REP19150

• Permit No: M1986104
• IBM Index Class Name: Report
• Doc Date: 2/12/1999
• Doc Name: AMENDMENT TO SAMPLING AND ANALYSIS PLAN MONTGOMERY PIT PN M-86-104
• From: DMG
• To: B&B EXCAVATING INC
• Media Type: D
• Archive: No

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STATE OF
DIVISION OF MINERALS AND GEOLOGY
Department of Natural Resources
1 313 Sherman Si.. Roam 215
Denver, Colorado 80203
Phone. {3031 866-3567
FAX: [phone]
February 12, 1999
Mr. Scott Hoover
B & B Excavating, Inc.
Drawer 249
COLORADO
J
DEPARTMENT
NATURA~a
RESOURCE
Roy Romer
Governor
tames 5. Lochhead
Fzecutive Director
Michael B. Long
Vall, C~ 81658 Division Duector
RE: Amendment to Sampling and Analysis Plan, Montgomery Pit, Permit No. M-86-104
Dear Mr. Hoover:
The Division of Minerals and Geology (DMG) has completed a review of the "Amendment to
Sampling and Analysis Plan" (SAP amendment) for the Montgomery Pit herbicide release. The SAP
amendment was prepared by Greg Lewicki and Associates and submitted to DMG on February 2,
1999. The following issues remain to be addressed to the satisfaction of DMG prior to implementation
of the SAP amendment.
Please provide a statement that those portions of the Draft Sampling and Analysis Plan
prepared by Dames and Moore and submitted to DMG on December 18, 1999 [hat are no[
modified by the SAP amendment will remain as components of the sampling and analysis plan.
Specifically, sections 4.4, 4.5, 4.6, 4.7, 5.0, and Appendix D from the Dames and Moore
sampling and analysis plan must be adhered to during implementation of the SAP amendment.
In addition, pertinent portions of section 4.3 must be adhered to relative to the procedure for
conducting ambient temperature headspace testing with the photo-ionization detector.
Under the terms of the SAP amendment, an on-site hazardous waste repository and treatment
cell may or may not be needed depending on whether or not contamination in excess of ]0
mg/kg 2,4-D is found at the site. The DMG suggests that the treatment cell be constructed with
a composite liner rather than with the clay liner that is proposed, for the following reasons:
a) It is not known how long it will take for the 2, 4-D [o decompose to below the ]0 mg/kg
limit in the treatment cell. During the period [hat the hazardous material is present in
the cell a clay liner would be susceptible to damage by desiccation cracking and
freeze/thaw effects.
b) 2,4-D, bromacil, or diesel fuel may permeate through the clay and be released to [he
environment during the period of storage in the treatment cell. The likelihood of this
occurring would be increased if any precipitation were to accumulate in the cell.
Assuming a hydraulic conductivity for the clay of 4.7 x 10' m/s and an areal extent for
the cell of 1,800 square feet, permeation of contaminants through the proposed 6 inch