The Florida Department of Environmental Protection (Department) and water management districts (WMDs) are initiating rulemaking as required by Section 5 of Chapter 2020-150, Laws of Florida, to update the stormwater design and operation regulations adopted under Section 373.4131, Fla. Stat., including updates to the Environmental Resource Permit Applicant’s Handbook (AH), using the most recent scientific information available. The legislation dictates that the required rulemaking is initiated by December 31, 2020. The AH contains two volumes. Volume I, which is adopted by the Department, contains stormwater design and operation regulations that apply statewide. Volume II, a version of which is adopted by each WMD, contains stormwater design and operation regulations that only apply to that respective WMD. The updates required by Chapter 2020-150 necessitate that the Department and each of the WMDs engage in rulemaking simultaneously to ensure that each WMD’s AH Volume II is consistent with the Department’s AH Volume I. As a result, the Southwest Florida Water Management District will amend 40D-1.660, F.A.C, which incorporates by reference its AH Volume II, and will update the stormwater design and operation regulations contained within Volume II.