NCG020000_Email with EPA Comments on Draft_20201201

Georgoulias, Bethany
From: Lucas, Annette
Sent: Thursday, December 3, 2020 7:13 AM
To: Georgoulias, Bethany
Subject: FW: [External] EPA Comments on NCG020000
Attachments: Final EPA Comments - NC mineral mining GP (NCG020000).docx
From: Hesterlee, Craig <[e-mail]>
Sent: Tuesday, December 1, 2020 4:04 PM
To: Lucas, Annette <[e-mail]>
Cc: Tyler, Kip <[e-mail]>; Wahlstrom-Ramler, Meghan <[e-mail]>
Subject: [External] EPA Comments on NCG020000
External email. Do not click links or open attachments unless you verify. Send all suspicious email as an attachment to
[e-mail]
Annette- please see EPA's comments regarding the NC Mineral Mining General permit and thank you for working closely
with our staff on the permit provisions. We always enjoy collaborating with North Carolina and I hope that these
comments are useful moving forward.
Craig Hesterlee, Chief
NPDES Permitting Section
EPA Region 4 Water Division
404.562.9749

EPA Region 4 Comments on North Carolina's General NPDES Permit for Mineral Mining Discharges of
Wastewater and Stormwater (NCG020000)
1. Continuous discharges are required to have both maximum daily limits (MDL) and average monthly limits
(AML) in accordance with 40 CFR § 122.45(d)(1).1
Certain mining discharges (brick pits, feldspar, lithium ore, phosphate, and industrial sand) within Tables 9 and
10 of the draft permit only contain an MDL.
Unless impracticable,2 EPA recommends that the permit contain AML and MDL for all mining wastewater
discharges that are continuous, pursuant to the NPDES implementing regulations (similar to the parameters
listed in Table 8). In circumstances where the mining -related discharge is less than continuous, but the discharge
occurs frequently enough such that the discharge may cause or contribute to chronic water quality impacts (i.e.,
a continuously intermittent duration), EPA recommends these discharges also have an AML and MDL.
2. The samples and measurements for certain treatment basins should be representative of the monitored
activity pursuant to 40 CFR § 122.41(j)(1).3
The draft permit provides monitoring exemptions for certain ponds designed for the 10-year, 24-hour storm
event and the 25-year, 24-hour storm event. Draft permit condition (B-14) states that "only basins or ponds
designed to contain the 25-year, 24-hour storm event without discharging, and that can regain capacity to hold
such an event within five (5) days' time through means other than discharge to surface waters, may be exempt
from analytical monitoring requirements." Draft permit condition H-2(g) states that "except for clay pits, grab
sampling is not required for discharges from a basin/pond designed to contain or treat mine dewatering
wastewater which only discharges in response to rainfall in excess of the 10-yr, 24-hr storm."
EPA recognizes that these treatment basins are designed to retain or treat the water from certain precipitation
events in order to keep them from discharging pollutants to a Waters of the United States, which may effectively
eliminate the outfalls as a point source during storm events below their design capacity. The EPA has comments
regarding this approach as provided below:
- The draft factsheet does not contain an explanation about why the basins that are designed to contain
certain storm events are exempt from the permit's monitoring or limit requirements. The exemption
language in Section H-2(g) of the draft permit also contradicts the requirements stated in Section B-14
which only exempts ponds designed to contain the 25-year, 24-hour storm without discharging, and that
can regain capacity to hold such an event during five days through means other than discharge to surface
waters. The language in both sections seems to indicate that sampling is never required for these basins
and ponds, even if the outfalls were to discharge.
- The draft permit does not address situations where the treatment basins would discharge. EPA believes
there are circumstances when a treatment pond may discharge even if it meets the stated precipitation
design requirements: 1) the occurrence of a storm event larger than the basin holding capacity; 2) multiple
1 40 CFR § 122.45(d)(1): For continuous discharges all permit effluent limitations, standards, and prohibitions, including those necessary to
achieve water quality standards, shall unless impracticable be stated as: (1) Maximum daily and average monthly discharge limitations for all
dischargers other than publicly owned treatment works; and (2) Average weekly and average monthly discharge limitations for POTWs.
z EPA notes that there are only a limited number of technical considerations that would make it "impracticable" or infeasible to develop
appropriate limit expressions.
3 40 CFR § 122.41(j)(1): Samples and measurements taken for the purpose of monitoring shall be representative of the monitored activity.

storm events occurring near one another; 3) ponds being placed in an ephemeral or intermittent stream;
4) lack of proper operation and maintenance to remove material from the pond when the sediment storage
capacity has been reduced; and/or 5) if the facility pumps water from other areas of the site that may
increase the discharge duration or frequency.
EPA notes that certain mineral mines have effluent limit guidelines (ELG) monitoring exemptions for treatment
basins that are designed, constructed, and maintained to contain or treat the volume of water resulting from a
10-year, 24-hr precipitation event.4 The ELG monitoring exemptions are only available to the technology -based
effluent limits (TBEL) applicable to specific mineral mining subcategories, and do not apply to any water quality -
based effluent limits (WQBEL) that NCDEQ determined were appropriate to protect water quality standards
(WQS).
Given that the ELG-based monitoring exemption only applies to TBEL-limited parameters, EPA suggests that all
discharges with water quality -based conditions in the final permit, regardless of the holding capacity, should be
monitored at an appropriate frequency that yields sufficient data to be representative of the activity. In
addition, EPA suggests that the TBEL-exemptions only be applied to those specific mineral mining subcategories
allowed by the regulations (See 40 CFR Part 436 — Subpart R for an example). NCDEQ could consider limiting
monitoring at appropriately representative discharges (i.e., substantially identical outfalls) provided that
sufficient information is available to show effluent character is similar, and that valid information exists showing
that the outfall has been designed, constructed, and properly operated and maintained.
3. NCDEQ should consider increasing the monitoring frequency for stormwater and wastewater discharges to a
frequency sufficient to yield data that are representative of the activity pursuant to 40 CFR § 122.48(b).5
The wastewater monitoring frequency in the draft permit is quarterly for the first year, and then semi-annually
thereafter. For stormwater, the effluent monitoring frequency is semi-annually.
Given the highly variable nature of mining related discharges in terms of frequency, duration, and pollutant
concentrations, increased monitoring frequencies more accurately characterize the effluent and protect water
quality. EPA suggests increasing the monitoring frequency to 2/month or monthly for all wastewater discharges,
and a monthly or quarterly monitoring frequency for stormwater discharges. EPA's recommendation is
especially applicable in circumstances where the outfall discharges to high quality waters, water bodies with
mining related impairments or total maximum daily loads (TMDLs), or receiving waters with Endangered Species
Act (ESA) -listed species or critical habitat.
EPA also notes that the NPDES regulations in North Carolina (15 NCAC 02B.0508(d)) state that monthly sampling
is the minimum monitoring frequency required for turbidity, settleable matter, total suspended solids (TSS),
and pH for wastewater discharges at mining facilities with SIC codes 1400-1499.E It is EPA's understanding that
all mining facilities covered by the general permit are within in the SIC codes listed in North Carolina's
implementing regulations. Unless NCDEQ has made a written determination that a monthly monitoring
4 40 CFR § 436.42(b) provides an example precipitation exemption that applies to TBEL for the industrial sand mining industry.
s 40 CFR § 122.48(b): Required monitoring including type, intervals, and frequency sufficient to yield data which are representative of the
monitored activity including, when appropriate, continuous monitoring;
6 For toxics and toxicity, 15 NCAC 0213.0508 also states the "Specific test type, conditions, and limitations shall be defined by permit. Toxicity
limits shall be applied to all major discharges and all discharges of complex wastewater. Toxicity limitations and monitoring requirements
may be applied to permits for other discharges when such discharge may impair the best use of the receiving water by the discharge of toxic
substances in toxic amounts. Specific frequency shall be defined by individual permit conditions. For most facilities with continuous and
regularly occurring discharges, frequency will be defined as a minimum of quarterly."

frequency is not applicable to the mineral mining industry as allowed by North Carolina's regulations,' EPA
suggests that the final permit contain the minimum monthly monitoring for all discharges that have the four
pollutants listed within the NPDES implementing regulations in North Carolina.
4. Stormwater control measure inspections and monitoring at dormant facilities should include annual
inspections, or a certification by a Professional Engineer if annual inspections are impracticable pursuant to
40 CFR § 122.44(i)(4)(iv).8
Part D of the draft permit covers the monitoring and reporting requirements for mining facilities that are in
dormant status. It is unclear if the facility is still required to perform annual inspections at dormant facilities as
part of the Stormwater Pollution Prevention Plan annual update, even if the facility has received a written
temporary exemption from the monitoring requirements.
EPA recommends that annual inspections be required in order to discover unanticipated threats to surface
waters at facilities that may be viewed infrequently. Alternatively, if the annual inspections are impracticable,
EPA recommends that a dormant facility obtain a Professional Engineer certification at least every three years
stating that the facility is in compliance with the permit pursuant to 40 CFR § 122.44(i)(4)(iv).
5. The benchmarks and limits for certain mineral mining industries should include either limits or an additional
explanation that there is no reasonable potential to cause or contribute to an in -stream exceedance above a
narrative or numeric criteria within North Carolina's WQS consistent with 40 CFR § 122.44(d)(1).'
Chromium Limits for Stormwater Discharges
The draft permit contains chromium effluent limits for wastewater discharges from brick pits and industrial
sand mines (Tables 9 and 10), and chromium benchmarks for stormwater discharges from brick pits (Table 3).
The draft permit does not have a similar chromium benchmark for stormwater discharges from industrial sand
mines.
The draft fact sheet indicates that chromium, along with several other additional parameters, were included
based on NCDEQ staff recommendations. EPA recommends that stormwater discharges from industrial sand
mines also contain chromium benchmarks or that additional justification is included in the fact sheet that
clarifies if the stormwater has the reasonable potential to cause or contribute to a violation of North Carolina's
WQS.
TSS Benchmarks for Stormwater Discharges
The stormwater effluent benchmarks for TSS are listed as 50 mg/L for all discharges to higher quality waters
and 100 mg/L for all other waters. The draft permit contains a more stringent TSS limits for several categories
of higher quality waters at wastewater outfalls.
' 15 NCAC 0213.0508(b)(1): If any of the tests and measurements, sampling points, or frequency of sampling requirements, as required in this
Rule for a particular SIC group, are not applicable to the discharge of a particular water pollution control facility, or if it can be demonstrated
that the objectives of this Section can be achieved by other acceptable means, then such requirements may be waived or modified to the
extent that the Director determines to be appropriate.
s 40 CFR § 122.4(i)(4)(iv): Permits for stormwater discharges associated with industrial activity from inactive mining operations may, where
annual inspections are impracticable, require certification once every three years by a Registered Professional Engineer that the facility is in
compliance with the permit, or alternative requirements.
9 40 CFR § 122.44(d)(1)(iii): When the permitting authority determines, using the procedures in paragraph (d)(1)(ii) of this section, that a
discharge causes, has the reasonable potential to cause, or contributes to an in -stream excursion above the allowable ambient concentration
of a State numeric criteria within a State water quality standard for an individual pollutant, the permit must contain effluent limits for
that pollutant.

EPA suggests changing the TSS stormwater benchmarks to match the MDL for wastewater discharges to all
higher quality waters (HQW/ORW = 30 mg/L; Trout and PNA = 15 mg/L).10 This recommendation would ensure
that aquatic life is protected in certain high -quality waters during precipitation events that may cause acute
harm. Alternatively, NCDEQ could provide an explanation in the fact sheet about why the less stringent TSS
stormwater benchmarks do not have the reasonable potential to cause or contribute to a violation of WQS in
North Carolina.
pH Benchmarks for Stormwater Discharges
Table 8 establishes pH limits of 6.0 — 9.0 standard units (s.u.) for mine wastewater discharging to freshwater
and 6.8 — 8.5 s.u. for mine wastewater discharging to saltwater. The pH limitations provided in Tables 3 and 9
for wastewater discharges from brick pits to all receiving stream types is 6.0 — 9.0 s.u. Tables 8 and 9 appear to
be contradictory.
EPA recommends clarifying the pH requirements for brick pits discharging to salt water. If separate saltwater
limitations are not required, further explanation should be provided in the fact sheet about whether there is
reasonable potential to cause or contribute to an exceedance of North Carolina's WQS for pH.
Additionally, it is unclear if the limits for pH in Table 9 are required for feldspar or lithium mines. EPA suggests
clarifying if the pH limits in Table 8 are applicable to feldspar and lithium mining operations.
6. TSS limitations are required for discharges from phosphate mines pursuant to 40 CFR § 436 Subpart R.11
Except for facilities discharging to various types of higher quality waters, the draft permit does not limit TSS in
the wastewater effluent from phosphate mines.
TBELs for TSS are applicable to phosphate mines according to ELGs applicable to the mineral mining industry.
For phosphate mining outfalls discharging to receiving waterbodies other than high quality, EPA suggests that
the final permit have appropriate effluent limits for TSS to comply with 40 CFR § 436 subpart R.
7. NCDEQ should consider revisions to the Notice of Intent (NOI) to support effluent limitations or monitoring
conditions in the final permit in accordance with 40 CFR § 122.28(b)(2)(ii).12
The NOI accompanying the draft permit requests that applicants provide outfall location, description of
wastewater, and the maximum flow rate; however, the NOI does not contain requests for information about
other effluent characteristics regarding outfall discharge frequency or duration.
EPA recommends that NCDEQ add to the NOI topics related to discharge frequency and discharge duration
(continuous vs non -continuous) to comply with the application requirements within the NPDES implementing
10 The TSS limits for high quality waters for new and expanded discharges are based on 15A NCAC 0213.0224(c)(2)(13).
11 40 CFR § 436.182 and 40 CFR § 436.185 state that TSS shall be limited (MDL = 60 mg/L; AML = 30 mg/L) for the existing and new source
performance categories.
12 40 CFR § 122.28(b)(2)(ii): The contents of the notice of intent shall be specified in the general permit and shall require the submission of
information necessaryfor adequate program implementation, including at a minimum, the legal name and address of the owner or operator,
the facility name and address, type of facility or discharges, the receiving stream(s), and other required data elements as identified in
appendix A to part 127. General permits for stormwater discharges associated with industrial activity from inactive mining, inactive oil and
gas operations, or inactive landfills occurring on Federal lands where an operator cannot be identified may contain alternative notice of intent
requirements.

regulations in 40 CFR § 122.21(g)13 and 40 CFR § 122.21(k).14 NCDEQ should also consider requiring information
about ESA -listed species or critical habitat that is publicly available to applicants online.15 EPA believes that
these additions will help the permittee to understand the permit requirements that are applicable to the
covered facility, support conditions in the draft permit, and protect water quality. Additionally, this extra
information is important for NCDEQ to consider during the general permit coverage process to adequately
implement the program (and potentially require an individual permit if necessary).
8. NCDEQ should include an explanation in the fact sheet about how new and expanded discharges to high
quality waters from mineral mines conform with 15 NCAC 02113.0224(c)(2).
Nutrients
North Carolina regulations require effluent limitations for phosphorus or nitrogen, or both, when nutrient over
enrichment is projected to be a concern (15 NCAC 02B.0224(c)(2)(F)). The draft permit does not include any
nutrient monitoring or limits for phosphate mining activities.
Phosphate mines can discharge nutrient related parameters. Nutrient effluent conditions are often found in
other NPDES permits within Region 4 states with phosphate mining facilities. EPA suggests including monitoring
or limits for nutrients from phosphate mining discharges to high quality waters with enrichment concerns, or
an explanation that the discharge will not cause or contribute to a numeric or narrative excursion above any
North Carolina WQS. Alternatively, NCDEQ can consider making a determination that there are no expanded or
new discharges from phosphate mines that will flow into any high quality waters for which nutrient enrichment
is an issue.
Toxic Substances
North Carolina regulations require, in cases where complex wastes (those containing or potentially containing
toxicants) may be present in a discharge, an additional safety factor be applied to the discharge of toxic
substances. 15 NCAC 02B.0224(c)(2)(G) states that "the limit for a specific chemical constituent shall be
allocated at one-half of the normal standard design conditions".
In order to document protection of North Carolina's WQS, EPA recommends that the fact sheet explain how
the outfalls at each mining facility covered under the general permit would not be considered to discharge toxic
substances. Alternatively, the limits for those parameters that could be considered a toxic substance could be
limited using one-half the normal standard design conditions.
9. NCDEQ should consider revising the permit language regarding the Secondary Containment Plan.
The draft permit requires that the applicant visually observe any accumulated stormwater prior to release for
color, foam, outfall staining, visible sheens, and dry weather flow, as these could be indications of
contamination. A record must be kept of every release from a secondary containment system (see draft permit
Sections B-9(c) and B-9(d)).
13 40 CFR § 122.21(g)(2), (3), and (4) requires existing mines to submit average flows at discharge points and intermittent effluent flow data
(frequency, duration, and magnitude).
14 40 CFR § 122.21(k)(3) and (5) requires new mining operations to submit estimated effluent information regarding frequency, duration,
maximum, and average flow rates.
15 ESA -listed species information is available at: ecos.fws.gov/ipac/

As currently stated, language in the draft permit could be interpreted as allowing the release of visibly
contaminated stormwater, so long as a record of the release is noted. EPA suggests adding in language to clarify
that accumulated stormwater should be released only if it is found to be uncontaminated.