TMDL

Question 1

What is a TMDL?

Answer 1

The calculation of the maximum amount of a pollutant allowed to enter a waterbody so that the waterbody will meet and continue to meet water quality standards for that particular pollutant. Determines a pollutant reduction target and allocates load reductions necessary to the source(s) of the pollutant.

Question 2

Pollutant sources

Answer 2

Point source or nonpoint source

Question 3

WLA

Answer 3

For point sources, include all sources subject to regulation under the npdes program.

Question 4

LA

Answer 4

Assigned to nonpoint sources, include all remaining sources of the pollutant as well as natural background sources. Nonpoint source pollution NOT covered by an apdes permit (ie. Construction or msgp)

Question 5

TMDL calculation

Answer 5

TMDL = sumWLA + sumLA + MOS

Where WLA is the sum of wasteload allocation (point sources), LA is the sum of load allocations (nonpoint source and background) and MOS is the margin of safety.

Question 6

Waterbody/pollutant combination

Answer 6

Each pollutant causing a waterbody to be impaired or threatened. A TMDL is developed for each combination.

Question 7

TMDL objective

Answer 7

To determine the loading capacity of the waterbody and to allocate that load among different pollutant sources so that the appropriate control actions can be taken and water quality standards achieved.

Question 8

TMDL Approach

Answer 8

1. Selection of the pollutant(s) to consider.
2. Estimation of the waterbody’s assimilative capacity (i.e., loading capacity).
3. Estimation of the pollutant loading from all sources to the waterbody.
4. Analysis of current pollutant load and determination of needed reductions to meet assimilative capacity.
5. Allocation (with a margin of safety) of the allowable pollutant load among the different pollutant sources in a manner such that water quality standards are achieved.

Question 9

TMDLs should identify

Answer 9

The links betwrrn the waterbody use and the impairment, the causes of impairment, and the pollutant load reductions needed to meet the applicable water quality standards.

Question 10

Public/stakeholder roles in the TMDL process

Answer 10

1. Providing data and information to the states
2. Reviewing and commenting on impaired water list
3. Reviewing and commenting on draft TMDLs
4. Assisting in development of TMDLs

Question 11

How are TMDLs implemented

Answer 11

Best management practices that will reduce water pollution. Can include a combination of bmps and or effluent limits and monitoring through apdes permits. Grants to local governments to reduce water pollution.