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Photograph 25: <br /> 4 � q <br /> • Stormwater had a pH of approximately 5, indicating that the stormwater is being <br /> impacted by facility operation, in particular the acid product packaging and storage <br /> areas. <br /> RESPONSE: U.S. EPA's observation was based on inaccurate pH strips that were not intended <br /> to be used for testing stormwater. The facility had a hand-held monitor designated for this <br /> purpose, and it is unclear why the pH strips were used during the inspection instead of the <br /> monitor. After U.S. EPA's inspection,the facility rechecked the pH at four sites in the retention <br /> pond using the monitor, and the results showed that the pH was within normal range: 8.8 at site <br /> 1, 8.8 at site 2, 8.7 at site 3, and 8.6 at site 4. See results attached as Exhibit F. Furthermore, the <br /> facility checks pH after every rain event when water is released to the pond, and past testing <br /> results have also been within normal range. See testing log, attached as Exhibit G.4 <br /> • Significant corrosion of the structure which supports elevated tank is observed. The <br /> corrosion should be removed and a coating resistant to corrosive materials should be <br /> applied. <br /> RESPONSE: The Company notes that the corrosion observed is minimal and primarily surface <br /> corrosion.Nonetheless, Sierra is in the process of scraping and repainting the structure. See <br /> Photograph 26, below. Updated photos following the repainting can be provided upon request. <br /> 4Note that some testing results are displayed as whole numbers without decimals. Because the <br /> pHs were within normal range, some employees conducting the tests omitted the decimal <br /> numbers. The facility has since retrained employees to record the complete test result number <br /> when logging pH test results. <br /> 21 <br /> 26731756v.9 <br />