<Page>

                                                                     EXHIBIT 4.5

================================================================================


                            SALT HOLDINGS CORPORATION

                                       and

                              THE BANK OF NEW YORK,
                                   as Trustee

                                   ----------


                      12 3/4 SENIOR DISCOUNT NOTES DUE 2012


                                   ----------

                          FIRST SUPPLEMENTAL INDENTURE
                            Dated as of May 21, 2003

                                to THE INDENTURE
                          Dated as of December 20, 2002


================================================================================

<Page>

          FIRST SUPPLEMENTAL INDENTURE dated as of May 21, 2003 (this "FIRST
SUPPLEMENTAL INDENTURE") by and between Salt Holdings Corporation, a Delaware
corporation (the "COMPANY"), and The Bank of New York, as trustee (the
"TRUSTEE").

                                   WITNESSETH

          WHEREAS, the parties to this First Supplemental Indenture entered into
an Indenture dated as of December 20, 2002 (the "INDENTURE").

          WHEREAS, on December 20, 2002, the Company issued $123,500,000
aggregate principal amount at maturity of 12 3/4% Senior Discount Notes due 2012
under the Indenture (the "December Notes.")

          WHEREAS, on May 19, 2003, the Company entered into an agreement for
the sale of the Company's 12% Senior Subordinated Discount Notes due 2013 (the
"New Notes"), the gross proceeds from which will be distributed to the Company's
stockholders in the form of a dividend.

          WHEREAS, the Company desires to amend Section 4.3 of the Indenture in
order to permit the Company to distribute the gross proceeds from the offering
of the New Notes to the Company's stockholders in the form of a dividend.

          WHEREAS, Section 9.02 of the Indenture provides, among other things,
that the Company and the Trustee, together with the written consent of the
Holders of at least a majority in aggregate principal amount at maturity of the
outstanding December Notes, may amend or supplement the Indenture or the
December Notes without notice to any other holder of the December Notes.

          WHEREAS, the Company has received the requisite consents from the
holders of a majority of the aggregate principal amount at maturity of the
December Notes to this First Supplemental Indenture and officers of the Company
has certified the same to the Trustee in the form of an Officers' Certificate.

          WHEREAS, this First Supplemental Indenture has been duly authorized by
all necessary corporate action on the part of the Company.

          WHEREAS, the Company has directed the Trustee to execute and deliver
this First Supplemental Indenture in accordance with the terms of the Indenture.

          NOW THEREFORE, in consideration of the foregoing and for other good
and valuable consideration the receipt of which is hereby acknowledged, the
Company and the Trustee mutually covenant and agree for the benefit of each
other and for the equal and ratable benefit of the Holders as follows:

     SECTION 1.  AMENDMENT TO THE INDENTURE. The amendment set forth in this
First Supplemental Indenture shall become effective as of the date hereof.
Section 4.3 of the Indenture is hereby amended, and replaced in its entirety,
with the following:

<Page>

Section 4.3 LIMITATION ON RESTRICTED PAYMENTS

               The Company shall not, and shall not cause or permit any of its
Restricted Subsidiaries to, directly or indirectly, (1) declare or pay any
dividend or make any distribution (other than dividends or distributions payable
in Qualified Capital Stock of the Company) on or in respect of shares of the
Company's Capital Stock to holders of such Capital Stock; (2) purchase, redeem
or otherwise acquire or retire for value any Capital Stock of the Company or any
warrants, rights or options to purchase or acquire shares of any class of such
Capital Stock of the Company; (3) make any principal payment on, purchase,
defease, redeem, prepay, decrease or otherwise acquire or retire for value,
prior to any scheduled final maturity, scheduled repayment or scheduled sinking
fund payment, any Indebtedness of the Company that is subordinate or junior in
right of payment to the Securities or any Guarantee (other than Indebtedness
described in clause (7) of the definition of "Permitted Indebtedness"); or (4)
make any Investment (other than Permitted Investments) (each of the foregoing
actions set forth in clauses (1), (2), (3) and (4) being referred to as a
"RESTRICTED PAYMENT"), if at the time of such Restricted Payment or immediately
after giving effect thereto:

          (a)  a Default or an Event of Default shall have occurred and be
     continuing; or

          (b)  the Company is not able to incur at least $1.00 of additional
     Indebtedness (other than Permitted Indebtedness) in compliance with Section
     4.4; or

          (c)  the aggregate amount of Restricted Payments (including such
     proposed Restricted Payment) made subsequent to November 28, 2001 (the
     amount expended for such purposes, if other than in cash, being the fair
     market value of such property as determined reasonably and in good faith by
     the Board of Directors of the Company whose determination shall be
     conclusive) shall exceed the sum of:

               (i)    50% of the cumulative Consolidated Net Income (or if
          cumulative Consolidated Net Income shall be a loss, minus 100% of such
          loss) of the Company earned subsequent to November 28, 2001 and on or
          prior to the date the Restricted Payment is made (the "REFERENCE
          DATE") (treating such period as a single accounting period); plus

               (ii)   100% of the aggregate Net Cash Proceeds and the fair
          market value, as determined in good faith by the Board of Directors of
          the Company, of property other than cash received by the Company from
          any Person (other than a Subsidiary of the Company) from the issuance
          and sale subsequent to November 28, 2001 and on or prior to the
          Reference Date of Qualified Capital Stock of the Company (other than
          Excluded Contributions); plus

               (iii)  without duplication of any amounts included in clause
          (c)(ii) above, 100% of the aggregate Net Cash Proceeds of any equity
          contribution received by the Company subsequent to November 28, 2001
          from a holder of the Company's Capital Stock (other than Excluded
          Contributions); plus

                                        2
<Page>

               (iv)   the amount by which Indebtedness of the Company or any of
          its Restricted Subsidiaries is reduced on the Company's balance sheet
          upon the conversion or exchange subsequent to November 28, 2001 of any
          Indebtedness of the Company or any of its Restricted Subsidiaries
          incurred after November 28, 2001 into or for Qualified Capital Stock;
          plus

               (v)    without duplication, the sum of:

                      (a) the aggregate amount returned in cash on or with
               respect to Investments (other than Permitted Investments) made
               subsequent to November 28, 2001 whether through interest
               payments, principal payments, dividends or other distributions or
               payments;

                      (b) the net cash proceeds received by the Company or any
               Restricted Subsidiary of the Company from the disposition of all
               or any portion of such Investments (other than to a Subsidiary of
               the Company); and

                      (c) upon redesignation of an Unrestricted Subsidiary as a
               Restricted Subsidiary, the fair market value of such Subsidiary
               (valued in each case as provided in the definition of
               "Investment");

PROVIDED, HOWEVER, that the sum of clauses (a), (b) and (c) above shall not
exceed the aggregate amount of all such Investments made by the Company or any
Restricted Subsidiary in the relevant Person or Unrestricted Subsidiary
subsequent to November 28, 2001.

          Notwithstanding the foregoing, the provisions set forth in the
immediately preceding paragraph do not prohibit:

          (1)  the payment of any dividend or other distribution within 60 days
     after the date of declaration of such dividend or other distribution if the
     dividend or other distribution would have been permitted on the date of
     declaration;

          (2)  if no Default or Event of Default shall have occurred and be
     continuing, the acquisition of any shares of Capital Stock of the Company,
     either (a) solely in exchange for shares of Qualified Capital Stock of the
     Company, or (b) through the application of net proceeds of a substantially
     concurrent sale for cash (other than to a Subsidiary of the Company) of
     shares of Qualified Capital Stock of the Company;

          (3)  if no Default or Event of Default shall have occurred and be
     continuing, the acquisition of any Indebtedness of the Company that is
     subordinate or junior in right of payment to the Securities or a Guarantee
     either (a) solely in exchange for shares of Qualified Capital Stock of the
     Company, or (b) through the application of net proceeds of a substantially
     concurrent sale for cash (other than to a Subsidiary of the Company) of (i)
     shares of Qualified Capital Stock of the Company, or (ii) Refinancing
     Indebtedness;

                                        3
<Page>

          (4)  if no Default or Event of Default shall have occurred and be
     continuing, repurchases by the Company or any Restricted Subsidiary of the
     Company of securities of the Company from employees, directors or
     consultants of the Company or any Subsidiaries of the Company or their
     authorized representatives (a) upon the death, disability or termination of
     employment of such employees, directors or consultants or to the extent
     required pursuant to employee benefit plans, employment agreements or
     consulting agreements or (b) pursuant to any other agreements with such
     employees or directors of or consultants to the Company or any Subsidiaries
     of the Company, in an aggregate amount not to exceed $7.5 million in any
     calendar year (with unused amounts in any calendar year being carried over
     to succeeding years subject to a maximum of $15.0 million in any calendar
     year), provided that the cancellation of Indebtedness owing to the Company
     or any Restricted Subsidiary of the Company from such employees, directors
     or consultants of the Company or any of its Restricted Subsidiaries in
     connection with a repurchase of Capital Stock of the Company will not be
     deemed to constitute a Restricted Payment under this Indenture;

          (5)  the declaration and payment of dividends to holders of any class
     or series of Preferred Stock of the Company, provided that for the most
     recently ended four full fiscal quarters for which internal financial
     statements are available immediately preceding the date of issuance of such
     Preferred Stock, after giving effect to such issuance on a pro forma basis,
     the Company would have been able to incur at least $1.00 of Indebtedness
     (other than Permitted Indebtedness) pursuant to Section 4.4;

          (6)  the payment of dividends on the Company's Common Stock following
     the first public offering of the Company's Common Stock after the Issue
     Date, of up to 6% per annum of the net proceeds received by the Company in
     such public offering (other than public offerings with respect to the
     Company's Common Stock registered on Form S-8);

          (7)  the repurchase, retirement or other acquisition or retirement for
     value of any securities of the Company in existence on the Issue Date and
     from the Persons holding such securities on the Issue Date and which are
     not held by Apollo or any of its Affiliates or members of management of the
     Company and its Subsidiaries on the Issue Date (including any equity
     interests issued in respect of any such securities constituting equity
     interests as a result of a stock split, recapitalization, merger,
     combination, consolidation or similar transaction); provided, however, that
     the Company shall be permitted to make Restricted Payments under this
     clause only if after giving effect thereto, the Company would be permitted
     to incur at least $1.00 of additional Indebtedness (other than Permitted
     Indebtedness) pursuant to Section 4.4;

          (8)  other Restricted Payments in an aggregate amount not to exceed
     $15.0 million;

          (9)  if no Default or Event of Default shall have occurred and be
     continuing, payments or distributions to dissenting stockholders pursuant
     to applicable law, pursuant to or in connection with  a consolidation,
     merger or transfer of assets that complies with

                                        4
<Page>

     the provisions of this Indenture applicable to mergers, consolidations and
     transfers of all or substantially all of the property and assets of the
     Company;

          (10) Investments that are made with Excluded Contributions;

          (11) any payments made to consummate the Transactions pursuant to or
     contemplated by the Merger Agreement and any other agreements related to
     the Recapitalization in effect on the closing date of the Recapitalization,
     in each case, as such agreements or documents are in effect on the Issue
     Date as amended from time to time so long as such amendment is in the good
     faith judgment of the Board of Directors of the Company not more
     disadvantageous to the Holders of the Securities in any material respect
     than such agreements or documents as in effect on the Issue Date;

          (12) repurchases of Capital Stock deemed to occur upon the exercise of
     stock options, warrants or other convertible securities, to the extent such
     Capital Stock represents a portion of the consideration for such exercise;

          (13) the acquisition of any shares of Disqualified Capital Stock of
     the Company either (a) solely in exchange for shares of Disqualified
     Capital Stock of the Company or (b) through the application of the net
     proceeds of a substantially concurrent sale for cash (other than to a
     Subsidiary of the Company) of shares of Disqualified Capital Stock of the
     Company;

          (14) any purchase or redemption of Indebtedness that ranks junior to
     the Securities utilizing any Net Cash Proceeds remaining after the Company
     has complied with the requirements of the covenants described under
     Sections 4.16 and 4.17;

          (15) the payment of dividends, other distributions or amounts by the
     Company to any direct or indirect parents of the Company in amounts
     required to pay the tax obligations of the Company and its Subsidiaries and
     the tax obligations of any direct or indirect parents of the Company
     attributable to the Company and its Subsidiaries; provided that (x) the
     amount of dividends paid pursuant to this clause (15) to enable any direct
     or indirect parents of the Company to pay Federal and state income taxes at
     any time shall not exceed the amount of such Federal and state income taxes
     actually owing by any direct or indirect parents of the Company at such
     time for the respective period and (y) any refunds received by any direct
     or indirect parents of the Company attributable to the Company and its
     Subsidiaries shall promptly be returned by such direct or indirect parents
     to the Company;

          (16) if no Default or Event of Default shall have occurred and be
     continuing, payments by the Company of cash, in lieu of the issuance of
     fractional shares upon the exercise of warrants or upon the conversion or
     exchange of, or issuance of Capital Stock in lieu of cash dividends on, any
     Capital Stock of the Company or any Restricted Subsidiary, which in the
     aggregate do not exceed $3.0 million; and

          (17) the payment of a Restricted Payment in an aggregate amount of up
     to $100.0 million to holders of the Company's Capital Stock with the gross
     proceeds received by the Company from the issuance of the Company's Senior
     Subordinated

                                        5
<Page>

     Discount Notes Due 2013 having substantially the terms set forth in the
     preliminary offering circular of the Company, dated May 16, 2003, relating
     to the issuance of the Company's Senior Subordinated Discount Notes Due
     2013.

In determining the aggregate amount of Restricted Payments made subsequent to
November 28, 2001, in accordance with clause (c) of the immediately preceding
paragraph, amounts expended pursuant to clauses (1), (2), (4), (5), (6), (7),
(8), (9), (14) and (16) shall be included in such calculation.

Not later than the date of making any Restricted Payment, the Company shall
deliver to the Trustee an Officers' Certificate stating that such Restricted
Payment complies with this Indenture and setting forth in reasonable detail the
basis upon which the required calculations were computed, which calculations may
be based upon the Company's latest available internal quarterly financial
statements.

     SECTION 2.  DEFINITIONS.  Capitalized terms used herein without definition
shall have the meanings assigned to them in the Indenture.

     SECTION 3.  RATIFICATION OF INDENTURE; FIRST SUPPLEMENTAL INDENTURE PART OF
INDENTURE. Except as expressly amended hereby, the Indenture is in all respects
ratified and confirmed and all the terms, conditions and provisions thereof
shall remain in full force and effect. Upon the execution and delivery of this
First Supplemental Indenture by the Company and the Trustee, this First
Supplemental Indenture shall form a part of the Indenture for all purposes, and
every holder of December Notes heretofore or hereafter authenticated and
delivered shall be bound hereby. Any and all references to the Indenture,
whether within the Indenture or in any notice, certificate or other instrument
or document, shall be deemed to include a reference to this First Supplemental
Indenture (whether or not made), unless the context shall otherwise require.

     SECTION 4.  GOVERNING LAW; GOVERNANCE, ETC. THE INTERNAL LAWS OF THE STATE
OF NEW YORK SHALL GOVERN AND BE USED TO CONSTRUE THIS FIRST SUPPLEMENTAL
INDENTURE WITHOUT GIVING EFFECT TO PRINCIPLES OF CONFLICTS OF LAW.

     SECTION 5.  SUCCESSORS.  All agreements of the Company in this First
Supplemental Indenture shall bind its successors. All agreements of the Trustee
in this First Supplemental Indenture shall bind its successors.

     SECTION 6.  SEVERABILITY. In case any provision in this First Supplemental
Indenture shall be invalid, illegal or unenforceable, the validity, legality and
enforceability of the remaining provisions shall not in any way be affected or
impaired thereby.

     SECTION 7.  COUNTERPART ORIGINALS.  The parties may sign any number of
copies of this First Supplemental Indenture. Each signed copy shall be an
original, but all of them together represent the same agreement.

     SECTION 8.  EFFECT OF HEADINGS. The headings of the Sections of this First
Supplemental Indenture have been inserted for convenience of reference only, are
not to be

                                        6
<Page>

considered a part of this First Supplemental Indenture and shall in no way
modify or restrict any of the terms or provisions hereof.

     SECTION 9.  ENTIRE AGREEMENT. This First Supplemental Indenture, together
with the Indenture as amended hereby and the December Notes, contains the entire
agreement of the parties, and supersedes all other representations, warranties,
agreements and understandings between the parties, oral or otherwise, with
respect to the matters contained herein and therein.

     SECTION 10. BENEFITS OF FIRST SUPPLEMENTAL INDENTURE. Nothing in this First
Supplemental Indenture, the Indenture, or the December Notes, express or
implied, shall give to any Person, other than the parties hereto and thereto and
their successors hereunder and thereunder, and the Holders, any benefit of any
legal or equitable right, remedy or claim under the Indenture, this First
Supplemental Indenture, or the December Notes.

     SECTION 11. NOT RESPONSIBLE FOR RECITALS OR NEW NOTES. The recitals
contained herein shall be taken as the statements of the Company, and the
Trustee assumes no responsibility for their correctness. The Trustee makes no
representations as to the validity or sufficiency of this First Supplemental
Indenture. The Trustee shall not be accountable for the use or application by
the Company of the New Notes or the proceeds thereof.

                                        7
<Page>

                                   SIGNATURES

     IN WITNESS WHEREOF, the parties hereto have caused this First Supplemental
Indenture to be duly executed all as of the date first written above.


                                         SALT HOLDINGS CORPORATION


                                         By:
                                            ----------------------
                                         Name:
                                         Title:


                                         THE BANK OF NEW YORK
                                         as Trustee


                                         By:
                                            ----------------------
                                         Name:
                                         Title:

                                        8