Archival Data Finder for the Unregulated Contaminant Monitoring Rule (UCMR 1-4)
On this page:
Background
This tool allows people to search for, summarize, and download analytical results from past cycles of the Unregulated Contaminant Monitoring Rule (UCMR). The EPA uses the UCMR program to gather information for contaminants that are suspected to be present in drinking water and do not have health-based standards set under the Safe Drinking Water Act. These data can support future regulatory determinations (i.e., the process that addresses potential regulatory actions for unregulated contaminants) and other actions to protect public health.
The UCMR data from past cycles may no longer represent current drinking water exposures at specific public water systems (PWSs). For example, PWSs may have taken steps to reduce exposures by closing wells, blending water sources, or installing treatment. The original source of the contaminant may also be variable and change over time. If you are concerned about the results of past UCMR monitoring, the EPA recommends reaching out to your PWS for the latest information about your water quality.
More information about each UCMR cycle, including the list of contaminants and analytical methods, types of PWSs required to monitor, frequency and location of sample collection, and sampling design, can be found in the respective UCMR Data Summary and on the UCMR website.
Results in the UCMR Archival Data Finder can be filtered using multiple data fields, including UCMR cycle, PWS ID or name, PWS size, state, EPA Region, contaminant, source water type, and results at or above UCMR minimum reporting levels (MRLs). Selected results can be downloaded as a Microsoft Excel file (.xlsx).
Data Considerations
Prior to using the UCMR Archival Data Finder:
- Watch the UCMR Archival Data Finder Walkthrough (video)
- Review the Instructions for Accessing UCMR Results and
- Read the UCMR 1-4 Data Summary documents.
Detailed data definitions for the UCMR Archival Data Finder are provided for each cycle in the documents above.
For UCMR 1, caution should be used in any interpretation of the data since some untreated (i.e., raw) source water data from several states are also included in the tool. Any positive result from untreated source waters, which are subsequently treated, is generally not used to conduct drinking water exposure assessments. Rather, such cases generally triggered finished water sampling at the entry point to the distribution system.
Understanding the Results
UCMR Minimum Reporting Levels (MRLs) are the lowest concentrations that laboratories could report to the EPA for UCMR results and were determined using data from multiple laboratories that participate in EPA’s UCMR MRL-setting studies. The UCMR MRLs are based on laboratory capability and are not associated with contaminant health effects information. The EPA establishes MRLs to ensure consistency in the quality of the information reported to the agency. The UCMR MRLs can be found in all three tabs of the Data Finder: Summary Pivot Table, Review Data Table, and Contaminant Information.
If you cannot find results for a specific PWS: the PWS may not have been required to monitor for the UCMR cycle; the PWS may have had a valid reason for missing results at certain sampling locations after multiple resampling attempts (e.g., quality control or matrix issues during sample analysis); or the PWS may have been out of compliance, failing to collect all or some of their samples. For more information, visit the UCMR website. PWS IDs, names, and sampling location information (i.e., facility and sample point IDs and names) can change between UCMR cycles.
Results for chemical contaminants are provided in micrograms/liter (µg/L, or parts per billion). To convert results in µg/L to nanograms/liter (ng/L, or parts per trillion), multiply the value by 1,000.
Results below the UCMR minimum reporting level (MRL) are shown as “< MRL” because the UCMR MRL was the lowest concentration that could be reported for UCMR. The UCMR MRLs are based on laboratory capability and are not associated with contaminant health effects information.
Each result represents a single contaminant in drinking water for one sampling point and sampling event from a PWS; UCMR results do not represent a locational running annual average.
Additional Resources
For those interested in large-scale data processing using statistical or data analysis software, use the UCMR 1-4 occurrence data text files which contain the analytical results for each cycle as well as additional information reported during monitoring, if applicable.