ML20140B423
| ML20140B423 | |
| Person / Time | |
|---|---|
| Issue date: | 01/09/1986 |
| From: | Hawkins E NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION IV) |
| To: | Themelis J ENERGY, DEPT. OF |
| References | |
| REF-WM-48 NUDOCS 8601240406 | |
| Download: ML20140B423 (3) | |
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DISTRIBUTION Docket File WM-175 PDR/DCS DBangart, RIV UM-175/HDR/86/01/07/0 H
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RBrich URF0 r/f JAN 0 91986 LLW Branch, WMLU URF0:HDR WM-175 Mr. John Themelis U.S. Department of Energy Albuquerque Operations Office P.O. Box 5400 Albuquerque, New Mexico 87115
Dear Mr. Themelis:
We have completed our review of the Durango (Bodo Canyon) Preliminary Final Design.
Based on this review, we concluded that the design, as proposed, is deficient in several areas and will not meet EPA standards.
These deficiencies are outlined in the specific comments which are provided as an enclosure to this letter.
Should you have any questions regarding our review or the items discussed in this letter, please contact me at FTS 236-2805 or Ted Johnson at FTS 427-4490.
Sincerely, o g!vnt 7i_~;,.>
r TJ m d:'.rint-n Edward F. Hawkins, Chief Licensing Branch 1 Uranium Recovery Field Office Region IV
Enclosure:
As stated cc:
T. Johnson 1FC m _ _ _ _ : _U_
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8601240406 860109 PDR WASTE WM-175 PDR
Durango (Bodo Canyon) Preliminary Final Design Questions and Comments 1.
In the determination of peak flood flows in the ditches, the minimum time of concentration that was used was 5 minutes, even though the actual times of concentration are much shorter than 5 minutes in many cases.
The NRC staff considers that rainfall intensities should be extrapolated to the appropriate time of concentration (tc) or to a minimum of 21 minutes (per NRC/ TAC /RAC agreements).
Additionally, the method used to compute tc may not be applicable to small, steep drainage areas. Peak flows in the ditches should be re-evaluated, as necessary.
2.
At those locations where the diversion ditches transition into the existing channels and where the erosion protection blanket transitions into natural ground, the erosion protection that will be keyed into bedrock has not apparently been adequately designed.
In developing the proposed design, the computational method allows for a significant portion of the flow to pass through the rock.
In these areas, where the slope transitions from IV on SH to IV on 2H, the flow will not be carried in the rock voids because the rock toe will be covered with soil, and the voids will be filled.
Even if the rock toe is not covered with soil, it S unreasonable to expect that the flow will suddenly go into the wids on the IV on 2H slope after flowing over the top of the IV on 5H slope.
In addition, it is also unreasonabk to expect that the voids will always be available to carry flows since sedimentation is likely to cause blockage over long periods of time.
Rock sizes in the ditches and rock toes should be rectmputed, assuming no flow through the rock voids.
(See also Comment 4.)
Ir addition, turbulence and energy dissipation need to be considered in the design, especially for the rock toes and ditch junctions.
3.
Riprap sizes should be increased in those portions of the diversion ditches located at channel bends.
Corps of Engineers EM1110-2-1601 provides acceptable guidance.
4.
The computations of rock sizes for the ditches appear to be very sensitive to selection of a Manning's n" value.
In addition, it is difficult to understand why riprap sizes are larger for certain ditch segments where the computed velocities are actually lower than in other segments. One reason is the "nd values (and resulting velocities) may not vary as widely as shown in the calculations.
Another reason is that flow is assumed to pass through the voids of the rock layer.
We conclude that no credit should be taken for flow through the rock voids in the ditches or in those locations where 1
l the ditches are keyed into bedrock.
The flow should be assumed to pass over the rock layer, with appropriate adjustments made to "n" values.
(See also Comment 2.)
5.
The erosion protection that will be keyed into bedrock should also be designed to resist the flow velocities produced in adjacent existing off-pile gullies which will flow approximately parallel to the remediated pile. Calculations should be provided which document the ability of these rock layers to resist PMF velocities in the existing gullies to the north and southwest of the proposed pile.
Particularly in the north gully termination, additional protection (in both size and areal extent) may be needed to adequately prevent off-pile flooding from affecting the integrity of the rock toe.
6.
Information provided is still not adequate to alleviate concern regarding the swell and dispersion potential of the radon barrier soils. The staff concern involves the possibility that excessive soil swelling will cause disruption of reclamation contours leading to concentration of sheet water flow, removal of the rock erosion protection and finally, exposure of the radon barrier soils to flowing water.
The results of additional laboratory testing of the radon barrier soils for both swell and dispersion potential should therefore be provided.
7.
Insufficient site-specific information regarding the RAECOM input parameters exists.
Therefore, the results obtained from the recently conducted soil testing should be provided.
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