HYDRO25056

• Permit No: C1980005
• IBM Index Class Name: Hydrology
• Doc Date: 5/30/1989
• Doc Name: WOLF CREEK UNDERDRAIN
• From: MLRD
• To: SENECA II MINE FN C-80-005
• Permit Index Doc Type: CORRESPONDENCE
• Media Type: D
• Archive: No

III III III III IIII III
999
STATF, OF COLORADO
Roy Romer, Govei
DEPARTMENT OF NATURAL RESOURCES
MINED LAND RECLAMATION DIVISION
FRED R. BANTA, Dlreetor
DATE: May 30, 1989
T0: Seneca II Mine File, C-80-005
G^~$
FROM: Cathy Begej
RE: Wolf Creek Underdrain
During 5/24/89 inspection, no water was draining out of the Wolf Creek
underdrain. I was surprised at this despite the fact that it was a low water
year. Roy Karo showed us photos of construction. Large rocks (D50 = 2.5')
apparently were covered with a 2' thick sand filter blanket, and subsoil was
dumped above it.
Specifications for the construction of the filter blankets did not appear to
have been reviewed. The Bureau of Reclamation's Design of Small Dams suggests
that a filter blanket should be at least 3' thick, an na cer a1n criteria
for the size of the filter be followed:
1. D15 of the filter = 5 to 40
>fi5 0o t~1le~ase mmaterial
2. D15 of the filter = 5 or less
llgro a ase material
3. Grain size curve of the filter should be parallel to that of the base
material.
Using a D15 of the drain of 300mm and a D15 and D85 of the filters of
0.125 and 0.5mm respectively.
Case I gives 300mm(1') = 2400
~mm
Case II gives 300mm(1') = 600
~mm
This may mean that the filter blanket has clogged the drain.
It would be valuable to watch this drain for flow during a year of high
snowfall. No discharge may indicate that the manner in which the drain was
constructed may serve to impair the drain's ability to function properly.
cc: J. Pendleton
6662F/scg
i~wr+~ic Fi rQ
215 Centennial Building, 1313 Sherman Street Denver, Colorado 80203-2273 Tel. [phone]