Good — Average Score 84/100
State Overview
Water quality across South Dakota receives an overall grade of B (Good) with an average score of 84 out of 100, based on EPA compliance data from 332 ZIP codes statewide. This places South Dakota 9 points above the national average of 75, indicating relatively strong water quality management across the state. A majority of ZIP codes (55%) earn an A grade, reflecting strong compliance across most water systems. The lowest-scoring area is ZIP code 57703 (Rapid City) with a score of 34/100. Scores are calculated from EPA Safe Drinking Water Information System (SDWIS) violation records, lead and copper testing results, PFAS monitoring data from UCMR5, and enforcement actions over the past 5 years.
Lowest Scoring ZIP Codes