Protecting the Environment - Clifty Creek
Clifty Creek Station meets or exceeds the environmental
standards set by state and federal regulations. Originally built
for $158 million, Clifty Creek has invested more than $1 billion
on environmental upgrades since its original construction.
Plant employees take great pride in providing low-cost
electricity while protecting air and water quality, recycling of
materials, and maintaining an exemplary record of public and
- In the mid 1990's, almost $80 million was invested to
modify the coal yard and each of its six boilers to burn
low-sulfur Western coal.
- Overfire air systems reduce nitrogen oxide (NOx) emissions
by up to 60 percent. An overfire air design injects air
above the burning zone in the boiler to enhance combustion.
This infusion of air limits the formation of nitrogen dioxide,
thereby reducing the formation of NOx, a percursor to ozone.
Overfire air was installed in the late 1990's at a cost of
approximately $4 million.
- Selective catalytic reduction (SCR) systems and an ammonia
production facility operate year round on five of the six units
to reduce nitrogen oxide (NOx) emissions up to 90 percent.
Ammonia injected into the plant's exhaust gases causes a chemical
reaction as the gases pass over a catalyst, converting the nitrogen
oxide to harmless atmospheric nitrogen and water. The ammonia
is manufactured on an as-needed basis through a unique process
that coverts urea (commonly used as a fertilizer) into ammonia.
Total capital investment for the entire project was approximately
$164 million. The SCR system began operation in 2003, a full
year earlier than required.
- Electrostatic precipitators remove more than 99 percent
of all fly ash particles produced by coal combustion.
In precipitators, fly ash from burning coal passes through
electrically-charged plates, which pull the ash particles out of
the exhaust gas stream. The original precipitators were
replaced at a cost of $105 million in the late 1970's.
- In 2013, Jet Bubbling Reactor (JBR) scrubbers came online, with
nearly $670 million invested in the project. JBR systems use
a limestone-water slurry to remove up to 98 percent of the sulfur
dioxide (SO2) in the flue gas. The resulting by-product of
this JBR process is gypsum, which can be used as an agricultural
soil amender, or safely managed in a landfill.
- Automated Continuous Emission Monitoring Systems (CEMS) installed
in the plant stacks monitor stack gas emissions. These highly
accurate systems help ensure compliance with clean air requirements
for SO2 and NOx emissions and opacity.
- A portion of the plant's fly ash is sold and used as an additive in concrete.