low elevations near the current Coosa River channel as well as at
higher topographic levels. These alluvial deposits are reported to
range from approximately 20 to 30 feet in thickness. Most of the
downgradient compliance monitoring wells in the approved network are
screened in these shallow materials, and most of the wells are screened
only in the gravel.\69\ Additional compliance wells are needed both at
the upper and lower bounds of the uppermost aquifer system, including
within alluvial deposits and hydraulically connected weathered bedrock
and bedrock zones, to ensure all potential contaminant pathways will be
monitored in all relevant flow zones.
---------------------------------------------------------------------------

    \69\ The Plant Gadsden Permit Application at page 111 includes a
statement that ``[m]onitoring wells target the uppermost aquifer
with wells screened in coarse fractions of the alluvial materials or
more weathered, fractured upper bedrock beneath the Site.''
---------------------------------------------------------------------------

    A few wells are screened near the top of the Conasauga bedrock
formation, and a few wells are cross screened across the interface
between the alluvium (the gravel) and the underlying bedrock. As
depicted on the cross-section in Figure 5A in the Permit Application,
no wells appear to have been screened in either the sand or silt layers
that are situated above the gravel; and a single well on the cross-
section in Figure 5B in the Permit Application appears to be partially
screened in the silt. But additional compliance wells should have been
installed in those upper zones given that the sand and silt layers are
saturated with groundwater. Even when the gravel layers were not
present, the well screens were set at the bottom of the alluvium or at
the top of bedrock, and not in the silts. Wells in each of the
saturated units are needed in order to monitor all potential
contaminant pathways.
    In addition, as previously discussed, key interfaces, such as the
interface between alluvium and weathered bedrock have apparently not
been fully characterized; as this portion of the bedrock system is
hydraulically connected to the overlying alluvium, additional
compliance wells are needed in the upper part of the bedrock in most
areas of the Ash Pond unit to ensure that all potential contaminant
pathways are monitored. Additional wells also

need to be installed in deeper intervals of the underlying Conasauga
mudstones which are hydraulically connected the uppermost zone of
weathered bedrock. The relevant zone of interest in the upper part of
the Conasauga group is at least 100 feet in thickness, as discussed
previously, but the true thickness of the uppermost aquifer has not
been determined. As such additional monitoring wells may need to be
screened more deeply to ensure all potential contaminant pathways are
monitored.
(3) Preferential Pathways Are Not Monitored
    Preferential pathways have been documented in the uppermost aquifer
under the Ash Pond. Yet under the approved GWMP, these significant
potential contaminant pathways do not appear to be adequately
monitored, despite the express requirement in Sec.  257.91(a)(2).
    Based on the boring logs and cross-sections in the Permit
Application and the 2021 Semi-Annual GWMCA Report, several types of
preferential pathways are present at the site. These include, among
others, continuous lenses or channel-like bodies of coarse sand and
gravel in overburden, low-lying areas along the overburden/bedrock
interface, laterally continuous zones of weathered bedrock in the
uppermost part of the bedrock section, and zones of fracturing and/or
weathering and/or dissolution within deeper levels of the bedrock. The
current monitoring network only incompletely monitors some of these.
    While some monitoring wells are installed in sand and gravel bodies
in the alluvium, it appears that the monitoring network does not target
all such zones that may be serving as preferential pathways. As just
one example, consider the southwestern unit boundary that borders the
Coosa River; as indicated on Figures 5B and 6 of the approved GWMP,
while the wells installed along this boundary (GSD-AP-MW-8 thru GSD-AP-
MW-12) are screened along a zone where groundwater flow is likely
occurring along preferential pathways, they are spaced over 500 feet
apart. Considering the unique geologic conditions at the site that
could result in the presence of more localized preferential pathways,
it is not known whether the gravel materials screened by GSD-AP-MW-11
are present elsewhere along this boundary. In short, there could be
sand and gravel alluvial zones or highly fractured zones in bedrock
near the bedrock/alluvium interface that have not been identified and
are unmonitored. EPA is proposing to determine that additional borings
(and possibly monitoring wells) should have been installed along this
boundary, and it appears that this level of detailed investigation to
identify preferential pathways was not performed elsewhere along the
unit.
    It is clear that preferential pathways in the bedrock exist based
on the characterization and monitoring Alabama Power conducted as part
of the continuing corrective action at the site. However, there is
little to no discussion in the Permit Application regarding how these
pathways were identified and how the lateral/vertical dimensions of the
pathways were delineated to ensure that compliance wells were installed
correctly to monitor these pathways. As illustrated on Figures 9 and 10
of the 2021 Semi-Annual GWMCA Report, assessment monitoring has
identified plumes emanating from the unit to the northeast in
overburden and bedrock. After installing additional monitoring wells to
delineate the contaminant plume, Alabama Power identified that
contamination was present deeper in the Conasauga bedrock formation
than any of the compliance wells previously installed as part of the
groundwater monitoring system. For example, Figures 5 and 10 of the
2021 Semi-Annual GWMCA Report indicate that pathway in bedrock has
influenced migration of a lithium plume beyond the unit boundary at
least hundreds of feet to the northeast to depths of at least 130 feet
into the bedrock. It is reasonable to expect that similar pathways may
exist also along the same regional northeast to southwest geologic
strike to the southwest of the unit, exploiting these same inherent
zones of fracturing in the bedrock, yet the southwestern waste
boundary, along the Coosa River, generally lacks any monitoring points
in deeper bedrock.
    In summary, after reviewing the GWMP and all the materials in the
permit record, EPA is proposing to determine that the monitoring
network that ADEM approved is not likely to detect all groundwater
contamination in the uppermost aquifer and is therefore less protective
than the Federal regulations.
c. Plant Gadsden Corrective Action Issues
    In January 2020, the first SSLs above groundwater protection
standards were reported for arsenic and lithium. An ACM was prepared in
July 2020. On December 18, 2020, ADEM issued the Final Permit to
Alabama Power for Gadsden Ash Pond. EPA is proposing to determine that
the Final Permit issued to the Gadsden Ash Pond, as with the other
permits discussed in this notice, fails to require Alabama Power to
achieve compliance with the Federal corrective action requirements.
    The Gadsden Final Permit states that the Permittee is required ``.
. . to manage CCR in accordance with the conditions of the permit, ADEM
Admin. Code r. 335- 13- 15, `Standards for the Disposal of Coal
Combustion Residuals in Landfills and Surface Impoundments,' and the
approved permit application.'' \70\ The permit also contains the same
recitation of the corrective action regulations as the Colbert Final
Permit did.
---------------------------------------------------------------------------

    \70\ Alabama Department of Environmental Management. Initial
Permit and Variance, Gadsden Steam Plant, Permit No. 28-09. December
18, 2020. PDF p. 2.
---------------------------------------------------------------------------

Corrective Action
    1. Assessment of Corrective Measures. The Permittee must initiate
an assessment of corrective measures as specified in 335-13-15-. 06(7)
if any constituent listed in Appendix IV of 335- 13- 15 has been
detected at a statistically significant level exceeding the groundwater
protection standard, or immediately upon detection of a release from
the CCR unit.
    a. The permittee must continue to monitor groundwater in accordance
with the assessment monitoring program while assessing corrective
measures.
    2. Selection of Remedy. Based on the results of the corrective
measures assessment, the Permittee must select a remedy as specified in
335-13-15-. 06(8).
    3. Implementation of the Corrective Action Program. Within 90 days
of selecting a remedy, the Permittee must initiate remedial activities
as specified in 335-13-15-. 06(9), and shall be required to modify the
permit in accordance with Section II. E. 9.
    In the RTC for the Gadsden Final Permit, ADEM states that, ``The
ACM is currently under review. Once the final review is complete, the
Department will provide comments to Alabama Power related to the
submitted ACM and proposed final remedy.'' The preferred remedy in the
ACM was MNA with adaptive site management and ``remediation system
enhancement.'' \71\ Any comments provided by ADEM to

Alabama Power on the 2020 ACM were not available for review.
---------------------------------------------------------------------------

    \71\ It is not clear what is meant by ``remediation system
enhancement'' with respect to MNA, because MNA relies upon naturally
occurring processes for remediation. The only systems installed are
for performance monitoring. Any ``enhancement'' would require action
on the part of Alabama Power to remediate the releases and would be,
by definition, a different remedy.
---------------------------------------------------------------------------

    As with Colbert, incorporating the regulations verbatim in the
permit does not require Gadsden to achieve compliance with those
requirements. This is because ADEM did not take into account relevant
facts about the status of corrective action at Gadsden, such as whether
the 2020 ACM, which was completed more than 2 years prior to issuance
of the permit, complied with the regulatory requirements. Most
importantly, ADEM did not adjudicate what actions are still necessary
in light of those facts to achieve compliance with the regulations and
include those actions as requirements in the Final Permit.
    Whether the 2020 ACM meets the requirements of the regulations and
what actions Alabama Power must take to remediate groundwater in
compliance with Sec.  257.97 are precisely the types of adjudication
required in a permit. What the permittee is required to do in order to
achieve compliance with the regulations must be determined prior to
final permit issuance, because the permit must contain these
requirements. This is the role of a permitting authority (i.e., ADEM).
Delaying this decision effectively allows Alabama Power to continue
operating out of compliance with the regulations, while operating in
compliance with the permit. In this case, that means Alabama Power can
continue to pursue a remedy that does not appear to meet the
requirements of Sec.  257.97, and consequently, delay or avoid the
cleanup. This results in a permit program that is less protective than
the Federal regulations.
    In sum, EPA is proposing to determine that, by failing to determine
the adequacy of the revised ACM or the permittee's proposed remedy, the
permit in essence authorizes Alabama Power to continue to pursue a
remedy that does not appear to meet the requirements in Sec.  257.97(b)
and is based on the results of a deficient ACM. Accordingly, EPA is
proposing to determine that this permit does not require compliance
with the Federal requirements and, because it allows the facility to
continue to delay initiating corrective action that would address the
continuing groundwater contamination, the State requirement is less
protective than the Federal regulations.
i. Gadsden Final Permit Does Not Require an ACM That Includes an
Assessment of Source Control Measures in Accordance With 40 CFR 257.96
    40 CFR 257.97(b)(3) requires that all remedies control the source
of releases in order to reduce or eliminate, to the maximum extent
feasible, further releases of contaminants into the environment. The
ACM for Gadsden contains no assessment of control measures to achieve
this requirement (i.e., source control). Instead, section 2.5 describes
the closure of the unit, which has already occurred, and states, ``Site
closure appears to have already been effective in controlling the
source and reducing infiltration into the underlying aquifer.''
However, the ACM must include more than one source control measure and
must actually analyze how effectively each of the potential measures
would meet the criteria in Sec.  257.96(c). See, 40 CFR 257.96(a), (c).
Here, as was the case with Plant Colbert, there is no assessment of the
one source control measure identified in the ACM--the closure of the
Ash Pond, which left a significant amount of CCR in contact with
groundwater--and how effectively it would achieve the criteria in Sec.
257.96(c) compared to other source control alternatives, such as clean
closure or the imposition of engineering measures to control or
eliminate the groundwater that continues to flow in and out of the
impoundment. Yet the permit issued by ADEM does not require any actions
to remedy these readily apparent deficiencies.
    ADEM's failure to require Alabama Power to submit an ACM that
actually evaluates whether the closure of the Ash Pond meets the source
control requirements in Sec.  257.97(b)(3) also undercuts their claim
that they will use the corrective action process to address any
remaining concerns with respect to the closure of the Ash Pond. As
discussed above, closure construction activities for the Ash Pond were
certified as completed in October 2018, and a certification of the
completion of closure activities was submitted in April 2020. As
discussed above, in the two years between the time closure was
completed and the permit was issued in December 2020, groundwater
elevations were measured between 2 and 7 feet above the average base
elevation of the closed unit. Yet ADEM issued the permit without
evaluating the ACM. Nor did the State take any further action when they
approved the closure of the Ash Pond in 2022.
ii. The Gadsden Permit Does Not Require Alabama Power To Collect Site
Data Needed To Characterize Site Conditions That May Affect a Remedy To
Support Assessments in the ACM
    As discussed above, Sec.  257.95(g)(1) requires a facility to
characterize the nature and extent of the release and any relevant site
conditions that may affect the remedy ultimately selected. The
characterization must be sufficient to support a complete and accurate
assessment of the corrective measures necessary to effectively clean up
all releases from the CCR unit pursuant to Sec.  257.96. The 2020 ACM
delineates releases but does not characterize any site conditions that
would affect its preferred remedy of in-situ immobilization through
treatment or MNA (e.g., testing for the presence of released
constituents in soils to demonstrate they are being removed from the
groundwater and immobilized on-site). As discussed in subsequent
sections, these data are necessary to accurately assess any of the
remedies identified in the ACM, particularly MNA. The Final Permit
issued by ADEM does not require collection of these data or any
revisions to the ACM to remedy this deficiency.
iii. The Assessment of In-situ Geochemical Treatment and MNA in the
ACMs Is More Favorable Than Can Be Supported by the Available Data
    The 2020 ACM for Gadsden identified in-situ geochemical treatment
and MNA as corrective measures to address groundwater contamination, in
addition to hydraulic control and treatment. As discussed previously,
MNA relies on natural processes to treat releases; in-situ geochemical
treatment adds chemicals to the subsurface to create conditions for
this immobilization to occur. For arsenic and lithium, in-situ
geochemical treatment and MNA can reduce mobility through sorption to
soils, but they do not remove the contaminants from the environment.
Therefore, MNA and geochemical in-situ treatment generally would not
perform well with respect to the requirement in Sec.  257.97(b)(4) that
remedies ``remove from the environment as much of the contaminated
material that was released from the CCR unit as is feasible,'' since
the constituents remain in the subsurface soils, albeit immobilized.
    In order for immobilization through MNA or in-situ treatment to be
assessed favorably with respect to reliability, the chemical reactions
and processes involved in this immobilization must be demonstrated to
be irreversible. Immobilization that is not permanent could be
reversed, causing contaminants to be released back into groundwater,
where they can migrate off-site. Immobilization that is not permanent
would also require ongoing monitoring in accordance with Sec.
257.98(a)(1) as long as immobilized constituents remain in the
subsurface. Determining the viability and demonstrating the
irreversibility of immobilization

mechanisms is necessary to assess the performance, reliability, ease of
implementation, and the time required to begin and complete the remedy.
40 CFR 257.96(c)(1) and (2). These assessments would need to be
supported with site-specific characterization data and analysis. This
information would ultimately be necessary to show that MNA and
geochemical in-situ treatment meet all the requirements of Sec.
257.97(b), but the permit record does not include such information.
(1) The 2020 ACM Does Not Include Data That Characterize Site
Conditions or Identify Any Attenuation Mechanisms Occurring at the Ash
Pond
    The 2020 ACM assessed the performance of MNA favorably without any
supporting data to characterize site conditions that may ultimately
affect a remedy, as required by Sec.  257.95(g)(1). For example, site-
specific groundwater data (e.g., pH or oxidation potential, speciated
concentrations of constituents of concern) were not considered in the
assessment narrative, and analytical results of soil samples to
identify the presence of immobilized constituents in the subsurface
were not provided. The site data that were collected focus only on
contaminant concentrations and trend analyses regarding the presence of
contaminants. The ACM also does not discuss how attenuation may be
naturally occurring through any particular MNA mechanisms (e.g.,
adsorption, precipitation, dispersion). EPA was not able to find any
indication in the permit or supporting documentation to confirm that
the Permittee has identified the mechanisms by which MNA would occur at
the site for both arsenic and lithium. Nor is there any condition in
the permit requiring the development and submission of such
information.
(2) MNA Is Not a Viable Remedy Without Source Control
    As discussed previously for Plant Colbert, MNA is not viable
without source control, because the total amount of contaminants in the
groundwater will continue to increase as the releases from the unit
continue and potential releases of new constituents will occur.
Therefore, it is impossible to determine whether the aquifer has
sufficient chemical and physical materials required to complete any
identified immobilization reactions because the total amount of the
release is not yet known.
    Source control has not been achieved here, as releases from the Ash
Pond are ongoing. The closure of the Ash Pond with waste remaining in
place in the aquifer has resulted in a continual source of groundwater
contamination from the unit. Therefore, MNA is not a viable remedy for
the Ash Pond and should not be included in the 2020 ACM unless the ACM
is revised to include an alternative that achieves source control.
(3) Plant Gadsden's Permit Does Not Require an ACM That Accurately
Assesses Groundwater Remediation Alternatives According to the Criteria
in 40 CFR 257.96(c)
    The 2020 ACM also fails to meet the requirements at Sec.
257.96(c)(3) to consider safety impacts, cross-media impacts, and
control of exposure to any residual contamination in its assessment of
MNA. Neither the narrative nor Table 5 in the 2020 ACM consider these
impacts for MNA. Table 5 in the 2020 ACM, in the column labeled
``potential impacts of remedy'' assesses the potential impacts from MNA
as ``none.'' This conclusion is not only unsupported by data or
analysis but is also inconsistent with other information in the ACM.
The Ash Pond is next to a river and groundwater flow is depicted toward
the river in Figure 3 in the 2020 ACM. Because no site data were
collected that would demonstrate immobilization of constituents is
occurring, the only MNA that is known to occur is dilution and
dispersion (i.e., the normal transport associated with groundwater
releases). This means that contaminants are migrating out of the Ash
Pond in groundwater toward the river. Migration of contamination from
groundwater to surface water is a cross-media impact. Thus, the
assessment of potential impacts from the remedy for MNA in Table 5,
which includes these cross-media impacts, should be ``high.''
    The lack of data to support the assessments in the ACMs means they
may not accurately reflect MNA's ``effectiveness in meeting all of the
requirements and objectives'' in Sec.  257.97(b). Conclusions without a
supporting assessment or data do not constitute ``an analysis of the
effectiveness of potential control measures.'' 40 CFR 257.96(c)
(emphasis added). Inaccurate assessments in an ACM can ultimately
result in selection of a remedy that will not meet the requirements of
Sec.  257.97(b). Yet the Final Permit issued by ADEM does not require
any actions to remedy this deficiency.
3. Plant Gorgas
    EPA reviewed the Initial Permit and Variance (Final Permit) for the
Alabama Power Company, William C. Gorgas Electric Generating Plant
(Plant Gorgas), issued by ADEM under Permit No. 64-12 on February 28,
2022.\72\ Plant Gorgas is located near Parrish, Alabama. The units
covered by the Final Permit include the Plant Gorgas Ash Pond, Plant
Gorgas Gypsum Pond, Plant Gorgas Bottom Ash Landfill, and Plant Gorgas
CCR and Gypsum Landfill. The Plant Gorgas CCR and Gypsum Landfill is
still in operation while the other three CCR units are in the process
of closing or closed. For this proposal, of the CCR units at Plant
Gorgas, EPA only evaluated the Final Permit for the Plant Gorgas Ash
Pond (Ash Pond) because it is directly comparable to the other State
CCR permits evaluated in this proposal, and because, based on the
characteristics of the unit and the surrounding hydrogeology, it has
the greatest potential for significant environmental and human health
effects if mismanaged.
---------------------------------------------------------------------------

    \72\ Alabama Department of Environmental Management. Initial
Permit and Variance William C. Gorgas Electric Generating Plant
Permit Number 64-12. February 28, 2022.
---------------------------------------------------------------------------

    The Plant Gorgas Ash Pond is a ``CCR surface impoundment located in
Sections 20, 21, 28 and 29, Township 16 South, Range 6 West in Walker
County, Alabama . . . with a disposal area that consists of
approximately 423.32 acres.'' Final Permit at pg. 2. The Ash Pond is
located southeast of Plant Gorgas on the opposite side of the Mulberry
Fork of the Black Warrior River. The Permit Application describes that
the Ash Pond was originally formed by a cross-valley dam in 1953, with
the original dam located on the northern boundary of the impoundment
adjacent to Mulberry Fork.\73\ The original dam was raised to increase
the capacity of the impoundment in the mid-1970's, and then raised once
again in 2007. Id. at Appendix 4. When the Ash Pond was in operation,
the impoundment covered an approximate area of 420 acres containing 25
million CY of waste.
---------------------------------------------------------------------------

    \73\ Alabama Power Company. Revised Closure Permit Application
for the Plant Gorgas Ash Pond. April 30, 2020.
---------------------------------------------------------------------------

    EPA has identified issues with closure, groundwater monitoring
networks, and corrective action at Plant Gorgas, and we discuss those
issues below.
a. Plant Gorgas Closure Issues
    As noted, the closure at Plant Gorgas is not yet complete. To
evaluate the closures at Plants Colbert and Gadsden, EPA reviewed the
measured post-closure groundwater elevations to determine whether the
Sec.  257.102(d) performance standards were met. But since the closure
of the Gorgas Ash

Pond is not yet complete, that same information (``measured post-
closure groundwater elevations'') is not available. As discussed below,
however, it is clear that CCR in the Ash Pond is currently saturated by
groundwater. Despite the saturated CCR currently in the unit, it may be
possible for the Ash Pond to close with waste in place if engineering
measures are implemented to meet the performance standards in Sec.
257.102(d). Although some engineering measures are described in the
Closure Plan, EPA was unable to locate the information in the permit
record to support a definitive conclusion that the proposed closure
will meet the performance standards in Sec.  257.102(d). For example,
EPA was unable to locate any evaluation of the expected impact of the
proposed engineering measures on groundwater elevations conducted by
either the permittee or ADEM. EPA's inability to reliably estimate
post-closure conditions is a consequence of the complexity of the site,
the absence of critical information in the Closure Plan, and the
inadequacy of the groundwater monitoring system at the site (which is
discussed in the next section). Nevertheless, as described below, based
on the available information there are several reasons to determine
that it is unlikely that the proposed closure of the Ash Pond will meet
the performance standards in Sec.  257.102(d). EPA is therefore
proposing to determine that the approved Closure Plan fails to
demonstrate that the closure will meet the performance standards in
Sec.  257.102(d), as required by Sec.  257.102(b)(1)(i). Based on
ADEM's failure to require the permittee to provide this information, or
to otherwise resolve the issues presented below before approving the
Closure Plan, EPA is proposing to determine that the Final Permit fails
to require the Gorgas Ash Pond to achieve compliance with either Sec.
257.102(d), or with an equally protective State alternative. See 42
U.S.C. 6945(d)(1)(B).
i. CCR in the Ash Pond Is Currently Saturated by Groundwater and Is
Likely To Remain so Once Closure Is Complete
    Given the complexity of the site and the absence of detailed
information in the Permit Application, EPA lacks the data to reliably
estimate the amount of CCR that will remain saturated after closure
activities are complete. These deficiencies are significant enough that
ADEM's approval of a Closure Plan with these deficiencies, and in the
absence of any evaluation, leads to the conclusion that the State CCR
permit program does not meet the standard in 42 U.S.C. 6945(d)(1).
However, based on the available information in the Permit Application,
there are many reasons to determine that the proposed closure of the
Ash Pond will not meet the performance standards in Sec.  257.102(d).
Based on the limited data available, EPA estimates that groundwater
will continue to saturate a substantial amount of CCR, even after the
activities described in the approved Closure Plan have been completed.
As described below, available groundwater measurements recorded between
2021 and 2022 show that groundwater levels at the Ash Pond continue to
be present above the base of the unlined impoundment, saturating
substantial amounts of CCR in the closing unit. Moreover, comparison of
groundwater elevation data from 2021 and 2022 to elevation data in the
same wells for prior years does not yet indicate any statistically
significant or sustained declines, further supporting EPA's conclusions
about future persistence of saturated CCR waste.
    As shown on the center line cross section B-B' on construction
drawing G-204 in the Permit Application, the base of the Ash Pond
varies substantially. In view of this information, EPA conducted an
analysis using existing monitoring wells near the waste boundary and
south of the planned closure buttress. Few monitoring wells are located
directly adjacent to the CCR; most are located hundreds of feet away
from the waste boundary, with many at distances of over 1,000 feet
away. Faced with these significant limitations, EPA based estimates of
saturated waste presence and thickness on the limited available pairs
of wells which are in close proximity to the waste material and are
located on opposite sides of the main waste body or larger fingers of
CCR waste. Using this approach allowed for limited direct comparison of
recent water levels data collected in 2021 and 2022 to the top and
bottom elevations of the CCR in that area of the unit. EPA considered
transects between the following well pair or pairs of clustered wells:

 [GS-AP-MW-16S/GS-AP-MW-16D/GS-AP-PZ-16] to [GP-AP-MW-19]
 [GS-AP-MW-21/GS-AP-MW-21V] to [GS-AP-MW-1/GS-AP-MW-1R/GS-AP-
MW-46]
 [GS-AP-MW-12/GS-AP-MW-12V] to [GS-AP-MW-1/GS-AP-MW-1R/GS-AP-
MW-46]

    Lastly, it is also important to note that EPA's assessment of water
levels in this action focused primarily on those monitoring wells which
were screened nearest the CCR in the unit at those specific locations.
These included wells screened in a variety of different levels within
the uppermost aquifer system. It must be recognized that this exercise
suffered from the limitations of the well network as screened interval
elevations varied somewhat from transect to transect. Regardless of
these complexities, water levels in most screened intervals were
consistently above the base of the impoundment.
    This assessment suggests the sustained presence of significant
thickness of saturated waste in all of the areas EPA investigated. For
the [GS-AP-MW-16S/GS-AP-MW-16D/GS-AP-PZ-16] to [GP-AP-MW-19] transect
near the southern end of the Ash Pond, reported groundwater elevation
measurements from monitoring wells GS-AP-MW-16S and GS-AP-MW-19 range
from roughly 381 to 407 ft above MSL. In this area near the center of
the unit, the bottom of the CCR unit is located at approximately 335
feet above MSL and the top of the waste at closure is planned to be
roughly 450 feet above MSL. Based on these data EPA estimates that at
the deepest point of this transect a layer of CCR between 46 and 72 ft
in thickness is saturated. As stated above, EPA's estimates were
complicated by Alabama Power's failure to install many of the
monitoring wells at the waste boundary which is inconsistent with the
requirement in Sec.  257.91(a)(2)). In this case, EPA used data from
GS-AP-MW-16S and GS-AP-MW-19 because, based on the materials in the
Permit Application, they are a well pair that are located along
opposite sides of the unit from each other, or in other words, the two
wells span across a large portion of the unit. Nevertheless, the
lateral distance between GS-AP-MW-16S and GS-AP-MW-19 is still roughly
2,000 feet, and the bottom unit elevation is highly variable over that
distance given the incised valley setting in which the unit sits.
    EPA also evaluated the most recent groundwater elevation data from
the Plant Gorgas 2022 Annual Groundwater Monitoring and Corrective
Action Report to determine if any recent closure activity at the site
has influenced groundwater elevations.\74\ Regarding the impact of
closure activity on groundwater elevations, the report itself is
contradictory. On page 20, the report indicates that no significant
changes in groundwater elevations or flow have been noted at the site
as ash

pond dewatering activities have not been initiated. However, on pages
21 and 22, the report states that dewatering operations began in 2022
and may be contributing to the groundwater elevations observed.
Further, on page 56 of the report, there is an acknowledgment that
``[t]he lack of obvious or significant trends [or changes in
groundwater quality] is likely in part due to (1) dewatering operations
not starting until the first week of July 2022, (2) the low
permeability nature of the subsurface flow systems, and (3) the number
of wells that have been recently installed or replaced (too few data
points for trend analyses).'' In any event, EPA's evaluation indicated
that groundwater elevation data collected in July 2022 is mostly
comparable to historical data, suggesting little influence thus far
from dewatering efforts. For example, most decreases in groundwater
elevations were observed to be less than a few feet. Some larger
decreases (greater than 10 feet) were observed at the southern portion
of the Ash Pond, but the report indicated that these decreases may be
the result of resumed mining activity south or southwest of the Ash
Pond, rather than closure activity related to the Ash Pond. Therefore,
while some uncertainty remains as to just how much CCR is currently
saturated, the available site data indicates that considerable areas,
thicknesses, and volumes of saturated CCR remain in the impoundment.
---------------------------------------------------------------------------

    \74\ Southern Company Services 2022 Annual Groundwater
Monitoring and Corrective Action Report, Alabama Power Company Plant
Gorgas Ash Pond. Prepared for Alabama Power Company. January 31,
2023.
---------------------------------------------------------------------------

    Similarly, along the [GS-AP-MW-21/GS-AP-MW-21V] to [GS-AP-MW-1/GS-
AP-MW-1R/GS-AP-MW-46] transect through Finger 1 of the Ash Pond, water
levels reported in 2021 and 2022 for GS-AP-MW-21 and GS-AP-MW-46 ranged
from 335 to 367 feet above MSL. The elevation of the bottom of the CCR
is roughly 322 feet above MSL and the top of the CCR unit is planned to
be approximately 428 feet above MSL in that part of the unit. Based on
these data EPA estimates that at the deepest point of this transect a
layer of CCR between 13 and 45 ft in thickness is saturated.
    EPA also considered groundwater and waste elevations along the [GS-
AP-MW-12/GS-AP-MW-12V] to [GS-AP-MW-1/GS-AP-MW-1R/GS-AP-MW-46] transect
near the center main valley of the Ash Pond and extending eastward
along the northern side of Finger 1. Water levels from 2021 and 2022
from GS-AP-MW-12 and GS-AP-MW-46 ranged from 360 to 380 feet above MSL.
Given that the bottom of and top of the CCR are approximately 270 feet
and 390 ft above MSL respectively in the center of the impoundment, EPA
estimates that between 90 to 110 feet of saturated waste are present.
Similarly, for Finger 1 of the unit, EPA estimates that between 35 and
55 feet of saturated waste are present, based on bottom and top of the
CCR being at 325 feet and 430 ft above MSL, respectively. Based on
these limited available data, significant thicknesses of saturated CCR
are present in these areas.
    Lastly, EPA evaluated groundwater elevations along a north to south
transect, south of the planned closure buttress, along the west side of
the main valley containing CCR. From north to south, this included
monitoring wells, GS-AP-MW-12, -13, -14, -47, -15, -16, and -18. This
transect is approximately 6,150 feet in length, or over a mile. Over
this distance the available monitoring wells were located from
approximately 25 to 1,100 feet away from the edge of the CCR waste and
from 50 to 1,500 feet from the central part of the valley filled with
CCR. EPA used engineering drawings available in the Permit Application
to estimate CCR top and bottom elevations adjacent to each groundwater
monitoring point (e.g., construction drawings G-204, C-200 to C-205).
CCR thickness values varied from 65 to 149 feet along the transect. In
some locations more than one estimate was made due to the complexity of
the subsurface. EPA then subtracted the CCR waste bottom elevation from
the most recent water levels for each location (primarily July 18,
2022), to determine the thickness of saturated CCR, which varied from
zero (no saturated waste) to approximately 115 feet of saturated CCR.
This analysis supported the overall conclusion that saturated CCR is
present in all of these locations and is therefore likely present at
all locations south of the planned closure buttress. Even at those
locations where pinpoint estimates of waste bottom elevations exceeded
the groundwater elevation values, there were also immediately adjacent
measurements indicating lower elevations of CCR that were below
groundwater elevation values. For example, in the GS-AP-MW-15 area,
estimates of waste bottom elevations varied by over 52 feet: at the
lower end of the range in Finger 6, EPA estimates there are 13 feet of
saturated CCR, compared with over 65 feet of saturated waste in the
adjacent main valley of the unit (i.e., station 70+00 on section B-B'
on construction drawing G-204). The only area arguably without any
saturated CCR is the extreme southern tip of the unit; on July 18,
2022, groundwater elevation values at GS-AP-MW-18 indicate that the
waste is above the water table. However, groundwater elevation values
measured at the closely adjacent well, GS-AP-MW-18R, which is also
screened in the Pratt strata, but more shallowly at elevations
comparable to the waste, on the same day, indicate approximately 63
feet of saturated waste.
    According to the Closure Plan, it appears that dewatering may have
commenced relatively recently in 2022, so the measured groundwater
elevations described above from 2022 may not reflect early stage
decreases in hydraulic head within the unit from any initial dewatering
efforts. But as discussed below, the Closure Plan contains neither
meaningful details nor supporting analysis to demonstrate that the
saturated CCR in the consolidated southern portion of the unit will
ever be dewatered sufficiently to meet the performance standards in
Sec.  257.102(d)(2). Moreover, as discussed below, in the absence of
any engineering measures that would effectively prevent the continued
migration of groundwater into the closed unit, there is no information
in the Permit Application that suggests any meaningful decline is
likely in the groundwater elevations proximal to and within the CCR
unit. Significant thickness of saturated waste is therefore expected to
persist in the areas south of the closure buttress where CCR is still
present at elevations at or above the basal excavation level for the
consolidation effort (i.e., > 270 ft above MSL).
(1) In Order To Close the Ash Pond With Waste in Place Effective
Engineering Measures Must Be Implemented
    The fact that prior to closure the base of the Ash Pond intersects
with groundwater does not mean that the unit may not ultimately be able
to meet the performance standards in Sec.  257.102(d) for closure with
waste in place. Depending on the site conditions a facility may be able
to meet these performance standards by demonstrating that a combination
of engineering measures and site-specific circumstances will ensure
that, after closure of the unit has been completed, the groundwater is
no longer in contact with the waste in the closed unit. In this case
EPA is proposing to determine that the approved Closure Plan fails to
demonstrate that either performance standard in Sec.  257.102(d) will
be met. In addition, neither the approved Closure Plan nor the Permit
requires any engineering measures, such as the slurry wall proposed for
Plant Greene, described in Unit IV.C.4 of this preamble, or a
groundwater extraction system (e.g., pumping wells) to control

or prevent the continued infiltration of liquids (groundwater) into the
CCR from the sides and beneath. Nor does the approved Closure Plan or
the Permit require any engineering measure that will effectively
control releases of leachate to the groundwater. Based on these facts,
and as discussed in more detail below, EPA is proposing to determine
that the approved Closure Plan fails to demonstrate that the closure at
Plant Gorgas will meet the Federal performance standards in Sec.
257.102(d) or an equally protective alternative State standard.
ii. Consistency With 40 CFR 257.102(d)(2)
    As discussed previously, the Federal CCR regulations applicable to
surface impoundments closing with waste in place require that ``[f]ree
liquids must be eliminated by removing liquid wastes or solidifying the
remaining waste and waste residues, [and] remaining wastes must be
stabilized sufficient to support final cover system.'' 40 CFR
257.102(d)(2). But due to the lack of meaningful details and supporting
analysis in the Closure Plan, EPA is proposing to determine that the
Closure Plan approved by ADEM does not demonstrate that the proposed
closure at Plant Gorgas will meet either standard.
    According to the approved Closure Plan, various dewatering
techniques will be employed before and during closure; however, the
Closure Plan appears to largely limit the use of these techniques to
the CCR in the northern portion of the unit that will be excavated and
transported to the consolidated area, and to the areas under the new
Closure Buttress.\75\ For example, in the sections specifically
discussing dewatering, the Closure Plan states:
---------------------------------------------------------------------------

    \75\ Alabama Power Company. Revised Closure Permit Application
for the Plant Gorgas Ash Pond. April 30, 2020. Revised Closure Plan
for the Plant Gorgas Ash Pond. Appendix 11, pp 7-8 (Emphasis added).

4.3 Procedures During Closure
4.3.1 Dewatering
This conceptual dewatering plan was developed to provide a summary
of the removal of free water, interstitial water, contact water, and
surface water as defined below.
 Free water--water contained in the CCR unit above the
surface of CCR material
 Interstitial water--water within the pore space of CCR
material
 Contact water--surface or ground water that comes in
contact with CCR material
 Surface water--non-contact surface water at the site that
requires management
. . .
The free water in the northern portion of the pond will be decanted
by pumping to a water treatment facility prior to discharge off-
site. The management of the free water levels in the pond are
important for site water management controls including coordination
with the proposed dredging and other construction processes.
Interstitial water levels will be monitored in critical areas to
allow for safe excavation and working on ash as needed to facilitate
construction activities.
The main pond free water management pumps will deliver water to the
water treatment plant for treatment and discharge up to a treatment
rate of 12,000 gpm. The pumping system will be equipped with a
floating intake, including a sediment curtain around the intake.

Removal of contact water will be completed within the limits of the
Ash Pond using both in-situ (in place prior to excavation/handling)
and ex-situ (after initial handling/excavation) techniques.
Dewatering of ash during closure activities includes removing water
using a variety of methods, including but not limited to passive,
gravity-based methods (e.g. trench drains, rim ditching, wick
points) and/or active dewatering methods (e.g. use of the ash
thickening plant, and in-situ pumps or well points) as needed to
allow for CCR removal and transportation. Ex-situ dewatering
techniques consist of but are not limited to the following: gravity
dewatering (settling basins and/or lateral trenching), racking and
windrowing, mechanical thickening, and absorbent desiccation.

EPA expects that Alabama Power intends to dewater the entire unit to
some extent, if only to ensure that the consolidated unit can support
the weight of the earthmoving equipment needed to grade the surface and
to install the cover system. But EPA was unable to find any discussion
of the methods that will be used to dewater the significant volumes of
saturated CCR in the southern portion of the impoundment in sufficient
detail to evaluate whether the free liquids (and not simply the ``free
water'' defined above) will be eliminated as required by Sec.
257.102(d)(2)(i). For example, on page three, the Closure Plan states
only that ``During closure, the ash pond will be progressively
dewatered as required to facilitate closure.'' And on page 5, the Plan
states

Initial stages of construction and dewatering will include lowering
of the pond levels through pumping and treatment at the onsite water
treatment facility to optimize dredge performance. Once the desired
initial free water depth is achieved in the pond, further dewatering
will occur incrementally in response to storm events in order to
maintain the free water at a relatively constant depth that will
lower as ash removal from the designated areas progresses.

    Moreover, the narrative in the Closure Plan does not explain how
the liquids within the consolidated southern portion of the unit will
be eliminated in light of the groundwater that, as described above, is
expected to continue to saturate the remaining CCR. None of the
proposed engineering measures mentioned in the Closure Plan are
discussed in sufficient detail to support a determination that the
proposed measures could effectively remove these liquids. For example,
the approved plan mentions that a leachate collection system will be
installed at the downgradient limit of the Closure Buttress but fails
to explain which liquids the proposed drain system will capture and how
well or extensively it will do so.
    However, based on the limited information available, the leachate
collection system that ADEM has approved appears to likely have only a
minimal impact on the level of liquids in the closed unit, as it is
designed to capture only a limited amount of leachate. According to the
construction drawings submitted with the Permit Application, it appears
the drain will only extend approximately 1,200 feet laterally beneath a
portion of the 274-acre impoundment and appears to rely exclusively on
gravity to direct any residual pore water or other free liquids to the
drains. In essence, the leachate collection system appears to be
designed to only collect leachate along its 1,200 foot design length,
and to only address residual leachate produced from limited pore water
within the CCR, which was perhaps expected to drain over a shorter
limited time frame, during the so-called ``dewatering phase.'' But
since not all groundwater leaving the unit will flow to the drain
system, any collection of free liquids from saturated CCR farther south
in the unit or along the eastern fingers would be purely coincidental,
even without considering the likely ongoing inputs of ``new''
groundwater (``contact water'') into the system south of the
Buttress.\76\
---------------------------------------------------------------------------

    \76\ ADEM confirmed these details during conversations with EPA
in July 2022.
---------------------------------------------------------------------------

    In addition, to be effective the leachate treatment system would
need to address not only leachate generated from short-term
``dewatering'' activities, but also the significantly greater long-term
volumes of leachate emanating from the continuously saturated CCR
resulting from ongoing groundwater inputs into the unit from the sides
and bottom. More critically, the system was not designed to handle the
volumes of ``new'' leachate that will continue to be generated from the
continued groundwater flow into the unit. The Closure Plan therefore
appears to have grossly underestimated the amount of

free liquids that will continue to flow through the saturated waste to
the face drain and associated leachate collection system.
    To illustrate this concern, EPA performed a rough estimate of
potential recharge to the groundwater system within the 1,300-acre
watershed area which contains the unit. After subtracting the 274 acres
representing the closed, capped and consolidated unit, and assuming all
precipitation directly contacting the cap will be effectively managed
by the drainage system and other engineering controls, one is left with
1,026 acres available for potential recharge to the groundwater system.
Conservatively assuming 1-ft of effective recharge to groundwater in
one year over the 1,026-acre catchment area results in approximately
334 million gallons of effective recharge. Assuming this total
effective recharge is evenly distributed over time and remains in the
catchment area that contains the unit, and all flows into the unit,
this would result in a value on the order of 636 gallons per minute of
groundwater flow focused to the subsurface CCR waste beneath the capped
unit. In other words, additional engineering controls capable of
managing (and treating as necessary) this additional ongoing input of
groundwater into the unit would be a minimum necessity for a successful
Closure Plan.
    Based on all of the above, it appears that further engineering
measures would be necessary to ensure that all free liquids are
eliminated prior to installing the final cover system, as required by
Sec.  257.102(d)(2)(i).
    Additional data are necessary to demonstrate that saturated CCR
will not be present in the base of the closed unit prior to the
installation of the final cover system. Absent such data, the permit
record does not support a finding that the remaining wastes will be
stabilized sufficiently to support the final cover system, as required
by Sec.  257.102(d)(2)(ii). If the CCR in the unit is not sufficiently
stabilized, e.g., if it has not been completely drained, differential
settlement of the CCR after installation of the cover system is
possible, especially given the substantial added load from the
consolidation of CCR from the northern portion of the Ash Pond. If the
settlement is great enough, it could cause a disruption in the
continuity, and potentially failure of, the final cover system.
Additional information is needed to determine that the permit meets
Federal requirements. This could have been accomplished either by
requiring submission of the information prior to the issuance of the
permit or by including a permit term requiring submission of the
information, along with a clause allowing for further permit conditions
if necessary.
iii. Consistency With 40 CFR 257.102(d)(1)(i)
    The available information indicates groundwater is likely to
continue to infiltrate into the unit and yet the only measures
described in the Closure Plan and the Permit to address this continued
infiltration are those taken to facilitate consolidation and cap
construction. As explained in previous sections, the exclusive reliance
on a cover system in this circumstance would not ``control, minimize,
or eliminate, to maximum extent feasible'' the post-closure
infiltration of the groundwater into the waste. 40 CFR
257.102(d)(1)(i).
    The approved Closure Plan does not adequately account for the
hydrogeology of the site, which includes complex topography,
stratigraphy, hydrology, and other complex site characteristics such as
preferential pathways (faults, mines, etc.) that make it likely that
groundwater elevations will be higher than the bottom elevation of the
surface impoundment, even after the cover system is installed. The
cover system will only prevent liquids (precipitation) from entering
directly into the unit from the surface/top of the unit. But as shown
on the construction drawings in the Closure Plan (e.g., drawing C-100),
precipitation will continue to fall onto the surrounding higher ground
surfaces in the catchment area beyond the lateral extent of cover
system and then percolate down below the ground surface, the underlying
aquifer will recharge and groundwater levels will continue to
infiltrate into the CCR from beneath the unit, as well as from the
sides.
    There are commonly used engineering measures that can prevent, or
at least control, the post-closure flow of groundwater into the unit;
for example, physical barriers such as slurry walls or liner systems or
by other means such as hydraulic containment systems (e.g., groundwater
extraction wells), additional backfilling to create a buffer between
the bottom of the unit and groundwater, CCR relocation, etc. EPA is
therefore proposing to determine that ADEM's approval of a Closure Plan
that relies exclusively on consolidation and cap construction to
control infiltration into the Ash Pond is inconsistent with Sec.
257.102(d)(1)(i).
    EPA is also proposing to determine that the approved Closure Plan
fails to demonstrate that post-closure releases of CCR or leachate to
the groundwater will be controlled ``to the maximum extent feasible.''
40 CFR 257.102(d)(2)(i). While a leachate collection system is proposed
in the Closure Plan, EPA was unable to find either analysis or evidence
demonstrating the extent to which the proposed leachate collection
system will control ``post-closure releases of CCR or leachate to the
groundwater to the maximum extent feasible.'' 40 CFR 257.102(d)(2)(i).
Moreover, the available information does not support a determination
that the proposed system will meet this performance standard. As
previously discussed, the leachate collection system is not designed to
control the volume of leachate that is likely to be created from the
continued infiltration of groundwater, nor does it extend underneath
the entire unit.
    In addition, there is substantial evidence that the hydrogeologic
pathways that will allow unimpeded migration of groundwater into the
unit from the bottom and sides of the unit will also allow leachate to
migrate laterally and vertically out of the unit at particular
locations. The absence of natural or engineered hydraulic barriers
along the base and sides of the unit, which allows for both
infiltration and exfiltration of liquids, will likely result in
additional releases of contaminated groundwater (i.e., ``plumes'') out
of the unit via the bottom or sides. For example, preferential
pathways, such as geologic faults and mine shafts from former mining
operations, are present beneath the unit that would be expected to draw
contamination from any uncaptured leachate down into the aquifer. The
existence of preferential pathways was clearly acknowledged in the GWMP
that was included in the Permit Application as Appendix C.\77\
---------------------------------------------------------------------------

    \77\ Alabama Power Company. Revised Closure Permit Application
for the Plant Gorgas Ash Pond. April 30, 2020. Response to Comments,
Approved Groundwater Monitoring Plan included in the October 20,
2021. For example, the following statements were made within the RTC
for the GWMP:
    [i]n-conjunction [with statements made earlier in the letter],
the geology at Plant Gorgas dictates preferential flow through coal
seams and vertical to subvertical joints, fractures, and faults.
Targeting such features for monitoring, even if stepped back from
the waste boundary, is technically justified. This because
preferential flow paths concentrate groundwater migration through
enhanced fracture interconnectivity within otherwise impermeable
rock strata. Therefore, given the travel-times described [earlier in
the letter], and the age of the facility--it was appropriate to
target these features for determining potential impacts to
groundwater.
---------------------------------------------------------------------------

    The approved Closure Plan does not account for these pathways or
otherwise evaluate how well the proposed drain system will capture
liquids. To meet the performance standard in Sec.  257.102(d)(1)(i),
the approved Closure Plan would have to show that the

leachate will be channeled to the leachate collection system rather
than to the preferential pathways, EPA was unable to find anything in
the Permit Application or permit record to show that either Alabama
Power or ADEM made any such showing. As discussed previously, the
available information indicates that the face drain and under-designed
leachate collection system would likely be ineffective in preventing
such releases, given the under-designed leachate collection system.
b. Plant Gorgas Groundwater Monitoring Issues
    The Final Permit incorporated the GWMP submitted with the Permit
Application, and directed Alabama Power to comply with the State
regulations and the approved plan:

A. Groundwater Monitoring System. The Permittee shall install and/or
maintain a groundwater monitoring system, identified in Table 1, as
specified in 335-13-15-.06(2) and the approved groundwater
monitoring plan.

Once ADEM approved and adopted the GWMP into the permit, the GWMP,
rather than the referenced State regulations, became the State
requirements with which the facility is required to comply.
    Based on EPA's review of the approved GWMP, EPA is proposing to
determine that the groundwater monitoring well network approved by ADEM
does not meet the performance standards in Sec.  257.91(a) or (b). As
discussed in more detail below, EPA is proposing to determine that the
groundwater monitoring system does not ``yield groundwater samples from
the uppermost aquifer,'' but has been screened instead in only a
portion of the aquifer. 40 CFR 257.91(a). EPA is also proposing to
determine that approved groundwater monitoring system is not based on a
thorough characterization of any of the elements listed in Sec.
257.91(b). Further, EPA is proposing to determine that the approved
monitoring system inappropriately includes numerous downgradient
monitoring wells that are not located at the waste boundary. See 40 CFR
257.91(a)(2). In addition, based on the documentation provided in the
Permit Application, it appears that there are an insufficient number of
monitoring wells at necessary locations and depths to meet the Federal
performance standards for either the background wells or the compliance
wells. See, 40 CFR 257.91(a)(1)-(2). Therefore, EPA is proposing to
determine that ADEM's Final Permit fails to require Alabama Power to
achieve compliance with either the Federal regulations or with an
equally protective State requirement.
i. Failure To Delineate the ``Uppermost Aquifer''
    The Federal regulations require that a groundwater monitoring
system sample ``the uppermost aquifer,'' which is defined as ``the
geologic formation nearest the natural ground surface that is an
aquifer, as well as lower aquifers that are hydraulically
interconnected with this aquifer within the facility's property
boundary.'' 40 CFR 257.53, 257.91(a). The design of the monitoring
systems must be based on a thorough characterization of, among other
things, the ``aquifer thickness, groundwater flow rate, groundwater
flow direction including seasonal and temporal fluctuations in
groundwater flow; and saturated and unsaturated geologic units and fill
materials overlying the uppermost aquifer, materials comprising the
uppermost aquifer, and materials comprising the confining unit defining
the lower boundary of the uppermost aquifer.'' 40 CFR 257.91(b)(2). EPA
is proposing to determine that ADEM approved a groundwater monitoring
plan that does not meet these requirements.
    Based on the limited information in the permit record, it appears
the facility failed to define both the upper and lower limits of the
uppermost aquifer. The GWMP provided in the Permit Application provides
only limited characterization of the geologic units beneath the Ash
Pond. In addition, the technical information provided in the Permit
Application and available on Alabama Power's CCR website is
insufficient to support a determination of the lateral and vertical
limits of the entire uppermost aquifer; for example, EPA found only
limited data on the ``saturated and unsaturated geologic units and fill
materials overlying the uppermost aquifer and materials comprising the
uppermost aquifer.'' 40 CFR 257.91(b)(2). And EPA was only able to find
limited and conflicting information about the ``materials comprising
the confining unit defining the lower boundary of the uppermost
aquifer.'' Id. In the absence of such key information it is impossible
to determine that the monitoring system adequately covers the entire
uppermost aquifer, which includes all ``lower aquifers that are
hydraulically interconnected'' with the aquifer nearest the ground
surface. 40 CFR 257.53 (definition of ``uppermost aquifer'').
Nevertheless, ADEM approved Alabama Power's GWMP unconditionally.
    A representation of the various aquifers beneath the Ash Pond can
be obtained by examining the cross sections found in the 2021 Remedy
Selection Report.\78\ The uppermost aquifer may be described in its
most basic expression as a ``layer cake'' with interbedded layers of
sub-horizontal sedimentary rocks. As depicted in these cross sections,
for example Figure 9B of Appendix B of this report, for instance the
aquifer nearest the ground surface is shown as the Cobb Group. A
portion of the Cobb Group is present in higher elevations of the site,
overlying the Pratt Group. Both the Cobb and Pratt Groups are part of
the regionally significant Pottsville Formation. Coal beds known to be
present regionally in the Cobb Group were not identified near the unit
and Cobb Group rocks near the unit consist of sandstones, mudstones,
and shales. Some individual sandstone beds are depicted as having
thicknesses of over 50 feet as well as significant lateral extent, on
the order of thousands of feet. The Cobb Group also contains thick
laterally extensive mudstones, and the mudstones are interbedded with
thinner sand layers in the northern part of the unit. The aggregate
thickness of the Cobb Group is on the order of 200 to 250 feet or more
at the unit. As the stratigraphically highest rock layer, the Cobb
Group thickness varies across the unit due to differences of the
uppermost surface elevation of the Cobb Group resulting from
differential erosion. Alluvial materials and/or fill deposits rest
unconformably and discontinuously on top of the Cobb Group's upper
erosional surface in many areas of the unit, particularly to the south.
These Cobb Group stratigraphic intervals are poorly characterized in
comparison to the underlying Pratt Group, with few monitoring wells
installed in the Cobb Group rocks.
---------------------------------------------------------------------------

    \78\ Southern Company Services. 2021 Groundwater Remedy
Selection Report, Alabama Power Company Plant Gorgas Ash Pond.
Prepared for Alabama Power Company. December 2021.
---------------------------------------------------------------------------

    The upper part of the Pratt Group includes interbedded sandstones,
siltstones, mudstones, as well as several distinct coal beds. The
uppermost of these named coal beds is the Pratt Coal Seam and
associated layers, but additional named coal seams are present at
successively deeper levels, as described in Section 3 of the approved
GWMP: ``The Pratt Coal Group generally contains three named coal seams
each separated by 10 to 30 feet of intraburden. In descending order,
they are, the Pratt, Nickel Plate, and American coal seams.''
    Beneath the upper part of the Pratt Group and its named coal seams,
a significant thickness of interbedded

sandstones and mudstones on the order of 50 feet or more is present.
These intervals are described as the Lower Pratt Group, which has
received comparatively little characterization and few monitoring
wells. The Pratt Group, including both the lower and upper portions, is
depicted as having an aggregate thickness of approximately 200 feet
beneath the unit. Differential erosion, particularly within the main
channel-like finger of the Ash Pond, has locally resulted in alluvial
materials and/or fill deposits resting unconformably on top of the
Pratt Group's upper erosional surface, particularly in the central part
of the unit.
    In the southern portion of the unit, the Gillespy Group, also of
the Pottsville Formation, is shown on cross sections as underlying the
Pratt Group at great depths, but characterization of this interval is
extremely limited. The cross sections in the 2022 Semi-Annual
Groundwater Monitoring and Corrective Action Report show that the
Gillespy Group also has an aggregate thickness on the order of 200
feet, yet the upper and lower contacts between the Gillespy and
underlying and overlying layers is poorly characterized, particularly
with respect to the lower contact, and the thus the variability and
full vertical extent (i.e., thickness) of the Gillespy Group under the
Ash Pond has not been precisely determined. On cross section F-F'
(Figure 4F), the Gillespy Group is depicted as just over 200 feet in
thickness. The cross section also depicts the contact with the
underlying Mary Lee Group mudstones at a depth of several hundred feet
below the unit at a corresponding elevation just above MSL. However, it
is not clear what data informs this interpretation as no borings are
known to have penetrated the full thickness of the Gillespy Group near
the unit based on the cross sections and monitoring well installation
details. As such the true thickness of the uppermost aquifer and
hydraulically connected aquifers is not known, nor has it been
established whether the Gillespy Group constitutes an effective lower
confining unit to the uppermost or aquifer system. See 40 CFR
257.91(b). It is also notable that the elevation of the top of the
Gillespy Group is relatively high near the northern part of the unit,
and differential erosion has resulted in deposits of overburden,
alluvium and/or fill, including fill/dam materials resting
unconformably on top of the upper part of the Gillespy Group in the
northern part of the unit, as shown of cross section F-F'.
    The additional relevant geologic aspects of the aggregate layering
which constitutes the uppermost aquifer system includes faulting and
folding of the layering. Following the ``layer cake'' analogy, the
layers of rocks have been disrupted locally on several steep fault
lines that predominantly strike north-northwest in the vicinity of the
unit, as such the ``layer cake'' package of rocks has been disrupted
and contains many distinct ``slices'' separated by these faults. The
faults indicate significant vertical offset on cross sectional
representations, and the rock layers are locally bent or ``folded''
near these fault structures, resulting in steeper dips. The entire
package has been slightly tilted regionally to the south as if the
northern end of the ``layer cake's serving platter'' had been lifted
slightly.
    The final element, following the ``layer cake'' analogy, is the
``icing on the cake.'' Like drizzled icing, unconsolidated fill and
alluvial materials irregularly cover the tilted, faulted, and eroded
surface of the ``layer cake'' of rock layers. It is expected that
overburden including alluvial materials (e.g., sands and gravels)
originally present as stream deposits in the incised erosional stream
valleys were covered by the introduced CCR materials. These buried
alluvial materials therefore represent the uppermost veneer of the
uppermost aquifer system. Since there are few wells screened in these
former stream valleys, this element of the uppermost aquifer system is
significantly underrepresented in the monitoring network.
(1) Uppermost Aquifer
    Within this complex ``layer cake'' geology of variable sedimentary
layering, Alabama Power screened most of its monitoring wells in the
Upper Pottsville Aquifer system, which is described in Section 3.2.2 of
the 2022 Semi-Annual Groundwater Monitoring and Corrective Action
Report as follows:

Groundwater occurs in the Pratt Coal Group of the Upper Pottsville
Formation at the site. The primary occurrences of groundwater in the
uppermost aquifer are: (1) coal seams, (2) rock fractures or zones
of fracture enhanced permeability, and to a lesser extent (3)
bedding planes. Fractured intervals are sparse across the site as
defined by caliper logging and tend to occur with greater density in
the upper 100 feet of rock.
Groundwater yield at the site is considered low and typical of the
Pottsville aquifer system in areas without major geologic
structures. Wells were generally screened in the Pratt coal seam or
across groundwater yielding fractures. Depth to groundwater
producing zones were highly variable at the site and typically
ranged from 30 to 240 feet BGS.

It is further noted in Section 3.2.3 of the 2022 Semi-Annual GWMCA
Report that,

Groundwater flow is accomplished primarily by means of fracture
flow, where groundwater flows along more conductive secondary
discontinuities in the rock mass such as joints or cleat fabric in
coal seams. Fracture flow in complex geologic media such as the
heterogenous Pottsville Formation can be complex. Groundwater in the
Pottsville aquifer is most commonly regarded as confined due to
large permeability contrasts within the aquifer (Stricklin, 1989).
The Pottsville at the Site is probably better described as a series
of discrete, confined to semi-confined, groundwater yielding zones
where groundwater elevations can vary significantly laterally and
vertically and are governed by the heterogeneity of the lithology
and degree of fracture network interconnectivity . . . .
    At higher stratigraphic intervals (water-table flow system),
groundwater flows towards the Ash Pond or other surface water
bodies. This flow system is driven by gravity and mimics the
topography of the site. Within deeper rock strata such as coals of
the Pratt Group (Pratt Coal Group or deep bedrock flow system),
groundwater flows radially away from the site.

Most of the characterization and monitoring is concentrated in the
named coal seams of the Pratt Coal Group, and three primary flow
systems (i.e., aquifers) have been identified, as follows:

    At the Site, the groundwater flow regime is now grouped into
three general flow systems: (1) shallow water-table flow system, (2)
Pratt Coal flow system, and (3) American Coal flow system.

    In this system of nomenclature, the Nickel Plate Coal Seam is
generally included within the Pratt Coal System. EPA also noted that
the Pratt Coal System and the American Coal Systems are mapped together
and separately in different groundwater monitoring reports. For
example, the approved GWMP (Figure 6B) has them mapped together and the
2020 Annual GWMCA Report \79\ has them mapped separately (Figures 6B
and 6C). Accordingly, subsequent references to aquifers in the coal
seams, below, if not specifically described as the ``Pratt'' or
``American'' aquifers, describe the three coal seam flow systems of the
Pratt Coal Group jointly as an aggregate combined system.
---------------------------------------------------------------------------

    \79\ Southern Company Services. 2020 Annual Groundwater
Monitoring and Corrective Action Report, Alabama Power Company Plant
Gorgas Ash Pond. Prepared for Alabama Power Company. January 31,
2021.
---------------------------------------------------------------------------

    In addition to the three systems designated above (shallow water
table, Pratt, and American), lower intervals of the stratigraphic
section have been designated \80\ as another (fourth) system, which is
primarily localized to the northern part of the unit in the vicinity

of the Ash Pond dam and northward.\81\ In this area, the geologic units
located at depths corresponding to the transition zone from the lower
Pratt Group to rocks of the underlying Gillespy Group are mapped
together as the ``Base of Pratt to Gillespy Transition'' aquifer zone.
This interval is at much higher elevations in the northern part of the
site than in the southern portion. In any case, based on these aquifer
designations various interpretive representations of groundwater flow
have been constructed and were provided in the Permit Application and
annual monitoring reports. Based on these interpretations, in the Cobb
Group, above the Pratt Coal Group, groundwater is within an unconfined
aquifer and flows toward the unit. Within the Pratt Coal Group,
groundwater flow is interpreted to be mainly within the American and
Pratt Aquifers and flows radially away from the unit. However, these
interpretations are informed by insufficient data considering the large
geographic area represented by the Ash Pond as well as the topographic
and hydrogeologic complexity. The Ash Pond is approximately 500 acres
and sits within a watershed of roughly 1,300 acres with hundreds of
feet of topographic relief. The small number of wells installed in each
of the respective aquifer layers simply does not allow for a sufficient
level of resolution regarding the true configuration of the
potentiometric surface and related groundwater flow directions. As
such, the interpretations represented by the various potentiometric
surface contour maps included in the 2022 Semi-Annual GWMCA Report
contain a large degree of uncertainty.\82\ For example, there are just
a few wells screened in the unconfined materials above the coal seams.
Figure 6A of the 2022 Semi-Annual GWMCA Report, entitled Potentiometric
Surface Contour Map (Upper) Water Table Aquifer, February 7, 2022,
Plant Gorgas Ash Pond, is based on just 10 water level monitoring
points over an area hundreds of acres in size. Figure 6B of the same
report Potentiometric Surface Contour Map, Pratt Aquifer, February 7,
2022, is based on just 31 water level monitoring points over the same
area. Figure 6C of the same report is entitled Potentiometric Surface
Contour Map, American Aquifer, February 7, 2022. This interpretation is
based on just 21 water level monitoring points over the same immense
area. Lastly, there are a limited number of water level monitoring
points (13) that intersect the Gillespy; nearly all of the these are
screened across the interface between the Gillespy and the lower part
of the Pottsville Formation (see inset map on Figure 6B) entitled,
Generalized Potentiometric Surface Contour Map--Base of Pratt to
Gillespy Transition (North of Dam). In summary, given the large size of
the Ash Pond and the surrounding area, interpretations of the flow
systems are highly generalized because of the limited number of
monitoring points in each hydrostratigraphic units.
---------------------------------------------------------------------------

    \80\ Id.
    \81\ Southern Company Services. 2022 Semi-Annual Groundwater
Monitoring and Corrective Action Report, Alabama Power Company Plant
Gorgas Ash Pond. Prepared for Alabama Power Company. July 31, 2022.
See inset map entitled, ``Generalized Potentiometric Surface Contour
Map--Base of Pratt to Gillespy Transition zone (North of Dam)''
included on Figure 6B.
    \82\ Id.
---------------------------------------------------------------------------

    Additionally, the nature of the lower boundary of the aggregate
``uppermost aquifer'' system has not been sufficiently characterized or
monitored due to the limited number of wells installed into this zone,
and the documented importance of fracturing, where present, such as in
the subsurface beneath the unit, and its association with increased
permeability values. This issue is discussed below. A key consideration
with respect to the base of the Pratt to Gillespy transition is whether
this transitional formation contact represents the boundary between the
materials comprising the ``uppermost aquifer,'' and materials
comprising the ``confining unit defining the lower boundary of the
uppermost aquifer.'' 40 CFR 257.91(b)(2). It is asserted in the 2022
Semi-Annual GWMCA Report that,

Except for the far northern portion of the Ash Pond, conceptually,
there is likely to be little hydraulic communication with strata
deeper than the sandstone unit immediately underlying the American
Coal Seam (American Coal Flow System). Below this interval, a low
permeability mudstone to interbedded mudstone-sandstone unit likely
forms a barrier to vertical migration of groundwater as hydraulic
conductivity values in the 10-\7\ centimeter per second
(cm/s) range are reported for shales at the site as derived from
packer testing. This interval reflects the transition to Gillespy
Coal Group.

    Additional information presented in the same report presents
contradictory information regarding the confining potential of the
basal portion of the Gillespy Coal Group:

However, to the north and underlying the Ash Pond dam, strong
hydraulic gradients likely force groundwater along vertical
fractures and bedding planes through the upper part of the Gillespy
Coal Group. Geophysical and hydrophysical logs obtained in well
locations north of the dam suggest that three to four discrete
bedding planes occurring between 30 and 90 ft BGS transmit
groundwater. The most prominent typically occurring at a depth of 49
to 56 ft BGS (likely Gillespy equivalent; approximately 100 feet
below American Coal Seam).

    The potential for vertical flow, within the Gillespy is further
described as follows:

Strong upward vertical gradients are observed in paired well
locations (see groundwater elevations in MW-6S/6D and MW-41HS/HD
pairs) installed north of the ash pond dam. Potentiometric data
suggests upward vertical flows along with northerly lateral flow.

Lastly, the same report discusses permeability test results, which
again present an inconsistent picture of the Gillespy formation's
potential to act as a ``confining unit defining the lower boundary of
the uppermost aquifer,'' as follows:

Forty-three packer tests were conducted resulting in a range of
hydraulic conductivity (k) values from an estimated low of 7 x
10-\7\ cm/sec to a high of 4 x 10-\3\ cm/sec,
with most tests (31) in the moderate range (10-\5\ cm/sec
to 10-\4\ cm/sec), two test results in the more permeable
range (10-\3\ to 10-\2\ cm/sec), and ten test
results in the less permeable range (10-\6\ cm/sec).
There is a general trend of decreasing estimated hydraulic
conductivity with depth. Packer test results vary over 4 orders of
magnitude. Test intervals at the high end of the data range are
associated with weathered discontinuities (fractures/joints).
Moderate values are associated with minor fractures or bedding
planes. The lowest values are associated with more shale intervals
without substantial fractures. Test intervals with coal seams are in
the moderate to high end of the data range.

    EPA disagrees that this information supports a determination that
the lower part of the Gillespy formation constitutes a ``confining unit
defining the lower boundary of the uppermost aquifer.'' The totality of
the information instead supports the opposite conclusion. Since
vertical flow is clearly a recognized phenomenon within the Gillespy
within the northern part of the unit, and this flow is described as
being associated with fractures,\83\ it is logical to expect similar
vertical flow and enhanced permeability in other areas where fractures
are present. Given the prevalence of steeply dipping north-northwest
striking fracturing in the area, as well as the likelihood that the
linear valley that underlies the unit, which also strikes north
northwest, is also controlled by underlying fractures of this
orientation, it is reasonable to expect enhanced flow potential along

and in the vicinity of these fractures where they may exist. Since the
subsurface directly beneath the unit is likely the locus of such
fracturing (see Unit IV.C.3.b.i.(4)(c) of this preamble for more
information on the existence of preferential pathways), it is logical
to determine that vertical permeability is high beneath the unit where
it matters most. In other words, this situation suggests that rather
than a ``confining unit defining the lower boundary of the uppermost
aquifer,'' the near vertical fracturing which penetrates all units (see
cross sections), including the Gillespy, creates the opposite condition
in the uppermost aquifer system, directly beneath the unit. It is
therefore unlikely that the uppermost aquifer beneath the Ash Pond has
been adequately characterized, and its full thickness in the vertical
dimension remains unknown based on the information in the permit
record. As was noted above, the lowest measured permeability values are
associated with shale intervals without substantial fractures. Although
conditions are not sufficiently documented directly beneath the unit,
the likely presence of fractures here would be expected to invalidate
the presence of ``shale intervals without substantial fractures,'' and
hence the ``lowest measured permeability values,'' while present in
other areas around the unit, would likely not be present directly
beneath the unit.
---------------------------------------------------------------------------

    \83\ Southern Company Services. 2022 Annual Groundwater
Monitoring and Corrective Action Report, Alabama Power Company Plant
Gorgas Ash Pond. Prepared for Alabama Power Company. January 31,
2023. Section 3.2.3.
---------------------------------------------------------------------------

    In sum, the uppermost aquifer system- that is, the aquifer nearest
the ground surface and the underlying aquifers that are hydraulically
connected to it--has not been fully assessed. EPA's assessment of the
available information is that there are at least four flow systems that
are appropriately considered the ``uppermost aquifer'' at the Ash Pond:
(1) the upper unconfined water table (locally includes unconfined Cobb
Group); (2) the Pratt Coal seam; (3) the American Coal seam; and (4)
the Lower Pratt/Gillespy Transition zone.
    The geologic units above and beneath the coal seams are sandstones
and interbedded sandstones with mudstone or shale, and both are capable
of storing and transmitting groundwater, and therefore should have been
more fully characterized and included in the monitoring network. In
particular, the depth of the lower confining unit has not been
established, and as such, the full extent of the uppermost aquifer
system has not yet been established in the vertical (depth) dimension.
At several locations, the geologic units immediately below detected
groundwater contamination are entirely uncharacterized and unmonitored.
This situation hobbles the monitoring network's ability to identify and
evaluate potential migration of contaminated groundwater out of the
unit at the lower levels, which is discussed further in Unit
IV.C.3.b.i.(4)(b) of this preamble.
(2) Background Wells Do Not Meet the 40 CFR 257.91(a)(1) Performance
Standard
    The Federal CCR regulations require that a groundwater monitoring
system consist of a sufficient number of wells at appropriate locations
and depths to yield samples from the uppermost aquifer that accurately
represent the quality of the background groundwater that has not been
affected by leakage from a CCR unit. 40 CFR 257.91(a)(1). The
regulations also specify that background wells must normally be
hydraulically upgradient of the CCR unit unless specific showings have
been made. See, Id. EPA is proposing to determine that the approved
GWMP fails to document either that the background wells are upgradient
of the CCR unit or that the wells meet the performance standards in
Sec.  257.91(a)(1)(i) or (ii). EPA is also proposing to determine that
the background wells in the approved groundwater monitoring system do
not ``accurately represent the quality of the background groundwater''
because no background wells were installed in the lower flow systems of
the uppermost aquifer: i.e., the Pratt Coal seam; the American coal
seam, and the Lower Pratt/Gillespy Transition Zone.
    Four groundwater monitoring wells have been used at various times
to characterize background water quality (GS-AP-MW-8, GS-AP-MW-13, GS-
AP-MW-16S, and GS-AP-MW-17V). One of the wells, GS-AP-MW-13 was
installed in 2016 and later abandoned in 2019. The three remaining
monitoring wells (GS-AP-MW-8, GS-AP-MW-16S, and GS-AP-MW-17V) were
installed exclusively in the upper flow system (i.e., in the upper
water table aquifer/unconfined Cobb Group formation), where Alabama
Power has concluded that groundwater flows toward the Ash Pond. No
background wells were ever installed in the three lower flow systems of
the uppermost aquifer, which is where contamination is currently
present.
    According to the 2021 Plant Gorgas Annual GWMCA Report, to the
north and underlying the Ash Pond dam, strong hydraulic gradients force
groundwater along vertical fractures and bedding planes through the
upper part of the Gillespy Coal Group toward the Ash Pond.\84\ The
approved GWMP also provides details regarding vertical gradients and
the potential for using monitoring wells in the shallow flow system as
background wells. For example, page 10 states:
---------------------------------------------------------------------------

    \84\ Southern Company Services. 2021 Annual Groundwater
Monitoring and Corrective Action Report Alabama Power Company Plant
Gorgas Ash Pond. Prepared for Alabama Power Company. January 31,
2022.

It is because vertical flow is the dominant mechanism for movement
through these flow systems and that is a function of the Pottsville
operating as a series of discrete, confined to semi-confined
groundwater yielding zones. Upgradient well locations monitor
younger, recharging waters that will eventually migrate vertically
---------------------------------------------------------------------------
downward into groundwater yielding zones of the Pratt Coal Group.

    Based on the limited data available it appears that groundwater in
the upper water table (or un-confined Cobb) aquifer may migrate
downward into the lower flow systems due to vertical hydraulic
gradients. However, as discussed at length above, these interpretations
contain a large degree of uncertainty because they are informed by very
little data, given the size of the Ash Pond as well as the topographic
and hydrogeologic complexity of the site. The complexity of the site is
of particular concern here; in addition to the compositional
variability of the layers, differential fracturing also creates
variable hydraulic conditions which needed to be carefully considered
in selecting upgradient background well locations. Lastly, the wells
currently selected for background monitoring ignore horizontal flow in
the lower flow systems where groundwater contamination is present and
migrating laterally. EPA is proposing to determine there is
insufficient data to conclude that the approved background wells meet
the performance standards in Sec.  257.91(a)(1).\85\
---------------------------------------------------------------------------

    \85\ Because Alabama Power believes the background wells to be
hydraulically upgradient, the Permit Application did not include a
demonstration that the background wells will be ``as representative
or more representative'' as hydraulically up gradient wells. 40 CFR
257.91(a)(1)(ii).
---------------------------------------------------------------------------

    EPA is also proposing to determine that there are insufficient
number of background wells in the approved groundwater monitoring
system. As discussed in the preceding section, there are at least four
flow systems that would each require background wells focused on the
specific hydrogeologic conditions in each of these zones: (1) The upper
water table aquifer; (2) The Pratt Coal seam; (3) The American Coal
seam; and (4) The Lower Pratt/Gillespy Transition zone. In addition to
these

four, it remains unclear whether other flow systems should have been
included in the monitoring program, which would require the
installation of appropriate zone-specific background wells. For
example, the Cobb Group appears to contain multiple permeable sandstone
units, as do portions of the Pratt Group both above and below the named
coal seam aquifers. It would appear that background wells should have
been installed in one or both of these geological formations to capture
this geologic variability. As noted above, in addition to the
compositional variability of the layers, differential fracturing also
creates variable hydraulic conditions that needed to be more carefully
considered in selecting background well locations.
    The Federal regulations require a monitoring well system that
accurately represents the quality of background groundwater. 40 CFR
257.91(a)(1). Background concentrations need to be determined for the
entire uppermost aquifer system and must be supported by an explanation
of the hydraulic and geologic factors that validate the selection of
particular locations as representative background conditions. If the
uppermost aquifer varies laterally and vertically in terms of geology
and chemical composition, it is necessary for the background monitoring
wells installed to adequately reflect this same range of variability
(i.e., representative conditions in these same layers absent CCR-
related impacts). This requires enough monitoring wells to capture the
variability represented by the natural system in appropriate
dimensions, such as lateral and/or vertical variability. Consequently,
in cases of multiple flow systems comprised of variable geology, as a
first order requirement, background wells in each hydrostratigraphic
unit of interest would be technically necessary.
    The specific conditions at Plant Gorgas further illustrate this;
the geochemistry of the groundwater within the shallow water table
aquifer (consisting of younger groundwater within sandstone and shales)
would not represent the geochemistry of deeper flow systems (consisting
of older groundwater within interbedded sandstones with coal seams). It
is also uncertain how unique conditions in the lower flow systems, such
as the presence of coal seams and current and historical mining
operations could affect background water quality in the lower flow
systems.
    In summary, the uncontaminated ``flavors'' (i.e., representative
conditions) of each relevant aquifer zone need to be established to
provide a representative direct comparison relative to CCR impacts in
these same zones on an ``apples to apples'' basis. However, the
approved background monitoring system is insufficient in terms of
general numbers of background monitoring wells as well as a general
failure to include background monitoring in key sub-elements of the
layered hydrogeologic system representing the uppermost aquifer. It
therefore does not appear to accurately represent the full range of
``background'' conditions in the uppermost aquifer.
(3) Compliance Wells Are Not Installed at the Downgradient Waste
Boundary
    40 CFR 257.92(a)(2) requires that downgradient compliance wells
``be installed at the waste boundary that ensures detection of
groundwater contamination in the uppermost aquifer.'' The waste
boundary is ``a vertical surface located at the hydraulically
downgradient limit of the CCR unit. The vertical surface extends down
into the uppermost aquifer.'' 40 CFR 257.53. Notwithstanding this clear
direction, most wells in the monitoring network installed at Plant
Gorgas were located far from the waste boundary. Yet ADEM approved the
system without condition or revision.
    For example, EPA evaluated well placement along a north to south
transect, south of the buttress, along the west side of the main valley
containing CCR. From north to south, this included, GS-AP-MW-9, -10, -
11, 12, -13, -14, -47, -15, -16, and -18. This transect is
approximately 8,400 feet in length, or over a mile and a half. Over
this distance the monitoring wells were located from 55 feet to 510
feet away from the waste boundary, with and average distance from the
waste boundary near 295 feet. On average, over the entire unit,
monitoring wells here were located approximately 740 feet from the
waste boundary.
ii. Insufficient Locations and Depths of Downgradient Compliance Wells
To Monitor the Uppermost Aquifer
    As previously discussed, the Federal regulations specify that a
groundwater monitoring system must ``consist[ ] of a sufficient number
of wells, installed at appropriate locations and depths, that . . .
accurately represent the quality of the groundwater passing the waste
boundary of the CCR unit.'' 40 CFR 257.91(a)(2). The regulations
further specify that ``[a]ll potential contaminant pathways must be
monitored.'' Id. But the groundwater monitoring system that ADEM
approved meets none of these requirements. As discussed in more detail
below, EPA is proposing to determine that ADEM approved a GWMP with an
insufficient number of wells laterally along the downgradient perimeter
of the unit to monitor all potential contaminant pathways. EPA is also
proposing to determine that monitoring wells in the approved plan were
not installed at appropriate depths to ensure that all potential
contaminant pathways were monitored. Finally, EPA is proposing to
determine that the approved groundwater monitoring system fails to
account for preferential pathways beneath the Ash Pond.
(1) Insufficient Lateral Spacing of Compliance Wells To Monitor All
Potential Contaminant Pathways
    The majority of the compliance wells along the perimeter of the
Plant Gorgas Ash Pond are spaced hundreds and sometimes thousands of
feet apart. For example, only a single detection monitoring well (GS-
AP-MW-2) was installed near the waste boundary to monitor groundwater
over a large area flowing from the Plant Gorgas Ash Pond along the
northeastern boundary. The lateral distances from GS-AP-MW-2 to the
adjacent compliance wells to the north and south, GS-AP-MW-3, and GS-
AP-MW-1R, respectively, both approach 2,000 feet (as the crow flies).
Furthermore, the waste boundary between the two compliance wells GS-AP-
MW-2 and GS-AP-MW-1R is approximately two miles. This unmonitored two-
mile portion of the waste boundary runs along three sides of an
adjacent offsite 16-acre parcel that appears to include residential
structures. In effect, this leaves a two-mile stretch without any
compliance wells to detect contamination before it migrates off-
site.\86\ See Figure 5A in the 2021 Plant Gorgas Annual GWMCA
Report.\87\
---------------------------------------------------------------------------

    \86\ Two wells (GS-AP-MW-43H and GS-AP-MW-44HO) are also
situated in the vicinity of the adjacent offsite 16-acre parcel, but
these wells are designed to horizontally delineate the plume of
contamination that has already migrated beyond the unit boundary.
    \87\ According to a representative from the Copeland Ferry--
Pumpkin Center Water Authority Publicly Owned Treatment Works, they
serve public drinking water to residents in the vicinity of the Ash
Pond. EPA is also working to confirm whether nearby households are
on public or private water supply.
---------------------------------------------------------------------------

    This is not an anomaly, and extremely large lateral well spacings
and large lateral gaps in monitoring well coverage are not an isolated
occurrence. Prior to closure, the perimeter of the unit was roughly
14.7 miles in length, and following closure, the perimeter of the
consolidated CCR will be approximately 7.8 miles in lateral extent.\88\
Because

ADEM approved the groundwater monitoring system in its current form,
and it appears that the monitoring network will change little during
the ongoing closure activities, it is reasonable to evaluate the
lateral well spacing in terms of the current (pre-closure) perimeter,
i.e., 14.7 miles. Over this 14.7-mile unit boundary there are presently
only 30 downgradient compliance wells, indicating an average spacing of
approximately 2,600 feet, or roughly half a mile between monitoring
wells. Prior to 2021, there were only 20 downgradient compliance wells,
indicating an average lateral spacing of downgradient compliance wells
in the lateral dimension was on the order of 3,900 feet apart, or
almost three quarters of a mile.
---------------------------------------------------------------------------

    \88\ This approach is further supported in view of the fact that
the original footprint, although reconfigured, is still integral to
the overall closure strategy. Further, SSLs have been detected in
the reconfigured northern region, which will require monitoring and/
or corrective action into the future.
---------------------------------------------------------------------------

    Because wells installed to characterize the release in accordance
with Sec.  257.95(g)(1)(i) are not located on the downgradient waste
boundary and are monitored for different constituents at different
frequencies, these wells are not properly included in an evaluation of
adequacy of the detection and assessment wells installed to comply with
requirements in Sec.  257.91(a). And even if EPA were to consider the
delineation wells as part of the detection and assessment monitoring
systems, that would only bring the total number of monitoring wells to
68, which would equate to one well per every 1,150 feet of boundary.
    However, by any reasonable standard, lateral well spacings on the
order of thousands of feet would be excessive. While appropriate
lateral well spacing is site-specific, and varies from site to site,
lateral well spacing appropriate for a site such as the Ash Pond at
Plant Gorgas may be determined by several factors. These include, but
are not limited to, the character, the degree of homogeneity, and
dimensions of the emplaced waste body itself; the nature, variability,
and complexity of the subsurface geology; as well as the dynamics,
complexities, and boundary conditions of the hydraulic flow system into
which the CCR has been emplaced. A greater degree of complexity and
variability concerning these elements would translate to a greater
number of compliance wells in the lateral dimension, i.e., a smaller
inter-well spacing, for the well network to adequately monitor such a
system. Conversely, a well characterized system, based on geological,
hydrogeological, and geotechnical investigations at the site, which has
been demonstrated to be simple, stable, and uniform would allow for a
fewer number of compliance wells to capture the limited inherent
variability. In addition, factors related to resolution and uncertainty
also affect the lateral well spacing appropriate to a given site. In
this regard it should be noted that the Federal regulations indicate
clear expectations regarding expected levels of resolution, which are
generally described as that necessary to ensure that all potential
contaminant pathways in the entire uppermost aquifer are monitored,
including preferential pathways. Uncertainties and data gaps also
equate to the need for greater levels of monitoring than would
otherwise be required to compensate for these deficiencies. In other
words, if characterization data are not available to support a larger
minimum lateral well spacing, a default to a more rigid general
standard is needed, requiring more wells. At the Ash Pond at Plant
Gorgas, a much smaller lateral well spacing is needed to meet the
requirements. This is due to (1) The complexity of the buried CCR; (2)
The low resolution and extreme uncertainties in the characterization of
the groundwater flow system which encompasses the unit; (3) The
demonstrated complexity of the geologic layering in the vertical
dimension; and (4) The presence of significant localized fracturing and
numerous mapped faults which cut through the unit and surrounding
areas. In a general sense, therefore, instead of thousands of feet
apart, monitoring well spacings should have been on the order of
hundreds of feet, except where known features such as narrow buried
erosional stream valleys or fracture zones dictate even tighter lateral
spacing. For example, the lateral spacings between wells MW-9, -10, -
11, and -12 ranges from roughly 700-1,200 feet apart, yet none of these
monitoring wells were located sufficiently close together to intersect
the mapped fracture which cuts through this area of the site. A tighter
well spacing is needed to adequately characterize the site. As another
example, many wells are screened in zones which intersect underground
coal mines. These mine tunnels represent potential preferential
pathways which should have been more intensively monitored. The lateral
and vertical dimensions of these types of underground workings are
knowable and should be factored into decisions concerning appropriate
monitoring well spacings to effectively ensure these preferential
pathways are monitored. Much smaller lateral and vertical wells
spacings are necessary to meet the requirements in this scenario,
instead of wells that are thousands of feet apart.
(2) Insufficient Number of Downgradient Compliance Wells Installed at
Appropriate Depths To Monitor the Entire Aquifer (Inadequate Vertical
Spacing)
    EPA is also proposing to determine that ADEM approved a GWMP that
lacked ``a sufficient number of wells, installed at appropriate
locations and depths'' to ensure that all potential contaminant
pathways in the entire uppermost aquifer are monitored. As discussed
above, the uppermost aquifer contains at least four flow systems: (1)
the upper water table; (2) the Pratt Coal seam; (3) the American Coal
seam; and (4) the Lower Pratt/Gillespy Transition zone. A system of
compliance wells that meet the performance standards of Sec.
257.91(a)(2) must be installed in each of them. But none of the four
flow systems contain sufficient numbers of wells to meet these
standards.
    Nearly all the compliance wells installed in the three lower flow
systems were screened across the shallow coal seams located between
approximately 250 and 350 ft-MSL, i.e., in the Pratt Coal seam and the
American Coal seam. Of the eight cross sections reviewed,\89\ it
appears that only two downgradient compliance wells were screened below
the coal seams in the Lower Pratt/Gillespy Transition zone (GS-AP-MW-6S
and -6D). These wells are downgradient due to the unit's radial flow at
this depth, and two wells are insufficient to comprehensively monitor
this portion of the uppermost aquifer. First, all the monitoring wells
installed below the coal seams are focused along the western and
northern section of the unit, leaving the northeastern, southwestern,
southern, and eastern sections with little to no data in the aquifer
below the coal seams. Conservatively, this means the lower flow systems
within the Lower Pratt/Gillespy Transition for over half of the pre-
closure extent of the unit (at least 237 acres) are not being
monitored.
---------------------------------------------------------------------------

    \89\ Anchor QEA. Prepared for Alabama Power Company. Plant
Gorgas Groundwater Remedy Selection Report. December 2021. Figures
5A and 5B in the revised GWMP and Figures 9A thru 16 in the
---------------------------------------------------------------------------

    This is further corroborated by the cross-sections in Figures 11A,
14A, 15, and 16 of the Groundwater Remedy Selection Report, which
document the large portions of the uppermost aquifer below the coal
seams where no data

have been obtained.\90\ According to Figure 14A, there appears to be
only one well cluster (GS-AP-MW-6S/6V/6D) installed below the coal
seams, approximately 900 feet from the edge of the ash pond immediately
downgradient of the current dam. Given the unit's pre-closure size of
474 acres and a vast downgradient waste boundary exceeding fourteen
miles in length, this single well cluster would certainly not monitor
all potential contaminant pathways in this lower flow system.
---------------------------------------------------------------------------

    \90\ Id at pp 81, 83 of the revised Groundwater Monitoring Plan
and Figures 9A thru 16.
---------------------------------------------------------------------------

    There are also only 10 wells screened in the upper water table
(i.e., in the unconfined materials above the coal seams in the Cobb
Group). As shown in Figure 6A of the 2022 Semi-Annual GWMCA Report,
entitled Potentiometric Surface Contour Map (Upper) Water Table
Aquifer, February 7, 2022, Plant Gorgas Ash Pond, these 10 water level
monitoring points are installed over hundreds of acres, only 7 of these
are designated as compliance wells, and there is conflicting
information between the Permit Application and the most recent Annual
GWMCA Report from 2022 regarding the stratigraphic layers in which
these compliance wells are screened. For example, the 2022 Annual GWMCA
Report only indicates that two of these 7 wells are screened across the
``shallow water table.'' EPA therefore is proposing to determine that
the compliance monitoring with respect to the shallow unconfined water
table aquifer zone is not adequate to comply with the regulations.
    Similarly, based on the 2022 Semi-Annual GWMCA Report, 52 wells
were installed in the Pratt Group as a whole across the entire 274-acre
Ash Pond.\91\ Of these, based on the interpretation of the flow system
provided in the 2022 Semi-Annual GWMCA Report, water levels were
measured at 31 wells installed in Pratt Coal seam,\92\ and water levels
were measured at 21 wells screened in the American Coal seam.\93\
However, the compliance well network listed in Table 1A in the Permit
Application indicates only 15 compliance wells screened in the Pratt
coal seam zone, and only 11 compliance wells screened in the American
Coal seam.
---------------------------------------------------------------------------

    \91\ Monitoring wells screened in the Nickel Plate coal seam are
included in the Pratt Coal seam category for this discussion.
    \92\ Southern Company Services. 2022 Semi-Annual Groundwater
Monitoring and Corrective Action Report, Alabama Power Company,
Plant Gorgas Ash Pond. Prepared for Alabama Power Company. July 31,
2022. Figure 6B, Potentiometric Surface Contour Map, Pratt Aquifer,
February 7, 2022.
    \93\ Id at Figure 6C of the same report is entitled
Potentiometric Surface Contour Map, American Aquifer,
---------------------------------------------------------------------------

    Lastly, based on the interpretation of the flow system provided in
the 2022 Semi-Annual GWMCA Report, water levels were measured and
plotted for 15 wells to inform a representation of potentiometric
contours for the Base of the Pratt--Gillespy transition zone.\94\
However, these 15 wells do not appear to be screened in equivalent
levels of the transition zone and only 13 of these are listed on Tables
1A (3 Wells), 1B (8 Wells), and 1C (2 wells) in the 2022 Semi-Annual
GWMCA Report. Moreover, not all of 13 wells were included/depicted on
Figure 6B \95\ and only 3 ``Pottsville Fm--Gillespy zone transition''
wells are listed as compliance wells on Table 1A in the Permit
Application. This lack of clarity concerning the characterization and
monitoring of the transition zone between the lower Pratt Group and
Gillespy Group, supports EPA's basic conclusion above, that the base of
the uppermost aquifer has not been determined or sufficiently
characterized vertically (or laterally).
---------------------------------------------------------------------------

    \94\ Id at inset map on Figure 6B entitled, Generalized
Potentiometric Surface Contour Map--Base of Pratt to Gillespy
Transition (North of Dam).
    \95\ Id.
---------------------------------------------------------------------------

    In summary, installing so few compliance monitoring wells over such
great lateral distances and over such significant vertical intervals
cannot possibly monitor all the potential contaminant pathways at Plant
Gorgas, given the size of the Ash Pond as well as the topographic and
hydrogeologic complexity of the site.
(3) Preferential Pathways Are Not Monitored
    Numerous preferential pathways have been documented in the
uppermost aquifer under the Ash Pond. Yet under the approved GWMP, none
of these significant potential contaminant pathways appear to be
adequately monitored, despite the express requirement in Sec.
257.91(a)(2).
    The approved GWMP states that, ``Locally, Pratt Coal Group strata
gently dip (0.5[deg] to 1.0[deg]) to the south and south-southwest.
Figure 5A Geologic Cross-Section A-A' and Figure 5B Geologic Cross-
Section B-B' illustrate the geologic layering beneath the site.'' It is
immediately apparent from these cross sections that a simple, nearly
flat series of geologic layers is an overly simplistic representation
of the site. As has been noted in many reports from Alabama Power in
the permit record, the geologic layering is disrupted in many locations
by mappable faults which indicate significant displacement and have
steepened dips resulting in folding in some areas of the subsurface.
    Nevertheless, the monitoring network does not include monitoring
wells with screens deliberately targeted to these mapped faults and
associated fractures. Given the presence of these significant fault
zones, some of which have been mapped and delineated within the
aquifer, additional monitoring wells should have been installed to
detect whether CCR contaminants are migrating beyond the unit
boundaries in pathways that follow these fracture lines. As an
illustrative example, as shown on Figures 7A, 7B, 8A and 8B of the 2022
Semi-Annual GWMCA Report, a series of north-northwest striking
fractures with steep dips to the west cut through the unit. One such
fracture is mapped from the region of MW-10R north-northwestward 3600
feet (over half a mile) to the Mulberry Fork and beyond, further to the
north-northwest. Monitoring wells MW-12 and 12V are located hundreds of
feet to the east of the fault and therefore did not intersect it.
Similarly, MW-11 is too far away from the feature and too shallow, so
it also failed to intersect the feature. Ultimately it does not appear
that any monitoring wells effectively monitor this significant
potential contaminant pathway, which is particularly problematic as the
fault appears to intersect the river in the general downgradient
direction and thus has the (unassessed) potential to directly discharge
CCR-related contaminants to the river system. This natural fracture-
controlled ``pipeline'' represents a likely conduit for preferential
groundwater flow which follows the strike of the fracture and thus
represents a significant, unmonitored, potential contaminant pathway.
It is notable that none of these identified fractures are included on
Figure 5, Monitoring Well Location Map Plant Gorgas Ash Pond, of the
same report.
    Additional preferential pathways are associated with underground
mine workings which impinge on parts of the unit. Coal mining
operations, including underground workings, are also well documented in
the vicinity of the site, and coal beds have been generally targeted
for most of the monitoring well installations. But while some
monitoring points appear to be screened at the same horizon as these
underground mine workings, their lateral extent in the subsurface
remains unknown, and as such the potential for preferential pathways
which exploit these zones represents a clear data gap. For example, the
geologic cross sections included in the 2021 Plant Gorgas

Annual GWMCA Report indicate the presence of former mine shafts that
could significantly impact groundwater flow, and therefore warranted
additional characterization and focused monitoring. These pathways were
also documented in the December 2021 Remedy Selection Report, which
ADEM received 3 months prior to its issuance of the Plant Gorgas permit
in February 2022. In addition, according to the cross section in Figure
5A in the revised GWMP and Figure 12A in the Groundwater Remedy
Selection Report, at least one fault that could serve as a potential
preferential pathway for groundwater has been mapped immediately
adjacent to the Ash Pond and penetrates below the coal seams. It is
therefore another significant failure of the approved groundwater
monitoring system that it does not include wells to monitor the
targeted and delineated contaminant pathways that follow coal seams,
underground workings, or other natural and/or man-made features that
can act as preferential pathways for groundwater and contaminant
migration. See 40 CFR 257.91(a)(2). The significance of ADEM's failure
to address this deficiency is illustrated by the numerous and
documented SSIs and SSLs detected in the monitoring wells which are
screened within the coal layers.
    In summary EPA is proposing to determine that the groundwater
monitoring network ADEM approved for the Ash Pond at Plant Gorgas falls
far short of the performance standards in Sec.  257.91(a) and (b). The
uppermost aquifer has not been sufficiently characterized or monitored.
In particular, the lower limits of the uppermost aquifer and
hydraulically connected aquifers beneath it have not been defined.
Compliance monitoring wells have not been located at the waste boundary
in most locations. There are an insufficient number of monitoring wells
along the perimeter of the downgradient waste boundary, and at
insufficient depths, to monitor all potential contaminant pathways in
the entire uppermost aquifer, given the potential for radial flow in
deeper aquifer zones. Finally, numerous preferential pathways have not
been monitored.
    ADEM's permit does include a permit condition that states:

The Permittee shall install and maintain additional groundwater
monitoring wells as necessary to assess changes in the rate and
extent of any plume of contamination or as otherwise deemed
necessary to maintain compliance with [ADEM Admin. Code] 335-13-15-.
06. A plan in the form of a permit modification request should be
submitted to the Department as required by Section V.D.

However, this condition does not actually require any action that will
bring the groundwater monitoring system into compliance; for example,
by requiring the facility to fully characterize the uppermost aquifer
system or install additional monitoring wells at the waste boundary.
Or, more broadly, it does nothing to compel the facility to meet the
requirements in 40 CFR 257.91(a) and (b).
c. Plant Gorgas Corrective Action Issues
    In November 2018, the first SSLs above a groundwater protection
standard were detected at the Gorgas Plant. SSLs were reported for
lithium, arsenic, and molybdenum. The Ash Pond reported SSLs of all
three constituents; the Gypsum Pond, CCR Landfill, and Gypsum Landfills
reported SSLs of lithium only; and the Bottom Ash Landfill reported
SSLs of arsenic. One ACM was developed for all the units at the
facility in June 2019 and revised in February 2020 (``revised
ACM'').\96\ On February 28, 2022, ADEM issued a Final Permit to Alabama
Power for Plant Gorgas Ash Pond, Gypsum Pond, and Bottom Ash Landfill.
---------------------------------------------------------------------------

    \96\ Anchor QEA. Assessment of Corrective Measures, Plant
Gorgas. Prepared for Alabama Power Company. June 2019 (Revised:
February 2020).
---------------------------------------------------------------------------

    In the RTC for the Gorgas Final Permit,\97\ ADEM states:
---------------------------------------------------------------------------

    \97\ Alabama Department of Environmental Management. Initial
Permit and Variance, William C. Gorgas Electric Generating Plant,
Permit No. 64-12, Public Commenters. February 28, 2022.

In November of 2019, the Department provided extensive comments to
Alabama Power related to the submitted ACM and proposed final
remedy. The Department's comments addressed many of the concerns
raised by commenters, including the selection of monitored natural
attenuation (MNA) as the final remedy despite providing limited data
to its efficiency as a remedy. To date, Alabama Power has not
submitted a revised ACM, as the facility has been collecting
---------------------------------------------------------------------------
additional data to support a final remedy proposal.

    It appears the permit record (Final Permit and RTC) may not reflect
all the relevant information about the status of corrective actions at
Plant Gorgas that was available to ADEM when the permit was issued.
According to Alabama Power ``[a] Groundwater Remedy Selection Report
was prepared and submitted on December 17, 2021, to meet the
requirements of 40 CFR 257.97, ADEM Admin. Code r. 335-13-15-.06(8),
and Part C of ADEM Administrative Order AO 18-096-GW . . .''.\98\ The
remedy the facility selected for the Ash Pond, Gypsum Pond, and Bottom
Ash Landfill consists of closure with waste in place and capping,
permeation grouting at the Ash Pond, and MNA. Additionally, any
comments that may have been provided by ADEM to Alabama Power on the
2020 ACM were not available for review.
---------------------------------------------------------------------------

    \98\ Southern Company Services 2022 Annual Groundwater
Monitoring and Corrective Action Report, Alabama Power Company Plant
Gorgas Ash Pond. Prepared for Alabama Power Company. February 1,
2023. p 2.
---------------------------------------------------------------------------

    The Plant Gorgas Final Permit contained the same recitation of the
corrective action regulations as the other permits issued by ADEM. As
with the others, incorporating the regulations verbatim in the permit
does not require Alabama Power to achieve compliance with those
requirements at Plant Gorgas. Here as well, it appears that ADEM did
not take into account relevant facts about the status of corrective
action at Plant Gorgas, such as whether the 2020 revised ACM or the
selected remedy submitted to ADEM in December 2021 complied with the
regulatory requirements. Most importantly, ADEM did not determine what
actions are still necessary in light of those facts to achieve
compliance with the regulations and include those actions as
requirements in the Final Permit. Instead, two months later, ADEM
issued a Final Permit that was silent on the adequacy of the revised
ACM and the applicant's selected remedy. Over a year later, it does not
appear that ADEM has evaluated the adequacy of the revised ACM and the
applicant's selected remedy. As a consequence, EPA is proposing to
determine that, by remaining silent, the permit in essence authorized
Alabama Power to continue to pursue a remedy based on the results of an
ACM that does not meet the requirements of Sec.  257.96, even though
the selected remedy does not appear to meet the requirements in Sec.
257.97(b), and the ACM identified other measures that would meet those
requirements.
    Delaying a decision on the adequacy of the facility's selected
remedy until some unspecified point after permit issuance \99\
effectively allows Alabama Power to continue operating out of
compliance with the regulations, while operating in compliance with the
permit. Releases continue to migrate off-site during this delay, and in
this case, it appears the contamination may have already migrated off-
site to residential

property.100 101 The sanctioned delay in implementing an
effective remedy with no schedule for compliance results in a permit
program that is less protective than the Federal regulations.
---------------------------------------------------------------------------

    \99\ It appears that ADEM has still not evaluated either the
revised 2020 ACM or Alabama Power's selected remedy.
    \100\ Alabama Power. Letter to Mr. Taylor. Alabama Power Plant
Gorgas Ash Pond Closure and Groundwater Investigations. July 6,
2020.
    \101\ Alabama Power. Letter to Mrs. Salter. Alabama Power Plant
Gorgas Ash Pond Closure and Groundwater Investigations. October 30,
2020.
---------------------------------------------------------------------------

    EPA is proposing to determine that the Final Permit contains many
of the same issues discussed with respect to the other permits. The
Final Permit does not contain a deadline for correction and resubmittal
of the ACM to address any of the deficiencies ADEM identified in its
2019 comments, or any response to Alabama Power's selected remedy. EPA
has also identified deficiencies in the revised ACM beyond those ADEM
discussed in the RTC.
i. The Plant Gorgas Final Permit Does Not Require Collection of Site
Data Needed To Support Assessments in the ACM
    As discussed previously, Sec.  257.95(g)(1) requires a facility to
characterize the nature and extent of the release and any relevant site
conditions that may affect the remedy ultimately selected. The
characterization must be sufficient to support a complete and accurate
assessment of the corrective measures necessary to effectively clean up
all releases from the CCR unit pursuant to Sec.  257.96.
    The revised ACM identified MNA as a corrective measure to address
groundwater contamination, in addition to other corrective measures
(e.g., hydraulic control and treatment; in-situ treatment). The revised
ACM delineates releases of lithium, arsenic, and molybdenum but does
not characterize the site conditions that would affect Alabama Power's
selected remedy of MNA. Although the ACM identifies a number of
potential attenuation mechanisms that might be effective for arsenic,
lithium, and molybdenum, the ACM does not demonstrate that any of these
mechanisms occur on site. EPA was unable to locate any data confirming
that any of those potential attenuation mechanisms are occurring at
Plant Gorgas. For example, this could include testing for the presence
and quantity of lithium detected in the aquifer matrix solids to
demonstrate that the constituent is being removed from the groundwater
and immobilized on-site. But no site data were discussed in the ACM.
    The subsequent Remedy Selection Report also fails to contain the
necessary site data. Although the Report, like the ACM, identifies a
number of potential attenuation mechanisms that might be occurring on-
site for arsenic, lithium, and molybdenum, the Report does not conclude
that any of these mechanisms occur on-site. Some site data that were
not available in the ACM are discussed in Section 5.3 of the Remedy
Selection Report, but they do not demonstrate that any significant
amount of lithium, molybdenum, or arsenic is being immobilized in the
``solids'' samples,\102\ (e.g., aquifer matrix) or otherwise confirm
the presence of attenuated constituents in the aquatic matrix. The
Report identifies only dispersion and dilution as an MNA mechanism that
currently occurs at Plant Gorgas. Ultimately none of the data presented
support selection of MNA as a primary remedy.
---------------------------------------------------------------------------

    \102\ Anchor QEA. Prepared for Alabama Power Company. Plant
Gorgas Groundwater Remedy Selection Report. December 2021. Tables 6
and 12 in Appendix D.
---------------------------------------------------------------------------

    Site data would also be needed to support any assessment of the
performance, reliability, ease of implementation, and the time required
to begin and complete the remedy must also be assessed and supported
with site characterization data and analysis. 40 CFR 257.96(c)(1) and
(2). But the Final Permit issued by ADEM requires neither the
collection of data, or any revisions to the ACM, or any change in the
facility's selected remedy to address these deficiencies.
ii. The Final Permit Does Not Require Submission of a Revised ACM That
Accurately Assesses MNA
    In the revised ACM, Alabama Power acknowledges that, ``USEPA (2015)
discourages using dilution and dispersion as primary MNA mechanisms, as
these mechanisms disperse contaminant mass rather than immobilize it.''
\103\ ADEM also raised this as a concern in its 2019 comments on the
original ACM.\104\ However, as noted neither the revised ACM or the
Remedy Selection Report identifies any natural attenuation mechanisms
other than dilution and dispersion that have been demonstrated to be
occurring on-site: ``The performance of MNA requires further
investigation, especially related to the identification of an
attenuating mechanisms, capacity of the Pottsville Formation for
attenuation, and time to achieve GWPS.'' \105\ This investigation was
not completed prior to completion of the ACM. Regardless, Alabama Power
assessed the performance of MNA as ``medium'' based on the dilution and
dispersion (i.e., releases of contaminants) occurring on-site and the
identification of potential attenuation mechanisms.
---------------------------------------------------------------------------

    \103\ Anchor QEA. Assessment of Corrective Measures, Plant
Gorgas. Prepared for Alabama Power Company. June 2019 (Revised:
February 2020). p. 14.
    \104\ Alabama Department of Environmental Management. Response
to CCR Documents Submitted to the Department. Alabama Power Company.
November 14, 2019.
    \105\ Anchor QEA. Assessment of Corrective Measures, Plant
Gorgas. Prepared for Alabama Power Company. June 2019 (Revised:
February 2020). p. 17.
---------------------------------------------------------------------------

    Such a favorable assessment of MNA is contrary to the requirement
in Sec.  257.97(b)(4) that ``[r]emedies must . . . [r]emove from the
environment as much of the contaminated material that was released from
the CCR unit as is feasible.'' As previously discussed, while MNA can
reduce the concentration or mobility of inorganic contaminants in
groundwater if immobilization occurs through adsorption or absorption