AttachmentH_USGS_EMRI_Protocols_01.22.2025.pdf

This draft manuscript is distributed solely for the purposes of scientific peer review. Its content is deliberative and predecisional, so it must not be disclosed or released by reviewers. Because the manuscript has not yet been approved for publication by the U.S. Geological Survey (USGS), it does not represent any official

USGS finding or policy.

Earth Mapping Resources Initiative Protocols: Sampling solid hard-rock mine waste and perpetual mine water sources

Kate Campbell1,*, Robert Seal2, Nadine Piatak2, Jaime Azain1, Jean Morrison1, Sarah Jane White2, Andrew Manning1, Katie

Walton-Day1, JoAnn Holloway1, Bronwen Wang3

1US Geological Survey, Denver, CO 2US Geological Survey, Reston, VA 3US Geological Survey, Anchorage, AK

* kcampbell@usgs.gov; (720) 682-2220

Abstract Critical minerals are materials essential to the economic and national security of the United States with possible vulnerability to supply chain disruption (Nassar et al., 2020). Supporting the overarching goal to evaluate critical minerals nationwide, the mine waste characterization effort in the United States Geological Survey (USGS) Earth

Mapping Resources Initiative (Earth MRI) has created a series of protocols to standardize sampling carried out under this effort by the participating state geological surveys and their cooperators. The protocols are based on published, reviewed methods, and are intended as methods to be deployed in the field as described here. The protocols include:

(1) collecting and processing composite samples of mine and mill waste, including tailings, waste rock, gangue, heap leach piles, ore stockpiles, slag, or other mineralized/processed materials and (2) collecting and preserving water samples from perpetual or long-term mine water sources. The protocols also specify required information to be documented on field sheets and detail the collection of geospatial data. The analytical methods used by the USGS and

USGS contract laboratories are described, including the data delivery pathway for USGS-derived data.

Introduction The USGS Earth MRI initiative is an effort to modernize mapping of the surface and subsurface across multiple types of data including geologic, geophysical, geochemical, and topographical data. Areas across the United States with the potential to host both subsurface and surface deposits of critical mineral resources (‘focus areas’) have been identified by the USGS and their state geological survey collaborators (Hammarstrom, et al., 2023). Earth MRI focus areas are based on mineral systems, deposit types, and known and potential critical mineral commodities. The mineral systems classification links large mineral systems that may contain multiple deposit types to the mineral commodities associated with each deposit type (Hofstra and Kreiner, 2020). Earth MRI takes a mineral systems approach for prioritizing data collection efforts for both above ground and below ground critical mineral resources. One aspect of Earth MRI is to understand the distribution of critical minerals in above-ground mine waste.

The Earth MRI mine waste characterization effort collects compositional data to help identify mine waste sites that potentially contain critical mineral resources. The data can be used to estimate the critical mineral endowment of mine waste in the United States. Additionally, the data can be used to identify potential mineral hosts of critical minerals and provide a cursory evaluation of the environmental characteristics of the mine waste to help delineate potential reprocessing, environmental management, reclamation strategies, and other attendant costs. Identification of sites with critical mineral potential is the first step toward fostering economic development in conjunction with environmental remediation. Whether mine waste is a potential resource, an environmental liability, or both will depend on the geochemical and mineralogical characteristics of the waste. In addition, compositional characterization of mine waste may inform use of new technologies to reprocess mine waste more efficiently for extraction of critical minerals in the future. This information will be useful when assessing the total costs and benefits of reuse, recycling, reprocessing, reclamation, and restoration of ecosystem services. Evaluation of the future recoverability of critical minerals from mine waste is beyond the scope of this effort and will depend on a variety of factors including prevailing commodity prices, mailto:kcampbell@usgs.gov

This draft manuscript is distributed solely for the purposes of scientific peer review. Its content is deliberative and predecisional, so it must not be disclosed or released by reviewers. Because the manuscript has not yet been approved for publication by the U.S. Geological Survey (USGS), it does not represent any official

USGS finding or policy.

technological innovations, and financial incentives, among others. The goal is to develop a comprehensive and internally consistent national database of mine waste locations, volume and mass estimates, bulk geochemical composition, bulk mineralogical composition, and contained mineral commodities. To this end, this document describes the methods followed by participating state geological surveys and their cooperators to standardize sampling carried out by Earth

MRI’s mine waste characterization effort.

Scope The scope of these protocols encompasses sampling of solid mine waste and large, perpetual mine-related water sources (for example, pit lakes and draining adits). Presented is an approach to sampling a variety of solid waste types, including tailings, waste rock, gangue, heap leach piles, ore stockpiles, slag, or other mineralized/processed materials. If other types of materials are present at the site (for example, efflorescent salts, secondary precipitates, or streambed sediments) and the opportunity to sample is available during the course of the study, please consult with USGS personnel associated with Earth MRI on methodologies for sampling. Guidance on field notes, geospatial data, and

USGS geochemical analysis is also provided in this document. This document is intended to supplement the in-person training provided by the USGS to participating state geological surveys.

We recognize that many mine waste sites may be vertically heterogeneous. Vertical profile sampling in addition to composited surface samples may be considered. These protocols include an approach to sampling drill core, with the understanding that methodologies for drilling, trench sampling, or other vertical sampling techniques will not be discussed in detail as they will be highly site dependent.

Safety Safety planning, including, but not limited to, job hazard analysis, selection of personal protective equipment (PPE), and appropriate safety training, is the responsibility of the state agency conducting the work. The USGS is not responsible for providing equipment, safety training, or evaluating site hazards and risks. Please work with your organization’s safety officer to determine and complete the necessary safety requirements to perform the proposed work in a safe manner. Required PPE described in the sections below is provided as a guide for sample collection requirements.

Additional PPE may be needed to conduct the work safely.

This draft manuscript is distributed solely for the purposes of scientific peer review. Its content is deliberative and predecisional, so it must not be disclosed or released by reviewers. Because the manuscript has not yet been approved for publication by the U.S. Geological Survey (USGS), it does not represent any official

USGS finding or policy.

Protocols

Sampling approach for solids

Overview Sampling of solid mine waste is complex due to the varied nature of source material, waste management approaches, climatological influence, and site accessibility. Sampling described in these protocols will be primarily focused on surficial material (0-10 cm depth; exceptions described below) using a statistically based, relatively rapid, composite approach based on Smith et al. (2000) and Naftz and Walton-Day (2016). Before sampling, the site should be divided into appropriate sample units, described in detail in the next section. Within each sample unit, the area will be subdivided into a grid or randomized distribution of least 30 subsample locations. For statistical rigor, a minimum of 30 subsample locations are required; more than 30 subsamples are acceptable. Subsamples of equal volume will be collected, combined into a single composite sample, and have a minimum combined dry weight of 1 kg (details described below). When a composite sample arrives at the USGS, it will be crushed and homogenized prior to submission for analysis.

Defining sample units, locations of subsamples, and depths of subsamples The overall objective of designating sample units is to differentiate parts of the site that potentially could have different material composition or to divide a very large area into smaller units to obtain a series of composite samples that are more representative of site. The number of sample units will depend upon the size, topography, mine waste type, ore-processing history, geography of the site and other objective criteria, such as color. For example, if the tailings pile has discrete benches, each bench may be considered as a separate sample unit. Prior to going to the field, it is valuable to identify the features and boundaries to be sampled by recent satellite, aerial photography, or other imagery. The features may be subdivided into sample units if the feature is large and has topographical or other distinguishing attributes that indicate a change in composition or site management (for example, benches, discrete piles, tailings color). If the site is large with no clear distinguishing features, sample units of approximately 0.04-0.06 km2 (10-15 acres) should be selected. If a pile has mixed types of waste or has areas that contain vastly different sizes of material, sample units can be drawn to reflect those differences. For example, if a pile has mixed fine-grained material and larger pieces (up to 30 cm) on the top of the pile, and boulder-sized rocks with no fine material around the base of the pile, the top of the pile may be considered a separate sample unit from the base. Different sampling methods can then be used to collect composite samples in each of the two sample units.

Site history is an important tool in understanding site features. For example, locations of pipes used to convey tailings, if available, can help guide distribution patterns on the landscape. Similarly, if the site went through multiple phases of ore processing, that information may be useful in interpreting different possible stratigraphy or topographical features at a site. Aerial imagery is incredibly helpful in understanding a site but is generally not sufficient to make final decisions about sampling approach. As such, site reconnaissance can be useful to more clearly identify the geography and topography of the features, and to determine if there are any coverings over the waste material.

Once sample units have been identified, at least 30 subsampling locations per sample unit should be selected using a systematic grid or randomized location scheme that adequately covers the sample unit. Subsample locations may be planned in advance of field work using geographic information system (GIS) tools, with any deviations from the plan noted in field notes or with a global positioning system (GPS) device. For example, if a particular preselected subsample location is inaccessible, an alternative may be selected on-site as close to the original location as possible. Pin flags or flagging tape are helpful for marking out subsample locations on-site prior to sample collection. If subsample locations are not selected in advance of the field work, pin flags or flagging tape should be laid out by the sampling team, visually confirming that the subsample locations adequately cover the sample unit before sampling begins, adjusting the locations and/or adding additional subsample locations as needed. A minimum of 30 subsamples are required, but more than 30 subsamples are acceptable. The subsample locations should be logged by GPS in the field if not pre-determined.

This draft manuscript is distributed solely for the purposes of scientific peer review. Its content is deliberative and predecisional, so it must not be disclosed or released by reviewers. Because the manuscript has not yet been approved for publication by the U.S. Geological Survey (USGS), it does not represent any official

USGS finding or policy.

If a subsample location falls on a clearly unique or different feature within the sample unit, it should be collected and composited as planned (see also Grab Samples, below).

If the site has an obvious soil horizon, clay cap, engineered cover (for example, a geomembrane), or other natural or anthropogenic covering, the sampling procedure described below may need to be modified to collect the waste material below the cover as long as the sampling does not compromise the integrity of an engineered cover. Site history will be helpful in determining if an engineered cover is expected at the site. Negotiating with the landowners for sampling permission, especially if a cover is expected, is the responsibility of the state agency conducting the work. Once on site for sampling or during a reconnaissance visit, it is recommended that a test hole be dug (usually approximately 0.5 m deep but may vary depending on site characteristics) to visually determine if samples should be collected below the surface. For example, non-acid generating tailings may have vegetative growth and a surficial layer with roots and some soil formation. This soil layer is usually apparent in the test hole, and the sample collection depth should be below this layer for all subsamples, and the sample depth noted on the field sheets. As each site has a unique setting, please reach out to USGS personnel associated with Earth MRI to discuss variations in sampling design.

Grab samples Within the sample allotment and budget, additional grab samples may be collected of any unusual or notable feature in addition to the composited sample. If the subsample location falls on a feature that is notable or different, it should be collected and composited as planned. Additional grab samples of that feature may then be collected. For example, if a pile has a distinct orange weathered layer on the surface with continuous primary black unweathered tailings material below, the composite sample should be collected below the weathered surface layer, but collecting a grab sample of the weathered orange surface layer at one or more subsampling locations would be beneficial. If available, 1-2 kg of grab sample material should be collected and submitted for analysis. However, if that mass is not available (for example, within a drill core, or a smaller distinct layer in tailings), a smaller amount of material may be collected, and fewer chemical analyses may be completed on that sample at the discretion of the USGS.

Protocols for composite sample collection of several mine waste material types

Tailings and fine-grained waste material

In general, tailings are the waste material from ore that has been processed to recover a concentrated form of the target commodity. Processing usually includes some form of grinding or milling of the ore, and as a result, tailings are usually fine grained (<2 mm). For most tailings, material on the surface that is >2 mm may be the result of cover or extraneous material deposition that should not be included in the composite sample. Sieving to <2 mm ensures that the sample collected is primarily the tailings material. Although unlikely in tailings piles, if the majority of the tailings have a grain size larger than 2 mm, the methodology described below for larger material types should be used. One composite sample will be collected for each sample unit, not including duplicate samples (described below) or additional grab samples.

Personal Protective Equipment (PPE) :

• Nitrile gloves. It is possible to cover work gloves with nitrile gloves, if desired, but work gloves alone cannot be used. New nitrile gloves should be donned for each sample unit to prevent cross-contamination.

• Additional PPE may be required (for example, masks, eye protection, clothing covering) depending on the site conditions and hazards (see Safety, above).

Equipment:

• Shovel

• Trowel, small shovel, or incremental sampler (stainless steel or plastic are necessary to prevent metal contamination)

• 5-gallon plastic bucket

This draft manuscript is distributed solely for the purposes of scientific peer review. Its content is deliberative and predecisional, so it must not be disclosed or released by reviewers. Because the manuscript has not yet been approved for publication by the U.S. Geological Survey (USGS), it does not represent any official

USGS finding or policy.

• Large (1 gallon) plastic bags or other sealable container

• Labels and permanent markers

• 2 mm plastic or stainless-steel sieve

• Flagging tape and/or pin flags to mark subsample locations. Consider the choice of color so that the flags stand out in the sampling landscape.

• Wire brush to remove particles from sieve as needed in between samples

• Deionized (DI) water (or equivalent) and a squirt bottle for cleaning equipment. If DI water is not available, distilled water can be substituted. Tap water should not be used.

• Paper towels or kimwipes

Sampling tools, sieve, and buckets should be rinsed with DI water and air dried prior to sample collection.

Subsample depth and amount collected: Subsamples should be collected from the upper layer of the tailings pile, 0-5 cm deep, unless it is necessary to sample below a soil layer, cap, oxidized layer, hardpan or crust. A test hole should be dug prior to first subsample collection to determine whether there is a soil, cap, or oxidized layer on the surface of the tailings pile. Although aerial imagery and site history are extremely helpful for guiding sampling strategy, the best way of determining if there is a layer on top of the tailings is to dig to a depth of 0.25-1 m and observe any variation in color, particle size, plant roots (if present), moisture content, and/or other properties. If there is an obvious soil layer or cap on top of the tailings, then subsamples should be collected at the same depth below the anomalous surface layer.

Evidence of weathering (often indicated by a color change or hardpan layer) should be noted in the field sheet. The training provided by the USGS can help identify these types of situations and inform the sampling strategy on a site-by-site basis.

Each subsample within a sample unit should be collected to the same depth and volume using the same equipment. The mass should be at least approximately 50 g per subsample. The amount collected for each subsample can be approximated using the sampling equipment, a bag, or other container, as long as the same amount of sample collected is consistent at each subsample location. For example, if using a trowel to collect the subsample, the trowel should be filled to approximately the same amount of sample at each location. If using a plastic bag or container, the fill level should be marked with a permanent marker on the bag or container and filled to that level at each location. The method used may depend on the wetness, particle size, or other factors specific to the site material. It is not necessary to weigh each subsample. The total mass of the sieved composite sample after all of the 30 or more subsamples have been combined should be at least 1-2 kg dry weight.

Compositing subsamples and sieving: Composited samples should be sieved to <2 mm in the field or after being transported to a laboratory setting. If possible, it is recommended that subsamples be sieved in the field during collection. As each subsample is collected, it can be sieved directly into the bucket; each subsample is sieved and sequentially added to the same bucket, which becomes the composite sample. Tailings materials that are damp are usually able to be sieved, unless the sample has very high clay content.

If the sample cannot be sieved in the field (for example, very high clay content), the bulk material from each subsample can be directly added to the bucket for sieving at a later time. If there are large particles (>1 cm) in the subsample, the particles should be removed. Similarly, large items (>1 cm) of manufactured material (for example, bolts, screws, rebar) should be removed and recorded in field notes. If the material has a large amount of coarse (>2 mm) material, additional mass may need to be sampled at every subsample location to accommodate the amount of >2 mm mass discarded during sieving.

If the samples have a high clay content, sieving will be challenging in the field and in the laboratory, as clay can be sticky when wet and harden into large aggregates upon drying. In this case, please contact USGS personnel associated with

Earth MRI for more guidance, and the USGS may be able to assist with sample preparation.

This draft manuscript is distributed solely for the purposes of scientific peer review. Its content is deliberative and predecisional, so it must not be disclosed or released by reviewers. Because the manuscript has not yet been approved for publication by the U.S. Geological Survey (USGS), it does not represent any official

USGS finding or policy.

If tailings samples are wet upon collection, the samples should be air dried before submitting to USGS sample control. If sieving is occurring in a laboratory setting after collection, any particle agglomerates that have formed upon drying a wet sample should be disaggregated before sieving.

The dry, sieved composite sample should be at least 1-2 kg, dry weight. The >2 mm fraction will not be submitted or analyzed and can be discarded. Once the composite sample has been sieved, the material can be transferred to a plastic bag, sealed and labeled. Double- or triple-bagging is highly recommended prior to shipping to prevent loss of material during transit.

Detailed notes about soil/surface anomalies, subsample depth, volume, sieving and other decisions for each sample unit should be made in the field sheets. Sample containers should be labeled in the field. If the composite sample needs to be sieved in the laboratory, a note should be made in the field sheet and on the sample container (for example, “unsieved bulk composite sample”) in addition to the label with the site name, date, and other information. Any deviations from the described methods should be noted in the field sheet.

Material containing <2 mm particles mixed with pieces larger than 2 mm, but generally smaller than about 30 cm

It is not uncommon to have mine waste that is a mixture of fine material and larger pieces, such as in an ore stockpile that has had some initial bulk crushing but was never milled. In these piles, both the <2 mm fraction and the >2 mm fraction are important to collect and analyze. Two composite samples will be collected at each sample unit, not including duplicates (described below) and additional grab samples. The approach consists of sieving the material to <2 mm and retaining the >2 mm fraction, with additional processing required for larger pieces of material, as needed, to prevent a single large piece from biasing the >2 mm fraction. The two fractions will provide end-member compositions for the overall pile.

Personal Protective Equipment (PPE) :

• Nitrile gloves. It is possible to cover work gloves with nitrile gloves, if desired, but work gloves alone cannot be used. New nitrile gloves should be donned for each sample unit to prevent cross-contamination.

• Eye protection. Safety glasses are recommended especially if the material is large enough to require rock chipping.

• Additional PPE may be required (for example, masks, clothing covering) depending on the site conditions and hazards (see Safety, above).

Equipment:

• Shovel

• Rock hammer, small sledge, and/or pickaxe

• Trowel, small shovel, or incremental sampler (stainless steel or plastic are necessary to prevent metal contamination)

• 5-gallon plastic buckets (2 per sample unit: one for the <2mm fraction and one for the >2mm fraction)

• Large (1 gallon) plastic bags or other spill-proof container

• Labels and permanent markers

• 2 mm plastic or stainless-steel sieve

• Flagging tape and/or pin flags to mark subsample locations. Consider the choice of color so that the flags stand out in the sampling landscape.

• Wire brush to remove particles from sieve

• Deionized (DI) water (or equivalent) and a squirt bottle for cleaning equipment. If DI water is not available, distilled water can be substituted. Tap water should not be used.

• Paper towels or kimwipes

Sampling tools, sieve, and buckets should be rinsed with DI water and air dried prior to sample collection.

This draft manuscript is distributed solely for the purposes of scientific peer review. Its content is deliberative and predecisional, so it must not be disclosed or released by reviewers. Because the manuscript has not yet been approved for publication by the U.S. Geological Survey (USGS), it does not represent any official

USGS finding or policy.

Subsample depth and amount collected: If the material allows, a test hole will yield valuable information about material size and distribution. If some of the material is larger than 10-15 cm in diameter or length, it may be challenging to dig and a surficial sampling approach will suffice. However, it is important to confirm, if possible, that the surficial material is not a cover on top of the mine waste.

Each subsample within a sample unit should be collected to the same depth and volume using the same equipment. The amount collected for each subsample can be approximated using the sampling equipment, a bag, or other container, as long as the same amount of sample is consistent at each subsample location. For this material type, a shovel or similarly sized container is usually a reasonable tool to estimate the sample amount, unless the material is mainly fine-grained, in which case a trowel can be used. It is not necessary to weigh each subsample. Enough material should be collected at each subsample to yield about 50 g at each subsample location for both the <2 mm and >2 mm fractions. If the material is mainly fine-grained, this protocol will be functionally similar to the tailings protocol above, with the exception of retaining the >2 mm fraction. If the material has a larger proportion of >2 mm material, assure the subsample is large enough to collect about 50 g of <2 mm material at most locations. The total mass of each composite sample (< 2 mm and >2 mm) after all 30 or more subsamples have been combined should be at least 1-2 kg, dry weight.

Compositing subsamples, sieving, and processing >2 mm fraction: The <2 mm and >2 mm fractions of the sample will be collected in two separate buckets. If possible, each subsample should be sieved to <2 mm directly into a bucket in the field. The material that does not pass through the 2 mm sieve should be retained and processed as follows:

• If most of the >2 mm fraction retained on the sieve is less than approximately 4 cm in length or diameter and is about 50 g worth of material, it can be placed directly into the second bucket. If this fraction is substantially more than approximately 50 g of material, a ~50 g randomized subset of material should be selected and placed into the second bucket, and the remainder discarded. It is important to not bias the selection toward items of a particular size or color; the subset of material should be representative of the bulk >2 mm material.

• If there are pieces larger than approximately 4 cm, they should be removed from the shovel directly and placed aside. Large pieces of material can bias the overall composition of a composite sample and need to be reduced in size to be included in the sample. A random selection of large pieces should be chosen, with care taken to not bias the selection toward items of a particular size or color. These large pieces should then be broken with a sledge or rock hammer and a single chip (~4 cm in length or diameter) collected into the second bucket.

• If there is a mix of <4 cm and >4 cm pieces in the >2 mm fraction, then a combination of the two processes should be used. For example, a random selection of <4 cm pieces should be placed in the second bucket, along with ~4 cm chipped samples from the larger pieces.

• Subsamples may exhibit different distributions of large and fine material within a single sample unit. Continue to sample at all locations using the same approach, even if it results in <50 g material for a size fraction at a single subsample location. For example, most subsample locations may have a roughly equal distribution of <2 mm and >2 mm fractions, but one subsample location only has 20 cm rocks and no fine-grained material. At this location, collect the rock chips and no fine-grained material. The composite approach normalizes over the individual subsample location variations to collect an average composition across the entire sample unit.

Each subsample should be collected as described above, resulting in two buckets: one bucket with <2 mm sieved material, and one bucket with >2 mm material including rock chips. Each composite sample (<2 mm and >2 mm) should be at least 1-2 kg, dry weight. The composite sample from each bucket can be transferred to two different plastic bags, sealed, and labeled. Double- or triple-bagging is highly recommended prior to shipping to prevent loss of material during transit.

Large material predominantly >30 cm

Some waste material, such as waste rock, may have very little fine material and only large pieces that can range from several kg to many hundreds of kg. In these cases, a <2 mm fraction should not be collected, and we present a method to subsample these large items to collect a representative composite sample.

This draft manuscript is distributed solely for the purposes of scientific peer review. Its content is deliberative and predecisional, so it must not be disclosed or released by reviewers. Because the manuscript has not yet been approved for publication by the U.S. Geological Survey (USGS), it does not represent any official

USGS finding or policy.

Personal Protective Equipment (PPE) :

• Nitrile gloves. It is possible to cover work gloves with nitrile gloves, if desired, but work gloves alone cannot be used. New nitrile gloves should be donned for each sample unit to prevent cross-contamination.

• Eye protection. Safety glasses are strongly encouraged because the protocol requires rock chipping.

• Additional PPE may be required (for example, masks, clothing covering) depending on the site conditions and hazards (see safety, above).

Equipment:

• Rock hammer, small sledge, and/or pickaxe

• 5-gallon plastic bucket

• Large (1 gallon) plastic bags or other spill-proof container

• Labels and permanent markers

• Flagging tape and/or pin flags to mark subsample locations. Consider the choice of color so that the flags stand out in the sampling landscape.

• Deionized (DI) water (or equivalent) and a squirt bottle for cleaning equipment. If DI water is not available, distilled water can be substituted. Tap water should not be used.

• Paper towels or kimwipes

Sampling tools and buckets should be rinsed with DI water and air dried prior to sample collection.

Subsampling approach: With this material type, the subsample points likely will fall on large rocks or boulders. To subsample a large rock, use a rock hammer, sledge, or other tool to chip off 3-5 randomly selected pieces of material approximately 4 cm from the surface of each rock. These pieces should be placed directly into the bucket, accumulating rock chips across all of the subsample locations. The composite sample will be the mixed rock chips in the bucket from at least 30 subsample locations and should be at least 1-2 kg dry weight. The composite sample can be transferred to a plastic bag, sealed, and labeled. Double- or triple-bagging is highly recommended prior to shipping to prevent loss of material during transit.

Drill cores

Drilling is not required for site characterization, but if equipment and budget allow, is encouraged because it allows for samples to be collected across the third dimension of a pile. The details of the best equipment, techniques, and PPE for drilling at the site will be at the discretion of the state agency conducting the work. Tailings and other fine-grained mine waste are good candidate materials for drilling, resulting in a poorly consolidated core with some larger clasts possibly present. The methods described below assume the core is relatively unconsolidated and does not need a rock saw to split or collect samples. If the core does not meet this description, a discussion with USGS personnel associated with

Earth MRI may be warranted.

Equipment:

• Trowel and/or scoop (stainless steel or plastic are necessary to prevent metal contamination)

• Rock hammer or other tool to split clasts as needed

• Plastic buckets or other containers for the composited samples

• Large (1 gallon) plastic bags or other spill-proof container

• Labels and permanent markers

• Tape measure for measuring sample unit intervals

• Deionized (DI) water (or equivalent) and a squirt bottle for cleaning equipment. If DI water is not available, distilled water can be substituted.

• Paper towels or kimwipes

This draft manuscript is distributed solely for the purposes of scientific peer review. Its content is deliberative and predecisional, so it must not be disclosed or released by reviewers. Because the manuscript has not yet been approved for publication by the U.S. Geological Survey (USGS), it does not represent any official

USGS finding or policy.

Sampling tools and buckets should be rinsed with DI water and air dried prior to sample collection.

Determining sample intervals (sample units) within a core: If core logs are available, it is recommended that they be reviewed to identify where stratigraphic breaks occur in the core and how frequently they occur. Laying the core out to visually identify the stratigraphic breaks is also suggested. If the material is homogeneous, then dividing the core into equal sections over the entire core depth is an option depending on how many samples per core is reasonable for the budget. It is more likely, however, that there are apparent heterogeneities in the core. These heterogeneities or stratigraphic beaks can define sample units within the core such that a sample unit includes depths in between the stratigraphic breaks. Samples will be composited across a sample unit defined within the core (described below), so that composition is not dominated by only collecting individual or interesting layers within the core. Distinct or unusual layers may be used to separate sample units but should be included in the composite sample. Depending on the stratigraphy of the core, sample units may be of variable lengths. In sample sheets, note the depths/location in the core where sample units begin and end after laying out the entire core. Each sample unit will result in one composite sample.

In the case of highly variable or closely spaced breaks, some judgement will need to be applied to balance the need to define sample units for compositing and capturing every heterogeneity presented in the cores. In addition to composite samples, grab samples are encouraged, particularly if there are distinct layers that are different from the surrounding material. The grab samples can be collected after the core is split and the composite sample collected. This ensures that the composite sample includes the distinct layers while the composition of the layers may also be captured individually in grab samples. The balance between the number of composite samples and grab samples will depend upon the overall scope of the project, including the number of drill cores, other samples collected (for example, surface composite samples), and sample budget.

Collecting composite samples: Depending upon the diameter of the core, splitting the core vertically in half or quarters will likely be necessary. If there is a rock or clast in the core, split it with a rock hammer or similar tool. The composite sample should be collected by taking the split material in a sample unit (within the determined stratigraphic interval) and combining it in a bucket. The composite sample should be approximately 1-2 kg, dry weight. The sample material should be transferred to a plastic bag, sealed and labeled. Double- or triple-bagging is highly recommended prior to shipping to prevent loss of material during transit. Grab samples may be collected from the uncomposited split section of the core.

Quality assurance and quality control (QA/QC) and equipment cleaning for all sample types

Duplicates and blanks

Field duplicate samples give an important indicator of overall sampling variability at a site. A duplicate sample should be collected at a frequency of one per 10 samples. If fewer than 10 samples are collected at a site, then one sample unit should be selected for a duplicate sample collection. A duplicate sample should go through the same subsample collection, composite, and sieving process and labeled as a separate sample with a unique ID. Subsamples for the duplicate sample can be collected nearby (within ~1 m radius) and use the same GPS location of the original subsample location but should not be collected from the same hole as the original subsample.

For drill cores, a duplicate sample should be collected from a sample unit within a core at a frequency of one in 10 samples. Duplicates should be collected by compositing a separate split of the core. If grab samples are also planned to be collected from the core in that section, the core in that sample unit should be vertically split into thirds or quarters so material is not excluded from the composite sample or duplicate sample.

A process blank is optional but recommended. A blank consists of a known material, typically clean quartz from a commercial supplier, that is put through the sampling process using all of the equipment. For example, if a trowel is being used to collect the tailings subsamples, the clean trowel will be used to scoop the blank material through the sieve into a bucket and bagged as if it were a tailings sample. If you are interested in including a blank, please reach out to the

This draft manuscript is distributed solely for the purposes of scientific peer review. Its content is deliberative and predecisional, so it must not be disclosed or released by reviewers. Because the manuscript has not yet been approved for publication by the U.S. Geological Survey (USGS), it does not represent any official

USGS finding or policy.

USGS Earth MRI personnel and we will supply the quartz blank material and discuss safety considerations when working with quartz.

Equipment cleaning in between sample units

The trowel/shovel/sampler, sieves, and buckets should be cleaned before next sample collection. They should be wiped with a clean rag, paper towel, or lab wipe, then care should be taken to remove any particles stuck within the sieve mesh before washing. The wire brush may be necessary to remove particles from the sieve mesh. Lastly, equipment should be rinsed with DI water at least 3 times, and completely air dried before next sample collection. CThe wire brush may be used to clean the sieve in between subsample locations if the mesh is substantially occluded (for example, with clay).

Sample labeling, handling, and storage for all sample types Sieved samples should be secured in a plastic bag or other spill-proof container and labeled with indelible ink. Double-or triple-bagging is recommended to prevent loss of sample during transport. The sample label should contain a unique site and sample unit ID, date of collection and size fraction (for example, <2 mm) once sieved. Including a project ID that indicates the program (Earth MRI-Mine Waste Characterization) and state is also highly recommended. Duplicate samples should be labeled with a unique ID. Unique IDs will need to be tailored for the particular site and sample type, but we suggest using a consistent format. For example, if the sample is from a site called “Example Tailings Site” in state

YY and is a composite sample from sample unit 1 collected on November 1, 2022 at 15:00, the unique sample ID could be: “22_ETS_SU1_composite”, with details about the exact date and time recorded in the field sheet and on the label. A duplicate sample could be labeled “22_ETS_SU1_composite_dup” to differentiate it from the first sample. If the mine waste material is a mix of fine-grained and larger materials, resulting in two composite samples from a single sample unit, additional information needs to be added to the label to identify the sample size fraction (for example, add “<2 mm” or “>2 mm” on the sample label; see figure 1).

Figure 1. An example sample label.

Holding temperature of samples does not have to be controlled. Samples should be air-dried, inventoried, and submitted to USGS Sample Control (see section on Sample Submission below).

Extra equipment for sampling solids Even with the best planning possible, it is almost always necessary to have extra supplies on hand. We recommend packing extra DI water, buckets, and other supplies.

22_ETS_SU1_composite 1 Nov 2022 15:00

<2 mm

EMRI-MWC-YY

This draft manuscript is distributed solely for the purposes of scientific peer review. Its content is deliberative and predecisional, so it must not be disclosed or released by reviewers. Because the manuscript has not yet been approved for publication by the U.S. Geological Survey (USGS), it does not represent any official

USGS finding or policy.

Water Sample Collection, Preservation, and Measurement of Field Parameters and Flow

Overview Methods for water sample collection and preservation are derived from the USGS National Field Manual for the

Collection of Water-Quality Data (NFM; Wilde, 2011), specifically chapters A1 (USGS, 2018), A2 (Wilde, et al., 2014), A3

(Wilde, 2003), A4 (USGS, 2006), A5 (USGS, 2002), and A6 (Nordstrom and Wilde, 2005; USGS, 2019; USGS, 2020; USGS, 2021; USGS, 2023; USGS, 2024). An overview of the sample collection and preservation methods is presented in Figure

1. Depending on the type of site sampled (for example, pit lake, or adit drainage), additional equipment may be needed to collect the water sample (for example, boat, sampling pole,or other equipment). Generally, water will be extracted via a peristaltic pump and through a filtration apparatus or directly into a bottle, although alternate methods such as syringe filtration are acceptable. When water samples are collected, field parameters (pH, temperature (T), specific conductance (SC); optionally dissolved oxygen (DO) and oxidation-reduction potential (ORP)) should also be measured.

Figure 1. Conceptual flow chart of water sample collection and preservation.

Equipment and preparation

PPE

• Clean nitrile or similar laboratory-grade gloves should be worn when handling equipment that comes in contact with sample water and during sample and field parameter collection.

• Note about sunscreen: personnel should be aware that some sunscreens contain Zn and/or Ti oxides, and should be avoided if possible during water sampling. If not avoidable, personnel should be extra careful about minimizing any possible direct contact with equipment without clean gloves.

• Safety glasses

• Other PPE may be necessary depending on sample collection method (for example, if collecting via boat) and site conditions (for example, masks, eye protection, clothing covering); see Safety section, above.

Bottle sets

Each sample collected will be distributed into a set of 5 bottles:

This draft manuscript is distributed solely for the purposes of scientific peer review. Its content is deliberative and predecisional, so it must not be disclosed or released by reviewers. Because the manuscript has not yet been approved for publication by the U.S. Geological Survey (USGS), it does not represent any official

USGS finding or policy.

• Metals and cations: Two 125 mL acid-washed plastic bottles

• Precious metals: One 125 mL acid-washed plastic bottle

• Anions: One 125 mL deionized water-rinsed plastic bottle (NOT acid washed)

• Alkalinity/Acidity: One 125 mL deionized water-rinsed plastic bottle (NOT acid washed)

Table 1. Overview of bottles, preparation, and preservation for water samples. Filtration pore size is 0.45 m.

Analysis Bottle Preparation Filtration Preservation Label suffix

Metals and cations, raw

125 mL plastic bottle

Acid wash None 1% v/v concentrated nitric acid -RA

Metals and cations, filtered

125 mL plastic bottle

Acid wash Filter (0.45 µm) 1% v/v concentrated nitric acid -FA

Precious metals 125 mL plastic bottle

Acid wash Filter (0.45 µm) 1% v/v concentrated nitric acid -FA

Anions 125 mL plastic bottle

Deionized water rinse

Filter (0.45 µm) Chill at 4 °C -FU

Alkalinity/acidity 125 mL plastic bottle

Deionized water rinse

Filter (0.45 µm) Chill at 4 °C -FALK

Bottles should be labeled with waterproof labels (recommended) or lab tape. If labeling with tape, the tape should be wrapped around the entire circumference of the bottle and secured by overlapping to prevent detachment. Labels should be printed and/or written in indelible ink. Each bottle must be uniquely labeled with the site name, date and time of collection, the analysis, and associated preservation. Including a project ID that indicates the program (Earth

MRI-Mine Waste Characterization) and state abbreviation is also highly recommended. Abbreviations for preservation should be added to the sample name according to Table 1 (for example, unfiltered metals/cations should be labeled with the suffix “-RA” for “raw, acidified”; filtered metals/cations and precious metals should be labeled with the suffix “-

FA” for “filtered, acidified”; filtered anions should be labeled with the suffix “-FU” for “filtered, unacidified”; filtered alkalinity splits should be labeled with the suffix “-FALK” for “filtered, alkalinity”).

Figure 2. Example label for a hypothetical sample collected at the “Example Water Site” from the “Big Pit Lake” in State

YY on November 1, 2022, at 15:00 hours, the bottle for filtered metals and cations.

or

In the first example label in Figure 2, the “_001” was added in the event that multiple samples are collected from the same site on different days (time series); the second sample could be indexed to “_002”. In the second examplelabel in

Figure 2, the time and date are incorporated into the unique ID; however, take care to prevent typographical errors in

22_EWS_BPL_001-FA

1 Nov 2022 15:00

Metals and Cations

Me

EWS_BPL01_20220111_1500-FA

1 Nov 2022 15:00

Metals and Cations

Me

This draft manuscript is distributed solely for the purposes of scientific peer review. Its content is deliberative and predecisional, so it must not be disclosed or released by reviewers. Because the manuscript has not yet been approved for publication by the U.S. Geological Survey (USGS), it does not represent any official

USGS finding or policy.

long strings of numbers such as a date when writing the labels. The abbreviation for a specific location (in this case, BPL) may depend on where and how many samples are collected. If sampling multiple locations at a single large feature, “BPL01” may be used to delineate specific locations. In all cases, details about the site, sample location, date, time, etc., should be clearly described in the field sheet notes.

Bottle preparation

Acid washing bottles for cation/metal sample splits

All metals/cations and precious metals bottles should be acid washed prior to use. Some laboratory supply companies have the option to purchase pre-cleaned bottles, but this is not required as long as the bottles can be sufficiently cleaned. If using a water collection container, it also should be acid washed prior to use.

If acid washing bottles, the acid bath should be a 10-20% reagent grade nitric or hydrochloric acid solution, and the bottles and caps should be soaked for at least 12 hours. The bottles should be well-rinsed at least 3 times with deionized water (DI water, 18 M preferred, or similar). The bottles should be air dried in a clean environment (for example, laminar flow hood). The acid bath should be made fresh every 6 months.

Deionized (DI) water rinse for anion and alkalinity/acidity sample splits

Anion and alkalinity/acidity bottles and caps should be soaked overnight in DI water prior to use. Some laboratory supply companies have the option to purchase pre-cleaned bottles, but this is not required as long as the bottles can be sufficiently cleaned. Bottles for anion and alkalinity/acidity sample splits should not be acid washed.

Cleaning pumps and tubing

Peristaltic pumps are generally the best option for collecting water samples, as long as the height of the pump above the water body does not exceed the hydraulic head rating of the pump. If the water needs to be pumped to a height that exceeds the pump rating, then an alternate pump will need to be considered. Tubing will need to be acquired that is compatible with the pump and pump head used. The tubing should be rinsed with DI water and air dried completely prior to sampling. If feasible, each site should have its own dedicated tubing to prevent carryover between sites.

However, if the tubing needs to be reused, it is recommended that it be rinsed with DI water in the field, if possible, or thoroughly rinsed with sample water before collecting the sample. Rinsing with sample water should not be done if sampling water with low concentrations immediately following water with high concentrations, or if the relative concentrations cannot be determined.

Filte…