An Underground Storage Tank (UST), in United States environmental law, is a tank and any underground piping connected to the tank that has at least 10 percent of its combined volume underground. USTs used to store petroleum are regulated in the United States to prevent release of petroleum and contamination of groundwater. USTs are used throughout North America at automobile filling stations and many have leaked, allowing petroleum to contaminate the soil and groundwater. From the EPA website: Many USTs installed made before 1980 consisted of bare steel pipes, which corrode over time, and may eventually result in leakage. Faulty installation and inadequate handling may also cause leaks. In 1984, in the United States, the Congress developed laws to minimize and prevent environmental damage, by charging owners with the task of verifying, maintaining and if the case comes to it, cleaning up sites damaged by petroleum contamination. Legislation requiring owners to locate, remove, upgrade, or replace underground storage tanks became effective December 24, 1989. Each State was given authority to establish a program within its own jurisdiction to set up a program to compensate owners for the cleanup of underground petroleum leaks, to set standards and licensing for installers, and to register and inspect underground tanks. Most upgrades to USTs consisted of the installation of corrosion control (cathodic protection), overfill protection (to prevent overfills of the tank during tank filling operations), spill containment (to catch spills when filling), and leak detection for both the tank and piping. More on USTs: wikipedia.org/ Cathodic Protection (CP) is a technique to control the corrosion of a metal surface by making that surface the cathode of an electrochemical cell. It is a method used to protect metal structures from corrosion. Cathodic protection systems are most commonly used to protect steel, water and fuel pipelines and storage tanks; steel pier piles, ships, offshore oil platforms and onshore oil well casings. A side effect of improperly performed cathodic protection may be production of molecular hydrogen, leading to its absorption in the protected metal and subsequent hydrogen embrittlement. Cathodic protection is an effective method of preventing stress corrosion cracking. The first use of CP was in 1824, when Sir Humphry Davy, of the British Navy, attached chunks of iron to the external, below water line, hull of a copper clad ship. Iron has a stronger tendency to corrode (rust) than copper and when connected to the hull, the corrosion rate of the copper was dramatically reduced. Today, galvanic or sacrificial anodes are made in various shapes using alloys of zinc, magnesium and aluminium. The electrochemical potential, current capacity, and consumption rate of these alloys are superior for CP than iron. More on Cathodic Protection: wikipedia.org/ A Phase I Environmental Site Assessment is a report prepared for a real estate holding which identifies specific environmental contamination liabilities. The analysis, often called a Phase I ESA, typically addresses both the underlying land as well as physical improvements to the property; however, techniques applied in a Phase I ESA never include actual collection of physical samples or chemical analyses of any kind. Scrutiny of the land includes examination of potential soil contamination, groundwater quality, surface water quality and sometimes issues related to toxic uptake by biota. The examination of a site may include: definition of any chemical residues within structures; identification of possible asbestos containing building materials; inventory of toxic substances stored or used on site; assessment of mold and mildew; and evaluation of other indoor air quality parameters. Actual sampling of soil, air, groundwater and/or building materials is typically not conducted during a Phase I ESA. The Phase I ESA is generally considered the first step in the process of environmental Due Diligence. This type of study is alternatively called a Level I Environmental Site Assessment. Standards for performing a Phase I site assessment have been promulgated by ASTM in Standard E1527-05.[2] If a site is considered contaminated, a Phase II Environmental Site Assessment may be conducted, ASTM test E1903, a more detailed investigation involving chemical analysis for toxics. More on Phase I ESAs: wikipedia.org/ For Info on Soil Contamination: wikipedia.org/ For Info on Remediation: wikipedia.org/ For Info on American Petroleum Institute: wikipedia.org/