Sediment grab sampling is a method used to obtain samples for characterization of surficial material. Grab sampling is useful for acquisition of samples used for grain size analysis, benthic habitat delineation, or ground truthing of sonar records. OSI maintains a wide variety of industry-standard grab samplers including Van Veen, Ponar, Shipek, Ekman Box, and Smith McIntyre samplers. This versatile inventory of sampling devices provides cross-sectional sampling areas from 6” x 6” up to 14 1/8” x 11”.
OSI also operates custom designed and fabricated pneumatically actuated grab samplers (PAGS). The system is equipped with an underwater camera which enables the operator to view the sample site prior to landing the sampler on the bottom. This enables the operator to “dodge” obstructions and/or debris that would be likely to prevent sample acquisition and/or obstruct the closure of the sampler jaws. Likewise, the camera may provide an explanation for poor recovery if this is in fact the end result. Once the sampler is landed and penetrates into the sediments, the jaws are closed by the operator from the surface using a pneumatic actuator. Unlike a Van Veen sampler, the PAGS gives the operator control over sample acquisition and increases the likelihood of acquiring an acceptable sample with the fewest attempts. The sampler is configured with doors to minimize washout and disturbance of the sediment surface. Penetration is adjustable to a maximum of 12 inches with realistic sample retention at penetration depths of 10 inches. As with any grab sampler deployable from an economical sampling vessel, in coarse material, penetration may be limited. The PAGS may be fitted with a low energy, high-frequency vibrator that may be engaged, as needed, to assist penetration in certain substrates such as gravel or small cobbles.