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Page 10 <br />kimley-horn.com 2828 Colby Avenue, Suite 200 Everett, WA 98201 425-708-8275 <br />After each of the boreholes have reached the required target depth of 75 feet or 30 feet <br />below the ground surface, the boreholes that are not completed as monitoring wells will <br />be decommissioned using a bentonite grout slurry in accordance with Washington State <br />Department of Ecology (Ecology) requirements. HWA assumes that completion of the <br />six (6) borings will require six (6) days of drilling. <br />·GeoEnvironmental Sampling: Based on a cursory review of Ecology information <br />available online, it appears that several gasoline service station properties are located <br />adjacent or in close proximity to the proposed bridge alignment. To assess the potential <br />for contamination at the locations of the geotechnical borings, and for disposal of <br />investigation derived waste (IDW) from the drilling activities; HWA will perform <br />geoenvironmental sampling of each of the six geotechnical borings. <br />o During drilling activities, HWA will field screen soils for organic vapors by <br />headspace analysis using a photoionization detector (PID), a water sheen test, <br />and visual and olfactory methods (i.e., stained or discolored soils and/or adverse <br />odors). One (1) environmental soil sample will be collected from each of the <br />geotechnical borings to assess for potential contamination in the areas drilled. <br />o In the four borings that are not completed as permanent monitoring wells, the <br />drillers will install temporary wells for collection of reconnaissance groundwater <br />grab samples. After all drilling activities have been completed and each <br />permanent monitoring well has been developed, HWA will return to the site at <br />least 24 hours after development of the final monitoring well to collect a <br />groundwater sample from each of these wells. <br />o All environmental soil and groundwater samples collected will be placed into <br />clean laboratory-supplied containers for the purposes of chemical laboratory <br />analysis. Soil and groundwater samples will be submitted to an Ecology <br />accredited chemical laboratory for analysis of one or more of the following <br />potential contaminants of concern (PCOC): <br />§Petroleum hydrocarbons – diesel, oil via Ecology test method NWTPH- <br />Dx; <br />§Petroleum hydrocarbons – gasoline via Ecology test method NWTPH-Gx; <br />§Volatile organic compounds (VOCs) via Environmental Protection Agency <br />(EPA) test method EPA 8260D; <br />§Semi-volatile organic compounds (SVOCs) with low level polycyclic <br />aromatic hydrocarbons (PAHs) via EPA test method EPA 8270E/SIM; <br />§Total (soil) and dissolved (water) RCRA Metals 11 Analytes (Ag, As, Ba, <br />Cd, Cr, Cu, Hg, Ni, Pb, Se, and Zn) via EPA test methods, EPA test <br />methods 6010D/6020B/200.7/200.8/245.1/7470A/7471B; <br />§Hexavalent chromium via EPA test method 7196A (if deemed necessary); <br />§Toxicity Characteristic Leaching Procedure (TCLP) via EPA test method <br />1311/1312 (if deemed necessary). <br />Geoenvironmental soil and groundwater samples will be submitted for <br />standard laboratory turnaround time, which is approximately 5 to 10 <br />business days. Follow-up analyses, based on initial analytical results <br />(e.g., VOCs and SVOCs based on TPH results, hexavalent chromium, <br />TCLP, etc.) may result in a total standard turnaround time of up to three <br />weeks. Faster turnaround times are available at increased cost.