UNITED STATES ENVIRONMENTAL PROTECTION AGENCY REGION 5

March 20,2014

Mr. Todd Konechne The Dow Chemical Company 1111 Washington Street Midland, MI 48640

77 W. JACKSON BOULEVARD CIDCAGO, ILLINOIS 60604-3590

RE: Draft Tittabawassee River Floodplain Response Proposal Tittabawassee River, Saginaw River & Bay Site, Michigan EPA Document #EPA2014.001

Dear Mr. Konechne:

Reply to the Attention Of: SR -6J

The United States Environmental Protection Agency (EPA), in consultation with the Michigan Department of Environmental Quality (MDEQ) (jointly, the Agencies), has reviewed the draft Tittabawassee River Floodplain Response Proposal (FP RP) for the Tittabawassee River, Saginaw River & Bay site. The draft FP RP, dated December 2, 2013, was submitted by The Dow Chemical Company (Dow) pursuant to requirements of the January 2010 Administrative Settlement Agreement and Order on Consent (AOC), and Section VI, Task 8 of the Statement of Work (SOW)~ Appendix A to the AOC.

The Agencies have reviewed the draft FP RP in accordance with Sections X and XI ofthe AOC. The Trustees also provided review comments. Consolidated comments are attached. In accordance with paragraph 37 of the AOC, EPA is requesting Dow to review the comments, revise the FP RP accordingly, and resubmit the document in accordance with the AOC and SOW. EPA is requesting that Dow submit the revised FP RP no later than May 9, 2014. EPA is also requesting Dow to submit a written response to comments along with the revised document.

Please contact me at (312) 886-4699 if you have any questions.

Sincerely,

··'1t, :A-1 r j , u :r

Mary P. Logan Remedial Project Manager

cc via email: A. Taylor- MDEQ L. Williams- FWS T. Prendiville, D. Russell, J. Cahn, C. Garypie- EPA J. Pistro, K. Cosan- Dow S. Hayter- Environ

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Agencies' Review Comments on Draft Tittabawassee River Floodplain Response Proposal Dated December 2, 2013

Tittabawassee River, Saginaw River & Bay Site, Michigan

A. Major Comments

1. Nature and Extent of Contamination- The FP RP should include additional detail about the nature and extent of contamination in the floodplain. The document does not have to reproduce the level of detail that is included in the Geomorph reports (which will be in the Administrative Record for the site), but should include enough detail for unfamiliar reviewers. Specific comments follow below. The areas that need more detail include: summary of PCOI distribution (e.g., by segment and/or reach, north vs. south side of river, depth); the focus on the 8-year floodplain; and updated figures.

2. Secondary Constituents oflnterest (SCOis)- The draft FP RP does not contain a detailed evaluation of SCOis. At this time, the Agencies are neither accepting nor rejecting the SCOI conclusions in Section 3.3 and Appendix B, because sufficient information is not available. SCOis will need to be evaluated (and addressed, as needed) before the Agencies can determine that the floodplain is complete. At this point, there are two options:

a. The draft FP RP could be revised to present a systematic evaluation of other contaminants that have been detected in floodplain soils for screening and comparison against applicable environmental clean-up standards and screening criteria (e.g., number of detections, background levels, EPA Regional Screening Levels, Part 201 criteria, etc.). OR

b. Because the current focus is on potential unacceptable PCOI risks from soil, EPA can agree that the SCOI evaluation should not hinder the development and selection of response options based on mitigating human direct contact with TEQ in floodplain soil. However, floodplain soil SCOis will need to be thoroughly evaluated in Task 10 or sooner. The Agencies want to avoid a situation where re-work due to SCOis (if any) is required at properties.

3. Section 3.2- Hydrologic Conditions. The conclusions regarding the potential significance for erosion of floodplain soils (and associated TEQ) back into the river or relocated from one floodplain area to another are not fully accepted. Specific comments are offered below. However, EPA has determined that this should not hinder the development and selection of response options based on mitigating human direct contact with floodplain soil, but may result in additional analysis/work and/or post-construction monitoring. Please be aware that even if the Response Proposal is finalized for the purposes of soliciting public input on the floodplain cleanup options, the Agencies reserve our rights to comment on the technical analysis around this issue.

4. Section 3.3 and Appendix B- Biological Conditions. Specific comments are offered below. This section discusses EPA guidance on conducting ecological risk assessments (ERAs) and risk management. While this document is not and does not contend it is the floodplain ERA, it does make risk conclusions and risk management recommendations. Until an ERA is conducted, the Agencies are neither agreeing nor disagreeing with the conclusions and

recommendations. However, EPA has determined that this should not hinder the development and selection of response options based on mitigating human direct contact with floodplain soil, but may result in additional analysis/work, post-construction monitoring, and/or Task 10 analysis/work. Please be aware that even if the Response Proposal is finalized for the purposes of soliciting public input on the floodplain cleanup options, the Agencies reserve our rights to comment on the technical analysis around this issue.

5. Section 4.1, Conceptual Site Model (CSM) and Figure 4-1 and Section 4.2, Remedial Action Objectives (RAOs):

a. Superfund non-time critical removal authority is being used for this Response Proposal. As such, and pursuant to the 20 I 0 AOC, any decision made by EPA, in consultation with the MDEQ, will not constitute the final remedy for the Tittabawassee River Floodplain- a final remedy determination will be made in a later Record of Decision (ROD). At the time ofthe final ROD (or earlier, if warranted) the Agencies will evaluate whether additional response actions may be necessary for the Floodplain. Including, but not limited to the Agencies potential evaluation tools, a residual risk assessment (Task I 0) that completely and fully evaluates all potential floodplain exposure pathways (human and ecological, PCOis and SCOis) will be used to assess the need for further actions at the site.

b. Please see specific comments below. The draft FP RP appears to focus solely on the incidental soil ingestion component of the direct human contact pathway for TEQ. The FP RP needs to clearly identify those exposure pathways that are not being explicitly addressed and identify where in the overall remedial process these pathways will be addressed. The CSM and basis for action are fundamentally important and the Agencies are willing to discuss how best to represent them in the revised FP RP.

6. Floodplain Response Action Criteria, Sections 3.5 and 4.4 and Appendix C-As you know, the Agencies have been evaluating site-specific exposure input parameters to develop numeric site-specific preliminary remediation goals (PRGs) that would be used to trigger a response action for floodplain soil. Region 5 is currently working with EPA Headquarters on PRGs based on human direct contact (ingestion and dermal absorption) exposures. The PRGs proposed by EPA, in consultation with MDEQ, will be communicated separately to Dow for inclusion in tl1e FP RP. The PRGs will be subject to public comment before being finalized. EPA anticipates developing a detailed technical memorandum, in consultation with MDEQ, explaining the PRG development. Simpler explanations for the public will also be developed. These materials will become part of the Administrative Record for the site. While Dow's team has met with the Agencies to discuss exposure input parameters and the supporting data sets, EPA believes that Appendix C will not be necessary because the Agencies will have developed the technical PRG memo and other materials.

7. Section 6.2, Common Elements, Land Use Management. Because this is such an important component of the FP RP, please provide a significantly expanded discussion. Specific comments follow below.

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8. Implementation Detail- Under the Superfund process, EPA implementation detail typically is developed during design. However, in this case it is reasonable to expect the public to have some implementation questions and concems. Therefore, EPA, working with MDEQ and Dow, plans to develop some high level materials to try to address some reasonably expected implementation questions. We will be developing these over the next several months. This is not intended to circumvent the process discussed in Section 7, but to try to prepare for possible public questions. We also anticipate that, in addition to the public comment process for the proposed decision, we will conduct outreach as more information is developed and as the cleanup proceeds.

9. Most, if not all figures in the draft TRFR-RP should be revised to include stationing and be printed (and have electronic resolution) at a scale that will allow for easier review.

10. It would be very helpful if the shape files used to generate Figures 2-2A-F, 2-3A-F, 2-4A-F, 3-1A-F, and 3-2A-F were provided as a geodatabase. This will allow the reviewers to project the TEQ concentrations on land use, geomorphic features, etc.

B. Specific Comments

11. Section 1 - Introduction. Page 1. Paragraph 2. The description of EPA's approvals of the Tittabawassee River Segment 1 and Segment 2 Response Proposals should be clarified to indicate that the Response Proposals were approved with modifications.

12. Section 1 -Introduction. Page 1. Paragraph 4. The first sentence in this paragraph should be revised as follows (or similar): "This Floodplain Response Proposal identifies and evaluates potential response options for addressing specific exposure pathways in the Tittabawassee River floodplain ... "

13. Section 1.1, -p.2, paragraph 3, first sentence: should read "between Dow and EPA leading to the decision that. ; . "

14. Section 2.1, p. 4 a. paragraph 1, last sentence: should read "miles ofthe Tittabawassee River ... "

b. Paragraph 2. The defmition of floodplain in the first sentence should be revised to clarify that it includes the riverbanks.

c. Paragraph 2. It would help if this section provides a more complete description of the rationale for why the draft TRFP-RP focuses on the 8-year floodplain. The simplest approach might be to reference Section 3.1.2 (see comments on that section, below).

15. Section 2.3- Source Control. Page 6. Last Paragraph. This paragraph should be revised to indicate that primary sources are being controlled and monitored at the Dow plant site- they have not been "eliminated."

16. Section 2.4 - Geomorphic Characteristics. Page 7. Paragraph 5. Two clarifications would be useful here: 1) Pre-industrial levees may contain PCOis at the surface of the feature; and 2)

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The industrial-age levees are located closer to the river channel and may contain deposits of contaminants that began being released to the river more than 100 years ago.

17. Section 2.5.1- Land Types. Page 8. Some terms would benefit from greater clarity: "active agriculture" -does this include all "farm" land use such as fallow field and pasture or only cultivated fields as indicated on page 11 ?; "unforested upland" - does this include park, or pasture/field?; "hard surface" - does this include urban areas, paved roads, unpaved roads?

18. Section 2.5.2- Habitat. ·The habitat descriptions appear to be general habitat types in Michigan rather than being specific to the Tittabawassee River floodplain. Please provide more accurate descriptions of the actual, existing habitats. The following are several examples where information could be clarified in lieu of using general descriptions

a . Floodplain forests along the Tittabawassee River include eastern cottonwood as a dominant species. Also, ash trees in the area are dead or dying because of the emerald ash borer (note: the scientific name of green ash is Fraxinus pennsylvanica, not Frazinus pennsylvanica.)

b. The Proposal includes language about how Indiana bat "often establishes roosts and nurseries in standing snags", yet the Indiana bat is an endangered species and the Tittabawassee River floodplain is at the northern edge of its range. The Indiana bat may establish roosts and nurseries in standing snags along the Tittabawassee River, but this species is not likely to be abundant as implied by the word "often".

c. For forested uplands, the general list of dominant hardwood species given in the Proposal is not appropriate for the Tittabawassee River floodplain.

19. Section 2.5.2. Accurate descriptions of the presence and value of existing habitats in areas requiring access and cleanup will assist in design and implementation (i.e., a more valuable habitat may necessitate a less invasive remedy approach). This can be done on a segment­by-segment basis as the cleanup proceeds upstream to downstream; however, this information for Segment 2 will be necessary in the short te1m to evaluate work proposed to be conducted in Segment 2.

20. Section 2.5.2. Top ofp. 10. The State of Michigan's definition of wetlands should be described and cited in addition to the other definitions given. Additional infmmation should be provided here or elsewhere on actual, on-the-ground wetland delineations that have been done or are planned for the floodplain.

21. Section 2.5.2. Bottom ofp. 10. The conect scientific name for mink is Neovison vison.

22. Section 2.5.3 - Floodplain Services and Beneficial Uses. Page 11. Paragraph 1. The following is a suggested addition to this section: "The beneficial shading effect of woody stream bank vegetation helps to avoid temperature stress on plants and animals. Large woody vegetation and debris provides cover, nesting, resting areas, and food for fish and wildlife." This section could be further expanded to note that these areas also reduce runoff into the river.

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23 . Section 2.6 - Floodplain Land Use. Please provide more detail on how land uses were delineated and how they will be applied to remedy implementation:

a. Please clarify that the initial dete1mination of land uses will be verified as the remedial activities are implemented, on a segment-by-segment and/or property-by­property basis.

b. From the perspective of Michigan's corrective action program, remedial decisions will need to be made on current and reasonably foreseeable land uses. Therefore, the zoning status of properties will be important to evaluate during design and implementation because they relate to reasonably foreseeable land uses.

c. The description of active agriculture should be clarified. For example, the first bullet indicates that active agriculture includes areas used for crop cultivation, such as com and soybeans. Does it also include pasture areas and agricultural land that is zoned agricultural but is currently fallow? It would be helpful to expand the definition to indicate what agricultural activities, if any, are not included.

d. It would be helpful to expand the "unmaintained" discussion to include how much is "residential unmaintained" and the acreage of agricultural property identified as "unmaintained."

e. Under the business/commercial land use category, the Proposal lists "a golf course in the city of Saginaw". Is this the former Germania golf course? If so, the acreage associated with this parcel should be removed from this category. Germania is undergoing succession to a grassland/savanna habitat type, and is currently owned by The Nature Conservancy pending transfer to the U.S. Fish and Wildlife Service to become part of the Shiawassee National Wildlife Refuge.

24. Section 2.7- Previous Floodplain Response Actions. Pages 12- 13. a. Please clarify paragraph 6. Certain actions that were conducted under DEQ oversight

are interim response activities and are not conservative as indicated in the text. In pmiicular, interim response actions that were conducted on residential properties such as providing soil cover and establishing grass in areas of bare soil and house cleaning were conducted as short term exposure controls until a final remedy could be implemented. All references to response actions in Paragraph 6 on page 12 should be replaced with "interim response actions."

b. The description ofresponse actions conducted at public parks is incomplete. 1. These activities were conducted as "interim responses" and will have to be

evaluated to determine if ce1iain components of these interim responses will be adequate for fmal remedy.

n. At Freeland Festival Pm·k, the stone wall was constrUcted to direct access to a Dow constructed fishing dock in order to limit contact with bank soils. In addition, a warning layer was placed in the excavated areas to identify. the bottom of the placed clean soils.

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111. At !merman Park, interim response activities also included moving the "bark park" up out of the frequently flooded area and the construction of a cross country prep area/roller hockey rink to limit contact with soils.

c. The description of work conducted at Riverside Drive should indicate the gravel road was replaced with pavement and drainage was improved.

d. The number of Task 1 properties is believed to be 46, not 44.

e. Consider including the removal action at J/K that involved soil removal and fencing in an area with high concentrations of PCOis in the floodplain soils to limit human exposure.

25. Section 3 .1.1 Floodplain Soil Sampling. a. Page 14. Paragraph 3. This paragraph indicates that a change in sampling approach

for the lower Tittabawassee River to identifY areas with TEQ levels greater than 1000 ppt TEQ was conducted in consultation with the DEQ. This is an incomplete description. As noted in the July 10, 2008 approval with modifications letter for the 2008 GeoMorph Sampling and Analysis Plan, Dow retains the obligation to conduct additional characterization, as necessary to define the areas of the floodplain that will require remedial actions.

b. Page 15. Paragraph 1. It should be noted that the step out sampling identified by the Interim Response Activities (IRA) Implementation Decision Tree was approved specifically for the purposes of identifYing those areas where early actions to control exposure to higher TEQ levels may be necessary in the short term.

c. Page 15, 2nd bullet- Please check the dates when post-flood sampling was conducted. At Riverside, we believe that sampling was done in 2009, 2011 and 2013.

26. Section 3.1.2 Floodplain Soil PCOis- See Major Comment 1, above. a. Please provide some manageable summaries of the data. Consider the following to

better describe the nature and extent of PCOis: surface and sub-surface sununary statistics by reach and/or segment; patterns ofPCOI distribution within the different land types, land uses, and geomorphic features; and/or patterns of PCOI distribution within the entire floodplain (e.g., north vs. south sides, reaches).

b. Figures 3-1A through 3-1F. As noted earlier, these figures would be more useful at a larger scale and with stationing. Without stationing it is not possible to associate a sample location with a concentration in this document. Please produce new figures that include the sample location identification number and the actual surface soil concentrations. In addition, please include a set of figures showing the maximum soil concentration at each sample location and the depth interval of the maximum soil concentration ..

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c. Page 16. Paragraphs 1 and 2. It is not clear that it will be appropriate to only use the existing SAC for remedial decision making. Additional data may be required pre­design depending on the level of uncertainty that can be tolerated for the specific remedial decision. In addition, it is not clear that it is appropriate to base the SAC on the top six inches of soil vs. the concentration present throughout some specified depth of the soil column. These issues must be resolved as part of design planning.

d. Page 16. Additional data may be necessary in some cases to confirm the estimated proxy values - again depending on the level of uncertainty that can be tolerated for the specific remedial decision.

e. Figures 3-2A through 3-2F. Page 17. The actual calculated SAC concentrations for each SAC polygon should be provided (preferably actual SAC values plotted on the maps and included as an Appendix to the draft TRFP-RP with supporting underlying data). In addition, the concentration ranges shown on the figures are too coarse to be meaningful for remedial decision making. Once the site-specific cleanup or "trigger" criteria are identified, the maps should be revised to focus on ranges that are meaningful with respect to those criteria.

f. Page 17. Paragraph 3 - Please expand this discussion to provide more information on the use of the 8-year floodplain boundary. It would be helpful to include the information on the 8-year floodplain presented in 2/20/2014 meeting. That would clarity the data distribution outside that boundary. For example, the statement "over 80% of these samples are less than 50 ppt" could be interpreted in multiple ways. The Agencies do not consider the 8-year floodplain boundary to be a "bright line" and the actual boundary will be refined, as needed, during design. We will also consider the potential for soil relocation outside of the 8-year floodplain, as needed.

g. Page 17. Paragraph 4. Please provide a more complete treatment of the depth distribution ofPCOis in floodplain soils. Statistical summaries of subsurface PCOI data would be helpful by reach, segment and/or geomorphic unit. The RP also should clarify that "surface" for the purpose of presenting nature and extent of TEQ in the FP RP vs. "surface" as applied to decisions about property cleanup may be different. The description of how much (percentage) subsurface contamination level decreases as you move away from the levees is not meaningful in terms of identifying the actual depth of contamination that may need to be addressed in the response actions. Additional representative cross sections should be provided to illustrate how and where the depth of contamination changes as you move downriver. In addition, the range of contamination plotted on the example cross-sections (Figures 3-3A and 3-3B) is too coarse to be useful for review purposes (see above comments on SAC map concentration ranges).

27. Section 3.2- Hydrologic Conditions. See Major Comment 3, above. Some reviewers believe that the FP RP has not made a credible case that the erosion and movement of contaminated floodplain soils within the floodplain and/or back into the river is insignificant in terms of transport and exposure risks.

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a. The Agencies may need to better understand the hydrodynamic modeling assumptions and results in order to evaluate the model predictions for floodplain inundation frequency, bed shear stresses, and erosion potential. For example, what topography and bathymetry were used in developing the flow field? How was vegetation on the floodplain parameterized in terms of its influence on surface roughness? How well do simulated water smface elevations and velocities compare to observations, both for in-channel and overbank flows? Would active agricultmal fields with representative farming teclmologies (e.g., no-till, plowed, etc.) and sparse spring vegetation affect the results? It is possible that all of this information is contained in another repmi that is not cited here; however, the information cited and presented in the Response Proposal is insufficient to evaluate the erosion potential of different flow regimes. [NOTE: Section 3.2 indicates that the details of the hydrodynamic model can be found in Appendix D2 of the Tittabawassee River Segment 1 Response Proposal. However, Appendix D is actually titled "Response Technology Case Histories from Other Sites." Should this be Appendix C?]

b. Section 3.2.1. Should floodplain inundation frequency be evaluated based on the entire historical record, rather than a 22-year simulation period? The USGS has posted statistics on armual maximum flows at Midland dating back to 1876, and complete daily data are available from 1936 to the present (USGS, 2013). Given the inherent uncertainty in estimating extreme flows based on short dmation time series, the floodplain inundation analysis should take advantage of this long record to evaluate erosion risk. The simulation period used affects the results significantly. For example, Table 3-2 indicates that a flow rate of 12,800 cfs represents an approximately 2-year recurrence interval event based on the 22-year model run. However, based on an analysis of the armual maximum time series from the USGS Midland gage, a 2-year event is approximately 10% larger, or 14,200 cfs. The 5 and 10 year events are also underestimated in Table 3-2, by approximately 15% each. The flow that is simulated as a I 0-year event is actually closer to a 5-year event based on the USGS annual maximum time series; a flow that inundates 75% of the floodplain actually occms approximately twice as often as the repmi suggests (see Table 3-2). Put another way, the text on page 18 indicates floods with return periods between 2 and 5 years occurred 27 times in the 22 year simulation period. This suggests a flood frequency of between 9 months and 1 year rather than 2 to 5 years. Hence, quantification of the risk of COI erosion and resuspension may be systematically underestimated based on the use of only a portion of the streamflow record.

c. Sections 3 .2.1 and 3 .2.2 the hydrodynamic model results would be more useful presented as maps, rather than bar graphs. As currently presented, the results of the hydrodynamic modeling are presented in Figures 3-5 and 3-6 as bar graphs showing the proportion of the 1 00-year floodplain inundated under various flow conditions. However, given that the distribution ofTEQ in the floodplain is non-uniform, this presentation does not provide a way of evaluating the risk of TEQ resuspension. Model results should instead be shown as maps, to illustrate which portions of the floodplain are inundated under different flow conditions (Figme 3-5) and where on the floodplain bed shear stresses are projected to exceed threshold values (Figme 3-

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6). Instead of proportions, acreage should be reported. If proportions are included, they should be of the 8-year floodplain, not 1 00-year floodplain, since the 8-year floodplain is predominantly considered the impacted extent. These comments also apply to the floodplain inundation column provided in Table 3-2.

28. Section 3.3 and Appendix B- Biological Conditions. See Major Comment 4, above. a. Based solely upon the information provided in this document, it is unclear whether or

not exposure data was collected to support the claims that contaminant wildlife adverse effects are acceptable. Documentation should be presented which indicate the wildlife evaluated are within the exposure pathway, are exposed to site contaminants and at what levels. A full presentation of all of the data is not necessary. However, there should be a level of presentation which allows the reader to assess the exposures evaluated and the conclusions drawn.

b. The document or the ERA should provide a discussion of the "measures of adverse effects" and why the measures studied were selected. Stating that a measure has individual, reproductive and/or has population level implications does not mean it was the correct measure for the contaminant and or ecosystem. While the conclusions made may be correct, there does not appear to have been a process through which the stakeholders had input to the studies conducted. The selection of "measures of effects" is one of the critical steps in the problem formulation of an ERA. While this document is not and does not contend it is the floodplain ERA or that a floodplain ERA was conducted, it does make risk conclusions and risk management recommendations. The document concludes that wildlife within the floodplain are not substantively impacted by the contamination present. That conclusion is effectively an ERA conclusion, that any ecological risk which exists is acceptable. Again, while the conclusion may be correct, the endpoints used to reach the conclusion do not appear to have been vetted and/or agreed to by the Site Stakeholders. Since the measures of effects were not agreed to by EPA for the ERA (SMDP Step 4 ofthe ERA process) it is problematic to concur with the ultimate conclusion presented. A presentation of the measures of effects utilized compared to other alternatives would allow the reader to evaluate the document conclusions. Alternatively, such an evaluation would be valuable for the ERA which is yet to be conducted.

c. The Trustees made a number of comments that may need to be considered in the ERA. However, there appear to be several inconsistencies between the FP RP's summary of the MSU-ATL study results and the results as published by the MSU­ATL investigators in peer-reviewed publications and dissertations. In some instances, they could not corroborate information summarized in the RP when they reviewed the originally cited publications. Examples include the following.

1. For house wren, tree swallow, and eastern bluebird, the RP states "It was determined that nests that were preyed upon or abandoned comprised the majority of nests that were not successful," citing results presented by Fredricks et al. (2012). However, a review of Fredricks et al. (2012) reveals that the authors did not find that these failed nests comprised a majority,

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reporting that ' 'Nest abandonment and predation events accounted for approximately 25, 23, and 27% ofHOWR, TRES, and EABL clutches that failed during 2005 through 2007." Additionally, Fredricks (2009) repmied that predation caused the failure of "17%, 16%, and 16% of initiated clutches for house wrens, tree swallows, and eastern bluebirds, respectively."

u. The RP states that "For the canine species, a certified veterinarian pathologist noted good overall health, and no histological malformations in the liver, kidney, lymph nodes, brain, and jaw tissues upon examination," citing Moore (2009) as the source of canine information. However, we could find no mention of brain and jaw tissue malformations in Moore (2009). In fact, jaw histology was cited by Moore (2009) as a potential biomarker endpoint that needed further study.

111. The RP cites Fredricks et al. (2012) when stating that reproductive endpoints (hatching success, fledging success, and productivity) are similar or greater in downriver Tittabawassee River sites than in reference sites. This is an overly general statement that is not supported by the data presented in Table B.3c in the Appendix of the Response Proposal, nor in the cited publication. In fact, values reported by Fredricks et al. (2012) for the studied endpoints were all lower in downriver Tittabawassee River sites for house wren and tree swallow; eastern bluebird is the only passerine species in which downriver reproductive parameters were similar or greater than in reference sites.

IV. There are also a suite of biological endpoints that the RP repo11s were included from the MSUATL study for which (1) the RP makes conclusions regarding no adverse effects, but does not provide any data to support the conclusions, and (2) the cited sources do not corroborate the summary. For example the RP reports that great horned owl radio telemetry studies occurred, citing Coefield (2010) and Coefield et al. (2010a, 2010b). However, when we reviewed these publications, we could not find any mention of radio telemetry studies (Coefield, 201 0; Coefield et al., 201 Oa, 201 Ob ).

29. Section 3.3.2. Threatened and Endangered Species, pages 27-28, Tables 3-4 and 3-5. a. We recommend the text on pages 27-28 and Table 3-4 be revised to include two

species currently proposed for listing under the Act. These include the northern long­eared bat (Myotis septentrionalis), and the rufa red knot (Calidris canutus rufa). Both species are identified as potentially occurring in Saginaw County.

b. Tables 3-4 and 3-5 identify a list of documented occurrences and the listed status of rare animals and plants within the Tittabawassee River Floodplain. According to footnote f, " ... potential species presence in the OUl Floodplain were based on documented occurrences in Midland County and the species habitat requirements." Saginaw County also needs to be included.

c. Table 3-4 also characterizes the potential for exposure of each rare animal species to floodplain soils. Exposure through dietary pathways is often more significant than incidental soil ingestion for insectivores and predators. Without additional

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explanations, we do not agree with many ofthe determinations of no exposure to floodplain soil for even an incidental soil ingestion pathway.

d. Table 3-5 also characterizes the potential for exposure of each rare plant species to floodplain soils. Tlus is not really an appropriate question for plants. Beak grass is listed as "Potentially, but not likely" and we know that it is present in the floodplain and relocated during the Reach N bank work.

30. Section 3.4.3. The RP reports not identifying any historic and cultural sites in the floodplain when using an online tool (http://tps.cr.nps.gov/nhl/result2 .cfm ) to search for historic and cultural sites in Midland and Saginaw counties. In the Trustees' letter of June 15, 2012 to EPA, they reported 31 archeological sites are located in the Shiawassee National Wildlife Refuge (SNWR), 42 sites or historical artifacts reported in the SNWR expansion area, and additional attifacts found in the confluence area of the Shiawassee and Tittabawassee Rivers. The Tribe provided additional information in their letter ofNovember 20, 2012.

31. Section 3.5 -Approach for Identifying Floodplain Areas. a. We have not yet determined how the PRGs will be evaluated at a particular propetty

to determine if cleanup would be required. Please remove tlus section or rewrite it to be more general. While the surface-weighted average concentration (SW AC) may be an approach that is used, these details should be deferred until the Design and Implementation Work Plan. The PRGs are cunently anticipated to be developed for the floodplain portion of the property, not an entire property SWAC. Additionally, it is not clear at this point whether there will be one or more "decision units" for a pro petty. The Agencies will be working with Dow to develop an approach that considers the available data and degree of uncertainty with the data. ·

b. The statement on the top of page 30: "The supporting evidence presented in Section 4.4 and Appendix C demonstrate these site-specific floodplain soil TEQ criteria are protective of human health and the environment" is overly broad, since the soil PRGs are anticipated to be based on human direct contact.

32. Section 4. RAOs and Conceptual Site Model. Page 31. a. Paragraph 2. Tills paragraph states that" . .. PCOI concentrations in surface soils are

the basis for action in this Response Proposal." Willie the Agencies cettainly agree that the concentrations of PCOis in some floodplain soils ARE a basis for action, the Agencies have not agreed that this should be the only basis for action for tills FP RP. See comments on Sections 4.2 and 4.3, below. As noted in comment 14.b, the Agencies expect that surficial riverbank soil is fully included in the evaluation of exposure to floodplain soil in tills FP RP and the response actions that will result.

b. Paragraph 3. While the Agencies agree that sufficient data is available to generally develop response proposals for the direct human contact pathway, additional data may needed to implement the selected response actions. Because this draft FP RP, as proposed, is focused solely on the direct human contact pathway, the last sentence in this paragraph needs to be qualified to indicate " .. . there are no substantive data gaps

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that limit appropriate development and evaluation of response action alternatives for the direct human contact pathways," or similar.

c. One way of clarifying the scope of the draft FP RP (and future assessments and response proposals), to ensure that relevant exposure and transport pathways will be addressed would be to have two CSM figures. The first would provide a more complete Tittabawassee River CSM that shows all of the potentially relevant exposure and transpott pathways (including the banks, in-channel and floodplain) . This figure could be used to explicitly identify which tmnsport and exposure pathways are and are not being directly addressed by the relevant response proposal and identify where these pathways would be addressed in the overall remedial process. A second figure which shows the "Basis for Current Action CSM" would focus on the exposure and/or transport pathways that are being proposed by the response proposal.

33 . Section 4.1- Floodplain Conceptual Site Model: Historical Sources and Transport Pathways. Page 31 and Figure 4-1.

a. Please see Major Comment 3 regarding the potential significance of erosion and movement of floodplain soils. Further evaluation may be needed to see if this potential transport pathway should be added to an updated CSM.

b. Page 32. Paragraph 2. This paragraph indicates that less contaminated solids over time will reduce concentrations within the surface-sediment active bed. It would probably be accurate to also state that floodplain soil concentrations would be expected to reduce over time, as well, as less contaminated sediment is deposited on the floodplain.

34. Section 4.2 - Floodplain Conceptual Site Model: Human and Ecological Exposure Pathways and the Basis for Action. Pages 32 and 33 and Figure 4-1. The CSM and basis for action is fundamentally important and the Agencies are willing to discuss how best to represent this in the revised FP RP.

a. The draft FP RP, as written, only addresses the direct human contact pathways for the PCOis. Other potential human exposure pathways include the consumption of wild game from the floodplain and food chain exposures via livestock and poultry consumption. As noted, these pathways will need to be fiuther evaluated in Task 10. However, they should be included now in Section 4.2 of the CSM and on Figure 4-1.

1. Livestock and poultry~ Historically, exposures of an individual who raised beef cattle and a family that ate eggs h-om chickens in the floodplain of the Tittabawassee River have been documented. While these types of exposures are not thought to be typical on the Tittabawassee River floodplain, and are not believed to be occUlTing now, a goal should be to prevent future occunences.

11. Wild game consumption. Based on Dow's collection of game from the Tittabawassee River floodplain, the State of Michigan issued a Wild Game Advisory in 2004 and updated it in 2007. The studies link contaminated game

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with contaminated floodplain soils. As noted, actions taken to address human direct contact may contribute to reduced exposures from this pathway.

b. Please see Major Comments 2 and 4. In the future, after additional evaluation, SCOis and/or wildlife exposures could become the basis for additional floodplain response, if wananted.

c. Figure 4-1 -Please consider the following changes: 1. As noted above, please add human consumption of livestock/poultry and

game to the figure. u. At the top of the figure please delete "Segment 1" and Segment 2 through 7"

as these labels are confusing. 111. Please rewrite the legend: Pathways indirectly addressed in the Segment 2

Response upstream Segment responses" or similar. tv. Based on 34.a, above, the title of the figure may need to be reevaluated. After

these changes, it may represent a human exposure pathway CSM

35. Section 4.3, Remedial Action Objectives- The RAOs should relate to the CSM. The RAOs are fundamentally important and the Agencies are willing to discuss how best to represent these in the revised FP RP.

a. The cunent only proposed RAO is "Limit the potential for human TEQ exposure from floodplain soil." However, the proposed RAO should incorporate the concept of limiting exposure to reduce risks to acceptable levels.

b. Please review Section 8.3 of the SOW regarding RAOs. Section 8.3.1 of the SOW includes four example General Response Objectives. Please evaluate how these will be addressed- either under this response proposal or later (and where in the 2010 AOC process).

c. In accordance with the SOW, as appropriate, please indicate short vs. long-term RAOs.

d. A separate RAO for the livestock/poultry consumer pathway should be considered related to preventing unacceptable exposures to consumers. The performance objective would relate to managing land use in the future and the measurable metrics would consider the effectiveness and reliability of ICs.

36. Section 4 .3 - RAOs. Page 33. Performance Objectives. a. Please rewrite the performance objective "Conduct and/or maintain response actions

that reduce soil TEQ levels to site-specific cleanup levels."

b. The second performance objective, reads somewhat awkwardly. Can this be clarified or simplified?

c. Additional perfmmance objectives may need to be developed based on the RAO comments directly above.

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37. Section 4.3 - RAOs. Page 33. Additional measureable metrics may need to be developed based on the RAO comments directly above.

38. Section 4.4- Floodplain Response Action Criteria. Page 34. a. Please remove the reference to "property SWAC." Implementation details on the

application of the PRGs have yet to be developed.

b. Please clarify the receptors that are protected by the proposed PRGs for each land use type (once they are developed and communicated to Dow). The PRGs are expected to be driven by the most sensitive receptor and endpoint- in both cases non-cancer and direct soil contact (ingestion and dem1al absorption) for the young child. The PRGs will also be protective for older children and adult residents, recreational users of all ages, and workers.

c. In order to simplify the discussion of site-specific inputs, please remove the bullet "Absorption ofTEQ from floodplain soil" and please modify the bullet "Bioavailability ofTEQ in the gastrointestinal tract." We are trying to keep this explanation more streamlined for the public.

d. Please modify the last paragraph of this section. Perhaps instead of the specific reference dose and the MDEQ cancer slope factor, the discussion is simplified to indicate that each agency evaluated both non-cancer and cancer endpoints for a number of receptors and exposure scenarios in accordance with each agency' s requirements. Both agencies use the same reference dose. However, cancer was assessed using both MDEQ's and EPA' s slope factors. As noted in Major Comment 6, elimination of Appendix C is preferred.

39. Section 4.5 : a. 1st paragraph -Please modify 1st sentence: "Any removal response actions

implemented on-site must comply with substantive requirements of applicable or relevant and appropriate requirements (ARARs), to the extent practicable. ARARs may be waived in certain circumstances."

b. 4th paragraph - Please modify 1st sentence "In addition, per the NCP ( 40 CFR 300.400(g)(3)), EPA, other federal agencies, or states .. . "

c. Tables 4-1, 4-2 and 4-3 should be changed to reflect the comments on Section 4.5.1 , 4.5.2, and 4.5.3, below.

40. Section 4.5.1, Potential Chemical-Specific Requirements - Add a period to the end of the last sentence in the introduction.

41. Section 4.5.2, Potential Action-Specific Requirements a. Bald and Golden Eagle Protection Act - Please modify the 1st sentence: " .. . by

prohibiting the take, possession, sale, purchase, barter, offer to sell, pUTchase or baftef, transport, export or import ... " It is redundant.

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b. Please add:

Michigan Natural Resources and Environmental Protection Act- Part 55 Part 55 addresses air emissions in the state of Michigan. Part 55 may be an ARAR to the extent that the response action involves dust emissions.

Michigan Natural Resources and Environmental Protection Act- Part 121 Part 121 addresses storage, handling and transportation of liquid waste in the state of Michigan. Part 121 may be an ARAR to the extent that the response action involves the storage, handling and transportation liquid waste.

Michigan Natural Resources and Environmental Protection Act- Part 413 Part 413 addresses the introduction of a prohibited species, a restricted species, or a genetically engineered or nonnative aquatic plant, bird, crustacean, fish, mammal, or mollusk in the state of Michigan. Part 121 may be an ARAR to the extent that the response action involves the planting of nonnative species.

42. Section 4.5.3, Potential Location-Specific Requirements or TBCs. Please add:

Archeological and Historic Preservation Act The ARPA, 16 U.S.C. 469-469c, provides for the preservation of historic and archeological data that might otherwise be lost as a result of dam construction or alterations of the tenain. If activities in connection with an EPA-approved project may cause irreparable loss to significant scientific, prehistorical, or archeological data, EPA is required to preserve the data or request to DOl to do so. The ARPA may be an ARAR to the extent that historic and archeological data might be lost as a result of alterations of the tenain in the floodplain.

American Indian Religious Freedom Act (42 U.S.C, 1996 et seq.) The AIRFA states that the policy of the U.S. is to protect and preserve for American Indians, Eskimo, Aleut, and native Hawaiians, their inherent rights of freedom to believe, express, and exercise traditional religions. These rights include, but are not limited to, access to sites, use and possession of sacred objects, and the freedom to worship through ceremony and traditional rites. To the extent the floodplain response action may limit access to a location in order to believe, express and exercise traditional religions, the AIRF A is an ARAR.

Archeological Resources Protection Act The APRA, 16 U.S.C. 470aa-mm, requires the protection of archaeological resources and sites on public lands and Indian lands and to foster increased cooperation and exchange of infotmation between governmental authorities, the professional archaeological community, and private individuals. Although the floodplain is not located on public or Indian lands, to the extent archeological resources and/or sites are determined to be present in the floodplain, the APRA is relevant and appropriate.

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Native American Graves Protection and Repatriation Act The NAGPRA, 25 U.S. C. 3001 et seq., prioritizes ownership or control over Native American cultural items, including human remains, funerary objects and sacred objects excavated or discovered on Federal or tribal lands. Although the floodplain is not located on Federal or tribal lands, to the extent Native American cultural items, including human remains, funerary objects and sacred objects excavated or discovered in the floodplain, the NAGPRA is relevant and appropliate.

43 .Section 5.2 - Soil Cover. Page 40. a. Depending on conditions and design, a cap that is thicker than one foot in maintained

residential areas and six inches in the other land use areas may be necessary.

b. A warning or "marker" layer may be needed to alert residents not to disturb the soil below the cap (e.g., when soil concentrations below the cap are high).

c. Please provide more detail on how the area will be restored/replanted after the cover is placed.

44. Section 5.3 - Soil Removal and Management. Pages 40 and 41. a. More than one foot of soil may require removal and replacement at residential

properties. This will depend on site conditions and the depth of contamination.

b. A warning or "marker" layer may be needed to alert residents not to disturb the soil below a certain level (e.g., when soil concentrations below the backfill are high).

c. Please provide more detail on how the area will be restored/replanted after the backfill is placed.

d. Long term maintenance and monitoring will be required if soil cover is placed over remaining subsurface soil with TEQ levels that exceed the established cleanup criteria. In addition, there will be restrictions on the disturbance of the soil if contamination above criteria is left in place.

45. Section 5.5- Monitored Natural Attenuation. Pages 41 and 42. a. This option would also require site control to prevent unacceptable exposmes from

occmring during the attenuation period.

b. The Agencies agree that deposition of cleaner sediment in the floodplain is not expected to reduce surface soil TEQ levels below the site-specific response action criteria in an acceptable timeframe. However, not including this as a response option does not preclude floodplain soil monitoling from being considered as part of Task 4.

46. Section 6.1.1- Effectiveness. Page 43. Overall Protection ofHuman Health and the Environment. This section should be revised to read: " ... ability of an alternative to eliminate, reduce or control potential exposmes to contaminants to acceptable levels over both the short and the long term.

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47. Section 6.2 - Common Elements. Pages 44-45. a. Common elements to address: coordination with property owners (e.g., access,

design; scheduling); project-specific health and safety plans; and prope1ty restoration/replanting should be considered for inclusion.

b. Source Control: It would be helpful to reiterate the upstream to downstream sequencing that will help to minimize recontamination.

c. Hydraulic Assessment. This sentence should be expanded as follows (or similar): " .. . have the potential to affect flooding elevations and to determine the need for any compensating cuts."

· d. Scheduling. More detail should be provided in the schedule element, such as identifying what subsequent document( s) will contain specific schedules for implementation.

48. Common Elements, Land Use Management. See Major Comment 7, above. a. This section refers to "existing land use controls imposed by federal, state, and local

government statutes, regulations and ordinances." Please provide more specific information on these. Also, as appropriate, please ensure that relevant federal and state laws and regulations are included in Section 4.5, ARARs.

b. 1st paragraph, second to last sentence. Please rewrite (or similar) "There are no construction related impacts to the environment when land use management is put into place." While it is true that land use management may have no short-term effects, there may be environmental impacts to ecological receptors and/or wild game exposures.

c. Please update the IC references on page 45 and Section 9 to include an additional guidance, OSWER 9355.0-89 at http://www.epa.gov/superfund/policy/ic/guide/Final%20PIME%20Guidance%20Dec ember%2020 12 .pdf

d. Bullets on page 45 -EPA usually considers four main categories of ICs: Governmental; Proprietary; Enforcement and permit; and Informational. Please add "Informational" to the list. Please consider including descriptions or examples of each category. Informational devices provide information or notification often as recorded notice in property records or as advisories to local communities. Typical informational devices include state registries of contaminated sites, notices in deeds, tracking systems, and fish or game consumption advisories. Please also mention that the ICs are often "layered" to increase reliability. That is, more than one type ofiC may be applied at a site.

e. Please mention that an Institutional Control Implementation and Assurance Plan (ICIAP) will be a submittal under the expected settlement agreement. The ICIAP will have details on implementing, maintaining, monitoring, and reporting on the institutional controls to ensure their reliability.

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f. Please see comment 34.a.i regarding potential exposure of people from consumption of livestock (including poultry) raised in the floodplain. Because ICs are likely to be required for many properties for other reasons, the Agencies view this as an opportunity to reliably prevent these types of potential exposures. Therefore, it is the Agencies' expectation that these pathways and reliable exposure controls for these pathways will be addressed through the ICIAP. We expect that this work may need to be coordinated by the Agencies with the Michigan Department of Agriculture and Rural Development and the Michigan Department of Community Health.

g. Please see comment 34.a.ii regarding potential exposure of people from consumption of wild game caught in the floodplain. As noted above, the State of Michigan has put consumption advisories in place for certain game. As noted above, consumption advisories are generally considered by EPA to be a type of infmmational IC. Please add a discussion of the existing advisories to this section, and they should be included in the ICIAP, as well. We expect that this part of the ICIAP may need to be coordinated by the Agencies with the Michigan Department of Natural Resources and the Michigan Department of Community Health.

49. Section 6.3, Cost- Please rewrite "Alternatives Alternatives that are more intrusive larger in scale and/or take longer to implement tend to be more costly.

50. Section 6.3.1 a. Pages 47-48, Overall Protection of Human Health and the Environment. Please

rewrite: "As discussed in Sections 3, 4, and Appendix B, the exposme ofTEQ­impacted soil to ecological receptors is not currently considered a basis for a response action; therefore, the response alternatives are not evaluated on the impacts to ecological receptors. This will be further assessed in Task 10."

b. p. 48, Compliance with ARARs, 1. Second paragraph: Change to read "Action-specific ARARs such as soil and

water management requirements are remedy-specific and location-action specific, and weuld compliance with ARARs will be managed in the design and implementation phases of the work."

n. It would be useful to expand this section to discuss chemical-specific ARARs with respect to such issues as: DEQ preliminary determination that the proposed PRGs meet 201; soil relocation; "facility" status, etc

c. Page 48 - 49, Reduction of TMV: 1. Change as follows: "Through the soil removal alternative, TEQ-impacted

surface soil would be removed and disposed of in an approved, local landfill or designated soil relocation area. This results in a reduction of toxicity, mobility, and volume ofTEQ in the floodplain, but not through treatment."

n. Because incineration has been used to treat dioxin in soil, please rewrite as follows, or similar: "However, ex situ soil treatment technologies have challenges associated with the potential volumes and concentratio11s of the

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floodplain soil. It would limited proven reliability at full scale and tend to have very high costs and likely involve the transport of the soil to a treatment facility located in another region or country."

d. Short-Term Effectiveness 1. Pages 50, 52 and 53 - The discussion on greenhouse gas and emissions should

mention that attempts to manage these effects will be made and refer to Section 6.4.

11. Bottom of page 51 - The worker H&S discussion refers to a lot of tree work. Since this discussion relates to Maintained Residential Areas, the sentence should probably be moved to the Other Land Use Areas discussion.

111. Other Land Use Areas pages 50-51 and 52-53- Mention that work in agricultural fields or unforested upland would easier to replace and have less short-term impacts

e. Long-Term Effectiveness and Permanence 1. Soil Cover, Other Land Use Areas - discuss that a soil cover would be very

difficult (if not impossible) to maintain in an active agriculture area. 11. Long-term effectiveness of soil cover and soil removal with backfill with

residual subsurface TEQ-impacted soils relies on appropriate cover for the land use, recognition by the property owner where the contamination remains over the long-term, as well as monitoring and maintenance of the cover. An effective way to enhance both the effectiveness of the cover and the recognition by the property owner, any contractor, maintenance/utility worker, or other person working on a property with contamination remaining at depth is to have an obvious barrier layer, such as an appropriate geotextile. An appropriate geotextile would have a long working life, allow water percolation, and be easily recognized as an indicator that there are contaminated soils underneath.

111. Appropriate thickness of soil cover and/or backfill does depend on land use as discussed in the draft TRFP-RP for maintained residential areas, but may also apply for some other land uses. Heavily trafficked areas, areas with gardens, or other similar uses may require a thicker cover or backfill.

1v. The text should be expanded to describe how careful consideration of the tradeoffs for high value areas within the floodplain is appropriate prior to any remedial decision being made based on contaminant concentration alone. Understanding the existing local habitats and uses within each property and their value (with and without the existing PCOI concentrations) is necessary to make these types of decisions. Removal actions and soil cover actions are often able to strategically maintain high value components of a property (e.g. , some mature trees, ornamentals, etc.) and still meet cleanup goals.

51. Section 6.3.2 1st paragraph page 56 - Mention that administrative feasibility also will involve access and working with the landowners.

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52. Section 6.3.3- Please add costs. See comments on Sections 5.2 and 5.3 . The cost estimates should reflect a range of different excavation and cover depths.

53. Section 7, page 61 , a. Please see Major Comment 8 regarding EPA's intent to work with MDEQ and Dow

to develop some high level implementation detail before issuing the proposed plan for public comment.

b. 1st paragraph- See Major Comment 6 and comments on Sections 3.5 and 4.4 above. Please rewrite as follows: "This Floodplain Response Proposal provides the approach numeric criteria that will be used for identifying areas that will require a response (Section 3.5 and 4.4) and evaluates floodplain response alternatives that may be implemented (Section 6) iftlzose criteria are exceeded. However, details on tlte implementation approach will be developed tltrouglz design and implementation plans. This section ... "

c. Please review the titles and capitalizations of the documents discussed and make the usage consistent.

54. Section 8 - Several reviewers found the use of the sediment principles confusing, so please omit this section.

55. Appendix C-As noted in Major Comment 6, please eliminate Appendix C.

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