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xylenes) were reported above detection limits in certain samples collected in Yule Creek on <br /> October 30, 2019, following the completion of the flushing activities that took place on October <br /> 29, 2019. Trace amounts of fluorene and naphthalene were also identified in certain instances. <br /> Benzene was reported as non-detect for all samples. The reported concentrations of those <br /> parameters were all de minimis, were well below (in some instances by more than an order of <br /> magnitude) applicable state and federal screening thresholds, and presented no risk to Yule <br /> Creek. <br /> The fact that trace amounts of certain parameters were detected was not surprising. During these <br /> types of response actions, where a large volume of water is introduced into an impacted area, it is <br /> not uncommon for the water to come into contact with areas of contamination in the un-saturated <br /> zone. When this occurs, the more soluble constituents such as BTEX will partition off the <br /> impacted soil and enter the water in a dissolved phase. This is likely what occurred and what was <br /> observed in sample DG 3, which is located immediately downstream from the collection sump. <br /> Once again, although small amounts of dissolved phase constituents were observed in sample <br /> DG 3, and to a lesser extent in DG 4, as noted above, the concentrations were well below any <br /> regulatory thresholds and do not present a risk to Yule Creek. <br /> DRMS Comment: The report states that when the water level in the sump rose during <br /> flushing operations clean water was able to pass through the berm while contaminated <br /> water was contained within the sump. Please explain how only clean water was able to <br /> infiltrate the berm. <br /> Response: The reference to "clean" was imprecise. "Clean" was intended to mean <br /> concentrations less than screening threshold levels. As noted in the Spill Report, GLA was <br /> aware that infiltration from the sump would occur through the berm, but anticipated that any <br /> diesel product on the surface of the water in the sump would be captured by the booms that had <br /> been placed in the sump and the earthen surface of the berm. As was noted in the report, <br /> following the flushing operations that occurred at the site and a large precipitation event that <br /> occurred prior to October 30, 2019, there was a significant amount of water that collected in the <br /> sump and a visible flow of water through the berm (i.e., seepage) was observed. This event was <br /> immediately reported to the CDPHE and DRMS on October 30, 2019. Upon observing the <br /> seepage through the berm, additional absorbent booms were placed within Yule Creek and <br /> additional downgradient sample locations added. No free phase product was observed on the <br /> downstream side of the berm. As discussed above in regard to Comment 1, the only detection of <br /> hydrocarbons were observed within the BTEX constituents and polyaromatic hydrocarbons, <br /> which were well below screening thresholds. <br /> Please contact me if you have any questions or require additional information. <br /> Regards, <br /> O�IWA* <br />