AMENDMENT TO THE RETIREMENT PLAN FOR KOPPERS INC

Exhibit 10.59

AMENDMENT TO THE

RETIREMENT PLAN FOR KOPPERS INC.

The Retirement Plan for Koppers Inc. hereby is amended, effective January 1, 2008, to add new Annex I to the Plan to read as follows:

ANNEX I

Maximum Annual Retirement Benefits

for Limitation Years beginning on and after January 1, 2008

Except as otherwise provided below, the provisions of this Annex I shall be effective as of the Limitation Year beginning on January 1, 2008. The limitations, adjustments and other requirements prescribed herein shall at all times comply with the provisions of Code Section 415 and the final regulations thereunder, the terms of which are specifically incorporated herein by reference. These provisions shall supersede the provisions of the Plan to the extent they are inconsistent with the provisions of this Annex I.

(a) Notwithstanding anything in the Plan to the contrary, in no event shall the combined Annual Benefit payable with respect to a Participant on a single life basis under this or any other defined benefit plan maintained by the Employer or any Affiliate under which the Participant is covered as a participant exceed the lesser of: (1) $160,000 (or such other figure determined in accordance with the cost of living adjustment procedure under Code Section 415(d) and Treas. Reg. Section 1.415(d)-1(a), but only for the year in which such adjustment is effective); and (2) 100% of the Participant’s average annual Compensation during the three consecutive years (as adjusted pursuant to Code Section 415(d) and Treas. Reg. Sections 1.415(d)-1(a) and 1.415(b)-1(a)) in which the Participant received the greatest amount of Compensation. The Plan may use any 12-month period to determine a year of service, provided that such period is determined consistently and applied uniformly to all Participants. Such 12 month period shall be the Plan Year. For a Participant who is employed by the Employer for fewer than three consecutive years, the period of the Participant’s high three years of service is the actual number of consecutive years of service (including fractions of a year, but not less than one year). With respect to a Participant who incurs a break in service and is rehired by the Employer, the Participant’s high three years of service shall be calculated by excluding all years for which the Participant performs no services for and receives no Compensation from the Employer maintaining the Plan and by bridging the years of service before and after the break in service and treating such years as if they were consecutive.

(b) Notwithstanding subsection (a) above, benefits up to $10,000 for a Limitation Year may be paid without regard to the 100% of Compensation limitation if the total retirement benefits payable to a Participant under all defined benefit plans maintained by the Employer and any Affiliate for the present and any prior Limitation Year do not exceed $10,000 and the Employer (or a predecessor employer) and any Affiliate has not at any time maintained a defined contribution plan under which the Participant was covered. For purposes of determining the $10,000 amount, the benefit payable with respect to the Participant under a plan for a Limitation Year reflects all amounts payable under the plan for the Limitation Year (except as otherwise provided in Treas. Reg. Section 1.415(d)-1) and is not adjusted for form of benefit or commencement date.

(c) If a Participant has multiple Annuity Starting Dates, the limitations of Code Section 415 and the regulations thereunder must be met separately as of each of Annuity Starting Date taking into account the benefits that have been or will be provided as of each Annuity Starting Date.

(d) If a Participant’s Annual Benefit (or a retirement benefit to which the Participant is entitled under any other defined benefit plan maintained by the Employer or any Affiliate) is payable in a form other

than a single life annuity or qualified joint and survivor annuity, the Annual Benefit shall be converted to a single life annuity using the interest rate and mortality assumptions specified in the Plan for Actuarial Equivalence for the particular form of benefit payable. The single life annuity, which has been so determined, shall be compared to the single life annuity that has the same actuarial present value as the form of benefit payable to the Participant, computed using a 5 percent interest rate assumption (or for any form of benefit subject to Code Section 417(e)(3), the applicable interest rate as defined in Code Section 417(e)(3)) and the applicable mortality table prescribed in Code Section 415(b)(2)(E)(v). The greater of these two amounts shall be the applicable limit for the Annual Benefit payable in a form other than a single life annuity or qualified joint and survivor annuity.

Notwithstanding the foregoing, the following shall not be taken into account: any ancillary benefit that is not related to retirement income benefits; and the survivor annuity provided under the portion of any annuity that constitutes a qualified joint and survivor annuity (as defined in Code Section 417(b)).