I saw an article the other day slamming the use of end pit lakes in mining. I think it's relatively easy to have a strong opinion an aspect of mining like this, and mining in general.

My personal opinion is that mining is primarily a necessary evil. It has vast capacity to royally fuck up a landscape for a very long time, but it also has the ability to provide us with metals and materials we need.

In this vein, I don't much care for mining of materials that don't support industrial uses or the green transition (e.g., diamonds). I also don't think mining is going anywhere soon. It's about as old as humanity, with some mines dating to 20,000 BCE.

My viewpoint aligns pretty well with the ICMM which aims to allow sustainable mining, through careful planning.

Anyway, My point is not to debate the merits or risks of mining.

I want to talk a bit about why pits are used for tailings and other mine wastes, and the engineering and planning that goes into them.

General

As we know, mining entails the removal of rock that contains minerals or metals of interest. In the case of metals, exploratory drilling will identify areas/veins of ore. The ore is a mix of local rock and the metal of interest. There are cut-off grades, where below a certain concentration, it's not feasible to mine, but I won't get into that. I'm going to primarily focus on metal mining, since that's my strength.

Anyway, since metals are contained with in the rock, the rock must be crushed and milled (e.g., leached with chemicals, and the solution precipitated to get condensate). Here's a really simplified diagram

This process results in the condensate, and a by-product slurry called tailings, which comprises of extra chemicals, water, and the crushed rock. In addition, to get to the ore rock, waste rock (ore rock below cut-off grade) is cast to the side as spoil in huge stockpiles millions of tons in size.

Geochemistry

The issue, however, is that sulphur or other metals often occur with the ore rock. For instance, it's common for a copper mine to also produce gold or molybdenum, or for zinc mines to produce lead as well.

If the ore rock is high in sulphur (commonly in the form of pyrite), when it is exposed to air it weathers to produce sulphuric acid, which rapidly lowers pH in the immediate vicinity, and can really cause a pile of trouble with water. Tailings, since they're just crushed ore rock, and the waste rock that was moved out of the way to get to the ore are common sources of potentially acid generating (PAG). Not all rock is acid generating (called NAG - non-acid generating). Further, metals can leach from rock on their own, but it's more common with the lower pHs associated with PAG.

So really, the issue is exposing rock that was once in anoxic conditions to oxygen. That's where a lot of the problems start.

Water

Another thing to note (briefly) is that any water that hits the mine disturbance footprint is considered 'contact water' and generally must be managed, treated, and released, regardless of its water quality values (e.g., it could be below environmental guidelines, but since we can't easily distinguish, and water quality can change rapidly, we blanket treat everything).

So how do we put a bunch of material on the surface in anoxic conditions?

Well, we have this pit, right over here, where we just dug it out of... and we have a bunch of water that we'd have to treat, which is expensive...

I bet you can see where this is going.

Pit Lakes

To deal with contact water and to prevent metal-leaching/acid rock drainage (collectively; ML/ARD), companies deposit tailings, waste rock, or other ML/ARD material into the pit and cover it with water.

A lot of thinking goes into this. Geological and Hydrogeological studies are conducted, to determine contact water will make its way into the ground water.

Water balance models are created, under several different climate scenarios and projections on the pit lake water elevation (level) are given to mine closure planners and regulators.Water balance modelling aims to ensure that the wastes stay covered no matter what.

Water quality modeling is also conducted, as sometimes specific contaminants can be bioremeidated, or remeidated in the pit itself using chemicals to improve water quality and mitigate risk.

further, human health risk assessments (HHERAs) and environmental risk assessments (ERAs) are a key component for successful mine closures.

What about tailings ponds?

Another way to manage tailings is though a tailings pond (Tailings Storage Facilities - TSFs). These are designed to prevent ML/ARD issues during operations. during active closure and reclamation, they are dewatered (usually though evaporation or other water mgt. means) capped with an impermeable layer (to reduce oxygen infiltration through gas exchange or dissolved oxygen in water) and revegetated.

Some tailings are really fine, and really wet, so they pose very large post-closure geotechincal issues for the TSF. There's a lot of research going on around dry-stacking or paste-stacking tailings. This is essentially changing the milling process to create tailings that are more geotechnically stable, and then capping them with a similar impermable layer and placing coversoil on them and revegating them.

Why are you telling me all this?

The point that I'm trying to make is that there's a lot of thinking that goes into the lifecycle of most mines, particularly in the developed world. Developing world mining and artisinal mining can be abhorent. However, if careful planning is done, then things are less hairy.

cross-posted from: https://beehaw.org/post/8863969

Folks who know me closely know that I'm kind of a geek for patterns - I see them in behavior, in housing, in gardens and natural structures, everywhere. They are at play all around us at varying levels of scale, and anyone who's ever said "oh this again" can hopefully relate.

Christopher Alexander (author along with others of A Pattern Language, The Nature of Order, Notes on the Synthesis of Form), the speaker in this video, has been formative in my understanding of patterns in a way few others have. His approach to design as a conduit for improving the lives of people and the world writ large have been an inspiration.

I want you to forget that he's talking to a room full of programmers. Some of it is abstract, and heady, but think about the patterns in your lives and how even slight alterations to them can influence the course of things. I'm coming to this talk from the aspect of a gardener, of a nursery owner interested in restoration ecology, of someone who wants each of us to have a closer connection to the natural systems at play. Bring who you are to this, and (hopefully) let it inspire you. I'll leave you with this quote from the talk (punctuation mine):

"I want you to help me. I want you to realize that the problem of generating living structure is not being handled by architects or planners or developers or construction people now; there is no way that they're ever going to be able to do that because the methods they use are not capable of it.

The methods that you have at your fingertips and deal with every day in the normal course of events are perfectly designed to do this ... if you have the interest, you have the capacity, you have the means.... And what I'm proposing here is something a little bit different from that which is a view of ~~programming~~ as the natural genetic infrastructure of a living world which you are capable of creating, managing, making available - and which could then have the result that a living structure - in our towns, houses, workplaces, cities - is an attainable thing. Which it has not been for the last 50 to 100 years.

That is an incredible thing! I realize that you probably think I'm nuts because this is not what I'm supposed to be talking about to you. And you may say, 'gosh great idea but we're not interested' but I do think you are capable of that and I don't think anybody else is going to do this job.

First, sorry this community has been kind of dead. I've been pretty preoccupied with work, and blowing of steam shitposting memes

One thing we often encounter in reclamation, if you're a consultant, is clients wanting research done to confirm their methods are feasible and will work when it comes to close a site. As such, they often want to look at all the things, and get the most data for the cheapest price. This leads them to wanting to have a bunch of treatments, often using a factorial design (i.e. split-split plots), where you'll have 20 plot (for example) and each plot has 2 or more treatments within it.

The problem with this is that by nature, you're limited to a low number of reps, since adding one extra rep can significantly impact the amount of money spent on analysis. The thing, though, is that reps serve to smooth out highly variable data (like soil!), and by having a bunch of treatments all smushed together, you get a lot of confoundment going on in your data sets. Further, even when you're militant about controlling variability, you essentially answer many questions poorly and end up needing to do more research to answer them all. You get a 'well kinda' answer.

Alternatively, if you design your experiment in stages, you can better answer questions, and can have the flexibility to adjust in between experimental phases.

For instance, say I want to look at the effect of two subsoil decompaction methods, two amendments, and two planting prescriptions. You could design this easily with a factorial approach, and get data all at once.

Alternatively, if you look at one of each type of treatment (e.g., 1 decompaction method, 1 soil amendment) and 2 planting prescriptions with more reps, you'll have stronger statistical power, and be able to answer questions better. It's more defensible. It's usable data. The kind that gets you another budget to find out the other half of the experiment. In round 2 you look at the other configuration.

Ex//

Round 1
Decompact A x Amend A x plant A
Decompact A x Amend A x plant B
Decompact A x Amend B X Plant A
Decompact A x Amend B x Plant B

Round 2
Decompact B x Amend B x plant A
Decompact B x Amend B x plant B
Decompact B x Amend A X Plant A
Decompact B x Amend A x Plant B

In a factorial, you'd have something like:

Decompact A x Amend A (half plot) X Amend B (half plot) X Plant A (half Plot) x Plant (B) (half Plot) in this case, there's generally too much spatial overlap/noise.

While this approach is a little more expensive in the long run, it's generally cheaper in the short term, and more palatable to clients, particularly when you get solid answers rather than non-answers.

This applies to all field trials, not just Reclamation. Simple experimental designs are elegant. Think of it as a field of vision. If you use a factorial you have a broad field but narrow depth. More elegant approaches? More depth less field. Each has their merits, but reserve factorials for occasions where you aren't sure what is important or aren't trying to prove something

E: some minor spelling mistakes that my phone didn't catch. tweaked design to include overlapping treatments my 11 pm brain didn't catch. Principles remain the same.

This was an interesting presentation covering use cases for various water slowing techniques like BDA's (Beaver Dam Analogues) and PALS (Post Assisted Log Structures), along with recommendations for implementation. There were also some fantastic slides showing some of the patterns that emerge in streams and rivers as they move towards equilibrium from repair work.

ABSTRACT

Land reclamation following surface mining in the Athabasca oils sands region will be extensive, with various challenges specific to local reclamation cover soils. The high economic costs associated with pre-disturbance soil salvage and placement in reclamation necessitates judicious management and application of salvaged cover soils. Soil microbial community activity and bioavailable nutrient supply are largely overlooked in reclamation analyses despite their potential in providing a sensitive measurement of ecosystem function. This study evaluates these parameters by comparing two continuous cover soils, a coarse-textured forest floor mineral mix (FFM) and an organic matter-rich peat soil (PM) at Syncrude Canada's Aurora Soil Capping Study. Shallow (10 cm) and Deep (20–30 cm) placement depths of FFM and PM were compared to a control receiving no cover soil and a harvested jack pine site as a reference. Soil function was assessed by measuring bioavailable nutrient supply rates, soil respiration, phospholipid fatty acid analysis (PLFA), and community level physiological profiles (CLPP). Non-metric multidimensional scaling (NMS) was used to quantify functional similarity with reference conditions. NMS revealed the greatest similarity between FFM and the reference site for bioavailable nutrient supply, PLFA, and CLPP. Deep FFM application shared greatest PLFA similarity to the reference site, while Shallow FFM was more similar in CLPP. Shallow PM was more similar to reference conditions than Deep for all parameters measured, suggesting that shallow cover soil applications might be sufficient for the reclamation target. Soil respiration rates were greatest in FFM, followed by the reference site and PM treatments, with no difference attributable to placement depth. PM had greater nitrogen and sulfur availability, but was lower in phosphorus and potassium when compared to FFM and the reference site. Ecosystem function was more similar in cover soils that mimicked the reference site conditions as much as possible, which in this case meant shallow placement and material salvaged from upland forests

Just give me a couple trucks and dozers and turn me loose.

This reclamation is 10 years old and no soil was placed - these are going directly into waste rock. This is high elevation, so the trees grow slowly

While I'm a bit skeptical of the anti-Eucalyptus crusade in California, there are certainly situations where the trees need to be thinned or removed, and this seemed an interesting technique for those who wish to avoid herbicides. I wonder if it could be done with an edible species to provide an edible harvest as well.

Abstract Topsoil stockpiled for 4 years resulted in an accumulation of NH4-N at depths of 1m or more in mound, as measured by an ammonia gas-sensing electrode. When leached with water these soils were also found to contain high concentrations of dissolved organic C below lm. Both NH4-N and DOC were products of microbial mineralisation of soil organic matter that accumulated under anaerobic conditions. When these soils were restored a flush of decomposition took place, fuelled by labile organic matter and soluble nitrogen. Stockpiled soil which underwent an ammonium-rich perfusion regime in the laboratory indicated that in-mound soils rapidly attained greater nitrification potential than surface mound soils and also had greater potential for further mineralisation of organic matter to NH4-N. This further production was seen as a contribution from the bacterial flush, stimulated by the large labile-C pool already present. As the bulk of stored soil was anaerobic, restored soils were seen as potentially wasteful of their N-reserves; the fate of nitrogen and soluble carbon compounds in restored soils is discussed.

Abstract One technique used to combat the growing global species extinction crisis has been to create artificial refuges—human-made replacements for natural refuges destroyed during habitat modification. However, there is limited knowledge of how closely artificial refuges replicate the natural refuges they seek to replace. Mining threatens many species worldwide through large-scale habitat modification, and artificial refuges have been proposed as a method to offset the resulting habitat loss. Here, we examined the microclimatic, physical, and biotic characteristics of natural dens occupied by the northern quoll (Dasyurus hallucatus)—an endangered marsupial threatened by habitat loss—and compared these to (a) superficially similar unoccupied crevices, and (b) artificial dens created by mining companies for northern quolls. Northern quolls occupied natural dens that were cooler and deeper than unoccupied crevices, likely to avoid lethal air temperatures as well as predators. Artificial dens provided similar thermal properties to occupied dens, but lacked key characteristics in having shallower den cavities, less complex surrounding habitat, increased feral cat visitation, and less small mammal prey compared to occupied dens. This study highlights the need to consider multiple facets when constructing artificial refuges, in order to avoid perverse outcomes, such as inadequate shelter, increased predation, and food shortages.

ABSTRACT Soil stockpiling is a necessary component of opencast coal mining and, because most of the soils involved have arable potential, this involves the possibility of serious soil degradation. A study at four mines on the Highveld of South Africa involved sampling a number of stockpiles of various ages and origins. Samples were also collected from unmined adjacent soils, as well as rehabilitated areas. Results of stockpiling showed a deterioration in all physical and chemical parameters studied. The soil profile texture gradient was disturbed, due to mixing of surface and subsurface materials. Stockpile bulk density rose by 4% from unmined soils and by a further 6% in rehabilitated areas, indicating continuing compaction problems. Cation exchange capacity values did not entirely correspond with the textural changes, suggesting increased leaching, whereas pH values decreased for many stockpiles, requiring post-mining liming to re-establish suitable environments. Organic carbon levels on stockpiles fell by 5%,

and by a further 35% to rehabilitated areas. Increasing age of stockpile did not seem to equate to a correspond- ing increase in degradation, except possibly for pH, which showed a weak correlation. Recommendations from

the study include the use of ‘cut and cover’ rehabilitation techniques; continuous soil specialist consultation, and limitations on stockpile height and duration.___

This rewinding group puts out videos on their progress

cross-posted from: https://mander.xyz/post/2967556

I know I can send soil samples to my local university extension office for testing, but how do I test soil for glyphosate-based herbicides, lead, arsenic, and other contaminates?

As a citizen scientist I'm about to get into composting more on my property and would like to know more.

Organic amendments have been used to restore productivity to disturbed soils such as those on abandoned oil and natural gas wellsites. A study was conducted on three abandoned well- sites in southern Alberta, Canada to examine the effects of one-time applications of alfalfa (Medicago sativa L.) hay or beef cattle (Bos taurus) feedlot manure compost on soil properties under continuous wheat (Triticum aestivum L.). The base amendment rate (1×) [dry wt.] was 5.3 Mg ha−1 for compost and 3.1 Mg ha−1 for alfalfa. The fi ve amendment rates of 0, 1×, 2×, 4×, and 8× were soil-incorporated at the wellsites. Although approximately twice as much C was applied with alfalfa than with compost, fi nal SOC content was similar for the two amendment treatments, indicating the greater stability of compost-derived C. Nitrate N content in the 0- to 60-cm depth was not affected by compost rate (mean 213 kg ha−1) but increased by 7.78 kg ha−1 for each Mg ha−1 increase in alfalfa rate. This result refl ects the greater stability of compost-N compared with alfalfa-N and suggests a lower risk of NO3–N leaching with compost application. Compost rates >20 Mg ha−1 resulted in excessive extract- able P build-up in the topsoil (up to 95.7 mg kg−1), which may pose environmental risk to surface water. We recommend amending wellsites with up to 12 Mg ha−1 of alfalfa or <20 Mg ha−1 of compost during reclamation to improve C storage and nutrient cycling while minimizing nutrient loss to water systems.

Abstract Tomorrow’s forests face extreme pressures from contemporary climate change, invasive pests, and anthropogenic demands for other land uses. These pressures, collectively, demand land managers to reassess current and potential forest management practices. We discuss three considerations, functional restoration, assisted migration, and bioengineering, which are currently being debated in the literature and have the potential to be applied independently or concurrently across a variety of scales. The emphasis of functional restoration is to reestablish or maintain functions provided by the forest ecosystem, such as water quality, wildlife habitat, or carbon sequestration. Maintaining function may call upon actions such as assisted migration—moving tree populations within a species current range to aid adaptation to climate change or moving a species far outside its current range to avoid extinction—and we attempt to synthesize an array of assisted migration terminology. In addition, maintenance of species and the functions they provide may also require new technologies, such as genetic engineering, which, compared with traditional approaches to breeding for pest resistance, may be accomplished more rapidly to meet and overcome the challenges of invasive insect and disease pests. As managers develop holistic adaptive strategies to current and future anthropogenic stresses, functional restoration, assisted migration, and bioengineering, either separately or in combinations, deserve consideration, but must be addressed within the context of the restoration goal.