Document:

<PAGE>

                                                                   EXHIBIT 10.15

                  Summary of Non-Employee Director Compensation

      Commencing January 1, 2005, directors who are not employees of Sterling
Construction Company, Inc. or its subsidiaries shall be paid fees according to
the following schedule:

Annual Fees

<TABLE>
<S>                                                                       <C>
-     All Directors..................................................     $7,500

-     All Directors (at the Annual Meeting of Stockholders)..........     A ten-year option to purchase
                                                                          5,000 shares of Sterling Common
                                                                          Stock at market on the date of
                                                                          grant and vesting in full on the
                                                                          date of grant.
</TABLE>

Additional Annual Fees

<TABLE>
<S>                                                                       <C>
-     Chairman of the Audit Committee................................     $7,500

-     Chairman of the Compensation Committee.........................     $2,500
</TABLE>

Meeting Fees

<TABLE>
<S>                                                                       <C>
-     Regularly Scheduled In-Person Board Meeting....................     $1,250

-     Regularly Scheduled Telephone Board Meeting....................     $1,000

-     Unscheduled Telephone Board Meeting............................     $  500

-     Audit Committee Meeting (including the Chairman)...............     $  750

-     Compensation Committee Meeting (including the Chairman)........     $  750
</TABLE>

      Notwithstanding the foregoing, in order to save the company the travel
expenses of directors living outside of the North American continent, such
directors may attend in-person meetings of the Board of Directors by telephone,
but shall nevertheless be paid an attendance fee as if they had attended in
person.

      The foregoing fees shall also constitute compensation for service on the
board of directors of any subsidiary of Sterling Construction Company, Inc.

      All directors shall be reimbursed for their reasonable out-of-pocket
travel and lodging expenses incurred in attendance at meetings of the board and
board committees of Sterling Construction Company, Inc. and its subsidiaries.<PAGE>

                                                                   EXHIBIT 10.17

                       STERLING CONSTRUCTION COMPANY, INC.

July 16, 2004

The Stockholders of Sterling Houston Holdings Listed on Exhibit A
c/o Joseph P. Harper, Sr.
Sterling Houston Holdings, Inc.
20810 Fernbush Lane
Houston, Texas 77073

Dear Stockholders:

The purpose of this letter is to set forth our agreement on certain matters
relating to that certain Transaction Agreement between you, Sterling
Construction Company, Inc., then known as Oakhurst Company, Inc. (the "Company")
and the other parties named therein dated on or about July 18, 2001 (the
"Transaction Agreement") as amended by that certain Restructuring Agreement
dated as of September 19, 2003 (the "Restructuring Agreement"). All terms used
but not defined in this letter shall have the meanings given to them in the
Transaction Agreement.

Pursuant to the Transaction Agreement, you have the right to cause the Company
to purchase each of your shares of Sterling Houston Holdings, Inc. ("SHH") for
the Put Payment Amount. Pursuant to the Restructuring Agreement, you and the
Company agreed that the Company may pay the Exercise Price for all SHH shares in
the aggregate by the payment and issuance of --

      -     Cash in the amount of $2,415,525;

      -     Five-year 12% amortizing subordinated promissory notes in the
            aggregate principal amount of $6,353,913; and

      -     Five-year 14% subordinated cash availability notes in the aggregate
            principal amount of $3,230,562 (the "CAN's").

and that the Company may pay the Earnout Payment for all SHH shares in the
aggregate by the issuance of CAN's.

The Restructuring Agreement also provides that the Company has the right to
negotiate with you the issuance of common stock of the Company in lieu of the
issuance of some or all of the CAN's.

As a result of negotiations between us, you and we have agreed as follows:

      -     You will exercise the Put on July 19, 2004, the date you and the
            Company agree that the Put first becomes exercisable;

      -     Within thirty days of the date that the amount of the Earnout
            Payment has been finally determined, the Company will issue to you
            in the aggregate such number of shares of common stock of the
            Company as is computed from the application of the following formula
            (the "Shares:")

                  -     The sum of the Put Exercise Price and the Earnout
                        Payment multiplied by 114,000;

                  -     Less $2,415,525;

                  -     Less $6,353,913

                  -     Divided by 4.

The allocation of the Shares among you shall be in accordance with such
arrangement as you may unanimously agree upon among yourselves.

If the foregoing accurately states our agreement on the subject matter of this
letter, please so indicate by signing and returning a copy of this letter to me.

                                                                          Page 1
<PAGE>

Very truly yours,
Sterling Construction Company, Inc.

By: /s/ Maarten D. Hemsley
    ----------------------
    Maarten D. Hemsley, Chief Financial Officer

                                                                          Page 2
<PAGE>

                                    EXHIBIT A

/s/ James D. Manning
-----------------------------
JAMES D. MANNING

/s/ Patrick T. Manning            /s/ Linda Manning
-----------------------------     ----------------------------------------------
PATRICK T. MANNING                LINDA MANNING

/s/ Joseph P. Harper, Sr.
-----------------------------
JOSEPH P. HARPER, SR.

/s/ Terry D. Williamson           /s/ Karen Williamson
-----------------------------     ----------------------------------------------
TERRY D. WILLIAMSON               KAREN WILLIAMSON

/s/ Anthony F. Colombo
-----------------------------
ANTHONY F. COLOMBO

/s/ Kevin J. Manning
-----------------------------
KEVIN J. MANNING

/s/ Joseph P. Harper, Jr.
-----------------------------
JOSEPH P. HARPER, JR.

/s/ Julie M. Crump
-----------------------------
JULIE M. CRUMP

/s/ Brian R. Manning
-----------------------------
BRIAN R. MANNING

/s/ Jeffrey Manning
-----------------------------
JEFFREY MANNING

                                                                          Page 3<PAGE>

                                                                   EXHIBIT 10.25

                      NOTE AND WARRANT AMENDMENT AGREEMENT

      This NOTE AND WARRANT AMENDMENT AGREEMENT (this "Agreement") is entered
into as of the 3rd day of February 2005 by and among the following parties:

      STERLING CONSTRUCTION COMPANY, INC., a Delaware corporation ("SCC;")

      HARE & CO. A/C BANK OF NEW YORK ("Hare,") and

      THE HOLDERS OF CERTAIN PROMISSORY NOTES issued by SCC whose names appear
      on the signature page of this Agreement (the "Noteholders") under that
      heading.

                                   BACKGROUND

Effective October 31, 2001, SCC issued to North Atlantic Small Companies
Investment Trust Plc ("NASCIT") Warrant No. ST-12 to purchase 322,661 shares of
the common stock of SCC. NASCIT subsequently assigned that warrant to Hare
whereupon it was reissued as Warrant No. ST-22 and is hereinafter referred to as
the "Warrant."

Effective November 13, 2004, SCC issued Five-Year Subordinated Promissory Notes
to certain of the Noteholders and on December 22, 2004, SCC issued a Five-Year
Subordinated Promissory Note to each of the Noteholders, all as set forth in the
schedule attached hereto as Schedule A. Each of such notes is referred to herein
as a "Note" and together they are referred to as the "Notes."

On December 22, 2004 SCC also issued a Five-Year Subordinated Promissory Note to
Hare in the principal amount of one million four hundred four thousand seven
hundred fifty-eight dollars ($1,404,758) (the "Hare Note.")

1.    CONSIDERATION. The parties now wish to enter into various transactions
      with respect to the Warrant, the Notes and the Hare Note for and in
      consideration of the foregoing recitals, the mutual covenants contained
      herein and other good and valuable consideration, the receipt and
      sufficiency of which are hereby acknowledged.

2.    THE WARRANT.

            2.1   The first sentence of Section 1 of the Warrant is hereby
                  amended in its entirety to read as follows:

                        "Subject to the terms and conditions set forth herein
                        and except as provided below, this Warrant shall be
                        exercisable in whole or in part during the term
                        commencing on the date that is forty-two (42) months
                        after July 13, 2001 and ending at 5:00 p.m., Eastern
                        Time on July 13, 2011, and shall be void thereafter."

            2.2   On or before March 31, 2005, Hare shall exercise the entire
                  Warrant as so amended and shall pay to SCC by wire transfer of
                  immediately available funds the Warrant exercise price of one
                  dollar and fifty cents ($1.50) per share, aggregating
                  $483,991.50.

                                                                     Page 1 of 3
<PAGE>

3.    THE NOTES. Simultaneously with the execution of this Agreement, each of
      the Noteholders will execute the form of note amendment attached hereto as
      Exhibit A (the "Note Amendment") for each Note then held by him or her.

4.    THE HARE NOTE.

            4.1   On the earlier of March 31, 2005 and the date of receipt of
                  the funds described in Section 2.2, above, SCC will prepay one
                  million twenty-seven thousand six hundred three dollars
                  ($1,027,603) of the principal of the Hare Note; and

            4.2   On or before June 30, 2005, SCC will pre-pay the then
                  outstanding balance of the Hare Note together with all accrued
                  but unpaid interest thereon, whereupon Hare shall return the
                  Hare Note to SCC for cancellation.

5.    GOVERNING LAW. This Agreement shall be governed by, and construed in
      accordance with, the domestic laws of the State of Delaware without giving
      effect to any choice of law or conflict of law provision or rule (whether
      of the State of Delaware or of any other jurisdiction) that would cause
      the application hereto of the laws of any jurisdiction other than the
      State of Delaware.

6.    MISCELLANEOUS.

            6.1   This Agreement and any attachments referred to herein set
                  forth the full and complete understanding of the parties with
                  respect to the matters herein; shall not be amended except by
                  written agreement of the parties signed by each of them; and
                  shall be binding upon, and inure to the benefit of, the
                  parties and their successors, personal representatives and
                  assigns.

            6.2   This Agreement and any amendment hereof may be executed in any
                  number of counterparts, each of which may be executed by fewer
                  than all of the parties hereto (provided that each party
                  executes at least one counterpart) each of which counterparts
                  shall be enforceable against the party or parties actually
                  executing the counterpart, and all of which counterparts
                  together shall constitute but one and the same agreement. This
                  Agreement may be delivered by telecopier or other facsimile
                  transmission with the same force and effect as if the same
                  were a fully executed and delivered original manual
                  counterpart.

            6.3   This Agreement shall not become effective or binding on any
                  party until --

                  (a)   It has been executed and delivered by all of the
                        individuals and entities listed on the signature page
                        hereof; and

                  (b)   Each Noteholder shall have executed and delivered the
                        Note Amendment with respect to each of his or her Note
                        or Notes, and SCC has executed and delivered each such
                        Note Amendment.

             [The balance of this page is intentionally left blank]

Note and Warrant Amendment Agreement

                                                                     Page 2 of 3
<PAGE>

      IN WITNESS WHEREOF, the parties have executed this Agreement as of the
date first set forth above.

STERLING CONSTRUCTION COMPANY, INC.      HARE & CO. A/C BANK OF NEW YORK BY: J
O HAMBRO CAPITAL MANAGEMENT

By: /s/ John D. Abernathy                By: /s/ R. G. Barret
    ----------------------------------       --------------------------------
    John D. Abernathy                        Name:  R. G. Barret
    Chairman of the Audit Committee          Title: Director, J O Hambro Capital
                                                    Management Ltd as
                                                    investor manager

                                   NOTEHOLDERS

/s/ James D. Manning                          /s/ Maarten D. Hemsley
--------------------------------------        --------------------------------
James D. Manning                              Maarten D. Hemsley

/s/ Patrick T. Manning                        /s/ Robert M. Davies
--------------------------------------        --------------------------------
Patrick T. Manning                            Robert M. Davies

/s/ Linda Manning
--------------------------------------
Linda Manning

/s/ Joseph P. Harper, Sr.
--------------------------------------
Joseph P. Harper, Sr.

/s/ Joseph P. Harper, Jr.
--------------------------------------
Joseph P. Harper, Jr.

/s/ Terry D. Williamson
--------------------------------------
Terry D. Williamson

/s/ Anthony F. Colombo
--------------------------------------
Anthony F. Colombo

/s/ Kevin J. Manning
--------------------------------------
Kevin J. Manning

/s/ Brian R. Manning
--------------------------------------
Brian R. Manning

/s/ Jeffrey Manning
--------------------------------------
Jeffrey Manning

Note and Warrant Amendment Agreement

                                                                     Page 3 of 3

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