HomeMy WebLinkAboutDERR-2024-006805
www.rbwhitepe.com
March 28, 2024
Gary Crocker
Silver Reef Investment Holdings, LLC
2825 Est Cottonwood Parkway
Suite 330
Salt Lake City, UT 84121
Subject: Silver Pointe Estates - Report of Site Maintenance
Following September 2023 Inspection
Dear Gary:
On September 18, 2023 I conducted the annual inspection of Silver Pointe Estates in accordance with
the requirements of the location’s Site Management Plan. The final report associated with that
inspection was issued on November 30, 2023. That report identified the following four items requiring
attention:
• Remove small piles of waste rock and adjacent soil discovered in an area north of the large
headframe.
• Post a sign and place soil and gravel at the entrance to a closed mine adit.
• Move a group of large boulder into the adjacent “glory hole.”
• Place additional soil and gravel on locations where erosion has occurred in areas required by the
Site Management Plan to maintain a minimum of 6 inches of soil cover.
The purpose of this report is to present the results of the above maintenance efforts. These efforts
were observed in the field by myself and by David Bird, Project Manager in the Voluntary Cleanup
Program/Brownfields Section of the Utah Division of Environmental Response and Remediation
(“DERR”).
Waste Rock Removal
During the September 2023 site inspection, Mr. Bird and I observed approximately 40 to 50 yd3 of waste
rock that existed in three adjacent piles located approximately 230 feet north of the large headframe.
To assist with cleanup of this material, I scanned the area of this waste rock and adjacent soil on January
29, 2024 using a Ludlum 2221 scaler with a 49-10 gamma detector. I then placed pin flags at the extent
of areas where gamma radioactivity exceeded background.
Removal of the waste rock and soil began on January 29, 2024. Substantial precipitation during the
prior few weeks left the soil in a moist condition, thereby precluding the need for dust control during
removal operations. The soil was excavated by Raintree Landscaping using a trackhoe and placed in a
stockpile adjacent to Bonanza Flat Road. The soil was then loaded from the stockpile into haul trucks
which were tarped prior to hauling the material to the Washington County landfill.
Richard B. White, PE, PLLC 13441 South Lone Peak Lane Draper, Utah 84020 801-673-6647
Gary Crocker
March 28, 2024
Page 2
I occasionally scanned the excavated area for gamma radiation as waste rock and soil were being
removed to ensure that background conditions were achieved. I marked areas with pin flags where
additional soil removal was required. Those areas were then re-excavated.
We had previously understood that the waste rock and soil from the site could be hauled to the landfill
without special approval. However, the first loads of material were rejected since paper work had not
been filed. Therefore, I submitted a Special Waste Profile to Republic Services (the landfill operator) on
January 31, 2024. A copy of that profile, together with the supporting information submitted at the
request of Republic Services, is provided in Attachment A. In the interim, as we were awaiting approval
from the landfill, I covered the excavated soil stockpile with 6-mil black polyethylene sheeting to protect
the stockpile against wind and water erosion during the delay. The sheeting was weighted down with
rocks on the top and a soil berm on the south (uphill) side.
Approval to dispose of the material at the Washington County landfill was issued by Republic Services on
February 9, 2024. A copy of this approval is provided in Attachment B. Hauling of the waste rock and
impacted soil resumed on February 13, 2024 and was completed that day. Copies of the transport
manifests are provided in Attachment C. Photographs of the removal effort are provided in Attachment
D.
Following removal of all excavated waste rock and soil from the site, I again scanned the area for gamma
radiation and found levels to be consistent with background. I then collected soil samples from the
excavated area for laboratory analyses to confirm that the extent of excavation was sufficient. These
samples were collected in accordance with the 2010 Remedial-Action Plan (“RAP”) used for prior
cleanup of the area.
Based on field measurements, I determined that the excavated zone covered an area of 6,290 ft2. The
RAP requires that confirmation samples be collected from remediated areas at a frequency of at least
one composite per 10,000 ft2 of excavated area. With an affected area of less than 10,000 ft2, I collected
one composite sample from the excavated area. In accordance with the RAP, I marked locations for
subsample collection by laying a measuring tape along the northern boundary of the excavated area and
then, using a random number generator, I selected 10 locations west and south of the starting point
within the excavated area and marked those locations with pin flags.
Prior to collecting each subsample, I measured the concentrations of several of the contaminants of
potential concern (as identified in the RAP) using a SciApps X200 x-ray fluorescence (“XRF”) analyzer.
The analyzer had been calibrated in the laboratory prior to receipt and I conducted field calibrations in
accordance with the manufacturer’s recommendation prior to use. I scanned each sample location by
pressing the face of the analyzer against the soil for a minimum of 50 seconds (the rate set by the
company from which I rented the analyzer). The results of those analyses are provided in Table 1.
These analyses, together with the post-excavation gamma radiation measurements, suggested that
sufficient rock and soil had been removed for the residual soil to meet the RAP remediation goals.
Gary Crocker
March 28, 2024
Page 3
After obtaining field gamma and XRF measurements, I collected each subsample in accordance with the
RAP as follows:
• At each location, I collected a subsample with a stainless steel spoon to a depth of 2 to 3 inches
and placed the subsamples in a stainless steel bowl.
• Following the collection of all subsamples, I mixed the subsamples in the bowl using the
stainless steel spoon.
• I then filled sample containers with the mixed soil to provide three confirmation samples - one
representing the original sample, one representing a blind duplicate, and one that I provided to
Mr. Bird for analyses at another laboratory selected by DERR.
I submitted the original and blind duplicate samples to Eurofins at their laboratory in Earth City,
Missouri. Mr. Bird submitted the DERR split sample to Pace Analytical at their laboratory in Mount
Juliet, Tennessee. The results of the laboratory analyses are presented in Attachment E and summarized
in Table 2.
Comparisons of the primary sample with the blind duplicate and the laboratory duplicate are provided
in Table 3. Some comparisons exceeded the precision goal of 15% as stated in the 2010 Quality
Assurance Project Plan that was prepared for sampling of the Phase 1 and Phase 2 development areas.
Such exceedances are not unusual in cases where concentrations are low. Given the fact that the
maximum concentrations detected in all samples (primary and duplicate) are substantially below the
remedial-action goals, it is apparent that sufficient waste rock and soil were removed from the area to
meet the remedial-action goals of the RAP. Therefore, I consider concerns about this location to be
resolved.
Adit Sign and Cover
On January 29, 2024 I posted a sign on the grate covering the face of the adit indicating that elevated
radiation levels exist in the area. Raintree Landscaping then placed a minimum of 6 inches of soil and 2
inches of 2-inch minus gravel on the floor of the portal leading to the adit on February 13, 2024.
Photographs of that effort are included in Attachment D.
In a meeting on March 11, 2024, Mr. Bird requested that a line item be added to the annual inspection
form addressing the status of the sign that was hung on the adit grate. The revised form with that
added line item is provided in Attachment F. With these efforts having been completed, I consider
concerns about this location to be resolved.
Boulder Removal
During the September 2023 site inspection, Mr. Bird and I observed a large boulder on the ridge near
the “glory hole” that exhibited high gamma radiation levels. At the request of Mr. Bird, this boulder and
the adjacent boulders were placed into the bottom of the “glory hole” on January 29, 2024.
Gary Crocker
March 28, 2024
Page 4
Photographs of this effort are provided in Attachment D. With this work having been completed, I
consider concerns about this location to be resolved.
Erosion Repair
During the September 2023 site inspection, Mr. Bird and I observed rill erosion in some areas where the
Site Management Plan requires maintenance of a minimum of 6 inches of soil cover. The erosion of
concern occurred in the following areas, as labeled on Figures 8 and 9 of the 2016 Remedial Action
Report (see Attachment G for copies of the figures):
• PCA5-0
• PCA6-SE
• PCA8-SE
• PCA8-NEA-R
• PCA8-NEB-R
• PCA10-0
• PCA12-0
Prior to repair, I scanned the areas of concern for gamma radiation. Gamma radiation across most of
the areas of concern was consistent with background. I then placed pin flags at the edges of the areas
of concern based on aerial photographs included in Attachment G.
Based on my pre-maintenance observations, I estimated that an average of at least 3 inches of soil
remained at each area of concern. Therefore, I instructed Raintree Landscaping to regrade each area
and added a minimum of 3 inches of soil and 2 inches of 2-inch minus gravel as an erosion protection
cover. This was accomplished during the period of January 29 through February 13, 2024, with breaks
during that period when precipitation made working conditions difficult. Based on my observations
during this work, I estimate that 4 to 5 inches of soil and 2 to 3 inches of gravel were added to most of
the areas of concern, thus exceeding the requirements.
Soil added to the areas of concern consisted of clean soil obtained from a location in St. George and
from a stockpile in Leeds. Prior to borrowing from the Leeds stockpile, I scanned the stockpile for
gamma radiation and conducted XRF analyses of three arbitrary locations on the pile. I found the
gamma radiation levels to be consistent with background. The results of the XRF analyses are provided
in Table 4. The XRF results were all substantially below site remedial-action goals.
Photographs of the erosion repair efforts are provided in Attachment D. Based on my field
observations, the repair efforts resulted in a minimum of 6 inches of clean soil and a minimum of 2
inches of gravel over the areas of concern. Therefore, I consider concerns about these locations to be
resolved.
Gary Crocker
March 28, 2024
Page 5
Please contact me if you have any questions or need additional information.
Sincerely,
Richard B. White, P.E.
Consulting Civil and Environmental Engineer
Tables and Attachments
Gary Crocker
March 28, 2024
Page 6
TABLE 1
Results of Field XRF Analyses in
Waste Rock Removal Area
Subsample
Number
Concentration (ppm)
Arsenic Copper Lead Mercury Vanadium
1 4.0 12.9 11.4 <1.2 57.8
2 3.7 17.6 11.2 <1.0 <30.2
3 3.7 7.7 11.4 <1.0 47.8
4 2.7 18.5 9.0 <1.0 42.2
5 3.4 27.3 13.6 <1.0 53.2
6 4.9 9.1 13.2 <1.0 44.8
7 4.4 31.2 10.2 <1.0 49.0
8 3.4 17.6 10.3 <1.0 35.0
9 <2.0 13.8 10.3 <1.0 35.9
10 <2.2 15.20 13.3 <1.0 36.3
RAP Remedial
Action Goal 35 3,100 400 23 390
Note: The XRF analyzer used on this project was not configured to measure thallium or uranium.
TABLE 2
Results of Laboratory Analyses of Confirmation Samples
Collected From the Waste Rock Removal Area
Analyte
Concentration(a)
RAP Remedial-
Action Goal
Original Sample
(SILV-1)
Blind Duplicate
(BD-1)
DERR Split
(SILV-1-DEQ)
Arsenic 35 2.5 2.3 2.09
Copper 3,100 12 17 12.8
Lead 400 5.4 5.8 4.35
Mercury 23 0.27 0.21 0.244
Radium-226 5.6/15.6(b) 1.24 1.21 1.68
Thallium 5.1 0.11 0.097 <2.00
Uranium 230 2.2 3.3 <15.0
Vanadium 390 19 22 21.2
(a) All analytical results expressed in mg/kg dry weight except Radium-226 which is expressed in pCi/g dry weight.
(b) Upper 6 inches and deeper, respectively.
Gary Crocker
March 28, 2024
Page 7
TABLE 3
Results of Relative Percent Difference Calculations
Sample Arsenic
(mg/kg)
Copper
(mg/kg)
Lead
(mg/kg)
Mercury
(mg/kg)
Radium-
226 (pCi/g)
Thallium
(mg/kg)
Uranium
(mg/kg)
Vanadium
(mg/kg)
Comparison with Blind Duplicate
SILV-1 2.5 12 5.4 0.27 1.24 0.11 J 2.2 19
BD-1 2.3 17 5.8 0.21 1.21 0.097 J 3.3 22
Primary RL 0.94 0.94 0.28 0.092 1.0 0.47 0.094 0.94
Blind Duplicate RL 1.00 1.00 0.30 0.11 1.0 0.50 0.10 1.0
RPD (%) 8.3% 34.5% 7.1% 25.0% 2.4% 12.6% 40.0% 14.6%
Comparison with Laboratory Duplicate
SILV-1 2.5 12 5.4 0.27 1.24 0.11 J 2.2 19
SILV-1-DEQ 2.09 12.8 4.35 0.244 1.68 ND ND 21.2
Primary RL 0.94 0.94 0.28 0.092 0.2 0.47 0.094 0.94
Duplicate Lab RL 1.00 5.00 2.00 0.04 NR 2.00 15.0 2.50
RPD (%) 17.9% 6.5% 21.5% 10.1% 30.1% NA NA 10.9%
Remedial Action Goal 35 3,100 400 23 5.6/15.6 5.1 230 390
Max Concentration as %
of Rem Action Goal 7.1% 0.5% 1.5% 1.2% 30.0% 2.2% 1.4% 5.6%
RL = Reporting limit. RPD = Relative percent difference. RPDs greater than 15% are shown in bold red. NA = Not applicable; ND = Not detected at the reporting limit; NR = Not reported J = Results is less than the reporting limit but greater than or equal to the method detection limit and the concentration is an approximate value
TABLE 4
Results of Field XRF Analyses of
Borrow Soil Used as Cover Material
Subsample
Number
Concentration (ppm)
Arsenic Copper Lead Mercury Vanadium
1 5.0 17.1 13.1 <1.0 48.4
2 5.7 22.2 12.7 <1.0 42.1
3 3.8 14.7 11.4 <1.0 51.4
RAP Remedial
Action Goal 35 3,100 400 23 390
Note: The XRF analyzer used on this project was not configured to measure thallium or uranium.
ATTACHMENT A
Documentation Submitted to Republic Services
for Waste Rock and Soil Disposal Approval
INFORMATION REGARDING SOIL AND ROCK
EXCAVATED FROM SILVER POINT ESTATES TO BE
DISPOSED OF AT THE WASHINGTON COUNTY LANDFILL
An area east of I-15 in Leeds, UT is being considered for residen�al development as Silver Pointe Estates.
Because this area was the subject of substan�al mining ac�vity from the 1860s through the 1950s, the
land owner (Silver Reef Investment Holdings, “SRIH”) entered into the Voluntary Cleanup Program with
the Utah Division of Environmental Response and Remedia�on. Under that program, SRIH contracted
with an environmental engineering company to collect mul�ple soil samples from the area and
recommend a course of ac�on to remediate past contamina�on. Substan�al work has been directed
during that remedia�on effort.
A limited amount of uranium mining occurred in a por�on of Silver Pointe Estates during the 1950s. The
resul�ng ore was hauled off site for processing. Although substan�al remedia�on work has been
conducted on the property, a small amount of waste rock with elevated gamma radia�on was recently
discovered. In order to ensure that the land is acceptable for residen�al development, SRIH has decided
to remove this waste rock and the adjacent soil. SRIH desires to dispose of this material at the
Washington County Landfill.
Atached to this summary are the results of laboratory analyses of several samples that were collected in
the vicinity of the uranium mining opera�on. These samples were collected prior to site remedia�on
and are, therefore, considered representa�ve of the material from which the subject waste rock was
generated. In addi�on, Richard B. White (consul�ng civil and environmental engineer) analyzed the
waste rock at three arbitrary loca�ons using X-Ray Fluorescence and gamma spectroscopy on January 31,
2024. These results of these analyses are presented below:
Analyte Concentra�on
Sample #1 Sample #2 Sample #3
Gamma 59,000 ct/min 39,000 ct/min 23,000 ct/min
Arsenic 4.3 + 1.5 ppm 2.4 + 1.5 ppm 4.7 + 1.6 ppm
Copper 26.5 + 5.2 ppm 19.0 + 4.9 ppm 49.4 + 5.9 ppm
Lead 12.0 + 2.3 ppm 14.2 + 2.4 ppm 14.9 + 2.4 ppm
Mercury <1 ppm <1 ppm 1.3 + <1 ppm
Vanadium 45.5 + 4.9 ppm 40.7 +5.0 ppm 45.1 + 5.3 ppm
Prepared by:
Richard B. White, P.E.
Consul�ng Civil and Environmental Engineer
Richard B. White, PE, PLLC
13441 South Lone Peak Lane
Draper, UT 84020
801-673-6647
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