(a) For purposes of this article, the following definitions shall apply:

1. (1) “Baseline concentration” means the initial concentration of a constituent of concern prior to conducting corrective action pursuant to a performance-based contract.
2. (2) “Constituent of concern” means the chemical element, compound, or grouping, including, but not limited to, total petroleum hydrocarbons, as in gasoline, that is present in the soil or groundwater and subject to corrective action.
3. (3) “Performance-based contract” means a written agreement approved by the board between a claimant and an appropriately licensed contractor, where the contractor agrees for a fixed price to take corrective action to reduce the concentrations of designated constituents of concern to specified concentrations.
4. (4) “Remediation milestone” means that a specified reduction in the concentrations of constituents of concern from baseline concentrations has been attained through corrective action. The reduction is expressed as a percentage of the total reduction required by the performance-based contract.

(d) The board shall make payments based upon the reduction in the concentrations of designated constituents of concern to specified concentrations. If corrective action is estimated to take six months or more to achieve these concentrations and the remediation technology proposed is a pump-and-treat or other type of mechanical remediation technology, the board may pay a portion of the fixed price based on the attainment of specified remediation milestones or other performance parameters, in the following manner:

1. (1) The first payment shall include the amount of incurred capital costs upon successful installation and startup of the mechanical remediation system.
2. (2) The second payment shall be an amount equal to the agreed upon percent of the total contract price when the 25 percent remediation milestone is attained.
3. (3) The third payment shall be equal to an agreed upon percent of the total contract price when the 50 percent remediation milestone is attained.
4. (4) The fourth payment shall be equal to an agreed upon percent of the total contract price when the 75 percent remediation milestone is attained.
5. (5) The fifth payment shall be equal to an agreed upon percent of the total contract price when the 100 percent remediation milestone is attained.
6. (6) The final payment shall be the amount of the remaining contract price that shall be paid when the 100 percent remediation milestone has been maintained for one year following cessation of all active remediation.