1. Prepared by: Stefanie Coxe – Congressman Keating’s Office
The anatomy of TMDLs in Wastewater
Potential Solutions to water quality issues in bodies of water based on reductions required from each sector and source.
TMDLs = Total Maximum Daily Loads (of nitrogen for a particular water body) formulated by DEP and
submitted to EPA for approval after public comment
A water body is listed as impaired on a 303(d) list (EPA), triggering a requirement for a TMDL and
restoration plan. MEP and others quantify the causes of the problem, generally are due to nitrogen
loads. Water quality sampling and models are used to determine how much is too much so a plan of
action can be formulated.
Computer Model
EPA
Regulatory
requirement
for TMDLs to
achieve
designated uses
=
Wasteload Allocation
(WLA) of Point
Sources (including
municipal stormwater
discharge)
+
Load Allocation
(LA) of Nonpoint
Sources (including
septic systems and
wastewater
treatment facilities)
+
Margin of
Safety
Inputs
Data from
Embayments/ponds
Management Control
Scenarios (dredging, breach,
source reduction/control,
enhanced attenuation)
EPA approves TMDLs for water body
Other factors: Local by-
laws, proximity to shore,
etc.
Technical Reports to DEP
Towns undertake Comprehensive Wastewater Management Planning (CWMP) process
to evaluate solutions.