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5.1. Soil Screening <br />Former Oasis Mart RAP /CCP <br />Project SP- 09- 003784A <br />November 16, 2009 <br />Page 7 <br />A Braun Intertec environmental technician will be on -Site during demolition activities to document <br />subsurface conditions. The technician will observe demolition excavation activities in the vicinity of the <br />Oasis Mart building and pump islands for the presence of visual and incidental olfactory indications of <br />contamination that are different from that which we have already observed. The technician will screen <br />suspect areas using MPCA- approved headspace methodology utilizing a photoionization detector (PID) <br />equipped with a 10.6 -eV lamp to monitor soil for organic vapors. <br />A minimum of one sample for headspace analysis will be collected for approximately every 50 cubic <br />yards of impacted material removed. Screening results will be documented. The technician will monitor <br />the subsurface continuously for indications of suspect ACM. Based on prior Site evaluations, we do not <br />anticipate encountering ACM. <br />The headspace analytical procedure is used to field- screen organic vapor levels in soils. The procedure <br />consists of half - filling a new quart -sized sealable bag with a soil sample. The bag is quickly closed and <br />headspace development proceeds for at least 10 minutes. The bag is shaken vigorously for 15 seconds, <br />both at the beginning and the end of headspace development. After headspace development, the PID <br />probe is inserted into the bag to one -half the headspace depth. The highest reading observed on the <br />PID is then recorded. <br />In the event that the construction contractor encounters contaminated soils (based on visual, olfactory <br />and /or PID measurements) materially different from those observed and tested during previous Site <br />evaluations, those soils will be excavated and stockpiled as follows: <br />• Soils that exhibit PID headspace readings above background concentrations and /or display <br />visual or olfactory indications of contamination will be segregated and stockpiled on <br />polyethylene sheeting or an impermeable surface such as asphalt or concrete. Materially <br />different fill /waste will be stockpiled separately. Direct olfactory evaluation of potentially <br />contaminated soil is not recommended for safety reasons, but incidental observations will be <br />noted and acted on. <br />