EXHIBIT 10.21

                                    AGREEMENT


         THIS  AGREEMENT  is made as of November  30,  1995,  between  EMCON,  A
California corporation, (the "Company"), and Eugene M. Herson, (the "Employee").
Unless  otherwise  indicated,  certain of the capitalized  terms used herein are
defined in Exhibit A and shall have the meaning as assigned.

                                    RECITALS

         A. The Company  recognizes  that the possibility of a Change of Control
Event  exists and that the  Employee  possesses  an  intimate  knowledge  of the
Company. The Board of Directors of the Company (the "Board") believes that it is
necessary  that the Company be able to call on the  Employee for advice upon the
occurrence  of a Change of  Control  Event.  The Board  also  believes  that the
existence of this  Agreement  will enhance the Company's  ability to call on and
rely upon such Employee.

         B. The Company and the Employee  desire to enter into this Agreement in
order to  provide  additional  compensation  and  benefits  to the  Employee  in
recognition  of past services and to encourage  Employee to continue  employment
with the Employer.

         C. It is intended by the parties that the  provisions  of  paragraphs 2
and 3 of this Agreement shall be effective during the eighteen (18) month period
following a Change of Control Event.

                                    AGREEMENT

         NOW, THEREFORE,  for good and valuable consideration,  receipt of which
is hereby acknowledged, the Company and Employee agree as follows:

         1. TERM:  OPERATION OF AGREEMENT.  Except as provided in paragraph 1(a)
below, this Agreement shall be effective immediately, and, except as provided in
paragraph 1(b) below,  shall  terminate on the eightieth (18) month  anniversary
following any Change of Control Event.

                  (a) The provisions of paragraphs (2) and (3) of this Agreement
shall not become  effective  unless  (i) there is a Change of Control  Event and
(ii) the Employee is employed by the Company  immediately prior to the Change of
Control Event.  Notwithstanding the foregoing, if the Employee's employment with
the  Company  is  terminated  within  the  ninety  (90) day  period  immediately


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preceding a Change of Control Event and such termination  would have constituted
a  Termination  as defined in Exhibit A if  termination  had occurred  after the
Change of Control Event, the termination will be deemed to have occurred the day
after the  Change  of  Control  Event,  such  that  paragraphs  2 and 3 shall be
effective as to such termination.

                  (b) This  Agreement  shall  terminate on the first to occur of
the following:

                         (i) The  termination of the Employee's  employment with
the Company prior to a Change of Control Event unless such termination is deemed
to occur the day after such Change of Control  Event as  provided  in  paragraph
1(a) above.

                         (ii) Subject to the provisions of paragraph 3(f) below,
the termination of the Employee's employment following a Change of Control Event
is due to any of the following:  (a) termination by the Company with Cause,  (b)
death of the Employee, (c) Permanent Disability of the Employee or (d) voluntary
termination of employment by the Employee without Good Reasons.

         2. Service.  Once a Change of Control Event occurs,  the Employee shall
not voluntarily terminate his employment with the Company until ninety (90) days
after such Event has occurred.  Following a Change of Control Event, the Company
shall not  terminate  the  Employee's  employment  with the  Company,  except in
accordance  with this  Agreement  and the  Company  shall  provide not less than
ninety (90) days prior written notice of such Termination to the Employee.

         3.  Payments  and Benefits  Upon  Termination.  The  Employee  shall be
entitled to the following payments and benefits following Termination:

                  (a)  Termination  Payment.  The Company shall pay the Employee
within ten (10) days of the date of  Termination  an amount  equal to the sum of
twenty-four  (24) months cash  salary and a prorated  cash bonus,  if earned and
otherwise due.

                  (b) Welfare Plan  Benefits.  The Employee shall be entitled to
continuation of medical insurance  coverage under the Company's  Continuation of
Benefits  Program for Former Senior  Executives  (originally  implemented by the
Company on January 1, 1993). The Company shall pay the cost of medical insurance
coverage for a period equal to the lesser of (i)  twenty-four  months  following
the date of  Termination  or (ii)  until the  Employee  is  provided  by another
employer with medical insurance benefits.  The Employee shall notify the Company
within ten (10) days of any  employment  by the  Employee  during the period the
Company is paying for medical  insurance  coverage  pursuant  to this  paragraph
3(b).

                  (c) Vesting of Benefits.  Employee  shall  become  immediately
vested  in  full  in  any  and  all  employment  benefits,   including,  without
limitation:

                         (i) Employee's interest in the EMCON Shared Savings and
Profit Sharing Plan, including the Company match portion;  provided that if such
action is found to be a violation of ERISA, the Company shall have the option of


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instead  paying the Employee an amount which after taking account for applicable
withholding,  equals the unvested  balance of the Company  match  portion of the
Employees account.

                         (ii) all  amounts  payable as salary  continuation  and
noncompetition  payments under the salary  continuation  agreements  between the
Employee and the Company dated  November 1990 and November  1994;  provided that
(A) the portion of such payments representing salary continuation payments shall
be  immediately  due and payable  upon full  vesting and (B) the portion of such
payments representing noncompetition payments shall be paid to Employee in equal
monthly  installments  over a  three-year  period  commencing  from  the date of
departure  from the  Company and for so long  during the  subsequent  three-year
period as the Employee is not employed by a competitor  or potential  competitor
of the  Company.  For  purposes of the  foregoing,  a  competitor  or  potential
competitor  of the  Company  shall be defined as an  environmental  engineering,
consulting or construction company not affiliated with the Company.

                         (iii) all incentive and non-qualified  stock options to
purchase the Company's (or its successor's) capital stock, and

                         (iv) all restricted stock agreements.

                  (d) Continued Right to Exercise Options. Employee shall retain
the right to exercise all of the incentive and  nonqualified  stock options held
by you and referred to in paragraph  3(c)(iii) above for a period of up to three
years  after  Employee's  departure  from the  Company  or,  if  earlier,  until
expiration of the original term of the  respective  option  agreements,  and for
these purposes you shall be considered a continuing employee of EMCON.

                  (e) No  Mitigation.  All  payments  and  benefits to which the
Employee is entitled  under this  Agreement  shall be made and provided  without
offset,  deduction or  mitigation  on account of income the Employee may receive
from other employment or otherwise, except as provided in paragraph 3(b) above.

                  (f)  Death of the  Employee.  In the  event of the  Employee's
death  subsequent  to  Termination,  all payments and benefits  required by this
Agreement   shall  be  paid  to  the   Employee's   designated   beneficiary  or
beneficiaries  or, if he has not designated a beneficiary or  beneficiaries,  to
his estate.

         4. Arbitration.  Any claim, dispute or controversy arising out of or in
any way relating to the parties'  employment  relationship  (including,  but not
limited  to,  any  claims  of  wrongful   termination   or  age,  sex  or  other
discrimination),  this Agreement,  the  interpretation  of this Agreement or the
alleged breach thereof shall be submitted by the parties to binding  arbitration
by the  American  Arbitration  Association  in  San  Mateo  County,  California;


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provided,  however,  that  this  arbitration  provision  shall  not apply to any
disputes or claims relating to or arising out of the misuse or  misappropriation
of the Company's trade secrets or confidential and proprietary information.

         5.  Conflict in Benefits.  This  Agreement  shall  supersede  all prior
arrangements,  whether written or oral, and understandings regarding the subject
matter of this Agreement; provided, however, that this Agreement is not intended
to and  shall  not  affect,  limit or  terminate  (i) any  plans,  programs,  or
arrangements  of the  company  that are  either in  writing  or  regularly  made
available  to a  significant  number  of  employees  of the  Company,  (ii)  any
agreement or arrangement with the Employee that has been reduced to writing,  or
(iii) any agreements or  arrangements  hereafter  entered into by the parties in
writing.

         6.   Miscellaneous.

                  (a) Notices. Any notice or other communication provided for in
this Agreement or contemplated  hereby shall be  sufficiently  given if given in
writing and personally  delivered or delivered by certified mail, return receipt
requested, and addressed, in the case of the Company, to the Company at:

                           EMCON
                           400 S. El Camino Real, Suite 1200
                           San Mateo, CA  94402
                           Attn:  Chairman of the Board

and, in the case of the Employee, to the Employee at:

                           Eugene M. Herson
                           400 S. El Camino Real, Suite 1200
                           San Mateo, CA  94402

Either  party may  designate a  different  address by giving  written  notice of
change of address in the manner provided above.

                  (b) Waiver.  No waiver or  modification in whole or in part of
this Agreement,  or any term or condition hereof, shall be effective against any
party  unless in writing  and duly signed by the party  sought to be bound.  Any
waiver of any breach of any provision  hereof or any right or power by any party
on one occasion shall not be construed as a waiver of, or a bar to, the exercise
of such right or power on any other  occasion  or as a waiver of any  subsequent
breach.

                  (c)  Binding  Effect;  Successors.  This  Agreement  shall  be
binding upon,  inure to the benefit of, and be  enforceable  by, the Company and
the Employee and their respective heirs, legal  representatives,  successors and
assigns.  For purposes of the  foregoing,  the  successors  to the Company shall
include,  without  limitation,   successors  (whether  direct  or  indirect,  by
purchase,  merger,  consolidation,  or otherwise) to all or substantially all of
the  business or assets of the Company (a "Company  Successor").  If the Company
shall be merged into or consolidated with another entity, the provisions of this


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Agreement shall be binding upon and inure to the benefit of the entity surviving
such  merger  or  resulting  from such  consolidation.  The  provisions  of this
paragraph  6(c)  shall  continue  to apply to each  subsequent  employer  of the
Employee  hereunder  in the event of any  subsequent  merger,  consolidation  or
transfer or assets of such subsequent employer.

                  (d)  Separability.  Any provision of this  Agreement  which is
unenforceable  or  invalid  in any  jurisdiction  shall be  ineffective  in such
jurisdiction to the extent that it is unenforceable or invalid without affecting
the remaining  provisions hereof, which shall continue in full force and effect.
The  unenforceability  or  invalidity  of a provision  of this  Agreement in one
jurisdiction shall not invalidate or render  unenforceable such provision in any
other jurisdiction.

                  (e)  Controlling  Law. This Agreement shall be governed by and
construed in accordance  with the laws of the State of California  applicable to
contracts made and to be performed therein.

         IN WITNESS  WHEREOF,  the Company and the Employee  have  executed this
Agreement as of the day and year first above written.

ATTEST:                                COMPANY:
                                       EMCON, a California Corporation



/s/  Mollie C. Mortyn                  By:  /s/ Douglas P. Crane
- ----------------------                 ---------------------------
Title: Secretary                       Douglas P. Crane, Chairman of the Board


                                       EMPLOYEE:



                                       By: /s/ Eugene M. Herson
                                       ---------------------------
                                       Eugene M. Herson, President,
                                       Chief Executive Officer and Director



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