Selenium: The
Curse of the West
Steve Canton
WESTCAS June 21, 2017
SELENIUM CRITERIA HISTORY:
OVERVIEW FROM A WESTCAS
PERSPECTIVE
Selenium in the Arid West
• The West has large areas of underlying marine shales
that results in elevated selenium in surface water
– Studies on fish populations have indicated that fish seem
to have adapted to elevated selenium, and have healthy
reproducing populations
• Water is also limited – with approximately 90 percent
ephemeral or intermittent streams
– Populations limited by habitat, not water quality
First concerns with “what is appropriate
criteria?” raised by those in the Arid West
• 1987 EPA chronic criteria – 5 µg/L (acute= 20 µg/L)
– Colorado initially refused to adopt
• 1995 – Many dischargers in Colorado predict having difficulty
meeting selenium criteria
– Began studies on the issue prior to state adoption of EPA criteria by Colorado
– Result was footnote to standards “selenium is a bioaccumulative metal and subject to a
range of toxicity values depending upon numerous site specific variables”
• 1997 – Kennecott Selenium Symposium in Utah
– to discuss Se issues in the west
• 1998 – EPA held a Peer Consultation Workshop
– to assess the state of the science on selenium toxicity
– concluded tissues likely best predictor, not water or sediment
• 1999 – USFWS recommended 2 µg/L
– Adopted by Arizona
EPA Se criteria repeatedly
revised over time
• 2002 and 2004
– Draft tissue-based criterion of 7.9 mg/kg
– Never finalized
• 2014
– Draft tissue-based criterion – for public comment
• 2015
– Second draft of tissue-based criterion – for public
comment (producing yet another draft is a first for EPA)
• 2016
– Final tissue-based selenium criterion
• 2016
– Draft implementation guidance – still pending
EPA 2016 SELENIUM
CRITERIA
2016 EPA Final Criteria
• Tissue-based Criteria Element
– 15.1 mg/kg egg/ovary
– 8.5 mg/kg whole body
– 11.3 mg/kg muscle tissue
• Default Water Column Criteria
– Monthly average - chronic
• 1.5 µg/L lakes
• 3.1 µg/L rivers
• Acute – not included
– “Intermittent Criteria” –simply an equation based on
number of days/month exceeding default value
Derivation of EPA Default
Water Column Criteria
• Modeled – using sediment, algae, invert, and fish
– Used site-specific data for 26 lake / 39 stream sites
• The data set is very limited
– With most data well over 20 years old
• GEI tested the calculation with additional sitespecific stream data from Colorado
– Resulted in lotic value of 5.8 µg/L
• Arid Western states should review EPA’s water
column numbers and develop more state-specific
water column values
EPA DRAFT IMPLEMENTATION
GUIDANCE
Draft Implementation Guidance
• Four documents
1. Technical Support for Adopting and Implementing EPA’s
2016 Selenium Criterion in Water Quality Standards
2. Technical Support for Fish Tissue Monitoring for
Implementation of EPA’s 2016 Selenium Criterion
3. FAQ’s: Implementing WQS that Include Elements Similar
or Identical to EPA’s 2016 Selenium Criterion in Clean
Water Act Section 402 NPDES Programs
4. FAQ’s: Implementing the 2016 Selenium Criterion in
Clean Water Act Section 303(d) and 305(b) Assessment,
Listing, and TMDL Programs
• What do these documents say?
– More importantly, how could they be improved for the
Arid West?!
1) Tech Support for Adopting and
Implementing in WQS
• EPA provides only two scenarios for when SSS are
appropriate
– Water column exceeded – fish tissue attained
– Water column attained – fish tissue exceeded
– No option for situations in which both are exceeded, as is common in the
Arid West due to native geology
• EPA modeling (using mechanistic or bioaccumulation
approaches) only derive SS water column criteria
– SS tissue criteria are also necessary
– Example: St. Charles River near Pueblo
• Existing SSS of 173 µg/L (ac) and 50 µg/L (ch) based on ambient conditions
• Tissue concentrations also elevated – up to 105.9 mg/kg (WB), yet fish
communities healthy and unaffected
• Our data suggest modeling does not work in areas
with naturally elevated selenium in the Arid West
1) Tech Support for Adopting and
Implementing in WQS
• EPA allows use of recalculation procedure for sitespecific tissue criteria
– Difficult to apply since Se database is limited
• Deletion of “non-resident” fish would likely eliminate over
half the database for most arid west streams!
– Likely result would be defaulting to the lowest chronic
value for species present?
• Most sensitive species in database is White
Sturgeon
– No sturgeon in Arid West streams
– Simple option would be for default tissue criterion
after excluding sturgeon?
3) FAQs: Implementation in 402
NPDES Programs
• Reasonable potential analysis
– Ultimately based on water column, even if fish
tissues are meeting the criterion
– We believe this is inappropriate – water column
criterion is based on modeling, not actual toxicity
data
– If tissue overrides water in the criteria document,
it should override for RP
– Tissue data should be used to determine RP in
systems in steady-state, but permitting programs
not ready for something “this radical”!
3) FAQs: Implementation in 402
NPDES Programs
• Acute limits in permits needed?
– Some permit writers think so…
• If necessary - an option would be to use the acute
criteria from EPA’s 2004 draft Se criteria document
– Separate criteria for selenite and selenite, with sulfate
modifier
• In western states elevated selenium coincides with elevated
sulfate, explains the healthy populations in high Se regions
– Biokinetic modeling suggests this approach would still be
protective of the chronic tissue criterion
• Still, you don’t have to have an acute limit
– Many permits only require chronic WET, for example
4) FAQs: Implementation in 303(d),
305(b) and TMDL programs
• Fishless streams – common in Arid West states
due to limited water and ephemeral or
intermittent systems
– Defaults to water column value
– We do not agree – criterion is intended to protect fish.
• If fish are not present, the default water value is
overprotective
– Better approach - collect tissues in the nearest
downstream location with fish
– Alternatively, base attainment on invertebrate tissues
(i.e., protect the attainable use) using values in criteria
document
So, what does it all mean for
WESTCAS members ?!
• The new EPA selenium criteria have the
potential to be beneficial for Arid West
states
• But, unless significant changes are made
to the implementation guidance,
selenium will continue to be the
“Curse of the West”!!
Questions?