SAMPLE COLLECTION TECHNIQUES Clause Samples

SAMPLE COLLECTION TECHNIQUES. EQUIPMENT‌ 1. SAMPLING TECHNIQUES‌ The surface sediment sampling procedures include the following: • All data from sediment grab collection is recorded real-time onto field logs. • The sampling vessel is maneuvered to the designated target coordinates for dredge prism stations using the Differential Global Positioning System (DGPS) and an on- board navigation system. • Prior to occupying a sampling station a pre-cleaned grab sampler is prepared. • Once the sampling vessel is in the general proximity of the planned sampling station, the grab sampler is lowered into the water column. The sampling vessel will be repositioned so the grab sampler is within ±5 ft of the designated target coordinates. • The samples will be obtained by lowering the grab sampler to the sediment surface and allowing the line connected to the grab sampler to go slack. • The sampler is retrieved after each sample and brought back onboard. The amount of material retained in the grab sampler is measured and recorded in the field log. Samples will be classified in the field as to material type using ASTM D 2488 as a general guide. Visual observations of sediment type, stratigraphic features, and the presence or absence of any visible contamination will be recorded for each sample. • For each grab attempt, the station name, latitude/longitude, time of collection, and depth to mudline are noted in the field log. In addition, photographs of each grab sample will be taken. • Samples will be collected from the exposed center portion of the grab sample from the surface down to 10 cm; the outermost sediment that contacts grab sampler walls will be discarded if at all possible. • If the sample is discarded due to insufficient retention or because the target strata are not represented in the core sample, three additional grab attempts within 10 feet of the original location will be. One option to be evaluated after three failed attempts is relocation of the station to a more suitable location that is still representative of the dredge prism. The subsurface sediment sampling procedures include the following: • All data from sediment core collection is recorded real-time onto field logs. • The sampling vessel is maneuvered to the designated target coordinates for dredge prism stations using the Differential Global Positioning System (DGPS) and an on- board navigation system. • Prior to occupying a sampling station a pre-cleaned split barrel sampler is set into the drill rig apparatus. • The borings w...