<PAGE>   1
                                                                   EXHIBIT 10.16


                    SECOND AMENDMENT TO EMPLOYMENT AGREEMENT

         This Second Amendment to Employment Agreement (the "Second Amendment")
is made and entered into as of this 25th day of October, 1996, by and between
Allwaste, Inc., a Delaware corporation (the "Company"), and Robert M. Chiste
(the "Employee").

         WHEREAS, the Company and the Employee are parties to an Employment
Agreement dated October 17, 1994, as amended by that certain First Amendment to
Employment Agreement dated October 26, 1995 (the "First Amendment") (as
amended, the "Agreement"),  which is attached hereto as Addendum 1 and is
incorporated herein in its entirety by reference, pursuant to which the
Employee has performed certain services to the Company; and

         WHEREAS, the Company and the Employee desire to amend the Agreement to
extend the vesting schedule of the shares of restricted stock granted to the
Employee pursuant to the Agreement.

         NOW, THEREFORE, for and in consideration of the mutual covenants and
promises and representations contained herein, and other good and valuable
consideration, the receipt and sufficiency of which are acknowledged herein,
the Company and the Employee agree as follows:

         1.      Subparagraph 2(b)(ii) of the Agreement (as amended by
paragraph 1 of the First Amendment) is hereby amended by deleting the
subparagraph in its entirety and substituting the following in replacement
thereof:

                 (ii)     In addition to the bonus described in subparagraph
                 2(b)(i) hereof, the Employee shall be entitled to receive
                 126,316 shares (the "Shares") of the Company's common stock,
                 par value $.01 per share (the "Common Stock"), such Shares to
                 vest cumulatively as follows:  31,579 of the Shares shall vest
                 on January 1, 1997; 31,579 of the Shares shall vest on January
                 1, 1998; 31,579 of the Shares shall vest on January 1, 1999;
                 and the remainder, 31,579 of the Shares, shall vest on January
                 1, 2000.  The Employee acknowledges that such shares shall be
                 restricted shares, subject to forfeiture as provided in the
                 Restricted Stock Agreement attached hereto as Exhibit A and
                 incorporated herein in its entirety by reference.

         2.      Except as modified by this Second Amendment, all other terms
of the Agreement shall continue in full force and effect without modification.

         IN WITNESS WHEREOF, the parties have executed this Second Amendment to
Employment Agreement in duplicate originals, effective as of October 25, 1996.

                          ALLWASTE, INC.


                          By:     /s/ William L. Fiedler                      
                             -----------------------------------              
                                  William L. Fiedler
                                  Vice President, General 
                                  Counsel and Secretary


                                  /s/ Robert M. Chiste                        
                             ------------------------------------              
                                      Robert M. Chiste