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Page 17 Attachment B: Supporting Research November 24, 2020 Update 2 — Research Review Phase of IRL Plan The U.S. Geological Surveys (USGS) maintains monitoring stations on each of the Relief Canals. The stations do not record all canal flows, but can give an indication of the average canal flows over various time periods. From 2014 through 2018, the approximate average flows in million gallons per day (MGD) in the three Relief Canals were: North Relief Canal = 28.3 MGD Main Relief Canal = 45.0 MGD South Relief Canal = 39.7 MGD The average pounds of nutrients discharged into the Lagoon per year can be estimated using the data above as: North Relief Canal = 85,287 pounds/year of TN and 14,645 pounds/year of TP Main Relief Canal = 116,437 pounds/year of TN and 15,068 pounds/year of TP South Relief Canal = 107,557 pounds/year of TN and 14,502 pounds/year of TP The County has undertaken some regional scale nitrogen and phosphorus reducing projects such as Osprey Acres, Osprey Marsh, Spoonbill Marsh, and Egret Marsh. It is estimated that the County removes approximately 80,170 pounds/year of TN and 12,123 pounds/year of TP from reaching the Lagoon through these facilities. The County should continue to promote and expand education efforts surrounding the removal of excess nutrients, such as the continuation of the fertilizer ordinance, the education of residents to be mindful of storm drains and the impacts of what goes down them, and Florida Friendly Yards. The County is proactive in removing excess nutrients, with the continued creation and completion of projects aimed at lessening the load of nutrients from wastewater and stormwater. These projects can be costly, so the County should continue to pursue grants in order to help fund these initiatives. Once the runoff enters into the Lagoon, various water quality monitoring stations from different entities track water quality trends measured. Some of these entities include Florida Atlantic University's Harbor Branch, Ocean Research & Conservation Association (ORCA), SJRWMD, and FDEP. The data measured by these entities are available on their respective websites. Using SJRWMD data, average nutrient levels for 2020 data collected thus far are listed below: Average Nitrogen and Phosphorus Levels Measured in the Lagoon by SJRWMD (January 2020 through July 2020) Parameter IRLIRJ01— North IRLIRJ04 — Central I1RLIRJ08 — South Total Kjeldahl Nitrogen (mg/L) 0.41 0.51 0.47 TP (mg/L) 0.05 0.08 0.06 118