Neighborhoods in the north end of Everett have had numerous homes fenced in as part of an arsenic cleanup.
The arsenic was deposited over a wide area from a time when a metal smelter was located at the north end of Everett in the early 1900s.
Approximate boundary of arsenic plume impact in Everett
Washington State Department of Ecology has been conducting residential yard cleanups in north Everett. The project is funded in part by a settlement agreement with the former owner of the smelter combined with a Toxic Cleanup fund from a tax on hazardous chemicals and petroleum.
The approach has been to excavate identified shallow contaminated soils from yard areas and follow up with clean top soil and planting. The fencing was to allow the new vegetation to stabilize before the fences will be removed. In the future develop projects in the area will require permitting specific to the potential that arsenic contaminated soils will be encountered. On the positive side Ecology review of the permits and any cleanup work will be free of charges or fees and potentially future Ecology funded cleanups will be conducted.
More info http://www.ecy.wa.gov/PROGRAMS/tcp/sites_brochure/asarco/es_main.html.
There is another even larger arsenic plume deposition area in Washington associated with former smelter that operated in Tacoma for a much longer period than the Everett facility.