The field season is well underway up here at Hubbard Brook. Cody is finished with his total station surveys and has moved in to characterizing soils, while I have been installing lysimeters and otherwise preparing for a big storm sampling push. Another thing that has been on our minds, however, is validating some points on the GPR profiles we ran this winter. There are several places where we see interesting returns in the profile at relatively shallow depths. We need to figure out if these returns are from water tables, changes in till characteristics, or…. bedrock? We have been trying to come up with a way to get some kind of remote well drilling equipment up into the watershed to obtain depth to bedrock validation points, but haven’t found anything yet. In the mean time, we are looking for any opportunity to prod deeper below the surface to see what we’ve been seeing.
Naturally, when it came time to dig a pit with his FIA soils crew to teach some finer points of pit description, Scott and I chose a spot where we might be able to manually dig to a depth where something is going on in the GPR profile. We think we see something between 150-200 cm. Getting to that depth would be no small feat: Scott’s record for pit digging stood at 165 cm. Sure enough at about 70 cm we hit dense till. Cue hacking away at a cement-like surface for precious centimeters of pit depth…
After turning in short of the goal after the first day of digging, we returned with a big, heavy, metal bar to continue chopping away at the dense till. When it came time to get out of the watershed on our second day of digging we had made it to 195 cm. A watershed 3 record for pit depth (maybe even Hubbard Brook?) but not quite deep enough to completely determine what we may be seeing in the GPR profile. We will be returning soon for some more centimeters.
See the photo for scale, 195 cm swallows a grad student effectively. “Stay down there, dig deeper!” says Scott.