| EPA Action: |
EPA Approved |
Comments: |
THIS IS A TRANS-BOUNDARY TMDL BETWEEN IOWA AND SOUTH DAKOTA. FOR THE PURPOSES OF THE TMDL DOCUMENT, FIVE SEGMENTS WERE DELINEATED (WHICH ARE UNIQUE TO THE TMDL DOCUMENT ITSELF) THAT ENCOMPASS THE PRE-EXISTING IOWA AND SOUTH DAKOTA SEGMENTS (I.E., EACH STATE'S 303(D) LISTED SEGMENTS). THIS SD SEGMENT INCLUDES BSR TMDL SEGMENT 1 IN THE TMDL DOCUMENT. THE IMPAIRING POLLUTANT IN IOWA IS E. COLI, WHILE IT IS FECAL COLIFORM IN SOUTH DAKOTA. IOWA USES A RATIO METHOD BASED ON THEIR OLDER FECAL COLIFORM WQS (400 CFU/100ML) TO CONVERT THEIR FECAL COLIFORM DATA INTO E. COLI VALUES, THUS THE NUMERIC VALUE OF IOWA'S PATHOGEN STANDARD IS ROUGHLY EQUIVALENT TO THE NUMERIC VALUE OF SOUTH DAKOTA'S PATHOGEN STANDARD FOR THE BIG SIOUX RIVER (I.E., 400 CFU/100 ML - NEVER TO BE EXCEEDED). IT SHOULD ALSO BE NOTED THAT IOWA'S RECREATIONAL SEASON IS LONGER THAN SOUTH DAKOTA'S (MAR 15-NOV 15 VS. MAY 1-SEPT 30), THUS IOWA'S SEASON WAS USED TO CALCULATE THE TMDL BECAUSE THEIR STANDARD IS MORE STRINGENT.
THERE ARE 39 PERMIT HOLDERS ALONG THE ENTIRE LEGNTH OF SEGMENTS 1-5 (36 ARE IA PERMITEES, AND 3 SD PERMITEES), THUS THERE ARE NUMEROUS WASTELOAD ALLOCATIONS (WLAS) FOR EACH OF THE FIVE TMDLS INCLUDED IN THE TMDL DOCUMENT. LOAD ALLOCATIONS (LAS) WERE BASED ON LOAD DURATION CURVES, WHICH EXPRESS UNIQUE LAS FOR UP TO FOUR DIFFERENT FLOW REGIMES FOR EACH SEGMENT. LAS EXPRESSED IN NTTS REFLECT THE LOWEST LA IN THE TMDL. BECAUSE OF THE NUMEROUS AND CUMBERSOME NATURE OF THE WLAS AND LAS, PLEASE REFER TO THE TMDL DOCUMENT FOR SPECIFIC WLAS AND LAS, AS THEY CANNOT BE CLEARLY EXPRESSED IN THE NTTS DATABASE FORMAT.
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