What is Total Maximum Daily Load (TMDL)

WHEN WORKING UNDER A MUNICIPAL SEPARATE STORM SEWER SYSTEM (MS4) PERMIT, MEETING COMPLIANCE REQUIREMENTS ARE IMPORTANT. COMPLIANCE GOALS ARE ACHIEVED WHEN JURISDICTIONAL WATER QUALITY MEETS WATER QUALITY STANDARDS. IN OTHER WORDS, THERE IS A POLLUTION BUDGET FOR EACH WATERBODY. IF A WATERBODY EXCEEDS THE BUDGET, THEN A STRATEGY TO GET BACK UNDER THE BUDGET IS PARAMOUNT.

UNFORTUNEATELY, MANY WATERBODIES EXCEED THE BUDGET ON CERTAIN POLLUTANTS, LIKE BACTERIA, FOR EXAMPLE.

EACH STATE REGULATOR HAS TO IDENTIFY AND SUBMIT A LIST TO THE ENVIRONMENTAL PROTECTION AGENCY (EPA) WATERBODIES THAT CONSISTENTLY EXCEED THE LIMIT (BUDGET) OF A POLLUTANT(S ).  ONCE THE LIST IS SUBMITTED, THE POLLUTED WATERBODIES ARE PLACED ON SOMETHING CALLED THE 303d IMPAIRED LIST UNDER THE CLEAN WATER ACT LEGISLATION.

ONCE A WATERBODY IS PLACED ON THE LIST, A TOTAL MAXIMUM DAILY LOAD (TMDL) PLAN BETWEEN THE EPA, AND THE STATE REGULATOR BEGINS. THIS DEVELOPMENT STAGE CAN TAKE A LONG TIME TO IDENTIFY AND VERIFY THE SOURCES OF IMPAIRMENT. IT IS DEFINITELY NOT A QUICK PROCESS!

EVENTUALLY THE MS4 WILL BE THE LAST LINK ON THE CHAIN TO VERIFY THE SOURCES OR IDENTIFY ADDITIONAL SOURCES CAUSING THE IMPAIRMENT. IF THE EPA AND STATE REGULATOR ACCEPT THE PLAN AFTER MS4 VERIFICATION THEN IT BECOMES ACTIVE.

THE PURPOSE OF A TMDL IS TO IDENTIFY THE SOURCES, PROVIDE A GAME PLAN ON HOW TO REMOVE THEM, AND A DEVELOP A SCHEDULE OF COMPLIANCE.  A SCHEDULE OF COMPLIANCE IDENTIFIES INTERIM AND FINAL GOALS WITH SPECIFIC DATES WHICH HAVE TO BE MET. IF AN MS4 MEETS THE GOALS, THEN THEY HAVE MET ANTIDEGREDATION. IF NOT, THERE ARE OTHER OPTIONS AVAILABLE TO STAY COMPLIANT.

SO, THE ULTIMATE GOAL FOR EACH MS4 IS TO ACHIEVE ANTIDEGREDATION BY MEETING STATE WATER QUALITY STANDARDS FOR EACH WATERBODY IN THEIR JURISDICTION. SOMETIMES THE WATERBODY IS INTERJURISDICTIONAL, MEANING THAT NEIGHBORING MS4’S MAY ALSO HAVE TO REDUCE THEIR CONTRIBUTION OF THE POLLUTANT SOURCE DISCHARGING INTO THE 303d IMPAIRED WATERBODY.

PHASE II MUNICIPAL SEPARATE STORM SEWER SYSTEMS, (MS4’S) HAVE AN EXCELLENT OPPORTUNITY TO INCORPORATE A PLAN TO REMOVE THE POLLUTANTS THROUGH THE SIX MINIMUM CONTROL MEASURES. FOR EXAMPLE, IF BACTERIA IS A POLLUTANT OF CONCERN THAT IS PLACING A WATERBODY(S) ON THE 303d LIST, THEN PUTTING TOGETHER A PUBLIC EDUCATION PROGRAM THAT TARGETS DOG OWNERS, RESIDENTS WITH SEPTIC TANKS, OR EVEN AGRICULTURAL AREAS.

IT BEGINS WITH FOUR MAIN COMPONENTS:

1. TYPE OF POLLUTANT
2. SOURCE OF POLLUTANT-WHO OR WHAT IS GENERATING IT
3. DEVELOPMENT OF MINIMUM CONTROL MEASURE TO MEET REDUCTION
4. EVALUATE

WHEN EVALUATING THE CONTROL MEASURE TO REDUCE THE SOURCE, REMEMBER, IN ORDER FOR IT TO WORK, WE NEED A WAY TO MEASURE IT.

BECAUSE, IF YOU CAN MEASURE IT, YOU CAN MANAGE IT!

YOU MAY WANT TO ASK YOURSELF “IS THERE A REDUCTION OF “BACTERIA” NOTICABLE IN THE RESULTS OF OUR OUTFALL SAMPLING? IF THE PLAN IS WORKING, KEEP IT. IF IT’S NOT, THEN TRY ANOTHER AVENUE.

SOMETIMES IT’S ALL ABOUT TRIAL AND ERROR.

REMEMBER THAT THE ULTIMATE GOAL IS TO MEET ANTIDEGREDATION. IF YOU HAVE AN IMPAIRED WATERBODY FROM AN EXCEEDANCE OF A POLLUTANT, FOLLOW THE FOUR MAIN COMPONENTS FOR EACH MINIMUM CONTROL MEASURE. THIS WAY YOU ARE TARGETING THE PROBLEM FROM THE FRONT END AND NOT THE BACK END! NO-ONE WANTS TO BE REACTIVE!

LAURIE MURPHY