WA DNR Webster Nursery

The Washington State Department of Natural Resources (WA DNR) did cleanup work at this site in 1996 and 2018. Cleanup included removing the source of contamination (a leaking, underground storage tank full of pesticides) and a total of 215 cubic yards of contaminated soil. Some contaminated soil deeper in the ground was left behind during cleanup for structural stability of the warehouse.

Groundwater monitoring wells showed that contamination never left the property.

After the 2018 cleanup, six years of quarterly groundwater testing showed that groundwater contamination dropped below cleanup levels. Ecology determined that no more cleanup is necessary. The site is ready to be removed from the Contaminated Sites List. Because some contamination was left behind, Ecology required WA DNR to file an Environmental Covenant with Thurston County.

An Environmental Covenant sets rules to prevent people and wildlife from being exposed to the contamination that was left behind. For example, the property can never be used for schools, childcares, homes, growing food, or grazing animals. Also, Ecology must review and approve before any activities that could disrupt soil in the excavated area. Ecology will conduct a periodic review for this site about every five years to make sure the rules in the Environmental Covenant are being followed.

Ecology is holding a public comment period from October 2nd to November 3rd, 2025, to gather public input on removing the site from the Contaminated Sites List.

Webster Nursery is a 300-acre tree nursery run by the Washington State Department of Natural Resources (WA DNR). The nursery grows and sells 9 million seedlings each year. The nursery uses herbicides and fungicides to control weeds and protect seedlings from disease. 

In the past, the nursery used organochlorine pesticides, including chlordane and heptachlor. These chemicals were very effective at killing insects but are also toxic to human health. The nursery has not used insecticides since the early 1990s.

Ecology added this site to the Contaminated Sites List because an underground storage tank leaked pesticides into soil and groundwater.

1978: WA DNR built a 40-feet wide by 180-feet long pesticide storage warehouse. The building included floor drains that were connected to a 750-gallon, concrete, underground storage tank (UST) that was located a few feet south of the building. The building was designed and constructed to have three areas for different purposes. The southern portion was used for barrel, mulch, and peat storage. The middle portion was used for seed and fertilizer storage, and the northern portion was used as a chemical storage area. The chemical storage area included two central floor drains plus a floor drain for a shower and a service sink.

1982: WA DNR replaced the concrete UST with a steel UST.

1996: WA DNR found that the steel UST was leaking and full. WA DNR removed the UST and 70 cubic yards of contaminated soil (about 7 dump trucks full). It was not possible to remove all of the contaminated soil because of the structural stability of the warehouse, and groundwater seeping into the excavation hole. Contaminated soil and water were taken offsite for proper recycling and disposal. Soil around the drains and pipes were tested and did not have any contamination. Available information indicates that the sink and shower within the chemical storage portion of the warehouse were the most likely source of the pesticide contamination that went into the tank.

1997: Thurston County Health Department and Washington State Department of Health sampled public wells in 1997. They did not detect pesticides above lab reporting limits and concluded that the water was safe.

1998: Ecology and WA DNR entered an agreement to investigate the extent of contamination, consider cleanup alternatives, and develop a cleanup plan.

2001: Ecology and WA DNR entered into an agreement to finalize the cleanup plan, monitor the site, and prevent water from moving through the contaminated area.

2001-2016: Yearly groundwater monitoring showed heptachlor epoxide concentration in groundwater near the former UST was above the state cleanup level.

2014: WA DNR tested soil and groundwater to find the extent of contamination.

2016: Ecology and WA DNR entered into an agreement to remove more contaminated soil and monitor groundwater. The cleanup work was delayed to 2018 because of state budget issues.

2018: WA DNR removed about 145 cubic yards (about 14 dump trucks full) of contaminated soil, backfilled with clean soil, and covered it with grass. Not all the contaminated soil could be removed due to structural constraints.

2018-2024: WA DNR monitored groundwater quarterly to make sure that the 2018 soil excavation was an effective cleanup.

2025: After reviewing six years of groundwater data, Ecology proposes removing the site from the Contaminated Sites List and an Environmental Covenant was recorded with Thurston County.