• -~ Focus

e i:r·l~ft'I·(/~&~i Washington Ranking Method

Every hazardous waste site in Washington is unique and poses potentially different type and level of

risk to human health and the environment. The Model ToxicsControl Act requires lhcsc sitC'S to be

ranked relative to each other to guide Ecology's uscof cleanup I"t"5OUI"Ct'S. Working with theScience

Advisory Board,Eco~ has developed a ranking system for hazardous sites known as the

Washington RankingMethod.· .

Ecology ranks a site after the agency gathers enough information to complete a site hazard assessment.

Owners/operators and any other potentially liable personsknown to the agency are notified when

their hazardoos waste site is ranked and placed on Ecology's Hazardous Sites list. Additions to the list

are announced twice each year. .

What Does the Washington Ranking Method 007

A site's potential threat to human health and the environment is estimated using thedata gathered

during the site hazard assessment. The Washington Ranking Method categorizessites on the basis of

this information. Sites are ranked on a scale of one to five, with a score of one representing the highest

level of concern and five the lowest.

The Washington Ra.nJdng Method is designed to:

• Provide a consistent, objective means of assessing sites

• Establish a scientifically defensible method of evaluating sites

• Maximize accuracy with minimum data

• Provide adequate distinction between sites

How Will the Rankings Be Used?

11 isimporlanJ 10 keep ill mind tJuzt IttuArdous sittranJ:ing isnottheSGme lIS risIc ~ml. Rather, it is an

estimation ofthe potential threat posed by a siterelative to an other ranked sites in thestate. An actual

assessment ol site's health risk is detennined after analysis by the state Department ofHealth or by a

county health department. .

The Washington Ranldng Method provides a framework in wNdl to organize and oom~sites.

However, it is not the only factor used to determine which sites receive priority for Ecology'S

resources.Other considerations include the availability of funds, the potential cost of cleanup, the level

of cooperation. shown by a responsible party, and public concern about a site. --..

The ModeJ Taxies Control Act was implemented in March, 1989, after voter approval oflnJtiative 97.

Some of thesites being investigated and cleaned up under the Ad were already receiving attention

under previoasJaws.ln the interest of efficiency, work will continue on most ofthese sites even if they

rank lower than newly added sites. . . .

How Does the Washington Ranking Method Work?

When ranking a site, Ecology considers the primary routes through which humans or the environment

could be exposed to hazardous substances found on that site. "These routes include air, surface water

and ground water. For each "exposure route", the following information is evaluated to determine the

relative risk posed by each site.

SubstanceOYracteri.stics Site Chuaeterlstics Exposure Potential

Toxicity ofsubstance Migration potential Population .

Quantity ofsubstance Soil permeability Sensitiveenvironment

Mobility 01 substance Average rainfaU Surface water uses

Containment flood plain (irriga~ d.rinJc.ing

Terrain sJope water, fisheries)

Distance to ground water Ground water uses

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April, 1991