Although this drilling is going to go through sand and silt, it also has to be able to break up small rocks, and push aside slightly larger rocks. ... and it costs about $1000, so while it's very durable, it's also something that you don't want to be worry-free over.
This is one of the reasons why they decided to just pull up, pull out, and restart yesterday after hitting a large, immovable rock about 10 yards down.
And the drillers need to put in about 216' of drill sections. Each of these sections is 5'. There are 120' of drill section on this pallet, with another such pallet with sections being pulled upon.
Each drill section is 7" wide (4" tube, with 3" flange), meaning that for each 5' section, the drill removes roughly 1.3 cu.ft. of material, and after the 216', there will be a rough volume of 57.7 cu.ft. of material removed. And the removed material goes into this truck.
At every 10' of drilling, a water sample is taken (when the new section isn't in silt) for later testing. If a water sample comes back with new evidence of 1,4 dioxane in it (i.e., the existing wells aren't monitoring at the depth where it was found), another well might be sunk to monitor that depth, however, it isn't expected that new contamination will be found. However, because time is taken to take soil samples at each 10' interval (in order to determine if a water sample can be taken) followed by a water sample (when needed), each 10' section will take longer to process as the well gets deeper, since the soil sampler needs to be lowered and removed, as well as the subsequent water sampler. Therefore, although the drilling has gotten roughly half way to the expected bedrock level over just one day, it's unlikely that they will finish by the end of the day on Friday. Monday is almost definite (unless they hit another large rock).
UPDATE: They DID hit another large rock at 170' depth.
UPDATE 2: A monitoring well has been installed.
(Sorry I missed commenting on this post earlier... here is my response to the MDNRE about the recent drilling results in Saginaw Forest...)
ReplyDeleteThose darn boulders!
Boulders or not, Pall should be required to drill and sample all the way to bedrock. Why? The 400+ ppb just found there is way outside where Pall maps showed that high of concentration of dioxane and contrary to the trends depicted on their recent maps, which showed that not even the 85ppb boundary extended that far south and west. Plus the presence of dioxane above non-detect for all samples from 50-170 feet deep show that this is not just a single seam of dioxane. There might significant concentrations deeper than the current deepest sample of 68ppb at 170 feet deep.
This is not Pall/Gelman property. This is University of Michigan property ... and apparently moving in a direction not predicted by Pall's simplistic modeling. It's 500-1000 feet away from any other wells with concentrations that high. This could be very bad news for wells south and west of Saginaw Forest... and maybe eventually for the City of Ann Arbor's Steere Farm well field near the airport where the City gets 20% of its water.
It could be another Unit E fiasco. Maybe this is where the 4000-5000ppb at TW-4 went. Or maybe its where the 30000ppb at MW-37 went.
Also, this delayed finding is another example why the proposed Part 201 rule changes to allow polluters to prematurely terminate cleanup operations could transfer huge costs and risks to the public.
--Roger Rayle--
Vice-Chair, Scio Residents for Safe Water(SRSW)
www.srsw.org
9/20/2010 UPDATE: At the monthly CARD meeting today, the MDNRE released the first sampling results from the newly installed monitoring well (MW-125) at that location... 801ppb! Plus there is a steep gradient in the static water level near that location. All present agreed that more investigation is warranted since these results are contrary to all prior analyses.
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