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Home My WebLink AboutDSHW-2024-004301215 South State Street, Suite 500 Salt Lake City, UT 84111 PH 801.853.8308 www.geosyntec.com December 21, 2023 Ms. Paige Walton, P.G. Program Manager Division of Waste Management and Radiation Control Utah Department of Environmental Quality 195 North 1950 West Salt Lake City, Utah 84114 Subject: Response to Comments - Screening Level Ecological Risk Assessment and Ecological Screening Report NGSC Promontory Facility UTD009081357 Dear Ms. Walton, On behalf of Northrop Grumman Systems Corporation (NGSC), formerly ATK Launch Systems, LLC (ATK), a wholly owned subsidiary of Northrop Grumman Corporation (Northrop Grumman), Geosyntec Consultants (Geosyntec) has prepared this letter to provide written responses to the comments provided by the Utah Department of Environmental Quality (UDEQ) Division Waste Management and Radiation Control’s (DWMRC’s) March 7, 2023 comments on the Screening Level Ecological Risk Assessment (SLERA) and Ecological Screening Report (ESR) for the NGSC Promontory, Utah Facility (Facility or Site). Project Background In December 2017, DWMRC provided comments on the 2009 Screening Level Ecological Risk Assessment (SLERA) for Groundwater. As part of NGSC’s response to these comments, a screening process was conducted for surface water and sediment and the Ecological Screening Report (ESR) was submitted to the DWMRC in 2019. In March 2023, the DWMRC provided feedback on two comments that remained unresolved from the 2009 SLERA, as well as additional comments on the 2019 ESR. Provided below are the DWMRC comments in italics, followed by our corresponding response. an updated copy of the ESR has also been provided for UDWMRC review (Attachment A). DSHW-2024-004301 Ms. Paige Walton December 21, 2023 Page 2 Outstanding DWMRC Comments on the 2009 SLERA: 1. Response to General Comment 1, Page 1: It is stated in the last sentence of the response that the groundwater model remains limited to trichloroethylene (TCE) and perchlorate because these are the only groundwater contaminants of concern (COCs) upgradient of the ponds. Issues regarding potential future COCs at the springs are addressed below in Comment #5 on the Ecological Screening Report. Response: Please see our response to Comment #5 below. 2. Response to General Comment 2, Page 2: Issues regarding the future concentrations predicted by the updated groundwater model are addressed below in Comment #6 on the Ecological Screening Report. Response: Please see our response to Comment #6 below. Division Comments on 2019 Ecological Screening Report 1. Section 1.1 - Conceptual Site Model, Page 1: The text states that the only point at which groundwater is available for contact by ecological receptors is at seeps that flow into Ponds. Please add a discussion on the potential for exposure to ecological receptors, to include native and migratory avian and mammalian receptors, at the watering troughs at Plant 3 that are supplied by groundwater pumped from well TCC3A. Response: Text has been added to Section 1.1 of the updated ESR (Attachment A) to explain why the livestock troughs at Plant 3 that are filled with groundwater from well TCC3A are not a significant exposure pathway for ecological receptors. 2. Section 1.3 - Report Objectives, Page 1: The text in the second paragraph states that while the source for chromium and lead in the springs is unknown as neither COC are present in groundwater, using the lowest available benthic invertebrate community screening levels for sediment chromium and lead concentrations exceed screening levels. How do the detected concentrations in sediment compare to background soil levels? If groundwater is not the source for chromium and lead, is it likely that the concentrations in the sediment are from surface runoff? Response: It is unlikely that the chromium and lead concentrations in the sediment are from surface runoff. See below for a brief discussion on each compound. Lead: Sediment samples from the springs were only analyzed for lead in 2018. Lead was non-detect in Shotgun Spring sediment. The sediment from Pipe Ms. Paige Walton December 21, 2023 Page 3 Spring had a lead concentration of 545 mg/kg. Given the proximity of the springs, if the source were regional runoff the springs would both be expected to experience similar sediment concentrations. Furthermore, soil samples from the Site do not show lead concentrations high enough for runoff to result in sediment concentrations of 545 mg/kg in sediment. Background lead concentrations in soil at the Site is between 0.75 and 32.5 mg/kg according to the 2000 RFI Report1. Furthermore, soil samples from the M153 sump and M16 sump, both of which are upgradient of the springs, had lead concentrations of 15.8 mg/kg and non- detect, respectively. Chromium: Chromium was measured in the spring sediments in 2008 and 2018. The detected concentrations are summarized below: Table 1. Measured Chromium Concentrations (mg/kg) Location 2008 2018 Pipe Spring <1 1,110 Shotgun Spring 12.5 286 Horse Spring 4.5 J NS FishSpring 8.21 NS As with lead, if the source to Pipe Spring and Shotgun Spring were regional runoff, the concentrations would be expected to be similar at both springs. Chromium was measured in background soil samples as part of the Soil Monitoring Plan (SMP) for NGSC Promontory OBOD2. In 2018, the highest detected chromium concentration in background soils was 17 mg/kg. Hexavalent chromium was resampled in 2020 due to analytical interference in the 2018 samples and was detected at a maximum concentration of 1.34 mg/kg in background soils3. Chromium was sampled in soils at the M-16 Sump area in 1998 and detected at a maximum concentration of 18 mg/kg. At the M153 Sump Area, chromium was detected at a maximum concentration of 52.9 mg/kg. These concentrations are 1 Thiokol Propulsion. 2000. RCRA Facility Investigation Report: Source and Contamination Characterization. 2 ATK, 2018. Soil Monitoring Plan. Promontory Hazardous Waste Storage and Subpart X Treatment Permit. April. 3 ATK, 2020. Chromium Soil Resampling Report. Promontory Hazardous Waste Storage and Subpart X Treatment Permit. December. Ms. Paige Walton December 21, 2023 Page 4 also not high enough to be the source of the chromium concentrations seen in spring sediments. Sampling of sediments in 2008 also showed multiple orders of magnitude lower chromium concentrations than were detected in 2018. This kind of extreme variation over a 10-year period with no known groundwater or upland soil source suggests that the concentrations are not related to transport from the Facility. 3. Section 2.0-Surface Water Screening Results, Page 3: In the last paragraph of this section, it is stated that based on the known ecological receptors at the springs, it is "appropriate to use ecological screening criteria that are intended to protect fish or other aquatic life that are representative of site receptors." Please add a statement that the general aquatic screening levels applied for the assessment are the most conservative screening levels and are deemed protective for all other potential ecological receptors, to include invertebrate, avian, and mammalian receptors, at the springs. Response: The surface water screening levels applied are suitable for all aquatic ecological receptors at the springs. The text in question was intended to emphasize that the screening level for trout was not used because trout are not present at the springs and are not expected to be present due to the water quality (e.g., elevated calcium, potassium, sodium, and chloride). Furthermore, birds do not typically drink enough water to receive significant exposures from surface water. The use of the springs as a drinking water source by wildlife is outside the scope of a SLERA. Specifically, it is not typical of a SLERA to evaluate exposure to higher trophic level carnivorous birds and mammals due to consumption of aquatic receptors. The text in Section 2.0 of the updated ESR (Attachment A) has been updated for further clarification. 4. Section 2.2 - Lead, Page 4: At the end of the second paragraph, it is stated that background lead concentrations at Blue Creek are 14.5 micrograms per liter (µg/L). Where in Blue Creek, in relation to the wastewater outfalls, were the background samples collected and how many samples were collected to derive the background concentration? Discuss whether there is any variation in concentrations of lead, other metals, and essential nutrient concentrations in surface water collected upstream and downstream of the ATK wastewater outfalls. Response: The lead background value of 14.5 µg/L was obtained from the 2002 Screening Level Endangerment Assessment (SLEA) prepared by Walsh Environmental Scientists and Engineers, LLC. A citation has been added to Section 2.2 of the ESR. Ms. Paige Walton December 21, 2023 Page 5 For the SLEA, four background surface water samples were collected by NGSC in 1999 at locations in Blue Creek “upstream of the facility.” Although the exact location of the samples taken for the SLEA was not specified in the report, NGSC background samples are typically collected at three locations that have been designated as Blue Creek Below Dam, Blue Creek Crossing, and Blue Creek Upper. These locations are all upstream of the two NGSC outfalls (see Figure 1). Figure 1. Blue Creek Background Surface Water Sampling Locations Comparison of medians of the collected data from Blue Creek background samples and samples from NGSC Outfall 001 from 2004 to 2013 showed that in most cases metals and nutrients are similar or higher in the background samples than at Outfall 001. Statistical testing of metals concentrations at Outfall 001 compared to the Blue Creek Upper background location (Wilcoxon rank-sum test, p<0.05) found that the following are not significantly higher at Outfall 001 than at the Blue Creek Upper background location:  Alkalinity Ms. Paige Walton December 21, 2023 Page 6  Aluminum  Cadmium  Calcium  Chloride  Copper  Hardness  Magnesium  Sodium  Sulfate  Total Organic Carbon Only potassium and barium were significantly higher below Outfall 001 than at the Blue Creek Upper background location. Based on these findings, the concentrations of metals below the outfalls are statistically similar to background conditions. This is in agreement with the 2009 SLERA conducted by Terra Mentis, which states that “the Utah Division of Solid and Hazardous Waste (UDSHW) has agreed that groundwater is of low quality due to the high levels of minerals in native soil. These constituents are also found in surface water because of groundwater discharge. The UDSHW has agreed that the high levels of metals in surface water are considered background.” A summary of this finding has been added to the updated ESR (Attachment A). 5. Section 3.0- Groundwater Modeling, Page 8: It is stated in this section that all other constituents, in addition to perchlorate and TCE "are considered background and should not impact the analysis presented here." In addition to TCE and perchlorate, the following constituents of potential concern (COPCs) were detected in well G-2 in 2018 and 2019: 1,1,1-trichloroethane (1,1,1- TCA), 1,2-dichloroethane (1,1-DCA), 1,1-dichloroethene (1,1-DCE), cis-1,2-DCE and chloroform, and the following COPCs were detected in well EW-6 in 2019 and 2021: 1,1-DCA, 1,1-DCE, cis-1,2-DCE and chloroform. Both G-2 and EW-6 are located approximately two miles upgradient from Pipe and Shotgun Springs. Discuss the fate and transport of the organics detected in these two wells and the potential for impact to the springs. Also, based on Table 1 of the Ecological Screening Report, 1,1-DCE and 1,1-DCA have been detected at very low concentrations in Pipe and Shotgun Springs. Neither chemical is related to background but rather are site related, negating the statement in the report. Please provide information to support ATK's assumption that TCE and perchlorate will be the only COPCs that impact the springs in the future. Ms. Paige Walton December 21, 2023 Page 7 Response: The sentence has been revised within the updated ESR (Attachment A) to make it clear that it is referring to inorganic constituents and naphthalene. A sentence has also been added to acknowledge that 1,1-DCE and 1,1-DCA have been detected previously but at very low concentrations. As discussed below, 1,1-DCE and 1,1-DCA are unlikely to impact the springs above the lowest ecological screening level in the future, based on groundwater modeling analyses. This has also been clarified in the text of the updated ESR (Attachment A). Analyses conducted as part of the 2023 Groundwater Model Update4 found that COC concentrations at the springs within the next 30 years are anticipated to remain below the following concentration ranges: Table 2. Modeled COC Concentration Ranges Chemical of Concern Lower Bound (µg/L) Upper Bound (µg/L) Lowest Screening Level (µg/L) 1,1,1-TCA 1 15 11 1,1-DCA 0.1 2 100 1,1-DCE 2 20 25 Cis-1,2-DCE 0.5 6 590 Chloroform 1 10 1.8 In addition, due to longer travel times and degradation, concentrations are anticipated to remain at lower levels beyond 30 years. As shown in the above table, it is possible that 1,1,1-TCA and/or chloroform could exceed the lowest ecological screening levels in the future. Since TCE concentrations are predicted to increase at Pipe Spring and Shotgun Spring based on the 2023 Groundwater Model Update, it is possible that other COCs related to TCE could also increase at the Springs. Continued monitoring of COC concentrations in the Springs through the Facility’s monitoring program will detect increases in other COCs if they occur. 4 Geosyntec Consultants, Inc. (Geosyntec). 2023. Groundwater Flow and Contaminant Transport Model Update, ATK Launch Systems – Promontory, Utah. December Ms. Paige Walton December 21, 2023 Page 8 6. Section 3.2 - Groundwater Modeling Perchlorate, Page 8: The text states that TCE concentrations in Pipe Springs are projected to increase from 11 µg/L in 2017 to 38 µg/L after 30 years and decrease from 18 µg/L in 2017 to 7 µg/L after 30 years in Shotgun Springs. In regard to perchlorate, the text states that based on the model, perchlorate concentrations are predicted to be stable over the next 30 years in both Pipe and Shotgun Springs and are not projected to exceed 500 µg/L in that time period. Based on the surface water data that has been collected at the springs since 2011, TCE concentrations in Pipe Springs have increased from an average of 6.4 µg/L in 2011/2012 to an average of 14.5 µg/L in 2021/2022 (a factor of 2.3x per 10-year period). If this trend were to continue, TCE at Pipe Springs would be approximately 176 µg/L in 2052. Perchlorate concentrations in Pipe Springs have increased from an average of 331 µg/L in 2011/2012 to an average of 661 µg/L in 2021/2022 (a factor of2x per 10-year period). If this trend were to continue, perchlorate at Pipe Springs would be approximately 5,288 µg/L in 2052. TCE concentrations in Shotgun Springs have increased from an average of 5.9 µg/L in 2011/2012 to an average of 20.0 µg/L in 2021/2022 (a factor of 3.4x per 10-year period). If this trend were to continue, TCE at Shotgun Springs would be approximately 786 µg/L in 2052. Perchlorate concentrations in Shotgun Springs have increased from an average of 56.5 µg/L in 2011/2012 to an average of 526.5 µg/L in 2021/2022 (a factor of 9.3x per 10-year period). If this trend were to continue, perchlorate at Shotgun Springs would be approximately 423,091 µg/L in 2052. While the above analyses include extrapolation of assumptions regarding source areas and plume movement, they illustrate uncertainties on the increasing TCE and perchlorate trends that have been observed at the springs, highlighting concerns that the updated model may significantly underestimate future concentrations. If the actual observed trends continue, the screening levels cited in the report would be exceeded for TCE in Pipe Spring in approximately 2042 and Shotgun Spring in approximately 2032. If the observed increasing trend for perchlorate in Shotgun Spring were to continue, the cited screening level would be exceeded by approximately 2037. Significant uncertainty exists in the modeled concentrations for the springs. If the increasing ꞏ trends that have been observed continue, the model will differ Ms. Paige Walton December 21, 2023 Page 9 significantly from measured concentrations and the future ecological risk calculated for the springs will be underestimated. While the Division acknowledges that assuming the increasing trend observed will continue for 30 years is a conservative approach, please provide additional lines of evidence supporting the future concentrations predicted by the updated groundwater model are realistic. Also, in addition to estimating the future ecological risk at the springs based on the concentrations predicted by the model, the future risk should also be estimated based on concentrations that are consistent with the observed increasing trend. Future concentrations could be estimated through trend analyses and by fitting a curve to the concentrations that have been detected to date. Response: For TCE, the following text has been added to the report in place of the previous model results: “Under modeling Scenario 1 (conservative scenario), the predicted concentration of TCE in Pipe Spring and Shotgun Spring after 30 years is 320 μg/L. Under Scenario 2 (sensitivity analysis scenario), the predicted concentration of TCE is 107 μg/L. Both of these values exceed the selected ecological screening level of 47 μg/L. Based on the model results, TCE may exceed the ecological screening level at Pipe Spring and/or Shotgun Spring in the future.” For perchlorate, the following text has been added to the report in place of the previous model results in Section 3.2: “Under modeling Scenario 1 (conservative scenario), the predicted concentration of perchlorate in Pipe Spring and Shotgun Spring after 30 years is 10,427 μg/L. Under modeling Scenario 2 (sensitivity analysis scenario), the predicted concentration of perchlorate is 951 μg/L. The conservative scenario prediction exceeds the selected ecological screening level by a factor of 1.1 and the sensitivity analysis scenario does not exceed the selected ecological screening level. Based on the model results, perchlorate is not likely to impact Pipe or Shotgun Spring at levels above the lowest chronic screening level.” 7. Section 4 - Sediment Screening Results, Page 9: Please refer to Ecological Screening Report Comment #2. The text states that while the source for chromium and lead in the springs is unknown as neither COC are present in groundwater, using the lowest available benthic invertebrate community screening levels for sediment, chromium and lead concentrations exceed screening levels. How do the detected concentrations in sediment compare to background soil levels? If groundwater is not Ms. Paige Walton December 21, 2023 Page 10 the source for chromium and lead, is it likely that the concentrations in the sediment are from runoff of soil? Response: Please see our response to Comment #2 above. 8. Section 5 - Conclusions, Page 10: Please address the uncertainty in the risk assessment associated with potential future concentrations of TCE and perchlorate at the springs and the potential for other constituents to impact the springs in the future. Response: Please see our responses to Comments #5 and #6 above. Closing We appreciate your review of the provided responses to the UDWMRCs comments. If you have any questions or would like additional information, please contact us at 801- 618-0483. Additionally, Mr. Tim Jimenez of NGSC can be reached at 801-251-2142. Sincerely, Brian Smith, P.G. Senior Geologist Brent C. Robinson, P.E. Senior Principal cc: Kris Blauer (NGSC) Tim Jimenez, P.E. (NGSC) Blair Palmer (NGSC) Caitlin Johnson, Ph.D. (Geosyntec) Attachments Attachment A – Updated Ecological Screening Report ATTACHMENT A UPDATED ECOLOGICAL SCREENING REPORT (Provided Electronically) ECOLOGICAL SCREENING REPORT PROMONTORY, UTAH FACILITY Prepared for Northrop Grumman Systems Corporation P.O. Box 707 Brigham City, Utah 84302-0707 Prepared by Geosyntec Consultants, Inc. 215 South State Street, Suite 500 Salt Lake City, UT 84111 Project Number: DE0188C December 2023 Ecological Screening Report Promontory, Utah Facility Prepared for Northrop Grumman Systems Corporation P.O. Box 707 Brigham City, Utah 84302-0707 Prepared by Geosyntec Consultants, Inc. 215 South State Street, Suite 500 Salt Lake City, UT 84111 Jeanmarie Zodrow, Ph.D., IBERAD Caitlin Johnson, Ph.D. Senior Risk Assessor Risk Assessor Brent C. Robinson, PE (UT) Brian Smith, PG (UT) Senior Principal Senior Geologist Project Number: DE0188C December 21, 2023 Ecological Screening Report Northrop Grumman Systems Corporation - Promontory Facility Promontory, Utah eco screening report_december 2023 rtc_final.docx ii December 21, 2023 TABLE OF CONTENTS 1. INTRODUCTION ....................................................................................................................1 1.1 Conceptual Site Model ....................................................................................................1 1.2 Data Collected .................................................................................................................1 1.3 Report Objectives ............................................................................................................2 2. SURFACE WATER SCREENING RESULTS .......................................................................3 2.1 Arsenic Sampling ............................................................................................................4 2.1.1 Arsenic Sampling: May 2018 ..............................................................................4 2.2 Lead .................................................................................................................................4 2.2.1 Lead Sampling: May 2018 ..................................................................................5 2.3 Barium .............................................................................................................................5 2.4 Naphthalene .....................................................................................................................5 2.5 Trichloroethene ...............................................................................................................6 2.5.1 Site-specific TCE Screening Level .....................................................................6 2.6 Essential Nutrients: Calcium, Potassium, Sodium and Chloride ....................................7 3. GROUNDWATER MODELING .............................................................................................8 3.1 Trichloroethene ...............................................................................................................8 3.2 Pipe SpringShotgun SpringPerchlorate ...........................................................................9 4. SEDIMENT SCREENING RESULTS ..................................................................................10 5. CONCLUSIONS ....................................................................................................................11 6. REFERENCES .......................................................................................................................12 LIST OF TABLES Table 1: Spring Water Screening Results Table 2: Spring Water Screening Results: May 2018 Table 3: Sediment Screening Results Ecological Screening Report Northrop Grumman Systems Corporation - Promontory Facility Promontory, Utah eco screening report_december 2023 rtc_final.docx iii December 21, 2023 ACRONYMS AND ABBREVIATIONS µg/L micrograms per liter bgs below ground surface CaCO3 calcium carbonate COC chemicals of concern COPEC chemicals of potential ecological concern DWMRC Division of Waste Management and Radiation Control LANL Los Alamos National Laboratory MDL method detection limit ND non-detect NOAA National Oceanic and Atmospheric Administration PAH polynuclear aromatic hydrocarbon RL reporting limit SLERA Screening Level Ecological Risk Assessment SQuiRTs Screening Quick Reference Tables TCE trichloroethene TDS total dissolved solids Ecological Screening Report Northrop Grumman Systems Corporation - Promontory Facility Promontory, Utah eco screening report_december 2023 rtc_final.docx 1 December 21, 2023 1. INTRODUCTION This Ecological Screening Report (ESR) was prepared by Geosyntec Consultants (Geosyntec) on behalf of Northrop Grumman Systems Corporation (NGSC), formerly ATK Launch Systems, LLC (ATK), a wholly owned subsidiary of Northrop Grumman Corporation (Northrop Grumman), in response to the Utah Department of Environmental Quality (UDEQ) Division of Waste Management and Radiation Control (DWMRC, or “the Division”) comments on the 2009 Screening Level Ecological Risk Assessment (SLERA) for Groundwater at the ATK, Promontory Facility (Facility or Site) (Terra Mentis, 2009) dated Marcy 7, 2023. The previous SLERA focused only on trichloroethene (TCE) and perchlorate as chemicals of concern (COCs). The Division questioned how these two COCs were selected, or more importantly, why other chemicals were eliminated from consideration. In response, this document evaluates all of the chemicals detected, at any time, in Pipe Spring and Shotgun Spring and screens the data against available United States Environmental Protection Agency (EPA) established and/or literature-derived screening levels for the protection of aquatic life. This document is intended to be viewed alongside the 2009 SLERA as an addendum to, and not necessarily a replacement of, the work conducted therein. 1.1 Conceptual Site Model The 2009 SLERA provides Facility, groundwater flow and groundwater quality background information and a Conceptual Site Model (CSM). The CSM demonstrates that ecological receptors primarily come in contact with groundwater at seeps that flow into ponds at the southeastern end of the Facility. The four ponds fed from groundwater seeps are Shotgun Spring, Pipe Spring, Fish Spring, and Horse Spring. The ponds are located next to and down gradient of Utah State Route 83, which may contribute road run-off. Blue Creek is a nearby creek that runs along the western edge of the Facility, but that does not impact the springs directly. Blue Creek is a losing stream and is not impacted by groundwater, so it was not evaluated in the 2009 SLERA or this ESR; however, data from upstream portions of Blue Creek are used to understand potential background concentrations of naturally-occurring metals at the ponds. Groundwater from well TCC-3A is also a potential exposure point for ecological receptors as it is used to fill a livestock watering trough at Plant 3. However, this is not expected to be a significant source of exposure for wildlife receptors for the following reasons: (1) wildlife are much more likely to seek water at the natural water sources of the springs, rather than a livestock trough; (2) drinking water is a very small fraction of the exposure for most wildlife, especially for mammals; and (3) the water from well TCC-3A is treated using a carbon filter prior to filling the trough. 1.2 Data Collected Environmental surface water and sediment samples collected from the Promontory area between 2004 and June 2017 are included in this screening process, along with additional surface water Ecological Screening Report Northrop Grumman Systems Corporation - Promontory Facility Promontory, Utah eco screening report_december 2023 rtc_final.docx 2 December 21, 2023 samples collected in May 2018 that were analyzed for metals using a method with lower detection limits than those provided in the historical dataset. The dataset for this ESR includes a significant amount of surface water data that were collected between 2009 and 2017. Therefore, the screening process includes a larger suite of chemicals than the 2009 SLERA to identify chemicals of potential ecological concern (COPEC) from the detected chemicals and to determine whether further evaluation is warranted. 1.3 Report Objectives In addition to presenting the results of the revised ecological risk screen, the report also responds to the Division’s 2017 and 2023 comments. The information and screening evaluation presented herein, and the associated data tables demonstrate that no adverse ecological risks are anticipated based on aquatic life exposure to surface water. The screening level evaluation of the sediment data indicated that potential adverse effects to the benthic invertebrate community from chromium and lead could not be excluded. However, these metals are not present at high concentrations in groundwater and a source of these metals has yet to be determined. Additionally, the first-round data screening evaluation, using the lowest available benthic invertebrate community screening levels for sediment, indicated chromium and lead concentrations exceed screening levels. These screening levels are generally based on highly conservative assumptions and represent a level at which no ecological harm is expected to aquatic life. The content and organization of the remainder of this document are as follows: • Section 2: Surface Water Screening Results; • Section 3: Groundwater Model; • Section 4: Sediment Screening Results; • Section 5: Conclusions; • Section 6: References. Ecological Screening Report Northrop Grumman Systems Corporation - Promontory Facility Promontory, Utah eco screening report_december 2023 rtc_final.docx 3 December 21, 2023 2. SURFACE WATER SCREENING RESULTS The maximum spring water concentrations throughout the 13-year sampling period (2004 to 2017) were compared with the lowest applicable ecological screening levels presented in Tables 1 and 2. The method detection limits (MDLs) in the 2004 to 2017 data for some metals were not adequate to meet the selected screening levels; therefore, in May 2018 additional surface water samples were analyzed for metals using methods with lower detection limits than those historically reported. These data were also included in the screening process (Table 2). If a screening level was exceeded, the chemical was re-evaluated considering site-specific background values and site- specific conditions and receptors. As shown in Table 1, the following chemicals exceeded the screening levels in surface water: • Metals: Arsenic and lead, • Volatile organic compounds (VOCs): TCE • Polynuclear aromatic hydrocarbons (PAHs): naphthalene • Essential nutrients/ions: calcium, potassium, sodium and chloride Since the initial screening step is a preliminary and conservative approach, the screening level does not take into consideration site-specific background concentrations or site-specific receptors or conditions. When these factors are considered, surface water metals and ion concentrations are consistent with Blue Creek (regional background). Furthermore, the naphthalene is not present in groundwater and is likely from road run-off. These are discussed further below. Metals and inorganic constituents are naturally elevated in Blue Creek (regional background), as detailed in the 2009 SLERA, and Site surface water concentrations of these compounds reflect regional background rather than Site effects (Terra Mentis Environmental Consulting 2009). The lowest ecological screening levels, which were used for preliminary screening, may not be applicable to the Site ecology. The ponds at Promontory contain aquatic life such as benthic invertebrates, as well as small fish (including speckled dace and mosquito fish and the Utah chub (BIO-WEST 2008)) which are considered unwelcome and nuisance species, that compete with trout species for food and habitat in waters where they co-exist (Fuller and Nico 2018). It is appropriate to use ecological screening criteria that are intended to protect fish or other aquatic life that are representative of Site receptors, rather than generic receptors such as trout, which are not present at the ponds. Generic screening levels may also be below natural site-specific background concentrations, therefore comparison to background may indicate that concentrations represent naturally occurring conditions rather than Site-related impacts. Each case in which a site- specific screening criterion was chosen and/or background concentrations were considered is discussed in more detail in the following sections. Ecological Screening Report Northrop Grumman Systems Corporation - Promontory Facility Promontory, Utah eco screening report_december 2023 rtc_final.docx 4 December 21, 2023 Surface water screening levels were not applied for wildlife drinking water exposures or for exposure to higher trophic level carnivorous birds and mammals due to consumption of aquatic receptors, as this is outside the scope of a SLERA. 2.1 Arsenic Sampling Prior to 2018, all arsenic data were collected between 2007 and 2010. In November 2008, 26 surface water data points were collected ranging in concentration from non- detect (ND) (<100 micrograms per liter (µg/L)) to a detected concentration as high as 741 µg/L. A review of the 2008 data revealed anomalous elevated results that are over 7 times higher when compared with the years prior and subsequent to 2008. This anomaly was brought to the attention of the laboratory, who reviewed the data and documented a problem with the instrumentation at that time. The laboratory found a loss of sensitivity for the primary arsenic wavelength and they implemented a dual wavelength technique late in 2008. Arsenic concentrations returned to historic levels after the correction to the instrumentation. Therefore, the arsenic data from 2008 have been rejected by the laboratory and removed from the dataset used for ecological screening. The remaining data points are all ND at a method detection limit (MDL) of either 100 µg/L or 1,000 µg/L, the latter of which was the reporting limit in June 2009 due to sample dilutions that were associated with analyzing high total dissolved solids (TDS) concentrations. The lowest selected ecological screening level for arsenic is 148 µg/L from US EPA Region 5 (EPA, 2003). The MDL for the June 2009 results (1,000 µg/L) is not adequate to demonstrate concentrations lower than the screening level. However, the results for the other years in the dataset have an MDL of 100 µg/L, which is below the screening level of 148 µg/L. Since the June 2009 results are bracketed by lower detection limits, there is no reason to suggest that the arsenic concentrations exceeded 100 µg/L. 2.1.1 Arsenic Sampling: May 2018 In the spring of 2018, NGSC conducted one round of sampling from the ponds using EPA Method 200.7 for arsenic to achieve lower detection limits (of 50 µg/L). The historic detection limit of 100 µg/L is four times higher than detected arsenic concentrations measured in Blue Creek (approximately 25 µg/L), which are considered to be a good estimate of background arsenic in surface water. The additional round of sampling was conducted in May 2018, and the results are presented in Table 2. The May 2018 arsenic results at Pipe Spring and Shotgun Spring are 5.4 and 6.9 µg/L, respectively, which are well below the selected screening value of 148 µg/L. Therefore, the screening criteria was met for arsenic, and arsenic does not pose a risk to ecological receptors in surface water at the ponds. 2.2 Lead Concentrations of lead measured in surface water at the Site prior to 2018 are limited to four results in 2007 and two results in 2010. There are three low-level detections in 2007 at Shotgun Spring, Fish Spring and Horse Spring ponds at concentrations of 23 to 24 µg/L (“J” coded to indicate Ecological Screening Report Northrop Grumman Systems Corporation - Promontory Facility Promontory, Utah eco screening report_december 2023 rtc_final.docx 5 December 21, 2023 estimated values) followed by two non-detect values at Pipe Spring and Shotgun Spring (MDL of 20 µg/L) in 2010. The lead screening level was adjusted to account for water hardness and background concentrations in surface water were also considered. The lowest selected ecological screening level of 1 µg/L is based on aquatic community organisms at a standard hardness value of 100 mg/L because hardness affects lead toxicity. Due to the water quality, hardness is elevated at Blue Creek and the ponds, and as hardness increases, lead toxicity decreases. As described in EPA National Water Quality Criteria documents (EPA, 1986), screening levels for lead should be adjusted for site-specific hardness. Applying a hardness value of 400 mg/L as calcium carbonate (CaCO3) (the maximum hardness allowed in the equation), the screening level for hardness was adjusted to 10.9 µg/L. The actual hardness (as CaCO3) in Shotgun Spring is higher than 400 mg/L at 765 mg/L (Table 1), but site-specific lead screening levels at that hardness cannot be calculated. Hardness in Blue Creek is similar to Shotgun Spring and ranges from 450 to 900 mg/L (USGS, 1972). Median background lead concentrations at Blue Creek were found to be 14.5 µg/L in the 2002 Screening Level Endangerment Assessment (SLEA) (Walsh Environmental Scientists and Engineers, LLC [Walsh] 2002). Therefore, surface water lead concentrations in the sampled ponds are consistent with background. Like arsenic, the laboratory analyzed one round of lead samples (both filtered and unfiltered) under EPA Method 200.8 in May 2018 to achieve lower detection limits. The results of that analysis are discussed below. 2.2.1 Lead Sampling: May 2018 In May 2018, sampling was conducted at Pipe Spring and Shotgun Spring ponds and samples were analyzed using lower detection limits for lead (Table 2). The concentrations of lead in surface water were below the detection limit of 0.5 µg/L in both Pipe Spring and Shotgun Spring, well below the hardness-adjusted screening value of 10.9 µg/L. Therefore, the screening criteria are met for lead, and it is not a risk to surface water receptors at the ponds. 2.3 Barium Surface water data for barium were collected between 2007 and 2010. There are 26 results ranging in concentration from 49 to 85 µg/L. The lowest selected ecological screening level of 3.9 µg/L is based on aquatic community organisms and originates from the Los Alamos National Laboratory (LANL) EcoRisk database. The median background barium concentration in Blue Creek is 117 µg/L (Walsh 2002). Based on this, barium concentrations are consistent with/below background. Therefore, barium is not considered a COPEC for surface water. 2.4 Naphthalene The naphthalene data spans twelve years with mostly non-detect results (MDL of 4 µg/L). Naphthalene was detected in 2016 in Shotgun Spring and Pipe Spring ponds at concentrations Ecological Screening Report Northrop Grumman Systems Corporation - Promontory Facility Promontory, Utah eco screening report_december 2023 rtc_final.docx 6 December 21, 2023 ranging from 4 – 5.9 µg/L. Subsequent samples in 2017 were non-detects. The naphthalene data for upgradient groundwater wells J-5 and J-6 are all non-detects (< 4 µg/L), indicating that naphthalene does not originate from groundwater. Instead, the low-level detections in the ponds in 2016 may be related to surface water runoff from the road that is nearby and at a higher elevation than both Shotgun Spring and Pipe Spring. Naphthalene is a common chemical associated with vehicle exhaust, road surfaces, and other anthropogenic activities and is often found in road and parking lot run-off. The lowest selected ecological screening level is 1.1 µg/L and it originates from the LANL EcoRisk database and is based on aquatic community organisms. Although the detected concentrations in 2016 exceed the screening level, because of the sporadic low-level nature of the detections naphthalene is not considered a COPEC for surface water. 2.5 Trichloroethene The TCE surface water data was collected from 2004 to 2017. For the selected ponds, there are 100 data points, and 66 detections, ranging in concentration from 0.8 to 25 µg/L. The maximum detected value of 25 µg/L was reported from a June 2016 sample from Shotgun Spring. The most recent TCE concentration in Shotgun Spring is 18 µg/L from October 2017. TCE concentrations at other ponds are lower. 2.5.1 Site-specific TCE Screening Level The lowest screening level for TCE is 21 µg/L. It originates from the LANL EcoRisk database and the National Oceanic and Atmospheric Administration (NOAA) Screening Quick Reference Tables (SQuiRTs) and is based on the Canada brook trout (Salbelinus fontinalis). There are no trout species in the surface water ponds because the natural water quality conditions (including high TDS) are not suitable for their survival. The next lowest screening level is 47 µg/L, which is from EPA Region 5 (EPA, 2003) and is based on the flagfish (Jordanella floridae). There are no flagfish in the ponds, but this is a more suitable, site-specific screening level because it is based on a non-game fish that is more similar to the species observed in the ponds (speckled dace, mosquito fish, and Utah chub). Historic concentrations at all four ponds are below the flagfish screening level of 47 µg/L. In addition, comparing the historic TCE concentrations to the lowest screening level for Canada brook trout of 21 µg/L, only two samples with concentrations up to 25 µg/L at Shotgun Spring have exceeded that value. TCE concentrations at Pipe Spring range from 2.8 to 10.5 µg/L. Detected concentrations at Horse Springs range from 0.8 to 4.8 µg/L between 2004 and 2010, followed by non-detects (<10 µg/L) from 2011 to 2016. Concentrations at Fish Springs are mostly ND (< 10 µg/L) with one detection at 1.8 µg/L in 2006. Based on the use of the site-specific screening level, current TCE concentrations in the ponds do not pose an ecological risk to the site’s aquatic wildlife. Ecological Screening Report Northrop Grumman Systems Corporation - Promontory Facility Promontory, Utah eco screening report_december 2023 rtc_final.docx 7 December 21, 2023 2.6 Essential Nutrients: Calcium, Potassium, Sodium and Chloride The essential nutrients/ions that exceed screening levels at the ponds are related to the high dissolved solids water chemistry that is characteristic of the Great Salt Lake region and therefore are not likely to pose an unacceptable risk to aquatic receptors. • Calcium – The maximum calcium concentration in the ponds (186,000 µg/L) is slightly greater than the range of concentrations found in Blue Creek (68,600 to 173,000 µg/L). Additionally, the maximum concentration exceeds the screening level by less than a factor of two. • Sodium – The maximum sodium concentration in the ponds (2,500,000 µg/L) falls within the range of concentrations found in Blue Creek (2,180,000 to 49,565,000 µg/L). • Potassium – The maximum potassium concentration in the ponds (67,700) falls within the range of concentrations found in Blue Creek (31,100 to 73,100 µg/L). • Chloride – The maximum chloride concentration in the ponds (4,130,000 µg/L) is only slightly above the range reported for Blue Creek (1,300,000 to 3,700,000 µg/L) (USGS, 1972). Chloride is known to be a principal component of dissolved solids. Therefore, the chloride in the ponds and Blue Creek are likely related to elevated TDS in that area. • Sulfate – There is no screening level for sulfate; however, a site-specific standard was developed by the Utah Division of Water Quality (UDWQ) for Quitchupah Creek using sulfur toxicology data for cattle (although cattle are generally not included as ecological risk receptors, this is the best available comparison value). The acceptable maximum concentration of sulfate in water was estimated as 2,000 mg/L (UDWQ, 2009). The maximum concentration in the ponds is 195 mg/L, which is well below the Quitchupah Creek standard and also below the range reported for Blue Creek (350 to 700 mg/L) (USGS, 1972). • Alkalinity – The alkalinity is considered to be typical to the water chemistry of the Great Salt Lake region. • Total Dissolved Solids – There is no screening level for TDS, however a site-specific standard was developed for Blue Creek, the reservoir and tributaries. The daily maximum for March through October is 4,900 mg/L and for November through February is 6,300 mg/L (UDWQ, 2013). The maximum for the ponds is approximately 7,000 mg/L; slightly exceeding the winter maximum and the range of concentrations reported for Blue Creek Upper (UDWQ, 2013). Ecological Screening Report Northrop Grumman Systems Corporation - Promontory Facility Promontory, Utah eco screening report_december 2023 rtc_final.docx 8 December 21, 2023 3. GROUNDWATER MODELING The current ecological screening is for baseline conditions at Pipe Spring and Shotgun Spring. To understand future potential chemical concentrations, a groundwater model was developed to predict concentration trends at Pipe Spring and Shotgun Spring for TCE and perchlorate. The groundwater model was developed by EarthFax in 2008. This model was updated in 2018, and again by Geosyntec in 2023. The 2023 updated model is currently under review by the DWMRC (Geosyntec, 2023). The model estimates future concentrations of TCE and perchlorate at the springs are presented below in Sections 3.1 and 3.2, respectively. The inorganic constituents and naphthalene discussed above are considered background and therefore are not expected to change over time. Two other VOCs, (1,1-DCE and 1,1-DCA) have been detected at concentrations below ecologic screening levels in the ponds. The 2023 Groundwater Model Update (Geosyntec, 2023) found that neither of these VOCs is likely to increase above their respective ecological screening levels in the future. The hydrostratigraphy encountered in the vicinity of the Site is complex and includes several features that control groundwater flow, such as unconsolidated alluvium, confining units, unfractured bedrock, and fractured bedrock with highly interconnected fracture networks that can act as both conduits and barriers for groundwater flow. To account for this highly complex geology, two model scenarios were used to predict concentrations at the springs: • Scenario 1 is a conservative scenario for future conditions and is expected to provide an upper bound for the simulated concentrations. In this scenario, the perchlorate and TCE source terms are kept constant for 30 years at the values used for model calibration. • Scenario 2 is a sensitivity analysis scenario that accounts for the potential for higher dilution within the fracture zones. In this scenario, the perchlorate and TCE specified concentrations are decreased to be equal to the estimated long-term source concentrations in the fracture zones that would result in observed concentrations at Pipe Spring and Shotgun Spring. 3.1 Trichloroethene Under modeling Scenario 1 (conservative scenario), the predicted concentration of TCE in Pipe Spring and Shotgun Spring after 30 years is 320 μg/L. Under Scenario 2 (sensitivity analysis scenario), the predicted concentration of TCE is 107 μg/L. Both of these values exceed the selected ecological screening level of 47 μg/L. Based on the model results, TCE may exceed the ecological screening level at Pipe Spring and/or Shotgun Spring in the future. TCE, which may present an unacceptable risk to ecological receptors in surface water in the future based on this initial screening process, will continue to be monitored in surface water and groundwater. There is no current unacceptable risk to ecological receptors from either Pipe Spring or Shotgun Spring, and the planned continued monitoring of the Springs will detect if and when concentrations exceed risk-based thresholds. Ecological Screening Report Northrop Grumman Systems Corporation - Promontory Facility Promontory, Utah eco screening report_december 2023 rtc_final.docx 9 December 21, 2023 3.2 Perchlorate Perchlorate was evaluated in the 2009 SLERA using a chronic water criterion value of 9,300 µg/L (Dean, 2004), which is still the lowest selected ecological screening level for surface water. This value is a literature-derived toxicity threshold. The Dean study included both acute and chronic toxicity tests on a variety of freshwater aquatic species, including fish (bluegill, fathead minnow and rainbow trout), amphibians (green frog), and invertebrates (crustacean, oligochaete, clam and midge). The chronic value selected is a calculated estimate of the concentration of perchlorate such that 95% of the genera tested will not experience adverse effects at concentrations below 9,300 µg/L (Dean, 2004), meaning that 9,300 µg/L is a conservative and protective value. A review of the available ecological screening level databases provided in Table 1 revealed that most of the sources do not provide a screening value for perchlorate. Only one other value was identified as part of the current screening, and it was higher than the Dean threshold value at 35,000 µg/L. It originates from the LANL Ecorisk database and is not based on an aquatic community and is therefore not applicable. The maximum detected perchlorate concentration of 694 µg/L was reported in Pipe Spring in 2015. Under modeling Scenario 1 (conservative scenario), the predicted concentration of perchlorate in Pipe Spring and Shotgun Spring after 30 years is 10,427 μg/L. Under modeling Scenario 2 (sensitivity analysis scenario), the predicted concentration of perchlorate is 951 μg/L. The conservative scenario prediction exceeds the selected ecological screening level by a factor of 1.1 and the sensitivity analysis scenario does not exceed the selected ecological screening level. Based on the model results, perchlorate is not likely to impact Pipe or Shotgun Spring at levels above the lowest chronic screening level. Perchlorate will continue to be monitored in surface water and groundwater, but it does not present an unacceptable risk to ecological receptors in surface water, based on this initial screening process. Ecological Screening Report Northrop Grumman Systems Corporation - Promontory Facility Promontory, Utah eco screening report_december 2023 rtc_final.docx 10 December 21, 2023 4. SEDIMENT SCREENING RESULTS Sediment samples were collected from Shotgun and Pipe Spring in 2008 and 2018. Metals and perchlorate data are summarized in Table 3. Sediment chemical concentrations are below screening levels for all analytes except chromium and lead. The 2018 chromium concentrations in Pipe Spring and Shotgun Spring are 1,110,000 and 286,000 µg/kg, respectively, which exceed the screening level of 37,300 µg/kg. The 2018 lead concentration in Pipe Spring is 545,000 µg/kg which exceeds the screening level of 35,000 µg/kg. Lead was not detected (< 2,000 µg/kg) in Shotgun Spring. While the sediment samples contain elevated chromium and lead concentrations, a source for the contamination has not been identified. The two groundwater wells upgradient of Pipe Spring and Shotgun Spring (wells J-5 and J-6) do not contain concentrations of these metals at levels to warrant the elevated concentrations observed in the sediment spring samples. In well J-6, chromium is detected but at concentrations ranging from 16 µg/L to 87 µg/L. In well J-5, chromium was detected in one sample at 17 µg/L but was J flagged. There were no detections of lead in either wells J-5 or J-6. Furthermore, neither lead nor chromium are COPECs for surface water. Based on this, it seems unlikely that the elevated chromium and lead sediment concentrations are originating from NGSC. Ecological Screening Report Northrop Grumman Systems Corporation - Promontory Facility Promontory, Utah eco screening report_december 2023 rtc_final.docx 11 December 21, 2023 5. CONCLUSIONS For arsenic and lead in surface water, the historic detection limits were insufficient to meet the screening levels, and an additional sampling event was conducted in May 2018 to obtain data with detection limits that are adequate for comparison to the selected ecological screening levels. Results from this sampling event confirmed that arsenic and lead are below the selected ecological screening levels in surface water. Barium is present at concentrations below surface water background and should not be carried forward as a COPEC. For naphthalene, there are no upgradient detected concentrations in the two closest wells, and therefore groundwater source is not considered a source. The few low-level exceedances of the naphthalene screening level in Pipe Spring and Shotgun Spring ponds are likely due to runoff from the road; therefore, naphthalene is not considered a COPEC. TCE is Site related and some concentrations of TCE in surface water exceeded the lowest selected non-site-specific ecological screening level. However, all TCE concentrations are well below the selected site-specific ecological screening level. These data demonstrate that the analytes of interest are currently below either the relevant screening value or background concentrations and are considered to meet the screening criteria, as follows: • Current arsenic concentrations are below the relevant screening value. • Current lead concentrations are below both the hardness-adjusted screening level and the background value. • Naphthalene was detected in surface water, but it is likely due to run-off from the adjacent road. • All TCE results are well below the site-specific value based on flagfish, a non-game fish. • The four essential nutrients are related to the water chemistry that is typical in the Great Salt Lake region, are typically within the same concentration ranges as Blue Creek and are not expected to pose ecological risks based on site-specific standards. • Perchlorate concentrations do not exceed the lowest screening level available. All chemicals in surface water at the ponds pass the ecological screening, and no further evaluation is necessary at this time. However, further evaluation of TCE may be necessary if it exceeds the screening value in the future based on the predicted concentrations from the 2023 Groundwater Model Update. The maximum detected concentrations in sediment are below their corresponding screening levels, with the exception of chromium and lead. There is no evident source of chromium or lead contamination upgradient of Pipe Spring and Shotgun Spring. Additional sediment and pore water samples may help assess the presence and bioavailability of metals in sediments for Pipe Spring and Shotgun Spring. Ecological Screening Report Northrop Grumman Systems Corporation - Promontory Facility Promontory, Utah eco screening report_december 2023 rtc_final.docx 12 December 21, 2023 6. REFERENCES BIO-WEST 2008. Aquatic Species Inventory of Shotgun, Pipe, Fish, and Horseshoe Springs near Promontory, Utah. December. Dean et al, 2004. Development of freshwater water-quality criteria for perchlorate. Environmental Toxicology and Chemistry. 23(6): 1441-1451. EarthFax 2018. Updated Groundwater Flow and Contaminant Transport Model of the ATK Promontory, Utah Facility. July. EPA 1986. Quality Criteria for Water. Office of Water Regulations and Standards. EPA 440/5-86- 001. Washington, DC. May Geosyntec Consultants, Inc. (Geosyntec). 2023. Groundwater Flow and Contaminant Transport Model Update, ATK Launch Systems – Promontory, Utah. December Pam Fuller, and Leo Nico, 2018, Gila atraria (Girard, 1856): U.S. Geological Survey, Nonindigenous Aquatic Species Database, Gainesville, FL, https://nas.er.usgs.gov/queries/FactSheet.aspx?speciesID=531, Revision Date: 8/5/2004, Peer Review Date: 4/1/2016, Access Date: 11/28/2018 Terra Mentis Environmental Consultants, 2009. Screening Level Ecological Risk Assessment (SLERA) for Groundwater at the ATK, Promontory Facility. September. UDWQ, 2013. Proposed Site-Specific Standard for Total Dissolved Solids Blue Creek, Box Elder County, Utah. Utah Division of Water Quality. September Draft. USGS, 1972. Hydrologic Reconnaissance of the Blue Creek Valley Area, Box Elder County, Utah. Prepared by the U.S. Geologic Survey in cooperation with the Utah Department of Natural Resources Division of Water Rights. Walsh Environmental Scientists and Engineers, LLC. 2002. Final Screening Level Endangerment Assessment, Thiokol Propulsion, Northern Utah. WALSH Project Number 4866-040. May. eco screening report_december 2023 rtc_final.docx i December 21, 2023 TABLES Table 1: Spring Water Screening Results Northrop Grumman Systems Corporation - Promontory Facility Promontory, UT Chemicals Maximum Pond Surface Water Concentration (µg/L) Background Water Quality Values for Blue Creek (Median Value from Walsh, 2002) [1] (µg/L) Lowest Surface Water Screening Level (µg/L) Selected Screening Value: Lowest Screening Level or Background (whichever is highest) (µg/L) Exceeds SL or Background (which ever is highest)? Metals Arsenic <1,000 25 148 148 Yes - see Table 2 Barium 85.2 117 3.9 117 No Beryllium ----0.66 0.66 -- Cobalt ----3 3 -- Chromium 11 2.5 11 11 No Chromium, hexavalent ----11 11 -- Lead 24 14.5 1 14.5 Yes - see Table 2 Magnesium 72,900 --82,000 82,000 No Manganese 6.62 --80 80 No Molybdenum 3.2 --34 34 No VOCs Acetone 15.7 --1,500 1,500 No Bromomethane 2.7 --16 16 No Chlorobenzene 0.4 --25 25 No 1,1-dichloroethane 1.2 --47 47 No 1,1-dichloroethene 1.2 --25 25 No Methylene chloride 4.6 --210 210 No Trichloroethene 25.2 --21 47 No Initial Screening Results Table 1: Spring Water Screening Results Northrop Grumman Systems Corporation - Promontory Facility Promontory, UT Chemicals Maximum Pond Surface Water Concentration (µg/L) Background Water Quality Values for Blue Creek (Median Value from Walsh, 2002) [1] (µg/L) Lowest Surface Water Screening Level (µg/L) Selected Screening Value: Lowest Screening Level or Background (whichever is highest) (µg/L) Exceeds SL or Background (which ever is highest)? Initial Screening Results PAHs Naphthalene 5.9 --1.1 1.1 Yes Other Compounds Bicarbonate 251,000 ------no SL Bromide 4,110 ------no SL Calcium 186,000 --116,000 116,000 Yes Chloride 4,130,000 --230 230 Yes Perchlorate6 694 --9,300 9,300 n Potassium 67,700 --53,000 53,000 Yes Sodium 2,500,000 --680,000 680,000 Yes Sulfate 195,000 350,000-700,000 ----no SL General Chemistry Alkalinity 251,000 --20,000 20,000 Yes Conductivity7 12400 ------no SL Hardness (as CaCO3)8 765 450 - 900 [9]--no SL Total Dissolved Solids 7,170,000 2,260,000 - 6,270,000 --0 Yes Table 1: Spring Water Screening Results Northrop Grumman Systems Corporation - Promontory Facility Promontory, UT Chemicals Metals Arsenic Barium Beryllium Cobalt Chromium Chromium, hexavalent Lead Magnesium Manganese Molybdenum VOCs Acetone Bromomethane Chlorobenzene 1,1-dichloroethane 1,1-dichloroethene Methylene chloride Trichloroethene Region 4 Eco SL 2017: Surface Water [2] (µg/L) Region 5 Eco SL 2003: Water (µg/L) SQuiRTs: Freshwater (acute) (µg/L) SQuiRTs: Freshwater (chronic) (µg/L) Adjusted for Hardness of 400 mg/L as CaCO3 National Recommended Water Quality Criteria- Aquatic Life Criteria Table [3] (µg/L) LANL EcoRisk Database Minimum Screening Level [4] (µg/L) NOAEL based Drinking Water Wildlife Screening Level [5] (µg/L) Dean et al 2004 (URS document on Fat-whorled pond snail 2006) (µg/L) 150 148 340 150 --150 150 292 -- 220 220 110 3.9 ----3.9 23,100 -- 11 3.6 35 0.66 ----0.66 2,830 -- 19 24 1,500 3 ----3 ---- 42 42 570 74 230 74 11 4,300 -- 11 --16 11 --11 11 14,050 -- 1.25 1.17 65 2.5 10.9 2.5 1 4,860 -- 82,000 ---------------- 93 2,300 80 ----1,300 377,000 -- 800 16,000 34 ----1,800 600 -- 1,700 1,700 28,000 1,500 ----1,500 42,800 -- 16 16 -------------- 25 47 --130 ----130 ---- 410 47 830 47 ----47 ---- 130 65 450 25 ----25 33,000 -- 1,500 940 26,000 2,200 ----210 25,100 -- --47 --21 ----21 1,623 -- Surface Water Ecological Screening Criteria (µg/L) Table 1: Spring Water Screening Results Northrop Grumman Systems Corporation - Promontory Facility Promontory, UT Chemicals PAHs Naphthalene Other Compounds Bicarbonate Bromide Calcium Chloride Perchlorate6 Potassium Sodium Sulfate General Chemistry Alkalinity Conductivity7 Hardness (as CaCO3)8 Total Dissolved Solids Region 4 Eco SL 2017: Surface Water [2] (µg/L) Region 5 Eco SL 2003: Water (µg/L) SQuiRTs: Freshwater (acute) (µg/L) SQuiRTs: Freshwater (chronic) (µg/L) Adjusted for Hardness of 400 mg/L as CaCO3 National Recommended Water Quality Criteria- Aquatic Life Criteria Table [3] (µg/L) LANL EcoRisk Database Minimum Screening Level [4] (µg/L) NOAEL based Drinking Water Wildlife Screening Level [5] (µg/L) Dean et al 2004 (URS document on Fat-whorled pond snail 2006) (µg/L) Surface Water Ecological Screening Criteria (µg/L) 13 190 1.1 ----1.1 -- ------------------ ------------------ 116,000 ---------------- 230,000 --------230,000 230 ---- ------------35,000 --9,300 53,000 ---------------- 680,000 ---------------- ------------------ 20000 --------20,000 ------ ------------------ ------------------ ------------------ Notes & Abbreviations: CCC: Criterion Continuous Concentration; CMC = criterion maximum concentration; LANL = Los Alamos National Laboratory; NOAEL = no observable adverse effects level; SL = screening level; µg/L = microgram per liter [9] There are no screening levels available for hardness, but in general toxicity decreases as hardness increases [4] The lowest surface water screening level for aquatic community organisms was selected. Screening levels are for total metals. [5] The lowest screening level for drinking water by wildlife was selected from Sample et al. 1996 [6] LANL value is for perchlorate Ion and was not for aquatic community but was the only available value [7] Conductivity in units of uS/cm [8] Hardness was calculated as follows: (2.5*Calcium)+(4.1*Magnesium) [1] Background water quality values for Blue Creek are provided for arsenic, barium, chromium and lead (median value from Table 12 in Walsh, 2002). The remainder of the values shown for general chemistry parameters and major ions were obtained from a 1972 USGS hydrologic study of the Blue Creek Valley. [2] Region 4 Freshwater surface water screening values, chronic values selected. [3] The CCC (chronic) was selected over the CMC (acute) for the National Water Quality Criteria values. Table 2: Spring Water Screening Results: May 2018 Northrop Grumman Systems Corporation - Promontory Facility Promontory, UT Pipe Spring Shotgun Spring Arsenic 5.4 6.9 <1,000 148 25 No Total Chromium [1]17.1 10.2 11 42 2.5 No Copper [2]1 1.7 NR 4.95 --No Lead <0.5 <0.5 24 1 14.5 No Manganese 0.6 1 6.62 80 NA No Molybdenum 3.1 2.7 3.2 34 NA No Nickel 7.3 11.9 NR 28.9 --No Selenium 11.2 15.2 ND 5 30 No Vanadium 4.5 2.4 NR 12 --No Chemical Historic Maximum Concentration (prior to 2018) (µg/L) Lowest Eco SL (µg/L) Background Concentration (µg/L) [3] Exceed SL or Background (which ever is highest)? May 2018 Max Spring Concentration (µg/L) Table 2: Spring Water Screening Results: May 2018 Northrop Grumman Systems Corporation - Promontory Facility Promontory, UT Arsenic Total Chromium [1] Copper [2] Lead Manganese Molybdenum Nickel Selenium Vanadium Chemical 150 148 340 150 --150 150 292 42 42 570 74 230 74 11 4,300 4.95 1.58 13 9 29 --5 65,200 1.25 1.17 65 2.5 10.9 2.5 1 4860 93 --2,300 80 ----1,300 377,000 800 --16,000 34 ----1,800 600 28.9 28.9 470 52 168 52 29 171,360 5 5 13-186 5 ----5 857 27 12 280 19 ----19 835 Surface Water Ecological Screening Criteria (µg/L) Region 4 Eco SL 2017: Surface Water [4] Region 5 Eco SL 2003: Water SQuiRTs: Freshwater (acute) SQuiRTs: Freshwater (chronic) Adjusted for Hardness of 400 mg/L CaCO3 National Recommended Water Quality Criteria- Aquatic Life Criteria Table [5] [6] The lowest surface water screening level for aquatic community organisms was selected. Screening levels are for total metals. [7] The lowest screening level for drinking water by wildlife was selected from Sample et al. 1996 SQuiRTS= National Oceanic and Atmospheric Administration Screening Quick Reference Tables; LANL= Los Almos National Laboratory; NOAEL = no observable adverse effect limit; NR = no results; ND = non-detect; SL = screening level; µg/L = microgram per liter LANL EcoRisk Database Minimum Screening Level [6] NOAEL based Drinking Water Wildlife Screening Level [7] Notes & Abbreviations: [1] The lowest screening level for Total Chromium originates from the LANL EcoRisk database (11 µg/L) and is based on hexavalent chromium (Cr(VI)). Since the chromium data for the site is for total chromium, the LANL value is not an appropriate screening level, and the next lowest value of 42 µg/L from EPA Region 4 and 5 will be as the screening level instead. [2] Region 5 Eco SL 2003 for Copper is based on the US EPA National Recommended Water Quality Criteria (2002) and was adjusted (recalculated) to accommodate soft water that is characteristic within Region 5. Since the Site is known to have hard water, this value is not appropriate and we therefore went with the next highest value for Copper which is 4.95 µg/L (USEPA Region 4 Eco SL 2017). [3] Background water quality values for Blue Creek (median value from Walsh, 2002) [4] Region 4 Freshwater surface water screening values, chronic values selected. [5] The CCC (chronic) was selected over the CMC (acute) for the National Water Quality Criteria values. Table 3: Sediment Screening Results Northrop Grumman Systems Corporation - Promontory Facility Promontory, UT Region 3 Eco SL 2006: Sediment Region 5 Eco SL 2003: Sediment SQuiRTs: Sediment (TEL) LANL Sediment [3] Metals µg/kg µg/kg µg/kg µg/kg µg/kg µg/kg µg/kg Arsenic <2,000 <2,000 5,900 No 9,800 9,790 5,900 97,000 Barium 54,800 --150,000 No ------150,000 Beryllium 274 --73,000 No ------73,000 Chromium 12,500 1,110,000 37,300 Yes 43,400 43,400 37,300 43,000 Cobalt <100 --50,000 No 50,000 50,000 --230,000 Lead --545,000 35,000 Yes 35,800 35,800 35,000 35,000 Molybdenum <100 --27,000 No ------27,000 Perchlorate <1,000 ----No SL -------- Notes & Abbreviations: TEL: Threshold-Effects Level LANL: Los Almos National Laboratory SL: Screening Level µg/kg = microgram per kilogram Chemicals[1] Sediment Ecological Screening LevelsMaximum Sediment Concentration 2008 [2] Lowest Sediment Screening Level Maximum Sediment Concentration 2018 [2] The Sediment Exceed the Screening Level? [1] Only chemicals with sediment data are shown [2] For non-detected concentrations the Method Detection Limit (MDL) is provided. [3] If there was no applicable sediment aquatic organism screening level, the lowest no effect level was selected out of the available ecological receptors (this applied to beryllium, cobalt and molybdenum) Other Compounds