[Federal Register Volume 75, Number 219 (Monday, November 15, 2010)]
[Notices]
[Pages 69711-69715]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 2010-28638]
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NUCLEAR REGULATORY COMMISSION
[Docket Nos. 52-012 and 52-013; NRC-2010-0343]
STP Nuclear Operating Company, South Texas Project Nuclear Power
Plant, Units 3 and 4; Exemption
1.0 Background
By letters dated February 2, 2010 (Agency wide Documents Access and
Management System (ADAMS) Accession Number ML100350219), March 23, 2010
(ADAMS Accession Number ML100880055) and July 21, 2010 (ADAMS Accession
Number ML102070274), STP Nuclear Operating Company (STPNOC) submitted a
request for an exemption from Title 10 of the Code of Federal
Regulations (10 CFR) part 50, section 50.10: License required; limited
work authorization. The U.S. Nuclear Regulatory Commission (NRC or the
NRC staff) has reviewed this request for exemption, pursuant to 10 CFR
50.12, as it relates to STPNOC's application for combined licenses
(COLs) for South Texas Project (STP) Units 3 and 4, which is currently
under review by the NRC staff. This exemption would authorize STPNOC to
install two crane foundation retaining walls (CFRWs) prior to issuance
of the COLs. Granting this exemption would not constitute a commitment
by the NRC to issue COLs for STP Units 3 and 4. STPNOC would install
the CFRWs assuming the risk that its COL application may later be
denied.
2.0 Request/Action
The proposed action, as described in STPNOC's request for an
exemption to 10 CFR 50.10, would allow STPNOC to install two CFRWs (one
for Unit 3 and one for Unit 4), prior to issuance of COLs. According to
STPNOC, the CFRWs are non-safety related, and have no adverse
interactions with any structures, systems, or components as identified
in 50.10. STPNOC states that the CFRWs are required to facilitate
excavation activities by retaining soil next to the excavations of the
Reactor Building, Control Building and Turbine Building Foundations,
while allowing the crane areas to be at grade and near the buildings.
Installation of the CFRWs would include the following activities:
Performing a full-depth and width-slurry excavation;
Placing of reinforcement in the slurry trench;
Displacing the slurry with concrete from the bottom up;
and
Installing tiebacks and whalers to stabilize the CFRWs, as
excavation for permanent plant structures proceeds.
As construction of the permanent plant structures proceeds, the
CFRWs would be abandoned in place following crane use. After
abandonment, the CFRWs would have no function during operation of STP
Units 3 and 4.
In its exemption request, STPNOC stated that the proposed exemption
is needed because installation of the CFRWs must occur before
excavation for permanent plant structures, and compliance with the
requirements for a limited work authorization as indicated in 10 CFR
50.10 would result in undue hardship or other costs that are
significantly in excess of those contemplated during the development of
10 CFR 50.10. According to the exemption request, installation of the
CFRWs is needed to allow STPNOC to complete certain on-site activities
in parallel with the licensing process, so that it can begin
construction promptly upon issuance of COLs.
3.0 Discussion
Pursuant to 10 CFR 50.12(a) the Commission may, upon application by
any interested person or upon its own initiative, grant exemptions from
the requirements of 10 CFR 50.10 when (1) the exemption authorized by
law, will not present an undue risk to public health or safety, and are
consistent with the common defense and security; and (2) when special
circumstances are present.
[[Page 69712]]
Authorized by Law
This exemption would authorize the applicant to install two CFRWs
(one for Unit 3 and one for Unit 4) prior to issuance of COLs. As
stated above, 10 CFR 50.12(a) allows the NRC to grant exemptions from
the requirements of 10 CFR 50.10. The NRC staff has determined that
granting of the applicant's proposed exemption will not result in a
violation of the Atomic Energy Act of 1954, as amended, or the
Commission's regulations. Therefore, the exemption is authorized by
law.
No Undue Risk to Public Health and Safety
The underlying purpose of 10 CFR 50.10 is to define clearly the
licensing requirements for a limited work authorization (LWA). In
determining that the proposed exemption would not pose an undue risk to
public health and safety and that the applicant could be exempted from
the LWA, for the limited purpose of the installation of the CFRWs, the
NRC staff evaluated the exemption in the areas of Geotechnical
Engineering, Structural Engineering and Hydrology.
Geotechnical Engineering
The NRC staff evaluated STPNOC's exemption request using the
criteria in NUREG-0800, Standard Review Plan (SRP), Chapter 2.5.4,
``Stability of Subsurface Materials and Foundations''.
The specific criteria that apply include:
1. RG 1.132, ``Site Investigations for Foundations of Nuclear Power
Plants.''
2. RG 1.138 ``Laboratory Investigations of Soils and Rocks for
Engineering Analysis and Design of Nuclear Power Plants.''
In this exemption request, the applicant addressed the above
criteria. The applicant evaluated the static and dynamic effects the
CFRWs could have on safety-related structures, systems, or components
(SSC's) identified by 10 CFR 50.10(a)(1)(i) through (vii). These SSCs
included: (1) Reactor Building, (2) Control Building, (3) Ultimate Heat
Sink and Reactor Service Water Pump House, (4) Turbine Building, (4)
Service Building, (5) Diesel Generator Fuel Oil Storage Vault and
Tunnel, (6) Reactor Service Water Piping Tunnel, and (7) Fire
Protection Pump House. This evaluation included soil-structure
interaction (SSI) analysis for SSCs. In addition, the applicant's
stability evaluation included a static a dynamic bearing capacity and
settlement analysis. The applicant concluded that the construction of
the CFRWs has no adverse influence on the static and dynamic stability
of any of the SSCs listed above.
The staff evaluated the applicant's static and seismic stability
analysis of the SSCs identified in 10 CFR 50.10(a)(1). Specifically,
the staff evaluated the applicant's SSI analysis as well as the
settlement, bearing capacity and dynamic lateral earth pressure effects
the CFRWs could have on the aforementioned SSCs. The staff's detailed
evaluation is provided below.
Dynamic Lateral Earth Pressures
The staff reviewed the soil properties, presented in Revision 3 of
the Final Safety Analysis Report (FSAR) Appendix 3H, Table 3H6.2, used
as input for the SSI analysis. The applicant assumed a mean, upper and
lower bound for the shear and compression wave velocities, and a
constant value for unit weight. Poisson's ratio is assumed to vary
above and below the water table. The accuracy of these assumed values
will be verified in future testing, but the NRC staff concludes that
because of the significant margin in the computed lateral earth
pressures shown in Figure 2.5 of the attachment, Appendix A, ``Crane
Foundation Retaining Wall Evaluation Summary'', the staff has
reasonable assurance that variations in the soil properties of soil
backfill properly compacted to 95 percent modified Proctor would not be
significant enough to cause exceedence of the lateral pressures assumed
in the design of the wall. Hence, the staff concludes that, the
resulting static and dynamic earth pressures will be bounded by the
lateral earth pressures used in design.
Bearing Capacity
The applicant stated that the presence of the wall will not affect
the static bearing capacity. The staff concludes that the presence of
the CFRWs and the retained natural ground behind the wall will provide
additional resistance to a bearing capacity failure in the direction of
the wall due to the surcharge provided by the natural ground behind the
wall, and the strength of the reinforced concrete wall. The applicant
stated that dynamic bearing capacity is not affected by the presence of
the wall once the backfill is in place, and the staff concurs with this
assessment.
Settlement
The applicant considers the settlement due to the wall and retained
natural soils to be insignificant. The staff concludes that the weight
of the wall versus the weight of the natural soil that it is replacing
is minor and the stresses induced by the additional weight of the wall
and any additional downward force caused by the battered anchors is
minor due to the 3 foot width of the footing. Stresses induced by the
linear wall footing can be ignored for the following reasons: (1) The
foundations soils below the wall are over-consolidated and any
settlement will occur rapidly, prior to the construction of adjacent
structures, and (2) the additional vertical stresses due to the 3 ft.
wide footing would contribute insignificant additional stress within
the zone of influence created by structures placed in close proximity
to the wall. Regarding the change in the pattern of stress distribution
on the East side of the Reactor Building due to the presence of the
wall, the applicant stated that those stresses would be increased, but
the settlement due to those increased stresses would be offset by the
reduction in stress due to backfill placement above the foundation
level due to friction between the wall and the backfill. The staff
believes that the presence of the wall will also minimize heave during
excavation, and that will therefore reduce the magnitude of re-
settlement upon reloading. Additional settlement that may be caused by
additional loading due to the pattern of stress distribution on the
east side of the Reactor Building due to the presence of the wall will
be offset by reduced vertical stresses as indicated by the applicant,
and also due to reduced re-settlement that results from less heave
because of the presence of the wall. The staff therefore concludes that
settlement caused by the presence of the wall is not significant.
Structural Engineering
In 10 CFR Part 50, Appendix A, General Design Criterion (GDC) 2
requires that the design basis shall reflect appropriate considerations
of the most severe earthquakes that have been historically reported for
a site and the surrounding area. 10 CFR Part 50, Appendix S further
delineates the earthquake engineering criteria for seismic evaluation
of nuclear power plants. Pursuant to Appendix S, the evaluation of SSCs
required to withstand the effects of the safe-shutdown earthquake (SSE)
ground motion must take into account soil-structure interaction (SSI)
effects. Using the guidance of SRP Section 3.7.2 in part, the NRC staff
performed a review of the applicant's exemption request to ensure that
leaving the CFRWs in place after the plant is constructed does not
adversely affect the seismic design basis of safety related structures
required to withstand effects of the SSE in the vicinity of the CFRWs.
[[Page 69713]]
In this exemption request, the applicant has addressed the above
regulations as to the potential effect of the CFRWs on seismic response
of the applicable SSCs. The applicant evaluated the potential dynamic
effects of the CFRWs on SSC's, which are identified by 10 CFR
50.10(a)(1)(i) through (vii). These SSCs included: (1) Reactor
Building, (2) Control Building, (3) Ultimate Heat Sink and Reactor
Service Water Pump House, (4) Turbine Building, (4) Service Building,
(5) Diesel Generator Fuel Oil Storage Vault and Tunnel, (6) Reactor
Service water Piping Tunnel, and (7) Fire Protection Pump House. The
CFRWs occupies a very small volume relative to the overall soil mass
and represents a small increase in overall weight as compared to the
replaced soil. As such, the applicant stated that the CFRWs are
expected to have negligible interaction on the other nearby heavy
structures such as Reactor Building (RB) or Control Building (CB).
In order to demonstrate that there is no adverse seismic
interaction of the CFRWs on SSCs, the applicant performed a SSI
analysis of the Reactor and Control Buildings for the STP Units 3 and 4
site-specific conditions, including site-specific SSE and the soil
parameters described in Revision 3 of the STP Units 3 and 4 Combined
License Final Safety Analysis Report (FSAR) Section 3.7.1 and
Appendices 3A and 3C, except that a 2D model was used instead of a 3D
model. The SSI analyses were performed with and without the CFRWs using
the computer program SASSI2000 as described in FSAR Appendix 3C.8.
Based on the analyses results and an assessment of the configuration
and locations of the SSCs (listed above) as compared to the location of
the CFRWs, the applicant concluded that the construction of the CFRWs
has no adverse interactions with SSC's listed above.
The staff evaluated the applicant's SSI analysis of the Reactor and
Control Buildings with and without the CFRWs as well as the applicant's
engineering evaluation for the other SSCs for any potential effects of
the CFRWs on SSCs. The staff based its review on the applicable
regulations and SRP guidance for SSI analysis as well as the following
engineering principles: (1) Much lighter CFRWs will not significantly
affect the dynamic response of nearby massive buildings (such as RB,
CB, TB, etc.), (b) the influence of a heavy structure on the SSE input
of the other nearby lighter structure exceeds any influence from much
lighter CFRWs, and (c) CFRWs will not influence the dynamic response of
heavy or light structures located at a significant distance away from
the CFRWs. The seismic input response spectrum used in the RB and CB
SSI analysis envelops the site specific Foundation Input Response
Spectra (FIRS). The input response spectrum also envelops a broad band
spectrum anchored at 0.1g in the horizontal direction as required by
Appendix S to 10 CFR Part 50, ``Earthquake Engineering Criteria for
Nuclear Power Plants.'' In addition, the staff verified consistency of
the analytical model and the site soil parameters used in the exemption
request and the COL application. The staff's detailed evaluation is
provided below.
Reactor Building and Control Building
The RB and CB are part of the Advanced Boiling Water Reactor (ABWR)
design certification. The CFRWs are located approximately 15 feet from
the exterior wall of the RB and about 80 feet from the exterior wall of
the CB. The applicant performed 2-D SSI analyses of the RB and CB, with
and without the CFRWs, to assess the potential impact of the crane wall
installation on the seismic response of the RB and CB for the site-
specific conditions, including site-specific SSE and soil properties.
The staff needed more information about the analytical models to
conclude that impact of the seismic interaction of CFRWs has been
appropriately accounted for in SSI analysis of RB and CB. The staff, in
a request for additional information (RAI 1) dated May 24, 2010 (ADAMS
Accession Number ML101400240), asked the applicant to provide this
needed information.
In response to the staff's request for additional information, RAI
1, the applicant stated that there were some inconsistencies in the
mass and stiffness properties of the 2-D SSI analytical models used in
the analysis described in the response to the RAI 03.07.01-24 (U7-C-
STP-NRC-100083) and the original exemption request of March 23, 2010.
However, the conclusions of these analyses remain the same. In the
revised exemption request of July 21, 2010 (U7-C-STP-NRC-100147), the
applicant described the updated analytical models used in the
reanalysis. The results including the dynamic lateral soil pressure
obtained from the SSI analysis for the RB and CB, with and without
CFRWs for the mean in-situ soil parameters are reported in Appendices A
and B of the exemption request (U7-C-STP-NRC-100143) which concluded
that CFRWs does not have significant effect on the response of the RB
and CB.
The staff reviewed the analytical model and comparative analysis
results with and without the CFRWs as described in Appendix A and B of
the exemption request of July 21, 2010. The comparison of in-structure
response spectra (ISRS) is provided in Figures 2.1 through 2.4 for the
RB and in Figures 2.6 through 2.7 for the CB. For the RB, the ISRS with
and without the CFRWs were compared at four locations: Bottom of base
mat, reactor pressure vessel/main steam nozzle, top of the reinforced
concrete containment vessel, and top of the RB. For the CB, the ISRS
with and without the CFRWs were compared at the top of the base mat and
the top of the CB. Tables 2.1 and 2.2 of the July 21, 2010 exemption
request compare the maximum forces and moments at the above four for
the RB and two locations for the CB, respectively, for the RB and CB
with and without the CFRWs. These comparisons demonstrate that the
CFRWs do not have a significant effect on the seismic response, ISRS,
and maximum forces for the RB and the CB. This determination is also
consistent with the expectation that lighter nearby structures like the
CFRWs will have a minimal influence on the seismic response of nearby
heavy structures like RB, CB, and TB.
While the inertia of the CFRWs are not expected to affect the
seismic response of the nearby heavy structures, the stiff CFRWs can
act as a barrier to reflect the seismic waves and could affect seismic
lateral soil pressure on the adjacent building walls. The applicant
addressed this issue by comparing the lateral soil pressures on the RB
and CB walls obtained from the site-specific SSI analysis, with and
without the CFRWs as shown in Figures 2.5 and 2.8. As expected, the
lateral seismic soil pressure increased due to the presence of the
CFRWs. However, the increase was not significant enough to affect the
design pressures for the RB and CB walls. The RB and CB exterior walls
are designed for the larger of: (1) the pressure provided in the ABWR
Design Control Document (DCD) Tier 2 Figure 3H.1-11 and (2) the
pressure obtained from the alternate modified Ostadan method described
in the COLA Part 2, Tier 2, Section 2.5S.4.10.5.2. Therefore, the staff
agrees with the applicant's conclusion that the increase in soil
pressure due to the presence of CFRWs will be bounded by the design
seismic soil pressure.
Ultimate Heat Sink and Reactor Service Water Pump House
The Ultimate Heat Sink (UHS) and Reactor Service Water Pump House
(RSWPH) are large Category I structures. Its smallest separation
distance from the CFRWs is 60 feet. Based upon the
[[Page 69714]]
results of the RB and CB SSI analysis, the applicant stated that the
CFRWs do not have a significant effect on the response of the UHS and
RSWPH. The staff reviewed the configuration of the UHS and RSWPH as
well as the STP Units 3 & 4 site layout in reference to the CFRWs.
Staff noted that these structures are massive and are not located in
close proximity of the CFRWs. Therefore, based on the review of these
structures, their locations in relation to the CFRWs, and the
comparative SSI analysis performed in support of the RB and CB, the
staff agrees with the applicant's conclusion that CFRWs do not have a
significant effect on the seismic design of the UHS and RSWPH.
Turbine Building
The Turbine Building (TB) is a large structure. The CFRWs are
installed approximately 15 feet from the exterior wall of the TB. The
applicant stated that because CFRWs are a much smaller structure, its
influence on the seismic response of large TB is expected to be
insignificant. The staff reviewed the configuration of the TB as well
as their site layout in reference to the CFRWs. The staff noted that
similarly to the RB, the TB is also a heavy structure as compared to
the CFRWs. Therefore, the staff concludes that the installation of
CFRWs does not have a significant effect on the seismic response of the
TB.
Service Building
The Service Building (SB) is a non-Seismic Category I structure
designed for the SSE, and meets the Seismic Category II/I interaction
requirements. The horizontal separation distance of the SB from the
CFRWs is approximately 15 feet. The SSE input for the II/I evaluation
is determined based on the influence of the CB (which is a heavy
structure near the SB) on the lighter nearby SB structure. The
influence of the CB on the SSE input and design of the SB far exceeds
any influence from the much lighter CFRWs structure.
The applicant stated that the influence of the nearby heavier CB
structure is considered for determining the SSE input for the SB. Based
on the configuration of the CB and the CFRWs, the staff agrees with the
applicant that influence of the nearby CB on the SSE input and design
of the SB will be much more significant than any influence on the
seismic response of the SB from the much lighter CFRWs.
Diesel Generator Fuel Oil Storage Vault and Tunnel
The applicant stated that the Diesel Generator Fuel Oil Storage
Vault and Tunnel are designed for the SSE input considering the
influence of a heavy structure (i.e., RB) on the lighter nearby
structures (Diesel Generator Fuel Oil Storage Vault and Tunnel). The
influence of the RB on the SSE input and design of the Diesel generator
Fuel Oil Storage Vault and Tunnel far exceeds any influence from much
lighter CFRWs. As such, the applicant stated that the presence of the
CFRWs has no influence on the design of the Diesel Generator Fuel Oil
Storage Vault and Tunnel.
The design calls for three Diesel Generator Fuel Oil Storage Vaults
and the associated tunnels per unit surrounded by the RB and RSWPH.
Based on the configuration of the RB, RSWPH, and the CFRWs, the staff
agrees with the applicant that influence of the nearby massive RB on
the SSE input and design of the Diesel Generator Fuel Oil Storage Vault
and Tunnel will be much more significant than any influence from the
much lighter CFRWs.
Reactor Service Water Piping Tunnel
The applicant stated that the Reactor Service Water (RSW) Piping
Tunnel is located more than 250 feet away from the CFRWs. At this
location, the applicant stated that the CFRWs have no effect on the RSW
Piping Tunnel.
The staff reviewed the site layout of the RSW Piping Tunnel and
determined that there will be no seismic interaction from the CFRWs to
influence the seismic input to RSW Piping Tunnel.
Fire Protection Pump House
The Fire Protection Pump House is located more than 300 feet away
from the CFRWs. At this location, the applicant stated that the CFRWs
have no effect on the Fire Protection Pump House. Because of sufficient
separation distance (more than 300 feet), the staff agrees with the
applicant's conclusion that the seismic input for the Fire Protection
Pump House is not affected by the CFRWs.
The staff concludes that leaving the CFRWs in place after the plant
is constructed does not adversely affect the seismic design basis of
safety related structures required to withstand the effects of the SSE
in the vicinity of the CFRWs. This conclusion is based on the analysis
and engineering evaluation performed by the applicant and the review
performed by the staff as discussed in this report on the above SSCs as
defined in 10 CFR 50.10(a)(1).
The staff also concludes that applicant has met the relevant
requirements of GDC 2 and 10 CFR Part 50, Appendix S by appropriately
considering the most severe earthquake and site parameters as seismic
input in performing the comparative SSI analysis with and without the
CFRWs.
Hydrology
STPNOC stated that the CFRWs will not affect the safe operation of
STP Units 3 and 4 or have a reasonable nexus to safety. NRC staff
reviewed the impacts of proposed action on safety-related groundwater
issues as they relate to the SSCs as defined in 10 CFR 50.10 (a)(1).
First, in regard to groundwater use, the STPNOC COLA proposed a
Deep Aquifer well to provide make up water for the Ultimate Heat Sink
(UHS). However, the make-up water for the UHS is not safety-related and
thus there are no safety-related impacts.
Second, ABWR DC requires a maximum groundwater level of two feet
below the plant grade. The applicant stated in FSAR 2.4.12 that the
estimated maximum groundwater level is about 28 feet Mean Sea Level
(MSL). STPNOC is now re-evaluating the maximum groundwater level using
a detailed groundwater model. However, NRC staff expects that the
maximum groundwater level with the CFRWs will remain significantly
below the plant grade of 34 ft MSL.
Third, in terms of the groundwater contamination, STPNOC is now re-
evaluating the impacts of CFRWs on the groundwater pathways. However,
NRC staff expects that the CFRWs will create a longer pathway and
travel time that will result in less severe radiological consequences.
Finally, the CFRWs will not have an adverse impact on the safety-
related groundwater issues at STP Units 1 and 2 because there is a
sufficient separation distance between the proposed and existing units.
The staff concludes that the installation of the CFRWs for Units 3
and 4 will not affect the safe operation of STP Units 3 and 4 or have a
reasonable nexus to safety related to groundwater at the STP site.
Consistent With Common Defense and Security
The proposed exemption would allow the applicant to install CFRWs
as a preconstruction activity without the authorization provided in a
construction permit, combined license or a Limited Work Authorization
(LWA). This exemption from 10 CFR 50.10 is for the sole purpose of the
installation the
[[Page 69715]]
CFRWs and has no relation to security issues. Therefore, the common
defense and security is not impacted by this exemption.
Special Circumstances
Special circumstances, in accordance with 10 CFR 50.12(a)(2)(iii)
is present whenever ``compliance would result in undue hardship or
other costs that are significantly in excess of those contemplated when
the regulation as adopted, or that are significantly in excess of those
incurred by others similarly situated.'' The underlying purpose of 10
CFR 50.10 is to define clearly the licensing requirements for a LWA.
The applicant has demonstrated and the NRC staff has confirmed that the
influence of the CFRWs on interactions with the SSCs will have a
negligible nexus to safety. The applicant also cites undue hardship or
other costs as a special circumstance that would warrant granting this
exemption. The applicant has provided two potentially viable alternate
construction plans to avoid delay in their schedule: (1) Redesign the
CFRWs to make it more practical to remove prior to fuel load and (2)
increase the size of the excavation and locate the crane in the
excavation. STPNOC states that both options will increase the
construction cost by $22 million and $260 million respectively.
Therefore, since the underlying purpose of 10 CFR 50.10 is still being
achieved concerning the safety of the SSCs during construction
activities and the applicant has demonstrated an undue hardship, the
special circumstance required by 10 CFR 50.12(a)(2)(iii) for the
granting of an exemption from 10 CFR 50.10 exists.
The applicant has also provided information on this proposed action
pursuant to 10 CFR 50.12(b) which states any person may request an
exemption permitting the conduct of activities prior to the issuance of
the construction permit prohibited by 10 CFR 50.10. The balancing
factors for granting such an exemption are evaluated in the
environmental assessment (EA) that is attached to this package. The
ADAMS Accession number for this associated EA is ML101580541.
4.0 Conclusion
Accordingly, the Commission has determined that, pursuant to 10 CFR
50.12(a) and 10 CFR 50.12(b), the exemption is authorized by law, will
not present an undue risk to the public health and safety, and is
consistent with the common defense and security. Also, special
circumstances are present. Therefore, the Commission hereby grants
South Texas Project Nuclear Operating Company an exemption from the
requirements in 10 CFR 50.10 for the installation of the CFRWs for
Units 3 and 4.
Pursuant to 10 CFR 51.32, the Commission has determined that the
granting of this exemption will not have a significant effect on the
quality of the human environment (75 FR 67784).
This exemption is effective upon issuance.
Dated at Rockville, Maryland on November 5, 2010.
For the Commission.
David B. Matthews,
Director, Division of New Reactor Licensing, Office of New Reactors.
[FR Doc. 2010-28638 Filed 11-12-10; 8:45 am]
BILLING CODE 7590-01-P