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Summary of tasks and properties


 

Tasks for the tailings project

To learn what is needed about the subsurface at our site, the following four specific tasks were identified:

  1. Locate an old buried gas pipeline.
  2. determine the volume of calcine (a by product of the mining process that was dumped in pits at our site);
  3. map the topography of the bedrock horizon underlying sediments and calcine;
  4. find out if a plume of contaminated ground water exists.

We also learned that there are several types of information that will tell us about the subsurface. This table is a summary:

Finally, there was a summary of expected physical properties:

Unit Comments Possible electrical resistivity (ohm-m) Possible density (gm/cc) Possible velocity (m/s)
bedrock Granite (see outcrops). > 3000
2.67
2300-3300
Surficial cover Pebbly soil with some grass. 20 to 100 (variable owing to wide range of grain size, presence of organics, and existance of a vados zone.
1.5 - 1.8
450-650
Natural sediments Sandy till (porosity around 18%). 50 - 80 dry, 20 - 40 wet
2.2 - 2.4
1000-1400
Calcine An iron-oxide compound. 1 - 10 wet
2.75 - 2.85
600-800
Pipeline Likely metal, and it could be up to 10 m deep owing to calcine and soil cover added since emplacement. High if metal (which it will be for gas), but clay or plastic pipes can be hard to detect
N/A
N/A
Backfill materials Roads, places where construction occured, trenches with utilities. Likely higher conductivity than natural sediments.
1.5 - 1.8
500-700
Water Natural groundwater at this site will be mainly fresh rain water that has had a relatively short residence-time in the ground. The actual effect of groundwater resistivity depends upon porosity.
N/A
N/A
Contaminated water The plume. Water from tailings can be acidic, and hence conductive. As above, the actual resistivity of ground depends upon the resistivity of this water.
N/A
N/A