GLOSSARY OF TERMS AND ACRONYMS A B C D E F G H I J K L M N O P Q R S T U V W X Y Z P Percolation The movement of water downward and radially through subsurface soil layers, usually continuing downward toward groundwater. Permeability The degree to which groundwater can move freely through an aquifer. Pesticide Any chemical used to kill or control undesired insects, weeds, rodents, fungi, bacteria or other organisms. Some pesticides are known to cause cancer. Phenotype The manifest characteristics of an organism collectively, including anatomical, psychological, etc. Point source A stationary location or fixed facility from which pollutants are discharged; any single identifiable source of pollution; e.g., a pipe, ditch, ship, ore pit, factory smokestack. Potentially Responsible Parties (PRPs) Any individual or company that may have contributed to contamination at a Superfund site. Under CERCLA, PRPs are expected to conduct or pay for site cleanup. Preliminary Assessment (PA) and Site Inspection (SI) EPA uses the Preliminary Assessment (PA) and Site Inspection (SI) to evaluate the potential for a release of hazardous substances from a site. Information collected during the PA and SI is used to calculate a Hazardous Ranking System (HRS) score. Sites with an HRS score of 28.50 or greater are eligible for listing on the National Priorities List (NPL) and require the preparation of an HRS scoring package. Proposed plan A Superfund site cleanup strategy prepared by EPA that is subject to public comments.