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| 4 | This heavy mineral mining wastewater treatment system provides acidification with ferric chloride, sulfuric acid, aluminum sulfate, or ferric sulfate to a pH between 3.0 and 3.5 standard units for flocculation of colloidal material followed by settling in a series of diked ponds, neutralization with hydrated lime to a pH between 6.0 to 8.5, and additional settling with final discharge to Alligator Creek. Upon Department approval, polymer addition may be provided after neutralization for aluminum reduction prior to final discharge to Alligator Creek, at D-001, which flows west in Bradford County. Storm water and rainfall from the mined areas are also collected and treated as described above. The treatment train consists of the addition of barium chloride to the wastewater at the location where ferric chloride, aluminum sulfate and or ferric sulfate is added (prior to the humate settling ponds). A portion of the effluent is directed to the Southwest Quadrant Pond. The existing recycle line from D-001 was tapped and a pipeline was constructed to route approximately 400 gallons per minute (gpm) of the treated wastewater to an existing ditch which then discharges into the Southwest Quadrant Pond (location D-002) with eventual discharge into Blue Pond, which is the portion of Alligator Creek that flows south in Clay County. This rerouting of final effluent is the result of an effort by The Keystone Stakeholders to help improve lake water levels in the Keystone Heights area. |
| 44 | A review of the discharge flow through D-001 indicates that the 99th percentile is 42.55 MGD. Four times in the last permit cycle the flow exceeded 20 MGD, one time exceeding 30 MGD (where the permit limit is 40 MGD) with the one-time maximum value of 55.3 MGD during Tropical storm Debbie [sic]. Because of the impacts of Tropical Storm Debby, Governor Rick Scott on June 25, 2012 signed Executive Order 12-140, declaring a statewide state of emergency. DEP issued an emergency authorization for Repairs, Replacement, Restoration and Certain Other Measures made Necessary by Tropical Storm Debbie [sic], OGC No. 12-1264 dated July 2, 2012. Within the Emergency Area (Bradford, Clay and other counties) the requirements and effects of statutes and rules which conflict with the provisions of the Order were suspended to the extent necessary to implement this Order. For the May 2013 rainfall event, the peak day discharge for D-001 was 29.8 MGD with May 2-May 6 rainfall totaling 7.71 inches. At this flow level, the Trailridge discharge accounted for 1.13% of total flow to Alligator Creek Basin. The May 2013 event was the only documented abnormal event in this permit cycle. Looking at the monthly average flow for D-001, the 50th percentile is 3.0 MGD and the 95th percentile is 10.45 MGD. |
| 46 | Alligator Creek has a contributing drainage area of 19.4 square miles. Low-flow frequency of the creek is following: 7Q2 = 3.2 ft3/s, 7Q10 = 0.3 ft3/s, 30Q2 = 8.0 ft3/s; 30Q10 = 1.1 ft3/s. There is a SRWMD and USGS stage station at Alligator Creek below US 301 in Starke, Station ID: 02320734 (reference document: USGS Drainage Areas of Selected Surface water sites in Florida, Report 81-482, 1981). |