Section 2: Site Assessment Process
The multi-step process leading to the final National Priorities List (NPL) listing decision begins when a site is discovered and listed in CERCLIS. All sites in CERCLIS undergo a Preliminary Assessment. Historically, about three out of five sites have required a Site Inspection; one in about 15 to 20 warrant placement on the NPL.
The Preliminary Assessment (PA) is a limited-scope assessment designed to distinguish between sites that clearly pose little or no threat to human health or the environment and sites that may pose a threat and require further investigation. Environmental samples are rarely collected during a PA.
A preliminary score for the site can be developed using Hazard Ranking System (HRS) Quickscore and PA data to determine if a site inspection (SI) is necessary and to assist in designing the SI. HRS Quickscore is an electronic set of HRS score sheets that executes real time, site score calculations.
The site inspection (SI) builds on the information gathered in the PA and may lead to HRS scoring if the site warrants it. SI sampling is limited and oriented towards worst-case conditions. Sampling concentrates on determining the presence of:
- highly toxic contaminants;
- contamination significantly above background;
- contamination at points of potential human exposure; and/or
- contamination in sensitive environments.
Acceptable documentation of the SI is critical in supporting HRS scoring.
NPL listing informs the public that the site appears to present sufficient relative risk to warrant the more extensive site characterization of a remedial investigation and feasibility study (RI/FS). The EPA region, in consultation with the state, identifies a site as an NPL candidate based on the PA/SI results. The region is responsible for seeing that an HRS scoring package is developed. The EPA region conducts a Quality Control (QC) review of the package and submits it to EPA headquarters (HQ).
EPA HQ conducts a policy review and a Quality Assurance (review of the HRS scoring package. After necessary revisions, the site is proposed for listing on the NPL through a published notice in the Federal Register. Three proposals are scheduled each year. Proposal is followed by a 60-day comment period during which the public may submit input on the listing proposal. Commenters frequently dispute the basis for the listing proposal and include detailed analyses of the quality of the documentation. EPA HQ reviews all comments and responds as needed to the comment in a published support document. Preparation of the response may require Regional input if clarification is needed. Site scores are re-calculated based on comments and responses.
The site is listed as final on the NPL, withdrawn from the proposal, or reproposed. Only sites with scores above 28.50 (as re-calculated) can be finally listed. At least two final updates are scheduled each year. After listing, there is a 90-day period for interested parties to enter a legal challenge to the listing of the site.
NPL listing does not promise remedial action, only detailed investigation.
The HRS is a numerically based scoring system that uses information obtained primarily from the initial, limited investigations conducted at a site: the PA and SI. The HRS score is the primary criterion EPA uses to determine whether a site should be placed on the NPL.
The HRS is a screening tool and not a site specific risk assessment.
NPL listing informs the public that the site appears to present sufficient relative risk to warrant the more extensive site characterization of a remedial investigation and feasibility study (RI/FS).
The HRS scoring package contains:
- NPL site narrative summary;
- HRS documentation record (hard copy/electronic copy);
- HRS scoresheets (hard copy/electronic copy);
- copies of references and maps; and
- NPL Data Characteristics Form.
Adequate documentation is essential in preparing an HRS documentation record. The documentation record must be legally defensible.
The documentation record explains EPA's basis for assigning the HRS site score. It does the following:
- describes sources;
- describes pathways;
- identifies targets;
- includes maps and figures;
- cites primary references for every statement of fact;
- is available for public review and comment; and
- must be legally defensible.
- Obtain and Read all site information. Keep clean copies of all references you might use.
- Take notes and organize them by source or pathway.
- Keep a running score.
- Identify sources and significant pathways.
- Gather maps and diagrams.
- Identify HRS data gaps.
When you document a site score, you will move back and forth among these tasks.
Keep a Running Score
Back-of-the-envelope scoring will focus your attention on the HRS implications of the information you are gathering.
- Is a number "at risk" because it lies near a breakpoint on an HRS table?
- The more important an item of information is to the score, the better the quality of information should be.
- "Killer" issues are those that can drop the score under 28.50.
The attempt to score the site will also focus attention on what information is still missing.
Gather Maps and Diagrams
- Refer to Appendix D: Map Specifications For The HRS Documentation Record of the Regional QC Guidance for NPL Candidate Sites.
- Choose a base map and annotate it with site-specific information (i.e., sources, site boundaries, locations of targets).
- Present pathway-specific maps (i.e., tax assessor's parcel maps, geological cross-sections, and Wetland Inventory Maps).
- Insert maps within the text of the documentation record.
- Aerial photographs may be useful to show historical conditions.
- Maps should be reproducible, legible, and to scale.
List and Cite References
List only the references you use in the documentation record. (Be sure to use all references that EPA might need to justify listing the site.)
- Every assertion of fact must be referenced in the documentation record. (Example: Ref. 9, p.43; Ref. 24, p.B-158.)
- Use a recognized style for the list of references in the documentation record.
- The HRS rule is always Reference 1 and the Superfund Chemical Data Matrix (SCDM) is always Reference 2.
- References should be numbered sequentially as they appear in the documentation record.
Identify HRS Data Gaps
Review each HRS factor for completeness of documentation.
Are any data of inadequate quality?
- Pay particular attention to the significant pathways and to data that are important to the site score.
- Develop technically accurate rationale when data are questionable.
- Compare all data to the breakpoints in the HRS tables.
- Look for conflicting assertions or for differences in the numbers that are reported.
- Review the analytical data carefully for all critical samples.
- Do not use inadequate or unsupported data. It only slows the process down.
The identification of data gaps will focus on further information gathering.
Notes on the Final Product
- Every assertion and fact can be challenged.
- The HRS score begins at zero and rises as you present evidence that supports a higher score.
- Every assertion of fact must be referenced and every professional judgement presented with a clear, documented rationale.
- You are writing for the general public...which includes everyone from local citizens to lawyers to consulting engineers.
- Weave the facts together into a "story" that states EPA's case for placing the site on the NPL.
- Most documentation records are written in the WordPerfect format, but PREScore or any other format that presents the information in an understandable and defensible manner is acceptable.
- Do not include extraneous information that might be challenged.
Common Problem Areas
- Referencing: The referencing problems are generally oversights or incorrect pages. Other problems include secondary and tertiary references (for example, the SI is a secondary reference, but the analytical data package, well logs, or field notebooks attached to the SI are primary references), listing a reference not cited in the text, wrong reference numbers, and not referencing statements of fact.
- Maps: The primary problem is the absence of detailed maps. Also problematic is illegibility and missing information such as scale, north arrows, direction of ground water flow, sample locations, and detailed legends for inserted boundaries, points of interest, and shaded areas. Also. All information added to a map needs to be supported by a reference.
- Aquifer interconnection: This is one of the most commonly disputed and questioned portions of the ground water pathway. Problems include; insufficient documentation; incorrect/inaccurate interpretation and documentation of technical reports; not mentioning conflicting references; not meeting the HRS aquifer definition; and confusing geologic descriptions.
- Analytical Data: The most common problem is the absence of good quality analytical data to document HRS factors. Other problems include: lack of a data validation report; incorrect use or interpretation; matching the appropriate HRS factor with level of data quality; misunderstanding qualifiers; and incomplete presentation in the text. CLP data is a known quality, but may not be the best. If QA/QC reports are not included in the scoring package, they should be made readily available.
- Background levels: Background locations are commonly inappropriate. Background levels should ideally reflect conditions in the media minus influences caused by the site you are evaluating. Therefore, background and release samples should be as similar as possible, and the degree of similarity/dissimilarity should be documented. Background levels for ubiquituous or naturally occurring hazardous substances should be established using more data than simply the results of a single background sample.
- Read references, organize information, rough out scores, identify data gaps, then develop a plan for closing the data gaps.
- Watch for eligibility issues that have not been previously caught.
- Ask for guidance in special cases and work closely with other experienced co-workers.
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