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About System Scores

A system score is a point-based value that provides a comprehensive approach for assessing a water system's level of compliance. A single value is calculated for each water system based on compliance with all rules, instead of using the rule-based SNC (significant non-compliance) status which was based on failure to comply with individual drinking water rules. System scores are used to identify systems that are a high priority for enforcement (see Priority Non-Compliers, below).

Priority Non-Compliers (PNCs)

When a water system's system score reaches 11 or higher, the system is considered to be a priority non-complier (PNC). The system remains a PNC until its system score falls below 11 and all MCL violations have been addressed.

How System Scores Are Calculated

The system score is based on all unaddressed violations (those that have not been returned to compliance and are not under formal enforcement) for monitoring periods ending within the last five years. Violations for monitoring periods ending more than five years ago and those that have been addressed are not counted in the system score. Each violation type is assigned a point value indicating its relative threat to public health, or severity (see the points table, below). The system score is calculated by adding together the points of the unaddressed violations and adding a time factor; the time factor is the number of years that the oldest violation has been unaddressed (from 0 to 5 years). For each water system, a system score is calculated using this formula:

          System Score = Sum (S1, S2, S3, ...) + n

where S represents the points for each violation and n represents the time factor. Water systems with a system score of 11 and higher are considered a higher priority for enforcement.


Violation Severity Factors (Points)

Violation Description Points
Acute MCL for E. coli 10
Acute MCL for Fecal Coliform or E. coli 10
Chemical MCL based on 1 Sample, Nitrate 10
Chemical MCL based on Average of Samples, Nitrate 10
Failure to Install or Use SW Treatment 10
Failure to Maintain 4-log Treatment 10
Failure to Maintain EP Disinfection 10
Failure to Meet CT, Swtr 10
Turbidity Standards Not Met (95% NTU) 10
Turbidity Standards Not Met (Max NTU) 10
Action Level Exceeded 5
Chemical Late/Nonreporting, Nitrate 5
Chemical MCL based on 1 Sample 5
Chemical MCL based on Average of Samples 5
Chemical MCL based on Locational Average of Samples 5
Coliform Investigation Defects Not Corrected 5
Coliform Investigation Nonreporting 5
Corrosion Control Non-Compliance 5
Deficiencies Not Corrected or Plan Not Received 5
Failure to Collect MPA Sample 5
Failure to Correct Source Contamination 5
Failure to Install CC Treatment 5
Failure to Install Disinfection 5
Failure to Meet Enforcement Deadline 5
Failure to Replace Plumbing 5
Failure to Submit CCT Recommendation 5
Failure to Treat for Cryptosporidium 5
Violation Description Points
No Designated DRC 5
No Qualified Treatment Plant Operator 5
Prevented Level 2 Investigation 5
Public Education Late/Nonreporting 5
Repeat Coliform - Did Not Report ANY 5
Repeat Coliform - Did Not Report Enough 5
Repeat Coliform - Late/Nonreporting 5
Total Coliform MCL 5
CCR Late/Nonreporting 1
Chemical Late/Nonreporting 1
Consumer Notification of Results Late/Nonreporting 1
Corrosion Control Late/Nonreporting 1
DBP Late/Nonreporting 1
LCR Late/Nonreporting 1
Monthly GW Compliance Report - Late/Nonreporting 1
Monthly SW Report - Late/Nonreporting 1
Public Notice Late/Nonreporting 1
Raw Source Monitoring Incorrect Sample Date 1
Raw Source Monitoring Late/Nonreporting 1
Routine Coliform - Did Not Report ANY 1
Routine Coliform - Did Not Report Enough 1
Source Assessment Sample - Late/Nonreporting 1
Source Sample - Late/Nonreporting 1
Temporary Routine Coliform - Did Not Report ANY 1
Temporary Routine Coliform - Did Not Report Enough 1
Treatment Requirements Not Met 1
  See list of SDWIS codes

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