On August 5, 2022, EPA received a report from the National Response Center (NRC) regarding an incident at the Star Valley Trailer Court, north of Grover, Wyoming. The NRC report stated an individual who lives at the trailer court deliberately injected an unknown oily substance into the drinking water distribution system.  The trailer court gets its drinking water from an artesian groundwater well and has approximately 32 connections, serving a population of roughly 72 persons.  The well was not contaminated but six homes are known to have been impacted.  The drinking water owner/operator shut down the system, notified all residents and quickly installed two valves to isolate the contaminated homes.

EPA has primary authority to enforce the public water supply protection program in Wyoming and issued the system operator an order detailing the steps required to bring the system back online. EPA dispatched an emergency response team to assist the system operator with flushing the distribution system and taking water samples.

EPA is conducting response activities to:

1. Flush the water distribution system.
2. Assist in the collection of water quality samples necessary to reopen the system.

Residents should not use the water until water quality samples are analyzed and show the water is safe. A water tank is available at the end of the trailer court for non-potable water. The system has been flushed and EPA's Response Team has no indication that the system is currently contaminated. If water in the system is required in urgent situations such as flushing toilets, it must not be ingested until residents receive clearance from the system operator or owner of the trailer court.

The water main is a loop beginning and ending at the well house. The six homes that are known to have been contaminated were isolated from the system by the water system operator on August 5, 2022, when he installed isolation valves in the main on the north side of the well house as well as at a low point just west of the last impacted home. EPA’s operational goals are to:

• Flush the segment of the system that is considered unimpacted.
• Flush the segment of the system that has been impacted.
• Help the system operator collect confirmation samples.

EPA resources (1 OSC, 4 ERRS, 2 START) arrived at the Site on August 6, 2022, and formed a Response Team with the system operator and property owner. Residents in the impacted homes reported an oily substance in their taps, being covered in the substance while taking showers and laundry that had been covered in oil after wash cycles. Oily residue was visible in toilet bowls, sinks and on the ground near several outdoor taps at these homes. No residents outside the six impacted homes reported any issues.

Portable toilets and hand wash stations were set up in the neighborhood. Legal access was obtained from the owner of the trailer court for all outdoor areas, a majority of the unimpacted owners, and five of the six impacted homeowners. The owner of the sixth home is the property owner who reportedly put the material in the system and was not responsive. This sixth impacted home was completely disconnected from the water distribution system on August 6, 2022, so that flushing of the system could proceed.

Flushing involved systematically opening all the hot and cold water taps at each property moving away from the well house.  The homes in the unimpacted zone were flushed on August 6, 2022. No visible sheen, oily substances nor odors were encountered during this process.

The Response Team flushed the 5 impacted homes on August 7, 2022. This process started by cutting the main line behind the isolation valve that was installed just west of the last impacted home. This segment of the main line was drained to install a water collection bib next to the isolation valve. When the main was cut, approximately 15 gallons of water mixed with a heavy oily substance was released. This material was collected and sampled. The main line was then pressurized and flushed for 15 minutes. Little to no visibly contaminated water was generated.

After the main line was flushed, the Team flushed each of the five homes working away from the well house for 30 minutes. The Team insured that each hot water tap ran until cold. Small globs of oil were noticed on only a few occasions during the first few seconds of flushing but the water quickly ran clear. Residual contamination was cleaned out of several toilet tanks. No additional contamination was witnessed.

The Team then flushed the main in this isolated segment again for 15 minutes before opening the isolation valve and reversing the flow in the main so that the water ran from the well, through the unimpacted segment and finally to through the impacted segment. The entire main was flushed again under this configuration for approximately 30 minutes with no visual signs of contamination.

The septic tanks servicing the impacted homes were pumped clean.

The collection of confirmation samples began on August 7 and the system operator will be collecting the final bacteria samples on August 8. All samples will be sent to various laboratories on August 8.

EPA's response assets have demobilized.

All the samples will be analyzed and the results will be reviewed by EPA's Drinking Water Program before the system is re-opened to full use.