ML20137E386
| ML20137E386 | |
| Person / Time | |
|---|---|
| Issue date: | 12/23/1985 |
| 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 8601170243 | |
| Download: ML20137E386 (9) | |
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WMGT r/f Luigginbotham DEC23.M NMSS r/f PGarcia URF0 RBrowning "EM0/KC l EVAL /T]/85/12/19 MBell JBunting MKNapp TJohnson & r/f MFliegel MEMORANDUM FOR:
ED HAWKINS, URF0 POR GGnugnoli, WMLU FROM:
MYRON H. FLIEGEL, WMGT DMartin, WMLU TECHNICAL EVALUATION REPORT - LAKEVIEW SITE
SUBJECT:
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 22,1985. Our remedial action contractor (RAC) by letter dated OctoberAs agreed between you and Ted, technical evaluation report (TER) is enclosed.
this document principally addresses acceptability of design bases and any unacceptable aspects of the design as determined by a preliminary review of the documents.
In general, we conclude that the design, as proposed, is deficient in several Comments and questions delineating areas and will not meet EPA standards.
these deficiencies were transmitted to you by letter dated December 13, 1985.
If you have any auestions, please contact Ted Johnson at extension 74490.
6 Myron H. Fliegel, WMGT
Enclosure:
As Stated
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Dxut No.
8601170243 851223 PDR WASTE PDR DjsiribuUcn:
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- MFliegel EDTE:85/12/93
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l DRAFT TECHNICAL EVALUATION REPORT SURFACE WATER HYDROLOGY AND EROSION PROTECTION EVALUATION OF THE LAKEVIEW - COLLINS RANCH - REMEDIAL ACTION SITE 1.
Hydrologic Description The Lakeview (Collins Ranch) site is located approximately seven miles northwest of Lakeview, Oregon.
The site is situated in a relatively steep area against the southwest slope of Mt. Augur.
Flood runoff in drainage channels is produced by rainfall on very small-drainage areas at the site.
The remediated embankment will be constructed at the Collins Ranch site by relocation, mixing, and consolidation of the Lakeview site-tailings-(presently located one mile northwest of Lakeview, Oregon).
In order to comply with EPA standards, which require stability of the uranium tailings for a 1,000-year (or minimum 200-year) period, DOE oroposes to stabilize the tailings and contaminated materials in an engineered embankment to protect them from flooding and erosion. Design criteria for protection of this embankment included the Probable faximum Precipitation (PMP) and the Probable Maximum Flood (PMF) events, both of which are considered to have very low probabilities of occurrence during the 1000-year stabilization period.
The tailings will be consolidated into a single pile, which will be protected by soil and rock covers. The covers will have maximum slopes of 3% on the top and 20% on the sides. Disposal will be partially below grade, and the irregularly-shaped pile will be surrounded by drainage channels and access roads.
2.
Geomorphic Considerations The geomorphic setting at the site is relatively stable. The slopes in the area are generally well-protected by a natural gravel and cobbl_e armoring.
There are no nearby water bodies which have a potential to affect the site by treandering or erosion.
3.
Flooding Determinations In order to determine site impacts from flooding, DOE analyzed flooding in various on-site drainage channels to ' determine peak flows and velocities and-to evaluate the need for erosion protection features.
DOE estimated the PMF peaks in the channels resulting from an occurrence of the PMP over the limited areas draining into~the channels. These design events meet the criteria outlined in the Standard Review Plan (Reference 15) and are,
therefore, acceptable. However, our review of the preliminary design indicates that several aspects of the PMP and PMF determinations were not appropriately applied. The details of the flood computations were analyzed by the NRC staff as follows:
A.
Probable Maximum precioitation (PMP)
A PMP rainfall was developed by DOE using Hydrometeorological Report (HMR) 43 (Reference 9). Based on a check of the rainfall computations, we conclude that the PMP from HMR 43 was acceptably derived for this site'. However, the rainfall was not extrapolated to the proper duration (See C, below). In addition,- the location of the site is such that HMR 49 (Reference 14) could be.iust as applicable as HMR 43, because even though tne site is located in the' region covered by HMR 43, it is only about twenty miles from the region covered by HMR 49. Therefore, it may be more appropriate to use HMR 49 rather than HMR 43 to determine PMP and PMP distributions. A comparison should be made and the most conservative estimate should.
be used, if there is a significant difference. This information will be requested from DOE.
B.
Infiltration Losses DOE estimated no infiltration losses to occur. Based on a review of the computations, we conclude that this is a very conservative assumption.
C.
Tine of Concentration Various times of concentration (tc) for the ditches and embankments were estimated by DOE using procedures discussed in Reference 3.
In general, the method used for computing te may not be appropriate or conservative. Specifically, sheet flow and channel flow will occur at fairly high velocities, and DOE's computed times of concentration may be overestimated. DOE should use methods which are representative of the small steep drainage areas present at the site.
The NRC staff concludes that the stream hydraulics method (Reference
- 3) would likely be more appropriate for this site, and should be used, particularly for flow in the ditches.
D.
PMP Rainfall Distributions
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DOE derived rainfall distributions and intensities from HMR 43, which is acceptable. However, in the determination of peak flood flows in ditches, the minimum time of concentration and rainfall duration that was adopted 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 or to a minimum of 21 minutes (per NRC/ TAC /RAC agreements). Additionally, the rainfall intensities should be compared with those extrapolated from HMR 49, and the more conservative distribution applied, if there is a significant difference between the two.
E.
Computation of PMF DOE utilized the rational formula (Reference 3) to compute the peak PMF flows in the ditches, given the input parameters discussed above.
Based on NRC's review of the calculations presented, we conclude that this method of computation is acceptable, but that the peak PMF flows have not be acceptably derived.
This is principally due to improper application of times of concentration (See 3C, above) and rainfall distribution (See 3D, above).
4 Upstream Dam Failures There are no dams whose failure could affect the site. The site is not located near any surface water impoundments.
5.
Design of Erosion Protection A. Perimeter Ditches DOE proposes that the erosion protection in the perimeter drainage ditches will be designed for an occurrence of a local PMP. This desian basis meets the criteria outlined in the SRP and is, therefore, acceptable.
However, there are several aspects regarding the design and layout of the ditches which are not acceptable and will require additional changes.
These aspects are as follows:
a.
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 at the outlets are not produced.
In the proposed design, it appears that the termination areas of the riprap have not been sufficiently protected.
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I b.
. 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 IV on 31 H side slopes of the road and should be designed for the velocities and turbulence which will be produced there.
c.
Riprap sizes should be increased in those portions of the diversion ditches located at channel bends.
d.
The possibility of one drainage ditch overtopping into an ad.iacent diversion ditch should be considered in the design.
3; The computations of rock sizes'for the ditches' appear to be very e.
sensitive to selection of a Manning's'"n" value. Sensitivity analyses should be conducted for this parameter, with adjustments made accordingly.
In addition..it11s 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 one likely explanation is that "n" values (and resulting velocities) may not vary as widely as shown in the calculations.
Another possible explanation ~is that too much flow is assumed to pass through the rock.. and the resulting calculations are distorted.
f.
The use of average ditch side slopes-(if the slopes differ) for computation of erosion protection may not be appropriate. The
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most critical slope should be evaluated for design.of the riprap.
i B.
Top and Sides of Piles The rock covers, which will be_used to protect the soil cover from i
wind and water erosion, are designed to resist an occurrence of the i -
local PMP. For the top of the pile (3% slopes), DOE proposesL o t
provide _ an 18-inch layer of rock with a D50 of.about 5 inches.
For the sides of the pile (20% slopes), DOE proposes'an'18-inch layer of rock with a 050 of about 9 inches. Each of-the rock' lavers' will be placed on a ' gravel filter layer. The Safety Factors Method (Reference l
- 12) was used to determine required rock sizes.
e Based on a review of the calculations provided, we conclude that the proposed rock for the top and sides of the pile have been conservatively computed.
C.
Rock Durability For the rock to be placed in the ditches and on the pile, proposed gradation and rock durability criteria were presented. However, our review indicates that 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 prooosed, the rock will have difficulty meeting minimum USBR criteria for poor-quality rock. We suggest that one or more of the followirg 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,'or c.
perfor,n additional tests (such as petrographic examination and freeze-thaw tests) that will further document the acceptability of the rock.
D.
Construction Considerations At the present time, the design details for many hydrologic protective features, which implement the site conceptual design, are not known. Such details include: 1) specifications for the monitoring and maintenance programs needed to insure the integrity of the on-site slopes and erosion protectinn; 2) final specifications for riprap layer size, thickness, durability, placement, testing, and source; and 3) testing and quality assurance programs that will be used during construction.
As a minimum, the NRC staff will reouire that the above construction and monitoring programs be submitted for NRC staff review and approval prior to their implementation. This will assure that adequate measures have-been taken to provide long-term protection, consistent with the EPA-standards.
In addition, the NRC staff should conduct a site visit during construction to verify that erosion protection features' have been constructed according to design specifications.
.t-6.
Conclusions and Recommendations Based on our review of the information submitted by DOE, we are unable to conclude that the site conceptual design will meet EPA requirements as stated in 40 CFR 192 with regard to flood design measures and erosion protection. We are unable to conclude that an adequate hydraulic design has been provided to -
reasonably assure stability of the contaminated material at Collins Ranch for a period of up to 1000 years. Additional information, analyses, and redesign of ercsfon protection will be requested from DOE to satisfy the above concerns.
-4.
REFERENCES and BIBLIOGRAPHY 1.
U.S. Army Corps of Engineer s, Hydrologic-Engineering Center," Flood Hydrograph Package, HEC-1," continuously updated and revised.
2.
U.S. Nuclear Regulatory Commission, Regulatory Guide 1.59, " Design Basis Floods For Nuclear Power Plants," January,1983.
3.
U.S. Bureau of Reclamation U.S. Department of the Interior, Design of Small Dams,1973.
4 Staff Technical Position WM-8201, " Hydrologic Design Criteria for Tailings Retention Systems," January.-1983.
5.
U.S. Army Corps of Engireers, Hydrologic Engineering Center, " Water
]
Surface Profiles, HEC-2." continuously updated and revised.
)
- 6. -
Chow, V.
T., "Open Channel Hydraulics," McGraw-Hill Book Company, New t
York, 1959.
7.
U.S. Army Corps of Engineers, " Hydraulic Design of Flood Control Channels," EM 1110-2-1601, 1970.
8.
U.S. Army Corps of Engineers, " Additional Guidance for Riprap Channel Protection," ETL 1110-2-120, May, 1971.
9.
U.S. Department of Connerce, U.S. Army Corps of Engineers, Hydrometeorological Report No. 43, " Probable Maximum Precipatation Northwest States, " 1966.
10.
U.S. Army Corps of Engineers, " Engineering and Design - Standard Project Flood Determinations " EM 1110-2-1411, 1965.
- 11. Crippen, J. R. and Bue, C. D., " Maximum Floodflows in the Conterminous United States," USGS Water Supply Paper 1887(1977).
- 12. Simons, D. B., and Senturk, F., Sediment Transport Technology, Fort Collins, Colorado, 1976.
- 13. Codell, R.
B., " Design of Rock Armor for Uranium Mill Tallings Embankments," U.S. Nuclear Regulatory Commission, Unpublished Draft Report, February, 1985.
k
a 14.
U.S. Department of Comerce, U.S. Army Corps of Engineers, Hydrometeorological Report No. 49, " Probable Maximum Precipitation Estimates, Colorado River and Great Basin Drainages," 1977.
15.
U.S. Nuclear Regulatory Commission, Standard Review Plan for UMTRCA Title I Mill Tailings Remedial Action Plans October,1985.
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