CDPHE Investigation: Special Attorneys General Find Inconsistency in Modeling, Some Validity in Employee Claims

CDPHE building in Cherry Creek, Colorado.
Special Attorneys General have determined that allegations against the CDPHE about hiding air quality standard violations are unsubstantiated, and noted that there is validity in some points raised by a trio of CDPHE employees who wrote a letter outlining the allegations to the Environmental Protection Agency’s Office of Inspector General. / Photo courtesy Wikimedia Commons.

Continuing our coverage of the recent report from the Colorado Attorney General’s Office released from special assistant attorneys general found validity in concerns raised and others unsubstantiated in potential whistleblower allegations relating to air pollutant monitoring at the Colorado Department of Public Health and Environment. 

While this article focuses on the background of the situations explored in the report, our previous article covered the findings and takeaways by the investigation undertaken about the alleged violations.

Earlier this year, Colorado Attorney General Phil Weiser released a statement that the CDPHE’s executive director had requested an independent assessment of the claims submitted, as previously reported by Law Week. Following a competitive process, the office appointed attorneys at the firm of Troutman Pepper Hamilton Sanders LLP who conducted the investigation and released the report.

The issues at play in the letter sent by three CDPHE employees to the Environmental Protection Agency’s Office of Inspector General, or OIG, came out of a highly technical part of air permitting for stationary sources of air pollutants, according to the report.

Computers are used to create simulations called “air quality models” to predict whether a source air pollutant source would violate the National Ambient Air Quality Standards, or NAAQS, established by EPA, and its defined state and EPA modeling requirements for so-called “major sources.”

However, for minor sources, the state and EPA requirements are less well-defined, according to the report.

Allegations of unlawful acts and omissions by the CDPHE include suppressing information that pending permits could violate NAAQS; approving permits violating NAAQS; and ordering staff to ignore modeled violations conflicting with “nonbinding agency guidance documents,” according to the letter sent by CDPHE staff.

Under the Clean Air Act, the EPA requires states to create and get EPA approval of state implementation plans to meet those NAAQS. Also, owners and operators of sources of air pollutants must obtain CAA-approved permits consistent with state plans meeting NAAQS.

The EPA periodically revises the NAAQS based on new information, and the standards can be revised, revoked or retained to match requirements protecting public health. This is usually checked by monitoring stations taking samples of “ambient air” accessed by the public. Where sufficient data isn’t readily available, computer modeling is used to evaluate compliance, the report states.

Since air pollutant concentrations in the ambient air are the result of many different factors and sources, the EPA has repeatedly made it clear that compliance with NAAQS is an obligation of states through the implementation of plans imposing enforceable requirements on individual emission sources, according to the report.

However, the “EPA lacks clear guidance on the issue, leaving the states to craft their own,” the report states.

To meet that state requirement back in 2002, the CDPHE’s Air Pollution Control Division developed its first comprehensive Modeling Guideline, according to the report. The guideline covered both major and minor sources and is based on modeling analysis which includes emission rate thresholds for use in determining when it’s necessary to model minor sources.

“Since emission rates below these thresholds were determined to be unlikely to exceed the NAAQS, the thresholds served as an easy-to-apply tool in deciding whether to model a minor source,” the report states. Although, the use of the tool still required expert judgment, and wasn’t intended “as a ‘bright line’ exemption.”

In 2010, the EPA adopted new NAAQS for certain pollutants, nitrogen and sulfur dioxide, which were already subject to NAAQS on an annual average. However, this time the NAAQS were much more stringent — reviewing a single hour of production, instead an entire year.

In turn, this made the APCD modeling group try to expand the Modeling Guideline to include new thresholds for one hour. However, when they conducted the same hypothetical modeling used to develop the yearly thresholds they found “much lower hourly thresholds were needed to ensure compliance,” according to the report.

Shortly after, the APCD modeling group developed new hourly modeling thresholds and the APCD developed its own guidance in implementing the one-hour standards for those two chemicals, according to the report.

“Based on EPA guidance for major sources, and a belief that minor sources should not be regulated more stringently than major sources, APCD’s permitting group prepared an interoffice communication entitled ‘PS Memo 10-01,” the report states.

That memo indicated that modeling should only be required for minor sources if they exceeded a 40-tons-per-year emission rate the EPA uses as a trigger for major permitting at an existing major source, according to the report. However, the memo didn’t evaluate whether the annual threshold would prevent exceedances of the one-hour NAAQS.

This conflict caused confusion, according to the report. The permitting group, who relied solely on the memo, didn’t require applicants with emissions below that threshold to model for NO2 or SO2, even though the threshold wasn’t well supported. On the flip side, the modeling group often performed its own modeling for facilities with emissions over the Guideline’s threshold of .46 pounds per hour under the 2002 guidance, even though the threshold was “highly conservative.”

“In some cases, the modeling group predicted exceedances of NAAQS but APCD issued permits without addressing those predicted exceedances,” the report states.

As a result, tensions grew between the APCD modeling and permitting groups. Then, in March, APCD management withdrew the Modeling Guideline and relied solely on the annual 40 tpy thresholds referenced in the memo, the report states.

“Although the decision was not motivated by an intent to circumvent the law, but rather to resolve the conflict in APCD’s own guidance, the decision left APCD without a well-justified approach for determining whether emissions from a minor source may exceed a NAAQS,” the report states.

That in turn led to the CDPHE employees to share concerns about APCD’s permitting and modeling procedures, according to the report.

Despite the employee’s claiming all minor sources must “verify through air quality modeling” that emissions from the source won’t cause or contribute to NAAQS exceedance, that requirement only applies to major sources — and minor sources requirements “are different,” according to the report.

“That said, the letter is correct that APCD may not ignore the air quality impacts of a minor source simply because it does not have the potential to emit more than 40 tpy, particularly given that its own modeling group has determined that emissions of 40 tpy are likely to exceed the 1-hour NAAQS,” the report states.

In terms of the question about when minor source modeling is required, the APCD must implement legally enforceable procedures ensuring permits won’t exceed requirements, but it doesn’t have to require air quality modeling for every permit issued, according to the report. Instead, other methods could be applied such as ambient air monitoring.

“Accordingly, the letter to the EPA OIG is incorrect in alleging that APCD must conduct air quality modeling for all minor source permits,” the report states. “APCD’s policy, however, was inadequate to ensure minor sources would not exceed the NAAQS.”

As previously reported by Law Week, the special attorneys general included Mack McGuffey, Charlie Peeler, Melissa Horne and Shawn O’Brien of the Troutman Pepper firm.

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