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COC, as well as the laboratory's reliable detection limits (RDLs), and minimum detection limits (MDLs) based
<br /> on selected laboratory methods.The project laboratory to be used is Origins Laboratory, Inc. (Origins), located
<br /> in Denver, Colorado and their sub-lab,Waypoint Analytical, LLC (Waypoint), located in Memphis, Tennessee.
<br /> Sampling Rationale
<br /> The spatial boundaries are the extents of sampleable sand and gravel materials mined, processed,and placed in
<br /> final, ready to be sold stockpiles on-site. The current sampleable stockpile locations, identification numbers,
<br /> and volumes,for material produced on-site, are provided on Figure I. In addition,there are various small piles
<br /> of materials such as surge piles from the processing plant, materials staged to top off trucks, and materials that
<br /> have been washed. These piles are depicted on Figure 2. The material volumes were estimated using recently
<br /> collected aerial photogrammetry and LiDAR data. These piles will be sampled as follows:
<br /> • Surge piles contain materials dropping off of conveyers from the plant. These materials are collected and
<br /> moved to stockpiles. The materials in the surge piles are I inch or greater. Therefore,the current surge
<br /> piles will be inspected to determine whether creosote is present, but samples will not be collected.
<br /> • Small piles maintained for topping off trucks will be visually inspected if the materials are greater than I
<br /> inch. For small materials, one composite sample will be collected from each pile or bin.
<br /> • The crushed slag piles have been in place for 25 or more years, are consistent in size to historical satellite
<br /> imagery, and visibly are distinctly different material than the gravels and sands. Therefore, it is clear that
<br /> Mine Restricted Area materials were not moved to these locations and no samples will be collected from
<br /> these piles.
<br /> • There are several material stockpiles that have been imported to the Mine from an off-site source. Those
<br /> material locations and volumes are provided on Figure 2. These imported materials are assumed to be
<br /> free of creosote, and will not be sampled.
<br /> • A small amount of sediment removed from settling ponds also is located on site. This material will not be
<br /> sampled.
<br /> Field observations for creosote staining will be made. If creosote staining is identified, no samples will be
<br /> collected, and the stockpile will be assumed impacted.
<br /> If no creosote staining is observed, composite samples will be collected in 4-ounce wide mouth glass jars,which
<br /> have an opening diameter of approximately 1.75 inches. The material must be small enough to allow collection
<br /> of a representative sample using this sample container. Most of the material that will not fit in the sample jar
<br /> has already been visually evaluated and those results were provided under separate cover. The on-site
<br /> produced materials that will be sampled versus those that are too large for the sample containers are identified
<br /> on Figure I.
<br /> Stockpile Sampling
<br /> Stockpiles I - 24 are identified on Figure I. Stockpiles IOI - 115 are identified on Figure 2. The following
<br /> stockpiles will be sampled using the methods outlined below: I, 2, 3, 4, 6, 7, 8, 9, 10, 11, 12, 17, 20, 21, 22,
<br /> smaller gradation materials (less than I inch) in 109, and 113.The following stockpiles have either already been
<br /> visually evaluated and cleared as non-impacted or will be visually evaluated during the upcoming sampling event:
<br /> 13, 14, 15, 16, 18, 19, 23, 24, 110, III, 112, and 115. Stockpiles that have been visually evaluated with data
<br /> presented in the June 23, 2023 Submittal of Observations and Findings, Inspection of Stockpiles with Material
<br /> Larger than 1-inch Diameter, prepared by Pinyon include 13, 14, 15, and 19. Stockpiles 16, 18, 23, 24, 110,
<br /> I I I, 112,and 115 have not yet been visually inspected, but will be during the sampling event.
<br /> Mr. Lucas West Page 3
<br /> Environmental Protection Specialist
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