EPA Keeps Data Analysis on Stream and Wetland Protections in the Dark

Published Jan 17, 2019

The EPA proposed a rule that would shrink what waterways are federally protected under the Clean Water Act. The agency said that they could not quantify the impact of rolling back this rule; however, a 2017 analysis shows enormous impacts of the proposed rollback.

What happened: In December 2018, the Environmental Protection Agency (EPA) proposed a rule that would shrink what waterways are federally protected under the Clean Water Act. The agency said that they could not quantify the impact of rolling back this rule; however, a 2017 analysis by the EPA and US Army Corps of Engineers shows enormous impacts of the proposed rollback. This analysis, which was previously presented to Administrator Scott Pruitt, was never mentioned or brought to light by the EPA. After news broke of the analysis, the EPA acknowledged the existence of the analysis. EPA officials then claimed the analysis was based on weak, irrelevant science.

Why it matters: The 2017 analysis, conducted by the EPA and US Army Corps of Engineers, attempted to calculate the percentage of different types of streams and wetlands across the country. A willingness by the EPA to hide the science produced in part by its own agency during the policy-making process is a disquieting message to federal scientists and the public.


A scientific analysis conducted by the Environmental Protection Agency (EPA) and US Army Corps of Engineers, showing the quantity of different types of waterway, was not considered by the EPA when the agency proposed to weaken the protection on millions of acres of streams and wetlands. The analysis is important as it can be used to estimate the percentage of streams and wetlands in the US that would lose federal protections under the Trump administration’s new definition of what constitutes the Waters of the United States (WOTUS). Using this analysis shows that at least 18% of streams and 51% of wetlands in the US will lose federal protections if the agency’s proposed rule shrinks the definition of WOTUS. Experts agree that these numbers are minimum estimates – an estimated 35% of streams in the arid parts of the US West will lose federal protection under the proposed WOTUS redefinition.

Given that the use of this analysis demonstrates that many wetlands and streams would lose federal protections, these results should have been vital to the EPA’s decision on whether or not to proceed with redefining WOTUS. The results of this 2017 analysis, obtained by E&E News under a Freedom of Information Act request, were considered important enough to be presented at a September 2017 briefing with former EPA Administrator Scott Pruitt and former Army Corps Deputy Assistant Secretary Douglas Lamont. Despite this, in December 2018 the EPA Office of Water chief Dave Ross claimed that the data does not exist, "If you see percentages of water features that are claimed to be in, or reductions, there really isn't the data to support those statistics. No one has that data." When Acting Administrator Wheeler was asked by reporters whether an analysis was done, he said, "We have not done... a detailed mapping of all the wetlands in the country."

When news broke of the 2017 analysis and that the results of the analysis showed potential far-reaching environmental consequences from the proposed WOTUS rollback, the EPA pivoted to attacking the legitimacy of the analysis’ science. When spokeswoman for EPA, Molly Block, was asked why the results of the analysis were not used to quantify the impacts of its rule, she said that "the datasets are not robust enough to accurately or precisely depict federally regulated waters." However, there is consensus in the scientific community that the underlying dataset are robust enough to yield accurate results. The analysis used data from the National Hydrography Dataset (NHD), a mapped dataset of surface water systems across the United States that was produced by the United States Geological Survey (USGS) and is maintained by the EPA. According to the USGS, the NHD is used by most water science federal agencies because it is a common national framework for surface-water geospatial information. The data has been considered robust enough for use by the EPA in 2005 under the George W. Bush administration. Even the text of the EPA’s proposed rollback includes a portion of the NHD dataset for each of the 50 states in its appendix.

However, like any scientific database, the NHD dataset has its imperfections. For instance, wetlands in forested areas or wetlands facing droughts are less likely to be captured in the NHD dataset. However, when EPA spokeswoman Molly Block said that, "The NHD data does not differentiate between intermittent and ephemeral streams and therefore could not be used to assess the proposed rule," her statement was an inaccurate representation of the science. The EPA’s proposed rule is set to rollback protections on ephemeral streams – which only flow after rain or during a snowmelt – and keep most of the federal protections on intermittent streams – which flow seasonally or when the groundwater table intersects with a streambed. The NHD data has had trouble differentiating ephemeral streams from intermittent streams. A data methodology was put into place starting in 2015 that allows the differentiation of ephemeral and intermittent streams but only for the arid West. This approach was independently verified by both the Bureau of Land Management (BLM) and USGS, according to an USGS August 2015 newsletter. The 2017 analysis acknowledged this data caveat and said that it “may result in an underestimation of the number of ephemeral streams throughout the country.” This means that the estimated 18% of streams likely to be rollbacked under the proposed rule is almost certainly a higher number.

Much has been written describing the negative consequences of the EPA’s new WOTUS proposal, including opening millions of acres of wetlands to more pollution; endangering the drinking water of the approximately 1 in 3 Americans that rely on drinking sources affected, at least in part, by ephemeral or intermittent streams; and, potentially opening up these once-protected waterways to development projects. The language in the draft rule leaves open the possibility of expanding the rollback to intermittent streams in the final version, which according to the 2017 analysis represents 52% of US waterways. Using tactics straight out the disinformation playbook, 48 members of water-polluting industries actively lobbied for the rule. The EPA invited several members of one of these groups – the American Farm Bureau Federation, a powerful agricultural lobbying arm – to its celebratory event to unveil the WOTUS rule.

Crucial information on the EPA’s proposed WOTUS rule, as was contained in the 2017 analysis, was not disseminated to the public. EPA political appointees cast doubt on the existence of the data and the analysis, and later on they attempted to interject doubt on the science itself. The lack of consideration of the best available science puts the health of many of the US’s streams and wetlands at risk. When EPA officials decide that it is a better idea to conceal and deny the existence of a dataset or an analysis they find to be politically contentious, they are doing a disservice to the American people who rely on their government to carry out policies that are supported by the best available science.