Exhibit 10.6

    

    

    

    

    

    January 29, 2021

    

    

    William A. Zartler

    

    
      	
              RE:

            	
              Modification of Profits Units Agreement

            


    

    

    

    Dear Bill:

    

    

    You have been employed by Solaris Midstream Holdings, LLC and its affiliates (the “Company”) since January 1, 2015.  As part of your compensation package, you entered into a certain Profits Units Grant Agreement dated
      September 21, 2016, (“Grant Agreement”) by and between you, Solaris Midstream Investment, LLC (“SMI”), and the Company, as the beneficiary pursuant to which you were granted Beneficiary Class B and/or Beneficiary Class C Units (as defined in the
      Grant Agreements).  As of the date of this letter, 60% of your Profits Units are vested under the Profits Units Grant Agreement.  Your remaining Profits Units will vest as set forth in the Grant Agreement.

    

    

    We are pleased to inform you that the Board of Directors of the Company and SMI have agreed to make certain changes to the Grant Agreements; and the Company wishes to set forth the terms of a separation plan that will
      be available to you as outlined in this Letter Agreement (“Letter Agreement”)

    

    

    Definitions:  Capitalized terms used in this
        Letter Agreement (“Letter Agreement”) but not defined herein, shall have the meanings ascribed thereto in your most recently executed Grant Agreement.

    

    

    Effective Date:  The effective date of this
        Letter Agreement is February 1, 2021 (the “Effective Date”).

    

    

    Separation of Employment:

    
      	 	
              1.

            	
              Should you voluntarily resign your position with the Company or otherwise cease to provide services to the Company, except for Termination with or without Cause, death or Disability, or for Good Reason:

            


    

    
      	 	
              a.

            	
              As set forth in the Grant Agreement your Unvested Profits Units and Vested Profits Units will be forfeited.

            


    

    
      	 	
              b.

            	
              Your non-competition, non-solicitation of customers and employee’s agreement set forth in Section 4 (a) (ii) of the Grant Agreements (“Non-Compete”) will be reduced from a period of eighteen (18) months, to a
                period of twelve (12) months from and after your Termination Date, and

            


    

    
      	 	
              c.

            	
              All other applicable terms related to your separation from the Company and termination of your employment shall remain the same.

            


    

     

      

    
      
        


      Page 2

    

    
    
      	 	
              2.

            	
              If you are terminated by the Company for Cause, all the applicable terms of the Grant Agreements shall remain the same and in full force and effect and you will receive no additional compensation under this
                Letter Agreement.

            


    

    

    

    
      	 	
              3.

            	
              If you cease to provide services to the company by reason of death or Disability, the terms of your Grant Agreements will remain in effect.

            


    

    

    

    
      	 	
              4.

            	
              If you are terminated by the Company for any reason except for Cause, then you may elect, one of the following options:

            


    

    
      	 	
              a.

            	
              Option 1

            


    

    
      	 	
              i.

            	
              You will be paid twelve (12) months of your base salary upon termination (“Severance Payment”)

            


    

    
      	 	
              ii.

            	
              All other terms of the Grant Agreements shall remain in effect, provided, your Non-Compete will be for a period of twelve (12) months from your Termination Date, or

            


    

    

    

    
      	 	
              b.

            	
              Option 2

            


    

    
      	 	
              i.

            	
              You can elect to forgo your Severance Payment in which event, the terms of the Grant Agreements shall remain in effect with the following exceptions:

            


    

    
      	 	
              1.

            	
              Your Non-Compete will be reduced to a period of six (6) months, and

            


    

    
      	 	
              2.

            	
              All your Vested and Unvested Profits Units will be forfeited.

            


    

    

    

    
      	 	
              5.

            	
              In the event a Monetization Event, occurs, and if within nine (9) months following a Monetization Event you are terminated for any reason except Cause, Option 1 in paragraph 4 above will apply.

            


    

    

    

    
      	 	
              6.

            	
              Any election under this section must be made in writing to the Company’s Chief Executive Officer within ten (10) days of your Termination Date.  If you do not make an election within that time, Option 1 in
                paragraph 4 above will apply.

            


    

    

    

    
      	 	
              7.

            	
              You may be required to execute a general release of claims against the Company and SMI in exchange for any payments you receive under this provision.

            


    

    

    

    Governing Law:  This
        Letter Agreement shall be governed by and construed in accordance with the laws of the State of Texas (without giving effect to the choice of law principles thereof).

    

    

    Entire Agreement:  Except
        as specifically set forth herein, this Letter Agreement does not supersede any other representations or promises made to you by anyone, whether oral or written, relating to your employment with the Company and it can only be modified in a written
        agreement signed by you and the Chief Executive Officer of the Company or SMI (or their express designee). 

    

    

    ** Signature Page to Follow **

    

    

    
      
        


      Page 3

    

    If you accept the terms of this Letter Agreement relating to severance and the Non-Compete, the terms described in this Letter Agreement constitute the complete agreement of changes to the terms of your employment with
      the Company.

    

    

    Sincerely,

    

    

    /s/ Amanda Brock

    

    

    Amanda Brock

    President & Chief Operating Officer 

    Solaris Water Midstream

    

    

    	 	
            Acknowledged and Agreed as of

          	 
	 	 	 
	 	
            this 2 day of February 2021:

          	 
	 	 	 
	 	 	 
	 	
            /s/ William Zartler

          	 
	 	
            William Zartler