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The Boeing Company Santa Susana Field Laboratory 5800 Woolsey Canyon Road Canoga Park, CA 91304-1148

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Via FedEx May 24, 2018 In reply, refer to SHEA-115876 Mr. Roger Paulson, P.E. Chief, SSFL Unit Department of Toxic Substances Control 8800 Cal Center Drive Sacramento, CA 95826-3200 Subject: Responses to DTSC Comments on the RCRA Facility Investigation Data Summary and Findings Reports,

Boeing RFI Subarea 5/9 South, Santa Susana Field Laboratory, Ventura County, California Dear Mr. Paulson: Enclosed for your review are responses to DTSC’s April 25, 2018 comments on The Boeing Company (Boeing) April 2017 RCRA Facility Investigation Data Summary and Findings Reports, Boeing RFI Subarea 5/9 South, Santa Susana Field Laboratory, Ventura County, California.

Once DTSC approves the responses, Boeing will prepare a Final DSFR submittal for Boeing RFI Subarea 5/9 South. Consistent with previous discussions with DTSC, only portions of the report require changes. Boeing proposes that the Final Boeing RFI Subarea 5/9 South DSFR submittal consist of the following:

• Printed copies of:

o Boeing RFI Subarea 5/9 South DSFR

Cover Page to reflect that the document is Final (to be stamped and signed).

Executive Summary (to reference a future addendum to the Boeing Groundwater RFI Report that will document additional chemicals and areas recommended for further evaluation during CMS).

Table of Contents (to reference new Appendixes C [Method Reporting Limit Evaluation] and D [Total Petroleum Hydrocarbon Evaluation]).

Section 1 text (to reference the April 2017 DSFR for Boeing RFI Subarea 5/9 South, DTSC’s April 2018 comments on the April 2017 DSFR for Boeing RFI Subarea 5/9 South, and new Appendixes C and D).

Section 2.2.2 text (to introduce Method Reporting Limit and Total Petroleum Hydrocarbon evaluations performed in response to DTSC’s April 2018 comments and refer to new Appendixes C and D).

Section 4 (to add reference documentation for the April 2017 DSFR for Boeing RFI Subarea 5/9 South and DTSC’s April 2018 comments on the April 2017 DSFR for Boeing RFI Subarea 5/9 South).

o DSFRs for Environmental Effects Laboratory RFI Site, Area III Sewage Treatment Plant RFI Site, Compound A Facility RFI Site, Systems Test Laboratory IV (STL-IV) RFI Site, and Areas Unaffiliated with RFI Sites

jlincoln

Text Box

Text In This Box Was Inserted by DTSC The attached document related to the Santa Susana Field Laboratory (SSFL) project is a DRAFT, submitted to the Department of Toxic Substances Control (DTSC) for review and comment. DTSC's review of the document is currently in progress. DTSC has not approved the document and revisions may be required. Currently, DTSC does not approve or endorse the content, conclusions, or proposals in this draft document, nor do we stand by the accuracy of any statements made in the document. After review, DTSC will release our comments or recommendations in the form of an official letter, which will be posted to the DTSC SSFL website at: http://www.dtsc.ca.gov/SiteCleanup/Santa_Susana_Field_Lab/ If you have any questions related to this draft document, please contact DTSC's SSFL Public Participation Specialist Michelle Banks-Ordone at (818) 717-6573, or [email protected].

Draft DTSC Review Comments RCRA Facility Investigation Data Summary and Findings Report – April 2017

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Boeing RFI Subarea 5/9 South, Compound A Santa Susana Field Laboratory, Ventura County, California

No. Section Page Comment Response to Comment

1 Various Various Method Reporting Limit Evaluation – The following parameters have method reporting limits that exceed the characterization levels for more than 25% of the samples that were analyzed for these parameters and were not detected at the site: 2,4,6-Trinitrotoluene, 2-Amino-4,6-Dinitrotoluene, 2- Chloroethylvinyl ether, Aroclor 1248, Cyanides, Di-n-butyl phthalate, Hexachlorobutadiene, Monomethylhydrazine, and RDX. Please evaluate if these chemicals were used at the site, determine if the method reporting limits for these chemicals are acceptable, and provide the rationale regarding why the method reporting limits are acceptable. If the chemical was used at the site and the method reporting limits are not acceptable please present this as a datagap in the RFI report so that it can be carried through the corrective measures study and additional sampling can be conducted during corrective measures implementation.

With the exception of di-n-butyl phthalate, the chemicals mentioned in this comment will be evaluated to determine if the method reporting limits are acceptable. This evaluation will consider multiple lines of evidence, such as whether these chemicals were used at the site, various reporting limit statistics, and analysis of the reporting limits for samples collected in areas of chemical use. The results of this evaluation will be provided in a new appendix (Appendix C) to the Boeing RFI Subarea 5/9 South DSFR to document whether the method reporting limits are acceptable. If there are cases where the method reporting limits are deemed unacceptable, the appendix will document that there is a data gap and recommend that that additional sampling be performed during CMS. Di-n-butyl phthalate will not be included in this evaluation because this chemical was previously detected in two samples collected in the Compound A Facility RFI site reporting area (CFBS2029S002SP and SL-159-SA5B-SB-4.0-5.0). Three additional chemicals (m-terphenyl, o-terphenyl, and p-terphenyl) will be evaluated in the appendix, as these chemicals have been analyzed but not detected in the Compound A Facility RFI site reporting area and more than 25% of the non-detect results have reporting limits that exceed the characterization levels.

2 Various Various TPH concentrations were evaluated to determine if adequate BTEX (for light end TPH concentrations such as GRO) and PAH (for heavier end TPH such as DRO and ORO) were collected to represent TPH concentrations in the risk assessment process. Based on the evaluation of the Compound A data, soil samples were typically analyzed for BTEX and GRO, therefore, BTEX can be used to evaluate the carcinogenic risks from GRO. Additionally, soil samples were typically analyzed for PAHs and DRO, EFH, or ORO, therefore, PAHs can be used to evaluate the risks from these

Comment noted.


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Boeing RFI Subarea 5/9 South, Compound A Santa Susana Field Laboratory, Ventura County, California

No. Section Page Comment Response to Comment parameters.

3 Appendix E

1 of 4 Location ID CFBS3000 – Based on data presented in the MXD, nickel was also analyzed in soil samples collected at this location but is not shown in the table. Please rectify the discrepancy.

Nickel was inadvertently analyzed at this location. The deviations column in Appendix E will be revised to read “The 6-feet bgs sample was not collected because of bedrock refusal at 1-foot bgs. The base of alluvium sample was collected at 0.5 feet bgs. Nickel was inadvertently analyzed in this sample.” A blue “X” will also be added under “Metal-Nickel” to indicate the addition of nickel analysis to the table. The updated version of Appendix E will be provided in a revised DSFR submittal.

4 Appendix E

1 of 4 Row with location ID CFBS3001, the text in the Rationale/Objectives column is cut off. Please fix this. Please confirm the location ID that is cut off is CFBS2010.

It has been confirmed that CFBS2010 was cut off. This will be fixed in the updated version of Appendix E.

5 Appendix E

1 of 4 Row with location ID CFBS3003, the location column indicates the sample could be collected approximately 100 feet south of CFBS1018, however, CFBS3003 is located approximately 70 feet southeast of CFBS1018. Please explain why the shorter distance was used, especially given the sample collected was not below the characterization level for cadmium.

CFBS3003 is positioned at the approximate location (within 6 feet) of the location proposed for this boring in the Addendum to Master RFI Data Gap Work Plan – Iteration 2, Boeing RFI Subarea 5/9 South, Compound A RFI Site, Santa Susana Field Laboratory, Ventura County, California (CH2M, 2014). Therefore, the location of CFBS3003 does not represent a deviation from the proposed location. The information presented in the location column was incorrect and will be corrected in the updated version of Appendix E. In accordance with the DQO Report, step-out samples were generally collected 25 to 100 feet from the original sample location with exceedances. The proposed step-out distance within this range was determined on a case-by-case basis by considering multiple factors such as field conditions, the mobility of the chemical, and magnitude of exceedance. Seventy feet was selected as the step-out distance from CFBS1018 based on consideration of these factors and the DQOs specific to this sample location.


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Boeing RFI Subarea 5/9 South, EEL Santa Susana Field Laboratory, Ventura County, California


1 Various Various Method Reporting Limit Evaluation – The following parameters have method reporting limits that exceed the characterization levels for more than 25% of the samples that were analyzed for these parameters and were not detected at the site: 2,4,6-Trinitrotoluene, 2-Amino-4,6-Dinitrotoluene, 2- Chloroethylvinyl ether, Aroclor 1248, Cyanides, m-Terphenyl, o-Terphenyl, and RDX. Please evaluate if these chemicals were used at the site, determine if the method reporting limits for these chemicals are acceptable, and provide the rationale regarding why the method reporting limits are acceptable. If the chemical was used at the site and the method reporting limits are not acceptable please present this as a datagap in the RFI report so that it can be carried through the corrective measures study and additional sampling can be conducted during corrective measures implementation.

The chemicals mentioned in this comment will be evaluated to determine if the method reporting limits are acceptable. This evaluation will consider multiple lines of evidence, such as whether these chemicals were used at the site, various reporting limit statistics, and analysis of the reporting limits for samples collected in areas of chemical use. The results of this evaluation will be provided in a new appendix (Appendix C) to the Boeing RFI Subarea 5/9 South DSFR to document whether the method reporting limits are acceptable. If there are cases where the method reporting limits are deemed unacceptable, the appendix will document that there is a data gap and recommend that that additional sampling be performed during CMS. Two additional chemicals (hexachlorobutadiene by Method 8270C and p-terphenyl) will be evaluated in the appendix, as these chemicals have been analyzed but not detected in the EEL RFI site reporting area and more than 25% of the non-detect results have reporting limits that exceed the characterization levels.

2 Various Various TPH concentrations were evaluated to determine if adequate BTEX (for light end TPH concentrations such as GRO) and PAH (for heavier end TPH such as DRO and ORO) were collected to represent TPH concentrations in the risk assessment process. Based on the evaluation of the EEL data, soil samples were not always analyzed for BTEX or were analyzed in the sample interval below where GRO was analyzed. This results in some uncertainty for the site. Additionally, soil samples were not always analyzed for PAHs and DRO, EFH, or ORO. The samples were often analyzed for PAHs in the interval below where the sample was collected for TPH analysis. Please discuss the uncertainty associated with this and whether it is anticipated to affect the results of the risk assessment.

Detected light-end TPH results that do not have co-located (including data collected within one foot vertically) BTEX data and detected higher-end TPH results that do not have co-located (including data collected within one foot vertically) PAH data will be evaluated to determine the uncertainty of future risk assessment results associated with not having co-located BTEX and PAH data. Multiple factors will be considered in the evaluation, such as the distance between the TPH concentration and the nearest BTEX or PAH data, the ratio of the TPH concentration to a risk-based screening level, the TPH concentration relative to other TPH results that have co-located data at the RFI site, and proximity to historical operations involving petroleum hydrocarbons. This evaluation will be provided in a new appendix (Appendix D) to the Boeing RFI Subarea 5/9 South DSFR.


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Boeing RFI Subarea 5/9 South, Sewage Treatment Plant – 3 Santa Susana Field Laboratory, Ventura County, California


1 Various Various Method Reporting Limit Evaluation – The following parameters have method reporting limits that exceed the characterization levels for more than 25% of the samples that were analyzed for these parameters and were not detected at the site: 2,4,6-Trinitrotoluene, 2-Amino-4,6-Dinitrotoluene, 2- Chloroethylvinyl ether, Cyanides, Gasoline Range Organics (C4-C12), and RDX. Please evaluate if these chemicals were used at the site, determine if the method reporting limits for these chemicals are acceptable, and provide the rationale regarding why the method reporting limits are acceptable. If the chemical was used at the site and the method reporting limits are not acceptable please present this as a datagap in the RFI report so that it can be carried through the corrective measures study and additional sampling can be conducted during corrective measures implementation.

The chemicals mentioned in this comment will be evaluated to determine if the method reporting limits are acceptable. This evaluation will consider multiple lines of evidence, such as whether these chemicals were used at the site, various reporting limit statistics, and analysis of the reporting limits for samples collected in areas of chemical use. The results of this evaluation will be provided in a new appendix (Appendix C) to the Boeing RFI Subarea 5/9 South DSFR to document whether the method reporting limits are acceptable. If there are cases where the method reporting limits are deemed unacceptable, the appendix will document that there is a data gap and recommend that that additional sampling be performed during CMS.

2 Various Various TPH concentrations were evaluated to determine if adequate BTEX (for light end TPH concentrations such as GRO) and PAH (for heavier end TPH such as DRO and ORO) were collected to represent TPH concentrations in the risk assessment process. Based on the evaluation of the STP-3 data, soil samples were typically analyzed for BTEX and GRO, therefore, BTEX can be used to evaluate the risks from GRO. Additionally, soil samples were typically analyzed for PAHs and DRO, EFH, or ORO, therefore, PAHs can be used to evaluate the risks from these parameters.

Comment noted.


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Boeing RFI Subarea 5/9 South, Systems Test Laboratory IV Santa Susana Field Laboratory, Ventura County, California


1 Various Various Method Reporting Limit (MRL) Evaluation – The MRL evaluation was conducted and no significant issues with detection limits were identified.

Comment noted.

2 Various Various TPH concentrations were evaluated to determine if adequate BTEX (for light end TPH concentrations such as GRO) and PAH (for heavier end TPH such as DRO and ORO) were collected to represent TPH concentrations in the risk assessment process. Based on the evaluation of the STL-IV data, soil samples were not always analyzed for BTEX or were analyzed in the sample interval below where GRO was analyzed. This results in some uncertainty for the site. Additionally, soil samples were not always analyzed for PAHs and DRO, EFH, or ORO. This samples were often analyzed for PAHs in the interval below where the sample was collected for TPH analysis. Please discuss the uncertainty associated with this and whether it is anticipated to affect the results of the risk assessment.

Detected light-end TPH results that do not have co-located (including data collected within one foot vertically) BTEX data and detected higher-end TPH results that do not have co-located (including data collected within one foot vertically) PAH data will be evaluated to determine the uncertainty of future risk assessment results associated with not having co-located BTEX and PAH data. Multiple factors will be considered in the evaluation, such as the distance between the TPH concentration and the nearest BTEX or PAH data, the ratio of the TPH concentration to a risk-based screening level, the TPH concentration relative to other TPH results that have co-located data at the RFI site, and proximity to historical operations involving petroleum hydrocarbons. This evaluation will be provided in a new appendix (Appendix D) to the Boeing RFI Subarea 5/9 South DSFR.

3 4.3 4-6 Please explain why CUA Cluster 5 is a CUA cluster as there are no exceedances.

CUA cluster 5 is identified as such because it includes CUA 11, which was identified in the 2008 RFI Report (CH2M, 2008) based on potential use of energetics and propellants at an explosives storage area. By definition, each CUA must be located within a CUA cluster.

4 Table 4-1 9 The location described for radionuclides under CC 4 is not included in GIS for 5/9 South or in the 2016 Gold Copy. In addition, RTC #26 states that the radiological error will be fixed in the 5/9 South DSFR mxd. However, the 5/9 South DSFR mxd does not include radionuclides. Please provide a revised 5/9 South DSFR mxd that includes all of the radionuclides related to this DSFR (including DOE data removed from the 2016 Gold Copy).

The Subarea 5/9 South DSFR mxd submitted in April 2017 excluded radionuclide data. A separate Subarea 5/9 South DSFR mxd was submitted to DTSC on June 2, 2017, which includes radionuclide data. The location described for radionuclides in CC 4 is included in the June 2017 version of the 59S mxd and the 2016 Gold Copy (as updated through the most recent quarterly update issued March 2018). The response to DTSC Comment #26 on the Draft STL-IV DSFR (CH2M, 2015) relates to sample S-4. As specified in the response to DTSC Comment #26, sample S-4 was not collected in STL-IV, nor was it collected elsewhere in


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No. Section Page Comment Response to Comment Boeing RFI Subarea 5/9 South. As such, this sample location was not included in the Subarea 5/9 South DSFR mxd.

5 Table 4-1 SQ #4

9 A template sentence is included for many of the CCs that don’t contain radionuclides: “Sufficient data have been collected to proceed with risk assessments, which will be used to determine if chemicals and radionuclides within the CC exceed action levels and to support future CMS recommendations.” Verify whether this template language should be used for CCs without radionuclides.

It is accurate that radionuclides do not need to be referenced in this statement for CCs that do not have radionuclide data associated with them. However, no changes to the table are proposed in response to this comment.

6 Table 4-1 13 See comment #3 above for CC7. DTSC comment is assumed to refer to comment #4 rather than comment #3. Comment #3 is not applicable to CC7.

The Subarea 5/9 South DSFR mxd submitted in April 2017 excluded radionuclide data. A separate Subarea 5/9 South DSFR mxd was submitted on June 2, 2017, which includes radionuclide data. The location described for radionuclides in CC 7 is included in the June 2017 version of the mxd.

7 Table 4-1 SQ#3

20 For CC13, verify whether perchlorate should be mentioned under study question #3 in accordance with RTC #39.

Soil samples collected from CC13 were not analyzed for perchlorate. Therefore, perchlorate should not be mentioned in Table 4-1 for this CC. Sample location SLBS2048, which was analyzed for perchlorate and is referenced in DTSC Comment #39 on the Draft STL-IV DSFR (CH2M, 2015), was evaluated with STL-IV CC 9 as described in the 2017 STL-IV DSFR (Appendix C, Table C-1). This sample was collected outside but immediately adjacent to the CC9 boundary. Perchlorate is recommended for further evaluation during CMS at this location, as reflected in Table 4-1 and elsewhere in the 2017 STL-IV DSFR. No changes to Table 4-1 are proposed to address this comment.

8 Appendix E

N/A The deviations column is missing from the deviations table. While Boeing provided a revised table for DTSC review, the table needs to be included in the final electronic version so it can be uploaded to the SSFL document library.

Comment noted. An updated version of Appendix E will be provided in a revised DSFR submittal.


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9 Appendix E

1 of 18 This comment pertains to the row containing location ID SLBS3005. Based on review of the mxd for hexavalent chromium was sampled for at the 1.5 and 5.8 foot intervals but it is not called out in the table. Should this be called out in the table? This analysis does not appear to be called out in the 2nd

Iteration Work Plan Table C-1 or the 3rd or 4th Iteration Work Plan tables. Was this a deviation?

This was a deviation that was inadvertently omitted from Appendix E. Hexavalent chromium was added to the analyte list for both SLBS3005 and SLBS3004 after the hexavalent chromium results were received for samples collected at SLBS3022. Analysis of hexavalent chromium was added to samples collected from SLBS3005 and SLBS3004 to define the northern extent of hexavalent chromium detected at SLBS3022. The deviation description will be corrected for both SLBS3005 and SLBS3004. An updated version of Appendix E will be provided in a revised DSFR submittal.


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Boeing RFI Subarea 5/9 South, Unaffiliated Areas Santa Susana Field Laboratory, Ventura County, California


1 Various Various Method Reporting Limit Evaluation – The following parameters have method reporting limits that exceed the characterization levels for more than 25% of the samples that were analyzed for these parameters and were not detected at the site: 2-Chloroethylvinyl ether and Cyanides. Please evaluate if these chemicals were used at the site, determine if the method reporting limits for these chemicals are acceptable, and provide the rationale regarding why the method reporting limits are acceptable. If the chemical was used at the site and the method reporting limits are not acceptable please present this as a datagap in the RFI report so that it can be carried through the corrective measures study and additional sampling can be conducted during corrective measures implementation.

The chemicals mentioned in this comment will be evaluated to determine if the method reporting limits are acceptable. This evaluation will consider multiple lines of evidence, such as whether these chemicals were used at the site, various reporting limit statistics, and analysis of the reporting limits for samples collected in areas of chemical use. The results of this evaluation will be provided in a new appendix (Appendix C) to the Boeing RFI Subarea 5/9 South DSFR to document whether the method reporting limits are acceptable. If there are cases where the method reporting limits are deemed unacceptable, the appendix will document that there is a data gap and recommend that that additional sampling be performed during CMS.

2 Various Various TPH concentrations were evaluated to determine if adequate BTEX (for light end TPH concentrations such as GRO) and PAH (for heavier end TPH such as DRO and ORO) were collected to represent TPH concentrations in the risk assessment process. Based on the evaluation of the Unaffiliated data, soil samples were typically analyzed for BTEX and GRO. Additionally, soil samples were typically analyzed for PAHs and DRO. These data can be used in risk assessment.

Comment noted. However, as discussed in the DSFR, no chemicals were detected at concentrations that exceed human health or ecological-based characterization levels in the Unaffiliated Areas. Consequently, a human health risk assessment and an ecological risk assessment will not be performed for the Unaffiliated Areas.

Groundwater-Related Comments RCRA Facility Investigation Data Summary and Findings Report – April 2017

Boeing RFI Subarea 5/9 South Santa Susana Field Laboratory, Ventura County, California

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Page(s) Comment Proposed Response

General Comments from GSU

1 N/A N/A

The description of the soil areas and bedrock areas recommended for evaluation in the CMS are briefly listed in the report and generally depicted on two figures for each RFI site. However, there are no separate summaries of each source zone within each RFI site with details/ information documenting how the source zone location(s) and extent(s) were determined. This information is only accessible by reading through the body of the report text and associated tables. Separate summaries for each groundwater source would create the record/inventory of each identified source zone that would be advanced through the Groundwater RFI, CMS, and Corrective Measures Implementation (CMI) processes without the need to reference back to the DSFR. Accordingly, the GSU recommends that a separate, complete description of each identified groundwater contaminant source be prepared that includes a summary of relevant data (e.g., soil/ soil vapor, bedrock, and groundwater data along with historical/operational information) used to determine and delineate the groundwater source zone. Each summary should include, but is not limited to, the following elements:

A brief description of the operational area (e.g., pond, sump, storage area, etc.);

A summary (including necessary figures) of the nature of the chemical impacts (i.e., range of concentration and depths of relevant soil/ soil vapor, bedrock, and groundwater data);

A cross-section(s) that clearly depicts the vertical relationship between soil source zone(s), bedrock source zone(s), and groundwater quality that support the nature of the groundwater source and the interpreted impact to groundwater;

A description of the identified source area (lateral and vertical extents); A figure showing the soil/bedrock groundwater source zone

recommended for CMS. The summaries should be comprehensive to include all Area I and III source zones, and included in the draft final groundwater RFI report, or as a single addendum to the DSFRs.

Boeing is proposing to describe soil and bedrock vadose zone source areas and potential source areas to hopefully address DTSC’s concerns and achieve DSFR approval. These areas will be carried forward in the CMS. An example of Boeing’s proposal will be presented using the STL-IV RFI Site. A figure and table with the requested information will be provided for each source area at each RFI site. Boeing proposes to include similar source area figures and tables for each RFI site in an addendum to the final groundwater RFI report. Boeing is not proposing to include additional cross-sections in its final groundwater RFI report as such information has been provided (as previously agreed-upon with DTSC) in the RFI site reports and in the 3-D plume visualization efforts.



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2 N/A N/A

For each RFI site, the DSFR dismisses several metals with the following or similar statement, “Professional judgment indicates that these metals are not related to releases from site operations and fall within the natural variability of measurement. This professional judgment is informed by operational information, soil sampling results, vadose zone transport evaluation, and groundwater sampling results.” The operational information, soil sampling results, vadose zone transport evaluation, and groundwater sampling results, along with a presentation of the analysis that support the professional judgment determinations need to be included (at least in summary). A discussion of the range of results in the different media and a comparison of those results to appropriate screening levels and background levels is fundamental. It is not possible to assess the merits of conclusions based on professional judgment without understanding what information is being relied on for the determination. Clarify the portion of the statement “…fall within the natural variability of measurement.” It is not clear if “natural variability” is a new background threshold, separate from the Groundwater Comparison Concentrations (the equivalent to the groundwater characterization levels [GCLs]) derived jointly by both the RPs and DTSC, and approved by DTSC; or, does “measurement” refer to the variability created by field and laboratory methodologies, even though it is accounted for in the derivation of the Groundwater Comparison Concentrations. Although clarification is needed on the statement and terminology, any exceedance of the GCL should be initially considered anthropogenic and retained for further evaluation in CMS. Further, the GCLs cited for beryllium, mercury, silver, thallium, and tin are incorrectly derived. During the development of the Groundwater Comparison Concentrations (in which the GCLs are based on), it was determined that these metals do not naturally occur at the site in concentrations above the existing laboratory reporting limits in the dataset. Table 3-6, Groundwater Comparison Concentrations for Metals and Selected Inorganic Compounds, presented in the September 2005 Standardized Risk Assessment Methodology (SRAM) Work Plan, Revision 2, the Groundwater Comparison Concentrations are: “ND<0.14”

Boeing proposes to address DTSC’s concerns about this topic by considering all soil and bedrock within the perimeter of all chemical use area clusters at each RFI site as a potential source area to groundwater. A figure presenting potential source areas will be included in a forthcoming addendum to the Boeing Groundwater RFI Report. As directed, all chemicals specified by DTSC will be considered in the CMS.



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μg/L for beryllium; “ND<0.063” μg/L for mercury; “ND<0.17” μg/L for silver; “ND<0.13” μg/L for thallium; and “ND<2.4” μg/L for tin. The values presented were achievable reporting limits at that time, as determined during the development of the Groundwater Comparison Concentrations. However, any detection of these metals (even if below the previously achievable reporting limits) should be viewed as anthropogenic, considered to be above the respective GCL, and retained for further evaluation in the CMS. Based on the information presented in the DSFR, the GSU recommends that all metal exceedances be moved forward for further consideration in CMS in the absence of further documentation. Additional information, if available, or a comprehensive and compelling case on why a metal exceedance should not be considered further can be submitted to DTSC for further consideration as an addendum to the DSFR.

3 N/A N/A

A large number of shallow wells in each of the RFI sites were dry during the collection of data in support of the DSFR. Even in the case where there are sufficient data from nearby wells for evaluating remedy alternatives, the absence of data from these dry wells results in uncertainty that will need to be evaluated once a remedy is selected. The July 19, 2017 letter to the RPs, regarding the 2016 Annual Groundwater Reports, directed “…the RPs evaluate and identify all wells that could not be sampled since 2010.” and “…submit this evaluation with a work plan proposing all necessary modifications to the groundwater monitoring network and applicable WQSAPs.” It is expected, therefore, that the wells that were dry during the collection of data in support of the DSFR, will be evaluated as part of this effort. Based on the evaluation, additional, deeper wells may be needed, to augment the current groundwater monitoring network or to support remedy implementation or performance monitoring.

Boeing’s proposed response is to acknowledge DTSC’s comment. Boeing will consider installation of additional shallow wells as indicated by data quality objectives in subsequent project phases. However, we believe the existing monitoring network is sufficient for characterizing impacts to groundwater considering the variability in groundwater recharge resulting from seasonal differences in precipitation.

4 N/A N/A

The lack of bedrock data results in a dependence on methodology and decision processes that use comparison criteria, numerical modeling, and professional judgment. This approach, in the DSFR, even given its limitations, may be reasonable for identifying areas where the current vadose contamination is a



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potential threat to the underlying groundwater and that require further evaluation in CMS. However, the numerical modeling approach evaluates transport in only one dimension. This, along with the lack of bedrock data, makes it impossible to understand the three-dimensional extent or mass of contamination in the bedrock at each individual source area. The DSFR attempts to address this issue by establishing a correlation between the extent of the soil/soil vapor contamination and underlying bedrock. However, both soil/soil vapor data and bedrock data are only available in limited locations and, where both exists, there is no apparent correlation. For example, within Compound A, a small zone around PZ-013 is designated as impacted bedrock based on bedrock porewater data (Figure 4-7), but no VOC or perchlorate contaminated soil/soil vapor exists here. All VOC soil/soil vapor data in the vicinity of PZ-013 are depicted as either “Non-Detect” or “<CL” on Figures 4-7, 4-1 and 4-2 (VOC results in soil/soil vapor). One soil data point on Figure 4-3 “Comparison of Other Analytical Results to Characterization Levels for Surface Water and Soil” is depicted as being “>100x RBSL,” but review of the GIS data revealed the contaminants detected at this point are numerous metals and one PCB (Aroclor 1254), not VOCs or perchlorate. This same scenario exists in the vicinity of PZ-014 and PZ-018 within the Compound A CUAs. A small area around both these piezometers is designated as “impacted vadose zone bedrock” based on bedrock porewater data in Figure 4-7, but no VOC or perchlorate contaminated soil/soil vapor is detected. This lack of correlation is likely due to the thin nature of the soil and the chemical’s propensity to be flushed downward into the bedrock and groundwater via recharge, or volatilization upward. It is therefore expected that additional bedrock data will be required to assess the downward pathway and the lateral extent of impact in the bedrock vadose zone. The nature and quantity of the data needed will be dependent on the remedy(ies) selected and the data required to implement and monitor the remedy(ies). For transparency and clarity, this uncertainty and data gap must be acknowledged in the responses to comments on the DSFRs, in the draft final GW RFI, and evaluated further in the CMS/CMI.

Boeing’s proposed response is to acknowledge DTSC’s comment and to indicate that additional bedrock vadose zone samples may be collected during the CMS/CMI as required based on specified data quality objectives. Samples could be collected from the unsaturated zone in existing un-cased monitoring wells using straddle packers and/or dry wells.



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5 N/A N/A

The 2011 DTSC Comment Letter stated “The data evaluated to determine the total depth of contamination is not adequate. Twenty-three core holes, 21 well clusters, and several multilevel well installations over the site are not adequate especially considering that most are not located at release locations.” It further stated that results were generally “limited to TCE, cis- and trans- isomers of 1,2-DCE, 1,1-DCE; and chlorofluorocarbon (CFC)-113” and approximately only “five percent (5%) of the samples were also analyzed for a full suite of compounds using EPA analytical method 8260, but the distribution of these data provided very limited information regarding the vertical extent of contaminants.” The lack of deep chemical data to define the vertical extent of contamination at the site was raised in the 2011 DTSC Comment Letter and this continues to be an issue for the 5/9 South area along with other areas of the site. Specifically, data bounding the depth of the contamination present in RFI Subarea 5/9 South is relatively sparse and the cross-sections included in Appendix B – Results of 3D Visualization for Groundwater confirm the necessity for additional deep groundwater data as part of any feasible remedy implementation and/or monitoring. Figure 7, Figure 20A, Figure 20B, Figure 22, Figure 23, and Figure 24 show cross sections across the 5/9 South area. Figure 7 shows the deep vertical geologic data are limited to 3 wells/well clusters (RD-55AB, RD-58ABC, and WS-9A). Figures 20A, 20B, 22, 23, and 24 show cross sections reflecting a larger area and additional deep vertical geologic data from a total of 5 locations (RD-55AB, RD-58ABC, WS-9A, WS-11, and C-6/C-15). The three-dimensional interpretation of vertical extent of Maximum Equivalent TCE concentrations is primarily based on detected chemical data observed at C-6/C-15 to depths of approximately 1200 feet. The deep occurrence of Maximum Equivalent TCE is projected from C-6/C-15 (Delta Pond area) southeast to WS-9A. Relatively deep contamination attributed to WS-9A is projected northwest through RD-58ABC and RD-55AB and is bounded by data from WS-11.

Boeing’s proposed response is to acknowledge DTSC’s comment and to indicate that additional deep wells may be installed as directed by DTSC during the CMI consistent with specified data quality objectives.



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A fundamental weakness of the data visualization in the 5/9 South Area is the lack of vertical data. Wells WS-9A and WS-11 are relatively poor information sources because historically long open boreholes can provide biased results. Further, there is uncertainty regarding the well seal of WS-9A and the potential effects from Bell Creek intermittent surface water flow. The significant influence that C-6/C-15 data has on the depth of contamination interpretation in 5/9 South is problematic because C-6/C-15 is outside of the 5/9 South Subarea and occurs in the relatively highly fractured Delta Structure, adjacent to a very significant former pond/VOC source location. Extrapolation of C-6/C-15 data to the 5/9 South Subarea, which occurs down gradient from the 5/9 South area, is inconsistent with assumptions of groundwater flow and expected contaminant transport. In addition, GSU notes that deep vertical data from the vicinity of significant VOC source areas within the 5/9 South Subarea, such as the Compound A Pond, STL-IV Impoundments, and EEL PZ-18A-E area, do not exist. Further, the vertical distribution of TCE shown in cross sections in Figures 20A, 20B, 22, 23, and 24 is not bounded by any data. It should be acknowledged that the cross sections in the DSFR depicting the vertical extent of the groundwater contamination are not bounded by data (i.e., the solid lines imply that the vertical extent is bounded). Further, depictions of the vertical extent of the groundwater contamination in the GW RFI report and subsequent submittals should query the extents of the groundwater plumes where data is absent to clearly convey that the extents are interpreted as data are not available.

6 N/A N/A

The DTSC has concerns regarding how contaminant transport distances were calculated, which are the basis for the distances that the particle tracks were truncated. It is important to note that there is disagreement between Boeing and DTSC on how contaminant transport should be modeled for the site as noted in the 2011 DTSC Comment Letter. DTSC directed the RPs to develop a Contaminant Transport Model work plan to refine the approach and model presented in the Sitewide GW RI. Even though DTSC had significant concerns



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regarding the methods presented in the Sitewide GW RI, the same methods are utilized in the DSFR. In response to the DTSC concerns regarding contaminant transport/truncation distances, Boeing’s RTC states “In the 2009 Draft GWRI report, two-dimensional discrete fracture network (2D-DFN) model simulations were generated for three RFI sites representing the full range of `Darcy fluxes’ (e.g., low, medium, high). Hydraulic conditions representing this range of Darcy fluxes were used as targets for the hydraulic conditions in the 2D-DFN models. Transport simulations incorporating the effects of matrix diffusion were then run with the 2D-DFN model (Fractran) to obtain estimates of transport distances. These three transport distance/Darcy Flux results were plotted and used as a basis for estimating the transport distances for other RFI sites using the model-generated Darcy flux to obtain an estimate of the transport distance length.” The plotted results related to the “…three transport distance/Darcy Flux results…” were not presented in the 2009 GW RI and DTSC assumes that the results were used to generate the “Front Distance” curve presented on the plot contained in Attachment C-1. Although this is not clearly stated in the DSFR, data from the three RFI sites: the Delta RFI; the IEL RFI; and the ELV RFI were not plotted. Aside from DTSC’s fundamental concerns about the contaminant transport approach which were presented in the 2011 DTSC Comment Letter and are expected to be addressed in the Contaminant Transport Model work plan, clarification is needed on the following:

It is assumed that the “Front Distance” curve was generated based on the Darcy Flux calculated from the flow model and 2D-DFN model results from the three RFI sites. Explain why the results from the three RFI sites were not plotted on the curve. Explain how the curve was generated with only three RFI sites.

Explain why the points from STL-IV, STP-3, EEL, and Compound A do not plot on the curve. If the 2D-DFN was not used for the RFI sites from the 5/9 South Area, only the calculated Darcy Flux values are available and these points must fall on the curve.

Boeing’s proposed response is to acknowledge DTSC’s comment and refer to Figures 9-1 and 9-2 of Appendix 6-A of the 2009 Groundwater RI report, which depicts particle tracks from RFI site to the distance identified by DTSC. These 1,000 meter particle tracks were also previously provided in the 2016 Gold Copy. Boeing believes that the truncated particle paths have been effective for identifying wells that may have been impacted by releases from chemical use area clusters. It should be noted that additional 3-D groundwater flow simulations are being developed and that additional depictions of flow paths from sources will be generated in the future. Different path lengths and/or monitoring targets can be chosen at that time as needed.



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Given the status of the groundwater flow model and the contaminant transport model, the GSU believes the particle tracks, as presented in the DSFR, are of limited value and, therefore, are only considered as providing a guide to an interpretation of the groundwater plume extents. In addition, in the absence of an approved contaminant fate and transport model/approach, particle tracks should be extended to a designated distance of 1,000-meters for consistency and transparency.

7 N/A N/A

Groundwater cleanup levels will be evaluated in the Corrective Measures Study and will include consideration for aquifer restoration and compliance with Applicable or Relevant and Appropriate Requirements (ARARs). It is, therefore, not appropriate to make de facto cleanup decisions in the RFI by screening out areas that have anthropogenic chemical concentrations below the GCLs when these levels may not be the final cleanup levels and there is a vadose-zone source associated with it. The 2016 DTSC Comment Letter recommended that chemicals with exceedances in both the vadose zone and groundwater or chemicals with any predicted leachate concentrations through soil transport modeling should be considered sources to groundwater and further evaluated in the CMS. Further, GSU recommends that chemicals with exceedances in the vadose zone and detectable concentrations in the groundwater (or above the groundwater comparison concentration for naturally occurring chemicals) also be considered further in CMS. Chemical exceedances, therefore, should be re-evaluated and the evaluation should be submitted to DTSC for evaluation as an addendum to the DSFR.

Boeing proposes to address DTSC’s concerns about this topic by considering all soil and bedrock within the perimeter of all chemical use area clusters at each RFI site as a potential source area to groundwater and will carry it forward to the CMS. A figure presenting potential source areas at each RFI site will be included in an addendum to the Boeing Groundwater RFI Report. Boeing will also consider chemicals in groundwater with detectable concentrations (or concentrations above the groundwater comparison concentrations for naturally occurring constituents) in the CMS.



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Specific Comments from GSU

1

RCRA Facility

Investigation DSFR

Boeing RFI Subarea 5/9

South

N/A

Additional work will be needed near WS-9A. WS-9A well construction precludes its ability to produce vertically discrete and high-quality groundwater samples. The WS-9A area should be investigated with deep borehole and multilevel monitoring system installations to confirm depth of contamination and vertical gradients.

Comment acknowledged. See Boeing response to General Comment 5.

2

Compound A RFI Site/

Appendix C/ C.2.1 Vadose

Data Evaluation

Methodology

C-2

The DSFR states “Site-specific groundwater comparison concentrations for metals and selected inorganic compounds developed by the Department of Toxic Substances Control (DTSC).” The statement is incorrect. The groundwater comparison concentrations were developed, in consultation with DTSC, by the Boeing Company and its consultants.

According to Boeing’s contractor, they agree that consultation was conducted to discuss the groundwater sampling results for metals and their statistical distribution, but that DTSC selected the numerical comparison value.

3

Compound A RFI Site/

Appendix C/ C.2.2

Groundwater Data

Evaluation Methodology

C-3 Particles were released either “to depth of 10 meters” or “to depths of 200 meters.” It is assumed the interval is 10 meters but clarification is needed on the release depth intervals for the particle tracking.

Correct, particles were released every 10 meters from the water table to a depth of 200 meters at locations where dense immiscible phase liquids are suspected to have entered the groundwater system.

4 Compound A/ Appendix

C C-7

Bedrock vadose zone data is absent from CC2 and CC3 and limited in CC1 (1 location) and CC4 (2 locations). The three locations where bedrock vadose zone data exists are identified as being impacted. Impacts to bedrock within the remainder of the Compound A Facility is evaluated using transport simulations. See General Comment 4.


5

Compound A /

Appendix C / Section C-2

C-8 /C-12 The following limitations in the data, used in the evaluation of the vadose zone impacts to groundwater, were identified:

Comment acknowledged. See Boeing responses to General Comments 3, 4, and 5.



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Bedrock vadose zone samples were only collected from three locations (PZ-014, PZ-015, and PZ-018). Bedrock should be investigated in all identified soil source zones.

Twenty-seven well locations/intervals were recommended to be sampled from 2013 to 2015 (C.3 - Fieldwork, page C-8) for the vadose zone to groundwater evaluation for Compound A, but 20 of these wells/intervals were either dry or contained insufficient water for sampling during this time frame (ES-24, ES-27, PZ-013A/B/C/D/E, PZ-014A/B/C/D/E, PZ-030, PZ-031, PZ-032, PZ-033, PZ-034, RS-09, RS-15, and RS-33).

Twenty-nine (29) of the forty-nine (49) wells (ES-15, ES-16, ES-23, ES-25, PZ-013A/B/C/D/E, PZ-014A/B/C/D/E, PZ-018A/B/C/E, PZ-028, PZ-31, PZ-032, PZ-033, PZ-034, PZ-038, PZ-039, PZ-052, RS-09, RS-12, and RS-14) from the list of wells selected for evaluation of the Compound A CUA clusters (C.4.2- Groundwater Data Evaluation Results, p. C-12) do not have available recent groundwater data (from 2010 until the 1st quarter of 2015) either because they are dry or were not sampled during this time frame.

GSU expects further evaluation of potential source areas within the CMS using the updated model and future data collected from existing representative monitoring wells and additional deeper replacement wells at locations where existing monitoring system is not adequate (see General Comment 3).

6 Compound A / Appendix C C-12

The following wells should be considered to evaluate potential impacts to groundwater: RD-153, ES-26, ES-32, ES-17, PZ-015A-G, PZ-054, RS-17, RS-37. The particle tracks come through or are nearby these monitoring points. The particle tracks do not define actual groundwater flow paths and only estimate groundwater flow paths based on a model. As such, these additional wells should also be used to monitor current and future groundwater impacts from Compound A. Wells that fall within the boundary of another chemical cluster should not be excluded from evaluation for a specific chemical cluster, especially if different COCs are being evaluated for impacts to groundwater. Based on particle tracks, the following wells should be additionally included in the evaluation specific to the identified chemical cluster:

The monitoring wells selected for the evaluation included those within the RFI site and downgradient based on an evaluation of the particle tracks from the existing flow model. The wells within the footprint of the RFI site are expected to provide the first indication of chemical transport to groundwater, and evaluation of the full record of chemical data for these wells is considered an appropriate indicator



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CC1: RD-153, RS-37, RS-17, RS-41, PZ-038, ES-16, RS-09, ES-25, PZ-032, PZ-034, RS-12, ES-14, PZ-014, ES-15

CC2: WS-11, PZ-034, ES-16, RS-09, PZ-033, PZ-035, RS-33 CC3: PZ-035, ES-16, RS-09, RS-33 CC4: ES-15, PZ-033, HAR-17, PZ-035, PZ-015, ES-17, ES-32, ES-26

of impacts to groundwater from the RFI site in question. Wells outside of the site boundaries are considered a secondary indicator of how chemicals may have been transported over time. For each chemical use area cluster, wells outside of site boundaries were selected for evaluation if they were interpreted to intercept particle tracks and were not considered to be primarily impacted by another RFI site. In addition, a larger net is cast as part of the annual site-wide monitoring program during which groundwater is evaluated at the site scale. Results from the site-wide evaluations were also reviewed to support groundwater evaluations presented in the DSFRs. Furthermore, as noted in the response to General Comment 2, Boeing proposes to consider all soil and vadose zone bedrock within the perimeter of all chemical use area clusters at each RFI site as a potential source area to groundwater.

7 Compound A / Appendix C / Section C-4

C-12/ Table C-1

Several of the wells selected to evaluate the Compound A CUAs are dry: CC1: According to Table C-1, there is no recent groundwater data for 7

of the 23 wells selected to monitor CC1 and data in several other wells are limited to only one class of COCs per sampling event. This makes a complete evaluation of CC1 difficult to complete.




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CC2: According to Table C-1, there is no recent groundwater data for 8 of the 9 wells selected to monitor CC2, making a complete evaluation of this area difficult.

CC3: According to Table C-1, there is no recent groundwater data for 7 of the 11 wells selected to monitor CC3, making a complete evaluation of this area difficult.

CC4: According to Table C-1, there is no recent groundwater data for 6 of the 13 wells selected to monitor CC4 and data in several other wells are limited to only one class of COCs per sampling event. This makes a complete evaluation of CC4 difficult to complete.

Additional data may be needed in CMS to further verify and refine the nature and extent of groundwater contamination near these wells (see General Comment 3).

8

Compound A /


C-15/ Table

C-ES-1

In addition to the compounds identified as being carried forward to CMS, the following compounds occur in both the vadose zone and groundwater above their respective BTVs/GCLs, or are predicted to do so. They should also be carried forward to CMS:

CC1: bis(2-ethylhexyl) phthalate, antimony, cadmium, chromium, copper, lithium, mercury, nickel, selenium, silver, and thallium. Benzo(ghi)perylene should also be carried forward (there is no toxicity criteria, but it is a human health concern).

CC2: selenium CC3: copper, lithium, molybdenum, and nitrate-N. CC4: trans-1,2-DCE, bis-2(ethyl-hexyl) phthalate, lithium, molybdenum,

nickel, selenium, silver. Benzo(ghi)perylene should also be carried forward (it was detected in soil above BTV/GCV, but not evaluated in groundwater).

See Boeing’s response to General Comment 2. As directed, all chemicals specified by DTSC will be considered in the CMS.

9 Compound A

RFI Site/ Appendix C

Figure C-2

The figures showing the particle tracks are not useful to the reader due to their scale. The GSU recommends adding additional figures at scales where the particle tracks can be evaluated. Each Chemical Cluster should be broken out into its own set of figures (one for forward particle tracks and one for backward particle tracks). The depth of the particles as they travel away from their input source zone should also be represented, perhaps via a color scale. These figures should be scaled to show the 1,000-meter particle tracks for the chemical cluster being represented and presented on 11x17-inch sized paper.

See Boeing’s response to General Comment 6 regarding 1,000-meter particle tracks. Boeing had previously provided 1,000 meter length particle tracks to DTSC in the 2016 Gold Copy.



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10

Compound A /

Section 4 & Appendix C

Figure 4-3, Figure

4-5, Attachment C-2 (p.

3-4)

Figures 4-3 through 4-5 show sample locations with COC data at progressively deeper depths. There are numerous locations where data points exceed their respective RBSLs by 10x or more in the shallower depths (<10 ft. bgs), and no data exists deeper than 10 ft. bgs. Several of these locations are not included in Figures 4-6 and 4-7 (which depict the areas of impacted soil and bedrock that need to be evaluated in CMS) presumably indicating that the transport modeling did not indicate the concentrations posed a threat to groundwater. Current inputs to the transport model are as follows: If the maximum concentration was detected in the A/C and no sample was collected from the WS/UWS, then the model assigns a value of “0 mg/kg” to organic compounds or “BTV” to inorganic compounds for the portion of the profile within the WS/UWS. If the maximum concentration was detected within the WS/UWS and there were no deeper samples, the model assigns a value of “0 mg/kg” to organic compounds or “BTV” to inorganic compounds just below the sampling point for the remainder of the profile. There were only 3 locations where samples were collected at a depth greater than 10 ft. bgs within the Compound A CUA. Since groundwater occurs at depths of 12 to 34 ft. bgs within Compound A, there is a significant vadose zone thickness without characterization. Assigning a concentration value of “0 mg/kg” just below its deepest sample point in vadose zone transport model creates uncertainty that increases with the thickness of the bedrock vadose zone. Because of the uncertainty inherent in the transport model, additional data may be needed in CMS to further verify the model results and refine the nature and extent of bedrock vadose zone impacts and potential threat to groundwater (see General Comment 4).

Comment acknowledged. See Boeing’s response to General Comment 4.

11

Compound A /

Appendix D/ D.4 Source

Zone Evaluation

D-6

The monitoring wells selected cannot by verified. The monitoring wells selected for evaluating the potential impacts to groundwater at Compound A were based on the particle tracks. Figure C-2 (which shows the particle tracks) cannot be used to verify if the wells are appropriate since, as stated in Specific Comment 9 above, the figure is at an inappropriate scale. Further, there is no evaluation presented to assess the flow path depths compared to the screen intervals of the target wells to determine if they intersect.

See response to Specific Comment 6 regarding selection of monitoring wells. Additionally, Boeing recognizes some uncertainty inherently exists



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There are limitations associated with using computer model and the associated particle tracks to select the monitoring wells. As stated in previous GSU comments, the groundwater model has calibration issues and therefore may not represent the flow field in portions of the site. Even adequately calibrated, groundwater models represent single representations of the system at the site and, as in this case, are seldom the only unique valid representation of the flow system. Further, the groundwater model is currently being updated which will require a reevaluation of the particle tracks and reassessment of impacts and adequacy of the monitoring well locations and construction.

when evaluating a subsurface environment; however, the combination of the use of chemical and water level data through time with flow model simulations is an accepted practice in environmental site investigation and is considered a reasonable approach, despite the potential limitations. If the updated flow model shows an altered depiction of flow at the site, the monitoring network can be adjusted at that time as needed.

12

Compound A /

Appendix D / Section D-5

D-8

This sections states that both recent data (from 2010 to 2014, with select Q1 2015) and historical data (prior to 2010) were used to assess the nature and extent of chemical impacts to groundwater beneath the Compound A facility. The use of historical data is not discussed in the remainder of the text and appears to only be used in the statistical trend analyses and to delineate the extent of TCE groundwater impacts (Figure 4-8). Historical data is not used to assess vadose zone transport. The use of only recent data to assess impacts to groundwater limits the data available (.e.g., 17 locations instead of 40 locations) for assessment of the subsurface. Additional data will be needed in CMS/CMI to further refine the nature and extent of bedrock vadose zone impacts.

Comment acknowledged. See Boeing’s response to General Comments 3, 4, and 5.

13

Compound A /

Appendix D/ D.5- Nature

and Extent

D-9

The explanation that 12 metals (antimony, cadmium, chromium, copper, iron, lithium, manganese, molybdenum, nickel, selenium, silver, and thallium) detected in soil above vadose zone screening levels and in groundwater above GCL are not related to releases from the site based on professional judgement needs to be explained with additional information and rationale. See General Comment 2.




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As currently described, GSU recommends that the four metals identified in both vadose zone soil and groundwater be assumed to be site related and recommended for CMS.

14

Compound A /

Appendix D/ D.5- Nature

and Extent

D-10

The conclusion that elevated fluoride concentrations detected in wells associated with the Compound A site originated from the STL-IV site because fluoride concentrations were detected in wells associated with the adjacent STL-IV impoundments is not adequately established by the data. The presence of fluoride concentrations associated with the STL-IV impoundments does not preclude Compound A features such as the Compound A pond from also impacting underlying groundwater. In general, an explanation that metal concentrations observed in a well(s) originate from an adjacent RFI site(s) is not acceptable without strong information establishing the site/groundwater relationship at each applicable RFI site. Inspection of Table D-2 indicates that shallow monitoring wells near Compound A pond (RS-12, ES-14, ES-24) have not been sampled for fluoride except for single sample collected from ES-24 in 1987. As currently described, GSU recommends that the fluoride identified in both vadose zone soil and groundwater be assumed to be site related and recommended for CMS.


15

Compound A /


D-11 to D-12

This section states “The potential transport of chemicals of concern at the Compound A Facility RFI Site was assessed by plume stability analysis. Statistical trend analysis was performed to evaluate trends in concentration over time for chemicals detected in the vadose zone above their screening levels at the Compound A Facility RFI Site and chemicals detected in groundwater above GCLs in recent data (2010 to 2014) for wells interpreted to monitor groundwater flow from beneath the Compound A Facility RFI Site.” The same problem exists here as stated previously, in that there are significantly fewer locations sampled in the recent time frame (2010 to 2014). Trend analyses were completed for 22 of the 49 wells/intervals selected for evaluation of the Compound A CUA clusters, and were limited to constituents that met the criteria necessary for analysis. Evaluating concentration time series plots for selected compounds is a good exercise, but additional analyses are needed to assess the nature of plume stability, including an evaluation of any natural attenuation processes. This should be presented in the Groundwater RFI.

Contaminant attenuation processes have been previously presented and described in section 8 of the Draft Site-wide Groundwater Remedial Investigation Report (MWH, 2009). Further information regarding the effects of natural attenuation will be forthcoming in Boeing’s Corrective Measure Study Report for the Chatsworth Formation Operable Unit.



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16 EEL / Section 4 Figure 4-6

Figure 4-6 “Areas and Locations of Soil Recommended for Further Evaluation in CMS for Protection of Groundwater EEL RFI Site” indicate there are two areas and 5 individual points that are recommended for evaluation in CMS. Given that the 5 individual points appear to be along a drainage channel, it is likely that there are other points within the drainage channel that are affected. GSU recommends the area in and around the length of the drainage channel within CUA Cluster CC1 be included for further evaluation in the CMS.

See Boeing’s response to General Comment 2. All soil and bedrock within the perimeter of all chemical use area clusters at each RFI site will be considered as a potential source area to groundwater. A figure presenting potential source areas will be included in a forthcoming addendum to the Boeing Groundwater RFI Report.

17 EEL / Section 4 Figure 4-8

Figure 4-8 indicates there are no TCE data for RS-37 or PZ-018. There are data for RS-37 and PZ-018 and it is presented below.

The maximum TCE concentration detected in RS-37 was 0.94 ug/L in October 2014. This data should be used as further support that TCE has not significantly affected groundwater in this area.

The maximum TCE concentration detected in PZ-018D was 91 ug/L (January 2014). This data should be indicated on the figure and used to evaluate the extent of groundwater contamination. Earlier data also exists for PZ-018B, PZ-018C, and PZ-018E.

It should be noted that evaluation of the data indicates that the interpretation of the lateral extent of the TCE would not change. However, the GSU recommends that this data be incorporated into the interpretations and discussions in the report.

Figure 4-8 shows equivalent TCE concentrations for data collected from 2008 to 2013. Data were not available for this time period to calculate equivalent TCE concentrations for RS-37 and PZ-018.

18 EEL /


C-7

No bedrock vadose zone data has been collected within the EEL CC1. Impacts to bedrock within the EEL CC1 are evaluated only using transport simulations with only one small area being identified as impacted. Additional data may be needed in CMI to further verify and refine the nature and extent of bedrock vadose zone impacts.


19 EEL / Appendix C C-11

Based on the particle tracks and well proximity, additional wells that should be considered to evaluate potential impacts to groundwater for the EEL are: PZ-018, RD-55A, RD-55B, PZ-036, and HAR-34. Well PZ-018 is located adjacent to ES-30 (which is used for EEL evaluation) and has provided recent groundwater data. Wells HAR-34, RD-55A, RD-55B, and PZ-036 are located near the southern extent of the particle tracks simulated to emanate from the

Comment acknowledged. See Boeing’s response to Specific Comment 6.



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EEL during non-pumping conditions. Wells that fall within the boundary of another chemical cluster should not be excluded from evaluation for a specific chemical cluster, especially if different COCs are being evaluated for impacts to groundwater.

20 EEL / Appendix C

C-11 / Table C-1

Four of the twelve (12) wells selected to evaluate the EEL are dry, damaged, or no recent data exist (ES-23, ES-28, PZ-038, and PZ-039), and 2 more wells have been dry since 2011 (RS-15 and RS-17). Additional data may be needed in CMS to further verify and refine the nature and extent of groundwater contamination near these wells (see General Comment 3).


21 EEL /


C-13 / Table

C-ES-1

In addition to the compounds identified as being carried forward to CMS, the following compounds occur in both the vadose zone and groundwater above their respective BTVs/GCLs, or are predicted to do so. They should be carried forward to CMS:

Metals: barium, cadmium, manganese, mercury, selenium, silver, sodium, and strontium. No transport modeling evaluation was performed for calcium and zinc, which were detected in soil above their respective BTVs, and detected in water (below their respective GCLs). This evaluation should either be performed, or these metals should also be carried forward to CMS.

Inorganics: fluoride and nitrate-NO3.


22 EEL /


C-14

Well locations recommended for additional groundwater monitoring include PZ-050 and RS-37. GSU also recommends monitoring wells RS-15, ES-23, and PZ-018 as they are within the impacted area and are not part of the Sitewide Groundwater Monitoring Program. Monitoring well ES-26 should also be monitored since backward particle tracks indicate water in this well is potentially sourced from the EEL CC1. All the wells identified in this comment should be sampled for the chemicals specified on page C-14.

The wells in question fall within CUA cluster boundaries for adjacent sites: RS-15, ES-23, and PZ-018 are located in Compound A CC 1 and ES-26 is located within STL-IV CC 1. These monitoring wells are not proposed for additional groundwater monitoring of the chemicals specified on page C-14 because they are not considered to be the wells that most closely monitor potential impacts from EEL CC 1.



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23

EEL / Appendix D/ D.4-Source Zone

Evaluation

D-7, 3rd Paragrap

h

The text indicates that when metals and inorganics are detected in soil above vadose zone screening levels and detected in groundwater above GCLs, that the groundwater detections are considered representative of background concentrations. The explanation that metals observed in groundwater above GCLs is representative of background concentrations is not acceptable without data establishing the presence or absence of a vadose/ groundwater relationship. As currently described, GSU recommends that the four metals identified in both vadose zone soil and groundwater be assumed to be site related and recommended for CMS. See General Comment 2.


24 EEL /


D-8

This section states that both recent data (from 2010 to 2014, with select Q1 2015) and historical data (prior to 2010) were used to assess the nature and extent of chemical impacts to groundwater beneath the EEL. The use of historical data is not discussed in the remainder of the text and appears to only be used in the statistical trend analyses and to delineate the extent of TCE groundwater impacts (Figure 4-8). Historical data is not used to assess vadose zone transport. The use of only recent data to assess impacts to groundwater limits the data available for assessment of the subsurface. Additional data will be needed in CMS/CMI to further refine the nature and extent of bedrock vadose zone impacts.


25 EEL / Appendix D

Figure D-1

In Figure D-1, the symbol for RS-17 indicates that TCE trend analysis was not evaluated, yet a trend graph for RS-17 is present on the right-hand panel and is noted as being “Indeterminate” in Table D-3. Please reconcile the information in the figure.

The symbol for RS-17 should have indicated an indeterminate trend for TCE on Figure D-1. Any future presentation of this data will be corrected as such.

26 STL-IV / Appendix C C-7

Bedrock vadose zone data was only collected from 1 location (PZ-015) within the STL-IV site. Bedrock vadose zone thickness within STL-IV is up to 114 feet thick with it commonly ranging between 30 to 50 feet thick. A significant number of source areas have been identified in soil, with impacts to bedrock and groundwater evaluated using transport simulations. Additional data may be needed in CMI to further verify and refine the nature and extent of bedrock vadose zone impacts.




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27 STL-IV /

Appendix C / Section 4

C-8, C-13-14

The following limitations in the data, used in the evaluation of the vadose zone impacts to groundwater, were identified:

Bedrock vadose zone samples were only collected from one location (PZ-015).

Twenty-two (22) well locations/intervals were recommended to be sampled from 2013 to 2015 (C.3 Fieldwork, page C-8), but eight (8) of these wells (ES-26, ES-27, HAR-32, HAR-33, PZ-037, RD-58A, WS-09A, PZ-040) were either dry or contained insufficient water for sampling during this time frame.

Eighteen (18) of forty-five (45) key wells (ES-32, PZ-015A/B/C/D/E/F, PZ-040, HAR-34, PZ-037, RS-13, WS-09A, RD-67, FDP-881, FDP-882, SP-881A/B, OS-14/FDP-890, SP-890A/B)) from the list of wells selected for evaluation of the STL-IV CUA clusters do not have available recent groundwater data (from 2010 to 1st quarter 2015).

GSU expects further evaluation of potential source areas within the CMI using the updated model and future data collected from existing representative monitoring wells and additional deeper replacement wells at locations where existing monitoring system is not adequate (see General Comment 3).


28 STL-IV /

Appendix C / Appendix D

C-13 D-6

The following wells should be considered to evaluate potential impacts to groundwater: HAR-17, PZ-014A-E, PZ-032, PZ-033, PZ-034, PZ-035, PZ-036, PZ-053, PZ-054, ES-14, ES-15, ES-16, ES-24, ES-25, RS-09, RS-12, RS-14, RD-06, FDP-A56, FDP-882B, FDP-882E, ND-115, ND-117, and SH-11. The particle tracks emanating from the different chemical clusters of STL-IV appear to come through or are nearby these monitoring points. Wells FDP-882B, FDP-882E, PZ-053, PZ-054, and RD-06 are identified as wells selected to evaluate potential impacts to groundwater from chemicals in the vadose zone in Appendix D (p. D-6), however these wells are not identified in Appendix C as being selected to evaluate any of the CUA clusters. Wells ES-14, ES-15, ES-16, ES-24, RS-09, PZ-014, PZ-033, and PZ-034 are identified as being “considered” for evaluation, but not “selected” for evaluation, likely because they are identified as Compound A wells. In addition to being included in the STL-IV groundwater evaluation, the wells identified above should also be used to monitor current and future groundwater impacts from STL-IV.




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Wells that fall within the boundary of another chemical cluster should not be excluded from evaluation for a specific chemical cluster, especially if different COCs are being evaluated for impacts to groundwater. For each specific chemical cluster, all wells that fall within the boundary of the chemical cluster and that intersect forward or backward particle tracks from/to that chemical cluster should be additionally included in the evaluation specific to the identified chemical cluster. Not including a well because it is in another CUA or is monitored elsewhere is not acceptable if groundwater has the potential to flow toward that well.

29 STL-IV /

Appendix C / Appendix C

Figure C-2

Figure D-1

The particle track figures, are not useful to the reader. The GSU recommends adding additional figures at scales where the particle tracks are clearer and the monitoring well network can be further evaluated. The depth of the particles as they travel away from their input source zone should also be represented, perhaps via a color scale. Each Chemical Cluster should be broken out into its own set of figures (one for forward particle tracks and one for backward particle tracks). These figures should be scaled to show the 1,000-meter particle tracks for the chemical cluster being represented and presented on 11x17-inch sized paper.

See Boeing’s response to General Comment 6 regarding 1,000-meter particle tracks. Boeing had previously provided 1,000 meter length particle tracks to DTSC in the 2016 Gold Copy.

30 STL-IV / Appendix C

Table C-ES-1

In addition to the compounds identified as being carried forward to CMS, the following compounds occur in both the vadose zone and groundwater above their respective BTVs/GCLs, or are predicted to do so. They should be carried forward to CMS:

CC1: bis(2-ethylhexyl)phthalate, benzo(ghi)perylene, boron, manganese, molybdenum, nickel, silver, sodium, and fluoride

CC2: benzo(ghi)perylene, barium, lithium, mercury, molybdenum, selenium, silver, sodium, and fluoride

CC3: benzo(ghi)perylene, calcium, mercury, silver, and sodium CC4: bis(2-ethylhexyl) phthalate, benzo(ghi)perylene, fluoride, and

Nitrate-NO3 CC6: benzo(ghi)perylene, fluoride, and Nitrate-NO3 CC7: benzo(ghi)perylene, sodium, and fluoride CC9: benzo(ghi)perylene, boron, molybdenum, and fluoride CC10: benzo(ghi)perylene CC11: boron, lithium, and potassium CC12-2: silver




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31 STL-IV / Appendix C

Table C-ES-1

The qualifier (d) is used throughout the Groundwater Data column with no explanation as to what (d) is referring to in the footnotes to the table. Please clarify what the qualifier (d) means.

Table C-ES-1 should have included the following note: “(d) No groundwater data from 2010 through 2014 is available for this chemical at the wells selected for evaluation of the CUA cluster. Transport modeling was performed to determine whether this chemical will leach from the vadose zone to groundwater at concentrations above the GCL.”

32

STL-IV / Appendix D/ D.4-Source

Zone Evaluation

D-5 – D-7

The explanation that 8 metals (copper, lithium, manganese, molybdenum, nickel, potassium, selenium, and silver) detected in soil above vadose zone screening levels and in groundwater above GCL are not related to releases from the site based on professional judgement needs to be explained with additional information and rationale. As currently described, GSU recommends that the 8 metals identified in both vadose zone soil and groundwater be assumed to be site related and recommended for CMS. See General Comment 2.


33 STL-IV Appendix D D-12

See Specific Comment 15 (above) for application to the STL-IV RFI Site. Trend analyses were only completed for 18 of the 53 wells/intervals selected for evaluation of the STL-IV CUA clusters, and only for constituents that met the criteria necessary for analysis.

See response to Specific Comment 15.

34 STL-IV /


D-8

This section states that both recent data (from 2010 to 2014, with select Q1 2015) and historical data (prior to 2010) were used to assess the nature and extent of chemical impacts to groundwater beneath the STL-IV RFI site. The use of historical data is not discussed in the remainder of the text and appears to only be used in the statistical trend analyses and to delineate the extent of TCE groundwater impacts (Figure 4-8). Historical data is not used to assess vadose zone transport. The use of only recent data to assess impacts to groundwater limits the data available for assessment of the subsurface.




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Additional data will be needed in CMS/CMI to further refine the nature and extent of bedrock vadose zone impacts.

35

STP-3 Appendix C Section C-2,

C-3, C-4

The following limitations in the data, used in the evaluation of the vadose zone impacts to groundwater, were identified:

Fifteen wells/intervals were recommended to be sampled in 2013 to 2015 data gap sampling for the vadose zone to groundwater evaluation for STP-3, but 13 wells were either damaged, dry, or did not contain sufficient water to collect a sample.

Several wells (10 out of 15 wells) from the list of wells selected for evaluation of the STP-3 CUA cluster do not have recent groundwater data, either because they are dry or were not sampled during this time frame or were not considered in the analysis.

GSU believes an additional 13 wells (ES-14, ES-16, ES-17, ES-24, ES-25, ES-32, HAR-33, PZ-015A-G, PZ-032, PZ-034, RS-09, RS-12, and RS-14) should be included in the groundwater evaluation for STP-3 (based on particle tracks).

GSU expects further evaluation of potential source areas during remedy selection or implementation using the updated model and future data collected from existing representative monitoring wells and additional deeper replacement wells at locations where existing monitoring system is not functional (see General Comment 3).


36

STP-3 Appendix C / Section C-4 Appendix D / Section D-4

C-11 / D-7

The following wells should be considered to evaluate potential impacts to groundwater: ES-14, ES-16, ES-17, ES-24, ES-25, ES-32, HAR-33, PZ-015AG, PZ-032, PZ-034, RS-09, RS-12, and RS-14. The forward and backward particle tracks created for STP-3 CC1 come through or are nearby these monitoring points. In addition to being included in the STP-3 groundwater evaluation, the wells identified above should also be used to monitor current and future groundwater impacts from STP-3. Wells that fall within the boundary of another chemical cluster should not be excluded from evaluation for a specific chemical cluster.


37

STP-3 / Appendix D/ D.5-Nature

and Extent

D-8

The explanation that 4 metals (lithium, molybdenum, nickel, and selenium) detected in soil above vadose zone screening levels and in groundwater above GCL are not related to releases from the site based on professional judgement needs to be explained with additional information and rationale. See General Comment 2.




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It should be noted that there are no monitoring wells within this RFI Site so that groundwater data cited for the Area III Sewage Treatment Plant is located within adjacent RFI Sites. Due to the lack of groundwater data from the RFI Site, GSU recommends that the four metals identified in vadose zone soil be assumed to be have impacted groundwater and evaluated in CMS.

38 STP-3 /


C-13

In addition to the compounds identified as being carried forward to CMS, DTSC GSU also recommends benzo(ghi)perylene, lithium, molybdenum, nickel, and selenium be carried forward to CMS. These chemicals occur in both the vadose zone and groundwater above their respective BTVs/GCLs (metals) or were not sampled for in groundwater (benzo(ghi)perylene).


39 STP-3 /


D-7

This section states that both recent data (from 2010 to 2014, with select Q1 2015) and historical data (prior to 2010) were used to assess the nature and extent of chemical impacts to groundwater beneath the STP-3 RFI site. The use of historical data is not discussed in the remainder of the text and appears to only be used in the statistical trend analyses and to delineate the extent of TCE groundwater impacts (Figure 4-8). Historical data is not used to assess vadose zone transport. The use of only recent data to assess impacts to groundwater limits the data available for assessment of the subsurface. Additional data will be needed in CMS/CMI to further refine the nature and extent of bedrock vadose zone impacts.




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Comment from Radiologic Health Branch, California Department of Health

1

RFI Data Summary Report for

Subarea 5/9 South,

Appendix C, “Summary of Radiological

Data” attachment

NA

RHB’s review included a dose assessment for each radionuclide that exceeded the soil characterization level (SCL) using RESRAD Onsite (Version 7). The results of the review were summarized as: The data provided in the site reports supports the recommendations in the “Summary of Radiological Data” attachment with the following exception:

The STL-IV sample location for sample A3-SED-DG-16 (result of 0.817 pCi/g Strontium-90 (Sr90) seems high compared to the SCL of 0.24 pCi/g. The sample location A3-SED-DG-16 should be part of the remediation action.

Radiological data associated with Boeing RFI Subarea 5/9 South will be evaluated in upcoming human health and ecological risk assessments following a standardized risk assessment methodology. The areas recommended for further evaluation during CMS to address potential exposure to future potential human receptors will be determined based on the results of the human health risk assessments.

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