On January 13, 2021, The Worland Wyoming Fire Department (WFD) requested assistance with a spill of mercury inside a residential garage that is adjacent to a park in Powell, Wyoming. The garage property is unoccupied and had recently been inherited. Upon inheriting the unoccupied property, the new owner discovered several abandoned containers of chemicals. One 10 ounce container held elemental mercury. The owner was packing the abandoned chemicals in the garage in order to facilitate their disposal when the mercury container broke and released its contents into the garage.  The property owner then went to his truck and drove to his nearby home where he showered. The WFD secured the garage, but remained concerned that the mercury may have also been tracked inside the unoccupied residence, as well as into the owner's truck and current home.

EPA dispatched an OSC, 4 ERRS and 3 START to Powell, Wyoming on January 14, 2021. At 1600, START conducted an initial assessment of the occupied residence and the property owner's truck. Mercury vapors were not observed nor detected on the majority of the surface areas in the occupied residence but levels as high as 17,000 ng/m3 were detected in the area around the front entry, a closet and the shower drain. Breathing zone levels in the house exceeded 1000 ng/m3. Mercury vapor levels as high as 6,000 ng/m3 were detected in the truck. 

At 1700, ERRS accessed the occupied residence (including the truck), removed contaminated rugs, towels and clothing and began focusing its efforts on the shower drain. The homeowners turned up the heat and opened up the windows. A dog was found to have a small amount of mercury on his paw and his owners gave him a bath.

Before leaving for the night, ERRS sealed the drain pipes and secured a gallon jug of nitric acid that the property owner found on the inherited property. The home was vented overnight and the dog was cold.

Exposure to metallic mercury can cause health effects when inhaled as a vapor and absorbed through the lungs.  Symptoms include:

• Tremors, emotional changes (mood swings, irritability, nervousness)
• Insomnia
• Neuromuscular changes (i.e. weakness and twitching), changes in nerve responses
• Headaches
• Higher exposure may cause kidney effects, respiratory failure and death.

Key Health and Safety Messages for the Crew:  Don’t spread the mercury.  Follow proper Covid procedures.

• Wear your proper PPE and do not spread the mercury outside the hot zone or to your boots, trucks and own homes.
• Pay attention to proper decon.  Wear booties and switch them out.  We will be checking your boots.  If you don’t keep your boots clean, you may lose them.
• Follow proper Covid procedures.  When you take off your respirator, put on a mask.

1.  Identify areas in the following three impacted exposure units where mercury vapor levels exceed 300-1,000 ng/m3: the Occupied Residence, the Owner's Truck, and the Inherited Residence.

2.  Collect and package all visible elemental mercury from the three exposure units.

3.  Remove and properly dispose of contaminated clothing, rugs and other materials from the three exposure units as needed.

4.  Reduce mercury vapor levels to below 300-1,000 ng/m3 in the breathing zones of all three exposure units.

5.  Remove and properly dispose of all the abandoned chemical containers, including the mercury found at the Inherited Residence.

ERRS focused on the drain, closet and several floors. The house was aggressively heated and vented. The property owners truck was vented as well and his keys were returned. At 1700, the levels of mercury vapor in the shower drain were 450 ng/m3 down from 17,000 ng/m3. START identified 3 separate 1 square foot areas of carpet near the entry where vapor levels were elevated. All other readings were reduced.

EPA began work at the unoccupied property, the location of the spill. START did not detect mercury contamination in the unoccupied house itself. Mercury vapors in the garage breathing zone however were measured at 27,000 ng/m3 upon entry. Tiny beads of mercury were observed in the detached garage, around the doorway exiting the garage and approximately 20 feet down a walkway leading from the garage to the alley. Larger beads were discovered around the 10 oz bottle which was upright and remained 80-90% full. ERRS carefully collected all visible elemental mercury in and around the garage (including the upright bottle). As darkness fell, mercury vapor readings remained elevated in the garage.

- Screen occupied property in the morning after house has remained heated and closed overnight.

- Address area of carpet at the entry of the occupied property.

- Remove shelving, hardware and other materials as necessary from around the location of the spill in the garage.

- Focus on removing mercury from the concrete floor in the garage. 

START screened the occupied residence first thing in the morning. Mercury readings in the breathing zone remained above 1000 ng/m3. Readings from the shower drain were 1400 ng/m3.

ERRS removed the carpeting between the front door and the bathroom including the carpet in the closet near the bathroom. ERRS also removed the floor threshold between the kitchen and the living room and re-cleaned the floors in the utility room, kitchen and bathrooms well as the shower drain area. The home was aggressively heated and vented.

At the unoccupied garage, ERRS removed shelving, the side entry door and lower few feet of its door jams, and the drywall around location of the spill. ERRS continued to collect all visible mercury and applied an initial layer of floor sealant on the concrete in the garage.

The response team continued to emphasis containment procedures to prevent the spread of mercury from the garage, the proper decontamination of PPE and diligent COVID health and safety practice.

- Screen the occupied property in the morning after house has remained heated and closed overnight.

- Use this screening data to either initiate clearance monitoring in the occupied house or continue mercury collection activities.

- Continue sealing the concrete in the unoccupied garage and screen mercury levels.

- Continue segregation of waste for disposal.

START screened the occupied residence first thing in the morning. Mercury vapor readings in the breathing zone were reduced to below 1000 ng/m3 and readings from the shower drain were also below that level. These readings are still on the high side within the range of the OSC's target of 300 - 1000 ng/m3 for the occupied residence.

START did identify a few more source areas of concern in the occupied residence including an additional area of carpet and the threshold between the hallway and the bathroom. ERRS removed the identified carpet and performed a third thorough cleaning of hard surfaces. ERRS heated and vented the home again and START set up instruments to initiate the collection of clearance data overnight.

At the unoccupied garage, ERRS applied a second coat of sealant on the concrete garage floor. START then screened the garage. Mercury vapor readings in the breathing zone exceeded 2000 ng/m3 and several remaining source were as high as 9,000 ng/m3. START did not detect any areas of concern on the walls of the garage but the concrete floor remains an issue.

The response team continued to emphasis containment procedures to prevent the spread of mercury from the garage, the proper decontamination of PPE and diligent COVID health and safety practice.

- Review the data log in the instruments that were left overnight at the occupied residence to determine if clearance has been achieved.

- Continue attempting to seal the concrete floor.

- Aggressively heat and vent the unoccupied garage.

START reviewed the data log of the clearance monitors in the occupied residence first thing in the morning. Mercury vapor level readings in the breathing zone of the highest impacted areas in the home (bathroom and entry/hallway) were below 300 ng/m3. START conducted a second 8-hour verification run which resulted in even lower results. No further action is anticipated at the occupied residence.

ERRS applied a third coat of sealant to the concrete floor in the unoccupied garage. The garage was aggressively heated and vented for most of the day.

ERRS packaged the mercury that was collected during EPA's response effort and prepared it for transport to a disposal facility. The debris generated during the effort was moved to a roll-off located at a nearby Fire Department. TCLP sample results from this waste (drywall, carpet, clothing, rugs, furniture, shelving, etc.) are expected in 5-7 days. Once these results are received, the material will be disposed of as universal waste at a local landfill. 

The response team continued to emphasis containment procedures to prevent the spread of mercury from the garage, the proper decontamination of PPE and diligent COVID health and safety practice.

- Heat the garage and measure mercury vapor levels in the breathing zone.

- Either a) initiate clearance monitoring or b) continue to gently demolish the lower part of the entry to the unoccupied garage.

- Generate final report.