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GEOPROBE OPERATION CATEGORY: GEO 4.12 P"I"Is March 1998 1 . Introduction 1 .1 Scope This document provides basic information on the operation and application of the Geoprobe Model 8-A hydraulic sampler for subsurface investigations. E&E uses the Geoprobe for hazardous waste site investigations. In addition, field procedures and limitations of the Geoprobe are discussed. This document is meant to be used in conjunction with other E &E standard operating procedures for field operations and incorporates all of the safety precautions that should be followed when planning a Geoprobe subsurface investigation. 1 .2 Objectives Geoprobes can collect one-time subsurface samples to determine the presence and/or extent of contaminants in soil gas, groundwater, and soils with a minimum disturbance of the ground surface. The Geoprobe Model 8-A is a hydraulically powered, van-mounted subsurface sampling device capable of collecting subsurface soil gas samples, subsurface soil samples, and groundwater samples. The information obtained from the Geoprobe investigation can be used to define the extent of contamination in the area and assist in determining the placement of monitoring wells. 1.3 Method Selection Considerations The Geoprobe provides a means of rapidly assessing the presence of contaminants in near-surface unconsolidated soils. The Geoprobe 8-A can penetrate much farther in dry, loose soil than in tightly bound clay and is not recommended for use in rocky soils or tightly com- pacted glacial till deposits. Other subsurface investigation methods should be considered for sampling in consolidated deposits. Use of the Geoprobe 8-A in these situations may result either in damage to the Geoprobe or injury to the operator. 2. Description The Geoprobe 8-A is a hydraulically powered probing device. The unit consists of a powered percussion hammer that is slide-mounted on a derrick and has a 3.5-foot stroke. The derrick assembly hydraulically folds and unfolds from the traveling or storage position in the rear compartment of the van. The derrick is also adjustable in both the fore and aft directions, as well as angle, to ensure the derrick is vertical. There are no side-to-side adjustments on E &E's commercial Geoprobes. The Geoprobe 8-A uses the weight of the van and a hydraulically powered percussion hammer to advance 3-foot-long rods into the ground. The probe rods are hardened steel with an inside diameter (ID) of 0.5 inch and an outside diameter(OD) of 1 inch. The operator controls the hydraulic hammer through the use of levers, and the helper assists by adding sections of rod. 1