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Home My WebLink AboutDSHW-2005-009321 - 0901a0688016601e (8)September 13, 2005 Paul Hancock, Manager Environmental Remediation ATK Thiokol Inc.-Promontory P.O. Box 707 Brigham City, Utah 84302-0707 Subject: Results of Post-Excavation Sampling at M-39 and M-636 ATK Thiokol - Promontory EPA ID #009081357 Dear Mr. Hancock: This letter provides comments from the review of the above referenced document dated March 30, 2005. Hazardous waste management units (HWMUs) M-39 and M-636 were formerly used for disposal of wastewater generated from photo processing operations. As a result of these past disposal activities, soil in the disposal areas was contaminated with cadmium and silver. Contaminated soil was removed from each of these sites in 1995, and closure certification reports were submitted following the removal actions. A review of the reports indicated the need for additional confirmation sampling to determine if contaminant concentrations met the risk-based closure requirements of R315-101. An approved sampling plan proposing collection of this additional data was implemented in September 2004. The 2004 confirmation sampling activities included collection of eight three-point composite soil samples and 11 passive soil gas samples at M-39, and collection of 41 three-point composite soil samples at M-636. The soil samples were collected from systematic grids at each site as outlined in the approved sample plan. The soil samples were analyzed for cadmium, perchlorate and silver and the soil gas samples were analyzed for volatile organics (VOCs), which were previously determined to be the only contaminants of potential concern. The soil sample results show that cadmium and silver were detected at maximum concentrations of 3.6 mg/kg and 384 mg/kg respectively at M-36 and at maximum concentrations of 5.9 mg/kg and 1,380 mg/kg respectively at M-636. Perchlorate was not detected in any of the soil samples at a detection limit of 0.1 mg/kg and VOCs were not detected in any of the soil gas samples. Though a few comments regarding the sampling are included in the enclosure, the Division concurs that the nature and extent of contamination at these sites has been adequately defined to make final decisions regarding site closure. To satisfy the requirements of R315-101, the sample results described above were evaluated with respect to risk-based Preliminary Remediation Goals (PRGs). Based on this evaluation, Thiokol proposes that M-39 qualifies for residential use or no further action (NFA) and that M-636 qualifies for industrial use. The proposed residential PRGs for cadmium and silver are 24 mg/kg and 390 mg/kg respectively, and the proposed industrial PRGs for cadmium and silver are 130 mg/kg and 5,100 mg/kg respectively. Perchlorate was not detected in any of the soil samples and did not need to be evaluated further. The residential and industrial PRGs for perchlorate are one to two orders of magnitude greater than the perchlorate detection limit. In addition, volatile organics were not detected in the soil gas samples at M-39 and are not suspected to be contaminants at M-636, and an evaluation of the future use indoor air scenario using the Johnson and Etinger or some other model was not necessary. Though a few comments have been drafted regarding the risk assessment and the need for an ecological risk assessment, the Division generally concurs that both sites meet the human health risk-based closure requirements of R315-101 as proposed. An evaluation of the potential for residual contamination in soil to impact groundwater was presented in earlier reports completed by Utah State University (USU). Though this issue was not addressed in this report, an evaluation of final sample results presented in this report and in USU reports satisfies the requirements of R315-101-3. Although it appears that the operations at M-39 and M-636 have not caused the groundwater to be contaminated with cadmium or silver, VOCs and perchlorate have been detected in monitoring wells located at these sites. This groundwater contamination is not addressed in the closure plans for these sites. The Division recommends that groundwater related issues for these sites be addressed under the Post-Closure Permit that is currently being reissued. The Division concurs that the soil gas data do not indicate a potential source of VOC contamination in soil at M-39, and soil sampling for VOCs is not recommended. A general comment regarding post-closure requirements and groundwater has been drafted. Please provide a written response to each enclosed comment and a revised document or change pages within 45 days of your receipt of this letter. If you have any questions, please contact Dave Larsen or Chris Bittner of my staff at 538-6170. Sincerely, Original Document signed by Dennis R. Downs on 9/13/05 Dennis R. Downs, Director Utah Division of Solid and Hazardous Waste DRD/DL/kk Enclosure c: Lloyd C. Berentzen, M.B.A., Health Officer, Bear River Health Department Mike Ganseski, USEPA Region VIII Utah Division of Solid and Hazardous Waste Comments Results of Post-Excavation Sampling at M-39 and M-636 ATK Thiokol General Comments: The text reports a value of 4,900 mg/kg as the industrial preliminary risk goal (PRG) for silver, but the EPA Region 9 value is 5,100 mg/kg. Please clarify. Please modify the second paragraph on page 1 and indicate that the Division recommended additional sampling to determine if the site met the requirements of R315-101, and that Thiokol agreed with this recommendation and submitted a sampling plan. Please modify the third paragraph on page 1 and indicate that this document has three purposes; 1) presenting the results of a nature and extent investigation, 2) human health and ecological risk assessment and 3) that an evaluation of the potential for migration of metals contamination from soil to groundwater was presented in the USU study. Perchlorate sampling is not acknowledged in the field notes in Appendix B, but it is noted that the data in Appendix A show that all samples were collected on the same day. Please provide copies of the chain-of-custody forms used as part of this project. The Division evaluated the data in this report and previously submitted reports with regard to the potential for residual contamination in soil to impact groundwater. Based on this evaluation, the Division believes that groundwater will not be impacted and that Thiokol has satisfied the requirements of R315-101-3 (Principle of Non-degradation). The evaluation completed by the Division is described below: The USU reports identify several uncertainties with regard to the potential for leaching of metals to groundwater at M-39 and M-636. To further evaluate these uncertainties since completing the removal action and confirmation sampling, the Division compared the recent soil sample results with the EPA Region IX default soil screening values for cadmium (8.0 mg/kg) and silver (34 mg/kg). This comparison indicates that cadmium contamination in the soil is not expected to migrate to groundwater at either site, but silver may migrate to groundwater at both sites. The average silver concentration in the soil is about 125 mg/kg at M-39 and about 325 mg/kg at M-636. Both values are greater than the EPA default value of 34 mg/kg, but less than the site-specific soil screen value of about 400 mg/kg estimated by the Division. This soil screen value was estimated using the EPA tap water PRG of 0.18 mg/L, default Dilution Attenuation Factor (DAF) of 20 and a site-specific soil-water partition co-efficient (Kd) of 110 L/kg (EPA, 1996);(0.18 mg/L x 20 (unitless) x 110 L/kg = 396 mg/kg). Please note that the Kd value used above is based on a soil pH of 8 (assumed limestone provenance and moderate alkalinity of the soil) and that some of the values used in the soil screening equation such as air porosity, water porosity and bulk density become negligible in the estimate of soil screen values for silver. Please note this estimate is site specific and may not be applicable at other sites. Please add a section titled Post-Closure Plans. This section should indicate how groundwater related issues at both sites will be addressed, and that Thiokol will produce a Land-Use Tracking Plan addressing long-term management of soil at M-636. The plan should address tracking to monitor excavation of soil at M-636 and to insure that site use remains compatible with an industrial closure. In addition, a notice on the land deed is needed to acknowledge the soil contamination and land use limitation at the M-636 site. These requirements also applied to the M-508 site, as was stated in the letter regarding the closure of HWMUs M-114 and M-508 that was sent to your office on July 25, 2003. The cover letter with this document indicates there is no ecological risk associated with this site, but no data or other information is provided in the report to support this conclusion. Please provide an ecological risk assessment for each site as required in R315-101. Please modify Section 2.2.3 and address accuracy and completeness for the soil sample results. Spike recoveries should be presented and discussed in the report. It appears that all planned samples were collected and that all sample results are usable, therefore; completeness should be close to 100%, but a project completeness value should be added to the text. Sample representativeness is adequately addressed in the text. An assessment of precision, accuracy, representativeness and completeness (PARC) for the soil gas samples should also be presented. It is noted that, although several duplicate results have relative percent differences (RPDs) exceeding analytical control limit goals, all of the duplicate sample results are less than the respective PRGs proposed for each site. Please provide additional detail regarding sample collection procedures for duplicates. REFERENCES USEPA, 1996, Soil Screening Guidance for Chemicals, http://risk.lsd.ornl.gov/calc_start.shtml and http://www.epa.gov/docs/earth1r6/6pd/rcra_c/protocol/volume_2/a_3_173.pdf September 13, 2005 Page 2 TN200500485.doc 288 North 1460 West • PO Box 144880 • Salt Lake City, UT 84114-4880 • phone (801) 538-6170 • fax (801) 538-6715 T.D.D. (801) 536-4414 • www.deq.utah.gov 1 TN200500485.doc 288 North 1460 West • PO Box 144880 • Salt Lake City, UT 84114-4880 • phone (801) 538-6170 • fax (801) 538-6715 T.D.D. (801) 536-4414 • www.deq.utah.gov State of Utah Department of Environmental Quality Dianne R. Nielson, Ph.D. Executive Director DIVISION OF SOLID AND HAZARDOUS WASTE Dennis R. Downs Director JON M. HUNTSMAN, JR. Governor GARY HERBERT Lieutenant Governor State of Utah Department of Environmental Quality Dianne R. Nielson, Ph.D. Executive Director DIVISION OF SOLID AND HAZARDOUS WASTE Dennis R. Downs Director JON M. HUNTSMAN, JR. Governor GARY HERBERT Lieutenant Governor