Leon County, FL Environmental Rules: Stormwater Management (2026)

Under LDC § 10-4.303, the design of stormwater management facilities must control the rate of flow of stormwater runoff for all intensities, durations and return frequencies up to and including the 25-year storm, and all treatment facilities must be designed and constructed to remain completely functional during the 25-year flood. Increases in post-development stormwater runoff above pre-development volumes must be either retained on-site or filtered through an approved regional stormwater management facility. Under the County's restricted-discharge standard, a facility may be designed so post-development discharge is restricted to the critical-duration two-year pre-development discharge rate for all durations and return frequencies up to and including the 25-year, 24-hour storm event, with the required detention volume again available within 90 hours following a rainfall event. Where a site exceeds 2 acres and its discharge exceeds 2.5% of the flow in the downstream conveyance for the critical storm, a conveyance analysis (covering storms up to the 25-year frequency, and up to the 100-year if downstream flooding exists) or restricted discharge is required. A stormwater permit (Short Form B-Low, Short Form B-High, or Standard Form) is obtained through DSEM, accompanied by a signed and sealed stormwater report.