Presentation for Office of Surface Mines on Potential Use of the Leaching Environmental Assessment Framework to enhance source terms for use of CCRs in mine reclamation Greg Helms, OSWER/ORCR Susan Thorneloe, ORD/NRMRL/APPCD May 13, 2014

Background Groundwater contamination is a key waste management concern. Leach testing has been used in EPA regulatory programs to help determine: What waste is hazardous: listings, delistings, Toxicity Characteristic (TC) regulation What treatment is adequate: Land Disposal Restriction (LDR) treatment requirements What constituent concentrations in waste are likely to result in groundwater contamination (risk assessment). 2

Leaching Basics Waste exposure to rainfall or other precipitation in the environment results in dissolution and release, or leaching of constituents. A number of factors affect the total and rate of constituent release from a waste or other material:  The amount of rainfall, or infiltration contacting the waste (over time)  For many inorganic constituents, the pH of the contact water  Particle size (granular) or physical form (monolithic), durability  Redox conditions of leaching  Waste aging (i.e., changes over time)  DOC/organic matter  Common ions, ions at high concentrations  Effects of microbes 3

Context for New Leaching Test Methods TCLP is the most used leaching test. Developed to implement the national RCRA regulatory program (not tailored to be site-specific). Based on RCRA def of hazardous waste (“may pose hazard when improperly managed”). Simulates plausible mis-management scenario for waste disposal (i.e., co-disposal with municipal solid waste) for TC regulation. Because it is the “regulatory test”, TCLP is used, even when not required by regulation: EPA SAB has twice (1991,1999) expressed concern about over-broad use of TCLP. Conditions at most contaminated sites do not resemble MSW/TCLP conditions. 4

Why the Leaching Environmental Assessment Framework Tests? Most tests (including TCLP & SPLP) assess leaching potential for a single set of conditions: Tests tend to focus in initial conditions; final test leaching conditions are often unknown. However, final test conditions represent conditions under which leaching actually occurs, and so better represent field leaching. Site conditions can have a significant impact on leaching: Metal solubility and aqueous-solid partitioning vary with pH. Infiltration rates vary nationally (varying weather, soil type) Redox conditions can determine which metal salts are present (and so change solubility). Site conditions can change over time. Leach tests that do not consider the range of key site or waste management conditions may prove to be unreliable predictors of leaching in many cases. 5

6 TCLP/SLPLLEAFWhy is LEAF different ? Test typeBatchBatch, column & dynamic (tank) Achieve more accurate upper bound leach estimate; more realistic lower bound. Scenario evaluated MSWLF or monofill Common data set allows evaluation of multiple scenarios Data allows assessment of disposal or re-use scenarios, including site-specific or national basis. Data PointsSingle data point Multiple data points Considers effects of pH, L/S, and particle size or physical form. Multiple points show effect of relevant ranges likely in the field. pH measured: Before waste added At the end of the extraction period Better reflects actual leaching conditions (approaches equilibrium). Particle size9.5 mm or less;18 hr extraction mm; batch extraction; hr; monolith All batch intended to achieve equilibrium; monolith and upflow column tests are dynamic.

Summary The LEAF methods were designed to account for the impact on leaching of varying values of the most important of these factors (in most cases):  The rate of water infiltration and pore water (Methods 1314 and 1316)  The pH of the material-water system (Method 1313)  Particle size, physical form and durability (Method 1315) For wastes containing some constituents (e.g., As, Se, Cr), oxidized and reduced forms may have different solubility; redox conditions may become significant. 7