2019-12-05_HYDROLOGY - M1999058 (4)

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plans were created: one under the direction of Clean Harbors, Inc. and a second plan that was created by CSQ, GLA and HRL. On Thursday, October 171", a plan was suggested by Clean Harbors and was developed among CSQ, GLA, and Clean Harbors representatives. The primary goal of mitigation efforts was to prevent diesel laden waters from entering and impacting Yule Creek. The general plan commonly used by Clean Harbors to clean-up diesel spills within large volumes of fill is to flush the fill with clean water followed by insertion of Simple Green. Simple Green is a biodegradable, non-toxic EPA-approved (2013) surface washing agent. Following Simple Green application, more clean water is flushed into the system. Once flushing is complete, Micro-Blaze would be introduced to the flush input site as well as across the surface of the spill area. Clean Harbors suggested flushing clean water in at a volume 3x the spill volume with a Ix volume of diluted Simple Green. Therefore, the plan for this spill event included introduction of 5,000 gallons of clean water, followed by 5,000 gallons of diluted Simple Green, followed by 10,000 gallons of clean water. Micro-Blaze was to be applied at the diluted rate suggested by the manufacturer to appropriately accommodate a 5,000 gallon diesel spill. This plan was approved by the DRMS and corroborated by HRL as the appropriate initial response. On Tuesday, October 29, 5,000 gallons of clean water was pumped from Yule Creek up gradient of the spill location and was flushed into the hole pre-dug at the spill location near the generator Conex. As detailed above, the return of water into the sump was much greater than anticipated; therefore, the plan to introduce Simple Green and 10,000 additional gallons of water was abandoned. This change in plan was determined by: - >90,000 gallons water that flowed through the fill into the sump effectively diluted the diesel spill beyond the need for Simple Green. - Following consultation with HRL, it was learned that Simple Green had the strong potential to behave effervescently and potentially flood Yule Creek with bubbles. - 5,000 gallons of diesel in the road fill was flushed with >90,000 gallons of water resulting in an at least 18x dilution of the spilled diesel. - The source of the additional water was due to the precipitation that occurred during the mitigation process. Furthermore, the high return of water into the sump switched the plan from a mitigation plan to another emergency response plan centered on maintaining an appropriate sump level to not allow for surface flow of diesel-laden water into Yule Creek. Following the order to stop pumping very late in the evening on October 29, 2019. CSQ, GLA, and HRL representatives began developing a short term plan as well as a long-term sampling and remediation plans. The post-pumping short term plan involved removal of pumps, fortifying the northern edge of the sump, temporary filling of the sump, planned sample locations for monitoring wells, and removal of diesel-laden soils around the generator and the sump. The intent of the plan was to further prevent migration of diesel, 36