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Page 22 of 38 <br /> Permit No: MNR040000 <br /> F. Alum or Ferric Chloride Phosphorus Treatment Systems <br /> If the permittee uses an alum or ferric chloride phosphorus treatment system,the permittee <br /> shall comply with the following: <br /> 1. Minimum Requirements of an Alum or Ferric Chloride Phosphorus Treatment System <br /> a. Limitations <br /> (1) The permittee shall use the treatment system for the treatment of phosphorus in <br /> stormwater. Non-stormwater discharges shall not be treated by this system. <br /> (2) The treatment system must be contained within the conveyances and structural <br /> stormwater BIVIPs of a small IVIS4.The utilized conveyances and structural <br /> stormwater BIVIPs shall not include any receiving waters. <br /> (3) Phosphorus treatment systems utilizing chemicals other than alum or ferric chloride <br /> must receive written approval from the Agency. <br /> (4) In-lake phosphorus treatment activities are not authorized under this permit. <br /> b. Treatment System Design <br /> (1) The treatment system shall be constructed in a manner that diverts the stormwater <br /> flow to be treated from the main conveyance system. <br /> (2) A High Flow Bypass shall be part of the inlet design. <br /> (3) A flocculent storage/settling area shall be incorporated into the design, and <br /> adequate maintenance access must be provided (minimum of 8 feet wide)for the <br /> removal of accumulated sediment. <br /> 2. Monitoring During Operation <br /> a. A designated person shall perform visual monitoring of the treatment system for proper <br /> performance at least once every seven (7) days, and within 24 hours after a rainfall <br /> event greater than 2.5 inches in 24 hours. Following visual monitoring which occurs <br /> within 24 hours after a rainfall event, the next visual monitoring must be conducted <br /> within seven (7) days after that rainfall event. <br /> b. Three benchmark monitoring stations shall be established.Table B-1 shall be used for <br /> the parameters, units of measure, and frequency of measurement for each station. <br /> c. Samples shall be collected as grab samples or flow-weighted 24-hour composite samples. <br /> d. Each sample, excluding pH samples, must be analyzed by a laboratory certified by the <br /> MDH and/or the MPCA, and: <br /> (1) Sample preservation and test procedures for the analysis of pollutants shall conform <br /> to 40 CFR Part 136 and Minn. R. 7041.3200. <br /> (2) Detection limits for dissolved phosphorus, dissolved aluminum, and dissolved iron <br /> shall be a minimum of 6 micrograms per liter (µg/L), 10 µg/L, and 20 µg/L, <br /> respectively. <br /> (3) pH must be measured within 15 minutes of sample collection using calibrated and <br /> maintained equipment. <br />