Underground Storage Tanks

Underground Storage Tanks By Steven Ross, CHMM Underground Storage Tanks • High visibility • There are 3 to 5 million USTs located through out country. • Only 1.8 million officially accounted for • More than 35 % tanks leaked. • Most liquid products have been stored underground since WW I. What is a UST? • Any tank, including underground piping connected to the tank, that has at least 10 percent of its volume underground. • Holds petroleum product or hazardous material. What is a UST? Above Ground >10% Below Ground Underground Storage Tanks • The majority of underground storage tanks (UST) contain petroleum products: – – – – – Gasoline Diesel Heating oil Kerosene Jet fuel Exempted USTs • Farms or residential tanks holding 1,100 gallons or less of motor fuel used for non-commercial purposes. • Heating oil tanks used on the premises. • Tanks on or above the floor of underground areas, such as basements or tunnels. • Septic tanks and systems for collecting storm water and wastewater. • Tanks holding 110 gallons or less. Why Regulate USTs? • Small leaks of gasoline or hazardous material from USTs can contaminate large groundwater supplies. • Leaks can also create health and fire hazards in nearby buildings. • Liability of clean-up (CERCLA) Program History • Federal UST rules first issued in 1984. • Subtitle I added to Resource Conservation and Recovery Act (RCRA). • EPA required to develop regulations to protect human health and the environment from Leaking Underground Storage Tanks (LUST). – Purpose of program is to minimize and detect releases through proper operation and maintenance of existing facilities; and – To prevent future releases through technical standards for new installations, replacements, and upgrades. Program History • Amendments in 1992 required all new UST’s to install: – Double-walled, corrosion protected tanks. – Piping with continuous interstitial monitoring – Register all commercial heating oil tanks. • If installed before 1988, owners had to upgrade with spill, overfill, and corrosion protection, or properly close or replace with a new UST. Program History • Amendments in 1985 required new installations to be corrosion protected, and continuously monitored; included alternatives: – required spill and overfill protection. – allowed single-walled tanks and piping. – set upgrade requirement for existing UST systems. Tank Closure • Notify State at least 30 days before UST is taken out of service for closure or replacement. • Determine if any releases have occurred into the environment if evidence indicates. • Tank must be emptied of all liquids and flammable gases. • If UST is left in the ground, it must be filled with a harmless and chemically inactive solid (sand). UST Registration • Commercial USTs of any size storing motor fuel or hazardous materials must be registered: – includes waste oil USTs – includes holding tanks serving floor drains • USTs storing fuel oil for heating commercial facilities must be registered. Leaking Underground Storage Tanks (LUST) • Since the early 1980s, USTs containing petroleum products have resulted in wide spread groundwater contamination throughout the U.S. and Europe. • Because nearly half of all Americans depend on groundwater for their drinking water, leaking USTs represent a significant public health hazard. Leaking Underground Storage Tanks (LUST) • The major hazard of petroleum products is gasoline which includes BTEX compounds: – Benzene – Toluene – Ethylbenzene – Xylene • Causes of leaks include: – Spills and overfills – No corrosion protection – Installation mistakes – Piping failures Spill Prevention • Spills often occur when the delivery trucks hose is disconnected. • Even though these spills are usually small, repeated small releases can cause big environmental problems. • To help prevent spills, catchment basins are used as spill containment manholes or spill buckets around the fill pipe. • Install double-walled piping to contain leking pipes. Overfill Prevention • Overfills usually release much larger volumes than spills. • When a tank is overfilled, large volumes can be released at the fill pipe. • Overfill probes are used to activate an alarm when the tank is either 90% full or within 1 minute of being overfilled. Corrosion Protection • Leaks occur when unprotected steel corrodes and releases the product through corrosion holes in the tank or piping. • Cathodic protection must be added to the the tank and piping to prevent corrosion. e- Anode Current Cathode (Tank) (Ground) e- Cathodic Protection + Cathode Anode Petroleum Fund • The “Petroleum Fund” was initially implemented in 1989. • The Fund assists owners and operators of USTs in meeting the federal requirement for financial responsibility of LUSTs. • The Fund provides reimbursement to the qualified storage tank owner/operators for corrective action costs associated with cleaning up petroleum product releases. Soil Remediation • Methods used to clean-up contaminated soil have been successfully used for over a decade. • Several specific characteristics of the site must be determined before clean-up can occur: – – – – Soil type Depth of groundwater Type of contaminant Direction of migration Soil Remediation • Containment/Removal • Soil vapor extraction – Air sparging (above the water table) • Bioremediation • Thermal treatment • Solidification/Stabilization In-situ vs. Ex-situ • In-situ – Contaminants are unmoved and are treated in their original place, or remaining at the site or in the subsurface. • Ex-situ – Contaminants are removed from their original place and then treated away from the site. Containment/Removal (Ex-situ) • Containment and removal technologies immobilize contaminants through: – – – – Stabilization Solidification Removal and placement in a secure landfill The application of passive/active containment control systems. • Each of these processes focus not on remediation, but rather on: – Minimizing the rate of contaminant migration and mobility – Reducing a waste’s risk and threat to human health and the environment. Containment/Removal (Ex-situ) Contaminated Soil Ground Surface Contaminated Soil Water Table Soil Vapor Extraction (In-situ) • Air flow is induced through the soil by applying a vacuum to extract volatile contaminants in the unsaturated zone. • Effective for volatile and semivolatile contaminants Soil Vapor Extraction (In-situ) Treated Air Blower Vapor Treatment Ground Surface Air Flow Contaminated Soil Air Flow Water Table Soil Vapor Extraction (Ex-situ) • Performed by placing excavated soil over a network of vacuum pipes to cause airflow through the soil pile. • Effective for volatile and semivolatile contaminants Soil Vapor Extraction (Ex-situ) Condensate Collection Tank Blower Vapor Treatment Treated Air Extraction Piping Contaminated Soil Clean Base Soil Bioremediation (In-situ) • Bioremediation technologies degrade organic wastes by the action of microorganisms. • Degradation alters the molecular structure of organic compounds and either simplifies the compounds into non-hazardous products or completely breaks down the organic molecules. • Bioremediation can be accomplished either through in-situ or ex-situ methods. • Effective for diesel fuel and heavy fuel oil. Bioremediation (In-situ) Pump Water Recycle Pump Nutrient Solution Preparation Ground Surface Contaminated Soil Nutrient Solution Flow Water Table Bioremediation (Ex-situ) Nutrients Thin layer of excavated material Water Contaminated Soil Thermal Treatment (Ex-situ) • Thermal treatment is implemented by heating and agitating soil while it is exposed to a vacuum that transports volatilized water and organic contaminants to a treatment system. • Specific temperatures are designed into these systems to volatilize selected contaminants but typically will not oxidize or destroy them. • Thermal treatment is proven successful for remediating all types of volatile organic compounds (VOC). Thermal Treatment (Ex-situ) Heating jacket Off-gas Treatment Exhaust Bag house Contaminated Soil Treated Soil Solidification/Stabilization (Ex-situ) • Contaminated soil is mixed with a binder that provides a combination of physical entrapment and chemical neutralization. • Binders can include portland cement, pozzolans, silicates, bitumen, and polymers. • Used primarily to treat inorganic contaminates. (acids, bases) Solidification/Stabilization (Ex-situ) Dry Additives Water Feeder Mixer Contaminated Soil Treated Soil