HomeMy WebLinkAboutPSD-130-03
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Cl~mgton
REPORT
PLANNING SERVICES
Meeting:
GENERAL PURPOSE AND ADMINISTRATION COMMITTEE
E:o~ G-PA -l(- I '3 .-03
Monday, October 6,2003
Date:
Report #: PSD-130-03
File #: PLN 33.4.3
By-law #:
Subject:
PORT GRANBY PROJECT
TECHNICAL STUDIES RELATED TO OPTION 82
RECOMMENDATIONS:
It is respectfully recommended that the General Purpose and Administration Committee
recommend to Council the following:
1. THAT Report PSD-130-03 be received for information.
Submitted by:
Reviewed by:
O~~~.
a Crome, M.C.I.P. R.P.P.
Director, Planning Services
Franklin Wu
Chief Administrative Officer
JAS*FL *DJC*df
29 September 2003
CORPORATION OF THE MUNICIPALITY OF CLARINGTON
40 TEMPERANCE STREET, BOWMANVILLE, ONTARIO L 1 C 3A6 T (905)623-3379 F (905)623-0830
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REPORT NO.: PSD-130-03
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1.0 BACKGROUND
1.1 In August 1999, Council adopted a resolution to advise Natural Resources Canada of
the Municipality's preferred option for the management of the low level radioactive
wastes at the Port Granby Waste Management Facility (WMF). This option, called
Option B2, involves the in-situ stabilization of the existing waste site with the following
key components:
. relocation of the wastes in the East Gorge to an engineered mound in the
northwest portion of the site;
. the installation of an impermeable cover over the wastes left in place to minimize
the infiltration of precipitation into the waste and the generation of leachate;
. reducing groundwater contact with the waste through the construction of
o an in-ground barrier wall around the northem perimeter of the waste to
deflect upgradient groundwater around the waste;
o a groundwater diversion trench just inside and adjacent to the barrier
wall;
. a system for leachate collection and treatment at the south end of the site;
. construction of an armoured structure to stabilize the lakeshore bluffs, and a toe
berm on the lake bed to retard further erosion.
1.2 Council further resolved that their selection of Option B2 as the preferred option was
conditional, subject to the results of a detailed comprehensive environmental
assessment and four additional studies to address the following issues:
. the concentration of Thorium - 230 in the East Gorge wastes;
. groundwater flow through the site and contact with the wastes;
. potential impacts of shoreline control measures; and
. a contingency plan for the relocation of the wastes in the event of system failure.
The requirement for the preparation of studies related to these issues was specifically
included in the legal agreement related to the project signed by both Clarington and
the federal government.
1.3 The four studies have now been completed by the Low Level Radioactive Waste
Management Office (LLRWMO) and reviewed by the Municipality's peer review
consultants (Hardy Stevenson and Associates) and the Port Granby Project
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Community Advisory Committee (CAC). In particular, Hardy Stevenson held detailed
discussions with the LLRWMO regarding their peer review comments. Many of the
comments resulted in changes to the studies or were acknowledged by the LLRWMO
as areas requiring more in depth study as part of the environmental assessment
process.
1.4 The purpose of this report is to provide an overview of the four studies and the
comments provided by the peer reviewers and the CAe.
2.0 THORIUM-230 IMPACT ASSESSMENT
2.1 Overview of Report
2.1.1 The waste in the East Gorge comprises about 20% ofthe waste (about 100,000 cubic
metres) at the existing Port Granby WMF. The concentration of the radioactive
contaminant Thorium-230 in the East Gorge wastes was identified as an issue of
specific concern. The report prepared by the LLRWMO addressed the following
specific issues related to Thorium-230:
· Is Thorium-230 a contaminant of concern with regard to the relocation of the
waste, particularly from the East Gorge?
· What would be the impacts on the public and workers related to Thorium-230 if
the waste has to be relocated, with particular focus on the inhalation hazard?
· What procedures would be needed for carrying out the relocation of the waste to
minimize the impacts related to Thorium-230?
2.1.2 The study reviewed Thorium-230 concentrations for the entire Port Granby WMF. It
was determined that the concentration of Thorium-230 across the site, and specifically
in the East Gorge, was not unusually high. The study confirmed that inhalation is the
most important route of human exposure for Thorium-230, but that these impacts can
be mitigated through the use of standard and readily available methods, such as dust
suppression, air filters for workers, and active monitoring. The study concluded that all
of the wastes at the existing WMF could be relocated safely with the use of these
mitigation measures.
2.2 Peer Review Comments
2.2.1 The Municipality's peer review consultants provided a number of detailed technical
comments on the Thorium-230 study. These comments included a request for
additional information on realistic radiological risk under actual project conditions, and
the development of steps for analyzing and relocating the waste to better understand
cost and safety implications.
2.2.2 Overall Hardy Stevenson concluded that the study was sufficiently detailed in
developing an understanding of the health implications of Thorium-230 and the
measures that may be required to mitigate adverse human health effects. They also
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concluded that the study provided a good basis for further development of the Project,
particularly with respect to the evaluation of altematives, detailed scope of the safety
assessments, and the procedural steps that may be needed for Thorium-230 control
during project implementation.
2.3 CAC Comments
2.3.1 The CAC generally agreed with the measures for controlling worker exposure to
contaminants from both external radiation and ingestion. They also acknowledged that
procedures can be developed to control both surface and airborne contamination
during excavation and relocation of the waste. The CAC noted that, due to the
difficulties in measuring airborne Thorium-230, it may be difficult to adequately monitor
inhalation exposure by workers during waste relocation and recommended further
study on this matter. They also noted the presence of unknown quantities of water in
the waste may make sampling results unreliable. They recommended that dry waste
be used to measure and establish contaminant levels in the waste.
3. GROUND WATER FLOW AND TRANSPORT MODELING STUDY
3.1 Overview of Report
3.1.1 Existing borehole, ground water and soil sample data were used to develop a
conceptual model that describes the geological and groundwater units underlying the
existing Port Granby WMF. This information was then used to develop a computer
model that could analyze groundwater flow and contaminant migration through the site
under different management scenarios. The scenarios analyzed included existing site
conditions (base case), an option with an impermeable cover with no waste removal
(Option 1), and an option with partial waste removal, also with an impermeable cover
over the waste (Option 2). Both options involved the use of a diversion trench and
interceptor wall, and the latter option, which involves the partial movement of waste, is
very similar to the management option (Option B2) selected in 1999. A third scenario
(contamination from existing operations) was evaluated to assess the time required to
flush contaminated groundwater from the system.
3.1.2 The study found that Option 1 was only marginally more effective in reducing
contamination in comparison to the base case. Option 2 offered better performance if
most of the waste is removed although it was also recognized that this is not possible.
Neither of the management options provided complete containment of the
contamination. In all cases studied, including the third scenario, contaminants will be
present at above background concentrations in the groundwater for periods exceeding
500 years.
3.1.3 The study also concluded that the proposed groundwater interceptor trench would be
ineffective in capturing groundwater flow from the north and diverting it around the
waste. The barrier wall was found to be ineffective and unnecessary, having no
significant effect on the diversion of groundwater flow away from the interceptor trench.
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The study concluded that the proposed remediation measures do not significantly
inhibit groundwater flow through the site Most contaminated groundwater will flow
down through the upper regions of the soil, and discharge into Lake Ontario either
through the middle till region or the lower sands region, directly by-passing the planned
leachate collection system.
3.2 Peer Review Comments
3.2.1 Hardy Stevenson and Associates concluded that the computer model for groundwater
flow and contaminant transport was developed using accepted engineering and
hydrologic practices. They also found that it provided a reasonable and sufficiently
accurate representation of conditions at the existing Port Granby WMF, and
groundwater flow and contaminant transport conditions under the different
management scenarios studied.
3.2.2 Tile peer review noted the existing site is characterized by strong downward
groundwater gradients and that there is a significant volume of regional ground water
flow beneath the site. Because of these ground water conditions and the fact that the
existing waste materials have been placed without a liner or underlying leachate
control system, leachate will always escape from the waste into the ground water
system. Perpetual monitoring, control and collection and treatment of the leachate will
be required to prevent its escape to the environment. They also suggested that
complete containment and control of the leachate could only be achieved if the waste
is excavated and isolated in an engineered containment cell.
3.2.3 The peer reviewers have requested that future studies address a number of issues
related to groundwater and contamination at the Port Granby site. These issues
included determining an acceptable concentration of contaminants in groundwater;
allowable rates of release of contaminants to the environment; and an assessment of
impacts to aquatic life in Lake Ontario and the potential future use of the ground water
for drinking.
3.3 CAC Comments
3.3.1 The CAC commented that the study is missing important information, such as the
percentage of waste that is currently below the water table, and the location and depth
of waste in the East Gorge. They also noted that the future waste characterization
studies to be carried out through the Environmental Assessment should provide a
more realistic portrayal of the waste. The CAC have requested that Option B2 be re-
examined to determine the effectiveness of placing a groundwater cut-off wall deeper
into the site down to the lower sands.
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4. ASSESSMENT OF SHORELINE PROTECTION COMPONENT OF OPTION B2
4.1 Overview of Report
4.1.1 The study undertook an assessment of the effectiveness of the proposed shoreline
protection feature over 500 years, and the potential impact of the structure on the
adjacent shoreline. The study found that, without shoreline protection, the bluffs
would erode by about 130 m (427 feet) over a 470 year period, leading to a loss of
waste into the lake. The study suggested that the proposed armouring be replaced
with less extensive works with a more natural appearance.
4.1.2 The study also found that down-cutting of the nearshore profile is the primary driver of
bluff recession at the site and that, over the same period, down-cutting of about 2.2 m
(7.2 feet) would occur in the nearshore profile. To prevent further downcutting, an
armoured toe berm would have to be constructed from approximately the base of the
bluffs into the lake, potentially covering approximately 10,000 sq. m. to 20,000 sq. m.
(2.5 to 5 acres) of lakebed, depending on the final stabilization alternative chosen.
Because of the potential impact of the toe berm on lake processes and fish and fish
habitat, approval under the federal Fisheries Act would be required.
4.1.3 The study notes that insufficient natural heritage data was available to allow an impact
assessment to be undertaken. A concem was identified that the proposed shoreline
stabilization concept may not be able to obtain the necessary approvals from the
Department of Fisheries and Oceans.
4.1.4 The study concluded that the proposed bluff stabilization feature and toe berm would
be technically feasible at halting erosion at the Port Granby WMF. However, the study
also noted that the adjacent unprotected shoreline would continue to retreat at
approximately the same rate. As a result, after 470 years the protected waste site
would form a promontory extending approximately 130 m (427 feet) into the lake.
4.1.5 The study also noted that, due to the harsh marine environment (eg. wave action,
abrasion by suspended sediment, ice forces, freezing and thawing), future repairs and
maintenance will be required, including the likely replacement of the primary armour
layer within the specified 500 year project life.
4.2 Peer Review Comments
4.2.1 Hardy Stevenson commented that the shoreline study adequately assesses the
technical feasibility of the proposed shoreline stabilization works. They note that the
proposed 500 year life of the facility is quite unusual for most coastal structures. They
suggest that granite should be used for the armour stones, given its higher resistance
to damage caused by freezing, drying, and frost. They also feel that there is not
enough information to predict that the primary armour may need to be replaced within
the life of the project.
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4.2.2 The peer reviewers agree that more natural heritage information must be obtained to
enable a proper impact assessment to be undertaken, and suggests that any future
studies must place natural heritage issues on an equal footing with engineering
feasibility. As well, they echoed the concern expressed by the study authors that the
proposed shoreline stabilization may not obtain the required approvals under the
Fisheries Act.
4.3 CAC Comments
4.3.1 The CAC noted that the emphasis of the shoreline study has been largely on the
technical feasibility of containment options. They recommended that the natural
heritage component be given greater attention in the Environmental Assessment to
provide a better balance between engineering and the environmental feasibility of the
shoreline measures proposed.
5.0 CONCEPTUAL CONTINGENCY STUDY FOR OPTION 82
5.1 Overview of Report
5.1.1 The purpose of the study was to develop a conceptual contingency plan for the
relocation of the low level radioactive waste (LLRW) and associated marginally
contaminated spoils (MCS) from the stabilized Port Granby WMF in the event of a
future system failure of that facility. "System failure" would include the unanticipated
failure of a key component of the long term WMF, such as the toe berm, slope
stabilization works, low permeability cap, and the groundwater diversion works.
Mechanisms that may cause the failure of these key components include:
· progressive and uncontrollable undercutting of the toe berm
· excessive erosion of the toe berm due to severe or repetitive storm events,
· excessive or uncontrollable differential settlement of the low permeability cap, or
· no long term reduction in contaminant loading to Lake Ontario.
5.1.2 The proposed contingency plan for the Port Granby WMF involves relocating the
LLRW and the MCS to a new, long term storage facility located at an undetermined
location within the local area but away from the Lake Ontario shoreline. An
engineered above-grade mound is proposed as the long term WMF under the
Contingency Plan. The mound would have a low permeability cap and a low
permeability liner, with provision for the periodic collection/treatment of leachate
throughout the service life of the mound (ie. 500 years). The outer dimensions of the
mound would be approximately 427 m (1400 feet) long by 247 m (810 feet) wide, with
a maximum height of 12.5 m (41 feet). The storage mound would have an overall
volume capacity of approximately 760,000 m3 to accommodate the anticipated volume
of waste and dailylinterim soil cover of 110,000 m3, plus an additional 97,000 m3
contingency. Approximately 28 ha (69 acres) of land would be required to
accommodate the mound and a 100 m buffer.
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5.2 Peer Review Comments
5.2.1 Hardy Stevenson noted the difficulties in implementing the Contingency Plan, such as
the need for EA studies and site selection activities. As a result, responses to major
failures at the WMF would tend to favour less complex actions, such as the repair or
replacement of the affected structure, leading to a concem that the Contingency Plan
may not be implemented as quickly as it should be. They suggested that, if the
proponent believes there is a reasonable risk of major system failure, then the new
engineered long term storage facility would be better addressed as an alternative
through the EA process, rather than as a contingency planning process.
5.2.2 The peer reviewers also noted that the thorium, groundwater and shoreline studies
identified a number of more probable but less significant events that were likely to
occur at the WMF. These events include contaminated groundwater by-passing the
leachate collection system, and the need for on-going maintenance and repairs of the
shoreline structure. They suggested that the difficulties associated with the repair and
long-term maintenance of the in-situ stabilization option may also be of sufficient
concern so as to require contingency planning.
5.2.3 It was also noted that the Contingency Plan assumes that the necessary institutional
support for remediation or movement of waste will be available throughout the 500
year design lifetime of the WMF. There is no provision in the Contingency Plan for
insuring that the necessary skills, people and financial resources will be available for
safe management of the waste in the event of a system failure.
5.3 CAC Comments
5.3.1 The CAC adopted a motion stating that the proposed Contingency Plan is unsuitable
for the long term storage of LLRW, and that no scientific data was provided to justify
the suitability of the plan. They suggested that the Contingency Plan should focus
more scientific study on how to make in-situ stabilization viable over the 500 year life
of the WMF.
5.3.2 The CAC expressed concern that, given the expense of implementing the Contingency
Plan, too much emphasis will be placed on repairing the WMF. As a consequence,
the WMF could continue in a repair mode long after the Contingency Plan should have
been implemented. If there is deemed to be sufficient risk of Option B2 experiencing a
system failure, the current EA should consider appropriate sites for a contingency
facility to ensure that the Contingency Plan could be implemented in a timely fashion
should Option B2 fail.
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6.0 CONCLUSIONS
6.1 The LLRWMO has completed the four studies regarding Option B2 as requested by
Council. The studies have identified significant issues regarding the in-situ stabilization
option for the management of the Port Granby wastes conditionally supported by the
Municipality in 1999.
6.2 Staff and the Municipality's peer review consultants have thoroughly reviewed the
studies and are satisfied that they have addressed the issues identified by the
Municipality and meet accepted professional standards of quality for technical studies
of this nature. In this regard, the LLRWMO, as the proponent for the Port Granby
Project, has fulfilled it obligations related to the studies as required by the legal
agreement with the federal government.
6.3 The information from the four studies will serve as valuable input into the technical
assessment of options for the long term management of the Port Granby wastes.
Options being considered by the LLRWMO are: 1) in-situ management of the waste,
with or without movement of the East Gorge wastes; and 2) the relocation of the waste
to an engineered mound away from Lake Ontario on the north side of Lakeshore
Road.
6.4 Following a comprehensive analysis of these options, the LLRWMO will be making a
recommendation to Council on a facility design and location early in 2004. Both staff
and the peer review consultants will be extensively involved in the technical
discussions related to the evaluation of the various options, and will also be making a
recommendation to Council on a preferred facility design and location.
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