0208 Study Update_WQC_May 2024_PPT

Update on Study of Narrative
Standards per SL 2023-137(8)
DRAFT for EMC Consideration
May 8, 2024
1
Questions and Responses
•If I remember correctly, Greensboro with your help was able to
reduce the level of 1-4 dioxane to 10. The number from EPA is
3.2?
•Response: Greensboro has reduced the level of 1,4-dioxane to below
10. EPA has not developed a value for Greensboro.
•Is there technology for a city that size to reduce to that level?
•Response: As has been shown, the best “technology” is to seek source
reductions. There are treatment technologies that can be used, such
as reverse osmosis, ion exchange resins and advanced oxidation.
However, these technologies are better implemented at the source.
2
Questions and Responses
•I believe you stated 28 systems monitored. When will all the
systems in the state be required to monitor?
•Response: In 2019, we asked 28 municipalities and 19 industries in the
Cape Fear to monitor for 1,4-dioxane and PFAS. UCMR3 data did not
show significant 1,4-dioxane levels in other basins. Monitoring will only
be required of those facilities showing reasonable potential to exceed
the standard or levels > 50% of their allowable discharge
concentration.
•How long of time will these systems be allowed to reduce the
level to acceptable?
•Response: Compliance schedules will be worked out with each
industrial and municipal permittee on an individual basis.
3
Questions and Responses
•Could monitoring and/or requirement treatment only be
triggered when there is a drinking water supply downstream of
the wastewater discharge?
•Response: DWR is recommending source reduction as opposed to treatment at the POTWs as this has been shown to be more effective. Limits, monitoring, source reduction or treatment will only be required of those facilities showing reasonable potential to exceed the standard.
Of the 6 POTWs likely to have permit limits, all discharge into or above
a drinking water supply.
•Provide EPA recommended study re 1,4-dioxane
•Response: Final Risk Evaluation for 1,4-Dioxane CASRN: 123-91-1 December 2020 (EPA-740-R1-8007)
4
Questions and Responses
•Can the narrative allow 10-5 rather than 10-6? If so, what would
be EPA’s response?
•Response: Changing the risk level would be a change to the water
quality standard, which requires EPA review and approval. The state
will have to demonstrate that increasing the cancer risk level by a factor
of 10 protects the designated uses and provide a scientific justification
for the change. The state will also need to identify the most highly
exposed subpopulation and demonstrate that the 10-5 risk level is
adequately protective for this subpopulation.
5
Comments and Report Edits
•Better explain difference between narrative and numeric
criteria
•Response: new section added on page 3
6
Comments and Report Edits
•Clarify process for narrative vs. numeric
•Response: statement added on page 7
7
Comments and Report Edits
•Explain UAA in more detail outside of footnote
•Response: paragraph added on page 9
8
Comments and Report Edits
•Clarify “higher” fish consumption value for Alabama
•Response: language edited on page 10
9
Comments and Report Edits
•Add current federal regulatory requirements
•Response: language added on page 18-19
10
11
Questions
Department of Environmental Quality