APPCOR10034

• Permit No: C1992079
• IBM Index Class Name: Application Correspondence
• Doc Date: 1/7/1993
• Doc Name: PROPOSED COMPLETION DIAGRAMS MEMO
• From: DMG
• To: HARRY RANNEY
• Media Type: D
• Archive: No

•
STATE OF iiiiiiiiiiiiiiiim
COLORADO
DIVISION OF MINERALS AND GEOLOGY oe cow
Department of Natural Resources ,~~:_

1313 Sherman St., Room ? I S
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Denver, CO 80203 •
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Phone: [phone] revs'
FAX: [phone]
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DATE: January 7, 1993 Governor
Michael B. Long
Divi.ron Dveaor
TO: Harry Ranney
FROM: Cathy Begej
RE: Proposed Completion Diagra ms, Coal Gulch, C-92-07 9
We had asked Paul Baker to give us generic well completion diagrams and he has taken
the 'generic' to heart. I have some specific questions and then some general advice.
1) What are the diameters of the boreholes?
2) What is the composition of the packer seals, and how thick will they be?
3) What is the perforation size on the perforated casing? What type of intakes
will be present?
4) What is the thickness of the perforated interval on each of these wells?
5) Is the surface casing constructed of grout in all wells? How thick is it and
what depth are you anticipating?
6) Where are these wells going to be drilled?
The filter pack has been specified as pea gravel, and this may have been at my suggestion.
Review of the NWWA Handbook of Suggested Practices of the Design and Installation of
Ground Water Monitoring Wells indicates that a 'gravel pack' is a misnomer, as gravel
typically is not clean and has variable grain sizes. This reference recommends the use of a
clean, well-rounded, uniform coarse or medium grain quartz sand with less than 5% non-
siliceous material. This will be easier to install than the pea gravel and improve the
recharge of non-muddy water.
This filter pack should be 2" - 4" thick in the well. As noted in the diagram, the filter pack
should extend some distance above the perforated interval to allow for settling and to
minimize the possibility of contamination between the packer and the water in the well.
I have several comments on the perforated interval. Perforations on the casing should
probably be less than or equal to 0.010". The perforated interval definitely needs to
intersect the target zone of interest but should be less than 20' in total length (proposed
well 92-2 appears to have 40' of lengthl. Short perforated intervals (less than 5') should
have a 5' - 10' interval between the bottom of the perforated casing and the bottom of the
well to ensure that the perforations do not get clogged with material sloughed during
construction.
CWB/yjb
m:\oss\yjb\coal.gulch