United States Steel Corporation Gary Works
One North Broadway, MS 70-A
GARY, IN 46402

VIA CERTIFIED MAIL 7011 01900 0000 8508 E?lcl
October 31, 2017

David Greinke

Of?ce of Water Quality

Indiana Department of Environmental Management
100 North Senate Avenue Post Of?ce Box 6015
Indianapolis, IN 46206

Subject: United States Steel Corporation Gary Works Midwest Plant
NPDES Permit IN0000337
Total Chromium Exceedance Outfall 304

Dear Mr. Greinke

This letter is the written ?ve-day submission regarding a total chromium exceedance at the U. S.
Steel Corporation Gary Works Midwest Plant (?Midwest?) Outfall 304 (NPDES Permit
IN00003 37 effective April 1, 2016). The total chrome loading for the 24-hour period from 7:00
am October 25, 2017 through 7:00 am October 26, 2017 at Outfall 304 was 56.7 lbs/day as
compared to the Permit limit of 30.0 lbs/day. Outfall 304 is an administrative outfall that is the
sum of the reported mass of both internal Outfalls 104 and 204. The reported mass during this
period was 0.06 lbs/day and 56.7 lbs/day, at Outfalls 104 and 204, respectively. The sample
collected at Outfall 204 was retested and the results verified. IDEM was noti?ed at 11:26 am on
October 27, 2017 Via telephone.

At 7:43 am on October 2017, USS management was notified by the technician who was
collecting samples that the daily 24-hour composite sample for Outfall 204 was discolored. Upon
visual con?rmation by USS management of the discoloration, U. S. Steel immediately began the
process of shutting down train of the chrome treatment plant, and bringing the parallel 
train online. train not running at the time the discoloration was identified. At roughly 8:10
am train was in operation and train was no longer discharging. As train was the
source of the discoloration, when train was brought online the discoloration of the ef?uent
ceased. Investigation revealed that ?ow through the train lamella clarifier was not uniform
across the lamella due to heavier solids buildup on one side of the lamella, and as a result there
was excessive solids carryover. The sludge in the lamella was pumped out to restore uniformity
to the ?ow through the lamella. Upon removing the sludge build~up in the train lamella
clari?er, train was put into recirculation mode. During recirculation mode the discharge of
train is recirculated back to the in?uent of the chrome treatment plant in order to verify
uniform ?ow through train?s lamella clari?er. This ensured that excessive solids carryover
was no longer occurring, and that train was ready to be put back into service when needed.

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Midwest continues to evaluate future actions as a result of this incident and has so far determined

these steps to help prevent reoccurrence:

1. Re~train operators

2. Enhance turbidity monitoring con?guration to more accurately reflect Iamella

clari?er performance.

U. S. Steel requests that this submittal be afforded con?dential treatment under all applicable

statutes.

If you have any questions about this matter, please call me at (219) 888-4500 or email me at

EHanning@uss.com.

Sincerely,

   
  

a

eph E. Hanning, PE
Environmental Control
United States Steel Corporation
Gary Works, Midwest Plant, East Chicago Tin

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