Soil in many areas of Washington State has elevated levels of arsenic and lead from historical smelter emissions, historical use of lead arsenate pesticides, and past combustion of leaded gasoline. Areas where elevated levels of arsenic and lead are more likely to be present may be identified based on their proximity to these historical sources. Maps show a greater or lesser probability of encountering elevated levels of arsenic and lead in soil based on proximity to historical sources. For certainty, individual property evaluations are needed.

The Task Force recommends a tiered approach to maps, as follows.

Care should be taken to avoid misinterpretation of the maps. The maps do not show where properties have been sampled and area-wide soil contamination found. The maps only communicate where elevated levels of arsenic and lead in soil are more likely, relative to other areas in Washington State. Due to the variability of the distribution of area-wide soil contamination, properties outside of areas identified on maps may contain elevated levels of arsenic and lead, while properties inside areas identified on maps may not, in fact, have elevated levels of arsenic and lead. The maps include disclaimers to explain these limitations so that individuals are not given a false sense of assurance or concern about whether their property is affected by area-wide soil contamination.

The tier 1 smelter map (Figure 3:  Estimate of Areas Potentially Affected by Historical Smelter Emissions: Estimate of Areas Potentially Affected by Historical Smelter Emissions [Based on Data Available as of January 2003]) shows the portions of counties where area-wide soil contamination is likely to be present based on the historical emissions from four former smelter areas in Washington, based on information currently available. Metal smelters were historically located in the Tacoma, Harbor Island, Everett, and Northport areas of Washington, and a lead smelter currently operates in Trail, BC near Stevens county. This figure identifies the historical locations of smelters in Washington and shows the portions of counties potentially affected by smelter emissions in a darker color.

The areas indicated as potentially affected by smelter emissions do not necessarily include all affected areas, because the complete extent of effects has not been determined. The areas shown were derived from actual soil sampling results for the Tacoma and Harbor Island smelters, sampling and air modeling for the Everett smelter, and maps of sulfur dioxide injury to vegetation from the Northport and Trail, BC smelters. These regions include areas where arsenic and lead levels are likely to exceed cleanup levels based on soil sampling studies that have been conducted (as shown in the Tier 2 smelter maps for most of the smelters described below) as well as other areas where air modeling or other information indicated that some level of impact from smelter emissions exists.

More detailed, local maps have been developed to delineate the potential extent of arsenic and lead soil contamination from smelter emissions for the following smelter areas:

For the Tacoma, Harbor Island, and Everett smelters, the figures show the extent of area known to be likely to contain elevated levels of arsenic and lead (above 20 mg/kg for arsenic or above 250 mg/kg for lead) based on soil sampling results. The Tacoma and Everett smelter plume maps also show the larger areas potentially affected by smelter emissions (including areas where arsenic and lead levels may occasionally exceed cleanup levels). All three Westside smelter figures include wind-rose diagrams illustrating the predominant wind patterns around the smelters.

For the Northport and Trail smelters (Figure I-4), the area potentially affected by smelter emissions has been estimated based on observed historic effects of sulfur dioxide emissions from the smelters, rather than actual soil sampling results for arsenic and lead, since soil sampling data do not currently exist for the area outside the Northport smelter property. The area of potential impact from Northport and Trail smelter emissions has been identified based on evaluation of another smelter emission contaminant, sulfur dioxide, and the maximum extent of injury to trees from this contaminant observed and documented in 1929. The area of possible arsenic and lead soil contamination from smelter emissions is conservatively assumed to approximate the same area as that affected by sulfur dioxide emissions, since the emissions occurred together.

Along with emissions from the Northport smelter, the area has also been affected by the Trail smelter, located approximately 18 miles upriver from the Northport smelter in the West Kootenay region of British Columbia. Smoke from Trail historically has reportedly been detected at Kettle Falls, Washington, 50 miles south along the river. As shown in Figure I-4, the defined area of potential impact from both smelters is influenced by the local topography. The deep valley of the Columbia River where sites of the Northport and Trail smelters are located provides a channel which influences air dispersion, in part by limiting wind direction along the axis of the river, with the prevailing winds carrying smoke from Trail down the Columbia River valley past Northport.  The area-wide risks of elevated arsenic and lead remaining in soils along the upper Columbia River have not yet been established.  The potential effects of the Trail smelter and Northport smelter on soils in Stevens County will be part of a U.S. Environmental Protection Agency investigation of the Upper Columbia River.  In 2004 the USEPA conducted residential yard cleanups in the town of Northport, which was the site of the historic LeRoi Smelter in Northport.

Tier 1 Lead Arsenate Pesticides Map

The location of areas affected by historical use of arsenical pesticides are not as well known or as extensively studied as areas affected by historical smelter emissions in Washington. Although data currently available do not permit the development of a state map of areas affected by lead arsenate contamination comparable to the tier 1 smelter map, agricultural and land-use data are available to provide a general indication of the distribution of lead arsenate pesticide contamination based on where apple and pear trees were located historically. The Task Force recommends that the following map be used to show the total acreage of land potentially affected by lead arsenate pesticide use in each county.

Sources: Data on historical apple and pear tree acreages from the Washington State Agricultural Census for the period 1905-1947; data on public land areas from the Washington State Department of Ecology’s database on state and federal public lands in Washington.

Although data are not available to precisely delineate areas affected by lead arsenate in all counties, certain general areas in the State may be assumed to have low probability of lead arsenate contamination based on their location or land use history. Two types of smaller scale maps of areas potentially affected by historical use of lead arsenate pesticide are provided:

Because of the limitations of the data sources used in these maps, it is important to conduct individual property evaluations (see section 3) to determine whether elevated levels of arsenic and lead are likely to be present in soil on specific properties.

The Task Force recommends that local maps such as the following examples be developed to show the general locations of areas potentially affected by lead arsenate contamination within individual counties, based on available land-use information such as elevation and public lands.

More detailed maps for lead arsenate pesticide contamination can be developed for counties or portions of counties to further delineate areas where elevated levels of arsenic and lead may be present based on using historical aerial photographs to roughly identify the former locations of orchards. These locations can then be matched with information known about the current uses of the property (e.g., whether the property is a school, park, or in a residential area). The following examples are included.

These maps were developed by analyzing 1947 aerial photographs to identify the locations of historical orchards, entering this information into a geographic information system (GIS) database, and overlaying the locations of the historical orchards onto aerial photographs or other geographic data, such city and county boundaries and highways. These maps have two important limitations:

The Individual Property Evaluation Flowchart (see section 3) and the tier 2 lead arsenate pesticide maps provide additional information and a guide for determining whether individual properties are likely to have lead arsenate contamination.

Many factors can influence the concentration of lead in soil adjacent to roadways from historical use of leaded gasoline. These factors include distance from the road, soil depth, traffic volume, traffic speed, whether the soil has been disturbed, and physical features of the location such as degree of vegetation, topography, average wind speed, and prevailing wind direction. In general, any road constructed before 1995 has potential for some contribution of lead to roadside soil. For any land parcel adjacent to a road that was present before 1995, the top foot of soil (soil surface to one foot below ground surface) within 25 feet of the edge of the road has the highest potential for containing soil lead contamination from past leaded gasoline emissions (assuming the soil bordering the road has not been disturbed). In highly populated urban areas, elevated lead soil concentrations have the potential to be elevated throughout the city core due to high road density and traffic volume. If the soil near the road edge or within an urban area has been disturbed, elevated levels of lead in soil may also be present below the top foot of soil or in areas where contaminated soil was moved.