dredging

Hudson River Tidal Marshes And Sea Level Rise | Earth Wise

January 29, 2021 By EarthWise Leave a Comment

A new study at the University of Massachusetts Amherst looked at the resilience of Hudson River Estuary marshes to rising sea levels. They observed that these marshes are growing upward at a rate two or three times faster than sea level rise, suggesting that they should be resilient to accelerated sea level rise in the future.

The study documented the fact that more than half of Hudson River tidal marshes actually formed since 1850. In that year, the river channel was straightened, and a riverside railroad, berms, jetties and human-made islands of dredged soil were built. All of these human-made features trapped sediment and created backwaters that often turned into marshes.

The research centered on seven sites spanning more than 100 miles of the Hudson Estuary from Wall Street up to Albany. Although these marshes were an unintended result of early industrial development, they serve to protect the shoreline and provide rich ecosystems in terms of direct ecological and human benefits. Marshes are a first line of defense against coastal flooding, provide an essential habitat for juvenile commercial fish species, store huge amounts of carbon that mitigates climate change, provide habitat for migratory birds, and filter nutrients coming off the land.

The study determined that such marches form relatively quickly. When sediment is readily available, freshwater tidal wetlands can develop rapidly in sheltered settings. There is concern that marshes globally will be drowned by rising sea levels, but this Hudson River case study shows how marshes may be able to resist the rising seas. The research will help guide future land acquisition and land conservation strategies for areas adjacent to the river.

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New Study Finds More than Half of Hudson River Tidal Marshes were Created Accidentally by Humans; Resilient Against Sea Level Rise

Photo, posted December 4, 2008, courtesy of Daina Dajevskis via Flickr.

Earth Wise is a production of WAMC Northeast Public Radio.

Concrete Production And Diminishing Coal Burning | Earth Wise

June 5, 2020 By EarthWise Leave a Comment

Coal burning is still one of the primary means of generating electricity in the United States, but its use is diminishing and doing so fairly rapidly. The coal burning process produces residual, incombustible materials. One of them is fly ash, which is composed of fine, glassy, rounded particles rich in silicon, aluminum, calcium, and iron oxides. Fly ash is captured from coal plant flue gas by precipitators and bag filters. It turns out that two-thirds of this fly ash is not dumped into landfills or impoundments, but rather is put to use.

Because of its chemical and physical characteristics, fly ash can substitute for a portion of portland cement in concrete. Using this byproduct material in making cement actually reduces its cost. Beyond cost, the addition of fly ash as a so-called supplementary cementitious material or SCM improves concrete’s long-term strength and reduces porosity and permeability. It reduces the risk of thermal cracking and provides good long-term mechanical properties.

The amount of fly ash used in concrete products increased by 5% between 2011 and 2017 while the amount produced dropped by 36%. Concrete production continues to increase steadily while fly ash production is steadily dropping.

Therefore, the concrete industry is looking for alternative sources of SCM. The most obvious is the approximately 1/3 of fly ash that hasn’t been used to make concrete. Much of that is landfilled or ponded onsite at power plants. So, opportunities exist for excavating or dredging and recovering these materials.

As coal burning goes away, concrete manufacturing needs to make some changes.

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What Does the Changing Face of Electricity Production Mean for Concrete?

Photo, posted February 16, 2017, courtesy of Flickr.

Earth Wise is a production of WAMC Northeast Public Radio.

Sand Mining And The Environment

April 2, 2019 By EarthWise Leave a Comment

In discussions of the environment, we don’t hear much about sand mining. But sand mining is the world’s largest mining endeavor, responsible for 85% of all mineral extraction. Sand and gravel are mined on a huge scale around the world. The UN estimates that the total exceeds 40 billion tons a year. Most of this activity is unregulated and unmeasured, and much of it is corrupt and environmentally destructive.

Concrete is the predominant use for sand. Every ton of cement requires six to seven tons of sand and gravel in order to make concrete. But sand also makes up 90% of asphalt on roads and it is used for land reclamation in places like Singapore. Sand is also widely used in industries such as glass manufacturing and fracking.

There are different sorts of sand. Desert sand is mostly useless for making concrete because its grains are too rounded by erosion and don’t bind well in the concrete. Marine sand is not great for concrete either because it has to be washed clean of corrosive salts.

As a result, salt miners mostly get sand from pits on land and dredged up from lakes and riverbeds. Dredging massive quantities of sand from rivers and lakes drastically alters river flow, erodes riverbanks, dries up tributaries, lowers water tables, and trashes wetlands and fisheries. In many countries, this even goes on in national parks where officials turn a blind eye to the activity. India is the world’s second-largest sand mining country (after China) and widespread illegal extraction occurs throughout the country run by highly organized and even violent “sand mafias.”

Sand mining is a huge problem and, to date, is one that is pretty much off of most people’s radar.

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The Hidden Environmental Toll of Mining the World’s Sand

Photo, posted June 3, 2017, courtesy of Andrey Talalov via Flickr.

Earth Wise is a production of WAMC Northeast Public Radio.

Can The Great Barrier Reef Be Saved?

August 17, 2017 By EarthWise

There have been many stories in the media about the ongoing environmental crisis at Australia’s Great Barrier Reef. Over the past two years, the reef has lost almost half of its coral because of bleaching events. Faced with this situation, the Australian government created the Reef 2050 Plan, a strategy to protect and maintain the reef through the year 2050.