,000 authorized shares of Class A
Common Stock, of which 1,250,000 shares are issued and  outstanding;  10,000,000
authorized  shares of Class A Super Common Stock, of which 4,000,000  shares are
issued and  outstanding;  and  500,000  authorized  shares of Class A  Preferred
Stock, of which 500,000 shares are issued and outstanding.  All of the foregoing
outstanding shares are owned by Seller. To Seller's  knowledge,  all outstanding
shares  have  been  duly  authorized  and  are  validly   issued,   fully  paid,
nonassessable  and issued in full compliance  with the preemptive  rights of any
existing  shareholders  and in full compliance  with all applicable  federal and
state  securities  laws.  Except  as set  forth in  Schedule  5.4,  to  Seller's
knowledge, no shares of the capital stock of CAS have been reserved for issuance
for any purposes, and there are no outstanding rights, subscriptions,  warrants,
options, conversion rights, commitments or agreements of any kind outstanding to
purchase  or  otherwise  acquire  from CAS, or to cause CAS to issue or sell any
shares  of its  authorized  stock  or  securities  or  obligations  of any  kind
convertible into, exchangeable for or evidencing the right to acquire any shares
of its authorized stock.

        (b) To Seller's actual  knowledge,  there are no other shares or classes
of shares of authorized or outstanding capital stock of CAS. Notwithstanding the
fact that Stephen  Vincent or any other  executive  officer of CAS may have been
deemed to be an executive officer of Seller under the Securities Exchange Act of
1934  or any  other  law or  regulation.  Seller  shall  not be  deemed  to have
possessed  knowledge  of any  facts or  circumstances  solely  by  virtue of Mr.
Vincent's  or  such  other  executive  officer's  knowledge  of  such  facts  or
circumstances for the purposes of the  representation  set forth in this Section
5.4(b).

     5.5 Taxes. Seller has duly filed all consolidated federal, state, local and
foreign  income tax returns  necessary to be filed by it (all such returns being
true and  correct  in all  material  respects)  and Seller has duly paid or made
provisions  for the payment of all taxes  (including  any interest or penalties)
which are due or payable  pursuant to such returns or pursuant to any assessment
with  respect to  federal,  state,  and local  income  taxes,  whether or not in
conjunction with such returns, through the date of Closing.

     Except as set forth on Schedule 5.5 attached hereto, to Seller's knowledge,
there are no pending or  threatened  examinations  or audits of the  returns and
reports  of Seller for CAS's  operations  or any  claims  asserted  for taxes or
assessments of Seller for CAS operations nor are there outstanding agreements or
waivers  extending  the  statutory  period  of  limitations  applicable  to  any
consolidated income tax return of Seller for any period. Seller has not prepared
and filed a  consolidated  income tax return for the year  ending  December  31,



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1996. Taxes will be due on account of the filing of said returns. Seller has and
will have  obligations to pay all local,  state and federal income taxes for CAS
operations with respect to periods up to April 4, 1997.

     5.6 Undisclosed  Liabilities.  Except as set forth on Schedule 5.6 attached
hereto,  Seller has not obligated  CAS nor caused CAS to incur any  liabilities,
whether absolute, accrued, contingent or otherwise, whether due or to become due
other than such liabilities Seller shall continue to be solely responsible for.

     5.7 Benefit Plan.  Except as set forth on Schedule 5.7, Seller has no plans
of the following  types which may result in any liability to CAS or its officers
or  directors:  pension,  profit-sharing,  stock  bonus,  or other plan which is
"qualified," or is intended to be "qualified"  under Section 401(a) of the Code,
or any bonus,  deferred  compensation,  hospitalization  or other  medical stock
purchase, life or other insurance, golden parachute agreements or other employee
benefit plan or arrangement.

     5.8  Financial  Statements.  Attached  hereto as Schedule  5.8 are true and
complete copies of Seller's  auditors  workpapers  showing the balance sheets of
CAS at December 31,  1994,  December 31,  1995,  and the related  statements  of
income,  stockholders'  equity and cash  flows for the  fiscal  years then ended
(collectively,  the "Annual Financial Statements"), and an audited balance sheet
and related  statement  of income of EMCON for the year ended  December 31, 1996
(collectively,  the Balance Sheet and the Statements may hereinafter be referred
to as the "Financial Statements").

        (a) To Seller's knowledge,  the Annual Financial  Statements  (including
the notes  thereto)  present  fairly  the  financial  condition  and  results of
operations  of CAS at and for the periods  indicated,  and have been prepared in
accordance with generally accepted accounting principles applied on a consistent
basis.

        (b) To  Seller's  knowledge,  CAS  has no  liabilities,  commitments  or
obligations  of any nature,  whether  absolute,  accrued,  contingent,  known or
unknown, due or to become due or otherwise,  which, in accordance with generally
accepted accounting  principles are required to be set forth on a balance sheet,
except (i) as reflected in its December 31, 1996, balance sheet included as part
of the Financial Statements and not heretofore discharged, (ii) as incurred as a
result of the normal and ordinary  course of its business since the date of such
balance sheet, none of which is materially adverse.

     5.9 No Liens and  Encumbrances.  Except as set forth on Schedule 5.9, or as
otherwise contemplated by this Agreement,  Seller has not placed or caused to be
placed any lien,  security  interest,  or other  encumbrance  upon the  personal
property of CAS.

     5.10 Representations  Complete.  None of the representations and warranties
made by the Seller herein,  nor any statement  made in any Schedule,  Exhibit or
certificate  furnished pursuant to this Agreement,  contains or will contain any
untrue statement of a material fact, or omit to state any material fact required
to be stated  therein,  or necessary in order to make the  statements  made, not
misleading.

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                                   ARTICLE 6.
       Sellers' and Management Purchasers' Representations and Warranties

     The Management  Purchasers  jointly and severally  represent and warrant to
the ESOT  Purchaser as follows,  and,  subject to the  limitations  set forth in
Article 10 hereof, the Seller represents and warrants to the ESOT Purchaser,  to
Seller's knowledge, as follows:

     6.1  Subsidiaries.  Schedule  6.1 attached  hereto lists all  subsidiaries,
partnerships and other entities which CAS has organized or in which it has owned
an interest (other than publicly traded corporations or entities in which it has
held a de minimis  interest  for  investment  purposes)  and the status of CAS's
ownership in such  entitles on the date hereof.  Except as disclosed in Schedule
6.1,  immediately  after the Closing,  there will be no  corporation  which is a
member of the same  "controlled  group of  corporations"  as CAS, as  determined
under Section 1563(a) of the Code.

     6.2 Litigation and Contracts.  Schedule 6.2 attached hereto contains a true
and  complete  list  of  all  actions,  suits,   proceedings,   arbitrations  or
investigations  pending  or  threatened  against  CAS (or any of its  respective
officers or directors in  connection  with the business or affairs of CAS or the
transactions contemplated hereby), before any court or governmental body, United
States or foreign ("Proceeding" or "Proceedings"). The status of each Proceeding
is set forth on Schedule  6.2. As of the date  hereof,  except as  described  in
Schedule  6.2,  the  claims  which are the  subject of each  Proceeding  and the
defense  thereof is covered by  insurance  as  described  on  Schedule  6.2 or a
sufficient  cash  reserve  has been set  aside by CAS with the  result  that the
Proceedings,  in the aggregate, will not require any currently unfunded material
payments  by CAS or any  other  commitments,  other  than the time  expended  by
officers and employees in connection  with testimony or other  participation  in
the defense of the Proceedings. CAS is not in default in any material respect on
any of its contracts,  agreements or evidences of indebtedness,  and no party to
any  contract  or  agreement  with CAS which is material to the conduct of CAS's
business,  is in default in any  material  respect  under any such  contract  or
agreement.

                                   ARTICLE 7.
          CAS and Management Purchasers Representations and Warranties

     CAS and the  Management  Purchasers  jointly and  severally  represent  and
warrant to Seller and the ESOT Purchaser as follows:

     7.1 Necessary  Power and Authority;  Enforceability.  CAS has all requisite
power and  authority to enter into,  deliver and perform this  Agreement  and to
consummate the transactions  contemplated  herein.  The execution,  delivery and
performance  of  the  Agreement  and  the   consummation  of  the   transactions
contemplated  herein,  have been duly authorized by all necessary  action on the
part of CAS's Board of Directors and shareholders.  This Agreement has been duly
executed and delivered on behalf of CAS by the authorized corporate officers and
constitutes CAS's valid and legally binding obligation,  enforceable against CAS
in accordance  with its terms,  except as the same may be limited by bankruptcy,
insolvency, reorganization or other laws affecting the enforcement of creditors'
rights generally now or hereafter in effect,  and subject to the availability of
equitable remedies.

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     7.2 No  Conflicts.  Except for the consents  listed on Schedule 7.2, all of
which  consents  have been or are being  delivered  concurrently  herewith,  the
execution,  delivery  and  performance  of  this  Agreement  by  CAS  and  CAS's
consummation of the transactions  contemplated  hereby,  do not and will not (i)
require the consent,  approval,  authorization,  order, filing,  registration or
qualification of or with any court, governmental authority or third person, (ii)
conflict  with or result in any  violation of or default  under any provision of
any  mortgage,   indenture,  lease,  agreement  or  other  instrument,   permit,
concession, grant, franchise or license to which CAS is party or by which any of
its outstanding Shares are or may be bound, (iii) conflict with or result in any
violation of or default under any provision of the Articles of  Incorporation or
the By-Laws of CAS, (iv) violate any law, ordinance, rule, regulation, judgment,
order or decree applicable to CAS, or (v) result in the creation of any security
interest,  claim, lien, charge or encumbrance upon any of the outstanding Shares
of CAS, except as set forth in the ESOT Loan Agreement and EMCON Notes.

        Authorized  and  Outstanding  Stock.  Prior  to  implementation  of  the
Recapitalization,  the  authorized  stock of CAS consisted of 100,000  shares of
common stock,  of which 10,000 shares were issued and outstanding in the name of
Seller.  After the  Recapitalization,  the  capitalization of CAS is as follows:
3,500,000  authorized  shares of Class A Common Stock, of which 1,250,000 shares
are issued and outstanding; 10,000,000 authorized shares of Class A Super Common
Stock,  of which  4,000,000  shares  are  issued and  outstanding;  and  500,000
authorized shares of Class A Preferred Stock of CAS, of which 500,000 shares are
issued and  outstanding.  All of the foregoing  outstanding  shares are owned by
Seller.  There  are no other  shares or  classes  of  shares  of  authorized  or
outstanding  capital  stock  of CAS.  All  outstanding  shares  have  been  duly
authorized and are validly issued, fully paid,  nonassessable and issued in full
compliance with the preemptive  rights of any existing  shareholders and in full
compliance with all applicable federal and state securities laws.

        Except as set forth in Schedule  7.3, no shares of the capital  stock of
CAS  have  been  reserved  for  issuance  for any  purposes,  and  there  are no
outstanding  rights,   subscriptions,   warrants,  options,  conversion  rights,
commitments  or  agreements  of any kind  outstanding  to purchase or  otherwise
acquire  from  CAS,  or to cause  CAS to issue or  purchase,  any  shares of its
authorized  stock or securities or  obligations  of any kind  convertible  into,
exchangeable  for or  evidencing  the right to acquire any shares of  authorized
stock.

     7.4 Litigation and Contracts.  Schedule 7.4 attached hereto contains a true
and  complete  list  of  all  actions,  suits,   proceedings,   arbitrations  or
investigations  pending  or  threatened  against  CAS (or any of its  respective
officers or directors in  connection  with the business or affairs of CAS or the
transactions  contemplated  herewith),  before any court or  governmental  body,
United States or foreign  ("Proceeding"  or  "Proceedings").  The status of each
Proceeding  is set  forth on  Schedule  7.4.  As of the date  hereof,  except as
described in Schedule  7.4, the claims which are the subject of each  Proceeding
and the defense  thereof is covered by insurance as described on Schedule 7.4 or
a  sufficient  cash  reserve  has been set aside by CAS with the result that the
Proceedings,  in the aggregate, will not require any currently unfunded material
payments  by CAS or any  other  commitments,  other  than the time  expended  by
officers and employees in connection  with testimony or other  participation  in
the defense of the Proceedings. CAS is not in default in any material respect on
any of its contracts,  agreements or evidences of indebtedness,  and no party to
any  contract  or  agreement  with CAS which is material to the conduct of CAS's
business,  is in default in any  material  respect  under any such  contract  or
agreement.

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     7.5 Corporate  Organization  and Good Standing of CAS. CAS is a corporation
duly incorporated and organized, validly existing and in good standing under the
laws of the  State of  Washington  and has all  requisite  power  and  authority
(corporate  and other) to own,  operate and lease its properties and to carry on
its business as such business is now being  conducted.  CAS is duly qualified or
licensed to transact  business as a foreign  corporation and is in good standing
in all jurisdictions where its present activities require it to be so qualified,
licensed or in good standing.  Schedule 7.5 attached  hereto  contains a list of
all  jurisdictions in which CAS is qualified or licensed to transact business as
a foreign  corporation.  CAS has not  received  any written  notice or assertion
within the last three years from the Secretary of State or  comparable  official
of any  jurisdiction  to the effect  that CAS is  required  to be  qualified  or
otherwise  authorized to do business therein,  in which CAS has not qualified or
obtained such authorization.

     7.6 Employee  Benefit  Plans.  Except as set forth on Schedule 7.6 attached
hereto,  CAS  maintains  no pension,  profit-sharing,  stock bonus or other plan
which is "qualified,"  or is intended to be "qualified"  under Section 401(a) of
the Code.  Schedule 7.6  contains an accurate  and complete  list of each bonus,
deferred compensation, hospitalization or other medical, stock purchase, life or
other  insurance,  and each other  employee  benefit plan or  arrangement of CAS
(collectively,  the "Plans"). CAS has heretofore delivered to the ESOT Purchaser
true and complete copies of the documents  governing all such Plans as in effect
on the  date  hereof.  Each of the  Plans  has  been  administered  in  material
compliance  with its  terms  and all  filing,  reporting,  disclosure  and other
requirements of the Employee  Retirement Income Security Act of 1974, as amended
"ERISA"). CAS has no plan or commitment,  whether formal or informal and whether
legally  binding or not, to create any additional  such Plan or modify or change
any existing plan or arrangement. The trustee has been duly appointed.

     7.7 Personnel.

        (a) Schedule 7.7 attached hereto lists the names and current salaries of
all directors  and officers of CAS and the amount of all bonuses  accrued and to
be paid by CAS to all directors and officers of CAS for services rendered to CAS
through December 31, 1996.

        (b) Except as contained on Schedule 7.7 attached hereto,  CAS is not, or
will not be,  by  reason of  anything  done  hereafter  in  connection  with the
execution of this Agreement or the consummation of the transactions contemplated
hereby,  liable to any  employees of CAS for any amount of severance  pay or for
any other similar payments.

        (c) There is no unfair  labor  practice  pending  against CAS before the
National Labor Relations Board. There is no labor strike,  slowdown or stoppage,
or any union organizing campaign, actually pending or to the knowledge of CAS of
the Management  Purchasers,  threatened  against or involving CAS. No collective
bargaining agreement is currently being negotiated by CAS.

        (d) Except as set forth on Schedule  7.7,  CAS has not entered  into any
employment agreements or similar arrangements related to the compensation of its
officers.

                                       26
<PAGE>

     7.8 Sales and Use Taxes.  CAS has duly filed all sales and use tax  returns
necessary  to be filed by it, and CAS has duly paid or made  provisions  for the
payment of all such taxes,  (including any interest or penalties)  which are due
and payable to such returns or pursuant to any  assessments  with respect to all
such taxes, whether or not in conjunction with such returns, through the date of
closing.

        Except  as set  forth on  Schedule  7.8  attached  hereto,  there are no
pending or threatened  examinations  or audits of the returns or reports of CAS,
or claims  asserted for sales or use taxes or assessments  (other than as listed
by CAS on  Schedule  7.8  attached  hereto)  for CAS  operations,  nor are there
outstanding waivers or agreements  extending the statutory period of limitations
applicable to any tax return or report for any period.

     7.9  Corporate  Documents.  Complete and correct  copies of the Articles of
Incorporation of CAS ("Articles") and all amendments  thereto,  certified by the
Secretary  of  State of  Washington,  and of the  By-Laws  of CAS,  as  amended,
certified by the Secretary of CAS, have been furnished to the ESOT Purchaser and
no  amendments  to the Articles or the By-Laws have been adopted  subsequent  to
said  furnishing.  CAS is not in  default  in the  performance,  observation  or
fulfillment of its Articles or By-Laws.

     7.10 Liabilities.  There are no material transactions in which CAS has been
involved  or in  which  CAS has  participated  in the last  five  years or which
represents  a  current  or  contingent  commitment  or  liability  which are not
reflected on Schedule 7.10 attached hereto,  in the Annual Financial  Statements
(defined in Section  6.8) or in  resolutions,  or minutes,  certified  copies of
which have been delivered to all parties.

     7.11 Environmental  Matters.  Except as set forth on Schedule 7.11 attached
hereto, to the best of Management Purchasers' knowledge,  no condition exists at
any facility of, or real  property  owned by, CAS with respect to the storage or
discharge  into  the  earth  or its  atmosphere  of  effluents,  waste  or other
materials,  solid, liquid or gaseous,  nor has any waste been disposed of in any
way or manner,  in  violation  of law.  CAS has not received any notice from any
governmental  body  claiming  any material  violation  of any zoning,  building,
health or safety law or  ordinance,  or requiring  any material  work,  repairs,
construction,  alterations,  noise reduction,  cleanup or installation which has
not been fully complied with.

     7.12 No Violation.  Except as disclosed on Schedule  7.12 attached  hereto,
CAS is not in violation  of, or is under  investigation  with respect to, or has
been charged  with or given  notice of any  violation  of, any  applicable  law,
statute, order, rule, regulation,  policy or guideline promulgated,  or judgment
entered, by any federal, state, local or foreign court or governmental authority
relating to or affecting  CAS, or any of its  properties,  where such  violation
could have a  material  adverse  effect on CAS.  Neither  CAS nor any  director,
officer,  agent, employee or other person associated with or acting on behalf of
any of them in  connection  with the business of CAS, has (i) used any corporate
funds for unlawful contributions,  payments,  gifts or entertainment or made any
unlawful  expenditures  relating to  political  activity,  or made any direct or
indirect unlawful  payments to government  officials or others, or (ii) accepted
or received any unlawful contributions, payments, gifts or expenditures.

                                       27
<PAGE>

     7.13 Licenses, Patents, Trademarks.  Schedule 7.13 attached hereto contains
a list and rief description of all domestic and foreign letters patent, patents,
patent  applications,  patent and  know-how  licenses,  trade  names,  trademark
registrations   and   applications,   common  law   trademarks,   and  copyright
registrations and applications (collectively, the "Intangibles"),  owned by CAS.
The  business  of CAS is being  carried  on  without  conflict  with  registered
patents, licenses, trademarks,  copyrights, and trade names or other proprietary
rights of others. CAS has not received notice that it infringed or is infringing
on any Intangible,  invention,  technology,  process,  design, computer program,
know-how or formulae of another.  Except as described in Schedule  7.13, CAS has
not  assigned  any rights in, or granted any  security  interest  in, any of its
trade secrets, trademarks or copyrights and no current or previous key employees
or consultants of CAS have any rights in any  inventions,  software  programs or
designs  or  other   proprietary   concepts,   whether  or  not   patentable  or
copyrightable, which relate in any material respect to the business of CAS.

     7.14  Title to and  Condition  of Assets.  Schedule  7.14  attached  hereto
contains a list and brief  description  of each parcel of real property owned by
CAS or under  which  CAS is a  lessee,  true  copies  of any  applicable  leases
(including  all  amendments  thereof  and  modifications  thereto)  having  been
delivered to the ESOT Purchaser prior to the date hereof.

        (a) Except as set forth on Schedule  7.14,  CAS has good and valid title
to all of its  personal  property and  leasehold  interests,  including  but not
limited to the property and assets reflected on its balance sheet as of December
31, 1996,  included in the Financial  Statements (other than property and assets
disposed of in the ordinary  course of business  since such date) free and clear
of all material title defects and all liens, pledges, claims, charges,  security
interests, and other encumbrances. Except as set forth in Schedule 7.14, CAS has
not received notice of any existing claims adverse or challenges to the title or
ownership of any personal property of CAS.

        (b) All  personal  property  material  to the  condition  (financial  or
otherwise),  operations,  business  or  prospects  of CAS,  and  all  buildings,
structures  and  fixtures  used  by CAS  in the  conduct  of its  business  are,
considering their ages and uses, in satisfactory operating condition (subject to
normal  maintenance  and repair).  CAS has not received  notice of any violation
(which has not been cured) of any  building,  zoning or other law,  ordinance or
regulation  in respect of any notice that it has failed to comply in any respect
with such obligations.

     7.15 No Material  Change.  Since December 31, 1996,  except as disclosed in
Schedule 7.15 attached  hereto,  there has not been: (i) any materially  adverse
change  (whether or not in the  ordinary  and usual  course of  business) in the
financial condition,  net worth, assets,  liabilities,  personnel,  business, or
results of operations of CAS, (ii) any damage,  destruction  or loss (whether or
not covered by insurance)  materially  affecting the business of CAS,  (iii) any
material increase in the compensation payable or to become payable by CAS to its
officers or key employees,  pursuant to any agreement, bonus, insurance, pension
or other  beneficial plan or arrangement  made to or for the benefit of any such
officers or key employees,  other than in a manner  consistent  with  historical
practice,  (iv) any loans to or  borrowing  by CAS,  any mortgage or pledge with
respect  to any of their  properties  or  assets or any  assumption,  guarantee,
endorsement  or other  agreement to become  liable  (directly,  contingently  or
otherwise)  for any  loans  to any  other  person  or  entity,  (v) any  sale or
disposition  (or  agreement  to sell or  dispose)  of any  assets,  tangible  or


                                       28
<PAGE>

intangible,  of CAS,  except  in the  ordinary  course  of  business,  (vi)  any
cancellation  (or  agreement to cancel) of more than $10,000 in the aggregate of
any debts owed to or claims of CAS, except in the ordinary course of business or
(vii) any  amendment  or  termination  of any  material  contract,  agreement or
license to which CAS is a party, (viii) any amendment to the Articles or By-Laws
of, or any merger or consolidation of, CAS.

     7.16  Accounts  Receivable.  Schedule  7.16  attached  hereto sets forth an
accurate,  correct and  complete  aging of all  outstanding  accounts  and notes
receivable  as  of  December  31,  1996.  All  outstanding  accounts  and  notes
receivable reflected on the Financial Statements delivered to the ESOT Purchaser
are due and valid claims against account debtors for goods or services delivered
or  rendered.  All  receivables  arose in the ordinary  course of  business.  No
receivables are subject to prior assignment, claim, lien or security interest.

     7.17  Contracts.  Schedule 7.17  attached  hereto sets forth a complete and
accurate list of all outstanding  contracts to which CAS is a party,  other than
purchase orders and any contract which involves an aggregate  expenditure  after
the date of this  Agreement  of not more than  $10,000  and which is not already
reflected  in  the  Annual  or  Interim  Financial  Statements.   Schedule  7.17
identifies all contracts of CAS with its officers,  directors,  shareholders  or
any other person, firm or corporation affiliated with such persons.

     7.18  Insurance.  Schedule  7.18  attached  hereto sets forth an  accurate,
correct and complete  list and summary  description  (including  the name of the
insurer,  coverage,  premium and  expiration  date) of all binders,  policies of
insurance, sell insurance programs or fidelity bonds ("Insurance") maintained by
CAS or in which CAS is a named  insured.  Except as set forth on Schedule  7.18,
since  December 31,  1996,  there have been no claims or events which could form
the basis of a claim  against any  Insurance  as to which any insurer has denied
liability,  and there are no claims filed after  December  31,  1996,  under any
Insurance  that  have  been  disallowed  or  improperly   filed.  No  notice  of
cancellation  or non-renewal  with respect to any insurance has been received by
CAS.

                                   ARTICLE 8.
             Representations and Warranties Concerning the Property

     In connection with the conveyance of the Property to Seller, CAS represents
and warrants to Seller as follows:

     8.1  Compliance.  To the best of CAS's  actual  knowledge,  and  except  as
otherwise  disclosed to Seller by CAS,  CAS has not received any written  notice
that the current use and  operation  of the Property is not in  compliance  with
actual building codes, local, state, and federal laws and regulations.

     8.2  Procedures.  CAS has not  received  any  notice  of any  condemnation,
environmental,  zoning, or any other land use regulations or proceedings  either
instituted or, to CAS's actual knowledge, threatened or planned to be instituted
which would materially affect the use and operation of the Property.

     8.3  Litigation.  There is no  litigation  pending,  or,  to  CAS's  actual
knowledge,  threatened  against CAS arising out of the  ownership  or use of the
Property.

                                       29
<PAGE>

     8.4  Ownership.  CAS is the  sole  owner of the  Property  and has the full
right, power, and authority to convey the Property to Seller.

     8.5 Hazardous Materials. To CAS's knowledge, except to the extent set forth
in this Agreement, CAS has not received any written notice from any governmental
agency and has no actual knowledge that there exists any hazardous  materials in
or under the Property in  violation  of  applicable  laws,  rules,  regulations,
ordinances, or orders.

     For  purposes of this  Section 8.5,  the term  "hazardous  material"  shall
include  any  substance,  chemical,  compound,  or  mixture  which is (or  which
contains any substance, chemical compound, or mixture which is:

        (a) a "Hazardous Substance," "Hazardous Material," "Hazardous Waste," or
"Toxic Substance" under the Comprehensive  Environmental Response,  Compensation
and Liability Act of 1980, 42 U.S.C.  ss. 9601, et seq., the Hazardous  Material
Transportation  Act, 49 U.S.C.  ss. 1801, et seq., or the Resource  Conservation
and Recovery Act, 42 U.S.C. ss. 6901, et seq.;

        (b)  an  "Extremely   Hazardous  Waste,"  a  "Hazardous   Waste,"  or  a
"Restricted  Hazardous  Waste," under Section  25115,  25117,  or 25112.7 of the
California Health and Safety Code, or is listed pursuant to Section 25140 of the
California Health and Safety Code;

        (c) a "Hazardous Material," "Hazardous  Substance," or "Hazardous Waste"
under Section 25281, 25316, or 25501 of the California Health and Safety Code;

        (d) "Oil" or a "Hazardous  Substance"  under  Section 311 of the Federal
Water  Pollution  Control  Act,  33  U.S.C.  ss.  1321  as  well  as  any  other
hydrocarbonic substance or by-product.

        (e)  listed  under  any  law,  rules,  or  regulations  of the  State of
Washington as hazardous or toxic;

        (f) a material which, due to its characteristics or interaction with one
or more other substances,  chemical compounds, or mixtures, damages or threatens
to damage  health,  safety,  or the  environment,  or is  required by any law or
public agency to be remediated,  including  remediation which such law or public
agency requires in order for the property to be put to any lawful purpose; or

        (g) any  material  the  presence  of  which  would  require  remediation
pursuant  to the  guidelines  set  forth  in the  State  of  California  Leaking
Underground Fuel Tank Field Manual, whether or not the presence of such material
resulted from a leaking underground fuel tank.

     8.6  No  Encumbrances.  The  Property  is  free  and  clear  of  liens  and
encumbrances other than as described or referenced in Section 4.6 hereof.

                                       30
<PAGE>

     8.7 Condition of  Structures.  To CAS's  knowledge,  (i) no building on the
Property is in need of repairs to any structural  components,  including but not
limited to the foundation,  floor slabs, load-bearing walls, roof structure, and
roof  membrane;  and (ii) the parking  areas and related  paved areas within the
Property are in good condition and are not in need of repair or repaving.

                                   ARTICLE 9.
              Representations and Warranties of the ESOT Purchaser

         The  Trustee,  in its  capacity  as  such  and on  behalf  of the  ESOT
Purchaser, represents and warrants to the Seller and the CAS as follows:

     9.1 Necessary Authority. The Trustee has full power and authority under the
ESOT to execute and deliver this  Agreement on behalf of the ESOT  Purchaser and
to consummate the transactions contemplated hereby. This Agreement has been duly
authorized,  executed  and  delivered  by the  Trustee  on  behalf  of the  ESOT
Purchaser and  constitutes the legal,  valid and binding  obligation of the ESOT
Purchaser,  enforceable against the ESOT Purchaser in accordance with its terms,
except  as  the  same  may  be   limited  by  ERISA,   bankruptcy,   insolvency,
reorganization  or other laws  affecting the  enforcement  of creditors'  rights
generally  now or  hereafter  in  effect,  and  subject to the  availability  of
equitable remedies.

     9.2 No Conflicts. The execution, delivery and performance of this Agreement
by the Trustee,  in its capacity as such and on behalf of the ESOT Purchaser and
the consummation of the transactions  contemplated herein do not (a) require the
consent or approval  of, or filing  with,  any person or public  authority;  (b)
constitute  or result in the breach of any provision of, or constitute a default
under, the Columbia  Analytical  Services,  Inc.,  Employee Stock Ownership Plan
("ESOP"),  the ESOT Loan and Pledge  Agreement,  or any agreement,  indenture or
other instrument  known to the Trustee to which the Trustee,  in its capacity as
such,  or the ESOT  Purchaser  is a party or by  which it or its  assets  may be
bound;  or (c) violate any law,  regulation,  judgment or order binding upon the
Trustee,  in its  capacity as such,  or the ESOT  Purchaser  or give rise to any
liability  to the ESOT  Purchaser  under Title I of ERISA or Section 4975 of the
Code.

     9.3 Qualification. The ESOP is, in form, an "employee stock ownership plan"
within the meaning of Section  4975(e)(7)  of the Code and,  in form,  qualifies
under Section 401(a) of the Code.  The ESOT Purchaser has been duly  constituted
in accordance with valid and binding trust instruments, is validly existing and,
in form, qualifies under Section 501(a) of the Code.

                                   ARTICLE 10.
            Seller and Management Purchasers Obligations to Indemnify

     10.1 Seller.  Subject to Section  10.10,  Seller shall  indemnify  and hold
harmless  CAS,  Management  Purchasers,   the  ESOT  Purchaser,   and  the  ESOT
Purchaser's  authorized agents and  representatives,  against any and all costs,
losses,  claims  (including  claims  by  third  parties),   liabilities,  fines,
penalties,  damages,  and expenses  (including  interest which may be imposed in
connection  therewith,  court costs and  reasonable  fees and  disbursements  of
counsel)  suffered by any of them in connection  with:  (a) any inaccuracy in or
breach of any representations or warranties of the Seller made in Articles 5 and


                                       31
<PAGE>

6 hereof or in any document,  certificate, or exhibit delivered by the Seller in
accordance with the provisions of this  Agreement;  (b) any breach by the Seller
of this Agreement;  or (c) all past and present liabilities relative to Seller's
operations,  excluding any  operations  related to the operations of CAS and for
all of Seller's  other  operations,  including any such  operations no longer in
existence.

     10.2   Management   Purchasers.   Subject  to  Section  10.10,   Management
Purchasers,  jointly and severally,  shall  indemnify and hold harmless CAS, the
ESOT Purchaser and the ESOT Purchaser's  authorized agents and  representatives,
against any and all costs,  losses,  claims (including claims by third parties),
liabilities,  fines,  penalties,  damages and expenses (including interest which
may be imposed in  connection  therewith,  court costs and  reasonable  fees and
disbursements  of  counsel)  suffered  by any of them  in  connection  with  any
inaccuracy in or breach of any  representations  or warranties of the Management
Purchasers set forth in Article 6 hereof.

     10.3 CAS and  Management  Purchasers.  CAS and the  Management  Purchasers,
jointly and  severally,  shall  indemnify  and hold  harmless  Seller,  the ESOT
Purchaser  and the  ESOT  Purchaser's  authorized  agents  and  representatives,
against any and all costs,  losses,  claims (including claims by third parties),
liabilities,  fines,  penalties,  damages and expenses (including interest which
may be imposed in  connection  therewith,  court costs and  reasonable  fees and
disbursements  of  counsel)  suffered  by any of them  in  connection  with  any
inaccuracy  in or  breach  of any  representations  or  warranties  of  CAS  and
Management Purchasers set forth in Article 7 hereof.

     10.4 CAS. CAS will indemnify and hold harmless  Seller from and against any
and all costs, losses, claims (including claims by third parties),  liabilities,
fines, penalties,  damages and expenses (including interest which may be imposed
in connection  therewith,  court costs, and reasonable fees and disbursements of
counsel)  suffered by Seller in connection  with (a) any inaccuracy in or breach
of  any  representation  or  warranties  of  CAS  herein  or  in  any  document,
certificate,  or exhibit delivered by CAS or any officer of CAS pursuant to this
Agreement; and (b) relative to CAS's past, present, and future operations.

     10.5  Environmental  Indemnity.  From and after the Closing,  CAS agrees to
indemnify,  defend,  and  hold  Seller  harmless  from and  against  any and all
Environmental  Claims (as defined below) that may arise in connection with or in
any way related to the  handling,  storage,  existence,  or release of Hazardous
Materials (as defined in Section 8.5 hereof) at, beneath, to, from, or above (a)
the  Property,  (b) in  connection  with  any CAS  operations  conducted  at the
Bothell,  Washington facility occupied by CAS ("Bothell  Facility") during CAS's
occupation  of  such  facility,  or  (c) in  connection  with  CAS's  operations
conducted at the laboratory facility on Ringwood Avenue in San Jose,  California
during CAS's occupation of such facility.  CAS shall defend Seller in connection
with  the  foregoing   indemnity   obligations  with  legal  counsel  reasonably
acceptable to Seller. As used herein, the term "Environmental  Claims" means any
and all actual,  threatened, or potential claims,  proceedings,  suits, actions,
causes  of  actions,  demands,  losses,   obligations,   orders,   requirements,
restrictions,  or  directives  of any  governmental  agency  or  entity,  liens,
penalties,  fines, charges,  deaths,  damages, costs, and expenses of every kind
and nature whether now known or unknown,  whether  foreseeable or unforeseeable,


                                       32
<PAGE>

whether under any foreign,  federal,  or state or local law (both  statutory and
nonstatutory)  and whether  asserted or demanded by a third party against Seller
or incurred  directly or indirectly by Seller.  The provisions of this indemnity
shall survive the Closing and  recordation of the warranty deed and shall run to
the benefit of Seller's successors and assigns.

     10.6 Limitation of Seller's Liability; Offset of Notes.

        (a)  Seller's  liability  under  Section  10.1  shall be  limited to the
aggregate amount of Six Million Dollars ($6,000,000.00).

        (b)  Should  Seller  become  obligated  to  indemnify  CAS or  the  ESOT
Purchaser prior to such time as the Notes have been repaid in full, Seller shall
be entitled to offset any portion of its  liability  against the amounts owed to
Seller  under the Notes,  regardless  whether  such  amounts have become due and
payable.

     10.7 Survival. All representations, warranties, indemnities, covenants, and
agreements made by the Seller,  Management Purchasers,  and CAS herein or in any
other document executed by Seller,  Management Purchasers,  or CAS in connection
herewith shall survive the Closing.

     10.8  Limitations.  Notwithstanding  the foregoing or anything else in this
Agreement   to  the   contrary,   an   indemnitee   shall  not  be  entitled  to
indemnification  for losses  arising out of matters  referred to in this Article
10,  unless each such entity shall have given written  notice to the  indemnitor
and,  each other,  setting  forth its claim for  indemnification  in  reasonable
detail.

     10.9  Defense.  Indemnitee  shall  promptly  give  written  notice  to  the
indemnitor  and each  other  after  such  entity  has  knowledge  that any legal
proceeding  has been brought or any claim has been  asserted in respect of which
indemnification  may be sought under the  provisions  of this Article 10. If the
indemnitor,  within 10 days  after such  notice  has been given (or within  such
shorter period of time as an answer or other responsive motion may be required),
shall have  acknowledged  in writing the  indemnitor's  obligation to indemnify,
then the indemnitor shall have the right to control the defense of such claim or
proceeding,  and the  indemnitee  shall not settle or  compromise  such claim or
proceeding  without the written consent of the  indemnitor,  which consent shall
not  unreasonably  be  withheld  or  delayed.  The  indemnitee  may in any event
participate in any such defense with its own counsel and at its own expense.

     10.10 Seller's Reliance on CAS Management

        (a) The Management  Purchasers,  CAS and the ESOT Purchaser  acknowledge
that, in making the representations and warranties set forth in paragraph (a) of
Section 5.4, paragraphs (a) and (b) of Section 5.8, and Article 6 hereof, Seller
has  relied  exclusively  upon  (i)  the  truthfulness  of  statements  made  by
management  of CAS  from  time  to  time  and  the  statements  set  forth  in a
certificate of Stephen W. Vincent in the form attached hereto as Exhibit "10.10"
(the "CAS Officer's  Certificate");  (ii) the opinion letter of Alan L. Engstrom
delivered  at the Closing  pursuant  to Section  11.3(f)  hereof  (the  "Opinion
Letter");  and (iii) the  assumption  that,  during  such time as CAS has been a
subsidiary of Seller,  CAS's Board of Directors and management have at all times
acted in the best  interests of CAS and Seller.  Seller has made no  independent
investigation of the matters discussed in such  representations  and warranties.
Seller  shall have no liability to the  Management  Purchasers,  CAS or the ESOT


                                       33
<PAGE>

Purchaser in connection with any breach of such  representations  and warranties
to  the  extend  such  breach  is  related  to any of  the  following  facts  or
circumstances,  unless such facts or circumstances were known to Seller prior to
the Closing:

           (1) any facts or circumstances  that are inaccurately or incompletely
described in the CAS Officer's Certificate;

           (2) any inaccurate legal opinion  contained in the Opinion Letter, or
any inaccurate statement of fact upon which the Opinion Letter has relied;

           (3) a breach by CAS's Board of  Directors,  or any of its officers of
his/her or its fiduciary duties to CAS or Seller; and

           (4) a failure of CAS's Board of Directors to follow the  instructions
of Seller,  or the failure of CAS's  management  to follow the  instructions  of
Seller or the Board of Directors of CAS.

        (b) Notwithstanding the fact that Stephen Vincent or any other executive
officer of CAS may have been deemed to be an  executive  officer of Seller under
the Securities Exchange Act of 1934 or any other law or regulation, Seller shall
not be deemed to have possessed  knowledge of any facts or circumstances  solely
by virtue of Mr. Vincent's or such other executive  officer's  knowledge of such
facts or circumstances.

                                   ARTICLE 11.
                              Conditions to Closing

     11.1 Conditions to Each Party's Obligations at the Closing.  The respective
obligations  of each party to this  Agreement to effect the purchase and sale of
the  Common  Shares  and  the  Super  Common  Shares  shall  be  subject  to the
satisfaction at or prior to the Closing of the following conditions:

        (a) At the  time of the  Closing,  the  purchase  of the  Common  Shares
hereunder by CAS, the purchase of the Super Common Shares  hereunder by the ESOT
Purchaser,  and the  purchase  of the shares of Common  Stock by the  Management
Purchasers  from CAS shall be legally  permitted by all laws and  regulations to
which CAS and the Seller are subject.

        (b) All third party  consents  required in connection  with the purchase
and sale of the Common  Shares and the Super  Common  Shares  hereunder  and the
conveyance of the Property shall have been obtained.

        (c) No temporary restraining order, preliminary or permanent injunction,
or other order issued by any court of competent  jurisdiction  or other legal or
regulatory restraint of prohibition  preventing the consummation of the purchase
and sale of the Common  Shares or the Super Common  Shares or the  conveyance of
Property  shall  have  been  issued,  nor shall any  proceeding  brought  by any
governmental agency seeking any of the foregoing be pending; nor shall there, by


                                       34
<PAGE>

any action taken, or any statute, rule, regulation,  or order enacted,  entered,
enforced,  or deemed applicable to the purchase and sale of the Common Shares or
the Super  Common  Shares or the  conveyance  of the  Property  which  makes the
consummation of any of such transactions illegal.

        (d) The Recapitalization shall have been completed.

       11.2 Additional  Conditions to Obligations of CAS and the ESOT Purchaser.
In addition to the conditions set forth in Section 11.1, the  obligations of CAS
and the ESOT  Purchaser to purchase the Common  Shares and Super Common  Shares,
respectively,  and to convey  the  Property  to Seller  shall be  subject to the
satisfaction at or prior to the Closing of the following conditions:

        (a) All of the  representations  and  warranties  made by Seller  herein
shall be true and correct in all  material  respects as of the Closing Date with
the same force and effect as if such  representations  and  warranties  had been
made as of the Closing Date, except as expressly contemplated herein and CAS and
the ESOT  Purchaser  shall have received a certificate  to such effect signed on
behalf of Seller by the Chief Executive  Officer or Chief  Financial  Officer of
Seller.

        (b) Seller shall have performed in all material respects all obligations
required to be performed  by it under this  Agreement on or prior to the Closing
Date and CAS and the ESOT  Purchaser  shall have received a certificate  to such
effect  signed on behalf of  Seller  by the  Chief  Executive  Officer  or Chief
Financial Officer of Seller.

        (c) CAS shall have obtained financing for the ESOT Loan from a qualified
financial institution and shall have loaned such amount to ESOT Purchaser.

        (d) The ESOT Purchaser  shall have received a fairness  opinion from its
financial  advisor to the effect that the portion of the Purchase  Price payable
by the ESOT does not exceed the fair market value of the Super Common Shares and
that  the  purchase  of the  Super  Common  Shares  is fair to the  ESOT  from a
financial point of view.

        (e) Seller shall have executed and delivered a Master Services Agreement
in substantially the form attached as Exhibit 11.2(e) hereto (the "MSA").

        (f) Seller shall have executed and  delivered the Lease  Agreement and a
sublease for the Bothell Facility in the form of Exhibit 11.2(f) attached hereto
(the "Sublease").

        (g) EMCON shall have executed and delivered a Right of First Refusal and
Stock Option Agreement in the form attached hereto as Exhibit 11.2(g);

        (h) The ESOT  Purchaser and CAS shall have received a legal opinion from
R.  Michael  Momboisse,  Chief  Financial  Officer and  Vice-President-Legal  of
Seller, in substantially the form of Exhibit 11.2(h) attached hereto.

        (i) The ESOT  Purchaser  shall have  received a legal  opinion from Alan
Engstrom,  counsel to CAS, in substantially the form of Exhibit 11.2(i) attached
hereto.

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<PAGE>

        (j) All other  agreements  and  documents  required  to be  executed  or
delivered  by Seller or  Management  Purchasers  shall  have been  executed  and
delivered by them as contemplated hereby.

     11.3  Additional  Conditions  to Seller's  Obligations.  In addition to the
conditions  set forth in Section 11.1,  Seller's  obligations to sell the Common
Shares and the Super Common Shares to CAS and the ESOT Purchaser,  respectively,
shall be subject to the satisfaction at or prior to the Closing of the following
conditions:

        (a)  All  of  the  representations  and  warranties  made  by  the  ESOT
Purchaser,  Management  Purchasers,  and CAS herein shall be true and correct in
all  material  respects as of the Closing Date with the same force and effect as
if such  representations  and  warranties  had been made as of the Closing Date,
except  as  expressly  contemplated  herein,  and  Seller  shall  have  received
certificates  to such  effect  signed  by the  Trustee  on  behalf  of the  ESOT
Purchaser and signed by Stephen W. Vincent,  as Chief  Executive  Officer of CAS
and on behalf of the  Management  Purchasers,  each of whom hereby  appoints Mr.
Vincent to act as his or her representative for such purpose.

        (b) The ESOT  Purchasers,  CAS,  and  Management  Purchaser  shall  have
performed in all material  respects all obligations  required to be performed by
them under this Agreement on or prior to the Closing Date, and Seller shall have
received certificates to such effect signed by the Trustee on behalf of the ESOT
Purchaser and signed by Stephen W. Vincent,  as Chief  Executive  Officer of CAS
and on behalf of the  Management  Purchasers,  each of whom hereby  appoints Mr.
Vincent to act as his or her representative for such purpose.

        (c) CAS shall have executed and delivered the EMCON Notes and Assignment
of Stock Pledge Agreement.

        (d) CAS shall have executed and delivered the MSA.

        (e) CAS shall have executed and  delivered  the Lease  Agreement and the
Sublease.

        (f) Seller  shall  have  received a legal  opinion  from Alan  Engstrom,
counsel to CAS, in substantially the form of Exhibit 11.3(f) attached hereto.

        (g) Seller shall have  received a legal opinion from  McDermott,  Will &
Emery,  counsel  to the  ESOT,  in  substantially  the form of  Exhibit  11.3(g)
attached hereto.

        (h) The CAS  Officer's  Certificate  shall be executed and  delivered to
Seller.

        (i) Seller shall have received a letter from  Houlihan,  Lokey,  Howard,
and Zukin ("Houlihan")  stating in substance that, in its opinion,  the approach
taken by Williamette Management Associates,  Inc. with respect to the evaluation
of CAS,  and its  conclusion  regarding  the  purchase  price  paid by the  ESOT
Purchaser for the Super Common Shares are  reasonable  based on the  information
reviewed by Houlihan in connection with its engagement by Seller.

                                       36
<PAGE>

        (j) All  other  agreements  or  documents  required  to be  executed  or
delivered by CAS, the ESOT  Purchaser,  or Management  Purchaser shall have been
executed and delivered by them as contemplated hereby.

     11.4  Additional  Conditions to  Obligations of Management  Purchasers.  In
addition to the conditions set forth in Section 11.1, the Management Purchasers'
obligations  to purchase the shares of Common Stock from CAS shall be subject to
the  satisfaction  of all the  conditions  set  forth in  Sections  11.2 and the
additional  condition  that CAS shall have  executed  and  delivered  employment
agreements with members of senior  management  listed on Schedule 11.4 hereto in
the form attached hereto as Exhibit 11.4

                                   ARTICLE 12.
              Pre-Closing and Post-Closing Covenants of the Parties

     12.1 Plan  Operation.  CAS shall submit the Columbia  Analytical  Services,
Inc.,  Employee Stock  Ownership Plan ("ESOP") to the Internal  Revenue  Service
("IRS") for a  favorable  determination  letter  within the  remedial  amendment
period  set forth in Section  401(b) of the Code and shall make such  changes to
the  ESOP  as  the  IRS  requires  as  a  condition  to  the  issuance  of  such
determination  letter.  Further,  CAS shall  cause the ESOP to be  operated  and
administered  as a qualified  plan under  Sections  401(a) and 4975(e)(7) of the
Code and in material  compliance  with all applicable  requirements of ERISA and
regulations  thereunder  as from time to time in effect  and  applicable  to the
ESOP.

     12.2 401(k) Plan  Rollover.  Seller  shall  provide  pre- and  post-closing
assistance  to CAS in the  transfer  of CAS  Employees'  401(k)  Plan  accounts,
including converting 401(k) loan assets to a new 401(k) plan administrator.  All
CAS employees  participating  in the Seller's  401(k) Plan shall be deemed fully
vested in such plan as of Closing and  entitled to rollover of their  vested and
unvested account balances  conditioned upon  satisfaction of all remaining ERISA
requirements.

     12.3 Purchase of Stock by Management  Purchasers.  Following  Closing,  the
Management  Purchasers  shall  purchase  the stock from CAS as  contemplated  by
Section 1.4.

     12.4  Reimbursement of Long Distance.  Seller currently has a contract with
MCI for long  distance  service.  Seller and CAS agree that CAS will continue to
use MCI under the terms of this contract until such time as the parties mutually
agree  otherwise.  Seller shall invoice CAS monthly for its actual charges under
the MCI  contract  and CAS shall  timely pay such invoice as is customary in the
industry.

     12.5  Expenses.  CAS shall pay its  expenses  and the  expenses of the ESOT
Purchaser, incurred in connection with the authorization, preparation, execution
and performance of this Agreement.

     12.6 Further  Assurance.  Consistent with the terms and conditions  hereof,
each party hereto shall execute and deliver such instruments and take such other
action as the other parties hereto may reasonably  require in order to carry out
this Agreement and the transactions contemplated hereby.

                                       37
<PAGE>

     12.7 Confidentiality.  All written and unwritten information made available
to the ESOT  Purchaser  and its  representatives  and all copies,  excerpts  and
summaries  thereof  shall be treated and held by them in  confidence,  excepting
only that such data may be disclosed in confidence to advisors and agents of the
ESOT  Purchaser and  potential  lenders for the sole purpose of carrying out the
terms of this Agreement.

     12.8 Cooperation in Financial  Reporting and Tax. After the Closing CAS and
the Management Purchasers agree to cooperate,  and to cause CAS's accountants to
cooperate, with Seller and its accountants in:

        (a) the preparation or auditing of any consolidated financial statements
of Seller and any reports required to be filed by Seller with the Securities and
Exchange Commission;

        (b) the  preparation of any tax return or compliance with any tax audit;
or

        (c) any matter of a similar  nature;  with respect to any period  during
which CAS was a subsidiary of Seller.

     12.9  Continued  Coverage  Under Seller Group Plans.  From the Closing Date
through April 30, 1997,  Seller agrees to maintain  coverage  under its standard
life, accidental death and dismemberment, long-term disability, and supplemental
life  insurance  plans for the benefit of each person who was an employee of CAS
on the  Closing  Date to the same  extent as any such  employee  would have been
eligible  for  coverage  under  such  plans  were CAS to  remain a  wholly-owned
subsidiary  of Seller.  CAS agrees to reimburse  Seller for all premiums paid by
Seller on behalf of such employees for coverage on or after the Closing Date, as
well as any  additional  costs  incurred  by  Seller  in  connection  with  such
coverage.

     12.10 Issuances of Additional Equity Security. After the date hereof, until
such time as the ESOT  Notes have been  repaid in full,  CAS shall not issue any
equity  securities  (including  instruments  or  securities  exercisable  for or
convertible into equity securities) without the written consent of EMCON and the
ESOT Purchaser, other than:

        (i) the  shares  of  Common  Stock  to be  purchased  by the  Management
Purchasers pursuant to Section 1.4 hereof; and

        (ii) the  options  granted  to the  Management  Purchasers  pursuant  to
Section  1.5 hereof  and up to  1,516,666  shares of Common  Stock  issued  upon
exercise of such options.

                                   ARTICLE 13.
                                     General

     13.1 Execution of  Counterparts.  For the convenience of the parties,  this
Agreement  may be executed in one or more  counterparts,  each of which shall be
deemed an original,  but all of which together shall constitute one and the same
document.

                                       38
<PAGE>

     13.2 Notices.  All notices  which are required or may be given  pursuant to
the terms of this  Agreement  shall be in writing and shall be sufficient in all
respects if delivered  personally,  by  registered  or certified  mail,  postage
prepaid, overnight courier, or by facsimile, as follows:

                  If to the Seller:
                  EMCON
                  Attention:  R. Michael Momboisse, CFO
                  400 South El Camino Real, Suite 1200
                  San Mateo, CA 94402-1708
                  Facsimile:  (415) 375-0763

                  If to the Management Purchasers:
                  Columbia Analytical Services, Inc.
                  Attention:  Stephen W. Vincent
                  1317 S. 13th Ave.
                  P.O. Box 479
                  Kelso, WA  98626
                  Facsimile: (360) 425-9096

                  If to the ESOT Purchaser:
                  CAS Employee Stock Ownership Trust.
                  c/o Columbia Analytical Services, Inc.
                  1317 S. 13th Ave.
                  P.O. Box 479
                  Kelso, WA 98626
                  Facsimile:  (360) 425-9096

                  If to CAS to:
                  Columbia Analytical Services, Inc.
                  Attention: Stephen W. Vincent, President
                  1317 S. 13th Ave.
                  P.O. Box 479
                  Kelso, WA 98626
                  Facsimile:  (360) 425-9096

or to such  other  address or  facsimile  number as shall be  furnished  in like
manner by any party to the others.  Any such notice shall be deemed to have been
given,  received and become effective for all purposes at the time it shall have
been (a)  delivered to the  addressee  as  indicated  by the return  receipt (if
transmitted  by mail) or the  affidavit  of the  messenger  (if  transmitted  by
personal   delivery)  or  the   confirmation  of  receipt  (if  transmitted  via
facsimile);  or (b)  presented  for  delivery to the  addressee  as so indicated
during normal  business  hours, if such delivery shall have been refused for any
reason.

     13.3  Assignment,  Successors and. This Agreement shall be binding upon and
inure to the benefit of the parties hereto and their  respective  successors and
assigns.  No party  shall  assign  any of its  rights or  obligations  hereunder


                                       39
<PAGE>

without the prior  written  consent of the other  parties  other than to a party
that acquired  substantially all of the transferor's  assets through a merger or
asset purchase.

     13.4 Governing Law. This Agreement shall be governed by, and interpreted in
accordance  with, the  substantive  laws of the State of  Washington,  except as
preempted by ERISA or required by the Code.  Venue and jurisdiction for any suit
or proceeding with respect to the interpretation or enforcement of any provision
hereof shall be in the County of Cowlitz, State of Washington.

     13.5 Entire  Agreement.  This  Agreement,  together  with the schedules and
exhibits  attached  hereto,  constitutes the entire  agreement among the parties
hereto, and no party hereto shall be bound by any communications between them on
the subject matter hereof unless such  communications  are in writing and bear a
date  contemporaneous  with or subsequent to the date hereof.  Any prior written
agreements or letters of intent among the parties  shall,  upon the execution of
this Agreement, be null and void.

     13.6 Headings.  The headings in the sections of this Agreement are inserted
for  convenience  only and  shall not  constitute  a part  hereof or affect  the
meaning or interpretation hereof.

     13.7  Representations  as to Compliance with Law. Whenever a representation
or  warranty  is made  herein  with  respect to  compliance  with any law,  that
representation  means  the  applicable  subject  matter  is in  compliance  with
applicable  statutes,  regulations  and  ordinances  as in existence on the date
hereof  and on the  Closing  Date and  does  not  extend  to any  amendments  or
revisions of such laws adopted subsequent to such dates.

     13.8 Severability.  The invalidity or  unenforceability of any provision of
this  Agreement  shall not affect the  validity or  enforceability  of any other
provision hereunder.

     13.9  Facsimile  Signatures.  Delivery  of  an  executed  counterpart  of a
signature page to this Agreement by facsimile  shall be effective as delivery of
a manually executed counterpart of this Agreement.

     13.10  ERISA  Construction.  Whenever  possible,  each  provision  of  this
Agreement  shall be construed and  interpreted in such manner as to be effective
and valid under ERISA and the Code, and regulations  issued  thereunder,  but if
any  provision  of  this  Agreement  shall  be  prohibited  by,  or  invalid  or
unenforceable  under,  such statutes or  regulations,  such  provision  shall be
ineffective and  unenforceable  to the extent of such prohibition or invalidity,
without invalidating the remainder of such provision or the remaining provisions
of this Agreement.

     13.11  Waiver,   Discharge,  etc.  This  Agreement  may  not  be  released,
discharged or modified  except by an  instrument in writing  signed on behalf of
each of the parties  hereto.  The failure of a party to enforce any provision of
this Agreement shall not be deemed a waiver by such party of any other provision
or subsequent breach of the same or any other obligation hereunder.

     13.12 Action Taken as Trustee.  This  document was executed by the Trustee,
not in its individual or corporate capacity, but solely as Trustee of the Trust.
The  performance  of this  Agreement  by the  Trustee  and  any and all  duties,


                                       40
<PAGE>

obligations  and  liabilities of the Trustee  hereunder  shall be effected by it
only as Trustee. The Trustee does not undertake nor shall it have any individual
or corporate  liability or obligation of any nature  whatsoever by virtue of the
execution and delivery of this Agreement,  or the representations,  covenants or
warranties contained herein.

     13.13  Consents  or  Waivers by  Management  Purchasers.  The  holders of a
majority  of the  shares  of  Common  Stock  sold to the  Management  Purchasers
pursuant to paragraph  1.4 hereof shall have the power and  authority to execute
any waiver,  consent, or amendment of or pursuant to this Agreement on behalf of
all of the Management  Purchasers;  provided,  however, that any such instrument
that  materially and adversely  affects the rights of any  Management  Purchaser
relative to the rights of the other Management Purchasers shall not be effective
against such Management Purchaser unless signed by him/her.

     IN WITNESS WHEREOF, the parties have signed this Agreement the day and year
first above written.

EMCON, a California corporation          __/s/________________________________
                                         STEPHEN W VINCENT

By  /s/R. Michael Momboisse              _/s/_________________________________
   ------------------------------------  GENE BENNETT
        Its  CFO & VP Legal
             --------------------------   

"Seller"
COLUMBIA ANALYTICAL SERVICES, INC.,
a Washington corporation                 ____/s/______________________________
                                         DAVID L. EDELMAN, JR.

By /s/Stephen W. Vincent
   ------------------------------------
         Its President                   _______/s/___________________________
             --------------------------  JEFF CHRISTIAN
"CAS"
NORTHWESTERN TRUST, Trustee of the
COLUMBIA ANALYTICAL SERVICES, INC.,
EMPLOYEE STOCK OWNERSHIP TRUST           _____/s/_____________________________
                                         JUDIE A. SCHOLES
By /s/Stephen W. Vincent
   -----------------------------------
    Its President
        -------------------------------

                  "ESOT Purchaser"       ___/s/_______________________________
                                         JOHN S. TAI

                                         ___/s/_______________________________
                                         ERIC H. GRINDELAND

                                      
                                         By____/s/____________________________
                                           STEPHEN W. VINCENT, Attorney-in-Fact

                                       41
<PAGE>
                                         _____/s/_____________________________
                                         MICHAEL SHELTON
                                         

                                         By_______/s/_________________________
                                           STEPHEN W. VINCENT, Attorney-in-Fact

                                                         "Management Purchasers"


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