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Pentachlorophenol (PCP)
PCP, a chemical compound containing carbon, chlorine, oxygen, and hydrogen, is a chemical now used primarily as a wood preservative but which was previously used as a herbicide, defoliant, algicide, fungicide, and disinfectant.

Performance-Based Measurement System (PBMS)
EPA defines a PBMS as a set of processes through which the data needs or limitations of a program or project are specified and serve as criteria for selecting appropriate methods to meet those needs in a cost-effective manner. EPA uses the term to convey what must be accomplished, but not prescriptively how to do it. The PBMS initiative places regulatory emphasis on obtaining analytical results that provide adequate information to support the regulatory decision, but leaves the choice of analytical procedures up to the user. The PBMS approach gives regulators and members of the regulated community increased flexibility in selecting technologies, while still meeting mandated monitoring requirements. The use of PBMS is intended to reduce barriers to the use of new monitoring technologies.

Permeability is a characteristic that represents a qualitative description of the relative ease with which rock, soil, or sediment will transmit a fluid (liquid or gas).

Permeable Reactive Barriers (PRB)
PRBs, also known as passive treatment walls, are installed across the flow path of a contaminated plume. As groundwater flows through the PRB, contaminants are either degraded or retained in a concentrated form by the reactive material. Examples of reactive media include zero-valent metals, chelators, sorbents, and microbes.

A pesticide is a substance or mixture of substances intended to prevent or mitigate infestation by, or destroy or repel, any pest. Pesticides can accumulate in the food chain and or contaminate the environment if misused.

Phase I Environmental Site Assessment
Environmental site assessments, or all appropriate inquiries, are conducted to evaluate existing environmental problems from past operations and potential environmental problems from current or proposed operations at a site. The practice of conducting site assessments is intended to satisfy one requirement for obtaining protection from CERCLA liability for potential property owners. Most environmental site assessments are called Phase I assessments because they are conducted in conformance with ASTM E1527-00 Standard Practice for Environmental Site Assessments: Phase 1 Environmental Site Assessment Process. Phase I site assessments include: an inspection of the property; a review of pertinent records for evidence of current and past use of the property and adjacent properties; interviews with current owners and occupants as well as local government officials; evaluation of information gathered and development of a report; and, in some cases, samples are collected of building materials to determine if PCBs, asbestos, or lead are present. The need for additional sampling to confirm contamination or to determine the nature and extent of contamination leads into a "Phase II" assessment.

Phase II Environmental Site Assessment
Environmental site assessments are conducted to evaluate existing environmental problems from past operations and potential environmental problems from current or proposed operations at a site. The primary objective of conducting a Phase II assessment is to confirm and evaluate the environmental conditions identified in the Phase I environmental site assessment or transaction screening process. During the Phase II, additional investigation and sampling is needed to determine the nature and extent, source, and significance of contamination following a Phase I environmental assessment for the purpose of supporting subsequent cleanup and reuse decisions.

A phenol is one of a group of organic compounds that are byproducts of petroleum refining, tanning, and textile, dye, gas, and resin manufacturing.

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Phytoremediation is an innovative treatment technology that uses plants and trees to clean up contaminated soil and water. Plants can break down, or degrade, organic pollutants or stabilize metal contaminants by acting as filters or traps. Phytoremediation can be used to clean up metals, pesticides, solvents, explosives, crude oil, polyaromatic carbons, and landfill leachates. Its use generally is limited to sites at which concentrations of contaminants are relatively low and contamination is found in shallow soils, streams, and groundwater.

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The term phytotechnology refers to technologies that use living plants.

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The term phytotoxic is used to describe a substance that is harmful to plants.

A plume is a visible or measurable emission or discharge of a contaminant from a given point of origin into any medium. The term also is used to refer to measurable and potentially harmful radiation leaking from a damaged reactor.

Polychlorinated Biphenyl (PCB)
PCBs are a group of toxic, persistent chemicals produced by chlorination of biphenyl that once were used in high-voltage electrical transformers because they conducted heat well while being fire-resistant and good electrical insulators.

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Polycyclic Aromatic Hydrocarbon (PAH)
A PAH is a chemical compound that contains more than one fused benzene ring. They are commonly found in petroleum fuels, coal products, and tar.

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Potassium Permanganate
Potassium permanganate is a crystalline compound that is soluble in water, acetone, and methanol, but is decomposed by ethanol. It is used widely as a powerful oxidizing agent, as a disinfectant in a variety of applications, and as an analytical oxidant reagent in redox titrations.

Potentially Responsible Party (PRP)
A PRP is an individual or company (such as owners, operators, transporters, or generators of hazardous waste) that is potentially responsible for, or contributing to, the contamination problems at a Superfund site. Whenever possible, EPA requires PRPs, through administrative and legal actions, to clean up hazardous waste sites they have contaminated.

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Presumptive Remedies
Presumptive remedies are preferred technologies for common categories of CERCLA sites that have been identified through historical patterns of remedy selection and EPA's scientific and engineering evaluation of performance data on technology implementation.

Pump and Treat (P&T)
P&T is a general term used to describe remediation methods that involve the pumping of groundwater to the surface for treatment. P&T is one of the most common methods of treating polluted aquifers and groundwater.

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