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Six-Year Review 2 Contaminant Occurrence Data (1998-2005)

In March 2010, EPA announced the review results for the Agency’s second Six-Year Review (called Six-Year Review 2).  EPA analyzed occurrence data for the Six-Year Review 2 for 69 regulated contaminants, using data provided by 47 states/primacy agencies.  This data represents compliance monitoring sample results collected between January 1998 and December 2005. (Note: While the Six-Year Review 2 effort included a detailed review of 71 national primary drinking water regulations (NPDWRS), acrylamide and epichlorohydrin are treatment technique regulations and occurrence monitoring data are not required).
The zip files below contain 69 individual Microsoft Access files (one file per contaminant).  The number of records and the size of the files range considerably from contaminant to contaminant, generally reflecting the frequency of required sampling. The files below incorporate a corrected data set for nitrate monitoring data that was posted in November 2010 to correct an inconsistency in a state data set that was identified.

Second Six-Year Review zip files (grouped alphabetically by chemical names)


Data Elements Contained in the Six-Year Review 2 MS Access files

The following two tables are data dictionaries for the chemical data sets; they contain the list of data elements, column names, and a brief description of the data for each data element. Table 1 describes inventory data and Table 2 describes chemical specific information.

Table 1: Six-Year Review-ICR Dataset Data Element List - Inventory Data

Data Element Column Name Description
State Code STATE 2- digit state code
Public Water System Identification Number (PWSID) PWSID The code used to identify each PWS. The code begins with the standard 2-character postal state abbreviation or region code; the remaining 7 numbers are unique to each PWS in the state.
System Name PWSNAME Name of the PWS.
Federal Public Water System Type Code PWSTYPE A code to identify whether a system is:
• Community Water System (C);
• Non-transient Non-community Water System (NTNC); or
• Transient Non-community Water System (NC; nitrate/nitrite only).
Population-served POPULATION Highest average daily number of people served by a PWS, when in operation.
Source Water Type SRCWATER Type of water at the source. Source water type can be:
• Ground water (GW); or
• Surface water (SW); or
• Ground water under the direct influence of surface water (GU)

Table 2: Six-Year Review-ICR Dataset Data Element List - Chemical-Specific Information

Data Element Column Name Description
State ID ID State-specific unique identification code
Sampling Point Identification Code SAMPLEPOINTID A sampling point identifier established by the state, unique within each applicable facility, for each applicable sampling location (e.g., entry point to the distribution system). This information enables occurrence assessments that address intra-system variability.
Sample Identification Number SAMPLEID Identifier assigned by state or the laboratory that uniquely identifies a sample.
Sample Collection Date DATE Date the sample was collected, including month, day, and year.
Contaminant CHEMID 4-digit SDWIS contaminant identification number for which the sample is being analyzed.
Sample Analytical Result - Sign DETECT The sign indicates whether the sample analytical result was:
• (0) "less than" means the contaminant was not detected or was detected at a level "less than" the MRL.
• (1) "equal to" means the contaminant was detected at a level "equal to" the value reported in "Sample Analytical Result - Value."
Sample Analytical Result - Value VALUE Actual numeric (decimal) value of the analysis for the chemical result, or the MRL if the analytical result is less than the contaminant's MRL.
Sample Analytical Result - Unit of Measure UNITS Unit of measurement for the analytical results reported (usually expressed in either µg/L or mg/L for chemicals; or pCi/L for radionuclides).