Designing de minimis
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Designing De Minimis. Indiana Antidegradation Workshop April 29, 2008 Brad Klein -- Environmental Law & Policy Center. Scope of de minimis doctrine.

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Designing de minimis

Designing De Minimis

Indiana Antidegradation Workshop

April 29, 2008

Brad Klein -- Environmental Law & Policy Center

Scope of de minimis doctrine
Scope of de minimis doctrine

  • Not mentioned in federal antidegradation regulation but under common law courts allow that a limited exception for insignificant cases be implied into a regulation.

  • EPA will review state rules on a “case-by-case basis” to ensure that exemption does not allow significant degradation either individually or cumulatively.

Ic 13 18 3 a k a sea 431
IC 13-18-3 (a/k/a SEA 431)

  • Requires a de minimis threshold for Outstanding State Resource Waters

  • Does not limit IDEM to any specific approach for defining what qualifies as de minimis

Limits on de minimis exceptions
Limits on De minimis Exceptions

  • An allowable de minimis test will only exempt “trifling matters” from detailed study, but avoid unnecessary pollution and trigger full antidegradation review for all significant new or expanded discharges.

U s epa s interpretation
U.S. EPA’s interpretation

  • Can’t allow “significant degradation”

  • States should consider the extent of the loading capacity (USEPA calls this “assimilative capacity”) used by the increase as part of the test

  • Incorporate a “cumulative cap”

  • Also consider overall pollutant loading

    E. King memo (2005)

De minimis draft rule sec 6
De Minimis– Draft Rule Sec. 6

IDEM draft uses three concepts:

  • DTBELs

  • “end of pipe” WQBELs

  • 10% “unused loading capacity”

Concerns with dtbels
Concerns with DTBELs

  • Focus exclusively on treatment technology, rather than pollution avoidance or minimization.

  • May be difficult and/or controversial to identify and keep current.

  • Will be inappropriate in many situations (e.g. little assimilative capacity, discharge to sensitive or important waters)

Dtbel solutions
DTBEL solutions

  • Must consider pollution avoidance or minimization alternatives before applying DTBEL.

  • Ensure limits reflect best treatment technology possible.

  • Consider restricting DTBELs in sensitive waters and where little dilution available.

Loading or assimilative capacity
Loading or “Assimilative” capacity

“The difference between the applicable water quality criterion for a pollutant parameter and the ambient water quality for that pollutant parameter where it is better than the criterion…”

E. King memo (2005)

Loading capacity example
Loading capacity example

Water quality criterion = 100 mg/L

100 mg/L

Loading or “assimilative” capacity

“The available assimilative capacity of a waterbody is a valuable natural resource.” (U.S. EPA, 2005)

Ambient concentration = 20 mg/L

20 mg/L



0 mg/L

Loading capacity example 5 de minimis first bite
Loading capacity example: 5% de minimis – first “bite”

Water quality criterion = 100 mg/L

100 mg/L

5 percent of loading capacity: (100 mg/L – 20 mg/L) x (5%) = 4 mg/L

24 mg/L

de minimis if new conc. < 24 mg/L

baseline concentration = 20 mg/L

20 mg/L



0 mg/L

5 de minimis second bite
5% de minimis – second “bite”

Water quality criterion = 100 mg/L

100 mg/L

5 percent of remaining loading capacity: (100 mg/L – 24 mg/L) x (5%) = 3.8 mg/L

27.8 mg/L

de minimis if new conc. < 27.8 mg/L

24 mg/L

ambient concentration = 24 mg/L



baseline concentration = 20 mg/L

0 mg/L

Flaws in loading capacity approach
Flaws in Loading Capacity Approach:

  • Allows incremental “creeping” degradation

  • Allows huge unnecessary new pollution in large volume waters

  • Cannot apply % of loading capacity for pollutants lacking numeric criteria

  • Cannot apply to General Permits

Problem 1
Problem 1:

How do we prevent incremental degradation over time from consuming majority of loading capacity without a single antidegradation review?

Potential solutions
Potential Solutions

  • Use a cumulative cap

    • Strongly recommended by U.S. EPA

    • Required by law

    • Cap > 20% would likely be disapproved under Ohio Valley Environmental Coalition.

Loading capacity 20 cumulative cap
Loading capacity: 20% cumulative cap

Water quality criterion = 100 mg/L

100 mg/L

20 percent of baseline loading capacity: (100 mg/L – 20 mg/L) x (20%) = 16 mg/L


Total de minimis “bites” capped at 36 mg/L

36 mg/L

27.8 mg/L

Baseline concentration = 20 mg/L

20 mg/L



0 mg/L

Problem 2
Problem 2:

How do we identify significant new or expanded loadings in large waters like Lake Michigan or the Ohio River?


  • Indiana must place overall limit on volume of de minimis new/expanded loading.

  • For example, expansions of more than .5 MGD cannot be considered de minimis.

Problem 3
Problem 3:

What should be done with pollutants that lack numeric criteria?

Possible solutions
Possible Solutions

  • First consider options for minimizing or redirecting the discharge.

  • Apply narrative criteria “translator” if practicable

  • For common pollutants (e.g. nitrogen and phosphorus) use DTBELs.

  • Restrict or eliminate de minimis for certain pollutants (e.g. bioaccumulative pollutants, potential carcinogenic or hormone disrupting pollutants).

Problem 4
Problem 4:

  • How do we ensure that the use of general permits does not undermine the antidegradation policy?

    “the EPA has not explained how the type of review called for in § 131.12(a)(2), which is location-specific and requires public participation, can be done on a statewide or nationwide basis …”

    Ohio Valley Environmental Coalition, 279 F. Supp 2d at 762.


  • Design general permits so that they allow only de minimis degradation in all cases.

  • Do not allow use of general permits in sensitive waters.

  • Ensure that there is a loading cap on general permit sources.

  • Build in public notice of general permit usage.

  • Preserve authority of IDEM to require individual permits where general permit would allow more than trivial degradation.

Revised draft should
Revised draft should

  • Refine DTBEL concept to ensure use of best technology.

  • Consider opportunities to minimize or redirect discharges for all permits for new or increased loadings.

  • Incorporate reasonable cumulative cap (i.e. no more than 20%) on consumption of loading capacity.

  • Make clear that substantial new or increased discharges to large waters like Lake Michigan and the Ohio River are not considered de minimis.

  • Make clear that pollutants are covered that lack numeric criteria.

  • Ensure that general permits allow only de minimis pollution.