[alma-config]Re: borehole locations

[John Conway]

On Mon, 17 Dec 2001, Simon Radford wrote:

> As we discussed, the APEX group will have several boreholes drilled in January to examine the 
> underlying rock structure at their candidate antenna locations. 
> For  ALMA, Daniel Hofstadt and I agreed to make 16 more boreholes at the
> same time: 
> 
>   - a 3 x 3, 500 m grid centered on the existing borehole for Chajnantor South (8 holes),
>   - 1 hole on each of 2 fingers running SW from the array center (2 holes),
>   - 6 holes on the ridge NE of Cordon Honar, 3 above the existing road, and three below.
> 

I give suggestions below   forpositions of extra bore holes, mainly
around the perimeter  of the 4km area. I assume that the APEX drillings
will well  sample the NW  region, so this selection concentrates on other
areas. As an attachment I include a .jpg file map of  with the bore hole
positions in purple - old bore positions as '+' and proposed new ones as
'*'.

I think this  selection will give a pretty good coverage. Most are at 
positions we visited during the site campaign and most have been 
'staked out'. The list below contains 10 additional positions in addition
to the grid of 8 holes arond Chan S, which is 2 more than you proposed, I
hope this is OK, I could suggest a couple to delete if you think its
needed.

Of course the exact position of the borings is not so critical  - we could 
instruct the crew that they can be varied by say by 50m or so, if there is
a local slope, or other problems to avoid.

  John


--------------------------------------------------------------------------------------
%
% Slope of Honar ridge
%
628715.2 7452087.2 % C170 
629443.2 7452605.3 % C172 
%
% On Honar ridge
%
628754 7450977 % W150 
629486 7452054
%
% Western Fingers
%
626392 7453061 % C180 
626719 7452012 % C183 
627039 7451504 % C166
%
% The North West of the 4km area
%
629611 7454439 % C159 
630400 7453550 % Chan E
%
% Central
%
628590 7454000 % Zoom centre 
%
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