Safe Drinking Water Information System (SDWIS) Federal Reporting Services

Your Drinking Water Query results from SDWIS Fed Reporting Services

PWS ID	010106001
PWS Name	Mashantucket Pequot Water System
PWS Type	Community water system
Owner Type	Tribal Government
Primary Source	Groundwater under influence of surface water
Primacy Type	Tribal
Is Wholesaler?	Yes
Population Served	26445
County Served

The tables below list all violations that the state reported to EPA for this water system. Health-based violations are listed first, followed by treatment technique, MRDL, monitoring, reporting, and other violations.

Health-based	Violations of maximum contaminant levels (MCLs) or maximum residual disinfectant levels (MRDLs), which specify the highest concentrations of contaminants or disinfectants, respectively, allowed in drinking water; or of treatment technique (TT) rules, which specify required processes intended to reduce the amounts of contaminants in drinking water. MCLs, MRDLs, and treatment technique rules are all health-based drinking water standards.
Maximum Contaminant Level or MCL	The highest level of a contaminant that is allowed in drinking water. MCLs are set as close to the MCLGs as feasible using the best available treatment technology.
Treatment Technique	A required process intended to reduce the level of a contaminant in drinking water.
Maximum residual disinfectant level or MRDL	The highest level of a disinfectant allowed in drinking water. There is convincing evidence that addition of a disinfectant is necessary for control of microbial contaminants.
Monitoring & reporting	Failure to conduct regular monitoring of drinking water quality, as required by SDWA, or to submit monitoring results in a timely fashion to the primacy agency or EPA.
Public notification & other	Failure to provide notification to the public as required by the Violations of Public Notification Rule and the Consumer Confidence Report Rule, and violations of other requirements such as those violations related to variances and exemptions.

Violations

Violation Category Code	Violation Type Description	Rule Name	Contaminant Name	Violation ID	Compliance Status Description	Compliance Period Begin Date	Compliance Period End Date	Is Health Based Ind
Other	Consumer Confidence Report Inadequate Reporting	Consumer Confidence Rule	Consumer Confidence Rule	010600172700072025	Returned to Compliance	01-JUL-2025	-	No
Other	Consumer Confidence Report Inadequate Reporting	Consumer Confidence Rule	Consumer Confidence Rule	010600172700072024	Returned to Compliance	01-JUL-2024	-	No
RPT	Report Sample Result/Fail Monitor (RTCR)	Revised Total Coliform Rule	Revised Total Coliform Rule	01060014B8000112018	Returned to Compliance	01-NOV-2018	-	No
MCL	Maximum Contaminant Level Violation, Average	Stage 2 Disinfectants and Disinfection Byproducts Rule	TTHM	0106001022950102018	Returned to Compliance	01-OCT-2018	31-DEC-2018	Yes
Other	Public Notification Violation for NPDWR Violation	Public Notice Rule and Revised PN Rule	Public Notice	010600175750092018	Returned to Compliance	28-SEP-2018	-	No
MR	Failure Submit IDSE/Subpart V Plan Rpt	Stage 2 Disinfectants and Disinfection Byproducts Rule	TTHM	010600135295082018	Returned to Compliance	09-AUG-2018	-	No
MCL	Maximum Contaminant Level Violation, Average	Stage 2 Disinfectants and Disinfection Byproducts Rule	TTHM	010600102295072018	Returned to Compliance	01-JUL-2018	30-SEP-2018	Yes
MR	Failure Submit IDSE/Subpart V Plan Rpt	Stage 2 Disinfectants and Disinfection Byproducts Rule	TTHM	010600135295072018	Returned to Compliance	01-JUL-2018	-	No
Other	Public Notification Violation for NPDWR Violation	Public Notice Rule and Revised PN Rule	Public Notice	9999900000000000001	Known	02-APR-2018	04-APR-2018	No
MR	Monitoring, Regular	Synthetic Organic Chemicals	Dinoseb	010600103204112016	Returned to Compliance	01-JAN-2016	31-DEC-2016	No
MR	Monitoring, Regular	Synthetic Organic Chemicals	Endrin	010600103200512016	Returned to Compliance	01-JAN-2016	31-DEC-2016	No
MR	Monitoring, Regular	Synthetic Organic Chemicals	BHC-GAMMA	010600103201012016	Returned to Compliance	01-JAN-2016	31-DEC-2016	No
MR	Monitoring, Regular	Synthetic Organic Chemicals	Methoxychlor	010600103201512016	Returned to Compliance	01-JAN-2016	31-DEC-2016	No
MR	Monitoring, Regular	Synthetic Organic Chemicals	Toxaphene	010600103202012016	Returned to Compliance	01-JAN-2016	31-DEC-2016	No
MR	Monitoring, Regular	Synthetic Organic Chemicals	Dalapon	010600103203112016	Returned to Compliance	01-JAN-2016	31-DEC-2016	No
MR	Monitoring, Regular	Synthetic Organic Chemicals	Diquat	010600103203212016	Returned to Compliance	01-JAN-2016	31-DEC-2016	No
MR	Monitoring, Regular	Synthetic Organic Chemicals	Endothall	010600103203312016	Returned to Compliance	01-JAN-2016	31-DEC-2016	No
MR	Monitoring, Regular	Synthetic Organic Chemicals	Glyphosate	010600103203412016	Returned to Compliance	01-JAN-2016	31-DEC-2016	No
MR	Monitoring, Regular	Synthetic Organic Chemicals	ETHYLENE DIBROMIDE	010600103294612016	Returned to Compliance	01-JAN-2016	31-DEC-2016	No
MR	Monitoring, Regular	Synthetic Organic Chemicals	1,2-DIBROMO-3-CHLOROPROPANE	010600103293112016	Returned to Compliance	01-JAN-2016	31-DEC-2016	No
MR	Monitoring, Regular	Synthetic Organic Chemicals	Chlordane	010600103295912016	Returned to Compliance	01-JAN-2016	31-DEC-2016	No
MR	Monitoring, Regular	Synthetic Organic Chemicals	Pentachlorophenol	010600103232612016	Returned to Compliance	01-JAN-2016	31-DEC-2016	No
MR	Monitoring, Regular	Synthetic Organic Chemicals	Benzo(a)pyrene	010600103230612016	Returned to Compliance	01-JAN-2016	31-DEC-2016	No
MR	Monitoring, Regular	Synthetic Organic Chemicals	HEXACHLOROBENZENE	010600103227412016	Returned to Compliance	01-JAN-2016	31-DEC-2016	No
MR	Monitoring, Regular	Synthetic Organic Chemicals	2,4,5-TP	010600103211012016	Returned to Compliance	01-JAN-2016	31-DEC-2016	No
MR	Monitoring, Regular	Synthetic Organic Chemicals	2,4-D	010600103210512016	Returned to Compliance	01-JAN-2016	31-DEC-2016	No
MR	Monitoring, Regular	Synthetic Organic Chemicals	Total Polychlorinated Biphenyls (PCB)	010600103238312016	Returned to Compliance	01-JAN-2016	31-DEC-2016	No
MR	Monitoring, Regular	Synthetic Organic Chemicals	Heptachlor epoxide	010600103206712016	Returned to Compliance	01-JAN-2016	31-DEC-2016	No
MR	Monitoring, Regular	Synthetic Organic Chemicals	Heptachlor	010600103206512016	Returned to Compliance	01-JAN-2016	31-DEC-2016	No
MR	Monitoring, Regular	Synthetic Organic Chemicals	LASSO	010600103205112016	Returned to Compliance	01-JAN-2016	31-DEC-2016	No
MR	Monitoring, Regular	Synthetic Organic Chemicals	Atrazine	010600103205012016	Returned to Compliance	01-JAN-2016	31-DEC-2016	No
MR	Monitoring, Regular	Synthetic Organic Chemicals	Carbofuran	010600103204612016	Returned to Compliance	01-JAN-2016	31-DEC-2016	No
MR	Monitoring, Regular	Synthetic Organic Chemicals	Hexachlorocyclopentadiene	010600103204212016	Returned to Compliance	01-JAN-2016	31-DEC-2016	No
MR	Monitoring, Regular	Synthetic Organic Chemicals	Picloram	010600103204012016	Returned to Compliance	01-JAN-2016	31-DEC-2016	No
MR	Monitoring, Regular	Synthetic Organic Chemicals	Di(2-ethylhexyl) phthalate	010600103203912016	Returned to Compliance	01-JAN-2016	31-DEC-2016	No
MR	Monitoring, Regular	Synthetic Organic Chemicals	Simazine	010600103203712016	Returned to Compliance	01-JAN-2016	31-DEC-2016	No
MR	Monitoring, Regular	Synthetic Organic Chemicals	OXAMYL	010600103203612016	Returned to Compliance	01-JAN-2016	31-DEC-2016	No
MR	Monitoring, Regular	Synthetic Organic Chemicals	Di(2-ethylhexyl) adipate	010600103203512016	Returned to Compliance	01-JAN-2016	31-DEC-2016	No
MR	Monitoring, Routine Minor (TCR)	Total Coliform Rule	Coliform (TCR)	01060012431001119930	Returned to Compliance	01-NOV-1993	30-NOV-1993	No
MR	Water Quality Parameter M/R	Lead and Copper Rule	Lead and Copper Rule	0106001535000719931	Returned to Compliance	01-JUL-1993	31-DEC-1993	No
MR	Water Quality Parameter M/R	Lead and Copper Rule	Lead and Copper Rule	0106001535000719930	Returned to Compliance	01-JUL-1993	31-DEC-1993	No
MCL	Maximum Contaminant Level Violation, Acute (TCR)	Total Coliform Rule	Coliform (TCR)	0106001213100219930	Returned to Compliance	01-FEB-1993	28-FEB-1993	Yes
MCL	Maximum Contaminant Level Violation, Acute (TCR)	Total Coliform Rule	Coliform (TCR)	0106001213100119930	Returned to Compliance	01-JAN-1993	31-JAN-1993	Yes
MCL	Maximum Contaminant Level Violation, Acute (TCR)	Total Coliform Rule	Coliform (TCR)	01060012131001219920	Returned to Compliance	01-DEC-1992	31-DEC-1992	Yes
MCL	Maximum Contaminant Level Violation, Acute (TCR)	Total Coliform Rule	Coliform (TCR)	01060012131001119920	Returned to Compliance	01-NOV-1992	30-NOV-1992	Yes
MCL	Maximum Contaminant Level Violation, Acute (TCR)	Total Coliform Rule	Coliform (TCR)	0106001213100319920	Returned to Compliance	01-MAR-1992	31-MAR-1992	Yes
MR	Monitoring, Routine Major (TCR)	Total Coliform Rule	Coliform (TCR)	0106001233100119920	Returned to Compliance	01-JAN-1992	31-JAN-1992	No

1 - 47 of 47

Enforcement Actions

Latest Enforcement ID	Associated To Violation ID	Enforcement Action Type Code	Enforcement Action Description	Enforcement Date	Originator Description	Enforcement Comment
0106001OX10022523404	010600172700072025	EOX	Federal Compliance achieved	02-OCT-2025	Region	Received copies of the revised CCRs and the certification of delivery and the PN. All requirements met.
0106001OX10022523403	010600172700072024	EOX	Federal Compliance achieved	02-OCT-2025	Region	Received copies of the revised CCRs and the certification of delivery and the PN. All requirements met.
0106001OX02121923091	0106001022950102018	EOX	Federal Compliance achieved	12-FEB-2019	Region	Results reported below MCL (or LRAA below MCL).
0106001OX02121923090	010600102295072018	EOX	Federal Compliance achieved	12-FEB-2019	Region	Results reported below MCL (or LRAA below MCL).
0106001OX01081922964	01060014B8000112018	EOX	Federal Compliance achieved	08-JAN-2019	Region	All results were reported on time in Dec.
0106001IF12271822971	010600135295082018	EIF	Federal Public Notification received from PWS	27-DEC-2018	Region	-
0106001IF12271822972	010600135295072018	EIF	Federal Public Notification received from PWS	27-DEC-2018	Region	-
0106001OX12271822968	010600175750092018	EOX	Federal Compliance achieved	27-DEC-2018	Region	Received a copy of the PN and a signed certification that the notice was posted as required.
0106001OX08031722909	010600103295912016	EOX	Federal Compliance achieved	03-AUG-2017	Region	Received SOC results from lab.
0106001OX08031722916	010600103238312016	EOX	Federal Compliance achieved	03-AUG-2017	Region	Received SOC results from lab.
0106001OX08031722910	010600103293112016	EOX	Federal Compliance achieved	03-AUG-2017	Region	Received SOC results from lab.
0106001OX08031722926	010600103200512016	EOX	Federal Compliance achieved	03-AUG-2017	Region	Received SOC results from lab.
0106001OX08031722914	010600103201012016	EOX	Federal Compliance achieved	03-AUG-2017	Region	Received SOC results from lab.
0106001OX08031722915	010600103201512016	EOX	Federal Compliance achieved	03-AUG-2017	Region	Received SOC results from lab.
0106001OX08031722918	010600103202012016	EOX	Federal Compliance achieved	03-AUG-2017	Region	Received SOC results from lab.
0106001OX08031722920	010600103203112016	EOX	Federal Compliance achieved	03-AUG-2017	Region	Received SOC results from lab.
0106001OX08031722924	010600103203212016	EOX	Federal Compliance achieved	03-AUG-2017	Region	Received SOC results from lab.
0106001OX08031722925	010600103203312016	EOX	Federal Compliance achieved	03-AUG-2017	Region	Received SOC results from lab.
0106001OX08031722927	010600103203412016	EOX	Federal Compliance achieved	03-AUG-2017	Region	Received SOC results from lab.
0106001OX08031722921	010600103203512016	EOX	Federal Compliance achieved	03-AUG-2017	Region	Received SOC results from lab.
0106001OX08031722930	010600103203612016	EOX	Federal Compliance achieved	03-AUG-2017	Region	Received SOC results from lab.
0106001OX08031722932	010600103203712016	EOX	Federal Compliance achieved	03-AUG-2017	Region	Received SOC results from lab.
0106001OX08031722922	010600103203912016	EOX	Federal Compliance achieved	03-AUG-2017	Region	Received SOC results from lab.
0106001OX08031722931	010600103204012016	EOX	Federal Compliance achieved	03-AUG-2017	Region	Received SOC results from lab.
0106001OX08031722923	010600103204112016	EOX	Federal Compliance achieved	03-AUG-2017	Region	Received SOC results from lab.
0106001OX08031722929	010600103204212016	EOX	Federal Compliance achieved	03-AUG-2017	Region	Received SOC results from lab.
0106001OX08031722908	010600103204612016	EOX	Federal Compliance achieved	03-AUG-2017	Region	Received SOC results from lab.
0106001OX08031722907	010600103205012016	EOX	Federal Compliance achieved	03-AUG-2017	Region	Received SOC results from lab.
0106001OX08031722906	010600103205112016	EOX	Federal Compliance achieved	03-AUG-2017	Region	Received SOC results from lab.
0106001OX08031722912	010600103206512016	EOX	Federal Compliance achieved	03-AUG-2017	Region	Received SOC results from lab.
0106001OX08031722913	010600103206712016	EOX	Federal Compliance achieved	03-AUG-2017	Region	Received SOC results from lab.
0106001OX08031722905	010600103210512016	EOX	Federal Compliance achieved	03-AUG-2017	Region	Received SOC results from lab.
0106001OX08031722904	010600103211012016	EOX	Federal Compliance achieved	03-AUG-2017	Region	Received SOC results from lab.
0106001OX08031722928	010600103227412016	EOX	Federal Compliance achieved	03-AUG-2017	Region	Received SOC results from lab.
0106001OX08031722919	010600103230612016	EOX	Federal Compliance achieved	03-AUG-2017	Region	Received SOC results from lab.
0106001OX08031722917	010600103232612016	EOX	Federal Compliance achieved	03-AUG-2017	Region	Received SOC results from lab.
0106001OX08031722911	010600103294612016	EOX	Federal Compliance achieved	03-AUG-2017	Region	Received SOC results from lab.
0106001OX06029821878	01060012131001219920	EOX	Federal Compliance achieved	02-JUN-1998	Region	-
0106001OX06029821893	0106001213100119930	EOX	Federal Compliance achieved	02-JUN-1998	Region	-
0106001OX06029822465	0106001535000719931	EOX	Federal Compliance achieved	02-JUN-1998	Region	-
0106001OX06029821859	01060012131001119920	EOX	Federal Compliance achieved	02-JUN-1998	Region	-
0106001OX06029821902	0106001213100219930	EOX	Federal Compliance achieved	02-JUN-1998	Region	-
0106001IB02209822459	0106001535000719930	EIB	Federal Compliance Meeting conducted	20-FEB-1998	Region	-
0106001OX01109422153	01060012431001119930	EOX	Federal Compliance achieved	10-JAN-1994	Region	-
0106001OX03189221913	0106001213100319920	EOX	Federal Compliance achieved	18-MAR-1992	Region	-
0106001OX02249222009	0106001233100119920	EOX	Federal Compliance achieved	24-FEB-1992	Region	-

1 - 46 of 46

All Facilities

Facility Name	Facility ID	Is Source	Facility Type Description	Water Type Description	Availability Description	Facility Activity Status
WELL #4 (Northern Wellfield)	0106001GW004	Yes	Well	Ground water under the influence of surface water	Other	Inactive
Well #2a (Southern Wellfield)	0106001GW007	Yes	Well	Ground water	Permanent	Active
WELL #3a (Southern Wellfield)	0106001GW003	Yes	Well	Ground water	Permanent	Active
Well #3b (Southern Wellfield)	0106001GW001	Yes	Well	Ground water	Permanent	Active
Well #6 (Northern Wellfield)	0106001GW006	Yes	Well	Ground water under the influence of surface water	Permanent	Active
WELL #5 (Northern Wellfield)	0106001GW005	Yes	Well	Ground water under the influence of surface water	Permanent	Active
WELL #2 (Southern Wellfield)	0106001GW002	Yes	Well	Ground water	Other	Inactive
Entry Point to Distribution	0106001EP001	No	Common Headers	-	-	Active
Entry Point 2 - Southern Well Field - Discontinued	0106001EP002	No	Common Headers	-	-	Active
DISTRIBUTION SYSTEM	0106001DS001	No	Distribution System/Zone	-	-	Active
Residential Portion of System	0106001DS002	No	Distribution System/Zone	-	-	Active
Well 3 Combined	0106001CH001	No	Other	-	-	Active
Common Headers for Wells 3a and 3b	0106001CH003	No	Other	-	-	Active
Blended Phosphate Addition	0106001OT001	No	Other	-	-	Active
Transmission Main from Treatment Plant	0106001TM001	No	Other	-	-	Active
Transmission Main from Wellhouse	0106001TM002	No	Other	-	-	Active
Booster Station 7a	0106001PF001	No	Pump Facility	-	-	Active
Lake of Isles Booster Station	0106001PF002	No	Pump Facility	-	-	Active
Clearwell	0106001ST001	No	Storage	-	-	Active
Horton Water Sphere	0106001ST002	No	Storage	-	-	Active
North Stonington Tank	0106001ST003	No	Storage	-	-	Active
Lake of Isles Tank	0106001ST004	No	Storage	-	-	Active
TREATMENT PLANT (Northern Wellfield)	0106001TP001	No	Treatment Plant	-	-	Active
WELL HOUSE (Southern Wellfield)	0106001TP002	No	Treatment Plant	-	-	Active
GAC Filters	0106001TP003	No	Treatment Plant	-	-	Active

1 - 25 of 25

Treatment Processes

Facility Name	Facility ID	Treatment Process	Treatment Objective
TREATMENT PLANT (Northern Wellfield)	0106001TP001	pH Adjustment	Iron removal
TREATMENT PLANT (Northern Wellfield)	0106001TP001	Aeration, Diffused	Iron removal
TREATMENT PLANT (Northern Wellfield)	0106001TP001	Sedimentation	Iron removal
TREATMENT PLANT (Northern Wellfield)	0106001TP001	Filtration, Ultrafiltration	Particulate removal
TREATMENT PLANT (Northern Wellfield)	0106001TP001	3-Log Treatment of Crypto	Particulate removal
TREATMENT PLANT (Northern Wellfield)	0106001TP001	3-Log Remove/Inactivate G Lamblia	Particulate removal
TREATMENT PLANT (Northern Wellfield)	0106001TP001	Hypochlorination, Post	Disinfection
WELL HOUSE (Southern Wellfield)	0106001TP002	pH Adjustment	Corrosion control
WELL HOUSE (Southern Wellfield)	0106001TP002	Inhibitor, Polyphosphate	Corrosion control
WELL HOUSE (Southern Wellfield)	0106001TP002	Hypochlorination, Post	Disinfection
GAC Filters	0106001TP003	Activated Carbon, Granular	Disinfection by-products control

1 - 11 of 11

For more information on a Water System:
Ask the operators of your water system, contact your primacy agency or file a Freedom of Information Act (FOIA) request.
Drinking water in general: Find out more about your drinking water web site or call the Safe Drinking Water Hotline (1-800-426-4791). EPA has also prepared a table about various regulated drinking water contaminants.
Tools for accessing EPA drinking water data: Safe Drinking Water Information System (SDWIS) Federal Reporting Services and Drinking Water Performance and Results Report.
Research Data: As well as monitoring the levels of drinking water contaminants for which EPA has set standards, EPA, states, and water systems also carry out studies of contaminants that may need to be regulated in the future. For more information about these contaminants, please see the National Contaminant Occurrence Database.

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