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2	Introduction There is reluctance in using secondary-materials due to the lack of information involving their potential risks, via leachate, to human health and the environment (e.g. groundwater) A recent research project at the RMRC evaluated the extent to which EPA’s IWEM can aid in the assessment of risks associated with recycled materials use. This presentation will summarize the investigation.
3	Introduction (con’t) But first, we’ll take quick look at past research aimed at a more robust, detailed estimation of risk associated with recycled materials use. And then, we will put the risk assessment into its appropriate life cycle perspective by considering other risks and benefits associated with recycled materials use.
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7	Salt leaching under intact pavement
8	Velocity vectors
9	Velocity vectors: Early in rain event
10	Later in rain event
11	Diffusion versus Advection
12	Fraction reaching groundwater
13	Normalized porewater concentrations over time for different scenarios (mult. by kg/kg in recycled material)
14	IWEM - Model Description Easily used fate-and-transport groundwater model Designed specifically for Waste Management Units. User Input Data WMU type (e.g. land application unit) Constituent type and leachate concentrations Regional hydrogeologic data Time of analysis Receptor well distance from source Information built into database Regional climate data (annual precipitation, recharge, soil types, aquifer characteristics) Regulatory standards (e.g. MCL)
15	Model Description Output Data Groundwater concentration at receptor well based on no-liner situation Concentration comparison to contaminant standards Liner recommendations http://www.epa.gov/epaoswer/non-hw/industd/iwem.htm
16	Purpose of research Ground-truth model using case studies. Develop recommendations for model use, changes to model for use in recycled materials applications.
17	Schematic Highway Cross-Section – University of Wisconsin study
18	Data Leachate data from Sept. ’00 to March ‘04 for active road sections Monitoring well sample results Regional hydrogeologic data Regional climate data (e.g. annual precipitation recharge and infiltration rates)
19	Model behavior
20	Cd predictions at well 6 m away
21	Se prediction in well 6 m away
22	Adsorption K_d is most significant variable that influences predicted concentrations in the groundwater. K_d values estimated by MINTEQA2, and are not explicitly output for user.
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24	Highway 301, Battleboro, NC
25	As vs. time
26	Pb vs. time
27	Back-calculation of K_d
28	Battleboro, NC
29	Conclusions - IWEM IWEM appears to simulate the transport of the metals of concern accurately given set of parameters. K_d values used in IWEM appear to be very conservative. For Cd, K_d values in soil are reported by EPA to be distributed normally between 50 and 3000 – K_d in IWEM is less than 1. K_d values are not explicitly stated in IWEM output.
30	So why bother? Why recycle? If all we do is create risk where there was none before. Are there benefits? If so, what are they? Can they be quantified, measured? Do they matter? Do they help put the risk from materials use in perspective?
31	Life Cycle Assessment What are environmental costs and benefits of using recycled materials? Are there additional environmental or societal benefits that off-set potential site-specific risks? Will analysis of the more holistic Environmental System change the US viewpoint and regulatory approach to recycled materials?
32	Case Study – state of Wisconsin, USA Coal burning power plants are concentrated in high population density regions. Aggregate sources in almost all counties of Wisconsin Studies have indicated that higher population density areas tend to have aggregate deficiencies, due to higher infrastructure needs (Robinson, 2001). Coal ash sources are located in high infrastructure regions, where there are aggregate deficiencies.
33	Scenario Field study conducted by UW. Replacement of crushed rock aggregate by coal ash. Contaminants detected in leachate: Cd, Cr, Se, and Ag Soil composition of the application site: silty loam (USGS reports) Material source distances: 50 miles 100 miles
34	Modeling Tool Pavement Life Cycle Assessment Tool for Environmental and Economic Effects (PaLATE) Looks at materials, design parameters, equipment and maintenance and cost inputs and provides full life cycle costs and environmental assessment. Macro-scale analysis based on the US Dept of Commerce census data (Economic Input-Output) Provides estimates of life cycle air emissions, contaminant releases, water and energy consumption and cancerous and non-cancerous human toxicity potentials. Developed by Arpad Horvath (UC Berkeley) under contract to the RMRC. Available on RMRC web site: http://www.rmrc.unh.edu/Research/Rprojects/Project23/p23researchproducts.asp
35	LCA Results – Impact bottom ash / virgin
36	LCA results All impacts less for recycled materials except HTP-Cancer. There is a trade-off here – many environmental impacts reduced, HTP cancer increased. We should look more closely at the Potential for risk from use of the recycled materials.
37	Modeling Tool Hydrus 2D a finite element modeling program for simulating the movement of water, heat, and multiple solutes in variably saturated media. Predicts local scale transport of contaminants from the recycled materials to groundwater over a specified period.
38	Hydrus 2D Results - Cr Cr transport from bottom ash in the road sub-base to groundwater (5 m below recycled materials), assuming constant flux.
39	Results: System-level Impacts Impacts from use of bottom ash instead of virgin crushed rock (PaLATE) Reduced energy and water consumption, Reduced CO₂, NO_x, CO & PM₁₀ emissions, Reduced RCRA Hazardous Waste generation Reduced non-cancer HTP Increased cancer HTP – due to potential contaminant releases into groundwater
40	Site-level Impacts More detailed investigation of site-specific risks associated with contaminant leaching Contaminants released from bottom ash in roadway will only reach groundwater in very small concentrations for this scenario for over 200 years. Concentration in 200 years will be significantly less than Maximum Contaminant Level allowed in drinking water. Likelihood of environmental degradation and human toxicity is extremely low in this case.
41	Conclusions (cont) The US still has land and natural resources. We should explicitly recognize the value of these and should have recycling policies that consider the entirety of the environmental and social systems. Virtually all decisions are trade-offs. We should explicitly recognize these. Saying “no” to recycled materials is saying “yes” to traditional materials. Regulator seeking to protect environment can do more harm than good with a myopic viewpoint. “stovepipe” regulations eliminate possibility for system-wide optimization.
42	Thank You