May 23 , 2011 Memorandum to the Docket Listing Additional Information to Update and to Enhance the Risk Assessment , New Toxicological Benchmarks , and EPA Exposure Guidance 1. New human health toxicological benchmarks have been developed since the preparation of EPA‟s 2010 Risk Assessment. Benchmarks used in the 2002 risk screening, “Constituent Screening for Coal Combustion Wastes,” were updated in 2002 and the benchmarks used in the 2010 Risk Assessment were updated in 2009. EPA is considering new values in accordance with the hierarchy outlined in the EPA Office of Solid Waste and Emergency Response 2003 Human Health Toxicity Values in Superfund Risk Assessments Memorandum (Di rective 9285.7 - 53) available on - line at: www.epa.gov/oswer/riskassessment/pdf/hhmemo.pdf . a. Integrated Risk Information System (IRIS) benchmarks, available on - line at: www.epa.gov/iris/ . b. Provisional Peer - Reviewed Toxicity Values (PPRTVs), available on - line at: http://hhpprtv.ornl.gov/quickview/pprtv_papers.php . c. An IRIS cancer slope fact or (CSF) for arsenic is still under revision. As well as using the current IRIS benchmarks for arsenic, EPA is considering using an updated CSF used in the 2010 proposed rule‟s RIA at: www.regulations.gov (EPA - HQ - R CRA - 2009 - 0640 - 0003) . This CSF is based on National Research Council„s ( NRC ) Arsenic in Drinking Water (1999) and NRC Arsenic in Drinking Water : 2001 Update. These documents are available at http://www.nap.edu/openbook.php?isbn=0309063337&page=R1 and http://www.nap.edu/catalog.php?record_id=10194 respectively. d. An ora l CSF for chromium (VI) is being developed by IRIS. To evaluate this endpoint, EPA is considering using a New Jersey Department of Environmental Protection CSF as a Tier III value. NJDEP 2009.

“ Derivation of Ingestion - Based Soil Remediation Criterion for Cr+6 Based on the NTP Chronic Bioassay

UNITED STATES ENVIRONMENTAL PROTECTION AGENCY

WASHINGTON, D.C. 20460 OFFICE OF SOLID WASTE AND EMERGENCY

RESPONSEData for Sodium Dichromate Dihydrate.” Available in the docket supporting this Notice ( EPA - HQ - RCRA 2011 - 0392) and on - line at: http://www.nj.gov/dep/dsr/chromium/ 2. EPA i s considering updating ecological toxicity benchmarks based on: a. EPA‟s ecological soil screening levels for soil receptors available on - line at: www.epa.gov/ecotox/ecossl/ . b. EPA‟s ambient water quality criteri a for aquatic receptors available on - line at: http://water.epa.gov/scitech/swguidance/standards/current/index.cfm . c. EPA is also considering the use of the National Oceanic and Atmospheric Administration‟s SQuiRTs (Screening Quick Reference Tables) available in the docket supporting this Notice ( EPA - HQ - RCRA - 2011 - 0392) and on - line at: http://response.restoration.noaa.gov/book_shelf/122_NEW - SQuiRTs.pdf . d. One commenter, the Utility Solid Waste Activities Group (USWAG), provided an ecological benchmark for boron (See Appendix 20, pages 4 - 13 and 4 - 14 of EPA - HQ - RCRA - 2009 - 0640 - 10483.1 available at www.regulations.gov ). 3. New EPA human exposure guidance has become available. a. Guidance on Selecting Age Groups for Monitoring and Assessing Childhood Exposures to Environmental Contaminants, 2005 (EPA/630/P - 03/003F) available on - line at: www.epa.gov/raf/publications/guidance - on selecting - age - groups.htm . b. Child - Specific Exposure Fac tors Handbook, 2008 (EPA/600/R - 06 - 096F) available on - line at: http://cfpub.epa.gov/ncea/cfm/recordisplay.cfm?deid=199243 .