Comments from U.S. Environmental Protection Agency

The U.S. Environmental Protection Agency (EPA) has reviewed the Preliminary (Deliberative) Draft Environmental Impact Statement (PDEIS) for the proposed Rosemont Copper Mine Project (Project), in Pima County, Arizona. Our comments are provided pursuant to the National Environmental Policy Act (NEPA), Council on Environmental Quality (CEQ) regulations (40 CFR Parts 1500-1508), and our NEPA review authority under Section 309 of the Clean Air Act. These comments were also prepared under the authority of, and in accordance with, the provisions of the Federal Guidelines (Guidelines) promulgated at 40 CFR 230 under Section 404(b)(1) of the Clean Water Act (CWA).

EPA has reviewed this preliminary document to the extent that workloads and scheduling allowed, however, the comments below should in no way be considered all encompassing of EPA's concerns and input related to this project. We would like to continue to work with the Forest Service in the coming weeks to further expand upon the input provided below. Also, in light of the broad scope of EPA's review and referral authority under section 309 of the Clean Air Act, we have not separated our comments into “jurisdictional” and “non-jurisdictional”.

(Note: Some comments refer to an issue/information that is contained in multiple sections of the PDEIS. The “Comment Location” citation has been filled in only for the first occurrence of that information; however, to the extent applicable, comments and recommendations should be applied to all occurrences of that issue.)


Comment / Rationale / Basis

Comment Location


EPA believes that the discussion in regards to the project's Purpose and Need should be expanded. While EPA understands the Forest Service's obligation to respond to the Mine Plan of Operations application, this purpose and need statement does not fully or accurately encompass the “Purpose and Need” as intended by the NEPA. The Purpose and Need for a project should focus on the underlying problems to address (e.g., the US demand for copper) and the reasons a project is considered. The Purpose and Need for a project should be broad enough to organically lead to the exploration of a full range of reasonable alternatives, regardless of what the future findings of an alternatives analysis may be. It is critical that the Purpose and Need should not prescribe or imply a solution or particular alternative.

2/Water Control/13/7-8

According to the PDEIS “The heap leach pad and ponds would ultimately be encapsulated within the waste rock storage area.” EPA recommends that additional detail be added to this section such as that contained in Rosemont's Reclamation and Closure Plan (2007). EPA also recommends that in this section or a new Reclamation and Closure Plan prepared for the DEIS that examples of where this type of approach has been conducted in the past, and any information available concerning results from such practices. EPA is not aware of any prior examples of this practice being proposed or utilized and believes this warrants additional information in the DEIS and supporting documents.

2/Water Control/13/14

The Compliance Point Dam uses waters of the US to settle out sediment and should be moved upstream into the two canyons next to the proposed facilities instead of being at the confluence in order to minimize the impacts to water of the U.S.

2/Water Control/15/11-14

According to the PDEIS “Control of process water…and maintaining the water content of the dry-stack tailings at a level that reduces seepage from the tailings disposal facility.” EPA agrees that dry-stack tailings will overall result in a reduction in seepage. However, that is highly dependent on realizing process and operational limitations and EPA believes significant seepage is likely to occur, although it likely will be periodic and in response to short-term climatic conditions and/or operational upsets. The DEIS should address potential seepage from the tailings (e.g. capture and re-use).

2/Water Control/15/23-25

According to the PDEIS “…all precipitation that falls on top of the active tailings area would remain on top and evaporate.” The DEIS should include additional information concerning the potential for the evaporated water to concentrate contaminants and become toxic to wildlife, particularly birds. A similar practice at closed tailings impoundments at the Tyrone Mine in New Mexico resulted in unexpected concentration of deleterious constituents and significant bird mortality. EPA believes alternatives which do not allow for ponded water to be stored on top of the tailings area should be considered in the DEIS.

2/Water Control/15/31

If the use of engineered stormwater storage on top of tailings and waste rock facilities is being considered as a possible design feature of the Rosemont Mine, the DEIS should address this as an alternative and outline the possible advantages and disadvantages to this system, the environmental impacts that may be avoided or associated with this design feature and the reasons for controversy in regards to this matter. To simply indicate that this possible design feature is undergoing peer review does not sufficiently inform the public or decision makers of the pros and cons of the issue.

2/Water Control/15/14 and 18/25

The PDEIS makes frequent reference to the best available demonstrated control technology criteria and regulatory requirements of the Arizona Department of Environmental Quality's Aquifer Protection Permit Program/Plan. Much of the discussion of engineering design and performance, seepage and leakage monitoring and recovery, and potential groundwater impacts hinges on the adequacy and success of this Program. Therefore, EPA recommends that the specific provisions of this Program be discussed to the extent possible in the DEIS. For example, this passage makes reference to ensuring that groundwater impacts do not occur “beyond the level allowed by the aquifer protection permit”. These threshold values should be included in the DEIS along with the specific actions to be taken should monitoring indicate that thresholds have been exceeded.


2/Waste Rock and Tailings/19/19

EPA is aware that a great deal of geochemical data has been generated for the proposed project and that these data are available through Rosemont Copper's website. While EPA notes that brief discussions of geochemistry occur throughout the PDEIS (such as in Chapter 3, Surface Water Quality, beginning on page 17), due to its importance to the overall risk of environmental contamination from the proposed project, we recommend that the DEIS contain a thorough summary and discussion of these data in their own section within the “Physical Environment” portion of Chapter 3. The discussion should address geochemistry of the open pit, waste rock, heap leach and tailings. This discussion should include elements such as whole rock and mineralogical analysis, the static and kinetic testing procedures employed, the classification system for Potentially Acid Generating Rock (PAG), Non-PAG and Net Neutralizing materials, and the proposed strategies for the management of PAG materials (encapsulation, neutralization, etc). The discussion should also address the potential for contamination resulting from neutral drainage, in particular for arsenic, which is noted as a potential contaminant of concern in the waste rock and other geochemical analysis. The discussion should also address why kinetics tests were not conducted for periods longer than 20 weeks and why tests were limited to composite samples and not done on samples specific to acid generating and PAG morphologies (for waste rock only).

2/Reclamation and Closure/21/9

The PDEIS indicates that the Reclamation and Closure plan would be completed “prior to the publication of the FEIS”. EPA feels that this is not an appropriate approach to Reclamation and Closure. NEPA is intended to consider the entire life and potential impacts of a proposed action. Experience has shown that reclamation and closure is a key issue and may represent the greatest area of public liability, if not public interest, and is of major importance in regulatory decision-making. Improper or poorly executed Reclamation and Closure can and has led to severe and irretrievable environmental impacts at other mine sites, including those in the state of Arizona. EPA therefore considers Reclamation and Closure to be an absolutely critical component of the DEIS. The DEIS should contain a detailed discussion and summary of the Reclamation and Closure Plan and the ways in which the Plan will address and prevent potential post-closure contamination (including issue specific measures to the extent feasible). As a key part of the alternatives analysis, the reclamation and closure plan should be altered for each alternative, or reclamation measures can be considered themselves as an alternative. Some reclamation and closure measures may be common to all alternatives, but some measures may be specific to a given alternative. A given alternative likewise might better accomplish reclamation and closure objectives. We also recommend that the Reclamation and Closure Plan be attached as an appendix to the DEIS.
   EPA has noted that Rosemont has published a Reclamation and Closure Plan (Tetra Tech Project No. 320614-400 July 2007) for the project as proposed. Because many investigations were in progress at the time the plan was produced, it is considered an incomplete document for specific comment purposes. However, EPA notes that it contains a very good description appropriate for the DEIS of both Arizona and Forest Service regulatory requirements. EPA also notes that the Reclamation and Closure Plan includes a financial assurance cost estimate. EPA suggests that the Reclamation and Closure Plan be updated and included as suggested above in the DEIS, and that the DEIS include discussion on the estimated reclamation and closure cost estimate, as well as how it might be affected by the various alternatives considered in the DEIS.

2/Design Elements and Mitigation Measures/22/26

This line states: “The Forest Service plans to explore the status of geomorphic land form design in the mining industry… if it is feasible… this investigation and potential design work will take place between the DEIS and FEIS.” Firstly, there is a typographical error on line 25 (“deign rather than design”. Secondly, EPA again feels that it is not appropriate to exclude important design elements from the DEIS. If these design elements have not yet been fully assessed, the Forest Service should wait until a determination can be made in regards to these design features prior to the completion and publication of the DEIS. EPA has experience with geomorphic landform design and believes it can have technical validity if properly applied (e.g. not used as an excuse to not perform standard reclamation tasks such as angle of repose slope reduction) and should be considered as a reclamation alternative in the DEIS.


2/ Design Elements and Mitigation Measures/ Water Resources/25/18

EPA believes based on the geochemistry evaluations there is significant evidence of risk of release of arsenic in leachates from waste rock and/or tailings. EPA recommends that the Forest Service require the project proponent to develop a “contingency/adaptive management plan” that would recognize the potential for various adverse impacts to occur including release of arsenic to groundwater at concentrations exceeding applicable standards. EPA recommends that a means of mitigating those events be considered as part of the original Plan of Operations. By considering what might be necessary as a contingency measure, it is possible to affect initial designs to more easily and readily (e.g. efficiently and cost-effectively) mitigate potential future issues.

2/Air Resources/23/11

For comments on Air Quality, see below.

2/Water Resources/26/1

The DEIS should contain a more detailed discussion of the Central Arizona Project water. How secure is this water source? What is Rosemont's allocation right priority? What is the likelihood of drought and therefore loss of this water source and how will the project proponent respond in the event that this source of mitigation is lost?

2/Water Resources/26/16

& 3/Ground water Quality/9/9

These mitigation measures seem to contradict one another. Rosemont proposes to encourage infiltration through the waste rock and tails to reduce impacts on ground water quantity, while simultaneously stating that groundwater quality will not be impacted by infiltration through waste rock or tails because total infiltration through waste rock and tails are expected to be “negligible". Please explain and/or rectify this contradiction.

2/Riparian and Offsite Land Mitigation/29/28

The PDEIS states that Rosemont will develop and implement a land mitigation plan that addresses offsite compensatory mitigation. As required by the US Army Corps of Engineers and Clean Water Act Section 404. EPA believes that the provisions of this plan should be included in the DEIS at the greatest level of detail feasible in order to ensure that impacts to waters of the US are adequately addressed and fully mitigated. For example, what ratio of compensatory mitigation would be applied? It has been demonstrated that the loss of naturally occurring wetlands cannot be replaced by simply purchasing an equal number of credits at a mitigation bank. Studies have shown that functions of naturally occurring wetlands are rarely replaced by created wetlands (Kentula et al. 1992; An approach to improving decision making in wetland restoration and creation, EPA/600/R-92/15 August 1992). What actions will the Forest Service and project proponent take to ensure that its mitigation realistically offsets losses and meets the no-net-loss of functions threshold?

2/Stormwater Pollution Prevention Plan/31/1

We note that the PDEIS contains no discussion of the possible need for a NPDES discharge permit. We understand that the Proponent intends to design the facility as a no net discharge facility, however the DEIS would benefit from a discussion of how this will be achieved in relation to NPDES.

2/Reclamation Plan/31/33

As discussed previously, EPA considers Reclamation and Closure to be critical components of mine design that should be discussed in detail in the DEIS. At line 33, the PDEIS states that the “key initiatives of the reclamation and closure plan are described below in the “Voluntary Resource Protection Plans” section. This must be an error. The section cited does not contain a discussion of issues that EPA would consider to be “key” in regards to Reclamation and Closure of a mine site.

2/Water Source Enhancement and Mitigation Plan/33/3

EPA supports the general concept of a Water Source Enhancement and Mitigation Plan to ensure that no net loss of grazing and wildlife water sources is achieved, however the PDEIS does not contain sufficient information on how the Project Proponent and/or Forest Service intends to achieve this. The DEIS should include the specific Plan procedures and methods to achieve this goal to the extent feasible.

2/-/34/figure 8

Figure 8 and the similar “Plant Facilities” figures for the other alternatives appear to have an error in regards to labeling. Unless we are misunderstanding, the figure seems to indicate that sulfide ore processing will occur via SX/EW. The process of solvent extraction and electrowinning would traditionally be a process associated with oxide ore, not sulfide.

2/Central Drain/36/17 & 2/Alternative 3-Phased Tailings Alternative in Detail/38/35

The DEIS should contain more information on the design of the Central Drain. For instance, how will the design ensure that stormwater does not contact tails or contaminant generating waste rock while passing through the Central Drain? How will the Drain be constructed such that fine grain material is not allowed to settle and eventually migrate into the Central Drain? What long term maintenance is necessary to ensure that the Central Drain remains clear and clog free into perpetuity ? What would be the potential impacts, contingency plan and potential costs were the drain to plug? Where would the funding for long term maintenance come from?
    Also, the DEIS should contain a discussion of the benefits and drawbacks of the alternative stormwater drainage concept presented as a component of the Phased Tailings Alternative. While this section states that the series of flow-through drains utilized by this alternative would be a more conservative approach to stormwater management, EPA was unable to locate an adequately detailed comparison of the two designs.

2/Financial Assurance/61/35

In addition to a description of the closure and reclamation plan, EPA recommends that the Draft EIS identify the bond amounts for each closure and reclamation activity at all of the proposed project facilities. The Draft EIS provides the public the opportunity to weigh in on the adequacy of the bond amount. The viability of the bond can be a critical factor in whether a project is environmentally acceptable. Therefore, this information should be disclosed in the DEIS. The DEIS should also discuss whether and how the Forest Service can modify the bond during the course of operations if temporary, long-term, or perpetual treatment and/or remediation needs are discovered during operations. Identify who would be responsible for any post-closure cleanup actions should they be necessary. In addition to determining the actual cost of reclamation, the bond calculation should consider the extra expense of taking over reclamation at a critical time during operations, such as at the end of heap leach operations prior to additional mining accomplishing encapsulation of the acid spent ore, during wet periods when the water balance is high and surplus water must be treated, or when environmental or reclamation measures have not been successful in controlling pollution and must be redone. The Draft EIS should describe bonding requirements or other measures that the Forest Service will have in place to ensure funds would be immediately available should the mine operator or its insurer be unable to fund the required reclamation or closure activities.
    The Draft EIS should also discuss whether long-term post-closure operations and maintenance may be necessary, describe these activities, indicate the projected costs for these activities, and discuss any requirements the Forest Service would impose on the mine operator to establish a trust fund or other funding mechanism to ensure post-closure care. The financial assurance necessary to fund post-closure activities must be kept current as conditions change at the mine, and the Forest Service should ensure that the form of the financial assurance does not depend on the continued financial health of the mine operator or its parent corporation. The Draft EIS should include a general description of the trust fund intended for long-term post-closure care. The mechanics of the fund are critical to determining whether sufficient funds would be available to implement the post-closure plan and reduce the possibility of long-term contamination problems. The discussion in the DEIS should include the following information:

· Requirements for timing of payments into the trust fund;
· How Forest Service would ensure the trust fund would be bankruptcy
· Acceptable financial instruments;
· Tax status of the trust fund;
· Identify the trust fund beneficiaries; and
· Identify the operator with responsibility/liability for financial
   assurance at this site.

If a long-term trust fund will be part of the proposed project, EPA believes this information is essential in the DEIS because it could make the difference between a project sufficiently managed over the long-term by the site operator, or an unfunded/under-funded contaminated site that becomes a liability for the Federal government. In the absence of an appropriate guarantee, EPA could consider a project unacceptable if it could result in unmitigated impacts exceeding environmental standards on a long-term basis.

3/Groundwater Quantity/56/41

This discussion of impacts to Stream Flow only considers those impacts that would be present after a period of 1,000 years. Based on the discussion here, it would appear that Montgomery and Associates and/or Tetra Tech did substantial modeling in regards to impacts to flow volumes. EPA recommends that this discussion be expanded to consider not just impacts occurring 1,000 years from the cessation of mining, but also impacts occurring at various points between the cessation of mining and 1,000 years (for example 50 years post-closure, 100 years post closure, 300 years, etc).

3/Groundwater Quantity/67/31


As mentioned above, this mitigation measure seems contradictory to others stated in the document. Generally speaking, it is beneficial (and often times essential) to minimize the infiltration of precipitation through waste rock and tails so as to minimize oxidation of potential acid generating rock and/or the liberation of other contaminants contained in these materials. It is unclear how/why this particular design feature is advisable or beneficial. Greater detail and justification is required.


3/Surface Water Quantity/1/6

This section discusses the amount of existing surface water resources in the project area, however, seep and springs are discussed in the "Ground Water Quantity" section.  The analysis of seeps and springs should be included in section of surface water, as well.

3/Surface Water Quantity/1/14

The ADEIS states Cienega Creek has not been included in the analysis for surface water quantity because the proposed project represents a small proportion of Cienaga Creek watershed (roughly 2 percent), and unlike that for Davidson Canyon, the expected reductions in ephemeral flows are considered negligible. Where is the supporting documentation regarding this assumption?
   With the proposed reduction in stormwater flows and 100-year flood peaks for the alternatives being evaluated, cascading effects could occur at the junction of Davidson Canyon and Cienaga Creek, as well as further downstream.  Because it is a small effect (2%), it does not mean there are no indirect and cumulative impacts to Cienaga Creek.

3/Surface Water Quantity/3/25

Not all construction areas for power lines and access roads have been field surveyed. The ADEIS assumes that culverts and dip crossings will likely not impact surface water.  Without disclosure of the location of these activities and the design of road crossings, it cannot be assumed there will be no impact.  Culverted road crossing can often lead to headcutting, erosion and alteration of stream flows.

Is this the only area where cumulative impacts are disclosed? A cumulative impact analysis is necessary which should include a discussion of past projects as well as projects in the reasonably foreseeable future.

3/Surface Water Quantity/8/25

3/Surface Water Quantity/18/13

The indirect analysis of seeps and springs should be addressed under Surface Water.

3/Surface Water Quantity/19/15

Why are impacts to riparian vegetation detailed in Ground Water Quantity section?  They should be addressed in Surface Water, as well as Biological Resources.

3/Surface Water Quantity/20/16


Permanent diversion structures are intended to divert waters upgradient of the project site to the downgradient side of the project.  The ADEIS should describe the design and location of all proposed diversion structures.  


3/Surface Water Quantity/24/4

The cumulative impact analysis is incomplete.  What is the geographic extent of their analysis?  For example, Rosemont-owned off-site alternatives such as Peach-Elgin, Copper World and Broad Top Butte, should be analyzed.


3/Surface Water Quantity/25/15

EPA is concerned with the applicant proposing to use stormwater diversions structures as mitigation.  This would not be acceptable for CWA purposes

3/Surface Water Quality/1/36

The PDEIS states riparian issue factors addressing springs and seeps as well as qualitative impacts to riparian areas are analyzed in the Ground Water Quantity section.  These waters/wetlands should be analyzed in the Surface Water Quality and Biological Resources sections.

3/Surface Water Quality/3/5

The PDEIS states that impacts on riparian habitat and wildlife are detailed in Biological Resources section.  As we have recommended earlier, all analysis of impacts to aquatic resources should be consolidated.


3/Surface Water Quality/4/Table 3.1

Why are the direct impacts to waters and riparian areas drastically different than the summary of impacts (Table 5) in the December 16, 2010 Draft 404(b)(1) Alternatives Analysis prepared by Westland Resources for Rosemont Copper?  Why hasn't the Modified Pit Configuration alternative described in the 404(b)(1) been included in the PDEIS?

3/Surface Water Quality/14/Table 3.5

See above comment.

3/Surface Water Quality/15/26

Please see comment from Ch 3, Surface Water Quantity, p.1, line 14 - Based on the significant decrease in sediment yield downstream, indirect effects to Cienaga Creek should be analyzed.

3/Biological Resources/-/-

The information provided in this section does not comprehensively assess the significant impacts to waters of the U.S. from the proposed mining project.  The analysis in ADEIS fails to comply with the substantive requirements under Section 404(b)(1) of the CWA.  
    A functional assessment of the waters on the proposed project site, as well as downstream in Davidson Canyon and Cienaga Creek should be conducted to fully characterize the condition of these waters as well as the direct, indirect impacts to all waters from the proposed project.  This is also necessary due to the important hydrologic and biogeochemical role these waters play in direct relationship to higher-order waters downstream.  

3/Biological Resources/60/20

This section on Cumulative Effects is superficial and does not adequately evaluate the cumulative effects of projects in the area.

3/Biological Resources/61/1

EPA was unable to identify any detailed discussion regarding compensation for unavoidable impacts.  Based on information in this section, the project fails to compensate for loss of waters under the Guidelines.  Appendix C does not adequately address compensation for unavoidable impacts to waters.

Appendix D/Mitigation Plan


This “Mitigation Plan” is extremely vague and generic. It contains statements such as “If monitoring determines that control efforts need to be modified to improve performance, these plans will be updated.” Such statements are insufficient. The Mitigation Plan should provide specific monitoring thresholds with similarly specific associated mitigating actions. Furthermore, the monitoring and mitigation set forth in the DEIS should be stated in such a way as to make it enforceable and legally binding.

Rosemont Geochemistry Report June 2007/May 2009


In reviewing this PDEIS, EPA also investigated the geochemical baseline reports provided by Rosemont Copper on their website ( EPA has a number of concerns regarding this data. Firstly, we note that the kinetic tests run for both waste rock and tailings material appear to have been arbitrarily ceased at 20 weeks. This is troubling because kinetic tests inappropriately abbreviated may not accurately describing the acid generating potential of mined materials, thereby understating risks to surface and ground waters associated with the proposed mine. We recommend that the Forest Service re-examine Rosemont Copper's geochemistry reports and consider whether a 20 week cut-off was scientifically supported by the data. EPA would like to further engage the Forest Service in regards to the project's geochemistry in the coming weeks.

Air Quality Modeling


In processing a synthetic minor source permit application, the air permitting agency must show that it has followed proper permitting procedures to ensure that the impacts of the project would not interfere with the attainment or maintenance of the NAAQS, and that the permit terms and conditions that govern the facility would be practically and legally enforceable. To that end, the agency should review the application's modeled predicted NAAQS concentrations, including background, and the modeling should account for “worst case” scenarios, especially for those impacts where the modeled concentrations produce a risk of any NAAQS exceedance. The agency is expected to thoroughly review the application's supporting documentation that have been used to derive emission rates and emission control parameters in the modeling and to draft enforceable permit conditions to adequately keep emission levels below the applicable thresholds. For the reasons above, the draft EIS must provide adequate assurance that the modeled results properly reflect worst case scenarios.

3/Air Quality and Climate Change/21/ Table 3.9 and 3.10


We note that the Maximum Ambient Concentrations modeled for NO2 (1-hour) and PM10 (24-hour) would exceed or produce higher risks of exceedances of their respective NAAQS thresholds. We also note that page 12 of Chapter 3 states that “the average 8-hour level across all [ozone] monitoring stations was 0.068 part per million, or 91 percent of the [NAAQS].” Because EPA will propose a revised ozone (8-hour) NAAQS in July, the agency must also ensure that the levels of NOx (acting as an ozone precursor) emitted from the facility would not cause or contribute to a violation of the NAAQS for these areas to avoid the risk of a nonattainment designation.

3/Air Quality and Climate Change/22/8


Modeling results show that the NAAQS for 1-hour NO2 would not be maintained at the project site under modeling scenario 3. While results from modeling scenario 4 would show compliance with the NAAQS, the draft EIS should explain why one scenario would be more protective or representative than the other in predicting accurate NOx emissions. Proper mitigation measures would need to be applied in either case.

3/Air Quality/23/4


For Class I areas, modeling results show increased risk of exceeding the NAAQS for PM10 (24-hour). Since the higher end of the modeled impacts are within 98 percent of the NAAQS, with one exceedance, proper mitigation measures would need to be applied to address this finding.

3/Air Quality and Climate Change/23/10


While ozone levels (8-hour average) in the Tucson and Saguaro National Park East areas are already within 99 percent of the NAAQS, and as the mining operations could be expected to increase NOx emissions by 5 percent in Pima County, ozone levels could reach even higher, thereby increasing the risk of NAAQS exceedances. Proper mitigation measures would need to be applied to address this finding.

2/Air Resources/22/29

& Appendix D/Mitigation Plan


While these sections provide a very cursory list of mitigation measures common to all actions and alternatives, the measures are general and do not articulate applicable operating conditions, control equipment, engineering or work practice standards, and/or maintenance techniques that would help ensure compliance with applicable regulations and standards. The draft EIS should provide adequate assurance that the modeled results properly reflect worst case scenarios and include mitigation measures to ensure that the emission levels would not interfere with the attainment or maintenance of the NAAQS.



If the location where the tailings are stored is susceptible to moderate or high wind speeds and wind erosion, we believe PM10 emissions in the windblown dust from the area would increase greatly as a result. Thus, the draft EIS should state the calculated amounts of PM10 anticipated in the windblown dust that results from erosion of both tailings and waste rock and the assumptions that have been built into the calculations.

3/Air Quality and Climate Change/17/15


While Chapter 2 – Alternatives pointed out that the footprints of the proposed action and all action alternatives are generally different from one another, it is unclear how the conclusion in these lines, was reached – that is, “[the] emissions, and consequently impacts, will remain the same or less than the proposed action for all action alternatives based on equipment described and the number of hours it will operate.” Maximum ambient concentrations modeled for a criteria pollutant, and whether exceedances would result, can vary depending on the placement of facilities and therefore the action alternative selected. Each action alternative should have its own set of modeled results for demonstrating compliance with the NAAQS and the Regional Haze Rule regarding visibility in Class I areas or it should be empirically demonstrated why this is not necessary.

3/Air Quality and Climate Change/25/25

This discussion is too vague. The DEIS needs to specify clearly the point sources that are being referred to here, the applicable pollution control equipment for each, the identification of “all process equipment with significant emissions potential,” and specify levels that are significant.

3/Air Quality and Climate Change/

The DEIS needs to specify clearly the measures that constitute “containment,” the processes being referred, specify levels of “low emissions potential.”

3/Air Quality and Climate Change/

The DEIS should specify the point sources that are being referred, the emission limits that are “stricter than Federal and County requirements,” and the specific requirements that apply to the point source.

3/Air Quality and Climate Change/25/22


This section (“Mitigation Effectiveness and Remaining Effects”) appears to be missing measures that would be used to mitigate fugitive emissions of PM10 that result from the operations and dry-stack tailings, including the storage area. Similarly, details on dust control mitigation are missing from this section. The DEIS needs to include mitigation measures and elaborate how they would be achieved. We note that the document states elsewhere that inert polymer binders may be used for this purpose (2/Air Resources/23/10), but the document should include more details regarding this mitigation, its effectiveness, and the likelihood that it will be employed. Furthermore, the DEIS should also be more consistent in its discussion of these measures so as to avoid confusion.
    Also, based on a sentence in this section that states “all of these measures were included in the analytical and modeling work referred to in the discussion of environmental consequences for the action alternatives,” it is unclear whether the modeling work definitively included PM10 resulting from the operations and dry-stack tailings, including the storage area. The DEIS should clarify these issues.


3/Air Quality and Climate Change/26/19


The draft EIS should elaborate on the indirect air impacts created by the large amounts of energy the site will consume (emissions from the power plants that would supply the project's considering power needs).