ENFORCE27071

• Permit No: C1981048
• IBM Index Class Name: Enforcement
• Doc Date: 11/10/1992
• Doc Name: OPERATORS REQUEST TO VACATE NOVS C-92-013 & C-92-014 TRINIDAD BASIN MINE C-81-048
• From: DMG
• To: JOE DUDASH
• Violation No.: CV1992013
• Media Type: D
• Archive: No

J~ , ~ III III III III IIII III
999 51ATE Or COLOIZ~D~
DIVISION OF MINERALS AND GEOLOGY oe cow
Department of Natural Resources r`"=Qo
N ;,
~~
of
1313 Sherman St.. Room 215 ~
' • ~
• r~"'~ •
Denver, CO 80:07 ~ /Bi6 ~
Phone: U031866~3567
FAX: [phone] Ros Romer
Governor
an~chael B. LOng
Division Director
DATE: November 10, 1992
T0: Joe Dudash
FROM: Cathy Begej
RE: Operator's Request to Vacate NOVs C-92-013 and C-92-014,
Trinidad Basin Mine, C-81-048
I have reviewed the arguments from Greg Lewicki and Associates found in
correspondence dated September 10, 1992 and October lU, 1992. The operator
appears to have six basic arguments in defense of the failure of the surface
water control system. These arguments are either not.germane to maintenance
of performance standards or an inappropriate manipulation of hydrologic
principles. Each argument is reviewed individually below.
I. The storm on June 29, 1992 was a nigh frequency storm equivalent to an
8-year 24-hour event.
Road drainage must accommodate a 10-year 24-hour event per Rule 4.0s.l(4).
II. Rainfall in the precediny five days resulted in a modification of the
antecedent moisture condition and a subsequent higher runoff.
Mr. Lewicki utilized a method described in Barfield, Warner & Haan to
suggest that the 1.1" of rainfall that had fallen in the previous five
days had saturated the soil and resulted in more runoff. The book has a
table which describes antecedent moisture condition and indicates that
the standard antecedent moisture condition, AMC II, reflects an average
value for annual floods and is equivalent to 0.5" - 1.1" of the 5-day
rainfall during the dormant season, and 1.4" - 2.1" of 5-day rainfall
during the growing season. Conversion to AMC III would require more than
2.1" of rainfall in the previous five days during the growing season to
be equivalent. This reflects moister conditions than seen by the
Trinidad Basin i~lines in which 1.1" of rain fell in the previous five
days. Mr. Lewicki argues that the table describes conditions from the
eastern half of the United States. This caveat is not mentioned in the
description. Rather, the values reflect average conditions.
Furthermore, the technique of modifying the antecedent moisture condition
is introduced as an extrapolation of the curve number method that may not
be appropriate.