Monday, December 22, 2014

Fracking Banned in New York

In 2012, the New York State Department of Environmental Conservation (DEC) requested that the New York State Department of Health (DOH) review and assess DEC’s analysis of potential health impacts of hydraulic Fracturing (fracking). Last week the DOH has issued a 186 page report that finds fracking is a complex activity that could affect many communities in New York State because the Marcellus Shale covers a large portion of the state. The number of well pads could be vast and spread out over a significant portion of the state with different environmental conditions. This increase the risk of equipment failures and human error, and increases the risk for exposure to dust, methane gas, air pollution from the operation of equipment, water pollution and adverse health outcomes. Because of these concerns for potential impact to the environment and citizens of the state, New York has banned fracking.

The major findings of the New York DOH report are that there are potential environmental and human health impacts from fracking that include:
  • Increased truck traffic associated with fracking could have air quality impacts that could affect respiratory health due to increased levels of particulate matter, diesel exhaust, or volatile organic chemicals.
  • Fracking could contribute to increasing climate change by releasing methane to the atmosphere and making it cheaper to use natural gas to heat homes and make electricity delaying the adoption of renewable energy sources..
  • Faulty well construction could allow methane and/or fracking water containing a mix of chemical to contaminate potential drinking water supplies.
  • Surface spills potentially resulting in soil and water contamination.
  • Surface-water contamination resulting from inadequate wastewater treatment.
  • Earthquakes induced during fracturing. (Though federal studies have found that induced earthquakes are associated with deep well disposal of waste water not fracking itself.) 
  • Community impacts associated with boom-town economic effects such as increased vehicle traffic, road damage, noise, odor complaints, increased demand for housing and medical care, and stress.
This report from the DOH served more as the argument for the ban rather than a scientific study. A recent study by scientists reviewed all 166 fracking studies that have been performed and peer reviewed to consolidate all that we know about fracking and identify the areas where more research needs to be performed. This paper is  a complete and thorough review of all the risks and benefits and area where more study needs to be performed for the hydrocarbon extraction method known as fracking. The paper: “The Environmental Costs and Benefits of Fracking” in the Annual Review of Environment and Resources.( Annu. Rev. Environ. Resour. 2014. 39:7.1–7.36) by Robert B. Jackson formerly of Duke University and now at Stanford, Avner Vengosh, still at Duke University, J. William Carey, from Los Alamos National Laboratory, Richard J. Davies, from Durham University, Thomas H. Darrah, for Ohio State University, Francis O’Sullivan, from MIT and Gabrielle P´etron from the University of Colorado at Boulder.

Fracking is the current method of extracting unconventional oil and natural gas that is locked inside impermeable geological formations. Fracking is enabled by horizontal drilling and hydraulic fracturing (thus the name fracking). Fracking or hydraulic fracturing as it is more properly known involves the pressurized injection of fluids made up of mostly water and chemical additives into a geologic formation. The pressure used exceeds the rock strength and the fluid opens or enlarges fractures in the rock. As the formation is fractured, a “propping agent,” such as sand or ceramic beads, is pumped into the fractures to keep them from closing as the pumping pressure is released. The fracturing fluids (water and chemical additives) are partially recovered and returned to the surface or deep well injected for disposal. Natural gas or oil will flow from pores and fractures in the rock into the wells allowing for enhanced access to the methane or oil reserves.
From USGS the extent of the Marcellus Shale


Throughout their study the scientist recommend a series of research questions that should be answered to more fully model and understand fracking, but not banning . In addition they emphasize the need for greater transparency from companies and regulating agencies in information and the need for baseline studies prior to drilling is critical to even know if water or human health has been impacted. Predrilling data needs to include measurements of groundwater and surface-water quality and quantity as well as air quality, and human health. The scientists pointed out that there have been virtually no comprehensive studies on the impact of fracking on human health while state regulators and law in some instances allow fracking virtually in people’s backyards. The New York regulators have now banned fracking because it is not completely understood, the risks imperfectly managed and will likely contribute to climate change.

Thursday, December 18, 2014

What Caused the Mineral Virginia Earthquake?


from USGS

On August 23, 2011 just outside of Mineral, Virginia a 5.8 earthquake occurred about five miles beneath the earth. The earthquake was felt by people from Georgia to Canada. The earthquake caused wells in my neighborhood to spew mud and foundations to crack and we are more than 60 miles northeast. The question is why did the earthquake occur near Mineral, Virginia and why was the earthquake felt here?

Those of us who took rocks for jocks (survey of geology) in college know that the Earth's crust is comprised of a series of continental and oceanic plates that are constantly moving. The plates ram into each other, sliding underneath or above each other, or pull apart. Most earthquakes arise along such fault zones and is triggered by the plate movement. The ground first bends and then snaps forming an earthquake to release energy along faults. There are no plate boundaries in Virginia, so, why did we have an earthquake?

The U.S. Geological Survey (USGS) scientists have been investigation why seismic events occur in certain parts of the central and eastern United States, like the Central Virginia seismic zone, since there are no plate boundaries there, unlike the San Andreas Fault in California, or the Aleutian Trench in Alaska.

In 2012 USGS scientists conducted low-altitude geophysical (gravity and magnetic) flight surveys over the epicenter of the earthquake, located about eight miles from Mineral, Virginia. Deep imaging tools were used because the earthquake occurred about five miles beneath the earth’s surface. Maps of the earth’s magnetic field and gravitational pull can show subtle variations that reflect the physical properties of the deeply buried rocks. From this information deep earth maps of the region were drawn.

According to Anji Shah, the lead author of the study: “These surveys unveiled not only one fault, which is roughly aligned with a fault defined by the earthquake’s aftershocks, but a second fault or contact between different rock types that comes in at an angle to the first one. This ... suggests that the earthquake occurred near a ‘crossroads,’ or junction, between the fault that caused the earthquake and another fault or geologic contact.”

The magnetic data obtained by the USGS showed a wide bend in the deeply buried rocks within the Central Virginia seismic zone. This anomaly suggests to the USGS scientists that seismic activity may be increased in other nearby areas with locally increased rock weakness or permeability. The primary fault line of Mineral earthquake (and its aftershocks) runs to the northeast almost continually for tens of miles practically to Haymarket. According to Dr. Shah the continuity of the associated geologic structures probably allowed the seismic energy to be carried in that direction, consistent with moderate to high levels of damage from Louisa County to Washington, D.C., and neighboring communities.

The gravity and magnetic data found that a fault seems to separate different types of rocks with varying densities and strengths. The scientists believe that the junction between the faults may be the origin of the earthquake and wonder if similar junctures exist elsewhere. There is still so much to learn about Earth and this is just one small step towards a deeper understanding the earth around us.

Monday, December 15, 2014

Demographics Doom Climate Talks

The most recent United Nations Framework Convention on Climate Change meeting held in Lima, Peru to once more discuss, negotiate and talk about climate change finally ended early Sunday morning.  Despite  being extended over 30 hours to try to salvage some sort of agreement, nothing was really accomplished. The agreement announced and issued in the wee hours of Sunday morning was so watered down as to be practically meaningless. The agreement calls for:

Reaching an agreement next year in Paris that reflects "differentiated responsibilities and respective capabilities" of each nation. Developed countries will provide financial support to "vulnerable" developing nations. And countries will set targets that go beyond their "current undertaking" without any accountability.

The talks in Paris next year will fail to produce a plan that will make any difference despite the “historic” climate agreement between President Barack Obama of the United States and President Xi Jinping of China announced last month. If you will recall the United States promised to reduce greenhouse gas emissions (primarily carbon dioxide, CO2) 26-28% from 2005 levels by 2025. This was an increase from the previously promised reduction made by President Obama for the United States to reduce CO2 emissions 17% by 2020 and 83 % by 2050. To achieve this goal the United States will have to reduce their standard of living and quality of life even with increases in efficiency of electrical production and gas mileage it cannot be accomplished any other way given the current and foreseeable technology . This would require approximately doubling annual CO2 reductions from 1.2% from 2005-2020 to 2.3-2.8 % from 2020-2025.


China will not cap their greenhouse gas emissions or economic growth, but instead announced its intent to peak CO2 emissions around 2030 (right about the time their population is due to peak). China also plans to increase the share of non-fossil fuels in electrical generation to around 20% by 2030. China had previously pledged to increase the share of non-fossil fuels for energy to around 15%.

The climate talks in Paris next year will fail to produce a meaningful plan to reduce world CO2 emissions because it can’t be done. The developing world will not cap their greenhouse gas emissions or economic growth while they are still poor. The developed world no longer represents the lion’s share of CO2 emissions. In 1990’s when the Kyoto Treaty was signed by the European Union, Japan and Canada, the developed world represented 72% of global CO2 emissions from fuel, now they represent about 43% and falling. Europe’s birth rate has plummeted and Europe’s population (including Russia and Eastern Europe) of 740 million is projected to decrease to 726 million by 2050. The population of the United States is projected to grow from about 316 million today to 440 million by 2050.

Asia is home to 60% of global population. China and India account for more than half of Asia’s total population. China’s total fertility rate is a very low 1.5 children per woman. India is projected to pass China in population size in about 15 years, becoming the world’s most populous country and is projected to have 1.625 billion people by 2050 while China’s population is projected to begin to fall from 1.357 billion today to 1.314 billion in 2050. Combined, they will represent about 30% of the world’s population. At the climate talks in 2012 China’s chief climate negotiator Xie Zhenhua announced that China’s CO2 emission would peak around 2030, pointing out that its per capita gross domestic product would have only reached half the level of other developed countries’ CO2 emissions when they peaked. No comment was made on the projected peak per capita CO2 emissions we are left to guess..


The only way to improve the standard of living and quality of life of their citizens is through the use of energy, for industry, transportation, lighting, water treatment and delivery, sewage treatment, growing food everything depends on energy most of which comes from fossil fuels. Even with increasing efficiency more carbon will have to be burnt to raise the standard of living of the developing world.

The world carbon emissions are growing each year faster than the developed nations can cut them even if we had the will to reduce our living standards to accomplish that. In addition, the developed world is growing older and will not have the financial resources to meet the promises that were made in their national social contracts. We may be rationing healthcare along with electricity and be unable to provide financial support to "vulnerable" developing nations. The United States will face a trade off of reducing living standards even further or missing the President's goals. .

Thursday, December 11, 2014

Arsenic in Well Water a Heart Attack Risk

Worldwide, cardiovascular disease is the leading cause of death. In a growing number of studies that began in Asia where chronic arsenic poisoning is a huge problem it has been found that drinking water contaminated with arsenic increases the risk of cardiovascular disease. The higher the levels of arsenic the higher the death rate. (The risk was significantly increased for anyone who smoked or had ever smoked.) This has been confirmed in recent years in studies performed in Bangladesh, Taiwan, Chile and Mexico. Older studies have linked long-term exposure to arsenic in drinking water to cancer of the bladder, lungs, skin, kidney, nasal passages, liver, and prostate. Non-cancer effects of ingesting arsenic include cardiovascular, pulmonary, immunological, neurological, and endocrine (e.g., diabetes) effects.

Arsenic exposure is not just a risk in Asia and South America. As recently reported in the New York Times a meta-analysis of data from the quarter century of data from the Strong Heart Study of 13 American Indian tribes and communities in three geographic areas: an area near Phoenix, Arizona, the southwestern area of Oklahoma, and western and central North and South Dakota found an association between chronic arsenic exposure and heart disease. The scientists compared urinary arsenic levels in the population and found that as levels of arsenic rose so did the incidence of atherosclerosis, stroke and heart attacks. For those with chronic long term exposure to arsenic the risk of cardiovascular disease could be as high as two times dependent on concentration of arsenic exposure. In general, though, the dose response is about 25% increase in death from cardiovascular disease from each increase in arsenic concentrations by about 115 parts per billion. The U.S. Environmental Protection Agency (EPA) drinking water standard for arsenic in public water supplies is 10 parts per billion.

The Bangladesh study (by Dr. Yu Chen et al) they quantified the relationship between even low levels of arsenic exposure and increased risk of death for smokers. Study participants who were current smokers, had smoked for at least 20 years, or had smoked for at least 10 pack years at the beginning of the study were found to be 2.2-2.7 times more likely to die from heart disease.

Arsenic is a ubiquitous metal in the earth’s crust. Arsenic occurs naturally in rocks and soil, water, air, and plants and animals. It can be further released into the environment through natural activities such as volcanic action, erosion of rocks, and forest fires, or through the use of arsenic by mankind. In the United States arsenic is still widely used as a wood preservative, but arsenic is also used in paints, dyes, metals, drugs, soaps, and semi-conductors. Agricultural use in fertilizer, mining, and smelting also have contributed to arsenic releases in the environment. People are also exposed to elevated levels of arsenic through diet.

Higher levels of arsenic tend to be found more in ground water sources than in surface water sources of drinking water like rivers and lakes. Compared to the rest of the United States, western states have higher naturally occurring arsenic levels- more groundwater basins have arsenic levels higher than the 10 ppb level the EPA has identified as safe. Parts of the Midwest and New England also have some areas where groundwater arsenic concentration are greater than 10 ppb, sometimes much greater. Though the EPA regulates public water supplies, in private wells (used by 13% of the U.S. population) you are on your own for ensuring that your water is safe. The USGS believes most groundwater basins have natural arsenic concentrations that range from 2-10 ppb (the most common testing method is accurate to 5 ppb). While many groundwater systems may not have detected arsenic in their water above 10 ppb, groundwater is not uniformly mixed like surface water. The USGS states ther may be geographic "hot spots" that may have higher levels of arsenic than the predicted occurrence for that area. You should test your groundwater to know it.

The most common source of arsenic contamination in ground water is the mobilization of naturally occurring arsenic on sediments. Given the right chemical conditions in the subsurface arsenic can dissolve into ground water used for drinking water. The U.S. Geological Survey (USGS) scientists have been conducting field experiments to understand the bio-geochemical processes that control arsenic mobility in ground water and might create hot spots or regions of elevated concentration of arsenic. Recent results published in the Journal of Contaminant Hydrology, show that chemical reactions between nitrate, iron, and oxygen can affect the mobility of trace amounts of arsenic. Septic systems can increase the nitrate level of groundwater. Site specific conditions, impact from your neighbors, or historic use of arsenic containing pesticides can impact the quality of your drinking water. Test you well, regularly so that you can take actions to protect your health (and don’t smoke).

Monday, December 8, 2014

Water Use In Virginia 2010

The Commonwealth of Virginia is a water rich state. The U.S. Geological Survey (USGS) report “Estimated use of water in the United States in 2010” breaks out the water use by states and tells the story of Virginia by how we use water. Since 1950 the USGS has collected data on water use in the U.S. every 5 years. This report allows us to see and understand our water use to prevent Virginia from ever running out of water. Throughout 2010 Virginia used an average of 7,650 million gallons of water each day.

As you can see in the chart above, not all water use is fresh water use. Almost 42% of the water used each day and each day is salt water used primarily for thermoelectric power generation. Thermoelectric power generation uses almost 79% of all water in Virginia and over 64% of fresh water. Water for thermoelectric power is used in generating electricity with steam-driven turbine generators. Water is used in more than one way in power generation. Once-through cooling systems circulate water through heat exchangers and then return the water to the source these tend to be older systems. A recirculation system has cooling ponds or towers to cool the water so that it can be constantly reused. Water withdrawals for a recirculating system are used to replace water lost to evaporation, blowdown, drift, and leakage. Newer power plants tend to use less water. It is also to be recalled that Virginia only produces about 64% of the electricity used each day in Virginia. We, like most states are a net importer of electricity.

Of the 664 million gallons of water that is withdrawn from rivers and groundwater each day for public supply, 476 million gallon a day or 72% goes for domestic supply. Domestic water use includes indoor and outdoor use at homes and apartments in Virginia for drinking, food preparation, washing clothes and dishes, bathing and flushing toilets. Common outdoor uses are watering lawns and gardens or maintaining pools or landscape features at your home. Domestic water is either self-supplied or provided by public water companies. In Virginia a total 600 million gallons of water a day is used for domestic supply- 476 million gallons a day is from public water companies and 124 million gallons a day is self-supplied from private wells. According to the USGS 1,650,000 Virginians or 21% of the population of the Commonwealth get their water from private wells. Virginia is still a very rural state with 21% of domestic water coming from private wells which are only in rural or semi-rural locations, nationally only about 14% of domestic water is from private wells. Domestic use, both from private wells and public supplied accounts for less than 14% of all fresh water use in Virginia and less than 8% of total daily water use in the Commonwealth. The typical Virginian uses 75 gallons of water a day for all domestic uses and is the same for public supplies households as well as households supplied by private well. In most states, households on private well use less water than those on public water supplies. On average in the United States a person with a private well uses 81 gallons of water a day and a person on public water supply uses 89 gallons of water a day.

Despite being a very rural state, less than 3% of fresh water withdrawn from rivers, streams, and groundwater is used for agriculture. It rains in Virginia and only 1.4% of fresh water is used for irrigation which includes water for crop irrigation, frost protection, application of chemicals, weed control, field preparation, crop cooling, harvesting, dust suppression, a well as watering of golf courses, parks, nurseries, turf farms, cemeteries, and landscape-watering for businesses and public buildings. Livestock water use which is less than 1.4% is for livestock watering, feedlots, dairy operations, and other on-farm needs.

In mining water is used for the extraction of minerals that may be in the form of solids, such as coal, iron, sand, and gravel; liquids, such as crude petroleum; and gases, such as natural gas. The category includes quarrying, milling of mined materials, injection of water for secondary oil recovery or for unconventional oil and gas recovery (such as hydraulic fracturing), and other operations associated with mining activities. Today, the 35 million gallons a day of water used for mining is primarily for coal mining in the Appalachian plateau.

Water used in aquaculture in Virginia is primarily used in raising shellfish for food, and restoration, conservation of the habitat. Aquaculture production occurs under controlled feeding, sanitation, and harvesting procedures primarily in ponds, flow-through raceways, and, to a lesser extent, cages, net pens, and closed recirculation tanks. Approximately 295 million gallons of water a day are used for aquaculture in Virginia. Much of the water used for aquaculture is maintaining flow for habitat.



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Thursday, December 4, 2014

Water Well Basics

from VAMWON
Nationally about 14% of domestic water is supplied from private wells. In Virginia, still a very rural state, about 21% of domestic water is supplied from private wells. If you have a private well you are responsible for making sure that you have water in your home and it is safe and pleasant to drink yet, I’ll bet that no one ever taught you the fundamentals of a well so that when there is a problem, you have a frame work to narrow down the causes and solve it.

Wells are a combination of natural and mechanical systems that serve to move water from fractures or cracks in the bedrock or pore space between grains of sediment or sand in the earth into the well and from there into the house. Generally speaking a modern well should be drilled through the loose “overburden” of top soil, sand and sediment into the bedrock below. In geology that has groundwater, water will flow from any fractures that intersect the open borehole. In wells drilled in areas where the sediment and sand are more than a hundred or two hundred feet deep, water will flow from the pores or spaces into the well. A well should have a casing that extends at east through the overburden and possibly to the water table. In bedrock a well borehole can simply be open, but in sandy soils the borehole will require a well screen liner or slotted casing to prevent the borehole from collapsing or filling with sand and silt. Well casings used to be made of steel, but these days plastic piping is becoming more common.
from VAMWON


For the plumbing system to function properly, the recharge rate in the well would either have to equal the pumping rate or there has to be adequate storage in the system- either a storage tank or the well itself. The recharge rate or the well recovery rate is the rate that water actually flows into the well through the rock fissures. If the well cannot recharge at the same rate at which water is being removed and does not have adequate water reserves then the well, the system would suffer intermittent episodes of severe water pressure loss. The information on your wells performance can be obtained from the water well completion report on file with the department of health. The “stabilized yield” is the recharge rate.

While many wells will last decades, it is reported that 20 years is the average age of well failure. Over time every component of a water system will fail. Older well pumps are more likely to leak lubricating oil or fail. Well casings are subject to corrosion, pitting and perforation. Iron bacteria and scale will build up in fittings and clog pitless adaptors and pipes. A water pressure loss can result from a pump that is too small for demand, inadequate or a failing pressure tank, or a buildup of scale in the pipes. There are a number of reasons why a well might stop producing water, but basically they break down into equipment failure, depletion of the aquifer or other groundwater problems and failing well design and construction.
Sanitary well cap

The essential mechanical components of a modern drilled well system are: a submersible pump, a check valve (and additional valve every 100 feet), a pitless adaptor (a fitting that makes a 90 degree turn to make the connection between the water line in the well and the horizontal pipe that runs below the frost line to the house), a well cap (sanitary sealed), electrical wiring including a control box, pressure switch, and interior water delivery system. There are additional fittings and cut-off switches for system protection, but the above are the basics. To keep the home supplied with water the system and well must remain operational.
The components within the house (usually in the basement) provide consistent water pressure at the fixtures. The pump moves water to the basement water pressure tank, inside the tank is an air bladder that becomes compressed as water is pumped in. The pressure tank moves the water through the house pipes so that the pump does not have to run every time you open a faucet. The pressure tank maintains the water pressure between 40-60 psi. After the pressure drops to 40 psi, the switch turns on the pump and the pressure in the tank increases. Over time the bladder becomes stiffer and water pressure is lost. Also, the pressure tank can lose some of it’s charge or become water logged.
my pressure tank- Goulds made my pump and slapped their label on the pressure tank

Monday, December 1, 2014

Earth’s Shields are Up

High above Earth's atmosphere, the Earth is surrounded by two belts of high energy particles mainly electrons moving a close to the speed of light and protons that are held in place by the magnetic fields. These belts were discovered in 1958, by James Van Allen. The Van Allen belts can wax and wane in response to incoming energy from the sun in the form of solar flares and coronal plasma ejections. A slot of fairly empty space typically separates the belts, but its width changes. Under extreme conditions, when a strong solar wind or a giant solar eruption such as a coronal mass ejection sends clouds of material into near-Earth space the electrons from the outer belt can be pushed into the usually-empty slot region between the belts.

In August 2012 the twin Van Allen Probes were launched into space to study the Van Allen Belts. The probes were built and are operated by the Johns Hopkins Applied Physics Laboratory in Laurel, Maryland for NASA’s Science Mission Directorate. While you and I go about our daily lives scientists at the University of Colorado, Massachusetts Institute of Technology (MIT), Johns Hopkins, University of California at Los Angeles and elsewhere are still learning about our planet using probes and satellites.

The electrons in the outer band of Van Allen’s belts are ultra-relativistic traveling near the speed of light and can circle the planet in just five minutes, bombarding anything in their path. Exposure to such high-energy radiation can disrupt on satellite electronics. These probes were designed to withstand constant radiation bombardment so it can measure the behavior of these ultra-relativistic electrons.

During the past decade scientists at MIT have studied plasma plume phenomena using radio signals transmitted from GPS satellites to more than 1,000 receivers on the ground. Large space-weather events can alter the incoming radio waves and allow scientists to see the concentration of plasma particles in the upper atmosphere during space weather events. Combining data from the ground based observations and the new space data from the Van Allen probes has given scientists a highly detailed picture of a natural defensive mechanism for Earth.

Now researchers at the University of Colorado, MIT, Johns Hopkins, University of California and elsewhere have found there is an absolute limit to how close ultra-relativistic electrons can get to the Earth. The team found that no matter where these electrons are circling around the planet's equator, they can get no further than about 6,800 miles from the Earth's surface. No matter how intense the energy of the particle there is a barrier that prevents it from penetrating our atmosphere. Earth has a shield.

This shield is created neither by the Earth's magnetic field nor long-range radio waves, but rather by extremely low frequency electromagnetic waves in the upper atmosphere. The Van Allen radiation belts are not the only particle structures surrounding Earth. A giant cloud of relatively cool, charged particles called the plasmasphere fills the outermost region of Earth's atmosphere, beginning at about 600 miles up and extending partially into the outer Van Allen belt. The particles at the outer boundary of the plasmasphere cause particles in the outer radiation belt to scatter, draining them and their energy from the belt. The scientists call this phenomenon "plasmaspheric hiss,” because when the low-frequency electromagnetic waves are played through a speaker sound like a static or a hiss.

This scattering effect is fairly weak and might not be enough to keep the electrons at the boundary of the outer Van Allen belt in place, except that the belt electrons move incredibly quickly, but not toward Earth. Instead all their speed is in loops around Earth. The Van Allen Probes data show that in the direction toward Earth, the ultra-relativistic electrons have only a slow drift towards earth that can be measured in months. This is a movement so slow and weak that it can be countered d by the scattering caused by the plasmasphere.

Based on their analysis published on Thanksgiving in the journal Nature believe that plasmaspheric hiss essentially deflects incoming electrons, causing them to collide with neutral gas atoms in the Earth's upper atmosphere, and ultimately disappear. This natural, impenetrable barrier appears to be extremely rigid, keeping high-energy electrons from coming no closer than about 6,800 from the Earth's surface, but a massive inflow of matter from the sun can erode the outer plasmasphere, pushing its boundaries inward and allowing electrons from the radiation belts to move further inward, too. So the shield is not rigid.