HYDRO26784

• Permit No: C1981071
• IBM Index Class Name: Hydrology
• Doc Date: 4/7/1989
• Doc Name: CHANNEL CERTIFICATIONS- DRAINAGES 7 31-1 31-2 41 51 51W ECKMAN PARK-C81-071
• From: MLRD
• To: COLO YAMPA COAL CO
• Permit Index Doc Type: PROF POND CERTIFICATIONS
• Media Type: D
• Archive: No

'.
~~°;~~°, STATF OF COLORADO
Roy Romer, Governor

DEPARTMENT OF NATURAL RESOURCES
MINED LAND RECLAMATION DIVISION
FRED R. BANTA, Dlrattor
DATE: March 23, 1989 --
T0: David Berry
FROM: Jim Pendleton
RE: Eckman Park-Channe
(Permit No.`C=81~
1
ifications - Areas 7, 31, 41, 51 and 51W
I have the reviewed the packet of information you forwarded to me concerning
the riprap installation in reconstructed drainage channels within the above
referenced areas at the Eckman Park mine. In the cases of areas 41 and 51 the
as-built riprap appears to be somewhat finer in gradation than that specified
in the design documents. In these instances I believe it is appropriate to
require the operator to demonstrate that the as-built riprap Gradation and
sizing will meet the design requirements and is, therefore, capable of
resisting erosion.
The operator has submitted a collection of inspection reports, prepared by
ACZ, Inc., a consultant engineering firm. In general, these reports are
descriptive of the services conducted at the site and the riprap gradation
findings. These reports contain occasional comments suggesting that the
as-built riprap sizing, gradation and shape do not correspond exactly with the
approved plan's specifications. In addition, these reports often include
suggested steps to be followed to resolve a problem and to achieve compliance
with the specifications. Except for the final September 230 (23), 1989
inspection report, all deficiencies found were later resolved and noted as
resolved to the satisfaction of the inspecting consultant engineer. I suspect
that a final report exists which has not been submitted. However, resolution
of these final deficiencies should be documented.
Testing and laboratory reports were included from Ground Engineering
Consultants, Inc., which addressed the riprap sizing and gradation. In
several instances in testing reports dated June 23 through September 12, 1988,
the consultant states: "Based on the in-place gradation results, it appears
that the material sampled on this date is close to the engineered
specifications. However, the specifications don't give a range for the
percent passing for each size. We believe that a range should be given for
these sizes, as is the case for most gradation specifications". (For example,
see Paragraph 3, Page 1, August 31, 1988). In their final report, dated
September 7, 1988, a table is included which presents a specified range of
gradation sizing for each size of riprap.
215 Centennial Building, 1313 Sherman Street Denver, Colorado 80203-2273 Tel. [phone]