In today’s economy, it is common for wastewater treatment plant administrators to seek funding. Repairs, equipment replacement, and upgrades or expansion to meet increasing flows and loadings or to meet more stringent regulatory requirements all require investment. Unlocking hidden capacity can provide some relief to the question of how much funding is needed and when. To help find this capacity, a group of engineers developed a tool that administrators and operators alike can use to evaluate a plant’s capability to treat higher flows and loadings. This tool also provides a guide to future capital investments that will maximize a plant’s treatment potential and its flexibility to accommodate increasingly stringent regulatory demands. Assessing plant capacity is nothing new. Some methods focus on desktop analyses based on rules of thumb, engineers’ and operators’ experience, and vendors’ recommended limits of performance. Others use design standards that were established more than 40 years ago. These traditional methods provide static assessments — that is, they evaluate a plant’s ability to treat a particular design flow and loading or satisfy particular effluent performance criteria at a particular point in time. Dynamic modeling tools, on the other hand, have moved capacity assessment to a time-based analysis in which plant capacity is related to changing flows and loads, changing effluent performance criteria, and aging equipment. With the improved accuracy that can be achieved, a dynamic approach offers greater savings potential.