Notes
Washington State Department of Ecology Implementation Memo No. 3, authored by Steve Robb of the Toxics Cleanup Program, dated November 24, 1993. Addresses two issues under the Model Toxics Control Act (MTCA): (1) long-term liability for potentially liable persons (PLPs) when cleanup levels are set at practical quantitation limits (PQLs) rather than risk-based levels, including eligibility for covenants not to sue, institutional controls, and long-term monitoring requirements under WAC 173-340-700(6), WAC 173-340-707(2), WAC 173-340-707(3), WAC 173-340-707(4), and WAC 173-340-440(1)(a); (2) risk summation calculations when risk-based compliance values are below PQLs, including use of 1×10-5 and 1×10-6 cumulative site risk thresholds, trichloroethylene (TCE) groundwater example at 3.98 ppb with PQL of 0.5 ppb, and Method B and Method C cleanup level standards. Includes analytical guidelines, risk communication guidance, and references to MDL/PQL comparison tables for groundwater, surface water, and soil.