ARCHIVED REPORTS SOIL EXCAVATION SUMMARY

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Soil Excavation Summary Report, August 28, 2014 Combined Support Maintenance Shop, California Army National Guard P o g e i 3 Following the review of the supporting documentation, Ms. McCartney provided verbal confirmation to backfill the excavation. Additional detail regarding analytical methods used is provided in Section 2.4 below. 2.4 Summary of Soil Excavation Activities During June 25 and 30, 2014, Innovated Construction Solutions Inc. (ICS), conducted soil excavation and site restoration activities onsite using a backhoe/excavator. ECM was onsite to document soil excavation activities and to collect headspace readings and soil confirmation samples. Picture 1 of Attachment A shows the site prior to beginning the excavation on June 25, 2014. Approximately 14 cubic yards of soil were excavated during the removal action (Attachment A - Picture 2). Soil waste manifests for this removal are included in Attachment B. A schematic of the soil excavation is shown in Figure 3. The approximate dimensions of the soil excavation were as follows: • Length North Wall - 11 -feet; • Length South Wall - 8 -feet; • Length East and West Walls - 12 -feet; and • Depth of Excavation - 4 -feet maximum along northern portion of excavation (the south wall was sloped towards the middle of the excavation to allow for safe access and regress of the excavated area). Soil was selected to be excavated based on visual staining and headspace readings using a photoionization detector (PID). Headspace readings were performed by collecting a soil sample from the excavation sidewall or floor and placing the sample into a plastic bag. The plastic bag was then sealed, and the sample was given ten minutes to equilibrate, before the PID inlet was inserted into the bag to measure the volatile organic compound concentration in the headspace vapors. Soil with staining exhibiting elevated headspace readings of greater than 100 parts per million (ppm) by volume was targeted for removal. Once the stained soil was removed, additional samples were collected from the excavation sidewalls and floor to confirm headspace readings greater than 100 ppm were no longer observed. The results of the headspace readings are shown in Table 1 and Figure 3. A total of 18 headspace samples were collected during soil excavation activities. Two headspace readings exhibited elevated readings greater than 100 ppm. The first elevated headspace reading (350 ppm) was observed at the sidewall of the northwest corner. The second elevated headspace reading (329 ppm) was observed at the midpoint of the northern sidewall. Of the remaining 16 headspace readings collected, the highest reading observed was located at the midpoint of the southern sidewall at 5.0 ppm.