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                                                                   EXHIBIT 10.37


             SENIOR SUBORDINATED SECURED CONVERTIBLE PROMISSORY NOTE


$100,000                                                       DECEMBER 31, 2001


FOR VALUE RECEIVED, STERLING CONSTRUCTION COMPANY, INC., (formerly known as
Oakhurst Company, Inc.) a corporation organized under the laws of the State of
Delaware (the "Maker,") hereby promises to pay to the order of JOSEPH P. HARPER,
SR. (the "Holder") or assigns, the principal sum of One Hundred Thousand Dollars
($100,000.)

1.   MATURITY DATE. All principal and accrued but unpaid interest shall be due
     to the Holder on the third anniversary of the original date of issuance of
     this Note (the "Maturity Date.")

2.   INTEREST. The Maker shall pay interest on the balance of the principal of
     this Note outstanding from time to time monthly, in arrears, on the first
     business day of each month, at the rate of twelve percent (12%) per annum,
     pro rated for any period of less than a full month that this Note is
     outstanding based on the number of days in such month. Any accrued but
     unpaid interest on this Note shall be added to the outstanding principal of
     this Note for the purpose of computing subsequent interest payments.

3.   NO SET-OFFS. All payments by the Maker under this Note shall be made
     without set-off, defense or counterclaim and free and clear and without any
     deduction or withholding for any taxes or fees of any nature whatever,
     unless the obligation to make any such deduction or withholding is imposed
     by law.

4.   SUBORDINATION.

     (a)  This Note is one of a series of notes issued by the Maker on the date
          hereof that are identical except for the principal amount and the name
          of the payee (the "WC Notes.") No payment on account of the principal
          of, or interest on, the WC Notes shall be made, and the WC Notes shall
          not be redeemed or purchased directly or indirectly by the Issuer (or
          any of its subsidiaries,) if at the time of such payment or purchase
          or immediately after giving effect thereto, (i) there shall exist a
          default in any payment with respect to any Senior Indebtedness (as
          defined below;) or (ii) there shall have occurred any other default or
          event of default as those terms may be defined in the instrument under
          which such Senior Indebtedness is outstanding (other than a default in
          the payment of amounts due hereon) with respect to the Senior
          Indebtedness permitting the holders thereof to accelerate the maturity
          thereof, and such default or event of default shall not have been
          cured or waived or shall not have ceased to exist.

     (b)  Subject to payment in full of the Senior Indebtedness, the holders of
          the WC Notes shall be subrogated to the rights of the holders of
          Senior Indebtedness to receive payments or distributions of the assets
          of the Issuer made on such Senior Indebtedness until all principal and
          interest on the WC Notes shall be paid in full. For purposes of such
          subrogation, no payments or distributions to the holders of Senior
          Indebtedness of any cash, property or securities to which any holder
          of the WC Notes would be entitled except for the subordination
          provisions of this Section 4 shall, as between the holders of the WC
          Notes and the Issuer and/or its creditors (other than the holders of
          the Senior Indebtedness) be deemed to be a payment on account of the
          Senior Indebtedness.

     (c)  The provisions of this Section 4 are and are intended solely for the
          purposes of defining the relative rights of the holders of the WC
          Notes and the holders of Senior Indebtedness, and nothing in this
          Section 4 shall impair, as between the Issuer and the holders of the
          WC Notes, the obligation of the Issuer, which is unconditional and
          absolute, to pay to the holders of the WC Notes the principal thereof
          and interest thereon in accordance with the terms thereof; nor shall
          anything herein prevent the holders of the WC Notes from exercising
          all remedies otherwise permitted by


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          applicable law or hereunder upon default, subject to the rights set
          forth above of holders of Senior Indebtedness to receive cash,
          property or securities otherwise payable or deliverable to the holders
          of the WC Notes.

     (d)  Upon any payment (including by redemption) which is not a payment in
          full of all of the principal amount and accrued interest of the WC
          Notes, the aggregate amount of the payment shall be allocated to all
          the WC Notes then outstanding in proportion to the amounts of
          principal and interest due thereunder, so that the amount of principal
          paid under this Note shall bear the same ratio to the aggregate
          principal and accrued interest paid under all of the WC Notes as the
          then outstanding principal then owed under this Note (as if the same
          were then being prepaid pursuant to Section 6) bears to the aggregate
          principal and accrued interest then owed under all of the WC Notes
          then outstanding.

     (e)  For purposes of this Note and all WC Notes, "Senior Indebtedness"
          means

          (i)    that certain promissory note, as amended, dated October 18,
                 1999 payable to Robert M. Davies in the original principal
                 amount of $539,117;

          (ii)   obligations of the Issuer under that certain promissory note
                 issued to KTI, Inc. on July 3, 2001 in the original principal
                 amount of $1,000,000;

          (iii)  that certain promissory note dated July 13, 2001 payable to
                 Robert M. Davies in the original principal amount of $250,623;

          (iv)   that certain promissory note dated July 13, 2001 payable to
                 Maarten D. Hemsley in the original principal amount of
                 $136,421;

          (v)    those three promissory notes dated October 19, 2001 payable,
                 respectively, to James D. Manning ($400,000,) Joseph P. Harper,
                 Sr. ($300,000) and Anthony Colombo ($100,000);

          (vi)   all obligations of the Issuer to Comerica Bank-Texas under any
                 guaranty by the Issuer of the obligations of any affiliate of
                 the Issuer (the "Comerica Obligations;")

          (vii)  any and all working capital financing of the Issuer consummated
                 after the date of this Note with one or more lending entities
                 (a "Working Capital Financing;") and

          (viii) any and all replacements or refinancings of the Comerica
                 Obligations or a Working Capital Financing (whether any such
                 replacement or refinancing is for a greater or lesser amount
                 than the amount replaced or refinanced) with one or more other
                 lending institutions that is guaranteed by, or is the direct
                 obligation of, the Issuer.

5.   EVENTS OF DEFAULT. At the option of the Holder, all unpaid principal and
     accrued but unpaid interest under this Note shall become immediately due
     and payable without presentment, demand, protest or notice of any kind if
     any one or more of the events described in clauses (a) and (b), below (each
     an "Event of Default") occurs:

     (a)  If the Maker--

          (i)    fails to pay the principal on the Maturity Date;

          (ii)   fails to pay any accrued interest hereunder within ten (10)
                 days after the due date thereof;

          (iii)  commences any voluntary proceeding under any provision of Title
                 11 of the United States Code, as now in effect or as or
                 hereafter amended, or commences any other proceeding under any
                 law, now or hereafter in force relating to bankruptcy,
                 insolvency, reorganization, liquidation, or otherwise relating
                 to the relief of debtors or the readjustment of indebtedness,


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          (iv)   makes any assignment for the benefit of creditors or a
                 composition or similar arrangement with creditors;

          (v)    appoints a receiver, trustee or similar judicial officer or
                 agent to take charge of, or liquidate any of its property or
                 assets; or

     (b)  If any involuntary proceeding of the kind described in clauses
          (a)(iii), (a)(iv) or (a)(v), above, is commenced against the Maker.

6.   PREPAYMENT. At the option of the Maker, this Note may be prepaid in whole
     or in part at any time without penalty or premium. Any such prepayment
     shall be applied first to the payment of accrued but unpaid interest as of
     the date of such prepayment and then to the payment of the principal
     balance hereof.

7.   CONVERSION.

     (a)  By written notice to the Issuer, the Holder shall have the right,
          exercisable at any time or from time to time prior to the close of
          business on the Maturity Date, to convert all or any portion of the
          then outstanding principal balance of this Note into that number of
          fully paid and nonassessable shares of common stock, par value $0.01
          per share, of the Issuer ("Common Stock") that is equal to the amount
          of the principal of this Note to be converted divided by the
          Conversion Price (as defined below) rounded down to the nearest whole
          share. No fractional shares of Common Stock shall be issued upon any
          conversion of this Note.

     (b)  Any conversion shall be deemed to have been effected on the date when
          delivery of this Note is made to the Issuer with a request for
          conversion indicating the amount of this Note to be converted (the
          "Conversion Date.") As promptly as practicable thereafter, the Issuer
          shall issue and deliver to, or upon the written order of, the Holder,
          at the place designated by the Holder, a certificate or certificates
          for the number of full shares of Common Stock to which the Holder is
          entitled.

     (c)  The person in whose name the certificate or certificates for Common
          Stock are to be issued shall be deemed to have become a holder of
          record of Common Stock on the Conversion Date unless the transfer
          books of the Issuer are closed on that date, in which event, such
          person shall be deemed to have become a stockholder of record on the
          next succeeding date on which the transfer books are open.

     (d)  Upon conversion of only a portion of this Note, the Issuer shall issue
          and deliver to, or upon the written order of, the Holder a new note
          covering the principal balance of this Note that was not converted.

     (e)  If at any time after the date of this Note, the number of shares of
          Common Stock outstanding is increased by a stock split, subdivision or
          split-up of shares of Common Stock, then following the record date
          fixed for the determination of holders of Common Stock entitled to
          receive such stock split, subdivision or split-up, the Conversion
          Price shall each be appropriately decreased so that the number of
          shares of Common Stock issuable on conversion of this Note immediately
          prior to such record date shall be increased in proportion to such
          increase in the outstanding shares.

     (f)  If at any time after the date of this Note, the number of shares of
          Common Stock outstanding is decreased by a reverse stock split or
          combination of the outstanding shares of Common Stock, then following
          the record date for such combination, the Conversion Price shall be
          appropriately increased so that the number of shares of Common Stock
          issuable on conversion of this Note immediately prior to such record
          date shall be decreased in proportion to such decrease in outstanding
          shares.

     (g)  In the event, at any time after the date of this Note, of any capital
          reorganization, or any reclassification of the capital stock of the
          Issuer (other than a change in par value or from par value to no par
          value or from no par value to par value or as a result of a
          subdivision, split-up or combination of shares,) or the consolidation
          or merger of the


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          Issuer with or into another person (other than consolidation or merger
          in which the Issuer is the continuing corporation and which does not
          result in any change in the powers, designations, preferences and
          rights, or the qualifications, limitations or restrictions, if any, of
          the capital stock of the Issuer) or of the sale or other disposition
          of all or substantially all the properties and assets of the Issuer as
          an entirety to any other person (any such transaction being referred
          to as an "Extraordinary Transaction,") then the Issuer shall provide
          appropriate adjustment to the Conversion Price such that the principal
          balance of this Note outstanding immediately prior to the
          effectiveness of the Extraordinary Transaction shall be convertible
          into the kind and number of shares of stock or other securities or
          property of the Issuer, or of the corporation resulting from or
          surviving such Extraordinary Transaction, that a holder of the number
          of shares of Common Stock deliverable (immediately prior to the
          effectiveness of the Extraordinary Transaction) upon conversion of the
          then outstanding principal balance of this Note would have been
          entitled to receive upon such Extraordinary Transaction.

     (h)  The "Conversion Price" shall mean two dollars and fifty cents ($2.50)
          as the same may be adjusted as provided herein.

8.   SECURITY INTEREST. The Issuer hereby grants to the Holder and has granted
     to each other holder of a WC Note a present security interest in that
     certain subordinated promissory note issued by Steel City Products, Inc.
     ("SCPI") to the Issuer in the original principal amount of $550,000 to
     secure payment and performance of the Issuer's obligations under this Note.
     This security interest is equal in right of payment, performance and
     priority to the indebtedness of the Issuer to the holders of the other WC
     Notes, and is subordinate in right of payment, performance and priority to
     any and all indebtedness of SCPI to National City Bank of Pennsylvania. The
     Issuer agrees to execute and deliver to the Holder such security
     agreements, UCC forms and other documents as the Holder may reasonably
     request to further evidence or perfect this security interest.

9.   GENERAL.

     (a)  None of the terms or provisions of this Note may be excluded, modified
          or amended except by a written instrument duly executed by the Holder
          expressly referring to this Note and setting forth the provision so
          excluded, modified or amended; provided however, no amendment to the
          subordination provisions of this Note that benefit the Holder unless a
          similar amendment is made to the other WC Notes.

     (b)  The Maker hereby waives presentment, demand, presentment for payment,
          protest, notice of protest, notice of dishonor of this Note and all
          other demands and notices in connection with the delivery, acceptance,
          performance and enforcement of this Note.

     (c)  This Note shall be governed by, and construed in accordance with, the
          laws of the State of Delaware applicable to agreements made and
          performed entirely in such State, without regard to conflict of laws
          principles thereof, and shall be binding upon the successors and
          assigns of the Maker and shall inure to the benefit of the successors
          and assigns of the Holder.


STERLING CONSTRUCTION COMPANY, INC.

By:       /s/ Patrick T. Manning
    -----------------------------------
     Patrick T. Manning
     Chairman and Chief Executive Officer



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