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<br />2.0 POTENTIALLY RELEASED CHEMICALS <br />AND POTENTIALLY AFFECTED MEDIA <br />This section summarizes the available information regarding the reported 1997 and 1998 <br />chemical releases at the Montgomery Pit facility. The selection of sampling locations and <br />analytical parameters described in subsequent sections of this plan are based to a large extent <br />on Dames & Moore's understanding of when and how the reported releases occured. <br />Chemical releases reportedly occured at the Montgomery Pit facility on two occasions. The <br />most recent release occured during July of 1998. The earlier release occurred in September of <br />1997. The following paragraphs describe the circumstances and timing of these two incidents. <br />Figures 3 presents a schematic flow diagram illustrating the process flow of materials at the <br />facility, and the resulting potential transport and exposure pathways that could result from the <br />1998 chemical release. These figures are referenced throughout the following discussions. <br />1 2.1 1998 Release <br />The 1998 release reportedly occured in July of 1998 (Figure 3). A supervisor at the facility <br />disposed of two drums containing what is now believed to have been Repco Kill IITW weed killer. <br />According to the MSDS, this weed killer consists of a blend of approximately 2 percent 2,4-D, 2 <br />percent Bromacil, and more than 90 percent diesel fuel. Workers also reported one drum of a <br />dilute water and antifreeze solution may have been dumped during the 1998 incident. The <br />contents of the drums were dumped on a large stockpile of minus'/+ road base. At the time of <br />the incident, the road base pile was estimated at approximately 15 to 20 feet tall and contained <br />' approximately 1,000 cubic yards of material. <br />Minus'/, inch road base consists of crushed pit run material that has been screened to remove <br />particles greater than'/. inch in diameter. Hence, the road base material contains a wide range <br />~: of particle sizes, including gravels, sands, silts, and clays. The road base contains <br />approximately 10 percent fines and also contains naturally occuring organic matter. The silt, <br />clay, and organic matter in the road base would have significantly retarded the downward <br />mobility of the weed killer by adsorbing and dispersing the diesel fuel carrier. Due to the large <br />size and height of the road base stockpile at the time of the incident and its tendency to adsorb <br />' and disperse the spilled chemicals, it is unlikely any of the liquids penetrated into the soils <br />beneath the pile. Additionally, it was reported that afront-end loader was used to mix the weed <br />killer into the pile, thereby reducing the likelihood that any weed killer penetrated into the <br />subsurface soils. <br />Subsequent to the dumping incident, part of the road base stockpile was screened using a <br />vibratory classifier. The products from the screening process included minus'/~ inch road base, <br />and'/. inch rock (Figure 3). The'/. inch rock produced from the affected stockpile was sold for <br />use as construction materials, aggregate, structural fill, bedding or drainage material, and other <br />possible uses. The minus % inch road base was used in the production of asphaltic concrete in <br />the facility's hot mix batch plant. <br />B88 Excavating, Inc., Edwards, Colorado December 17, 1998 <br />Montgomery Pit Facility 39210-003-034 <br />Draft Sampling and Analysis Plan 6 DAMES 8 MOORE <br />