{"schema_version":"1.2","pwsid":"IL1110600","system_name":"MCHENRY","city":"MCHENRY","state":"IL","population_served":22335,"source_type":"GW","summary":"MCHENRY serves approximately 22,335 people in MCHENRY, Illinois. Based on contaminant analyses from DNR, WQP, EPA ECHO, EPA UCMR5, 0 contaminants have been measured above federal EPA standards (MCL) and 2 exceed health-based guidelines. The most significant finding is Lead (90th Percentile) at 0.0067 mg/L, which is 33.5x the health guideline. Data is drawn from source-level compliance monitoring and covers 1996 through 2026. Results reflect conditions at the point of collection (wells, treatment plants), not necessarily at the tap.","data_period":{"start":"1996-08-06","end":"2026-07-23"},"contaminants_tested":45,"contaminants_detected":21,"exceedances":0,"guideline_exceedances":2,"contaminants":[{"name":"Barium","code":"BARIUM","cas_number":"7440-39-3","group":"inorganics","section":"other_detected","measured_value":0.088,"unit":"mg/L","sample_date":"2026-07-23","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":0.375,"unit":"mg/L","sample_date":"2026-07-23","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":"Combined Radium (226+228)","code":"4010","cas_number":null,"group":"radionuclides","section":"other_detected","measured_value":1.053,"unit":"pCi/L","sample_date":"2026-07-23","source":"DNR","source_scope":"source_monitoring","health_guideline_value":0,"health_guideline_source":"EPA MCLG","epa_mcl_value":5,"status":"below_limits","detection_limit":null},{"name":"PFHpA (Perfluoroheptanoic Acid)","code":"PFHPA","cas_number":null,"group":"pfas","section":"other_detected","measured_value":0.6,"unit":"ng/L","sample_date":"2026-07-23","source":"DNR","source_scope":"source_monitoring","health_guideline_value":null,"health_guideline_source":null,"epa_mcl_value":null,"status":"detected","detection_limit":null},{"name":"PFPeA (Perfluoropentanoic Acid)","code":"PFPEA","cas_number":null,"group":"pfas","section":"other_detected","measured_value":1.8,"unit":"ng/L","sample_date":"2026-07-23","source":"DNR","source_scope":"source_monitoring","health_guideline_value":null,"health_guideline_source":null,"epa_mcl_value":null,"status":"detected","detection_limit":null},{"name":"Haloacetic Acids (HAA5)","code":"2456","cas_number":null,"group":"dbps","section":"other_detected","measured_value":10.87,"unit":"ug/L","sample_date":"2026-06-11","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":"Total Trihalomethanes (TTHMs)","code":"2950","cas_number":null,"group":"dbps","section":"other_detected","measured_value":46.5,"unit":"ug/L","sample_date":"2026-06-11","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":"cis-1,2-Dichloroethylene","code":"2943","cas_number":"156-59-2","group":"vocs","section":"other_detected","measured_value":0.97,"unit":"ug/L","sample_date":"2026-05-19","source":"DNR","source_scope":"source_monitoring","health_guideline_value":0.07,"health_guideline_source":"EPA MCLG","epa_mcl_value":0.07,"status":"below_limits","detection_limit":null},{"name":"Methyl Tert Butyl Ether","code":"METHYL_TERT_BUTYL_ETHER","cas_number":null,"group":"other","section":"other_detected","measured_value":1.6,"unit":"ug/L","sample_date":"2026-04-20","source":"DNR","source_scope":"source_monitoring","health_guideline_value":null,"health_guideline_source":null,"epa_mcl_value":null,"status":"detected","detection_limit":null},{"name":"Nitrate (as N)","code":"NITRATE","cas_number":"14797-55-8","group":"inorganics","section":"other_detected","measured_value":0.3,"unit":"mg/L","sample_date":"2025-10-30","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":"Arsenic","code":"ARSENIC","cas_number":"7440-38-2","group":"inorganics","section":"other_detected","measured_value":5.1,"unit":"ug/L","sample_date":"2023-08-08","source":"WQP","source_scope":"regional_groundwater","health_guideline_value":0.000004,"health_guideline_source":"OEHHA PHG","epa_mcl_value":0.01,"status":"exceeds_guideline","detection_limit":null},{"name":"Chromium (total)","code":"CHROMIUM","cas_number":"7440-47-3","group":"inorganics","section":"other_detected","measured_value":1.2,"unit":"ug/L","sample_date":"2021-05-26","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":"Phosphorus Total","code":"PHOSPHORUS_TOTAL","cas_number":null,"group":"other","section":"other_detected","measured_value":12,"unit":"ug/L","sample_date":"2026-07-21","source":"DNR","source_scope":"source_monitoring","health_guideline_value":null,"health_guideline_source":null,"epa_mcl_value":null,"status":"detected","detection_limit":null},{"name":"Orthophosphate","code":"ORTHOPHOSPHATE","cas_number":null,"group":"other","section":"other_detected","measured_value":320,"unit":"ug/L","sample_date":"2026-06-19","source":"DNR","source_scope":"source_monitoring","health_guideline_value":null,"health_guideline_source":null,"epa_mcl_value":null,"status":"detected","detection_limit":null},{"name":"Lead (90th Percentile)","code":"PB90","cas_number":"7439-92-1","group":"lead_copper","section":"guideline_exceedance","measured_value":0.0067,"unit":"mg/L","sample_date":"2026-06-30","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":"guideline_exceedance","measured_value":490,"unit":"ug/L","sample_date":"2026-06-19","source":"DNR","source_scope":"source_monitoring","health_guideline_value":0.3,"health_guideline_source":"OEHHA PHG","epa_mcl_value":null,"status":"exceeds_guideline","detection_limit":null},{"name":"Lithium","code":"lithium","cas_number":null,"group":"other","section":"pfas","measured_value":9.09,"unit":"ug/L","sample_date":"2023-05-23","source":"EPA UCMR5","source_scope":"federal_program","health_guideline_value":null,"health_guideline_source":null,"epa_mcl_value":null,"status":"detected","detection_limit":9},{"name":"PFOA (Perfluorooctanoic Acid)","code":"PFOA","cas_number":"335-67-1","group":"pfas","section":"pfas","measured_value":1.1,"unit":"ng/L","sample_date":"2026-07-23","source":"DNR","source_scope":"source_monitoring","health_guideline_value":0,"health_guideline_source":"EPA MCLG","epa_mcl_value":0.004,"status":"below_limits","detection_limit":null},{"name":"PFOS (Perfluorooctane Sulfonate)","code":"PFOS","cas_number":"1763-23-1","group":"pfas","section":"pfas","measured_value":0.5,"unit":"ng/L","sample_date":"2026-07-23","source":"DNR","source_scope":"source_monitoring","health_guideline_value":0,"health_guideline_source":"EPA MCLG","epa_mcl_value":0.004,"status":"below_limits","detection_limit":null},{"name":"PFBA (Perfluorobutanoic Acid)","code":"PFBA","cas_number":null,"group":"pfas","section":"pfas","measured_value":2.5,"unit":"ng/L","sample_date":"2026-07-23","source":"DNR","source_scope":"source_monitoring","health_guideline_value":null,"health_guideline_source":null,"epa_mcl_value":null,"status":"detected","detection_limit":null},{"name":"PFBS (Perfluorobutane Sulfonate)","code":"PFBS","cas_number":"375-73-5","group":"pfas","section":"pfas","measured_value":3.8,"unit":"ng/L","sample_date":"2026-07-23","source":"DNR","source_scope":"source_monitoring","health_guideline_value":null,"health_guideline_source":null,"epa_mcl_value":null,"status":"detected","detection_limit":null},{"name":"PFHxS (Perfluorohexane Sulfonate)","code":"PFHXS","cas_number":"355-46-4","group":"pfas","section":"pfas","measured_value":1.6,"unit":"ng/L","sample_date":"2026-07-23","source":"DNR","source_scope":"source_monitoring","health_guideline_value":0.01,"health_guideline_source":"EPA MCLG","epa_mcl_value":0.01,"status":"below_limits","detection_limit":null},{"name":"PFHxA (Perfluorohexanoic Acid)","code":"PFHXA","cas_number":"307-24-4","group":"pfas","section":"pfas","measured_value":1.5,"unit":"ng/L","sample_date":"2026-07-23","source":"DNR","source_scope":"source_monitoring","health_guideline_value":null,"health_guideline_source":null,"epa_mcl_value":null,"status":"detected","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/"},{"name":"EPA UCMR5","url":"https://www.epa.gov/dwucmr/fifth-unregulated-contaminant-monitoring-rule"}],"pfas_combined_display":null,"well_counts":{"active":10,"retired":2,"facilities_synced_at":"2026-11-02T01:09:07.370Z"},"historical_wells":[],"has_only_historical_data":false,"pfas_hazard_index":{"value":0.1619,"compounds_used":["PFHXS","PFBS"],"is_partial":true,"threshold":1,"components":[{"code":"PFHXS","value_ng_l":1.6,"hbwc_ng_l":10,"ratio":0.16},{"code":"PFBS","value_ng_l":3.8,"hbwc_ng_l":2000,"ratio":0.0019}]},"tthm_lraa":[],"haa5_lraa":[]}