ML20140B415
| ML20140B415 | |
| Person / Time | |
|---|---|
| Issue date: | 12/19/1985 |
| From: | Hawkins E NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION IV) |
| To: | Themelis J ENERGY, DEPT. OF |
| References | |
| REF-WM-64 NUDOCS 8601240400 | |
| Download: ML20140B415 (3) | |
Text
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DISTRIBUTION Docket File WM-181 PDR/DCS DBangart, RIV WM-181/SLW/85/12/13/0 SWastler URF0 r/f WDEQ JHaes, RCPD, WY DEC 191985 LLW Branch, WMLU URF0:SLW WM-181 040WM181501E Mr. John Themelis U.S. Department of Energy Albuquerque Operations Office P.O. Box 5400 Albuquerque, New flexico 87115
Dear Mr. Themelis:
We have completed the review of the Lakeview Preliminary Final Design in the areas of surface water hydrology and erosion protection.
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 'n 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.
Originn1 Etcnc6 97 Ednord ?. l!ta21os Edward F. Hawkins, Chief Licensing Branch 1 Uranium Recovery Field Office Region IV
Enclosure:
As stated cc:
T. Johnson j
OFC U8F URF j
NAME -SWa,5 e /10 EHawkins :
., )
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DATE 85/12/13 :
8601240400 851219 PDR WASTIE bM1-t B1 PDR
Surface Water Hydrology and Erosion Protection Questions and Comments Lakeview Preliminary Final Design 1.
The rock durability criteria and duracility tests proposed may not be adequate to assure that rock of acceptable quality will be provided at this site.
As proposed, the rock will have difficulty meeting minimum United States Bureau of Reclamation (USBR) criteria for poor-quality rock.
We suggest that one or more of the following additional measures be adopted:
a.
modify the acceptance criteria so that USBR criteria for good-quality rock is met.
b.
find other sources of rock that meet USBR criteria for good-quality rock.
c.
perform additional tests (such as petrographic examination and freeze-thaw tests) that will further document the acceptability of the rock.
2.
In the determination of peak flood flows in the ditches, the minimum time of concentration that was adopted by the RAC 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 is generally not applicable to small, steep, drainage areas.
3.
At those locations where the proposed diversion ditches transition into existing channels and gullies, the riprap protection should be keyed into bedrock or designed so that erosive velocities in the existing gullies are not produced.
In the proposed design, it appears that the termination of the riprap has not been sufficiently protected against erosion.
If the riprap is not keyed into the bedrock, the basis for terminating the riprap should be clearly defined.
4.
At those locations where the ditches merge and discharge flows over the access road, the riprap protection in the ditches should be increased to account for turbulence, hydraulic jumps, and energy dissipation.
Additionally, the access road in these areas should be designed with riprap which is sufficient in size to resist expected
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velocities. Also, additional erosion protection should be provided on the 1 Vertical and 31 Horizontal side slopes of the road and
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should be designed for the velocities and turbulence which will be produced there.
5.
Riprap sizes should be increased in those portions of the diversion ditches located at channel bends.
6.
The possibility of one drainage ditch overtopping into an adjacent diversion ditch should be considered in the design, if this has not already been considered.
7.
The computations of rock sizes for the ditch appear to be very sensitive to selection of a Manning's "n" value.
Sensitivity 1
analyses should be conducted for this parameter, with adjustments made accordingly.
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.
It appears that the most likely explanation is that "n" values (and resulting velocities) may not vary as widely as shown in the calculations.
8.
Discuss those site features which were designed for the "1,000-year" storm.
Provide the basis for selection of that storm for design purposes, and substantiate that your selection will meet the standards for long-term stability.
Discuss how it is appropriate i
to extrapolate to a 1,000-year recurrence interval using a limited data base.
9.
The proposed grading specifications of plus or minus 6 inches could produce concentrations in some areas.
A grading tolerance, such as 0.1 percent of the specified grade, would be more appropriate.
- 10. The use of average ditch side slopes (if the slopes differ) may not be appropriate.
The most critical slope should be evaluated for design of the riprap.
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- 11. Due to the location of the site, it may be more appropriate to use Hydrometeorological Report (HMR) 49, rather than HMR 43, to determine Probable Maximum Precipitation (PMP) and PfiP distributions.
A comparison should be made, and the most i
conservative estimate should be used.
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