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removed in order to demonstrate credit towards achieving the TMDL for this basin. A Preliminary Effectiveness Monitoring Plan has been included in this work plan as Appendix A. TP kg/yr TN kg/yr ESTIMATED POLLUTANT LOAD REDUCTION: BMPs Installed OF THE THEORETICAL POLLUTANT LOAD REMOVAL EFFECIENCY BY THE TREATMENT SYSTEM: The following engineering approach was taken Other Other of the proposed vortex units TSS kg/yr TP kg/yr TN kg/yr Sediment kg/yr BOD kg/yr k / r kg/yr Canal Treatment Structure Pre -Project 911907.00 8744.00 94314.00 Post -Project 362821.00 5234.00 80117.00 Load Reduction 549086.00 3510.00 14197.00 0 rL % Reduction 60.00 40.00 15.00 RATIONAL ESTIMATE OF THE THEORETICAL POLLUTANT LOAD REMOVAL EFFECIENCY BY THE TREATMENT SYSTEM: The following engineering approach was taken to determine the pollutant load removal efficiency of the proposed vortex units for the Main Relief Canal: Therefore, multiple pre -cast units or a single large To determine the optimal size of the vortex unit for the IRFWCD application, the anticipated flow rates were estimated. For this purpose, ten years of USGS data were analyzed. The daily flows were sorted to determine the frequency with which a given flow occurred. The frequency that flow rates exceeded 80%, 90%, 95% and 98% of the daily flows was estimated. Assuming that all of the flows smaller than this flow rate and a portion of the flows greater than this flow rate are treated, the percent of flows treated annually was estimated. Table I shows the results of the flow analysis for the Main Relief Canal, followed by an example of how the percentage of annual flow treated was calculated. Table 1 - Main Relief Canal Peak and Annual Flow Treatment Summary Percent of Days All Flow is Treated Flow Rate Percent of Cumulative Annual Flow Treated 80% 76 cfs 53% 90% 184 cfs 75% 95% 294 cfs 86% 98% 450 cfs 94% Calculations: Known Information from USGS gauging station information: 80% of the days (2924 days) had a recorded flow of less than or equal to 76 cfs With the goal to achieve treatment of 80% to 90% of the total annual flows, a single pre -cast 64 The average flow on days when the flow was less that 76 cfs was 27.42 cfs and this occurred on 2924 days The average flow for all of the days (3653 days) was 69.84 cfs The largest pre -cast CDS structure is rated at a maximum of 64 cfs. However, larger cast -in-place units can be designed and constructed. With the goal to achieve treatment of 80% to 90% of the total annual flows, a single pre -cast 64 cfs unit will not be sufficient. Therefore, multiple pre -cast units or a single large cast -in-place unit will need to be designed. the average TSS removal efficiency at 52%. The treatment efficiency of the CDS unit (floating boom not included) is highly dependent on particle size. The capture efficiency of CDS units measured under laboratory conditions is estimated to be 10% to 40% for fine sand, 40% to 80% for medium sands, and 80% to 100% for larger particles. This wide range of efficiency is confirmed by field research. A study of a CDS unit installed in Brevard County estimated the average TSS removal efficiency at 52%. However, it was noted in DEP Agreement No. G0182, Attachment A, Page 5 of 10