DRC-2008-002241 - 0901a0688070e189

OENISONI)��
MINES
VIA FEDERAL EXPRESS
August 29, 2008
Dane L. Finerfrock, Executive Secretary
Utah Radiation Control Board
Utah Department of Environmental Quality
168 North 1950 West
P.O. Box 144810
Salt Lake City, Utah 84114-4810
Dear Mr. Finerfrock:
Denison Mines (USA) Corp.
1050 17th Street, Suite 950
Denver, CO 80265
USA
Tel : [phone]
Fax : [phone]
www.denisonmines.com
Re: Transmittal of 2nd Quarter 2008 Chloroform Monitoring Report-White Mesa Uranium Mill
Enclosed are two copies of the White Mesa Uranium Mill Chloroform Monitoring Report for the 2nd Quarter of
2008, as required under the State of Utah Notice of Violation and Groundwater Corrective Action Order No.
UGQ-20-01.
Yours very truly,
DENISON MINES (USA) CORP.
Steven D. Landau
Manager-Environmental Affairs
White Mesa Uranium Mill
Chloroform Monitoring Report
State of Utah
Notice of Violation and Groundwater Corrective Action Order UDEQ
Docket No. UGQ-20-01
2nd Quarter (January through March)
2008
Prepared by:
Denison Mines (USA) Corp. (DUSA)
1050 17th Street, Suite 950
Denver CO 80265
August 29, 2008
1. INTRODUCTION
This is the Quarterly Chloroform Monitoring Report, as required under State of Utah Notice of
Violation and Groundwater Corrective Action Order State of Utah Department of Environmental
Quality ("UDEQ") Docket No. UGQ-20-01 for the 481 Quarter of 2008 (the "Quarter") for
Denison Mines (USA) Corp.'s ("DUSA's") White Mesa Uranium Mill (the "Mill"). This Report
also includes the Operations Report for the Long Term Pump Test at MW-4, TW4-19, TW4-15
(MW-26) and TW4-20 for the Quarter.
2. SAMPLING AND MONITORING PLAN
2.1. Description of Monitor Wells Sampled During the Quarter
During the Quarter, the following chloroform contaminant investigation groundwater samples
and measurements were taken:
2.1.1. Groundwater Monitoring
Groundwater Monitoring was performed in all of the chloroform monitoring wells, being the
following wells:
• MW-4 • TW4-13
• TW4-A • TW4-14
• TW4-1 • TW4-15(MW-26)
• TW4-2 • TW4-16
• TW4-3 • TW4-17(MW-32)
• TW4-4 • TW4-18
• TW4-5 • TW4-19
• TW4-6 • TW4-20
• TW4-7 • TW4-21
• TW4-8 • TW4-22
• TW4-9 • TW4-23
• TW4-10 • TW4-24
• TW4-11 • TW4-25
• TW4-12
The locations of these wells are indicated on the map attached under Tab A.
Wells sampled during this reporting period were analyzed for the following constituents:
• Chloroform
• Chloromethane
• Carbon tetrachloride
• Methylene chloride
• Chloride
• Nitrogen, Nitrate + Nitrite as N
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2.1.2. Groundwater Head Monitoring
Depth to groundwater was taken in the following wells and/or piezometers during the Quarter:
a) All of the chloroform contaminant investigation wells listed in paragraph 2.1.1 above on
6/24 & 6/25/08;
b) All of the point of compliance monitoring wells under the Mill's Groundwater Discharge
Permit ("GWDP") on 5/28/08 through 6/18/08.
c) Piezometers-P-1, P-2, P-3, P-4 and P-5 on 5/29/08.
In addition, weekly depth to groundwater measurements were taken in MW-4, TW4-15 (MW-
26), TW4-19 and TW4-20, as part of the long term pumping test for MW-4.
2.2. Sampling Methodology, Equipment and Decontamination Procedures
The sampling methodology, equipment and decontamination procedures that were performed for
the chloroform contaminant investigation during the Quarter can be summarized as follows:
2.2.1. Well Purging and Depth to Groundwater
a) A list is gathered of the wells in order of increasing chloroform contamination. The
order for purging is thus established. Mill personnel start purging with all of the non­
detect wells and then move to the more contaminated wells in order of chloroform
contamination, starting with the wells having the lowest chloroform contamination; and
b) Before leaving the Mill office, the pump and hose are rinsed with de-ionized ("DI")
water. Mill personnel then proceed to the first well which is the well indicating the
lowest concentration of chloroform based on the previous quarters sampling results.
Well depth measurements are taken and the two casing volumes are calculated
(measurements are made using the same instrument used for the monitoring wells under
the Mill's GWDP). The Grundfos pump (a 6 gpm pump) is then lowered to the bottom
of the well and purging is begun. At the first well, the purge rate is established for the
purging event by using a calibrated 5 gallon bucket. After the evacuation of the first
well has been completed, the pump is removed from the well and the process is repeated
at each well location moving from least contaminated to most contaminated. All wells
are capped and secured prior to leaving the sampling location.
2.2.2. Sampling
a) Following the purging of all chloroform investigation wells, the sampling takes place
(usually the next morning). Prior to leaving the Mill office to sample, a cooler along
with blue ice is prepared. The trip blank is also gathered at that time (the trip blank for
these events is provided by the Analytical Laboratory). Once Mill Personnel arrive at
the well sites, labels are filled out for the various samples to be collected. All personnel
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involved with the collection of water and samples are the outfitted with rubber gloves.
Chloroform investigation samples are collected by means of dedicated bailers and the
wells are purged by means of a dedicated portable pump. Each quarterly pumping and
sample collection event begins at the location least affected by chloroform (based on the
previous quarters sampling event) and proceeds by affected concentration to the most
affected location. The dedicated portable pump is appropriately decontaminated prior to
each purging sampling event and the QA rinsate sample is collected after said
decontamination but prior to the commencement of the sampling event.
b) Mill personnel use a disposable bailer to sample each well. The bailer is attached to a
reel of approximately 150 feet of nylon rope and then lowered into the well. After
coming into contact with the water, the bailer is allowed to sink into the water in order to
fill. Once full, the bailer is reeled up out of the well and the sample bottles are filled as
follows;
(i) First, a set of VOC vials is filled. This set consists of three 40 ml vials provided
by the Analytical Laboratory. The set is not filtered and is preserved with HCL;
(ii) Second, a 500 ml sample is collected for Nitrates/Nitrites. This sample is also
not filtered and is preserved with H2S04 (the bottle for this set is also provided
by the Analytical Laboratory);
(iii) Third, a 500 ml sample is collected for Chloride. This sample is not filtered and
is not preserved; and
c) After the samples have been collected for a particular well, the bailer is disposed of and
the samples are placed into the cooler that contains blue ice. The well is then recapped
and Mill personnel proceed to the next well.
DUSA completed (and transmitted to UDEQ on May 25, 2006) a revised Quality Assurance Plan
("QAP") for sampling under the Mill's GWDP. The GWDP QAP was reviewed by UDEQ and
has been approved for implementation. The QAP provides a detailed presentation of procedures
utilized for groundwater sampling activities under the GWDP. While the water sampling
conducted for chloroform investigation purposes has been conformant with the general principles
set out in the QAP, some of the requirements in the QAP were not fully implemented prior to
UDEQ's approval for reasons set out in correspondence to UDEQ dated December 8, 2006.
Subsequent to the delivery of the December 8, 2006 letter, DUSA discussed the issues brought
forward in the letter with UDEQ and has received correspondence from UDEQ about those
issues. In response to UDEQ's letter and subsequent discussions with UDEQ, DUSA has
incorporated changes in chloroform QA procedures in the form of a separate document. The
chloroform QA document describes the differing needs of the chloroform investigation program,
and is and attachment to the GWDP QAP where QA needs other than those described in the
chloroform QA document are addressed. The current version of the QAP dated June 18, 2008
has been approved by UDEQ, including those requirements for Chloroform monitoring under
separate attachment to the QAP.
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2.3 Field Data Worksheets
Attached under Tab B are copies of all Field Data Worksheets that were completed during the
Quarter for the chloroform contaminant investigation monitoring wells listed in paragraph 2.1.1
above and sampled June 25, 2008.
2.4 Depth to Groundwater Sheets
Attached under Tab C are copies of the Depth to Water Sheets for the weekly monitoring of
MW-4, TW4-15 (MW-26), TW4-19 and TW4-20 as well as the monthly depth to groundwater
monitoring data for chloroform contaminant investigation wells measured during the quarter.
Depth-to-groundwater measurements collected on June 24 & 25, 2008 for the Chloroform wells
were utilized for groundwater contours are included on the Field Data Worksheets at Tab B of
this report.
3. DATA INTERPRETATION
3.1. Interpretation of Groundwater Levels, Gradients and Flow Directions.
3 .1.1. Current Site Groundwater Contour Map
Included under Tab D is a water table contour map, which provides the location of all of the
wells and piezometers listed in item 2.1.2 above for which depth to groundwater was taken
during the Quarter, the groundwater elevation at each such well and piezometer, measured in feet
above mean sea level, and isocontour lines to delineate groundwater flow directions observed
during the Quarter's sampling event. The contour map uses the June 24 & 25, 2008 data for the
temporary Chloroform monitoring wells listed in paragraph 2.1.2 (a) above, May 28 through
June 18, 2008 data for the wells listed in paragraph 2.1.2 (b), and May 29, 2008 for Piezometers
or the piezometers listed in paragraph 2.1.2 (c) above.
Also included under Tab D is a groundwater contour map of the portion of the Mill site where
the four chloroform pumping wells are located, with hand-drawn stream tubes, in order to
demonstrate hydraulic capture from the pumping.
3 .1.2. Comparison of Current Groundwater Contour Maps to Groundwater Contour
Maps for Previous Quarter
The groundwater contour maps for the Mill site for the first quarter of 2008, as submitted with
the Chloroform Monitoring Report for the first quarter of 2008, are attached under Tab E.
A comparison of the water table contour maps for the Quarter to the water table contour maps for
the previous quarter indicates similar patterns of drawdown related to pumping of MW -4, MW-
26 (TW4-15), TW4-19 and TW4-20. Water levels and water level contours for the site have not
changed significantly since the last quarter, except for a few locations.
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Reported decreases in water levels of approximately 9 feet in TW 4-11, of approximately 7 feet
in TW4-2 1, and of approximately 4 feet in MW-28 occurred, and a reported increase of
approximately 5 feet occurred at MW-19. The decrease in water level at TW4-11 results in a
water level that is more typical for that well than the apparently anomalous value reported for the
previous quarter.
Water level decreases occurred at MW-4, MW-26 (TW4-15), TW4-19, and TW4-20. Water
level fluctuations in these pumping wells are due in part to fluctuations in pumping conditions
just prior to and at the time the measurements are. The largest decrease (increase in drawdown)
of approximately 33 feet occurred at TW4-19, and the smallest decrease, of nearly 3 feet,
occurred at MW-4.
3.1.3. Hydrographs
Attached under Tab F are hydrographs showing groundwater elevation in each chloroform
contaminant investigation monitor well over time.
3.1.4. Depth to Groundwater Measured and Groundwater Elevation
Attached under Tab G are tables showing depth to groundwater measured and groundwater
elevation over time for each of the wells listed in Section 2.1.1 above.
3.1.5. Evaluation of the Effectiveness of Hydraulic Capture
Perched water containing chloroform has been removed from the subsurface by pumping MW -4,
TW4-19, MW-26 (TW4-15), and TW4-20. The purpose of the pumping is to reduce total
chloroform mass in the perched zone as rapidly as is practical. These wells were chosen for
pumping because 1) they are located in areas of the perched zone having relatively high
permeability and saturated thickness, and 2) high concentrations of chloroform were detected at
these locations. The relatively high transmissivity of the perched zone in the vicinity of the
pumping wells results in the wells having a relatively high productivity. The combination of
relatively high productivity and high chloroform concentrations allows a high rate of chloroform
mass removal.
The impact of pumping these wells is indicated by the water level contour maps attached under
Tabs D and E. Cones of depression have developed in the vicinity of the pumping wells which
continue to remove significant quantities of chloroform from the perched zone. The water level
contour maps indicate that effective capture of water containing high chloroform concentrations
in the vicinity of the pumping wells is occurring. As noted in Section 3.1.2, decreases in
measured water levels (increases in drawdowns) occurred at pumping wells MW-4, MW-26
(TW4-15), TW4-19 and TW4-20 between the first and second quarters of 2008. Overall, the
combined capture of TW4-19, TW4-20, MW-4 and MW-26 (TW4-15) has not changed
significantly, but has increased slightly, since the last quarter. The large increase in drawdown at
TW 4-19 has increased the apparent capture zone of this well relative to that of other nearby
pumping wells.
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Although high chloroform concentrations exist at some locations downgradient of the pumping
wells (for example, near TW4-4), the low permeability of the perched zone at these locations
would prevent significant rates of chloroform mass removal should these wells be pumped. By
pumping at the more productive, upgradient locations, however, the rate of downgradient
chloroform migration will be diminished because of the reduction in hydraulic gradients, and
natural attenuation will be more effective.
3.2. Interpretation of Analytical Results
3 .2.1. Copy of Laboratory Results
Included under Tab H of this Report are copies of all laboratory analytical results for the
groundwater quality samples collected under the chloroform contaminant investigation on June
25, 2008 along with the laboratory analytical results for a trip blank.
3.2.2. Electronic Data Files and Format
DUSA has provided to the Executive Secretary an electronic copy of all laboratory results for
groundwater quality monitoring conducted under the chloroform contaminant investigation
during the Quarter, in Comma Separated Values (CSV). A copy of the transmittal e-mail is
included under Tab I.
3 .2.3 Current Chloroform Isoconcentration Map
Included under Tab J of this Report is a current chloroform isoconcentration map for the Mill
site.
3.2.4 Data and Graphs Showing Chloroform Concentration Trends
Attached under Tab K is a table summarizing chloroform and nitrate values for each well over
time. TW4-14 had a small amount of water just sufficient for sampling (see the discussion in
Section 2.1.1 above)
Attached under Tab L are graphs showing chloroform concentration trends in each monitor well
over time. As TW4-14 was previously dry, a trend graph for that well has not been included.
3.2.5 Analysis of Analytical Results
Comparing the analytical results to those of the previous quarter, as summarized in the table
included under Tab K, the following observations can be made:
a) Chloroform concentrations have increased by more than 20% in the following wells,
compared to last quarter: TW4-11, MW-26 (TW4-15), and TW4-20.
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b) Chloroform concentrations have decreased by more than 20% in the following wells,
compared to last quarter: TW4-6, TW4-9, TW4-16, TW4-19, and TW4-21;
c) Chloroform concentrations have remained within 20% in the following wells compared
to last quarter: MW-4, TW4-1, TW4-2, TW4-4, TW4-5, TW4-7, TW4-10, TW4-18,
TW4-22, and TW4-24;
d) Chloroform concentrations at TW 4-16 decreased from 11 !lg/L to non-detect; and
e) TW4-3, TW4-8, TW4-12, TW4-13, TW4-14, MW-32 (TW4-17), TW4-23, and TW4-25
remained non-detect.
In addition, between the first and second quarters of 2008, the chloroform concentration in well
TW4-20 increased from 13,000 !lg/L to 30,000 !lg/L, the concentration in TW4-21 decreased
from 390 !lg/L to 160 !lg/L, and the concentration in TW4-22 decreased from 1,400 !lg/L to
1,200 !lg/L. Wells TW4-23 and TW4-25 remained non-detect for chloroform, and the
concentration in well TW4-24 decreased slightly from 1.5 to 1.4 !lg/L. TW4-24, located west of
TW4-22, and TW4-25, located north of TW4-21, bound the chloroform plume to the west and
north.
Chloroform concentrations in TW 4-6, which was the most downgradient temporary perched
well prior to installation of temporary well TW4-23, decreased from 52 to 24 !lg/L. This well has
likely remained outside the chloroform plume due to a combination of 1) slow rates of
downgradient chloroform migration in this area due to low permeability conditions and the
effects of upgradient chloroform removal by pumping, and 2) natural attenuation. Both TW4-6
and TW4-23 bound the chloroform plume to the south.
3.3. Quality Assurance Evaluation And Data Validation
Quality assurance evaluation and data validation procedures in effect at the time of sampling
were followed. These involve three basic types of evaluations: field QC checks; Analytical
Laboratory checks; and checks performed by DUSA personnel, as described below.
3.3.1 Field QC Checks
Field Quality Control samples for the chloroform investigation program consist of a field
duplicate sample, a field blank and a trip blank. These check samples are to be generated for
each quarterly sampling episode. During the 2nd Quarter of 2008 duplicates (TW4-65, duplicate
of TW 4-17 and TW 4-70, duplicate of TW 4-17), a D I blank (TW 4-60), an equipment rinsate
sample (TW4-63) and a trip blank were collected and analyzed. The results of these analyses are
included with the routine analyses under Tab H.
3.3.2 Analytical Laboratory QA/QC Procedures
The Analytical Laboratory has provided summary reports of the analytical . quality
assurance/quality control (QA/QC) measurements necessary to maintain conformance with
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NELAC certification and reporting protocol. The Analytical Laboratory QA/QC Summary
Report, including copies of the Mill's Chain of Custody and Analytical Request Record forms,
for the November sampling event, are included under Tab H.
3.3.3 Mill OA Manager Review
The Mill QA Manager, which, for these sampling events was DUSA's Manager of
Environmental Affairs, performed four types of reviews: a determination of whether Mill
sampling personnel followed Mill sampling procedures; a review of the results from the Field
QC Checks; a review of analytical reports for holding times and qualifying indicators for the
data; and a review of the Analytical Laboratory QA/QC analysis. The results of the QA
Manager's review are discussed below.
a) Adherence to Mill Sampling SOPs
On a review of adherence by Mill personnel to the sampling procedures summarized in Section
2.2 above, the QA Manager concluded that such procedures had been followed.
b) Results From Field QC Checks
All parameters were within the limitation for the TW 4-17 duplication exercise, however, one
parameter (Chloride) is annotated for the duplication of TW4-8 with a relative percent difference
of. As such the results fo Nitrogen, Nitrate + Nitrite as N and for Methylene Chloride are
provided with qualification relative to duplicability of data. The results of the QC evaluation of
duplicate samples for this 1 tst Quarter, 2008 event is provided in the table below:
Chloride 29 29 45 29 43%
Nitrogen, Nitrate + Nitrite as N ND ND ND ND 0
Carbon tetrachloride ND ND ND ND 0
Chloroform ND ND ND ND 0
Chloromethane ND ND ND ND 0
Methylene Chloride ND ND ND ND 0
The quarterly results over time have shown improvement in the presence of chloroform in the
field blank and rinsate sample. This quarters field blank TW 4-60 found Chloroform at 13 ug/L
whereas the equipment rinsate blank TW 4-63 found chlormethane at slightly above the detection
limit (1.4 ug/L). While improvement is noted, the QA Manager has on July 9, 2008 required the
sampling personnel to purchase laboratory grade De-ionized (DI) water for field blank and
equipment decontamination and to discontinue the use of onsite DI water.
c) Review of Analytical Laboratory QA/QC Analysis and Analytical Reports
The QA Manager reviewed the Analytical Laboratory's QA/QC Summary Reports and made the
following conclusions;
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(i) Check samples were analyzed for each method used in analyzing the
Chloroform investigation samples. These methods were:
Parameter
Nitrogen, (Nitrate +Nitrite as N)
Chloroform,
Carbon tetrachloride
Chloromethane
Methylene chloride
Chloride
Method
E353.2
E624
E624
E624
E624
A4500-CL B
(ii) The check samples included at least the following: a method blank, a laboratory
control spike (sample), a matrix spike and a matrix spike duplicate;
(iii) All qualifiers and the corresponding explanations in the summary reports are
reviewed by the QA Manager. The qualifiers reported were for matrix
interference in chloroform analyses in some of the analyzed monitoring location
samples, however, the results exceeded the re-established reporting limit. The
other qualifying data were for spike recovery on a surrogate analysis related to
chloroform recovery for one of the surrogates, all other surrogates were
acceptable. The recovery in surrogate analysis for chloroform relates to matrix
interference.
(iv) The laboratory holding time for all analyses was within chloroform specification
and sample temperature was acceptable upon receipt.
4. LONG TERM PUMP TEST AT MW-4, TW4-15 (MW-26), TW4-19 AND
TW4-20, OPERATIONS REPORT
4.1. Introduction
As a part of the investigation of chloroform contamination at the Mill site, DUSA has been
conducting a Long Term Pump Test on MW-4, TW4-19, TW4-15 (MW-26) and TW4-20. The
purpose of the test is to serve as an interim action that will remove a significant amount of
chloroform-contaminated water while gathering additional data on hydraulic properties in the
area of investigation. The following information documents the operational activities during the
Quarter.
4.2. Pump Test Data Collection
The long term pump test for MW-4 was started on April 14, 2003, followed by the start of
pumping from TW4-19 on April 30, 2003, from TW4-15 (MW-26) on August 8, 2003 and from
TW4-20 on August 4, 2005. Personnel from Hydro Geo Chern, Inc. were on site to conduct the
9
first phase of the pump test and collect the initial two days of monitoring data for MW -4. DUSA
personnel have gathered subsequent water level and pumping data.
Analyses of hydraulic parameters and discussions of perched zone hydrogeology near MW-4 has
been provided by Hydro Geo Chern in a separate report, dated November 12, 2001, and in the
May 26,2004 Final Report on the Long Term Pumping Test.
Data collected during the Quarter included the following:
a) Measurement of water levels at MW-4, TW4-19, TW4-15 (MW-26), and TW4-20 on a
weekly basis, and at selected temporary wells and permanent monitoring wells on a
monthly basis (See Section 3.1 and Tabs Band C for a discussion of the water levels);
b) Measurement of pumping history:
(i) pumping rates
(ii) total pumped volume
(iii) operational and non-operational periods;
c) Periodic sampling of pumped water for chloroform and nitrate & nitrite analysis and
other constituents, as discussed in detail in Section 3.2 above.
4.3. Water Level Measurements
Beginning August 16, 2003, the frequency of water level measurements from MW-4, TW4-15
(MW-26), and TW4-19 was reduced to weekly. From commencement of pumping TW4-20,
water levels in that well have been measured weekly. Depth to groundwater in all other
chloroform contaminant investigation wells is monitored monthly. Copies of the weekly Depth
to Water monitoring sheets for MW-4, TW4-15 (MW-26), TW4-19 and TW4-20 are included
under Tab C. Monthly depth-to-water measurements for October are recorded in the Field Data
Worksheets included under Tab B.
4.4. Pumping Rates and Volumes
4.4.1. MW-4
Approximately 62,780 gallons of water were pumped from MW -4 during the Quarter. The
average pumping rate from MW-4, when the pump was pumping, was approximately 4.0 gpm
throughout the Quarter. The well is not purging continuously, but is on a delay device. The well
purges for a set amount of time and then shuts off to allow the well to recharge. Water from
MW-4 was transferred to the Cell 1 evaporation pond through a pipeline installed specifically for
that purpose. At the end of the 3rd Quarter, 2007, and since commencement of pumping on
April 14, 2003, an estimated total of approximately 1,644,740 gallons of water have been purged
from MW-4.
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4.4.2. TW4-19
Approximately 3 80,310 gallons of water were pumped from TW 4-19 during the Quarter. The
average pumping rate from TW4-19, when the pump was pumping, was approximately 3.1 gpm
throughout the Quarter. The pump in this well is operating on a delay. It pumps for
approximately one and a half minutes and then is off for two to three minutes. Water from TW4-
19 was directly transferred to the Cell 1 evaporation pond through a pipeline installed
specifically for that purpose. At the end of the 1st Quarter, 2007, and since commencement of
pumping on April 30, 2003, an estimated total of approximately 8,104,510 gallons of water have
been purged from TW 4-19.
4.4.3. TW4-15 (MW-26)
Approximately 44,840 gallons of water were pumped from TW4-15 (MW-26) during the
Quarter. The average flow rate from TW4-15, when the pump was pumping, was approximately
5.5 gpm throughout the Quarter. The well is not purging continuously, but is on a delay device.
The well now purges for a set amount of time and then shuts off to allow the well to recharge.
The water is directly transferred to the Celli evaporation pond through a pipeline installed
specifically for that purpose. At the end of the 1st Quarter, 2006, and since commencement of
pumping on August 8, 2003, an estimated total of approximately 1,156,960 gallons of water have
been purged from TW 4-15.
4.4.4. TW4-20
Approximately 39,360 gallons of water were pumped from TW4-20 during the Quarter. The
average flow rate from TW4-20, when the pump was pumping, was approximately 6.0 gpm
throughout the Quarter. The well is not purging continuously but is on a delay device. The well
pump is set on a water elevation device. When the water reaches a set point, the pump turns on
until the water level drops to another set point. The water is directly transferred to the Cell 1
evaporation pond through a pipeline installed specifically for that purpose. Since
commencement of pumping on August 4, 2005, an estimated total of approximately 882,160
gallons of water have been purged from TW4-20.
4.5 Daily Inspections
Denison has submitted an Operations and Maintenance Plan, Chloroform Pumping System,
White Mesa Mill, Blanding, Utah, Revision 1.0 to UDEQ for approval. Upon approval of that
plan, the Mill will commence documenting its daily inspections of the operational status of the
chloroform pumping wells on the daily inspection form, an example of the form of which is
attached as Tab M.
4.6 Operational Problems
There were no operational problems reported for this period.
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4. 7 Conditions That May Affect Water Levels in Piezometers
No water was added to any of the three wildlife diversion ponds during the Quarter.
5. CONCLUSIONS AND RECOMMENDATIONS
The water level contour map for the Quarter indicates that effective capture of water containing
high chloroform concentrations in the vicinity of the pumping wells is occurring.
Between the first and second quarters of 2008, the chloroform concentration in well TW4-20
increased from 13,000 Jlg/L to 30,000 Jlg/L, the concentration in TW4-21 decreased from 390
J..tg/L to 160 J..tg/L, and the concentration in TW4-22 decreased from 1,400 Jlg/L to 1,200 J..tg/L.
Fluctuations in concentrations in these wells are likely related to variations in pumping in TW 4-
20 and nearby wells, and their location near the suspected former office leach field source area.
Regardless of these measured fluctuations in chloroform concentrations, sampling of temporary
wells TW4-24 (located west of TW4-22) and TW4-25 (located north of TW4-21), indicated
these wells remain outside the chloroform plume and thus bound the plume to the west and
north. Chloroform was not detected at TW4-25 and was detected at a concentration of less than 2
Jlg/L at TW4-24.
Continued pumping of TW4-19, TW4-20, MW-4, and MW-26 (TW4-15) is recommended.
Pumping these wells, regardless of any short term fluctuations in concentrations detected at the
wells (such as at TW4-20), helps to reduce downgradient chloroform migration by removing
chloroform mass and reducing average hydraulic gradients, thereby allowing natural attenuation
to be more effective.
The chloroform concentration at downgradient well TW 4-6 decreased from 52 to 24 Jlg/L.
Although fluctuations in concentrations have occurred, this well has likely remained outside the
chloroform plume due to a combination of 1) slow rates of downgradient chloroform migration
in this area due to low permeability conditions and the effects of up gradient chloroform removal
by pumping, and 2) natural attenuation. Chloroform remained non detect at downgradient
temporary well TW4-23. Both TW4-6 and TW4-23 bound the chloroform plume to the south.
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