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approximately as shown on Figure 2 The actual placement and depth will be dependent on the Ilocation of existing on-site utilities Piping installed in the trench will consists of 2-inch diameter schedule 40 PVC which shall be sloped toward each of the extraction wells The piping will be pressure tested prior to backfilling ASECOR field geologist will observe the construction of the soil vapor line trenches and screen the excavated soil with a photoiomzation detector (PID) If hydrocarbon impacted soils are observed in the trenches during the construction activities, 4-inch diameter schedule 40 PVC piping will be installed horizontally at the base of the trench and plumbed to the treatment ' compound The piping shall be fitted with 0 020-inch slotted well screen through the areas of impacted soil The horizontal vapor extraction piping shall be burred a minimum of 24 inches bgs ' with 318-inch pea gravel A layer of plastic sheeting shall be placed in the trench above the pea gravel backfill to reduce ground surface air flow once the extraction system is in operation The contractor shall compact the trench bottom and remove sharp objects to provide a smooth compacted trench bottom prior to placing bedding material The trench above the pea gravel and sheeted plastic which contains the 2-inch vapor lines may be backfilled with the soil removed during the trench excavation if petroleum hydrocarbons are not detected with the PID Otherwise, imported material will needed Backfill shall be free of organic material, rocks greater than 3-inches in diameter, and any deleterious material The lifts of the backfill shall not exceed 6- inches compacted using hand tamping equipment only The final lift shall be of portland concrete or asphalt concrete in accordance with the existing surface conditions A cross-section of the trench is shown in Figure 2 I23 Above Ground Ping The vapor transport lines shall be stubbed up vertically from the trench to the inside of the treatment compound Each pipe run shall be individually valved and manifolded together to form a "metering rack" (Figure 3) Valved sample ports with 114-inch barbed hose fittings shall be 1434VES ICU SECOR fab No NOW5-W2�41 March 13 1995 f