equipment such as coal storage and transferring, coal pulverizing, lime handling operations, and dry ash 

handling operations. 

On February 20, 2015, EPA received an application for a NSR permit from SRP for the construction and 

operation of a Coal Treatment System (CTS) within the plant boundaries on pre-disturbed land at NGS 

(See Attachment 3). SRP has an existing coal conveyor belt system that transfers untreated coal from 

railcar unloading piles, to the pulverizers for crushing, and then fed in to one of three existing boilers for 

combustion in order to generate steam and produce electricity. SRP is proposing to construct a CTS, 

which adds calcium bromide and cement kiln dust to the coal prior to being pulverized and combusted. 

The new equipment is being installed in order to reduce oxides of nitrogen (“NOx”) and mercury 

emissions. This CTS will consist of two new coal feed belt conveyors that would divert coal from the 

existing conveyor system to two new mixing pugmills where the coal is mixed with the additives. The 

treated coal is then fed back into the existing conveyor system to be pulverized and finally combusted. 

The belt conveyors will be controlled by two high efficiency dust collectors. Cement kiln dust will be 

delivered by truck and stored in three 150 ton silos and two 20 ton day bins, which will be controlled by 

baghouses. Some emissions increases from existing dirt roads can be expected because of the increased 

truck delivery traffic. 

The project will result in emissions increases in PM, PM10, and PM2.5. The construction and operation of 

the CTS will be within the existing footprint of NGS and the increase in emissions from the changes will 

not exceed the Prevention of Significant Deterioration (PSD) thresholds. Therefore, the changes do not 

trigger PSD, but the increase in emissions are above the Tribal NSR minor source thresholds. 

Proposed Area of Potential Effects 

The construction and operation of the NGS CTS Project is considered a minor modification under the 

Tribal NSR program and will be incorporating the coal treatment system into the existing coal handling 

operation. The effects of the proposed construction and operation will occur only within the existing 

footprint of the NGS. As such, the proposed area of potential effects (APE) includes the existing 

footprint of the NGS power plant as seen in Attachment 2. In addition, the increases in emissions due to 

this project do not exceed Significant Impact Levels (SILs) beyond the existing facility boundary. 

Therefore, EPA expects no effects due to this modification on any historic properties or cultural 

resources which may exist outside the NGS facility footprint. 

Effects on Historic Properties within the APE 

EPA was advised by the Navajo Nation Tribal Historic Preservation Officer (THPO) that the NGS itself 

is eligible for inclusion in the National Register of Historic Places. The NGS has been in existence since 

the early 1970’s and has been an integral part of the economy and community of Navajo Nation since 

that time. 

The area in which the construction of the NGS CTS Project and associated infrastructure, such as the 

cement kiln dust storage silos and new coal feed belt conveyors, is within the built-up environment of 

the power plant. The area shown in Figure 2 has been mechanically excavated and leveled and contains 

an established complex of structures, roads, parking areas, and electrical lines to the degree that the area 

no longer resembles natural conditions.