Exhibit 10.5

Brian Holt
President and CEO
Thermo Ecotek Corporation


May 18, 2000


Dear Brian:

As we have discussed,  Thermo Electron Corporation (the Company) has announced a
reorganization  of the company in which certain of the company's  assets will be
sold.  We  recognize  that your past  contributions  have been  integral  to the
success of the Company and that your continued  involvement will be necessary in
order to facilitate these sales and to assure a smooth  transition for potential
buyers.

In order to provide an incentive for you to remain with the company  through the
completion of these sales, we will pay you a Transaction Bonus.

Transaction Bonus

You will be paid the amounts  indicated below for the sale or disposition of the
following  businesses.  If the actual  sale price of any  business  exceeds  its
target price, .5% of the difference between the actual sale price and the target
price will be added to your transaction  bonus for that business.  If the actual
sale price on any business is below its target price, you will be paid a portion
of the Transaction  Bonus.  The portion will equal the sale price divided by the
target  price  times the listed  Transaction  Bonus  rounded  up to the  nearest
hundred.  (EXAMPLE:  If FES sold for  $40,000,000  your  bonus  would be $44,500
($40,000,000 divided by $45,000,000 times $50,000 equals $44,444.  Rounded up to
the next hundred equals $44,500)

These Transaction Bonuses will be paid to you in a lump sum payment on or before
ninety  (90) days  following  the  closing  date of each sale  unless  you and I
mutually agree to an alternate payment date.

Businesses to be sold              Target Price             Transaction Bonus
                                                            At Target Price


FES                                 $45,000,000                  $50,000
NuTemp Inc.                         $16,000,000                  $18,000
Tecogen                             $ 6,000,000                  $ 7,000


<PAGE>


Businesses to be sold              Target Price             Transaction Bonus
                                                            At Target Price

Optronics                          $  6,000,000                  $  7,000
Peek                               $ 85,000,000                  $ 93,000
Retec Consulting                   $ 45,000,000                  $ 49,000
Nutech                             $ 17,000,000                  $ 19,000
TPST Soil                          $ 15,000,000                  $ 16,000
Fluids                             $ 13,000,000                  $ 14,000

Killam                             $ 45,000,000                  $ 49,000
Lancaster Labs                     $ 60,000,000                  $ 66,000
Eurotech                           $  5,000,000                  $  6,000
Normandeau                         $  5,000,000                  $  6,000
Green Sunrise                      $  5,000,000                  $  6,000
Metal Treaters                     $ 12,000,000                  $ 13,000
Trilogy                            $ 30,000,000                  $ 31,000

Total                              $410,000,000                  $450,000

Terms of Agreement

1.   The Company agrees to continue to employ you on the same terms and with the
     same benefits you currently enjoy as an  employee-at-will.  In return,  you
     agree to remain in such employ and to continue to devote your full time and
     best efforts to the Company as an  employee-at-will  until the closing date
     of the sale of these businesses.

2.   You  understand  that the  Company  retains  the  right to  terminate  your
     services  without  cause (as  defined  below)  and you  retain the right to
     terminate your services from the Company at any time. If your employment is
     terminated  by the  company  without  cause  prior to the  closing of these
     business sales, you will be paid your full and unreduced  Transaction Bonus
     payments at the time of the sales. If you terminate your  employment  prior
     to the final closing date, or the Company  terminates  your  employment for
     "cause" (as defined below),  you will forfeit any and all payments that you
     would be entitled to for unsold businesses covered under this agreement.

3.   For the purposes of this  agreement,  "cause"  shall be  determined  by the
     Company in the  exercise  of good faith and  reasonable  judgment  and will
     include  any  breach  of this  agreement  by you or any act by you of gross
     personal  misconduct,  insubordination,  misappropriation  of funds, fraud,
     dishonesty,  gross  neglect of or failure to perform the duties  reasonably
     required of you  pursuant  to this  agreement  or any  conduct  which is in
     willful  violation of any  applicable  law or regulation  pertaining to the
     business.

4.   For  purposes  of this  agreement,  we agree  that the  businesses  will be
     considered  to be sold when any  person or  entity,  other than a person or
     entity affiliated with the Company,  purchases at least fifty percent (50%)
     of the assets or shares of the  individual  businesses,  whether  through a
     purchase of the business or a purchase of the company of which the business
     is a part.
<PAGE>

5.   You  understand  that all payments made under this agreement are subject to
     appropriate federal, state, city or other tax withholding requirements.

6.   You acknowledge that this Transaction Bonus Agreement  supersedes any prior
     agreements or  understandings  oral or written  between you and the Company
     pertaining to any  Transaction  Bonus  incentive  payments being offered to
     employees of businesses  being sold in connection  with the  reorganization
     and that this agreement  constitutes the entire  agreement  between us with
     regard to Transaction Bonuses.

On behalf of Thermo  Electron,  I thank you for your  continued  assistance  and
support. If you have any questions regarding any of the terms of this Agreement,
please do not hesitate to contact me.

Once you have read and understood the terms of this  Agreement,  please indicate
your agreement by signing below on the line above your typewritten  name, make a
copy for your records and return the original document to me.

                                        Very truly yours,



                                        /s/ Anne Pol
                                        -----------------------------
                                        Anne Pol
                                        Sr. Vice President
                                        Thermo Electron

Accepted and agreed:

/s/ Brian Holt
----------------------------
Brian Holt                              Date  June 1, 2000