Under various laws relating to the protection of the environment in the U.S., a current or previous owner or operator of real estate may be liable for contamination resulting from the presence or discharge of hazardous or toxic substances at a property and may be required to investigate and clean up such contamination at or emanating from a property. Such laws often impose liability without regard to whether the owner or operator knew of, or was responsible for, the presence of the contaminants, and the liability may be joint and several. In the U.S., the Comprehensive Environmental Response, Compensation, and Liability Act of 1980 ("CERCLA") established a regulatory and remedial program intended to provide for the investigation and clean-up of facilities where, or from which, a release of any hazardous substance into the environment has occurred or is threatened. CERCLA also imposes liability for the cost of evaluating and remedying any damage to natural resources. The costs of CERCLA investigations and clean-ups can be very substantial. CERCLA also authorizes the imposition of a lien in favor of the U.S. on all real property subject to, or affected by, a remedial action for all costs for which a party is liable. Subject to certain procedural restrictions, CERCLA gives a responsible party the right to bring a contribution action against other responsible parties for their allocable shares of investigative and remedial costs. Our ability to obtain reimbursement from others for their allocable shares of such costs would be limited by our ability to find other responsible parties and prove the extent of their responsibility, their financial resources, and other procedural requirements. Various U.S. state laws also impose in certain cases strict joint and several liability for investigation, clean-up and other damages associated with hazardous substance releases.
If previous owners of our current and future properties used such properties for industrial and manufacturing purposes, such properties may contain some level of environmental contamination. To date, independent environmental consultants have conducted Phase I or similar environmental site assessments on the properties in our portfolio. Site assessments are intended to discover and evaluate information regarding the environmental condition of the surveyed property and surrounding properties. These assessments, however, do not generally include soil samplings, subsurface investigations or an asbestos survey and the assessments may fail to reveal all environmental conditions, liabilities or compliance concerns. In addition, material environmental conditions, liabilities or compliance concerns may arise after these reviews are completed. We could be held jointly and severally liable under CERCLA and various state, local and national laws for the investigation and remediation of environmental contamination on our properties caused by previous owners or operators. Further, fuel storage tanks may be present at properties we may develop in the future, and if releases were to occur, we may be liable for the costs of cleaning any resulting contamination. The presence of contamination or the failure to remediate contamination at any of our properties may expose us to third-party liability or materially adversely affect our ability to sell, lease or develop the real estate or to borrow using the real estate as collateral.
Our properties and their uses have and may in the future require permits and entitlements from various government agencies, including permits and entitlements related to zoning and land use. Certain permits from state or local environmental regulatory agencies, including regulators of air quality, are usually required to install and operate diesel-powered generators, which provide emergency back-up power at most of our facilities. These permits often set emissions limits for certain air pollutants, including oxides of nitrogen. In addition, various federal, state, and local environmental, health and safety requirements, such as fire requirements and treated and storm water discharge requirements, apply to our properties. Our ability to comply with, as well as changes to, applicable regulations, such as air quality regulations, or the permit requirements for equipment at our facilities, could hinder or prevent our construction or operation of our data center facilities.
Governmental authorities have in the past sought to restrict data center development based on environmental considerations. For example, governmental authorities have in the past imposed moratoria on data center development, citing concerns about energy usage and requiring new data centers to meet energy efficiency requirements. Some government agencies have also sought to restrict the use of diesel generators for back-up power. We may face higher costs from any laws requiring enhanced energy efficiency measures, changes to cooling systems, caps on energy usage, land use restrictions, limitations on back-up power sources, or other environmental requirements. Moratoria on data center construction could hinder our ability to construct new data centers.
Also, drought conditions in certain markets have resulted in water usage restrictions and proposals to further restrict water usage. Our data center facilities could face restrictions on water usage, water efficiency mandates, or higher water prices. Climate change could also limit water availability. In addition, sea level rise and more frequent and severe weather events caused or contributed to by climate change pose physical risks to our facilities.