\"Mitchell, Jamie\" \<JMITCHELL@HRSD.COM\>

10/06/2006 11:09 AM

To

Group Ow-Docket@EPA

cc

\"Pletl, Jim\" \<JPLETL@HRSD.COM\>, \"Hogg, Paula\" \<PHOGG@HRSD.COM\>,
\"Lee,

Patty\" \<PRollins@hrsd.com\>

bcc

Subject

Docket ID No EPA-HQ-OW-2006-0656

Please find attached comments on Docket ID No EPA-HQ-OW-2006-0656,
\"Draft

Guidance for Implementing the January 2001 Methylmercury Water Quality

Criterion\"

\<\<HRSD Comments on MeHg guid w cover.doc\>\>

Jamie Heisig-Mitchell

Environmental Scientist

Hampton Roads Sanitation District

757-460-4220

October 6, 2006

RE: Docket ID No. EPA-HQ-OW-2006-0656

Notice of Draft Guidance for Implementing the January 2001 Methylmercury
Water Quality Criterion

The Hampton Roads Sanitation District (HRSD), a wastewater treatment
entity servicing 17 counties and cities in southeastern Virginia, is
pleased to offer the comments on the referenced document. Several of the
most important concerns are summarized below. Detailed comments follow.

1.  HRSD agrees that the use of the fish tissue criterion for
    methylmercury is the best-suited approach for implementing the
    methylmercury criterion as it provides direct assessment of risk to
    human health. Accurate and reliable implementation of this criterion
    as a water column-based standard requires site-specific information.
    The use of national default information for any aspect of this
    calculation is unacceptable in making regulatory decisions.

2.  HRSD strongly believes that the fish tissue criterion is the most
    important measure as to whether or not a water body is complying
    with methylmercury goals. There is no scientific basis for requiring
    NPDES effluent monitoring in water bodies that do not exhibit fish
    tissue impairment. Where there is no impairment, no further action
    should be necessary. Additionally, the guidance requires Mercury
    Minimization Plans (MMP) for all dischargers with quantifiable
    amounts of mercury in their effluent. HRSD supports the idea of
    pollutant minimization plans but in the absence of fish tissue
    impairment, this approach is highly overprotective and will likely
    result in ineffective use of limited resources. Fish tissue
    impairment must be the driver for all subsequent monitoring and
    regulatory action.

3.  The methods for measuring mercury and methylmercury in fish tissue
    are non-promulgated. The use of non-promulgated methods is
    unacceptable in a regulatory context, regardless of how often the
    method is documented in the literature or used in nonregulatory
    studies.

4.  Given that reductions in mercury emissions are anticipated to
    continue as a result of recent Clean Air Act legislation and that
    atmospheric sources have been documented to be the largest
    contributor in most water bodies, additional mercury TMDLs should be
    delayed to allow time for these regulations to have their expected
    impact. At this time, it would be more appropriate to focus limited
    resources on TMDL studies for pollutants that are not experiencing
    such dramatic fluxes from environmental inputs.

5.  The initial suggested and preferred approaches to implementation
    addressed in this document are typically well-defined. However, the
    direction and specificity in procedures become very nonspecific and
    lack scientific merit as one progresses through each implementation
    option. HRSD is concerned that this lack of specificity will allow
    for broad interpretation of the guidance, ultimately leading to
    significant inconsistencies and technically indefensible actions
    across the nation. More prescriptive language is required to ensure
    consistency and reliability in the document's application.

HRSD appreciates your consideration of these comments and looks forward
to reading the completed document. Should you have any questions, please
direct them to the contacts below.

Respectfully,

Jamie Heisig-Mitchell

Environmental Scientist

757-460-4220

Patty Lee

Laboratory Manager

757-460-4213

Hampton Roads Sanitation District

PO Box 5911

Virginia Beach, VA 23471-0911

**[Comments to]{.underline}**

***[Draft Guidance for Implementing the January 2001 Methylmercury Water
Quality Criterion]{.underline}***

# **[General Comments]{.underline}**

1.  HRSD, and most other permittees, agree that the use of the fish
    tissue criterion for methylmercury is the best-suited approach for
    implementing the methylmercury criterion. This approach provides
    direct assessment of risk to human health. Should a state choose not
    to implement this criterion as a fish tissue criterion, they must be
    instructed to utilize site-specific information to implement a water
    column-based standard with equal certainty in assessing risk. The
    use of national default information for any aspect of this
    calculation, particularly in calculating the bioaccumulative factors
    (BAFs), is unacceptable in making regulatory decisions. The
    uncertainty associated with this approach is great and would likely
    result in poor management decisions. It would be far more defensible
    to devote resources toward sound implementation of a water
    column-based standard than to waste resources responding to faulty
    decisions.

2.  The appeal of the fish tissue criterion for methylmercury lies in
    its direct applicability for human health risk assessment. HRSD
    strongly believes that the fish tissue criterion is the most
    important measure as to whether or not a water body is complying
    with methylmercury goals. As such, requiring NPDES effluent
    monitoring in water bodies that do not exhibit fish tissue
    impairment is not scientifically valid. The flow chart for
    determining "reasonable potential" (Figure 6, p.85) should begin
    with assessing fish tissue impairment. Where there is no impairment,
    no further action should be necessary.

3.  The primary intent of this document is clearly the protection of
    human health. However, a few references are made to wildlife
    criterion, particularly that associated with the Great Lakes
    Initiative (GLI). The majority of the document addresses the need
    for a methylmercury criterion that is protective of human health,
    leading the reader to believe that this is the purpose of the
    document. Based on the established criterion, it is apparent that
    protection of wildlife is the ultimate driving force for the
    criterion. Clarification on the purpose, scope and intent of the
    document and established criterion would prevent potential future
    misinterpretations.

4.  The use of non-promulgated methods is unacceptable in a regulatory
    context, regardless of how often the method is documented in the
    literature or used in nonregulatory studies. The integrity of
    criteria development and implementation is dependent on the
    reliability of analytical methods used to characterize environmental
    exposure and, hence, risk. Since EPA does not incorporate
    measurement quality objectives (MQOs) in its criterion development
    process, the public cannot be assured that the proposed criteria are
    reliable if the analytical methods used to measure contaminants are
    not properly validated and promulgated. Specific issues with regard
    to non-promulgated methods are addressed in several comments below.

> The reliability, precision and bias of analytical methods must be
> demonstrated and documented by EPA through inter-laboratory validation
> studies. These studies provide the foundation upon which analytical
> methods are promulgated in 40 CFR Part 136; the methods used to show
> compliance with NPDES permits. HRSD firmly believes that all criteria
> or other benchmarks used to make regulatory decisions must remain in
> draft form until promulgated analytical methods are in place to
> reliably determine if those criteria or benchmarks are technically and
> scientifically sound and defensible, and to provide reliable methods
> for evaluating compliance with those criteria. Additionally,
> analytical methods that have not been validated must not be specified
> in NPDES permits simply through guidance.

5.  Based on the flow chart for assessing "reasonable potential"
    (Figure 6. Determining reasonable potential, p.85), every facility
    will be forced into a Mercury Minimization Plan (MMP), regardless of
    fish tissue impairment. HRSD believes that every facility will be
    affected because of the required use of EPA Method 1631. Since
    Method 1631 can allegedly quantify at sub-part-per-trillion levels,
    it is highly unlikely that any facility will have non-detectable
    quantities of mercury in their effluent (NACWA study, *Evaluation of
    Domestic Sources of Mercury, August 2000*). While HRSD supports the
    idea of pollutant minimization plans, in the absence of fish tissue
    impairment, this approach is highly overprotective and will likely
    result in ineffective use of limited resources. Fish tissue
    impairment must be the driver for all subsequent monitoring.

6.  In the absence of fish tissue or water column data for a water body,
    the guidance suggests that the permitting authority require the
    permittee to collect the necessary data to calculate a site-specific
    BAF. While there are permittees that would welcome the opportunity
    to collect this data, the responsibility should fall to the
    permitting authority. If a permittee is unable to reasonably conduct
    the ambient sampling, the permitting authority must conduct all
    sampling and analyses required for calculation in order to make
    defensible decisions.

7.  Given that reductions in mercury emissions are anticipated to
    continue and that atmospheric sources have been documented to be the
    largest contributor in most water bodies, especially in the eastern
    United States, it is more appropriate to target other pollutants of
    concern for the TMDL process. Limited resources would be better
    utilized to address contaminants that are not experiencing dramatic
    fluxes from environmental inputs.

> Additionally, several regulations for mercury emissions to the
> atmosphere (e.g., Clean Air Mercury Rule) by coal-fire plants have
> recently been adopted. A more prudent and resource savvy approach
> would be to delay initiating additional mercury TMDLs and allow time
> for these regulations to have their expected impact.

8.  Guidance and information is very well defined at the top tier of the
    document's general approach. The direction and specificity in
    procedures become very nonspecific and vague as one moves down from
    the top tier of the guidance. HRSD is concerned that this lack of
    specificity will allow states or permitting authorities to broadly
    interpret the guidance, ultimately leading to significant
    inconsistencies and technically indefensible actions across the
    nation. These varying interpretations by states will cause undue
    hardships on POTWs, especially in cases where the water column
    and/or fish tissue criteria are not exceeded but monitoring may be
    required. More prescriptive language is needed in all levels of the
    document to ensure consistency and reliability in its application.

9.  This document clearly does not contain the most currently available
    information in several areas. For example, the food intake survey is
    from 1994-1996 and new analytical methods for low-level mercury have
    been promulgated since 2001. During the past decade, American's
    eating habits have changed to include more lean meats (i.e., fish).
    The USDA and DHHS have food survey information as recent as
    2003-2004.

The document also contains a great deal of information on how to
implement the varying approaches for determining compliance with the
methylmercury criterion. Unfortunately, a great deal of this information
may be missed because of the organization of the document.

# **[Chapter 2]{.underline}**

-   Section 2.1.2

    -   The text in the second paragraph indicates that the data
        presented in Figure 1 is biased high as a result of using data
        that had not been normalized to a set of standard species and
        lengths. The figure found in "The Regulatory Impact Analysis of
        the Clean Air Mercury Rule" (Figure **5-11** on page 5-16) has
        the bias removed and is, therefore, the more accurate of the
        figures. The more accurate figure should be used in place of the
        current biased figure.

# **[Chapter 3]{.underline}**

-   Section 3.1.2.1

    -   *"A fish tissue sample is currently easier to analyze for
        methylmercury and analysts are more experienced in analyzing
        methylmercury in fish tissue than in water samples."* This
        statement should be accompanied with documentation supporting
        the basis of the comment. From HRSD's experience, water samples
        are much easier to analyze due to the more complex steps
        required for tissue homogenization and sample analysis.
        Additionally, environmental labs have been analyzing mercury in
        water for far longer and more frequently than in tissue and
        therefore have more experience analyzing mercury in water than
        in tissue.

-   Section 3.1.2.2

    -   The national surveys for fish data are approximately 10 years
        old. More recent and relevant data must be required, not
        suggested. Current fish consumption levels are likely to have
        changed substantially in light of new dietary guidelines and
        habits resulting in greater fish consumption rates at varying
        trophic levels.

-   Section 3.1.3.1

    -   Should a state choose not to implement a fish tissue criterion,
        they must be instructed to utilize site-specific information to
        defensibly translate a water column-based standard. The BAF
        translator is a site- and species-specific measurement dependent
        on a number of physical and chemical characteristics in a water
        body and the organism itself. A state must not be permitted to
        use national default BAFs as this would contribute to an
        unacceptable level of uncertainty associated with subsequent
        management decisions.

-   Section 3.1.3.2

    -   *"EPA has not yet published analytical methods to measure
        methylmercury in either water or fish in 40 CFR Part 136.
        However, for fish tissue, states and authorized tribes can
        measure methylmercury concentrations using the same analytical
        method used to measure for total mercury..."*. Prior to this
        point, Method 1631 is the only method that has been referenced
        for total mercury. However, Method 1631, Rev. E Section 1.1
        states that this method is *"...for the determination of mercury
        in aqueous samples..."*. Method 1631, Rev. E must not be used
        for regulatory analysis of tissues or other solid samples.

    ```{=html}
    <!-- -->
    ```
    -   The supposition that total mercury and methylmercury are
        approximately equivalent in fish tissue is based on limited data
        and has a wide range of variability (80 -- 100%). This also only
        applies to trophic levels 3 and 4 for fish older than 3 years of
        age. These caveats are lost in later text in which fish tissue
        total mercury and methylmercury are claimed to be equivalent
        within 10%. These are critical conditions associated with this
        assumption and should be emphasized.

    ```{=html}
    <!-- -->
    ```
    -   With a methylmercury criterion for tissue of 0.3 mg/kg,
        consideration should be given to using SW-846 Method 7471A as a
        method for analysis of total recoverable mercury in solids and
        tissues. Method 7471A will easily meet the MQO of 0.3 mg/kg.

    -   *"...fish should be of similar size so that the smallest
        individual...is no less than 75 percent of the total length...of
        the largest individual."* While comments later in the text
        indicate that these fish are the same species, it would be
        helpful to provide clarification in this section of the text as
        to whether this is talking about within the same species or
        within the sample set collected.

    -   Site-specific data used to calculate BAFs will be generated
        using inappropriate, unvalidated and/or unpromulgated methods.
        The use of non-promulgated methods is unacceptable for use in a
        regulatory context, regardless of how often the method is
        documented in the literature. The uncertainty associated with
        this data can result in seriously flawed management and
        regulatory decisions resulting in inappropriate allocations of
        limited resources.

-   Section 3.1.3.2

    -   When discussing the applicability of "*Human caused conditions
        that cannot be remedied*", to granting variances, the text
        states that *"...if air deposition modeling shows that the
        atmospheric deposition from outside the United States was a
        substantial cause of impairment, the variance may be
        warranted*". Air deposition outside of the state should also
        warrant a variance; individual states cannot regulate
        atmospheric sources outside of their respective borders.

[]{.mark}

# **[Chapter 4]{.underline}**

-   Section 4.1

    -   Method 1631, Rev. E does not measure methylmercury, it only
        measures total and dissolved mercury (Sections 3.1 & 3.2 of
        Method 1631, Rev. E). This method was validated only for total
        and dissolved mercury in aqueous samples. Use of this method
        beyond the scope stated in the method is expressly prohibited in
        a regulatory context.

    -   UW-Madison's SOP and the USGS method have not been promulgated
        and are not found in 40 CFR Part 136. Therefore, regardless of
        the similarity of the methods, the use for nonregulatory studies
        or the number of citations in the literature, these methods did
        not meet the requirements in 40 CFR Part 122.41.4.

    -   Total and dissolved Hg methods are specified as *"...the most
        appropriate methods for measuring compliance with new or revised
        methylmercury criteria..."* Methods expressly developed for
        aqueous matrices must not be used for compliance monitoring of
        fish tissue. Often, the MQOs and DQOs for solid and aqueous
        samples are very different simply because of the matrix type.
        There are no methods that have been fully validated and
        promulgated in 40 CFR Part 136 for methylmercury in aqueous or
        solid samples; the document must make this clear.

    -   Method 1631 has gone through a full EPA validation study and
        MQOs have been developed from the study results. Method 1630 has
        not been fully validated, leaving the MQOs stated in the method
        as suspect. Regarding Method 1630, the guidance states that
        *"...already in the appropriate EPA format and include all
        standardized quality control (QC) elements needed to demonstrate
        that results are reliable enough to support permitting and
        enforcement programs."* This statement indicates that it is more
        important for EPA to use methods that are formatted correctly
        than to use methods that have been properly validated and have
        known precision and bias criteria. HRSD is more concerned, as
        states and EPA should be, about the validity and ruggedness of a
        method than the format in which it appears.

    -   Successful use of techniques in studies and literature does not
        ensure that the method(s) is appropriate for compliance
        monitoring. Study DQOs and MQOs may be very different than those
        for regulatory compliance. Also, since the studies were not for
        regulatory compliance, data may be skewed and/or invalid if the
        method was not followed exactly as written.

    -   Appendix A to Method 1631 references Method 1631, Rev. B. Only
        Rev. E has been promulgated. Just because an aqueous method has
        been "well-characterized and approved", does not infer that the
        method is appropriate for a tissue or solid matrix or for
        regulatory use. This is a poor assumption on EPA's part,
        especially since the method was validated by only one contract
        laboratory.

-   Section 4.1.1

    -   The detection and quantitation limits for Method 1631, App. A
        are largely unknown. It has only been validated by a single
        laboratory. Reports of these techniques in literature and the
        ability of one laboratory to use the method are not acceptable
        indicators of the appropriateness of the method for regulatory
        compliance monitoring. MQO criteria developed in aqueous
        matrices often do not directly translate to tissue or solid
        matrices.

-   Section 4.3.1

    -   It is very unclear whether the objective of this guidance is to
        quantify mercury as low as possible regardless of the need, or
        if it is to use an appropriate method that meets the DQOs.
        Forcing permittees to always use the most sensitive method
        available, even when unnecessary, will almost always yield
        detectable values and may result in needless expenditure of
        resources. No consideration has been given to using Method 245.7
        (which has been promulgated) as an alternative to Method 1631,
        even though it may meet regulatory objectives.

    ```{=html}
    <!-- -->
    ```
    -   The guidance recommends that ½ of the value of the MDL be used
        for all non-detect data. Should the data fall between the MDL
        and the QL, the value used is ½ the difference between the two
        values plus the MDL. This is a departure from the GLI and
        earlier EPA guidance in which nonquantifiable values are treated
        as 0. This guidance also contradicts the definition of EPA's MDL
        where values below the MDL are not statistically different from
        zero; they therefore cannot be represented as different from
        zero. The additional recommendation of a sensitivity analysis to
        ascertain the consequence of what value is used to quantify
        samples below the detection level is a defensible method for
        evaluating this data (1/2 the MDL vs 0). Should the results
        indicate that the choice of how to represent results below
        detection affects the management decision, then a more robust
        analysis must be performed. As this approach requires minimal
        resource expenditure, it should be required as opposed to
        recommended in order to increase the reliability and accuracy of
        the decision-making process.

# **[Chapter 6]{.underline}**

-   Section 6.2.2

    -   Much of the air modeling is limited in its accuracy and
        applicability. In particular, the Mercury Maps model is so
        riddled with limitations and disclaimers that it must not be
        used. Lack of a better, available option does not make these
        models acceptable for use in a regulatory context.

-   Section 6.2.3.2.5

    -   Without models capable of predicting methylation rates, the
        amount of uncertainty in developing TMDLs and subsequent Waste
        Load Allocations (WLAs) will be tremendous. This is
        inappropriate in a regulatory context because undue burdens
        (fiscal, legal) will result.

-   Section 6.2.3.4

    -   The TMDL process seems to assume that the total mercury
        discharged by the permittee is all methylated and, therefore,
        contributes to the fish tissue impairment of the water body.
        This may not be the case. Resources would be better utilized in
        studies aimed at characterizing methylation processes in order
        to reduce the uncertainty associated with the TMDL process.

# **[Chapter 7]{.underline}**

-   Section 7.2

    -   HRSD strongly believes that the fish tissue criterion is the
        most important measure as to whether or not a water body is
        complying with methylmercury goals. As such, requiring NPDES
        effluent monitoring in water bodies that do not exhibit fish
        tissue impairment is not scientifically valid. The flow chart
        for determining "reasonable potential" (Figure 6. Determining
        reasonable potential, p.85) should begin with assessing fish
        tissue impairment. Where there is no impairment, no further
        action is necessary. As the flowchart is depicted currently, all
        POTWs, with very few exceptions, will be required to implement a
        MMP as they will all have quantifiable mercury in their
        effluents when measured by Method 1631. This is due to the
        ubiquitous nature of mercury and its prevalence in domestic
        waste (NACWA Hg study).

    ```{=html}
    <!-- -->
    ```
    -   For states that adopt both the criterion as fish tissue and
        water column translation, it is unclear how exceedances of
        criteria are assessed. Unless the translation was calculated
        with a minimum of uncertainty (an very unlikely scenario), it is
        possible for a water body to be listed as impaired based upon a
        water column criterion even though the fish tissue criterion is
        not exceeded. Impairment of a water body into which a permittee
        discharges has direct regulatory consequences. The guidance
        should support use of the fish tissue criterion rather than of
        the water quality-based criterion when both are available.

    -   *"...EPA recommends that states and authorized tribes should
        make the procedures public..."*. Change statement to read
        *"...EPA recommends that states and authorized tribes
        [must]{.underline} make the procedures public..."* . These
        procedures must be made public to provide consistency in their
        application.

-   Section 7.3

    -   Specifying that *"...NPDES regulated discharges use the most
        sensitive method approved under 40 CFR Part 136 and report the
        quantitation level associated with that test"* means that NPDES
        dischargers are almost guaranteed to get a quantifiable value
        when using a method such as Method 1631. For example, even if a
        POTW accepts no industrial wastewater, there will still be
        mercury at quantifiable levels in the effluent when using Method
        1631 as a result of domestic source contributions. In a study
        performed by NACWA, it was found that domestic water contains
        \~50pptr of Hg (*Evaluation of Domestic Sources of Mercury,
        August 2000)*. This is indefensible since all permittees with
        quantifiable amounts of mercury in their effluent will be
        required to have, at a minimum, a MMP, regardless of fish tissue
        condition. The permittee will also likely be required to conduct
        routine and costly monitoring for mercury in their effluent.
        Again, with the current implementation guidance, this can be
        required despite the absence of fish tissue impairment.

-   Section 7.3

    -   Methylmercury test methods that have not been validated nor
        promulgated must not be specified in permits. There are
        promulgated low-level total mercury methods that are available
        for use and meet the MQOs of this document. Additionally, the
        use of total mercury methods would provide data describing the
        worst-case scenario, since methylmercury is a fraction of total
        mercury and methylation of effluents in varying water bodies is
        not adequately understood.

-   Section 7.5.1

    -   *"The NPDES permit fact sheet should provide the rationale..."*.
        Change to *"The NPDES permit fact sheet [must]{.underline}
        provide the rationale..."*. These procedures must be made public
        to provide consistency in their application and to support the
        rights of permittees to know the basis of their permit
        requirements.

    -   Using EPA Method 1631 will nearly always result in quantifiable
        levels of mercury in POTW effluent. Domestic waste alone is
        known to have mercury levels of \~50pptr. Fish tissue impairment
        must be the driver for all subsequent monitoring.

    -   Although this approach is consistent with the Great Lakes Basin
        regulations, it is important to note that the Great Lakes Basin
        is unique because it is a non-flushing water body. This unique
        characteristic presents issues that are not necessarily common
        to all other water bodies. Additionally, the use of this
        methodology for assessing reasonable potential is touted as
        "...significantly reducing environmental monitoring costs...".
        Requiring effluent monitoring only when fish tissue is impaired
        would represent even greater cost savings.

-   Section 7.5.1.1

    -   The presence of fish tissue impairment must drive additional
        effluent monitoring. Monitoring with Method 1631 will nearly
        always produce quantifiable amounts of mercury in effluents.
        Even POTWs that do not have an industrial component to their
        effluent will still likely have quantifiable amounts of mercury
        in their effluent as a result of domestic waste contributions.

-   Section 7.5.1.1.1

    -   In the absence of fish tissue impairments, recommending the use
        of Method 1631 when characterizing the discharger's effluent can
        be construed as data shopping. It is almost certain that a
        discharger will have quantifiable values of mercury in their
        effluent, therefore requiring a WQBEL. This can apply to a
        permittee that was meeting permit requirements when analyzing
        mercury with a less sensitive method.

    -   Fish tissue data collected by the regulator should be designated
        as the first line of screening. If fish tissue data is less than
        the criterion of 0.3mg/kg, monitoring by Method 1631 is not
        required.

    -   If the mercury concentration in the permittees effluent or fish
        tissue is unknown, the number of data points to determine
        compliance with the standard should be defined in this document.
        This will ensure that undue burdens for sampling and analysis
        will not be assumed yet decisions will not be based on
        inadequate quantities and quality of data.

-   Section 7.5.1.1.2

    -   The text refers to ensuring that the samples are representative
        only if data are below the limit of detection. Samples should be
        representative of the nature of discharge regardless of whether
        mercury is quantifiable or not. The reader gets the sense that
        unless the permittee has quantifiable data points, the
        regulatory authority will deem the data unrepresentative and
        require additional monitoring. This type of approach could be
        interpreted as data shopping and skewing data collection.

```{=html}
<!-- -->
```
-   Section 7.5.1.2.1

    -   It is unclear who should characterize a water body. It is HRSD's
        position that this role is the responsibility of the regulatory
        authority. While there are permittees that would welcome the
        opportunity to collect this data, the responsibility should lie
        with the permitting authority. If a permittee is unable to
        reasonably conduct ambient sampling, the permitting authority
        must conduct all sampling and analyses required to make
        defensible decisions.

    ```{=html}
    <!-- -->
    ```
    -   References are made to characterizing the entire water body and
        also to only characterizing the water body near the facility's
        discharge point. Some water bodies (e.g., Chesapeake Bay, James
        River, etc.) are tremendous in size. Further clarification on
        what is meant by "entire water body" is necessary. Definitions
        for the terms water body and water segment would be helpful and
        provide clarification.

```{=html}
<!-- -->
```
-   Section 7.5.1.2.2

    -   Recommendations for a MMP would, in some cases, help reduce
        mercury discharges to collection systems. However, some MMPs are
        very elaborate and would be fiscally unobtainable by some small
        POTWs. Description of MMP requirements would be helpful for
        regulators and permittees as well as provide consistency across
        agencies.

-   Section 7.5.2.1

    -   EPA recommends that permitting authorities take into account air
        deposition and other nonpoint sources into account when
        developing WQBELs. As described in this document, the mercury
        maps and air models are very unreliable at this time. Use of
        these tools cannot be used with any certainty and may place
        undue hardships on permittees. Only tools with known certainty
        should be used in the development of WQBELs and TMDLs.

    -   *"Municipal wastewater treatment plants and pulp and paper mills
        were considered significant when their estimated cumulative load
        contributed greater than 5 percent of the estimated
        waterbody-delivered air deposition load."* This is an
        all-encompassing statement. Sources from which this statement
        was developed must be included in this document.

    -   *"Point sources...could create hot spots... if fish stay in the
        immediate area."* Unless fish are tagged, there is no way to
        determine the movement of fish. This also assumes that the point
        source discharge of mercury is converting to methylmercury at
        some expected rate. Sources used to develop this statement must
        be included in this document since there are no methylation
        models available and the statement alleges responsibility on the
        part of wastewater plants that is not substantiated in the
        document.

-   Section 7.5.2.2

    -   Because domestic wastewater is known to contain \~50pptr Hg,
        public education may not be helpful in this area. Most of the
        products that were analyzed for trace levels of mercury were
        foods, personal hygiene products, and other household products.
        Mercury is not listed as an "ingredient" on the label and the
        average person is unaware of the trace levels of mercury present
        in products that are used daily in households. EPA and other
        regulatory authorities must realize that effectively "banning"
        mercury with this type of approach is not realistic because
        mercury is naturally occurring and ubiquitous.