HDD Soil Samples from Beneath Occupied Residences
Soil sample in acetate tube
DTD has finished a 2 week soil sampling project at a Superfund site on the west coast. A total of 12 samples were retrieved under 10 separate residences in an area spanning nearly 1 square mile. Each sample was required to be taken under an occupied residential building, 6′-15’ from the building edge, and at a depth no greater than 3′. The samples were then analyzed in a lab and the data will be used to characterize the extent of the contaminates of concern.
A Vermeer 24x40A drill rig was mobilized to the job and proved to be a perfect fit. The rig supplied the sufficient amount force required to advance the sampler into the undisturbed material and retrieve a sample. Site restrictions also required a rig with a small footprint to minimize disturbance to the residents and was capable of steering through a sharp bend radius to achieve the shallow sample depths.
Bore Profile and Sample Location
Access to residences and their back yards were not permitted throughout this project thus walkover navigation was limited to pitch data. DTD utilized a DCI F5 navigation system which is capable of transmitting pitch data up to 80’. Using pitch data collected outside the building’s footprint and DTD’s custom bore planner, each sample could still be collected from a known depth below ground.
HDD sampling has been available for a number of years (DTD began soil sampling before year 2000), but the technology tends to be overlooked. The process is relatively time consuming, due to the number of round trips that must be made in the bore in order to drill to the desired interval and then retrieve the sample. Despite this, HDD soil sampling provides a solution to sampling in areas otherwise inaccessible to any other method.