of Amber ReimondoEnergy Director

In 1986, the US Forest Service approved a plan to operate a private uranium mine in the Kaibab National Forest near Grand Canyon National Park. Based on the science available at the time, the Forest Service determined Mine Canyon (which would later be RENAMED Pinyon Plain Mine) did not threaten groundwater in the Grand Canyon region, including depth Redwall-Muav Aquifer which feed the springs in the Grand Canyon that flow into the Colorado River.

In 2012, revised the Forest Service its 1986 findings and determined that there was no reason to reassess the potential effects of uranium mining at the Canyon mine, reasoning that the science and facts on the ground had not changed.

Outdated science

But in the decade that has passed, things have changed. In 2016, miners developing the mine hit groundwater and the company was pumping it out of mine since then.

The science on which the mine was approved nearly four decades ago is outdated and in need of revision. The Arizona Attorney General did appointed for a new supplement to the outdated 1986 environmental impact statement, which initially assessed the mine’s risks to groundwater.

Scientists have learned a lot about the groundwater in the Grand Canyon region since 2012. studied indicates that the Canyon Mine, renamed the Pinyon Plain Mine in 2020, may endanger groundwater and associated springs and ecosystems in Grand Canyon National Park. It’s time for the Forest Service to take a hard look at mine and consider the science.

Since 2016, over 66 million gallons of water they had to be pumped out of the mine shaft.

We recently met with groundwater scientists Dr. Laura Crossey, Dr. Karl Karlstrom, and Dr. David Kreamerwho studies the groundwater in the Grand Canyon region. I asked them about some of the Forest Service’s scientific conclusions from 1986 and 2012, given the science available today.

You can talk about the idea that contamination from the mine can’t reach the depth of the Redwall-Muav Aquifer, which feeds the Grand Canyon springs, because there are thousands of feet of rock and clay acting as a barrier, and that the Coconino Aquifer (Aquifer C) sits above and is it not connected to the Redwall-Muav aquifer (RM Aquifer)?

1986 and 2012 Claims: The Redwall-Muav Aquifer is at least 2,500 feet below the mine surface.

The deep Redwall-Muav Aquifer feeds many springs in the Grand Canyon. AMY S. MARTIN

Crossey, Karlstrom and Kreamer: In fact, the mine has permission to operate just a few hundred meters above the deeper Redwall-Muav aquifer. Faults and fractures are known to connect the upper C aquifer and the lower RM aquifer – although we still do not know how well the aquifers are connected at any given site, including the Pinyon Plain Mine site, and this is the key question for the new environmental impact statement (EIS ).

Plus others nearby breccia pipes near the Pinyon Plain mine were not tested for vertical hydraulic conductivity. Such connections are not limited to being strictly vertical in nature. Many recent studies demonstrate simultaneous downward and lateral (lateral) migration over short timescales (months to years) over thousands of feet vertically and tens of kilometers laterally.

Is it true that water does not flow from the Coconino Aquifer into the deeper Redwall-Muav Aquifer?

1986 and 2012 Statements: Because of parallel-bed stratigraphy, groundwater flow from perched local aquifers should be southwestward toward Havasu Drainage and Cataracta Creek.

Crossey, Karlstrom and Kreamer: The term “perched aquifer” is often used to refer to the C aquifer, but we now know that it is incorrect at worst and incomplete at best. Stable isotopic values ​​for C and RM aquifers overlap in values ​​on both rims of the Grand Canyon, showing that water moves down through bedding from C to RM aquifers along faults and fractures (gravity).

This was proven for the North Rim by national park dye tracer studybut the downflow rate at the Pinyon Plain Mine site is not known and needs to be studied. This site is massively disturbed by the pumping of aquifer C, creating a cone of depression and additional water quantity concerns, so now is the time to quantify the rate of downward flow in a new EIS study.

How about the claim that the mine was unlikely to hit much or any groundwater?

1986 and 2012 Statements: The C Aquifer is generally not saturated as far west as the mine and should therefore be unaffected.

Mine vaporized water into the air to speed up evaporation. BLAKE MICCORD

Crossey, Karlstrom and Kreamer: This claim has now been proven to be untrue. The mine (and many hydrologists) were surprised when the mine began taking on water in 2013 and more significantly in 2016. The mine continues to have to pump 8-9 million gallons per year in order to dewater the well and continue mining operations. This draws all four shallow observation wells around the mine site, creating a cone of depression that proves both lateral and vertical fluid connectivity over the Hermit Shale, which was believed to be the confining layer below the aquifer superior.

The important long-term question that must now be answered is the extent to which this vertical flow follows natural faults and fractures versus the “Swiss cheese” following of the exploration wells (greater than 17.5 linear miles) that perforate the mine area, with some extending from the surface into the lower Redwall-Muav aquifer. In either case, a future remedial strategy requires a new EIS that recognizes the well-established science of flow direction and fast versus slow water pathways in the C aquifer and between the C aquifer and the lower RM. Aquifer.

Our mine numbers show that there are likely saturated zones in the upper Supai Group as well as the Coconino Sandstone, and the current configuration of four wells drilled only to the top of the Hermit Formation and one well deep in the RM aquifer is inadequate. to establish the direction of horizontal flow in any aquifer, the extent of saturated zones between aquifers, and the vertical pathways (faults, fractures, the breccia conduit itself) that likely transport water between them. Bills et al. (2007) showed that the C aquifer includes the upper five formations, that all may be variably saturated, not just the Coconino Sandstone.

Do you agree with the statements that the groundwater that hit the mine can be defined as “small” or “unsuitable for long-term water supply?”

1986 and 2012 Statements: Perched areas are generally small and unsuitable for long-term water supply.

AMY S. MARTIN

Crossey, Karlstrom and Kreamer: This has been denied by the mine itself, as they have had to pump millions of gallons of water from the main well over the past eight years.

Additional water is pumped from intercept rings in the upper aquifer and used in part for surface dust control. If the groundwater struck by the mine was truly insignificant, the flow would have stopped after a short period of pumping. The mine is currently dewatering an important regional aquifer with no sign of stopping. It’s not a question of if, it’s a question of when and in what directions this dehydration may affect the Grand Canyon springs and nearby wells.

Similarly, we do not know the level of contamination this causes in shallow or deep groundwater and this requires monitoring. The timescale of waterborne transport is now known to involve both fast and slow pathways, so the issue of long-term versus short-term effects needs to be reevaluated.

How many monitoring wells are needed to adequately test for contamination?

1986 and 2012 Statements: The single monitoring well at the mine site should be adequate for assessing any potential impacts to the perched aquifer.

Crossey, Karlstrom and Kreamer: This is incorrect. It has long been known that a minimum of three strategically placed wells are required in even the simplest groundwater system to determine the direction of flow in each aquifer. The deeper RM aquifer is in a very complex system (karst) and more than the minimum may be required.

In his book, Notable Springs of the United States (2024), Dr. Neven Kresic of the Karst Waters Institute said of similar claims by the Arizona Department of Environmental Quality (ADEQ) that attempt to justify only one deep well: “On based on my professional judgment, this statement by ADEQ is meaningless from a hydrogeological point of view and contrary to the entire professional and academic practice of groundwater science and engineering in any porous medium and type of aquifer, not just in karst.’

The four existing wells in the shallow aquifer are too shallow to be evaluated at the upper orebody level. There are no data available to assess flow direction and degree of contamination in the units of the lower Supai Group, above which the C aquifer is said to be perched. In other words, the mine has no data or comprehensive fracture analysis to show any barrier to vertical fluid movement between the C and RM aquifers. The single well in the RM aquifer is not adequate to determine the direction of flow and extent of any contamination in the RM aquifer.

The very complex passageways and compartmentalization known to occur in the karst aquifer in the Republic of Moldova is such that more frequent water level sampling and changes in contamination of this single borehole are now required (currently only the annual analysis of evidence), as well as a new plan. drill at least three to four deep wells to establish a valid monitoring program for future remediation.

The bottom line

In short, the science is clear. Things have changed since 2012. It’s time to supplement the 1986 environmental assessment and take a hard look at what scientists have learned in the nearly 40 years since the Canyon mine was first approved.