ML20148F912
| ML20148F912 | |
| Person / Time | |
|---|---|
| Issue date: | 02/18/1988 |
| From: | Johnson T NRC OFFICE OF NUCLEAR MATERIAL SAFETY & SAFEGUARDS (NMSS) |
| To: | Fliegel M, Starmer J, Wastler S NRC OFFICE OF NUCLEAR MATERIAL SAFETY & SAFEGUARDS (NMSS) |
| References | |
| REF-WM-62 NUDOCS 8803280320 | |
| Download: ML20148F912 (2) | |
Text
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FEB 1819b8 MEMORANDUM FOR: John Starmer, LLTB Mike Fliegel, LLOB Sandy Wastler, LLOB FROM:
Ted Johnson Technical Branch Division of Low-level Waste Management and Decommissioning, NMSS
SUBJECT:
TELECON WITH MKE ON RIFLE EROSION PROTECTION DESIGN On February 9, 1988, I was called by several design engineers from Morrison-Knudsen Engineers (MKE) regarding the design of the Rifle UMTRA site.
Participating in the call were:
Grant Sherrington, MKE Allen Htay, MKE Ted Johnson, NRC The purp.ise of the call was to discuss surface water hydrology and erosion protection concerns. MKE indicated that they had been thinking about resolution of NRC staff convents and wanted to discuss several design concepts which they thought might be able tr resolve our concerns at this site.
The first topic discussed was the possibility of providing a stilling basin structure of some sort at those locations where natural gullies discharge into the inter.eptor ditches. This type of design would limit the velocities in the natural gullies by slowing down the flow in a stilling basin or plunge pool.
I indicated to MKE that it was difficult to picture such a design while talking over the telephone, but it was likely that such an approach could lead to major problems with regard to sedimentation and debris collection in the area where reduced velocities occur.
I indicated that such an approach would likely not meet EPA standards, because of the need for routine maintenance in removing the debris and sediment.
The second topic discussed was the depth of gullies at the downstream end of the interceptor ditches and the toe ditch. MKE indicated that they hao performed some preliminary studies to determine depths of gullies at those locations where the ditches meet natural ground. They indicated that they had plotted gully depth vs. drainage area and had used those relationships to design the erosion protection for the ditch outlets.
I indicated that they probably needed to examine many geomorphic variables at this site in order to derive such relationships, and that such plots alone ate often not meaningful.
Further, I indicated that the problem with designing the erosion protection involved the determination of flow velocities in the gullies and that the depth of the gully at the present time was not necessarily the depth of gully that should be used for design purposes.
Also, I stated that such depths are not nece.isarily the depths of a gullies that would be produced by a PMF.
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The third topic discussed involved some work done by Jacobs Engineering, r,ho have apparently determined that the ditches will be self-cleaning and will never become clogged with sediment and debris.
I indicated to MKE that I was skeptical of such calculations, in light of test pit data and boring data which indicates that relatively large large cobbles ( up to 12 inches in diameter) are available to be transported by the natural gullies. I stated that the flatter slope of the ditches may not produce sufficient velocity to adequately flush the ditches, particularly for routine flood events and for 12-inch diameter cobbles.
I MKE indicated that they understood my concerns and requested that a meeting be held as soon as possible to discuss some other design concepts that they have.
I indicated that I would check to see if such a meeting could be held.
I also indicated that they should not hold up on their efforts to revise the design, in anticipation of such a meeting.
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Ted Johnson Technical Branch Division of Low-level Waste Management and Deconinissioning, NMSS DISTRIBUTION:
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ATE :02//B/88 0FFICIAL RECORD COPY
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