Sahuarita, AZ Environmental Rules: Stormwater Management (2026)

110(A) requires any development with a residential density of three or more units per acre, any residential development larger than one acre with a density of six units per developed acre, and all commercial and industrial developments to provide peak or volumetric stormwater runoff reduction, sized according to the Pima County Regional Flood Control District's November 2015 Design Standards for Stormwater Detention and Retention. The town directs applicants to detain runoff and harvest stormwater for irrigation where feasible. 110(B) layers stricter review onto "balanced" and "critical" drainage basins the Pima County Flood Control District mapped in 1987 as unsuitable for added development because of elevated flood risk; the floodplain administrator maintains that map for the town and can reclassify an unmapped basin as critical after study, and any further development in a critical or balanced basin needs adequate detention or flood control facilities regardless of project size or density.

110(C) allows structural flood control measures, such as channelization to a logical downstream conclusion, to substitute for detention if the applicant demonstrates the measure will not disturb the watercourse's water and sediment equilibrium and will mitigate environmental impacts, subject to the floodplain administrator's review. 110(D) lets the town engineer require alternative drainage solutions, including full retention. 110(E) allows the town to accept an in-lieu fee instead of an on-site system when detention would not provide off-site flood relief, with the fee set at the cost of the detention system the project would otherwise have to build.