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Toxics Cleanup Program


Areawide Soil Contamination Project

Toolbox Chapter 2

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

  • Tier 1: The first tier of maps identifies the general areas in the state where elevated levels of arsenic and lead soil contamination are more likely to be present based on historical smelter emissions and historical use of lead arsenate pesticides. The maps do not show areas that have been found to be contaminated, but simply show where contamination is more likely relative to other places. Tier 1 maps are designed to raise general awareness about area-wide soil contamination in the widest possible audience and to help users decide whether to look at the second tier of more detailed maps and informational tools for more information.  


  • Tier 2: Tier 2 maps allow individuals to refine their understanding of where area-wide soil contamination is likely to be present based on more detailed, smaller scale maps of smelter plumes and historical orchard areas. For sources such as leaded gasoline and lead arsenate pesticides where local maps may not exist, information and the individual property evaluation flowchart (see Section 3) are provided to help individuals determine whether elevated levels of arsenic and lead contamination are likely to be present based on the location and land-use history of specific properties.

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.

Areas Affected by Smelter Emissions

Tier 1 Smelter Map

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.

Tier 2 Smelter Maps

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:

  • Figure I-1: Estimate of Area Affected by Historical Tacoma Smelter Emissions with Wind Rose Diagram of Predominant Wind Directions at the Smelter Site (Based on Data Available as of January 2003)

  • Figure I-2: Estimate of Area Affected by Historical Everett Smelter Emissions with Wind Rose Diagram of Predominant Wind Directions at the Smelter Site (Based on Data Available as of January 2003)

  • Figure I-3: Estimate of Area Affected by Historical Harbor Island Smelter Emissions with Wind Rose Diagram of Predominant Wind Directions at the Smelter Site (Based on Data Available as of January 2003)

  • Figure I-4: Estimate of Area Potentially Affected by Emissions from the Northport and Trail, BC Smelters (Based on Data Available as of January 2003)

Tacoma, Harbor Island, and Everett Smelters

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.

Northport and Trail, BC 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.

Areas Affected by Lead Arsenate Pesticides

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.

Figure 4: County Acreage Potentially Affected by Historical Use of Lead Arsenate Pesticide on Apple and Pear Orchards. This map shows the area of land potentially affected by historical use of lead arsenate pesticide in each county based upon the peak-year acreage of apple and pear trees in each county over the period from 1905 to 1947, when lead arsenate pesticides were generally used. The table below lists these peak-year apple and pear tree acreages for each county and compares the total area potentially affected by lead arsenate pesticide use based on peak-year apple and pear tree acreages to the total area of each county and the total amount of private land in each county.

Total Areas Potentially Affected by Lead Arsenate Pesticide Contamination
Area-Wide by County and
Proportions of Total Land and Private Land Potentially Affected by County

County

Total County Acreage

Public Land Acreage

Private Land Acreage

Total Apple & Pear Tree Acreage

Percent of County Affected

Percent of Private Land Affected

Adams

1,235,072

80,728

1,154,344

536

0.04%

0.05%

Asotin

409,262

108,814

300,448

501

0.12%

0.17%

Benton

1,122,809

352,563

770,246

7,738

0.69%

1.00%

Chelan

1,915,838

1,695,939

219,899

30,463

1.59%

13.85%

Clallam

1,141,042

719,834

421,208

331

0.03%

0.08%

Clark

410,999

75,462

335,537

2,676

0.65%

0.80%

Columbia

556,220

182,342

373,878

1,161

0.21%

0.31%

Cowlitz

731,478

128,115

603,363

1,139

0.16%

0.19%

Douglas

1,179,695

165,502

1,014,193

7,467

0.63%

0.74%

Ferry

1,450,915

1,246,545

204,370

322

0.02%

0.16%

Franklin

807,391

97,656

709,735

314

0.04%

0.04%

Garfield

459,852

113,200

346,652

749

0.16%

0.22%

Grant

1,786,503

425,765

1,360,738

4,928

0.28%

0.36%

Grays Harbor

1,235,289

490,589

744,700

425

0.03%

0.06%

Island

137,021

14,310

122,711

605

0.44%

0.49%

Jefferson

1,162,696

924,553

238,143

324

0.03%

0.14%

King

1,403,508

631,641

771,867

2,700

0.19%

0.35%

Kitsap

255,339

41,354

213,985

969

0.38%

0.45%

Kittitas

1,494,741

1,019,122

475,619

1,642

0.11%

0.35%

Klickitat

1,212,167

238,612

973,555

4,632

0.38%

0.48%

Lewis

1,564,211

669,023

895,188

1,954

0.12%

0.22%

Lincoln

1,496,674

127,984

1,368,690

1,819

0.12%

0.13%

Mason

620,305

235,033

385,272

416

0.07%

0.11%

Okanogan

3,402,402

2,630,253

772,149

10,608

0.31%

1.37%

Pacific

597,842

99,369

498,473

238

0.04%

0.05%

Pend Oreille

910,089

613,346

296,743

222

0.02%

0.07%

Pierce

1,080,110

462,343

617,767

2,139

0.20%

0.35%

San Juan

110,755

13,721

97,034

1,407

1.27%

1.45%

Skagit

1,127,231

657,007

470,224

941

0.08%

0.20%

Skamania

1,072,343

955,884

116,459

2,376

0.22%

2.04%

Snohomish

1,345,933

831,391

514,542

1,670

0.12%

0.32%

Spokane

1,138,013

74,600

1,063,413

19,455

1.71%

1.83%

Stevens

1,623,630

666,365

957,265

3,542

0.22%

0.37%

Thurston

471,338

95,381

375,957

1,075

0.23%

0.29%

Wahkiakum

165,146

44,341

120,805

195

0.12%

0.16%

Walla Walla

825,730

34,516

791,214

3,092

0.37%

0.39%

Whatcom

1,390,935

984,655

406,280

1,948

0.14%

0.48%

Whitman

1,393,456

43,240

1,350,216

6,819

0.49%

0.51%

Yakima

2,757,047

2,144,184

612,863

58,050

2.11%

9.47%

Statewide

43,201,027

20,135,282

23,065,745

187,588

0.43%

0.81

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.

Tier 2 Lead Arsenate Pesticide Maps

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:

  • Maps of the general locations of areas potentially affected by lead arsenate contamination within individual counties, based on readily available land use information
     
  • Maps showing the locations of historical orchards based on aerial photographs

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.

  1.  Maps of Where Lead Arsenate May Have Been Used Based on Land Use Information

    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.

    • Figure I-5, Figure I-6, and FigureI-7: Potential Historical Orchard Areas in Chelan, Okanogan, and Yakima Counties (Based on the Use of the Individual Property Evaluation Flowchart). These maps show areas in Chelan, Okanogan, and Yakima counties show areas that are below 2,500 feet in elevation (2,000 feet for Yakima County) and that are not State, Federal, or tribal lands. With a few exceptions, fruit trees are not likely to have been grown on State and Federal public lands, or at elevations greater than 2,000 or 2,500 feet (based the highest elevation of historical orchard locations in Yakima and Chelan counties). On the Yakima County map (Figure I-7), an area west of Wapato where apple and pear trees were historically grown is shown as potentially affected, even though it is the property of the Yakama Indian Nation.

  2. Maps Showing the Locations of Historical Orchards Based on Historical Aerial Photographs

    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.

    • Figure I-8: Historical Orchards in Yakima County Circa 1947. This figure shows areas in Yakima County that were orchards in 1947, as determined based upon an analysis of historical aerial photographs, along with the current locations of city boundaries and highways within Yakima County.
       
    • Figure I-9: Historical Orchards in the Lake Chelan/Manson Area of Chelan County Circa 1947. This figure consists of black and white aerial photographs of the Manson area near Lake Chelan that have been overlain in purple with areas that used to be orchards in 1947, based on an analysis of aerial photographs.

    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:

    • They include all orchard areas from 1947, not simply apple and pear orchard locations, where lead and arsenic contamination from lead arsenate pesticide use is more likely.
       
    • Because apple and pear acreage was lower in these counties in 1947 than in previous years, these maps may fail to show lands that may be impacted by lead arsenate use.

    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.

Areas Affected by Combustion of Leaded Gasoline

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.