ML20132B606

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Forwards Request for Addl Info Re Util 830701 Rept, Potential Mudflow from Hypothetical Failure of Spirit Lake Blockage
ML20132B606
Person / Time
Site: Trojan File:Portland General Electric icon.png
Issue date: 07/19/1983
From: Ballard R
Office of Nuclear Reactor Regulation
To: Clark R
Office of Nuclear Reactor Regulation
Shared Package
ML19264D658 List:
References
FOIA-85-353 NUDOCS 8307250364
Download: ML20132B606 (3)
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  • DISTRIBUTION Docket File EHEB Rdg JUL 191983 R8allard

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50-344 MENORAULCl FOR: Robert A. Clark, Chief ,

Operating Reactor Oranch Ho. 3 i

Division of Licensing 1

TMP,U:

llilliam V. Johnston, Assistant Director q

Materials, Chenical and Environnental Technology

]. Division of Engineering FROM: Ronald L. Ballard, Chief Environmental and Hydrologic Engineering Branch

] f Division of Engineering

SUBJECT:

PORTLtND GENEP.AL ELECTRIC SPIRIT LAKE FAILURE i EFFECTS 0.'l TROJAN l Plant Nano: Trojan Dochet ihr.r.ber: 50-344 The report dated July 1,1983 from Portland General Electric (PGE) to you concerning flood potential at the Trojan site has been reviewed by the Hydrologic Engineering Section. L'e found that the recort is defi-cient in several respects. The PGE repcrt seens also to be an abbre-viated version of a nore detailed report fron the consultant. If this a

' is the case, it s:ould he far nore useful for us to work frr.c. the erininal '

report. i.'e have prepared a set of questions to elicit further infor-uation of the licensee. 1.'e would like to have the PGT report revioued by the USGS, who is performing an independent review, but no decision has yet been nade on extension of their contract. This reviou has been conducted by R. Codell, with input from fl. Fliegel and r.1yself.

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HYDROLOGIC EllGINEERING SECTI0tl i Additional Questions " Potential Mudflow from a Hypothetical Failure of Spirit Lake

,, , , Blockage" (July 1,1983 response from PGE) 1.

The report appears to be a summary of a more detailed analysis W report.

As such, however, it does not contain the information necessary to enable

us to evaluate it. If you have a more complete report please provMe it, a

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2. The important case of a mudflow during a low Columbia River flowrate, with consequent high sedimentation in the Columbia River, followed by a large flowrate has been neglected. Records have shown that high flow-rates (1,000,000 CFS) have followed periods of low flow by only a few days.

Analyse the potential for flooding of the site by this scenario, or justify why this case was not considered.

3. Item 1.3 The procedure used to reduce the sediment concentrations from 39, 52, and 65 percent to 20, 30, and 45 percent respectively, as summarized in Table 1 should be discussed and all assumptions should be justified.

For example, what is the basis for reducing the volume of material into i

the Cowlitz by 40% (column 2)? What is the basis for the ratio of sand to finer material of 2 to 1 (columns 3 and 4)? Etc.

4. Item 1.4 Please explain the basis for the 30 percent moisture assumption.

Is this figure based on available pore volume or on total volume of dry solid? What porosity was used and what is its basis?

5. Item 1.6 What is the basis for assuming a Columbia River sediment concentration of 500 ppm? What effect would varying this concentration ~

have on your results?

6. Several references are used in the text, but are not documented. For example, the "Colby method" in item 2.4 provide the references.
7. Item 2.5 Define the term " bulking Factor"
8. Item 2.6 Give bnis for your assumption that the shape of the mudflow sedi-ment deposit at the confluence of the Cowlitz and Columbia rivers can be ratioed from the configuration of the deposition following the May 18, 1980 mudflow. That mudflow deposition was rather flat compared to other known mudflow slopes. What is the sensitivety of your results to variations in the slope of deposited sediments?
9. Item 3.4 Give basis for calculations of sediment load. Were formulas employed derived from relationships for sediment transport in rivers?

If so, justify that these formulas are acceptable for the very-high sediment loads of the present case? *'

10. Item 3.8 Why is 400,000 CFS the "most reasonable Columbia River flow to evaluate"? Is there a probabilistic basis for this conclusion (e.g.,

flRC safety goal)? 8 l

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11. Table 1 .

. (a) Column 8 is unclear. I believe that the expression should

.i j be (col 6 +' col 4)/1.4. Explain the meaning of the value 1.4, and why i

ft is used here. '

j (b) - Explain the difference between column 1 and 2. Also, why is " material" used in column 1 and " sand, silt and clay" used-in column 27 o

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