GSI Mid-Atlantic, Inc. has added a Geoprobe 54lt to it’s fleet. The 54lt is a capable limited access and low clearance machine. The machine will fit through a standard 36″ doorway allowing access to inside most buildings, as well as through small fence openings and other narrow previously inaccessible areas. Our 54lt is equipped with a low clearance probe cylinder that allows the machine to operate with under 8′ of overhead clearance, perfect for low parking garages and inside of buildings.
GSI utilizes Geoprobe equipment to collect sediment samples from the bottom of Baltimore’s Inner Harbor. The Geoprobe tooling was lowered through holes cored in a concrete industrial pier that extended out into Baltimore’s Inner Harbor. Once the bottom was encountered the tooling was advanced into the bottom sediments. A modified core catcher was utilized in the sample liners to allow the soft sediments to enter the sample barrel, but still prevent sample loss upon retrieval.
GSI recently completed a scope of work in Delaware that included water sampling to 100′ below ground surface (BGS) and installation of prepack monitoring wells to 75′ BGS. The scope was follow-up sampling to fill data gaps from previous investigations GSI has assisted with at the same site.
The initial task consisted of vertical profiling at three locations by collecting a grab water sample from every 10′ to a depth of 100 feet. Static water level was between 6 and 8 feet. GSI utilized the Geoprobe Screen Point sampler(SP16). GSI used one of their Geoprobe 7822 machines to drive the closed SP16 sampler to the 100′ depth and then exposed the stainless sample screen. A peristaltic pump was used to purge the interval until the groundwater ran clear. Once the sample was collected the SP16 was pulled up 10′ to the next interval and again purged to remove water from the previous interval and produce clear formation water for a sample. This process was repeated until a sample from the shallow 6 to 10′ interval was collected. The three 100′ borings were completed on schedule in 1 1/2 days.
The next task consisted of installing nine (9) 1 1/2-inch prepack wells ranging from 45′ to 75′, with five of the nine specified for the 70 to 75′ range. Continuous soil cores were collected from each of the five deep well locations for logging the lithology. The more shallow wells were nested with a deep well and installed by driving closed casing to the target depth (45′-55′). Each well was completed with 10-foot prepack well screen and a 2-foot bentonite sleeve. Wells were then sealed with cement-bentonite grout placed through the drill casing . By grouting through the casing, GSI could be sure the wells were continuously sealed throughout the entire borehole. Wells were finished with flush mount covers and pumped for development. All wells were completed on schedule in about 5 days.
The photo below shows grouting the prepack wells through the casing and collection of the displaced water.
September found GSI Mid-Atlantic, Inc. completing work on two different landfill sites in Maryland.
On the first site, GSI was contracted to complete continuous soil borings at an inactive landfill site in Anne Arundel County. Using the Geoprobe dual tube 22 system and one of our Geoprobe 7822 machines, GSI successfully completed 13 soil borings ranging in depths from 55’ below ground surface to 75’ below ground surface. The purpose of the borings were for logging and identifying specific zones and geologic layers in the subsurface. During boring advancement, GSI successfully collected groundwater samples from multiple water bearing zones as identified by the on-site geologist. Below is a photo of soil cores from a 75’ boring. All borings were pressure grouted upon completion.
GSI was also contracted to install landfill gas monitoring wells along the perimeter of 2 landfills in Howard County. In a single day, GSI installed 3 landfill gas monitoring wells ranging from 20 to 35 feet below ground surface. Wells were installed using the Geoprobe dual-tube 32 system. This system creates a 3.5” borehole while continuously sampling the soil. Half-inch PVC well-screen and riser were installed though the casing. As seen below, the gravel pack was placed through the casing as the casing was removed. Each landfill gas monitoring well was completed with steel stick-up protection.
