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Page 18 Attachment B: Supporting Research November 24, 2020 Update 2 — Research Review Phase of IRL Plan As stated earlier, the County currently does not have a set value from FDEP on the mass of nitrogen and phosphorus that can be discharged into the water and still maintain a healthy ecosystem. For these reasons, the County currently relies on the numeric nutrient criteria set for the peninsular region of Florida by FDEP. Using this rule, TN concentrations should not exceed 1.54 mg/L and TP concentrations should not exceed 0.12 mg/L. One area that may benefit the County, and is currently lacking, is monitoring of groundwater nutrient concentrations. This information would not only benefit the County, it would also be pertinent to regulatory agencies in setting nutrient criteria. Whether this should be a task the County takes on or state -level regulatory agencies take on is undetermined. The County would also benefit from studying legacy loading to the Lagoon and understanding how many excess nutrients are being added to the system from historical uses surrounding the Lagoon area. The County should continue to support the Indian River Lagoon National Estuary Program (IRLNEP) in their studies about atmospheric deposition. Atmospheric deposition is starting to be studied at a greater extent, and these studies will hopefully add to the knowledge base of this subject. Finally, it is important for the County to continue to partner and support other entities within the Lagoon basin. Nutrients do not recognize municipal or county boundaries, and the reduction of excess nutrients throughout the system as a whole will benefit the health and prosperity of organisms in the Lagoon. S. Land Use Changes (Part 2) In order to develop a parcel of land within the County, various permits and approvals must be obtained from different levels of government. These permits cover numerous topics, but one important topic needing approval is for the management of stormwater as it changes with changing land use. The management of stormwater is important in the Lagoon's watershed to make sure pollutants and excess nutrients have time to filter and settle out of the water before eventually making its way into the Lagoon. The County regulates stormwater runoff through local ordinances and the issuance of stormwater management system permits for construction projects administered through the Public Works Engineering Division, Land Development section. The County's Stormwater Management and Flood Protection Ordinance (Chapter 930) was created to protect the health, safety, and welfare of the citizens of the County; to implement those policies and objectives found in the drainage sub -element of the County's comprehensive plan; to ensure protection of land and improvements together with natural resources through the use of responsible stormwater management and flood protection practices; to ensure replenishment of the County's aquifer systems to provide a continuing usable water supply; to reduce stormwater pollutant loading of the Lagoon; and to provide proper flood management. There are three types of stormwater permits that may be obtained at the County level: Type A (stormwater management system), Type B (flood protection-stormwater management system), and Type C (flood management system). Type A encompasses projects not located in flood hazard zones, whereas Types B and C encompass projects in flood hazard zones. In general, lands east of U.S. 1 throughout the County are located in flood hazard zones, as well as areas west of U.S. 1 located between C.R. 512 and S.R. 60. These permits require the submittal of various hydraulic data and calculations in order to ensure that they meet local ordinances for protection. Once received by the County, staff review the application and plans with other applicable permitting agencies, and with the 119