Hydrohistorian
Town of Larkspur
Serves Larkspur.
Boundary traced from Douglas County. About 4 km².
Where the water comes from
| Facility | Kind | Water |
|---|---|---|
| NO 1 WELL ARAPAHOE | Well | Groundwater |
| NO 2 DE1 WELL DENVER | Well | Groundwater |
| NO 3 WELL ARAPAHOE AR-3 | Well | Groundwater |
These are EPA's facility records, not DWR structures. Which decreed rights sit behind an intake is the next phase; nothing here is inferred.
DWR structures that name this system
Source Probable join · fetched 2026-10-06 · matched on DWR's recorded contact or an EPA intake name; verify on the dossier
No DWR structure on file records this system as its contact, and none of its EPA intakes matches a structure name in its districts. DWR records a contact on only a fraction of structures, and only for districts fetched from its live service, so this is absence of a record, not evidence of no rights.
Compliance record
Source Register of another agency · fetched 2026-10-07 · verify at EPA ECHO ↗
1 violation open now, none health-based. These are monitoring, reporting or notice requirements — a sample not taken, or a result not filed on time. They are real obligations, but they are not a finding about the water itself.
EPA's own summary: violations in 4 of the last 12 quarters. In violation for, in EPA's words: 2378=1,2,4-Trichlorobenzene; 2380=cis-1,2-Dichloroethylene; 2955=Xylenes, Total; 2964=DICHLOROMETHANE; 2968=o-Dichlorobenzene; 2969=p-Dichlorobenzene; 2976=Vinyl chloride; 2977=1,1-Dichloroethylene; 2979=trans-1,2-Dichloroethylene; 2980=1,2-Dichloroethane; 2981=1,1,1-Trichloroethane; 2982=Carbon tetrachloride; 2983=1,2-Dichloropropane; 2984=Trichloroethylene; 2985=1,1,2-Trichloroethane; 2987=Tetrachloroethylene; 2989=CHLOROBENZENE; 2990=Benzene; 2991=Toluene; 2992=Ethylbenzene; 2996=Styrene; 4010=Combined Radium (-226 and -228).
What happened
All 9 violation records on file, grouped into the 2 distinct things EPA's codes describe. Dates are the compliance period the violation is filed against.
Rule: Lead and Copper Rule -- corrosion of household plumbing.
Rule: Radionuclides -- radium, uranium and gross alpha.
Every violation record, as filed (9 of 9)
| Compliance period | What | About | Kind | Status | Measured |
|---|---|---|---|---|---|
| 2026-07-01 | Follow-up Or Routine LCR Tap M/R | Lead and Copper Rule | monitoring and reporting | open | |
| 2023-10-01 – 2023-12-31 | MCL, Average | Combined Radium (-226 and -228) | health-based | returned to compliance (2024-08-13) | 6.05 PCI/L (limit 5.0) |
| 2023-07-01 – 2023-09-30 | MCL, Average | Combined Radium (-226 and -228) | health-based | returned to compliance (2024-08-13) | 5.88 PCI/L (limit 5.0) |
| 2023-04-01 – 2023-06-30 | MCL, Average | Combined Radium (-226 and -228) | health-based | returned to compliance (2024-08-13) | 6.58 PCI/L (limit 5.0) |
| 2023-01-01 – 2023-03-31 | MCL, Average | Combined Radium (-226 and -228) | health-based | returned to compliance (2024-08-13) | 6.25 PCI/L (limit 5.0) |
| 2019-01-01 – 2019-03-31 | MCL, Average | Combined Radium (-226 and -228) | health-based | returned to compliance (2021-03-24) | 7.0 PCI/L (limit 5.0) |
| 2018-10-01 – 2018-12-31 | MCL, Average | Combined Radium (-226 and -228) | health-based | returned to compliance (2021-03-24) | 6.6 PCI/L (limit 5.0) |
| 2018-07-01 – 2018-09-30 | MCL, Average | Combined Radium (-226 and -228) | health-based | returned to compliance (2021-03-24) | 6.8 PCI/L (limit 5.0) |
| 2018-04-01 – 2018-06-30 | MCL, Average | Combined Radium (-226 and -228) | health-based | returned to compliance (2021-03-24) | 6.8 PCI/L (limit 5.0) |
What the regulator did about it
52 enforcement actions on this system's federal record. In Colorado the state is the primacy agency, so most actions are the state's; EPA acts directly on tribal systems and when it steps in.
| Date | Action | By |
|---|---|---|
| 2026-07-15 | St Violation/Reminder Notice | state |
| 2026-07-15 | St Public Notif requested | state |
| 2024-08-13 | St Compliance achieved Q3 2024 result collected 8/13/2024 is 5.1 pCi/L, Q3 LRAA = 4.85 pCi/L -STF 10/7/2024 |
state |
| 2024-03-19 | St Public Notif received | state |
| 2024-03-19 | St Compliance achieved PN and COD for Q4 2023 radium vio received via portal 3/19/2024 certifying 1/29/2024 distribution. PN vio RTC with reported date -STF 3/19/2024 |
state |
| 2024-03-15 | St Violation/Reminder Notice | state |
| 2024-01-16 | St Violation/Reminder Notice | state |
| 2024-01-16 | St Public Notif requested | state |
| 2024-01-04 | St Violation/Reminder Notice | state |
| 2024-01-04 | St Public Notif requested | state |
| 2023-12-01 | St Public Notif received | state |
| 2023-11-16 | St Compliance achieved RTC with late reporting of VOC samples. Sample collected 11/16/2023, reported 1/18/2024 -STF 1/23/2024 |
state |
| 2023-10-10 | St Violation/Reminder Notice | state |
| 2023-10-10 | St Public Notif requested | state |
| 2023-08-04 | St Public Notif received PN distributed 8/4/2023 per 8/21 COD, copy of PN and COD received 8/21/2023 -STF 11/9/2023 |
state |
| 2023-07-13 | St Violation/Reminder Notice | state |
| 2023-07-13 | St Public Notif requested | state |
| 2023-06-28 | St AO (w/o penalty) issued DW.06.23.118030 issued on 6/28/2023. ejc |
state |
| 2023-06-06 | St Public Notif received PN distributed 6/6/2023 for Q1 MCL vio, COD and pn copy received via portal 6/8/2023 -SKT |
state |
| 2023-06-06 | St Compliance achieved PN distributed 6/6/2023 for Q1 MCL vio, COD and pn copy received via portal 6/8/2023 -SKT |
state |
20 most recent of 52; the rest are on the ECHO report.
Lead and copper
The latest 90th-percentile lead result is 0.0005 mg/L (sampling period ending 2026-06-30) against an action level of 0.015 mg/L, below it. 11 results on file.
The action level is not a health limit: it is the level at which the rule requires a system to act (corrosion control, public education, and in some cases replacing lead service lines). Lead mostly enters water from household plumbing, so a system-wide percentile does not tell you what comes out of one tap.
Violation, enforcement and lead/copper records are EPA SDWIS federal reporting, fetched monthly; the summary is EPA ECHO. Code names come from EPA's own REF_CODE_VALUE table. SDWIS carries violations, not routine sample results — nitrate, disinfection by-product and PFAS values are not in it, and a clean record here means nothing was reported as a violation, not that nothing was ever detected. For what was measured, ask the system for its Consumer Confidence Report.
PFAS and lithium: EPA's UCMR 5 monitoring, 2023–2025
Source Register of another agency · fetched 2026-10-09 · verify at EPA UCMR occurrence data ↗
EPA did not sample this system under UCMR 5 (the rule covered every system serving more than 3,300 people and a drawn sample of smaller ones).
What changed recently
Differences EPA's monthly federal record showed against the month before. A date in brackets is EPA's own; otherwise it is when this site first saw the change.
- Enforcement action: St Violation/Reminder Notice (2026-07-15)
- Enforcement action: St Public Notif requested (2026-07-15)
- New violation: Follow-up Or Routine LCR Tap M/R — Lead and Copper Rule (2026-07-01)
Save this system to My Water and these changes appear there each time you visit.
Common questions
Who provides drinking water in Larkspur, Colorado?
The Town of Larkspur is the public water system serving 275 people in Douglas County, from groundwater. Its EPA public water system id is CO0118030.
Where does the Town of Larkspur get its water?
The Town of Larkspur reports groundwater as its primary source. EPA lists its source facilities as NO 1 WELL ARAPAHOE, NO 2 DE1 WELL DENVER, NO 3 WELL ARAPAHOE AR-3.
Does the Town of Larkspur have any drinking water violations?
EPA's compliance record shows no open health-based violations for the Town of Larkspur at the last monthly fetch. Older and non-health-based entries, if any, are listed on this page.
Places this system serves
Census places its EPA service-area boundary substantially covers. Each page lists every system serving that place.
Every provider in Douglas County.
The record
EPA SDWIS federal reporting as of 2026-10-06; the compliance record above is EPA's own, fetched monthly, and the ECHO report carries the rest. Report a problem →