Document:

EXHIBIT 10.23

                         ADA ENVIRONMENTAL SOLUTIONS LLC
                              EMPLOYMENT AGREEMENT

     THIS AGREEMENT made and entered into this day of May 1, 1997, by and
between ADA Environmental Solutions LLC a Colorado limited liability company,
whose principal offices are located at 304 Inverness Way South, Suite 365,
Englewood, Colorado 80112 (the "Company"), and C. Jean Bustard (the "Employee),
whose address is 9193 Buffalo Drive, Littleton, CO 80127.

                                    RECITALS:

     A.   The Company has made Employee an offer of employment.
     B.   Employee desires to accept the offer.
     C.   The Company and Employee desire to enter into this Agreement to set
          forth the terms and conditions of the employment.

     NOW, THEREFORE in consideration of the premises and the mutual covenants
and agreements hereinafter set forth and for other good and valuable
consideration the receipt and sufficiency of which are hereby acknowledged, the
parties, intending to be legally bound, hereby agree as follows:

     1. Definitions.

     Capitalized terms are used herein with the meanings as specified in
Paragraph 7 hereof:

     2. Employment.

     The Company hereby employs the Employee and Employee hereby accepts such
employment upon the terms and conditions set forth herein.

     3. Term.

     (a) Initial Term.

     The initial Term of employment under this Agreement shall commence on the
date hereof and it shall continue for a period of three years from such date.
The Term shall be automatically extended for successive one-year periods. Either
party may terminate this Agreement for any reason by giving the other written
notice of its intent to terminate the Agreement not less than three months prior
to the intended date of termination. In addition, the Company may immediately
terminate this Agreement at any time "for cause" as defined below. The initial
Term and any such extensions are hereinafter referred to as the "Term."

     (b) For Cause.

     Notwithstanding any other provision of this Agreement, the Company may
terminate this Agreement for cause immediately upon notice to Employee. The
phrase "for cause" as used in this Agreement shall include, but not be limited
to, breach of any fiduciary duty to the Company, failure to perform Employee's
duties hereunder in a manner satisfactory to the majority of the managers of the
Company, death, permanent disability, or conviction in a criminal proceeding
(excluding traffic violations or similar misdemeanors). In the event that
Employee, during the Term of his employment, should die, become permanently
disabled, or have his employment terminated for cause by the Company, then
Employee shall be entitled to (x) all salary which may accrue to him through the
end of the last month during which he shall have been an employee of the
Company, and (y) such other benefits, if any, to which he is entitled in
accordance with any other section of this Agreement.

                                       1
<PAGE>

     4. Position, Duties and Authority.

     During the Term of this Agreement, Employee shall be employed as the
Executive Vice President of the Company. Employee shall report to the President
of the Company.

     5. Obligations of Employee.

     Employee hereby agrees that he will devote full-time to the fulfillment of
his obligations hereunder. Nothing contained in this agreement shall prevent the
Employee from pursuing the projects listed on the attached Exhibit A.

     6. Compensation and Benefits.

     In consideration of Employee's agreement to be employed by the Company and
as reasonable compensation for services to be rendered hereunder, the Company
agrees as follows:

     (a) Benefits.

     Employee shall be entitled to the standard benefits and perquisites from
time to time available to full-time employees of the Company. These benefits are
listed in Exhibit B. In addition, Employee shall accrue vacation at a rate of
4.62 hours per bi-weekly pay period. If the employee continues to work for the
Company on a full-time basis, the vacation accrual rate will be increased to
6.16 hours per bi-weekly pay period on August 11, 1997.

     (b) Compensation.

     The Company shall pay Employee bi-weekly compensation of $2884.62 during
the Term of employment as part of the Company's normal payroll procedures.
Increases in compensation, if any, shall be at the discretion of the Managers of
the Company.

     7. Definitions.

     (a) "Invention" shall mean any idea, discovery, article, process,
formulation, composition, combination, design, modification or improvement,
whether or not patentable.

     (b) "Copyright Works" shall mean all literary works, graphic works,
pictorial works and other creative works for which copyright protection may be
obtained, including without limitation proposals and computer
software/documentation.

     (c) "Confidential Subject Matter" shall mean all Inventions, Copyright
Works, data, specifications, know-how, lists, printed materials, technical
information, cost/pricing/marketing information and other subject matter that is
not available to the general public in a substantially identical form without
restriction.

                                       2
<PAGE>

     8. Disclosure/Ownership of Invention and Confidential Subject Matter.

     (a) During Employment.

     Employee agrees that during the term of Employee's employment with Company,
Employee will immediately disclose in writing to Company all Inventions and
Confidential Subject Matter which (i) is conceived or generated by Employee
alone and/or jointly with others, and (ii) relates to the actual or anticipated
business of the Company and/or relates to the actual or anticipated research or
development activities of the Company and/or is otherwise suggested by or
results from any activity performed on behalf of the Company. Employee
acknowledges and agrees that immediately upon conception or generation,
whichever occurs earlier, all Inventions and Confidential Subject Matter
disclosed and to be disclosed by Employee to Company during the term of
Employee's employment with Company will be the sole and exclusive property of
the Company.

     (b) Post Employment.

     Employee further agrees that, during the two (2) year period following any
termination of Employee's employment with the Company, Employee will immediately
disclose in writing to the Company all Inventions and Confidential Subject
Matter which (i) is conceived or generated by Employee alone and /or jointly
with others, and (ii) is based upon or otherwise derived from any Inventions
and/or Confidential Subject Matter of the Company. Employee acknowledges and
agrees that immediately upon conception or generation, whichever occurs earlier,
all Inventions and Confidential Subject Matter to be disclosed by Employee to
Company during the two (2) year period following the termination of Employee's
employment with Company will become the sole and exclusive property of the
Company.

     9. Assignment of Inventions and Confidential Subject Matter/Documentation/
Commercialization.

     (a) Assignment.

     Employee hereby assigns to Company the Employee's entire right, title and
interest in and to all Inventions and Confidential Subject Matter disclosed and
to be disclosed by Employee to Company pursuant to Sections 8 (a) and (b).

     (b) Documentation.

     Employee agrees to execute, cooperate in the preparation of and deliver to
the Company, both during the term of Employee's employment with the Company and
thereafter, any and all documents deemed necessary by the Company for the
Company to protect, maintain, preserve and enjoy the full right, title and
interest to all Inventions and Confidential Subject Matter disclosed and to be
disclosed by Employee to Company, including without limitation, the execution
and delivery of patent assignments and, at Company's legal expense, the
preparation of patent applications.

     (c) Commercialization.

     Employee acknowledges and agrees that with respect to all Inventions and
Confidential Subject Matter transferred by Employee to Company, Company is not
obligated to commercialize the same, and that if Employee desires to
independently commercialize any of said Inventions and/or Confidential Subject
Matter, Employee must request and obtain a written license from Company
beforehand, which license request may be declined by Company in its sole
discretion.

                                       3
<PAGE>

     10. Copyright Works.

     Employee agrees that all Copyright Works and contributions to Copyright
Works prepared by Employee within the scope of Employee's employment with the
Company will be deemed "works for hire" and will be owned by the Company, and
Employee agrees to execute all documents deemed necessary by the Company for the
Company to protect, maintain, preserve and enjoy the Company's rights in such
Copyright Works and contributions. Employee further agrees that unless expressly
authorized by the Company in writing, Employee will not independently prepare or
otherwise distribute or publish any Copyright Work that embodies any
Confidential Subject Matter owned by the Company or held in confidence by the
Company for any third-party, including without limitation, all Confidential
Subject Matter disclosed and to be disclosed by Employee to the Company.

     11. Written Records.

     Employee agrees that to the extent reasonably possible, Employee will
maintain written records of all Inventions and Confidential Subject Matter
conceived or generated by Employee in the course of Employee's performance of
services for the Company, which records will be the exclusive property of the
Company and will be available to the Company at all times.

     12. Restrictive Obligations Relating to Confidential Subject Matter.

     (a) Obligations to Company.

     Employee agrees to maintain in strict confidence, and agrees not to use,
disclose, reproduce or publish, except to the extent necessary in the course of
the Employee's performance of services for the company and/or as otherwise
authorized by Company, any Confidential Subject Matter owned by the Company or
held in confidence by the Company for any third-party, including without
limitation, all Confidential Subject Matter disclosed and to be disclosed by
Employee to the Company.

     (b) Prior Obligations to Third-Parties.

     Employee agrees that, in the course of Employee's employment with the
Company, Employee will not use or disclose any third-party Confidential Subject
Matter with respect to which Employee, prior to Employee's initiation of
employment with the Company, assumed obligations restricting such use or
disclosure.

     13. Conflicting Obligations.

     (a) Prior Obligations.

     Employee acknowledges and agrees that Employee is under no obligations to
any third party which conflict or may conflict, in any way, with any of the
Employee's obligations hereunder, except for actual and/or potentially
conflicting obligations identified by Employee on Exhibit A attached hereto.
Employee agrees to provide the Company with a copy of any written agreements
relating to any obligations identified in Exhibit A.

                                       4
<PAGE>

     (b) Assumption of Obligations.

     Employee agrees that Employee will not assume any obligations to any
third-party that would conflict with any of Employee's obligation hereunder.
Except for projects referred to in Exhibit A Employee further agrees that,
during the term of Employee's employment with the Company, Employee will not
compete, and will not provide services to others who compete with the Company in
the research, development, production, marketing or servicing of any product,
process or service with respect to which the Company is involved.

     14. Termination of Employment.

     (a) Continuing Obligations.

     Employee's obligations under Sections 8 through 12 of this Agreement will
continue after any termination of Employee's employment with the Company.

     (b) Submission of Materials.

     Upon any termination of Employee's employment with Company, Employee will
submit to the Company all materials within Employee's possession that constitute
or include Confidential Subject Matter owned by the Company or held in
confidence by the Company for any third-party.

     (c) Exit Interview.

     Upon the termination of Employee's employment with the company, Employee
will attend an exit interview with an appropriate representative of the Company
to review the continuing obligations of Employee hereunder.

     15. Miscellaneous.

     (a) Binding-Effect/Assignability.

     This Agreement is not assignable by Employee and will be binding upon
Employee's heirs, executors, administrators and other legal representatives.
Employee agrees that the Company may freely assign this Agreement to any
successor-in-interest of the Company.

     (b) Severability.

     Should any provision of this Agreement be determined by a court of
competent jurisdiction to violate or contravene any applicable law or policy,
such provision will be severed and modified to the extent necessary to comply
with the applicable law or policy, and such modified provision and the remainder
of the provisions hereof will continue in full force and effect.

     (c) Waiver.

     Any delay or omission on the part of Company to exercise any right under
this Agreement will not automatically operate as a waiver of such right or any
other right; and that a waiver of any right of the Company hereunder on one
occasion will not be construed as a bar to or waiver of any right on any future
occasion.

                                       5
<PAGE>

     (d) Controlling Law.

     This Agreement will be interpreted under and enforced in accordance with
the laws of the State of Colorado.

     (e) Modification.

     This Agreement may only be modified by the mutual written agreement of
Employee and Company.

     (f) Notices.

     Any notice or communication required or permitted to be given by this
Agreement shall be deemed given and effective when delivered personally, or when
sent by registered or certified mail, postage prepaid, addressed as follows
(such addresses for giving of notice may be changed by notice similarly given):

          (i) If to the Company:

              ADA Environmental Solutions LLC
              Attention:  Manager
              304 Inverness Way South, Suite 365
              Englewood, Colorado 80112

              (ii) If to Employee:

              C. Jean Bustard
              9193 Buffalo Drive, Littleton, CO 80127

     (g) Arbitration.

     Any difference, claims or matters in dispute arising between Employee and
the Company out of this Agreement or connected with Employee's employment shall
be submitted by Employee and the Company to binding arbitration by a single
arbitrator selected by the mutual agreement of the parties from members of the
Judicial Arbiter Group of Denver, Colorado, or its successor. The arbitration
shall be governed by the rules and regulations of the Judicial Arbiter Group or
its successor and the pertinent provisions of the laws of the State of Colorado
relating to arbitration. The decision of the arbitrator may be entered as a
judgment in any court in the State of Colorado or elsewhere. The prevailing
party shall be entitled to receive reasonable attorneys' fees incurred in
connection with such arbitration in addition to such other costs and expenses as
the arbitrator may award.

     (h) Entire Agreement.

     This Agreement together with the exhibits hereto constitute the entire
agreement between the parties and their affiliates with respect to the subject
matter hereof, supersedes all prior and contemporaneous agreements or
understandings relating to said subject matter, and no amendment hereof shall be
deemed valid unless in writing and signed by the parties hereto.

                                       6
<PAGE>

     IN WITNESS WHEREOF, the parties have signed or caused this Agreement to be
signed by their duly authorized officers as of the day and year first above
written.

                                              ADA Environmental Solutions LLC

                                              By:

                                              ----------------------------------
                                              Michael D. Durham, Manager

                                              ----------------------------------
                                              C. Jean
                                              Bustard, Employee

                                        7
<PAGE>

                                    EXHIBIT A

Projects to be pursued by Employee that are exempt from employee agreement:

1.   Work on technologies covered by previous employment Agreement with ADA
     Technologies.

2.   Baghouse related technologies and troubleshooting with skills obtained
     while employed with Southern Research Institute.

                                        8
<PAGE>

                                    EXHIBIT B

                        ADA Environmental Solutions, LLC

                   Summary of Employee Benefits - May 1, 1997

The following includes a brief description of the benefits package that is
offered by ADA Environmental Solutions, LLC (ADA-ES). These benefits are subject
to change at any time, and the provisions of the official plan documents, in
addition to ADA-ES Policies, shall govern in the even of any differences or
discrepancies. This summary is intended to be a brief overview of the benefits
currently offered by ADA Environmental Solutions and not a comprehensive source
of information concerning exemptions, limitations, and eligibility requirements.
All staff members are encouraged to periodically review ADA-ES's Employee
Handbook and the Group Insurance Benefits Handbook for a more complete
explanation of the benefits and their provisions. This summary does not
constitute a contract between ADA-ES employees and the Company.

Staff members share a portion of the cost of some of the benefits described.

Holidays

     10 Holidays

Vacation

     Full-time staff members are entitled to 12 days of vacation per year for
the first three years of employment with ADA-ES. Vacation time is increased to
15 days after 3 years, and 20 days after 9 years.

Sick and Personal Days

     Full-time employees may receive up to 8 Sick and Personal days per year.

Medical Insurance

Retirement Plan

Disability

Life Insurance

                                        9EXHIBIT 10.24

                         ADA ENVIRONMENTAL SOLUTIONS LLC
                              EMPLOYMENT AGREEMENT

     THIS AGREEMENT made and entered into this day of May 1, 1997, by and
between ADA Environmental Solutions LLC a Colorado limited liability company,
whose principal offices are located at 304 Inverness Way South, Suite 365,
Englewood, Colorado 80112 (the "Company"), and Michael D. Durham (the
"Employee), whose address is 5252 Lariat Road, Castle Rock, Colorado, 80104.

                                    RECITALS:

     A.   The Company has made Employee an offer of employment.
     B.   Employee desires to accept the offer.
     C.   The Company and Employee desire to enter into this Agreement to set
          forth the terms and conditions of the employment.

     NOW, THEREFORE in consideration of the premises and the mutual covenants
and agreements hereinafter set forth and for other good and valuable
consideration the receipt and sufficiency of which are hereby acknowledged, the
parties, intending to be legally bound, hereby agree as follows:

     1. Definitions.

     Capitalized terms are used herein with the meanings as specified in
Paragraph 7 hereof:

     2. Employment.

     The Company hereby employs the Employee and Employee hereby accepts such
employment upon the terms and conditions set forth herein.

     3. Term.

     (a) Initial Term.

     The initial Term of employment under this Agreement shall commence on the
date hereof and it shall continue for a period of three years from such date.
The Term shall be automatically extended for successive one-year periods. Either
party may terminate this Agreement for any reason by giving the other written
notice of its intent to terminate the Agreement not less than three months prior
to the intended date of termination. In addition, the Company may immediately
terminate this Agreement at any time "for cause" as defined below. The initial
Term and any such extensions are hereinafter referred to as the "Term."

     (b) For Cause.

     Notwithstanding any other provision of this Agreement, the Company may
terminate this Agreement for cause immediately upon notice to Employee. The
phrase "for cause" as used in this Agreement shall include, but not be limited
to, breach of any fiduciary duty to the Company, failure to perform Employee's
duties hereunder in a manner satisfactory to the majority of the managers of the
Company, death, permanent disability, or conviction in a criminal proceeding
(excluding traffic violations or similar misdemeanors). In the event that
Employee, during the Term of his employment, should die, become permanently
disabled, or have his employment terminated for cause by the Company, then
Employee shall be entitled to (x) all salary which may accrue to him through the
end of the last month during which he shall have been an employee of the
Company, and (y) such other benefits, if any, to which he is entitled in
accordance with any other section of this Agreement.

                                       1
<PAGE>

     4. Position, Duties and Authority.

     During the Term of this Agreement, Employee shall be employed as the
Executive Vice President of the Company. Employee shall report to the President
of the Company.

     5. Obligations of Employee.

     Employee hereby agrees that he will devote full-time to the fulfillment of
his obligations hereunder. Nothing contained in this agreement shall prevent the
Employee from pursuing the projects listed on the attached Exhibit A.

     6. Compensation and Benefits.

     In consideration of Employee's agreement to be employed by the Company and
as reasonable compensation for services to be rendered hereunder, the Company
agrees as follows:

     (a) Benefits.

     Employee shall be entitled to the standard benefits and perquisites from
time to time available to full-time employees of the Company. These benefits are
listed in Exhibit B. In addition, Employee shall accrue vacation at a rate of
6.16 hours per bi-weekly pay period.

     (b) Compensation.

     The Company shall pay Employee bi-weekly compensation of $4,615.38 during
the Term of employment as part of the Company's normal payroll procedures.
Increases in compensation, if any, shall be at the discretion of the Managers of
the Company.

     7. Definitions.

     (a) "Invention" shall mean any idea, discovery, article, process,
formulation, composition, combination, design, modification or improvement,
whether or not patentable.

     (b) "Copyright Works" shall mean all literary works, graphic works,
pictorial works and other creative works for which copyright protection may be
obtained, including without limitation proposals and computer
software/documentation.

     (c) "Confidential Subject Matter" shall mean all Inventions, Copyright
Works, data, specifications, know-how, lists, printed materials, technical
information, cost/pricing/marketing information and other subject matter that is
not available to the general public in a substantially identical form without
restriction.

                                       2
<PAGE>

     8. Disclosure/Ownership of Invention and Confidential Subject Matter.

     (a) During Employment.

     Employee agrees that during the term of Employee's employment with Company,
Employee will immediately disclose in writing to Company all Inventions and
Confidential Subject Matter which (i) is conceived or generated by Employee
alone and/or jointly with others, and (ii) relates to the actual or anticipated
business of the Company and/or relates to the actual or anticipated research or
development activities of the Company and/or is otherwise suggested by or
results from any activity performed on behalf of the Company. Employee
acknowledges and agrees that immediately upon conception or generation,
whichever occurs earlier, all Inventions and Confidential Subject Matter
disclosed and to be disclosed by Employee to Company during the term of
Employee's employment with Company will be the sole and exclusive property of
the Company.

     (b) Post Employment.

     Employee further agrees that, during the two (2) year period following any
termination of Employee's employment with the Company, Employee will immediately
disclose in writing to the Company all Inventions and Confidential Subject
Matter which (i) is conceived or generated by Employee alone and /or jointly
with others, and (ii) is based upon or otherwise derived from any Inventions
and/or Confidential Subject Matter of the Company. Employee acknowledges and
agrees that immediately upon conception or generation, whichever occurs earlier,
all Inventions and Confidential Subject Matter to be disclosed by Employee to
Company during the two (2) year period following the termination of Employee's
employment with Company will become the sole and exclusive property of the
Company.

     9. Assignment of Inventions and Confidential Subject Matter/Documentation/
Commercialization.

     (a) Assignment.

     Employee hereby assigns to Company the Employee's entire right, title and
interest in and to all Inventions and Confidential Subject Matter disclosed and
to be disclosed by Employee to Company pursuant to Sections 8 (a) and (b).

     (b) Documentation.

     Employee agrees to execute, cooperate in the preparation of and deliver to
the Company, both during the term of Employee's employment with the Company and
thereafter, any and all documents deemed necessary by the Company for the
Company to protect, maintain, preserve and enjoy the full right, title and
interest to all Inventions and Confidential Subject Matter disclosed and to be
disclosed by Employee to Company, including without limitation, the execution
and delivery of patent assignments and, at Company's legal expense, the
preparation of patent applications.

     (c) Commercialization.

     Employee acknowledges and agrees that with respect to all Inventions and
Confidential Subject Matter transferred by Employee to Company, Company is not
obligated to commercialize the same, and that if Employee desires to
independently commercialize any of said Inventions and/or Confidential Subject
Matter, Employee must request and obtain a written license from Company
beforehand, which license request may be declined by Company in its sole
discretion.

                                       3
<PAGE>

     10. Copyright Works.

     Employee agrees that all Copyright Works and contributions to Copyright
Works prepared by Employee within the scope of Employee's employment with the
Company will be deemed "works for hire" and will be owned by the Company, and
Employee agrees to execute all documents deemed necessary by the Company for the
Company to protect, maintain, preserve and enjoy the Company's rights in such
Copyright Works and contributions. Employee further agrees that unless expressly
authorized by the Company in writing, Employee will not independently prepare or
otherwise distribute or publish any Copyright Work that embodies any
Confidential Subject Matter owned by the Company or held in confidence by the
Company for any third-party, including without limitation, all Confidential
Subject Matter disclosed and to be disclosed by Employee to the Company.

     11. Written Records.

     Employee agrees that to the extent reasonably possible, Employee will
maintain written records of all Inventions and Confidential Subject Matter
conceived or generated by Employee in the course of Employee's performance of
services for the Company, which records will be the exclusive property of the
Company and will be available to the Company at all times.

     12. Restrictive Obligations Relating to Confidential Subject Matter.

     (a) Obligations to Company.

     Employee agrees to maintain in strict confidence, and agrees not to use,
disclose, reproduce or publish, except to the extent necessary in the course of
the Employee's performance of services for the company and/or as otherwise
authorized by Company, any Confidential Subject Matter owned by the Company or
held in confidence by the Company for any third-party, including without
limitation, all Confidential Subject Matter disclosed and to be disclosed by
Employee to the Company.

     (b) Prior Obligations to Third-Parties.

     Employee agrees that, in the course of Employee's employment with the
Company, Employee will not use or disclose any third-party Confidential Subject
Matter with respect to which Employee, prior to Employee's initiation of
employment with the Company, assumed obligations restricting such use or
disclosure.

     13. Conflicting Obligations.

     (a) Prior Obligations.

     Employee acknowledges and agrees that Employee is under no obligations to
any third party which conflict or may conflict, in any way, with any of the
Employee's obligations hereunder, except for actual and/or potentially
conflicting obligations identified by Employee on Exhibit A attached hereto.
Employee agrees to provide the Company with a copy of any written agreements
relating to any obligations identified in Exhibit A.

                                       4
<PAGE>

     (b) Assumption of Obligations.

     Employee agrees that Employee will not assume any obligations to any
third-party that would conflict with any of Employee's obligation hereunder.
Except for projects referred to in Exhibit A Employee further agrees that,
during the Term of Employee's employment with the Company, Employee will not
compete, and will not provide services to others who compete with the Company in
the research, development, production, marketing or servicing of any product,
process or service with respect to which the Company is involved.

     14. Termination of Employment.

     (a) Continuing Obligations.

     Employee's obligations under Sections 8 through 12 of this Agreement will
continue after any termination of Employee's employment with the Company.

     (b) Submission of Materials.

     Upon any termination of Employee's employment with Company, Employee will
submit to the Company all materials within Employee's possession that constitute
or include Confidential Subject Matter owned by the Company or held in
confidence by the Company for any third-party.

     (c) Exit Interview.

     Upon the termination of Employee's employment with the company, Employee
will attend an exit interview with an appropriate representative of the Company
to review the continuing obligations of Employee hereunder.

     15. Miscellaneous.

     (a) Binding-Effect/Assignability.

     This Agreement is not assignable by Employee and will be binding upon
Employee's heirs, executors, administrators and other legal representatives.
Employee agrees that the Company may freely assign this Agreement to any
successor-in-interest of the Company.

     (b) Severability.

     Should any provision of this Agreement be determined by a court of
competent jurisdiction to violate or contravene any applicable law or policy,
such provision will be severed and modified to the extent necessary to comply
with the applicable law or policy, and such modified provision and the remainder
of the provisions hereof will continue in full force and effect.

     (c) Waiver.

     Any delay or omission on the part of Company to exercise any right under
this Agreement will not automatically operate as a waiver of such right or any
other right; and that a waiver of any right of the Company hereunder on one
occasion will not be construed as a bar to or waiver of any right on any future
occasion.

                                       5
<PAGE>

     (d) Controlling Law.

     This Agreement will be interpreted under and enforced in accordance with
the laws of the State of Colorado.

     (e) Modification.

     This Agreement may only be modified by the mutual written agreement of
Employee and Company.

     (f) Notices.

     Any notice or communication required or permitted to be given by this
Agreement shall be deemed given and effective when delivered personally, or when
sent by registered or certified mail, postage prepaid, addressed as follows
(such addresses for giving of notice may be changed by notice similarly given):

           (i) If to the Company:

               ADA Environmental Solutions LLC
               Attention:  Manager
               304 Inverness Way South, Suite 365
               Englewood, Colorado 80112

          (ii) If to Employee:

               Michael D. Durham
               5252 Lariat Road, Castle Rock, Colorado, 80104

     (g) Arbitration.

     Any difference, claims or matters in dispute arising between Employee and
the Company out of this Agreement or connected with Employee's employment shall
be submitted by Employee and the Company to binding arbitration by a single
arbitrator selected by the mutual agreement of the parties from members of the
Judicial Arbiter Group of Denver, Colorado, or its successor. The arbitration
shall be governed by the rules and regulations of the Judicial Arbiter Group or
its successor and the pertinent provisions of the laws of the State of Colorado
relating to arbitration. The decision of the arbitrator may be entered as a
judgment in any court in the State of Colorado or elsewhere. The prevailing
party shall be entitled to receive reasonable attorneys' fees incurred in
connection with such arbitration in addition to such other costs and expenses as
the arbitrator may award.

     (h) Entire Agreement.

     This Agreement together with the exhibits hereto constitute the entire
agreement between the parties and their affiliates with respect to the subject
matter hereof, supersedes all prior and contemporaneous agreements or
understandings relating to said subject matter, and no amendment hereof shall be
deemed valid unless in writing and signed by the parties hereto.

                                       6
<PAGE>

     IN WITNESS WHEREOF, the parties have signed or caused this Agreement to be
signed by their duly authorized officers as of the day and year first above
written.

                                           ADA Environmental Solutions LLC

                                           By: Earth Sciences, Inc., Manager

                                           By:
                                               ---------------------------------
                                                Mark H. McKinnies

                                           Its: President

                                           ADA Technologies, Inc., Manager

                                           By:
                                               ---------------------------------
                                                Judith A. Armstrong

                                           Its: President

                                           ADA Environmental Solutions, LLC

                                           -------------------------------------
                                           Michael D. Durham, Manager

                                           -------------------------------------
                                           Michael D. Durham, Employee

                                        7
<PAGE>

                                   EXHIBIT A

Projects to be pursued by Employee that are exempt from employee agreement:

1.   Work on technologies covered by previous Employee Agreement with ADA
     Technologies.

2.   Potential business consulting to be provided to small businesses such as
     ADA Technologies, Sky+, LaserWave, and Poinsettia Group.

3.   Environmental consulting with the Happy Canyon Homeowners Association to
     halt proposed development.

                                        8
<PAGE>

                                    EXHIBIT B

                        ADA Environmental Solutions, LLC

                   Summary of Employee Benefits - May 1, 1997

The following includes a brief description of the benefits package that is
offered by ADA Environmental Solutions, LLC (ADA-ES). These benefits are subject
to change at any time, and the provisions of the official plan documents, in
addition to ADA-ES Policies, shall govern in the even of any differences or
discrepancies. This summary is intended to be a brief overview of the benefits
currently offered by ADA Environmental Solutions and not a comprehensive source
of information concerning exemptions, limitations, and eligibility requirements.
All staff members are encouraged to periodically review ADA-ES's Employee
Handbook and the Group Insurance Benefits Handbook for a more complete
explanation of the benefits and their provisions. This summary does not
constitute a contract between ADA-ES employees and the Company.

Staff members share a portion of the cost of some of the benefits described.

Holidays

     10 Holidays

Vacation

     Full-time staff members are entitled to 12 days of vacation per year for
the first three years of employment with ADA-ES. Vacation time is increased to
15 days after 3 years, and 20 days after 9 years.

Sick and Personal Days

     Full-time employees may receive up to 8 Sick and Personal days per year.

Medical Insurance

Retirement Plan

Disability

Life Insurance

                                        9

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