Exhibit
4.5

    

    


    November
30, 2009

    


    Fidus
Mezzanine Capital, L.P.

    190 S.
LaSalle Street

    Suite 2140

    Chicago,
IL 60603

    


    Re:   Issuance of
Series C Convertible Preferred Stock; Deferral
of  Certain

                    Coupon
Payments on Series B Preferred Stock

    


    Gentlemen:

    


    Pure
Earth, Inc. (the “Company”)
has previously advised Fidus Mezzanine Capital, L.P., a Delaware limited
partnership (“FMC”), of
the Company’s proposal to issue, and the terms upon which it proposes to issue,
up 180,000 shares of Series C Convertible Preferred Stock (“Series C
Shares”) and FMC has indicated an interest in acquiring a portion of the
Series C Shares.

    


    FMC is also a holder of shares of our
Series B Preferred Stock, as well as a Warrant, dated March 4, 2008, to acquire
shares of our common stock.  In addition, FMC is a party to, or
beneficiary of, an Investment Agreement, dated March 4, 2008, with the Company
and certain other Investment Documents as defined
therein.  Capitalized terms used but not otherwise defined herein
shall have the meanings ascribed to such terms in the Investment
Documents.

    


    To facilitate the offer, sale and
issuance of the Series C Shares, FMC hereby:

    


    
      	
               
      

            	
              (i)

            	
              waives
      any and all further notice requirements with respect to the offer, sale
      and issuance of the Series C
Shares;

            


    

    
      	
               
      

            	
              (ii)

            	
              waives
      any and all rights of first refusal, preemptive rights or similar rights
      to acquire Series C Shares;

            


    

    
      	
               
      

            	
              (iii)

            	
              agrees
      that, notwithstanding any provision of the Investment Documents, the
      offer, sale and issuance of the Series C Shares, and any conversion of the
      Series C Shares in accordance with their terms, shall not result in any
      anti-dilution or similar adjustment to or in favor of the Series B
      Preferred Stock; and

            


    

    
      	
               
      

            	
              (iv)

            	
              waives
      application of any covenant or negative covenant in the Investment
      Documents which would, absent such waiver, preclude the offer, sale, or
      issuance of the Series C Shares (including sales to any officers or
      directors of the Company) or which would be breached by either the
      Company’s offer, sale, or issuance of the Series C
  Shares.

            


    

     

    
      One
Neshaminy Interplex, Suite 201 ∙ Trevose, PA 19053 ∙ Phone 215 639 8755 ∙ Fax
215 639 8756

      www.pureearthinc.com

    

     

    
      
         


      

      
         


        
          

        

      

      
         


      

    


    Fidus
Mezzanine Capital, L.P.

    Page 2 of
3

    


    Further,
in connection with that certain Seventh Amendment dated as of October 23, 2009
to that certain Credit and Security Agreement dated as of October 24, 2006 by
and among Well Fargo Bank, National Association (“Wells Fargo”), the Company and
certain of its affiliates, FMC has agreed that in lieu of making the dividend
coupon payment to holders of the Company’s Series B Preferred Stock otherwise
due on each of September 30, 2009 and December 31, 2009 (the amount of such
payments collectively, the “Coupon Amount”) pursuant to
the terms of the Company’s Series B Preferred Stock, the Company shall instead
pay holders of the Company’s Series B Preferred Stock in cash the Coupon Amount,
plus interest on the Coupon Amount at the rate of fourteen percent (14%) per
annum, either:

     

    (a) on
February 15, 2010; or

     

    (b) if
the Company either (i) refinances its outstanding obligations to Wells Fargo
with an alternative lender or (ii) renews such obligations for an extended
maturity date with Wells Fargo, in each case prior to the date set forth in
clause (a) above, then on the date such refinancing or renewal is
consummated.

     

    Notwithstanding the provisions of
this letter, in the event that the full Coupon Amount plus all accrued interest
with respect to such Coupon Amount is not paid in cash as provided in the
immediately preceding paragraph, the Event of Noncompliance with respect to the
failure of the Company to pay the Coupon Amount on September 30, 2009 or
December 31, 2009 shall be deemed to have occurred on September 30, 2009 and
December 31, 2009, respectively, and not on the date that the Company fails to
comply with the preceding paragraph and all rights and remedies of the holders
of the Series B Preferred Stock with respect to such failure shall be and remain
in full force and effect as if the agreement in the immediately preceding
paragraph had never been in effect.

     

    [signatures
on following page]


    
      
         


      

      
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    Fidus
Mezzanine Capital, L.P.

    Page 3 of
3

    


    
      
        
          
            
              	
                      Sincerely,

                    
	 
      	 
      
	
                      PURE
      EARTH, INC.

                    
	 
      	 
      
	
                      By:

                    	
                      /s/ Brent
  Kopenhaver

                    


            

          

        

      

    

    


    Acknowledge
and Agreed:

    


    FIDUS
MEZZANINE CAPITAL, L.P.

    


    By:   Fidus
Mezzanine Capital GP, LLC, its General Partner

    


    
      
        	
                By:

              	
                /s/ Edward H. Ross

              	 
      
	
                Printed
      Name:   

              	
                Edward H. Ross

              	 
      
	
                Title:

              	
                Managing Partner

              	 
      


      

    


    
      
         


      

      
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