CERCLA gives EPA the authority to respond to actual and threatened releases of hazardous substances to the environment, and of pollutants and contaminants that may pose an imminent and substantial danger to public health or the environment. CERCLA authorizes EPA to compel PRPs to clean up the sites; allows EPA to pay for cleanups and seek reimbursement from PRPs; and establishes a Hazardous Substance Superfund (trust fund) to help EPA pay for cleanups and related program activities. EPA’s 10 regional offices implement Superfund within several states and, in some cases, territories. In addition, the law establishes a process for federal agencies to identify their sites with hazardous releases and for the sites to be cleaned up with funding from federal agency appropriations. When EPA decides not to list a site on the NPL or otherwise retain oversight, it may defer oversight of the site’s cleanup to other federal and state cleanup programs. Under CERCLA, PRPs must conduct or pay for the cleanup of hazardous substances. In some cases, however, EPA cannot identify the PRPs, or these parties may be unwilling or financially unable to perform the cleanup. CERCLA authorizes EPA to pay for remedial cleanups at sites on the NPL and seek reimbursement from the PRPs. Historically, the trust fund was financed primarily by taxes on crude oil and certain chemicals, as well as by an environmental tax on corporations based on their taxable income. However, the authority for these taxes expired in 1995 and, shortly thereafter, the balance in the trust fund started diminishing. By the start of fiscal year 2009, the balance of the trust fund had decreased in value from its peak of $5.0 billion in 1997 to $137 million. Since the taxes expired, congressional appropriations have been the largest source of funding for the trust fund. For context, appropriations have averaged about $1.2 billion annually since 1981. Other sources of revenue include interest on the balance of the trust fund, fines and penalties collected for violations of cleanup requirements, and recovery of cleanup costs from PRPs. Under the Superfund program, EPA assesses hazardous release sites to determine if their contamination makes them eligible for the NPL. While over 40,000 potential hazardous release sites have been reported to the Superfund program over the past 30 years, EPA has only determined a few thousand of these sites pose a sufficient threat to human health and the environment to be eligible for the NPL. CERCLA and its implementing regulations establish a process of specific steps to evaluate and to clean up sites. The basic steps apply to both federal facilities and nonfederal sites. One difference is that CERCLA imposes additional requirements on federal agencies; for example, the law requires that, for federal facilities listed on the NPL, federal agencies must enter into an interagency agreement with EPA that includes schedules for completion of each remedy at the site. The key steps in this process for federal facilities are included in figure 1. During the initial phases of EPA’s assessment of sites reported to its Superfund program—known as preliminary assessment and site inspection—EPA regional officials or their state and tribal counterparts evaluate the potential need for additional investigation or action. Specifically, the preliminary assessment phase involves an evaluation of readily available information about a site and its surrounding area to determine if the release or potential release of hazardous substances poses a sufficient threat to human health and the environment to merit further investigation. If further investigation is needed, a site inspection follows the preliminary assessment. During this phase, investigators typically collect samples to identify the hazardous substances. Information from the preliminary assessment and site inspection is used to calculate and document a site’s preliminary Hazard Ranking System (HRS) score, which indicates a site’s relative threat to human health and the environment based on potential pathways of contamination. Sites with a HRS score of 28.50 or greater become eligible for listing on the NPL. The HRS calculation is not, however, intended to determine the extent of contamination or the appropriate cleanup approach. This occurs later when EPA, based on available information, selects an appropriate cleanup approach for those sites it decides to add to the NPL. In some cases, EPA may conduct a short-term cleanup known as a removal action or otherwise delay selection of a long-term cleanup approach. As we reported in April 2013, as of December 2012, EPA had identified over 3,400 sites—both federal facilities and nonfederal sites—that were reported to the Superfund program and have contamination that makes them eligible for listing on the NPL. Of these, 1,311 sites were on the NPL as of April 2013. EPA deferred most of the rest to cleanup approaches outside the Superfund program. As we reported in May 2010, according to EPA headquarters officials, the number of sites proposed for listing on the NPL had decreased over time as a result of the expanded use of other cleanup programs, including state programs. However, we also reported at that time that EPA regional officials estimated that an average of 20 to 25 sites per year—higher than the average of 16 over the previous 5 years—would be added to the NPL over the following 5 years. Most of the regional officials noted that economic conditions—which can limit states’ abilities to clean up sites under their own programs and PRPs’ abilities to pay for cleanup—were a contributing factor to the expected increase in sites listed on the NPL. So far, these estimations have been borne out—according to EPA’s website, the agency added an average of 23 sites each year to the NPL in fiscal years 2010 through 2012. As we reported in April 2013, states, in consultation with EPA, participate in the identification and cleanup of hazardous waste sites eligible for the NPL in many ways. Examples of this participation include the following: States may notify EPA of potential hazardous waste sites for listing in the Superfund program database; States may act under cooperative agreements with EPA to evaluate the relative potential for sites being considered for the NPL to pose a threat to human health and the environment; As a matter of policy, EPA seeks concurrence from state governors or environmental agency heads before proposing a site for listing on the NPL; States may assume the lead oversight role at NPL sites under cooperative agreements with EPA; and EPA may only pay for a remedial action at a site if the relevant state agrees, among other things, to pay a portion of the cleanup expenses, as well as all operations and maintenance costs after construction of the cleanup remedy is completed. In addition to overseeing cleanup at some sites on the NPL, states may oversee cleanup at sites that are eligible for listing on the NPL but that were not reported to EPA for listing in the Superfund program database. States do not have an obligation to report all potentially eligible sites to the federal Superfund program, and several of the environmental officials from 13 states we contacted in conducting the work for our April 2013 report confirmed that they have conducted or overseen cleanups at sites not listed in the Superfund program database that may have been eligible for the NPL. Alternatively, EPA may choose not to list sites that have been reported and that are eligible for listing on the NPL and instead defer oversight of these sites to programs outside of the Superfund program—typically to states. In fact, as we reported in April 2013, this approach is the most common for cleanup of sites that are eligible for listing on the NPL. As of December 2012, of the 3,402 sites EPA identified as eligible for the NPL, EPA regions had deferred oversight of 1,984 sites to cleanup approaches outside the Superfund program, including 1,606 deferrals to states (47 percent of all eligible sites). EPA officials in all 10 regions indicated that states’ preferences influence EPA’s selection of the cleanup program at sites eligible for the NPL. Most of these deferrals to states were made as Other Cleanup Activity (OCA) deferrals. OCA deferral to a state places a site under that particular state’s environmental regulations, rather than CERCLA authorities. As we reported in April 2013, EPA has not issued guidance for these deferrals as it has for other cleanup approaches. Moreover, EPA’s program guidance does not clearly define types of OCA deferrals or specify in detail the documentation EPA regions should have to support their decisions on OCA deferrals. OCA deferral to a state involves no formal EPA oversight other than periodic discussions between EPA regional officials and state officials. For OCA deferrals to states, EPA regions’ tracking activities range from checking state websites to meeting with states to receive status updates every 3 months, according to regional officials. In addition, according to EPA regional officials, the amount and type of documentation regions collect to support OCA deferrals covers a broad range, including no written documentation, an e-mail from a state official, letters from state officials attesting to the cleanup, or a copy of the legal order or agreement between the state and PRP. Without clearer guidance on OCA deferrals, EPA does not have reasonable assurance that its regions consistently track these sites or that their documentation will be appropriate or sufficient to verify that these sites have been deferred or have completed cleanup. In April of this year, we recommended that EPA provide guidance to its regions that defines each type of OCA deferral and what constitutes adequate documentation for OCA deferral and completion of cleanup. The agency agreed with this recommendation, acknowledging the need for more guidance. State cleanup programs vary in their capacity and resources to manage the cleanup of hazardous waste sites, according to EPA and state officials. According to officials in the EPA region with the most OCA deferrals to states, states in the region have mature environmental programs willing and capable of overseeing many sites, which makes the OCA deferral to states well-suited to that region. In contrast, officials we spoke with in some regions noted that they needed to consider states’ capacity to oversee a site before using the OCA deferral to states.