What is a TMDL?
A TMDL or Total Maximum Daily Load is the calculation of the maximum amount of a pollutant that a waterbody can receive and still meet Vermont Water Quality Standards. In a broader sense, a TMDL is a plan that identifies the pollutant reductions a waterbody needs to meet Vermont's Water Quality Standards and develops a means to implement those reductions. TMDLs can be calculated for correcting water pollution from specific point source discharges or throughout a watershed and balance the location and amount of needed pollution reductions.
When are TMDLs developed?
Under Section 303(d) of the Federal Clean Water Act, all states are required to develop lists of impaired waters. The list includes impaired lakes, ponds, rivers and streams that do not meet state-specific water quality standards. For Vermont, impairment is substantiated by chemical, physical or biological data collected through monitoring and these waters are noted on the State's current Priority List of Waters. The Federal Clean Water Act requires TMDLs to be developed for waters on the list, which provides a schedule indicative of TMDL completion priority.
What is the TMDL process?
TMDLs are unique to each waterbody. The general process by which they are developed can be summarized as follows:
- Problem Identification: the pollutant for which the TMDL is developed must be identified. Examples might include sediment that impacts habitat for aquatic organisms, nutrients that cause excessive algal growth, or bacteria that creates an unsafe environment for swimming.
- Identification of Target Values: this element establishes water quality goals for the TMDL. Target values may be stated explicitly in the Water Quality Standards or they may need to be interpreted.
- Source Assessment: all significant sources of the pollutant in question must be identified in the watershed. This often requires additional water quality monitoring.
- Linkage Between Targets and Sources: this element of the process establishes how much pollutant loading can occur while still meeting the Water Quality Standards. This step can vary in complexity from simple calculations to development of complex watershed models.
- Allocations: once the maximum pollutant loading is established, the needed reductions must be divided among the various sources. This is done for both point sources and nonpoint sources.
- Public Participation: stakeholder involvement is critical for the successful outcome of any TMDL. Draft TMDLs are released for public comment prior to their completion.
- EPA Approval: EPA approval is needed for all TMDLs as required by the Federal Clean Water Act. The New England regional office of EPA (Region 1), located in Boston, Massachusetts is responsible for TMDL approval.
- Follow-up Monitoring: additional monitoring may be needed to ensure the TMDL, once implemented, is effective in restoring the waters.
Approved TMDLs in Vermont since 2001:
Rivers and Streams
- Winooski River - Cabot - pathogens
- Black River - Ludlow - phosphorus
- Tributary #1, Ball Mountain Brook - Stratton - sediment
- Styles Brook - Stratton - sediment
- Potash Brook - South Burlington - stormwater
- Bartlett Brook - South Burlington- stormwater
- Centennial Brook - South Burlington & Burlington - stormwater
- Englsby Brook - Burlington - stormwater
- Morehouse Brook - Winooski & Colchester - stormwater
- Allen Brook - Williston - stormwater
- Indian Brook - Essex & Colchester - stormwater
- Munroe Brook - Shelburne - stormwater
- Sunderland Brook - Colchester - stormwater
- Moon Brook - Rutland - stormwater
- Rugg Brook - St. Albans - stormwater
- Stevens Brook - St. Albans - stormwater
- Moon Brook - Rutland - temperature
- Mussey Brook - Rutland - temperature
- Lake Carmi TMDL - Franklin - phosphorus
- Ticklenaked Pond TMDL - Ryegate - phosphorus
- Lake Champlain (12 segments) - phosphorus
- Lake Memphremagog - phosphorus
- Vermont, 5 other New England states & New York state - mercury (note: concerns 31 Vermont waters)
- 39 lakes and ponds - various locations - low pH
- Statewide TMDL for Bacteria-Impaired Waters
- Long Island Sound
Vermont Statewide Total Maximum Daily Load (TMDL) for Bacteria-Impaired Waters.
- Vermont Statewide TMDL for Bacteria-Impaired Waters Final Document (pdf 2.3 MB)
- EPA Approval Document (pdf 3.4 MB)
- Response to Comments (pdf 595KB)
Bacteria TMDL Appendices for Specific Waterbodies
Appendix 2 - Otter Creek
Appendix 3 - Little Otter Creek RM7
Appendix 4 - Little Otter Creek_RM16
Appendix 5 - Lewis Creek & Pond Brook
Appendix 6 - Middlebury River
Appndix 7 - Direct Drainages to Malletts Bay
Appendix 8 - Englesby Brook
Appendix 9 - LaPlatte River
Appendix 10 - Potash Brook
Appendix 11 - Berry, Godin, Sampsonville Brooks
Appendix 12 - Allen Brook
Appendix 13 - Huntington River
Appendix 14 - Mad River
Appendix 15 - West River
Appendix 16 - No Branch-Deerfield
Appendix 17 - Whetstone Brook
Appendix 18 - Ompompanoosuc River
Appendix 19 - CSO & WWTF Related