narrative rule. Once this set of waters was defined, the analysis proceeded to estimate the location and amount of land area that would require load controls to meet the numeric nutrient criteria in the waterbody. For the stormwater and agricultural sources, EPA identified the corresponding acreage draining to the potential incrementally impaired waterbodies, reduced the acreage considered based on best management programs that were already in place, selected a set of BMPs that EPA staff deemed adequate and cost-effective, and then applied a unit cost to the resulting acreage to estimate the total cost for the two sectors. For septic systems EPA determined the number of systems within 500 feet of a waterbody in a potential incrementally impaired watershed and multiplied this number by unit cost to upgrade septic systems to reduce their nutrient loads.
Several key regulatory assumptions were made by EPA and are discussed in the subsequent sector analyses only if the Committee took issue with them. These assumptions include the following
• Impaired waterbodies where a total maximum daily load (TMDL) has already been developed based on the narrative criteria were not considered, assuming that the TMDLs would serve as the basis for site-specific alternative criteria (SSAC), if needed.
• Waters that are currently listed as impaired based on the narrative criteria were also not considered, because it was assumed that a TMDL for nitrogen (N) and/or phosphorus (P) would be developed and that this TMDL would serve as the basis for an SSAC determination.
• Municipal and industrial plants discharging at 3 mg/L for total nitrogen (TN) and 0.1 mg/L for total phosphorus (TP) were considered “in compliance.”
• The cost of actions to reduce pollutant loads associated with implementation of the statewide Stormwater Rule, the Urban Turf Fertilizer Rule, the Florida Department of Environmental Protection (FDEP) Dairy Rule, and Concentrated Animal Feeding Operation (CAFO) Requirements would not necessarily be accruable to the NNC rule, since these programs are already in place.
Three analytical assumptions of the EPA analysis were accepted for this chapter (and are returned to in Chapter 3):
• The definition of the incremental effect of the NNC rule was defined and limited to (1) waters that would be newly listed and determined to be stressed by nutrients and (2) National Pollutant Discharge Elimination System (NPDES) municipal and industrial sources that would receive certain concentration limits in their discharge permits.