ML20136H975
| ML20136H975 | |
| Person / Time | |
|---|---|
| Issue date: | 12/13/1985 |
| From: | Fliegel M NRC OFFICE OF NUCLEAR MATERIAL SAFETY & SAFEGUARDS (NMSS) |
| To: | Hawkins E NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION IV) |
| References | |
| REF-WM-64 NUDOCS 8601130114 | |
| Download: ML20136H975 (3) | |
Text
.
WM s/f (Memo /Hawkins/85/12/06/TJ)
WMGT r/f NMSS r/f
, DEC 131985 RBrowning
/J)mdT MBell MM01HAntttsfe5/12/OSTJ JBunting MKnapp TJohnson & r/f MFliegel MEMORANDUM FOR: ED HAWKINS, URF0 PDR FROM: MYRON H. FLIEGEL, WMGT
SUBJECT:
REVIEW 0F RAC PRELIMINARY DESIGN - LAKEVIEW SITE In accordance with your recent verbal requests, Ted Johnson has reviewed surface water hydrology and erosion protection aspects of preliminary design documents for the Lakeview site. These documents were submitted by the remedial action contractor (RAC) by letter dated October 22, 1985. Our questions and comments are enclosed. As agreed between you and Ted, these comments were written in an abrreviated style tomeet schedule requirements.
In general, we conclude that the design, as proposed, is deficient in several areas and will not meet EPA standards. These deficiences are detailed in the enclosure. If you have any questions, please contact Ted Johnson at extension 74490 h M h, hd b/ M,N, k Myron H. Fliegel, WMGT
Enclosure:
As Stated WM Record file '//M Project _ b __. .
Docket No.
PDR.V LPDR____._. _ _
Distribution:
8601130114 851213 PDR WASTE PDR WM-64 (Return to 'lin! b?1 M) _
)FC :WMGT : Pc i
. . . _ _ : _ _ d _4 2 1AM E : TJT:o 6h JL
...__:.......I,___: MoSik. . . : . . . . . _ _d_ _ :: _ _ _ _ _ _ _ _ _ _ _ _ :: _ _ _ _ _
) ATE :85/12/ : W% : : : : :
l l _ _ _ _ _ _ _ _ _ _
, e i
1 Surface Water Hydrology and Erosion Protection Questions and Comments Lakeview Preliminary Final Design
- 1. The rock durability criteria and durability 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 We suggest the that one or more of the following aaditional measures be adopted:
- a. modify the acceptance criteria so that USBR criteria for good-quality rock is met.
l' 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 intensifies 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 char.nels and gullies, the riprap protection should be keyed into bedrock or designed so that ercsive velocities in the existing gullies are not produced. In the proposed design, it appears that the termination of
' the riprap has not been sufficientiv 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 velocities. Also, additional erosion protection should be provided on the 1 Vertical on 3}
Horizontal side slopes of the road and should be designed for the velocities and turbulence which will be produced there.
4
- 5. Riprap sizes should be increased in those portions of the diversion ditches located at channel bends.
y
r 2
I
- 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 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 ccmputed velocities are actually lower
! than in other segments. It appears that the most likely explanation is t
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.
- Discuss how it is appropriate 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.
- 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 PMP distributions. A comparison should be made and the most conservative estimate should be used.
t l
1
-- ,--- - - , - - - - . , ...n - - - - - - - , - - . - - - . - , . - - - - - - . - - - , , - , . . - - - , - - - - . . - - . - , - - , , , - - - - , , , , , -
- . .