This document provides an overview of Marcellus Shale drilling in Pennsylvania and discusses environmental and public health concerns associated with the process. It notes that 64% of PA underlies the Marcellus Shale formation and outlines concerns such as chemical and wastewater leaks threatening drinking water, air pollution, excessive water use, and impacts to public lands. It proposes actions citizens can take to strengthen regulations around water use, chemical disclosure, buffer zones, and ensuring industry pays for damages.
Paper: Water Pollution Risk Associated with Natural Gas Extraction from the M...Marcellus Drilling News
A research paper written by doctoral student Daniel Rozell and professor Dr. Sheldon Reaven, published in the August 2012 issue of the journal Risk Analysis. The paper creates mathematical risk models for five possible ways fresh water may become contaminated by fracking fluids during the process of drilling for natural gas. The authors conclude the most likely way it might happen is through the disposal of fracking wastewater.
This presentation was given by Professor Alastair Driver, Catchment restoration specialist and ecologist, at the EPA's October 2017 Catchment Science and Management Course. You can find more information about catchment management at www.catchments.ie
Maryland Environmental Site Design PresentationTheodore Scott
Overview presentation by Theodore E. Scott, PE, CPESC, LEED AP on recent changes to the Maryland Stormwater Management Design Manual that requires the use of Environmental Site Design (ESD).
Established in 1972 to restore and maintain the chemical, physical, and biological integrity of the nation's waters by preventing point and non-point pollution sources, providing assistance to publicly owned treatment works for the improvement of waste water treatment, and maintaining the integrity of wetlands.
Hydraulic Fracturing and Marcellus Shale Gas 11 22 2011Michael Klein
The drilling technique of Hydraulic Fracturing has allowed natural gas producers to extract natural gas economically from deep shale formations. This innovative drilling technique has made enormous quantities of natural gas available in wide areas of the United States from Texas, Louisiana, Pennsylvania, New York, Wyoming, North Carolina, and Colorado. The drilling technique of hydraulic fracturing accounts for roughly a quarter of total natural gas production in the United States as cited by the Energy Information Administration. With the increased emphasis on the use of natural gas in our federal energy policy, there will be new regulations, processes, and resources that will be required to mitigate the risks to human health and the environment from this new drilling technique. The presentation discusses the process of hydraulic fracturing; the threats that are posed to human health and the environment, areas in the USA where the process is used with an emphasis on the Marcellus Shale formation, current and new regulations being put into place, and plaintiff challenges to the process.
PA Forest Fragmentation from Marcellus Shale, Wind Turbines & Transmission LinesPaul Zeph
Overview of the habitat This is a captioned slideshow reviewing the fragmentation impacts of Marcellus Shale drilling, ridge-top wind development, and proposed new regional electricity transmission corridors to the forests of Pennsylvania.
Paper: Water Pollution Risk Associated with Natural Gas Extraction from the M...Marcellus Drilling News
A research paper written by doctoral student Daniel Rozell and professor Dr. Sheldon Reaven, published in the August 2012 issue of the journal Risk Analysis. The paper creates mathematical risk models for five possible ways fresh water may become contaminated by fracking fluids during the process of drilling for natural gas. The authors conclude the most likely way it might happen is through the disposal of fracking wastewater.
This presentation was given by Professor Alastair Driver, Catchment restoration specialist and ecologist, at the EPA's October 2017 Catchment Science and Management Course. You can find more information about catchment management at www.catchments.ie
Maryland Environmental Site Design PresentationTheodore Scott
Overview presentation by Theodore E. Scott, PE, CPESC, LEED AP on recent changes to the Maryland Stormwater Management Design Manual that requires the use of Environmental Site Design (ESD).
Established in 1972 to restore and maintain the chemical, physical, and biological integrity of the nation's waters by preventing point and non-point pollution sources, providing assistance to publicly owned treatment works for the improvement of waste water treatment, and maintaining the integrity of wetlands.
Hydraulic Fracturing and Marcellus Shale Gas 11 22 2011Michael Klein
The drilling technique of Hydraulic Fracturing has allowed natural gas producers to extract natural gas economically from deep shale formations. This innovative drilling technique has made enormous quantities of natural gas available in wide areas of the United States from Texas, Louisiana, Pennsylvania, New York, Wyoming, North Carolina, and Colorado. The drilling technique of hydraulic fracturing accounts for roughly a quarter of total natural gas production in the United States as cited by the Energy Information Administration. With the increased emphasis on the use of natural gas in our federal energy policy, there will be new regulations, processes, and resources that will be required to mitigate the risks to human health and the environment from this new drilling technique. The presentation discusses the process of hydraulic fracturing; the threats that are posed to human health and the environment, areas in the USA where the process is used with an emphasis on the Marcellus Shale formation, current and new regulations being put into place, and plaintiff challenges to the process.
PA Forest Fragmentation from Marcellus Shale, Wind Turbines & Transmission LinesPaul Zeph
Overview of the habitat This is a captioned slideshow reviewing the fragmentation impacts of Marcellus Shale drilling, ridge-top wind development, and proposed new regional electricity transmission corridors to the forests of Pennsylvania.
A so-called "fact sheet" prepared for the FreshWater Accountability Project Ohio by Dr. Marvin Resnikoff that purports to show dangers from Utica Shale drilling waste (rock, soil, etc.) that may contain low levels of radioactivity. Resnikoff is a well-known anti-driller who uses the radioactivity issue to push his agenda to curtail drilling.
The Great Lakes-St. Lawrence River Basin Water Resources Compact was signed into federal law with great fanfare in 2008. However, states must do more to realize the Compact’s potential to better manage Great Lakes waters in and outside of the basin through comprehensive water conservation and efficiency programs, improved data sharing and more comprehensive permitting.
Last Updated October 31, 2011Hydrofracking Is hydraulic fractu.docxsmile790243
Last Updated: October 31, 2011
Hydrofracking: Is hydraulic fracturing, or hydrofracking, a safe way to extract natural gas?
Pro/Con Article Media Editorials News
Page Tools Highlighting
FULL ARTICLE
Introduction
Background
Supporters Argue
Opponents Argue
Conclusion
Chronology
By the Numbers
Spotlights
Discussion Questions
Bibliography
Further Resources
Introduction
SUPPORTERS ARGUE
There is no proven case of hydrofracking contaminating drinking water, and the process is perfectly safe. Natural gas can revive local economies, reduce U.S. dependence on foreign oil, and provide a cleaner-burning fossil fuel. Further regulation is unnecessary and will only prevent an opportunity for the United States to develop an alternative energy source and create jobs.
OPPONENTS ARGUE
The chemicals used in fracking fluid are toxic and pose a danger to public health if they contaminate drinking water reserves or leak out of wells. Oil and gas companies are not being honest with the public about the dangers of hydrofracking, and the federal government should apply much stricter, nationwide regulations to ensure that hydrofracking does not cause widespread health problems that could plague the public for generations.
Issues and Controversies: Hydrofracking Workers
Workers at a natural gas well site in Burlington, Pennsylvania, in April 2010 prepare a drill to begin the process of hydraulic fracturing, or hydrofracking.
AP Photo/Ralph Wilson
Many observers have hailed natural gas as a solution to several energy problems facing the U.S. Utilizing the country's ample domestic supply of the resource, many have said, could greatly decrease U.S. dependence on foreign oil and possibly drive energy prices down. Furthermore, natural gas produces much less carbon dioxide than other fossil fuels, about half as much as coal, making it the cleanest burning fossil fuel available. Energy experts have also touted natural gas as a cheap alternative to renewable energy sources, such as wind or solar energy, until engineers devise a way to make renewable energy more cost efficient. According to the Department of Energy, natural gas already produces about one-fifth of the nation's electricity, a proportion that may increase as energy firms tap more domestic reserves of natural gas.
The Marcellus Shale, a 95,000-square-mile geologic formation deep underground that stretches from West Virginia through Pennsylvania to upstate New York, is estimated to contain as much as 500 trillion cubic feet of natural gas. In order to access the natural gas in the Marcellus Shale and other shale formations, however, energy companies have to employ a controversial procedure called hydraulic fracturing—also known as "hydrofracking" or simply "fracking." Hydrofracking is a technique that releases natural gas by pumping millions of gallons of water, laced with sand and chemicals, thousands of feet underground to blast open, or fracture, shale formations, freeing the gas. [See Today's Science: Nat ...
This slide show presentation was utilized at the Nov. 16, 2023 event "Think Science: Geoscience & Groundwater" and features contributions from:
Dr. Ben Surpless, Trinity University
Dr. Saugata Datta, UTSA
Dr. Brady Ziegler, Trinity University
Similar to Marcellus shaleempowermenttrainingmarcellu soverview (20)
Kubernetes & AI - Beauty and the Beast !?! @KCD Istanbul 2024Tobias Schneck
As AI technology is pushing into IT I was wondering myself, as an “infrastructure container kubernetes guy”, how get this fancy AI technology get managed from an infrastructure operational view? Is it possible to apply our lovely cloud native principals as well? What benefit’s both technologies could bring to each other?
Let me take this questions and provide you a short journey through existing deployment models and use cases for AI software. On practical examples, we discuss what cloud/on-premise strategy we may need for applying it to our own infrastructure to get it to work from an enterprise perspective. I want to give an overview about infrastructure requirements and technologies, what could be beneficial or limiting your AI use cases in an enterprise environment. An interactive Demo will give you some insides, what approaches I got already working for real.
GDG Cloud Southlake #33: Boule & Rebala: Effective AppSec in SDLC using Deplo...James Anderson
Effective Application Security in Software Delivery lifecycle using Deployment Firewall and DBOM
The modern software delivery process (or the CI/CD process) includes many tools, distributed teams, open-source code, and cloud platforms. Constant focus on speed to release software to market, along with the traditional slow and manual security checks has caused gaps in continuous security as an important piece in the software supply chain. Today organizations feel more susceptible to external and internal cyber threats due to the vast attack surface in their applications supply chain and the lack of end-to-end governance and risk management.
The software team must secure its software delivery process to avoid vulnerability and security breaches. This needs to be achieved with existing tool chains and without extensive rework of the delivery processes. This talk will present strategies and techniques for providing visibility into the true risk of the existing vulnerabilities, preventing the introduction of security issues in the software, resolving vulnerabilities in production environments quickly, and capturing the deployment bill of materials (DBOM).
Speakers:
Bob Boule
Robert Boule is a technology enthusiast with PASSION for technology and making things work along with a knack for helping others understand how things work. He comes with around 20 years of solution engineering experience in application security, software continuous delivery, and SaaS platforms. He is known for his dynamic presentations in CI/CD and application security integrated in software delivery lifecycle.
Gopinath Rebala
Gopinath Rebala is the CTO of OpsMx, where he has overall responsibility for the machine learning and data processing architectures for Secure Software Delivery. Gopi also has a strong connection with our customers, leading design and architecture for strategic implementations. Gopi is a frequent speaker and well-known leader in continuous delivery and integrating security into software delivery.
Software Delivery At the Speed of AI: Inflectra Invests In AI-Powered QualityInflectra
In this insightful webinar, Inflectra explores how artificial intelligence (AI) is transforming software development and testing. Discover how AI-powered tools are revolutionizing every stage of the software development lifecycle (SDLC), from design and prototyping to testing, deployment, and monitoring.
Learn about:
• The Future of Testing: How AI is shifting testing towards verification, analysis, and higher-level skills, while reducing repetitive tasks.
• Test Automation: How AI-powered test case generation, optimization, and self-healing tests are making testing more efficient and effective.
• Visual Testing: Explore the emerging capabilities of AI in visual testing and how it's set to revolutionize UI verification.
• Inflectra's AI Solutions: See demonstrations of Inflectra's cutting-edge AI tools like the ChatGPT plugin and Azure Open AI platform, designed to streamline your testing process.
Whether you're a developer, tester, or QA professional, this webinar will give you valuable insights into how AI is shaping the future of software delivery.
LF Energy Webinar: Electrical Grid Modelling and Simulation Through PowSyBl -...DanBrown980551
Do you want to learn how to model and simulate an electrical network from scratch in under an hour?
Then welcome to this PowSyBl workshop, hosted by Rte, the French Transmission System Operator (TSO)!
During the webinar, you will discover the PowSyBl ecosystem as well as handle and study an electrical network through an interactive Python notebook.
PowSyBl is an open source project hosted by LF Energy, which offers a comprehensive set of features for electrical grid modelling and simulation. Among other advanced features, PowSyBl provides:
- A fully editable and extendable library for grid component modelling;
- Visualization tools to display your network;
- Grid simulation tools, such as power flows, security analyses (with or without remedial actions) and sensitivity analyses;
The framework is mostly written in Java, with a Python binding so that Python developers can access PowSyBl functionalities as well.
What you will learn during the webinar:
- For beginners: discover PowSyBl's functionalities through a quick general presentation and the notebook, without needing any expert coding skills;
- For advanced developers: master the skills to efficiently apply PowSyBl functionalities to your real-world scenarios.
UiPath Test Automation using UiPath Test Suite series, part 3DianaGray10
Welcome to UiPath Test Automation using UiPath Test Suite series part 3. In this session, we will cover desktop automation along with UI automation.
Topics covered:
UI automation Introduction,
UI automation Sample
Desktop automation flow
Pradeep Chinnala, Senior Consultant Automation Developer @WonderBotz and UiPath MVP
Deepak Rai, Automation Practice Lead, Boundaryless Group and UiPath MVP
Securing your Kubernetes cluster_ a step-by-step guide to success !KatiaHIMEUR1
Today, after several years of existence, an extremely active community and an ultra-dynamic ecosystem, Kubernetes has established itself as the de facto standard in container orchestration. Thanks to a wide range of managed services, it has never been so easy to set up a ready-to-use Kubernetes cluster.
However, this ease of use means that the subject of security in Kubernetes is often left for later, or even neglected. This exposes companies to significant risks.
In this talk, I'll show you step-by-step how to secure your Kubernetes cluster for greater peace of mind and reliability.
Epistemic Interaction - tuning interfaces to provide information for AI supportAlan Dix
Paper presented at SYNERGY workshop at AVI 2024, Genoa, Italy. 3rd June 2024
https://alandix.com/academic/papers/synergy2024-epistemic/
As machine learning integrates deeper into human-computer interactions, the concept of epistemic interaction emerges, aiming to refine these interactions to enhance system adaptability. This approach encourages minor, intentional adjustments in user behaviour to enrich the data available for system learning. This paper introduces epistemic interaction within the context of human-system communication, illustrating how deliberate interaction design can improve system understanding and adaptation. Through concrete examples, we demonstrate the potential of epistemic interaction to significantly advance human-computer interaction by leveraging intuitive human communication strategies to inform system design and functionality, offering a novel pathway for enriching user-system engagements.
Encryption in Microsoft 365 - ExpertsLive Netherlands 2024Albert Hoitingh
In this session I delve into the encryption technology used in Microsoft 365 and Microsoft Purview. Including the concepts of Customer Key and Double Key Encryption.
Slack (or Teams) Automation for Bonterra Impact Management (fka Social Soluti...Jeffrey Haguewood
Sidekick Solutions uses Bonterra Impact Management (fka Social Solutions Apricot) and automation solutions to integrate data for business workflows.
We believe integration and automation are essential to user experience and the promise of efficient work through technology. Automation is the critical ingredient to realizing that full vision. We develop integration products and services for Bonterra Case Management software to support the deployment of automations for a variety of use cases.
This video focuses on the notifications, alerts, and approval requests using Slack for Bonterra Impact Management. The solutions covered in this webinar can also be deployed for Microsoft Teams.
Interested in deploying notification automations for Bonterra Impact Management? Contact us at sales@sidekicksolutionsllc.com to discuss next steps.
JMeter webinar - integration with InfluxDB and GrafanaRTTS
Watch this recorded webinar about real-time monitoring of application performance. See how to integrate Apache JMeter, the open-source leader in performance testing, with InfluxDB, the open-source time-series database, and Grafana, the open-source analytics and visualization application.
In this webinar, we will review the benefits of leveraging InfluxDB and Grafana when executing load tests and demonstrate how these tools are used to visualize performance metrics.
Length: 30 minutes
Session Overview
-------------------------------------------
During this webinar, we will cover the following topics while demonstrating the integrations of JMeter, InfluxDB and Grafana:
- What out-of-the-box solutions are available for real-time monitoring JMeter tests?
- What are the benefits of integrating InfluxDB and Grafana into the load testing stack?
- Which features are provided by Grafana?
- Demonstration of InfluxDB and Grafana using a practice web application
To view the webinar recording, go to:
https://www.rttsweb.com/jmeter-integration-webinar
Accelerate your Kubernetes clusters with Varnish CachingThijs Feryn
A presentation about the usage and availability of Varnish on Kubernetes. This talk explores the capabilities of Varnish caching and shows how to use the Varnish Helm chart to deploy it to Kubernetes.
This presentation was delivered at K8SUG Singapore. See https://feryn.eu/presentations/accelerate-your-kubernetes-clusters-with-varnish-caching-k8sug-singapore-28-2024 for more details.
DevOps and Testing slides at DASA ConnectKari Kakkonen
My and Rik Marselis slides at 30.5.2024 DASA Connect conference. We discuss about what is testing, then what is agile testing and finally what is Testing in DevOps. Finally we had lovely workshop with the participants trying to find out different ways to think about quality and testing in different parts of the DevOps infinity loop.
The Art of the Pitch: WordPress Relationships and SalesLaura Byrne
Clients don’t know what they don’t know. What web solutions are right for them? How does WordPress come into the picture? How do you make sure you understand scope and timeline? What do you do if sometime changes?
All these questions and more will be explored as we talk about matching clients’ needs with what your agency offers without pulling teeth or pulling your hair out. Practical tips, and strategies for successful relationship building that leads to closing the deal.
2. 64% of PA is underlain by Marcellus Shale. As of October 2011 more than 8,400 drilling
permits have been issued and nearly 4,000 wells Marcellus wells have been drilled.
http://www.dep.state.pa.us/dep/deputate/minres/oilgas/images/Marcellus%20Shale%20Formation.jpg
3. Environmental and Public Health
Concerns
Chemical & wastewater leaks and
accidents
Threatening drinking water
Endangering public and private lands
Harmful air pollution
Water use
4. Chemicals and wastewater leaks
PA DEP lists 85 hydraulic
fracturing components
Wastewater returns to
surface over lifetime of
Frack fluid pill at
Dimock gas well the well.
Drilling wastewater
often stored in open-air
pits before transported
to treatment facility.
Tioga State Forest Turner
Photo Credit: Jenne
5. Threatening drinking water
Leaks and spills can
also threaten nearby
drinking water sources.
Drilling allowed to
occur as close as 100
feet from rivers and
streams in PA and 200
feet from private water
wells. Beaver Run Reservoir
Several cases where
private water wells
contaminated or
depleted soon after
drilling begins (faulty
casing, human error).
6. Endangering public lands
As of May 2011,
companies had leased Loyalsock State Forest
appr. 7 million acres of
public & private land
(1/4 state land mass).
Each drilling pad takes
up an estimated 8 acres,
including access roads,
infrastructure
40 percent PA’s state
forest that sit on top of
Marcellus Shale have
been leased to drilling
companies – parks next?
7. Degrading Air Quality
At various phases of
extraction, invisible but
harmful emissions can
leak.
Smog-forming Volatile
Organic Compounds
(VOC);
Air toxics (benzene,
ethylbenzene
Methane (Potent
greenhouse gas)
Air is also the primary
pathway of concern for
fracturing chemicals in
contaminated water
(shower, cooking food).
8. Excessive water use
Each well requires 2
to 6 million gallons of
water for the process
Gas companies look
to local waterways to
access water
Many waterways
cannot handle these
excessive
withdrawals
Despite increased
water re-use, fresh
water still needed
Matthewbartholemew under license from Shutterstock.com
9.
10. Strengthen clean water laws
Setting water
withdrawal limits and
reporting requirements
on wastewater disposal
Expanding the
protective buffer zone
around streams and
drinking water supplies
11. Place pristine places off limits
PennEnvironment supports:
Designating pristine places
off limits for natural gas
drilling
Designating a safe distance
between drilling activities
and these places
Halting all new natural gas
drilling leases in public
Matt Dylan under license from Shutterstock.com
lands (state forests, state
parks).
12. Improve public right to know
Requiring natural gas
companies to report
the specific types and
volumes of the
chemicals used at
each well.
Requiring companies
to report withdrawals
Photo Credit: Robert Donnan
from Pennsylvania’s
waterways.
13. Increase public participation
Requiring a public
comment process for
decisions being made
about large tracts of
state land.
Improving
Pennsylvania’s property
rights and land use
laws.
Granting more rights to NicholasT under license for Shutterstock.com
surface owners.
14. Improve tools for Pennsylvania’s regulators
Increasing capacity and
funding for DEP’s
permitting department
and enforcement staff.
Increasing DEP’s time
period for reviewing
permits .
Allowing state health and
environment officials to
provide input on
Bob Donnan applications for
operations that could
affect public health or
wildlife habitat.
15. Ensuring industries pay for damages
Levying extraction fees on gas
drillers for the valuable
resources they remove form
underneath Pennsylvania.
Requiring drilling companies
to pay for environmental and
public health problems they
create.
Requiring natural gas Photo Credit: Wetzel County Action Group
companies to pay the entire
cost of reclaiming wells.
16. Opportunities for Action
U.S. EPA: Air rules on oil and gas sector
to reduce smog-forming pollutants, air
toxics and methane
Delaware River Basin Commission:
Likely to allow drilling in river basin soon:
October 21 decision.
Susquehanna River Basin
Commission: Fast-tracking of Marcellus
Shale projects
Editor's Notes
Largest part of the Marcellus Shale gas is found under Pennsylvania, across 64 percent of the state.
As part of the hydraulic fracturing process, drilling companies combine a cocktail of chemicals with sand and millions of gallons of water, forcing the fluid underground at high pressures in order to help break up the shale and access the natural gas. In total, 85 chemicals have been posted on PA DEP’s website as chemicals that could be used for hydraulic fracturing in the Marcellus Shale. Many of these chemicals, including toluene, xylene, trimethylbenzene, and petroleum distillates which often contain benzene are known or suspected carcinogens, or have other negative health effects. Chemicals are used in many phases of extracting gas from shale: added to the “muds” used to drill the bore hole. Chemicals added to increase weight of fluids, reduce friction, shorten drilling time.
Drilling can affect drinking water in a variety of waysA large volume of toxic wastewater is generated during the hydraulic fracturing processUnfortunately, most sewage treatment facilities in PA do not have the technology or capacity to deal with this type of industrial pollution, though many have been permitted to accept this water.In 2008, state environmental officials issued a drinking water advisory for 325,000 local residents after reporting that inadequately treated drilling wastewater was discharged into the Monongahela River, which serves as the drinking water sources for downstream communities.In Susquehanna County, Cabot Oil & Gas reported that private water sources has been contaminated with methane after Cabot’s natural gas drilling activities broke through nearby residents’ underground well water supply.In the photo above, you can see multiple Marcellus wells that have already been drilled near the Beaver Run Reservoir, which is owned by the Westmoreland Water Authority and is a source of drinking water for thousands of residents northeast of Pittsburgh.
With the growing pressure to promote natural gas exploration across the Commonwealth, state officials last year opened up 74,000 additional acres of state forestlands to bids from natural gas companies in spite of broad and deep public opposition to the proposal. Sadly, state regulators have already signed off on allowing companies to drill for natural gas on 660,000 acres of Pennsylvania’s state forestlands—a full 40 percent of the Commonwealth’s entire state forest system that sits on top of the Marcellus Shale formation.There’s now a ban in place on any additional leasing of state forestland for gas drilling, but this could be overturned by the current administration.Also, there has been exploratory drilling that has occurred in Ohiopyle State Park, which could mean that our state parks could be next.
When gas is being compressed, or when it is stored in a condensate tank, the harmful but invisible air emissions can leak into the atmosphere. This, combined with the diesel-powered drilling rigs, and roughly 1,500 diesel trucks necessary for every well hydraulically fractured, results in localized air pollution and oftentimes ground-level ozone. A recent study by Dr. Theo Colburn and the Endocrine Disruptor Exchange found that air is the primary pathway of concern for fracturing chemicals.
Each natural gas well requires roughly 2 to 6 million gallons of water for the hydraulic fracturing process. Natural gas companies often take this water from nearby rivers and streams, damaging local ecosystems. In some cases, especially in Western Pennsylvania, these withdraws have occurred without proper oversight or approval. Already, Pennsylvania’s Department of Environmental Protection (DEP) has fined companies for illegal water withdrawals. In the worst cases, so much water is removed that streams have completely dried up and disappeared. Sugarcamp Run in Washington County is one example of a waterway that ran dry in 2008 due to excessive water withdrawals from natural gas drilling companies. This type of stress is inevitably causes far-reaching damage to aquatic species in these streams. Especially of concern during summers like this past, where drought warnings were issued for 24 counties in PA