Hello,

This email is in reference to a permit application for a non-title V air quality permit submitted
on June 18, 2020, by Custom Landscape Materials, Log Number F032822, for an aggregate mine
originally planned to start operation in Spring of 2020 and located at 8436 East Apache Trail in a county island.

This mine location is surrounded by neighborhood homes as little as 80 feet from the mine boundary.

With potential impacts from dust-carried Valley Fever and Covid19 and this close proximity to surrounding homes,
the health impacts of this activity are troubling due to proximity only.
However, the mine is also located on a hill 130 feet above surrounding terrain.

Dust from mining operations can be difficult to manage in the best of circumstances.
However, this dust being generated 130 feet above the surrounding neighborhood presents unique and
extreme issues not encountered in any other permit request.

I'm concerned that the air quality permitting process is not adequate for this operation.
In reviewing documents, such as Rule 316, I see no considerations or adjustments for such a unique situation.

Dust control measures as stipulated may be adequate to a ground-level or below ground-level operation,
but fall significantly short of what is necessary to assure the safety of the neighborhood in this case.

Air flow over a hill of this size is much different than would occur over flat terrain.
As summarized by Holmes in 1986, the following air-flow changes do occur.

1. An increase of mean wind speed with height,
2. strong turbulent fluctuations of wind speed at all heights,
3. a broad band of frequencies of the fluctuations or gusts, and
4. similar patterns of gusts at all heights.

In consideration of these facts, your existing dust control requirements would be inadequate.

I urge you to consider a study in The Journal of Wind Engineering and Industrial Aerodynamics Volume 83,
Issues 1–3, November 1999, Pages 95-107, Titled:
"A wind tunnel study of turbulent flow over a three-dimensional steep hill".

It was observed that the maximum perturbations in the longitudinal and vertical velocity variances
were observed at the height of the hill.

Clearly this indicates that perturbations and turbulance will increase the amount of airborne dust from
a mine located at the top of this hill.

Further, consider a study in the Royal Meteorological Society, January 1981, titled:
"Air flow over a two dimensional hill: Studies of velocity speed up, roughness effects and turbulence."

They found that, even with the roughness of the hill surface as opposed to a smooth artificial surface,
the wind velocity over the hill still increases.
And Twin Knolls, while clearly not a smooth surface, is not wooded as considered in this study.

I submit this info for your consideration when you evaluate the appropriateness of approving this permit.

Dust control in these conditions in close proximity to homes and families is not a risk that should be asked of this neighborhood.

I respectfully ask that you deny this permit.

Thank you,