DRC-2010-004643 - 0901a068801bb2e9

C-2010-004645 Denbon Mines (USA) Corp.
10S017th Straet, Suite 950
DENISOIsri^^^ USA
AAINES ^ ^7-1..^ Tel: 303 62S-7798
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August 18, 2010 ' .. .
VIA E-MAIL AND OVERNIGHT DELIVERY
Rusty Lundberg, Co-Executive Secretary
Utah Water Quality Board
Utah Department of Environmental Quality
195 North 1950 West
P.O. Box 144810
Salt Lake City, UT 84114-4820
Re: State of Utah Ground Water Discharge Permit ("GWDP") No. UGW370004 White Mesa Uranium Mill -
Plan and Schedule for Cell 1 Inspection and Repairs
Dear Mr. Lundberg:
Reference is made to Denison Mines (USA) Corp's ("Denison's") notice letter of June 7, 2010 and telephone
conference with Utah Department of Environmental Quality ("UDEQ") personnel on August 12, 2010. Denison's
June 7, 2010 letter provided a notice to the Executive Secretary regarding the discovery of fluid in the Leak
Detection System ("LDS") of the White Mesa Mill's (the "Mill's") Cell 1. This letter responds to Denison's
commitment in the June 7, 2010 letter and the August 12, 2010 phone call in which Denison agreed to provide
UDEQ a written plan and schedule for:
• determination of the root cause,
• identification of the extent of damage, and
• execution and reporting of repairs to the Cell 1 liner system.
Background and Design of Cell 1
Tailings Cell 1 serves as the Mill's primary liquid evaporation basin. Cell 1 consists of the following major
design elements:
1) Cross-valley Dike and East Dike - constructed on the south side of the pond of native granular materials
with a 3:1 slope, a 20-foot crest width, and a crest elevation of about 5,620 ft above mean sea level (amsl).
A dike of similar design was constructed on the east margin of the pond, which forms a continuous earthen
structure with the south dike. The remaining interior slopes are cut-slopes at 3:1 grade.
2) Liner System - including a single 30 mil PVC flexible membrane liner (FML) constructed of solvent welded
seams on a prepared sub-base. The top elevation of the FML liner was 5,618.5 ft amsl on both the south
dike and the north cut-slope. A protective soil cover layer was constructed immediately over the FML with a
thickness of 12-inches on the cell floor and 18-inches on the interior sideslope.
Letter to Rusty Lundberg on Cell 1 Repair Plan
August 18, 2010
Page 2
3) Crushed Sandstone Underlay - immediately below the FML a nominal 6-inch thick layer of crushed
sandstone was prepared and rolled smooth as an FML sub-base layer. Beneath this underlay, native
sandstone and other foundation materials were graded to drain to a single low point near the upstream toe
of the south cross-valley dike. Inside this layer, an east-west oriented pipe was installed to gather fluids at
the upstream toe of the cross-valley dike.
As mentioned in item 2, above. Cell 1's FML is overlain by a protective soil layer. As a result, the FML, and any
tears or damage to seams or liner surfaces, are not readily visible. Thorough and complete inspection and
repair will require systematic removal of the soil cover by section, and stepwise inspection and repair of
uncovered FML sections in a phased approach, as discussed further in the proposed repair plan and schedule
below.
Regulatory Framework
Condition 11.3 of the Mill's State of Utah Radioactive Materials License No. UT1900479 (the "License") requires
that the licensee implement a leak detection monitoring system for each of the tailings cells. According to
condition 11.3:
(i) The licensee shall measure and record the "depth to fluid" in each of the tailings disposal cell
standpipes on a weekly basis. If sufficient fluid is present in the leak detection system (LDS) of
any cell, the licensee shall pump fluid from the LDS, to the extent reasonably possible, and
record the volume of fluid recovered. Any fluid pumped from an LDS shall be returned to a
disposal cell.
(ii) If fluid is pumped from an LDS, the licensee shall calculate the flow rate by dividing the
recorded volume of fluid recovered by the elapsed time since fluid was last pumped or
increases in the LDS fluid levels were recorded, whichever is the more recent. The licensee
shall document the results of this calculation.
(iii) Upon the initial pumping of fluid from an LDS, the licensee shall collect a fluid sample and
analyze the fluid for pH and the parameters listed in paragraph A of this license condition. The
licensee shall determine whether the LDS fluid originated from the constituents listed in
paragraph A of this license condition or has a pH level less than 5.0. If either elevated
constituent levels or a pH less than 5.0 is observed, the licensee shall assume that the disposal
cell is the origin of the fluid.
Condition 11.3 further requires the ongoing weekly measurement of depth to fluid if the calculated flow rate is
less than 1 gpm, and additional notification and mitigation requirements if the rate is greater than 1 gpm.
The above requirements have been incorporated into the Discharge Minimization Technology Plan in Section
3.1 ofthe Mill's Environmental Protection Manual.
Part I.E.7(f) of the Mill's GWDP requires that the Permittee shall inspect the liner system at Tailing Cells 1, 2,
and 3 on a daily basis pursuant to the requirements of Sections 2.1 and 2.2 of the currently approved DMT
Monitoring Plan. In the event that any liner defect or damage is identified during a liner system inspection, the
Permittee shall immediately: 1) report pursuant to Part I.G.3, 2) repair said defect or damage by
implementation of the currently approved Liner Maintenance Provisions, and 3) report all repairs made pursuant
to Part I.F.2.
DENISOl
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Letter to Rusty Lundberg on Cell 1 Repair Plan
August 18, 2010
Page 3
Section I.G.3 of the GWDP requires that in the event that the Permittee fails to maintain DMT or BAT or
otherwise fails to meet DMT or BAT standards as required by the Permit, the Permittee shall submit to the
Executive Secretary a notification and description of the failure according to R317-6-6.16(C)(1). Notification
shall be given orally within 24-hours of the Permittee's discovery of the failure of DMT or BAT, and shall be
followed up by written notification, including the information necessary to make a determination under R317-6-
6.16(C)(2), within five calendar days of the Permittee's discovery of the failure of best available technology.
UDEQ has not considered the Cell 1 liner system to meet BAT requirements and has excluded it from BAT and
DMT requirements in the Mill's GWDP. Hence, DMT reporting requirements do not specifically apply to the Cell
1 LDS. However, Denison chose to notify the Executive Secretary within 24 hours of the initial onset, by
telephone call on June 3, 2010, because the fluids in the Cell 1 LDS were assumed to represent a potential liner
defect that requires notice under Part I.E.7(f) of the GWDP. The Executive Secretary received written
notification within 5 days of the initial incident on June 7, 2010. Denison also provided a follow-up verbal
notification within 24 hours of the recurrence by phone call on August 8, 2010.
Initial Identification of Need for Repairs and Response Actions to Date
During the routine tailings inspection performed at approximately 2:50pm on June 2, 2010, the Cell 1 LDS
standpipe was observed to have accumulated approximately 7 feet 6 inches of liquid compared to the previous
day. The preceding day's recorded observation indicated that the LDS standpipe was "dry" (a measured level
of 63 feet 4 inches). Sufficient fluid had accumulated by 8:25am Thursday, June 3 to permit collection of
samples and initial pH testing to ascertain whether the fluid originated from the cell. The initial pH testing in at
8:45am on June 3, showed a pH of 2 to 3, indicating that the liquid originated from the cell. Initial notice of this
accumulation of liquid in the LDS was given by telephone to the Utah Department of Environmental Quality
Executive Secretary at 2:48pm on Thursday June 3, 2010 (within 24 hours of the discovery and within 7 hours
of determination of the origin of the fluid).
Upon receipt of the initial inspection result, the Mill's Environmental Coordinator notified the Mill Manager at
3:00pm that day. The Mill took the following steps, in accordance with License condition 11.3, the Mill's Liner
Maintenance Provisions, and Section 3.1 ofthe Mill's Environmental Protection Manual.
The Mill collected samples and duplicates on June 3 for analysis at Energy Laboratories and America West
Analytical Laboratories for the full suite of groundwater point of compliance analytes and parameters.
Characterization results confirmed that the source of the fluids in the LDS is tailings solutions.
Following the sampling on June 3, the Mill pumped the LDS to dryness, and began monitoring the level change
with time to estimate solution accumulation rate. The calculated rates estimated from this process indicated
that the solution accumulation rate did not exceed 1 gpm, and ranged from approximately 0.05 to 0.5 gpm.
At the time the LDS level was noted on June 3, the Cell 1 solution level was approximately 5614.57 feet amsl.
The Mill lowered the Cell 1 solution level during the month of June in order to reduce or eliminate the flow into
the LDS, and to allow inspection and repair of damage to the Cell 1 FML. The Cell 1 level was dropped to a low
of 5613.40 feet amsl during this period. Maintenance identified some FML damage and performed repairs
during the period when the level was lowest. Following the repairs, the Cell 1 liquid level was allowed to
gradually return to its June 3 level, and the LDS remained dry until a recurrence of the LDS liquid level was
identified on August 7.
The Mill experienced periodic heavy rains in late July and early August During the August 7, 2010 tailings
inspection, the Cell liquid level had reached 5614.22 feet amsl. At that time, the Environmental Technician
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Letter to Rusty Lundberg on Cell 1 Repair Plan
August 18, 2010
Page 4
identified that the LDS had an observable liquid level. Liquid samples and duplicates were once again collected
and shipped for analysis, and pumping and estimation of the LDS fill rate was resumed.
At this time. Mill management took a more aggressive approach to lowering the Cell 1 solution level. Cell 1 was
pumped at maximum transfer pump rate into Cell 4A, beginning approximately August 8. At the time of this
writing. Cell 1's solution level has been reduced to 5613.91 feet amsl and the Mill continues to pump and
monitor the recovery level in the LDS.
The Mill also continues to estimate the flow rate into the LDS between pumping. Since the August 8 detection,
the flow rate into the LDS has not exceeded 1 gpm, and has ranged from 0.01 to 0.02 gpm, or approximately
one tenth to one twentieth of the rate during the June detection.
During phone discussions with UDEQ personnel on August 12, 2010, UDEQ agreed with Denison that both the
June and August identifications of LDS solutions were all part of one event. At this time, Denison has
concluded that:
• The inspection and repairs performed on the Celll FML in June and July were apparently not
successful in identifying all ofthe damage which required repair.
• The temporary cessation of flow into the LDS between the June and August Cell 1 LDS fluid detections
may have resulted from the lowering of the solution level to a point below the remaining tears or
damage to the FML. However, as the solution level in Cell 1 rose, it reached the elevation of one or
more remaining defects in the liner. Additional systematic inspection and repair of the FML will
therefore be required.
Plan
Denison proposes the following plan of action to:
Identify and confirm the root cause of the observed solutions in the Cell 1 LDS.
Locate the specific areas of the FML requiring repair.
Conduct a systematic and orderly repair process that does not generate further damage to the FML
Confirm that the repairs have reduced or eliminated the flow into the LDS
Document the findings, root cause, and response actions.
This plan provides a phased approach to identification and repair of the defects in the Cell 1 liner. It is based on
the need for a stepwise schedule to systematically uncover and inspect all potentially damaged areas,
beginning with those areas with the highest potential for wear and resulting damage, and to perform the repairs
without incurring further damage to the FML during the removal of the protective soil cover. Denison does not
want to disturb any more of the soil cover, and expose more of the FML to the environment, than is necessary
in order to minimize the risk of further damage to the FML. In addition, the location of the repairs near the
tailings solution will require special safety precautions which add to the time required for repairs. Further, the
ability to perform any repairs during the winter months will be limited due to snow coverage and slippery
conditions. The key steps in the inspection and repair process will be as follows.
DENISO
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Letter to Rusty Lundberg on Cell 1 Repair Plan
August 18, 2010
Page 5
Phase I Plan and Schedule
1. Reduce the Cell 1 solution level approximately to the level it reached during the June repairs. Solutions
from Cell 1 are currently being pumped from Cell 1 to either Cell 3 or Cell 4A. The solution level should
be down to the June elevation by approximately August 31^'.
2. Identify areas in Cell 1 with highest potential for damage (where pipes enter and exit the cell, etc.). The
most obvious sections are in the southeast corner of Cell 1 and in the south central area of Cell 1 where
the pump barge is located. These areas are estimated to be approximately 200 feet of the Cell 1 bank.
3. Systematically inspect and repair the FML areas with the highest likelihood of damage first. The 200
feet of the highest risk areas will be uncovered and repaired as necessary. It is estimated that these
repairs will take approximately 10 weeks, until October 31, 2010.
4. Allow the level in the cell to recover and confirm that solutions do not reappear in the LDS. Solution
from the Mill process or from Cell 3 or Cell 4A will be pumped into the cell and the LDS sump will be
monitored. It is estimated that this step will take approximately 4 weeks, until November 30, 2010.
Phase II Plan and Schedule
5. If, after the process in steps 1 through 4 has been completed, solutions reappear in the LDS, the
solution level in Cell 1 will again be reduced in order to achieve dryness in the LDS. It is expected that
it will take some time for the Cell 1 pond solution to be reduced to the level necessary to achieve
dryness in the LDS, and for the LDS to be verified to be dry. However, this procedure is expected to be
accomplished by December 31, 2010.
6. After the solution level in Cell 1 is lowered, the next highest area of concern (likeliest area for damage)
will be uncovered, inspected, and repaired. Following the repairs, the Cell 1 solution level will be
allowed to gradually recover. The schedule for completion of this step will depend on winter conditions
and will be developed with the concurrence of the Executive Secretary.
7. If, after the process in steps 5 and 6 has been completed, solutions reappear in the LDS, the solution
level in Cell 1 will again be reduced in order to achieve dryness in the LDS. The cycle of steps 1 and 2
will be repeated, as necessary, until all the necessary repairs have been made to achieve dryness in
the LDS. The schedule of subsequent cycles of steps 5 and 6 will be developed with the concurrence
of the Executive Secretary.
Reporting
The Liner Maintenance Provisions appendix of the Mill's DMT Plan describes the types of repairs that will be
implemented following identification of solutions in the LDS, as well as requirements for a repair report
describing the nature of the damage and the repairs. As required by the Liner Maintenance Provisions, a repair
report will be submitted to the Executive Secretary following completion of repairs to the Cell 1 liner. The repair
report will contain, in addition to a root cause analysis, the following elements:
• Repair narrative describing the nature of the damage and the repair work completed to repair the
damage.
• Repair material type used to complete the repair
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Letter to Rusty Lundberg on Cell 1 Repair Plan
August 18, 2010
Page 6
Repair material description
Post repairs test specifications
Test Methods (ASTM or other)
Daily reports during the repair work
Repair test results
Quality Assurance/Quality Control Information
Data collected during the diagnostic steps, including solution accumulation rate estimations and analytical
results from characterization of LDS solution samples will also be included in the repair report.
Please contact the undersigned if you have any questions or require any further information.
Yours very truly,
DENISON MINES (USA) CORP.
Jo Ann Tischler
Director, Compliance and Permitting
cc: Rich E. Bartlett
David C, Frydenlund
Ron F. Hochstein
Ryan Palmer
Harold R. Roberts
David E. Turk
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