AllState Boring and RLH teamed up to achieve the unthinkable.... Boring under a live, flowing river.... with the help of a Casing Compass of course! This project presented many challenges, including
-Unstable and Varying soil conditions: Layers of sand & cobbles, followed by stiff clay
-Flowing Ground Water
-Hazardous Atmospheres
-Deep Excavations
The project was completed with precision and efficiency, with multiple casing installations and methodologies utilized. The project started off in stiff clay using a conventional auger boring installation. 60ft into the bore, AllState hit a vein of sand, cobbles, and flowing subterranean groundwater containing organic, hazardous gasses. They immediately stopped and switched to a pipe ramming installation method after pumping grout around the annulus of the casing, effectively creating a subterranean O-Ring around the casing, preventing water from reaching the bore pit around the casing. 20ft into the pipe ram, there was enough of a dirt plug in the casing to stop the groundwater and hazardous gasses from moving through the casing. It was estimated that hydraulic pressure of groundwater was up to 19ft of head on the front of the casing. This rendered the water level useless, as ground water was under enough pressure to work into the exit port and all the way back to the sight glass in the bore pit. The only navigational tool available to AllState during this time was the Casing Compass, which monitored the grade of the casing to ensure that it didn't pop up in the middle of the river. With a design elevation of only 5ft between top of casing and bottom of river, this was a tight squeeze when using a pneumatic hammer without grade control and in cobbly conditions.
The remainder of the project was completed using the 18" TT pneumatic hammer, and was completed without incident, with zero manned confined space entries made into the casing. The Casing Compass helped keep AllState's crews safe and provided cheap insurance to avoid uncorrectable grade changes to the casing that could have been disastrous.
YouTube Link
https://www.youtube.com/watch?v=ndimI-gtUqE