Many existing remediation systems are unable to achieve site closure in a reasonable time frame. The cost of operating an improperly designed treatment system can at times exceed the cost of redesigning the system so that it can effectively achieve site closure. Troubleshooting a problematic system involves review of the regulatory clean-up goals, evaluation of both the aboveground and below ground construction, and evaluation of the operation and maintenance of the system. Remedies range from optimization of the system operation and maintenance to the last resort of system redesign. In some cases, simple modifications to the aboveground equipment can result in major reductions in the cost and time to closure. CPEG professionals can provide full cost-benefit and time-to-closure analyses for any modifications to allow clients to evaluate the modifications from both an economic and a risk standpoint.