From: Ndoh, Tina [mailto:Ndoh.Tina@epa.gov] 

Sent: Monday, March 09, 2015 1:52 PM

To: Ackerman, Burl

Subject: Questions for upcoming meeting re: Simplot

Burl,

Thanks again for your call on Friday. Below are a few questions that we’d like to discuss during 

Thursday’s meeting:

(1) You mention that you have attempted to submerge the water discharge pipe at your Pocatello plant, 

but it created backpressure on the pump seals. What did that Pocatello plant do to resolve the 

backpressure issue? Also, you said that it is possible to create a siphon if the water discharge pipe is 

submerged; would this issue only occur if the pumps were off? Please elaborate on what you mean.

Since we are pumping up a mountain and gaining approx 450ft of elevation, there is already a 

backpressure in the pipe from gravity. Placing the end of the pipe under water gives a restriction against 

the discharging slurry that gets worse as the solids/mud buildup around and against the end of the pipe. 

Pulling the end up above the surface of the water alleviates any restriction against the end and keeps it 

away from mud building up around and against the end as well.

If the discharge end of the pipe is under water, and a pump is turned off then everything is in place to 

start a siphon. A pipe full of water, the upper end submerged, and no force to keep the slurry suspended 

up the 450ft slope. Pumps may be turned off for operational purposes or from power outages or blips. If 

there is a power outage/blip then the backflow of the slurry causes the pumps to spin backwards and 

prevents us from starting the pumps back up without major equipment damage. The resulting backflow 

also causes tanks at the bottom of the hill to overflow the gypsum slurry into areas and ground that we 

don’t want it to be on, nor have the containment to hold the slurry until action can be taken.

Also, if the piping is submerged under the surface of the water, inspection of our gyp bank discharge by 

our operators becomes difficult as they can’t see the flow to judge if there are any other problems they 

should be looking for.

(2) Please elaborate on the application of lime solution on the gypsum stack areas at the Rock Springs 

facility. How do you know when and where to apply the lime? 

Our procedure call for starting to lime when the 30-day standard hits 0.69 ug/m3 . We normally start 

before that and apply during the month of July.

(3) Please confirm that all of your plants use a rim ditch building technique for your gypsum stacks.

Yes

(4) What is the construction date of the oxidation reactor on the SPA line at the Pocatello plant (i.e., 

when did the oxidation step begin operation)?

Approximately 1990
(5) For the Rock Springs Title V air permit No. 3-2-125 (issued August 17, 2011 and expires on August 17, 

2016), State Condition S5 says you must “implement techniques for controlling fluoride emissions from 

the gypsum pond (unit 14) as outlined...” in an appendix titled: “Simplot Phosphates LLC 

Phosphogypsum Storage Area Fluoride Control Techniques Document August 2008”. Please confirm that 

August 2008 is the latest version of this Appendix. 

2008 is the latest version of the appendix. It has been transferred to newer versions of our operating 

permit.

Best Regards,

Tina Ndoh

Tina Ndoh, Environmental Engineer | Minerals & Manufacturing Group | Sector Policies & Programs 

Divison | Office of Air Quality Planning and Standards | U.S. Environmental Protection Agency

Research Triangle Park, NC | Mail Code D243-04 | Phone: 919-541-2750 | Email: ndoh.tina@epa.gov