In addition to the SYR3 ICR compliance monitoring data, the following supplemental data sources were referred to in the technical support documents for the Six-Year Review 3. Zip files for the specific databases may be downloaded by selecting the link below each description. Some additional information on the data sources and downloading the data files may be found in a User Guide to Downloading and Using SYR3 Data from EPA's Website.
Disinfection Byproducts (DBP) Information Collection Rule (ICR)
The DBP ICR “Aux 1” database contains monitoring data from large public water systems (PWSs serving a population greater than or equal to 100,000) for the 18-month period of July 1997 to December 1998. A total of 296 water systems reported data; included in the database are monitoring results for microbials and DBPs, plant treatment, source water characteristics and disinfectant type information.
EPA ICR Treatment Study Database (TSD)
The ICR TSD contains treatment study data submitted by systems required to conduct DBP precursor removal studies under the ICR. Results from 99 treatment studies (63 granular activated carbon and 36 membrane studies) are provided in the database.
Second Unregulated Contaminant Monitoring Rule (UCMR 2) Data
Data are available for nitrosamine occurrence in finished drinking water in public water systems (PWSs) from the nationally representative monitoring completed under the second round of the Unregulated Contaminant Monitoring Rule (UCMR 2). This dataset is available from the agency’s website:
Third Unregulated Contaminant Monitoring Rule (UCMR 3) Data – July 2016 version
Data are available for chlorate occurrence in finished drinking water in PWSs from the nationally representative monitoring completed under the third round of the Unregulated Contaminant Monitoring Rule (UCMR 3). The chlorate occurrence analyses presented in the Six- Year Review 3 Technical Support Document for Chlorate are based on data collected through May 2016 and released in July 2016.
LT2 Round 1 Monitoring Data
In support of the LT2 analyses, EPA used data from the Data Collection and Tracking System (DCTS) pull from April 2012, which contained 44,944 records representing all system sizes. EPA posted the original and “cleaned-up” datasets on the EPA website at: https://19january2021snapshot.epa.gov/dwsixyearreview/long-term-2-enhanced-surface-water-treatment-lt2-rule-round-1-source-water. Refer to the Six- Year Review 3 Technical Support Document for LT2 for additional information.
Safe Drinking Water Information System (SDWIS) Information
The Safe Drinking Water Act requires states to report drinking water information periodically to EPA. This information is maintained in a federal database, the SDWIS Fed Data Warehouse. The information below extracted from SDWIS was used during the development of Six-Year Review 3:
SDWIS 2011 Pivot Tables
SDWIS 2011 pivot table inventory data were used to assess representativeness of SYR3 ICR data on both state and national levels. This is discussed further in the Six- Year Review 3 Technical Support Document for D/DBPRs.
SDWIS Violation Data
SDWIS violation data from 2006 to 2011 were used to assess violation rates and representativeness of populations. EPA conducted this assessment for the Chemical Phase Rules and Radionuclide Rules.
2011 SDWIS/FED Freeze
A SDWIS/FED freeze from December 2011 was used to populate missing inventory information (e.g., source water type or population served) for some of the non-SDWIS states. This version of SDWIS was also used to evaluate the completeness of the data submitted for SYR3.
2010 SDWIS/FED Freeze
A SDWIS/FED freeze from December 2010 was used to identify the system type and for the national extrapolation of small system occurrence data for chlorates. This is discussed further in the Six- Year Review 3 Technical Support Document for Chlorate.
A list of buyer-wholesaler relationships from a fourth quarter 2010 SDWIS/FED freeze was used to adjust the population values of the wholesale systems to include the population of the systems that they sell water to (the purchased water systems). Refer to "The Analysis of Regulated Contaminant Occurrence Data from Public Water Systems in Support of the Third Six-Year Review of National Primary Drinking Water Regulations: Chemical Phase Rules and Radionuclides Rules” for additional information.
2005 SDWIS Freeze
A 2005 SDWIS freeze was used in the occurrence analyses of nitrosamines to categorize PWSs by their source water type and by the size of the population served. Refer to the Six- Year Review 3 Technical Support Document for Nitrosamines for additional information.