Available technologies were evaluated to demonstrate the technical feasibility and cost effectiveness of retrofitting existing facilities to handle wet-weather flow. Cost/benefit relationships were also compared t construction of new conventional control and treatment facilities. Desk top analyses of 13 separate retrofit examples were performed for (1) converting or retrofitting primary settling tanks with dissolved air flotation and lamellae and/or microsand-enhanced plate or tube settling units, (2) retrofitting existing wet-weather flow storage tanks to provide enhanced settling/treatment and post-storm solids removal, (3) converting dry ponds to wet ponds for enhanced treatment, (4) retrofitting wet-weather flow storage tanks for dry-weather flow augmentation, (5) using storage for sanitary sewer overflow control, (6) retrofitting for industrial wastewater control in a combined sewer system, and (7) bringing outdated/abandoned treatment plants back online as wet-weather flow treatment facilities. This analysis demonstrated that retrofitting existing wet-weather flow facilities can be technically feasible in most cases and may be more cost effective than construction of new conventional control and treatment facilities. The feasibility and cost effectiveness of retrofitting was found to be a function of site-specific conditions and treatment requirements. Retrofitting processes will better enable communities to meet EPA's National CSO Policy and stormwater permitting program requirements.