November 27, 2023

SCS Engineers Due Diligence

USEPA – Region 7 has been working on a mobile air emissions inventory (dubbed Gmap) to identify major immediate health concerns in the St. Louis area. On Oct 25, they also held two community meetings in the Lemp neighborhood to provide a status update on air monitoring efforts. So – if you don’t have your facility properly permitted and in compliance with construction or operational air emissions, you’re in for increased scrutiny from the agency and the public alike. The USEPA officials we work with stress that accuracy and timeliness in submitting your permit and responsiveness to agency questions are the keys to successful and relatively painless permitting, which many environmental consultants can assist with.

Another issue related to air permitting is keeping on top of the changing landscape of the National Ambient Air Quality Standards (NAAQS). East St. Louis and St. Louis, as well as St. Charles and Jefferson Counties, are currently mapped as non-attainment zones for ozone. Proposed reductions in the allowable limits for particulate matter (PM) 2.5 micrograms per cubic meter (µg/m³) under the Clean Air Act, which could go into effect at any time, will result in the designation of additional non-attainment areas in the region and, accordingly, far greater difficulty in air permitting for new or expanding facilities. The current annual average primary standard for PM 2.5 is 12 µg/m³, whereas the proposed standard will likely fall to between 9-10 µg/m³. It’s also important to know that EPA recently announced $3.5 million for Environmental Justice projects across Missouri and that EJ is becoming a bigger and bigger challenge for industrial facilities housed in EJ communities, so if your facility is an air emitter, even if properly permitted, you could face operational and PR challenges.

Another important thing to be proactive about is National Pollutant Discharge Elimination System (NPDES) permits for construction and wastewater or stormwater runoff. NPDES non-compliance is becoming a major concern for MDNR and EPA as Missouri has a higher non-compliance rate than many other states. And ditto for spill prevention, control, and countermeasure (SPCC) and stormwater pollution prevention plans (SWPPP). Facility compliance audits are a great tool to ensure you have everything in place so you don’t end up with unexpected notices of violation.

Finally, as hopefully many of you are aware, due diligence and permitting requirements will become increasingly strict as polyfluorinated substances (PFAS) are declared hazardous substances under CERCLA. There is likely to be a great deal of litigation over this. PFAS have already been added to other regulatory frameworks, such as the recent requirement for toxic release inventory reporting to include them as chemicals of special concern, removing the de minimis exemption formerly in place.

Successful industrial facilities I work with are proactive in their permitting and compliance efforts. They carve out ample time for due diligence and – if needed – remediation work before facility acquisitions and expansions. My advice is to know what you’re getting into and that front-end costs are nothing compared to fines or cleanup costs you might be subject to if you don’t get your ducks in a row. For example, the USEPA recently issued a sizeable fine related to a Clean Water Act violation for a scrap metal recycling facility in St. Louis alleged to have illegal discharges into the Mississippi River.


Rachel McShaneAbout the Author: Rachel McShane, LEP, has over 15 years of experience in environmental due diligence projects (Phase I, II and III Environmental Site Assessments) as well as Brownfields redevelopment, risk-based corrective action, and remediation projects. She is familiar with National Environmental Policy Act (NEPA) environmental assessments, vapor investigations and mitigation, radon, asbestos, lead-based paint surveys, and leachate monitoring/solid waste management. Reach Ms. McShane at  or via LinkedIn.



Posted by Diane Samuels at 6:00 am

September 18, 2023

usepa naaqs
Preparing for USEPA NAAQS from the Air Experts at SCS Engineers.


The other night, I woke up in a bit of a panic and thought that I must have missed an announcement by the USEPA regarding the PM2.5 NAAQS reconsideration! Did I?

The answer, thankfully, is no! However, that is not any reason to relax and take no action.

By way of background, the Clean Air Act requires that the USEPA set National Ambient Air Quality Standards (NAAQS) for each of the criteria air pollutants, including particulate matter (PM). These NAAQS are based on the best available science and aim to protect human health and welfare. In June of 2021, the USEPA announced that they would reconsider the 2020 PM NAAQS final action under the prior administration that did not lower any standards. Then, in January 2023, the USEPA published the proposed rule to revise the PM2.5 primary annual standard down from 12 micrograms per cubic meter (µg/m3) to within a range of 9-10 µg/m3. In that proposal, the agency retained the 24-hour standard of 35 µg/m3.

The comment period for this proposed rule has since closed, and the agency is now working through over 5,000 submitted comments. It is unclear when the USEPA will issue the final rule (it could be any day now) and if the new annual standard will be set at 9 or 10 or something in between.


What does this mean for me as a regulated source? What should you do? SCS Engineers recommends the following actions:

  • If you have any air quality modeling analyses in progress for PM2.5, review the annual PM2.5 analysis and ensure the results are at or below 10, or ideally 9 µg/m3.
    • NOTE: Once the proposed rule becomes final, required air dispersion modeling assessments must demonstrate compliance with the new standard before issuing a permit, even when submitting the application before the new NAAQS standard.
  • Review and understand local ambient air monitoring data and trends to develop permitting strategies depending on whether your airshed will become a non-attainment area, or if the background values will be very close to the new standard, leaving little room for regulated source emissions.
  • Review current emission inventories and calculation methodology to determine if there is room to modify conservative assumptions to reduce PM2.5 emissions.
  • Investigate potential emission reduction projects. The investigation is especially important if your area will become a non-attainment area so that you can generate offsets for future permitting needs or emission reduction banking.


Additional Resources:


About the Author: Rafe Christopherson, PE, is a project director and SCS’s industrial Clean Air Act leader. He is an air quality professional with a wide variety of experience over his 25-year career. His expertise includes consulting, working at an air quality regulatory agency and with industry. His expertise includes semiconductors, biofuels, pulp and paper, hardwoods, power generation, refineries, and general manufacturing. If you are interested in more information on this PM2.5 NAAQS reconsideration process and what it might mean for your business, you may reach Rafe at or via LinkedIn.






Posted by Diane Samuels at 6:00 am

May 6, 2020

CERLCA Jurisdiction and PRP Definition

A recent Meyers | Nave publication discusses the Supreme Court’s April 20, 2020 decision in Atlantic Richfield Co. v. Christian. The firm suggests the decision adds another layer of complexity to the Comprehensive Environmental Response, Compensation, and Liability Act – CERCLA, liability issue. The decision opens the door for state courts to hear claims that challenge EPA-defined approved clean-ups and has the potential to expand the “potentially responsible party” – PRP class for current “owners” of a “facility.”

The Court’s decision introduces new considerations into CERCLA liability analysis and settlement strategy. The Court’s holding will have many immediate ramifications, including the following:

  • It may be argued that the decision broadens the definition of PRP. CERCLA’s already-expansive definition of PRPs now includes landowners whose soil is contaminated by another PRP’s facility because a release has “come to be located” on their land.
  • The decision has the potential to unravel comprehensive and time-consuming CERCLA requirements in a federally-approved clean-up scheme. For example, if EPA waives the requirement to adopt state applicable or relevant and appropriate requirements (“ARARs”) at a federal CERCLA site, it seems entirely plausible that some litigants could use a nuisance or similar lawsuit to seek to impose ARARs that EPA specifically considered and waived.
  • The decision might have created an additional layer of CERCLA requirements that apply to PRPs that desire to bring state law claims in state court. Though they were found to be PRPs, the plaintiff landowners were allowed to present their own plan to restore their own private property as long as they obtained EPA approval, but it is unclear what process the landowners would use.
  • The decision might reduce the incentive to enter into CERCLA settlements with EPA if parties are not shielded from contribution claims − which now could arise by exposing settling parties to potential litigation at the state level. While the Court noted that CERCLA: (1) encourages covenants not to sue which cap liability to the Government and (2) protects settling parties from contribution claims by other PRPs, the decision seems to contradict both of those positions and undermines finality of settlements.


Clean Water Act Developments

In April, the courts and federal agencies announced major developments significantly affecting regulation under the Clean Water Act – CWA and how the CWA may be applied in the future.

  • First, a U.S. District Court in Montana issued a sweeping decision under Section 404 of the CWA that purports to invalidate and enjoin the use of Nationwide Permit 12 (NWP 12), the widely-used general CWA § 404 permit for construction of pipelines and other utility lines across regulated water bodies, for all projects anywhere in the country.
  • Second, the Trump Administration published its long-anticipated “Navigable Waters Protection Rule” in the Federal Register, defining what constitutes Waters of the United States (WOTUS) that are regulated under the CWA, which is narrower in scope than both the 2015 rule promulgated by the Obama Administration and the pre-2015 rule now in effect.
  • Third, the Supreme Court issued a decision in County of Maui, Hawaii v. Hawaii Wildlife Fund, et al. (No. 18-260) in which the majority held that a CWA discharge permit is required where “the addition of the pollutants through groundwater is the functional equivalent of direct discharge from [a] point source into navigable waters [i.e., WOTUS].”

Each of these developments could have far-reaching implications for regulations under the CWA. Assuming the 2020 Rule withstands legal challenges, it is seen as favorable for industry and other regulated entities, while the two judicial decisions are perceived as problematic for such entities. Davis Graham & Stubbs describes each development in more detail in the firm’s recently published article.


MATS Supplemental Cost Finding and Clean Air Act RTR 

On April 16, 2020, the U.S. Environmental Protection Agency (EPA) finalized the 2016 Supplemental Cost Finding for the Mercury and Air Toxics Standards – MATS, for coal- and oil-fired power plants, consistent with a 2015 U.S. Supreme Court decision. The agency also completed the Clean Air Act-required residual risk and technology review – RTR, for MATS. According to the EPA power plants are already complying with the standards that limit emissions of mercury and other hazardous air pollutants (HAPs), and this final action leaves those emission limits in place and unchanged.

However, with this final action, EPA is not removing coal- and oil-fired power plants from the list of affected source categories for regulation under section 112 of the Clean Air Act, consistent with existing case law. Those power plants remain subject to and must comply with the mercury emissions standards of the MATS rule, which remains fully in effect notwithstanding the revised cost-benefit analysis.

In addition, EPA has completed the required RTR for MATS and determined no changes to the rule are needed to further reduce residual risk. The RTR satisfies the statutory requirements set out by Congress in the Clean Air Act. More information is available on EPA’s Mercury and Air Toxics Standards website.


Proposal to Retain NAAQS for Particulate Matter

On April 14, 2020, the U.S. Environmental Protection Agency – EPA announced its proposal to retain, without changes, the National Ambient Air Quality Standards – NAAQS for particulate matter (PM) including both fine particles (PM2.5) and coarse particles (PM10).

According to the EPA because of Clean Air Act programs and efforts by state, local and tribal governments, as well as technological improvements, average PM2.5 concentrations in the U.S. fell by 39 percent between 2000 and 2018 while average PM10 concentrations fell by 31 percent during the same period.

EPA states it is following the principles established to streamline the NAAQS review process and to fulfill the statutory responsibility to complete the NAAQS review within a 5-year timeframe. More information about the rule can be found at EPA’s: National Ambient Air Quality Standards (NAAQS) for Particulate Matter (PM) Pollution website.

EPA will accept public comment for 60 days after the proposed standards are published in the Federal Register. EPA plans to issue the final standards by the end of 2020.


U.S. Greenhouse Gas Emissions and Sinks Inventory Announcement

The Environmental Protection Agency’s annual report, “Inventory of U.S. Greenhouse Gas Emissions and Sinks: 1990-2018,” provides a comprehensive look at U.S. emissions and removals by source, economic sector, and greenhouse gas – GHG. The gases covered by this inventory include carbon dioxide, methane, nitrous oxide, hydrofluorocarbons, perfluorocarbons, sulfur hexafluoride, and nitrogen trifluoride. The inventory also calculates carbon dioxide emissions that are removed from the atmosphere by “sinks,” e.g., through the uptake of carbon and storage in forests, vegetation, and soils.

On April 13, 2020, the EPA’s comprehensive annual report on nationwide GHG emissions released to the public. It shows that since 2005, national GHG emissions have fallen by 10%, and power sector emissions have fallen by 27%.

“While there was a small rise in emissions due to weather and increased energy demand from the prior year in this report, based on preliminary data, we expect next year’s report to show that the long-term downward trend will continue,” said EPA Administrator Andrew Wheeler.

According to the announcement, annual trends are responsive to weather variability and economic conditions. Year-over-year, national GHG emissions were 3% higher in 2018 than the prior year, due to multiple factors, including increased energy consumption from greater heating and cooling needs due to a colder winter and hotter summer in 2018 compared to 2017.

According to environmental and research groups, driving the drop’s long-term downward trend is chiefly due to a shift away from coal power generation. The 2019 drop was driven by a nearly 10 percent fall in emissions from the power sector, the biggest decline in decades [Rhodium Climate Service]. Utilities are closing coal plants in favor of cheaper natural gas and renewable energy.

Emissions from industry rose slightly last year, and are now greater than those from coal-fired power plants, most driven by a strong economy. Emissions from buildings were up, and emissions from other sectors of the economy collectively grew by more. The shift to lower-carbon energy is largely restricted to the electricity sector, and in order to meet international and state goals, state policies continue to target other sectors that collectively make up a majority of U.S. emissions.

More information is available at EPA’s website Inventory of U.S. Greenhouse Gas Emissions and Sinks.


For more information about potential impacts to waste, energy, or manufacturing please contact your nearest SCS Engineer’s office or your Project Manager. 





Posted by Diane Samuels at 6:00 am