EXHIBIT 10.30

                             SECURED PROMISSORY NOTE

$225,000                                                          April 3, 1998


     FOR VALUE RECEIVED, the undersigned, Timothy M. Keaten ("Borrower"), hereby
promises to pay to EMCON, a California  corporation  ("Lender"),  or order,  the
principal sum of Two Hundred Twenty-Five  Thousand Dollars ($225,000),  together
with accrued interest as provided herein.

A.  Interest.  Interest shall accrue with respect to the principal sum hereunder
at the per annum rate equal to eight percent (8.0%).  Interest payable hereunder
shall be  calculated  on the basis of a three  hundred  sixty (360) day year for
actual days elapsed.  Interest  shall be due and payable in arrears on the first
day of each third calendar month, commencing with the first month after the date
hereof.

B.       Payment.

         1. Scheduled Payment. The principal  indebtedness plus accrued interest
thereon  shall be payable in full on the third  anniversary  of the date  hereof
(the "Payment Date").

         2. Optional  Prepayment.  Borrower shall have the right at any time and
from time to time to prepay,  in whole or in part,  the  principal of this Note,
without  payment of any premium or penalty.  Any principal  prepayment  shall be
accompanied by a payment of all interest  accrued on the amount prepaid  through
the date of such prepayment.

         3. Form of Payment.  Principal  and interest and all other  amounts due
hereunder  are to be paid in lawful  money of the  United  States of  America in
federal or other immediately  available funds. At the option of Borrower, on the
Payment  Due Date,  Borrower  may assign all right,  title and  interest  to the
Collateral (as defined  herein) to Lender and Lender shall apply the Fair Market
Value  (as  defined  in this  Section  B(3)) of the  Collateral  to the  Secured
Obligations (as defined herein), provided that Lender's securities are listed on
the Nasdaq National Market on the Payment Date. For the purposes of this Section
B, the term "Fair Market Value" shall mean the average of the closing  prices of
Lender  Common Stock for the seven  trading days  preceding the Payment Date, as
reported  on the  Nasdaq  National  Market.  If the  Fair  Market  Value  of the
Collateral is  insufficient  to pay the full amount of the Secured  Obligations,
Borrower shall be liable for the deficiency as set forth above.

C.       Security Interest.

         1. Grant of  Security  Interest.  Borrower  grants to Lender a security
interest in the Collateral,  as defined herein,  to secure the payment of all of
the  indebtedness  hereunder (the "Secured  Obligations").  Notwithstanding  the
foregoing, Borrower acknowledges that this Note is a full recourse note and that
the  undersigned  is liable for full payment of this Note without  regard to the
value at any time or from  time to time of the  Collateral.  In the event of any
default in the payment of this Note, the Company shall have and may exercise any
and all remedies of a secured party under the  California  Commercial  Code, and
any  other  remedies  available  at  law  or in  equity,  with  respect  to  the
Collateral.

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         2.  Representations  and  Warranties  Regarding  Collateral.   Borrower
represents  and warrants to Lender that Borrower is the true and lawful owner of
the Collateral,  having good and marketable title thereto, free and clear of any
and all  Liens  other  than the Lien and  security  interest  granted  to Lender
hereunder.  Borrower  shall not create or assume any such Lien on or against any
of the  Collateral  except as created or  permitted  by this Note,  and Borrower
shall  promptly  notify Lender of any such other Lien against the Collateral and
shall  defend  the  Collateral  against,  and  take all  such  action  as may be
necessary to remove or discharge, any such Lien.

         3. Perfection of Security Interest. Borrower agrees to take all actions
requested  by Lender and  reasonably  necessary  to  perfect,  to  continue  the
perfection  of, and to  otherwise  give notice of, the Lien  granted  hereunder,
including, but not limited to, execution of financing statements.

D.       Events of Default.

         1. Definition of Event of Default. The occurrence of any one or more of
the following events shall constitute an "Event of Default" hereunder,  provided
that Borrower has been provided  written notice of such Event of Default and has
not cured such Event of Default with twenty (20) days of receipt of such notice:

                  (i)      Borrower's breach of the obligation to pay any amount
payable  hereunder on the date that it is due and payable;

                  (ii)  Borrower's  institution  of  proceedings  against it, or
Borrower's  filing of a petition or answer or consent seeking  reorganization or
release,  under the federal  Bankruptcy Code, or any other applicable federal or
state law relating to creditor rights and remedies, or Borrower's consent to the
filing  of any such  petition  or the  appointment  of a  receiver,  liquidator,
assignee,  trustee or other similar  official of Borrower or of any  substantial
part of its property,  or Borrower's  making of an assignment for the benefit of
creditors, or the taking of action in furtherance of such action;

                  (iii) the creation  (whether  voluntary or involuntary) of, or
any attempt to create, any Lien upon any of the Collateral, or the making or any
attempt to make any levy,  seizure or  attachment  thereof and such Lien,  levy,
seizure, or attachment has not been removed,  discharged or rescinded within ten
(10) days,  provided  that the Fair Market Value (as defined in Section  D(2)(a)
below)  of the  Collateral  is less  than  110% of the  aggregate  amount of the
Secured Obligations;

                  (iv) the entry of any judgment or order against Borrower which
remains  unsatisfied  or  undischarged  and in effect for thirty (30) days after
such entry without a stay of  enforcement  or execution,  provided that the Fair
Market Value (as defined in Section  D(2)(a)  below) of the  Collateral  is less
than 110% of the aggregate amount of the Secured Obligations.

                  (v)  Borrower's  breach  of  any   representation,   warranty,
covenant  or  agreement  of  Borrower  set  forth in the  Agreement  and Plan of
Reorganization by and among Lender,  Borrower,  Advanced  Analytical  Solutions,
Inc.  ("A2S"),  the  Shareholders  of  A2S  and  Advanced  Analytical  Solutions
Delaware, Inc. dated April 3, 1998.

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         2.       Rights and Remedies on Event of Default.

                  (a) During the continuance of an Event of Default and prior to
Lender  invoking its rights set forth below,  Lender agrees that upon assignment
by  Borrower to Lender of all of  Borrower's  right,  title and  interest to the
Collateral, Lender shall apply the Fair Market Value (as defined in this Section
D(2)(a))  of the  Collateral  to the  Secured  Obligations  as payment  for such
Secured  Obligations.  For the purposes of this Section D, the term "Fair Market
Value" shall mean shall mean the average of the closing  prices of Lender Common
Stock for the seven trading days preceding the initial date the Event of Default
first occurred,  as reported on the Nasdaq National  Market.  If the Fair Market
Value of the Collateral is  insufficient to cover the full amount of the Secured
Obligations,  Borrower  shall be liable for the  deficiency  and Lender shall be
entitled  to fully  exercise  its rights set forth  below.  Notwithstanding  the
foregoing,  in the event that Lender's  securities  are not listed on the Nasdaq
National  Market at the time of an Event of Default,  this Section D(2)(a) shall
have no effect and Lender  shall be  entitled to fully  exercise  its rights set
forth below.

                  (b)  During the  continuance  of an Event of  Default,  Lender
shall  have the  right,  itself or through  any of its  agents,  with or without
notice  (except as provided in Section  D(1)  above) to  Borrower  (as  provided
below), as to any or all of the Collateral, by any available judicial procedure,
or without judicial process  (provided,  however,  that it is in compliance with
the UCC),  to exercise any and all rights  afforded to a secured party under the
UCC or other  applicable law.  Without limiting the generality of the foregoing,
Lender shall have the right to sell or  otherwise  dispose of all or any part of
the  Collateral,  either at public or private sale, in lots or in bulk, for cash
or for credit,  with or without  warranties  or  representations,  and upon such
terms and conditions, all as Lender, in its sole discretion, may deem advisable,
and it shall have the right to purchase at any such sale. Borrower agrees that a
notice sent at least  fifteen (15) days before the time of any  intended  public
sale or of the time after which any  private  sale or other  disposition  of the
Collateral  is to be made  shall  be  reasonable  notice  of such  sale or other
disposition.  The  proceeds of any such sale,  or other  Collateral  disposition
shall  be  applied,  first  to  the  expenses  of  retaking,  holding,  storing,
processing  and  preparing  for sale,  selling,  and the like,  and to  Lender's
reasonable  attorneys'  fees  and  legal  expenses,  and  then  to  the  Secured
Obligations and to the payment of any other amounts  required by applicable law,
after which Lender shall account to Borrower for any surplus proceeds.  If, upon
the sale or other  disposition  of the  Collateral,  the  proceeds  thereof  are
insufficient  to pay all amounts to which Lender is legally  entitled,  Borrower
shall be liable  for the  deficiency,  together  with  interest  thereon  at the
Default Rate, and the reasonable fees of any attorneys Lender employs to collect
such deficiency.  To the extent permitted by applicable law, Borrower waives all
claims,  damages and demands against Lender arising out of the retention or sale
or lease of the  Collateral  or other  exercise of Lender's  rights and remedies
with respect thereto.

                  (c) To the extent permitted by law, Borrower covenants that it
will not at any time insist upon or plead,  or in any manner  whatever  claim or
take any benefit or advantage  of, any stay or extension  law now or at any time
hereafter in force,  nor claim,  take or insist upon any benefit or advantage of
or from  any law now or  hereafter  in  force  providing  for the  valuation  or
appraisal  of the  Collateral  or any part  thereof,  prior to any sale or sales
thereof to be made pursuant to any provision  herein  contained,  or the decree,
judgment or order of any court of competent jurisdiction; or, after such sale or
sales,  claim or exercise any right under any statute now or  hereafter  made or
enacted by any state or  otherwise  to redeem the  property  so sold or any part
thereof, and, to the full extent legally permitted,  hereby expressly waives all
benefit and advantage of any such law or laws,  and  covenants  that it will not
invoke or utilize any such law or

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laws or otherwise  hinder, delay or impede  the  execution of any power herein
granted and  delegated  to Lender,  but will suffer and permit the  execution of
every such power as though no such power, law or laws had been made or enacted.

                  (d) Any sale,  whether under any power of sale hereby given or
by virtue of judicial proceedings, shall operate to divest all Borrower's right,
title, interest, claim and demand whatsoever, either at law or in equity, in and
to the Collateral sold, and shall be a perpetual bar, both at law and in equity,
against  Borrower,  its  successors  and  assigns,  and  against all persons and
entities  claiming the Collateral  sold or any part thereof under, by or through
Borrower, its successors or assigns.

                  (e) Borrower  appoints  Lender,  and any officer,  employee or
agent of Lender, with full power of substitution,  as Borrower's true and lawful
attorney-in-fact,  effective as of the date hereof,  with power, in its own name
or in the name of Borrower,  during the  continuance of an Event of Default,  to
endorse any notes, checks, drafts, money orders, or other instruments of payment
in respect of the Collateral that may come into Lender's possession, to sign and
endorse any drafts against debtors,  assignments,  verifications  and notices in
connection with accounts, and other documents relating to Collateral;  to pay or
discharge  taxes or Liens at any time levied or placed on or threatened  against
the Collateral;  to demand,  collect, issue receipt for, compromise,  settle and
sue for monies due in respect of the Collateral;  to notify persons and entities
obligated  with respect to the  Collateral to make payments  directly to Lender;
and,  generally,  to do, at Lender's  option and at Borrower's  expense,  at any
time, or from time to time, all acts and things which Lender deems  necessary to
protect, preserve and realize upon the Collateral and Lender's security interest
therein  to effect  the intent of this  Note,  all as fully and  effectually  as
Borrower might or could do; and Borrower  hereby ratifies all that said attorney
shall lawfully do or cause to be done by virtue  hereof.  This power of attorney
shall be irrevocable as long as any of the Secured Obligations are outstanding.

                  (f) All of Lender's  rights and  remedies  with respect to the
Collateral,  whether established hereby or by any other agreements,  instruments
or  documents  or by law  shall be  cumulative  and may be  exercised  singly or
concurrently.

E.       Other Provisions.

         1.       Definitions.  As used herein, the following terms shall have 
the following meanings:

         "Collateral"  means all of  Borrower's  right,  title and  interest  in
55,944 shares of the capital  stock of EMCON,  a California  corporation,  owned
beneficially and of record by borrower.

         "Lien"  means  any  lien  (statutory  or  other),   mortgage,   pledge,
hypothecation, assignment, deposit arrangement, security interest, charge, claim
or other  encumbrance of any kind (including any conditional sale or other title
retention  agreement,  and any agreement to give any security  interest) and any
agreement   to  give  or  refrain   from  giving  a  lien,   mortgage,   pledge,
hypothecation, assignment, deposit arrangement, security interest, charge, claim
or other encumbrance of any kind.

         "UCC" means the Uniform  Commercial Code in effect from time to time in
the relevant jurisdiction.

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         2. Governing Law; Venue. This Note shall be governed by the laws of the
State of  California,  without  giving  effect to conflicts  of law  principles.
Borrower and Lender agree that all actions or proceedings  arising in connection
with this Note shall be tried and litigated only in the state and federal courts
located in the County of San Mateo,  State of California or, at Lender's option,
any court in which Lender  determines it is necessary or appropriate to initiate
legal or equitable proceedings in order to exercise, preserve, protect or defend
any of its rights and  remedies  under this Note or  otherwise  or to  exercise,
preserve,  protect or defend its Lien,  and the  priority  thereof,  against the
Collateral,  and  which  has  subject  matter  jurisdiction  over the  matter in
controversy.  Borrower  waives any right it may have to assert the  doctrine  of
forum non  conveniens  or to object to such  venue,  and  consents  to any court
ordered relief.  Borrower  waives personal  service of process and agrees that a
summons and complaint commencing an action or proceeding in any such court shall
be  promptly  served  and  shall  confer  personal  jurisdiction  if  served  by
registered or certified mail to Borrower.  If Borrower fails to appear or answer
any  summons,  complaint,  process or papers so served  within  thirty (30) days
after the mailing or other service thereof, it shall be deemed in default and an
order of  judgment  may be entered  against it as demanded or prayed for in such
summons,  complaint,  process  or papers.  The choice of forum set forth  herein
shall not be deemed to preclude the enforcement of any judgment obtained in such
forum,  or the taking of any action under this Note to enforce the same,  in any
appropriate jurisdiction.

         3.  Notices.  Any  notice or  communication  required  or desired to be
served,  given or delivered  hereunder shall be in the form and manner specified
below, and shall be addressed to the party to be notified as follows:

If to Lender:          EMCON
                       400 S. El Camino Real, Suite 200
                       San Mateo, California  94402
                       Attention: R. Michael Momboisse, Chief Financial Officer
                       Fax: (650) 375-0763
                       Phone: (650) 375-1522


If to Borrower:        Timothy M. Keaten
                       3048 East Clairton Drive
                       Highlands Ranch, Colorado 80126
                       Fax: (303) 292-3883
                       Phone: (303) 296-8880

or to such other address as each party  designates to the other by notice in the
manner  herein  prescribed.  Notice  shall  be  deemed  given  hereunder  if (i)
delivered  personally  or otherwise  actually  received,  (ii) sent by overnight
delivery  service,  (iii) mailed by  first-class  United  States  mail,  postage
prepaid,  registered or certified,  with return receipt requested,  or (iv) sent
via  telecopy  machine  with a  duplicate  signed  copy  sent on the same day as
provided in clause (ii) above.  Notice  mailed as provided in clause (iii) above
shall be effective  upon the  expiration  of three (3)  business  days after its
deposit in the United States mail,  and notice  telecopied as provided in clause
(iv) above shall be  effective  upon receipt of such  telecopy if the  duplicate
signed copy is sent under  clause (iv) above.  Notice  given in any other manner
described in this  section  shall be  effective  upon  receipt by the  addressee
thereof;  provided,  however, that if any notice is tendered to an addressee and
delivery  thereof is refused by such  addressee,  such notice shall be effective
upon such tender unless expressly set forth in such notice.

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         4. Lender's Rights; Borrower Waivers. Lender's acceptance of partial or
delinquent payment from Borrower hereunder,  or Lender's failure to exercise any
right  hereunder,  shall not  constitute a waiver of any  obligation of Borrower
hereunder, or any right of Lender hereunder, and shall not affect in any way the
right to require full  performance at any time  thereafter.  Except as otherwise
specifically provided herein, Borrower waives presentment,  diligence, demand of
payment,  notice,  protest and all other demands and notices in connection  with
the delivery, acceptance,  performance,  default or enforcement of this Note. In
any action on this Note,  Lender need not  produce or file the  original of this
Note,  but need only file a photocopy of this Note certified by Lender be a true
and correct copy of this Note in all material respects.

         5.  Enforcement  Costs.  Borrower  shall pay all  costs  and  expenses,
including,  without limitation,  reasonable  attorneys' fees and expenses Lender
expends  or  incurs  in  connection  with  the  enforcement  of this  Note,  the
collection of any sums due hereunder,  any actions for declaratory relief in any
way related to this Note, or the protection or preservation of any rights of the
holder hereunder.

         6. Severability. Whenever possible each provision of this Note shall be
interpreted  in such manner as to be effective and valid under  applicable  law,
but if any provision is prohibited by or invalid under  applicable law, it shall
be  ineffective  to the  extent  of  such  prohibition  or  invalidity,  without
invalidating the remainder of the provision or the remaining  provisions of this
Note.

         7. Amendment Provisions.  This Note may not be amended or modified, nor
may any of its terms be waived, except by written instruments signed by Borrower
and Lender.

         8. Binding Effect.  This Note shall be binding upon, and shall inure to
the benefit of, Borrower and the holder hereof and their  respective  successors
and assigns; provided, however, that Borrower's rights and obligations shall not
be assigned or delegated  without Lender's prior written  consent,  given in its
sole discretion, and any purported assignment or delegation without such consent
shall be void ab initio.

         9. Time of Essence.  Time is of the essence of each and every provision
of this Note.

         10.  Headings.  Section  headings used in this Note have been set forth
herein for  convenience of reference  only.  Unless the contrary is compelled by
the context, everything contained in each section hereof applies equally to this
entire Note.

                                        BORROWER



                                        By_________________________________
                                          Timothy M. Keaten




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