{"schema_version":"1.2","pwsid":"MN1250021","system_name":"Dennison","city":"Dennison","state":"MN","population_served":220,"source_type":"GW","summary":"Dennison serves approximately 220 people in Dennison, Minnesota. Based on contaminant analyses from DNR, WQP, EPA ECHO, the most recent monitoring readings are within federal EPA standards (MCL), but this system has active MCL violations on record for 1 contaminant. 3 contaminants exceed health-based guidelines. The most significant finding is Lead (90th Percentile) at 0.002 mg/L, which is 10x the health guideline. Data is drawn from source-level compliance monitoring and covers 1996 through 2025. Results reflect conditions at the point of collection (wells, treatment plants), not necessarily at the tap.","data_period":{"start":"1996-06-17","end":"2025-12-31"},"contaminants_tested":13,"contaminants_detected":13,"exceedances":0,"guideline_exceedances":3,"contaminants":[{"name":"Arsenic","code":"ARSENIC","cas_number":"7440-38-2","group":"inorganics","section":"guideline_exceedance","measured_value":0.0005,"unit":"mg/L","sample_date":"2025-12-31","source":"DNR","source_scope":"source_monitoring","health_guideline_value":0.000004,"health_guideline_source":"OEHHA PHG","epa_mcl_value":0.01,"status":"exceeds_guideline","detection_limit":null},{"name":"Haloacetic Acids (HAA5)","code":"2456","cas_number":null,"group":"dbps","section":"other_detected","measured_value":5.63,"unit":"ug/L","sample_date":"2025-12-31","source":"DNR","source_scope":"source_monitoring","health_guideline_value":0.0001,"health_guideline_source":"EWG Health Guideline","epa_mcl_value":0.06,"status":"below_limits","detection_limit":null},{"name":"Nitrate (as N)","code":"NITRATE","cas_number":"14797-55-8","group":"inorganics","section":"other_detected","measured_value":0.025,"unit":"mg/L","sample_date":"2025-12-31","source":"DNR","source_scope":"source_monitoring","health_guideline_value":10,"health_guideline_source":"EPA MCLG","epa_mcl_value":10,"status":"below_limits","detection_limit":null},{"name":"Tetrachloroethylene (PCE)","code":"2987","cas_number":null,"group":"vocs","section":"guideline_exceedance","measured_value":0.1,"unit":"ug/L","sample_date":"2025-12-31","source":"DNR","source_scope":"source_monitoring","health_guideline_value":0.00006,"health_guideline_source":"OEHHA PHG","epa_mcl_value":0.005,"status":"exceeds_guideline","detection_limit":null},{"name":"Combined Radium (226+228)","code":"4010","cas_number":null,"group":"radionuclides","section":"other_detected","measured_value":4.6,"unit":"pCi/L","sample_date":"2025-12-31","source":"DNR","source_scope":"source_monitoring","health_guideline_value":0,"health_guideline_source":"EPA MCLG","epa_mcl_value":5,"status":"approaching","detection_limit":null},{"name":"Trichloroethylene (TCE)","code":"2984","cas_number":null,"group":"vocs","section":"other_detected","measured_value":0.05,"unit":"ug/L","sample_date":"2025-12-31","source":"DNR","source_scope":"source_monitoring","health_guideline_value":0.0017,"health_guideline_source":"OEHHA PHG","epa_mcl_value":0.005,"status":"below_limits","detection_limit":null},{"name":"Total Trihalomethanes (TTHMs)","code":"2950","cas_number":null,"group":"dbps","section":"other_detected","measured_value":8.4,"unit":"ug/L","sample_date":"2025-12-31","source":"DNR","source_scope":"source_monitoring","health_guideline_value":0.00015,"health_guideline_source":"EWG Health Guideline","epa_mcl_value":0.08,"status":"below_limits","detection_limit":null},{"name":"Uranium","code":"4006","cas_number":"7440-61-1","group":"radionuclides","section":"other_detected","measured_value":0.4478,"unit":"ug/L","sample_date":"2025-12-31","source":"DNR","source_scope":"source_monitoring","health_guideline_value":0.0005,"health_guideline_source":"OEHHA PHG","epa_mcl_value":0.03,"status":"approaching","detection_limit":null},{"name":"Gross Alpha","code":"4000","cas_number":null,"group":"radionuclides","section":"other_detected","measured_value":10.7,"unit":"pCi/L","sample_date":"2025-12-31","source":"DNR","source_scope":"source_monitoring","health_guideline_value":0,"health_guideline_source":"EPA MCLG","epa_mcl_value":15,"status":"below_limits","detection_limit":null},{"name":"Barium","code":"BARIUM","cas_number":"7440-39-3","group":"inorganics","section":"other_detected","measured_value":0.07,"unit":"mg/L","sample_date":"2025-12-31","source":"DNR","source_scope":"source_monitoring","health_guideline_value":1,"health_guideline_source":"OEHHA PHG 2003 (hypertension endpoint)","epa_mcl_value":2,"status":"below_limits","detection_limit":null},{"name":"Fluoride (natural)","code":"FLUORIDE","cas_number":"16984-48-8","group":"inorganics","section":"other_detected","measured_value":0.62,"unit":"mg/L","sample_date":"2025-12-31","source":"DNR","source_scope":"source_monitoring","health_guideline_value":4,"health_guideline_source":"EPA MCLG","epa_mcl_value":4,"status":"below_limits","detection_limit":null},{"name":"PFBA (Perfluorobutanoic Acid)","code":"PFBA","cas_number":null,"group":"pfas","section":"other_detected","measured_value":0.6,"unit":"ng/L","sample_date":"2025-12-31","source":"DNR","source_scope":"source_monitoring","health_guideline_value":null,"health_guideline_source":null,"epa_mcl_value":null,"status":"detected","detection_limit":null},{"name":"Chromium (total)","code":"CHROMIUM","cas_number":"7440-47-3","group":"inorganics","section":"other_detected","measured_value":27.5,"unit":"ug/L","sample_date":"2025-08-28","source":"WQP","source_scope":"regional_groundwater","health_guideline_value":0.1,"health_guideline_source":"EPA MCLG","epa_mcl_value":0.1,"status":"below_limits","detection_limit":null},{"name":"Lead (90th Percentile)","code":"PB90","cas_number":"7439-92-1","group":"lead_copper","section":"guideline_exceedance","measured_value":0.002,"unit":"mg/L","sample_date":"2023-12-31","source":"EPA ECHO","source_scope":"federal_program","health_guideline_value":0.0002,"health_guideline_source":"OEHHA PHG","epa_mcl_value":null,"status":"exceeds_guideline","detection_limit":null},{"name":"Copper (90th Percentile)","code":"COPPER","cas_number":"7440-50-8","group":"lead_copper","section":"other_detected","measured_value":21.4,"unit":"ug/L","sample_date":"2025-06-18","source":"WQP","source_scope":"regional_groundwater","health_guideline_value":0.3,"health_guideline_source":"OEHHA PHG","epa_mcl_value":null,"status":"below_limits","detection_limit":null}],"sources":[{"name":"DNR","url":"https://apps.dnr.wi.gov/dwsportalpub"},{"name":"WQP","url":"https://www.waterqualitydata.us/"},{"name":"EPA ECHO","url":"https://echo.epa.gov/"}],"pfas_combined_display":null,"well_counts":{"active":1,"retired":0,"facilities_synced_at":"2026-10-26T01:03:17.192Z"},"historical_wells":[],"has_only_historical_data":false,"pfas_hazard_index":null,"tthm_lraa":[{"monitoring_point":"system_wide","value":8.4,"unit":"ug/L","quarters_used":["2020Q4","2021Q4","2022Q4","2025Q4"],"sample_count":5,"mcl":80,"exceeds_mcl":false}],"haa5_lraa":[{"monitoring_point":"system_wide","value":5.63,"unit":"ug/L","quarters_used":["2017Q4","2018Q4","2019Q4","2025Q4"],"sample_count":4,"mcl":60,"exceeds_mcl":false}]}