Page 5 - ESPP Plan Summary

Aegion Corporation
Employee Stock Purchase Plan

Purpose of Program

The purpose of the program is to provide an incentive for you to purchase shares of the
Company’s Class A common stock, at a discount to fair market value and without brokerage
commissions, mark-ups or other service charges, to participate in the success of the Company by
increasing your ownership interest in the Company.

Administrator of Program

The program is administered by the Compensation Committee of the Company’s Board of Directors
(the “Committee” or the “Administrator”). The Committee has designated American Stock Transfer & Trust
Company to serve as the custodian and recordkeeper of the plan.

Eligibility

Each employee of the Company and its U.S. subsidiaries (“Employer”) who is customarily
employed for more than five months in a calendar year and is regularly scheduled to work twenty
hours or more per week shall be eligible to participate in the plan; provided, however, the plan
excludes any employee who is included in a unit of employees covered by a collective bargaining
agreement where the collective bargaining representative has decided on behalf of such employees
not to participate in the Plan following good faith bargaining with respect to Plan participation.

Description of Benefits

Participation. Each eligible employee may elect to participate in the program by submitting
an enrollment form in the time and manner specified by the Company, which allows enrollment on a
quarterly basis. The enrollment form must state the dollar amount or percentage of pay the
employee wishes to contribute. Thereafter, employees will automatically be enrolled for each
subsequent calendar month, unless the employee files a written notice of withdrawal with the
Company before the beginning of the next calendar month or the employee is no longer eligible at the
beginning of the next calendar month.

Participation in the program is entirely voluntary on the part of any employee.

Contributions. You may make after-tax payroll deduction contributions in amounts not less
than $5 per week and not more than 10% of your pay per payroll period; provided that you may not
contribute more than $25,000 per calendar year. For purposes of the program, your pay means the
amount of your base pay, commissions and overtime pay payable in cash. Payroll deductions will be
made in conformity with the Employer’s payroll deduction schedule and practices.

All program contributions you make will be credited to a non-interest bearing program
account maintained by the Company or the Custodian on your behalf. The Company or Custodian will
make the credit as soon as practicable after the contributions are withheld from your pay.

No cash will be set aside with respect to your program account. The stock and cash held in
your program account are not held in a trust and there is no fiduciary relationship between you and the
Company or the Employer with respect to your program account.