March 29, 2005

Linda Boornazian

Director, Water Permits Division

Water Docket in the EPA Docket Center

Environmental Protection Agency

Mail Code 4101T

1200 Pennsylvania Ave., NW

Washington, DC 20460

**Attention: EPA Docket ID No. OW-2004-0037**

Dear Ms. Boornazian:

On behalf of Valero Energy Corporation, I thank you for the opportunity
to comment on the EPA's "Draft National Whole Effluent Toxicity (WET)
Implementation Guidance Under the NPDES Program" document. Valero Energy
Corporation is the largest independent Refiner and Marketer in the U.S.,
with 13 refineries in six states. As an affected stakeholder, we
appreciate the issues EPA faces in standardizing the WET program and in
developing solutions agreeable to both industry and environmental
organizations.

The draft guidance document encourages a regulatory agency to make
changes in how they make decisions regarding the appropriateness of a
WET limit in order to develop national consistency. This may result in
more stringent WET limits than are necessary or required, and put a
discharger at risk of noncompliance when there's no change in effluent
discharge quality. While specific comments are highlighted below, Valero
believes the guidance document should be clear in expressing that,
unless there is a change in effluent quality, the compliance
demonstration for the WET limits should be remain unchanged from
existing permits, and the States should clearly retain the right to
establish limits that they determine are appropriate for the receiving
water body. In addition, the final guidance should clearly indicate that
it has no legal effect on a State that has EPA approved water quality
standards and implementation procedures that address whole effluent
toxicity. Detailed comments are summarized below.

-   The guidance to require an average monthly limit and daily maximum
    limit should be clear that State Water Quality Standards may allow
    for other limits to be applied.

-   The guidance document undermines a State's discretion at applying
    limits and conditions that take into consideration the
    characteristics of a receiving water body that are unique to a
    particular area. As presented, the guidance document encourages a
    regulatory agency to make changes in how they make decisions
    regarding the applicability or appropriateness of a WET limit in the
    interest in developing national consistency. This unduly pressures a
    regulatory agency to apply practices that may result in more
    stringent WET limits and averaging requirements that may put a
    discharger at risk of noncompliance when no statistical shift in the
    average toxicity values or survival rates from historical values is
    present.

-   The guidance should clarify that in the absence of statistically
    significant changes in variability or method of operation, that the
    frequency of monitoring and compliance demonstration calculations
    should remain unchanged from existing permits.

-   40 CFR 122.45(d) requires all permit effluent limitations be stated
    as maximum daily and average monthly discharge limitations \"unless
    impracticable\".  It is not practicable to implement acute toxicity
    limits as daily maximum and monthly averages since they are a
    96-hour flow through test.  The probability that the proposed
    limitations would be exceeded due to factors other than effluent
    toxicity are high, and for the daily limit, there is uncertainty
    whether \<70% survival is indicative of true effluent toxicity.
    (referenced from "*Comments on the Proposed Amendments to the Water
    Quality Control Plan for San Francisco Bay (i.e., the Basin Plan):
    Implications of Test Variability on the Proposed Acute Toxicity Test
    Maximum Daily Limit\"* dated May 13, 2002 included as Attachment A)

-   The applicability of mixing zones should be clarified to avoid
    confusion and inconsistency in when they are applied or appropriate.
    The guidance is vague and allows too much discretion to a permit
    writer in deciding if a mixing zone is justified.

-   The guidance document should more explicitly encourage the use of
    tiered monitoring to more effectively address a dischargers
    probability of affecting receiving water quality. This should be
    encouraged for decreasing as well as increasing frequency.

-   As EPA notes in the draft guidance, EPA has not developed a Clean
    Water Act Section 304(a) criteria document for WET. When Section
    304(a) criteria are prepared and published by EPA, they are to be
    developed in consultation with appropriate federal and state
    agencies and other interested persons to accurately reflect latest
    scientific knowledge (33 U.S.C. Section 1314(a)). The draft WET
    guidance was not developed according to CWA procedures for criteria
    development.

-   Valero requests that the final version of the WET guidance clearly
    state that the document is for "information purposes only" and is
    not to be used by EPA regions as grounds to require changes in State
    water quality standards that EPA has previously approved.

Valero appreciates the opportunity to provide comments to EPA regarding
the WET guidance and the attention EPA provides in responding to
industry concerns.

> Sincerely,
>
> Patrick Covert
>
> Regional Environmental Director
>
> Valero

**VALERO DRAFT EPA WET GUIDANCE COMMENTS**

**ATTACHMENT A**

![](media/image2.wmf){width="7.911111111111111in" height="10.25in"}

# Comments on the Proposed Amendments

**to the Water Quality Control Plan for**

**San Francisco Bay (i.e., the Basin Plan):**

**Implications of Test Variability on the Proposed Acute Toxicity Test
Maximum Daily Limit**

**Prepared for:**

**Western States Petroleum Association**

**Prepared by:**

**Scott Ogle, Ph.D.**

**Pacific EcoRisk**

**835 Arnold Dr., Suite 104**

**Martinez, CA 94553**

**May 13, 2002**

# Comments on the Proposed Amendments to the

**Water Quality Control Plan for San Francisco Bay (i.e., the Basin
Plan):**

# Implications of Test Variability on the Proposed Acute Toxicity Test Maximum Daily Limit

The San Francisco Bay Regional Water Quality Control Board (Regional
Board) is currently proposing to amend the existing Water Quality
Control Plan for San Francisco Bay (Basin Plan) to revise the NPDES
compliance limits for acute toxicity testing. The proposed Amendment 3
states:

> *Compliance with the acute toxicity objective will be evaluated using
> flow-through exposure of larval fish to undiluted effluent. Toxicity
> limitations are:*
>
> *Maximum Daily Limitation = minimum of 70% survival*
>
> *Monthly Median Limitation = minimum of 90% survival [and]{.underline}
> a statistically significant difference between the effluent and
> control samples*.

## Effects of Test Variability on Compliance with the Proposed Maximum Daily Limit

As proposed, any single observation of \<70% survival in any acute test
will be considered a permit violation. However, it should be noted that
the EPA tests for measuring the toxicity of effluents are subject to
inherent variability from numerous potential sources, such that it is
possible for a given test to exhibit \<70% survival due, not to effluent
toxicity, but rather to other factors, such as the condition of the
particular batch of fish used in that test. An example of such
variability in the fish toxicity test survival response is provided
below:

1.  Inter-laboratory testing of effluent toxicity to fathead minnow
    survival (DeGraeve et al., 1988 \[as cited by Warren-Hicks and
    Parkhurst, 1992\]):

+----------+------+---------+-----------+-------------+-------------+
| Inter-la |      |         |           |             |             |
| boratory |      |         |           |             |             |
| fathead  |      |         |           |             |             |
| minnow   |      |         |           |             |             |
| survival |      |         |           |             |             |
| var      |      |         |           |             |             |
| iability |      |         |           |             |             |
| for      |      |         |           |             |             |
| effluent |      |         |           |             |             |
| toxicity |      |         |           |             |             |
| tests.   |      |         |           |             |             |
+----------+------+---------+-----------+-------------+-------------+
| Type     | Test | \%      | Co        | Number of   | Number of   |
| Effluent | \#   | S       | efficient | Labs        | labs        |
|          |      | urvival | of        | passing the | failing the |
|          |      |         | Variation | 70%         | 70%         |
|          |      | (Range) | (%)       | survival    | survival    |
|          |      |         |           | limit       | limit       |
+----------+------+---------+-----------+-------------+-------------+
| Refinery | 1    | 0 - 90  | 70.6      | 1           | 7           |
| 301      |      |         |           |             |             |
+----------+------+---------+-----------+-------------+-------------+
|          | 2    | 0 - 80  | 71.9      | 3           | 6           |
+----------+------+---------+-----------+-------------+-------------+
| Utility  | 1    | 0 - 85  | 58        | 3           | 5           |
+----------+------+---------+-----------+-------------+-------------+
|          | 2    | 0 - 85  | 53.9      | 4           | 4           |
+----------+------+---------+-----------+-------------+-------------+
| Refinery | 1    | 5 - 100 | 47        | 3           | 7           |
| 401      |      |         |           |             |             |
+----------+------+---------+-----------+-------------+-------------+
|          | 2    | 0 -- 95 | 54.7      | 4           | 5           |
+----------+------+---------+-----------+-------------+-------------+

Note- the DeGraeve et al. study examined % survival variability of
fathead minnows exposed to effluents in 7-day tests; given our
experience in performing numerous 7-day fathead minnow tests, we have
observed that fish mortality is typically expressed within the first 96
hrs of the test, and therefore believe this analysis of variability to
be relevant to the acute (96-hr) fish tests; furthermore, this is the
only study known to us that includes % survival data.

> CV -- Coefficient of variation, (= standard deviation/mean (x100)), is
> the typical measure of variability.

In their analysis of this effluent test variability (which included the
% survival response), Warren-Hicks and Parkhurst (1992) concluded that
due to such effluent test variability, "the probability that a
NPDES-permitted toxicity limit would be exceeded due to factors other
than the toxicity of the test material could be very high".

More commonly, toxicity test variability has been examined by analysis
of the variability in LC50 point estimates from reference toxicant
tests, although, as pointed out by Warren-Hicks et al. (2000), "a small
variance in the LC50 or IC25 does not necessarily reflect a small
variance in survival". Nevertheless, variability in toxicity test
estimates of EC50 and EC/IC 25 values can be significant. Moore et al.
(2000) reported a CV of 56% for the EC25 (analogous to 75% survival) for
fathead minnows exposed to SDS, well above the "limits that would be
acceptable by most scientists and permit holders (CVs \>30-40%)".

Data presented in the U.S. EPA 4^th^ edition acute toxicity testing
manual (U.S. EPA 1993) also indicates the potential for levels of high
levels of variability in 96-hr acute toxicity tests with fish:

> Table 1 (page 11 of the manual) indicates that the CVs of LC50 values
> for the fathead minnow acute toxicity test were 20% for SDS, 40% for
> NaPCP, and 120% for Cd.
>
> Table 3 (page 13 of the manual) indicates that the CVs of LC50 values
> for flow-through fathead minnow acute toxicity tests were 40% for
> silver and 46% for endosulfan; similar CVs for rainbow trout acute
> toxicity tests were 33% for silver and 42% for endosulfan.
>
> Table 4 (page 14 of the manual) indicates that the LC50 value CV for
> the fathead minnows acute toxicity test of KCl was 30%.

Finally, the recent EPA WET Variability Study reported a lower CV of 21%
for the fathead minnow acute toxicity test LC50 for KCL, and a CV of 22%
for a municipal effluent (U.S. EPA 2001).

The data and studies summarized above, when taken as a whole, clearly
indicate the potential for test variability to be a confounding factor
in the interpretation of any given test. As a result, there will be
uncertainty at whether or not an observation of \<70% survival is
indicative of true effluent toxicity, or whether the observed
mortalities are due to some other factor(s).

## 

## 

## Conclusion

The WSPA permit holders are reasonably concerned that the proposed
amendment of the Basin Plan to include a Maximum Daily Limit of a
minimum of 70% survival in acute toxicity tests may be problematic.
Their primary concern is that "the probability that a NPDES-permitted
toxicity limit would be exceeded due to factors other than the toxicity
of the test material could be very high". Dr. Don Mount, one of the
pioneers of WET testing, recently wrote that "WET testing has been
challenged for variability of test results, in large measure because of
the single exceedance violation requirement in the NPDES regulations"
(Mount 1998). In order to alleviate the problem with toxicity test
variability, Mount proposed to "allow permitees to average test values
rather than relying on a single test. While this approach does not
reduce variability *per se*, it greatly reduces the effect of
variability on non-compliance determinations".

In essence, Dr. Mount proposed the very system for regulating acute
toxicity tests that already exists in the current (un-amended) Basin
Plan, an approach that has served the Regional Board and the NPDES
dischargers very well for many years. Given this, the implementation of
the proposed Maximum Daily Limit, particularly at a time when the
dischargers are transitioning from testing with 3^rd^ edition fish life
stages to 4^th^ edition fish life stages, should be deferred until the
issues surrounding and factors causing acute toxicity test variability
are adequately addressed and resolved.

**Literature Cited:**

Moore DRJ, Warren-Hicks W, Parkhurst BR, Teed RS, Baird RB, Berger R,
Denton DL, Pletl JJ (2000) Intra- and intertreatment variability in
reference toxicant tests: Implications for whole effluent toxicity
testing programs. Env Toxicol Chem 19(1):105-112.

Mount D (1998) Midcourse corrections in WET testing program. SETAC News
18(2):19-20.

U.S. EPA (1993. Methods for measuring the acute toxicity of effluents
and receiving waters to freshwater and marine organisms, fourth edition.
EPA/600/4-90/027F. U.S. EPA, Office of Research and Development,
Washington, D.C.

U.S. EPA (2001) Final report: Interlaboratory variability study of EPA
short-term chronic and acute whole effluent toxicity test methods,
Vol. 1. EPA 821-B-01-004. U.S. EPA, Office of Water, Washington, D.C.

Warren-Hicks W, Parkhurst BR (1992) Performance characteristics of
effluent toxicity tests: Variability and its implications for regulatory
policy. Env Toxicol Chem 11:793-804.

Warren-Hicks WJ, Parkhurst BR, Moore DRJ, Teed RS, Baird RB, Berger R,
Denton DL, Pletl JJ (2000) Assessment of whole effluent toxicity test
variability: Partitioning sources of variability. Env Toxicol Chem
19(1):94-104.